Recently, the use of 700 MPa [101.5 ksi] rebars was permitted for the shear design of special walls in the current design code. In the present study, to investigate the effect of 700 MPa [101.5 ksi] reinforcement on the shear friction strength of RC walls, five wall specimens were tested under cyclic lateral loading. For the test parameters, interface roughness, vertical reinforcement ratio at boundary element, and use of flange wall (two flanges or single flange) were considered. The test results showed that the shear friction strength of walls with 700 MPa [101.5 ksi] rebars was greater than the ACI 318-19 shear friction strength. Particularly, in the wall with a low vertical reinforcement ratio (0.27%), the peak strength was greater than the shear friction strength corresponding to the actual high yield strength (700 MPa [101.5 ksi]) of vertical rebars. Further, the vertical rebars in the flange wall significantly increased the shear friction strength. The current ACI 318-19 design method and an improved model were evaluated based on the existing test results, including the present study.

Robust numerical representation of the behavior of reinforced concrete shear walls under simulated earthquake action is critical to support an accurate evaluation of the performance of concrete buildings. Reliable damage predictions of concrete shear walls are also essential to understand the response of components attached to walls via anchors. Previous studies have shown that anchor load capacity is reduced in the presence of concrete damage. Accordingly, current U.S. building code requirements prohibit anchor installation in sections of walls where yielding of the reinforcement is expected. The aim of this requirement is to minimize the potential for anchorage failure during a seismic event. Identification of concrete damage in shear walls of varying characteristics is therefore relevant to anchor performance. In this regard, the present paper describes a parametric study performed using a multiple-vertical line element model able to couple shear-flexure interaction. The aim of the study is to qualitatively identify regions of severe damage in concrete shear walls of varied geometric and detailing characteristics and thus better assist engineers in adhering to current code requirements. Results show that the regions where large damage is expected define a plastic hinge length and include the boundary elements in slender walls and the diagonal compression struts in squat walls. This information is used to suggest anchor installation locations to assure their robust performance when attaching nonstructural components and systems to reinforced concrete shear walls subject to seismic loading.

Laboratory experiments were conducted to quantify the structural capacity of two concrete anchorage systems employed in rail transit direct fixation track systems (i.e., threaded rod and female insert). Laboratory results were compared with both revenue service loading demands and ACI 318-14 calculated design capacity. The experimental results identified the controlling failure modes in tension as adhesive failure in threaded rods and a combination of splitting and insert thread failure in female insert connections. Concrete breakout is the controlling failure mode for both systems in shear. These findings demonstrate agreement between design calculations and laboratory experimentation. Laboratory capacities were measured at 46,000 lb. and 53,000 lb. [204 kN and 235 kN] in tension, and 22,400 lb. and 18,500 lb. [100 kN and 82 kN] in shear for threaded rod and female inserts, respectively. For threaded rods, the magnitude of laboratory failure capacities is between 2.3 and 21.3 times larger than the calculated ACI design capacity. Although improvements to the direct fixation system’s anchorage capacity are possible through design modifications, the current capacity is adequate for the representative heavy rail transit service environment studied.

There is a drastic change in design and construction trends of underground structures, where precast concrete (PC) shear wall system is quickly replacing cast-in-place (CIP) diaphragm wall (i.e., the so-called slurry wall) system in urban areas for better constructability and reliable performances. However, it is challenging to achieve the proper coupling action or composite performance through vertical connections between adjacent PC walls and in the horizontal connection between PC walls and foundation to satisfy the seismic design criteria specified in codes. To this end, this study introduced a cast-in-place (CIP) cap beam and waling beam at the top and mid-height of PC walls to connect individual precast wall panels by means of a coupling action. Precast specimens were carefully designed to be code-compliance as an intermediate precast shear wall system, and those were then fabricated and tested under the reversed cyclic loads to evaluate seismic performances. Detailed numerical models were also developed to identify how CIP beams can effectively improve the seismic performance of a precast shear wall system by restraining the free rotation and axial deformation of individual precast wall panels.

Integrating glass fiber-reinforced polymer (GFRP) bars into lightweight self-consolidating concrete (LWSCC) would effectively contribute to producing lighter and more durable reinforced concrete (RC) structures. Nonetheless, the shear behavior of GFRP RC structures cast with LWSCC has not yet been fully defined. This paper reports experimental results on the behavior and shear strength of LWSCC beams reinforced with GFRP bars. The beams measured 3,100 mm (122.05 in.) long, 200 mm (7.87 in.) wide, and 400 mm (15.75 in.) deep. The test program included six beams reinforced with GFRP bars and one control beam reinforced with conventional steel bars for comparison purposes. The test variables were the reinforcement type and ratio and concrete density. The experimental results indicate that using LWSCC allowed for decreasing the self-weight of the RC beams (density of 1,800 kg/m³) (112.4 lb/ft³) compared to normal-weight concrete (NWC). All beams failed as a result of diagonal tension cracking. Increasing the axial stiffness of the longitudinal GFRP reinforcing bars improved the concrete shear capacity of the LWSCC beams. The test results of this study and the results for 42 specimens in the literature were compared to the current FRP shear design equations in the design guidelines, codes, and literature. Applying a concrete density reduction factor of 0.8 and 0.75 in the ACI 440.1R-15 and CSA S806-12 shear design equations, respectively, to take into account the influence of concrete density achieved an appropriate degree of conservatism equal to that of the equations for NWC beams.