To improve the durability of reinforced concrete columns and avoid the cumbersome procedures associated with wet connections in precast construction, a novel precast ultra-high-performance concrete (UHPC)-encased concrete composite column with a core steel tube is proposed, together with an efficient dry connection system based on mechanical straight-thread anchorage. Through pseudo-static tests on four specimens and validated finite element simulations, the failure modes, hysteretic characteristics, load-resisting mechanisms, and flexural capacity of the composite columns were investigated. The results indicate that the composite columns exhibit typical flexural-compressive failure features under cyclic loading, with hysteretic curves displaying a "pinching" shape due to the "opening-closing" effect of dry joints, while the P-Delta second-order effect further aggravates the inward contraction of the hysteretic loops at large drift ratios. For a similar steel ratio, using a larger-diameter core steel tube provides more effective radial confinement to the inner concrete and reduces the outward transfer of lateral expansion pressure. This delays the longitudinal splitting of the UHPC jacket and improves the seismic deformation capacity of the members. The FE analysis shows that the tension-side longitudinal bars experience significant strain concentration and stress amplification in the unbonded threaded segment at the column base, while the compression side bears the load directly through the concrete end face. Based on these stress distributions, an effective stress factor of reinforcement is introduced to characterize the actual stress level of the tension bars in the unbonded threaded segment; this factor varies with the axial load ratio and ultimate-to-yield strength ratio and is used to derive a simplified flexural capacity formula. Validation results show the formula yields reasonably accurate and generally conservative predictions, providing a reliable design reference.

To efficiently utilize construction waste clay bricks and industrial by-products, this study proposes a novel structural frame system. The system consists of recycled brick aggregate geopolymer concrete-filled steel tube (RBGCFT) columns and reinforced recycled brick aggregate geopolymer concrete (RRBGC) beams. Low-cycle reversed loading tests were conducted on four exterior RRBGC beam-RBGCFT column joint subassemblages, with the recycled brick aggregate (RBA) replacement ratio (r) and axial load ratio (n) as test parameters. Experimental results indicated that the failure mode of the beam-column joints was characterized by a beam hinge mechanism, where the plastic hinge at the beam end exhibited favorable plastic deformation capacity and effectively dissipated energy. The replacement ratio of RBA had a limited influence on the load-carrying capacity and energy dissipation of the joint specimens. As the values of r increased from 0 % to 50 % and 100 %, the peak load Mu decreased by 3.2 % and 2.3 %, respectively, while the cumulative energy dissipation decreased by 6.4 % and 16.3 %, respectively. Moreover, finite element analysis was employed to investigate the effect of the beam-column flexural capacity ratio (Km) on the seismic behavior of interior joint subassemblages. Numerical results demonstrated that under the condition of Km = 1, the joint ultimately exhibited a damage pattern dominated by beam-end failure, attributed to the superior deformation capacity of the concrete-filled steel tube. The maximum shear drift in the joint panel zone reached 0.074 %, which accounted for only about 2.5 % of the total inter-story drift. These findings indicate that a properly designed RRBGC beam-RBGCFT column frame system can satisfy the desired seismic performance requirements.

A novel dual-stage friction-bearing connection (DFBC) is proposed as the connection for beamcolumn joints of steel moment-resisting frame, to solve the issue of insufficient ductility and energy dissipation capacity. Cyclic test was conducted and a parametric study was carried out to study the hysteresis behavior. The results demonstrated that the DFBC had stable hysteresis behavior, exhibiting good bearing behavior, deformability, and energy dissipation behavior. Obvious slip-bearing dual-stage mechanical behavior was observed, and it was mainly affected by the slipping distance. A sliding fuse plate with a larger width resulted in a higher moment capacity of the DFBC, while the ductility increased as the slipping distance grew. The slipping behavior was influenced by both the bolt load factor and the friction coefficient, whereas the maximum bending behavior was mainly affected by the width of the sliding fuse plate. The DFBC could effectively achieve energy dissipation concentration, dissipating more than 85 % of the total input energy. The moment (M)-rotation (phi) hysteresis model was developed based on the theoretical analysis on the hysteresis behavior, and the calculation methods for the primary performance indices were established. It was found that the moment-rotation hysteresis curves derived from the proposed M-phi model showed good agreement with those obtained from tests and numerical simulations. It indicates that the proposed M-phi model could well reflect the hysteresis behavior of the dual-stage friction-bearing connection, and the corresponding calculation methods had desirable accuracy.

To achieve comprehensive recycling of construction waste clay bricks and industrial waste residues, a novel structural column named recycled brick aggregate geopolymer concrete-filled corrugated steel tube (RBGCFCT) was proposed. An eccentric compression test was conducted on 10 RBGCFCT short columns to systematically analyze the effects of eccentricity, brick aggregate replacement ratio, and corrugated steel tube confinement level on their mechanical properties. The test results indicated that the eccentrically loaded RBGCFCT specimens generally exhibited bending deformation, with concrete crushing in the compression zone and flattening of the corrugated steel tube in the tension zone. Under small eccentric compression, the brick aggregate replacement ratio and the steel tube confinement level significantly influenced the specimen's bearing capacity. When the replacement ratio increased from 0% to 70%, the axial compressive load capacity of the specimens decreased by approximately 34%. As the failure mode shifted to large eccentric compression, the influence of these parameters gradually diminished with increasing eccentricity. Regarding the bearing capacity calculation, the cross-section of the RBGCFCT column can be equivalently modeled as a laterally confined reinforced concrete section. Based on this, a calculation formula for eccentric compressive bearing capacity was established, which can effectively predict the actual bearing capacity of such columns.

Utilization of replaceable damage-concentrated elements into steel moment-resisting frames (SMRFs) presents a promising solution to mitigate structural earthquake-induced damage and improve earthquake resilience. An innovative damage-concentrated connection (DCC) characterized with a friction-bearing mechanism was developed and applied to the SMRFs to improve the seismic performance, and the structural characteristics were elaborated. The configurations and the mechanical mechanism of the DCC were presented, and results from the cyclic test were used to verify the multiple moment-rotation behavior and damage control. A combined constitutive model was developed to reflect the friction-bearing mechanism, and the reliability was validated. SMRF with the DCCs was designed based on damage control and the nonlinear dynamic analysis was performed. The comparison of the dynamic response was conducted to study the effect of DCC on the seismic behavior of SMRF. The results demonstrated that the use of DCCs reduced the seismic response, and helped produce a more uniform distribution of inter-storey drift, thereby reducing the potential for weak story mechanism. The DCCs exhibited stable hysteresis behavior and excellent energy dissipation behavior. The plastic behavior was concentrated to the DCCs and the stress development of the framing components was greatly improved.

Recycled brick aggregate geopolymer concrete (RBGC) is an eco-friendly green material developed by recycling construction waste clay bricks and industrial byproducts. To enhance its mechanical properties cost-effectively, this study proposes a novel composite column formed by encasing RBGC within corrugated steel tubes, termed recycled brick aggregate geopolymer concrete-filled corrugated steel tube (RGCFCT) columns. Axial compression tests were conducted on 12 RGCFCT stub columns to investigate the influence of key parameters, including the reference strength (fc,0), brick aggregate replacement ratio (r), and confinement coefficient (xi). The experimental results indicated that the failure modes were dependent on the level of confinement provided by the corrugated steel tubes. Specimens with a confinement coefficient of xi = 0.4 exhibited drum-shaped failure, while those with xi <= 0.3 displayed shear-type failure. The corrugated steel tubes contributed less than 4 % to the direct loadcarrying capacity but significantly enhanced the core RBGC strength through confinement effects. The measured average effective confining stress reached approximately 0.77fy. Strong composite action between the corrugated steel tubes and RBGC was observed. The ratio of measured-to-material peak load ranged from 1.0 to 1.35 and increased with the confinement coefficient. The axial compressive capacity decreased with higher r, showing reductions of 13.8 % and 27.7 % at r = 30 % and 70 %, respectively. Conversely, the deformation capacity improved as r increased. Based on the experimental data, a uniaxial compressive stress-strain model for RBGC was established, incorporating the confinement effect of corrugated steel tubes.

Geopolymer recycled brick aggregate concrete-filled steel tube (GRBACFST) slender column has great potential application in structural engineering, owing to the advantages of green material and composite structures. This study presents the experimental investigation of the mechanical behavior of the GRBACFST slender column under compression-bending loading, including the failure modes, bearing capacity, and load-deflection curves. 22 GRBACFST slender columns were fabricated and tested, and the parameters involved the cross-section types, the brick aggregates (BA) replacement ratio, slenderness ratio, and load eccentricity. Results demonstrated that the failure modes of GRBACFST columns were similar, with local buckling of the steel tube and the crushing of the concrete infill. The bearing capacity of GRBACFST columns decreased with the increase in BA replacement ratio, load eccentricity, and slenderness ratio. The BA replacement ratio had little effect on the load-displacement curve, especially for circular specimens. A modified stress-strain constitutive model of the geopolymer recycled brick aggregate concrete (GRBAC) for numerical simulation was verified and then adopted for the parametric analysis on N/Nu- M/Mu relation curves of GRBACFST columns. A simplified calculation method for the bearing capacity of GRBACFST columns was proposed, and its accuracy was verified by comparing it with test results.

Precast shear wall structures have been extensively applied to high-rise buildings, especially in high seismic intensity regions, with advantages of high construction efficiency and good seismic performance. The connection between the precast components plays an important role in the seismic performance of precast shear walls. In the paper, a precast shear wall with steel energy-dissipating connection (PSW-SEC) is developed, featuring a decoupled bending-shear mechanism at the connection region. The feasibility and the effectiveness of the steel energy-dissipating connection were validated through test study. Results demonstrated that PSW-SEC could develop favorable structural integrity, stable hysteresis behavior, and good deformation capacity. The structural damage was controlled to the replaceable connecting steel members while the upper RC wall panel remained in good condition without serious damage. It turns out that the bearing capacity was enhanced by the increase in the thickness of the steel plate at the connection, while increasing the height-to-width ratio of the pilaster improved the deformation capacity and ductility behavior. The PSW-SEC had good seismic resilience, and the mechanical behavior was highly restored through replacing the damaged steel members. The theoretical analysis of the flexural capacity of PSW-SEC was preliminarily conducted, and the calculation method of the flexural capacity was proposed and validated.

The precast shear wall has been widely applied in the area with high seismic intensity, owing to the advantage of excellent lateral resistance and convenient construction. However, serious damage or failure of precast shear wall always occurs due to the insufficient strength or ductility of connections, leading to the structural failure and difficulties in post-earthquake resilience. In this paper, a new precast shear wall with damage-concentrated connectors was proposed based on the idea of damage control, and the seismic behavior was investigated experimentally. The failure process, load-displacement curves, ductility behaviour, degradation characteristics and energy dissipation behaviour were studied. Results showed that the proposed precast shear wall exhibited desired structural integrality, and it developed adequate stiffness and bearing capacity. The deformation capacity and the energy dissipation capacity were also enhanced since the failure process and the stress distribution were improved by the damage-concentrated connectors. No strength degradation for the precast shear wall occurred before the drift approached 1/50, while the ultimate drift ratio and energy dissipation capacity of proposed precast shear were about 2 times and 4.4-5.2 times of those for the monolithic shear wall, respectively. The damage was controlled in the connectors and more than 87 % of the total energy consumption was dissipated by damage-concentrated connectors. The proposed precast shear walls failed with the fracture at the damage- concentrated connectors, while the concrete shear wall remained in good condition with slight crack development. The utilization of damage-concentrated elements could avoid premature damage to precast concrete and improve the seismic resilience.

In the present study, recycled brick aggregate geopolymer concrete-filled steel tube (RBGCFT) members were proposed to make use of construction waste clay bricks and industrial waste. Five square and five circular RBGCFT members were tested under pure bending loading, with the replacement ratio of recycled brick aggregate (RBA) as the test variable. The results showed that all specimens exhibited good ductility, as the load-deflection curves did not show a significant decline. The flexural capacity of RBGCFT members decreased slightly as the RBA replacement ratio increased, with the peak load only decreasing by approximately 8.5 % when the RBA replacement ratio increased from 0 % to 100 %. Finite element analysis was also conducted to further study the flexural behavior of RBGCFT members and the influence of parameters. The results indicated that the steel tube primarily carried the bending moment of the RBGCFT members, while the concrete contributed about 14-22 % of the total bending moment at peak load. This proportion diminished as the RBA replacement ratio increased. Based on the experimental and finite element analysis results, expressions were established to predict the flexural capacity of square and circular RBGCFT members, respectively.

Ductility-based design for structural collapse prevention may not be sufficient for the higher performance demand of minimizing the time and cost for function recovery. A friction-bearing type connection with slit dampers was introduced to the beam system at the beam end, and it followed the characteristics of the damage-controlled type connection. The design considerations for the proposed connection were presented and the experimental investigation on the cyclic behavior of the designed specimens was conducted. The results demonstrated that the designed connection exhibited a stable and full hysteresis behavior under cyclic loading, without obvious performance degradation. With a longer slotted hole in the slit damper, the friction-slipping behavior was obvious and the maximum rotation angle could be up to 0.05 rad, while the bearing capacity was enhanced with a shorter slotted hole. The friction-slipping behavior also improved the stress development of main structural members and enhanced the ductile behavior. The proposed connection could develop two-stage energy dissipation behavior, and the frictional slippage was greatly helpful for dissipating energy. The damage concentration was achieved, and the energy dissipated by the proposed connection accounted for more than 75 % of the total dissipated energy. The the inelastic deformation was mainly concentrated in the slit damper, while the beam and the column remained elastic, greatly improving the seismic resilience.

The replaceable artificial steel hinge is adopted for beam-to-column joints at the intended beam-hinge location to achieve damage concentration and seismic resilience of steel structures. In this study, a detailed finite element model of damage-control beam-to-column joint with artificial steel hinge was developed and the feasibility was validated through the comparisons with the representative tested specimens, in terms of failure mode and hysteresis behavior. A subsequent numerical study on the seismic performance of the proposed damage-control beam-to-column joint was comprehensively conducted with the validated numerical model, and the influences of slipping distance, slip coefficient, bolt load, and width of the steel plate fuse were considered. The parametric study results demonstrated that the slipping distance had an obvious effect on the hysteresis behavior of the proposed damage-control beam-to-column joint. The beam-to-column joint with longer slotted holes behaved better energy dissipation and ductility behavior, while it exhibited better bearing capacity with shorter slotted holes. The effect of the slip coefficient and the bolt load was similar, and the maximum bearing capacity was barely affected. The slipping behavior was delayed with a higher slip coefficient or bolt load due to a larger load required for slippage, while the hysteretic curves were improved. The width of the steel plate fuse had an obvious effect on the development of bearing capacity, while it had little effect on the energy dissipation capacity and ductility.

Achievement of damage concentration is key to realizing structural resilience. In this study, a replaceable damage-tolerant beam-column connection is developed and the mechanical behavior was studied through experimental study. Results demonstrated that the proposed connection achieved damage concentration within the connecting region, and the failure mode and hysteresis behavior obtained by finite element modeling matched well with the test results. Then subsequent numerical study based on the validated detailed finite element model was carried out to investigate the influence of the width and thickness of the sliding plate, the length of slotted holes, the slip coefficient and the bolt load on the seismic behavior. The parametric study results demonstrated that the length of slotted holes significantly influenced the load-deformation characteristics while the width and thickness of sliding plates affected the bearing capacity once the bearing behavior occurred. A longer slotted hole could improve the ductility and energy dissipation capacity since it delayed the local buckling behavior of the flange segment. The bending moment was enhanced with the activation of bearing action and it was mainly affected by the width of the sliding plate. The increase of the friction coefficient and bolt pretension was beneficial to the energy dissipation behavior, while it did not influence the bearing behavior a lot.

通过控制粉煤灰、矿渣用量制备基准强度分别为C50、C60和C70的普通地质聚合物混凝土试件,再掺入不同体积量(0.3％,0.6％,0.9％和1.2％)的钢纤维制备出钢纤维地质聚合物混凝土试件.采用霍普金森压杆(split Hopkinson pressure bar,SHPB)对试件在不同冲击气压(对应不同应变率)下的抗冲击性能进行研究,探讨钢纤维掺量、应变率及混凝土基准强度对试件动态抗压强度和韧性指数的影响;采用ABAQUS软件进行数值模拟,对模拟与试验结果加以分析和验证;建立钢纤维地质聚合物混凝土动态应力-应变本构模型.结果表明:各组试件的动态抗压强度随着应变率、混凝土基准强度地提高逐渐增大,而钢纤维掺量仅对强度较低地质聚合物混凝土产生较大影响;应变率的提高使试件完整性逐渐变差,而随着钢纤维掺量与混凝土基准强度的提高,试件完整性逐渐变好,冲击耗能与韧性逐渐增加;数值分析与试验结果吻合较好,验证了结果的可靠性;钢纤维地质聚合物混凝土动态应力-应变本构模型计算结果与试验结果整体吻合较好,可用于预测冲击荷载下钢纤维地质聚合物混凝土的力学性能.

Geopolymer and recycled brick aggregates are applied into the concrete-filled steel tubular column to provide a promising solution to environmental sustainability. This paper investigates the mechanical behavior of geo-polymer recycled brick aggregate concrete-filled steel tubular (GRBAC-FST) slender columns under axial compression. Apart from cross-section type, the replacement ratio of brick aggregates (BA) and slenderness ratio are also selected as the main variables. The analysis of the failure mode, bearing capacity, deformation behavior, and strain behavior is conducted. A modified stress-strain model for the GRBAC-FST slender column is proposed and validated, then the parametric analysis on phi-lambda relation curves is performed to propose a simplified calcu-lation method for the bearing capacity. Results demonstrate that GRBAC-FST slender columns exhibit obvious lateral deflection, and mid-span bulging of steel tube. Compared with square specimens, circular specimens exhibit plane fracture of concrete, and developed higher bearing capacity and better plastic deformation ca-pacity. The ultimate strength of GRBAC-FST slender columns decreases with the increase of the replacement ratio of BA and slenderness ratio. The stability coefficient phi decreases with the increase of the slenderness ratio, the yield strength of the steel tube and the concrete strength, while it was little affected by the steel ratio. The modified stress-strain model could well reflect the full-range response of GRBAC-FST slender columns under axial loading. The proposed calculation method could be used for the compressive bearing capacity of GRBACFST slender columns, with satisfying accuracy and efficiency.

Steel fiber geo-polymer concrete（SFGC） specimens with different compressive strength were prepared by controlling the mixing amounts of fly ash, slag, and steel fiber. Axial compression test and field scanning electron microscope（FSEM） microstructure test were conducted to study the effect of steel fiber content on mechanical characteristics of SFGC of concrete specimens with different benchmark strength, such as strainstress curve and energy dissipation capacity.The results show that steel fiber improves the mechanical properties of ordinary geo-polymer concrete, such as axial compressive strength, peak strain, elastic modulus, energy dissipation capacity as well as ductility.It is observed by FSEM test that the bridging action of steel fiber and the bonding action of calcium silicate hydrate improve the bonding property between the materials inside the specimen, and the mechanical property of the specimen is better improved. The established axial compression stress-strain constitutive model is in good agreement with the experimental values,which provides a theoretical basis for the engineering application of steel fiber geo-polymer.

以砖骨料取代率、长细比和偏心率为主要研究参数，进行10根圆钢管地聚物砖骨料再生混凝土长柱的偏心受压试验，分析试件的失效模态，荷载-位移关系、荷载-应变关系、侧向变形、延性等力学性能；利用数值模拟开展偏压荷载作用下圆钢管地聚物砖骨料再生混凝土长柱的受力全过程分析，对N/N u -M/M u 相关曲线进行参数化分析，提出一种简化的偏心受压承载力计算方法并进行验证。研究表明：圆钢管地聚物砖骨料再生混凝土偏压长柱的力学行为与破坏模式与普通钢管混凝土偏压长柱相似；试件具有较高的承载力，且其峰值承载力随着砖骨料取代率、偏心率和长细比的增加而降低，其中偏心率对试件承载力的影响最大。相比无砖骨料取代是试件，当砖骨料取代率为100%时，试件承载力下降7.91%，当砖骨料取代率在70%以内时，试件承载力仅下降1.76%，说明砖骨料取代率对试件承载力的影响较小。利用所提承载力计算方法得到的计算结果与试验结果偏差小于10%，说明该方法可较准确预测圆钢管地聚物砖骨料再生混凝土长柱的偏压承载力。

Precast shear wall (PSW) has been widely applied in building structures with advantages of good mechanical behavior and construction efficiency. To improve the seismic performance and the earthquake resilience of PSW, a new earthquake-resilient precast shear wall with bolt-plate connectors (ERPSW) was developed. Experimental study was conducted to investigate the seismic performance of the proposed ERPSW, including the failure mode, shear resistance, ductility, energy dissipation capacity, degradation in stiffness, etc. Moreover, seismic-damaged ERPSW was repaired by replacing the damaged connectors and tested again to verify the earthquake resilience through the comparisons with original test. Results demonstrated that the proposed ERPSW exhibited the similar mechanical behavior compared with the cast-in-situ shear wall, while developed higher shear capacity, better ductility, and energy dissipation capacity. The damage was concentrated in the bolt-plate connectors, consuming more than 85% of the total energy dissipation, while precast concrete wall almost remained elastic with few cracks. The seismic performance of seismic-damaged ERPSW was recovered after replacing the damaged members, exhibiting as good as seismic performance with the original one. Consequently, the utilization of bolt-plate connectors could ensure the reliable connection of PSW, enhance the seismic performance as well as satisfy the requirement of earthquake resilience with convenient replacement.

提出一种装配式节点钢质耗能铰连接,对其关键部件开孔削弱钢板阻尼器,进行3种开孔削弱形式的试件轴向往复加载试验,考察开孔削弱钢板阻尼器的破坏模态,研究其滞回性能、骨架曲线、承载能力与延性性能等.探讨开孔削弱长度、开孔削弱宽度、宽厚比、厚度方向间隙等参数对钢板阻尼器滞回性能的影响.建立开孔削弱钢板阻尼器的简化力学模型,提出阻尼器滞回本构模型并对本构模型准确性进行验证.结果表明,阻尼器的开孔削弱钢板在开孔削弱处开裂或断裂,避免了面外屈曲的发生,实现塑性耗能与破坏模式可控;阻尼器滞回曲线饱满,承载力均高于297.31 kN,位移延性系数Δ/Δy均大于4.5,表现出良好的耗能能力、承载能力与延性性能;相比菱形开孔,竖缝开孔削弱阻尼器综合力学性能更优,建议开孔削弱长度a/L为0.25～0.55,开孔削弱宽度b/B为0.2～0.5,宽厚比为12.50～15.63,厚度方向间隙不超过2 mm;提出的开孔削弱钢板阻尼器滞回本构模型能准确地模拟阻尼器滞回性能.

提出了一种塑性可控的钢制连接装配式剪力墙,将结构的塑性损伤与破坏集中在钢制连接件上,主体结构基本保持完好,能够改善钢筋混凝土剪力墙的破坏模式,避免罕遇地震作用下剪力墙在墙体底部发生严重塑性损伤,提高剪力墙的震后可恢复性.对高宽比为1.0的现浇剪力墙、塑性可控的钢制连接装配式剪力墙及更换损伤钢制连接件的装配式剪力墙进行了拟静力试验研究,考察其破坏形态、抗剪承载力、滞回性能、耗能能力等抗震性能指标.结果表明:钢制连接装配式剪力墙的破坏集中在钢制连接件上,墙体损伤程度明显减轻,具有较高的抗剪承载力,其变形能力和等效黏滞阻尼系数均可达到现浇剪力墙相应值的2倍,损伤钢制连接件更换前后试件的总耗能分别为现浇剪力墙总耗能的5.23倍和4.55倍;位移角达到3％时,上部墙体出现细微裂缝,但钢筋未发生屈服,保持较好的完整性,钢制连接件的耗能占总耗能的89.2％以上,实现了结构的塑性耗能集中控制.更换损伤连接件后的装配式剪力墙可获得与原试件相接近的性能指标,表明更换损伤的钢制连接件可较快恢复剪力墙的力学性能,塑性可控的钢制连接装配式剪力墙具有较好的可恢复性.