钢框架抗震耗能节点梁的极限承载力分析1）

为提高结构的抗震性能,框架结构中以翼缘削弱型节点为代表的延性耗能节点逐渐代替传统节点,为研究翼缘削弱型节点框架梁在单向比例加载时的极限载荷,对削弱梁极限状态进行了分析,判定极限状态下削弱梁塑性铰生成的位置并计算极限载荷,将计算结果和普通梁进行对比.分析结果表明：削弱梁越长承载力下降越明显,对短梁需要选择合适的削弱参数,才能避免塑性铰出现在梁端.研究结果可为削弱梁塑性设计提供依据,同时拓展结构力学极限载荷学习内容.     

用变形和分解原理求混凝土板的受拉薄膜效应

利用变形梯度直和分解,提出了基于能量原理计算钢筋混凝土板大变形时极限承载力方法,该方法考虑了薄膜效应影响并与传统塑性铰线理论相统一,既适用于矩形板和方形板,也适用于各向同性配筋和各向异性配筋的板,认为薄膜效应主要是由于塑性铰线处钢筋的伸长耗能造成的,该方法还可以解释同样挠度下方形板比矩形板早破坏和同样配筋时在矩形板短跨方向钢筋断裂的试验现象.计算结果与试验具有很好的一致性.     

火灾后钢筋混凝土异形板的极限均布荷载

本文基于塑性铰线理论确定了钢筋混凝土异形板的破坏机构，并利用有限差分法计算了火灾时板内的温度场，根据高温后钢筋和混凝土的力学性能对塑性铰线截面的弯矩及灾后极限均布荷载进行了分析，为钢筋混凝土板火灾后的评估和维修提供依据．     

方钢管混凝土柱延性的实验研究

针对结构抗震设计对延性的要求,对不同轴压比、长细比和混凝土标号的7根方钢管混凝土柱试件进行了低周反复加载实验,得到了框架柱的荷载位移曲线、骨架曲线以及各阶段的荷载位移值,据此分析了各种因素对方钢管混凝土柱延性的影响.实验结果表明:剪力滞引发了方钢管混凝土柱的塑性铰,塑性铰的扩展是柱端承载力下降的根本原因,增大轴压比将引起塑性铰更早出现,进而降低框架柱的延性和水平抗剪能力;增大长细比可以延缓塑性铰出现,提高柱的延性和耗能能力,但是水平抗剪能力下降;提高混凝土强度等级可以降低大轴压比、大长细比带来的不利因素.实验结果与有限元计算数据吻合良好.     

用双剪屈服准则对钢筋混凝土板进行塑性铰线的极限分析

利用双剪屈服准则建立了用机动法计算钢筋混凝土薄板极限载荷的新的塑性铰线理论，并导出了双向布置钢筋的钢筋混凝土板的屈服条件，实例计算表明其更符合实验结果。     

钢框架翼缘削弱型和扩翼型节点受力性能研究

采用翼缘削弱型节点及扩翼型节点可以使塑性铰外移,缓解梁柱节点连接处应力集中,避免在焊接热影响区发生脆性破坏.针对削弱型节点、扩翼型和普通刚性节点进行了数值分析,结果表明:削弱型节点由于梁翼缘削弱,导致节点承载力降低,扩翼型节点增加了梁端翼缘板宽度,承载力高于削弱型节点和普通刚性节点.通过计算模型分析了节点的设计参数,并给出节点设计参数取值范围,为钢框架节点抗震设计提供理论分析依据.     

计算钢制三通管冷挤压胀型内压力的滑移线法

本文描绘在轴向压力、内压力、挤压力和摩擦力作用下钢制三通管冷挤压胀型的塑性流线,并由此分析滑移线分布,用滑移线法计算钢制三通管冷挤压胀型的内压力,最后给出应用实例.     

基于塑性铰理论的车身概念设计正碰分析与优化方法

在概念设计阶段,车身碰撞安全性能评价是一个难点问题,需要详细的结构模型,本文基于塑性铰理论提出采用梁单元简化模型对框架车身进行概念设计阶段的耐撞性评估和优化设计方法。首先,介绍了关于箱型截面薄壁梁弯曲特性研究的理论模型与计算过程,接着赋予梁单元塑性铰的特性,模拟薄壁梁变形,再对框架车身进行了碰撞仿真。将仿真结果与详细模型对比,以分析简化模型的精度及可靠性。最后,以此为基础对框架车身进行耐撞性优化。结果表明,该简化模型易于创建,且有较高的精度,可用于概念设计阶段梁结构的设计工作。     

偏心率效应对金属圆柱管轴压性能的影响

用含有偏心率因子的直链塑性铰叠缩模型来分析金属圆柱管轴向压缩能量吸收，根据能量原理推导了瞬时载荷，从而获得压缩过程的载荷-位移曲线．讨论了偏心率对平均压缩载荷和载荷-位移曲线形貌的影响．实验结果与模型分析符合得很好．     

双轴反复荷载作用下钢筋混凝土空间框架结构滞回全过程分析

实际地震中结构所承受的地震作用是多维的。结构的恢复力特性是反映其抗震性能的一个重要属性。对地震作用下钢筋混凝土柱、梁塑性铰区的计算模型进行了分析,给出了塑性铰区等效长度的简便计算公式;建立了“有限纤维”空间线性梁单元模型并推导出了其刚度矩阵;使用“弥散法”来考虑梁锚固钢筋在结点区的粘结滑移对结构整体变形的影响。最后使用空间杆系模型对一承受双向反复荷载的框架结构进行了计算分析。分析表明所建立的计算模型是精确有效的。     

端部受斜冲击的刚塑性悬臂梁的双铰模型

斜冲击载荷作用在刚塑性悬臂梁的端部,引起作用在梁横截面处的弯矩以及轴力;在发生塑性变形截面处,弯矩及轴力满足交互作用屈服条件。广义应力在移行铰的邻域不违背屈服条件,屈服函数可在移行铰的背面取极大值,移行铰处的剪切力不必为零。如果悬臂梁足够长,在响应的初始阶段移行铰处非零的剪力会在梁上引起多铰变形。通过对双铰模型与单铰模型的比较发现,双铰模型计算的结果与单铰模型计算的结果很接近,单铰模型作为一个近似模型具有一定的合理性。     

Energy absorption of an egg-box material

Conical frustra made from leaded gun-metal have been compressed axially. Collapse is either by a travelling plastic hinge or by tearing. An analytical model is developed for the travelling plastic hinge in a rigid, ideally plastic solid; its predictions are compared with the observed response, and with those of an axisymmetric finite element analysis. The travelling hinge mechanism is also observed in the compressive collapse of an egg-box material comprising a square array of conical frustra. Collapse mechanism maps are constructed for the egg-box material, and they show the regimes of dominance of elastic buckling, material tearing and the travelling plastic hinge. The maps are useful for selecting egg-box geometries that maximise the energy absorption per unit mass at any prescribed value of collapse stress. The optimisation indicates that the egg-box material has a similar energy absorption capacity to that of hexagonal honeycombs and is superior to that of metal foams.     

Elastic–plastic behavior of a semicircular frame being pressed against a rigid plane

As a simplified structural model, a semicircular frame is used to study the crashworthiness behavior of an aircraft fuselage. The quasi-static large elastic-plastic deformation of a semicircular frame in the process of its being pressed against a rigid ground is analyzed. First, based on the linear elastic assumption, the quasi-static large deformation contact process of the frame can be divided into three phases, i.e., point contact, line contact and post-buckling. By means of a shooting method, the relations between the displacement and contact force as well as the distribution of bending moment in the three phases are obtained. Then, by assuming an elastic, perfectly-plastic moment-curvature relationship for the semi-circular frame, the contact process is analyzed in detail to reveal the plastic collapse mechanism, the traveling of plastic hinge and the force-displacement relationship. In order to verify the analysis, a preliminary experiment was conducted, in which two types of half rings with clamped ends were pressed by a rigid plate. In addition, a numerical simulation is also conducted by employing ABAQUS to analyze both rectangular cross-sectional beam and I-beam. Finally, the theoretical predictions are compared with the experimental results and numerical solutions, showing that the elastic-plastic analysis can predict the contact process very well.     

A study of different modes of collapse in metallic hemispherical shells resting on flat platen and compressed with hemispherical nosed indenter

The paper presents experimental and analytical studies on axial compression of aluminium spherical shells having Radius/wall thickness (R/t) ratios between 23 and 135. Quasi-static compressive load was applied centrally and with offset through a indenter having diameter of 22 mm. Testing was carried out on an INSTRON machine having 250 T capacity. Shells having different radius and wall thickness were tested, to classify their modes of collapse and their corresponding energy absorption mechanism. In experiments shells of lower R/t values were found to collapse due to formation of an inward dimple associated with a rolling plastic hinge in central as well as in offset loading. On the other hand, shells of higher R/t values were collapsed initially with formation of an axisymmetric inward dimple, but in later stage of compression showed buckling of non-symmetric shape consisting of integral number of lobes and stationary plastic hinges. The stationary hinges were formed between consecutive lobes. Experimental observations are used to propose an analytical model for prediction of load–compression and energy–compression curves. The results obtained from analytical model compared with the experimental results and found match fairly well.     

结构非线性振动智能控制试验与分析

在结构动力学与控制领域中,试验验证对于理论与数值研究是非常重要的. 但是,目前的模型试验大部分都只考虑结构的线性行为,所以考虑结构非线性振动的试验模型成为一个研究热点. 采用磁流变旋转阻尼器来模拟结构中的塑性铰,并通过调整输入到此旋转阻尼器中的电压来实现不同的非线性行为,然后在不同的非线性行为下验证了动态神经网络观测器和自适应模糊滑模控制算法的有效性. 试验结果表明建立的结构非线性试验模型可以在试验完成后不需要任何代价而恢复到初始状态,并且能够实现不同的非线性行为,同时采用的智能控制算法对结构非线性振动也有较好的控制作用.