Research on the Restoring Force Model for T-Stub Connected Beam-Column Joints

Based on the results of low-cyclic reversed loading test of Double-Wall Precast Concrete (DWPC) shear walls, the hysteretic curves and skeleton curves are analyzed, the key points and calculation methods of skeleton curves are summarized through dimensionless treatment of skeleton curves, and the three-line restoring force model of DWPC shear walls is proposed, and its hysteretic rules are determined respectively. The formulas for calculating the loading stiffness and unloading stiffness are given, and the calculated skeleton curves are compared with the test results. The restoring force model presented in this paper is verified. The calculated values of the key points of the restoring force model are in good agreement with the test results. The proposed restoring force model can better reflect the hysteretic performance of the specimens. It can be used as a reference for elastic-plastic seismic response analysis of DWPC shear wall structures.

Seismic isolation system can be an effective alternative to protect the NPPs (Nuclear Power Plants) against to the strong seismic events. Therefore, some research activities to adopt the seismic isolation concept to the design of the next generation NPPs have been progressed for last few years in Korea. Nuclear structures, secondary systems and components must remain undamaged during and after the SSE (Safe Shutdown Earthquake) event. The seismic events will cause the high seismic response in the stiff structural systems and extremely high demands of deformation on the safety-related secondary systems like piping components. If seismic isolation devices are installed in nuclear power plant for seismic stability, safety against seismic load of power plant may be improved. But in some equipment, seismic risk may increase because displacement may become greater than before installation of seismic isolation device. Therefore, it is necessary to select the equipment in which seismic risk increases due to increase in displacement by the installation of seismic isolation device, and perform a research on seismic performance evaluation of equipment. In this study, one of the typical Korean NPPs assuming the application of seismic isolation devices, and one of the interface piping systems which introduced this NPP was used for seismic analysis. The numerical models include representations of seismic isolation devices. In order to validation of numerical piping system model and defining failure mode & limit states, quasi-static loading tests were conducted on the scale-modeled piping components before the analysis procedures. The fragility analysis was performed by using results of inelastic seismic response analysis. Inelastic seismic response analysis was carried out by using shell finite element model of piping system considering internal pressure. The implicit method was used for the direct integration time history analysis. Generally, PGA (Peak Ground Acceleration) was used for seismic intensity of fragility curve. However, in the case of the displacement sensitive system, lateral displacement could be an useful alternative measure for estimation of probability of failure. Thus in this paper, fragility curves were plotted based on maximum relative displacement.

Restoring-force model for HFC-filled CFS shear walls subjected to in-plane cyclic loading

Bending restoring force model of angle-steel reinforced concrete columns under combined torsion

A restoring force model for a novel type of precast beam-to-column joints using mechanical connections

This paper presents some quasi-static tests for 4 mixed columns composed of CFST column and RC column. The seismic performance and failure mode were studied under low-cyclic revised loading. The failure mode was observed under different axial compression ratios. The hysteretic curve and skeleton curve were obtained. The effects of axial compression ratio on yield mechanism, displacement ductility, energy dissipation, stiffness and strength attenuation were analyzed. The results indicate that the failure behavior of CFST-RC mixed column with archaized style is mainly caused by bending failure and accompanied by some shear failure. The axial compression ratio performs a control function on the yielding order of the upper and lower columns. The yielding mechanism has a great influence on the ductility and energy dissipation capacity of specimens. Based on the experiment, finite element analysis was made to further research the seismic performance by ABAQUS software. The variable parameters were stiffness ratio of upper and lower columns, axial compression ratio, yielding strength of steel tube, concrete strength and rebar ratio. The simulation results show that with the increase of stiffness ratio of the upper and lower columns, the bearing capacity and ductility of specimens can correspondingly increase. As the axial compression ratio increases, the ductility of the specimen decreases gradually. The other three parameters both have positive effect on the bearing capacity but have negative effect on the ductility. The results can provide reference for the design and engineering application of mixed column consisted of CFST-RC in Chinese archaized buildings.

Restoring force model of phosphogypsum-filled cold-formed thin-walled square steel tube composite wall

Experimental study on the seismic behavior of an innovative stepped beam-column joint

Low‐cycle reciprocating loading tests were carried out on a steel frame with prefabricated beam‐only connected steel plate shear wall (specimen A) and a steel frame with welded beam‐only connected steel plate shear wall (specimen B). The seismic performance of the two different types of steel frame‐steel plate shear wall specimens was studied and the failure modes, hysteresis curve, skeleton curve, and seismic performance index, etc of two groups of specimens were obtained, together with the studies of failure characteristics, ductility, energy dissipation, and stiffness degradation of the two specimens. The results showed that the assembled steel frame‐steel plate shear wall with connection joints of steel shear wall with discontinuous cover plate connected on both sides (DCPC) have good seismic performance. On the basis of no loss of seismic performance, DCPC joints can provide better energy dissipation capacity than traditional welded steel plate shear wall structures and ensure the good postearthquake repair function.

Experimental study on seismic performance of recycled aggregate concrete shear wall with high-strength steel bars

Seismic performance study on slipping bolted truss-to-column connections in modularized prefabricated steel structures

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.

Compared with the traditional integral cast-in-place piers, the assembled piers have many advantages. In order to study the seismic performance of the new fabricated concrete piers with the nested connection of steel pipes, the overall design of the cast-in-place, traditional grouting sleeves and new steel pipes is designed. The seismic performance of three types of piers was studied. The horizontal low-cycle repeated load tests of three square pier specimens were carried out. The hysteresis curves, skeleton curves, ductility, energy consumption, strength degradation, stiffness degradation and deformation recovery of the members were tested. The performance and laws of the other aspects were studied and compared. The results show that the overall bearing capacity of the existing cast-in-place pier is closer than that of the new type of prefabricated pier. The hysteresis curve is full, the failure mode is the overall compression and failure, the displacement ductility and cumulative energy dissipation capacity are slightly better, and the residual displacement is small. The stiffness is less degraded, has good seismic performance and does not show significant strength degradation.

The truss transfer story serves as a critical structural zone connecting different structural systems in high-rise buildings. This component incorporates numerous inclined-web trusses, which are prone to cracking and failure under seismic events. To enhance the seismic performance of long-span transfer structures and address the tensile cracking vulnerability of inclined-web trusses in conventional truss transfer stories, this study investigates the seismic behavior of a novel composite system: a prestressed CFRP tendon–steel-reinforced concrete transfer story structure with inclined-web trusses and two specimens of inclined-web truss transfer story frames—with and without prestressed CFRP tendons—were designed and fabricated. These specimens were subjected to horizontal low-cycle reversed loading to examine seismic performance indicators, including crack propagation patterns, failure modes, hysteretic curves, skeleton curves, stiffness degradation, ductility, and energy dissipation capacity. The results demonstrate that incorporating prestressed CFRP tendons into the inclined-web trusses did not alter the failure mode of the steel-reinforced concrete transfer story structure. The primary failure morphology consistently manifested as flexural-shear failure in the bottom chord columns. During the loading process, tensile cracking failure manifested in the inclined-web members of both specimens, with and without prestressing. Crack distribution remained uniform in all cases. The inclined-web trusses incorporating prestressed strands exhibited an 80% increase in cracking load compared to the non-prestressed specimen. Furthermore, the prestressed specimen demonstrated superior resistance to performance degradation and enhanced energy dissipation capacity. Both configurations exhibited significant deformation capacity and satisfactory seismic performance. The prestressed CFRP tendons enhance the crack resistance and deformation capacity of a transfer story structure with inclined-web trusses, providing novel insights for seismic design of truss transfer story structures.

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.