钢框架-支撑体系中支撑与框架的变形特点对结构分析的影响

提出多高层钢框架-支撑体系在水平荷载作用下的内力和变形计算应依支撑的变形型式的不同而采取不同的计算方法。当支撑的变形型式为剪切型时用 D 值法,当支撑变形型式为弯曲型时用与框架协同工作的位移法。重点就剪切型支撑计算中如何考虑弯曲变形的影响,弯曲型支撑如何考虑剪切变形的影响以及框架因整体弯曲产生的柱轴向变形的影响作了进一步分析,从而提出在结构分析中的若干改进措施。     

考虑剪切变形影响的框架结构稳定性

巨型框架结构由于框架梁柱截面的剪切变形较大,在分析巨型结构整体稳定性时,应当同时考虑巨型梁柱的弯曲变形与剪切变形。本文研究了框架梁和框架柱截面的剪切变形对框架结构整体稳定性的影响。分别研究了简单对称框架柱顶作用有相同集中荷载时、简单对称框架柱顶作用有不等集中荷载时、以及不对称框架柱顶作用不等集中荷载时,框架结构的整体稳定性。分析了不对称框架柱剪切变形对框架稳定性的影响及框架发生整体有侧移失稳的内在规律。着重讨论了框架梁截面的剪切变形对框架整体稳定性的影响规律,根据这一规律提出了简化方法以考虑横梁剪切变形的影响。本文提出了计算框架临界荷载的近似计算方法,与有限元法的结果对比,具有很好的精度,近似算法均考虑了框架梁和框架柱截面的剪切变形及弯曲变形。     

框剪结构弯扭耦合分析的精细积分法

将哈密顿求解体系应用于框架-剪力墙结构的弯扭耦合分析.假定楼板作用沿高度连续化,将框剪结构的抗侧力单元简化为同时考虑扭转、弯曲和剪切变形的悬臂梁的计算模型,通过刚性楼板的连接共同受力,能较好的反映建筑结构的受力情况,结合精细积分法得出结构内力和位移的高精度数值解,算例表明本方法可行性较高.     

钢网格式框架侧向变形性能研究

钢网格式框架结构是一种新型钢结构抗侧力体系,它是由小截面钢柱、小截面横梁以及楼层圈梁形成的网格式框架墙板,现场浇筑工业石膏废料作为墙体填充材料。由于其框架作用要强于普通钢框架,所以其侧向变形性能更加优异,分别采用柔度法和D值法推导了钢网格式框架的剪切变形计算式和整体弯曲变形计算式。通过算例,对比分析算式计算结果与有限元分析结果可知:剪切变形柔度法计算公式精度较高。分析表明:钢网格式框架侧向变形必须充分考虑杆件弯矩、剪力及轴力引起的剪切变形和倾覆弯矩引起的整体弯曲变形;钢网格式框架的剪切变形计算不能采用普通钢框架的D值法,应当采用柔度法。     

半刚性连接钢框架二阶内力和位移的简化计算

框架中梁柱连接大多介于完全刚接与理想铰接之间,即半刚性连接。提出了半刚性连接钢框架二阶内力与位移的简化计算方法。在计算内力时用弯矩放大法,连接的影响通过将梁的抗弯刚度乘以修正系数来考虑;计算位移时用D值法,连接的影响通过将梁的抗弯刚度转化为等效刚度来考虑。算例表明,在计算中应充分考虑半刚性连接的影响。     

半刚性连接钢框架二阶内力和位移的简化计算

框架中梁柱连接大多介于完全刚接与理想铰接之间,即半刚性连接.提出了半刚性连接钢框架二阶内力与位移的简化计算方法.在计算内力时用弯矩放大法,连接的影响通过将梁的抗弯刚度乘以修正系数来考虑;计算位移时用D值法,连接的影响通过将梁的抗弯刚度转化为等效刚度来考虑.算例表明,在计算中应充分考虑半刚性连接的影响.     

框架核心筒伸臂结构分析的哈密顿对偶体系

采用框架核心筒伸臂结构的简化计算模型,将核心筒看做底端固定上端自由的悬臂梁,伸臂对核心筒的约束作用看做抗扭弹簧,考虑核心筒和伸臂的弯曲、剪切变形及核心筒的宽度影响,导出了结构的Hamilton对偶求解体系,通过两端边值问题的精细积分法,求解核心筒的内力与变形。以施加倒三角水平荷载的框架核心筒伸臂结构为例,进行算例计算。     

基于精细梁模型的向量式有限元分析

<正>精细梁不同于Euler梁和Timos lenko梁,该模型在考虑剪切变形的同时还考虑了横向弯曲时截面转动产生的附加轴向位移及横向剪切变形影响截面抗弯刚度后产生的附加横向位移。推导了适用于向量式有限元分析的精细梁单元应变和内力表达式,采用FORTRAN自编了向量式有限元程序。对悬臂梁、两端固支梁和门式框架进行了算例分析,对比了采用不同梁单元模型下结构的竖向位移。结果表明:当高跨比较小时,3种梁单元的竖向位移     

梁翼缘削弱式钢框架考虑节点域剪切变形的力学性能研究

钢框架采用翼缘削弱型节点(RBS)可以提高结构延性,满足结构抗震设计要求。考虑框架节点域的剪切变形,导出连带节点域的RBS梁、柱单元刚度矩阵,利用计算软件MATLAB对RBS节点钢框架结构的内力及变形进行了分析和计算。分析结果表明:在水平荷载作用下节点域剪切变形对RBS节点钢框架变形影响较大,层位移、层间位移以及节点总转角的增量均随层数的增加而相应增大,节点域剪切变形对框架内力的影响较小;工程设计中应考虑节点域剪切变形对RBS节点钢框架侧向刚度的不利影响。     

@编辑部

<正>媒体重头文章概览基于精细梁模型的向量式有限元分析《土木建筑与环境工程》02/2015精细梁不同于Euler梁和rimoshenko梁,该模型在考虑剪切变形的同时还考虑了横向弯曲时截面转动产生的附加轴向位移及横向剪切变形影响截面抗弯刚度后产生的附加横向位移。推导了适用于向量式有限元分析的精细梁单元应变和内力表达式,采用FORTRAN自编了向量式有限元程序。对悬臂梁、两端固支梁和门式框架进行     

筒中筒结构的简化计算

A.Coull用等代筒体法分析框筒结果表明:剪力滞后对框筒变形的影响较小,可以近似地按等代筒体,乘以剪力滞后影响系数来考虑。因此,在筒中筒结构中我们可以将外缘框筒作为具有弯曲及剪切变形的等代筒体,按与只考虑弯曲变形的内筒的形变协调条件,建立微分方程,解出筒中筒结构的侧移计算公式及内外筒的荷载分配计算公式。由此,用顶点位移法可求出筒中筒结构的主振周期及地震力。当作用于外筒上的荷载分布公式确定后,可由此导出应力调整函数S(z)的计算式。利用程序计算器,可方便地求出框筒梁柱中的内力。     

钢筋混凝土框筒结构负剪力滞研究

框筒结构在水平荷载作用下的变形由剪切变形和弯曲变形两部分组成,弯曲变形必须考虑正、负剪力滞的影响。本文在框筒柱应力分布和剪力滞分布假定的基础上,取消连续化假定,推导出了框筒结构弯曲变形时柱轴力和侧移的简化计算公式,对影响框筒结构负剪力滞的几个主要因素进行了分析。     

Sources of elastic deformations in steel frame and framed-tube structures: Part 2: Detailed subassemblage models

This paper examines the accuracy of a set of equations for computing Displacement Participation Factors (DPFs) for beam-column subassemblages of steel moment resisting frame buildings. These factors allow the analyst to determine how the entire subassemblage or individual components of a subassemblage contribute to a given structural displacement. Additionally, the component’s contribution to displacement may be evaluated in terms of sources of axial, flexural, or shear deformation.When applied to a set of 12 isolated subassemblages, it was shown in Part 1 of the paper that deformations in the beam-column joint are very significant, and that flexural deformation in the joint, which is often ignored, should be considered in all analyses. The total displacement predicted through the use of the DPFs correlates extremely well with the results of detailed three dimensional finite element analyses of the same subassemblages. However, it was also shown that there is considerable uncertainty in the bending moments and moments of inertia that are used to compute joint flexural deformations.The objective of this paper, which is the second part of a two-part paper, is to further investigate the accuracy of the DPF expressions developed in Part 1. This is done by computing DPFs from the results of detailed three dimensional finite element analysis, and comparing these to those computed through the use of the simple expressions.The results of the analysis show that the joint flexural deformations are accurately predicted by the simple DPF expressions, but that this accuracy arises from compensating “errors” in the simplified analysis. It is also shown that the use of beam flange continuity plates has a marginal effect on computed displacements. The paper ends with recommendations for using the simplified expressions for computing subassemblage deformations, and for including such deformations in structural analysis of steel frame and tube structures.     

Shear and bending flexibility in closed-form moment solutions for continuous beams and bridge structures

Shear deformations can affect final member-end-moments for statically indeterminate continuous beams and frame structures, though for typical civil engineering structures their effect is small and moments can be based on flexural deformations only. When a member is deep relative to span length, however, shear deformations should be considered in the analysis. This can be included in the stiffness method and in a modified form of moment distribution where the carry-over factor is less than one-half due to the added flexibility from shear. In a prior paper the first author presented a new approach for solving statically indeterminate beams and bridge frames, with final end moments given in closed-form expressions. The advantages of this new approach are that no simultaneous equations are required as in the stiffness method, moments are not distributed back and forth as in moment distribution, and manual calculations may be used which give exact results for as many spans as desired. While only flexural deformations were considered in the original paper, this paper presents a closed-form approach that has been modified to include shear deformations. Final expressions are given for continuous beams and bridge frames, providing exact member-end-moments that match results from the stiffness method when shear deformations are included in the analysis.     

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.     

框筒结构的简化分析方法

考虑剪力滞后的影响,将高层框筒结构先离散成正交各向同性板,根据最小势能原理得到各板的应力和应变表达式,再根据角柱处的位移与内力相等效的原则,将空间框筒结构等效成平面框架结构。对一个高层算例进行了计算,并与按空间框架分析的结果进行了对比。结果表明,这种简化方法具有足够的精度。     

Simplified torsion analysis for high-rise structures

A simple approximate hand method of analysis is presented for determining the internal forces in multi-storey structures subject to torsional loading. The buildings may include plan-symmetric combinations of coupled walls, rigid frames, wall-frames, single shear walls, rigid frames with central shear walls and braced frames. The bending deformations in all individual structural members are taken into account as well as the axial shortening and lengthening of the columns. The method is based on the continuous medium analogy which enables the analysis to be reduced to simple closed formulae. It is restricted to structures with uniform geometry up the height and linear elastic behaviour of the structural members. It provides a simple and rapid means of estimating the internal forces in each individual structural element and it is appropriate to the preliminary stages of the design of proposed tall building structure.     

Sources of elastic deformation in steel frame and framed-tube structures: Part 1: Simplified subassemblage models

Three simple models for including the effect of beam-column joint deformation in the analysis of steel moment resisting frame and framed tube structures are presented. The first model, called the Fictitious Joint model, is based on two-dimensional frame analysis and is useful for preliminary analysis only. The second model, called the Krawinkler Joint model, and the third model, known as the Scissors Joint model, use an assembly of rigid links and rotational springs to represent the joint, and may be used in preliminary and final analysis of full structural systems. All derivations are provided in the form of “displacement participation factors”, which allow a detailed breakdown of the various components of subassemblage displacement.When applied to isolated beam-column subassemblages, it is shown that all three modeling approaches produce the same general expression for computing deflections arising from shear deformations in the panel zone region. However, the Krawinkler and Scissors models do not include the effects of flexural deformation within the beam-column joint, whereas the Fictitious Joint model does. While not the dominant source of deformation, it is shown in the paper that the effects of flexural deformations in the beam-column joint should not be ignored.It is also shown in this paper that the overall displacements predicted by the simplified models correlate very well with displacements computed from detailed three dimensional finite element analysis of the same subassemblage. However, the finite element analysis approach, taken alone, is not capable of providing a breakdown of the subassemblage displacements into components, such as panel zone shear, or column joint flexure. Part 2 of the paper presents a method for providing this information from the results of detailed finite element analysis.     

Simplified analysis of asymmetric high‐rise structures with cores

A simplified elastic hand‐method of analysis for asymmetric multi‐bent structures with cores subjected to horizontal loading is presented. The structures may consist of combinations of framed structures such as coupled walls, rigid frames and braced frames with planar and non‐planar shear walls. Results for structures that are uniform with height compare closely with results from stiffness matrix analyses. The method is developed from coupled‐wall deflection theory which is expressed in non‐dimensional structural parameters. It accounts for bending deformations in all individual members, axial deformations in the vertical members as well as torsion and warping in nonplanar walls. A closed solution of coupled differential equations for deflection and rotation gives the deflected shape along the height of the building from which all internal forces can be obtained. The proposed method of analysis offers a relatively simple and rapid means of comparing the deformations and internal forces of different stability systems for a proposed tall building in the preliminary stages of the design. The derivation of equations for analysis shown in this paper are for unisymmetric stability systems only, but the method is also applicable to general asymmetric structures with cores. Copyright © 2002 John Wiley & Sons, Ltd.     

The effect of shear deformations in floorbeams on the moment distribution in orthotropic plated bridge decks

Floorbeams of orthotropic plated bridge decks are generally elements with a low slenderness, especially in the case of railway bridges. When loaded, such elements generate not only flexural deformations but shear deformations as well. Depending on the configuration, these shear deformations can be considerably large and should certainly not be neglected. In a design according to the Pelikan-Esslinger method, this deformation is taken into account in the second stage of the calculation of the orthotropic deck. At this stage, the additional bending moments, shear forces and floorbeam reactions due to the floorbeam flexibility are evaluated. The deflection of a directly loaded floorbeam creates a distribution of the load to adjacent non-loaded floorbeams. In addition, the deflection will affect the longitudinal ribs, increasing the sagging moments at midspan and decreasing the bending moments at the supports of the ribs provided by the floorbeams. In this paper a method is developed to take the shear deformation in the floorbeam into account, thus correcting the Pelikan-Esslinger method. The correction is especially important since the floorbeam web is frequently further weakened by cutouts for the longitudinal ribs and in some cases additional cope holes. The floorbeam web resisting the shear deformation is further reduced by these openings, increasing the importance of shear deformations even for more slender floorbeams. The validity of the proposed method is checked by full finite element calculation using shell elements which inherently comprise shear deformation. The effect of the correction on the calculations in the second stage of the calculation are relatively small for the floorbeam reactions; on the contrary, it can be quite large for the additional bending moments in the longitudinal ribs. In that case, the effect is worth considering.