International Concrete Abstracts Portal

In this study, a shear strengthening method for lightly reinforced concrete columns with partial height masonry infills was proposed. Perforated steel jackets are attached to one face or both faces of the column without removing the cover concrete and mortar finish. The steel jackets were designed to provide additional shear resistance to the column through the interlocking of the ribs at both ends. To investigate the seismic strengthening effects, six column specimens with partial masonry infills were tested under cyclic loading. The tests showed that the specimens with double-face jacketing exhibited an improved seismic performance, whereas there was little or no strengthening effect for the specimens with single-face jacketing. For further investigation on the short column effects due to partial height infills, modeling parameters to define the stiffness and force-deformation relation of the column and masonry walls were proposed, and the modeling results were compared with the test results. Based on the investigation results, the detailing requirements of steel jacketing and the nonlinear modeling methods of the columns with partial masonry infills were discussed.

Slender reinforced concrete (RC) shear walls have become an integral part of the lateral load-resisting mechanism of modern high-rise structures, especially in earthquake-prone regions. Since the seismic behavior of the wall is governed by its design and detailing, a number of 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 enlarged Boundary Element (BE) designed in conformance to IS 13920:2016 is undertaken. The specimen was subjected to lateral slow cyclic displacement-controlled loading. The relation between the global and local response of the wall, by means of strain profiles, is documented in the present study. The evolution of the strain profiles clearly depicts the participation of the transverse reinforcement, indicating the mobilization of the confinement effect.

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 the 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 have been performed to analyze the seismic behavior of the connections. The conventional foundation with loading beams at top and bottom, to test the structural walls, was replaced with a special steel shoe set-up, achieving the real conditions, to minimize the testing cost. It has been observed that the connections using mild steel plates achieve the most desirable characteristics, like plate yielding, energy dissipation, and ductility. High-strength steel plates fail 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.

Two large-scale beam-column connections with beam longitudinal headed bars were tested to evaluate their susceptibility to breakout failures. The specimens were designed following the strength and transverse reinforcement detailing provisions in Chapter 15 of ACI 318-19. The variable investigated was the headed bar embedment length, which was determined based on either Chapter 25 of ACI 318-19 or recent research at the University of Kansas, the latter leading to a 22% shorter embedment length. Both specimens exhibited beam flexural yielding, but the specimen with shorter bar embedment length experienced significantly more connection damage followed by a concrete breakout failure. Based on the limited test results, it is recommended that nominal joint shear strength be calculated based on a joint effective depth equal to the headed bar embedment length and a shear stress of 1.0λ√(fc' ) (MPa) [12λ√(fc' ) (psi)]. A method for calculating headed bar group anchorage strength in exterior beam-column connections is proposed, which led to reasonable and conservative strength estimates in the test specimens.

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.