Gustavo J. Parra-Montesinos

BEHAVIOR OF BIAXIALLY LOADED SLAB-COLUMN CONNECTIONS WITH SHEAR STUDS

Results are presented from four non-prestressed concrete slabcolumn connection subassemblies tested under simulated gravity and earthquake-type loading. Each specimen consisted of a largescale first-story interior slab-column connection reinforced with headed shear studs, loaded to a gravity-shear ratio of 50%, and subjected to biaxial lateral displacements. The slabs, which were nominally identical aside from the shear stud reinforcement design, had a flexural reinforcement ratio in the column strip, based on the effective depth, of 0.7%. Shear stud reinforcement in the test specimens varied in terms of amount and spacing, both between and within stud peripheral lines. All four specimens exhibited drift capacities significantly lower than shown by previous studies. Although the lateral strength of the specimens was governed by the flexural capacity of the slab, severe concrete degradation ultimately limited the drift capacity of the connections. Signs of punching-related damage were first observed during the cycle to 1.85% drift in each loading direction. Test results suggest that the minimum amount of shear reinforcement required in Section 21.13.6 of ACI 318-11 when neither a drift nor a combined shear-stress check is performed (vs ≥ 3.5√fc′, psi [0.29√fc′, MPa]) is adequate for connections subjected to a gravity shear ratio of up to 50% and resultant drifts from biaxial displacements of up to 2.0% if studs are spaced at less than 2d within the first two peripheral lines. For larger drift demands, a maximum stud spacing within the first three peripheral lines of 1.5d is recommended.

Field Tests of Two Prestressed-Concrete Girder Bridges for Live-Load Distribution and Moment Continuity

AbstractTwo similar bridges constructed with a live-load continuous connection were tested for live-load distribution and joint continuity. Girder distribution factors (GDFs) were compared with AASHTO equivalent values. For positive moments on all girders as for negative moments on interior girders, results using AASHTO equivalent GDFs were found to be generally conservative. However, for negative moments on exterior girders, test results exceeded AASHTO values, significantly so with two-lane results. GDF results were verified with a finite-element analysis (FEA) model, which produced behavior similar to the field tests. With respect to joint continuity, it is estimated that a simple span would produce a maximum positive moment about 7% higher than the actual structure, whereas a completely continuous structure would produce a maximum positive moment about 16% lower than that of the actual structure. For negative moments, the actual structure experienced about 28% of that of a continuous structure. Shear ...

Seismic Response of Fiber-Reinforced Concrete Coupled Walls

to high shear and deformation reversals. These effects are attributed to the post-cracking toughness of HPFRC in tension and its response in compression, which resembles that of well-confined concrete. However, there have been no tests of coupled HPFRC structural walls, for which the distribution of base shear stresses and wall deformations differ significantly from those in isolated slender walls. This paper presents a detailed comparison of the behavior of four-story RC and HPFRC coupled wall specimens, with an emphasis on deformations in the first story of the walls and in the coupling beams. RESEARCH SIGNIFICANCE Data from large-scale tests of coupled walls linked by RC and HPFRC coupling beams are presented. The testing program included the first HPFRC coupled wall test and one of few tests of large-scale T-shaped RC coupled walls. The results presented should be useful to researchers, designers, and code officials interested in the seismic performance and modeling of RC structures constructed with HPFRC. EXPERIMENTAL PROGRAM