大型抽空式网架设计

本文介绍了大面积抽空式网架的设计和理论依据,首次应用到冶金重型工业厂房结构上,取得了较大的综合经济效益,并发现了大面积抽空式网架内力重分布的规律.为今后进一步在工业厂房的推广,积累了宝贵的实践经验.     

“梁强于柱”、“等强梁柱”单层单跨框架试验研究

通过对两榀分属“梁强于柱”、“等强梁柱”的单层单跨钢筋混凝土框架的试验和分析,研究了其内力重分布的特点,并对“柱强于梁”、“梁强于柱”、“等强梁柱”这三类框架的相关特点做了初步对比。通过对比,证实这三类框架是客观存在的,且每类框架的内力重分布特点各有不同,并提出这三类框架弯矩调幅设计必须综合考虑弹性弯矩图以及不同类型框架之间内力重分布特性的差异。     

Required and available moment redistribution of continuous steel-concrete composite beams

Based on the ultimate limit state analysis, the required moment redistribution to enable full plastic mechanism for continuous composite beams is derived. The composite beams studied are continuous over the internal support and with a uniform section along the beams which are one of the conventional steel structural forms in Chinese construction practice for buildings and medium span bridges. It is illustrated that the required moment redistribution for the beam increases as the ratio of negative to positive moment resistance reduces, but decreases as the span difference, or the difference of load in the two spans increases. A method to assess the available moment redistribution based on the rotation capacity at the notional plastic hinges of a composite beam is developed. The potential moment redistribution in a continuous composite beam is also assessed when the available rotation capacity at the notional hinge fails to satisfy the required capacity capable of a plastic design. For a continuous composite beam to develop full plastic design, the available moment redistribution for the beam should be greater than or at least equal to the moment redistribution required, hence the full moment redistribution from the hogging region to the sagging region in the beam is capable. The derived available moment redistributions agree with the test results and computer simulations, but in a general lower bound of the strength capacity. An example is given and the results are compared with that based on the moment redistribution proposed in the present Chinese design code for steel-concrete composite beams. The present study provide a design approach to assess the load carrying capacity for a continuous composite beam based on the available moment redistribution capable depending on the rotation capacity or the force ratio etc rather than a fixed value of moment redistribution proposed, so that in most cases, an economic design is capable.     

Experimental study of nonlinear stress mechanism ofsteel-asphalt composite isolation layer

进行了4组不同含钢量的钢筋-沥青复合隔震层的低周反复荷载试验,研究了钢筋-沥青复合隔震层钢筋竖向和水平力-位移关系,同时研究了钢筋-沥青复合隔震层竖向和水平内力重分布情况。试验结果表明：钢筋-沥青复合隔震层中钢筋和砖墩的受力与水平位移之间是非线性关系。在竖直方向,钢筋-沥青复合隔震层的破坏过程分为前期竖向钢筋受压,中期竖向钢筋受拉、砖墩受压和后期砖墩压坏三个阶段。在水平方向,钢筋-沥青复合隔震层的受力过程也分为前期钢筋受力从零开始缓慢增长,中期钢筋受力快速增长和后期钢筋受力下降三个阶段。基于试验结果,对钢筋-沥青复合隔震层钢筋竖向和水平力-位移曲线进行了分析,同时对钢筋-沥青复合隔震层竖向和水平内力重分布后力-位移曲线进行了分析,结果表明,荷载在钢筋和砖墩之间的重分布对隔震层的力-位移曲线有决定性影响。     

高温下钢筋混凝土连续梁的受力性能试验研究

本文介绍6根钢筋混凝土两跨连续梁的高温试验,考察不同加载位置、荷载水平以及单跨或双跨加温等因素下连续梁的变形和内力随温度的变化规律,分析了连续梁的破坏特征和机构等.结果表明,在升温过程中连续梁发生剧烈的内力重分布,塑性铰是一个可变铰,而且可能改变其破坏机构,与常温下具有显著的差异.     

高温下钢筋砼连续梁的破坏机构和内力重分布研究

通过对6根钢筋砼两跨连续梁进行高温试验,分析了连续梁的破坏特征、机构以及内力重分布情况.结果表明,在升温过程中,不但连续梁内力要发生剧烈的重分布,而且可能改变其破坏机构,与常温下具有显著的差异,塑性铰是一个可变铰.     

框架的非线性有限元优化设计

充分考虑了钢筋混凝土材料的非线性特征 ,在用二次积分迭代法进行R C 框架非线性有限元分析的基础上 ,进行框架结构造价最省为目标的优化设计。此法可以反映单个构件裂缝开展、钢筋屈服、混凝土被压碎、内力重分布等全部过程。非线性优化设计采用整体优化和分部优化相结合的优化方法 ,将非线性分析和系统优化紧密结合。分部优化的数学模型被有效简化 ,但充分考虑截面尺寸、纵向钢筋和箍筋这些在造价中起决定作用的设计变量和各种抗震约束条件 ,优化结果较精确。非线性有限元优化程序将非线性分析与系统优化穿插在一起 ,联合迭代 ,共同收敛 ,有效减少了迭代的次数。通过优化设计实例证明 ,非线性有限元优化设计的造价比弹性的优化设计有显著地节省。     

Ultimate strength of continuous composite box-girder bridges with precast decks

In order to apply precast decks to continuous composite bridges, several experiments and analytical studies were performed. From many previous studies, design criteria for crack controls in transverse joints of prefabricated slabs were confirmed. These considerations were needed for serviceability. The bridges which satisfy service limit states, also, should be evaluated for ultimate strengths to define limit states. In this paper, experimental and analytical studies of two-span continuous composite bridges with open box girder section were conducted. Cracking, yielding and ultimate loads were evaluated and compared with the test results for design of continuous composite bridges with precast decks. To evaluate yielding loads of continuous bridges, an uncracked section method considering moment redistribution which is defined in EUROCODE 4, was considered. In calculation of ultimate strengths, full or partial shear connection and sectional classes which were defined in EUROCODE or AASHTO LRFD specifications were considered. Also, through numerical analysis considering material nonlinearities, moment-curvature relationship and moment redistributions were estimated.     

钢筋混凝土短肢剪力墙结构试验

为了从试验角度研究混凝土随机性对结构反应的影响,以4片相同的4层1∶3比例缩尺模型的短肢剪力墙结构为研究对象,进行了拟静力试验研究,得到了荷载-位移曲线、混凝土和钢筋的应变曲线及墙体局部相对位移曲线.从水平承载力、侧向刚度、位移延性3个方面对比分析了各片墙体的反应,并对4片墙体的实测数据进行了统计分析,给出了不同顶点位移下的3个典型横截面受力状态的变化过程,最后研究了各试件在破坏特征上的差异性.研究结果表明:混凝土材料随机性的本质特征,使得混凝土结构在非线性发展阶段具有明显的损伤随机演化特性,因此,混凝土非线性与随机性的耦合效应对结构反应所造成的影响不可忽视.     

低高度混凝土单箱单室宽箱梁剪力滞效应研究

为明确宽跨比、宽高比均较大的低高度混凝土单箱单室连续梁桥在施工和成桥阶段主要荷栽作用下的剪力滞效应分布特点,通过空间实体模型与平面杆系模型相结合的有限元法对山东济南黄河三桥引桥预应力混凝土单箱单室宽箱梁的空间应力响应进行了研究。研究表明：施工和成桥运营阶段,边跨和中跨跨中断面的剪力滞效应均较小,而中支点断面的剪力滞效应十分显著,且在预应力张拉前后分别呈现明显的正、负剪力滞效应。计算结果还表明,剪力滞效应对该连续梁桥的结构内力影响并不明显,空间实体与平面杆系有限元分析存在的差别主要是由于顶底板刚度所占比例较大而带来的全断面内的应力重分布所导致的。研究成果可为今后类似工程的设计、施工及长期监测研究提供参考。