International Concrete Abstracts Portal

Several studies have revealed that slabs with cast-in-place over precast, prestressed panels (CIP-PCP) behave differently from traditional concrete slabs because of the panel joints between the PCP components. While high-strength reinforcing bars can improve load capacity or reduce reinforcing bar quantity in traditional slabs, limited research has focused on their application in CIP-PCP slabs. This study addressed this gap by conducting four-point bending tests on CIP-PCP slabs with normal- and high-strength reinforcing bars. Two configurations of high-strength steel were used: one with the same reinforcing bar layout as normal-strength reinforcing bars and another with increased reinforcing bar spacing to reduce the reinforcing bar quantity. Additionally, slab specimens were designed to replicate real-world bridge deck conditions, including longitudinal and transverse joints, for detailed analysis. The results indicated that reducing reinforcing bar quantity by adjusting reinforcing bar spacing based on the specified yield strength ratio between normal- and high-strength steels maintained a comparable load capacity, with crack widths magnitude similar to those in normal-strength steel layout in the service state.

Although the issue of progressive collapse has been significantly studied within the broader field of structural engineering, the literature on the analysis and design of connections in precast concrete cross-wall buildings is rather limited. This study aims to investigate the progressive collapse behaviour of a typical precast floor-to-floor system, considering the pull-out failure mode of the deformed bar into grouted keyways of slabs at the joints. To do so, the pull-out behaviour of deformed bars in grouted keyways of the connections was first experimentally studied. Subsequently, by integrating the pull-out force-displacement data with findings from full-scale floor-to-floor experiments, an approximate analytical approach was formulated and validated to estimate the resistance to progressive collapse. The findings reveal that the floor-to-floor system, when subjected to the pull-out failure mode following the removal of a wall support, demonstrates a secondary peak strength and considerable ductility in contrast to the bar fracture failure mode.

Slag-based zero-cement concrete (ZC) of high strength (60 MPa [8.70 ksi]) was developed as an eco-friendly construction material. In the present study, to investigate the structural behavior of precast columns using ZC, cyclic loading tests were performed for five column specimens with reinforcement details of ordinary moment frames. Longitudinal reinforcement was connected by sleeve splices at the precast column-footing joint. The test parameters included the concrete type (portland cement-based normal concrete [NC] versus ZC), construction method (monolithic versus precast), longitudinal reinforcement ratio, and sleeve size. The test results showed that the structural performance (failure mode, strength, stiffness, energy dissipation, and deformation capacity) of the precast ZC columns was comparable to that of the monolithic NC and precast NC columns, and the tested strengths agreed with the nominal strengths calculated by ACI 318-19. These results indicate that current design codes for cementitious materials and sleeve splice of longitudinal reinforcement are applicable to the design of precast ZC columns.

Prefabricated structural wall buildings exhibit superior strength, stiffness, and ductility under seismic loading effects. Segmental wall construction is popular due to easy transportation and on-site assembly. The present study deals with the performance of precast wall elements connected through welded plates vertically subjected to seismic loading conditions. The study proposes welded plates with varying thickness to connect two structural walls on one or both faces. Full-scale quasi-static load tests were performed to analyze the seismic behavior of the connections. A conventional foundation with loading beams at top and bottom, to test the structural walls, was replaced with a special steel shoe setup, achieving real conditions, to minimize the testing cost. It was observed that the connections using mild steel plates achieve the most desirable characteristics such as plate yielding, energy dissipation, and ductility. High-strength steel plates failed in brittle mode with poor post-peak response, indicating precautions in selecting the type of connecting steel plates in precast construction. The proposed connecting plates improve the ductility and post-peak response for easy retrofitting of the precast wall system. The study brings out improvement in the seismic performance, selection of materials, and connection detailing for resilient precast structures.

This study investigated the flexural behavior and seismic connection performance of precast lightweight aggregate concrete shear walls (PLCWs) using the relative emulation evaluation procedure specified in the Architectural Institute of Japan (AIJ). Six PLCW specimens connected through a bolting technique were prepared and tested under constant axial and cyclic lateral loads. In addition, three companion shear walls connected through the most commonly used spliced sleeve technique for precast concrete members were prepared to confirm the effectiveness of the bolting technique for the seismic connection performance. The main parameters were the concrete type (all-lightweight aggregate (ALWAC), sand-lightweight aggregate (SLWAC), and normal-weight concrete (NWC), the compressive strength of the concrete, and the connection technique. The test results showed that none of the specimens connected through the conventional spliced sleeve technique reached the allowable design drift ratio specified by the AIJ, indicating that the spliced sleeve is an unfavorable technique for obtaining a seismic connection performance of PLCWs equivalent to that of cast-in-place reinforced concrete shear walls. However, the specimens made of ALWAC or NWC and connected through the bolting technique not only reached the allowable design drift ratio specified by the AIJ but also satisfied the requirements of the seismic connection performance (lateral loads and allowable error at yield displacement) within the allowable design drift ratio. Consequently, the displacement ductility ratio of the specimens connected through the bolting technique was 1.52 times higher than that of the specimens connected through the conventional spliced sleeve technique, respectively. This difference was more prominent in the specimens made of ALWAC than in those made of SLWAC or NWC. Thus, the use of the bolting technique as a wall-to-base connection in shear walls can effectively achieve a seismic connection performance equivalent to that of cast-in-place shear walls while maintaining the medium ductility grades.