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which performed similar to SSMBLG6-Frosch, was units is provided by longitudinal joints (parallel to achieved with larger bars and a maximum transverse traffic direction). Figure 15 shows a DBT bridge being reinforcement spacing of 9 in., it was suggested that a constructed. design with No. 6 bars and less cage reinforcement The DBT bridge system eliminates the time nec- was likely to be more economical and easier to imple- essary to form, place, and cure a concrete deck at the ment in the field than the closely spaced reinforcement bridge site. In addition, the wide top flange provided cage provided in SSMBLG6-Frosch, which had a by the deck improves construction safety due to ease 4.5-in. bar spacing. of installation, enhances durability because the deck is fabricated with the girder in a controlled environ- Design Recommendations and Examples ment, and enhances structural performance with a more efficient contribution of the deck in stress dis- Recommended changes to the bridge design and tribution. Despite the major benefits of this type of construction specifications were proposed to imple- bridge, use has been limited to isolated regions of the ment this promising new system. The PCSSS bridge United States because of concerns about certain design guidelines cover both component and system design and construction issues. This project aimed to issues, including "spalling" reinforcement, load distri- address one of the hurdles to be overcome to enable bution, effect of restraint moments, composite action, a wider use of this technology: the development of and reinforcement to control reflective cracking. design guidelines and standard details for the joints Two MathCAD examples were created to illustrate used in these systems. The aim of the study was to the design issues associated with a simply supported produce full strength durable joints using CIP, but PCSSS and a three-span system made continuous. still allow for accelerated construction. Because of the effects of thermal gradients in generat- Figure 16 shows a typical DBT bridge consisting ing large restraint moments, it is suggested that the of five DBTs connected by four longitudinal joints PCSSS bridges be designed as a series of simply with welded steel connectors and grouted shear keys supported spans. (Stanton and Mattock 1986; Ma et al. 2007). In order to reduce the total DBT weight, the thickness of the LONGITUDINAL AND TRANSVERSE JOINTS deck is typically limited to 6 in. Welded steel con- IN DBT AND FULL-DEPTH PRECAST PANEL nectors are typically spaced at 4 ft. To make the con- ON GIRDER SYSTEMS nection, as shown in Figure 16, two steel angles are anchored into the top flange of the DBT and a steel Introduction plate is welded to steel angles in the field. Between Two issues that limited the PCSSS bridge concept two connectors, a shear key is provided at the verti- with regard to the potential for accelerated bridge con- cal edge of the top flange. Grout is filled into the struction applications were (1) the significant use of pocket of the connector and in the voids of the shear CIP to complete the composite system, which would slow the construction process and (2) the limitation of the system to short- to moderate-span lengths. As a consequence, the study included CIP connection concepts that minimized the use of CIP by limiting its application to the longitudinal and transverse joints between the flanges of DBTs or between full-depth precast deck panels on girders. Because of the simi- larity in these systems, the discussion herein focuses primarily on DBTs, which generally have greater con- straints on deck thickness than precast panel systems. The bridge deck in DBTs consists of the girder flange, which is precast and prestressed with the girder. DBTs are manufactured in the precast plant under closely monitored conditions, transported to the con- struction site, and erected such that the flanges of adjacent units abut. Load transfer between adjacent Figure 15 A DBT concrete bridge being constructed. 16

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Longitudinal Joint Bridge Rail (Typ.) B C Zone (Typ.) Welded Steel Grouted Top Flange Connector Shear Key DPPCG (Typ.) Cross-Section View Longitudinal Joint Zone (Typ.) Bridge Rail B C 4 feet (Typ.) Detail A Grout Steel Plate Grout 6 in. Detail A DPPCG (Typ.) Anchor bar (Typ.) Steel Angle Joint Backer Bar Plan View B-B C-C Figure 16 A typical DBT bridge connected by longitudinal joints with welded steel connectors. (Typ = typical, DPPCG = decked precast, prestressed concrete girder bridges, B-B and C-C = cross sections defined in Detail A.) key to tie the adjacent girders together. A joint backer reinforcement can control cracks much better than bar is placed at the bottom of the shear key to prevent widely spaced welded steel connectors. However, leakage when grouting. straight lap-spliced reinforcement requires a much The typical longitudinal joint shown in Figure wider joint to develop its strength. It is very impor- 16 has the strength needed to transfer shear and lim- tant for the proposed joint width to be as narrow as ited moment from one girder to adjacent girders. possible. Joint width minimization will reduce the The width of the joint zone is small so that it facili- amount of required expensive grout, which results in tates accelerated construction. However, because a reduction of cost and faster construction time. As a the welded steel plates are located 4 ft from each result, options to reduce the joint width were explored. other and at mid-depth of the flange, they cannot Such options included bars with hooks (U-bar), bars help to control flexural cracks along the longitudinal with headed terminations, and bars with spirals. To joint. Although the performance of this type of joint allow for accelerated construction, the details were was reported as good to excellent in a survey of cur- also developed to minimize deck thickness, which rent users, problems with joint cracking in these sys- would reduce the weight of DBT girders. tems have been reported in the literature (Stanton In total, five different connection concepts were and Mattock 1986; Martin and Osborn 1983). This proposed and evaluated for the longitudinal and/or joint cracking along with joint leakage is perceived to transverse connections between full-depth deck pan- be an issue limiting wider use of this type of bridge. els or deck flanges for this study. Feedback on the The State of Washington limited the use of DBTs for details was obtained through an in-depth phone sur- roads with high average daily traffic (ADT) and for vey that included 60 participants. The respondents continuous bridges. As part of a research project to included bridge engineers (including many individu- address issues that influence the performance of DBT als who serve as State Bridge Engineers), consulting bridges, a specific objective was defined to develop engineers, fabricators, material suppliers, industry rep- improved joint details that allow DBT bridge systems resentatives, and technical committee contacts. The to be more accepted as a viable system for accelerated five connection concepts that were addressed were bridge construction. loop bar (U-bar) detail, straight bar detail with spiral One of the connection concepts explored was to to reduce lap length, headed bar detail, welded wire replace the current welded steel connectors with dis- reinforcement (WWR) detail, and structural tube detail. tributed reinforcement to provide moment transfer as In general, many respondents considered all five well as shear transfer across the joint. Well-distributed of the connection concepts to be potentially useful 17

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in bridge construction and especially when rapid maybe due to a fatigue concern, though manufac- construction was critical. A common concern regard- turers are promoting its use. ing the connection of each of the precast elements Many of the respondents viewed the structural was that of differential camber, and many respon- tube detail as being exceptionally robust, with one dents who voiced this concern suggested that the use respondent describing it as being "bomb proof." A of a steel plate or haunch should be included to assist common concern regarding the structural tube detail with the leveling of adjacent precast panels. was the potential for alignment and other con- Many of the respondents preferred the U-bar structability issues. Also of concern was the potential detail over the other options and noted that a U-bar for sloppy field work to degrade the connection, espe- detail has been successful in Japan and Korea. Some cially if the tube were not correctly and completely expressed that although the U-bar detail was the filled with grout. most promising, it could require a thicker deck to To finalize the connection concepts investigated accommodate the bend radius of the U-bar detail, in the study, the following criteria were considered: which would add weight to the structure. It was sug- · The connection detail should not only be able gested by another that the key to the U-bar detail to transfer shear but also provide moment would be to obtain a waiver on the minimum bend continuity across the joint. Where possible, radius of the looped bar. Experience of a similar two layers of steel should be used in the joint. detail used in Nebraska indicated exceptional per- · The connection detail must allow the precast formance of the system; it was emphasized that the units to be joined together quickly to minimize connection must be either nonshrink or expansive to disruption to traffic. For the joint connections, prevent cracking. Some respondents commented it is desirable to minimize or eliminate form- that the U-bar detail would require perforations in ing of the joint to expedite construction and the formwork, and therefore, the bar spacing should reduce cost. Field placement of reinforcement be standardized as much as possible. within the longitudinal joint area after erection The straight bar with spiral reinforcement to should be minimized. In joints where forming reduce the lap length detail was also favored by many is required, provide sufficient room to facili- of the respondents. A common concern regarding the tate connection completion and use CIP rather connection was that it was expected to be more expen- than special grout mixes. sive and would also require additional field labor to · The closure pour (CP) material to precast unit complete the connection. In addition, it was suggested interface is an area of concern for durability. that the spiral reinforcement may create alignment The focus in this area must be on minimizing issues during construction, which could add to the cracking in this location to reduce intrusion of amount of construction time required. water that may result in corrosion. Place the The headed bar detail was often praised for the reinforcement as close as possible to the top fact that it would come to the field site nearly com- and bottom surfaces to help control cracking. pleted, which would reduce construction labor as well · Cumulative fabrication and erection tolerances, as the time required to construct the system. Many particularly differential camber in deck flanges, respondents conceded little experience with the will result in some degree of vertical flange mis- headed bar details and suggested that testing would matching. A temporary welded connector detail be required, though many said that they expected that should be considered for leveling flange mis- the detail would work adequately. Some respondents matching before the permanent connection is also suggested that the detail may be difficult to fab- placed. ricate and that the alignment and placement of the longitudinal steel could be complicated. The U-bar detail and the headed bar detail The WWR detail was generally liked by most of were selected as the most viable candidates in this the respondents, especially because the wire rein- research. U-bar details are oriented vertically in the forcement detail was expected to promote rapid con- joint to provide two layers of reinforcement fabri- struction in the field. A few respondents voiced cated with a single rebar. The U-bars provide conti- concern regarding the ability for the WWR to be nuity of the deck reinforcement across the joint by adequately developed in the space available. In Cal- lapping with the U-bars from the adjacent flanges. ifornia, it was noted that WWR was not permitted, The 180° bend of the U-bar, embedded in the joint, 18

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provides mechanical anchorage to the detail necessary length for these bars is less than that required to to minimize the required lap length. The extended develop a hooked bar per ACI 318-08 (2008). In the reinforcement of the U-bar details is staggered (i.e., current study, the headed reinforcement used was out of phase) with the adjacent lapped U-bar to facili- No. 5 bar with Lenton Terminator® bearing heads. tate constructability in the field. The stagger cannot The diameter of the head was 1.5 in., and the thick- be too large, or the transfer of forces across the joint ness of the head was 7/8 in., which gave an Abrg/Ab would be difficult to achieve. of 4.76. The smaller head dimension was neces- To minimize deck thickness, the U-bar detail sary in order to fit the two layers of reinforcement was designed to utilize an extremely tight bend. The within the deck while minimizing the deck thick- inside bend diameter that was used was three times ness. The large-headed bars in two layers would the diameter of the bar (3db), thus, with No. 5 bars have resulted in a much thicker, uneconomical deck used, the inside diameter of the bend was 17/8 in. The system. American Concrete Institute (ACI) Committee 318-08 In addition to the reinforcement details used for (2008) set minimum bend diameters for different the connection, a key to the success of robust accel- rebar sizes and materials. For a No. 5 bar made of erated construction is the development of durable conventional steel, the minimum bend diameter, per fast-curing CP materials. As a consequence, this ACI 318-08 (2008), was six times the diameter of investigation included the development of perfor- the bar (6db), and for D31 deformed wire reinforce- mance specifications to address the durability issues ment (DWR) the minimum bend diameter was four associated with the CP materials. Both overnight times the diameter of the bar (4db) when used as stir- cure and 7-day cure materials were evaluated. rups or ties. Clearly, the U-bar bend diameter that was used (3db) violated the minimum allowable bend diameters established by ACI 318-08 (2008). Research Methodology and Findings The minimum bend diameters were established pri- Determination of Most Viable Connection Detail marily for two reasons: feasibility of bending the rein- forcement without breaking it and possible crushing Experimental tests were conducted on the selected of the concrete within the tight bend. To ensure that reinforcement details to simulate the expected loading the reinforcement would not be broken while bend- conditions to be experienced in longitudinal and trans- ing, two ductile reinforcing materials were used: verse joint configurations. The investigated joints used DWR and stainless steel (SS) reinforcement. Con- two layers of reinforcement to provide the ability to crete crushing in the tight bend was closely observed transfer moment as well as shear through the deck. in the experimental investigation to determine if it The two types of details investigated to reduce the would occur. width of the joint were U-bar details (with DWR and As an alternative to the U-bar details, two layers SS) and headed reinforcement details. of headed bars were considered to provide continu- Initial tests were conducted using monolithic ity of the top and bottom deck steel through the joint. specimens that contained the two types of reinforce- The previous NCHRP Project 12-69 explored the ment details to simulate longitudinal and transverse use of single large-headed bars to provide continu- joint connection concepts (i.e., flexural and tension ity across the joint (Oesterle et al. 2009; Li et al. test specimens, respectively). Both joint directions 2010; Li et al. 2010a). In that project, Headed Rein- were investigated so that the results of this experi- forcement Corporation (HRC) provided the headed mental program could apply to several precast deck reinforcement, which consisted of a No. 5 bar with systems (e.g., DBT systems and full-depth precast a standard 2-in. diameter circular friction welded deck systems). Figure 17 shows the two joint direc- head with a head thickness of 0.5 in. Large-headed tions tested and the specimen orientations used to bars such as these with the bearing area (Abrg), represent the joints. The test setups for the longitu- exceeding nine times the area of the bar (Ab), are dinal joint test (i.e., flexural test setup) and trans- assumed to be able to develop the bar force through verse joint test (i.e., tension test setup) are given in bearing at the head. Bars with smaller heads (e.g., Figures 18 and 19, respectively. Abrg/Ab 4) are assumed to be able to develop the Three of the specimens represented longitudinal force in the bar through a combination of mechani- joint connections (flexural specimens) and three cal anchorage and bond, where the development represented transverse joint connections (tension 19

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Figure 17 Orientation of joints and corresponding test specimens. Actuator Actuator 96.0 in Deflection Deflection Reading Reading (LVDT) Deflection Reading (LVDT) (LVDT) Ext./Comp. Readings (LDVTs) Joint 6.25 in 28.0 in 40.0 in 28.0 in 120.0 in Figure 18 Flexural test set-up (longitudinal joint test) (LVDT = linear variable differential transformer). 20

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Support Beam Load Frame Longitudinal Beam Force Direction Joint Displacement Reading (LVDT) 72.0 in Actuator Loading Beam Load Frame Column Figure 19 Tension test setup (transverse joint). 21

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120.0 in 15.0 in 6.0 in 4.5 in #4 bars @ 12 in spacing 6.25 in #5 bars @ 6 in spacing Figure 20 U-bar longitudinal joint specimen. specimens). The three joint details investigated produced the largest capacities in both the bending included (1) lapped headed reinforcement, (2) lapped and tension tests without compromising ductility. U-bar reinforcement fabricated with deformed wire, Smaller crack widths at service-level loading were and (3) lapped U-bar reinforcement fabricated with also produced by the U-bar detail when compared to SS. The three specimens tested in flexure were sub- the headed bar detail. jected to forces that would be experienced in a lon- The constructability and reinforcement costs of gitudinal deck joint, and three specimens tested in the joint details were also compared. The U-bar tension were subjected to forces that would be expe- detail created a less congested joint, which made it rienced in a transverse joint over an interior pier. the easiest to construct. The bearing heads of the Based on the performance of the initial tests con- headed bar detail require more space due to the larger ducted on the U-bar detail (with DWR and SS) for diameter of the rebar heads. This extra space reduces the longitudinal joint shown in Figure 20, and headed construction tolerances and could therefore cause reinforcement details for the longitudinal joint shown problems in placement of precast deck components. in Figure 21, the most promising connection concept The U-bars can also be easily tied together to form in terms of behavior, constructability, and cost (the a rebar cage, which would allow for easy construc- U-bar detail), was investigated in additional tests tion in the precast yard when compared to the two where parameters were varied to refine the proposed single layers of reinforcement in the headed bar connection concepts. detail. The lowest material cost was the conven- The capacities of the joint details were used for tional rebar used for the headed bars. The material comparison and the selection of the best performing costs were competitive between the conventional joint detail. All joint details produced adequate rebar used in the headed bars and the DWR. The SS capacities and ductility in both the tension and flex- reinforcement had the highest cost. ural tests. Specimens with U-bar details and headed After consideration of capacity, service-level bar details both produced a capacity corresponding crack widths, constructability, and cost, the U-bar to their respective nominal design yield strengths. detail, with an overlap length of 6 in., a rebar spac- Because the U-bars had a higher nominal design ing of 4.5 in., and two transverse lacer bars con- yield strength (i.e., 75 ksi) than the headed bars (i.e., structed of DWR was recommended for the second Grade 60), specimens containing the U-bar joint detail phase of tests. 120.0 in 15.0 in 6.0 in 4.5 in #4 bars @ 12 in spacing 1" 6.25 in #5 bars @ 6 in spacing Figure 21 Headed bar longitudinal joint specimen. 22

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In the second phase of tests, another six speci- U-bars helps to explain the greater ductile failure mens with the U-bar detail were tested, three in mode observed in the U-bar tests. flexure and three in tension, to investigate effects of In summary, based on capacity, service level crack variables including overlap lengths, rebar spacings, widths, constructability, and cost, the U-bar detail, and concrete strengths. Based on results of the sec- with No. 5 equivalent DWR at 4.5-in. spacing with ond phase of tests, the following conclusions were 6-in. overlap length and two transverse lacer bars was made: recommended for the final longitudinal and transverse By reducing the concrete strength, both the flex- joint tests. It should be noted that all of the tests were ural and tensile capacities were reduced. When de- based on uncoated reinforcement. If epoxy-coated creasing the joint overlap length from 6 in. to 4 in., reinforcement were used, larger joint widths may be the crack widths were significantly enlarged, the flex- required to develop the reinforcement across the joint. ural capacity was decreased by 17.8%, and the ten- An alternative to epoxy-coated reinforcement would sile capacity was decreased by 18.9%. Increasing be to use SS reinforcement, which performed well in the spacing of the U-bar reinforcement from 4.5 in. the initial study but was an expensive alternative. to 6.0 in. was not observed to significantly change the In all of the initial tests to select the most viable behaviors of longitudinal and transverse joints joint details, the details were cast in monolithic con- in terms of their crack widths, flexural capacities, crete specimens. Prior to testing the details within and tensile capacities. In order to provide adequate jointed test specimens, an extensive study was con- ductility without significant loss of strength ulti- ducted to select high performance durable 7-day and mately, the joint overlap length should not be less overnight CP materials based on the specified perfor- than 6 in. and #4 lacer bars should be provided to mance criteria developed for freeze-thaw, shrinkage, enhance the mechanical anchorage of the U-bars as bond strength, and permeability. illustrated in Figure 22. Development of Performance Criteria The lacer bars provided confinement of concrete for CP Materials within the joint and served as a mechanical anchor- age for the U-bars. Figure 22 provides an example For precast bridge deck systems with CIP con- of the deformation the lacer bars underwent during nections, precast elements are brought to the con- the tests. The location of the lacer bars in relation to struction site ready to be set in place and quickly the U-bars enabled the lacer bar to provide bearing to joined together. Then, a concrete CP completes the U-bars. These "bearing" forces caused the lacer bar connection. The performance of the CP material is to bend. This interaction between the lacer bar and one of the key parameters affecting the overall per- formance of the bridge system. Longitudinal connections between the flanges of DBTs and between precast panels between girders require that the joints must be able to transfer shear and moment induced by vehicular loads. Shrinkage of CP materials and transverse shortening of precast members further subject the joints to direct tension. Freeze-thaw resistance and low permeability of joints are also important. An ideal CIP connection detail emulates monolithic behavior and results in a more durable and longer lasting structure. Traditionally, different types of grouts have been used as CP materials for precast bridge deck systems with CIP connections. Mrinmay (1986) documented a wide variety of materials used after 1973 to avoid joint failure in CPs. These materials included sand- epoxy mortars, latex-modified concrete, cement- based grout, nonshrink cement grout, epoxy-mortar grout, calcium-aluminate cement mortar and concrete, Figure 22 Deformation of lacer bar. methylmethacrylate-polymer concrete and mortar, and 23

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polymer mortar. Epoxy- or polymer-modified grouts coarse aggregate extension, typically 1/2- or 3/8-in. can have significant advantages, such as a high coarse aggregate, is extended grout. Compared with strength of 10 ksi in 6 hours, better bond, reduced chlo- neat grout, extended grout has the following potential ride permeability, and lower shrinkage (Issa et al. benefits: (1) more compatible with concrete; (2) better 2003) than different magnesium ammonium phos- interlock between connection components; (3) denser, phate (MAP) grouts. However, they are often signif- less permeable; (4) less drying shrinkage and creep; icantly more expensive and less compatible with and (5) larger grout volume per bag, hence less expen- surrounding concrete. In addition, if the resin is used sive. However, it was pointed out by Matsumoto et al. in too large of a volume, the heat of reaction may cause (2001) that the extended grout required more cement it to boil, and thereby develop less strength and lose paste than available in prepackaged bags, leading to bond. Cementitious grouts have been used more in lower strengths and poor workability. precast construction than have epoxy or polymer- As discussed above, numerous products are avail- modified grouts (Matsumoto et al. 2001). A primary able for CP materials, and various materials were stud- disadvantage of cementitious grouts is the shrinkage ied. However, limited research had been previously and cracking that result from the use of hydraulic conducted to provide consistent comparison among a cement. Nonshrink grout compensates for the shrink- large number of different types of CP materials. Also, age by incorporating expansive agents into the mix. adequate performance-based criteria need to be devel- With nonshrink grout, the effects of shrinkage cracks oped to ensure appropriate selection of CP materials, or entrapped air on the transfer of forces and bond are particularly for accelerated bridge construction. minimized, though not eliminated. ASTM C1107 Performance-based specifications focus on properties establishes strength, consistency, and expansion cri- such as consistency, strength, durability, and aesthet- teria for prepackaged, hydraulic-cement, nonshrink ics. They reward quality, innovation, and technical grout. knowledge in addition to promoting better use of Nottingham (1996) reported that the very nature of materials, and present an immense opportunity to opti- portland cement grouts virtually assures some shrink- mize materials design. age cracks in grout joints, regardless of quality control. Prepackaged MAP-based grout, often extended with As part of the process of developing the perfor- pea gravel, can meet requirements like high quality, mance criteria, eight candidate CP materials were low shrinkage, impermeability, high bond, high early selected and evaluated with respect to their potential strength, user friendly, and low-temperature curing effectiveness in accelerated bridge construction. ability (Nottingham 1996; Issa et al. 2003). Gulyas In this context, accelerated bridge construction is et al. (1995) undertook a laboratory study to compare defined with respect to two categories: overnight cure composite grouted keyway specimens using two dif- of CP materials and 7-day cure of CP materials. For ferent grouting materials: nonshrink grouts and MAP the overnight cure, published performance data from mortars, in which MAP materials performed better different grout materials were collected through con- than nonshrink grouts. Gulyas and Champa (1997) tacts with material suppliers and users. For the 7-day further examined inadequacies in the selection of a tra- cure, standard or special concrete mixtures and their ditional nonshrink grout for use in shear keyways. The performance data were collected through contacts MAP grout outperformed the nonshrink grout in all with HPC (High Performance Concrete) showcase areas tested, including direct vertical shear, direct ten- states as well as with material suppliers. Based on sion, longitudinal shear, bond, shrinkage, and so on. these initial collected data, four grouts were first Menkulasi and Roberts-Wollmann (2005) presented a selected as candidate overnight cure materials, and study of the horizontal shear resistance of the connec- four special concrete mixes as candidate 7-day cure tion between full-depth precast concrete bridge deck materials. The preliminary selection was based on panels and prestressed concrete girders. Two types of strength tests of selected materials or on prediction grout were evaluated: a latex modified grout and a models to narrow the candidate materials down to two MAP grout. For both types of grout, an angular pea materials in each of the two categories. Then long- gravel filler was added. The MAP grout developed term tests were performed on the final four selected slightly higher peak shear stresses than the latex mod- materials, including freezing-and-thawing durability, ified grout. shrinkage, bond, and permeability tests. Grout without coarse aggregate extension is For precast bridge deck systems with CIP connec- usually referred to as neat grout, while grout with tions, precast elements are brought to the construction 24

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Table 3 Proposed performance criteria of CP materials. Performance Characteristic Test Method Performance Criteria Compressive Strength (CS), ksi ASTM C39 modified 6.0 CS @ 8 hours (overnight cure) @ 7 days (7-day cure) Shrinkage1 (S), (Crack age, days) AASHTO PP34 modified 20 < S Bond Strength (BS), psi ASTM C882 modified 300 < BS 2 ASTM C1543 modified ChP < 1.5 Chloride Penetration (ChP), (Depth for percent chloride of 0.2% by mass of cement after 90-day ponding, in.) Freezing-and-Thawing ASTM C666 Grade3 1 Grade 2 Grade 3 Durability (F/T), (relative Procedure A modified 70% F/T 80% F/T 90% F/T modulus after 300 cycles) 1 No S criterion need be specified if the CP material is not exposed to moisture, chloride salts or soluble sulfate environments. 2 No ChP criterion need be specified if the CP material is not exposed to chloride salts or soluble sulfate environments. 3 Grades are defined in Table 4. site ready to be set in place and quickly joined ered parameters such as different loading locations, together. Then, a concrete CP completes the connec- effect of bridge width, design truck and lane loading tion. The performance of the CP material is one of the versus design tandem and lane loading, girder geo- key parameters affecting the overall performance of metry (depth, spacing and span), bridge skew, single- the bridge system. The final performance criteria lane loading versus multi-lane loading, and impact of for selecting durable CP materials given in Tables 3 cracking of the joints. Through this investigation, a and 4 were developed based on extensive literature database of maximum forces to be expected in the review which included proposals by Russell and Ozy- joint was developed. These forces were subsequently ildirim (2006) and Tepke and Tikalsky (2007) and the used to determine the fatigue loading demand for the results of the long-term tests. large-scale longitudinal joint specimen (flexure and shear-flexure) tests and the large-scale transverse joint Numerical Investigation to Determine Loadings specimen (tension) tests. to be Applied in Joint Tests Large-scale Tests on Longitudinal and Transverse To determine the service static and fatigue load- Joints with U-Bar Details and Both 7-Day ings that might be expected in the longitudinal and and Overnight Cure CP Materials transverse joint connection concepts, numerical stud- ies of bridge systems were conducted with a number Large-scale longitudinal and transverse jointed of variations. The analytical parametric study consid- specimens were fabricated to investigate the flexure Table 4 Application of CP material grades for freezing-and-thawing durability. Freezing- Is the concrete Yes Is the member Yes Will the Yes. and-thawing exposed to freezing- exposed to member Specify F/T- Durability and-thawing deicing salts? be saturated Grade 3 (F/T) environments? during No. freezing? Specify F/T- Grade 2 No. Specify F/T-Grade 1 No. F/T grade should not be specified. 25

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and flexure-shear behavior of the longitudinal joints Centerline of Joint See "Joint Reinforcement Detail" and the tension behavior of the transverse jointed spec- imens. The tension tests on the transverse jointed specimens were intended to simulate continuity 4.5'' (Typ.) provided by the joints over the piers, where it was assumed that the deck would transmit tension equili- brated by compression in the girder. The large-scale specimens were fabricated with the most promising connection detail, which was a U-bar connection concept fabricated with DWR. The specimens were subjected to static and fatigue tests with the loads determined in the numerical parametric study. The tests were evaluated in terms of load-deformation #4 bar spacing #5 U bar spacing response, strain distribution, crack control, and 12'' (Typ.) 4.5'' (Typ.) strength. 2'' 1 38'' (5d) Longitudinal Joint Tests. Figures 23 and 24 show the 1'' dimensions and the reinforcement layout in the longi- #5 bar spacing 6'' #4 lacer bar (Typ.) tudinal joint specimen. The specimens were fabricated 6'' (Typ.) with the U-bars extending out of both faces of the test Joint Reinforcement Detail specimens, such that the specimens could be reused by severing the panel after testing and rotating the panels Figure 24 Reinforcement layout in longitudinal joint to fabricate a new joint. Figure 25 shows a profile view specimen. of the joint surface before and after sand blasting. The longitudinal joint was filled with CP material to complete the connection, which simulated the lon- panel-to-panel connections, considered to be the struc- gitudinal joint connection at the interface of the top tural element of the bridge deck. To facilitate acceler- flange of adjacent DBT girders or full-depth precast ated bridge construction, it is important for the selected CP material to reach its design compressive Centerline strength in a relatively short period of time. In this See "Shear Panel 2 Panel 1 study, it was decided to use two primary CP materials, 6.25 '' of Joint Key Detail" SET® 45 Hot Weather (HW) for overnight cure and an 64'' 64'' HPC mix for the 7-day cure. The grout SET 45 HW used in the longitudinal joint study was investigated both without extension in two joints and with 60% extension in two joints for comparison. The uniform- sized sound 0.25 in. to 0.5 in. round pea gravel used 72 '' to extend the grouts was tested with 10% hydrochlo- ric acid (HCl) to confirm that it was not calcareous. Figure 26 shows the test specimen before and after grouting. The loading matrix describing the tests conducted on the longitudinal joint specimens is 4'' 4'' given in Table 5. The test setups used to investigate 0.625'' static flexure (SF), static shear (SS), fatigue flexure 2.5'' (FF), and fatigue shear (FS) are given in Figure 27, 2.5'' parts (a) through (d). 0.625'' The measured ultimate capacities of all of the 5.5'' 5.5'' specimens obtained following the service fatigue Shear Key Detail loading cycles exceeded their calculated capacities. The joints with the overnight cure materials had Figure 23 Dimensions of longitudinal joint lower capacities than those with the 7-day cure, due specimen. to the lower strength of the joint material. Based on the 26

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(a) Before sandblasting (b) After sandblasting Figure 25 Profile of joint surface. (a) Before grouting (b) After grouting Figure 26 Longitudinal joint specimen before and after grouting. Table 5 Slab specimen loading matrix. Overnight Cure 7-Day Cure Flexure Flexure-Shear Flexure Flexure-Shear Static Fatigue Static Fatigue Static Fatigue Static Fatigue (SF-O) (FF-O) (SS-O) (FS-O) (SF-7) (FF-7) (SS-7) (FS-7) SET 45 HW SET 45 HW SET 45 HW SET 45 HW HPC Mix 1 extended extended NOTE: SF = static flexure, FF = fatigue flexure, SS = static shear, FS = fatigue shear, O = overnight cure, and 7 = 7-day cure. 27

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12 in.12 in. LMT 1, 2 and 3 12 in. LMT 8, 9 and 10 LMT 8, 9 and 10 LMT 1, 2 and 3 P P P A A A A LMT 5 LMT 4, 6 LMT 4, 6 LMT 5 LMTs for and 7 and 7 LMTs for Curvature Curvature 36 in. 36 in. 36 in. 36 in. 4 in. 4 in. 8 4 1 8 4 1 32 in. 32 in. 10 in. 10 in. 20 in. 20 in. 9 2 9 2 32 in. 32 in. 5 6 6 5 4 in. 4 in. 10 7 3 10 7 3 A-A A-A (a) Static-Flexure (SF) test (b) Static Shear (SS) test 12 in.12 in. 2P 12 in.12 in. LMT 8, 9 and 10 LMT 1, 2 and 3 LMT 8, 9 and 10 LMT 1, 2 and 3 P1 P2 A A A A LMT 5 LMT 5 LMT 4, 6 LMT 4, 6 LMT for and 7 LMTs for and 7 Curvature Curvature 36 in. 36 in. 36 in. 36 in. 4 in. 4 in. 8 4 1 8 4 1 32 in. 32 in. 10 in. 10 in. 20 in. 20 in. 9 2 9 2 32 in. 32 in. 5 6 5 6 4 in. 10 7 3 4 in. 26 in. 42 in. 42 in. 26 in. 10 7 3 A-A A-A (c) Fatigue-Flexure (FF) test (d) Fatigue-Shear (FS) test Figure 27 Longitudinal joint specimen test setup. parametric study and the experimental program, the to the static load tests. For the specimens with following findings were made: 7-day cure material in the joint, fatigue loading had a negligible effect on the results for the · Fatigue loading had little influence on the flexure-shear tests. In the case of the flexure behavior of the longitudinal joints (flexure tests, the failure load was not reached due to and flexure-shear test specimens) in terms of limitations of the MTS test equipment. average curvature of the joint, deflection at · Joints with the 7-day cure material performed midspan, relative displacement of the joint better than those with the overnight cure mater- interface and joint center, as well as reinforce- ial in some cases. Examples included the ment strain under service live load. flexure-shear tests, SS and FS, where the joints · Fatigue loading was observed to have an effect with the 7-day cure material had larger failure on the loading capacity of the flexure specimens loads and curvatures than those of the specimen using the overnight cure material. After two with the overnight cure material. This was million cycles, the specimens fabricated with because the 7-day cure material used developed the overnight cure material had less load capac- higher strengths than could be achieved with the ity than the corresponding specimens subjected overnight cure material in the tests. 28

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Panel 1 Centerline See "Shear Panel 2 There were four layers of reinforcement in each 7.25 '' of Joint Key Detail" panel along the specimen depth direction with a 2-in. 32'' 32'' cover at the top and 1-in. cover at the bottom. The straight bars simulated the transverse reinforcement while the U-bars simulated the longitudinal reinforce- 15 '' ment that comprised the transverse joint connection reinforcement in the bridge deck. The reinforcement details in the specimen were as follows: #5 straight bar spaced at 6 in. at the bottom along the specimen 4'' 4'' width direction and #4 straight bar spaced at 12 in. at 1.125'' the top along the specimen width direction. The #5 2.5'' U-bars projected out of the panel to splice with the 2.5'' U-bars in the adjacent panel in the transverse joint. 1.125'' The spacing of the U-bars was 4.5 in. and the over- 5.5'' 5.5'' lap length (the distance between bearing surfaces of adjacent U-bars) was 6 in. The interior diameter of Shear Key Detail bend of the U-bar was 3db. All of the specimens exceeded the nominal service Figure 28 Dimension of transverse joint (tension) live load capacity. However, only ST-7 and FT-7 specimen. exceeded the calculated tensile capacity. It was concluded that tensile capacities were reduced by reducing the concrete strength. Please note that the Based on these tests, the U-bar detail was deemed longitudinal reinforcement was not continuous in the to be a viable connection system for longitudinal joints U-bar detail. And one reason that ST-O and FT-O had between full-depth precast deck panels and DBTs. lower capacities was due to the lower strength of the joint material. Attention needs be paid to the moisture Transverse Joint Tests. Figures 28 and 29 show the loss during the first 3 hours after placement, which dimensions and the reinforcement layout in the longi- may have caused the lower strengths in the tests. tudinal joint specimen. Figure 30 shows a profile view A similar phenomenon was observed in the of the joint surface before and after sand blasting. The monolithic transverse joint specimens. Typically, loading matrix describing the tests conducted on the the tensile capacity of a specimen under pure tension transverse joint specimens is given in Table 6. is a function of the amount and strength of steel if #4 H ea ded L acer B ars #5 B ars (T Y P ) 6" 4" S tr a in G a g e D e ta il (T Y P ) 41 2" 41 2" 1 '- 3 " 41 2" 6" 4" 11 2" 6' 1' 4" (T Y P ) #4 B ars (T Y P ) 2" 71 4" 17 8" 1" (3 d ) #5 B ars 6" 6" (T Y P ) (T Y P ) 6' Figure 29 Reinforcement layout in transverse joint (tension) specimen. 29

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(a) Before grouting (b) After grouting Figure 30 Transverse joint (tension) specimen before and after grouting. the steel is continuous. In the earlier tests, all four Based on the parametric study and the experimen- specimens exceeded the service-level load. How- tal program, the following findings were made for the ever, only two of the specimens exceeded the theo- transverse joint specimens: retical tensile capacity. Because the amount of steel was not varied among the test specimens, the tensile · The fatigue loading had no significant influ- capacity was attributed to the interaction between ence on the tensile capacity and reinforcement the concrete and steel as well as the steel arrange- strains. ment. The tensile capacity of the specimen, which · The fatigue loading was observed to have an from 10 to 7 ksi, was 4.6% less had a decrease in f c effect on the deflection development, particu- than the expected capacity based on nominal prop- larly for the joints with the 7-day cure material. erties, and the tensile capacity of the specimen that · The fatigue loading had some effect on the had a decrease in joint overlap length from 6 in. to measured crack widths in the specimens with 4 in. was 18.7% less than the expected capacity the overnight cure material. Under the same based on nominal properties. In the joint zone, the loading, the crack widths were observed to staggered U-bars tied with two lacer bars created a increase after the fatigue cycles. truss-like model. This truss model can also be con- · Undesirable wider crack widths will be devel- sidered a strut-and-tie model where the compression oped at service-load levels in transverse joints in the concrete represents the strut and the tension in designed with higher grades of steel (e.g., 75 ksi the reinforcement represents the tie. compared to 60 ksi) because smaller amounts of The transverse of forces through the joint region reinforcement can provide the required nominal to the staggered lapped U-bars needs to be considered strength. Under service loads, larger stresses in evaluating the tensile capacity. would be expected in the smaller bars, which lead to wider cracks at service. It is recom- Table 6 Transverse joint (tension) specimen mended that 60 ksi nominal yield strength loading matrix. be used in the design of transverse joints, or that stresses in the reinforcement are limited Overnight Cure 7-Day Cure at service. Static Fatigue Static Fatigue ST-O FT-O ST-7 FT-7 Based on these tests and with the aforemen- tioned caveats, the U-bar detail may be considered a SET 45 HW SET 45 HW HPC Mix 1 HPC Mix 1 viable connection system for transverse joints in NOTE: ST = static tension, FT = fatigue tension, O = overnight cure, continuous DBT and full-depth precast deck panel and 7 = 7-day cure. on girder bridges. 30