Pseudo-static Test Research Articles

Experimental investigation on the seismic resistance of RC columns after acid rain corrosion

Acid rain can significantly undermine the structural integrity and seismic resilience of concrete structures, posing substantial risks of catastrophic failures and jeopardizing safety. However, studies on the seismic behavior of reinforced concrete (RC) columns affected by acid rain corrosion remain nascent. Therefore, this study explored the impact of acid-rain corrosion extent and axial compression ratio on the seismic behavior of RC columns that experienced flexural failure using an artificial rapid corrosion method and pseudo-static test in sequence. The corrosion-induced damage, weight loss of the reinforcement, failure pattern, hysteretic behavior, load-bearing capacity, deformation capacity, stiffness degradation, and energy dissipation were analyzed. The test observations showed that the acid rain corrosion extent was more pronounced in the column peripheries compared to their central sections. As the number of ARCCs (acid rain corrosion cycles) increased, the damage extent of column specimens was gradually aggravated; the load-bearing, deformation, and energy absorption capacities were significantly reduced. Notably, the column specimen RCZ-4 compared to RCZ-1, with reductions of 14.54% in peak load, 22.58% in plastic rotation, and 28.6% in total cumulative energy dissipation. As the axial compression ratio was increased from 0.3 to 0.5, the column specimens exhibited a 17.12% increase in peak load, alongside a decline in plastic rotation by 25.40% and a reduction in cumulative energy dissipation by 25.85%. Based on the experimental results and the existing theoretical, a calculation formula for the flexural failure skeleton curve characteristic point parameters of RC columns was proposed, considering the impact of acid rain corrosion damage and axial compression ratio. The proposed calculation method could effectively determine the load-bearing and deformation capacity of RC columns under low cyclic loading. The results of this study enable engineers to better understand the seismic behavior of RC columns in an acid rain corrosion environment.

Effect of Vertical Location of Post-Opening on Seismic Behaviour of RC Shear Wall: Experimental and Numerical Analysis

The seismic performance of reinforced concrete (RC) shear walls with post-openings is critical in civil engineering. This study investigates the influence of post-opening positions on the seismic behaviour of RC shear walls through both experimental and numerical approaches. Four shear wall specimens with varying positions of post-openings were subjected to pseudo-static tests. Additionally, Finite Element Method (FEM) simulations were employed to further analyse the structural responses of shear walls with post-openings. The results show that the vertical position of post-openings significantly affects the failure mode, peak bearing capacity, and overall seismic performance. Peak bearing capacity reductions were observed, with central and bottom openings diminishing capacity by up to 17.5% and 15.1%, respectively, while top openings had a minimal impact. Openings also influenced pre-crack initiation, yielding behaviour, and stiffness degradation, with central openings causing the most significant effects. The ductility and energy dissipation capacities of the shear walls were also affected by opening positions. Bottom post-openings led to a maximum ductility reduction of 18.4%, while top openings increased ductility by up to 24.6%. Energy dissipation capacity decreased with lower post-opening locations, with central and bottom openings reducing capacity by 78.9% and 63.0%, respectively. These findings emphasize the importance of considering opening location in the seismic design of RC shear walls to optimize structural performance.

Seismic performance and calculation method for plastic hinge length of RC pier reinforced with UHPC

Piers are highly vulnerable load-bearing components, and their seismic performance determines the integral seismic resistance of bridges to a certain degree. They play crucial roles in evacuation during earthquakes and post-earthquake rescue. The manner in which piers meet the seismic performance requirements after reinforcement has become a popular research topic. In this study, ultra-high-performance concrete (UHPC) and HTRB600E high-tensile reinforcements were used to expand the cross section of a cast-in-place square pier with severe bending damage. The earthquake-resistant behaviour indicators of the pier were compared and analysed by conducting pseudo-static tests on a reinforced concrete pier before and after reinforcement. These indicators included the hysteretic curve, skeleton curve, energy dissipation curve, rigidity degradation, residual displacement, and pier body curvature. Based on the results of the seismic reinforcement quasi-static tests, a finite element model (FEM) of the bridge pier was constructed using the ABAQUS software, and the accuracy of the FEM was averaged. The impact of the reinforcement layer height, thickness, longitudinal strength and axial compression ratio on the equivalent plastic-hinge length of the reinforced pier was analysed, and the formula for the equivalent plastic-hinge length of the reinforced pier was obtained based on multiple linear regression fitting. The analysis results demonstrated that the broadened section method, utilising UHPC and high-tensile reinforcement, significantly enhanced the flexural capacity, energy dissipation, and first rigidity of the bridge pier. The earthquake-resistant behaviour of pier was effectively restored and improved, and the seismic reinforcement effect was significant. The equivalent plastic hinge length of the pier after reinforcement is proportional to the height of the reinforcement layer, the thickness of the reinforcement layer, the strength of the longitudinal reinforcement, and inversely proportional to the axial compression ratio.

Seismic performance assessment of existing low-ductility reinforced concrete double-column bridge piers retrofitted with buckling-restrained braces

In this study, buckling-restrained braces (BRBs) are utilized to improve the seismic performance of existing reinforced concrete (RC) double-column bridge piers. Two 1/2-scale models of RC double-column bridge piers—one retrofitted with a BRB (RC-Pier-BRB) and the other without a BRB (RC-Pier)—were designed and compared. The failure mode, stiffness, strength, energy dissipation, and curvature of RC-Pier-BRB and RC-Pier were compared through pseudo-static tests. Fiber finite element models were created using OpenSees to replicate the experimental results. The findings showed that BRBs effectively controlled seismic damage; compared to RC-Pier, RC-Pier-BRB demonstrated a 44.8 % reduction in the maximum curvature. The strength of RC-Pier-BRB increased by 59.2 %, and its energy-dissipation capacity grew by 18–40 % after BRB retrofitting. The numerical model accurately reproduced the trends in the strength, strength degradation, seismic behavior after BRB fracture, and curvature in the plastic zone of the test models. The differences in the peak strengths of RC-Pier and RC-Pier-BRB between the numerical and experimental results were 3.90 % and 0.43 %, respectively. The errors in the maximum curvatures for RC-Pier and RC-Pier-BRB between the numerical and experimental results were 2.03 % and 8.53 %, respectively. Therefore, retrofitting the existing RC double-column bridge piers with BRBs can improve seismic performance and damage control. Furthermore, the connection bases and plates of the BRB remained useable after the BRB buckled and fractured, suggesting a reliable technology for the replacement and recovery of the BRB after an earthquake.

Study on seismic performance and bearing capacity calculation of post-earthquake repairable high-strength steel joints with weakened-angle

This paper combines common steel and high-strength steel to design a post-earthquake, repairable joint, considering post-earthquake function repairable and seismic performance comprehensively. To prevent early plastic deformation of the joint during the initial loading, slot holes are cut in the web and obround holes are cut in the flange of the angle. This is done to enhance the joint's seismic performance and its capacity for repair. Carrying out the proposed pseudo-static test and finite element parameter expansion analysis on the designed joints to compare and analyze the post-earthquake function repairable capacity of the joint. According to the different failure mechanisms, the calculation method of the bearing capacity and the design method of the joints are proposed. The weakened angle joints have low bearing capacity but the damage is completely concentrated in the damage element, and shows excellent ductility and seismic performance. The damage element was replaced when the story-drift was reached at 0.04 rad, and the peak bearing capacity before and after replacement errored by only 7.1 %. The maximum residual deformation of the joint is 0.48 %, which is lower than the threshold value for residual deformation of the post-earthquake function repairable structure, indicating excellent post-earthquake function repairable capacity. Based on the parameter and theoretical analysis, it is recommended that the thickness of damage element is not greater than the thickness of the beam, the length of the cantilever beam takes the value range of 0.18–0.25 times the total length of the beam, the bolts spacing of angle flange should be in the range of 30 times the thickness of the angle, and the reducing rate of the flange cover plate is about 0.7. According to the full-section plasticity theory, the peak bearing capacity can be calculated. The experimental and simulated values have an error within the range of 10 %.

Isostatic and frictional energy dissipating connecting systems for UHPC curtain walls: Design and experimental validation

Ultra-high performance concrete (UHPC) curtain wall is a new type of non-structural building envelope component. Given its large size and high cost, rational connecting systems should be employed to prevent potential seismic damage and economic losses. In this study, two novel connecting systems, including an isostatic connecting system and a frictional energy dissipating connecting system, were proposed for reinforced concrete (RC) frame with UHPC curtain walls. The design methods for these two connecting system were provided first. Then, to evaluate the feasibility of the proposed connecting systems and the corresponding design methods, three 1/2-scale RC frame structures (i.e., one bare frame without curtain walls, one with isostatic curtain wall connecting system, and one with frictional energy dissipating curtain wall connecting system) were designed and fabricated for pseudo-static tests. The damage evolution, failure mode, strength, stiffness, and energy dissipation capacity of the three test substructures were assessed. The test results demonstrated that through reasonable design, independent rocking deformation of the curtain walls was achieved in both the isostatic and frictional energy dissipating connecting systems, allowing the curtain walls to remain free from damage even under an inter-story drift of 1/36, thus validating the reliability of the proposed connecting systems and design methods. Further, compared to the bare frame, curtain walls employing the isostatic connecting system exhibited a negligible effect on the seismic performance of the frame. On the contrary, curtain walls employing frictional energy dissipating connecting system effectively enhanced the strength and energy dissipation capacity of the frame, allowing dual damage control for both walls and frame. Consequently, the frictional energy dissipating connecting system is considered to be a more rational method for enhancing the seismic performance of buildings.

Numerical and experimental pseudo-static study on block arrangement effects in traditional dry-stone walls for out-of-plane mechanical behavior evaluation

In Lima’s slopes, the absence of urban planning has led to housing built on backfills contained by traditional dry-stone retaining walls, called “pircas,” which pose high seismic risk. A previous study [1], which combined numerical and experimental analyses, evaluated pircas through pseudo-static tests that reflected common construction methods in Lima’s eastern region. One recommendation from that study was to explore effective stone arrangements to enhance the seismic performance of pircas. Consequently, this study aims to examine how the construction process, particularly the arrangement of stones, impacts the out-of-plane behavior of pircas. The research focuses on identifying construction-feasible configurations that can effectively improve their seismic performance. For this purpose, natural-scale pseudo-static experimental studies and numerical modeling using the Discrete Element Method (DEM) were carried out. The experimental campaign consisted of nine pseudo-static tests on different wall arrangements. The pseudo-static numerical study included seventy wall arrangements. The geometry of the blocks was simplified to eliminate this component from the analysis, which focused on the arrangement of the wall. The numerical and experimental results showed the same trend. The study has demonstrated that the current construction technique can be significantly improved by regularly incorporating through-stones—tie stones that pass through the entire cross-section of the wall—and considering a cross-section with overlap. This approach leads to an increase of up to 50% in lateral strength compared to current practices, verifying the effectiveness of through-stones. The study does not intend to endorse the use of pirca for urban habitation in high seismic sectors. However, these traditional walls can be recommended for slope stability, environmental mitigation, urban agriculture, and protection of natural areas.

Experimental study on seismic performance of damaged masonry walls reinforced with high-polymer cementitious composite material

Masonry structures are one of the most traditional and economical structural forms that are extensively used worldwide. However, severe damage to the masonry structures during past earthquakes addresses their vulnerability to seismic loadings. Therefore, it is critical to develop effective and efficient seismic reinforcement measures for masonry structures. This study proposes a structural retrofitting method for masonry walls that employs a corrosion protection liner (CPL) and high-polymer cementitious composite material (HPCCM). Cyclic in-plane pseudo-static tests were performed on six masonry wall specimens comprising three unreinforced and three seismically damaged masonry walls retrofitted with CPL-HPCCM. This experimental study explored the hysteretic behavior, deformation capacity, and failure mechanism of masonry wails after rehabilitation with the proposed retrofitting method under cyclic loading. The test results indicate that the CPL-HPCCM structural retrofitting method is an effective structural retrofitting technique that significantly enhances the lateral load-bearing capacity and energy dissipation capability of masonry walls. Even for the severely damaged masonry wall specimens, the lateral load-bearing capacity, lateral stiffness, and overall ductility of the wall specimens after retrofitting with CPL-HPCCM were restored to or improved beyond those of the intact wall specimens. Compared with the non-retrofitted specimens, the lateral load-bearing capacity of the CPL-HPCCM retrofitted specimens exhibited a substantial improvement, with a minimal increase of 14.6 %. In addition, the CPL-HPCCM method also enhanced the energy dissipation capacity of the wall specimens over 1.95 times compared to the non-retrofitted specimens. Finally, a lateral load-bearing capacity prediction equation was proposed for CPL-HPCCM-reinforced masonry walls based on experimental results.

Pseudo-Static Test of Buckling-Restrained Braces Using Friction Energy Consumption

Pseudo-Static Test of Buckling-Restrained Braces Using Friction Energy Consumption

Experimental Study on Seismic Performance of Precast High-Titanium Heavy Slag Concrete Sandwich Panel Wall

Precast concrete (PC) shear wall members are essential components of the precast concrete shear wall structural system. Therefore, it is crucial to research their materials, and seismic performance is an important and vital indicator to promote the development of prefabricated buildings. This study introduced a new type of precast concrete sandwich shear wall, the precast high-titanium heavy slag concrete sandwich panel wall (PHCSPW), by replacing ordinary concrete coarse and fine aggregates with high-titanium heavy slag and adding insulation boards. This study constructed a cast-in-place high-titanium heavy slag concrete wall (CHCW) for comparative pseudo-static tests to validate its seismic performance. Finite element simulation analysis was conducted to compare and validate the reliability of the test. Considering the limitations of the test conditions, it also researched the seismic performance of PHCSPW by simulating different parameters such as reinforcement ratio, concrete strength, and axial compression ratio. It concludes the following: (1) The failure mode, stress-strain distribution, and ultimate bearing capacity values of PHCSPW and CHCW were consistent with theoretical and experimental analysis results. (2) PHCSPW exhibited high stiffness before cracking but experienced a rapid stiffness degradation rate after cracking. (3) The development trend of the PHCSPW and CHCW hysteresis curve is the same as the skeleton curve. There is little difference between the bearing capacity and deformation capacity after cracking. Comparing the hysteresis loops of CHCW and PHCSPW, it is found that PHCSPW has a larger hysteresis loop area, which indicates that PHCSPW has better energy dissipation capacity. The value of the yield load of the specimen compared with the peak load is between 0.636 and 0.888; that is, the difference inthe early-stage stiffness of the specimen is small. The yield load of PHCSPW is slightly larger than that of CHCW. The maximum carrying capacity of CHCW is about 68.31% of that of PHCSPW. (4) The simulation of different parameters revealed that the energy dissipation capacity of the members increased within a specific range with an increasing reinforcement ratio. PHCSPW demonstrated superior energy dissipation capacity. The influence of concrete strength on the energy dissipation capacity of the members was relatively small. The energy dissipation capacity of the members decreased with increasing axial compression ratio.

The Hysteresis Behavior of Steel Beam–Column Joint with the Load Bearing-Energy Dissipation Connection for Converter Station Building

Prefabricated converter station building has been gradually applied in the field of power engineering construction due to the advantages of standardized design, high construction efficiency, and quality control. The beam–column joint is the essential constitutive part to ensure structural integrity and reliable force transmission for the prefabricated structure. In this paper, a novel load bearing-energy dissipation connection is proposed and applied to the beam–column joint to improve seismic performance and seismic resilience. Pseudo-static tests were conducted on the beam–column joint with the load bearing-energy dissipation connection, and the test results demonstrated that the tested beam–column joints developed with similar failure modes, and the damage was concentrated in the load bearing-energy dissipation connection while the beam and column remained elastic. The beam–column joint with the load bearing-energy dissipation connection had stable hysteresis behavior, with favorable bearing capacity and energy dissipation behavior. A shorter slip length and a larger bolt distance could lead to better stress development and enhance the bearing capacity, while the slip length barely affected the ductile behavior. Moreover, a finite element model was established and validated to extend the parametric study to provide a preliminary understanding of the mechanical mechanism of the proposed beam–column joint with the load bearing-energy dissipation connection. It was confirmed that the load–-deformation behavior was greatly affected by the slip length, but the slip length barely affected the initial stiffness. The width of the sliding steel fuse influenced the bearing capacity and the degradation behavior. A wider width could lead to a higher bearing capacity and improve the degradation behavior. Based on the analysis of the stress development and stress distribution corresponding to different feature points, it was concluded that the use of bearing-energy dissipation improved the stress development in the framing components and achieved damage concentration.

Cyclic Behavior of Partially Prefabricated Steel Shape-Reinforced Concrete Composite Shear Walls: Experiments and Finite Element Analysis

Due to the higher lateral stiffness, load-carrying, and energy dissipation capacities compared with traditional reinforced concrete (R.C.) shear walls, steel shape-reinforced concrete (SRC) shear walls, in which steel profiles are encased in the boundary elements, have been widely applied in high-rise buildings. In order to simplify the on-site construction procedure, this paper proposes a novel partially prefabricated steel shape-reinforced concrete (PPSRC) shear wall using throat connectors. Based on the pseudo-static tests of two large-scale specimens, the effect of construction methods (prefabricated or cast in place) on the cyclic behavior of PPSRC shear walls was investigated by the hysteretic loops, skeleton curves, stiffness degradation, energy dissipation, and deformation decomposition. The test results indicated that PPSRC shear walls could exhibit a comparative cyclic response with the cast-in-place SRC shear walls, and the proposed throat connectors could effectively transfer the stress of the longitudinal reinforcements. Finally, a macro-modeling of PPSRC shear walls based on the multi-layer shell elements in OpenSees 3.3.0 was established and validated by the test results, and the parametric analysis of the axial compression, steel ratio, and concrete strength of prefabricated and cast-in-place parts was then conducted.

Investigation on special-shaped concrete-filled steel tubular column under combined compression and torsion

This paper discussed the combined compressive and torsional performance of special-shaped concrete-filled steel tubes (SCFST) columns. A pseudo-static test research of eight specimens including two kinds of stiffening forms was carried out under compression and torsion. The investigated factors include section shape, stiffening form, stiffening position and axial compression ratio. From the test, specimens presented the characteristics of compression-torsion failure. The steel tube experienced buckling deformation and separated from the concrete at the middle and bottom of the column. The welds of some specimens cracked from the top to the bottom at the concave corner during the stage of decreasing load capacity. This resulted in localized crushing and the generation of torsional oblique cracks in the concrete. The hysteresis curves of the SCFST columns were relatively full in spindle shape without obvious pinching phenomenon, representing a good energy dissipation capacity. The ductility of the multi-cell CFST (MCFST) column is slightly better than that of the tensile-bar stiffened CFST (BCFST) column. There is a positive correlation between the torsion bearing capacity and parameters, such as the column limb width-thickness ratio, steel tube thickness and yield strength. When the axial compression ratio is less than 0.5, the axial compression can improve the torsion bearing capacity; when the axial compression ratio exceeds 0.5, the existence of axial compression will weaken the torsional capacity. The finite element model was established for parameters analysis, and calculation method for the T/Tu-N/Nu bearing capacity correlation curve was proposed, and the calculation results are more conservative and have certain safety reserve.

Experimental study on seismic performance of CFRP bar reinforced concrete columns with magnetorheological damper

Concrete column with Carbon Fiber Reinforced Polymer (CFRP) bars as longitudinal reinforcement have good self-centering performance, but its energy dissipation property is relatively weak. This article proposed a method of adjust the energy dissipation capacity of the column without affecting its self-centering performance by installing magnetorheological (MR) damper outside the column. To verify the feasibility of this method, pseudo-static tests were conducted on a MR damper, one ordinary reinforced concrete column (RCC), and two CFRP bar reinforced concrete columns with MR damper (CFRP80 and CFRP150), and the currents of the MR damper were 80 mA and 150 mA. The experimental results showed that installing MR damper can effectively improve the carrying capacity, energy dissipation property and stiffness of CFRP bar reinforced concrete columns, and the greater the energizing current of the MR damper, the more obvious these effects. Compared with RCC, CFRP bar reinforced concrete columns have better self-centering performance and ultimate deformation. The residual drifts of RCC, CFRP80 and CFRP150 at the 4 % drift level were 2.50 %, 0.62 % and 0.58 %, respectively. The ultimate drifts of RCC, CFRP80 and CFRP150 were 2.79 %, 4.26 % and 4.34 %, respectively. In addition, the use method of the MR damper can ensure that it does not affect the self-centering performance of CFRP bar reinforced concrete columns.

Investigation on Seismic Performance of Reinforced Concrete Frame Retrofitted by Carbon Fiber-Reinforced Polymer

In order to improve the seismic performance of reinforced concrete (RC) frames, carbon fiber-reinforced polymer (CFRP) was used to retrofit reinforced concrete frame structures. The comparison pseudo-static test results show that the peak load, initial stiffness and ductility of the CFRP retrofitted model were increased by 43.89%, 39.27% and 30.1%, respectively. Based on the parametric study of the finite element model, the contribution of CFRP to the seismic upgrading effect of RC columns was quantitatively revealed, and an optimized design of retrofitted CFRP was proposed. The results show that the peak load, ductility and energy dissipation capacity of the whole structure are improved by using CFRP full-wrap reinforcement and strip reinforcement models with different coverage areas. The damage degree of the column decreases, the damage degree of the beam increases, and the failure mode changes from “column hinge” to “beam hinge”. Simultaneously, different CFRP reinforcement areas and the distance between strip CFRP have different reinforcement effects on concrete structures. Based on the investigation results, the recommended ratio of CFRP strip to spacing is 1 to 1.25.

Investigation on special-shaped concrete-filled steel tubular column under pure torsion

This paper discussed the torsional performance of special-shaped concrete-filled steel tubes (SCFST) columns. A pseudo-static test research of nine specimens was carried out under pure torsion. The investigated factors include section shape, stiffening form, width-to-thickness ratio of column limbs and steel tube thickness. The failure modes, hysteresis curves, skeleton curves, energy dissipation capacity, and stress distribution were analyzed to investigate the torsional performance of specimens. The overall failure modes of different section forms are ductile damage. There are a number of 45°oblique buckling in the steel tube, and the steel plates at the top and bottom of the column are transversely torn. At the concave corner, the weld of multi-cell and the welded point of the tensile steel bar were cracked from the top to bottom. Besides, the concrete is mainly crossed by torsional oblique cracks. The hysteresis curves of the SCFST columns are plump shape without pinching phenomenon, representing good energy dissipation capacity. The effect of stiffened methods is the most significant for the torsional performance. The ductility and bearing capacity of multi-cell specimens are better than those of tensile-bar stiffened specimens. Based on the same torsion ratio of concrete and steel tube and ignoring the effect on the tensile bars, calculation methods for initial torsional stiffness and torsional bearing capacity were proposed. Comparison results show that the calculation method has good performance in terms of the accuracy and efficiency.

Experimental and numerical investigations on the mechanical properties of precast segmental barriers with UHPC connections

A novel precast segmental barrier system was proposed to facilitate the connections between barriers and between the barrier and bridge deck by casting ultra-high-performance concrete joints in situ. To assess the performance of the barrier with this connection, a full-scale pseudo-static tests were conducted. At the same time, a comparative assessment was considered the failure mode and load capacity of the precast barrier for two different bridge deck stiffnesses. The results indicated that the ultimate capacity of the precast barrier was comparable to that of a traditional cast-in-place barrier and emphasised the critical role of the deck slab stiffness in the overall load capacity. Based on the damage patterns observed in the barrier and deck slab during the pseudo-static tests, a refined trapezoidal yield-line model considering the deck slab stiffness contribution was derived to more accurately evaluate the load capacity of a precast segmental barrier. Moreover, the calibrated numerical model of the barrier system was employed to investigate the structural dynamic performance under varying scenarios, specifically examining the effects of different impact masses and velocities. Numerical results demonstrated that upon impact by a high-mass, high-velocity object, the barrier experienced a shift in damage mode from flexural–shear to more critical punching shear. This transition concentrated the dynamic load exclusively on the impacted barrier segment, which in turn markedly diminished its dynamic load capacity.

Experimental and numerical analysis of assembled steel beam to CFDST column joint

A novel assembled joint between the concrete-filled double-skin steel tubular (CFDST) column and steel beams is developed in this paper. The joint is connected by extended endplates and high-strength bolts, and it is designed to facilitate post-disaster repairs. The pseudo-static test was performed on four 1:2 scaled joints, the endplate thickness, column form, and inner tube configuration were considered. The experimental results suggested excellent seismic performance of the joints, including plump hysteretic curves, high displacement ductility coefficients, and significant energy dissipation values. Then, accurate finite element (FE) models were established. Comparative results showed that the FE models better simulated the failure modes of endplate bending, weld tearing, local buckling of the flanges, and bolt fracture. In addition, there was a small deviation between the lateral load-bearing capacity obtained from tests and FE simulations. Next, stress analyses showed that the joint's yielding mode is from the flanges and endplates yielding to the outer tube web yielding. The stress on the inner tube was always lower than the yield stress, indicating that the CFDST column had a significant reserve of lateral load-bearing capacity. The main findings of numerous numerical analyses were that higher-strength endplates and steel beams with wider flanges substantially increased the lateral load-bearing capacity of the joint. Finally, a proposal was made to enhance the installation of ribs at beam ends. It improved the load-bearing capacity and initial stiffness and alleviated the stress concentration.

Study on the hysteretic characteristics of FRP-reinforced concrete shear wall with innovative friction dampers

FRP-reinforced concrete shear walls (FRCWs) are able to achieve satisfactory residual deformation and corrosion resistance compared with steel reinforced concrete walls (SRCWs). However, in the FRCWs, the failure of the plastic hinge region brings great challenges to the post-earthquake repair of the structure. Therefore, this paper designed one SRCW and two FRCWs with innovative friction dampers (FDs) at the feet, and steel truss and steel plate were embedded at the plastic hinge region of the two FRCWs respectively to supplement the weakened shear strength. Then pseudo-static tests were carried out twice before and after repairing the two FRCWs with FDs. Experimental results showed that compared with the SRCW at the same lateral drift, the damage of the FRCW was reduced by installing FDs at the feet, and the energy dissipation capacity was enhanced; the repaired FRCWs with FDs could still have acceptable seismic performance. Subsequently, the Park-Ang damage indices of wall webs of the FRCWs with FDs were calculated, which proved that the FRCWs with FDs could meet the four-level seismic fortification objective. In the end, two orthogonal tests were designed based on the established OpenSees models to evaluate the impact of the damper friction and FRP reinforcement ratio on the seismic behaviours of the FRCWs with FDs. It was recommended to adopt larger longitudinally distributed FRP reinforcement ratio to obtain satisfactory self-centering ability and hysteresis performance of the FRCW with FDs.

Experimental study on seismic performance of stainless steel full-scale frames: Global response

This paper presents an experimental study of the seismic performance of austenitic stainless steel full-scale frames using the pseudo-static test method. The bottom single-span, two-storey substructure of the designed prototype frame was chosen as the test frame. Two full-scale frames were tested, one with a bolt-welded joint and the other with an extended end-plate joint. This paper is the first of two accompanying papers to this experimental study and focuses on the specimen design, testing details and global response of the stainless steel frame under cyclic loading. The test results were utilized to analyse the global response of the frames, encompassing failure mode, bearing capacity, deformation capacity, energy dissipation capacity, the overstrength factor, ductility factor and seismic response modification factor. The experimental findings suggest that the stainless steel frames with two joint types demonstrate consistent ability to dissipate energy during cyclic loading. The structure also performs well in terms of deformation, with uniform inter-storey deformation and no soft-storey detected. The maximum storey drift ratio of the frame is 7%. Prior to reaching a storey drift ratio of 2%, the frames with both joint types exhibit similar cumulative plastic deformation, stiffness degradation, and cumulative energy dissipation.