In order to limit the excessive relative displacement between pier and beam, a latticed long-stroke restrainer(LLSR) based on shape memory alloy (SMA) bar is proposed on the basis of single long-stroke shape memory alloy restrainer (LSR). The device consists of SMA alloy bar with excellent superelasticity and re-centering performance, MC nylon, steel pipes and strips or plates. SMA bars can consume ground motion energy and provide re-centering capability. The MC nylon and steel pipe form an anti-buckling system to prevent the SMA bar from buckling under pressure. Firstly, the structure and working mechanism of single long-stroke shape memory alloy damper and lattice long-stroke shape memory alloy damper are described. Secondly, the tensile test of SMA bars under different heat treatment temperature was carried out to determine the SMA bar with the best superelasticity, which was then used as the inner core of the LSR. Then, the axial tension and compression experiment of a single LSR was conducted to further study its mechanical properties. Finally, based on the experimental data of the LSR and the finite element software of ABAQUS, the numerical analysis and parameter analysis of the LLSR were carried out, and the corresponding design method was proposed according to the results of numerical analysis and parameter analysis. The research shows that LLSR not only has stable energy dissipation capacity but also has good re-centering ability.

Environmental vibration is an important factor that affects the normal operation of various precision instruments and equipment. To solve the problem that the environmental vibration exceeds the vibration limit for the normal operation of equipment, the design of steel spring vibration isolation base is investigated. Through experimental verification and calculation analysis, the relationship between the vertical and horizontal stiffness of steel spring is derived, and the fuzzy problem of horizontal stiffness of steel spring is solved. A novel steel spring floating slab vibration isolation base is designed based on the requirements. The finite element method is utilized to study the vibration reduction and isolation effects of the pedestal under different steel spring stiffnesses. The deformation of the pedestal above the equipment with uneven mass distribution, the deformation of the pedestal with moving parts, and the vibration level of the pedestal are analyzed respectively. The analysis results show that the new steel spring floating slab vibration isolation base exhibits excellent horizontal and vertical vibration isolation effects. When the natural frequency of the base is 4.2 Hz, the maximum vibration reduction efficiency for the environmental vibration above 12 Hz can exceed 90%. The equipment with small moving parts on the base also demonstrates good stability. When the 50 kg moving parts move from one end of the base to the other, the vertical deformation of the base is less than 800 μm. When the disturbance force generated by equipment vibration is less than 1.5 kN, the base can still maintain the vibration level of VC-C. The research results can provide valuable references for the vibration isolation design of equipment in similar industrial plants.

In this paper, it is proposed that the frame structure of glulam pillar and steel beam can address the issues of complex joint structure, limited beam stiffness and low lateral stiffness of long span glulam beam and column structure joints. Three joint specimens without planted bar and three joint specimens with the diameter of planting reinforcement as a variable were designed. Monotonic loading experiment were conducted on two joint specimens without reinforcement, while other joint specimens underwent low-cycle repeated loading to obtain their seismic performance, including failure mode, hysteresis curve, skeleton curve and energy dissipation capacity. The experimental results show that the measure of reinforced with planted bar can effectively improve the local bearing capacity of the transverse grain, the flexural stiffness and ultimate bearing capacity of the joints, but the increase in the diameter of the reinforcing bar has little impact. The energy dissipation capacity of the joint can be significantly improved by the measure of reinforced with planted bar, and the seismic performance of the joint can be improved. The failure modes of flexible end plate and rigid end plate are different, the members of the flexible end plates are S-shaped deformation and failure mode, the joint angle deformation is large, the bending stiffness is small, and the rigid end plate members are the transverse compression deformation and failure of the wooden column, and the bending stiffness and bearing capacity of the joint are strong. The formulas for the ultimate flexural bearing capacity of the joints are derived, and the theoretical values agree well with the measured ones.

Clutching inerter damper (CID) has been extensively studied in structural vibration control recently. Because the passive CID device does not take into account flywheel speed reset and cannot achieve an ideal piecewise model, its control performance is limited. Therefore, this study explores the semi-active implementation of the ideal CID model. This paper begins with a comparative study of the ideal and passive analytical models of CID, providing insight into the performance differences and limitations of the two models. Subsequently, an electromechanical clutching inerter damper (ECID) scheme is proposed, which includes energy harvesting and variable inertance. The implementation of the electrical inertance, flywheel speed reset, and energy recovery functions are also discussed, and an electromechanical hybrid simulation model of the ECID is established. This paper thoroughly examines the control and energy recovery performance of the ECID through theoretical and simulation analyses. It explores the effects of resistance and capacitance in the ECID circuit on system performance and demonstrates that the ECID has significant vibration control and energy recovery capabilities. This study presents a comprehensive scheme for the implementation of CID, variable inertance, and energy recovery, which has theoretical reference significance for the development of self-powered semi-active variable inertance devices.

To clarify the degradation law of the mechanical property of 6061-T4 aluminum alloy after elevated temperatures as recommended by the GB 50429—2007 code for design of aluminium structures, a total of thirty-eight 6061-T4 aluminum alloy specimens were designed, and the unidirectional loading tests and cyclic tensile loading tests at room temperature and elevated temperature were performed. The effects of cooling type and loading protocol on the failure characteristics, initial elastic modulus, strength, stress degradation, and energy dissipation were evaluated. The experimental results show that the yield platform and strain hardening behavior in the unidirectional cyclic tensile stress-strain curve of 6061-T4 aluminum alloy were not observed. When the heating temperature was in the range of 100~300 ℃, the surface of 6061-T4 aluminum alloy specimens became slightly darker but not significantly. The surface condition of the 6061-T4 aluminum alloy can not be used as an indicator to evaluate the damage degree after fire. The temperature had a slight effect on the initial modulus of 6061-T4 aluminum alloy, and the cooling method also slightly affected the mechanical property of 6061-T4 aluminum alloy. When the temperature was below 200 ℃, the temperature did not have a significant effect on the strength of the aluminum alloy. When the temperature was above 200 ℃, the strength of 6061-T4 aluminum alloy exhibited a significant decreasing trend with the increase in temperature. During unidirectional cyclic tensile tests at room temperature, the yield strain of aluminum alloy specimens was slightly lower than that of unidirectional loaded specimens. Due to the plastic accumulation damage during the cyclic tensile process, the ductility of the specimens deteriorated under unidirectional cyclic loading. With the continuous increase in temperature, the yield of the specimens tended to occur earlier, and the deformation capacity changed from worse to better. The energy dissipation capacity of 6061-T4 aluminum alloy gradually decreased with the increase of temperature, and the cumulative energy was positively correlated to aluminum alloy strength and cycle number.

The Yellow River floodplain, covering an area of 250000 km² located in northern China, is a densely populated and economically developed region with a high level seismic background activity. In recent history, numerous earthquake-induced liquefactions occurred in this floodplain, however, relevant investigations and research are also lacking. So far, the knowledge of earthquake-induced liquefaction in the Yellow River floodplain is almost blank. In 2023, the Pingyuan M_S5.5 earthquake occurred in Shandong Province and induced soil liquefaction in the Yellow River floodplain. Through post-earthquake investigations, it is the first time that a case of real earthquake-induced liquefaction in the Yellow River floodplain has been analyzed in this paper. The characteristics of liquefaction induced by this earthquake have been obtained. The main points are as follows: this earthquake mainly induced soil liquefaction in silt and silty soils for 91% of sites in the total. The depth range of liquefied soil deposits is mainly of 7~12 m. The largest depth of liquefied soil deposit was confirmed at least 14 m, and possibly at an even deeper one. The depth of liquefied soil is beyond the common range of that in previous earthquakes. Liquefaction sites are mainly observed in the epicentral range of 6~12 km and are located in the seismic intensity 5 region and the boundary of intensity 6 region, which is significantly different from previous investigations. The abnormal distribution of liquefaction sites is closely related to the effect which is induced by the exclusive “highland-slope-lowland” microtopography in the Yellow River floodplain. In a moderate earthquake, the liquefaction in the Yellow River floodplain has induced moderate damage and has an especially different characteristic. It can be concluded that more severe liquefaction hazards may occur in large earthquakes. Therefore, it is urgent to develop a specific analysis procedure and evaluation method for soil liquefaction in the Yellow River floodplain. The work in this paper can improve the understanding of soil liquefaction during small and moderate earthquakes and provide firsthand information and new clues for research on soil liquefaction in the Yellow River floodplain.

The current seismic design codes for bridges primarily rely on design response spectra derived from far-field observational records, which fail to accurately reflect the ground motion characteristics and structural seismic response characteristics in near-fault regions. As a result, the seismic design for bridges in near-fault regions may be unsafe. To address the issue, near-fault ground motion time histories are selected from the Pacific Earthquake Engineering Research Center (PEER) database based on principles including source distance, moment magnitude, and peak ground acceleration(PGA). Average spectra are calculated using site foundation conditions and PGA as grouping principles, and then calibrated using a least-squares piecewise fitting method. This process yields statistical recommendations for three key parameters of the near-fault horizontal design gauge response spectrum: amplification factor, attenuation index, and characteristic period. Finally, adjustments were made to propose a gauge response spectrum that considers near-fault earthquake characteristics, providing a basis for incorporating near-fault ground motion effects into China's seismic design codes for bridges.

The dynamic response of compacted coarse-grained soil as a filling material for the surface layer of railway subgrade bedding is crucial for the overall performance of the subgrade structure under long-term cyclic train loads. This study conducted a series of cyclic triaxial tests to investigate the effects of fine content, confining pressure, and cyclic stress amplitude on the accumulated behavior of coarse-grained soils. The test results indicate that under the same cyclic loading conditions, specimens with higher fine content exhibit less accumulated axial strain. Furthermore, coarse-grained soil specimens exhibit less accumulated axial strain under higher confining pressure or lower cyclic stress amplitudes. Subsequently, the plastic shakedown limit of coarse-grained soils with different fine contents was determined based on a universal shakedown criterion. The results demonstrate that the plastic shakedown limit of coarse-grained soil specimens gradually increases with an increase in fine content. Under higher confining pressure, the corresponding plastic shakedown limit of coarse-grained soil is also higher. Additionally, by plotting the stress state corresponding to the plastic shakedown limit of coarse-grained soil on the plane of p-q, a relationship was established between the coefficient of fine content (FC) and the model parameters in the existing shakedown criterion. A united plastic shakedown criterion is then proposed for coarse-grained soils with different fine contents. The conclusions can provide a theoretical foundation for the design and stability assessment of railway subgrades.

A semi-active impact damper (SAID) with controllable timing is presented based on vibro-impact mechanism, aiming to control the multi-modal vibration of civil structures under earthquake excitations. The proper impact actuating force can interfere with the accumulation of structural vibration amplitude without additional controllable elements. In this paper, a device construction with adjustable collision clearance was proposed based on the SAID mechanical model and corresponding semi-active control strategy. The damping performance of the SAID system in a five-story frame structure is studied through shaking table tests. The results showed that the SAID system could effectively reduce the acceleration at the top floor of the structure and the inter-story drift. Time-frequency energy analysis revealed that the SAID system can transfer the structural vibration energy from low-order modes to high-order modes to accelerate the energy dissipation during the controlled impact process and suppress the structural response caused by dominant modes. An enhanced semi-active impact damper (ESAID) is further proposed to reduce the adverse effect of the acceleration sudden change caused by the impacts while improving the damping performance of the SAID system.

Buildings are essential fundamental for maintaining the economic, cultural, social, and functional aspects of urban life and are the basis for ensuring urban seismic resilience. The seismic resilience of buildings not only depends on the seismic capacity of structural components but also on non-structural components and equipment. Currently, there are no established methods for enhancing the seismic resilience of existing buildings. This paper outlines the basic approach for enhancing the seismic resilience of existing buildings, proposing methods aimed at ensuring structural safety, meeting predefined functional requirements, and enabling rapid recovery. The paper establishes seismic resilience enhancement objectives for existing buildings, considering both the function and the remaining service life of the buildings, and a “five-step” approach to enhancing seismic resilience is also developed. Finally, a case study of a specific building’s seismic resilience enhancement is presented to preliminarily verify the rationality and feasibility of the proposed methods. This paper can provide practical insights for enhancing the seismic resilience of buildings, as well as individual infrastructure components such as bridges and tunnels.