半刚性梁柱节点连接钢框架柱的计算长度取值初探

本文给出了具有半刚性梁柱节点连接框架梁的弯矩转角位移方程。按此方程导出了无侧移框架和有侧移框架柱的计算长度取值方法。该方法与我国规范规定的计算长度取值协调一致,不过考虑半刚性连接时要对横梁的约束刚度进行适当的修正。     

矩形钢管混凝土框架结构受力性能试验研究

以两榀单跨两层全矩形钢管混凝土框架结构为研究对象,通过拟静力试验,考虑柱截面含钢率的影响,研究分析了全矩形钢管混凝土结构在反复低周荷载作用下的破坏特征,承载能力,滞回曲线,变形能力,耗能能力以及强度、刚度退化性能;并分析了柱截面含钢率对结构受力性能及抗震性能的影响规律;同时将结构的各特征指标与钢筋混凝土框架结构和钢结构框架的对应特征指标进行对比分析。结果表明:在低周反复荷载作用下,矩形钢管混凝土框架结构承载力高,滞回曲线饱满,延性系数为5.56～6.80,有较好的变形能力和稳定的后期承载力,呈梁铰破坏机构,可初步判断该种结构具有良好的受力性能和较高的抗震能力;并且在同等条件下,钢管混凝土框架结构的受力性能和抗震性能明显优于钢筋混凝土框架和钢框架结构,有进一步研究的价值。     

Performance control for seismic design of moment frames

Performance control (PC) is the important mental task that is or should be the cornerstone of earthquake-resistant structural design. The fundamental notion behind PC is that the seismic structural response is largely a function of design and detailing, rather than conventional analysis. PC is a design strategy in which the strength, stiffness and other characteristics of groups of members are induced in accordance with predetermined objectives rather than investigated with respect to certain design criteria. PC methodology enables engineers to predict and control structural damage at preselected response stages such as at first yield, any fraction of the failure load or allowable drift ratio, etc. PC provides a wealth of important information that may not be readily available through traditional methods of design. The ultimate failure load solutions are “unique” and suitable for plastic design treatment in that they include P-delta and stiffness degradation effects, and satisfy the prescribed yield criteria as well as boundary support and static equilibrium conditions. The proposed procedures for seismic design of moment frames are entirely suitable for manual computations. The paper does not address irregularities in earthquake-resistant moment frames.     

Analytical behavior of frames with steel beams to concrete-filled steel tubular column

This paper reports the mechanism of composite frames with steel beams connected to concrete-filled square hollow section (SHS) columns. Detailed analysis was carried out on longitudinal stress in steel beams, axial stress distribution in concrete, and concrete stress along the column height and at the connection panel. Parametric studies were conducted to investigate the influence of axial load level, beam-to-column linear stiffness ratio on the structural behavior of composite frames. Simplified hysteretic lateral load (P) versus lateral displacement (Δ) models are proposed for such composite frames.     

Nonlinear static and cyclic analysis of concrete-filled steel columns

This paper presents the formulation of a one-dimensional (1D) composite frame element for the nonlinear static and cyclic analysis of concrete-filled steel (CFS) beam-columns. A two-node frame element is formulated using the force interpolation concept, and the material nonlinearity at section level is taken into account by employing a total secant stiffness and modified fibre element approach. The size effect and steel tube confinement on the concrete strength and ductility are taken into account. Further, the effect of steel tube local buckling on the member strength is addressed. Concerning geometrical nonlinearities at the element level, the equilibrium equations are satisfied for the deformed element to take account of P-Δ effects. The formulation accuracy and efficiency of the model are verified by some numerical examples of the static and cyclic analysis of CFS members.     

Analysis of composite connections in unbraced frames subjected to wind and gravity loading

A comparison between a simplified and an advanced method of elastoplastic analysis is made for unbraced frames with composite connections. The advanced method implements a mechanical model to represent the composite node in unbraced frames, which allows considering the behavior of each component of the composite connection individually. This method includes the determination of a moment-rotation curve for loading-unloading-reloading, considering gravity and wind loading. Physical and geometrical nonlinearities are taken into account in the analysis. In the simplified method an appropriate analysis for practical purposes is implemented, on which the connections are considered semirigid for unloading and flexible for loading, after yielding by gravity loads. Second order effects are included using the P-Δ procedure. Finally, a comparison is made between the two methods attempting to transform both methods in a useful tool for composite connection design.     

利用斜支撑提高异型柱框架结构抗扭性能的研究

采用有限元程序ANSYS和SAP ,对异型柱框架结构和异型柱加斜支撑结构进行了空间受力分析。单个结构单元的非线性分析说明 ,在异型柱框架中添加了人字形支撑后 ,结构的抗扭刚度和抗扭承载力有显著提高 ,延性也有所提高。通过对异型柱框架结构和矩形柱结构进行地震作用下的对比分析 ,说明异型柱框架的抗扭性能要远低于等惯性矩的矩形框架结构 ,而添加斜支撑对提高异型柱框架抗震性能有显著作用。并建议在刚心与质心不一致的异型柱框架结构中 ,应适当使用斜支撑结构以提高结构抗扭性能     

多层钢框架节点刚度分类方法研究

介绍了一些现有的梁柱节点分类标准,并通过参数分析的方法提出了一个新的多层钢框架结构的节点刚度分类标准.参数包括层数m,跨数n,层高H,跨度L,梁刚度Ib,柱刚度Ic.在计算了288个模型之后,得到了两个包含以上6个参数的表达式.其中一个表示了刚接和半刚接的分界,另一个表示了铰接和半刚接的分界.通过对几个多层钢框架结构静力性能的分析,这一分类标准的有效性得到了证明.与现有的分类标准相比,提供了一个更为合理的分类标准.     

Efficient semi-analytical generator of initial stiffness designs for steel frames under seismic loading. Part 1: Fundamental frame

The purpose of this paper is to propose a new efficient semi-analytical generator of initial stiffness designs for a moment-resisting steel building frame under seismic loading. Requirements on interstory drift under seismic loading are often active constraints in the usual structural design practice for steel building frames and simple methods of design and analysis are needed especially in the preliminary design stage. Interstory drifts and ratios of the angles of nodal rotation to the angles of column member rotation are selected as key parameters and specified based upon the designer's intention. A practical design formula for a frame with design variable grouping is proposed as well as one for a basic frame without design variable grouping. A recursive technique is introduced to evaluate the design story shear forces under a set of design-spectrum-compatible earthquakes. Numerical examples are presented to disclose the characteristics of member stiffness distributions and the response characteristics of frames designed by the present method. In the present paper (Part 1), a fundamental design formula is proposed for a simple frame without column elongation. A more practical design formula for a slender frame with column elongation will be presented in the companion paper. (Part 2). © 1997 John Wiley & Sons, Ltd.     

柔性连接钢框架稳定分析的计算长度

根据钢框架柱稳定设计的计算长度概念,以部分框架为计算单元,用变刚度的螺旋弹簧模拟梁柱节点连接的柔性,通过引入柔性连接刚度修正系数,建立了无侧移和有侧移柔性连接钢框架柱计算长度系数修正公式,其形式与我国钢结构设计规范(GB17—88)规定的计算长度稳定方程完全相同,可供工程设计人员使用.     

节点柔度对半刚性连接钢框架动力性能影响研究

采用ANSYS进行数值模拟分析,建立了具有不同节点初始刚度的多层钢框架及相应刚性连接框架的计算模型,分析了节点刚度对结构自振频率的影响。进一步对结构进行了时程分析,研究了在地震波激励下结构顶点位移和柱底剪力随节点刚度的变化规律。     

Full-scale dynamic testing of a steel frame building during construction

Full-scale testing of a six-story steel frame building with infill walls made primarily of autoclaved cellular concrete and curtain walls made of hollow core clay bricks using ambient and forced vibration methods are described in detail. The ambient vibration test took place in two stages of the construction—stage one, when only the frames and slabs where constructed, and stage two when all the walls were put in place. The forced vibration was carried out when some of the walls were constructed. The results from the two test methods are compared with each other and also with computer analysis results based on conventional design office assumptions for modeling. Dynamic characteristics of the structure including natural frequencies, damping ratios and mode shapes determined from the tests are presented. The effect of Autoclaved Cellular Concrete (ACC) block infill and partition walls on the dynamic properties and stiffness of the building are discussed in detail. The advantages of using ACC block walls as infill wall material for seismic regions are concluded.     

Consistent virtual work approach for the nonlinear and postbuckling analysis of steel frames under thermal and mechanical loadings

The aim of this paper is to provide a consistent virtual work formulation for the nonlinear and postbuckling analysis of steel frames at high temperatures. Central to this study is the derivation of the virtual work terms for the thermal stage, in addition to those for the loading stage, based on the updated Lagrangian formulation. The incremental stiffness equation derived for the beam element, considering both the geometrical and thermal effects, is qualified by the rigid body test. The generalized displacement control (GDC) method is adopted as the path-tracing scheme for postbuckling response. Eurocode-3 reduction factors and transformed section method are both adopted for steel I-sections. Two loading cases are studied. For structures loaded gradually under constant temperature, the critical or ultimate loading strength is obtained from the load-deflection curve. For structures heated gradually under constant loading, the critical or maximum temperature that can be sustained by the structure is computed. Conclusions are drawn for the examples studied in this paper.     

Performance of alternative CFRP retrofitting schemes used in infilled RC frames

A number of experimental studies have been reported in recent literature about the beneficial effects of infill walls on the seismic response of reinforced concrete (RC) frames. The experimental study presented in this paper mainly focuses on the behavior of bare and carbon fiber reinforced polymer (CFPR)-retrofitted infilled RC frames with different bracing configurations. Quasi-static experimental results are presented and discussed on six 1/3-scaled infilled RC frames that were retrofitted using CFRP material in various schemes. The test results showed a significant increase in the yield and ultimate strength capacities of the frames with a decrease in relative story drifts, especially in the cross-braced and the cross diamond-braced type of retrofitting schemes. The energy dissipation capacities of the retrofitted frames turned out to be more than those of the bare infilled frame, thus reducing the seismic demand imposed on the frames. The cross diamond-braced type of retrofitting scheme, which was positioned on the infill wall and outside the beam–column connection regions of RC frame, showed the best behavior among the other schemes. This scheme not only prevented brittle shear failures of the infill wall, but also prevented the transfer of additional forces to the weak and brittle beam–column connections.     

HF2V dissipator effects on the performance of a 3 story moment frame

In this paper, the seismic performance of the as-designed SAC Los Angeles 3 story seismic frame with rigid moment connections at the beam ends is compared with that of the same frame using semirigid connections with high force-to-volume (HF2V) lead dissipators. The presence of the gravity frames in the model is also considered. It was found that the placement of dissipators, ignoring the effect of the gravity frames, caused a 12% increase in period of the frame due to the decreased stiffness of the connections. During design level ground shaking the semi-rigid connections with HF2V dissipators have slightly lower accelerations, up to an 80% increase in peak drift, and a 200% increase in the permanent displacement compared to the as-designed case, but no structural damage is expected. When the gravity frames are considered, the floor accelerations decrease further, the peak displacements do not significantly change, but the residual story dirft ratios reduce to approximately 0.17%. This result is less than one half that of the as-designed frame, where typically gravity frame effects are not considered. The realistic analyses combining HF2V lead dissipators with gravity frames and well-designed non-structural elements creates a system with almost no structural damage and low residual displacements.     

非完全支撑的框架结构的稳定性

设置了支撑架的框架结构,当支撑刚度还不足以使框架柱可按无侧移框架确定计算长度时,如何确定框架柱的计算长度问题,本文对此进行了研究,提出了计算公式.本文还提出了使框架柱可按无侧移计算稳定性的支撑门槛刚度.适当考虑结构初始缺陷和侧向荷载的影响后,此刚度可作为确定框架柱计算长度时区分有侧移和无侧移框架的合理标准.     

钢框架-混凝土剪力墙混合结构的基本自振周期计算

分析了考虑钢梁与钢柱半刚性连接时钢框架-混凝土剪力墙混合结构的基本自振周期的计算,并与不考虑半刚性的钢框架-混凝土剪力墙混合结构体系做比较.分析考虑了钢框架部分节点的半刚性连接,推导了钢框架-混凝土剪力墙混合结构中钢框架部分的层抗侧移刚度,从而得到结构的基本自振周期.算例分析表明,考虑半刚性连接对结构的抗震有利.     

偏心支撑钢筋混凝土框架的试验研究与极限分析

通过对 4榀具有同一外形尺寸及配筋而具有不同形式的带有偏心角钢支撑的钢筋混凝土框架和 1榀相同尺寸及配筋的钢筋混凝土框架的对比性试验 ,研究了上述试件的抗侧刚度、极限承载力及结构的耗能等各项指标 ,探讨了偏心角钢支撑钢筋混凝土框架结构的受力特点 ,并对其极限状态进行了理论分析     

Storey-based stability of unbraced steel frames at elevated temperature

The evaluation of the lateral stability of steel frames subject to elevated temperatures is different from that at ambient temperature. This is because the degradation of the Young's Modulus of steel associated with elevated temperature will lead to the loss of column lateral stiffness. In this study, the lateral stability of unbraced steel frames subjected to elevated temperature is investigated based on the concept of storey based buckling. First, to simulate a steel column exposed to the elevated temperature, an analytical model was proposed to examine the effects of axial loading, elevated temperature, and thermal boundary restraints on the lateral stiffness of steel columns in unbraced frames. Then, a method of evaluating the stability capacity of unbraced steel frames at elevated temperature is proposed. Numerical examples are presented to demonstrate the evaluation procedure of the proposed method and investigate the frame stability subjected to different scenarios of frame members exposed to the elevated temperature. The validity of the proposed method is verified by the numerical analysis with the use of finite element analysis.     

钢筋混凝土异形柱框架斜撑结构特性探讨

以K形斜撑为代表 ,采用杆系空间分析模型 ,通过对一批异形柱框架 斜撑结构典型工程算例的系统理论分析 ,研究了地震作用下钢筋混凝土异形柱框架 斜撑结构的内力分布规律、水平位移特性及自振特性。提出了自振周期的近似计算公式、斜撑与框架侧移刚度比范围及确定斜撑截面高度的公式 ,供工程实用参考