Studies on damping behavior of vertically mixed structures with upper steel and lower concrete substructures

This paper presents 2 models to simulate the damping behavior of a 12‐story vertically mixed structure with upper steel and lower concrete substructures (S/RC structure). One is the modal strain energy damping model based on modal damping ratio. The other is the assembled Rayleigh damping model based on damping matrix that is obtained by combining Rayleigh damping matrix of steel components with that of concrete ones. Then a 12‐story S/RC frame and a 12‐story RC frame are designed and used for shaking table test. Based on the test, the expressions for the damping behavior of steel and concrete substructures of the S/RC frame are derived, and these expressions are utilized to form 2 different damping models of the S/RC structure separately. By comparing the damping behavior of the 2 models in analysis with what has been identified in the tests, the feasibility of the 2 models are assessed in both frequency domain and time domain. Theoretical analysis and experimental results show that the assembled Rayleigh damping model is not applicable to conventional modal analysis because of its nonproportional characteristics. However, the modal strain energy damping model based on equivalence of the dissipated modal strain energy of structure, which embodies the essence of damping, can give better predictions on damping behavior of the S/RC frame in both time and frequency domains. Finally, some suggestions are put forward on the selection of damping parameters in practical seismic design for vertically mixed structures.     

环梁连接的RC梁-钢管混凝土柱框架试验研究

介绍了一个采用钢筋混凝土 (RC)环梁连接的 2层 2跨RC梁 -钢管混凝土 (STCC)柱框架的拟动力试验和静力试验。为了研究环梁在地震作用下的破坏形态 ,大部分节点设计成“弱环梁、强框架梁” ,即环梁屈服先于框架梁 ;少量节点设计成“强环梁、弱框架梁” ,即框架梁屈服先于环梁。试验表明 :小震时 ,框架的刚度降低很少 ;中震时 ,刚度降低约 3 0 % ;大震时 ,层间位移角小于 1 10 0 ;即使弱环梁已经破坏、层间位移角达 1 3 4,框架的承载力仍未下降 ;能够实现“强柱弱梁”和实现塑性铰形成于框架梁端的“强连接、弱构件”的抗震设计概念。RC环梁与STCC柱之间局部范围的缝隙不影响框架的整体抗震性能 ;环梁与柱之间几乎无相对竖向滑移。采用RC环梁连接的RC梁 -STCC柱框架具有良好的抗震性能。     

Experimental and modeling study on the progressive collapse resistance of a reinforced concrete frame structure under a middle column removal scenario

A reinforced concrete (RC) frame structure is one of the widely used structural system. A localized damage caused by extreme events may lead to progressive collapse of entire structures. In this paper, progressive collapse test of three 1/3‐scaled reinforced concrete frame, including a single‐story without a slab, single‐story with a slab, and double‐story with slabs, are reported. Experimental results show that the progressive collapse process of RC frame consisted of five stages: an elastic stage, yield stage, beam mechanism stage, transient stage and catenary stage. The reinforced concrete slabs contribute to large progressive collapse resistance force compared with the specimen without slab. Furthermore, validation of the test results by using a refined solid finite element model was established. The effect of extensive parameters, including slab thickness, beam section height, seismic design intensity, and so forth, on the progressive collapse performance of RC frame structures was simulated as well. The simulation results indicated that the collapse resistance of RC structures was substantially improved with the increased of the slab thickness and seismic design intensity. Finally, a simplified model is proposed in accordance with experimental and numerical results to calculate the collapse resistance of RC frame structures.     

Shaking table tests of RC frame structure across the earth fissure under earthquake

To investigate the behavior of a reinforced concrete (RC) frame structure across earth fissure under strong earthquake, a series of shaking table tests on a scaled model were designed and conducted. Three earthquake motion records were selected as input excitations, and the Jiangyou motion has a dramatically greater dynamic effect on the structure mainly due to its inherent rich low‐frequency component. The structural acceleration amplification factor gradually decreased as the peak ground acceleration of input motions increased, implying the progressive degradation of the structure stiffness. The results indicated that the earth fissure site has amplification effect on acceleration of the soil, and the displacement response of frame across the earth fissure was different to that of a typical RC frame structure. The ground floor was the most vulnerable story of the RC frame across the earth fissure.     

Study on seismic performance of a super‐tall steel–concrete hybrid structure

Many steel–concrete hybrid buildings have been built in China. The seismic performance of such hybrid system is much more complicated than that of steel structure or reinforced concrete (RC) structure. A steel–concrete hybrid frame‐tube super‐tall building structure with new type of shear walls to be built in a district of seismic intensity 8 in China was studied for its structural complexity and irregularity. Both model test and numerical simulation were applied to obtain the detailed knowledge of seismic performance for this structure. First, a 1/30 scaled model structure was tested on the shaking table under different levels of earthquakes. The failure process and mechanism of the model structure are presented here. Nonlinear time‐history analysis of the prototype structure was then conducted by using the software PERFORM‐3D. The dynamic characteristics, inter‐story drift ratios and energy dissipation conditions are introduced. On the basis of the comparison between the deformation demand and capacity of main structural components at individual performance level under different earthquake level, the seismic performance at the member level was also evaluated. Despite the structural complexity and code‐exceeding height, both experimental and analytical results indicate that the overall seismic performance of the structure meet the requirements of the Chinese design code. Copyright © 2012 John Wiley & Sons, Ltd.     

Seismic response of self‐centering precast concrete frames with hysteretic dampers

With the rapid development of cities and the invasion of major natural disasters such as earthquakes, the resilience city as a new design concept has been paid more and more attention. As an important branch of self‐centering seismic resisting system, self‐centering concrete frame system has been studied by many scholars. These studies prove that self‐centering concrete frame structure has excellent self‐centering ability but poor energy dissipation capacity. Adhering to the working principle of self‐centering structure and considering the development concepts of building industrialization and modularization, this paper proposed a kind of self‐centering precast concrete frame with hysteretic damper (SCPCHD). In order to verify its energy dissipation capacity and seismic performance, elaborate finite element models were established and elastoplastic dynamic time history analyses were carried out. The results showed that the SCPCHD frame has a similar interstory displacement response to the reinforced concrete (RC) frame and the energy dissipation performance of its joint is obviously superior to the RC frame under rare earthquake because the SCPCHD frame has low damage characteristics and excellent damping device. In summary, this paper proves the feasibility and superiority of the SCPCHD frame, providing reliable support for further research.     

钢混框剪高层结构地震能量分布及耗散研究

为了研究复杂建筑结构在地震作用下地震能量的分配与耗散机制,基于能量平衡原理和Perform 3D软件对钢筋混凝土框架 剪力墙高层结构模型进行了动力弹塑性能量时程分析,得到了框剪高层结构在罕遇地震作用下地震能量的输入、分布及耗散规律;考察了地震动特性对钢混框剪高层结构地震能量输入及分配的影响,确定了地震耗能占输入能的比例时程;分析了结构阻尼比和结构延性对框剪高层结构地震输入能、阻尼耗能和滞回耗能及其耗能比例的影响规律,确定了阻尼比对滞回耗能和延性比对阻尼耗能的交互影响;研究了框剪高层结构地震滞回耗能沿结构竖向分布和沿横向构件内部分配的规律,确定了竖向刚度分布对结构地震滞回耗能的影响;揭示了钢混框剪高层结构地震输入能量及其分布规律。所得结论可为基于能量平衡原理的抗震设计理论在复杂钢筋混凝土高层建筑结构实际工程中的运用提供参考。     

钢和混凝土竖向混合结构阻尼特性研究

下部混凝土结构与上部钢结构串联形成竖向混合结构(以下简称S/RC结构),由于建筑和结构上优势,该结构体系已在国内重大工程中得以应用。S/RC体系上、下部分材料不同,整体结构的阻尼参数难以确定,工程设计被迫采用钢材和混凝土两种不同阻尼参数进行计算。从阻尼矩阵和模态阻尼比两个方面研究分块Rayleigh模型和模态应变能模型这两个阻尼模型,并从理论上对模型的物理意义和应用基础进行分析。之后,以12层RC框架和12层S/RC框架的振动台试验为基础,从频域和时域两个层面对两个阻尼模型的有效性进行检验。结果表明,分块Rayleigh模型的阻尼矩阵为非比例阻尼,其难以用于常规的模态分析。模态应变能阻尼模型具有耗能等效的物理概念,且该模型在时域和频域内均具有更高的预测精度,建议在S/RC结构抗震分析中采用。     

Capacity design for composite partially restrained steel frame‐reinforced concrete infill walls with concealed vertical slits

This paper presents an innovative capacity‐based design procedure that aims to achieve the ideal seismic performance for the composite partially restrained (PR) steel frame‐reinforced concrete (RC) infill wall with concealed vertical slits (PSRCW‐CVS). The proposed method adopts the direct capacity design principles and preselected preferred plastic mechanism such that the RC infill wall undergoes ductile failure prior to the other steel components in the event of a rare‐level earthquake (i.e., earthquake with a 2% probability of exceedance in 50 years). Based on the ultimate resisting capacity of RC infill walls, the free‐body diagrams and simplified design formulae for the surrounding steel components, including the vertical boundary element (VBE), horizontal boundary element (HBE), PR connection, and shear connectors, were proposed. To demonstrate the reasonability of the capacity‐based design procedure, a five‐story PSRCW‐CVS structure was designed according to the proposed design method, followed by a series of nonlinear time history analyses. The overall seismic response of this example was evaluated in terms of story displacement, interstory drift ratio, residual story displacement, and residual interstory drift ratio. The proposed method yielded a more uniform interstory drift ratio distribution along the height of the five‐story PSRCW‐CVS structure. Structural damage was controlled by achieving the preselected preferred plastic mechanism.     

重庆高科太阳座大厦模型结构振动台试验研究

重庆高科太阳座大厦是一幢建筑外立面扭转,结构平面、竖向不规则超限的复杂超高层建筑结构,采用了钢管（型钢）混凝土框架-钢筋混凝土核心筒混合结构体系。外立面扭转导致外框架中竖向构件不连续,形成受力复杂的空间斜柱,进而造成结构各层平面形状、布置不断变化,以及结构扭转不规则。通过1∶25缩尺模型振动台试验,对模型结构在6度多遇、设防和罕遇地震作用下的加速度、位移等动力响应以及结构的损伤破坏情况进行观测,评价该结构体系的整体抗震性能。研究结果表明：通过增大竖向构件截面方式提高结构层高较大的楼层刚度引起了结构局部刚度突变、应力集中,致使薄弱部位转移;结构顶部塔楼的收进导致鞭梢效应明显,急剧增大了楼层变形;CFST柱-SRC梁框架的SRC梁端和节点周围加强环梁,以及RC核心筒连梁为主要损伤部位;模型在6度罕遇地震作用下能保证“大震不倒”,该结构体系具有良好的抗震性能,能够满足预设抗震性能目标。     

基于拟力法的框架结构静力弹塑性分析

针对拟力法仅在刚性连接钢框架中应用的现状,根据钢筋混凝土框架以及半刚性连接钢框架的受力特点,并基于拟力法的基本假定与思路,得出了钢筋混凝土结构中塑性铰和半刚性连接钢框架中连接的弯矩-相对转角关系,从而推导并获得了拟力法在框架结构静力弹塑性分析中的通用公式。通过与有限元理论计算结果的比较,表明基于拟力法的框架结构静力弹塑性分析方法在应用于各类框架结构时都有着较高的精度,从而为将基于拟力法的动力弹塑性分析包括地震能量分析拓展到钢筋混凝土框架结构以及半刚性连接钢框架结构中奠定了基础。     

混凝土框架摇摆墙结构体系的抗震性能分析

为研究框架摇摆墙结构体系的抗震性能,以1个6层混凝土框架结构模型为例,利用通用有限元软件SAP2000建立了该结构的简化模型,并通过弹塑性动力时程分析,得到了附加摇摆墙前后结构的地震响应。分析结果表明:附加摇摆墙后,结构以摆动振型振动,各层的层间位移角趋于一致,结构层间变形的集中得到有效控制,从而使结构形成整体屈服破坏机制,防止局部层屈服破坏机制的产生,充分发挥整个结构的耗能能力;附加摇摆墙后,结构周期略有减小,不会显著增加结构基底剪力,即使仅附加高度为结构总高度一半的摇摆墙,也能有效控制结构底层的变形集中;该框架摇摆墙结构体系具有良好的抗震性能。     

组合梁刚度对组合框架的抗震性能影响分析

为研究钢-混凝土组合框架梁的刚度对组合框架抗震性能的影响,通过某多层钢结构工程实例,采用有限元软件ANSYS分别建立了纯钢框架、组合梁框架及其不同阻尼比下的框架计算模型,进行了纯钢框架与组合框架在不同阻尼比下的多遇地震反应谱分析及弹性时程分析。实例分析结果表明:考虑钢框架的组合作用后,结构整体自振周期变短,说明结构整体刚度变大,地震层间位移变小。虽然组合框架整体刚度的增大使地震力有所加大,但由于组合结构阻尼比接近混凝土结构阻尼比,组合框架无论是结构侧向位移还是地震力均小于纯钢框架,因此组合框架是一种良好的结构形式。     

型钢混凝土竖向混合结构过渡层抗震性能研究综述

型钢混凝土竖向混合结构是钢-混凝土混合结构的主要形式,包括型钢混凝土-钢结构竖向混合结构（SRC-S竖向混合结构）和型钢混凝土-钢筋混凝土土竖向混合结构（SRC-RC竖向混合结构）两种主要类型,在高层建筑中具有显著性能优势并且应用广泛。文章介绍了SRC-S竖向混合结构和SRC-RC竖向混合结构的受力特点和设计现状;针对我国和日本的相关规程及工程应用实践,结合日本阪神地震中SRC-RC竖向混合结构的主要震害特点,指出国内外SRC-RC竖向混合结构过渡层抗震设计方法所存在的主要问题及不足。在综合分析阪神地震后日本关于SRC-RC竖向混合结构过渡层抗震设计方法的最新研究进展的基础上,提出了SRC-RC竖向混合结构过渡层抗震设计的设计思路和方法。本文可为SRC-RC竖向混合结构过渡层抗震设计提供参考。     

附加与不附加粘滞阻尼墙的RC框架对比振动台试验研究

本文阐述了附加与不附加粘滞阻尼墙的两个相同的RC框架模型模拟地震振动台对比试验的情况。这两个钢筋混凝土框架模型为三层一跨两开间,几何相似关系大致为1∶2。首先进行力学性能试验,认识粘滞阻尼墙的耗能能力,得到其力学性能计算公式;然后将阻尼墙附加到一个RC框架模型当中,先后对附加与不附加阻尼墙的两个相同的RC框架模型进行振动台试验。试验结果表明,附加阻尼墙以后,框架模型的第1自振频率由1.66Hz提高到1.94Hz,第1振型阻尼比由2.4%提高到20.9%;在较小和中等加速度峰值的不同地震波作用下,结构的楼层位移反应、加速度反应和层间剪力都有不同程度的减小;输入结构的地震能量有大约60%~70%被阻尼墙吸收、耗散。在同样强烈的地震作用下,附加阻尼墙的耗能框架模型破坏较轻,不附加阻尼墙的普通框架模型破坏严重。     

Effect of RC wall on the development of plastic rotation in the beams of RC frame structures

The objective of this study is, to interpret the influence of reinforced concrete walls addition in reinforced concrete frame structures considering behavior laws that reflects the actual behavior of such structures, by means of Castem2000computer code (pushover analysis). A finite element model is proposed in this study, using the TAKEDA modified behavior model with Timoshenko beams elements. This model is validated initially on experimental model. Then the work has focused on the behavior of a RC frame with 3 levels and three bays to better visualize the behavior of plastic hinges. Once the plastic hinge control parameters are identified (plastic rotation, ultimate curvature), a strengthening by introduction of reinforced concrete walls (RC/wall) at the ends of the reinforced concrete frame (RC/frame) has been performed. The results show that these RC walls significantly improve the behavior, by a relocation of efforts towards the central part of the beams.     

高层屈曲约束钢板墙-混凝土框架结构抗震性能研究

为研究高层屈曲约束钢板墙-混凝土框架结构的抗震性能,分别设计了一个10层钢筋混凝土框架结构和屈曲约束钢板墙-混凝土框架结构模型,进行了地震作用下动力非线性分析。结果表明：屈曲约束钢板墙可显著减小高层钢筋混凝土框架结构在地震作用下的层间位移,同时在罕遇地震作用下框架中塑性铰的数量也有大幅减少,表现出良好的抗震性能。在此基础上,综合规范对框架结构和框架-抗震墙结构抗震等级和柱轴压比限值的规定,并结合屈曲约束钢板墙-混凝土框架结构的受力特点,提出了高层屈曲约束钢板墙-混凝土框架结构的抗震设计建议。建议屈曲约束钢板墙的边缘构件按框架结构确定抗震等级和柱的轴压比限值,其他框架部分根据其承担的地震倾覆力矩比例大小,按框架结构或框架-抗震墙结构确定抗震等级和柱的轴压比限值。     

The effect of roof systems on seismic performance of reinforced concrete frame‐bent main building of large‐scale thermal power plant

The roof systems of turbine hall in large‐scale thermal power plant are often simulated by approximate rigid beam model. Wenchuan earthquake again revealed the frequent destruction of these roof systems. In this study, three kinds of general roof systems as space grid, trapezoid steel roof truss and reinforced concrete (RC) mansard roof truss were considered. Also, the numerical model of RC frame‐bent main building in large‐scale thermal power plant was established. Seismic performance of main building was compared with approximate rigid beam model, and the damage mechanism of roof systems was also investigated. The results indicate that the response calculation of frame part by rigid beam model is feasible, and roof systems give most contribution to the response of bent part. After considering roof systems, overall collaborative performance is enhanced, but bent part is still unable to become a second defence part after shear walls fail. The torsional irregularity of roof systems is very serious, and more attentions should be paid to the bearing shear failure of space grid and components strength failure of RC roof systems. Copyright © 2014 John Wiley & Sons, Ltd.     

Nonlinear finite element analysis of behaviors of steel beam–continuous compound spiral stirrups reinforced concrete column frame structures

Many tests and numerical research for RCS frame consisted of reinforced concrete (RC) column and steel (S) beam have been conducted in the USA and Japan over the past decades; they showed that the performance of the RCS system is superior to traditional concrete frame and steel frame. Up to the present, no research reports on composite CCSHRCS frame structure consisted of high‐strength concrete columns confined with continuous compound spiral stirrups (CCSHRC) and steel (S) beam. Herein, an accurate finite element model of composite CCSHRCS frame is developed; the finite element model is investigated in order to fully include important factors such as local buckling of steel beam and nonlinear behavior of confined concrete; the validity of the proposed models is examined by comparing with the results of cyclic loading experiments on the RCS frame in reference. With the proposed model, the effect of composite CCSHRCS frame is discussed in detail. Copyright © 2012 John Wiley & Sons, Ltd.     

重庆解放碑威斯汀酒店伸臂桁架对比分析

重庆解放碑威斯汀酒店采用外框架(钢框架梁+型钢混凝土柱)+钢筋混凝土核心筒+伸臂桁架体系,在33层和49层的避难层设置了伸臂桁架,伸臂桁架的设置可以使外框架柱有效发挥作用,以增强整个结构的抗侧力刚度。结构整体分析表明,设置两道加强层,可有效地提高整个结构的抗侧力刚度,减小结构的水平位移,使其满足规范要求;同时,加强层的刚度不宜太大,太大了将造成严重的刚度突变;所以应对加强层的设置方式和层数进行对比分析,减少结构刚度突变。分析表明,在对加强层及相邻楼层采取专门措施后,整个结构在地震下仍可保持延性屈服机制。