支座刚度系数的取值对桥梁结构的动力响应有较大影响,选取合理的刚度系数可以优化桥梁的抗震性能.通过大型有限元软件ANSYS使用Combine14弹簧单元来模拟桥梁支座,选取0.1倍,1倍,10倍,20倍,50倍,100倍,200倍的初始法向刚度和切向刚度,通过数值计算所得的加速度、位移及应变峰值与振动台试验实测值的对比来进行取值率定.结果 表明,当取100倍的初始刚度系数时为较合理取值.通过增大地震动峰值加速度将数值模拟值与试验实测值进行误差比较,误差都在5％左右,验证了弹簧单元刚度系数率定的准确性.率定及验证过程可为类似工程的刚度系数计算提供参考.

为研究桥梁上部结构关键部位界面接触效应及其对结构的地震响应影响规律,基于接触面对法建立了非线性地震响应分析模型,利用ANSYS进行数值计算,对Goodman单元的切向与法向刚度进行率定,通过模型的位移云图及相对位移时程以及从地震动峰值加速度、材料的弹性模量、接触摩擦系数3个方面以接触面滑移距离为评价指标进行分析.结果表明:相对位移的总体趋势为先增大后减小至零,大小变化随时间无明显规律;接触面滑移程度随着地震动峰值加速度的增大而逐渐增大,随着材料弹性模量的增大而呈线性变小,随着接触界面摩擦系数的增大而逐渐减小.

In order to study the effect of various micro parameters of the soil-structure contact interface on the macro response, starting from the meso structure of the soil, a two-dimensional discrete element method is used to conduct a biaxial shear numerical test. The sensitivity analysis is carried out for the friction factor, particle shape, void ratio of the particles, normal stress, stiffness ratio and other parameters. The influence of various micro parameters on the macro response is found. It also establishes a cross-scale correlation of the micro-macro parameters of the granular material at the contact interface, and reveals the meso-mechanical behavior of the granular material at the contact interface mechanism. The results show that friction factor, porosity ratio, particle shape and normal stress have a greater influence on the peak strength of the contact interface, stiffness ratio has a smaller influence on the peak strength of the contact interface; friction factor, normal stress and stiffness ratio have an influence on the elastic modulus. The effect is significant, in which the friction factor is approximately proportional to the internal friction angle, and it has a greater impact on the shear strength and shear dilatancy of the soil. The combined arc particles are closer to the true sand shape than the round particles, and the simulation effect is better. The critical strength and critical porosity ratio are not affected by the initial porosity ratio and the shear strength of the combined arc particles is affected by the normal stress. The greater the normal stress, the greater the shear strength of the particles. The research results provide a theoretical reference for material optimization and modification of the contact interface.

The physical properties of coral sand are far more complicated than that of normal terrigenous sand. The recent advances are summarized in the fields of particle morphology, particle breakage and compressibility. Based on the mesoscopic structure of coral sand, the reasons of the particular mechanical properties are revealed. The low strength, porosity, irregular particle shape, and easy to break at edges and corners, all these above factors will aggravate the compressibility of coral sand. The interaction of the factors determine the particular mechanical properties of coral sand.

随着经济的发展和科技的进步,我国的城市化水平不断提高,但人口的过度集中导致了城市交通拥挤等问题,于是高架桥梁体系日趋完善.因此研究高架桥梁结构间的一系列动力学行为显得尤为重要,特别是在地震作用下的非线性动力相互作用问题.本文首先介绍了高架桥梁结构间接触面问题研究的发展现状,阐述了各种连接单元模型与研究方法,并集中起来进行全面、客观的对比评价,总结了其优点和不足.最后对高架桥非线性接触问题的研究进行了总结与展望.

综述了地震作用下,高架桥碰撞问题的研究现状,并简要介绍了现有的两种碰撞研究分析方法:恢复系数法与接触单元法.对常用的两种高架桥防碰撞措施进行了分析,同时也对高架桥在地震作用下的碰撞问题研究的发展做出了进一步展望.

Based on Multi-scale structure of granular materials, it is one of the challenges of granular materials research to set up the connection between the microscopic structure and macroscopic mechanical behavior and explore new formula to solve the coupled across scales process. Due to nonequilibrium and strong interaction of the microstructure, a statistical description of microcosmic physical quantities and geometrical parameters can provide the connection between the micro motion and macroscopic mechanical behavior. This paper introduces the statistical parameters of different structure levels of the granular material and summarizes achievements of the researchers about the relationship between the statistical parameters and the mechanical concept. It is concluded that for granular materials, correct selection of microscopic parameters and using scientific statistical methods are key to predict the macroscopic behavior.

The shearing induced dilatancy is an important deformation characteristic of granular materials during loading process. As the minimal unit to remain stable under external load, void cell is used to characterize the internal structure of granular materials. Based on the shear process of the individual void cell, it is found that the volume change of void cell is dependent on the stress ratio and the shape of void cell. It is explained the microscopic mechanism of the phenomenon that the dense granular materials compress first and then dilate. The evolutions of the shape of the individual void cell and volume deformation in them during biaxial shear test are simulated by using discrete element method (DEM). The results show that, the void cell is enlarged along the direction of the maximum principal stress and the volume deformation in the void cell compression first and then dilate as biaxial compression proceeds. Moreover, localization phenomenon is observed in the volume deformation in local void cells from the numerical results, i.e. voids with large dilatancy exhibit in the form of oblique bands at large deformation stage. The mechanical analysis of individual void cells and DEM results of dense granular array show that dilatancy of granular materials is dependent on the microscopic geometry fabric and the transmission of the force in them.