International Concrete Abstracts Portal

Precast concrete (PC) moment-resisting frame systems with wide beam sections have been increasingly adopted in the construction industry due to their advantages in reducing the span length of PC slabs perpendicular to wide beam members and improving the constructability of precast construction. To further facilitate fast-built construction, this study introduces a novel PC wide beam-column connection system, where the solid panel zone is prefabricated and integrated into the PC column, allowing the upper floor to be quickly constructed without delay due to the curing time of cast-in-place concrete. Meanwhile, the current ACI CODE-318-19 code imposes strict allowable limits on the width of wide beams and complex reinforcement details as part of a seismic force-resisting system to effectively transfer forces into the joint, considering the shear lag effect. To address this, two full-scale PC wide beam-column test specimens were carefully designed, fabricated, and tested to explore the impact of large beam width and simplified reinforcement details beyond the code limit. The seismic performance was evaluated in terms of lateral strength, deformation capacity, stiffness degradation, failure mechanism, and energy dissipation. Based on the evaluation, the proposed PC wide beam-column connections demonstrated equivalent, or even better, seismic performance than the reinforced concrete control specimen. Additionally, it was found that the presence of corbels can mitigate the shear lag effect in PC wide beam-column connections, and that the current effective beam width limit imposed by ACI CODE-318-19 is conservative for PC wide beam-column connections with corbels.

Filling reinforced concrete (RC) frame spans with RC shear walls constitutes a strategic intervention to existing sub-standard buildings. The efficiency of this intervention depends, among other things, on the behavior of interfaces between the shear wall and the frame elements. The failure of critical interfaces that may lead to undesirable shear sliding of the wall at its base can only be prevented if the interfaces are adequately designed. To investigate the cyclic behavior of interfaces within the composite frame-to-wall members, four frames filled with RC walls, as well as two reference specimens (i.e., a bare frame and a monolithic frame/wall specimen), were subjected to cyclic horizontal displacements. The crucial effect of the interface reinforcement ratio, the detailing, the dowel distribution along the interface, and the embedment length on the behavior of the specimens, in terms of maximum capacity, drift, and failure mode, was confirmed.

Slender reinforced concrete (RC) shear walls have become an integral part of lateral load-resisting mechanisms of modern high-rise structures, especially in earthquake-prone regions. Because the seismic behavior of the wall is governed by its design and detailing, several past studies are available regarding the same. However, limited studies have been carried out regarding the influence of the confinement effect in the web and the boundary elements on the wall behavior. To address this concern, an experimental study of an isolated slender shear wall with an enlarged boundary element (BE) designed in conformance to IS 13920:2016 was undertaken. The specimen was subjected to lateral slow cyclic displacement- controlled loading. The relation between the global and local responses of the wall by means of strain profiles is documented in the present study. The evolution of the strain profiles obtained clearly depict the participation of the transverse reinforcement, indicating the mobilization of the confinement effect.

Steel columns are commonly attached to concrete foundations with groups of cast-in-place headed anchors. Recent physical tests and simulations have shown that the strength of these connections can be limited by concrete breakout failure. Four full-scale physical specimens of axially loaded columns attached to a foundation slab were tested, varying the shear reinforcement configuration in the slab. All specimens were governed by concrete breakout failure. The tests suggest that adequately placed distributed shear reinforcement can increase connection strength and displacement capacity. Steep cone failures were observed to limit the beneficial effect of shear reinforcement. Calibrated finite element models were used to investigate critical parameters such as the extent of the shear-reinforced region and bar spacing. A design approach is proposed to calculate connection strength by adding the strength of the concrete and the distributed shear reinforcement. Design detailing is discussed.

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.