Abstract:A new type of vertical seismic isolation device， consisting of hydraulic jack and accumulator （VSI-HJA）， is proposed for vertical vibration isolation of building structures. Firstly， the working principle of VSI-HJA is introduced， and the non-linear stiffness model and the energy dissipation model of the isolation system are established. Secondly， cyclic loading tests were conducted to assess the frequency dependence and displacement amplitude dependence， and the equivalent stiffness and energy dissipating parameters of VSI-HJA were measured. The test results indicate that the vertical stiffness of the device varies nonlinearly with an error within ±3% between the theoretical and experimental values， the seismic isolation device develops a full hysteresis loop， shows strong energy dissipation capacity， has velocity-dependent damping property. The test results are in good agreement with the calculated results. Finally， the effectiveness of the proposed VSI-HJA is further investigated by simulating the seismic isolation effect of structures with different device parameters using the finite element method. The research results reveal that the displacement response of the isolated structure increases correspondingly with the weakening of their vertical stiffness， while the acceleration response decreases. The isolated structure demonstrates excellent seismic isolation performance， and the vertical displacement of the isolated structure under the earthquake can be effectively controlled by the damping adjustment.

Abstract:To study the bending hysteresis performance of aluminum alloy gusset joints and compare them with static performance， four full-scale specimens were tested and subjected to hysteresis and monotonic loading， and the entire experimental loading process was numerically simulated using the general finite element software package ABAQUS. The failure mode， bending moment-rotation angle relationship， and energy dissipation capacity of aluminum alloy gusset joints were studied. Adopting the symmetrical loading method， the joint area is a pure bending segment. The research results indicate that the aluminum alloy gusset joint is a typical semi-rigid joint， and its destructive process can be divided into elastic stage， bolt slip stage， bolt and screw hole extrusion stage， and failure stage. The relationship curve of bending moment and rotation angle is obtained. The failure mode of the joint is the fracture of the member end section， and the crack begins to expand from the outermost row of screw holes at the end of the member. The joint has no obvious warning before failure and it’s a typical brittle failure， with no decreasing load. The skeleton curve of joint is similar to the monotonic loading curve， but due to the accumulated damage of the joint during the hysteresis loading process， the ductility is lower than that of monotonic loading. Increasing the number of bolts can improve the energy consumption performance of the joint and make the hysteresis loop fuller.

Abstract:To address the longitudinal shear capacity of composite slabs，this paper finds a kind of interlocking effect existing in a new type of composite slab, which is a new kind of shear mechanism and expounds its mechanism. In order to verify the effectiveness of this type of shear mechanism, monodirectional pseudo-static tests for six composite specimens with three kinds of structural forms of the precast panel were conducted. By comparing the integral behavior of the composite slab in ultimate load, hysteric curve, self-resetting property and so on, the results indicate that, when compared with ordinary prestressed concrete composite slabs, owing to its less damage accumulation in the lamination of this new type of composite slab, the proposed interlocking effect can enhance the deformation recovery performance to some extent and ensure that the composite slabs have good interaction between the laminated layer and the precast panel to give full play to its ultimate load.