基于拟力法的纤维梁有限元非线性分析方法

以拟力法中的弹塑性分解思路和纤维梁理论为基础,将梁单元的截面变形分解为弹性变形和塑性变形,并引入塑性自由度,在材料层面建立了基于拟力法的纤维梁有限元非线性分析方法。该方法可以保持结构整体刚度矩阵不变,其非线性状态通过局部塑性矩阵加以体现,在迭代计算时避免了结构整体刚度矩阵的实时更新与分解,且塑性矩阵相比于结构整体刚度矩阵规模小,提高了计算效率。通过数值算例,将文中方法与采用有限元软件ABAQUS的分析结果进行对比,两者吻合较好,证明了该方法的有效性。     

Displacement estimation of nonlinear structures using the force analogy method

Significant effort has gone toward developing accurate and efficient displacement estimation procedures for the nonlinear multi‐degree‐of‐freedom (MDOF) system. Although the dynamic nonlinear analysis is capable of providing the high computational precision through the step‐by‐step time integration method, the simplified method is still expected and imperative for seismic design practices. The work presented in this paper focuses on the implementation of using the modal superposition method to estimate displacement responses of the nonlinear MDOF system based on the force analogy method (FAM). The current research demonstrated that the equation of motion for the nonlinear MDOF system can be decoupled, but other two governing equations in the FAM about the internal force, such as the moment and force of structural members, are not decomposable. Thus, the FAM is incorporated with the modal pushover analysis (MPA) method to determine the basic parameters of each mode such that the modal superposition method can be suitable for the solution of the nonlinear MDOF system. The procedure presented here is an approximately estimation method due to the application of MPA method. However, the value and potential for the maximum displacement estimation of the nonlinear MDOF system were demonstrated through the application in a framed structure. Copyright © 2014 John Wiley & Sons, Ltd.     

A force analogy method (FAM) assessment on different static condensation procedures for frames with full Rayleigh damping

In this paper, influence of different static condensation methods on nonlinear time history response of structures in presence of full Rayleigh damping matrix has been studied. Equation of motion is derived in details for 2 newly introduced cases; Full Static Condensation Model and Reduced Static Condensation Model (RSCM or RSCM‐1). Nonlinear analyses are performed with state‐space form of equation of motion along with force analogy method. A novel aspect of this study in comparison with previous researches is to consider full Rayleigh damping in formulations for static condensation in nonlinear structural analysis. Numerical examples are presented for the proposed methods. In addition, the same structure was modeled in finite element method and analyzed by the OpenSEES program. Comparisons demonstrate that results, which are obtained from introduced methods in this article, are in good agreement with the finite element method results. In addition to explaining the equation derivations in main article, proofs for some equations have been demonstrated in appendices. The comparisons show that both RSCM and Full Static Condensation Model lead to almost the same results but in case of using RSCM‐1, the responses have some deviation from other condensation methods.     

Nonlinear hysteretic behavior simulation of reinforced concrete shear walls using the force analogy method

Reinforced concrete (RC) shear walls that provide high strength and stiffness are widely used in buildings to resist lateral loads. It often exhibits complex and multiple hysteretic behaviors, including shear behavior, flexural behavior, strength softening, and deterioration, which are often influenced by the reinforcement and concrete material characteristics, vertical loads, and so on. Significant effort has gone toward developing accurate and efficient models, and these models fall into two categories: macroscopic and microscopic models. The microscopic models are accurate but computationally expensive and need more material information and experimental results for calibration. The present research is to implement an existing macroscopic model for use in the force analogy method, which is an accurate, efficient, and stable algorithm for conducting dynamic analysis when coupled with the state space formulation. The RC shear wall model with two vertical sliding hinges and one horizontal sliding hinge assigned to capture the relationship of the lateral deflection or rotation versus the RC shear wall force is validated against prior experimental results. The proposed model is also implemented in a frame, in which inelastic response occurs in both the frame and the RC shear wall members, to demonstrate the application of the model and the potential for simulating complex inelastic dynamic RC frame‐wall structural behavior with the force analogy method. Copyright © 2014 John Wiley & Sons, Ltd.     

A displacement‐based adaptive pushover method considering modal sign reversal for RC frame structures

Nonlinear static procedures are favored tools for practical applications in the structural engineering profession. However, some limitations are associated with them, including their deficiencies to properly reflect higher modal effects and inertial seismic forces fluctuations in their responses. Some different adaptive pushover methods intended to improve these limitations have been proposed in the literature, but each one has come out with a special deficiency. In this study, based on the concepts of the displacement‐based adaptive pushover, a new dual‐run procedure method called Improved DAP (IDAP) has been developed, aiming to improve higher modal and sign reversal consideration of pushover methods. The seismic scope of this study has been focused on near‐fault regions. Four concrete SMRF with different heights have been employed for the evaluations. The results of the proposed method in terms of capacity curves, interstory and shear profiles are compared with those of the IDA method. Results indicate that the ability of the new method in reproducing seismic story forces and capacity curves, as well as interstory drifts, has been improved in comparison with its primitive counterpart. Copyright © 2015 John Wiley & Sons, Ltd.     

A generalized method for estimating drifts and drift components of tall buildings under lateral loading

A generalized method for estimating the drifts of tall buildings composed of planar moment‐resisting frames and coupled shear walls under lateral loading is presented. This method establishes the stiffness equations at the story levels by assuming that all the nodes in the same floor of a planar lateral‐force‐resisting unit have an identical lateral displacement, an identical rotation component due to the axial deformations of the columns, and an identical rotation component due to the flexural and shear deformations of the beams. By adopting this simplification, the story drifts contributed by different types of deformations, namely, the axial deformations of the columns or wall piers, the flexural and shear deformations of the beams, and the double‐curvature bending and shear deformations of the columns or wall piers, can be identified. In the formulation of the stiffness matrix, the P‐Delta effects were also incorporated. Through comparisons between the lateral displacements and story drifts computed using the proposed method and those computed using the structural analysis software Midas/Gen, the proposed method is proved to have high accuracy in estimating the drifts of tall building structures.     

采用逐步增量弹塑性时程方法对RC框架结构推覆分析侧力模式的研究

以两个普通六层和十层钢筋混凝土框架结构为例,采用基于纤维模型的逐步增量弹塑性时程方法得到的层间剪力-位移关系曲线,与不同侧力模式的推覆分析结果进行了对比,研究了推覆分析结果的可靠程度。通过与不同场地的大量地震记录的弹塑性时程计算结果进行比较分析,建议采用多种合理的侧力模式进行推覆分析,对结构不同楼层的抗震性能进行全面的评价,即均布侧力模式适合于底部楼层的评价;考虑高度影响分布力模式适合于结构中部楼层的评价;而对结构上部楼层特别是顶层,可以采用SRSS侧力模式或规范侧力模式进行评价。分析研究表明,采用本文建议的侧力模式进行推覆分析,可在统计意义上可对钢筋混凝土规则框架结构的抗震能力作出偏于安全的估计。     

Experimental study on steel built‐up column moment connections with top and bottom trapezoidal side plates

Built‐up and box columns are used extensively in steel structures. A kind of built‐up column is composed of two I rolled shapes separated by calculated interval and welded between two cover plates. The uncertainties due to these columns are the flexibility of the column cover plates under the transferred beam flange plate forces and the brittle behavior of the groove weld between the beam flange plate and the column cover plate. The top and bottom trapezoidal side plates are proposed to improve the behavior of these column moment connections. Using this approach, the total beam flange forces transfer to the lateral sides of the column, parallel to the beam web, by means of top and bottom side plates. An experimental test is developed to study the behavior of the proposed connection under cyclic loading. The results indicate that the proposed connection has sufficient strength and ductility to apply in special moment frames. Also, the rehabilitated connection eliminates the vulnerabilities of deformation of the column cover plate and brittle fracture of groove welds in conventional connections. Copyright © 2016 John Wiley & Sons, Ltd.     

谈外雄水电站施工期变形监测方法及精度分析

简要介绍了外雄水电站变形监测点的布置情况,对施工阶段采用的水平位移、垂直位移的观测方法作了具体阐述,并对观测资料进行整理,对观测数据进行精度分析等,对今后同类工程施工测量具有一定指导意义。     

地下室无梁楼盖计算方法分析

无梁楼盖是近年来地下室常见的结构型式,目前计算方法多样,本文以实际工程为案例,通过对常用的几种计算方法结果进行分析对比,得出结论,供地下室工程无梁楼盖设计参考。     

Simplified analysis of a skew-plate bridge based on grillage analogy model

The structural behaviour of a continuous reinforced concrete skew slab bridge is particularly complicated and it is difficult for general analytical methods to acquire the internal forces in the structure directly. This article presents a spatial analogy model for the analysis of a skew-plate bridge. The proposed grillage analogy model had been validated by comparison with results based on the shell model and results obtained from field testing. Meanwhile, two different grillage analogy models of the skew-plate bridge are discussed. It is shown that it is the analysis of skew-plate bridges may be conveniently performed using the proposed grillage analogy model.     

矩阵位移法和有限元法在桁架结构分析中的区别

分析了矩阵位移法和有限元法两种理论,以及在实用结构中的应用计算,探索了两者之间的区别:矩阵位移法仅能应用在已知单元节点力、框架结构中单元节点间的关系,而不能应用在连续体结构中,提出两者的主要区别在于基本原理和分析方法。     

索结构的数值分析理论研究

本文对建筑中常用的索结构进行了数值分析，并建立了位移模型和进行了有限单无法的公式推导，数值算例的结果表明该数值分析方法是合理的，为进行索建筑结构的进一步理论研究奠定了基础。     

A static pushover method for identifying weak areas of earthquake resistant space frame structures

空间网格结构在强震下出现薄弱区的原因是该区域杆件的地震内力与决定其截面配置的非抗震设计内力差异较大，且该内力差异主要来自于少数模态的贡献。为此，利用非抗震设计和多遇地震验算的最不利内力，提出了一种疑似薄弱区杆件的简便判别方法。基于多遇地震下由振型分解反应谱法计算得到的结构响应，可以确定疑似薄弱区杆件地震内力的主要贡献模态。考虑这些主要贡献模态并参考振型质量参与系数，构造了能够近似反映最不利单向地震响应的综合模态，并基于结构应变能相等的原则确定了罕遇地震水平的等效静力推覆荷载。给出了一种能够计入三向地震动贡献的静力推覆方法，并对一个三心圆柱面双层网壳算例进行了推覆分析。通过与动力弹塑性时程分析结果对比发现，只要在建立推覆荷载时组合模态包括了疑似薄弱区杆件地震内力的主要贡献模态,并且所有组合模态的振型质量参与系数之和大于90%，则该静力推覆方法可以有效识别到该结构在罕遇地震下可能形成的薄弱区。     

空间网格结构抗震薄弱区识别的静力推覆方法

空间网格结构在强震下出现薄弱区的原因是该区域杆件的地震内力与决定其截面配置的非抗震设计内力差异较大,且该内力差异主要来自于少数模态的贡献。为此,利用非抗震设计和多遇地震验算的最不利内力,提出了一种疑似薄弱区杆件的简便判别方法。基于多遇地震下由振型分解反应谱法计算得到的结构响应,可以确定疑似薄弱区杆件地震内力的主要贡献模态。考虑这些主要贡献模态并参考振型质量参与系数,构造了能够近似反映最不利单向地震响应的综合模态,并基于结构应变能相等的原则确定了罕遇地震水平的等效静力推覆荷载。给出了一种能够计入三向地震动贡献的静力推覆方法,并对一个三心圆柱面双层网壳算例进行了推覆分析。通过与动力弹塑性时程分析结果对比发现,只要在建立推覆荷载时组合模态包括了疑似薄弱区杆件地震内力的主要贡献模态,并且所有组合模态的振型质量参与系数之和大于90%,则该静力推覆方法可以有效识别到该结构在罕遇地震下可能形成的薄弱区。     

位移补偿计算法在结构索力调整中的应用

预应力结构在使用过程中由于索松弛等原因导致结构处于误差状态,影响结构的正常使用。本文提出的位移补偿计算法可对结构的误差状态进行调整计算,对于结构存在力误差及几何误差两类误差状态,计算得到索张力调整控制值,实际施工中依照此值对索进行分批张拉即可完成结构索力的施工调整。分析结果表明,采用本计算方法,可使处于力误差状态的结构调整到设计状态,可使处于较小几何误差状态的结构调整后结构构件内力和节点位置满足施工精度要求。     

Prediction of nonlinear seismic demands of high‐rise rocking wall structures using a simplified modal pushover analysis procedure

This study presents a simplified analysis procedure for the convenient estimation of nonlinear seismic demands of high‐rise rocking wall structures. For this purpose, the displacement modification approach used in the nonlinear static procedure of ASCE/SEI 41‐13 is adopted. However, in the current study, this approach is extended to every significant vibration mode of the structure whereas the displacement modifying coefficients for different modes are calculated using the typical flag‐shaped hysteresis behavior of rocking walls. The parameters of this hysteresis behavior are selected to represent rocking walls with a practical range of energy dissipation capacity and postgap‐opening stiffness. The computed peak inelastic‐to‐elastic displacement ratios are presented as mean spectra, which can be used for the convenient estimation of pushover target displacement for every significant vibration mode. The accuracy of proposed procedure is examined using the seismic demands obtained from the nonlinear response history analysis of a 20‐story case study rocking wall structure. Furthermore, a modal decomposition technique is used to determine the individual modal seismic demands. The proposed procedure is found to predict both the combined and the individual modal demands with a reasonable accuracy and can serve as a convenient analysis option for the design and performance evaluation of high‐rise rocking wall systems.     

将弧长法应用于结构的几何非线性有限元分析

首先介绍了弧长法的发展及基本理论，随后根据笔者的研究，对其中的几个问题提出了相应的参考意见，最后给出了几个算例。     

单层球面网壳节点刚性反应的内力分析研究

节点刚度是影响单层球面网壳内力的重要因素之一.本文提出了＂变刚度＂的内力分析方法.基于梁单元有限元法,各杆件单元的刚度通过引入一个介于0～1之间的无量纲因子来考虑,当该系数取不同数值时,模型将分别退化为理想铰接和完全刚性连接的结构,并可方便分析具有任意刚度连接的网壳结构的内力.通过分析节点刚度、结构矢高、荷载对杆件内力的影响,得出了一些有意义的结论.     

考虑高阶振型影响的时程分析加权调整选波方法

针对长周期结构抗震时程分析输入地震波选择问题,提出一种在较宽的周期范围内实现反应谱与目标谱一致性匹配的地震波选择及调整方法。在匹配误差指标（SSE）和地震波幅值调整系数（SF）计算中采用了加权形式的最小二乘法,引入由归一化振型参与系数确定的结构前几阶振型的权重系数,以充分考虑高阶振型对结构地震反应的不同贡献。以美国SAC Steel Project提出的20层抗弯钢框架结构为实例,以该计划提出的代表3种超越概率（即50年超越概率50%、10%和2%）的各组地震波平均反应谱作为目标谱,以这3组地震波（每组10个台站双向记录,即20条波）时程分析得到的结构最大层间位移角均值为各超越概率下的目标反应;以简单地震信息初选的小型地震波数据库（共40条波）作为备选波,选用3条、7条和10条3种地震波数量及不同排序原则的6种分组方式,将加权调整选波方法与不考虑权重的等权调整方法所得各分组地震波反应谱,以及结构时程分析结果进行比较。研究表明,加权与等权方法对估计结构反应（如最大层间位移角）均值具有相同的准确性,但在降低结构反应离散性方面,加权方法具有较大优势。此外,若任意选择地震波组进行时程分析时,采用加权方法也可在一定程度上降低结构反应计算结果的离散性。