International Concrete Abstracts Portal

This research aims to provide a theoretical foundation for the structural design of magnesium phosphate cement (MPC) in high-temperature environments and facilitate the recycling of municipal solid waste incineration bottom ash (BA). Uniaxial compression tests of BA–MPC after exposure to temperatures from 20°C to 1000°C were carried out. Subsequently, the stress-strain curve, peak stress, peak strain, and deformation modulus are examined. The peak stress, peak strain, and deformation modulus, considering the influence of temperature factors, are proposed using regression analysis. Based on the continuum damage mechanics, the axial compression damage constitutive model of MPC is developed, accompanied by an analysis of its temperature damage characteristics. The results show that BA improves MPC strength and helps stabilize its deformation after exposure to high temperatures. The peak stress of MPC decreases after exposure to high temperatures, and the peak stress of BA–MPC is higher at the same temperature. At 1000°C, the peak stress of MPC ranges between 15.86 MPa and 28.38 MPa. After high thermal exposure, the peak strain fluctuation of the MPC with BA stays small, and the deformation modulus is higher than that of the MPC without BA. The developed MPC axial compression damage constitutive model can accurately describe the stress-strain relationship of MPC under axial compression following high-temperature exposure, with a correlation coefficient greater than 0.86. The temperature damage variable of MPC rapidly accumulates in the range of 20°C to 200°C. At 600°C, the temperature damage variable and the total damage variable without BA attained the maximum values of 0.656 and 0.751, respectively. BA can reduce the total damage and temperature damage of MPC to a certain extent.

This study introduces a new anchorage strategy using ultra-high-performance concrete (UHPC) to attach unbonded post- tensioning (PT) strands to existing foundations. This solution complements a seismic retrofit scheme investigated by the authors, which transforms nonductile cast-in-place reinforced concrete (RC) shear walls into unbonded PT rocking shear walls following concepts of selective weakening and self-centering. In the proposed PT anchorage scheme, mild steel reinforcements are inserted through the shear wall thickness and into the foundation. Subsequently, UHPC is cast around the wall base, forming a vertical extension connected to the foundation, which is used to anchor the unbonded PT strands. The feasibility and performance of the anchorage scheme was investigated through a combination of laboratory testing and numerical simulations. Pullout testing on four scaled-down anchorage specimens was conducted in the laboratory. Hairline cracks were observed in the UHPC during testing. Additionally, three-dimensional (3-D) finite element (FE) models were created, validated, and used to study the performance of the proposed anchorage scheme under lateral loading. The simulation results support the effectiveness of the proposed anchorage strategy.

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.

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.

Current design assumptions for precast prestressed concrete piles embedded in cast-in-place (CIP) pile caps or footings vary across states, leading to inconsistencies in engineering practices. Previous studies suggest that short embedment lengths (0.5 to 1.0 times the pile diameter) can develop approximately 60% of the bending capacity of the pile, with full fixity potentially achieved at shorter embedment lengths than current design specifications due to confinement stresses1. This study experimentally evaluates 10 full-scale pile-to-cap connection specimens with varying embedment lengths, aiming to investigate the required development length for full bending capacity. The findings demonstrate that full bending capacity can be achieved at the of pile-to-pile cap connection with shallower embedment than code provisions, challenging existing design standards and highlighting the need for more accurate guidelines for bridge foundation design.