灌注桩的承载性状分析研究

通过实测桩身应力得到桩的端承力和桩侧的摩擦力在载荷递增过程中相互交叉影响,且桩侧的摩擦力先于桩的端承力达到受力极限状态。另外,统计分析端承力与摩擦力的发挥情况,整桩设计的安全系数为2倍,实测端承力的安全系数为5.2倍,实测摩擦力的安全系数为1.7倍。S-lgQ法和Q-Sb法划分侧摩擦力和端承力,与实测内力结果比对,存在一定的误差,但是基本能够判定桩的承载性状。论证了桩的受力—位移曲线(Q-S),是桩的承载性状(侧摩擦力、端承力和桩身压缩量)的综合反映。

基于FIB MC 2010的混凝土塑性损伤模型参数确定及实证分析

为确定更加科学合理的混凝土塑性损伤模型参数,通过对ABAQUS中CDP模型特点进行分析,结合FIB MC 2010中混凝土单轴受力特性提出CDP模型参数确定方法;同时依托既有文献试验实例建立数值模型进行损伤破坏分析并与试验结果进行对比。结果表明:根据FIB MC 2010中混凝土单轴力学特性确定ABAQUS中CDP模型参数可用于无腹筋钢筋混凝土结构损伤破坏的数值分析;在不考虑模型初始损伤情况下,相同加载位移(挠度)基于FIB MC 2010的数值模型分析结果比试验结果稍大。

薄壁球壳压缩非对称屈曲特性的实验及有限元分析

采用实验方法研究了球壳在刚性板准静态和冲击压缩下变形特性及非对称屈曲模态,结合ABAQUS有限元分析了球壳冲击压缩下的屈曲变形过程、非对称屈曲特性,探讨了其影响因素.研究结果表明:(1)非对称屈曲模态与冲击速度相关,随着加载速度提高,薄壁球壳非对称屈曲从5边形转变为6边形.(2)在冲击速度较小时,力—位移响应曲线及失稳变形模态与准静态几乎相同,可近似按准静态过程分析.(3)在对称屈曲阶段的力—位移响应曲线,有限元与实验结果吻合较好.进一步对实验与有限元模拟结果在非对称屈曲阶段的差别进行了探讨,认为冲击实验中平板与球壳的接触约束变化对非对称变形过程有重要作用.

简谐荷载作用下斗拱的耗能分析

分析了三层木塔中选取的典型斗拱,运用ABAQUS建立实体模型,并对模型施加变幅简谐波荷载,分析斗拱结构在简谐波荷载作用下的力—位移曲线及斗拱在水平荷载作用下的传力路径,而后对斗拱模型滑移前后的刚度和模型的粘滞阻尼系数进行了求解,为仿古木塔结构的整体模型的抗震性能分析提供了参考。

Axial compression physical testing of traditional and bird beak SHS T-joints

The static tests of nine traditional and bird beak square hollow structure(SHS) T-joints with different β values and connection types under axial compression at brace end were carried out. Experimental test schemes, failure modes of specimens, jack load-vertical displacement curves, jack load-deformation of chord and strain intensity distribution curves of joints were presented. The effects of β and connection types on axial compression property of joints were studied. The results show that the ultimate axial compression capacity of common bird beak SHS T-joints and diamond bird beak SHS T-joints is larger than that of traditional SHS T-joint specimens with big values of β. The ultimate axial compression capacity of diamond bird beak SHS T-joints is larger than that of common bird beak SHS T-joints. As β increases, the increase of the ultimate axial compression capacity of diamond bird beak SHS T-joints over that of common bird beak joints grows. The ultimate axial compression capacity and the initial axial stiffness of all kinds of joints increase as β increases, and the initial axial stiffness of the diamond bird beak SHS T-joints is the largest. The ductilities of common bird beak and diamond bird beak SHS T-joints increase as β increases, but the ductility of the traditional SHS T-joints decreases as β increases.

Analytical analysis of pullout resistance of the hydraulic expansion rockbolts on a frictionally coupled model

This paper proposes an empirical formula to estimate the shear strength of hydraulic expansion rockbolts.The field experimental results were obtained from eleven pullout tests to evaluate the results computed by the proposed formula.It was found that shear resistance of hydraulic expansion rockbolts significantly depends on the uniaxial compressive strength and elastic modulus of rock,with high correlation coefficients of 0.7651 and0.8587,respectively.The developed formula enables estimation of the maximum pullout load in an analytical process without pullout tests in the field.Conversely,due to the poor interlocking at the initial pullout load,the measured displacements were higher than the estimated ones.To reduce the interlocking effects between bolt and rock,we recommend preloading of 29.4 kN.Preload allows reducing the distance between the measured and estimated displacement and making two load-displacement curves practically identical with marginal differences of 1.1 to 1.5 mm at the maximum pullout load.

A new method to determine the elastoplastic properties of ductile materials by conical indentation

Based on load-displacement curves,indentation is widely used to extract the elastoplastic properties of materials.It is generally believed that such a measure is non-unique and a full stress-strain curve cannot be obtained using plural sharp and deep spherical indenters.In this paper we show that by introducing an additional dimensionless function of A/A (the ratio of residual area to the area of an indenter profile) in the reverse analysis,the elastoplastic properties of several unknown materials that exhibit visually indistinguishable load-displacement curves can be uniquely determined with a sharp indentation.