Effect of stressed-skin action on optimal design of cold-formed steel square and rectangular-shaped portal frame buildings

Cold-formed steel (CFS) portal frames can be a viable alternative to conventional hot-rolled steel portal frames. They are commonly used for low-rise commercial, light industrial and agricultural buildings. In this paper, the effect of stressed-skin action on the optimum design of CFS portal frames is investigated by conducting a minimum cost design optimisation on a building of span of 6 m, height-to-eaves of 3 m and frame spacing of 3 m; the effect of different number of bays are considered. For the purpose of this study, it is assumed that gables are rigid.The effect of stressed-skin action is larger for“square-shaped” buildings (i.e. when the span and length are the same on plan) and decreases as more bays are added(i.e. as the building becomes more “rectangular-shaped” on plan). The results of the minimum cost optimisation indicate that if stressed-skin action is taken into account, the cost of the internal frame can be reduced by around half for “square-shaped” buildings. It should be noted that this is a minimum cost optimisation, which is not the same as a minimum weight optimisation. It is also shown that a safe design of internal frames could be obtained by ignoring wind loads (i.e. designing the frame only for gravity loads),but this is limited to buildings having a “square-shape”.     

门式刚架轻钢结构的优化设计

从结构的跨度、柱距、结构形式、节点连接等方面，对门式刚架主构件进行优化设计，并对刚架的围护结构——檩条、支撑方面进行优化设计探讨，为实际工程设计提供有益的借鉴。     

冷弯薄壁型钢门式刚架蒙皮效应研究

采用ANSYS软件对冷弯薄壁型钢门式刚架的蒙皮效应作了探讨性研究.对比分析了无蒙皮门式刚架和有蒙皮门式刚架的顶点竖向位移与柱顶水平位移.计算结果表明,蒙皮效应对刚架整体竖向和水平位移都有很大的限制作用.设计时,可以考虑适当放松按平面刚架计算的刚架柱顶水平位移值,来考虑蒙皮效应.     

实腹式冷弯薄壁型钢门式刚架模拟分析方法研究

提出采用梁-弹簧单元模拟冷弯薄壁型钢门式刚架节点的工作性能和考虑了构件初始几何缺陷影响的有限元模拟分析法,对已有冷弯薄壁型钢门式刚架试验模型进行模拟分析.对比计算结果显示,有限元计算结果与试验结果吻合较好,表明有限元模拟分析方法是正确、可靠的.     

门式轻钢结构建筑物防雷设计浅谈

在轻型钢结构建筑电气设计的基础上，对此类建筑防雷接地设计和施工的相关问题作出简要的论述，得出了具体结论，即厚度达到0．5mm的轻钢结构建筑物的金属屋面板且其下无易燃品时可以作为接闪器，用钢柱作引下线，利用混凝土独立基础钢筋作自然接地体，并通过镀锌扁钢连接成可靠的总等电位接地环网，是安全有效的防雷接地措施。     

门式刚架轻型钢结构最优化设计体会

根据多年设计经验,结合实际情况,对门式刚架轻型钢结构最优化设计中的结构形式,合理跨度与柱距,截面选择等关键问题进行了探讨,以充分发挥其特点,降低结构用钢量。     

门式刚架轻型房屋钢结构的设计要点

对门式刚架轻型房屋钢结构的设计过程进行了分析,从规范的选择、基本规定、结构布置、构件设计、关键节点处理等方面进行了论述,并进行了有关的设计要点的研究,从而达到了强化设计要点的效果。     

暴雪后门式刚架轻型房屋钢结构厂房的加固设计

2007年3月初,中国东北地区遭遇罕见暴雪,造成大量工程事故.其中,门式刚架轻型房屋钢结构自身超载能力较差,在罕遇荷载作用下发生事故,需要对其进行加固.针对某一工程实例,介绍了雪灾后门式刚架轻钢工业厂房的加固设计方法,包括加固设计原则、主刚架加固、维护结构加固等方面,并在最后提出了轻型房屋钢结构加固设计的相关建议.     

半刚性钢框架优化设计研究

推导了考虑连接柔性和几何非线性的局部坐标下的单元刚度矩阵,并对半刚性连接单元的固端力进行了修正;其次,采用增量加载法,给出了考虑连接柔性、框架的几何非线性和单元内力与连接之间耦合效应的半刚性钢框架结构分析计算机流程;按照GB50017-2003《钢结构设计规范》和实际施工的要求,建立了考虑构件和连接最小费用问题的半刚性钢框架优化数学模型;然后,在遗传算法和半刚性钢框架结构分析流程的基础上,给出了半刚性钢框架优化设计步骤;根据算例,对半刚性钢框架优化设计做了初步的探讨。     

Design of steel portal frame buildings for fire safety

This paper describes a study into the fire behaviour of steel portal frame buildings at elevated temperatures using the finite element programme SAFIR. The finite element analysis carried out in this report is three dimensional and covers different support conditions at the column bases, the presence of axial restraints provided by the end walls, different fire severities within the building, different levels of out-of-plane restraint to the columns and the effect of concrete encasement to the columns. From a large number of analyses, it is shown that the bases of the steel portal frames at the foundations must be designed and constructed with some level of fixity to ensure that the structure will deform in an acceptable way during fire, with no outwards collapse of the walls. The analyses also show that to avoid sidesway (i.e. collapse outwards) it is not necessary for steel portal frame columns to be fire-protected unless the designer wishes to ensure that the columns and the wall panels remain standing, during and after the fire.     

Recent developments in the design of cold-formed steel members and structures

Cold-formed steel members and structures are extremely widespread in use at the present time. The design analysis of such structures is often complex, as their behaviour can be influenced by effects, which arise due to the slenderness of members, walls and cross-sections. Prime among these effects are the various types of buckling which can occur, and which may interact with each other to promote failure at loads substantially less than those, which would be obtained in the absence of these effects. The complications induced by such effects must be taken into account in design, if the potential benefits offered by the use of such members are to be realised, and in recent design specifications this has been realised. In this paper the main types of cold-formed steel members are described, the particular characteristics affecting their design are discussed, as are the ways in which design specifications deal with these characteristics.     

高强超薄壁冷弯型钢低层住宅抗震设计方法

结合国内外已完成的冷弯薄壁型钢龙骨式复合墙体静力和动力试验研究成果,提出了冷弯薄壁型钢复合墙体的骨架曲线和恢复力模型。基于已经完成的屈服强度550 MPa高强超薄壁冷弯型钢足尺结构模型振动台试验,对结构在多遇和罕遇地震作用下的抗震分析方法进行了对比。结果表明：多遇地震作用下结构的弹性分析可采用底部剪力法、反应谱法和弹性时程分析法;罕遇地震作用下结构分析可采用静力非线性（推覆）分析和非线性时程分析法。依据GB 50011-2010《建筑抗震设计规范》的基本规定,提出了低层冷弯薄壁型钢龙骨体系结构的抗震设计实用方法建议。     

Optimum design of cold-formed steel columns by using micro genetic algorithms

Cold-formed steel members such as beams and columns have the great flexibility of cross-sectional profiles and sizes available to structural steel designers. However, this flexibility makes the selection of the most economical section difficult for a particular situation. In this study, micro genetic algorithm (MGA) is used to find an optimum cross section of cold-formed steel channel and lipped channel columns under axial compression. Flexural, torsional and torsional–flexural buckling of columns and flat-width-to-thickness ratio of web, flange and lip are considered as constraints. The design curves are generated for optimum values of the thickness, the web flat-depth-to-thickness ratio, the flange flat-width-to-thickness ratio for columns. As numerical results, the optimum design curves are presented for various load level and column lengths.     

优化设计门式刚架

结合多年工作实践,对门式刚架轻钢结构优化设计相关事项进行了探讨,分别阐述了门式刚架轻型钢结构截面形式的选择和材质要求及综合优化要点,以期为钢结构设计人员提供指寻。     

谈门式刚架轻型钢结构设计

针对门式刚架轻型钢结构设计进行了探讨,简要介绍了结构设计的基本原则,分别阐述了初步设计、施工图设计及施工详图绘制阶段门式刚架轻型钢结构设计要点,以期实现安全、耐久、美观的设计目标。     

Design approach of cold-formed steel portal frames

A structural arrangement of a portal frame that is easy to fabricate and assemble is developed. The rafter and column members are formed from single cold-formed channel sections, which are bolted, back-to-back at the eaves and apex joints, and connected to the foundation through angle irons. Variables in the frames include the span, width of the channel flanges and the strength of the channels. The design of the frame members follows the traditional approach of applying the effective width method to control local buckling, followed by an assessment of cross-sectional and buckling requirements. However, the yield and overall buckling requirements are modified by a factor of 0.8 to account for stress concentrations, shear lag and bearing deformations in the connections. All deflections of the frames considered are found to be within the limits provided in the literature and by the two codes of practice. It is proposed that the frames of the structure should be provided in a kit form and erected in “meccano” fashion     

Analysis and design reliability of axially compressed members with high-strength cold-formed thin-walled steel

High-strength cold-formed thin-walled steel has been widely used in developed countries in the last several years. However, the application and popularization of the new materials in China is still very limited, and there are no related provisions in current design codes for reference in engineering practice. In this paper, considering the effects of the variations from material strength in structural members, geometrical parameters of sections, analysis methods for limit load-carrying capacity and external loadings, the second-order moment probability method was used for conducting the design reliability analysis of 550 MPa high-strength cold-formed thin-walled steel structures, from which the reasonable target reliability index, the corresponding resistance partial coefficient and the design strength values were discussed and proposed. Existing experimental data related have been collected and used to demonstrate the suitability and reasonability of the proposed results, which shows that, with reasonable determination of the design strength value of 550 MPa high-strength cold-formed thin-walled steel sections, the effective width-to-thickness ratio method considering coupling stability of plates recommended by “Technical Code of Cold-formed Thin-Walled Steel Structures (GB50018-2002)” can be efficiently used to estimate the load-carrying capacities of the axially compressed elements of high-strength cold-formed thin-walled steel structures, and well satisfy the target reliability index in structural design.     

基于遗传算法钢框架抗震优化设计

采用遗传算法对钢框架结构进行了抗震优化设计,编制了分析程序,并分析了算例,证明将遗传算法运用于抗震优化设计是行之有效的,丰富了钢结构优化设计的理论和方法。     

Reliability-based integrated design of steel portal frames with tapered members

Integrated structural designs, with consideration of system reliability for steel portal frames comprising tapered members, are studied in this paper. The reliability-based integrated design (RID) directly checks the structural system limit states and the corresponding system reliability, based on structural nonlinear analysis. The nonlinear integrated analysis model, the semi-analytical simulation method employed for system reliability assessment, the development processes of RID format and the design application of RID formula and curves are presented in this paper. Design examples and comparisons among three different design formats demonstrate that RID proposed in this paper is of certain and consistent system reliability levels, and provides a feasible way for structural engineers to improve the design quality and flexibility of steel frame structures.     

冷弯薄壁型钢建筑体系的墙架结构设计

在用冷弯薄壁型钢构成的建筑中，立柱和底导梁、顶导梁的外面一般用板材来覆盖，组成抗侧力构件，以此来抵抗如风、地震等侧向荷载．本文对冷弯薄壁型钢结构体系中墙架的设计进行了介绍．