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9 CHAPTER 2 Findings 2.1 Introduction nent specimens is based on a representative portion of the cen- ter column and bent cap of the bridge, as shown in Figure 2.1. This chapter provides a synopsis of key findings of the The full design of the prototype and specimen are reported in experimental and analytical research program. This research Matsumoto et al. (15). This section summarizes key design program investigated the following: features of the CIP prototype bridge and CIP specimen. The CIP prototype bridge and full ductility component Emulative, nonintegral details specimens were designed in accordance with AASHTO LRFD Grouted duct connection Bridge Design Specifications (Third Edition with 2006 Interims) Cap pocket connection (2006 LRFD BDS) and Recommended LRFD Guidelines for the Hybrid, nonintegral details Seismic Design of Highway Bridges (2006) (2006 LRFD RSGS) Conventional system prepared as part of NCHRP Project 20-07/Task 193 and Concrete filled pipe system provided to the research team (16, 2). It is important to note Dual steel shell system that the 2006 LRFD RSGS was superseded by the Proposed Integral detail AASHTO Guide Specifications for LRFD Seismic Bridge Design Post-tensioned girder system detail (2007 LRFD PSGS) and later updated to the current 2009 AASHTO Guide Specifications for LRFD Seismic Bridge Design Findings include a description of the experimental test (2009 LRFD SGS) (17, 1). In addition, the 2006 LRFD RSGS program--including specimen design, fabrication, and test- contains different--and in some aspects more liberal (i.e., ing protocol--and response of the specimens. Detailed find- less conservative)--joint reinforcement requirements than ings can be found in the attachments to this report, available the current 2009 LRFD SGS. For example, in contrast the online at www.trb.org/Main/Blurbs/164089.aspx. 2006 LRFD RSGS, the 2009 LRFD SGS specifies vertical joint stirrups both inside and outside the joint region, a larger total 2.2 Description of Experimental area of joint stirrups, and a significant increase in bent cap Test Program longitudinal reinforcement. These provisions are compared in Chapter 3. This section describes the general development of the test- For a major seismic event, the CIP prototype bridge was ing program and associated experimental specimens. Detailed designed and detailed to exhibit ductile plastic hinging in the drawings are provided in the attachments to this report. column adjacent to the bent cap (and footing). Prototype bridge drawings are shown in the attachments. Initial member sizing was based on input from design engineers and refined through 2.2.1 Design of Nonintegral Prototype application of the 2006 LRFD BDS (16). Seismic analysis and Bridge and Specimens design were performed to finalize column and cap beam sec- In coordination with the NCHRP Project 12-74 panel, the tions. The prototype structure was considered nonessential prototype structure was selected as a two-span, nonintegral and designed for the associated life-safety performance objec- bridge with a three-column CIP bent cap supporting precast, tives defined in the 2006 LRFD RSGS (2). Because the system prestressed girders, intended to represent a typical highway is nonintegral, the specified earthquake resisting system in the overcrossing located in an urban area. Design of the compo- longitudinal direction consisted of cantilever response of the

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10 Figure 2.1. Portion of prototype used for specimen design. columns with plastic hinge formation at the base of columns. In the longitudinal direction, the displacement demand to One-way soil springs were used to account for the seismic capacity ratio, D/C, was 0.85. For determining transverse resistance of the abutment backfill. Transverse earthquake capacity, overturning effects were considered using an iterative resistance was provided by the three-column bent cap with procedure to refine the estimated column plastic moment plastic hinge formation occurring at both the top and bottom capacities based on column axial loads obtained from the push- of the columns. The design acceleration response spectrum over analysis. XSection was used to perform moment-curvature (ARS) curve incorporated 5% damping and was developed analysis, and WFrame was used for pushover analysis, includ- using a 1.0-sec acceleration of 0.8 g, a 0.2-sec acceleration of ing overturning effects and bent cap flexibility (19, 20). The 1.5 g, and coefficients for Site Class D soil. The resulting peak transverse displacement D/C ratio was 0.57. Ductility demand rock acceleration was 0.6 g. The ARS curve is representative ratios were approximately 5.0 for both the longitudinal and of a site located in a high seismic region such as Southern transverse directions, well below the limit of 8.0 (multicolumn California. If the design earthquake response spectral acceler- bent caps). The prototype structure thus satisfied the require- ation coefficient at a 1.0-sec period, SD1, was larger than 0.50, ments for displacement and ductility. P-delta effects were the structure was classified as SDC D. This category required checked in accordance with the 2006 LRFD RSGS (2). a demand analysis, displacement capacity pushover analysis, Capacity protection design principles were also applied. capacity design, and SDC D detailing. Flexural and shear demands on the bent cap were based on Elastic dynamic analysis was performed according to the force levels associated with the columns reaching their over- 2006 LRFD RSGS to estimate seismic displacement demands strength capacity. The bent cap design considered axial load (2). The columns were assumed to be fixed at the base, and effects due to transverse response in combination with grav- foundation design was not performed. Moment-curvature ity loads and overstrength demands imposed by columns. analysis was conducted to estimate the effective stiffness of the According to the 2006 LRFD RSGS, the bent cap was required columns. Seismic demands were determined using the SEISAB to remain "nominally elastic" (2). Bent cap transverse rein- program (18). Results from the seismic analysis indicated a first forcement outside of the joint region was designed according mode (longitudinal) period of 1.27 sec and associated displace- to the 2006 LRFD BDS (16) using modified compression field ment demand of 15.1 in. The second mode (transverse) period theory and considered seismic plus gravity loading. Column was 0.58 sec, with a displacement demand of 5.3 in, including transverse reinforcement was designed to resist overstrength magnification to account for demand underestimation for demands due to transverse response. shorter period structures. Shear keys at the abutments were The joint region of the bent cap was designed based on designed to fail during the design seismic event. transverse response using the external force transfer mecha-

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11 nism assumed in the 2006 LRFD RSGS (2). Joint design Full Ductility Emulative Specimens included vertical stirrups with horizontal cross ties in the The GD (grouted duct) and CPFD (cap pocket full ductil- region adjacent to the column (not within the joint), joint ity) specimens used the same full-ductility design basis as the transverse reinforcement (hoops), extension of column bars CIP specimen (22, 23). The GD and CPFD specimens were close to the top of the bent cap, and side face reinforcement. intended to be directly compared with the CIP control spec- In addition, two 2-leg construction stirrups were used within imen. Design of both precast specimens assumed emulative the joint region, as explained by Matsumoto (21). However, response would be achieved despite the following differences the prototype bridge did not incorporate the more conser- between these specimens and the CIP specimen: (1) separate vative joint reinforcement requirements of the 2009 LRFD precast elements, including the bent cap and column, and SGS (1), such as placement of the required area of stirrups (2) use of a 1.5-in bedding layer between the bent cap soffit inside the joint or the additional area of longitudinal bent and column to accommodate tolerances. cap reinforcement. In addition, the GD specimen used closely spaced, 1.75-in The CIP test specimen was designed using a 42% scale of diameter, 22-gage corrugated ducts in the bent cap and high- the central portion of the prototype bridge (see Figure 2.1). As strength, non-shrink, cementitious grout to anchor the col- the prototype bridge would be expected to exhibit ductile umn longitudinal reinforcement. Joint reinforcement matched plastic hinging in the column region adjacent to the bent cap that used for the CIP specimen, including two 2-leg construc- due to transverse response, the scaled CIP control specimen-- tion stirrups within the joint region. CIP and GD specimen loaded in the transverse direction under quasi-static force assembly details and bent cap reinforcement details are shown control and displacement control sequences--was expected in the attachments. to perform similarly. Dead load plus seismic load governed The CPFD specimen used a single 18-in nominal diameter, the bent cap flexural reinforcement in the prototype. This 16-gage steel pipe in the bent cap to house the column bars reinforcement was scaled for use in the bent cap. Bent cap and serve as a stay-in-place form as well as equivalent joint transverse reinforcement was designed per the 2006 LRFD BDS hoop reinforcement. Normal-weight concrete was placed in (16). The additional joint shear reinforcement was required the bent cap void and bedding layer to anchor the column per 2006 LRFD RSGS, although a larger principal tensile bars. The CPFD bent cap reinforcement details are shown in stress was found for the specimen than the prototype due the attachments. Matsumoto (23) summarizes the approach to the relatively smaller column load, larger cap and column used for selecting the readily available lock seam, helical cor- tension, and imperfect scaling of dimensions (2). However, this rugated steel pipe per ASTM A760, Standard Specification for was more desirable for examining joint behavior. Matsumoto Corrugated Steel Pipe, Metallic-Coated for Sewers and Drains (21) provides a detailed comparison of column, bent cap, (24). Figure 2.2 shows the corrugation and lock seam details and joint reinforcement for the prototype bridge and CIP for the pipe used in the specimen, and select joint details are specimen. summarized in Table 2.1. Seam (a) Corrugation and Lock Seam (b) Closeup of Lock Seam Figure 2.2. Corrugation and lock seam details for cap pocket specimen.

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12 Pipe thickness was a specific design parameter, calculated to two 2-leg construction stirrups were placed within the joint provide the same nominal circumferential hoop force in the region. Emulative Precast Bent Cap Connections for Seismic joint as that required for the CIP specimen per 2006 LRFD Regions: Component Test Report-Grouted Duct Specimen RSGS (2). Hoop force calculations assumed pipe nominal ten- (Unit 2) (22) and Emulative Precast Bent Cap Connections for sile yield strength of 30 ksi and used the horizontal component Seismic Regions: Component Tests-Cap Pocket Full Ductility of the helical pipe. Subsequent tensile coupon tests conducted Specimen (Unit 3) (23) provide detailed comparisons of col- on the pipe material indicated a tensile yield strength of approx- umn, bent cap, and joint reinforcement for the prototype imately 58 ksi. Nevertheless, calculations using the assumed bridge and full ductility specimens. 30 ksi yield strength resulted in a pipe thickness that matched the thinnest readily available pipe (16 gage). In addition, a Limited Ductility Emulative Specimen #3 hoop, matching the column hoop size, was placed approxi- mately 1 in from each end of the pipe to reinforce the pipe and The cap pocket limited ductility (CPLD) specimen (26) limit dilation and potential unraveling (see Figure 2.3). This was was intended to aid investigation of the response of a precast considered a reasonably simple yet conservative measure, given cap pocket connection designed according to the principles the limited number of specimen tests and unknown perform- of limited ductility per the 2006 LRFD RSGS rather than the ance of this innovative detail. Table 2.1 shows a hoop force ratio principles of full ductility used for the other specimens (2). (pipe/hoop) of 1.03 when supplementary hoops are neglected, For direct comparison, the CPLD specimen used the CPFD and 1.38 when accounting for the hoops. design as its initial basis. Emulative performance of the CPLD Joint reinforcement for the CPFD specimen did not include specimen was to be examined, especially through a displace- the horizontal J-bars used for the CIP specimen, although ment ductility of 2.0, even though a limited ductility CIP Table 2.1. Comparison of specimen details--CPLD versus CPFD. Item CPLD CPFD Notes Helical Pipe: (24, 25) Same basis allowed 18 in 18 in Pipe Diameter (nom) direct comparison of 0.065 in (16) 0.065 in (16) Pipe Thickness (gage) specimens 20 deg 20 deg Corrugation Angle 2.67 in 0.50 in 2.67 in 0.50 in Corrugation Dimensions 240 lb/in 240 lb/in Lock Seam Strength 57.5 ksi 57.9 ksi Steel Yield Strength 1.38 (extra end Hoop Force Ratio: Potential benefit of Joint hoops) CPFD Pipe / Design 1.03 (no end hoops) end hoops eliminated 1.03 (no end (#3 hoops) for CPLD hoops) External to Joint No joint Vertical Stirrups, Only None reinforcement used Horizontal Cross Ties (2006 LRFD for CPLD RSGS) (2) Two 2-leg Potential benefit of construction Other Reinforcement None construction stirrups stirrups placed in eliminated for CPLD joint 16#5 16#5 (1.58%, Longitudinal (1.58%, Specimen/ Specimen/ No note Reinforcement Prototype ratio = 1.14) Prototype ratio = Column 1.14) Same basis allows Transverse CPLD joint to poten- #3 hoops @ 2 in #3 hoops @ 2 in Reinforcement tially be challenged to greater extent 12#5 top and 8#5 and 2#4 top bottom Potential benefit of Longitudinal and bottom (0.65%, flexural Reinforcement (0.50%, Specimen/ Specimen/ reinforcement Bent Cap Prototype ratio = 0.99) Prototype ratio = reduced for CPLD 1.27) CPLD stirrups Transverse 2-leg #3 stirrups 2-leg #3 stirrups reduced to minimum Reinforcement @ 8 in @ 6 in requirement

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13 these measures were deemed conservative for testing to exam- ine potential failure modes, and it was understood that more stringent detailing could be adopted for design as required. In addition, CPLD column reinforcement (including con- fining reinforcement) was not reduced but designed to match the SDC D-based requirements of the CPFD design. This was intended to help ensure that the column would not prema- turely become a weak link in the system, but impose as large of a demand and as many cycles as possible on the joint so that potential failure modes associated with the joint could be fully investigated. Matsumoto (26) provides a detailed comparison Figure 2.3. Rebar cage with corrugated pipe and of column, bent cap, and joint reinforcement for the prototype supplementary hoops--CPFD. bridge and CPLD specimen. These measures were deemed reasonably conservative for testing to examine limited ductility performance and potential specimen was not tested for direct comparison. The CPLD failure modes. The impact of these measures was unknown. bent cap reinforcement details are shown in drawings pro- However, it was anticipated that more extensive joint damage vided in the attachments. would be exhibited than for the CPFD as the specimen dis- Table 2.1 summarizes select joint details for the CPLD spec- placement ductility approached 2 and could possibly result in imen, including the specifications for the helical corrugated joint failure at larger ductility levels. It was understood that pipe with lock seams, which were the same as the CPFD spec- more stringent detailing could be adopted for SDC B design as imen. A comparison of the overall CPLD and CPFD specimen required. details is also presented in Table 2.1. Table 2.2 summarizes the significant differences in SDC D and SDC B design and detail- Hybrid Specimens ing provisions. Significant joint reinforcement, including transverse (hoop) reinforcement, is required for SDC D but Lateral performance of hybrid systems differs from CIP and not for SDC B (17). The same pipe size and thickness were emulative systems due to the presence of unbonded post- used for the CPLD and CPFD specimens to allow a direct tensioning and reinforcement. The prototype bridge served as comparison of specimens. The pipe thickness was not consid- the basis for the design of the CIP and emulative systems; how- ered excessive and was the minimum size readily available for ever, differences in the design were required for the hybrid sys- construction. tems. To achieve a somewhat comparable lateral response, the Table 2.1 reveals important differences that were intention- hybrid specimens were designed to have similar lateral force ally incorporated into the CPLD joint detailing to severely chal- resistance when compared to the CIP specimen at a 1.0% lenge the limited ductility specimen, in accordance with the drift ratio. However, during the erection of the conventional intent and provisions of the 2006 LRFD RSGS for SDC B: hybrid specimen, the actual anchor set losses for the post- (1) elimination of the construction stirrups within the joint tensioning were significantly less than expected, resulting in a region, (2) elimination of all joint-related stirrups and horizon- greater effective post-tensioning force. This increase in effec- tal ties (Asjh, Asjv) placed external to the CPFD joint, and (3) elim- tive post-tensioning resulted in an appreciably greater lateral ination of the extra hoop at each end of the pipe (2). Table 2.1 resistance as compared to the CIP and emulative specimens. also reveals that bent cap flexural reinforcement was reduced Detailed descriptions of the performance objectives, design to eliminate potential strengthening of the joint due to higher methodology theory, and specimen designs for all three spec- bent cap flexural strength (and thus to allow potential yielding imens are highlighted in the attachments to this report as well of flexural reinforcement adjacent to and within the joint) and as by Tobolski (5). Complete design drawings for the hybrid to provide more accurate prototype scaling. In addition, bent specimens are provided as an attachment to this report. Each hybrid detail uses half of the conventional reinforcement as cap transverse reinforcement, including that adjacent to the compared to the CIP and emulative specimens connected to joint, was based on shear developed within the bent cap due to the bent cap using a grouted duct connection with a grouted forces associated with plastic hinging of the column, not a joint bedding layer joint dimension of 1 in. force transfer mechanism. These modifications were imple- The conventional hybrid specimen used closely spaced mented despite the possibility that principal tensile stresses in spiral reinforcement at the column end to provide lateral the joint could exceed the 2006 LRFD RSGS limit of 3.5 fc , at confinement of the concrete compression toe. The flexural which the additional joint reinforcement is required (2). Thus, reinforcement in the column extended full height and was

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14 Table 2.2. Design and detailing provisions--SDC D versus SDC B. NCHRP Project SDC D (Full Ductility) SDC B (Limited Ductility) 20-7/Task 193 Criteria Force Demands The lesser of the forces Based on forces resulting from the (8.3.2, 8.3.3) resulting from the overstrength overstrength plastic hinging moment plastic hinging moment capacity or the maximum connection capacity or unreduced elastic capacity following the capacity design seismic forces in columns or principles specified in Article 4.11.* pier walls. Ductility Demands The local displacement ductility demands, (8.3.4) D, of members shall be determined based on the analysis method adopted in Section 5. The local displacement ductility demand N/A shall not exceed the maximum allowable displacement ductilities established in Article 4.9. Column Shear Based on the force, Vpo, associated with the Based on the lesser of (1) force Demand, Vu overstrength moment, Mpo, defined in obtained from an elastic linear (8.6.1) Article 8.5 and outlined in Article 4.11. analysis and (2) force, Vpo, for plastic hinging of the column including an overstrength factor Concrete Shear Using concrete shear stress for circular Using concrete shear stress for Capacity (8.6.2) columns with hoops, modified by: circular columns with hoops, ' modified by: ' where is 6 (multicolumn bent) or lower inside plastic hinging region, per Eq. 4.9-5 where is 2 Minimum Column Shear Reinforcement (Spiral) (8.6.5) Minimum Longitudinal , Columns , Columns Reinforcement (8.8.2) Splicing of Longitudinal , Columns , Columns Reinforcement in Columns (8.8.2) Minimum Longitudinal Outside plastic hinging region N/A Reinforcement (8.8.3) Minimum Development , not to be reduced; Length into Cap N/A** extended as close as practically possible to Beams (8.8.4) opposite face Anchorage of Increased by 20% for a two-bar bundle and N/A Bundled Bars into 50% for a three-bar bundle. Four-bar Cap Beams (8.8.5) bundles are not permitted in ductile elements. Maximum Bar Diameter (8.8.6) N/A Lateral Butt-welded hoops or spirals Reinforcement Inside Plastic N/A Hinge Region (8.8.7) Lateral Volumetric ratio shall not be less than 50% Reinforcement of that determined in 8.8.7 and 8.6. Outside Plastic Reinforcement shall be of the same type. Hinge Region Lateral reinforcement shall extend into N/A (8.8.8) bent caps a distance that is as far as is practical and adequate to develop the reinforcement for development of plastic hinge mechanisms.

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15 Table 2.2. (Continued). NCHRP Project SDC D (Full Ductility) SDC B (Limited Ductility) 20-7/Task 193 Criteria Requirements for Various detailing requirements. Lateral N/A Reinforcement (8.8.9) Capacity Capacity-protected members such as bent Protection caps shall be designed to remain essentially Requirements (8.9) elastic when the plastic hinge reaches its overstrength moment capacity, Mpo. The N/A expected nominal capacity is used in establishing the capacity of essentially elastic members. Superstructure For longitudinal direction, the Capacity Design superstructure shall be designed as a (8.10, 8.11) capacity-protected member. For transverse direction, integral bent caps shall be designed as an essentially elastic member. Longitudinal flexural bent cap beam N/A reinforcement shall be continuous. Splicing of reinforcement shall, at a minimum, be accomplished using mechanical couplers capable of developing 125% of the expected yield strength, fye, of the reinforcing bars. Superstructure For superstructure to substructure Design for Non- connections not intended to fuse, provide a Integral Bent Cap lateral force transfer mechanism at the (8.12) interface. For connections intended to fuse, minimum lateral force at interface shall be 0.40 times the dead load reaction plus the N/A overstrength shear key(s) capacity. Non- integral cap beams supporting superstructures with expansion joints at the cap shall have sufficient support length to prevent unseating. Joint Design (8.13) Major joint design and detailing provisions, such as bent cap width, joint shear reinforcement (vertical stirrups inside and outside the joint, and horizontal cross N/A ties/J-bars), transverse joint reinforcement, additional bent cap longitudinal reinforcement, and side face reinforcement. *Articles, sections, and equation numbers cited in Table 2.2 refer to 2007 LRFD PSGS (17 ). **AASHTO LRFD Bridge Design Specifications (3) provisions (i.e., 5.10.11.4.3), in contrast to NCHRP Project 20-7/Task 193 provisions, require even longer lengths for column bar extension into joint. locally debonded across the bedding layer to facilitate dis- was intended to act as a stay-in-place form during fabrication tributed straining of the reinforcement. as well as to prevent the potential implosion of the concrete The concrete filled pipe hybrid specimen used a full height, section during large compressive strains associated with lateral steel shell that provided enhanced confinement at the column response. Similar to the concrete filled pipe specimen, the rein- end. The flexural reinforcement extending from the bent cap forcement extending from the bent cap into the column was into the column terminated after a given distance required for terminated following adequate development. development in the column. After the termination of the rein- The three bent caps for the hybrid specimens were identi- forcement, the shell, concrete, and unbonded post-tensioning cal and were designed in accordance with the 2006 LRFD were the only elements in the column. Similar to the conven- RSGS (2). This design and detailing considered the various tional specimen, the reinforcement was locally debonded increases in reinforcement required in the joint as well as the across the joint to prevent premature reinforcement fracture. flexural reinforcement in the bent cap. Joint shear design was The dual shell hybrid specimen used a full height exterior performed considering only the area of flexural steel when steel shell that provided confinement at the column end. To determining the required joint shear reinforcement. form the interior void, a corrugated metal pipe that was in con- During early discussions with the NCHRP Project 12-74 formance with ASTM A760 was used (24). This interior pipe panel, the decision was made to use stainless steel reinforcement

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16 strain capacity as A706 steel, indicating significantly greater material ductility and energy dissipation capacity. The effective yield for the two steel grades was similar with a slightly greater ultimate tension capacity observed for the 316LN steel. In addition to uniaxial tension testing, a series of cyclic rebar tests were conducted. Figure 2.5a depicts the cyclic response of the two rebar specimens that were tested with an unbraced length equal to six times the bar diameter. The bars were loaded to a compression strain equal to approximately one-third of the previously reached tension strain. From Figure 2.5, it is apparent that the A706 and 316LN reinforcing bars have sim- ilar cyclic response for realistic free lengths. This indicates that commonly accepted relationships for steel reinforcement Figure 2.4. Comparison of A706 and 316LN uniaxial may be acceptable for the use of stainless steel reinforcement. tension response (5). Further study is needed to fully investigate the potential seis- mic implications of using stainless steel reinforcement. across the joint for the experimental specimens. The reason- Figure 2.5b provides the complete cyclic stress-strain ing for this decision relates to the localized crack in the hybrid response of the two reinforcing bars. From this figure, it is system at nominal yield as opposed to the distributed cracking apparent that the 316LN reinforcing bar has significantly in a conventional CIP column. The extent of cracking at the greater ultimate tension strain capacity. The recording of bedding layer is highly localized due to the intention debond- strain was terminated at the last point on the 316LN plot due ing across the joint. This will result in slightly larger crack to the limits of the recording instrumentation. widths at the nominal yield point. The use of stainless steel reinforcement locally across the joint serves to provide added 2.2.2 Fabrication and Assembly comfort in the durability of these systems during their expected of Nonintegral Specimens service life. To consider the potential influence of stainless steel reinforcement, a variety of material tests were conducted. All nonintegral emulative specimens were fabricated at the Figure 2.4 provides a summary of a series of uniaxial tension precast yard of Clark Pacific (West Sacramento, California). tests conducted on No. 5 reinforcement for A706 steel and Precast bent cap and column segments were then assembled at 316LN stainless steel. These results indicate that the stainless California State University--Sacramento (CSUS). The fabrica- steel reinforcement has more than three times the uniform tion and assembly of the precast specimens replicated as much (a) (b) Figure 2.5. Comparison of A706 and 316LN cyclic stress-strain to (a) 3% strain and (b) failure (5).

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17 Figure 2.6. Lowering bent cap rebar cage into elevated formwork--CIP. Figure 2.7. Bent cap rebar cage in form during as possible the expected field process so constructability issues fabrication--CIP. could be examined. The construction sequence for precast specimens included the following: cap by at least 500 psi to ensure the connection grout was not 1. Fabricate rebar cages for the bent cap and column at CSUS. a weak link in the system. A hand pump system and collar 2. Transport rebar cages to Clark Pacific, prepare bent cap were used for grouting the bedding layer and ducts. Grout and column forms, and cast bent cap and column concrete. was pumped from the bottom of the bedding layer up into 3. Transport precast cap and column to CSUS. the ducts, and an air vent system at the top of the bedding 4. Prepare column and bent cap for assembly and conduct layer helped prevent air entrapment within the connection. cap setting operation in upright position. Fluidity of grout was determined before grouting using a flow 5. Prepare connection. For grouted duct connection, pump cone test in accordance with ASTM C939-02 (27). After the grout into the bedding layer to fill the bedding layer and bedding layer form was attached and sealed, the bedding layer ducts. For cap pocket connections, fill pocket and bedding layer with concrete from top of cap. 6. Invert specimen and install in test area. The following sections provide a brief summary and select photos of the specimen fabrication. Further details are pro- vided by Matsumoto (21, 22, 23, 26). Cast-in-Place Specimen Fabrication of the CIP specimen required building special elevated forms for casting the bent cap on top of the column (see Figure 2.6 and Figure 2.7), as well as inverting the entire T-shaped specimen in the yard for transportation. The speci- men was fabricated accurately according to the drawings. Grouted Duct Specimen Figures 2.8 through 2.12 show the bent cap rebar cage, cap setting operation, and grouting of the GD specimen. Grout Figure 2.8. Bent cap rebar cage in form during compressive strength was designed to exceed that of the bent fabrication--GD.

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18 dam at the top and bottom of the corrugated pipe and a column bar template were useful to form the cap pocket void full height of the bent cap, as the pipe is placed only between the top and bottom of the longitudinal rebar (see Figure 2.13b). Figure 2.14 shows concreting of the CPFD pocket. Fabrication and assem- bly operations for the CPLD and CPFD were the same. Concrete was placed in the pocket and bedding layer using a bucket at the top of the pocket. Concrete was cast into the pocket around the bent cap longitudinal reinforcement from above, and a collar with an air vent system was used to help remove entrapped air at the bedding layer. The concrete mix was selected to be close to that used for the bent cap and col- umn, with the intention of achieving a strength and stiffness at least 500 psi greater than that of the bent cap, ensuring that the connection would not be the weak link in the system. After the bedding layer form was attached and sealed (see Figure 2.15), Figure 2.9. Joint region of bent cap during the bedding layer was prewatered to ensure sealing and to pre- fabrication--GD. vent loss of moisture from the pocket concrete. Buckets were used to fill the pocket with concrete in several layers with was prewatered to ensure sealing and prevent loss of moisture vibration. Once concrete flowed through the air vents in the from the grout. After mixing the grout using a paddle-type bedding layer, the vents were sealed. After hardening, curing mortar mixer, grout with a flow cone efflux time of 20 to compound was applied to the top surface. After the bedding 30 sec was pumped into the connection. After grout flowed layer form was removed, the bedding layer and top of the pipe through air vents in the bedding layer, the vents were sealed. were inspected. Grout was added manually to top off each duct. After the The first column hoop below the top of the CPFD column grout cured several days, the bedding layer form was removed was placed approximately 2 in below its intended location dur- and the bedding layer and the top of the ducts were inspected. ing fabrication. This reduced the overall drift to some extent, but did not affect the maximum load induced in the joint. Cap Pocket Specimen Conventional Hybrid Specimen Figure 2.13 compares the bent cap rebar cage for the CPFD and CPLD specimens. The significant reduction of joint re- Figures 2.16 through 2.19 show the rebar cage, cap set- inforcement for the CPLD specimen is evident. A Sonotube ting operation, grouting, and post-tensioning of the con- Figure 2.10. Cap placement during and after cap setting operation--GD.

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19 Figure 2.11. Mixing and pumping of grout--GD. Figure 2.12. Topping off ducts with grout and cap top post-grouting--GD. ventional hybrid specimen. Unlike the emulative grouted Concrete Filled Pipe Hybrid Specimen duct specimen, the grouting of the bedding layer and ducts for this specimen were performed by pumping the grout in The reinforcing cage and details of the bent cap for the con- from the top. The grout tube was inserted into a corrugated crete filled pipe and dual shell specimens are the same as those duct extending near the bottom of the bedding layer. As the presented in Figure 2.16 for the conventional hybrid specimen. grout filled the bedding layer, the grout tube was slowly A view down the inside of the column prior to casting is shown extracted from the corrugated duct. The hydraulic head in Figure 2.20. In this figure, the installed curvature gages are pressure of the column of grout in the one duct was used apparent. Also in this photo, weld beads on the inside of the to fill the remaining ducts with some head loss. Similar to column can be observed. These weld beads were placed inside the grouted duct connection, each duct was then topped the column shell to promote reliable transfer of reinforcement off in a way similar to what is shown in Figure 2.12. Once tensile forces into the shell. The erection of this specimen was the grout had adequate time to cure, the column and bent cap same as the erection of the conventional specimen. The bedding assembly was post-tensioned, inverted, and installed in the layer form used during casting can be seen in Figure 2.21. testing frame. During the casting of the bedding layer for this specimen, minor

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22 Figure 2.17. Bent cap setting operation--HYB1. column. A top view of the column after casting is shown in Figure 2.23. From this figure, the internal corrugated metal pipe is observed with a polyvinyl chloride (PVC) pipe in the center for threading of column post-tensioning. This PVC pipe was used to ensure the easy threading of tendons from anchorage to anchorage. For corrosion purposes, this PVC pipe can be grouted following stressing to prevent moisture from reaching the tendon during its service life. This grout- ing will not affect the unbonded nature of the tendon because Figure 2.19. Post-tensioning operation--HYB1. the bond between the grout and PVC will break easily. 2.2.3 Nonintegral Testing Protocol and Instrumentation Emulative Specimens The specimen test setup, shown in Figure 2.24, included a simply supported inverted bent cap that allowed accurate Figure 2.18. Bedding layer and corrugated duct Figure 2.20. View inside steel shell showing weld grouting operation--HYB1. beads--HYB2.

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23 Figure 2.21. Bedding layer form--HYB2. establishment of specimen forces. The test setup ensured accu- rate conditions at each end of the joint so that the force trans- Figure 2.23. Top view of column after casting--HYB3. fer mechanism in the joint could be investigated (15, 28). The specimen was tested in inverted position with a column stub imen dropped below 30% of the maximum load: 1, 1.5, 2, that allowed biaxial loading of the specimen using a vertical 3, 4, 6, 8, and 10. hydraulic actuator to apply scaled gravity load and a horizon- Figure 2.24b shows the external gages, including linear and tal hydraulic actuator to induce seismic response. As required, string potentiometers and linear variable differential trans- different axial force conditions in the bent cap were produced formers (LVDTs), mounted on the column, joint, and bent for the push and pull directions. cap. Internal strain gages were placed on bent cap, joint, and Force control and displacement control sequences were column reinforcing bars, as well as on corrugated ducts or pipe. applied to all specimens, similar to the force and control In addition to the approximately 100 channels of data, speci- sequences shown in Figure 2.25 and Figure 2.26. Force control men response was also monitored using digital photos, crack loading was used for an approximate determination of first markings and measurements, video recording, and notes. yield of column longitudinal bars in the push and pull direc- tions, establishment of effective yield, and application of the Hybrid Specimens displacement control sequence including quasi-static displace- ment in three cycles. Nominal displacement ductility demand, The test setup for the hybrid specimens is shown in Fig- as multiples of system effective yield displacement, was applied ure 2.27. As shown in previous images, the hybrid specimens at the following levels, or until the residual capacity of the spec- were constructed in an upright condition and then inverted for installation in the test setup. The vertical actuator was set to apply a constant load during testing to simulate gravity load- ing. This force varied between hybrid specimens in order to try and match the lateral response of the three hybrid tests. The horizontal actuator was actively controlled to apply specified forces or displacements during testing. The initial stage of loading consisted of force controlled loading protocols, which apply positive and negative lateral forces of increasing magnitude until the first yield of the extreme mild reinforcing bar is reached. This force control protocol is shown in Figure 2.28. Each force loading cycle was repeated three times in both directions. Following the first yield of the system, the lateral loading was applied to a speci- fied lateral drift ratio. The basic loading protocol is shown in Figure 2.29. At each cycle to a given drift ratio, the column was subjected to two cycles in both directions followed by one Figure 2.22. View down dual shell prior to casting cycle to the previous lateral drift. This protocol was developed with rebar--HYB3. to help accurately calibrate nonlinear models of the system.

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24 (a) Schematic VERTICAL ACTUATOR HORIZONTAL ACTUATOR COLUMN DISPLACEMENT COLUMN COLUMN CURVATURE CURVATURE (SOUTH) (NORTH) PANEL DEFORMATION CAP CAP ROTATION ROTATION (b) Specimen in Test Bay with External Instrumentation Shown--GD Figure 2.24. Test setup for emulative specimens.

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25 50 40 30 20 Applied Force (kips) 10 0 -10 -20 -30 Note: Vertical Force held -40 constant at 38 kips -50 0 1 2 3 4 Cycles Figure 2.25. Representative force controlled sequence for emulative specimens. 8 5.5 7 4.8 6 4.1 5 3.4 4 2.8 Displacement Ductility, 3 2.1 2 1.4 Drift Ratio (%) 1 0.7 0 0.0 -1 -0.7 -2 -1.4 -3 -2.1 -4 -2.8 -5 -3.4 -6 Note: Vertical Force held -4.1 constant at 38 kips. -7 -4.8 -8 -5.5 0 3 6 9 12 15 18 21 Cycles Figure 2.26. Representative displacement controlled sequence for emulative specimens.

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26 60 40 20 Force, kips 0 -20 -40 -60 0 1 2 3 4 5 6 7 8 9 Cycle Figure 2.28. Representative hybrid force controlled Figure 2.27. Test setup for hybrid specimens. loading protocol. External instrumentation mounted on the specimens is used. The 74-in deep Washington DOT post-tensioning beam shown in Figure 2.30. Instrumentation consisted of linear was selected using recommended span limits published for potentiometers and inclinometers for measuring and isolating these girders. This girder section was selected over a bulb-tee various modes of deformation in the member. In addition to due to the increased bottom flange area desirable for nega- the external instrumentation, many internal strain gages were tive flexural demands at the bent cap. The design was refined employed to capture the local response of materials. through the application of LRFD design requirements, as needed. To minimize the neutral axis depth, a design 28-day compressive strength of 9 ksi was used for the prototype 2.2.4 Design of Integral Prototype structure. Bridge and Specimen Post-tensioning in the girders was designed so that the ulti- An overall elevation of the prototype bridge is shown in mate, extreme event and service limit states were satisfied. The Figure 2.31 with the connection detail shown in Figure 2.32. design of the post-tensioning was governed by the Strength I The design of the prototype bridge was completed in accor- limit state with the seismic demands of a similar magnitude. dance with the AASHTO LRFD Bridge Design Specifications Two stages of post-tensioning were specified, with the first (29) and the 2009 LRFD SGS (1). stage occurring prior to the deck casting and the second stage The selection of initial member sizing was based on conven- occurring after the deck casting. Service level performance of tional design practices and span range tables for girder systems the structure was considered in the prototype design through 10% 6% Drift Ratio 2% -2% -6% -10% 9 12 15 18 21 24 27 30 33 Cycle Figure 2.29. Representative hybrid displacement controlled loading protocol.

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27 Figure 2.30. Representative hybrid external instrumentation (HYB1 shown). Figure 2.31. Portion of integral prototype bridge. Figure 2.32. Girder to bent cap prototype connection detail.

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28 a construction staging analysis explicitly considering the devel- cap. For the prototype design, these hinges were based on opment of stresses in the system at various stages. moment-curvature analyses of the superstructure and an For seismic design, the prototype bridge was considered assumed equivalent plastic hinge length. The original design nonessential and designed to meet life safety requirements as considered an effective hinge length to be 1 ft; however, a more defined by the 2009 LRFD SGS (1). The specified mechanism realistic length is approximately one-half of the structure of inelastic deformation in the longitudinal direction consists depth. It is expected that allowing the superstructure joint to of flexural plastic hinge formation at both the tops and bottoms hinge will result in a redistribution of seismic moment demand of columns and knock off backwalls. Additionally, the super- due to the reduction in stiffness following hinging. The proto- structure to bent cap joint was allowed to open during seismic type design resulted in seismic moment redistribution of excitations as long as the response was essentially elastic. The approximately 20%. The observed response from analysis indi- transverse mechanism involved the development of flexural cated that the system is expected to respond in an essentially plastic hinging at both the tops and bottoms of columns and elastic manner. shearing of sacrificial shear keys at the abutments. In the longitudinal direction, the displacement capacity The design ARS was developed in accordance with the 2006 determined via pushover analysis is 11.0 in, which results in a LRFD RSGS (2). The ARS curve incorporated 5% damping demand-to-capacity ratio of 0.62. The results of the longi- and was developed using a 1-sec acceleration of 0.80 g, a 0.2-sec tudinal pushover analysis indicated that positive joint open- acceleration of 1.50 g, and site coefficients for Site Class D soil. ing is expected, but without appreciable rotation demand. The resulting peak rock acceleration for the prototype design The response of the joint is classified as essentially elastic for the study site was 0.60 g. The input seismic demand and site because the calculated rotations are only slightly greater classification resulted in a bridge subject to SDC D require- than the elastic rotation. For the transverse displacement ments. This ARS curve is representative of a site located in a capacity, overturning effects were considered in determining high seismic region such as Southern California. The imposed the column inelastic response. The transverse displacement demand levels required a seismic demand analysis, displace- capacity determined via pushover analysis was 10.6 in, which ment capacity analysis with pushover, capacity design provi- results in a demand-to-capacity ratio of 0.71. Ductility demands sions, and SDC D detailing. Due to the assumed site location, for both directions were approximately 5, well below the limit the bridge was considered located within 6 miles of a fault. of 8 for multicolumn bent caps. Therefore, vertical ground motion with a magnitude of 0.80 g Capacity design principles were applied to the design of the of vertical excitation was considered. superstructure to ensure that the seismic overstrength demands The structural system was modeled in the computer analysis could be resisted in a nominally elastic manner. Column program SAP2000 for service, strength, and seismic design. transverse reinforcement was designed based on overstrength Modeling procedures for seismic analysis were performed demands imposed by transverse response. Flexural and shear based on provisions of the 2009 LRFD SGS (1). Effective sec- demands on the cap beam were based on the demands devel- tion properties were modeled to accommodate the expected oped with flexural hinging of the columns at overstrength dynamic behavior of the bridge system, including column demands. Design of bent cap reinforcement was based on over- inelasticity. Dynamic analyses indicated that the dominant strength demands in addition to the longitudinal and trans- transverse period of vibration is equal to 0.73 sec and the verse force-transfer mechanisms assumed in the AASHTO dominant longitudinal period of vibration is equal to 0.69 sec. LRFD Bridge Design Specifications (3). The longitudinal analysis considered the effects of the backwall The main goal of the experimental effort was to determine stiffness in accordance with the provisions of the 2009 LRFD the response of the girder to bent cap joint when subjected to SGS. The resulting displacement demands in the longitudinal simulated seismic demands. To satisfy this goal, a portion of and transverse directions were 6.8 in and 7.5 in, respectively. the prototype structure was extracted for experimental testing. In order to determine the displacement capacity of the sys- The test specimen selected for testing consisted of a girder, deck, tem, an inertial pushover analysis was conducted in both the and reaction block. This specimen was based on an extracted longitudinal and transverse directions. In the longitudinal portion of the prototype bridge, as shown in Figure 2.33. The direction, the bent cap to girder joint was allowed to open scaled length of the girder used in the experimental program during seismic excitation. This decision was made based on was 31 ft, which is representative of 0.46 times the central extensive discussions with the research team and project panel. span length. It was decided that allowing the bridge to flex and open at the The bent cap was represented by a large reaction block in joint was acceptable as long as the joint responded in an essen- the testing of the specimen. The flexibility of the bent cap can tially elastic manner. be neglected in experimental efforts as the deformation from To consider the potential joint opening, a superstructure this member can be considered in analytical modeling. The moment-rotation hinge was modeled at the face of the bent extracted portion of the prototype bridge provides sufficient

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29 Figure 2.34. Girder reinforcing cage. nificant access for pencil vibrators in the duct. To ensure that adequate consolidation would be achieved during fabrication, a form vibrator was used in regions with limited pencil vibrator access. In addition, a superplasticized concrete mix was used to enhance flowability during casting. Concrete for the girder and reaction block was cast using a Figure 2.33. Test specimen representation-- bucket attached to the overhead crane in the laboratory. The post-tensioned integral specimen (INT). girder was cast first to ensure that the maximum flowability of the concrete mixture was obtained during the casting of information regarding the moment-rotation response of the the member with limited vibrator access. During casting of the joint and shear transfer across the joint. These two items are girder, an external form vibrator was attached to the form- the major unknowns in the performance of this integral work near the location at which concrete was being poured. bridge detail. This vibrator was moved around the formwork as concrete was placed in different locations and was used on both sides of the formwork. At the end regions, where more sufficient 2.2.5 Fabrication and Assembly vibrator access was provided, traditional pencil vibrators of Integral Specimen were used. The integral test specimen was fabricated and constructed The girder and reaction block were cast and allowed to at the University of California--San Diego (UCSD) Charles Lee harden until the girder had strength greater than 3 ksi. Inspec- Powell Structural Systems Laboratory. Labor for construction tion of the girder after form removal indicated only one region activities was provided by a combination of subcontracted of minor concrete segregation over a small portion of the bot- construction firms and lab staff. A local steel fabrication tom flange of the girder (approximately 4 in. in length). This company performed the majority of construction activities region was patched by lab staff following placement on tempo- related to fabrication of the steel reinforcement cages. A local rary supports. The girder was moved away from the reaction construction company experienced in bridge construction block to facilitate the construction of two temporary support performed the majority of construction activities related to towers. Following the completion of these towers, the girder building formwork. All post-tensioning activities were per- was lifted and placed on the towers in line with the reaction formed by a post-tensioning manufacturer and contractor. block (see Figure 2.35). The girder was leveled on the temporary Lab staff performed the casting of concrete and all activities supports and subsequently secured using chains to provide related to erection of members. stability during construction activities. The first stage of fabrication consisted of the construction The girder was placed to maintain an approximate 1-in clo- of the reinforcing cages for the girder and reaction block. sure joint between the reaction block and girder. This joint can The girder reinforcing cage can be seen in Figure 2.34 with the be seen in Figure 2.36. Additionally, the alignment was checked post-tensioning ducts installed and the cage installed in the to ensure the post-tensioning ducts were properly aligned. The formwork. The scaling of this specimen did not provide sig- careful activities carried out during the placement of the

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30 grouting). The edges of the formwork were sealed using a com- mercially available sealant and allowed to set prior to grouting. Grout material was mixed on the laboratory floor and lifted onto the top of the specimen. The grout was then gravity fed into the closure joint, as shown in Figure 2.37. The grout material was Masterflow 928 high-strength, non-shrink grout containing a 0.2% volume fraction of polypropylene fibers. This grout matrix was mixed to be flowable based on manu- facturer's recommended water content and considering the Figure 2.35. Girder on falsework prior to grouting presence of the fibers. The relatively low volume fraction of closure joint. fibers did not greatly affect the flowability of the matrix. No noticeable leakage was observed during the grouting activities. The grouting activities were completed without any observed girder resulted in a system in which the post-tensioning ducts complications. and closure joint were properly aligned with no noticeable Formwork was removed from the girder the following day. variations. The post-tensioning ducts were then jointed using Observations after removal of the formwork indicated no industrial adhesive tape, which was applied by hand. The scaled observable voids in the closure joint and overall a very success- specimen made the joining of these ducts slightly cumbersome, ful grouting operation. The grout was allowed to cure for 3 days as hand access was tight. However, the splicing of these ducts prior to the first stage post-tensioning. The first portion of the was performed without any major complications. post-tensioning operation consisted of setting the wedges for The girder formwork was modified and reused as the closure the bottom tendons. Each strand was stressed to approximately joint formwork by drilling new holes in the form and reusing 5% guaranteed ultimate tensile strength (GUTS) to allow for the original form tie holes in the girder. After installation of the sufficient seating of the wedge on the live end. The middle ten- side forms, the bottom of the joint was closed using a single don was then stressed to a target stress of 75% GUTS. Each piece of plywood. A drain hole was placed in the bottom of the strand was individually stressed using a monostrand jack. form to allow for draining of excess water (water is used to Both the bottom and middle ducts were then grouted using moisten the faces of the reaction block and girder prior to SikaGrout 300PT. Following 2 days of curing in the post- (a) (b) Figure 2.36. Girder post-tensioning duct (a) prior to splicing and (b) after splicing.

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31 The top post-tensioning tendon was stressed following the casting and curing of the deck. This tendon was stressed to 75% GUTS, similar to the middle tendon. Additionally, each strand in the tendon was individually stressed using a monostrand jack. Following post-tensioning, the duct was grouted using SikaGrout 300PT and allowed to cure. The specimen was then painted white to aid in the identification of cracking during testing. Loading frames and external instrumentation were subsequently installed on the specimen, in addition to the installation of vertical actuators in preparation of testing. 2.2.6 Integral Specimen Testing Protocol and Instrumentation The general testing system is shown in Figure 2.39. From Figure 2.37. Grouting of girder to reaction block this figure, the nomenclature for actuator reference and plan closure joint. location reference can be observed. For the integral testing protocol, the first stage of loading consisted of relieving the reaction from the temporary support tensioning grout, the temporary support near the reaction installed between Actuator 1 and Actuator 2. The goal of this block was removed, simulating the removal of the strong back stage was to relieve the reaction while minimizing the associ- in the prototype structure. The post-tensioning force in the ated displacement. Actuators 2 and 3 were set to force control middle tendon at this stage provides a sufficient shear friction with zero force. Actuator 1 was controlled in manual displace- mechanism in the system for casting of the deck and associated ment control and applied upward displacements until the load construction activities. on the temporary support tower was relieved. Formwork for the reinforced concrete deck was constructed The next stage of loading was designed to apply the simu- to react off the girder, as is customary in precast concrete lated dead loading. Actuator 1 was controlled in displacement bridge construction (see Figure 2.38). The construction of the control and applied upward displacements until a specified deck formwork utilized the existing holes in the girder from the force was reached. Actuators 2 and 3 were slaved to Actuator 1 form ties to secure the forms in place. With the formwork in in force control to apply moment and shear profiles as shown place, the deck reinforcing cage was fabricated. Similar to cast- in the prototype specimen section. ing of the deck and reaction block, the deck was cast using a For all additional stages, Actuator 1 was controlled in dis- bucket attached to the overhead crane. The deck formwork was placement until either a specified force or joint rotation limit removed after the minimum uniaxial compressive strength of was reached. A modified equation relating the force in the deck concrete was 3 ksi. Actuators 2 and 3 to the force in Actuator 1 was used. This new Figure 2.38. Construction of concrete deck reacting off girder. Figure 2.39. Integral specimen loading system.

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32 loading equation is based on the seismic flexural and shear apparent during testing that these calculated rotations were demand profiles determined via lateral analysis of the proto- not correct during increasing displacements due to cracking type structure. at potentiometer target supports and spalling of concrete. Following the application of the simulated dead loading, The actual achieved rotations were reassessed based on more 100 cycles of essentially elastic loading were imposed on the reliable inclinometer readings, which better match the observed system primarily in the negative flexural direction. This load- rotations during testing. The actual loading protocol used ing was meant to allow investigation of the potential response during the seismic cycle is shown in Figure 2.40. As a main of the system in service and ultimate loading. The system was goal of large joint rotation cycles is to determine the overall loaded initially in the negative flexural direction until the rotation capacity of the connection due to relative settlement system was nearing the expected limit of proportionality. potential, a reversed cyclic loading protocol, which produces a Following this, the system was loaded to 90% of the initial highly sever case, was used. This is because relative settlement dead load demand. This was repeated for 100 cycles in contin- demands on the connection will only occur in one loading uous operation. direction and not the reverse. This protocol probably caused The next stage of loading was simulated seismic demands. a reduction in the actual ultimate rotation capacity when The loading demands generated for the seismic stage were subjected to loading in a single direction. Another driving based on a combination of lateral seismic load demands and factor in the development of this testing protocol was the desire vertical seismic shear demand. The vertical seismic shear to determine the inelastic rotation response in the event of demand was held constant during all phases, with constant superstructure inelasticity. loading applied at the actuator nearest the joint. Flexural The test specimen was instrumented to capture the major moment and shear demands were based on scaled flexural response characteristics of the specimen when subjected to demands caused by simulated column overstrength demands. applied loadings. This instrumentation includes strain gages The simulated flexural demands impose flexural moments at mounted on rebar and post-tensioning and external gages the girder to reaction block interface that are applicable to mounted onto the specimen. vertical, lateral, or seismic settlement demands. The cyclic load- External instrumentation consists of linear potentiometers, ing is conservative for loadings generated by seismically string potentiometers, and inclinometers mounted on the induced settlement. Additionally, the additional shear demand exterior of the specimen. A summary of external instrumenta- applied at the joint is conservative for lateral loading scenarios. tion is shown in Figure 2.41. Linear potentiometers are placed This loading program was developed to conservatively encom- to capture opening of the joint, slip between the girder and pass the various potential loading cases. reaction block, and estimated rotation of the girder at the joint. The loading was controlled while operating Actuator 1 in String potentiometers are installed to capture the displacement displacement control set to hold when a specified joint rotation of the specimen at the actuator locations. Inclinometers are limit was reached. The rotation targets were initially specified installed to capture the rotation of the reaction block and girder using the linear potentiometers at the joint. However, it became at the joint. Strain gages were installed on deck longitudinal 1.25 0.75 Joint Rotation, rad * 100 0.25 -0.25 -0.75 -1.25 0 9 18 27 36 45 54 Cycle Figure 2.40. Integral specimen realized loading protocol.