Cast-in-Place Concrete Connections for Precast Deck Systems (2011) / Chapter Skim
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2 formwork such as steel or concrete panels, place deck reinforcement, cast deck concrete, and remove formwork if necessary. This project focused on systems that reduce the need to place and remove formwork thus accelerating on-site construction and improving safety.
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3 The following sections summarize the objective and list of tasks associated with the NCHRP 10-71 project, Cast-in-Place Concrete Connections for Precast Deck Systems.
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4 1.1.6. Task 6 – Execute the approved work plan for evaluation of the connections This task represented the bulk of the effort for this project during which the approved work plan was executed for the evaluation of the connections.
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5 Because of its similarity to slab-span bridge systems, the applicability of the AASHTO design provisions for slab-span systems were investigated in the study. The two primary considerations that distinguish PCSSS bridges from slab-span bridges are (1)
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6 The tests were evaluated in terms of load-deformation response, strain distribution, crack control, and strength.
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7 transverse joint specimens, respectively, and Chapter 14 presents a summary of the conclusions of the study. Appendix A contains the recommended design recommendations including suggested changes to the AASHTO LRFD Bridge Design code and commentary that were developed during the study, in accordance with Task 8.
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8 Chapter 2 PCSSS: Literature Review 2.0 Introduction to Literature Review The design and implementation of the experimental and numerical studies regarding precast composite slab span systems (PCSSS) associated with the NCHRP 10-71 project were completed after consideration of available previous research.
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9 Figure 2.1.1: Photograph of precast section used in Poutre Dalle System (Hagen, 2005)
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10 which was to observe early age behavior of bridge decks exposed to field conditions. The bridges selected for the study included three two-span continuous bridges, with equal spans of 76, 101, and 123 ft.
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11 Table 2.2.2: Characteristics of deck reinforcement in field investigation (Frosch et al., 2006) Bridge Type of Reinforcement Bar Size Longitudinal Reinforcement Spacing (in.)
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12 Table 2.2.3: Comparison of crack width statistics (Frosch et al., 2006) Crack Statistics SR 18 Thayer Rd AASHTO Purdue Number of Cracks (Total)
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13 Table 2.2.4: Range of variables considered in parametric study (Frosch et al., 2006) Variable Range Control Reinforcement Area (Bar Size)
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14 where fc is the concrete compressive strength at the initiation of cracking in psi (and the units of fc are in psi) , and ρg is the gross reinforcement ratio. The researchers plotted the average reinforcement stresses versus the ratio √fc / ρg, and found that a linear fit yielded a line with a slope of approximately 3, indicating that the average stress in the reinforcement bridging the crack was numerically determined to be about half of what would be expected if no slip occurred. The slip length utilized in the model was 2 in. Furthermore, the authors discovered that, on average, the reinforcement stresses increased by approximately a factor of two between the simulated initial and final shrinkage states, where the initial state was when cracking first occurred (6√fc)
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15 The calculation of the horizontal shear demand in a section can be completed using many different methods. The researchers investigated three of these methods: (1) global force equilibrium, (2)
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16 Table 2.3.1: Research parameters and specimen characteristics considered during the study (Naito et al., 2006) Beam Interface Finish Loading Method Interface Width (in.)
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17 Table 2.3.2: Horizontal shear stress at cracking (psi) during 5-point load tests (Naito et al., 2006)
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18 Table 2.3.3: Horizontal shear stress at ultimate (psi) during two-point load tests (Naito et al., 2006)
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19 d/4 from the end of the beam with the end stirrup placed as close to end of beam as practicable," where d is the effective depth. By 1969, the above requirements were not limited to just I-beams, and instead were made applicable to end zones of all pretensioned beams.
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20 vertical member height. Small spalling forces develop on the end face and a bursting force starts further into the member, as shown in Figure 2.4.1-a.
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21 tensioned experiments can provide conservative estimates of the spalling and bursting stresses in pretensioned members, because they simulate the case of a very short transfer length.
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