共查询到20条相似文献，搜索用时 421 毫秒
1.
A smeared crack approach has been proposed to model the static and dynamic behavior of mass concrete in three‐dimensional space. The proposed model simulates the tensile fracture on the mass concrete and contains pre‐softening behavior, softening initiation, fracture energy conservation and strain rate effects under dynamic loads. The validity of the proposed model has been checked using the available experimental results under static and dynamic loads. The direct and indirect displacement control algorithms have been employed under incremental increasing static loads. It was found that the proposed model gives excellent results and crack profiles when compared with the available data under static loads. The Koyna Dam in India has been used to verify the dynamic behavior of the proposed model. It was found that the resulting crack profiles were in good agreement with the available experimental results. Finally, the Morrow Point Dam was analyzed, including the dam–reservoir interaction effects, to consider its non‐linear seismic behavior. It was found that the resulting crack profiles were in good agreement with the contour of maximum principal stresses and no numerical instability occurred during the analysis. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
2.
为精细化模拟桥梁结构的非线性行为,在深入分析纤维梁柱单元模型原理的基础上,本文基于ABAQUS建立了钢筋混凝土精细化纤维梁柱单元模拟平台FENAP,开发了与其相适应的材料模型库FENAP/MAT,涵盖了多种材料本构模型,能够有效考虑构件的刚度退化和强度退化等损伤效应,以及模拟轴力和弯矩的多维耦合效应等复杂非线性动力行为,且可考虑箍筋对混凝土的约束作用等。利用该FENAP平台数值模拟了一个钢筋混凝土矩形截面悬臂梁,进行了Pushover分析,考虑了箍筋对核心混凝土约束效应的影响,并与OpenSEES的计算结果进行对比。结果表明:FENAP平台可有效模拟桥梁构件的多种复杂非线性行为,且具有很好的计算效率和求解精度。 相似文献
3.
A finite element method for seismic fracture analysis of concrete gravity dams is presented. The proposed smeared crack analysis model is based on the non-linear fracture behaviour of concrete. The following features have been considered in the development of the model: (i) the strain softening of concrete due to microcracking; (ii) the rotation of the fracture band with the progressive evolution of microcrack damage in finite elements; (iii) the conservation of fracture energy; (iv) the strain-rate sensitivity of concrete fracture parameters; (v) the softening initiation criterion under biaxial loading conditions; (vi) the closing-reopening of cracks under cyclic loading conditions. The seismic fracture and energy response of dams and the significance of viscous damping models to take account of non-cracking structural energy dissipation mechanisms are discussed. The influences of global or local degradation of the material fracture resistance on the seismic cracking response of concrete dams were also studied. Two-dimensional seismic response analyses of Koyna Dam were performed to demonstrate the application of the proposed non-linear fracture mechanics model. 相似文献
4.
针对在水库堤坝排水边坡混凝土裂纹的抗震性研究中,未考虑岩土体抗剪强度参数的劣化屈服效应以及混凝土裂纹的老化,存在抗震性判断结果准确率较差等问题,提出水库堤坝排水边坡混凝土考虑老化后产生裂纹的抗震性能研究方法。模拟强震下边坡混凝土的开裂破坏过程,根据D-P屈服准则,实现对闸墩混凝土材料的屈服判断。采用薄层整体单元模拟和分离式裂纹单元,实现混凝土裂纹的数值模拟,加载地震波后,获取混凝土裂纹的强震响应规律与破坏特征。实验结果可知,本文方法对坝体位移变化的研究精度高,得到的混凝土裂纹扩展范围更为准。运用本文方法对水库堤坝排水边坡混凝土的抗震性研究准确率以及可信度较高,说明本文方法具有一定的可取性。 相似文献
5.
This paper proposes a simple lattice model for collapse analysis of RC bridges subjected to earthquakes by using the extended distinct element method (EDEM). In the model, a concrete element consists of lumped masses connected to one another by springs, and a reinforcement bar is represented by a discrete model or an integrated model. The proposed lattice model is simple but its parameters are reasonably defined. It has fewer element nodes and connecting springs, which will be of benefit by shortening the CPU time. The processes to determine the initial stiffness of concrete and steel springs, the parameters of the constitutive model and the fracture criteria for springs are described. A re‐contact spring model is also proposed to simulate the re‐contact of the concrete after fracture of springs; and a general grid searching method is used to decrease the CPU time for judging re‐contact after fracture. The lattice model is assessed by numerical simulations and experiments. As an application, a damaged single‐column pier subjected to the Kobe Earthquake in 1995 is analysed by EDEM with the proposed model. The simulation results indicate that the proposed model predicts well qualitatively the collapse process of RC bridges. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
6.
采用地震工程开源模拟软件OpenSees（Open System for Earthquake Engineering Simulation）对CFRP（Carbon Fiber Reinforced Polymer,碳纤维增强复合材料）布加固高强钢筋混凝土方柱的抗震性能进行了数值分析。采用Steel02Material和Concrete02Material材料本构模型模拟了CFRP布加固高强混凝土方柱的抗震性能;在此基础上,进一步研究了轴压比和剪跨比这2个因素对试件抗震性能的影响。将所得数值分析结果与相同条件下的试验结果对比后发现：基于Steel02 Material和Concrete02 Material材料本构,利用OpenSees,可以较好地模拟CFRP布加固高强混凝土方柱的抗震性能,并且与试验结果（滞回曲线、骨架曲线、水平承载力和位移延性系数）能够较好地吻合,从而说明该数值分析方法还可以准确地反映出轴压比和剪跨比对高强混凝土柱抗震性能的影响规律。 相似文献
7.
建立了一种Timoshenko裂纹梁的分析模型并且获得了闭合形式的挠度解析解。首先,在一致梁的理论框架下,通过引入δ函数模拟裂纹导致的局部柔度,建立用广义函数表示的Timoshenko裂纹梁的微分控制方程,进而得到挠度的闭合形式的解答;其次,根据线弹性断裂力学理论,利用转角及挠度突变与局部柔度系数的关系,建立Timoshenko裂纹梁的模型参数与裂纹深度的显式表示;最后,通过对裂纹深度与挠度、转角和曲率间关系的分析,总结了结构响应的损伤敏感性及其特征,并且通过与引入裂纹奇异单元的有限元结果进行比较,验证了本文所建分析模型及求解方法的正确性。研究结果表明,本文所建立的Timoshenko裂纹梁的分析模型,具有较高的计算精度和效率,在结构模型修正和损伤识别中具有良好的应用前景。 相似文献
8.
三层地铁车站振动台试验的数值模拟 总被引：1，自引：0，他引：1
进行了三层地铁车站大型振动台试验,获得了可靠的试验数据。通过室内实验获取了模型材料和土体材料的力学参数。基于ABAQUS有限元计算平台,建立了振动台试验的二维有限元模型,处理了混凝土本构模型及其参数的选取、土体本构模型及其参数的选取、阻尼设置、边界条件设置等问题。对多种工况下的试验结果和模拟结果进行了对比分析。结果表明,按照本文建议的建模方法,可以很好地重现振动台试验,数值模拟结果无论在趋势上还是数值上都和试验结果符合得很好。 相似文献
9.
《地震工程与结构动力学》2018,47(5):1291-1308
Evaluating the inelastic seismic response of structures accurately is of great importance in earthquake engineering and generally requires refined simulation, which is a time‐consuming process. Because the material nonlinearity generally occurs in a small part of the whole structure, many researches focus on taking advantage of this characteristic to improve the computational efficiency and the inelasticity‐separated finite element method (IS‐FEM) proposed recently provide a generic finite element formulation for solving this kind of problems efficiently. Although the fiber beam‐column element is widely used for the simulation of reinforced concrete (RC) framed structures, the inelastic deformation is often detected in a large part of the numerical model under earthquake excitation so that it is hard to achieve high efficient computation when applying the IS‐FEM to the inelastic response analysis of RC fiber models directly. In this paper, a new numerical scheme for seismic response analysis of RC framed structures model by fiber beam‐column element is proposed based on the IS‐FEM. To implement the RC fiber model for use in IS‐FEM and improve the computational performance of proposed scheme, a method of identifying the local domains with severe section inelasticity level is proposed and a modified Kent‐Park concrete material model is developed. Because the Woodbury formula is adopted as the solver, the global stiffness matrix can keep unchanged throughout the analysis and the main computational effort is only invested on a small matrix representing local inelastic behavior. The numerical examples demonstrate the validity and efficiency of the proposed scheme. 相似文献
10.
Owing to the devastating M7.6 earthquake of 20 June 1990 that occurred in the northern province of Iran, Sefid‐rud concrete buttress dam located near the epicenter was severely shaken. The crack penetrated throughout the dam thickness near slope discontinuity, causing severe leakage, but with no general failure. In this study, nonlinear seismic response of the highest monolith with empty reservoir is investigated experimentally through model testing. A geometric‐scaled model of 1:30 was tested on a shaking table with high‐frequency capability to study dynamic cracking of the model and serve as data for nonlinear computer model calibration. Three construction joints are set up in the model to simulate effects of construction aspects. The experimental results are then compared with smeared crack and damage mechanics finite‐element simulations using nonlinear concrete constitutive models based on fracture mechanics. The crack patterns obtained from numerical models are in good agreement with those obtained from shaking table tests for the case of including construction joint effects and rigid foundation. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
11.
提出了一种既有钢筋混凝土框架结构的抗震加固方法,该法采用防屈曲支撑提高框架结构体系的水平承载力和耗能能力,利用外包钢进一步提高柱子的抗弯和抗剪承载力。采用开源有限元程序OpenSees,分别建立空钢筋混凝土框架和防屈曲支撑加固钢筋混凝土框架的分析模型,对2榀钢筋混凝土框架的抗震性能进行模拟。防屈曲支撑采用了弹塑性桁架单元模型,加固框架柱混凝土考虑了外包钢的约束作用。将分析结果与拟静力试验结果进行比较,以检验分析模型的准确性,以及研究防屈曲支撑和外包钢对混凝土框架抗震性能的影响。分析结果表明,数值模拟与试验结果吻合较好,验证了基于OpenSees建立的数值模型的准确性;外包钢有效改善了框架柱的抗弯承载力和变形能力;防屈曲支撑显著提高了加固框架体系的水平刚度、水平承载力和耗能能力。 相似文献
12.
Most of the finite element analyses of reinforced concrete structures are restricted to two‐dimensional elements. Three‐dimensional solid elements have rarely been used although nearly all reinforced concrete structures are under a triaxial stress state. In this work, a three‐dimensional solid element based on a smeared fixed crack model that has been used in the past mainly for monotonic static loading analysis is extended to cater for dynamic analysis. The only material parameter that needs to be input for this model is the uniaxial compressive strength of concrete. Steel bars are modelled as uniaxial elements and an embedded formulation allows them to have any orientation inside the concrete elements. The proposed strategy for loading or unloading renders a numerical procedure which is stable and efficient. The whole process is applied to two RC frames and compared against existing experiments in the literature. Results show that the proposed approach may adequately be used to predict the dynamic response of a structure. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
13.
A numerical procedure for evaluation of the fracture process of gravity dams during strong earthquakes is presented. The BEM is used to discretize the dam reservoir system including the crack surfaces, and stress intensity factors at the crack tip are employed in a stage by stage procedure which simulates the crack extension. For each stage of constant crack length the mode superposition technique is applied; this is made possible by simulating the impact process of crack closing by a load pulse applied at the contact points which permits the structural stiffness to be assumed unchanged. To verify the proposed procedure, a cantilever beam model structure made of gypsum was tested on a shaking table. Good correlation with the numerical results was obtained, from which it is concluded that the procedure can be employed for evaluation of the crack propagation process in concrete structures subjected to dynamic loadings. 相似文献
14.
通过3个施加常轴力的RPC箱型桥墩试件的水平反复荷载试验,考虑水平荷载作用方向对RPC箱型墩抗震性能的影响,分析各试件滞回特性和骨架曲线的特点,对影响RPC箱型桥墩恢复力模型的主要因素进行数值回归分析,建立了计入双轴水平力耦合效应的RPC箱型桥墩恢复力模型。利用基于平截面假定的纤维模型法编制考虑轴力二阶效应的双轴压弯构件非线性分析程序,并对RPC箱型桥墩试件的骨架曲线和滞回曲线进行数值模拟。通过与试验结果进行分析对比表明:所提出的恢复力模型具有较好的精确性,能够较好地模拟和反映RPC箱型桥墩的抗震性能。 相似文献
15.
In this paper, a simple cyclic cracking model incorporating crack dilatancy effect is proposed to model the behaviour of reinforced
concrete structures under earthquake-like dynamic loading. This model has been implemented into a FE programme [LUSAS (2004)
Luscas User Manual (version 12.3), FEA Ltd., London, England] to simulate reversed and cyclic loading. A shaking table test performed in Switzerland
at the Swiss Federal Institute of Technology at Zurich (ETHZ) has been chosen for comparison. The test performed on the shaking
table simulated a wall of a 3-storey building. The natural frequency and the crack pattern have been calculated and show reasonable
agreement with the experimental results 相似文献
16.
1 INTRODUCTION Evolution of the river bed in alluvial channels has been studied by many researchers using analytical and numerical approaches. The use of analytical approach alone is insufficient for solving natural river engineering problems. With rapid growth in computer technology, numerical models have become a popular means for the study of mobile bed hydraulics. During the past decade, several numerical models have been developed. Most of the computer codes, such as HEC2SR (Si… 相似文献
17.
地基-非线性结构相互作用体系的主共振与分叉 总被引：2，自引：1，他引：1
本文考虑上部结构的恢复力为双线型模型,地基上简化为集中参数模型,运用平均法研究相互作用体系的主共振,得到主共振的定数解并讨论其稳定性。文中导出相互作用体系的分叉方程,并根据厅异性理论给出开折参数平面下的分叉图和转迁集,讨论不同物理参数域内系统的振动行为并通过算例得到一些定性的结论。 相似文献
18.
采用大理岩圆柱试样,与轴线约成30角预制不连续裂缝,再用环氧树脂胶接,以实验观测裂缝尺度及其填充物对剪切破裂能的影响.结果表明:当裂缝相对面积从0增加到90%时,破裂能从(6.92.1)103焦耳/米2逐步降到(0.60.5)1O3焦耳/米2;而使用 Knopoff方法和引入滑动弱化模式后的方法,求得的理论应力降几乎不变.它们与实测应力降的比却逐步增大并达到10.同时,分析了地震时和岩石破裂时的应力降差别很大,以及不同方法所得破裂能差别很大的原因,认为断层的蜂窝状接触对上述问题可能有重要影响. 相似文献
19.
20.
有缝拱坝-地基系统非线性地震波动反应分析方法 总被引：12，自引：3，他引：9
拱坝坝体中缝界面在地震作用下的开、合模拟对拱坝地震反应有重要影响。目前在拱坝地震反应分析中应用的一些模型,如Ｆｅｎｖｅｓ模型、Ｄｏｗｌｉｎｇ的三参数模型,存在对缝界面的接触状态模拟精度不高的问题,这对于准确评价工程上关心的缝界面最大张开率是不足的。此外,坝基中存在的断层、节理、裂隙待软弱夹层的非线性力学特性和无限地基能量辐射作用对拱坝地震反应也有重要影响。在拱坝地震反应分析中同时考虑这三种影响因素 相似文献