Chapter Skim View of:

Currently Skimming:

Pages 44-81

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 44... ... 45 Chapter 4 PCSSS Numerical Studies: Practical Span Ranges, Applicability of Design Recommendations, and Other Issues 4.0 Introduction and Organization A combined numerical and experimental approach was used to investigate issues associated with the development of design recommendations for the precast composite slab span system. In a few cases, where appropriate, design recommendations for the PCSSS were based on information obtained from the literature or previous studies conducted by the researchers (Smith et al. Read the entire page →
From page 45... ... 46 PCSSS bridges are very similar to slab-span systems, with two exceptions. First, the adjacent flanges of the precast inverted-Ts used to create the PCSSS bridges cause discontinuities in the system along the interface of the adjacent flanges; and second, the composite nature of the PCSSS requires additional design considerations. Read the entire page →
From page 46... ... 47 lengths, as well as the required prestress forces and to ensure that the compression and tension stress limits were satisfied in the inverted-T sections. Span lengths of 20, 30, 50, and 65 ft. Read the entire page →
From page 47... ... 48 stress of 202.5 ksi (75 percent of fpu) Read the entire page →
From page 48... ... 49 controlled by truck load capacities in transport or crane capacities at erection. For the truck load limits, the sections should be limited to 80 kips (350 kN) Read the entire page →
From page 49... ... 50 0.5 in. diameter strands. Read the entire page →
From page 50... ... 51 cross section. The transverse hooked bars were debonded for 1-1/2 in. Read the entire page →
From page 51... ... 52 Table 4.2.1: Summary of FEM runs to investigate effects of transverse hooked bar spacing Description Run Number 1 2 3 4 Run configuration PCSSS w/crack (6in. hook spacing, hooks lapped w/1in. Read the entire page →
From page 52... ... 53 for a physical bridge, so the method of leaving every other element void of rebar was used throughout the analyses. Figure 4.2.2: Crack opening in loaded span for 6 in. Read the entire page →
From page 53... ... 54 Figure 4.2.3: Maximum crack opening and transverse bar stress versus transverse hooked bar spacing in loaded span for load case 1 The effect of the spacing of the transverse hooked bars on transverse and longitudinal load distribution was also investigated during the parametric study. The transverse and longitudinal stress fields created by loading due to both load cases provided insight into the ability for each model to distribute the load throughout the structure. Read the entire page →
From page 58... ... 59 4.3. Parametric Study to Investigate Live-Load Distribution Factors for PCSSS The Interim 2010 AASHTO LRFD Design Specification provided design equations to determine the appropriate longitudinal moment demand for a given slab bridge system based on an effective lane width. Read the entire page →
From page 59... ... 60 Figure 4.3.1: Tandem loading located 2 ft. from midspan utilized for FEM live-load distribution study Read the entire page →
From page 60... ... 61 Figure 4.3.2: Panel and joint numbering used in the placement of tandem loading for the center span of the continuous models and the simple-span models Read the entire page →
From page 61... ... 62 Table 4.3.1: Summary of FEM runs to investigate longitudinal and transverse live-load distribution factors Description Run Number 1 2 3 4 5 6 7 8 9 Run configuration PCSSS w/ 3" crack PCSSS w/ 3" crack PCSSS w/ 3" crack PCSSS w/o crack PCSSS w/ 3" crack PCSSS w/ 3" crack PCSSS w/ 3" crack PCSSS w/o crack PCSSS w/ 15" crack Geometry Spans: 3 Single Single Single 3 Single Single Single Single #Panels wide 10 -- 4lane bridge (12 ft. lanes + 6 ft. Read the entire page →
From page 62... ... 63 In Runs 1, 2, 5, and 6 the CIP was bonded only to the sides and top of the panel webs while in Runs 3 and 7 the CIP was also bonded to the top of the precast flanges. In Runs 4 and 8 the system was assumed to be a monolithic slab with the discontinuity from the joint between the precast panels absent. Read the entire page →
From page 63... ... 64 was assumed to have progressed vertically to within 3 in. of the extreme compression fiber, as in run 9, the design effective lane widths provided by AASHTO (2010) Read the entire page →
From page 64... ... 65 Three load cases were considered for this portion of the study, outlined below. Each load case included a 35 kip load applied over a 12 by 12 in. Read the entire page →
From page 65... ... 66 Table 4.4.1: Summary of FEM runs to investigate performance of skewed PCSSS Description Run Number 1 2 3 4 5 6 7 8 Run configuration PCSSS w/ 3" crack - 0 skew PCSSS w/ 3" crack - 15 skew PCSSS w/ 3" crack - 30 skew PCSSS w/ 3" crack - 45 skew PCSSS w/o crack - 0 skew PCSSS w/o crack - 15 skew PCSSS w/o crack - 30 skew PCSSS w/o crack - 45 skew Geometry Spans: Single Single Single Single Single Single Single Single #Panels wide 3 panels /18ft.wide Same Same Same Same Same Same Same Length 30ft Same Same Same Same Same Same Same Skew Angle 0 deg 15 deg 30 deg 45 deg 0 deg 15 deg 30 deg 45 deg Depth of precast section 3in.flange; 12in. web Same Same Same Same Same Same Same Depth of deck above precast web 6in. Read the entire page →
From page 66... ... 67 Figure 4.4.2: Simply supported, three panel wide bridge and location of loading used for FEM models For all cases, the horizontal shear stress in the cast-in-place concrete was measured along the entire length and depth of the structure in the plane of the precast joint adjacent to the loading. The maximum horizontal shear stress in this plane was investigated for a range of skew angles for each of the load cases. Read the entire page →
From page 67... ... 68 The horizontal shear stress in the models considered with load case 1, which had load applied near the acute pier connection, was observed to be reduced with increasing skew angles for both the section with the 3 in. flange joint as well as the monolithic model. Read the entire page →
From page 68... ... 69 pretensioned member end regions. This specification remained virtually unchanged since its introduction until the 2008 interim AASHTO LRFD specification incorporated changes to the specification, which included a change in the terminology of the end zone stresses from "bursting" to "splitting" resistance of the pretensioned anchorage zones. Read the entire page →
From page 69... ... 70 Beam theory is not applicable in the end regions of prestressed concrete beams because the longitudinal strain is not linearly distributed through the depth of the cross section due to the introduction of the prestress force. Spalling stresses are a maximum at the end face of the member, typically near mid-height of the section and result in cracking at the end face which can propagate further into the member (Gergely et al., 1963) Read the entire page →
From page 70... ... 71 Figure 4.5.2: Validation of FEM model with experimental results from Gergely (1963) -1.0E-05 0.0E+00 1.0E-05 2.0E-05 3.0E-05 4.0E-05 5.0E-05 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Distance from End Face (in.) Read the entire page →
From page 71... ... 72 Table 4.5.1: Description of models run during parametric study Run # h (in.) Read the entire page →
From page 72... ... 73 over which bursting stresses act. As member height increases, the magnitude of the bursting forces increase and the length over which the bursting stress acts is increased slightly. Read the entire page →
From page 73... ... 74 Figure 4.5.4: Ratio of spalling force to prestress force as a function of ratio of eccentricity to precast member depth for linear and uniform bond stress distributions, with h= 12 in and Lt = 20 in. Table 4.5.2: Ratio of Spalling Forces to Prestress Forces as Predicted by FE Models for Slabs with Equivalent e/h as Feasible Precast Inverted Tee Sections, using both Uniform and Linear Bond Stress Distributions, varying h and e/h and constant Lt Depth of Precast (in.) Read the entire page →
From page 74... ... 75 Table 4.5.3. The vertical reinforcement in configurations 1 and 2 provided less than half of the 1.0 in.2 required by the AASHTO (2010) Read the entire page →
From page 75... ... 76 time of transfer, which was measured to have a compressive strength of 7410 psi at an age of 1 day (Smith et al., 2008) , was sufficient to resist vertical tensile stresses in the end zones regardless of the reinforcement details. Read the entire page →
From page 76... ... 77 an average between these two assumptions was developed, as shown in Figure 4.5.5. The equation for this straight line approximation is , (4.5.1) Read the entire page →
From page 77... ... 78 the tensile force found in Eqn. Read the entire page →
From page 78... ... 79 bridge were precast, and the elevation view is shown through one of the sections featuring a vent hole through the pile cap into which dowels were placed prior to casting the CIP concrete. As shown in the figure, the main bearing support was provided by a 6 in. Read the entire page →
From page 79... ... 80 between adjacent precast panels at continuous piers. Because the reinforcement is not provided to prevent cracking, and is simply to provide dowel action in the case of differential displacement between the superstructure and substructure, it may be acceptable to place the reinforcement as a group in the 24 in. Read the entire page →
From page 80... ... 81 Figure 4.7.1: Separation of top of precast joint from CIP concrete in 30 ft. continuous and laboratory bridge models Figure 4.7.2: Three span 30-30-30 ft. Read the entire page →
From page 81... ... 82 set to be 1/100 of the modulus of elasticity of the CIP used in the loaded span modeled with a 3 in. flange, effectively creating a simply-supported boundary condition at the end of the bridge connected to the adjacent span. Read the entire page →

From page 44...

... 45 Chapter 4 PCSSS Numerical Studies: Practical Span Ranges, Applicability of Design Recommendations, and Other Issues 4.0 Introduction and Organization A combined numerical and experimental approach was used to investigate issues associated with the development of design recommendations for the precast composite slab span system. In a few cases, where appropriate, design recommendations for the PCSSS were based on information obtained from the literature or previous studies conducted by the researchers (Smith et al.