多层砌体填充墙框架结构抗震性能试验研究

为了研究砌体填充墙沿框架层不连续布置对框架结构抗震性能的影响,进行了3榀两层单跨砌体填充墙框架结构模型、1榀单层单跨砌体填充墙框架结构模型、1榀两层单跨框架结构模型和1榀单层单跨框架结构模型的对比试验,分析了各试件的破坏特征、滞回曲线、骨架曲线、位移延性、刚度退化、承载力退化和耗能性能等抗震性能指标。结果表明：无论是单层单跨还是两层单跨的砌体填充墙框架结构,其水平峰值荷载和初始刚度比相应的纯框架结构均有较大幅度的提高,且其刚度退化程度比相应纯框架结构要缓慢;砌体填充墙的存在提高了框架结构的抗侧刚度和水平峰值荷载,使框架结构的变形由剪切型逐渐转变为弯剪型;砌体填充墙参与了结构的滞回耗能,填充墙框架的位移延性和累积耗能能力明显优于框架;砌体填充墙沿框架层不连续布置会引起框架结构层间侧移刚度和层间受剪承载力发生突变,影响框架结构的破坏形态,但由于砌体填充墙参与了框架结构的滞回耗能,故其仍具有较好的抗震性能。     

Equivalent lateral force procedure for the seismic story drift design of tall frames using a hand‐calculated approach

The basic theory of the cantilever moment distribution method and the application of this method to conduct the equivalent lateral force procedure for the seismic design of tall frames are discussed in detail. Deflection–rotation formulas are introduced in this paper to determine the relative lateral story deflections and the joint rotations of laterally loaded rigid frames. An example is presented to conduct the seismic story drift design of a multistory, multi‐bay, moment‐resisting reinforced concrete frame using the cantilever moment distribution method and the deflection–rotation formulas developed in this paper. The hand‐calculated approach presented in the example can be used as a rapid and accurate method to determine the story drift for any laterally loaded multistory, multi‐bay rigid frames that are composed of identical single‐bay symmetrical bents. The following are the advantages of using this rapid approach: (1) this approach can be carried out by using hand calculations only (without the use of computer computations); (2) the results obtained from this approach are as accurate as those derived from the traditional moment distribution and the slope deflection methods; and (3) the results obtained from this approach can be used to verify the accuracy of the results obtained from computer computations. Copyright © 2005 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.     

Seismic behavior analysis for composite structures of steel frame‐reinforced concrete infill wall

The composite structure of steel frame–reinforced concrete infill wall (CSRC) combines the advantages of steel frames and reinforced concrete shear walls. Reinforced concrete infill walls increase the lateral stiffness of steel frames and reduce seismic demands on steel frames thus providing opportunities to use partially restrained connections. In order to study seismic behavior and load transfer mechanism of CSRC, a two‐story one‐bay specimen was tested under cyclic loads. With that, the main characters such as, strength, stiffness, ductility, energy dissipation, load distribution, performance of steel frames, partially restrained connections and studs, are analyzed and evaluated. The experimental results show that the structure has adequate strength redundancy and sufficient lateral stiffness. The CSRC system has good ductility and energy dissipation capability. Partially restrained connections could enhance ductility and avoid abrupt decreases in strength and stiffness after the failure of infill walls. The composite interaction is ensured by headed studs, which have failed because of low‐cycle fatigue. Steel frames bear 80%–100% of overturning moments, and the remainder is undertaken by infill walls; steel frames and infill walls resisted 10%–20% and 80%–90% of lateral loads, respectively. Furthermore, relevant design recommendations are presented. Copyright © 2011 John Wiley & Sons, Ltd.     

Analytical estimation of lateral resistance of low‐shear strength masonry infilled reinforced concrete frames with openings

Presence of openings in an infill wall alters its behavior and reduces load resistance and stiffness of the infilled frame. In this paper, a simple method for estimating the lateral resistance of infilled frames with openings is proposed based on experimental data. Six half‐scale, single‐story single‐bay reinforced concrete frame specimens were tested under in‐plane lateral loading. The lateral strength of reinforced concrete (RC) frame could be estimated by assuming the formation of plastic hinges in the end regions of the members. In the specimens with central openings, the major load resistance mechanism of the infill panel was the formation of a compression strut and lateral strength of infill panel could be considered as the smallest values of the diagonal tension and corner crushing modes. In the specimens with eccentric openings, the load resistance mechanism of masonry infill was the formation of a compression strut and bed‐joint sliding in 2 opposite loading directions; thus, the lateral resistance of infill panel could be estimated in diagonal tension and corner crushing modes in one direction and bed‐joint sliding mode in another direction. Furthermore, the deformation capacity and structural performance levels are suggested for solid and perforated infill panels based on test observations.     

刚性楼层框架剪力墙高层建筑结构研究

这篇文章提出了一个新的概念来增加框架剪力墙高层建筑结构的横向刚性，即通过在框架体系顶部平面或中间最优平面设置刚性楼层。在一个楼层平面中，框架体系剪力刚度的增加是通过在该楼层一个或多个框架间距间填充混凝土或水泥嵌板，或增加楼层支撑，或增加楼层周围柱子和梁的尺寸。在刚性楼层结构中涉及到的概念的有效性和参数的估计可用连续性模型解答来证明。作者表明在一些结构中横向刚度的增加可达百分之七十。     

The use of single diagonal bracing in improvement of the lateral response of tall buildings

The improvement of the lateral response of tall buildings is a subject of great concern both in high wind areas and seismic regions. The lateral deflection of a tall building subjected to lateral loads can be decomposed into shear and bending components. Properly oriented single diagonal bracings are introduced in order to bring advantageous interactions between these two modes of deflection resulting in a reduction of the overall lateral deflection of the frame. The deflection of a panel with a single diagonal, when subjected to vertical downward load, has a lateral component caused by the axial force developed in the single brace, which, due to asymmetry, results in the lateral deflection. In order to restrict the panel from lateral deflection a compensating lateral force is required. By locating the single diagonal bracings in an improved manner, the vertical tension and compression on the opposite sides of the frame caused by the bending effect automatically generate the above mentioned lateral compensating force which opposes the inter story drift. A simple truss model is introduced to study the relationship between the vertical loading and the lateral load required to retain the vertical alignment of a panel with a single diagonal. This relation is then studied in detail and the optimal values of the height-to-width and brace-to-column stiffness ratios, needed to produce the maximum equilibrating lateral force are computed. Further, the single diagonal bracings are applied to typical building frames. Results from elastic analyses are compared with that of the conventional X-braced frame. Pilot analysis shows a reduction of about 2% in the lateral deflection of a typical 24 story braced frame building with rigid connections and five bays using the proposed bracing scheme.     

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.     

Seismic performance of Y‐type eccentrically braced frames combined with high‐strength steel based on performance‐based seismic design

In the Y‐type eccentrically braced frame structures, the links as fuses are generally located outside the beams; the links can be easily repairable or replaceable after earthquake without obvious damage in the slab and beam. The non‐dissipative member (beams, braces, and columns) in the Y‐type eccentrically braced frames are overestimated designed to ensure adequate plastic deformation of links with dissipating sufficient energy. However, the traditionally code design not only wastes steel but also limits the application of eccentrically braced frames. In this paper, Y‐type eccentrically braced steel frames with high‐strength steel is proposed; links and braces are fabricated with Q345 steel (the nominal yield stress is 345 MPa); the beams and columns are fabricated with high‐strength steel. The usage of high‐strength steel effectively decreases the cross sections of structural members as well as reduces the construction cost. The performance‐based seismic design of eccentrically braced frames was proposed to achieve the ideal failure mode and the same objective. Based on this method, four groups Y‐type eccentrically braced frames of 5‐story, 10‐story, 15‐story, and 20‐story models with ideal failure modes were designed, and each group includes Y‐type eccentrically braced frames with ordinary steel and Y‐type eccentrically braced frames with high‐strength steel. Nonlinear pushover and nonlinear dynamic analyses were performed on all prototypes, and the near‐fault and far‐fault ground motions are considered. The bearing capacity, lateral stiffness, story drift, link rotations, and failure modes were compared. The results indicated that Y‐type eccentrically braced frames with high‐strength steel have a similar bearing capacity to ordinary steel; however, the lateral stiffness of Y‐type eccentrically braced frames with high‐strength steel is smaller. Similar failure modes and story drift distribution of the prototype structures designed using the performance‐based seismic design method are performed under rare earthquake conditions.     

高层主次结构受力特点及刚度计算方法

近年来,主次结构广泛应用在超高层建筑中,但对其受力特点和刚度形成机制的系统研究却很少。为明确主次结构刚度形成机制、指导主次结构结构设计,通过有限元分析对主次结构受力特点进行研究,给出主次结构抗侧刚度形成机制,并推导主次结构刚度计算方法。以巨型框架结构、主次框架结构、主次框架-单斜撑结构、主次框架-X斜撑结构为研究对象,以构件内力分布特点、变形特性、刚度贡献为重点关注指标。研究结果表明,主次结构在竖向及水平荷载作用下均表现出显著的二级受力特性。水平荷载作用下,主柱沿模块高度呈现弯剪型变形,主次框架-单斜撑、主次框架-X型支撑结构表现出显著的桁架受力特点。次柱轴力沿高度呈周期性分布,次结构传递荷载对主结构变形和内力影响不大,但是其对结构整体刚度贡献不可忽略。分析结果表明,主次结构抗侧刚度关键参数为支撑轴向刚度、主柱轴向刚度、主框架抗剪刚度、次框架抗剪刚度。基于刚度形成机制,给出主次结构刚度简化计算方法,并与有限元方法结果进行对比,验证了刚度形成机制及刚度简化计算方法的有效性。     

Optimal drift design model for multi‐story buildings subjected to dynamic lateral forces

An optimal drift design model for a linear multi‐story building structure under dynamic lateral forces is presented. The drift design model is formulated into a minimum weight design problem subjected to constraints on stresses, the displacement at the top of a building, and inter‐story drift. The optimal drift design model consists of three main components: an optimizer, a response spectrum analysis module, and a sensitivity analysis module. Using a small example, the validation of the proposed model has been tested by a comparison of optimal solutions. Then, the performance of the optimal drift design model is demonstrated by application to three steel frame structures including a 40‐story building. Various structural responses including lateral displacement and inter‐story drift distributions along the height of the structure at the initial and final design stages are presented in figures and tables. Time‐consuming trial‐and‐error processes related to drift control of a tall building subjected to lateral loads is avoided by the proposed optimal drift design method. Copyright © 2003 John Wiley & Sons, Ltd.     

Optimum structural modelling for tall buildings

It is a common practice to model multi‐storey tall buildings as frame structures where the loads for structural design are supported by beams and columns. Intrinsically, the structural strength provided by the walls and slabs are neglected. As the building height increases, the effect of lateral loads on multi‐storey structures increases considerably. The consideration of walls and slabs in addition to the frame structure modelling shall theoretically lead to improved lateral stiffness. Thus, a more economic structural design of multi‐storey buildings can be achieved. In this research, modelling and structural analysis of a 61‐storey building have been performed to investigate the effect of considering the walls, slabs and wall openings in addition to frame structure modelling. Sophisticated finite element approach has been adopted to configure the models, and various analyses have been performed. Parameters, such as maximum roof displacement and natural frequencies, are chosen to evaluate the structural performance. It has been observed that the consideration of slabs alone with the frame modelling may have negligible improvement on structural performance. However, when the slabs are combined with walls in addition to frame modelling, significant improvement in structural performance can be achieved. Copyright © 2012 John Wiley & Sons, Ltd.     

框架及底层框架砖房多层商住楼地震灾害的综合评价

地震灾害损失很大程度上决定于建筑结构的坡坏程度。针对钢筋混凝土框架及底层框架砖房多层商住楼震害的特点,进行了这两类房屋的结构易损性分析,给出了震害矩阵,震灾损失及其与工程投资之间关系的一般评价方法。     

Structural performance of multi‐outrigger‐braced tall buildings

The optimum designs of multi‐outriggers in tall building structures are presented and discussed in this paper, through the analysis of structural performance of outrigger‐braced frame‐core structures. The influences of the locations of outriggers and the variations of structural element stiffness on the base moment in core, top drift and fundamental vibration period of such tall building structures are analysed in detail. A non‐linear optimum design procedure for reducing the base moment in the core is presented based on the penalty function method. The computer programs are developed on the basis of the proposed methods for analysing the behaviour and optimum design of multi‐outrigger structures. A series of figures presented in this paper can be used for the design purposes of outrigger‐braced tall building structures. Copyright © 2003 John Wiley & Sons, Ltd.     

Full‐scale experimental assessment of new connection for columns in vertically mixed structures

More stiffness of concrete frames on one hand and fewer weight of steel frames on the other hand motivates using a composite system so called vertically mixed structures. The reinforced concrete and steel frames are connected together at a story called transition story. A major challenge for the designers is the connection columns in the transition story for proper transferring of efforts and preventing stress concentration phenomenon. There are some suggestions, in the literature, to build a transition composite column instead of constructing a local connection. Four full‐scale specimens of three connection types are constructed and tested experimentally under cyclic load to investigate hysteresis characteristics, failure mechanism, deformability, and energy dissipation capacity of the model. A novel through bolt lap connection adapted from concrete‐filled tube (CFT) column is proposed. Finally, backbone curves of proposed column for more accurate seismic studies are presented. No evident sign of local failure is observed in the proposed connection. Placing the steel around the reinforced concrete column section prepares the maximum possible geometrical dimensions for the steel column section and the connection. The experimental results show no strength loss for the new proposed connection under two different axial loads in lateral cyclic loading up to 4% drift.     

Seismic risk assessment of steel frames equipped with steel panel wall

This paper aims to conduct risk assessment on steel frame equipped with steel panel wall (SPWF) through probabilistic seismic demand analysis. First, cyclic test on a SPWF specimen with one‐third scale, one bay, and single story is performed, and the typical limit performance levels were determined in accordance with the test results and the stipulated in FEMA 356. Then, finite element models were built for a 12‐story steel frame and two 12‐story SPWF structures with different lateral stiffness ratio. The seismic performance of these models are investigated through nonlinear time–history analyses, and their limits capacities are determined from incremental dynamic analyses. Besides, fragility functions are developed for these models associated with 10%/50 years and 2%/50 years events, as defined in SAC project. Finally, the annual probabilities of each limits and the collapse probabilities in 50 years for the 3 models are calculated and analyzed, and the function associated with the collapse probability and lateral stiffness ratio is developed. The effectiveness of steel panel wall in reducing the seismic risk of the existing steel frame buildings is validated on the basis of the risk analyses.     

框架填充墙结构侧向荷载作用受力分析

用有限元法建立有填充墙的钢筋混凝土框架结构有限元模型,分别对钢筋混凝土框架结构在有、无填充墙情况下,有侧向荷载作用时,进行受力特性和侧向刚度的分析研究和比较。分析结果表明,填充墙不但可以明显改善框架结构梁柱的的受力情况,而且可以有效提高框架的侧移刚度。     

Approximate analysis of symmetrical structures consisting of different types of bents

An approximate analysis is presented for calculating the deflections of individual cantilever bents, under lateral loading, as a sum of deflections of two complementary subsystems: a flexural and a shear–flexure subsystem. The analysis accounts for axial deformations in the vertical members of bents, since it is based on the continuum approach as is used in the coupled wall theory, and is also applicable to other types of cantilever bents used in concrete structures, such as rigid frames and wall frame assemblies. The fact that the deflection equation of a cantilever bent may be decomposed into two components makes possible the development of an approximate method for estimating the deflections of uniform plan‐symmetrical buildings composed of different structural bents. The method provides a rapid estimate of deflections and load distribution in such multi‐bent structures and therefore it is appropriate for preliminary structural design. At this stage, it is desirable for the practising engineer to have a quick estimate of the maximum response, even if the actual sizes of the structural elements are not yet known and only assumptions can be made about the relative stiffnesses of the major structural elements. The proposed analysis, as based on distributed parameter formulations, has the advantage of providing a deep insight into the structural behaviour of high‐rise structures. Its accuracy is evaluated by comparing the approximate results with those obtained by stiffness matrix analyses. Copyright © 2007 John Wiley & Sons, Ltd.     

Elastic analysis of asymmetric tall building structures

A simplified elastic hand method for estimating forces in asymmetric multi‐bent structures subjected to horizontal loading is presented. The structures may consist of combinations of coupled walls, rigid frames, braced frames and wall‐frames with shear walls. Results for structures that are uniform in height compare closely with results from stiffness matrix analysis. The method is developed from coupled‐wall deflection theory, which is expressed in nondimensional structural parameters. It accounts for bending deformations in all individual members as well as for axial deformations in the vertical members and is, therefore, more accurate for very tall structures. A closed solution of coupled differential equations for deflection and rotation gives the deflected shape along the height of the building. The proposed method of analysis offers a relatively simple and rapid means of comparing the shear forces and bending moments of different stability systems for a proposed tall building. 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. Copyright © 2001 John Wiley & Sons, Ltd.     

Horizontal bracing to enhance progressive collapse resistance of steel moment frames

In this paper, the effect of horizontal bracing on enhancing the resistance of steel moment frames against progressive collapse is investigated. Previously designed 6 bay by 3 bay 18‐story steel frame prototype building with 6 m bay span (namely, unbraced frame), which was susceptible to progressive collapse, is retrofitted by four types of horizontal bracing systems on the perimeter of the topmost story and analyzed using 3D nonlinear dynamic method. Six different cross‐sections for each bracing system type are considered, and the capacity curves for each model are obtained. Three column removal circumstances, namely, Edge Short Column, First Edge Long Column, and Edge Long Column are considered in this paper. The results imply that horizontal bracing would increase the resistance of moment frames against progressive collapse. However, one of the bracing types in which axial compressive force is created in braces is not appropriate for retrofitting.