Displacement Ductility Coefficient Research Articles

Seismic performance of self-centering steel column base with buckling-restrained bars

Self-centering structures, emerging as a vital innovation in earthquake-resilient design, offer notable advantages in structural integrity, rapid functional recovery post-earthquake, and economic efficiency over the building's life cycle. This paper introduces a self-centering steel column base, employing buckling-restrained bars for energy dissipation. Through an analysis of its force mechanism, it conducts low-cycle reciprocating load test on four set of specimens with varying buckling-restrained bars and axial compression ratios. The results demonstrate the column base's superior seismic performance, characterized by its ability to rapidly restore seismic functionality after unloading and replacing the buckling-restrained bars. The force-displacement hysteresis curves exhibit a distinctive double-flag shape, with a minimal residual story drift of 0.001 rad, underscoring the structure's exceptional self-centering capability. The displacement ductility coefficients and equivalent viscous damping coefficients confirm the column base's excellent deformation and energy dissipation capabilities. Furthermore, a refined ABAQUS finite element model is developed and validated against the load test results, further analyzing the seismic performance relative to key structural parameters.

Numerical Investigation on the Seismic Behavior of Novel Precast Beam–Column Joints with Mechanical Connections

Traditional cast-in-place beam–column joints have the defects of high complexity and high construction difficulty, which seriously affect the efficiency and safety of the building construction line, and precast beam–column joints (PBCJs) can greatly improve the construction efficiency and quality. At present, the investigations on the seismic behavior of precast reinforced concrete structures are still mainly focused on experiments, while the numerical simulations for their own characteristics are still relatively lacking. In the present study, the seismic behavior of novel precast beam–column joints with mechanical connections (PBCJs-MCs) is investigated numerically. Based on the available experimental data, fiber models for four PBCJs-MCs are developed. Then, the simulated and experimental seismic behaviors of the prefabricated BCJs are compared and discussed. Finally, the factors influencing the seismic behavior of the PBCJs-MCs are further investigated numerically. The numerical results indicate that the fiber models can consider the effect of the bond–slip relationship of concrete and reinforcement under reciprocating loads. The relative errors of the simulated seismic behavior indexes are about 15%. The bearing capacity and displacement ductility coefficients of the PBCJs-MCs decrease rapidly as the shear-to-span ratio (λ) increases. It is recommended that the optimum λ for PBCJs-MCs is 2.0–2.5. The effect of the axial load ratio on the seismic behavior of PBCJs-MCs can be negligible in the case of the PBCJs-MCs with a moderate value of λ.

Experimental study on the seismic performance of concrete-filled steel tube columns with a multiple-chamber round-ended cross-section

Reinforced concrete bridge piers with round-ended sections are susceptible to bending, bending–shear, and shear failure after earthquakes in high-intensity areas, thus necessitating improved seismic performance. This study introduced a novel design for a concrete-filled steel tube (CFST) column, featuring a multi-chambered, round-ended cross-section. The use of longitudinal and transverse stiffeners divided the column section into distinct chambers, thereby enhancing the seismic performance of the columns. A total of 12 groups of static tests were performed to examine the effect of chamber layout, axial compression ratio, and aspect ratio on columns’ hysteresis behavior, and the hysteresis curves, skeleton curves, failure modes, stiffness degradation, ductility, and energy dissipation capacity were obtained. Results demonstrated the favorable seismic performance of composite columns. Additionally, an increase in chambers led to a full hysteresis curve, enhancing bearing and energy dissipation capacities. The displacement ductility coefficient (μ) ranged between 3.88 and 7.45, and the design parameters have minimal influence on the stiffness degradation of the composite beam. Based on the results, the long and short sides of the CFST columns with a large length–width ratio should be arranged to be relatively close in length.

Upgrading seismic performance of beam-column joints using steel-polypropylene hybrid fiber: Experiment and numerical simulation

Due to the exceptional resistance to concrete cracking, appropriate incorporation of steel-polypropylene hybrid fiber is anticipated to enhance the mechanical properties of beam-column joints that are crucial for ensuring the integrity of frame structures under earthquake excitations. In this study, twenty-eight steel-polypropylene hybrid fiber reinforced concrete beam-column joints (HFRC-BCJs) were tested under cyclic loading to investigate their seismic performance, in which the effects of fiber types, concrete strength, axial compression ratio, and characteristic parameters of hybrid fiber are taken into account. The results indicated that the incorporation of steel-polypropylene hybrid fiber can exert a beneficial synergetic effect on improving the seismic responses of beam-column joints in multiple aspects. Specifically, hybrid fiber not only alleviated the concrete damage within the core region significantly, but also augmented the initial cracking load, displacement ductility coefficient, and energy dissipation coefficient of the beam-column joints by an average of 40.5 %, 31.4 %, and 37.3 %, respectively. Moreover, with the purpose of enabling a reasonable prediction of the seismic responses of HFRC-BCJs, a modified super degree-of-freedom (DOF) element was adopted for the numerical simulation, in which a user-defined UMAT subroutine was developed to more accurately reflect the enhancements of fiber inclusion on the tensile and compressive stress-strain behaviors of HFRC, as well as the associated damage evolution.

Behavior of large SCFST column with different confinement effects under pseudo-static loading

In this study, tests of twenty-four square concrete filled steel tubular (SCFST) columns with different structural sizes by the pseudo-static method were conducted to investigate the influence of the confinement effects. In addition, the structural size and the confinement effect are respectively represented by column width and width-to-thickness ratio. The experimental results, including the failure mode, the lateral load-displacement curves and the indices of the seismic performance were recorded and analyzed. The mode of failure is typical compressive flexure pattern. As the structural size increases or the confinement effect decreases, the nominal flexure strength of SCFST column decreases. Compared of the nominal flexural strength of small column, the influence of confinement effect is more significant on that of large column. The displacement ductility coefficient, the mean energy dissipation factor and the relative stiffness decrease with the increasing column width. Then enhanced confinement effect has no obvious influence on the displacement ductility coefficient of the SCFST column. When the confinement effect increases, the energy dissipation capacity of the SCFST column increases. Finally, the modified calculated method considering size effect is established, and this method is applicable to predict the bending moment of the SCFST column with different confinement effects and structural sizes.

Experimental Study on Seismic Performance of Prefabricated Columns Connected Using a Novel Dry Sleeve

Prefabricated structures are widely used because of their advantages of energy savings, environmental protection, standardization, and universality. However, due to the complex structure of the joints, it is easy to make the joint installation difficult and the prefabricated column connection unreliable, and further lead to the poor seismic performance of the structure. Therefore, a new type of dry sleeve joint with double screw sleeve without support is proposed, and the seismic performance and influencing factors of the new dry-sleeve-joint prefabricated column are studied. This study encompasses seven reinforced concrete columns characterized by cross-sectional dimensions of 600 mm × 600 mm. Among these, five specimens feature a novel dry sleeve connection, while the remaining two specimens were entirely cast-in-place. Low-cycle reversed loading experiments were conducted on all specimens to analyze and compare the damage patterns, hysteresis curves, skeleton curves, displacement ductility, energy dissipation capacity, and ultimate bearing capacity between precast and cast-in-place columns. Several parameters, including fabrication method, axial compression ratio, longitudinal reinforcement diameter, and hoop spacing, were examined. The findings demonstrated that the calculated-to-tested ratio of the ultimate bearing capacity for the prefabricated specimens was determined to be 0.62, indicating a high level of safety. The displacement ductility coefficient for each specimen ranged from 2.43 to 3.31, while the ultimate drift ratio was within the range of 1/41 to 1/33, satisfying the specified requirements for seismic performance. However, the hysteresis curve of the prefabricated specimens exhibited a pinching effect, which may be related to the existence of a weak layer on the joint surface of the post-cast section. In general, the shape of the new dry sleeve is maintained in the test, the connection form can effectively transfer the force, and the longitudinal bars can be strained and yield when the prefabricated column reaches the peak load. The new type of dry sleeve connection can be used for longitudinal reinforcement connection of reinforced concrete columns with seismic design.

Experimental and Numerical Study on the Flexural Behaviors of Unbonded Prestressed I-Shaped Steel Encased in Ultra-High-Performance Concrete Beams

A novel type of traditional composite member-unbonded prestressed I-shaped steel encased in a UHPC (PSRUHPC) beam is proposed to reduce the brittleness of UHPC beams and improve their bearing capacity. A PSRUHPC beam, an unbonded prestressed UHPC (PRUHPC) beam, and an I-shape steel UHPC (SRUHPC) beam were manufactured, and their flexural static performances were assessed using a flexural comparison test. The test results reveal that the flexural process of the PSRUHPC beam is similar to that of ordinary reinforced concrete beams, and UHPC crushing in the compression zone is a sign of failure. Due to the bridge coupling effect of steel fiber, the crushed concrete still maintains good integrity without bursting, the UHPC in the tension zone remains functional after cracking, and the cracking inflection point of the load–deflection curve was not obvious. The PSRUHPC beam showed a significantly improved bearing capacity and flexural stiffness, its load–deflection curve exhibited significantly more energy consumption, and its bending ductility performance was improved, with better deformation properties. Compared with PRUHPC beams, PSRUHPC beams show a bearing capacity increase of 55.3%, a cracking load increase of 11.9%, and a displacement ductility coefficient increase of 76.2%. Compared with SRUHPC beams, PSRUHPC beams show a 15.4% increase in bearing capacity, a 50.2% increase in cracking load, and a 12.1% increase in displacement ductility coefficient. The application of prestress can significantly improve the stiffness of the beam prior to cracking. The cracking loads of prestressed ordinary concrete beams and steel-reinforced concrete beams account for 20–30% of their ultimate loads, which value was 40–50% for the tested beams. The change trend of strain in the section steel and UHPC is roughly the same at the same height, and the strains of the two deviated after most of the section steel yielded under tension, but they can generally work together. When the tested beams were cracked, multiple cracks appeared, which were fine and dense. The magnetic flux sensor cable force-monitoring system can better monitor the strand stress increment of unbonded prestressed steel UHPC beams, where the prestressed strand did not yield tension under the final state; the load–strand stress increment curve was basically the same as the load–deflection curve, and the stress increment of the unbonded steel strand positively correlated with the midspan deflection. Finite element simulation was used to verify the test results, and we determined the reinforcement ratios for non-prestressed and prestressed reinforcement, as well as the ratio of a steel-containing section, the effective prestress, the height of prestressed reinforcement, the position and strength of I-shaped steel, and whether or not the prestressed reinforcement was bonded. The effects of these parameters on the bearing capacity and displacement ductility coefficient of PSRUHPC beams were studied. The results can provide a reference for subsequent theoretical design calculations.

Seismic performance of precast reinforced concrete shear wall structure connected with vertical indirect-lapping joints

The current vertical joints of precast reinforced concrete shear wall structures (PRCSWS) usually have long protruding vertical connection bars, precise positioning of vertical connection bars and high time cost due to grouting, hence reducing construction efficiency and quality. This paper proposes a new indirect-lapping joint for the vertical connection of PRCSWS, which could potentially address the difficulties of wall panel transportation and installation. To investigate the seismic performance of the PRCSWS vertically connected with the proposed joint, one cast-in-situ specimen and three precast specimens with different joint designs were fabricated and tested under a pseudo-static setup. The failure mode, hysteretic responses, ductility, stiffness degradation, energy dissipation, and crack opening of the wall-foundation joint were compared for the seismic performance evaluation. The impacts of joint designs on the seismic performance of the specimens were further discussed, focusing on the confinement reinforcements and connection cage distribution. Compared to the cast-in-situ specimen, the research showed that the precast specimens had the same failure modes and similar ultimate capacities of around 600.0 kN. The precast specimen with smaller indirect lapping spacing had similar plastic deformability and energy dissipation ability, shown by the 27% difference in displacement ductility coefficient and similar energy dissipation accumulation, respectively. Although the precast specimens exhibited a lower initial stiffness than the cast-in-situ specimen by 17%, all the specimens tended to have similar stiffness degradation, reflected by the nearly overlapped equivalent stiffness curves. With the same connection cage design, the additional spiral confinement reinforcements for vertical joints could improve plastic deformability shown by the improvement of displacement ductility coefficient by up to 11%, and the crack opening of the wall-foundation joint could be reduced by up to 30%. Increasing the indirect lapping spacing weakened the plastic deformability and energy dissipation ability, shown by the decline of displacement ductility coefficient and energy dissipation accumulation by up to 43% and by 14% respectively, and the crack opening of the wall-foundation joint increased by up to 67%. This research could potentially promote the application of the proposed vertical joint and address the construction difficulties of the current vertical joints of PRCSWS.

The Axial Compression Behavior of Basalt Fiber-Reinforced Recycled Aggregate Concrete-Filled Circular Steel-Tubular Column

Recycled aggregate concrete (RAC) technology has received a lot of attention as a green environmental protection technology. However, the unsatisfactory mechanical behavior of RAC restricts its application in engineering practice. The structure of basalt fiber-recycled aggregate concrete-filled circular steel tubes (C-BFRACFST) can dually improve the mechanical behavior of RAC. To observe the axial compression behavior of the C-BFRACFST column, seven specimens were designed with recycled aggregate replacement ratio (0%, 50%, 100%), basalt fiber (BF) content (0 kg/m3, 2 kg/m3, 4 kg/m3) and length–diameter (L/D, 5, 8, 11) as variable parameters for axial compression tests. The failure mode, load–displacement/strain curve, axial compression deformation, ultimate bearing capacity, energy dissipation, and ductility of specimens have been analyzed. The derived constitutive relation of core basalt fiber-reinforced recycled aggregate concrete (BFRAC) constrained by the circular steel tube and the 3D finite element model of C-BFRACFST column have been established to simulate the whole process of compression. It is observed that instability or shear failure occurs in specimens under axial compression load. When the recycled aggregate replacement ratio was increased from 50% to 100%, the change in the energy-dissipation capacity of the specimens was not significant but the ultimate bearing capacity and displacement ductility coefficient decreased by 3.45% and 8.91%, respectively. When the BF content was increased from 2 kg/m3 to 4kg/m3, the change in the ultimate bearing capacity of specimens was not significant; the energy-dissipation capacity at the later stage of bearing increased, and the displacement ductility coefficient was noted to increase by 13.34%. When the L/D was increased from 8 to 11, the energy-dissipation capacity of specimens was decreased, and the ultimate bearing capacity and displacement ductility coefficient declined by 1.37% and 43.52%, respectively. The finite element simulation results are in agreement with the test results.

Plastic hinge and damage mechanism of RC assembly column base joint with post pouring area

Column base joint with post pouring area connected by grouted sleeves (PPCGS), which can solve the problems of poor controllability of grouting quality in the engineering application of traditional sleeves, is proposed in this paper. Based on the horizontal low-cycle reversed loading test results of six full-scale column base joints under axial pressure, the mechanics characteristic of plastic hinge, the length of equivalent plastic hinge, and the displacement ductility are mainly explored. The research results showed that the plastic hinge was formed above the sleeves in all precast column base joints, and the post pouring area of PPCGS column base joints can provide higher compressive strength, so it could protect the longitudinal rebar under the sleeve from premature buckling deformation, made the plastic hinge fully develop at the top of the sleeves. The ratio of the equivalent plastic hinge length to the section size of PPCGS column base joints decreases as the section size of column and the strength of the post pouring material increase. The average error between the calculated results and the test results of the displacement ductility coefficient of PPCGS column base joints is -3.93%, and the displacement ductility coefficient showed an increasing trend with the increase of the section size and the strength of post pouring material. In addition, a finite element analysis method for the PPCGS column base joint was verified through experimental results, and the influence law of post pouring height and tenon section size on the damage of column base joint was obtained through parametric analysis.

Experimental and Numerical Investigations of the Seismic Performance of Reinforced Concrete Frames Strengthened with CFRP Sheets

To study the seismic strengthening of damaged reinforced concrete (RC) frames using CFRP sheets, this study designed and tested the scaled 2-bay and 2-storey RC frame specimens. After applying a low cyclic horizontal load to simulate the initial damage to the specimen in an earthquake disaster, CFRP was used to strengthen the joints of the damaged RC frame. Pseudo-static tests of strengthened specimens and counterpart specimens were then carried out. Seismic performance, including stiffness, load capacity, ductility and energy dissipation were further analyzed. The failure mode of strengthened RC frame structures showed excellent ductility. The results demonstrated that the strengthening method involving wrapping CFRP can significantly improve the maximum horizontal bearing capacity, initial stiffness and energy dissipation capacity of the non-ductile reinforced concrete frame structure. The average displacement ductility coefficient of strengthened specimen can be enhanced to 3.41 compared with that of counterpart specimen (3.00). The pushover analysis based on the OpenSees model determined that the prototype frame with CFRP strengthening can maintain structural integrity and safety, with its maximum interstorey displacement angle below the limit of seismic specification (i.e., 1/50 in a severe earthquake). This study can contribute to the development of practical and efficient methods for restoring and improving the performance of damaged RC frames in seismic-prone regions.

Field testing of seismic performance of prestressed high strength concrete piles reinforced with non-prestressed tendons considering pile–soil interaction

Prestressed high-strength concrete (PHC) piles have been widely applied as foundations. However, the application of PHC piles was challenging under earthquake hazards. With the increasing demand for PHC piles in earthquake-prone areas, PHC piles reinforced with non-prestressed tendons (PRC piles) were proposed to address the problems. A full-scale field test for one PHC pile and four PRC piles with different non-prestressed tendon ratios (NPTRs) was conducted under horizontal cyclic loading, and their seismic performances were evaluated in terms of hysteretic behaviours, horizontal bearing capacity, ductility, pile deformation, and crack patterns. The results indicated that adding non-prestressed tendons led to an improvement in the hysteresis characteristics and deformation capacity but a decrease in the horizontal bearing capacity. The displacement ductility coefficients of all specimens reached or exceeded 2.8, and there was an optimal NPTR of 0.75% that maximized the ductility of PRC piles, which was 62.5% greater than that of the PHC pile. The pile-soil interaction was considered by analyzing the crack development of the surrounding soil and piles.

Seismic behavior of RC columns under high active confinement force

AbstractThis paper details the invention of a tensioning and anchoring device based on the “wedge‐cutting effect” that can tension and anchor multi‐layer carbon fiber reinforced polymer (CFRP) fabric. To achieve a high active confinement effect on an RC column, the device is characterized by its capability to lift the applied prestress to the greatest extent and minimize prestress loss. All eight RC columns with identical structural dimensions were designed and fabricated, including three unstrengthened and five strengthened columns. The seismic performance test and finite element simulation were conducted under a low cyclic reciprocating load. The test parameters include active confinement force and axial compression ratio, with active confinement force varying as a function of the number of layers of CFRP fabric. The results indicate that the seismic performance of RC columns with high active confinement can be significantly improved. Under a high axial compression ratio, the maximum displacement ductility coefficient and ultimate drift ratio of specimens strengthened with four layers of prestressed CFRP fabrics can increase by 87% and 152%, respectively, while the energy consumption can increase by 4.3 times. Additionally, the ultimate horizontal bearing capacity can be raised by 41%. The seismic performance of strengthened columns increases with the increase of active confinement, particularly under high axial compression. The finite element model is in good accord with the experiment. With an increase in active confinement force, the properties of confined concrete and CFRP are utilized to a greater extent, and more energy is dissipated by the opening and closing of numerous micro cracks.

Seismic Behavior Analysis of Recycled Aggregate Concrete-Filled Square Steel Tube Frames.

In this study, the seismic behavior of a recycled aggregate concrete-filled square steel tube (S-RACFST) frame under different design conditions was investigated. Based on previous studies, a finite element model for the seismic behavior of the S-RACFST frame was developed. Moreover, the axial compression ratio, beam-column line stiffness ratio, and yield bending moment ratio of the beam-column were regarded as the variation parameters. It was through these parameters that the seismic behavior of eight S-RACFST frame finite element specimens was discussed. The seismic behavior indexes, such as the hysteretic curve, ductility coefficient, energy dissipation coefficient, and stiffness degradation were obtained-which, in turn, revealed the influence law and the degree of the design parameters regarding seismic behavior. Moreover, the sensitivity of the various parameters with respect to the seismic behavior of the S-RACFST frame was evaluated via grey correlation analysis. The results show that the hysteretic curves of the specimens were fusiform and full with respect to the different parameters. Firstly, with the axial compression ratio increasing from 0.2 to 0.4, the ductility coefficient increased by 28.5%. In addition, the equivalent viscous damping coefficient of the specimen with the axial compression ratio of 0.4 was 17.9% higher than that of the specimen with the axial compression ratio of 0.2, which was 11.5% as well as that with an axial compression ratio of 0.3. Second, when the line stiffness ratio rises from 0.31 to 0.41, the specimens' bearing capacity and displacement ductility coefficient both get better. However, the displacement ductility coefficient gradually decreases when the line stiffness ratio is greater than 0.41. As a result, an optimal line stiffness ratio (0.41) thus exhibits good energy dissipation capacity. Thirdly, with the increase in the yield bending moment ratio from 0.10 to 0.31, the bearing capacity of the specimens improves. In addition, the positive and negative peak loads increased by 16.4% and 22.8%, respectively. Moreover, the ductility coefficients were all close to three, thus demonstrating good seismic behavior. The stiffness curve of the specimen with a large yield bending moment ratio with respect to the beam-column, is higher than those that possess a small beam-column yield moment ratio. In addition, the yield bending moment ratio of the beam-column possesses a significant influence on the seismic behavior of the S-RACFST frame. Furthermore, the yield bending moment ratio of the beam-column should be considered first in order to ensure the seismic behavior of the S-RACFST frame.

Structural performance of speed-lock joints with split bolts in steel storage racks

This paper aims to experimentally and numerically investigate the structural performance of speed-lock joints with split bolts in steel storage racks. There are no bolts in the typical speed-lock joint for its ease of installation, and the joint transmits and bears force through interactions of the tabs and upright beam holes. However, the joint under seismic loading shows large looseness and slippage with low stiffness. Also, the energy dissipation capacity is insufficient and the failure of tabs in the joints might lead to brittle behavior. In this study, new detail of the speed-lock joint with bolts is proposed by adding a pair of split bolts in the beam end plate while still preserving its merit of ease of installation. A double-cantilever beam test was designed to test this speed-lock joint with split bolts along with the typical speed-lock joint. Low cyclic loading tests were performed on both types of joints: with split bolts and without split bolts. The results revealed the benefits that the split bolts could bring to significantly enhance the performance of the joint in terms of the maximum bending moment, the initial stiffness, the displacement ductility coefficient, the equivalent viscous damping coefficient, and the energy consumption. In addition, a two-step analysis method was proposed for the high-fidelity finite element model of the joints to overcome the complex contact nonlinearity. The numerical model was then validated with the tests for further numerical studies on the performance of speed lock joints with/without bolts.

Experimental and analytical investigation on the compressive behavior of double-skin steel-concrete composite tube walls

An innovative structural wall named double-skin steel-concrete composite tube(DSCCT) wall is proposed in this paper. The proposed wall is composed of rectangular steel composite tube, in-filled concrete, external concrete and stud-tie bar connectors. Sixteen full-scaled DSCCT wall specimens and two reinforced concrete walls (RCW) specimens were tested under axial monotonic compression to investigate their load bearing capacity. Parameters included are the double-skin steel plates thickness, steel plate slenderness ratio (the distance to thickness ratio of the stud-tie bars), stud-tie bar arrangement etc. The vertical load-displacement responses of the test specimens are discussed along with their stiffness, strength, and deformation capacity. Experimental results indicate that the DSCCT specimens exhibited a fairly good bearing capacity, the external concrete, steel composite tube and in-filled concrete could work together well. The greater the thickness of the double-skin steel plate, the greater the buckling wavelength; The smaller steel plate slenderness ratio, the later the local buckling of the double-skin steel plate occurred, and the higher the bearing capacity of the DSCCT wall specimens. The displacement ductility coefficient of the DSCCT wall specimens was higher than that of RCW specimen. Considering the local buckling of the double-skin steel plates and the confinement effect of the steel composite tube on the internal concrete, a theoretical calculation formula of the axial compression bearing capacity of DSCCT wall was proposed. The proposed calculation values were in good agreement with the test values, and had higher calculation accuracy and stability in predicting the axial compression bearing capacity of DSCCT walls.

Influence of the axial load ratio on the mechanical behaviour of prefabricated concrete shear walls with Mortise–Tenon joints

Prefabricated concrete shear walls with mortise–tenon joints (MTJ shear walls), as innovative fully prefabricated concrete shear wall structures without extended reinforcements, can meet the development needs of the current construction industry in China. One cast-in-place concrete shear wall and four MTJ shear walls with different axial load ratios (ALRs) were tested by performing pseudostatic tests. The mechanical behaviour of the MTJ shear walls and the influence of the ALR were studied. The test results show that the construction of the mortise–tenon joint in the MTJ shear walls was reasonable and that the connection was reliable. The failure process of the MTJ shear walls was different from that of the cast-in-place concrete shear wall. Vertical cracks formed along the bottom of the transverse grooves, which weakened the integrity of the MTJ shear wall and contributed to improving the deformability. The damage to the MTJ shear walls was mainly concentrated around the mortise–tenon joints, resulting in a reduction in the concrete crushing area at the root of the cast-in-place concrete boundary elements (CBEs) on both sides of the shear wall. With an increase in the ALR, the yield load and peak load of the MTJ shear wall gradually increased, but the displacement ductility coefficient decreased. However, when the test ALR was 0.30, the displacement ductility coefficient of the corresponding MTJ shear wall still reached 3.73, exhibiting good deformability. Reasonable numerical analysis models were established with ABAQUS to systematically analyse the influence of the ALR on the mechanical behaviour of MTJ shear walls. The ALR limit value of the MTJ shear wall was recommended to be 0.45.

Experimental and numerical investigation on the seismic performance of RC squat shear walls with single post-opening reinforced by steel plates

The pseudo-static tests of one RC squat shear wall without opening and the other three RC squat shear walls with different arrangements (center, bottom, and top) of a single post-opening, reinforced by bonding steel plates, were carried out to simulate the defects caused by the post-opening at different locations and investigate the effect of post-opening location on the seismic performance of reinforced squat shear walls. The corresponding models of the tested specimens and also the other three models of the RC shear walls with the same opening and without any reinforcement were analyzed with Abaqus software. Results indicated that the shear wall without opening and the reinforced shear walls with a single post-opening show flexural shear failure. The relative difference between the bearing capacity of the three reinforced specimens and the reference specimen is not more than 6%. The average displacement ductility coefficients of reinforced shear walls with the central and bottom openings were reduced by 9.62%, while that of reinforced shear walls with the top opening was increased by 23.01%. FEA further reveals that the steel plate significantly reduces the uneven distribution of the reinforcement strain around the opening for shear walls with different post-opening locations.

Review of experimental investigations on seismic performance of precast segmental bridge columns in seismic regions

Due to the fast construction and low interference, precast segmental bridge columns have gained increasing attention for use in non-seismic regions. However, their applications in seismic areas remain scarce due to their ambiguous dynamic performance. To estimate the seismic performance of PSBCs, existing quasi-static cyclic tests and shaking table tests are gathered and reviewed in this study. According to the structural details and material property at the joints, the PSBCs are categorized as 11 types based on the connection type, namely grouted splice sleeve couplers (GSSCs), grouted corrugated duct connections (GCDCs), wet joint connections (WJCs), mechanical bar splice connections, socket connections (SCs), unbonded post-tensioned tendon connections (UPTCs), partial precast columns (PPCs), hybrid connections (HCs), high-strength steel bars (HSBs), high-performance concrete (HPC), and external dissipators (EXDs). Based on the experimental results, the failure reason of each connection types are discussed and the effective structural details are suggested. And also, the PSBCs are divided into those with ductile and resilient connections according to the damage levels, residual drift ratios, displacement ductility coefficients, equivalent viscous damping ratios and effective stiffness parameters. With the achievements in this research, the application of PSBCs is expected to be promoted in medium-to-high seismic regions.

Cyclic response of precast concrete shear walls with reduced grouted sleeves or corrugated metallic duct splices

The structural behavior of precast concrete shear walls (PSWs) is highly dependent on their vertical connections. Current PSWs mainly use two-row (paired) connections, which is relatively time-consuming and involves high cost and construction difficulties on wall assembly. Reducing the number of vertical connections from two-row to one-row or even partial could be economical and efficient solutions for the use of PSWs in practice. Reversed cyclic tests on seven full scale shear wall specimens were conducted under the axial compression ratio of 0.24. Grouted steel sleeves (GS) and grouted corrugated metallic duct (CMD) connections were used in the test program, considering three different layouts: two-row, one-row and partial. Test results showed that all shear walls failed by flexural-shear. The PSWs exhibited more and plumper hysteretic curves than the monolithic wall. The load carrying capacity of PSWs was close to the monolithic wall with an average difference of less than 7 %. The displacement ductility coefficients of the PSWs with two-row, one-row and partial GS were 2.5, 2.8 and 2.6 respectively, which were slightly higher than that of the monolithic specimen (2.2). The ductility of the PSWs with CMD were2.3, 2.9 and 2.3. It was also indicated that PSWs with GS or CMD connections had greater energy dissipation capacity than the monolithic shear wall. The decline in stiffness and energy dissipation capacities of all precast specimens were similar.