混合连接装配式框架内节点抗震性能研究

为了提供一种适用于高烈度抗震设防区的装配结构连接方式,并为建立该结构的抗震设计方法提供依据,通过6个混合连接装配式混凝土框架内节点试件在低周反复荷载下的加载试验,对其破坏形态、滞回特性、变形恢复能力、位移延性、能量耗散等进行了研究。结果表明,混合连接装配式混凝土框架节点的耗能能力与整体现浇混凝土节点相当,而其延性和变形恢复能力则优于整体现浇混凝土节点,其综合抗震性能优于整体现浇混凝土节点。     

基于哈密顿体系的框剪结构动力时程分析

本文采用框剪结构的并联铁摩辛柯梁模型,从结构总势能出发,求得框剪结构非连续化假定下协同分析的哈密顿对偶体系,由两端边值问题精细积分法中的区段混合能矩阵推导出结构的层单元刚度矩阵,利用有限元刚度集成法形成总刚矩阵;然后采用初值问题的精细积分法对框剪结构进行动力时程分析,并采用Matlab编制相应的程序。以某10层框剪结构为例,验证了本文方法的可靠性与可行性,本方法也适用于其它高层建筑结构如框架、剪力墙、筒中筒等结构。     

基于振动台模型试验的管桩-土-上部结构体系的地震响应试验研究

通过管桩振动台模型试脸,研究了地震作用下单桩基础结构体系的上部结构加速度放大系数、桩顶最大剪力和最大倾覆弯矩响应幅值的分布规律及其影响因素。研究表明,管桩结构体系的各种地震响应不仅与输入的加速度幅值有关,不同的上部结构和场地的动力特性也影响管桩基础地震响应幅值的变化趋势;坚硬场地上结构的地震反应与结构有关,软弱场地上结构的地震响应与场地有关;实际桩-土-上部结构体系不是一个简单结构,必须整体考虑上部和下部结构的动力特性。     

Non-singular antiplane fracture theory within nonlocal anisotropic elasticity

In the present paper, the distributed dislocation technique is applied for the analysis of anisotropic materials weakened by cracks. Eringen's theory of nonlocal elasticity of Helmholtz type is employed. The non-singular screw dislocation within anisotropic elasticity is distributed to model cracks of mode III. The corresponding dislocation density functions are evaluated using the proper crack-face boundary conditions. The nonlocal stress field within a plane weakened by cracks is determined. The crack opening displacement is also discussed within the framework of nonlocal elasticity. The stress singularity of the classical linear elasticity is removed by the introduction of the nonlocal theory of elasticity. The general anisotropic case and the special case of orthotropic material are studied. The effect of material orthotropy is presented for a crack which is not necessarily aligned with the principal orthotropy direction.     

Estimation of fatigue crack growth behavior for small-sized C-shaped inside edge-notched tension (CIET) specimen using compliance technique

Being restricted by the relative larger size requirement, traditional and standard fracture specimens are not applicable for the estimation of fatigue crack growth behavior of some very finite-sized components and precious materials. This study develops a small-sized C-shaped inside edge-notched tension (CIET) specimen which has an advantage of specimen minimization and a wide range of adaptability. A systemic compliance technique for estimating fatigue crack growth behavior of CIET specimen has been successfully constructed and experimentally verified. Groups of fatigue crack propagation rate tests of both CIET specimen and CT specimen for 5083-H112 aluminum alloy were carried out. The resulted da/dN ∼ ΔK curves are heavy affected by specimen configuration and load ratio, and the difference between these da/dN ∼ ΔK curves has been successfully removed by introducing the correction of plasticity-induced crack closure effect. Consequently, the feasibility of CIET specimen for estimating fatigue crack propagation behavior for small-sized components and precious materials has been evidently confirmed.     

On the formation mechanisms of fine granular area (FGA) on the fracture surface for high strength steels in the VHCF regime

The fine granular area (FGA) plays a crucial role in the VHCF regime. However, so far, the uniform understanding or conclusion about the formation mechanism of FGA has not been drawn. In view of the significance of FGA, the current studies on FGA, i.e., the FGA size, the stress intensity factor range at the periphery of FGA, the crack initiation and growth process in FGA, and the formation mechanisms of FGA, are reviewed in the present paper. The role of internal hydrogen in the VHCF regime is further discussed. In the end, two important definite conclusions are drawn based on the present investigations.     

并联复合隔震体系非线性性能的试验研究

对一并联复合隔震结构模型进行了振动台试验研究,通过逐渐增加摩擦滑板的数量来调整隔震层摩擦承压比的大小。分析了复合隔震体系不同摩擦承压比对隔震层滞回特性、基底剪力系数以及复合隔震体系非线性性能的影响。试验结果表明:复合隔震结构的非线性特性与摩擦承压比的大小及地震烈度大小有关,在合理的摩擦承压比取值范围内复合隔震结构具有良好的隔震性能。     

蜂窝梁模型设计及其破坏模式和滞回性能分析

介绍了利用I10工字型钢设计在一定扩张比下具有圆孔的蜂窝梁模型进行的研究,谊模型可以按相似比模拟工程应用中大跨度蜂窝梁.通过建立有限元模型并应用ANSYS软件对简支圆孔蜂窝梁在反复单项荷载、反复双项荷载和反复面荷载作用下的破坏模式和滞回性能进行了分析,得到蜂窝梁在不同荷载作用下的工作性能,为工程设计提供参考.     

Microstructure and properties of aluminum silicon/short fibre carbon composites fabricated by semi-solid thixomixing

A novel method was developed, based on thixotropic nature of semi-solid slurry of aluminum silicon alloy, for the effective dispersion and distribution of short carbon fibers (C_sf) under intensive shear stress (τ) into the eutectic without physical or chemical damage. The C_sf were distributed homogeneously into the matrix at optimum conditions: a temperature of 576–580 °C, around 48% of solid fraction, and rotation speed of mixing was at 100 rpm. The gas entrapment and porosity was a challenge in the fabrication the aluminum composite by thixomixing, and its size increased when the samples were heat treated. The extruded and heat treated composites had around 24% improvement of mechanical strength as assessed by tensile tests. The predominant deposition of silicon and its intermetallics at the interfacial region improved the wettability and adherence to achieve good mechanical properties. The formation of some intermetallics can be helpful to overcome low wettability effects and their structural evolutions were impressive. The fractography analysis illustrated the ductile fracture with some plastic deformation as the results of dimples and some fiber pull-out in the fractured surface. Ultra-micro hardness evaluation showed good interfacial bonding after heat treatment. The thixomixing process can be developed to produce various composites with different reinforcement.     

Separation of hot electrons and holes in Au/LaFeO3 to boost the photocatalytic activities both for water reduction and oxidation

Construction of plasmon-based nanostructures is an effective way to enhance the photocatalytic activities of semiconductor photocatalysts for water-splitting. However, the synergistic effect of plasmon-related hot electrons and holes for water splitting in the plasmon-hybrid photocatalyst is rarely considered. Herein, we construct a plasmon-based Au/LaFeO₃ composite photocatalyst to investigate the complex roles of hot electrons and holes for solar water splitting. Benefiting from the formation of Schottky junction and surface plasmon resonance effect of the Au nanoparticles, the synthesized photocatalyst exhibits an excellent photocatalytic activity for each half-reaction of water splitting, and the rates for H₂ and O₂ generation are obtained as high as 202 μmol g⁻¹ h⁻¹ and 23 μmol g⁻¹ h⁻¹, respectively. Moreover, an in-depth investigation reveals that the improved hydrogen evolution is caused by the hot electron injection from Au to LaFeO₃, and the hot holes in Au induced by the separation of hot charges can initiate the water oxidation directly on the surface of gold. Thus, this work provides a new insight into the synergistic effect of plasmon-related hot electrons and holes for boosting the photocatalytic reactions.