Building structure is composed of thousands of various components, and its damage development path and damage modes are complex and diverse. The variation in structural damage modes leads to degradation in structural functionality, consequently influencing the overall seismic resilience of the system. Accordingly, the progressive and intricate nature of damage evolution must be explicitly incorporated into the assessment of structural seismic resilience. Firstly, this paper uses the complex network theory to describe the performance loss under different structural damage modes. Next, by continuously updating the structural functional degradation and repair time during the component rehabilitation, a seismic performance recovery function is obtained, and a new structural seismic resilience index, reflecting the damage modes of structural system, is proposed. Finally, four structural damage modes (Modes A, B, C, and D) are designed based on the damage sequence of energy-dissipating components, and the structural seismic resilience is compared. Results show that structural damage modes can affect structural seismic resilience, and the differences in seismic resilience become more significant as structural damage develops. When the seismic action is large, compared with Mode C, Mode A reduces the performance loss by 48.8%, shortens the repair time by 18.8% and enhances the resilience by 190.2%.

Objective Under seismic actions, the internal force transfer relationships and damage-weighted relationships among components in high-rise structures continuously evolve with the progression of damage. Traditional loss evaluation methods based on fixed weighting coefficients, although applicable to specific damage patterns, fail to reflect the impact of varying structural damage states on inter-component weighting relationships, thereby exhibiting poor applicability to complex and diverse seismic damage patterns. High-rise structures, comprising numerous components, can be regarded as network systems whose states dynamically change with component damage. To address the limitations of traditional methods in evaluating loss degrees under complex seismic damage patterns, complex network theory was introduced to establish a structural performance loss evaluation method capable of updating weighting relationships according to the structural damage state.Methods First, a directed weighted complex network model was constructed based on the internal force transfer directions and component stiffness. Components were defined as nodes, and the constraints between adjacent components were defined as edges. Edge directions were determined by the internal force transfer directions under horizontal loads. Node weights were assigned based on the linear stiffness of components, and edge lengths were defined by heterogeneous weights inversely proportional to node weights, thereby determining the load transfer path lengths from nodes to the foundation. Combining complex network efficiency, closeness centrality, and independent path concepts, a structural complex load transfer network efficiency indicator was proposed by iteratively extracting and deleting the shortest load transfer paths of nodes. Second, a bilinear moment-rotation model was adopted for reinforced concrete components to define node damage indicators based on stiffness degradation, and empirical values for yield moment coefficients of shear walls, frame columns, frame beams, and coupling beams were provided using experimental data. Regarding network efficiency updates, as component damage progressed, node weights decreased and edge lengths increased, leading to the extension or transfer of independent path lengths and a consequent reduction in structural network efficiency. The seismic performance loss indicator was defined by the degradation degree of this network efficiency. Finally, referring to the correspondence between component damage state distributions and macroscopic structural damage levels in design codes, the threshold values for slight, moderate, and severe losses were calibrated based on the elasto-plastic analysis results of 12 frame-core tube structural cases. Three frame-core tube structures with different story numbers were designed, and dynamic elasto-plastic time-history analyses were conducted using Perform-3D finite element software. Five actual seismic waves were selected as inputs, and different performance loss degrees were induced by adjusting the peak ground acceleration. The proposed method was validated by comparison with three sets of traditional loss methods employing different component weighting coefficients.Results and Discussions The distributions of node and edge damage degrees indicated that as the peak ground acceleration increased, component damage initially developed in coupling beams and frame beams, and subsequently propagated to shear walls. The damage state distribution of network edges was updated with the progression of structural damage, reflecting the changes in component damage distributions. The updating process of network efficiency revealed that network efficiency continuously decreased with increasing peak ground acceleration, and significant differences were observed in the updating processes and endpoints under different seismic waves, demonstrating the sensitivity of the network efficiency indicator to variations in damage patterns and damage degree distributions. The evolution of the seismic performance loss indicator showed a monotonic increase with higher peak ground accelerations, with significant variations across different seismic waves. In terms of prediction accuracy, the overall accuracy of the proposed method reached 95%, compared to 84%, 79%, and 74% for the three sets of traditional methods, representing improvements of 13%, 20%, and 28%, respectively. Regarding recall, the proposed method achieved a recall rate above 91% for all loss levels, whereas traditional methods exhibited recall rates below 80% for certain levels. For precision, the proposed method maintained a precision rate above 87% across all loss levels. Specifically, for severe loss, the precision was improved by 133% compared to traditional method 1; for moderate and severe losses, it was improved by 13% and 138% compared to traditional method 2, respectively; and for slight, moderate, and severe losses, it was improved by 53%, 16%, and 100% compared to traditional method 3, respectively. In terms of the comprehensive F1-Score, compared to traditional method 2, the proposed method achieved improvements of 9%, 15%, 74%, and 102% under slight, moderate, severe, and complete loss conditions, respectively. The superiority of the proposed method over traditional methods became more pronounced as the structural loss degree increased.Conclusions A seismic performance loss evaluation method for high-rise structures based on an updatable network model was proposed. By constructing a directed weighted structural complex load transfer network model and proposing a structural complex network efficiency indicator, the network weights and path distributions were updated in real-time according to component stiffness degradation, establishing a quantitative relationship between component damage degrees and structural performance loss. The results indicate that the structural network efficiency indicator is highly sensitive to the progression of seismic damage and variations in damage degree distributions. The performance loss evaluation method based on this indicator demonstrated higher F1-Scores than traditional weighting methods under slight, moderate, severe, and complete loss conditions, with the advantages becoming more significant as the loss degree increased. The proposed method resolves the poor applicability of traditional weighting methods in evaluating loss degrees under complex seismic damage patterns in high-rise structures. The feasibility and effectiveness of introducing complex network theory into seismic performance loss evaluation for high-rise structures were verified, providing a novel theoretical approach for seismic loss assessment.

Many existing brick masonry structures require strengthening due to low mortar strength and inadequate seismic detailing. Considering their cost-effectiveness and ease of construction, a UHP-ECC surface layer combined with a wire mesh is proposed for strengthening brick masonry walls. The tests employed wall thicknesses of 180 mm and 240 mm and strengthening forms of single- and double-sided as parameters. Six specimens, including four strengthened walls and two unstrengthened walls, were tested under low-cycle reversed loading. A validated finite element model was further employed to analyze the effects of vertical compressive stress, aspect ratio, and mortar strength. The strengthened walls exhibited significant increases in peak and ultimate loads, stiffness, ductility, and energy dissipation, with double-sided strengthening performing the best. Thicker walls showed greater cumulative energy dissipation, whereas unstrengthened walls experienced early cracking and rapid damage progression. Parameter analysis showed that higher vertical compressive stress and mortar strength, as well as a lower aspect ratio, significantly increased load-bearing capacity. A shear capacity formula for UHP-ECC strengthened brick masonry walls is proposed, providing an experimental and theoretical basis for seismic strengthening design.

As urban land resources become increasingly scarce, the development of underground space has continued to expand. Subway stations and running tunnels are frequently located near buildings or beneath their foundations. These stations and structure clusters interact through the foundation soil, forming an integrated underground station-soil-structure cluster interaction (USSCI) system. Elucidating the interaction mechanisms and influence patterns of these systems under seismic loading has become a critical engineering issue. To address this, a series of shaking table tests were designed and conducted on soil-underground station interaction systems, soil-structure cluster interaction systems, and USSCI systems. This study systematically investigated the effects of the number of structures, as well as the amplitude and type of input ground motions, on the seismic responses of the soil, the underground station, and the structure cluster. The results indicate that (1) the USSCI effect can reduce the soil response at the center and boundary of the structure cluster by up to approximately 45% and 22%, respectively; (2) the underground station exerts a suppressing effect on the structural acceleration response, with peak accelerations at the mid-story and roof reduced by up to approximately 40% and 30%, respectively; and (3) the influence of the structure cluster on the station response is spatially nonuniform; the mid-span response is predominantly reduced by up to approximately 16%, whereas the response at the ends can be amplified by nearly 8%.

Lubricated curved surface sliders (L-CSSs) with modified ultrahigh-molecular-weight polyethylene (M-UHMWPE) are highlighted in the prevention of bearing failure due to the high-temperature degradation of friction materials during high-speed operation. This is vital for seismic isolation in large-span bridges; however, their hysteretic behavior under the variable contact pressure induced by seismic vertical actions is underexplored. For this reason, a theoretical model of the CSS under variable contact pressure was developed. It is evident that variable contact pressure primarily affects the hysteretic performance of the bearing by altering the restoring force and friction force in real-time. Dynamic cyclic tests were conducted at contact pressures ranging from 30 to 90 MPa and frequencies from 0.01 to 0.03 Hz. Test results demonstrated stable hysteretic behavior, with breakaway and average friction coefficients exhibiting minimal fluctuations. The accumulative dissipated energy increased significantly with contact pressure, achieving a maximum gain of 362.25%, while the equivalent damping ratio exhibited a maximum change of 14.6%, initially decreasing and then increasing. Loading frequency had a minor effect, with accumulated dissipated energy decreasing by up to 7.5% and the equivalent damping ratio varying by up to 6.7%. Finally, a validated finite element model further analyzed the influence of the amplitude, frequency, and time phase of variable contact pressure, revealing an irregular parallelogram-shaped hysteresis curve. The shape of hysteretic curves and energy dissipation capacity were significantly affected by these parameters. These findings enhance the understanding of L-CSS performance in bridge seismic isolation, providing critical insights for design under dynamic loading conditions.

Ultra-high performance engineered cementitious composite (UHP-ECC) has shown great promise as a reinforcement material for existing brick masonry structures due to its superior mechanical properties and crack resistance. However, the extremely low water-binder ratio and high cementitious content in UHP-ECC lead to significant shrinkage, potentially compromising durability and structural integrity. In this paper, the mechanical properties and shrinkage performance of UHP-ECC prepared with Polyoxymethylene (POM) fiber for the reinforcement of brick masonry walls were explored through the mechanical test, as well as the autogenous and restrained shrinkage measurements. The results show that reducing the water-binder ratio can enhance the mechanical properties of UHP-ECC, while the superplasticizer dosage has minimal effect. The optimal limestone powder and POM fiber contents are 35 % and 2.5 %, respectively. The shrinkage strain of UHP-ECC decreases with higher water-binder ratios, limestone powder content, and POM fiber volume, but is less affected by superplasticizer. Specially, the water-binder ratio most significantly affects UHP-ECC shrinkage, with specimens at 0.18 showing 62 % lower shrinkage than those at 0.15. Internal temperature and humidity also influence shrinkage, which exhibits a quadratic polynomial relationship with compressive strength. Under masonry constraint, with the number, spacing and depth of masonry mortar joints focused on, the shrinkage of UHP-ECC decreases with fewer mortar joints, larger joint spacing, and greater joint depth. Conversely, the interfacial stress exhibits the opposite trend, but remains below the tensile strength of UHP-ECC, indicating low cracking risk. These findings provide practical guidance for optimizing UHP-ECC mixtures and joint designs in masonry wall reinforcement applications.

To improve the vibration control performance of adjacent structures connected by viscous dampers under seismic excitation, this study proposes a damper parameter optimization method that integrates the MATLAB genetic algorithm with the SAP2000-OAPI. The effectiveness of the method is systematically verified through shaking table tests and an intelligent prediction model. First, a dynamic analytical model of adjacent asymmetric twin-tower structures was established. The installation locations and damping coefficients of viscous dampers were selected as optimization variables. Based on these variables, a GA-SAP2000 integrated optimization framework was developed to determine the optimal parameters for both single-damper and double-damper connection systems under different earthquake records. Subsequently, a shaking table test involving a 15-story main structure and a 7-story substructure was conducted to validate the finite element model and the optimized schemes. The results show that the discrepancies between the natural frequencies of the numerical and experimental models for the first two modes are within 5%. In addition, the errors in floor dynamic responses are less than 10%, indicating that the proposed finite element model is reliable. Compared with the uncontrolled adjacent structure system, the optimized viscous damper-connected system significantly reduces the displacement and acceleration responses of both the main and substructures. Moreover, the double-damper configuration provides better overall control performance than the single-damper configuration. This result indicates that multi-location collaborative deployment can further enhance vibration mitigation effectiveness. Based on these findings, an SSA-BP neural network model was established to rapidly predict the maximum displacement and acceleration responses of both the main and substructures. The results indicate that the proposed model achieves high prediction accuracy for both the training and testing datasets, with coefficients of determination greater than 0.92.

A large number of stone masonry buildings have been constructed in the southeastern oastal region of Fujian Province, China. However, most of these structures exhibit poor seismic performance, likely due to low mortar strength and the absence of effective seismic-resistant system. By analyzing the construction characteristics and seismic vulnerabilities of stone masonry walls between windows, this study proposed a novel retrofitting technique that utilizes POM fiber-reinforced ultra-high performance concrete (POM-UHPC) for mortar joint reinforcement. To investigate the seismic behavior of the retrofitted stone masonry walls between windows, pseudo-static tests were conducted on three wall specimens with an aspect ratio of 1.43 (i.e., one specimen with full-embedding mortar joint reinforcement, one specimen with discrete-point-embedding (localized) mortar joint reinforcement, and one unreinforced specimen for comparison). The results show that the cracking load, initial stiffness, and shear capacity of the specimens with both full- and discrete-point joint reinforcement are significantly increased, and varying degrees of enhancement in their deformation capacity and energy dissipation are observed. When the effective area of POM-UHPC replacing low-strength mortar is similar, the discrete-point-embedding reinforcement method provides a greater improvement in the shear capacity of the wall between windows compared to the full-joint embedding method, but its energy dissipation capacity is lower. In practical engineering in the study area, the discrete-point-embedding mortar joint reinforcement method is recommended as the preferred approach. The findings of this study provide new technical support for the seismic reinforcement of stone masonry buildings in Fujian Province.

The hourglass added damping and stiffness (HADAS) damper exhibits a continuous increase in load-carrying capacity after yielding due to strain hardening, which adversely transfers greater forces to the connected frame members and may cause increased damage. To mitigate this drawback, a novel metal damper (i.e., Graded Failure Damper (GFD)) was proposed. GFD consists of a weakly rhombic hole steel plate with varying heights or neck widths and multiple constant-section rhombic hole steel plates connected in parallel. Its staged failure is achieved by regulating the geometric parameters of the weakly rhombic hole steel plate and effectively controlling the trend of the horizontal force after yielding. Subsequently, the low-cycle reciprocating load tests of GFDs and HADAS demonstrated satisfactory performance in avoiding continuous load increase. Compared to HADAS, the GFD showed reductions in maximum load-bearing capacity, strengthening coefficient, and loop energy dissipation by 25.4 %, 25.8 %, and 20 %, respectively, while its maximum equivalent damping coefficient increased by 10 %. In addition, given that the ultimate bearing capacity of the weakly rhombic hole steel plate is a crucial design characteristic, a calculation formula for the ultimate load was proposed based on theoretical and finite-element parameter analysis. To avoid errors that affect calculation results, the calculation formula applies to the neck width of weakly rhombic hole steel plates with a thickness greater than 4 mm.

ObjectiveTraditional prefabricated beam-column joints mainly adopt grouted sleeve connections, classified as rigid joints, which suffer from excessive on-site wet work and potential defects like inadequate grouting. To address these issues, this study proposes a novel semi-rigid prefabricated joint with hoop panel-tenon connections: hoop plates connect longitudinal reinforcements of upper and lower precast columns, while beam-column assembly relies on corbel tenons and dowel bars, enabling easy installation and semi-rigid mechanical behavior. The research aims to systematically investigate the joint's seismic performance via experiments and numerical simulations, verify the reliability of a finite element (FE) model, and clarify the influence of key design parameters, providing technical support for its engineering application.MethodsTwo half-scaled interior beam-column joint specimens were fabricated: one cast-in-place (RCJ) as the benchmark and one precast (PCJ) with hoop panel-tenon connections. The prototype column and beam sections are 500 mm×500 mm and 300 mm×600 mm, respectively. The precast specimen features a 150 mm-long corbel (150 mm×100 mm section), 110 mm-long beam tenon (150 mm×125 mm section), and 65 mm-thick beam top composite layer. The hoop plate thickness is 15 mm to meet "equivalent to cast-in-place" requirements, and both specimens use C30 concrete. The test setup includes a 1000t hydraulic jack for constant axial load (axial load ratio=0.2) and a 150t MTS electro-hydraulic servo system for horizontal low-cycle reversed loading. Loading height is 1800 mm, with displacement control at angles of 0.20%, 0.25%, 0.35%, 0.50%, 0.75%, 1.00%, 1.50%, 2.00%, 2.75%, 3.50%, 4.25%, and 5% (3 cycles per level). Loading stops when bearing capacity drops to 85% of the peak load. Key indicators such as failure modes, hysteretic curves, skeleton curves, ductility, and stiffness degradation are recorded. A refined 3D FE model is established using ABAQUS. Concrete and hoop plates are simulated with C3D8R solid elements, and reinforcement with T3D2 truss elements (mesh size = 80 mm). The Concrete Damage Plasticity (CDP) model characterizes concrete nonlinearity (expansion angle = 30°, eccentricity = 0.1, σb0/σc0 = 1.16, K = 0.667, viscosity = 0.005), while steel uses a bilinear elastic-plastic hardening model. Cohesive elements simulate new-old concrete interfaces, and frictional contact (μ=0.7) is defined between corbels and tenons. Boundary conditions match the test: column bottom is hinged, and beam ends are sliding supports. The model is validated by comparing failure modes and peak loads with experimental results. Based on the validated model, parametric analysis is conducted on five parameters: beam top longitudinal bar diameter (8, 10, 14, 16 mm), dowel bar diameter (4C8, 4C10, 4C14, 4C16), corbel thickness (90, 100, 120, 130 mm), column longitudinal bar diameter (8, 10, 14, 16 mm), and hoop plate thickness (5, 8, 12, 15 mm). Combined parameter analysis includes four combinations of beam top bar and dowel bar diameters to evaluate synergistic effects.Results and Discussions Both specimens exhibit inverse "S"-shaped hysteretic curves with slight pinching. The RCJ shows extensive beam flexural cracks, while the PCJ's damage is concentrated in the corbel and tenon zone, with no severe damage to main members—consistent with semi-rigid behavior. The PCJ has a ductility coefficient of up to 4.24, with gradual post-peak strength degradation. Its peak bearing capacity and ultimate displacement are slightly lower than the RCJ, and loading stops at a 3.50% displacement angle (bearing capacity = 85% of peak). The FE model accurately reproduces experimental failure modes (concentrated compression damage in corbels/tenons) and hysteretic behavior. The average error in peak bearing capacity is less than 5%, confirming reliability. Minor initial stiffness discrepancies arise from neglecting reinforcement-concrete bond-slip in the "embedded region" function. FE results regarding parametric studies are as follows: 1)Beam top longitudinal rebar diameter: increasing from 8 mm to 16 mm raises peak bearing capacity by 69% and initial stiffness by 16%, with no significant ductility loss. 2) Dowel rebar diameter: enlarging from 8 mm to 16 mm improves peak bearing capacity by 20% but slightly reduces ductility and intensifies corbel damage. 3) Corbel thickness: its impact is minor. Reducing from 130 mm to 90 mm increases peak bearing capacity by 8%, with no changes to failure mode. Minimum thickness is recommended as 2/3 of beam width. 4) Column longitudinal rebar diameter and hoop plate thickness: both have negligible effects on seismic performance. Their variations do not alter force transmission paths, and conventional design values are acceptable.ConclusionsThe proposed hoop panel-tenon joint exhibits excellent semi-rigid characteristics, with a ductility coefficient of up to 4.24, stable energy dissipation, and damage concentrated in the corbel-tenon zone. The FE model reliably simulates the joint's seismic behavior, with peak load error less than 5%. Key design parameters are beam top longitudinal bar and dowel bar diameters, as their increase enhances bearing capacity and stiffness, while corbel thickness, column bar diameter, and hoop plate thickness have secondary effects. Combined parameter analysis shows the baseline configuration balances performance and economy. This research verifies the joint's feasibility, provides optimal parameter ranges, and offers valuable references for the design and application of semi-rigid prefabricated joints in seismic regions, enriching the precast concrete structure design system.

Single-tower structures with large podiums are prone to a concentration of seismic responses because of abrupt changes in stiffness, mass, and geometry between the podium and the tower. Inter-story isolation can mitigate this problem, but the role of pile–soil–structure interaction (PSSI) in soft-interlayer foundations remains unclear. This study investigates a single-tower structure with a large podium and inter-story isolation on a soft-interlayer foundation. A 1/12-scale shaking table test was conducted to compare the seismic responses of a conventional seismic-resistant structure (SRS) and an inter-story isolated structure (ISS). A validated three-dimensional finite element (FE) model was used to investigate the effects of foundation type and soft-interlayer thickness on the dynamic response of the PSSI system. Compared with the SRS, the ISS exhibits a significantly longer natural period and effectively reduces seismic responses in the upper tower. However, owing to PSSI effects, the floor accelerations in the podium do not decrease accordingly and may even increase on some floors. The FE model reasonably reproduces the response trends observed in the shaking table test. The parametric analysis shows that foundation conditions and soft-interlayer thickness can alter the system period, foundation-level input motion, and the distribution of floor responses. Therefore, assuming a rigid foundation may be inappropriate when designing inter-story isolated structures on a soft-interlayer foundation. Foundation nonlinearity, PSSI effects, the displacement capacity of the isolation layer, and the dynamic demands of the podium should be comprehensively considered in seismic design.

The coastal region of Fujian contains numerous existing stone masonry structures, many of which are constructed on soft soil sites. Previous studies have shown that the soil-structure interaction (SSI) effect on soft soil foundations can prolong the structure's natural vibration period and enhance its seismic response. We develops a soil-structure interaction system model and a comparative rigid foundation model using the finite element software LS-DYNA to investigate the impact of SSI on the dynamic characteristics and seismic response of stone structures. The results indicate that the SSI effect alters stone structures' dynamic properties and seismic response. This alteration is evident in the extended natural vibration period, which reduces overall stiffness, increases interstory displacement angles, and slightly decreases the acceleration response. Under both SSI and FIX systems, the structural failure mode is characterized by the external collapse of the second-story stone walls, which causes the roof stone slabs to lose support and fall, leading to overall collapse. The FIX system demonstrates better structural integrity and stability with slower crack development. In contrast, the SSI system exhibits cracks that appear earlier and develop more rapidly, causing more severe damage. The research findings provide a theoretical basis for the seismic reinforcement of existing stone structures on soft soil foundations.

The negative stiffness damper (NSD) has shown excellent effectiveness in reducing vibration. However, researches focusing on the analysis and optimization of the adjacent structures with negative stiffness damper (ASNSD) under non-stationary seismic excitation (NSSE) and varying soil conditions, remain scarce. This paper proposes a soil-dependent stochastic optimization procedure (SDSOP) to investigate the optimal parameters of ASNSD under NSSE considering firm, medium and soft soil conditions. The novelty of this procedure is it integrates stochastic optimization with non-stationary seismic excitation modeled using the Clough-Penzien spectrum combined with time modulation function, while considering different soil conditions. Firstly, the state-space representations of stochastic seismic excitation and ASNSD are combined to form the representations of the augmented structure-damper-earthquake systems. Subsequently, the optimal designs of ASNSD are defined via the solution of the deferential Lyapunov equation. Lastly, the obtained optimal parameters of ASNSD are further examined under artificially generated seismic excitation real earthquake records from the perspectives of dynamic response. The results demonstrate the effectiveness of the proposed SDSOP and highlight the advantages of ASNSD for all soil conditions. Compared to firm and medium soil conditions, the requirements for negative stiffness and damping values are significantly higher in soft soil conditions.

Ultra-high performance concrete (UHPC) is a promising cementitious engineering material with superior mechanical properties, which is an ideal potential rehabilitation material for stone masonry structures. However, the significant tensile stress generated from the UHPC overlay shrinkage under stone constraint is likely to have an adverse effect on rehabilitation. In this study, the development of workability, mechanical properties and shrinkage behavior of polyformaldehyde-UHPC (POM-UHPC) were investigated. The results showed that the optimum limestone powder content, POM fiber volume, water-binder ratio, and superplasticizer content in UHPC with excellent mechanical properties is about 40 %, 2 %, 0.19, 1.5 %, respectively. The increase of POM fiber volume and the decrease in water-binder ratio are beneficial to the development of mechanical properties while decreasing flowability. The autogenous shrinkage of UHPC is characterized by rapid growth in the early age, which could be mitigated by increasing the levels of water-binder ratio, limestone powder, POM fiber volume, and superplasticizer. The autogenous shrinkage development is positively correlated with the compressive strength. The increment of overlay thickness and stone surface roughness can reduce the constraint shrinkage of UHPC. The analyzed shrinkage-induced interfacial stresses between UHPC and stone increase with the UHPC layer thickness and the stone groove depth.

Thick-layer rubber bearings exhibit a more pronounced steel plate constraint effect due to the increased rubber layer thickness. However, current standards only specify the steel plate thickness range for ordinary rubber bearings, without providing dedicated guidelines for thick-layer rubber bearings. Through experimental research and simulation analysis, this study investigates the impact of steel plate thickness on the mechanical performance of thick-layer rubber bearings, refines the relevant theoretical formulas, and develops a predictive model based on the SSA-BP neural network. A thick-layer rubber bearing with a first shape factor of 2.84 was designed, and vertical compression and horizontal shear tests were conducted, complemented by refined numerical simulations. The results reveal that steel plate thickness significantly affects vertical stiffness but has a minimal impact on horizontal stiffness. When the steel plate thickness is 6 mm (thickness ratio 0.4), the vertical stiffness reaches over 80% of its maximum value, while increasing the thickness to 14 mm (thickness ratio 0.93) reduces the change in vertical stiffness to within 5%. Based on upper and lower bound analyses of ultimate stress and yield plasticity ratios, the study recommends that the steel plate thickness should be 1.3 to 1.6 times the rubber thickness, which is a key parameter for optimizing the performance of thick-layer rubber bearings. The developed SSA-BP neural network prediction model for the vertical stiffness of thick-layer rubber bearings demonstrates excellent generalization capability and high predictive accuracy.

The promotion of precast piers in high-intensity zones is still confronted with problems such as the weak integrity of connection parts and insufficient seismic resistance. To address these challenges, a novel connection combining grouted corrugated pipe and socket connection for precast double-column piers was proposed, and the precast piers were connected to the bearing platform by employing Ultra-high Performance Concrete (UHPC) grouting. Additionally, the plastic hinge zones of precast piers were cast with Engineered Cementitious Composite (ECC). Quasi-static tests of three double-column piers using combined connection, single socket connection, and cast-in-place connection, respectively, were conducted. The seismic performance of three specimens was analyzed in terms of hysteretic performance, stiffness degradation, residual displacement, energy dissipation and ductility, as well as the numerical analysis models of three specimens were developed, validated and utilized for parameter expansion analysis. The results show that the seismic performance of the specimens with combined grouted corrugated pipe and socket connection is generally superior to that of the other two specimens. The seismic performance of the combined connection specimen is enhanced by increasing the socket depth and reinforcement ratio. Moreover, the possibility of failure of the bearing platform is reduced by increasing the socket depth, UHPC joint strength, and width. A more reliable whole can be formed by employing the U-shaped steel reinforcement among the bearing platform, UHPC joint and steel reinforcement skeleton. A recommended socket depth for combined connection specimen was given for practical engineering.

Due to the long service period and irregularities in construction, a large amount of existing brick masonry structures around the world have been deteriorated in performance, which are in urgent need of reinforcement measures. Ultra-high performance engineered cementitious composite (UHPECC) is a promising material to the rehabilitation of existing brick wall, where, the mechanical properties of interface is essential to the reinforcement. In this study, the bonding behavior of interface between UHPECC and existing brick walls was investigated by double-sided shear test, and the influence of joint depth on shearing performance was analyzed by experiment and numerical simulation. The results show that the interfacial shear strength between UHPECC and existing-brick wall is increased with the increment of UHPECC joint depth. The shearing load-displacement curve generally includes initial stage, elastic stage and plastic stage, where, the specimen H0 only undergoes an elastic stage, H5 has no plastic stage, and the H15 and H25 have comparable load evolution curves. The optimal joint depth for UHPECC reinforced brick wall is 15 mm. The established model is reliable to simulate the interfacial shear performance of UHPECC reinforced brick wall. Due to the redistribution, the shear stress is mainly concentrated near the joint, which is obvious with the increasing of UHPECC joint depth. Based on the experimental and numerical simulation, a relationship of interfacial shear strength and UHPECC joint depth is proposed.

A new kind of functional gradient material (FGM) based on engineering cementitious composites (ECC) and normal concrete (NC) was proposed in this study. This material offers enhanced crack control while minimizing ECC consumption. Foremost, uniaxial compression tests were carried out on single-layer NC-ECC composites featuring varying ECC volume fractions (0%, 20%, 40%, 60%, 80%, and 100%). These tests yield an elastic modulus formula, E(y), for the NC-ECC composite. Subsequently, based on the E(y) formula, a 5-layer NC-ECC FGM is designed, with each sub-layer having distinct ECC volume fractions. This is contrasted with pure ECC and 2-layer NC-ECC specimens for reference. The study concludes with an analysis of the failure patterns, load-displacement curves, and elastic moduli of the NC-ECC FGM. The results demonstrate consistent performance trends of elastic modulus in single-layer NC-ECC composite specimens, confirming the feasibility of employing a functional gradient between NC and ECC. Utilizing the formula E(y) derived from single-layer NC-ECC, the ECC volume fractions in the 5-layer NC-ECC FGM are computed as 100%, 86.89%, 68.13%, 41.55%, and 0% for each layer. Importantly, the NC-ECC FGM exhibits a failure mode resembling ECC specimens, with primary cracks not extending along interfacial layers. In contrast, 2-layer NC-ECC specimens experience cracking along interfacial boundaries. The compressive strength of NC-ECC FGM surpasses that of ECC specimens by 1.42 times while retaining ECC-like ductility, showcasing a 25.85% improvement over 2-layer NC-ECC. The findings from this study provide valuable insights for the design and subsequent engineering applications of functional gradient materials.

福建沿海地区现存大量既有石砌体房屋,其石砌体墙多数为整毛石干砌甩浆砌筑,砂浆强度低且灰缝饱满度差,结构未设置抗震构造措施,整体性及抗震性能差,对此类房屋进行抗震加固是城乡建设工作的重点.分析既有石砌体房屋的构造组成特点及抗震薄弱环节,综述了整毛石墙体抗震加固技术研究进展与应用情况,总结了目前整毛石墙体抗震加固研究方面存在的不足.最后根据新材料、新技术的发展,提出采用与石材材性相匹配的超高性能混凝土进行整毛石墙体加固的研究展望.