【作者】 刘砚山；

【导师】 童丽萍；

【作者基本信息】 郑州大学 ， 结构工程， 2013， 硕士

【摘要】 底框砌体房屋是指底部为框架或者框架一剪力墙结构形式,上部各层为砌体结构形式的混合结构体系房屋。该类房屋底部房间布置灵活多变,可以营造大空间,主要用于商店、营业厅、餐馆、汽车库等；上部砌体结构由于横墙较多,房屋空间较小,一般用于办公室、住宅、小型旅馆等。由于具有良好的使用功能、造价低、施工方便等优点,其在我国大城市都市村庄、中小城镇临街建筑中得到广泛应用。作为适应我国经济发展水平的一种结构形式,该类建筑在今后相当长一段时期内,还将作为主要的结构形式被使用。然而,底框砌体房屋属于不同结构形式的竖向组合,上部砌体部分纵横墙较多,抗侧刚度大,下部比较空旷,最终形成了典型的“鸡腿”建筑。这种软首层结构在多次地震中表现不佳,底层和过渡层出现了较大的地震损坏或者倒塌,造成了严重的人员伤亡和财产损失。因此,进一步研究底框砌体房屋在大震中的地震反应规律,分析其抗震性能,并在此基础上揭示薄弱层转移机理,提出合适的抗侧刚度比值限值是十分必要和迫切的,同时相应研究也可为同类房屋的建造、加固及抗震性能评价提供技术参考。本文在郑州市“科技领军人才”项目(课题编号：10LJRC186)的支持下,主要进行了如下研究工作：(1)通过梳理底框砌体房屋在汶川、玉树地震中的震害特点,得到了房屋抗震薄弱环节和震害规律。基于震害规律分析,总结出过渡层与底层抗侧刚度比值不合理是震害发生的主要原因,并针对相应震害提出了抗震对策。(2)依据实例房屋基本尺寸,建立三维整体有限元模型,并采用Block Lanczos法进行模态分析,得到了结构动力参数和振型特征。分析结果表明,沿主轴方向结构纵向刚度弱于横向；沿楼层方向底层振动强烈,表现出“上刚下柔”的不利特性。(3)为评价该类房屋的抗震性能,本文沿结构纵横两向分别进行了大震作用下的动力弹塑性分析。提取结构的位移反应和裂缝开裂趋势,得出结构底层出现了严重弹塑性变形集中,是结构的薄弱层；上部过渡层砌体窗间墙、窗下墙和横墙下部出现较多开裂,是上部砌体的薄弱环节。(4)为探究过渡层破坏原因,寻求薄弱层转移机理,本文在房屋底层添加抗震墙,建立具有4种不同抗侧刚度比值的底框砌体房屋。通过各模型的模态分析和动力弹塑性分析,得到了添加抗震墙对结构动力参数及地震反应的影响。分析结果表明,添加抗震墙后过渡层破坏加重,因此需要对抗侧刚度比值进行相应的限制,防止薄弱层转移至材料强度低、变形能力弱的过渡层。(5)通过不同抗侧刚度比值房屋在大震作用下的弹塑性时程分析,依据过渡层与底层层间位移角相对比值等因素,本文对过渡层与底层抗侧刚度下限值做出了建议,该下限值处于我国抗震规范限值之内,具有比较理想的抗震安全性能和实际应用性能。(6)基于各模型的地震反应规律,本文总结了混凝土抗震墙和砖砌体进入非线性阶段时抗侧刚度退化不同步是薄弱层转移的主要原因。同时依据该主要因素和底层实际存在的填充墙,本文提出了弹塑性阶段有效抗侧刚度计算公式,该公式可为进一步深入研究抗侧刚度比限值等问题提供参考。更多还原

【Abstract】 Bottom frame masonry structure refers to hybrid structure system housing whose layers at bottom are the frame structure or frame-shear wall structure and the upper layers are the masonry structure. The bottom of such a house is flexible room layout which can create a large space and mainly used for shops, business offices, restaurants, garages, etc; because of more cross walls and smaller housing space, the upper masonry structure is usually used for office, residential, small hostel, etc.Due to good use function, low cost and convenient construction, bottom frame masonry structure is widely used in urban villages in major cities, small towns’street construction. Because this structure is adapted to China’s economic development level, in the future for quite a long time, it will also serve as the main structure form. However, because of many cross walls, the upper masonry structure’s lateral stiffness is big, and the bottom is open, which finally form the typical chicken leg building.This soft first layer structure has poor performance in earthquakes, whose bottom layer and transition layer appeared large earthquake damage or collapse, and caused serious casualties and property losses.Therefore, it is necessary and urgent to furtherly study on the seismic response of the bottom frame masonry structure in the large earthquake, analyse the seismic performance, reveal the weak layer transfer mechanism and recommend appropriate lateral stiffness ratio limit value. Meanwhile corresponding research can provide technical references for the construction and retrofit of such buildings and evaluation of seismic performance.Supported by "Scientific and Technological Leading Talent Project"(project number:10LJRC186), this thesis mainly has done the following works:(1)By combing the bottom frame masonry buildings’damage characteristics in Wenchuan and Yushu earthquake, housing seismic weaknesses and damage law are obtained. Based on analysis of the earthquake damage law, this thesis has summed up that the lateral stiffness ratio of the transition layer and the underlying is not reasonable is the main cause of damage, and seismic countermeasures have been proposed.(2)According to basic dimensions of the intance building, establish three-dimensional finite element model, and through modal analysis by using Block Lanczos method, get the structural dynamic parameters and the mode characteristics.Analysises show that along the major axis, the longitudinal lateral stiffness is weaker than the transverse; along the floors’direction, the bottom floor vibrates strongly, which shows "large rigidity of the upper and weak of the lower part".(3)In order to evaluate the seismic performance of such a house, along both transverse and longitudinal directions, undertake a structural elastic-plastic time history analysis under a great earthquake and extract the structural displacement response and development trend of cracks. The results show that the underlying appears serious elastic-plastic deformation which is the weak layer of the structure; the wall between windows, the wall under windows and the lower part of the cross wall in the transition layer occur more cracks, which are the weak links of the upper masonry.(4)In order to explore the reasons of transition layer destruction and seek weak layer transfer mechanism, four kinds of finite element models with different lateral stiffness ratios are established by adding different size shear walls in the bottom. Through modal anlysis and structural elastic-plastic time history analysis under the great earthquake, the impact on dynamic parameters and seismic response has been obtained after adding shear wall.Analysis results show that the transition layer destruction increases after adding the shear wall, and there is need to limit the lateral stiffness ratio to prevent weak layer from transferring to transition layer of which has low material strength and deformation capacity.(5)Through elastic-plastic time history analysis of buildings with different lateral stiffness ratios under the great earthquake, based on the relative ratio between the bottom layer and the transition layer displacement angle, suggestions of lower limit value of lateral stiffness ratio have been put forward.The limit value which is within the limits of our seismic code has ideal seismic safety performance and actual application performance. (6)Based on the seismic response law of the models, this thesis summarized that the lateral stiffness degradation of concere shear wall and brick masonry in nonlinear stage is the main reason of the weak layer transfer. At the same time, according to this main factors and the practical application of infill walls in bottom suggestion of effective lateral stiffness ratio formula at elastic-plastic stage has been put forward which can provide a reference for further study on the lateral stiffness ratio limit.更多还原