砌体墙抗冲击落锤试验方法研究与应用

阐述了砌体墙抗爆炸冲击试验研究现状,针对现有砌体墙试验方法的优缺点,结合湖南大学结构实验室已有的实验条件,提出了利用落锤试验机进行砌体墙抗冲击试验研究的方法;介绍了落锤试验机的试验原理、试验装置和测试系统,砌体墙抗冲击试验加载装置和试验方案。应用所提出的试验方法进行了碳纤维布加固砌体墙和未加固砌体墙的落锤冲击试验,通过试验现象和试验结果的分析,探讨了使用落锤试验机进行墙体抗冲击试验的可行性。     

爆炸荷载作用下顶底角钢螺栓连接的性能研究

爆炸或冲击荷载可致结构局部损坏,有时会影响整个结构的安全,结构设计时必须考虑这种情况。连接是增强钢结构延性和鲁棒性的重要手段,可减轻这种破坏。采用有限元方法研究爆炸荷载作用下顶底角钢螺栓连接的性能。采用ANSYS有限元软件,对有、无腹板角钢的顶底角钢螺栓连接进行分析。通过比较模型数值结果和试验数据,对有限元模型进行验证。对连接模型施加简化爆炸荷载,分析了爆炸荷载作用下连接的性能,确定连接临界面。对爆破荷载作用下连接的破坏模型和实用性进行简单讨论。     

横向冲击荷载下高强钢管混凝土构件的性能

介绍一组新的关于横向冲击荷载下钢管高强混凝土构件的试验数据。对总共12个圆型钢管混凝土样本和用于对照的中空钢管进行测试。所用的钢管混凝土构件的混凝土强度达到75 MPa。建立一个有限元分析(FEA)模型来预测钢管高强混凝土构件的冲击性能,试验结果验证了这个模型的准确性。使用有限元分析模型对冲击荷载下钢管混凝土构件的性能进行全过程分析,从而了解受力状态、内力分布和抗弯承载力。最后,根据参数分析得到一个简化模型,从而计算冲击荷载下钢管混凝土构件的抗弯承载力。     

强动载作用下起波配筋梁抗力性能的试验研究

为揭示起波配筋混凝土(KRC)梁的抗强动载作用机理,提出落锤冲击特制条形气囊的模拟加载试验方法,实现梁构件的实验室均布强动载加载,并设计开展一系列模拟冲击试验,研究爆炸冲击等强动载作用下原型KRC梁的动力响应和破坏特征。详细考察试验全过程和试件响应破坏模式,分析KRC梁的锤头冲击力、支座反力、整体变形和钢筋应变等数据,抓取混凝土开裂、塑性铰形成、构件破坏等动态失效现象,讨论起波矢高等参数对KRC梁抗力性能的影响规律。研究结果表明,起波配筋能显著降低梁受到的锤头力和支座反力峰值,并延长支座反力的升压时间;KRC梁以“三塑性铰”破坏模式耗散能量,抗强动载能力显著提高;在相同最大变形的情况下,合理设计的KRC梁抗力相对于普通钢筋混凝土(RC)梁提高约86.7%。     

爆炸荷载下CFRP筋与混凝土黏结滑移性能及数值模拟研究

为了研究CFRP筋在爆炸冲击荷载下的黏结滑移性能,运用大型有限元软件ABAQUS建立CFRP筋混凝土构件的精细化有限元模型并与CFRP筋静力拉拔试验数据结果进行对比,确定CFRP筋与混凝土的界面参数及验证有限元建模方法的正确性。然后利用ABAQUS软件中的CONWEP模块,研究爆炸冲击荷载作用下CFRP筋的黏结滑移行为。有限元分析表明：在爆炸冲击力从增加到衰减的过程中,CFRP筋的滑移量在爆炸冲击正相加载压力下迅速增加,然后在负相加载压力下发生回缩。还利用所建立的模型开展了拓展参数分析,研究不同折合距离对CFRP筋黏结滑移性能的影响。参数分析表明：随着折合距离的递减,CFRP筋的滑移量呈非线性递增,折合距离减小到一定程度后,CFRP筋的滑移量迅速增大;随着混凝土强度等级的增加,CFRP筋的滑移量呈减小趋势,其滑移量回落幅度随着混凝土强度的增加也在减小。CFRP筋在不同的爆炸冲击荷载下均因负相加载压力的作用在达到最大滑移量之后发生一定程度的回缩,但当爆炸荷载过大时,CFRP筋的滑移量因混凝土碎屑造成的二次冲击在回缩后又继续增大。     

均布荷载作用下高强钢筋混凝土深梁受剪性能研究及有限元分析

采用八点集中加载方式模拟均布荷载作用,完成7根高强钢筋混凝土深梁受剪性能试验。试验参数为纵筋配筋率、水平腹筋配筋率和竖向箍筋配筋率,分析这些参数对深梁受剪承载力的影响规律。在此试验基础上,建立ANSYS有限元模型,并采用GB 50010—2010《混凝土结构设计规范》中的计算式,对深梁受剪承载力进行计算,将有限元计算结果及规范计算结果与试验值进行对比分析。研究结果表明：均布荷载作用下的高强钢筋混凝土深梁,随着3种配筋率的增大,极限承载力显著提高;ANSYS计算结果接近试验值,有限元模型能够合理反映深梁构件的受剪机理;对于受均布荷载作用下的深梁,我国规范计算结果较为保守。     

矩形钢管弯扭构件的工作性能研究

利用通用有限元软件ABAQUS对矩形钢管弯扭构件的荷载一变形关系进行计算,计算结果与试验结果基本吻合。在此基础上,考虑不同加载路径的影响,对矩形钢管弯扭构件的工作性能进行分析,最后在参数分析结果的基础上,提出矩形钢管弯扭构件承载力相关方程的实用简化计算方法,该方法所得计算结果得到试验结果的验证。     

局部荷载作用下圆钢管混凝土有限元分析

对与构件垂直或成45°角的局部荷载作用下的圆钢管混凝土(CFST)进行有限元分析(FEA)。利用已发表在国际期刊上的试验结果对建立的有限元模型进行了验证。采用该有限元模型对局部荷载作用下的CFST进行有限元分析,研究其典型的失效模式和荷载-变形曲线。最后,给出计算局部荷载作用下CFST强度的简单计算公式。所提出的建议公式可避免支撑构件过早屈曲以及弦杆过早断裂。     

预压低碳钢和不锈钢空心钢管与钢管混凝土柱的冲击性能

研究受静力横向荷载和预压轴向冲击荷载下低碳钢和不锈钢空心钢管与钢管混凝土柱的性能。在柱中部或1/4处施加横向荷载。近来,在University of Western Sydney和University of Wollongong进行了3组试验,获得了受横向静力荷载和预压或无预压冲击荷载下的低碳钢和不锈钢空心钢管与钢管混凝土柱的性能。介绍关于对柱施加轴向和横向荷载的第三组试验的试验结果。研究静力和冲击荷载下低碳钢和不锈钢空心钢管与钢管混凝土柱的有限元建模方法。使用有限元分析软件ABAQUS建立一个包括非线性材料性能、钢的加强角性能和预压荷载三维的非线性有限元模型,从而模拟静力和冲击试验。研究主要目的是比较低碳钢和不锈钢空心钢管与钢管混凝土柱性能的试验结果和数值结果。此外,比较冲击荷载下内填钢管和空心钢管的性能。荷载-挠度响应和极限强度的试验结果与有限元结果较为一致。同时,比较静力和冲击荷载下空心与不锈钢钢管混凝土柱和空心与低碳钢钢管混凝土柱的结果。一般来讲,与低碳钢试验构件相比,不锈钢试验构件的强度更高,耗能能力更好。     

沿海地区超强台风作用下核电塔机抗风性能分析

基于GB/T 13752—2017《塔式起重机设计规范》确定了超强台风作用下QTP300(7526B)型核电塔机的风荷载及其荷载组合方式,并考虑风荷载的不同加载方式（立面加载和平面加载）,对核电塔机非工作状态下的抗风性能进行了有限元静力分析。结果表明：与将风荷载分配到有限元模型的所有节点上相比,选取指定节点施加风荷载所得到的结果更大,表明在风荷载应加载到所有立面节点上;迎风面构件对背风面构件的挡风作用对塔机结构的应力分布及最大应力均无显著影响,而塔机结构的最大位移则随挡风作用的增强而增大,表明风荷载加载应考虑迎风面构件的挡风作用;塔机整机结构最大应力出现在底部主肢构件上,其大小均小于钢材的允许应力,该型号核电塔机可以承受17级超强台风作用。     

不同加载路径对岩石变形特性的影响

以往在研究岩石的力学特性时，大都采用持续加载的方法进行试验。三向压缩试验也不例外。就绝大多数工程而言，所遇到的却是在某种应力状态下由于开挖而产生一个方向应力减小、其他几个方向应力增大的现象。根据工程对岩体稳定性评价的要求，应该模拟不同加载路径的应力状态下的试验条件，以便掌握在该试验条件下岩石所作出的力学响应。通过对红砂岩在不同加载路径条件下的三轴试验。分析了不同加载路径所得到的应力，应变曲线及其对岩石的变形影响，得出了在不同加载路径条件下，岩石变形表现与常规试验有较大差异，有着较明显的非线性特性的结论。     

考虑应变率效应的钢筋混凝土动态纤维梁单元模型

为准确描述钢筋混凝土结构的非线性地震灾变过程，建立了一种基于显式算法可考虑地震作用应变率效应的钢筋混凝土动态纤维梁单元模型，并以材料子程序(VUMAT)的形式嵌入ABAQUS有限元分析平台中。对混凝土、钢筋以及钢筋混凝土柱动态加载试验进行了数值模拟，测试并验证该模型用于钢筋混凝土材料及构件动态性能分析的准确性和有效性。研究结果表明，所提出的钢筋混凝土动态纤维梁单元模型计算精度较高，能够准确并实时反映地震作用下应变率对材料及构件动态性能的影响，可为精确计算钢筋混凝土结构在地震作用下的非线性动力反应提供理论基础。     

A dynamic gradient ratio test apparatus

The soil-geotextile filtration mechanism is a complex process which depends on physical compatibility between the geotextile and the soil to be retained. Several methods have been proposed by researchers for assessing the filtration behaviour of soil-geotextile composite systems under steady state conditions. The Gradient Ratio (GR) test is the most commonly used method for measuring filtration compatibility of soil-geotextile systems. This paper describes the design of a modified GR permeability test apparatus to overcome disadvantages associated with traditional GR test devices. The apparatus can perform filtration tests under static and dynamic conditions and can be used to evaluate the filtration compatibility of fine-grained soils with geotextiles. The apparatus is incorporated within a triaxial testing system, hence representative field stress conditions can be applied to test specimens. Some exemplar GR tests performed on coarse and fine-grained soils with a non-woven geotextile are presented in this paper. Unidirectional dynamic loads are applied within the filtration tests to replicate highway traffic loading. Test results show that dynamic loading affects the filtration behaviour at the soil-geotextile interface by increasing the fine particles migration towards the geotextile, but that, for the soil evaluated here, this effect was small.     

考虑率效应的岩石材料次加载面动态本构模型

为反映岩石材料在循环荷载下的滞回圈特性及在动态荷载作用下的率效应,首先基于次加载面理论,建立了基于Drucker-Prager准则的次加载面应力路径模型;其次,在此基础上,通过分析岩石材料率效应的体现,分别在弹性模量上考虑了刚度的率效应和在Drucker-Prager准则上考虑了强度的率效应,进而提出了考虑率效应的岩石材料次加载面动态本构模型;通过自编程序,实现了动态本构模型的植入,并模拟了岩石材料在动态荷载下的力学响应。结果表明,相对于Drucker-Prager准则,应力路径模型能较好地描述玄武岩在循环荷载下体现的曼辛效应和棘轮效应,同时揭示了玄武岩的发展形态;利用动态模型对岩石材料的动态单轴加载和循环加载模拟,发现加载的应变率越大,岩石材料的弹性模量越大,变形则越小,正好反映了岩石材料在动态加载过程中所体现的率效应;动态本构模型能同时反映岩石材料在地震荷载下的滞回圈特性和率效应,正好说明了地震荷载不但具有等效循环荷载的形式,还具有动态荷载的形式,也说明了次加载面动态本构模型模拟岩石材料在地震荷载作用下的力学性质是可行的。     

循环荷载下红层泥岩的动力特性及路用性能研究

 为验证达成(达州--成都)线红层泥岩能否满足高速铁路路基填料的要求,对其进行室内动三轴试验和红层泥岩路基的现场循环加载试验。由动三轴试验研究红层泥岩在循环荷载下的动强度和变形特性,引入动应力水平的概念,得到达成线红层泥岩的临界动应力水平约为30%;通过分析动剪应力比SRd与土体累积变形之间的关系,提出一个红层泥岩循环累积变形的计算模型,并明确模型参数的物理意义及确定方法。现场循环加载试验表明,用红层泥岩填筑路基基床底层,路基的沉降量和沉降速率均能满足高速铁路的要求;应用所提出的预测模型来计算红层泥岩路基层的累积变形,其达到稳定时的计算值和实测值很接近,但由于现场和室内试验条件的不同及加载频率的影响,在变形稳定以前,模型计算值和实测结果之间存在一定的差异。     

Concrete filled steel tube stub columns under combined temperature and loading

A finite element analysis (FEA) model was developed to predict the load versus deformation relationships of concrete filled steel tube (CFST) stub columns subjected to a combination of temperature and axial compression. This model was used to simulate a set of CFST stub column experiments under various thermal and mechanical loading conditions, including tests at high temperature, tests on the residual strength of specimens subjected to uniform heating, and tests on specimens exposed to the ISO-834 standard fire without initial loads. Comparisons between the predicted results and the test results show that this model can predict the load versus deformation relationships with reasonable accuracy. The FEA model was then used to investigate the behaviour of CFST stub columns in a complete loading history including initial loading, heating and cooling by examing the cross-sectional stress distribution and confinement stress development at different loading phases. All specimens were loaded to ultimate strength after cooling and the residual stress index was studied with respect to a group of parameters. It can be found that the ultimate strength when considering the mutual actions of temperature and loading was slightly lower than that after exposure to fire without initial load, but the peak strain corresponding to the ultimate strength was increased significantly.     

均匀柱荷载作用下梁板式筏形基础破坏性状的试验研究

梁板式筏形基础广泛应用于多层建筑和高层建筑的裙房部分的基础,其受力机理及破坏性状是急待解决的问题。通过室内模型试验,对天然地基上梁板式筏形基础与地基共同作用问题进行了研究。室内试验是在地基所试验室的实验坑内进行的,采用人工换填的均匀粉质黏土模拟天然地基,试验模型为单跨梁板式筏形基础,加载方式采用油压千斤顶在梁节点处同步加载以模拟均匀柱荷载,柱荷载均匀施加至试验模型发生结构破坏,测试内容为基底反力及沉降。通过试验及结果分析,发现了梁板式基础的荷载传递顺序及破坏性状,得出了梁板式筏基在大、小荷载作用下的不同变形特征和基底反力分布规律,并根据试验数据所反映出的变形规律,给出了大、小荷载作用下简化的基底反力分布模式。     

Buckling and dynamic instability analysis of stiffened shell panels

The static and dynamic instability characteristics of stiffened shell panels subjected to uniform in-plane harmonic edge loading are investigated in this paper. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners, respectively. As the usual formulation of degenerated beam element is found to overestimate the torsional rigidity, an attempt has been made to reformulate it in an efficient manner. Moreover, the new formulation for the beam element requires five degrees of freedom per node as that of shell element. The method of Hill's infinite determinant is applied to analyze the dynamic instability regions. Numerical results are presented through convergence and comparison with the published results from the literature. The effect of various parameters like shell geometry, stiffening scheme, static and dynamic load factors, stiffener size and position, and boundary conditions are considered in buckling and dynamic instability analysis of stiffened panels subjected to uniform in-plane harmonic loads along the boundaries.     

Impact-Resistant Design of RC Slabs Using Immune Algorithms

A three-dimensional nonlinear dynamic finite-element method (FEM) was applied to evaluate the ultimate behavior and failure modes of reinforced concrete (RC) slabs subjected to soft impact loads. In order to propose a practical impact-resistance evaluation method for RC slab structures, computer graphics (CGs) were used as a visualization technique to simulate impact-failure behavior of RC slabs until postfailure range was reached on the analytic results during impact loading. Immune algorithms are combined with a three-dimensional nonlinear dynamic FEM analysis for the purpose of proposing the design of RC slabs subject to soft impact loads. The results give evidence that presents complicated failure modes, and immune algorithms can be applied to the design of RC slabs effectively.     

A Heuristic Approach for Interactive Analysis of Bridge Trusses under Moving Loads

A heuristic approach is presented for interactive analysis of statically determinate and indeterminate bridge trusses subjected to moving loads such as the American Association of State Highway and Transportation Officials (AASHTO) specifications live loads. These loads consist of two-axle truck loading, two-axle truck plus one-axle semitrailer loading, and uniform lane loading. The procedure is based on using the information about the shape of the influence line diagrams (ILDs) for members of a truss. This information may be obtained through numerical experimentation for any given type of truss. A methodology is presented for classifying the ILDs for member axial forces of a bridge truss. The procedure is applied to Pratt trusses. Heuristic rules are developed for finding the maximum compression and tensile forces in the members of a Pratt truss based on its characteristic influence line diagrams and the type of the AASHTO live load. The procedure presented in this article results in substantial savings in structural analysis computations, and is specially suitable on microcomputers in an interactive environment.