钢结构交错桁架体系静力和动力性能

本文回顾了交错桁架结构体系的理论研究现状和工程应用概况,在此基础上,针对研究成果中的不足之处,主要完成了以下几个方面的工作: (1) 在静力弹性分析理论方面,根据交错桁架结构的受力特点,提出了竖向荷载作用下,交错桁架结构内力计算的力学模型和计算方法。对于空腹交错桁架结构,在引入桁架的转动刚度和传递系数的基础上,将单榀横向框架简化为无侧移刚架,算例分析表明:该方法使得参与迭代计算的构件数量大大减少,收敛速度提高,从而减少了计算工作量。对于混合交错桁架结构,本文给出了构件内力的计算公式和计算方法。根据交错桁架结构在水平荷载作用下的受力特点和传力方式,在楼板刚性假定和忽略扭转效应的基础上,本文提出了构件内力和楼层侧移计算的平面分析模型,并给出了结构层间侧移刚度计算公式以及内力和侧移的计算公式和计算方法,算例分析表明:该方法简便实用,具有较高的精度。本文给出了两种考虑二阶效应的方法:一种方法通过将二阶效应的影响等效为层间侧移刚度的折减,给出了考虑二阶效应后结构侧移刚度的计算公式和考虑二阶效应和空间整体作用的内力和侧移平面计算模型及计算方法,另一种方法将结构等效为一根组合压杆,通过求解压杆的微分方程,得出结构在水平荷载和竖向荷载作用下结构的变形曲线。通过将结构等效为一根组合压杆,本文提出了采用能量法计算结构整体失稳的临界荷载的计算方法。另外本文还研究了考虑楼板影响后弦杆截面特性的计算方法以及考虑扭转效应后结构抗侧力构件所分配剪力的修正公式。 (2) 在地震反应的有限元分析方面,根据钢结构交错桁架结构体系主要构件为薄壁杆件的特点,分析了薄壁杆件中各种变形之间的耦合关系,并在此基础上,推导出了考虑剪力影响,二阶效应、翘曲分布以及截面开口和闭口等因素的单元刚度矩阵。基于理想弹塑性假定,给出了单元的弹塑性刚度矩阵,在空间杆系一层模型假定的基础上,建立了结构的动力平衡方程,并对空腹节间距的大小、阻尼比以及地震波输入维数对地震响应的影响进行了研究,算例分析表明:空腹节间的节间距和阻尼比对结构的动力响应影响较大,而地震波输入维数对结构的位移影响较小。 (3) 在地震作用计算的简化分析方面,基于振型分解法,本文给出了多维地震动输入下结构地震反应计算的具体计算公式和方法,并讨论
电加热器
Based on the review of the theoretical study and practical application of staggered truss framing system, this dissertation mainly achieves the following aspects aiming at improving the defects in the study:With regard to the theory of static elastic analysis, the paper, applying the analysis of the bearing characteristic, puts forward a mechanical model and a calculating method of internal forces of staggered truss structure subjected to vertical loads. As for Vierendeel staggered truss structure, the staggered truss structure can be simplified as a rigid frame with no lateral deflection with the introduction of rotational stiffness and transfer coefficient. Examples and calculating results show that the number of members involved in interaction is decreased greatly and iterative convergent rated is improved to a large extent so as to lessen the amount of computation. Concerning the staggered truss frame with diagonal braces truss, calculating formula and methods of member internal forces are presented. According to the analysis of the bearing characteristics and the way of force transference in staggered truss structure under lateral loads, assuming that the stiffness of floor was infinite and torsional effect could be ignored, a plane cooperative mechanical model for calculating internal force in member is brought about and calculating formula and methods of relative lateral displacement between neighboring storeys and total lateral displacement stiffness between storeys are provided as well. Examples and calculating results reveal that the method adopted in the paper is simple and of great precision. Two methods of dealing with second-order effect are listed as follows: first, the influence of second-order effect can be regarded as equivalence to deduction of lateral displacement stiffness between storeys. In this way, calculating formula for lateral displacement stiffness between storeys considering second-order effect and a plane cooperative mechanical model for calculating internal force in member after taking second-order effect and space integral effect into account. Second, a structure is equal to a built-up compression member. By computing the differential equation for this member, deformation curve of the given structure under lateral load and vertical load can be obtained. Based on theassumption that the structure is viewed as a built-up compression member, the paper comes up with calculating method adopting energy method to work out critical load of overall stability. In addition, the paper offered calculating method of cross section characteristics of chord member in view of the influence on floor slabs, along with modified formula including torsional effects for the shear distribution in members.With relation to finite element analysis of seismic response, by virtue of the characteristics that principal members of staggered truss steel structure are thin-walled bar, the paper analyzes coupling relation among various deformation in thin-walled bars and deduces geometric stiffness matrix of elements considering factors, such as the influence of shear force, second-order effect, warp distribution and section opening and close. On the presupposition of ideal elastoplasticity, elastoplasticity stiffness matrix of elements is displayed. Dynamic equilibrium equation is established, based on space bar-floor model assumption. Then, a study is conducted through analysis examples of seismic response subjected to Vierendeel panel length, damping ratio and input dimension of seismic wave, analysis results show that the length of Vierendeel panel and damping ratio exert greater influence on structural dynamic response, while the input dimension of seismic wave has fewer impact on structural displacementIn the matter of simplified analysis about earthquake action, grounded on mode superposition method, the paper provides concrete calculating formula and method of seismic response affected by the input of multi-dimensional seismic wave and discusses the reasonable number of vibration mode. By means of constructing a structure with an easily-gained natural vibration frequency and vibration modes, the paper introduces simplified calculating approach to natural vibration frequency and vibration modes of staggered truss structure while referring to the matrix perturbation theory. With this approach, the structural interlayer shears achieved by equivalent base shear method and mode superposition method are compared and contrasted. The results make it clear that the percentage discrepancy will widen along with the numbers of stories, attributed to different computation results obtained by the equivalent base shear method and mode superposition method respectively.