桥梁板式橡胶支座抗震力学性能研究

根据强震下桥梁板式橡胶支座破坏情况,包括支座滑动位移、挡块变形以及桥墩位移,通过有限元数值模拟,找出相对应的力学变化情况,并建立桥梁板式橡胶支座的抗震力学性能评价指标。引入近年来某强震记录参数,输入相应数值进行模拟计算。结果表明,基于有限元数值模拟计算,能够再现强震时橡胶支座力学形变及损害情况。建议提高桥梁混凝土挡块的横向剪切力,从而提高板式橡胶支座的抗震力学性能。

Mechanical Properties and Thermal Shock Resistance of SrAl_(2)Si_(2)O_(8) Reinforced BN Ceramic Composites

Hexagonal boron nitride(h-BN)ceramics have become exceptional materials for heat-resistant components in hypersonic vehicles,owing to their superior thermal stability and excellent dielectric properties.However,their densification during sintering still poses challenges for researchers,and their mechanical properties are rather unsatisfactory.In this study,SrAl_(2)Si_(2)O_(8)(SAS),with low melting point and high strength,was introduced into the h-BN ceramics to facilitate the sintering and reinforce the strength and toughness.Then,BN-SAS ceramic composites were fabricated via hot press sintering using h-BN,SrCO_(3),Al_(2)O_(3),and SiO_(2) as raw materials,and effects of sintering pressure on their microstructure,mechanical property,and thermal property were investigated.The thermal shock resistance of BN-SAS ceramic composites was evaluated.Results show that phases of as-preparedBN-SAS ceramic composites are h-BN and h-SrAl_(2)Si_(2)O_(8).With the increase of sintering pressure,the composites’densities increase,and the mechanical properties shew a rising trend followed by a slight decline.At a sintering pressure of 20 MPa,their bending strength and fracture toughness are(138±4)MPa and(1.84±0.05)MPa·m^(1/2),respectively.Composites sintered at 10 MPa exhibit a low coefficient of thermal expansion,with an average of 2.96×10^(-6) K^(-1) in the temperature range from 200 to 1200℃.The BN-SAS ceramic composites prepared at 20 MPa display higher thermal conductivity from 12.42 to 28.42 W·m^(-1)·K^(-1) within the temperature range from room temperature to 1000℃.Notably,BN-SAS composites exhibit remarkable thermal shock resistance,with residual bending strength peaking and subsequently declining sharply under a thermal shock temperature difference ranging from 600 to 1400℃.The maximum residual bending strength is recorded at a temperature difference of 800℃,with a residual strength retention rate of 101%.As the thermal shock temperature difference increase,the degree of oxidation on the ceramic surface and cracks due to thermal stress are also increased gradually.

Numerical and experimental study on seismic behavior of concrete-filled T-section steel tubular columns and steel beam planar frames

The seismic behavior of planar frames with concrete-filled T-section columns to steel beam was experimentally and numerically studied. A finite element analysis （FEA） model was developed to investigate the engineering properties of the planar frames. Two 1：2.5 reduced-scale specimens of T-section concrete-filled steel tubular column and steel beam of single-story and single-bay plane frames were designed and fabricated based on the design principles of strong-column, weak-beam and stronger-joint. One three-dimensional entity model of the investigated frame structure was built using a large-scale nonlinear finite-element analysis software ABAQUS. Experimental results show that the axial compression ratio has no effect on the failure mode of the structure, while with the increase of axial compression ratio and the dissipated energy ability increasing, the structural ductility decreased. The results from both experiments and simulations agree with each other, which verifies the validity and accuracy of the developed finite element model. Furthermore, the developed finite element model helps to reflect the detailed stress status of the investigated frame at different time and different positions.