复合桩基桩土非线性相互作用的数值分析

为了对复合桩基桩土非线性相互作用的工作机理进行深入分析,利用ABAQUS对常规桩筏基础(3D桩距)和复合桩基(6D桩距)进行了三维弹塑性分析.利用无厚度接触面单元模拟筏板-桩-土的非线性接触特性,采用Mohr-Cou lomb弹塑性本构模型描述土的非线性特性,桩设为弹性,得到了沉降、桩土荷载分担比、土体绕桩流动等变化情况,并对二者进行了对比分析.分析结果基本反映了桩-土-筏的实际工作性状,并验证了复合桩基理论的正确性.     

素土挤密桩在湿陷性黄土中的应用

本文以G309固西高速公路项目为依托,通过当地地质条件、地层状况、黄土湿陷性等综合因素,采用素土挤密桩法加固湿陷性黄土路基。对不同深度的桩体土和桩间土钻芯取样进行物理指标检测和承载力测试,试验表明:素土挤密桩改变土体的物理性质,使土体加密,有效提高桩体土的压实系数和桩间土的挤密系数,路基湿陷性消除,复合地基承载力显著提高,该方法在深层处理地基问题上是一种较为提倡且经济的处理措施。     

长短桩复合地基的设计方法讨论

本文从复合地基桩和桩间土的应力发挥系数的影响因素分析入手,得到桩土应力发挥取决于桩顶刺入量、桩体的刚度和桩端刺入量决定,土的发挥相对于桩的发挥较被动。在长短桩复合地基的设计时,长桩、短桩和垫层厚度是设计中最重要的三个要素,长桩为第一道防线,分担了主要的荷载,同时控制着复合地基的沉降的,短桩为第二道防线,也分担了一部分荷载,调节长桩的荷载比例,垫层影响厚度影响着桩间土的应力,同时对长短桩应力也有一定影响。     

桩基静载试验的若干问题分析

桩基静载试验是一项方法成立,理论上无可争议的桩基检测技术。在确定单桩极限承载力方面,它是目前最为准确、可靠的检验方法,判定某种动载检验方法是否成熟,均以静载试验成果的对比误差大小为依据。因此,每种地基基础设计处理规范都把单桩静载试验列入首要位置。一般情况下,桩基静载试验的成果数据,如单桩承载力、沉降量等均认为是准确、可靠的,这已为无数的工程实例证明。     

桩-桩帽-系梁复合结构加固路基特性研究

高强预应力混凝土管桩(PHC管桩)加固深厚软土地基时,桩帽偏心会降低桩承式路基的整体加固效果,影响路堤稳定性。本文以某高速公路桩承式路堤工程为依托,利用有限元软件ABAQUS建立桩承式路堤三维数值模型,研究了桩帽向路基外侧不同偏心距对路堤边坡稳定性的影响,并提出桩-桩帽-系梁复合结构改进措施。研究结果表明:桩帽偏心时桩体荷载分担降低,地基沉降和侧向位移显著增大,桩土差异沉降增大,边坡稳定性降低,桩帽极限偏心距离为10cm;桩帽用系梁相连后,地基土沉降和差异沉降均明显减小,边坡稳定性提高,桩-桩帽-系梁复合结构改进措施有效。     

静压预应力混凝土管桩在工程应用中的研究

针对城市锤击送桩噪音控制,使静压桩得到广泛的应用。为此对静压预应力混凝土管桩的应用情况进行研究,采用静载试验+PDA高应变检测,对常用的φ400、φ500静压预应力管桩,在不同地质条件、不同歇后恢复时间、不同施工控制参数下的极限承载力进行试验研究。经统计分析后提出主要土(岩)层桩的极限端阻力和极限侧阻力指标,并根据工程实际情况,提出静压预应力混凝土管桩施工控制参数、质量检测等要求。     

疏桩基础在工程中的应用

本文结合工程实际，介绍了长、短桩复合桩基的设计过程:方案选择;桩体承力计算，承载力及沉降变形计算．通过载荷试验、试桩检测，夯实水泥土桩及CFG桩检测结果、复合桩基检测结果以及沉降观测结果，说明复合桩基符合设计要求，充分发挥桩及桩间土的性能，节省了工程造价．     

预应力管桩静载曲线异常分析及处理意见

由于预应力管桩承载力高、造价低、工业化生产及运输方便等特点,该桩型在无锡地区小高层建筑及工业厂房作为软基处理得到广泛应用。但该桩型在使用过程中由于场地工程地质情况,容易造成压桩力高导致桩身未进入设计要求持力层以及由于挤土效应导致桩身上浮。本文通过对江阴某工地预应力灌注静载试验结果进行分析,提出异常沉降的原因,以及处理意见。     

基于p-y曲线法的深埋桩桩-土相互作用研究

为了研究超长桩在承受水平荷载下的桩侧水平位移和桩侧土压力的理论计算方法,根据有限杆单元的等效荷载求解原理得到与p-y曲线相适应的非线性弹簧的设置方法,建立了超长桩非线性有限杆单元的理论模型;以实际工程为建模背景,通过ABAQUS软件模拟受到水平荷载时的桩侧水平位移和桩侧土压力,并与实际测得的数据进行对比,以验证数值模拟计算结果的准确性。结果表明：当桩端受到水平荷载作用时,桩侧土压力呈“M”型分布;数值模拟结果与实际工程测量数值之间误差较小,通过数值模拟计算得到的桩侧水平位移和桩侧土压力与实测值之间的相对误差分别在5%和2%以内;通过p-y曲线模型计算得到的桩侧土压力曲线与桩侧水平位移曲线与数值模拟计算得到的各点之间的相关系数R²分别为0.97和0.92,两种方法得到的计算结果基本一致;且利用p-y曲线模型进行计算比通过ABAQUS三维有限元软件计算节约了将近60%的计算时间。在实际工程中,可考虑p-y曲线模型作为超长桩的分析计算模型或作为一种辅助验证方法用以验证通过其它方法计算的准确性。     

静载试验在简支梁桥检测中的应用及分析

桥梁静载试验是简支梁桥质量检测的重要方法,本文以实际工程拟定了不同荷载工况下的静载试验方案,通过荷载试验结果与理论计算结果进行对比分析,提出了对简支梁桥的施工质量和安全度检测有益的结论,为同类桥梁的试验检测提供了参考。     

Multistep analysis of the mechanical performance of an air spring

New methods for testing air springs have received a lot of interest in recent years. In this article APDL (ANSYS parametric design language) was utilized to simulate static and dynamic test process of air springs. In the simulation, multiple load steps solution was carried out through APDL *DO‐LOOP and array parameter method. The program (capsule volume calculating macro) based on scatter sum method enabled the loop. The scalar quantity PRESSURE was established as inner tracking parameter to update inner pressure. Table parameter PRESSURES was established as inner pressure output parameter to export inner pressure of each load step. According to rubber elastic behavior and cord‐rubber composite aeolotropy, hyper elastic element and layer element were preferred for simulation. Comparison was done between static simulation results and corresponding test data to prove feasibility of multistep analysis. In consequence, some major parameters such as cord angle, initial inner pressure, and auxiliary chamber volume were taken into account, which have remarkable effect on static mechanical performance of EQ6111 air spring. Finally, the same method was applied to the simulation of dynamic test process, achieving abundant analysis results according to every 0.5 Hz increment of load frequencies varying from 0.5 to 2.5 Hz. Load frequency threw remarkable effect on the dynamic mechanical performance of EQ6111 air spring, because inertial effect and damping effect played important roles therein. The study aims to make contribution to the development of platform of air spring simulation and parameterized design (PASSPD). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterisation of the transverse mechanical properties of carbon/carbon composites by spherical indentation

The mechanical characterisation of the carbon/carbon composite in the transverse direction is essential for the design of braking discs. This paper presents a technique based on spherical indentation to identify the mechanical behaviour of such materials in the transverse direction.After the presentation of the material properties as determined from static and fatigue compression tests, the indentation technique is described in detail. The characterisation technique used takes into consideration the transverse isotropy of these materials. The method used allows to identify the material behaviour in elastic and inelastic fields. Characterisation of elastic parameters is carried out after identification of the Hertz law in the unloading indentation cycles. The hardening parameters and the elastic limit are identified by expressing the law of Hertz in strain/stress form.The identified parameters are used in a simulation of an indentation test by finite element method. A good agreement is found between numerical and experimental results.     

疲劳/蠕变交互作用下塑木复合材料的断裂损伤

塑木复合材料在动态载荷作用下，其断裂损伤并非纯疲劳或纯蠕变作用的结果。利用交变载荷的试验方法，研究了在疲劳／蠕变交互作用下塑木复合材料的断裂损伤行为。结果表明，在交变载荷为破坏载荷的80％和60％时，其疲劳／蠕变断裂曲线为三段式曲线，即瞬时弹性变形阶段、延迟弹性变形阶段和加速断裂阶段；在交变载荷为破坏载荷的40％时，38h内其疲劳／蠕变曲线为两段式曲线。随着最大载荷保持时间的增加，塑木复合材料进入延迟弹性变形阶段越晚，弯曲挠度增加越快，断裂寿命降低。     

热载荷对冷拔20/316L复合管结合强度影响的数值模拟及试验研究

为了探讨热载荷对冷拔20/316L双金属复合管内、外管间结合强度即残余接触压力的影响,运用有限元分析软件ABAQUS6.5模拟研究了复合管的拉拔成型过程,并通过重启动分析模拟了热加载、卸载时复合管应力状态及残余接触压力的变化,分析了不同温度对冷拔20/316L复合管残余接触压力的影响。结果表明,300℃是衬管发生弹性与塑性变形的临界温度,350℃是基管与衬管发生脱离的起始温度。最后通过复合管拉拔试样的热载荷试验,验证了数值模拟的正确性。     

基于ANSYS的聚丙烯围板箱的优化设计

旨在利用有限元方法对一种塑料围板箱进行优化,在保证其结构强度的基础上减轻其质量,降低生产成本。首先在进行蜂巢板三点弯曲试验的基础上进行有限元模型验证,接着运用ANSYS Workbench的多目标优化模块进行了敏感度分析、响应面分析和响应面优化。通过分析结果,优化后的蜂巢板质量减少了10.4%,等效应力下降了2.73%,强度得到了提高,质量下降,实现了优化目标。再将优化前后的蜂巢板模型代入围板箱模型中进行静载仿真,发现优化后围板箱静载最大等效应力下降了12.12%,等效应变下降了12.1%,实现了围板箱的轻量化设计。     

Energy absorption in glass‐reinforced continuous strand mat composites

A unique test fixture was developed for determining the energy‐absorbing mechanisms in automotive composite material systems. The objective of the test method was to quantify the energy absorption and identify the failure mechanisms associated with the observed frond formation in progressive crush testing of composite tubes by testing less costly composite plates under progressive crush load conditions. Quasi‐static progressive crush tests were performed on glass/polyurethane continuous strand mat (CSM) composite plate specimens. The effect of various test parameters on energy absorption was evaluated by varying the following parameters during testing: the loading rate, profile radius, and profile constraint condition. The experimental data in conjunction with the test observations were used to develop analytical models for predicting the crashworthiness of automotive composite structures. The crushing process and the load‐deflection curves were similar to the progressive crushing of tubes. Modification of the basic specimen geometry was required when testing material systems that have low axial stiffness to prevent a global buckling mode. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3222–3232, 2003     

The tension failure mechanisms of composite stepped bonding repairs and joints for the aircraft primary load-bearing structures

Stepped and scarf topology are still the preferred choices for repairs and joints of composite primary load-bearing structures. The stepped bonding scheme is easy to be implemented in real engineering process. The precise stress distribution, load capacity, damage mode and failure mechanism are not adequately clear. This paper adopts static stress analysis of FEM (Finite Element Method), experimental studies and CDM (Continuum Damage Mechanics) to reveal the tension failure mechanism for composite stepped bonding structures. In the static stress analysis, the mesoscale FEM model considered the adhesive thickness was created. It investigated the detail stress distribution and concentration of the step topology adhesive. Then seven specimens with tensile load were studied experimentally through relation of load-deformation and the appearance of damage. For more details, the adhesive damage was simulated by using CZM (Cohesive Zone Model) which includes the mix-mode fracture of normal force and sliding shear force. The process of damage propagation evolution can be clearly observed in the simulation results. The damage initiates at the vertical location of steps adhesive and propagates to the horizontal overlaps adhesive. Simulation for predicting the ultimate load capacity coincides with experiments. This paper’s work will be useful for designing and analyzing the full composite materials airframe and wing repaired by stepped bonding technique.     

全钢载重子午线轮胎胎冠高度变化的静态受力分析

以11.00R20全钢载重子午线轮胎为例,通过静负荷试验测量轮胎在充气压力为930kPa、负荷为3550kg条件下的变形参数,同时利用哈尔滨工业大学开发的轮胎有限元分析专用软件TYSYS对轮胎胎肩部位带束层端点以及胎圈部位胎体帘布和胎圈加强层反包端点周围橡胶材料单元应变能进行计算,并结合轮胎使用过程中退赔轮胎质量缺陷统计,分析胎冠高度变化对轮胎受力变形和内部应力分布以及轮胎整体使用性能的影响。结果表明,静负荷试验结果与有限元模拟分析结果一致,均与实际使用中退赔轮胎的质量缺陷相对应。     

玄武岩纤维增强复合材料板簧设计与制备

以某轻型货车用板簧为研究对象,以玄武岩纤维增强环氧树脂基复合材料代替弹簧钢减轻车辆板簧质量为目的,通过材料优化设计、结构优化设计,确定了复合材料设计方案,利用ANSYS仿真设计软件对复合材料板簧进行了力学性能分析,采用树脂传递模塑(RTM)制备工艺制备了玄武岩增强复合材料板簧。结果表明,优化后的玄武岩纤维增强复合材料板簧静态强度、动态疲劳寿命能够满足设计和使用要求,通过了静载和台架疲劳试验,且质量相对于弹簧钢板簧减重55%。