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Rehabilitation of precast deck panel bridges
h [electronic resource] /
by Atiq Alvi.
[Tampa, Fla] :
b University of South Florida,
Title from PDF of title page.
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Thesis (MSCE)--University of South Florida, 2010.
Includes bibliographical references.
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ABSTRACT: USF completed a research study in 2005, which prioritized the replacement of 85 deteriorating composite precast deck panel bridges. This thesis re-evaluates the original recommendations in the wake of failures of two of these bridges in 2007. Since funding will not allow all identified bridges to be replaced, it was necessary to determine the most effective repair methods. To assess USF's recommendations, a forensic study was undertaken in which the most current inspection and work program documents on the two failed bridges were reviewed and FDOT personnel interviewed. The best repair procedures were determined by reviewing repair plans, specifications, reports and site visits. The study found the two bridges that failed had been correctly prioritized by USF (No. 1 of 18 and No. 8 of 15). A new, accelerated repair method encompassing complete bay replacement was developed in a pilot project funded by the Florida Department of Transportation.
Advisor: Rajan Sen, Ph.D.
x Civil & Environmental Eng.
t USF Electronic Theses and Dissertations.
Rehabilitation of Precast Deck Panel Bridges by Atiq H. Alvi A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Civil Engineering Department of Civil and Environmental Engineering College of Engineering University of South Florida Major Professor: Rajan Sen, Ph.D. William Carpenter, Ph.D. Gray Mullins, Ph.D. Date of Approval October 26, 2010 Keywords: Deterioration, Sudden Failures, Forensic Analysis, Permanent Repairs, Full Depth Precast Panels Copyright 2010, Atiq H. Alvi
DEDICATIONFor my lovely daughter Lina.
ACKNOWLEDGEMENTS All praise is due to GOD, most gracious most merciful, for giving me the ability, determination and drive to complete my graduate studies at this stage of my career. I would like to first thank my parents and sist er, Mustafa, Amina, and Dr. Hayat Alvi, for their encouragement; and my wife Misbah for her loving support and understanding. I am grateful to my advisor Dr. Rajan Sen for his excellent mentorship, not only in graduate studies and thesis but also for his help in guiding me as an undergraduate student some twenty years ago. I am obliged to Dr. William Carpenter and Dr. Gray Mullins for serving on my committee. I am indebted to: Dr. Mohsen Shahawy for his mentorship since my time at FDOT; and for his innovative idea on replacing br idge deck bays with full depth precast panels used in this study; to Mr. Jose (Pep e) Garcia, my mentor and former boss at the FDOT for his continual encouragement, for always promoting technical excellence and for relentlessly working on so lutions to avoid bridge cata strophes; to Mr. James Moreno, my current boss at TY Lin International, for his unwavering support, which has been a big factor to my growth in the field of Bridge Rehabilitation; and finally, to Teddy Theryo, mentor at my former place of empl oyment, Parsons Brinckerhoff, for his help and technical guidance and for his encourag ement in pursuing my masterÂ’s degree. Last but not least, I woul d like to thank my friends and colleagues, Ms. Beth Steimle, Dr. Kwangsuk Suh and Dr. Seungwoo Lee for their help and support at work as well as in my graduate studies.
i TABLE OF CONTENTS LIST OF TABLES ............................................................................................................. ii i LIST OF FIGURES ........................................................................................................... iv ABSTRACT ...................................................................................................................... vi 1. INTRODUCTION .........................................................................................................1 1.1 Introduction ......................................................................................................1 1.2 Objectives ........................................................................................................4 1.3 Thesis Organization .........................................................................................5 2. BACKGROUND ...........................................................................................................6 2.1 Prior Research ..................................................................................................6 2.2 University of Florida Study (1982) ..................................................................6 2.3 University of Florida Study (1983) ..................................................................7 2.4 University of Florida Study (1984) ..................................................................8 2.5 University of South Florida Study (2005) .....................................................10 2.6 Summary and Conclusions ............................................................................13 3. DECK FAILURES IN 2007 ........................................................................................15 3.1 Introduction ....................................................................................................15 3.2 Bridge No. 100332 .........................................................................................16 3.3 Bridge No. 100436 .........................................................................................19 3.4 Summary and Conclusions ............................................................................23 4. ASSESSMENT OF USF PRIORITIZA TION RELATIVE TO NEW FAILURES ....25 4.1 Bridge No. 100332 .........................................................................................25 4.2 Bridge No. 100436 .........................................................................................27 4.3 Summary and Conclusions ............................................................................31 5. PRESENT STATUS OF PRECAST DECK PANEL BRIDGE REPLACEMENT ....32 5.1 Status ..............................................................................................................32 5.2 Summary and Conclusions ............................................................................38 6. BRIDGE DECK REPAIR METHODS .......................................................................39 6.1 Introduction ....................................................................................................39 6.2 Repair Materials .............................................................................................39 6.3 Repair Types ..................................................................................................42 6.4 Summary and Conclusions ............................................................................52
ii 7. SUMMARY AND CONCLUSIONS ..........................................................................53 LIST OF REFERENCES ...................................................................................................57 APPENDIX A: USF STUDYÂ’S PRIORITIZATION TABLES ........................................59 APPENDIX B: REPAIR METHODS ...............................................................................64 ABOUT THE AUTHOR ....................................................................................... End Page
iii LIST OF TABLES Table 2.1 Localized Deck Failures 2000 to 2003 ..........................................................11Table 3.1 Localized Deck Failures Following USF Study ............................................15Table 5.1 Recommended Distri ct 1 Bridge Replacement Sequence .............................33Table 5.2 District 1 Bridges in Good Condition ............................................................35Table 5.3 Recommended Distri ct 7 Bridge Replacement Sequence .............................36Table 5.4 District 7 Bridges in Good Condition ............................................................36Table 5.5 Recommended Crosstow n Expressway Replacement Sequence ...................37Table 6.1 Repair Methods ..............................................................................................42Table A.1 Recommended Distri ct 1 Bridge Replacement Sequence .............................60Table A.2 District 1 Bridges in Good Condition ............................................................61Table A.3 Recommended Distri ct 7 Bridge Replacement Sequence .............................62Table A.4 District 7 Bridges in Good Condition ............................................................62Table A.5 Recommended Crosstow n Expressway Replacement Sequence ...................63
iv LIST OF FIGURES Figure 1.1 Composite DeckPrecast Deck Panel and CIP Concrete ................................1 Figure 1.2 Precast Deck Panel Inventory in 2000 .............................................................2 Figure 1.3 Precast Deck Panel with CIP Component .......................................................2Figure 1.4 Precast Deck Panel Reinforcement Details .....................................................3 Figure 2.1 Deterioration Model ......................................................................................12Figure 3.1 Bridge No. 100332, Span 39 Failure (Deck Top) .........................................16Figure 3.2 Bridge No. 100332, Span 39 Failure (Deck Underside) ...............................17Figure 3.3 Excerpts from Emergency Inspection Report ................................................19Figure 3.4 Bridge No. 100436, Span 4 Failure (Deck Top) ...........................................20Figure 3.5 Bridge No. 100436, Span 4 Failure (Deck Underside) .................................20Figure 3.6 Excerpt from Emergency Inspection Report .................................................21Figure 3.7 Bridge No. 100436, Tr ansverse Cracking Pattern .........................................22Figure 3.8 Bridge No. 100436, Span 4 Fa ilure (3/4 in. Transverse Crack) ....................23Figure 4.1 Bridge No. 100436, Span 4 Failure (Temporary Steel Plate) ........................28Figure 4.2 Bridge No. 100436, Span 4 Failure (Timber Bracing) ..................................29Figure 4.3 Bridge No. 100436, Span 4 (F ailure in Patch Repair Material) ....................30Figure 6.1 Full Depth Precast Pa nel Design Plan Details  .......................................45Figure 6.2 Existing Deck Cut and Removal Using Strong Back ....................................46Figure 6.3 New Deck Susp ension Using Strong Back ...................................................47
v Figure 6.4 Installing Backer Rod for P ouring Epoxy and Finished Epoxy Joint for Bonding New Panel with Existing as well as Seating for New Panel ..........48Figure 6.5 Adhesive Anchors .........................................................................................49Figure 6.6 Sawcutting Grooves into D eck and Placing CFRP Rods in Epoxy ...............50Figure 6.7 Completed Deck (Transverse and Longitudinal NSM CF RP Installation) ...51Figure B.1 Bridge No. 100332, Span 38Asphalt Patch (2 Days Before Failure) .........66Figure B.2 Bridge No. 100332, Span 38Asphalt Patch (Failure) .................................68Figure B.3 Patched Spalls and Walking Spalls ...............................................................69Figure B.4 Localized Spall Repair Starting to Spall at the Edge ....................................70Figure B.5 Bearing Detail after Grout Packing Repair ...................................................71Figure B.6 M1 Repair Procedure (Stage #7). .................................................................72Figure B.7 M2 Repair Procedure  ..............................................................................75Figure B.8 Full Depth Bay Replacement Detail .............................................................76
vi ABSTRACT USF completed a research study in 2005, which prioritized the replacement of 85 deteriorating composite precast deck panel bridge s. This thesis re-evaluates the original recommendations in the wake of failures of two of these bridges in 2007. Since funding will not allow all identified bridges to be repl aced, it was necessary to determine the most effective repair methods. To assess USFÂ’s recommenda tions, a forensic study was undertaken in which the most current inspec tion and work program documents on the two failed bridges were reviewed and FDOT personnel interviewed. The best repair procedures were determined by reviewing re pair plans, specifications, reports and site visits. The study found the two bridges that fa iled had been correct ly prioritized by USF (No. 1 of 18 and No. 8 of 15). A new, acceler ated repair method encompassing complete bay replacement was developed in a pilot project funded by the Florida Department of Transportation.
1 1. INTRODUCTION 1.1 Introduction The use of composite precast deck pa nel slabs on bridges was initially implemented in the construction of highway br idges in Illinois in the early 1950Â’s. This innovation was never part of the bridge desi gn process but rather the result of value engineering during the construc tion phase. The precast deck panel was used as a stay-inplace form and a cast-in-place (CIP) compone nt was placed on top and in between the panels as shown in Figure 1.1, which cons iderably reduced construction time. By implementing this method, field forming wa s only needed for the exterior girder overhangs. Figure 1.1 Composite DeckPrec ast Deck Panel and CIP Concrete In the early to mid 2000s, Florida had approximately 200 precast deck panel bridges, with the majority of them, 127 bein g located in Districts 1 and 7; this is
2 including 18 on the Leroy Selmon Crosstow n Expressway (Crosstown Expressway) of the Florida Department of Transportation (FDOT) (see Figure 1.2) . Precast panel sizes vary with girder spacing but are typically 10 ft. x 10 ft. in plan and 3 in. to 4 in. thick. In design, it is assumed that the pane l acts compositely with the CIP reinforced concrete slab for resisting live load s as shown in Figures 1.3 and 1.4. Figure 1.2 Precast Deck Panel Inventory in 2000 Figure 1.3 Precast Deck Panel with CIP Component
3 Figure 1.4 Precast Deck Panel Reinforcement Details Despite successful performance in other states and satisfactory performance in other FDOT districts, precast deck panel bridges have a long history of premature deterioration in Districts 1 a nd 7 that has resulted in exce ssive maintenance for the FDOT and impacts to the traveling pub lic. Previous research has at tributed this to contractors using flexible fiberboard bearing material supports to simplify construction . The FDOT Districts 1 and 7 Structur es Maintenance Office (DSMO) has responded to numerous maintenance problems on precast deck pane l bridges throughout the I-75 corridor in southwest Florida. Initi ally, the response wa s reactionary, geared towards emergency situations in which a localiz ed failure of the bridge deck resulted in lane closures. Between 2000 and 2003, five failures occurred. Over time, the DSMO began a proactive approach to monitoring, ea rly detection and repair to avoid disruptive emergency situations. The DSMO had established a method to sy stematically replace selected precast deck panel bridges on I-75 in bo th Districts 1 and 7 with full depth, CIP concrete decks. The short-term goal was to replace the decks on bridges with high average daily traffic (ADT) and the long-term plans were to re place the decks on all precast deck panel bridges in both districts. The FDOT had allocated $78 million in 2001 for a period of 10
4 years to replace deck panel bridges on I-75 running through Districts 1 and 7, and $65 million in 2003 for the Crosstown Expressway Viaduct Bridges. In 2005 The University of South Florida (USF) completed a comprehensive study for FDOT. The objective of the study was to prevent any further failures by identifying and prioritizing deck replacement of high risk bridges in Districts 1 and 7. However, since finalization of the st udy, two subsequent sudden bridge deck failures have taken place. Both failures occu rred in 2007 within District 7: the first one on the Crosstown Expressw ay and the other on I-75. 1.2 Objectives The purpose of this research is to (1) r eassess the prioritizations assigned to the two bridges that experienced deck failures s ubsequent to the fina lization of the 2005 USF Study, (2) to provide an update of current stat us of composite precast deck panel bridges in FDOTÂ’s Districts 1 and 7, a nd (3) assess the effectiveness of repair methods used on this type of deck system. This was accomplished by participating in the emergency response teams for both subsequent failures, gathering information, such as bridge inspection reports, monthly (deck panel) inspection reports, special e ngineering reports, plan s, funding reports, 5Year Work Program report and construction st atus reports from the FDOT as well as meeting with key FDOT, consulta nt and contractor personnel.
5 1.3 Thesis Organization This report is organized into seven chap ters and two appendices that describe various components of the research. Chapter 2 presents a literatu re review on other studies that have been published on compos ite precast deck panel bridges. Chapter 3 provides details of the deck failures that occurred in 2007. Chapter 4 assesses the recent failures in comparison to USFÂ’s rankings. Chap ter 5 gives an update on the current status of composite precast deck panel bridges Districts 1 a nd 7. Chapter 6 assesses the effectiveness of the repair procedures us ed on composite deck panel bridges and the summary and conclusions are presented in Chapter 7.
6 2. BACKGROUND 2.1 Prior Research Research related to the deficiencies of composite precast deck panel bridges has been undertaken since as early as 1982. A brief description of the research in chronological orde r is as follows: 2.2 University of Florida Study (1982) In 1982, The University of Florida Study by Callis, et al.  was performed as a result of the excessive deck cracking on th e Peace River Bridge. It concluded that: The decks in their present cracked conditi on are structurally adequate to carry normal traffic. In spite of the simple ac tion of the decks, flexural stresses are not excessive. The shear stresses in the Peace River Bri dge are substantially higher than that of conventional bridge decks or panel bridges with positive bearing at the ends of panels. The increase in shear stress is brought about by the combination of the lack of bearing of or the end of the panels and the lo ss of bond on the end of the panels which is primarily due to creep of the panels under the action of the prestress. The observed cracking on the top of the deck is probably primarily due to the volume changes brought about by the diffe rential shrinkage between panels
7 and CIP component. However, temperatur e changes and live load stresses certainly increase the tensile st resses and the degree of cracking. Adding extra transverse or longitudinal steel is not felt to be sufficient to ensure adequate fatigue life of panel bridges. Removing the fiberboard and replacing it with a material providing positive bearing (mortar) would greatly increase the fatigue life expectancy of the Peace River Bridge. Whether this action is economically justifiable depends on further studies of the shear fa tigue behavior of the bridge. Future panel construction projects should include a de tail that provides positive bearing for panels. Strand extensions may also be useful. 2.3 University of Florida Study (1983) In 1983, The University of Florida study by Fagundo, et al.  was a follow up to the Peace River Bridge Study, with the objectives to evaluate the potentialfor shear fatigue failure of existing panel bridges cons tructed using details that did not provide positive bearing under the ends of the pane ls and to compare the performance of composite precast deck panel bridges construc ted using several support details against the performance of conventional reinforced c oncrete decks. The report concluded that: Composite decks without positive bearing act as simply supported beams with maximum positive moment in the center and negative moment at the ends. Replacing fiberboard with grout w ould reduce shear stresses at ends. Panel decks with positive bearing should have a service life comparable to conventional decks.
8 2.4 University of Florida Study (1984) In 1984, the third repo rt on this subject from Th e University of Florida was authored by Fagundo, et al.  with the objective of developing an immediate management plan that would allow FDOT to decide upon a reasonable, not necessarily optimum, program for grouting and repairing the bridge decks. The report concluded that: Bridges in which reasonable bond is ma intained between the ends of the panels and the CIP component concrete should not exhib it any significant longitudinal spalling. Thus many of the panel bridges should not exhibit any significant longitudinal spalling for a very long service life. It is known that the major factors th at cause the loss of bond on the end of panels are: poor end treatment of th e panel such as sawing, lack of strand extensions, creep of the pane ls after the deck is pour ed, shrinkage of the deck, and live load stresses after the deck is placed. However, it is impossible to predict for any given bridge the probability of loss of bond and the associated spalling. Bridges that exhibit longit udinal spalling can be repaired by the M1 procedure which includes grouting under the pane l. Once the repaired these bridges should have normal service lives. Panel bridges with reduced longitudinal steel, particularly those with longer panel pans (girder spacing) have th e potential for transverse spalling. Transverse spalls that occur can be re paired by the M2 procedure as modified in Chapter 4, and should restore the deck to the extent that it would give a long service life.
9 Furthermore, the study recommended that: No large scale grouting or repair of pa nel bridges that have not exhibited any significant spalling is recommended. This is based on the expectation that the majority of the panel bridges will not exhibit significant spalling during their service life. If any M1 or M2 repairs are made in a bridge span, that span should be thoroughly surveyed for delamination by the chain procedure and all areas that are suspected of being damaged s hould be repaired. Also, bearing should be restored to all panels within that span. If a damaged bridge contains multiple spans, than all spans should be thoroughly investigated for delaminating. If significant delaminations appear then serious consideration should be gi ven to repairing all damaged areas on the bridge. Further, any span that is re paired by either M1 or M2 procedures should be grouted under all panels. This recommendation is based on the fact that construction costs and inconvenien ce to the traveling public would be greater if a bridge is repaired one sp an at a time rather than all spans simultaneously. Data on bridges that are repaired should be carefully kept both with regards to physical variables and costs. Thus, afte r a few years an empirical prediction can be made of future costs. Field testing as part of research already planned s hould be directed towards verification of the repair techniques under field conditions. Attention should be given to testing spans with varying amount of longitudinal reinforcement.
10 The management plan for the panel bridges outlined in steps 1 through 5 should be reasonably cost effective ba sed on the present state of knowledge. To develop a truly optimum management plan a comprehensive research program extending over seve ral years is required. It suggested that the M1 and M2 repa ir methods be incorporated with the modification described in section 4.2. Th ese modifications should improve the ductility, strength, and durability of the repaired area. 2.5 University of South Florida Study (2005) In 2005, The University of South Florida performed a study by Sen, et al.  with the objective of examining the deterioration process that leads to sudden failures in composite precast deck panel bridges and in turn to develop a strategy to assist the FDOT in the prioritization for replacement of these bridges in Districts 1 and 7 to avoid such failures. This study is reviewed more thor oughly because one objective of the authorÂ’s research is to reassess the r ecommendations of the USF Study.The USF study analyzed five localized failu res that occurred in composite precast deck panel bridges in Districts 1 and 7 between 2000 and 2003. Table 2.1 summarizes relevant information relating to these failures. As indicated in the table, all failures had some type of repair while some had a combin ation of repairs. All the failures were narrowed down to only two cities within the two districts, Sarasota and Tampa. A survey was also conducted to determine the performance of deck panel bridges in other districts. No failures had occurred in Districts 2, 3, 5 and 6. District 4 reported failures in two bridges: Bridge No. 940126, carrying I-95 (S outhbound) over the Florida Turnpike and
11 Bridge No. 940127, I-95 (Northbound) over the Fl orida Turnpike but no details were provided. All failures occurred in bridges where th e deck was nominally 7 inches thick. No failures occurred in deck panel bridges with thic ker slabs. The percenta ge of trucks in the ADT varied between 8 and 30%. Table 2.1 Localized Deck Failures 2000 to 2003 Bridge No. District Year Built Age at Failure (Years) NBI Rating Before Failure Days Since Last Insp. Rain 7 Days Prior to Fail (in.) ADT Failure Size (In.) Loc. in Panel Comment Bridge Location Failure Date %Truck 170146 1 1981 19 6 90 days 0 34,000 18 x 24 Edge or Corner? Failure at asphalt patch within full depth spall repair Sarasota, I 75 NB Over Bee Ridge Rd 2/12/2000 (Sat) 10% 170086 1 1980 20 7 180 days 2 34,000 36 x 60 Corner Support Localized full depth CIP repair Sarasota, I 75 NB Over Clark Rd 11/27/2000 (Good) 0.68 9% 170085 1 1980 20 7 210 days 4 34,000 18 x 18 Corner Asphalt patch adjacent to M1 repair Sarasota, I 75 SB Over Clark Rd 12/20/2000 (Good) 0.2 10% 100332 7 1980 22 5 2 days 2 23,000 48 x 30 Near corner Asphalt Patch Tampa, Cross town Viaduct WB Span 38 10/2/2002 (Fair) 0.55 8% 100332 7 1980 23 5 23 days 3 23,000 24 x 36 Edge Failed M1 repair with flexible patch material Tampa, Cross town Viaduct WB Span 70 9/5/2003 (Fair) 1.1 8%
12 All failures occurred under the wheel loads applied close to the face of the girders where initial longitudinal cracks developed. Also in all five cases, the failure occurred in the right lane, (i.e. slow lane), where large and heavier loads (i.e. eighteen wheeler trucks and permit vehicles) generally tr avel. Failure was normally in the edge or co rner panels whose boundaries developed reflective l ongitudinal and transverse cracking. A deterioration model based on the field observations and anal ysis of localized failures was developed in the st udy (see Figure 2.1). However, as the structural behavior of composite precast deck panel bridges depend s on several factors, not all of which can be quantified, it makes it almost impossible to accurately predict future service life using numerical analysis. On the other hand, inspec tion data that tracks pr ogression of cracking can be more successful in pr edicting localized failure. Figure 2.1 Deterioration Model The simplified model indi cates that longitudinal cr acks first develop along the girder lines. This is followed by occasional reflective transverse cracking. Such defects appear within 5 years of construction. Thes e cracks may not change for nearly 10 years after which there is more widespread tran sverse cracking. Longit udinal and transverse Initial Condition Longitudinal Crack Parallel Longitudinal Crack (Shear) First Spall Spall Increase/ Spall Patching New Spall/ Spall Increase M1 Repair Parallel Longitudinal Cracking Adjacent to M1 Repair Walking Spalls Adjacent to M1 Repair M1 Cracking and Adjacent Spall Increase Adjacent Spall Patch A dditional Adjacent Spall Patching Localized Deck Failure
13 cracking result in spalling and delamination that require repair This is an important stage in the deterioration process because the type and quality of repair will dictate if the longterm performance of the bridge is satisfactor y or poor. In most cases, such damage occurs in regions where the panel is improperly s upported on fiberboard be aring material. Where deck repairs are combined with proper panel bearing (e.g., by placing non-shrink grout or injecting epoxy), repairs are sa tisfactory. Where this is not carried out, and repairs are limited to surface repairs, there is progressive degradation as shown in Figure 2.1, which can lead to failure. In several instances, fa ilures occurred at locations where temporary repairs had not been replaced. Simplified calculations performed in th e USF study proved that punching failures could result at loads below the design wheel lo ad. This assumed the CIP deck to provide no resistance and the panel to be supported on fiberboard bearing material with well developed cracking along the transverse a nd longitudinal panel boundaries. The failure load was calculated to be ar ound 15 kips. Otherwise, failure loads were nearly four times higher. Equipped with this information, the USF team created replacement prioritization for bridges in District 1, Di strict 7 and the Crosstown E xpressway, respectively (See Tables A.1-A.5). 2.6 Summary and Conclusions Various studies have been conducted on the problems with composite precast deck panel bridges. One such study was co mpleted by USF in 2005. It investigated the five failures occurring in Districts 1 and 7 between 2000 and 2003, with the goal of
14 prioritizing high risk bridges for replacemen t and consequently to eliminate sudden failures in the future.
15 3. DECK FAILURES IN 2007 3.1 Introduction The main objective of the USF Study wa s to prioritize high risk bridges for replacement and in turn eliminate further s udden failures. However, since finalization of the study in 2005, two subsequent failures have ta ke place. Both failures occurred in 2007 and within District 7. Details of the subs equent failures are pr ovided in Table 3.1. Table 3.1 Localized Deck Failures Following USF Study Bridge No. District Year Built Age at Failure (Years) NBI Rating Before Failure Days Since Last Insp. Rain 7 Days Prior to Fail (in.) ADT Failure Size (Inches) Loc. in Panel Comment Bridge Location Failure Date %Trucks 100332 7 1980 27 5 565 0.21 23,000 18 x 8 Edge Failed localized patch repair Tampa, Cross town Viaduct WB Span 39 3/5/2007 (Fair) 8% 100436 7 1983 24 5 685 0.54 46,250 12 x 24 Edge Failed localized patch repair I 75 over E. Broadway Ave., CR 574 and CSX Railroad 9/11/2007 (Fair) 8%
16 3.2 Bridge No. 100332 The first failure occurred on March 5, 2007, on Bridge No. 100332, The Crosstown Expressway (Westbound) Viaduct, Span 39, Lane 2 (see Figures 3.1 and 3.2), The failure size was approximately 18 in. x 8 in. hole through the deck and it occurred within the outside edges of a nearly 5 ft. x 7 ft. existing repair patch. It was located on the edge of the panel and the edge of the beam. Figure 3.1 Bridge No. 100332, Span 39 Failure (Deck Top)
17 Figure 3.2 Bridge No. 100332, Span 39 Failure (Deck Underside) Bridge No. 100332 is a 91 span (67 spans with precast deck panels) structure carrying the Crosstown Expressway westbound with two 12 ft. lanes and a 8 ft. wide right shoulder and 4 ft. wide left shoulder. The average daily traffic (ADT) in 2007 was 23,000, with 8% truck traffic. The supe rstructure consists of AASHTO Type III prestressed concrete beams. The failure happe ned on Span 39, which is approximately 55 ft. Â– 1 in. long, and the beams are spaced at 8 ft. -1 in. supporting a typical 7 in. thick composite deck. The last biennial inspection report prior to the failure was finalized August 17, 2005, 565 days before failure, and assigned th e deck an NBI Rating of 5 (fair) . The report makes general statements applying to all precast deck panel spans stating that the
18 deck top has light to moderate wear and is typically populated with minor cracks. Also that the deck top and deck undersides have minor multi-directional cracking in isolated locations and some of the deck top cracks have minor associated spalls. It noted that on some of the deck underside many cracks have light efflorescence. The report also indicated that there are minor delaminations in isolated locations up to 1.5 ft. x 3 in. along the construction joints. More specific details on deficiencies we re acquired from the monthly deck panel inspection reports  indicating that longit udinal cracks were sealed in October 2006. Some new spalls developed at the edge of an existing repair in the south wheel path of Lane 2 in January 2007. The spalls increased to high priority in the February report indicating there is a 2 ft. x 2 ft. x 2 in. spall with delamination on the topside of the deck and another of the same size on the deck unders ide. These deficiencies progressed into a punch through failure occurring on March 5, 20 07, consisting of an 18 in. x 8 in. hole, which had to be addressed with an emergenc y repair applying full depth bay replacement across two panels (see Figure 3.3) . The failure occurred after a heavy rainfa ll event . The precipitation according to the National Oceanic and Atmospheric Ad ministration (NOAA) archives was 0.21 in. seven days prior to the failure.
19 Figure 3.3 Excerpts from Emergency Inspection Report 3.3 Bridge No. 100436 The next failure took place on September 11, 2007, on Br. 100436, I-75 (Northbound) over E. Broadway Ave., CR 574 and CSX Railroad, in Span 4, Lane 3 (See Figures 3.4 and 3.5). The failure was approxima tely 12 in. x 24 in. and was located inside an existing repair patch, on th e edge of the panel as indicat ed in the emergency inspection report in Figure 3.6 . Like its predecessor, the failure was also located on the edge of the panel and the edge of the beam.
20 Figure 3.4 Bridge No. 100436, Span 4 Failure (Deck Top) Figure 3.5 Bridge No. 100436, Span 4 Failure (Deck Underside)
21 Figure 3.6 Excerpt from Emergency Inspection Report Bridge No. 100436 is a five span stru cture carrying I-75 Northbound with three 12Â’ Lanes and 10Â’ shoulders on both, right and left sides, The average daily traffic (ADT) in 2007 was 46,250, with 8% truc k traffic. The superstructure consists of AASHTO Type II, III and IV beams. The failure happened on Span 4, which is approximately 76 ft. in length and is comprised of Type III beams, spaced at 8 ft.-10 in., supporting a typical 7 in. thick composite deck. The last biennial inspection report prior to the failure was finalized October 27, 2005, 685 days before failure, which assigned the deck an NBI Rati ng of 5 (fair) . The report documented that there are numerous patches made with Â“epoxy typeÂ” material in the deck top, longitudinal cracking with maximum widths of 1/16 in. over the edge of beam lines and transverse cracks up to 12 ft long x 1/8 in. wide over the precast deck panel joints in all spans. It stated that most transverse cr acks are spaced 8 ft. apart, which is the approximate length of a deck panel on this bridge. Due to the problem with
22 excessive cracking throughout the bridge, a d eck cracking diagram was prepared for the inspection files as shown in Figure 3.7 . Figure 3.7 Bridge No. 100436, Transverse Cracking Pattern The monthly inspection reports indicate that localized repairs were made in Span 4 in April, July and September of 2005 and in February of 2007. The reports also indicate that there is a problem with transverse cracking throughout the bridge. Most of the cracking is 1/8 in. wide but thr ee cracks in particular were identified with an approximate
23 width of in. . The repor ts indicate that the three in. cracks have been present since August of 2006 as shown in Figure 3.8. Figure 3.8 Bridge No. 100436, Span 4 Failure (3/4 in. Transverse Crack) The precipitation was 0.54 in. seven days prior to the failure according to the NOAA archives. 3.4 Summary and Conclusions The USF StudyÂ’s goal was to prioritize high risk bridges for replacement and in order to eliminate any addi tional sudden failures in the future. However, since finalization of the study in 2005, two bridge s experienced sudden failures. The failures took place on Bridge No. 100332, Crosstown Expressway Viaduct, Span 39 and Bridge No. 100436, I-75 over E. Broadway Ave., CR 574 and CSX Railroad. Both failures occurred in 2007 and were located in District 7. Both failures were inside the limits of
24 existing repairs, were located on the edge of the precast panel, and edge of beam and occurred after rain events.
25 4. ASSESSMENT OF USF PRIORITIZA TION RELATIVE TO NEW FAILURES 4.1 Bridge No. 100332 The USF study had ranked this bridge as No. 1 for replacement on the Crosstown prioritization listing as shown in Table A.5. First priority replacement ranking was given to this bridge because it ranked the highest in the categories of Failing Repair Count, Weighted Index, FDOT Ranking, ADT, Importan ce, Normalized, Risk and Safety as quantified below: Year Built: 1975 Spall Count: 344.7 Failing Repair Count: 44.9 Weighted Index: 1018.7 FDOT Rank: 1 ADT: 23,000 Importance Rank: 1 Normalized Risk: 1.000 Risk Rank: 1 Safety Rank: 1 However, despite being ranked with highest replacement priority on the Crosstown Expressway, the FDOT was unabl e to acquire all the funding required to replace the bridge decks in time to avoid th e failure. It is because this bridge was
26 programmed for deck replacement along with its twin structure, Bridge No. 100333, Crosstown Expressway (Eastbound), which make s a total of 134 precast deck panel spans to be replaced. The large number of spans to be replaced required considerably more time to obtain funding than the typical three span bridges on I-75. Replacement funding in the amount of $65 million had been programmed in 2003 for this project . This amount was approved for use in 2009 and the deck replacemen t project was advertised and four design build firms were shortlisted on Marc h 12, 2010. However, it is currently on hold because The Tampa-Hillsborough Expressway Authority (THEA) requested that the bridges also be widened along with deck replacement . Alt hough widening was given as an option in FDOTÂ’s request for proposal the additional $65 million required for this work was not initially programmed. Consequent ly the project is at this time on hold and THEA is trying to obtain Â“stimulus fundingÂ” fr om the Federal Government to include the additional work. The FDOT is expecting to sel ect a firm from the f our shortlisted parties in early 2011 and begin work by midsummer. Taking all of this information into acc ount, USFÂ’s replacement prioritization for Bridge No. 100332 was very accurate. It was ju stified in being ranked No. 1. Had the FDOT been able to acquire the replacement fu nding for this bridge earlier, the failure might have been avoided.
27 4.2 Bridge No. 100436 The USF Study had ranked this bridge as No. 8 for replacement. The following factors were taken into consideration for ranking: Year Built: 1983 Spall Count: 5.5 Failing Repair Count: 1 Weighted Index: 17 USF Inspection Condition: Acceptable FDOT Rank: 7 ADT: 44,500 Normalized Risk: 0.142 Safety Rank: 9 Importance Rank: 6 Risk Rank: 8 The main reason why this bridge was not prioritized higher for replacement at the time of the study was because it only had one fa iling repair. The research team concluded that the very low count of failing repairs wa s a good indication that the bridge would not fail . However, immediately after th e study was finalized four repairs failed consecutively leading up to the date of deck failure as noted in the monthly inspection reports. The FDOT was not able to perform emergency repairs using the DSMOÂ’s preferred method of full depth bay replacement with CIP concrete because, due to the high
28 ADT on I-75, the lanes could not be closed to traffic to allow the concrete to cure as required. Instead, the DSMO instructed their asset maintenance contractor to temporarily fasten a in. thick steel plat e with anchor bolts on the deck top over the failure as shown in Figure 4.1. Then timber bracing was insta lled in the bays underneath to prevent beams from torsion (see Figure 4.2). A few days later, the steel plate was removed and replaced with high strength, fast setting concrete repair material. This repair was performed within a few hours during a night time lane closure . Figure 4.1 Bridge No. 100436, Span 4 Failure (Temporary Steel Plate)
29 Figure 4.2 Bridge No. 100436, Span 4 Failure (Timber Bracing) Approximately eleven months after th e failure, on August 19, 2009, DSMOÂ’s monthly inspection of deck panel bridges cite d significant deflection and deterioration in the repair patch material (see Figure 4.3). Asset maintenance personnel were summoned onsite, and it was agreed by all parties that an immediate repair was required. The lane once again had to be temporarily closed to traffic for a few hours. The deteriorated patch was removed and replaced with sound ma terial and additional timber bracing was installed in both north and s outh directions of the existi ng shoring between the beams .
30 Figure 4.3 Bridge No. 100436, Span 4 (Failure in Patch Repair Material) USF had ranked Bridge No. 100436 No. 8 out of 15 in priority for replacement. The main reason for not ranking this bridge higher provided by the USF research team was because it had only one failing spall repair. However, it is evident that six of the seven bridges ranked for replacement ahead of this bridge had no failing repairs. The same six also had a lower Weighted Index. Six bridges ranked lesser in priority in FDOT Rank, Safety Rank, Normalized Risk, Safety Rank, Importance Rank and had and lower ADTs. According to the Cracking Diagram in Figur e 3.7, the transverse cracking pattern appears to be consistent w ith spacing of the precast pa nels. Apparently lack of longitudinal continuity between precast deck panels resulted in the transverse cracks propagating in the Â“componentÂ” or CIP concre te portion. These cracks prevent the deck system from behaving compositely resulting in reduced punching shear capacity as supported by the punching shear calculations pe rformed in the USF Study. If the precast panel support is poor due to the fiberboard bearing material, then the punching shear is
31 resisted by only two sides. In this case, depending on fact ors like overload and material properties, the punching shear failure of the panel becomes possible. Considering that ranking categories of Bridge No. 100436 were higher in priority than the six other bridges ranked before it and discovering that this bridge had a prevalent problem with transverse cracking, it is determined that it wo uld probably have been more accurate to rank this bridge at replacement priority No. 2, be fore the other six bridges. However, since Bridge No. 100436 was on the replacement prioritization list and ranked approximately midway between the 15 bridges on that list, it is the authorÂ’s judgment that USFÂ’s ranking was on target. 4.3 Summary and Conclusions The USF prioritization for replacement of Bridge No. 100332 was accurate and totally justified in being ranked No. 1. The prioritization of Br idge No. 100436 was also on target. It was on the replacement prioritization lis t and ranked No. 8, approximate ly midway between the 15 bridges on that list. The USF Study replacement rankings for both bridges that subse quently failed in 2007, Bridge Nos. 100332 and 100436 were justifiable.
32 5. PRESENT STATUS OF PRECAST DECK PANEL BRIDGE REPLACEMENT 5.1 Status Utilizing the $78 million acquired in 2001a long with implementing strategies such as including deck replacement within in terstate widening projects, FDOT has been working vigorously on replacing the existing composite precast deck panel systems on bridges in Districts 1 and 7 with CIP concrete decks. At this point, the decks of 51 bridges in both districts comb ined have been replaced with CIP concrete decks. The majority of the funding by far was consumed in District 1 . The breakdown is as follows: District 1bridges ca rrying or over I-75: 36 District 7bridge s carrying I-75: 9 Crosstown Expressway Bridges: 6 The FDOT has shortlisted four design bu ild firms for deck panel replacement on Crosstown viaduct bridges. The contract is pending final selecti on and execution, which is expected to happen sometime in early 2011 and work should begin before the end of the year. However, due to the limited availabili ty of funding and the current condition of the stateÂ’s economy, the remaining deck panel bridges in both, Districts 1 and 7, will have to be addressed with repairs until additional funding, if any, can be acquired for complete deck replacement. Currently three precast deck panel bridges that were on District 7Â’s Work Program since 2000, Bridge Nos. 100468, 100469 and 100470, were
33 moved from the districtÂ’s plan ning category of Â“deck replacementÂ” to Â“deck repairs.Â” In addition, two more precast deck panel br idges, Bridge Nos.100358, 100359, have been added to the work program for deck repair as well . Along with the lack of funding, deck replacement on high ADT highways such as I -75 is no longer feasible due to the volume of traffic backup that is created as a result of closing lanes. District 7Â’s lane closure policy justifies closing lanes based on traffic counts. If the traffic count is too high as the case on I-75, the district will not al low any lane closures for planned projects. For this reason it is imperative to research the repair and rehabilitation methods to address precast deck panel bridge deficienci es and determine the effectiveness of each application. The USF Study recommended replacement prio ritization tables for District 1, District 7 and the Crosstown Expresswa y. Replacement rankings were provided for bridges that needed replacement as well as for bridges in good condition. As part of this research, the tables have been updated with current information regarding NBI condition rating and replacement status. Table 5.1 Recommended District 1 Bridge Replacement Sequence No. Bridge ID # Location Current Condition NBI Rating Replaced 1 130090 I-275 NB Over I-75 N.A. Yes 2 130112 I-275 SB R to I-75 NB & I-75 And I-275 Ramps 5 (Fair) Noremoved from program 3 170081 I-75 Over Palmer Blvd N.A. Yes 4 170080 I-75 Over Main A CanalN.A. Yes 5 030188 I-75 over CR-846 Information unavailable N.A.
34 Table 5.1 (Continued) 6 170094 I-75 NB Over Havana Road N.A. Yes 7 170099 SR-681 SB Over CSX RR 6 (Satisfactory) No 8 170089 I-75 Over River Road/Cr 777N.A. Yes 9 170100 SR-681 NB Over CSX RR 7 (Good) No 10 010064 Oil Well Road Over I-75 6 (Satisfactory) No 11 030187 I-75 Over CR-846 Information unavailable N.A. 12 170096 I-75 SB Over Jacaranda BlvdN.A. Yes 13 170079 I-75 Over Main A Canal N.A. Yes
35 Table 5.2 District 1 Br idges in Good Condition No. Bridge ID# Location Current Condition NBI Rating Replaced 1 10059 I-75 Over CR-776 N.A. Yes 2 10065 Airport Rd Over I-75 7 (Good) No 3 10066 CR-768 Over I-75 7 (Good) No 4 10067 US-17 Over Florida St. 6 (Satisfactory) No 5 10068 US-17 Over Florida St. 6 (Satisfactory) No 6 10075 Carmalite St. Over I-75 6 (Satisfactory) No 7 10090 US-17 Over Lavilla St. & Rr 6 (Satisfactory) No 8 10091 US-17 Over Lavilla St. & Rr 6 (Satisfactory) No 9 120085 US-41 Over Imperial River 7 (Good) No 10 120086 US-41 Over Imperial River Information unavailable N.A. 11 120088 SR-685 Over Matanzas Pass 6 (Satisfactory) No 12 120114 Slater Rd. Over I-75 6 (Satisfactory) Nomoved out to 2020 13 120126 I-75 NB Over Alico Rd./Canal Information unavailable N.A. 14 120127 I-75 SB Over Alico Rd./Canal Information unavailable N.A. 15 130085 I-75 NB Over SR-64 N.A. Yes 16 130089 Erie Rd Over I-75 6 (Satisfactory) No 17 130107 Mendoza Rd Over I-75 7 (Good) No 18 170082 I-75 Over Palmer Blvd. N.A. Yes 19 170083 I-75 SB Over SR-780 7 (Good) No 20 170084 I-75 NB Over SR-780 7 (Good) No 21 170090 I-75 Over River Rd. N.A. Yes 22 170091 I-75 SB Over Jackson Rd. N.A. Yes 23 170092 I-75 NB Over Jackson Rd. N.A. Yes 24 170093 I-75 Over SR-80 N.A. Yes 25 170095 I-75 NB Over Jacaranda Blvd. N.A. Yes
36 Table 5.3 Recommended District 7 Bridge Replacement Sequence No. Bridge ID# Location Current NBI Rating Replaced 1 100468 I-75 SB Over Woodberry Rd. 6 (Satisfactory) No 2 100347 I-75 NB Over SR-674 N.A. Yes 3 100470 I-75 SB Over CSX RR 6 (Satisfactory) No 4 100358 I-75 SB Over Alafia River 5 (Fair) No 5 100359 I-75 NB Over Alafia River 5 (Fair) No 6 150122 I-275 NB Over 5th Ave. North 7 (Good) No 7 100346 I-75 SB Over SR-674 N.A. Yes 8 100436 I-75 NB Over Broadway/CR-574 / CSX RR 5 (Fair) No 9 100338 US-41 Over Mackay Bay 5 (Fair) No 10 100357 I-75 NB Over Riverview Drive 5 (Fair) No 11 100356 I-75 SB Over Riverview Drive 5 (Fair) No 12 100080 SR 60 WB Over Bypass Canal 5 (Fair) No 13 100081 SR 60 EB Over Bypass Canal 5 (Fair) No 14 100049 US-41Over Palm River 7 (Good) No 15 100351 Valroy Road Over I-75 5 (Fair) No Table 5.4 District 7 Br idges in Good Condition No. Bridge ID# Location Current NBI Rating Replaced 1 100398 I-75 NB Over Sligh Ave./Ramp D-1 7 (Good) No 2 100339 US 301 Over Bypass Canal 6 (Satisfactory) No 3 100377 Gibsonton Dr. Over I-75 5 (Fair) No 4 100399 SR 582 WB Over Bypass Canal 6 (Satisfactory) No 5 100424 Ramp B Over US 92 7 (Good) No 6 100435 I-75 SB Over Broadway/CR574/CSX RR 6 (Satisfactory) No 7 100469 I-75 NB Over Woodberry Rd. 6 (Satisfactory) No 8 100471 I-75 Over CSX RR 6 (Satisfactory) No 9 150121 I-275 SB Over 5th Ave 7 (Good) No 10 150145 I-375 WB Over CR-689 7 (Good) No 11 150146 I-375 EB Over CR-689 7 (Good) No 12 150168 I-175 WB Over 6th St. S 7 (Good) No 13 150169 I-175 EB Over 6th St. S 7 (Good) No 14 150170 8th St. S. Over I-175 5 (Fair) No
37 Table 5.5 Recommended Crosstown Expressway Replacement Sequence No. Bridge ID # Location Current Condition NBI Rating Replaced 1 100332 SR 618 WB Over Hills River/ Downtown TPA 5 (Fair) Scheduled in 2011 2 100333 SR 618 EB Over Hills River/ Downtown TPA 6 (Satisfactory) Scheduled in 2011 3 100443 SR618 Over Ramp D & SR585/22nd Street & R/R 4 (Poor) Structurally Deficient No 4 100453 SR 618 Over 50th Street (US 41) N.A. Yes 5 100448 SR 618 Over CSX RR Removed to accommodate new elevated bridge. N.A. 6 100451 SR 618 Over 39th Street 6 (Satisfactory) No 7 100447 SR 618 Over RR 7 (Good) No 8 100457 SR 618 Over Maydell Drive N.A. Yes 9 100449 SR 618 Over 34th Street & Creek 6 (Satisfactory) No 10 100454 SR 618 Over 50th Street (US 41) N.A. Yes 11 100456 SR 618 Over CSX R/R N.A. Yes 12 100444 SR 618 Over SR 585 22nd St/CSX RR 6 (Satisfactory) No 13 100455 SR 618 Over CSX RR N.A. Yes 14 100450 SR 618 Over 34th Street & Creek Replaced to accommodate new elevated bridge. N.A. 15 100452 SR 618 Over 39th Street Removed to accommodate new elevated bridge. N.A. 16 100446 SR 618 Over 26th Street 6 (Satisfactory) No 17 100458 SR 618 Over Maydell Drive N.A. Yes 18 100445 SR 618 Over 26th Street 6 (Satisfactory) No
38 5.2 Summary and Conclusions At this point, the decks of 51 bridges in both districts combined have been replaced with CIP concrete decks. The major ity of the funding was consumed in District 1, followed by District 7, then the Crosst own Expressway. However due to budget restrictions, aside from three bridges on the work program for replacement, the remaining composite precast deck panel bridges will ha ve to be addressed with rehabilitation.
39 6. BRIDGE DECK REPAIR METHODS 6.1 Introduction As stated in the previous chapter, becau se of the difficulty in acquiring funding due to the sluggish condition of the state and national economy at this time, the remaining deck panel bridges in both, Dist ricts 1 and 7, will have to be addressed with rehabilitation rather than replacement as originally planned. 6.2 Repair Materials Repair material and method of construc tion can make the difference between a good and poor repair. Therefore, prior to pro ceeding with the repair procedures it is crucial to discuss some relevant issues re garding repair materials. Repair material selection is not an easy task because there are too many material manufacturing companies and even more so of products to select from. The information provided by the manufacturers and distributors is incomplete or in worse cases misleading. Additionally, new materials as well as new repair methods are constantly intr oduced and changes are frequently being applied to tried and true products. A good source for guidance on selecting a repair material is The American Concrete InstituteÂ’s 546.3R-06, Guide for the Selection of Material s for the Repair of Concrete . This publication was writte n with the goal to provide guidance on common repair material, emphasize relevant re pair material propertie s, test procedures,
40 minimum performance levels and applic ations for requirements and service environments. The first step of the process is to perform an in-depth inspection of the problem in the field and to document the deficiencies, potential damage and da mage cause. This is followed by an assessment of re pair service conditions, repair objectives, desired service life and future maintenance. The following are the most important repair material properti es  along with the relationship of repair material (R) to conc rete substrate (C)  listed in descending order: 1. Drying Shrinkage RC 3. Modulus of Elasticity RC 5. Thermal Expansion/Contraction RC 7. Compressive Strength R=C Volume stability i.e., dry shrinkage, refers to the dimensional change of the repair material. The existing concrete, or substrate, is almost always stable and if the repair is not, high shear stresses occur at the interf ace that can lead to debonding, cracking and ultimately failure of the repair. Dry shrinkage is arguably the most important property for a durable repair. Another important property is the tens ile strength. This is the maximum unit stress a repair material is capable of resisting under axial tension.
41 The modulus of elasticity is the ratio of normal stress to corresponding strain for tensile or compressive stress below the proportio nal limit of the material. If the repair is not structural, then it is pr eferable that the re pair material has a lower modulus of elasticity than the substrate. However, if the re pair is structural, then the repair material should have a modulus of elasticity as clos e as possible to the substrateÂ’s property. The tensile strain capacity is the concrete Â’s resistance of cracking from slow rates of stress development under uniaxial tension. In vestigation shows that the tensile strain capacity of concrete is a relativ ely independent parameter. . The coefficient of thermal expansion is the change in linear dimension per unit length of a material per degree of temperature change. In situations where temperature is not controlled, such as in exterior and some interior applications, it is desirable for the repair material to have a coe fficient of thermal expansion similar to that of the substrate concrete so that the two materials behave similarly under daily and seasonal temperature variations. If the coefficients vary significantly, the differential movements due to temperature fluctuations could affect the performance of the repair, and should be accounted for in the repair design. Creep is time-dependent deformation due to sustained load. Because many repairs are not subjected to significant compressive forces, compressive creep may not be a significant property of repair ma terials. Creep can be important if stress is induced in the repair material due to restraint of shrinkage strains or due to factors such as thermal movement or the appli cation of live loads. Compressive strength is the measured maxi mum resistance of a material to axial compressive loading, expressed as force per unit cross-sectional area. Th is is the property
42 that most material manufacturers and dist ributers like to tout with high numbers. However, a high compressive strength does not mean anything if the repair patch is separating from its substrate c oncrete due to shrinkage. 6.3 Repair Types The DSMO uses seven fundamental re pair methods used to address the deficiencies on precast deck panel bridges. Table 6.1 categorizes th e repairs with their positive and negative aspects, indicating the stage of the deterioration model in which they are generally implemented along with an overall assessment on the effectiveness of the repairs. Table 6.1 Repair Methods Repair Types Favorable Characteristics Unfavorable Characteristics Used at Stage of Deterioration model Effectiveness of Repair Crack Repair Helps keep out debris and impurities that may accelerate deterioration. Does not impede the deterioration process or help structurally. 1,3 Not effective Maintenance Spall Patching (Asphalt) Easy to place without much disruption to traffic. Very inexpensive repair. Only for temporary use If left longer than a week, could be detriment rather than a benefit to the bridge. 4,6,9,11,12 Not effective Localized Spall Repair Provides a repair with compressive strength in comparison to the maintenance patching with asphalt. Due to the nature of the deck panel system not acting compositely, the localized repairs start separating at the edges and new spalls described as Â“walking spallsÂ”. 4,6,9,11, 13 Not effective
43 Table 6.1 (Continued) Grout Packing Good to slow down deterioration process by providing positive bearing and extending bridge life. No traffic impact. Does not mitigate deficiencies that were present prior to grout packing. 2 thru 10 Good to slow down deterioration M1 Repair Repair replaces deteriorated CIP component by extending to the top of the precast panel. Can separate from panel, start separating at the edges and new walking spalls start to appear. Process is moderately labor intensive and impacts traffic. 7 Better than spall repair but not very effective Full Span M1 Repair with Grout Packing Last longer than any other type aside from full depth bay replacement. Process is labor intensive and causes impacts to traffic. 7 Effective Full Depth Bay Replacement Addresses the root cause of problem: elimination of vertical and longitudinal separation between the precast deck panel and CIP surfaces. Costly, very labor intensive and causes significant impacts to the traveling public. 8 thru 13 Very effective A more detailed write up on the repairs presented in Table 6.1 is provided in Appendix B. Assessment of the prevailing repair pro cedures tabulated a bove indicates that crack repair, maintenance spal l patching and localized spa ll repair are not effective because they do not mitigate the deterioration process caused by the panel and CIP sections not behaving compositely. Grout packing is a good method to slow down deterioration by providing positiv e bearing. However, if it is not applied at an early stage the deterioration that existed on the bridge will continue to intensify. Both M1 and M1 with grout packing are acceptable repair proc edures, but as seen in the deterioration model, these repairs eventually start to weak en because there is still a separation between
44 the precast panel and the cast in place sect ion. Full depth bay replacement with CIP concrete is the most effective repair method because it addresses the root cause of the deterioration by eliminating the vertical a nd longitudinal interface between the precast deck panel and CIP concrete surfaces and provides positive bearing for the deck. Even though full depth bay replacement is th e most effective repa ir, it is difficult to apply this method to high ADT highways due to the extended lane closures required to accommodate concrete curing time, as was the case on the emergency repair for Bridge No. 100436, I-75 over E. Broadway Ave. and CSX Railroad. Therefore, the deficiency was temporarily repaired and shored in September 2007 and a repair project was programmed to start cons truction in late 2009. The DSMO tasked Parsons Brinckerhoff (PB) to design a pilot project to replace the deficient bays on Bridge No. 100435 a nd 100436, twin bridges on I-75 that would minimize disruption to traffic. Traffic analysis and lane closure calcu lations indicated that this area of I-75 should only have nighttime lane closures due to high ADT conditions. Therefore the author, as PBÂ’s design project manager, teamed with SDR Engineering, Inc. to design the partial deck replacement us ing full depth precast deck panels to achieve the DMSOÂ’s goal . The design detailed th at the existing deteriorated deck be cut, demolished, removed and replaced with a fu ll depth precast concrete deck only at night. This limitation required partial installa tion of sections of the full depth precast panel per night. It was specified that a minimu m length of 30 ft. of fu ll depth panel was to be installed per night. Near surface mounted (NSM) Carbon Polymer Reinforced Fiber (CFRP) bars were installed to transfer shea r into the existing dec k. The construction was executed during the second qua rter of 2010 and although si milar technology has been
45 used in other states e.g., Issa , it was the first time that this method was applied in Florida. It is also innovative being that this is the only method of full depth precast panels that transfers forces longitudinally employing the use of NSM CFRP bars, rather than transversely. For this reason the design for this pilot project was closely monitored and scrutinized by the DSMO as well as F DOTÂ’s State Structures Design Office in Tallahassee. Key repair illustrations from the design plans are shown in Figure 6.1 and a more detailed description of the project is as follows. Figure 6.1 Full Depth Precast Panel Design Plan Details  The full depth 6,000 psi Class IV precas t concrete panels were cast in a prestressing yard and brought on to the site nightly as needed for construction.
46 The existing composite precast and CIP deck was sawcut, from the inside face of beam to the inside face of be am with an additional six inches on both sides. A platform was constructed under the bay for containment and subsequent disposal of debris. An overhead crane was used for the removal of the cut out existing section (see Figure 6.2) as well as for the placement of the new full depth precast concrete pa nel section as shown in Figure. A "strong back" system was used to suspend the precast panel from designed pick-up points the top as shown in Figure 6.3. Figure 6.2 Existing Deck Cut and Removal Using Strong Back
47 Figure 6.3 New Deck Suspension Using Strong Back The process started by cleani ng the edges of the top flanges of the beams with light sandblasting. After sandblasting, potable water was applied to surfaces of top flanges and vertical faces of existing deck slab to obtain a "saturated surface-dry" condition prior to grouting of the longitudinal joints. While the new panel is still suspende d in place using the strong back, low pressure grout pumps were used to ensure full penetration of th e epoxy grout below the edges of the panel to form proper seating as shown in Figure 6.4. The epoxy is kept in place between the top of beam and bottom of panel using backer rods, also shown in Figure 6.4. The epoxy was later placed on the pa nel and panel interface (i.e., transverse edges) of the previously installed full-depth panel section and the new section of panel to
48 be installed. The new section of the full de pth panel was pushed in place to form and seal the construction joint. Figure 6.4 Installing Backer Rod for Pouring Epoxy and Finished Epoxy Joint for Bonding New Panel with Existing as well as Seating for New Panel On the spans with AASHTO Type II Pr estressed Concrete Beams, the shear connectors had to be cut and removed in orde r to fit the new precast panels into place and to ensure that the panels have proper beari ng on the beams. Therefor e, to transfer shear from the deck into the beams, adhesive bonded anchors were installed through preformed holes in the precast concrete panel slabs as shown in Figure 6.5. Holes with specific diameters were drilled using a rotary hammer drill and bit into the beams for placement of the adhesive anchors. It was specified to use a metal detector specifically designed for locating steel in concrete to avoid conflicts with the beams existing steel reinforcement.
49 Core drilling was performed to clear existing steel reinforcement. Next, the holes were cleaned using oil-free compressed air to re move loose particles accumulated from drilling. Figure 6.5 Adhesive Anchors The anchors were installed and adequa te quantities of th e adhesive bonding material were used to fill the drilled hole to approximately 1/4 inch of the concrete surface measured after placement of the steel bar or anchor. Grooves, approximately 3 ft. long we re cut on both sides of the panel transversely, and extended 3 ft. into the existing deck. These were for the installation of the Near-Surface Mounted (NSM) CFRP Bars. The use of CFRP bars are required for flexural strengthening in th e negative moment regions of the bridge deck.
50 All grooves, where the NSM CFRP bars were to be placed were half-filled with embedding paste. It was specified to av oid entrapped air voids between concrete substrate and the embedding paste. The CFRP bars were cut to the specified length, cleaned and placed into the half filled groove and slightly pressed to force the paste to flow around the bar, completely filling the space between the bar and the sides of the groove. The groove was then filled with more paste until the surface leveled as shown in Figure 6.6.
51 Figure 6.6 Sawcutting Grooves into Deck and Placing CFRP Rods in Epoxy The CFRP system was allowed to cure then a protective coating was applied on the surface of the CFRP system. Limited planning and grooving of the new pa nel was required to match the finish and grade of the existing bridge deck. The pilot construction projec t was successful by resultin g in a sound repair with no disruption to daytime traffic. Lane clos ures were performed only during night and 30 lineal feet of the bay was replaced per night. A total of 8,831 ft. of bay replacement was performed using full depth precast panels, 2,944 ft. on Bridge No. 100435 and 5,887 ft. on Br. No. 100436. Deck following project completion is shown in Figure 6.7. Figure 6.7 Completed Deck (Transverse and Longitudinal NSM CFRP Installation)
52 6.4 Summary and Conclusions Being that the remaining composite precast deck panel bridges will have to be addressed with rehabilitatio n in lieu of replacement, this chapter reviewed the effectiveness of seven repair methods. Current ly the most effective method is full depth bay replacement with CIP concrete. If it is not possible to implement this method due to budget constraints, then grout packing should be used to replace the fiber board bearing material with non-shrink grout or epoxy provi de to positive beari ng to slow down the deterioration process. However, if conventiona l full depth bay replacement is not feasible due to traffic restrictions, then the favorable method of rehabilitati on is the use of full depth precast panels.
53 7. SUMMARY AND CONCLUSIONS Precast deck panel bridges since the mid 1980s have been experiencing premature deterioration in Florida, which has been a great source of inconveni ence to the FDOT in regards to time, money and impact to the tr aveling public. Five s udden deck failures occurred in Districts 1 and 7 between 2000 and 2003 as documented in Table 2.1. In 2005 USF completed a comprehensive study for the FDOT. The main goal of the study was identifying and prioritizing d eck replacement of high risk bridges in Districts 1 and 7, primarily to prevent the o ccurrence of similar failures. However, since finalization of the study in 2005, two subse quent failures have taken place. The objectives of this research were to reassess the prioritizations of USF Study regarding the two subsequent fa ilures, provide an update on the status of the composite precast deck panel bridges in Districts 1 an d 7 and assess the eff ectiveness of repair methods used for this type of bridge deck system. The sudden failures took place on Bridge No. 100332, Crosstown Expressway Viaduct, Span 39 and Bridge No. 100436, I-75 over E. Broadway Ave., CR 574 and CSX Railroad. Both failures occurred in 2007 and were located in Di strict 7 as shown in Table 3.1. Bridge No. 100332 was ranked as the No. 1 priority for replacement on the Crosstown prioritization list as indicated in Table A.5. Firs t priority replacement ranking was given to this bridge because it Ranked No. 1 in the categories of Safety, Risk,
54 Normalized Risk, Importance, ADT, FDOT Ranking, Weighted Index, Failing Repair Count, and Spall Count. However, despite being assigned with hi ghest priority for replacement on the Crosstown Expressway, the FDOT was unable to acquire the large amount of funding required for deck replacement in time to avoid the 2007 failure. Hence, the USF prioritization for replacement of Bridge No. 100332 was very accurate, and absolutely justified in being ranked No. 1. Had the FDOT been able to acquire the replacement funding for this bridge in time the failure might have been avoided. Bridge No. 100436 was ranked as No. 8 for replacement. The USF Study TeamÂ’s primary motive for not prioritizing this bri dge higher for replacement at the time of the study was because it only had one failing repa ir. However, as exhibited by the monthly inspection reports, the repairs began deteriora ting rapidly immediatel y after the study was finalized and continued until failure. Six of the seven bridges ranked for repl acement ahead of this bridge had no failing repairs. The same six also had a lower Weighted Index. Six bridges ranked lesser in priority in FDOT Rank, Safety Rank, Norma lized Risk, Safety Rank, Importance Rank and had and lower ADTs. This bridge also be gan showing signs of widespread transverse cracking since the early 2000s. Most of the tr ansverse cracking pattern appears to be consistent with spacing of the precast panels They are 1/8 in. widt h but three had grown to a in. width over time. Considering that ranking categories of Bridge No. 100436 were higher in priority than the six other bridges ranked ahead of it and discovering that this bridge had a prevalent problem with transverse cracking  it is determined that this bridge could
55 probably have been more accurately ranked at replacement priority No. 2, prior to the six other bridges. However, since Bridge N o. 100436 was on the replacement prioritization list and ranked No. 8, approximately midway be tween the 15 bridges on that list, it is the authorÂ’s judgment that USFÂ’ s ranking was justifiable. In summary, the USF StudyÂ’s replacement rankings for the bridges that subsequently failed in 2007, Bridge Nos. 100332 and 100436 were well-founded. Since completion of the USF Study in 2005, a total of 51 composite precast deck panel bridges in Districts 1 and 7 have been replaced with full depth CIP decks. The majority of the funding went to District 1, followed by District 7 and the Crosstown Expressway as indicated in the following breakdown: District 1bridges ca rrying or over I-75: 36 District 7bridge s carrying I-75: 9 Crosstown Expressway Bridges: 6 Three additional bridges are in District 1Â’ s work program to be replaced between now and 2020. However, due to the limited availability of f unding and the current condition of the stateÂ’s economy, the remaini ng interstate and high ADT highway deck panel bridges will have to be addressed w ith rehabilitation until additional funding, if any, can be acquired for complete deck re placement. The remaining high ADT bridges are as follows: District 1: 25 District 7: 27 Crosstown Expressway: 10
56 For this reason, research was performed on the repair methods used for precast deck panel bridge deficiencies to determ ine the effectiveness of each application. The repair method and materials play a big part in the performance and service life of the deck. Deck repairs are suitabl e when good concrete repair material and construction methods are applied. Where this is not carried out th ere is progressive degradation as indicated in the deteriora tion model shown in Figure 2.1, which can lead to punch through failure of the deck. This wa s the case in all seven failures where asphalt patching was used for repair. The effectiveness of seven repair methods was examined. Currently the most effective permanent repair for deck pane l bridge deficiencies is full depth bay replacement. If full depth replacement is not pos sible due to traffic or budget constraints, then grout packing should be used to repl ace the fiber board bearing material with nonshrink grout or epoxy to provide positive bearin g in order to slow down the deterioration process until the full depth bay replacem ent or entire span replacement can be accomplished. The conventional full depth bay replacement is not always feasible due to restrictions such as not being able to cl ose down lanes on high ADT highways. In this case it was found that the favorable method of construction for bay replacement was the use of full depth precast pa nels. The DSMO performed a pilot construction project employing this method on Bridge No. 100435 and 100436 earlier in the year. Lane closures were performed only during night a nd 30 lineal feet of the bay was replaced per night. The project ended successfully by pr oviding a sound repair, consisting of 8831 ft. of bay replacement using full depth precast pa nels. This was done without disrupting any daytime traffic.
57 LIST OF REFERENCES 1. Alvi, A., Precast Deck Panel Bridge Assessment Report Florida Department of Transportation, Districts 1 and 7 Structur es and Facilities Office, July 2001. 2. Callis, E.G., Fagundo, F.E., Hays, Jr., C.O., Study of Cracking of I-75 Composite Bridge over Peace River, University of Florida, Gainesville, FL, 1982. 3. Fagundo, F.E., Hays, C.O. Jr., Richardson, J.M ., Study of Composite Deck Bridges in Florida, University of Florida, Gainesville, FL, 1983. 4. Fagundo, F.E., Hays, C.O. Jr., Tabatabai, H., Soongswang, K, The Effect of Crack Development and Propagation on the Main tenance Requirements of Precast Deck Bridges, University of Florida, Gainesville, FL, 1984. 5. Sen, R, Mullins, G, Ayoub, A., Gualtero, I. Pai, N., Replacement Prioritization of Precast Deck Panel Bridges University of South Florida. Tampa, FL, March 2005. 6. Volkert & Associates, Inc. (2005) Â“ Bridge Inspection Report Bridge No. 100332 Â” dated Aug 17. 7. Florida Department of Tran sportation District 1&7 Stru ctures Maintenance Office. (2003-2007) Â“ Monthly Deck Panel Inspection Reports Â” Crosstown Expressway. 8. Volkert & Associates, Inc. (2007) Â“ Bridge Inspection Report Bridge No. 100332 Â”, dated Mar 5. 9. Novakoski, D. E-mail Communications, ICA (2007) 10. Volkert & Associates, Inc. (2007) Â“ Bridge Inspection Report Bridge No. 100436 Â”, dated Sep 11. 11. Volkert & Associates, Inc. (2005) Â“ Bridge Inspection Report Bridge No. 100436 Â”, dated Oct 27. 12. Volkert & Associates, Inc. (2007) Â“ Deck Cracking Diagram Â”. 13. Florida Department of Tran sportation District 1&7 Stru ctures Maintenance Office. (2003-2007) Â“ Monthly Deck Panel Inspection Reports Â” I-75. 14. Steimle, B. Personal Communications, TY Lin International (2010).
58 15. Ellis, J. Personal Communications FDOT (2010). 16. Pai, N. E-mail Communications (2008) dated Aug 12. 17. Buser, D. Personal Communications, ICA (2007). 18. Crissey, D. E-mail Communications, KCA (2009) dated Aug 19. 19. Pye, B. E-mail Communications FDOT (2008) 20. Jacobsen, J. Personal Communications, FDOT (2010). 21. The American Concrete Institute, Committ ee 546.3R-06, Â“Guide for the Selection of Materials for the Repair of Concrete.Â” August, 2006. 22. Emmons, P.H., 2003, Â“Where Are the Ne cessary Performance Criteria When Selecting Repair Materials?Â” ACI, Amer ican Concrete Institute, Fall 2003. 23. McDonald, J.E., Â“Performance Criteria of Concrete Repair Materials,Â” ICRI, International Concrete Re pair Institute: Spring 2001. 24. Swaddiwudhipong, S.,Hai-Rong, L.,Tiong-Huan, W., 2003, Â“Direct tension test and tensile strain capacity of c oncrete at early age,Â” Cement and concrete research, V. 33, No. 12, pp. 2077-2084. 25. Parsons Brinckerhoff and SDR Design for Fl orida Department of Transportation. Project 411536-1-32-01, Tampa, FL (2009). 26. Issa, Mohsen A. ; (Univ of Illinois at Chicago, Chicago, IL, USA) ; Idriss, AhmadTalal ; Kaspar, Iraj I. ; Khayyat, Salah Y. 1995, Â“Full depth precast and precast, prestressed concrete bridge deck panels,Â” PCI Journal, V. 40, No. 1 Jan-Feb, pp. 5980.
59 APPENDIX A: USF STUDYÂ’S PRIORITIZATION TABLES
60 APPENDIX A (Continued) Table A.1 Recommended Distri ct 1 Bridge Replacement Sequence No. Bridge No. Location 1 130090 I-275 NB Over I-75 2 130112 I-275 SB R to I-75 NB & I-75 And I-275 Ramps 3 170081 I-75 Over Palmer Blvd 4 170080 I-75 Over Main A Canal 5 030188 I-75 over CR-846 6 170094 I-75 NB Over Havana Road 7 170099 SR-681 SB Over CSX RR 8 170089 I-75 Over River Road/Cr 777 9 170100 SR-681 NB Over CSX RR 10 010064 Oil Well Road Over I-75 11 030187 I-75 Over CR-846 12 170096 I-75 SB Over Jacaranda Blvd 13 170079 I-75 Over Main A Canal
61 APPENDIX A (Continued) Table A.2 District 1 Bridges in Good Condition No. Bridge No. Location 1 10059 I-75 Over CR-776 2 10065 Airport Rd Over I-75 3 10066 CR-768 Over I-75 4 10067 US-17 Over Florida St. 5 10068 US-17 Over Florida St. 6 10075 Carmalite St. Over I-75 7 10090 US-17 Over Lavilla St. & Rr 8 10091 US-17 Over Lavilla St. & Rr 9 120085 US-41 Over Imperial River 10 120086 US-41 Over Imperial River 11 120088 SR-685 Over Matanzas Pass 12 120114 Slater Rd. Over I-75 13 120126 I-75 NB Over Alico Rd./Canal 14 120127 I-75 SB Over Alico Rd./Canal 15 130085 I-75 NB Over SR-64 16 130089 Erie Rd Over I-75 17 130107 Mendoza Rd Over I-75 18 170082 I-75 Over Palmer Blvd. 19 170083 I-75 SB Over SR-780 20 170084 I-75 NB Over SR-780 21 170090 I-75 Over River Rd. 22 170091 I-75 SB Over Jackson Rd. 23 170092 I-75 NB Over Jackson Rd. 24 170093 I-75 Over SR-80 25 170095 I-75 NB Over Jacaranda Blvd.
62 APPENDIX A (Continued)Table A.3 Recommended Distri ct 7 Bridge Replacement Sequence No. Bridge No. Location 1 100468 I-75 SB Over Woodberry Rd. 2 100347 I-75 NB Over SR-674 3 100470 I-75 SB Over CSX RR 4 100358 I-75 SB Over Alafia River 5 100359 I-75 NB Over Alafia River 6 150122 I-275 NB Over 5th Ave. North 7 100346 I-75 SB Over SR-674 8 100436 I-75 NB Over Broadway/CR-574 / CSX RR 9 100338 US-41 Over Mackay Bay 10 100357 I-75 NB Over Riverview Drive 11 100356 I-75 SB Over Riverview Drive 12 100080 SR 60 WB Over Bypass Canal 13 100081 SR 60 EB Over Bypass Canal 14 100049 US-41Over Palm River 15 100351 Valroy Road Over I-75 Table A.4 District 7 Bridges in Good Condition No. Bridge No. Location 1 100398 I-75 NB Over Sligh Ave./Ramp D-1 2 100339 US 301 Over Tampa Bypass Canal 3 100377 Gibsonton Dr. Over I-75 4 100399 SR 582 WB Over Bypass Canal 5 100424 Ramp B Over US 92 6 100435 I-75 SB Over Broadway/CR574/CSX 7 100469 I-75 NB Over Woodberry Rd. 8 100471 I-75 Over CSX RR 9 150121 I-275 SB Over 5th Ave 10 150145 I-375 WB Over CR-689 11 150146 I-375 EB Over CR-689 12 150168 I-175 WB Over 6th St. S 13 150169 I-175 EB Over 6th St. S 14 150170 8th St. S Over I-175
63 APPENDIX A (Continued) Table A.5 Recommended Crosstown Expressway Replacement Sequence No. Bridge No. Location 1 100332 SR 618 WB Over Hills River/ Downtown TPA 2 100333 SR 618 EB Over Hills River/ Downtown TPA 3 100443 SR618 Over Ramp D & SR585/22nd Street & R/R 4 100453 SR 618 Over 50th Street (US 41) 5 100448 SR 618 Over CSX RR 6 100451 SR 618 Over 39th Street 7 100447 SR 618 Over RR 8 100457 SR 618 Over Maydell Drive 9 100449 SR 618 Over 34th Street & Creek 10 100454 SR 618 Over 50th Street (US 41) 11 100456 SR 618 Over CSX R/R 12 100444 SR 618 Over SR 585 22nd St/CSX RR 13 100455 SR 618 Over CSX RR 14 100450 SR 618 Over 34th Street & Creek 15 100452 SR 618 Over 39th Street 16 100446 SR 618 Over 26th Street 17 100458 SR 618 Over Maydell Drive 18 100445 SR 618 Over 26th Street
64 APPENDIX B: REPAIR METHODS
65 APPENDIX B (Continued) B.1 Crack Repair The USF study reported that at the second st age of the deterioration model is the occurrence of longitudinal crack s over the edges of the gird ers. This type of cracking starts early in precast deck panel bridges a nd is the most common t ype of cracking. This crack is mainly the result of creep induced by prestressing forces in the precast panel, and the differential shrinkage between the CIP conc rete and the deck precast panel. Once the formation of longitudinal cracking has star ted, sporadic transverse cracks can also develop in the deck. The cracking can be repaired with epoxy cr ack injection or crack sealant. Crack injection is a structural repair meaning that it ideally restores the structural strength of the deck to original. Crack sealing penetrates and covers the cracking in order to avoid water, chlorides and other impurities from entering insi de the deck [B.1]. If it is determined that the crack is active, (i.e., opening and closi ng), then epoxy crack injection should not be used because it does not have the flexibility like crack sealant. The transverse cracks on Bridge No. 100436 were sealed using a flexible sealant following the first failure on September 11, 2007. B.2 Maintenance Spall Patching After the occurrence of the second parallel crack, the concrete trapped between the two cracks is already intern ally cracked and starts to crum ble. During the fourth stage of the deterioration model, a spall develops. At this stage, a new parameter is introduced,
66 APPENDIX B (Continued) the effect of the rainwater for ced inside the cracks by vehicl es. Although this is difficult to quantify, bridge inspectors have obse rved this phenomenon over the years. FDOT classifies deck patching in th ree different categories based upon depth [B.2]: Type AAbove the top layer of reinforcing steel Type BAt least one inch belo w the top layer of reinforcing Type CFull depth replacement The most common and simplest repair met hod is maintenance spall patching. It is used for spalls that are in the CIP portion of the deck. When a deficiency such as a spall would appear on the bridge deck (approximately ten years after cons truction as indicated in the simplified deck deterioration proce ss depicted in Figure 2.1), it was common practice for the FDOT maintenance crews to pa tch it with flexible (i.e., Â“cold patchÂ”) asphaltic concrete as i llustrated in Figure B.1. Figure B.1 Bridge No. 100332, Span 38Asphalt Patch (2 Days Before Failure)
67 APPENDIX B (Continued) The asphaltic concrete patching is not la bor intensive for the crews and can be performed in a matter of minutes with very mi nimal disruption to the traveling public. It is also a very inexpensive procedure. Th e maintenance crews would set up a temporary lane closure(s) as needed, clean debris out of the spall using hand tools and patch it using a ready mix bag. The purpose of asphalt patchi ng was to alleviate immediate danger to the motoring public as well as to avoid the spall from getting worse. This method of repair was never meant as a permanent solu tion, and although it was always the DSMOÂ’s policy for the maintenance crew to return within a week and perform a permanent repair, sometimes due to other priorities of the crews, these temporary patches would remain for a longer periods of time [B.3]. This type of patch for extended periods of time has proved to be a detriment rather than a benefit to the bridge. This is especially the case when asphalt is used in steps 11 and 12 of the dete rioration model, (i.e., when used to patch spalls inside or adjacent to a deficient M1 Re pair). Instead of distri buting the load evenly, when the flexible material, which has negligible compressive strength, was placed in the spall it would pound at the precas t panel beneath it and the ad jacent CIP section at its sides. In most cases this type of pounding acti on leads to an increase in the area and depth of the spalls and in some cases has led to cracking of the precast panel due to punching shear. In the absolute worst case scenarios, asphalt was used to repair existing repairs in the deck and the pounding resulted in punchi ng a hole through the deck as shown in Figure B.2. In most of the punch through failu res, rainy weather had been a catalyst. Water manages to find its way into the patched spall. Water is an incompressible fluid, even more so than the incompressible propert ies of asphalt. Th e wheel loading on the
68 APPENDIX B (Continued) patch causes pumping action between the as phalt and the precast panel until failure. Although there is no solid proof, it is strongly believed that this is a major cause of punch through failure in the deck. Six of the seve n failures in Tables 1 and 5 occurred after rainfall. Figure B.2 Bridge No. 100332, Span 38Asphalt Patch (Failure) Additionally, as indicated in Tables 2.1 a nd 3.1, six out of the seven failures had asphalt repairs. Four were standalone aspha lt patches and two were asphalt patches used to address deficiencies within existing repairs. B.3 Localized Spall Repair Unlike the maintenance spall patch, local ized spall repairs are theoretically a permanent type of repair. It is classified by FDOT as Type B or C. This repair method is the immediate follow-up step to the maintenan ce spall patch for the maintenance crews. It is mainly used for deficiencies that lie with in the depth of the CIP portion of the deck, but they have also been used for full depth repa ir. These repairs are performed using a con
69 APPENDIX B (Continued) crete repair material. This re pair method is not so labor intensive, can be done at a relatively low cost, and when using high st rength fast setting material, it can be performed using nighttime lane closures, redu cing major impacts on th e traveling public. Since bridge deck repair usually involves closing lane(s), the material most often used is some type of rapid-se tting concrete repair material. Most brands of this material usually attain 4000 psi in 4 hours. Although this is a permanent repair, the FDOT has not had much success with the longevity of these repairs. Due to the nature of the deck panel system not acting compositely, the localized repairs start separa ting at the edges and new spalls described as Â“walking spallsÂ” start appearing in front of these repa irs (see Figure B.3). Figure B.3 Patched Spalls and Walking Spalls Depending on all the associated factors, new spalls can appear in the areas adjacent to the repaired spall after some time. After the spall is created, the residual shear capacity of that region is almost zero, even af ter it has been patche d. Therefore, the shear that was to be supported by that region now has to be redistributed to sections adjacent to Patched ll New S p all
70 APPENDIX B (Continued) the spall. This creates additio nal stresses in that region, an d accelerates its deterioration generating new spalls, which are also generally treated with flexible repair material (see Figure B.4). Figure B.4 Localized Spall Repair Starting to Spall at the Edge One of the seven failures re ported in Tables 2.1 and 3.1 occurred at an area which had been repaired by localized full depth spall patching. B.4 Grout Packing The majority of deck panel bridges in Florida have been built with fiberboard bearing material or what is commonly referre d to as Â“roofing feltÂ” to support the precast deck panels on the girders. By use of this Fi berboard bearing material, positive bearing is not provided at the ends of th e precast panel. Due to the e ffects of creep and shrinkage, the initial separation and longi tudinal crack indicated in De terioration Stage No. 2 is inherent to precast deck panel construction. However, the few bridges in Florida that had used positive bearing have performed much better and in turn have had longer service lives. The most important conclusion drawn from the forensic study in the 2005 USF re
71 APPENDIX B (Continued) port is that the lack of positiv e panel bearing is clearly the ma in factor responsible for the occurrence of major deck dete rioration such as cracking, delamination, spalling, failing repairs, and in the worst case localized punch-through deck failures. Hence, grout packing is a good method of repair. The fiber board bearing material is replaced with non-shrink Portland cement grout or epoxy grout to provide positive bearing, (see Figure B.5). Figure B.5 Bearing Detail after Grout Packing Repair Grout packing is one of the most effec tive repair methods used to extend the service lives of precast deck panel bridges. It is very cost effective in comparison to other effective repair methods and it does not cause any interruption in tra ffic to the facility carried by the structure because the work can be performed utiliz ing a bucket truck or scissor lift underneath the bridge. It is important to note that none of the failures reporte d in Tables 2.1and 3.1 were retrofitted with grout packing. Replace Fiber Board w/ Grout Replace Fiber Board w/ Grout Panel Panel Deck Top
72 APPENDIX B (Continued) B.5 M1 Repair Generally, after several patch and re-patches, an M1 repair is done in the affected area. The M1 repair is used to repair longi tudinal spalling along the edge of a beam as illustrated in Figure B.6. The M1 and M2 were FDOTÂ’s recommended methods of repair in the 1980s [B.4]. Figure B.6 M1 Repair Procedure (Stage #7) Unlike localized repairs, the depth of the M1 goes to the top of the precast panel. Although the M1 repairs hold up be tter than localized repairs, again due to the bridge deck system not acting composite ly, they start separating at the edges and walking spalls start occurring in front of these repairs. Two of the seven failures in Tables 2.1 a nd 3.1 were associated with deteriorating M1 repairs. On Bridge No. 170085 there was a walking spall, patched with asphalt adja-
73 APPENDIX B (Continued) cent to an M1 repair and on Bridge 100332, Span 70, asphalt was used to patch a deficiency within an existing M1 repair. B.6 Full Span M1 Repair with Grout Packing This somewhat modified M1 repair is al so used to repair longitudinal spalling along the edge of a beam. The difference with th is repair is that the CIP concrete portion on top of the precast beams, as well as on top of the beams, is fully removed and additional steel is added to the area on top of the beams. The fiber board bearing material is replaced with non-shrink Portland cement gr out or epoxy as discussed previously to provide positive bearing. This repair is ex tended longitudinally throughout the length of the span. The durability of the modified M1 repa ir and the condition of the deck area around it depends on the following parameters: 1. Time period between spall, sp all repair, and M1 repair, 2. Possible internal damage to the pane l induced from previous stages, 3. Possible internal damage to the panel i nduced from removal of CIP concrete, 4. Bonding between the old concrete and the repair material, 5. Stress redistribution to adjacent areas (after removal of the damaged CIP concrete that deck region is no longe r transferring shear to the supports, so that shear is redistributed to the transverse edges of the repair), 6. Repair material, 7. Presence of panel shear connector s embedded in the M1 repair,
74 APPENDIX B (Continued) 8. Time interval between repair and passage of traffic. 9. And finally the most important paramete r, removal of the fiberboard and its replacement by non shrink epoxy. This procedure is labor intensive, costly and causes interruption to traffic. However, with the exception of full bridge bay replacement, it is the mo st effective repair method because it fills the spalled area under the wheel lines with sound incompressible material and provides positive bearing for the deck panels. Nevertheless, even these repairs can end up with deficiencies such as longitudinal cracks within them or adjacent to them. None of the failures reported in Tables 2.1 and 3.1 had M1 and grout packing as the method of repair. B.7 M2 Repair Although the M2 repair method was not encountered in a ny of the authors inspections or failures listed in Tables 2.1 a nd 3.1, it deserves to be mentioned because it was prescribed as a good method of repair by the FDOT in the 1980s [B.3]. The M2 repair, shown in Figure B.7, is used to fix the problem of cracki ng and spalling along the transverse joints of the pr ecast panel. The unsound material is removed approximately six inches on each side of the transverse join t and an inverted T-beam is formed with the bottom of the precast panel sitting on the flange of the inverted T-beam. The flange of the T-beam is required to be at least 24 inches wide. The inverted T-beam needs to be provided with positive bearing on the girders [B.3].
75 APPENDIX B (Continued) Figure B.7 M2 Repair Procedure  The M2 repairs are costly relative to othe r repair methods and cause impact to the traveling public. B.8 Full Depth Bay Replacement Full depth bay replacement is the most effective repair method for deficient precast deck panel bridges. In f act it is the direct ive of the DSMO to use this method for all permanent repairs. At a minimum, it is done in a bay (the transv erse distance between two beams) and throughout the le ngth of the span. Sometimes the entire deck on the span or all bays is replaced with full depth CIP concrete. When only a bay is replaced, the CIP concrete and precast panel is demolished, leaving only the reinforcing steel grid which was within the CIP section for continuity, then removed using jack hammers. A new bottom steel mat is designed as shown in Figure B.8 [B.5] and placed as an alternate to the precast panel.
76 APPENDIX B (Continued) Figure B.8 Full Depth Bay Replacement Detail A standard compression test is performed on 6 in. x 12 in. test cylinders at 24 hours, 48 hours, and 72 hours after the concrete is poured and finished. Although there is always pressure from the public and elected offi cials, the bridge is not opened to traffic until the minimum required compressive strength per design calculations is attained. After the concrete has gained the required stre ngth, the bridge or repaired area is opened to traffic. The conventional bay replacement is th e most expensive repair method and causes significant interruption to the traveling public. However, it is the most effective repair method because it addresses the root cau se of the problem which is the elimination of the vertical and longitudinal separation between the precast deck panel and CIP surfaces. None of the failures reported in Ta bles 2.1 and 3.1 occurred on decks which had been repaired by full depth bay replacement. It is difficult to apply this method to high ADT highways due to the extended lane closures required to accommodate concrete cu ring time. This was the case on Bridge No.
77 APPENDIX B (Continued) 100436, I-75 over E. Broadway Ave. and CSX Railroa d. It is the last re corded failure as shown in Table 3.1. This was temporarily re paired and shored in September 2007. Traffic analysis and lane closure calculations indicate that the I-75 in this area can only have nighttime lane closures due to high ADT conditions. B.9 References B.1 Johnson, K, Schultz, A, French, C, Rene son, J., Crack and Concrete Deck Sealant Performance, NCHRP Report MN/RC 2009-13, March 2009. pp. 74-76. B.2 Florida Department of Transportatio n, Â“FDOT Bridge Maintenance ManualÂ”, p. 33., 2009 Update. B.3 Fagundo, F.E., Hays, Jr., C.O., Tabatabai, H., The Effect of Crack Development and Propagation on the Maintenance Requirement of Precast Deck Bridges, University of Florida, Gainesville, FL, 1984. B.4 Parsons Brinckerhoff Design for Florid a Department of Transportation. I-75 over Alafia River Project, Tampa, FL (2000).
ABOUT THE AUTHOR Atiq H. Alvi is a graduate from the Un iversity of South Fl orida in 1991, with a Bachelor of Science in Civil Engineering a nd is professional engineer. He spent eight years serving at the Florida Department of Tr ansportation, with the fi nal years as District 7 Structures Maintenance Engineer at the Di strict 1 & 7 Structures Maintenance Office. Atiq spent another eight years at Parsons Br inckerhoff in Tampa, Florida managing the Bridge Rehabilitation Group. He is presently at TY Lin International in Tampa as Associate Vice President and Technical Direct or for Bridge Rehabilitation for the South Region of the United States. Atiq serves on The Transportation Research BoardÂ’s Fiber Reinforced Polymers Committee, Bridge Li fe-Cycle Cost Analys is Sub-Committee, Bridge Aesthetics Sub-Committee and N on-Destructive Testing Sub-Committee.