【作者】 王晓敏；

【导师】 谢礼立； 翟长海；

【作者基本信息】 哈尔滨工业大学 ， 防灾减灾工程及防护工程， 2017， 博士

【摘要】 砌体填充墙RC框架结构作为建筑工程中最常见的一种结构体系,在我国以及世界范围内都有着广泛的应用。在实际的结构分析和设计中,填充墙一般视作非结构构件,不考虑填充墙对结构抗震性能的影响。然而,在实际地震作用下,填充墙和外围框架之间的相互作用往往不可忽略,可能会改变结构的整体受力机制,对结构的抗震性能产生显著影响。在过去的几十年间,尽管对填充墙框架结构已经进行了大量的研究,取得了一定的进展;但是,由于填充墙与框架之间的相互作用非常复杂,涉及到框架梁柱构件中的分散型受弯裂缝和剪切裂缝、砂浆的抗拉开裂和受压破坏、砌块沿着砂浆层的剪切滑移以及砌块本身的开裂和受压失效等破坏行为,到目前为止依然缺乏合理的数值模拟方法来评估结构的受力性能。因此,本文在改进扩展有限元方法(XFEM)模拟拟脆性材料开裂界面受力性能的基础上,提出了基于扩展有限元的填充墙RC框架结构精细化数值模拟方法;研究了结构几何参数等对填充墙RC框架结构平面内性能的影响,揭示了填充墙RC框架结构的相互作用机制;考虑峰值承载力下结构各部分所处的实际状态,提出了填充墙RC框架结构的简化分析模型,可用于填充墙RC框架结构的整体性能分析。本文的主要研究内容包括以下四个部分:(1)扩展有限元方法是模拟不连续问题的最有效数值方法之一,考虑到目前扩展有限元方法对混凝土、砌体等拟脆性材料的开裂界面受力性能模拟还不够精确,本文对扩展有限单元开裂界面的非线性受力性能进行了改进,提出了可以精确模拟界面法向循环加载软化性能、摩擦滑移、几何膨胀、压应力作用下界面塑性压缩以及弹性受拉刚度退化等性能的精细界面本构模型;以及更加有效的单元划分方案用于对单元不连续情况进行数值积分,实现了模拟拟脆性材料开裂扩展时,既可以精准地模拟裂缝的开裂扩展路径,克服有限元网格依赖性,又可以精确地模拟拟脆性材料开裂过程中多方面的受力性能。采用MATLAB编制程序对三个拟脆性材料开裂试验进行数值模拟,表明本文提出的方法不仅能够准确地描述混凝土等拟脆性材料开裂过程中的不连续特性,同时可以精准地模拟裂缝界面上的受力性能。本文还分析了剪切断裂参数对混合开裂的影响,以更好地确定相关参数的取值,为填充墙RC框架有限元模型的校准程序提供有力的数据支持。(2)现有填充墙RC框架有限元模型由于自身局限性对裂缝扩展的模拟依然存在网格依赖性等问题,难以准确捕获RC框架梁柱以及填充墙砌块的开裂破坏模式,本文通过对扩展有限元进一步改进,充分考虑了框架混凝土以及砌块单元的受压屈服和开裂性能,以及多裂缝分布式开裂的情况,并通过与离散界面单元相结合,首次提出了基于扩展有限元的填充墙RC框架结构精细化有限元分析模型,实现了填充墙RC框架结构整个受力破坏过程的精准模拟。为此,本文基于有限元软件FEAP开发了三个用户单元、两个材料本构模型以及一个宏命令,解决了扩展有限元方法从理论到实际应用过程中的诸多技术难题。采用MATLAB编制有限元模型的前后处理程序,并通过对多个填充墙RC框架试件的数值模拟,验证了本文有限元分析模型的性能,结果表明本文提出的模型不仅可以准确地预测结构的承载能力,同时还可以成功地捕获填充墙RC框架结构的失效模式。(3)采用经过验证的填充墙RC框架精细化有限元模型,系统地研究了填充墙的高宽比、框架上施加的竖向荷载大小、框架梁与柱上竖向荷载所占比例、框架柱中纵向钢筋的配置、箍筋的配置、框架柱的截面尺寸、填充墙的厚度、砂浆灰缝摩擦系数以及框架梁的截面高度等不同的材料特性、几何尺寸以及设计参数的变化对填充墙RC框架结构受力性能的影响,探讨了各参数对结构的初始刚度、承载能力以及失效破坏模式的影响大小及规律,揭示了填充墙RC框架在水平力作用下的相互作用机制,为建立填充墙RC框架结构的简化承载力关系以及简化分析模型提供了有力的数据支持。(4)通过对试验模型的模拟和参数分析,结果表明填充墙RC框架结构的失效主要包括填充墙中的剪切滑移裂缝、迎风柱顶部和背风柱底部的对角剪切裂缝,但是这三部分未能同时达到峰值强度,结构的峰值承载力小于三者同时达到极限状态相应的承载力值。基于参数分析结果以及理论分析,本文研究了竖向荷载作用下填充墙上的竖向荷载分布规律,考虑峰值状态下结构各部分所处的实际状态,建立了填充墙RC框架的简化承载力曲线,并据此提出了等效撑杆模型。为了验证该简化分析模型的有效性,本文对填充墙RC框架试验结果进行了模拟分析,结果表明本文提出的简化分析模型可以精确地预测结构的承载力曲线,该模型可以进一步用于多层多跨填充墙RC框架结构的整体受力分析。更多还原

【Abstract】 Masonry-infilled reinforced concrete(RC)frames,as one of the most common forms of building constructions,have been built in many parts of the world.In the structural analysis and design,infill walls are generally treated as non-structural components and their effects on the seismic behavior of structures are ignored.However,they will interact with the bounding frame when the structure is subjected to a strong lateral load in the event of an earthquake.This interaction has a significant impact on the seismic performance of the structures,and it may alter the lateral load bearing capacity of buildings,and induce some failure mechanisms that are undesirable for the seismic performance of the structure.Despite significant research effort dedicated to such buildings during the last decades,there are neither clear understanding on the seismic performance of infilled frames nor a reliable numerical approach for evaluating the behavior of such structures.The main challenge is because of the complexity of interaction between the infill and the frame.Hence,it is necessary to develop a reliable analysis approach to reveal the interaction between the infill and the bounding frame and access the behavior of such structures.In this thesis,extended finite element method(XFEM)is improved to better simulate the cracking behaviors of quasi-brittle materials,then a sophisticated numerical simulation method using the improved XFEM is proposed for masonry-infilled RC frames.A parametric study is also conducted to consider the effect of different parameters on the behavior of masonry-infilled RC frames,which reveals the interaction mechanism.Finally,a simplified analysis model for masonry-infilled RC frame structures is proposed by considering th e actual state of all parts of the structure at peak load.The main content includes following four parts:(1)Extended finite element method is one of the most powerful method for dealing with the discontinuity problems.To properly modeling the fracture behavior of quasi-brittle materials such as concrete and masonry in infilled frames,a sophisticited plasticity-based rigid interface constitutive model coupling cohesion softening,contact,friction and shear dilatation,is proposed and efficiently incorporated into the XFEM formulation.An effective numerical integration scheme for accurately assembling the contribution to the weak form on both sides of the discontinuity is also introduced.The effectiveness of the proposed method has been assessed by simulating three well-known experimental tests in MATLAB.It is concluded that the numerical method can successfully capture the crack paths and accurately predict the fracture behavior of concrete structures.The influence of mode-II parameters on the mixed-mode fracture behavior is further investigated to better determine these parameters.(2)The current numerical models for masonry-infilled RC frames are struggling with the mesh-dependent problem,and failure patterns can not be successfully captured.On the basis of the further improvement on extended finite element method,with compressive yielding and cracking of the concrete and masonry units and multiple distributed cracks considered,a XFEM-based finite element modeling for masonry-infilled RC frames is implemented in the Finite element code FEAP,and it concerns three user defined elements and two material constitutive models and a macro command.In this modelling,the XFEM is adopted to model the cracking behavior and the compressive failure of con crete in RC frame members and masonry units in infill panels,and the discrete interface element is employed to simulate the behavior of mortar joints between masonry units and the behavior of the frame-to-infill interface.Preprocessing and postprocessing for the modelling are implemented in MATLAB.The models of several masonry-infilled RC frame specimens have been constructed in the FEAP software to demonstrate the applicability of the proposed finite element model.The numerical results have shown that the model can capture the damage patterns of the frame specimens.The results are also in good agreement with the load-displacement curves obtained from the experiments.(3)With the verified finite element modeling for masonry-infilled RC frames,a parametric study has been systematically conducted to consider the effect of different material properties,geometrical dimensions and design parameters on the behavior of masonry-infilled RC frames,which concerns aspect ratio of the infill panels,vertical loads applied on the specimens,the ratio of vertical loads between the frame columns and beam,longitudinal reinforcement and transverse reinforcement of the frame columns,sectional dimension of the frame columns,thickness of the infill panels and height of the frame beam.The results of the study indicate that the influence extent and general tendency of these parameters on the structural bearing capacity and failure patterns,reveal the interaction mechanism between the inflls and the bounding frames under the lateral loads.It provides a powerful data support for establish a simplified bearing capacity and numerical model for masonry-infilled RC frame structures.(4)Analyzing the results obtained from the simulation of the experiment and the parametric study,it found that in most cases considered here,the failure involves a dominant shear-sliding crack in the infill and diagonal shear cracks near the top of the windward column and the bottom of the leeward column.However,these three components have not reach their peak capacity simultaneously at the instant of peak capacity.Hence,the load carried by the structures is less than the load corresponding to failure of the three at the same instant.Finally,the results from the above study have been used to develop a simplified procedure for the behavior of a masonry-infilled RC frame.The vertical load distribution on the infill and the simplified lateral force-displacement curve is studied by numerical fitting analysis.Then,a diagonal strut model is proposed.The proposed simplified approach has been validated with the test results used above.The comparison indicates that the results of this method are very encouraging as it successfully captures the important features of the lateral force-vs.-drift response.This method can be further used to model multistory infilled frames as braced frames.更多还原