Experimental study on seismic performance of replaceable shear links with low-yield-point steel

Study on the seismic performance of high-strength steel framed-tube structures with replaceable shear links

Experimental and finite element study of high-strength steel framed-tube structures with replaceable shear links under cyclic loading

According to previous studies, it was accepted that masonry infills have a contribution to lateral strength, stiffness, and ductility of reinforced concrete (RC) frames structures. In the past studies, an analytical method of diagonal strut model has developed for evaluating the seismic performance of masonry infill. In this model, the masonry infills were presented by compression struts as distributed forces at the frame-infill interfaces in which the frame-infill contact lengths were evaluated by static equilibrium related to compression balance and lateral displacement compatibility. The lateral strength of infill was determined based on frame-infill contact length. In the current study, an experimental study of quasi-static cyclic lateral loading tests was conducted to evaluate the seismic performance of two-bay brick masonry infilled RC frames. This paper discusses the results of seismic performance brick infills based on experimental and analysis results of the multi-span masonry RC frame applying the diagonal strut model. According to the analytical model, antisymmetric strut was acted at the top and bottom of the middle column of the multi-span infilled frame from each infill. As a result, good agreements of lateral strength of structures were obtained between the experimental and analytical values.

Recent earthquakes have induced significant damage on reinforced concrete (RC) school buildings due to seismically deficient details, which can cause bonding failure between steel reinforcements and surrounding concrete due to low confinements. To mitigate the failure mechanism, a proper modeling method to capture the bond-slip effects is needed. This study aims to investigate hysteresis behavior of finite element (FE) models with three bonding modeling approaches (perfect, linear-elastic and nonlinear-inelastic bonding models) for a seismically vulnerable RC school building frame. The models were developed through three-step processes: (1) column model; (2) beam-column joint model; and (3) frame model. To quantify the simulation variation of bond-slip effects for key parameters of hysteresis curves (effective stiffness, maximum strength, and energy dissipation), the simulated responses were compared to the experimental results measured from quasi-static cyclic loading tests in each modeling process. While the perfect bonding model used by structural engineers overestimated all key parameters (e.g., 53.7% in energy dissipation) of the hysteresis curves, the nonlinear-inelastic bonding models reproduced the most accurate hysteresis behavior (less than 5.0%). Based on this investigation, uses of improper bonding models can exaggerate the seismic performance of the seismically vulnerable RC frames.

To address issues such as construction congestion， concrete casting defects， and shear-induced brittle failure in the core region of traditional concrete beam–column joints under severe earthquakes， this study proposes a novel joint system incorporating glass fiber-reinforced polymer （GFRP） tubes combined with high-ductility hybrid fiber-reinforced engineered cementitious composite （HECC）. This system is designed to replace stirrups in the joint core and improve interfacial bonding performance. Four exterior beam-column joint specimens were designed， with the core material （normal concrete （NC） or HECC） and GFRP tube fiber orientation （±45° or ±60°） as the main test variables. Quasi-static cyclic loading tests were conducted to evaluate and compare the seismic performance of the joints， including bearing capacity， ductility， energy dissipation， and stiffness degradation. The results demonstrated that the confinement provided by the GFRP tubes significantly enhanced joint ductility. Specimens with ±45° fiber-oriented tubes exhibited a 9.3% improvement in energy dissipation compared to those with ±60° tubes. Moreover， due to the lateral confinement provided by the GFRP tubes， which helps resist diagonal principal tensile/compressive stresses， and the improved reinforcement-to-matrix bond and crack propagation inhibition offered by the HECC， the joint combining GFRP tubes and HECC in the core region showed comparable ductility and stiffness retention to the conventional concrete joint， along with a 1.3% increase in bearing capacity and an 8.8% improvement in energy dissipation.Compared with traditional concrete joints， the proposed composite joint significantly reduces stirrup usage and construction difficulty， thus offering a viable solution for designing high-performance beam-column joints with minimal transverse reinforcement.

Seismic fragility functions for RC As-built and eccentric steel brace frames

Reinforced concrete (RC) precast shear walls are commonly used in building structures. For transportation ease, large walls are divided into smaller segments and assembled at the construction site with various connection methods. This study focussed on the RC precast shear wall assembled using steel shear keys, which is simply called the steel shear key wall (SSKW) in this paper. Three SSKW specimens were designed and built by considering different sizes and numbers of shear keys. Quasi-static cyclic loading tests were performed to investigate the strength and stiffness of the assembled SSKWs and the behaviour of the wall segments and floor slab. We found that adding strength and more shear keys gradually increased the lateral resistance and stiffness of the specimens and decreased the distortion and damage to the floor slabs. However, the specimens also exhibited lower ductility and energy dissipation with increasing link strength. Finally, an appropriate coupling ratio for SSKWs was suggested for their design in practical engineering.

Experimental study on seismic performance of low-yield point steel plate shear walls

Experimental investigation and numerical simulation on seismic performance of self-centering bridge bents with energy-dissipation beams

Seismic retrofitting of full-scale RC interior beam-column-slab subassemblies with CFRP wraps

In accelerated bridge construction (ABC), precast segmental piers (PSPs) have shown significant progress in shortening the construction period and reducing the cost. By combining multiple segments with post-tensioned (PT) tendons, the desired self-centering ability can be introduced; however, this may lead to a lower energy dissipation (ED) capacity and concentrated damage. To address this concern, the present study proposes a design concept that promotes multiple joint openings to achieve a better energy dissipation capacity and decentralized damage without compromising the self-centering ability. Two main approaches for this objective are discussed in detail. The first approach incorporates different arrangements of ED rebars at various joints, while the second introduces innovative damage control rubber joints (DCRJs) with varying stiffness beneath each segment. Four scaled specimens designed using these two approaches were quasi-statically tested. The observed damage, final failure mode, energy dissipation capacity, resilience index, and damage decentralization were further examined. The results revealed that for PSPs designed using the first approach, the joint openings were successfully decentralized only up to a certain level, after which they were still predominantly concentrated at a single joint, leading to strength degradation and damage concentration. PSPs designed using the second approach demonstrated decentralized joint openings, improved displacement ductility, and damage mitigation, resulting in both superior seismic and post-seismic performance.

Study on seismic behavior of prefabricated shear wall with pressed cone sleeves (PCSs)

This paper proposes a new post-tensioned (PT) precast bridge column (PBC) with a socket connection. PT steel tendons and unbonded steel rebars provide self-centering capability and energy-dissipating capacity, respectively. Because the PT tendons are off-site anchored, they can effectively shorten the on-site working time and improve the safety and tolerance of construction. After describing the configuration and mechanism of the PBC, the analytical equations governing its cyclic behavior are derived. In the quasi-static cyclic loading test results, five PBC specimens and one cast-in-place (CIP) bridge column are designed, based on the criteria that their lateral “yield” strengths are identical, i.e. the concept of equivalent lateral force design. The results show that the PBC specimens realized the targeted lateral strength and exhibited self-centering damping behavior. Compared with the test data, the errors of the “yield” and ultimate strengths predicted by the analytical equations were −9.3% and 8.0%, respectively. The PBC specimens remained nearly intact throughout the tests, although minor cracks were detected in the concrete. In contrast, spalling of concrete and buckling of rebars were observed in the CIP specimen. The comparisons between the PBC specimens indicated that the novel bridge column could maintain self-centering capability and achieve the largest damping capacity when the lateral force-resisting contribution ratio of energy-dissipating steel rebars is 35%, the PT tendons are prestressed to 35% of ultimate stress with a reinforcement ratio of 0.35%, and the embedded depth is 0.7 times the width of the column.

Rammed earth and rubble masonry walls are constructed using raw stones as aggregate and native soil as binding material. To investigate the impact of different configurations on the seismic performance of rammed earth and rubble masonry wall, four wall specimens were subjected to quasi-static testing. Through comparative analysis of hysteresis curves, skeleton curves, stiffness degradation curves, and energy dissipation capacity, the failure modes and seismic performance of the walls were elucidated. Research indicates that under horizontal low-cycle cyclic loading, rammed earth and rubble masonry walls undergo three stages of failure: microcrack initiation and propagation, macrocrack formation and local failure, and ultimate collapse. The arched counter-arch joint wall exhibits the highest energy dissipation capacity and maximum shear bearing capacity, demonstrating an 18.7% improvement over the standard wall. Timber reinforcement walls exhibited lower energy dissipation capacity than curved joint walls but higher than standard walls, with shear bearing capacity being 1.3% greater than standard walls. The opening wall demonstrated the poorest energy dissipation capacity, with shear bearing capacity being 35% lower than standard walls and having the weakest seismic performance. These findings provide theoretical support for optimizing the seismic design of traditional rammed earth and rubble masonry dwellings.

To study seismic performance of steel frame-bent structure, one specimen with one-tenth scale, three-bay, and five-story was tested under reversed cyclic lateral load. The entire loading process and failure mode were observed, and the seismic performance indexes including hysteretic loops, skeleton curve, ductility, load bearing capacity, drift ratio, energy dissipation capacity and stiffness degradation were analyzed. The results show that the steel frame-bent structure has good seismic performance. And the ductility and the energy dissipation capacity were good, the hysteresis loops were in spindle shape, which shape were full and had larger area. The ultimate elastic-plastic drift ratio is larger than the limit value specified by seismic code, showing the high capacity of collapse resistance. It can be helpful to design this kind of structure in high-risk seismic zone.