International Concrete Abstracts Portal

Eleven large-scale reinforced concrete coupling beam specimens were tested under reversed cyclic displacements of increasing magnitude. The main variables included yield stress (fy) of the primary longitudinal reinforcement (Grade 80, 100, or 120 ksi [550, 690, or 830 MPa]), span-depth (aspect) ratio (1.5, 2.5, or 3.5), and layout of the primary longitudinal reinforcement (diagonal [D] or parallel [P]). Specimens had the same nominal concrete strength (8000 psi [55 MPa]) and cross section (12 x 18 in. [310 x 460 mm]) and were designed for nominal shear stresses of 8 √__f c′ psi (0.67 √__f c′ MPa) for D-type beams and 6√ __f c′ psi (0.5 √ __f c′ MPa) for P-type beams. Transverse reinforcement was Grade 80 (550) in all but one beam (D120-2.5), which had Grade 120 (830) reinforcement. Test results show that, on average, D-type beams had chord rotation capacities in excess of 5%, 6%, and 7% for beams with aspect ratios of 1.5, 2.5, and 3.5, respectively. P-type beams with Grade 80 or 100 (550 or 690) longitudinal bars, tested only for an aspect ratio of 2.5, had chord rotation capacities of approximately 4%. Based on these results, the authors recommend permitting the use of high strength steel, Grade 80 (550) and higher, in D-type and P-type coupling beams for earthquake-resistant design. The spacing of confining reinforcement should be limited to 5db for fy = 80 ksi (550 MPa) and 4db for fy = 100 or 120 ksi (690 or 830 MPa). Consistent with prior findings, the results show that deformation capacity is correlated with span-depth ratio and more sensitive to spacing of the confining reinforcement than to uniform elongation of the longitudinal reinforcement. Finally, the test results illustrate the effects of reinforcement grade on stiffness and energy dissipation of pseudostatically loaded coupling beams.

This paper discusses the seismic performance of precast coupled structural walls with the influence of connections and their location. Full-scale quasi-static tests were conducted on the coupled structural walls by varying the number of connections. The test results show that the number of connections and their position along the height of the coupled wall significantly influence the lateral strength, stiffness, energy dissipation, and failure modes. Walls with two connections seem to improve the strength and hysteretic response, exhibiting superior cyclic performance. Increasing the number of connections improves the initial stiffness to a certain extent, but the designs are expensive. Walls with connections closer to lateral loading lines exhibit vulnerability, requiring design to optimize energy dissipation and crack control. Connections with over-strength may need to be avoided as they may not increase the energy dissipation under earthquake loading. The outcomes of the study help in designing precast systems with better seismic resilience, good ductility, and ease of replacement after an earthquake hits the system.

Accurate prediction of the cyclic response of reinforced concrete (RC) shear walls is critical for performance assessment of buildings under wind and earthquakes. Over the past few decades, various macro-models have been developed, based on different formulations and simplifying assumptions, to facilitate large-scale modeling of RC walls. However, there is limited research on the accuracy of these models for walls with different characteristics. This study evaluates the accuracy and application range of five prevalent macro-models using experimental results from 39 wall specimens with a wide range of design variables. Analytical and experimental results are compared in terms of cyclic load-deflection responses, failure modes, and a set of structural performance measures. The results indicate that while the evaluated macro-models can predict the behavior of shear walls reasonably well, there are important limitations that may restrict their application range. Strengths and weaknesses of each macro-model are identified to help engineers select the most suitable analysis method based on the characteristics of the wall.

Coastal reinforced concrete bridges are critical infrastructures, yet they face significant threats from corrosion due to saline environments and extreme loads like wave-induced forces and seismic events. This state-of-the-art review examines the resilience of corrosion-damaged RC bridges under such conditions. It compiles advanced methodologies and technological innovations to assess and enhance durability and safety. Key highlights include synthesizing loss estimation models with advanced reliability methods for a robust resilience assessment framework. Analyzing catastrophic bridge failures and environmental deterioration, the review underscores the urgent need for innovative materials and protective technologies. It emphasizes advanced analytical models like Performance-Based Earthquake Engineering (PBEE) and Incremental Dynamic Analysis (IDA) to evaluate combined impacts. The findings advocate for engineered cementitious composites (ECC) and advanced sensor systems for improved real-time monitoring and resilience. Future research should focus on developing comprehensive resilience models accounting for corrosion, seismic, and wave-induced loads to enhance infrastructure safety and sustainability.

Lap splicing of longitudinal reinforcing bars in shear walls is often encountered in practice, and the transfer of forces in lap-spliced reinforcing bars to the surrounding concrete depends on the bond strength. Buildings with shear walls during an earthquake develop plastic hinges in the shear walls, particularly where the reinforcing bars are lap-spliced. Brittle failure is commonly observed in reinforcing bar lap-spliced shear walls, which needs to be minimized by choosing the appropriate percentage of lap-spliced reinforcing bars. Therefore, it is essential to address the detailing of the lap-spliced regions of reinforced concrete (RC) shear walls. Several seismic design codes provide guidelines on lap-spliced detailing in shear walls related to its location, length of lap-splice, confinement reinforcement, and percentage of reinforcing bars to be lap-spliced. In this study, the percentage of reinforcing bars to be lap-spliced at a section is examined with staggered lap-splicing of 100, 50, and 33% of longitudinal reinforcing bars, in addition to a control RC shear wall without lap-splicing. This study tested four half-scale RC shear walls with boundary element (BE), designed as per IS 13920 and ACI 318, under quasi-static reversed cyclic loading. From the experimental study, it is observed that the staggered lap splicing of reinforcing bars nominally reduces the performance of shear walls under cyclic load in terms of the reduced flexural strength, deformation capacity, energy dissipation, and ductility of the shear walls compared to the control shear wall without lap splicing. It is also observed that the unspliced reinforcing bars do not sustain the cyclic loading in staggered lap-splice after the post-peak. Current provisions of ACI 318, EC2, and IS 13920 recommend staggered lap-splice detailing in shear walls. However, from the current study, shear walls with different percentages of staggered lap splice show that the staggered lap-splice detailing in shear walls does not improve its seismic performance.