Seismic performance of recycled concrete-filled square steel tube columns

An experimental study on the seismic performance of recycled concrete-filled square steel tube （RCFST） columns is carried out. Six specimens were designed and tested under constant axial compression and cyclic lateral loading. Two parameters, replacement percentage of recycled coarse aggregate （RCA） and axial compression level, were considered in the test. Based on the experimental data, the hysteretic loops, skeleton curves, ductility, energy dissipation capacity and stiffness degradation of RCFST columns were analyzed. The test results indicate that the failure modes of RCFST columns are the local buckling of the steel tube at the bottom of the columns, and the hysteretic loops are full and their shapes are similar to normal CFST columns. Furthermore, the ductility coefficient of all specimens are close to 3.0, and the equivalent viscous damping coefficient corresponding to the ultimate lateral load ranges from 0.323 to 0.360, which demonstrates that RCFST columns exhibit remarkable seismic performance.

Axial Compression Behavior and Analytical Method of L-Shaped Column Composed of Concrete-Filled Square Steel Tubes

Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical property of the L-shaped column. The load-displacement curve for the L-shaped column, the deflection and load-strain curves for the mono columns were obtained by the axial compression experiment. The results show that the L-shaped column exhibits a flexural-torsional buckling failure mode. The numerical simulation by the finite element analysis shows that the bearing capacity and failure mode are in accordance with those of the axial compression experiment and the feasi- bility of the finite element analysis is proved. For the calculation of the bearing capacity of the L-shaped column com- posed of concrete-filled square steel tubes, an analytical method is proposed based on the theory of the elastic stability and spatial truss model. The results of the analytical method are in good agreement with those of the axial compression experiment and the finite element analysis.

Ductility and Ultimate Capacity of Concrete-Filled Lattice Rectangular Steel Tube Columns

A kind of concrete-filled lattice rectangular steel tube(CFLRST)column was put forward.The numerical simulation was modeled to analyze the mechanical characteristic of CFLRST column.By comparing the load-deformation curves from the test results,the rationality and reliability of the finite element model has been confirmed,moreover,the change of the section stiffness and stress in the forcing process and the ultimate bearing capacity of the column were analyzed.Based on the model,the comparison of ultimate bearing capacity and ductility between CFLRST column and reinforced concrete(RC)column were also analyzed.The results of the finite element analysis show that the loading process of CFLRST column consists of elastic stage,yield stage and failure stage.The failure modes are mainly strength failure and failure of elastoplastic instability.CFLRST column has higher bearing capacities in comparison with reinforced concrete columns with the same steel ratio.In addition,the stiffness degeneration of CFLRST column is slower than RC column and CFLRST column has good ductility.

Axial Bearing Capacity of Short FRP Confined Concrete-filled Steel Tubular Columns

The bearing capacity of FRP confined concrete-filled steel tubular （FRP-CFST） columns under axial compression was investigated. This new type of composite column is a concrete-filled steel tube （CFST） confined with fiber-reinforced polymer （FRP） wraps. Totally 11 short column specimens were tested to failure under axial compression. The influences of the type and quantity of FRP, the thickness of steel tube and the concrete strength were studied. It was found that the bearing capacity of short FRP-CFST column was much higher than that of comparable CFST column. Furthermore, the formulas for calculating the bearing capacity of the FRP-CFST columns are proposed. The analytical calculated results agree well with the experimental results.

Prediction of Axial Capacity of Concrete-Filled Square Steel Tubes Using Neural Networks

The application of artificial neural network to predict the ultimate bearing capacity of CFST （ concrete-filled square steel tubes） short columns under axial loading is explored. Input parameters consiste of concrete compressive strength, yield strength of steel tube, confinement index, sectional dimension and width-to-thickness ratio. The ultimate bearing capacity is the only output parameter. A multilayer feedforward neural network is used to describe the nonlinear relationships between the input and output variables. Fifty-five experimental data of CFST short columns under axial loading are used to train and test the neural network. A comparison between the neural network model and three parameter models shows that the neural network model possesses good accuracy and could be a practical method for predicting the ultimate strength of axially loaded CFST short columns.

Behavior of High Strength Concrete Filled Square Steel Tube Stub Columns with Inner CFRP Tube Under Biaxial Eccentric Compression

This paper studies the contribution of CFRP(carbon fiber-reinforced polymer)to the mechanical behavior of high strength concrete-filled square steel tube(HCFST)under biaxial eccentric compression.The new type of composite member is composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes.The finite element analysis was made by ABAQUS on the behavior of high strength concrete filled square steel tubular columns with inner CFRP circular tube subjected to bi-axial eccentric loading.The results obtained from the finite element analysis were verified with the experimental results.In addition,the load-deflection curves in the whole process were calculated and analyzed,which can be divided into three segments:Elastic phase,plastic phase,descending phase.Based on the load-deflection curves,the stresses analysis on the core concrete,CFRP tube and steel tube were conducted.The confinement effect of the CFRP tube improves the ductility of HCFST-CFRP stub column.CFRP ratio and eccentricity affect the ultimate bearing capacity of HCFST stub column.Finally,a calculation formula of ultimate bearing capacity was proposed in the paper.

A simplified model to predict blast response of CFST columns

In order to study the dynamic response of concrete-filled steel tube(CFST) columns against blast loads,a simplified model is established utilizing the equivalent single-degree-of-freedom(SDOF) method,which considers the non-uniform distribution of blast loads on real column and the axial load-bending moment(P-M) interaction of CFST columns.Results of the SDOF analysis compare well with the experimental data reported in open literature and the values from finite element modeling(FEM) using the program LS-DYNA.Further comparisons between the results of SDOF and FEM analysis show that the proposed model is effective to predict the dynamic response of CFST columns with different blast conditions and column details.Also,it is found that the maximum responses of the columns are overestimated when ignoring the non-uniformity of blast loads,and that neglecting the effect of P-M interaction underestimates the maximum response of the columns with large axial load ratio against close range blast.The proposed SDOF model can be used in the design of the blast-loaded CFST columns.

超高层建筑结构体系契合性研究

为了研究超高层建筑外型与建筑功能对结构选型的影响,以两栋低烈度区约400m高的超高层建筑为案例,简要介绍了两个案例的建筑造型、使用功能、构件布置、荷载条件等基本情况;同时,对比了水平荷载作用下,两案例的主要计算结果;最后,将两案例的造价与同地区相似高度建筑的造价进行了对比。结果表明:两案例既满足了建筑使用和立面美观的要求,又满足了结构受力和整体稳定安全的要求,同时均比国内高度相近的超高层建筑具有更好的经济性。说明契合建筑外观与使用功能是结构布置合理性的根本,两者和谐结合方能实现综合最优。

临沂金水湾二期超高层结构设计

临沂金水湾二期超高层项目结构高度153.3m,属于高震区超高层超限结构,地上结构采用钢管混凝土框架⁃钢筋混凝土核心筒混合结构,塔楼外框柱均倾斜布置以满足建筑外立面的变化。采用YJK和ETABS两种软件对主塔楼结构进行了弹性分析,并采用PERFORM⁃3D软件进行了动力弹塑性分析。从结构体系、性能设计等方面对超高层结构设计进行了简要论述,并对梭形超高层建筑的斜柱设计要点、环带桁架、底层分叉柱以及结构动力弹塑性四个方面进行了详细分析、介绍,最后给出了上述要点的计算结论和构造建议。

钢板墙核心筒与混凝土核心筒的结构性能和经济成本分析

文中研究了一种在核心截面拐角处使用钢板柱的新型复合核心筒系统。使用此系统可以获得更好的结构性能和可施工性,文中使用该系统分别对原型核心筒截面和超高层建筑进行了非线性截面分析和三维结构分析。结果表明,与传统的RC核心筒相比,角钢钢板柱提供了更好的结构承载力,可使墙体厚度更薄,使用钢筋更少,有利于缩短施工时间及节约成本。

FRP-混凝土-钢双壁空心柱的抗爆性能分析

纤维增强复合材料(fiber reinforced polymer,FRP)-混凝土-钢双壁空心柱是一种新型混凝土组合柱,由外层FRP管、内层钢管及两管间填充的混凝土组成。针对FRP-混凝土-钢双壁空心柱在近场爆炸荷载下的抗爆性能进行了数值模拟。采用任意拉格朗日欧拉法(arbitrary Lagrangian Eulerian,ALE)进行建模,并基于已有的试验结果验证所建模型的准确性。利用验证后的数值模型,对爆炸冲击波传递过程、混凝土损伤发展、FRP管环向应变、爆炸后剩余力学性能以及参数进行了分析。结果表明,FRP管能有效约束爆炸区域内的夹层混凝土;爆炸后双壁空心柱的轴向承载力明显减小、轴向刚度明显下降;通过增加FRP管、钢管厚度,以及减小空心率能提高双壁空心柱的抗爆性能,其中前两项的影响更为显著。

钢管混凝土叠合柱边框组合核心筒抗震性能试验研究

为了比较带钢管混凝土叠合柱边框组合核心筒与带钢管混凝土边框组合核心筒的抗震性能,进行了1个钢管混凝土叠合柱边框组合核心筒模型和1个钢管混凝土柱边框组合核心筒模型的低周反复荷载试验研究,2个模型均按1/6缩尺.在试验基础上,分析比较了2个核心筒的承载力、延性、滞回特性、刚度及其衰减过程、耗能能力和破坏特征.研究表明,钢管混凝土叠合柱边框组合核心筒比钢管混凝土柱边框组合核心筒的抗震性能显著提高;承载力简化计算模型的计算结果与实测结果符合较好.

叠合柱边框内藏钢桁架带洞口组合核心筒抗震性能研究

提出了钢管混凝土叠合柱边框内藏钢桁架混凝土组合核心筒,为了解该新型多重组合带洞口核心筒的抗震性能,进行了1个钢管混凝土叠合柱边框带洞口混凝土组合核心筒和1个钢管混凝土叠合柱边框内藏钢桁架带洞口混凝土组合核心筒的低周反复荷载试验研究,2个试验模型按原型结构的1/6缩尺.在试验研究基础上,分析比较了2个核心筒的滞回特性、承载力、延性、刚度衰减、耗能能力和破坏形态.结果表明,与钢管混凝土叠合柱边框带洞口混凝土组合核心筒相比,钢管混凝土叠合柱边框内藏钢桁架带洞口混凝土组合核心筒的抗震性能显著提高,建立了其承载力简化力学模型,计算结果与试验结果符合较好.

新型装配式钢框架结构建筑体系研究与应用

近些年,我国开始大力推进装配式钢结构建筑的应用,国家和地方政府也相继推出多个政策来鼓励和促进其应用和推广,因此,装配式钢结构建筑体系得到了广泛的发展。东南大学、浙江东南网架股份有限公司、北京津西赛博思建筑设计有限公司以及天津大学等研究机构和企业依托"十三五"国家重点研发计划项目"新型框架钢结构体系建筑产业化技术与示范",针对当前装配式钢框架体系建筑在应用中存在的梁柱外露、工业化程度低、施工复杂等问题,提出多腔柱钢框架-支撑、多腔体框架-钢板组合剪力墙、新型框架-核心筒以及钢管混凝土组合异形柱框架结构等新型钢框架结构建筑体系,并对新体系建筑中的关键技术开展深入研究和工程应用,提高了我国装配式钢结构建筑的技术和应用水平,有利地促进了我国建筑工业化的发展。

钢管混凝土叠合柱边框内藏钢桁架核心筒抗震性能试验研究

为进一步改善混凝土核心筒的抗震性能,本文提出了钢管混凝土叠合柱边框内藏钢桁架组合核心筒。进行了2个1/6缩尺的核心筒模型在低周反复荷载下的抗震性能试验研究,1个为钢管混凝土叠合柱边框组合核心筒,1个为钢管混凝土叠合柱边框内藏钢桁架组合核心筒。通过试验,对比分析了2个核心筒的承载力、延性、刚度及其衰减、滞回特性、耗能能力及破坏特征,给出了钢管混凝土叠合柱边框内藏钢桁架组合核心筒的承载力计算模型,计算结果与实测值符合较好。研究表明,钢管混凝土叠合柱边框内藏钢桁架组合核心筒与钢管混凝土叠合柱边框组合核心筒相比,其抗震性能明显提高。

芯钢管连接的钢管混凝土中柱节点试验研究

提出了钢管混凝土结构的新型节点 ,这种节点将钢管混凝土柱的钢管在节点区间断 ,用节点区密排环形钢箍、竖向短筋和芯钢管来保证钢管混凝土柱在节点的连续性 ,梁中的纵筋在节点中连续 ,梁与节点区混凝土成为一体 ,能可靠传递梁中的弯矩、剪力及轴力 ;通过三个节点模型试验结果验证了新型节点的构思在概念上是正确的 ,试件的梁、柱破坏先于节点。主要分析了试验现象、破坏机理 。

T形钢管混凝土柱轴心受压稳定承载性能研究

基于9根T形钢管混凝土中长柱的单向、双向偏心受压试验的结果,建立了T形钢管混凝土柱用于纤维模型程序分析其承载力的本构模型.在验证纤维模型程序合理性的基础上,对T形钢管混凝土柱轴压稳定性能进行了参数研究.研究参数包括:钢材屈服强度、混凝土抗压强度、管壁宽厚比、截面肢宽厚比、长细比以及加载角度.理论结果表明:长细比是影响T形钢管混凝土柱轴压稳定承载力的主要因素,混凝土工作承担系数和加载角度也对钢管混凝土柱的承载力有一定影响.纤维模型计算的柱子曲线与钢结构规范的a,b,c,d类曲线之间的比较表明:不同参数截面的T形钢管混凝土柱的柱子曲线会在一个较宽带宽范围内变化.最后,在大量参数分析基础上,考虑长细比和混凝土工作承担系数的影响,提出了T形钢管混凝土轴压柱的稳定承载力系数的实用计算方法.理论公式计算结果与已有试验结果吻合良好,可为工程设计提供理论参考.

RC梁-核心区钢管壁开洞组合柱节点试验

为了研究核心钢管壁开洞对钢筋混凝土(RC)梁-组合柱节点区受力性能的影响,完成了4个试件的低周往复加载试验.试验结果表明:试件的力-位移滞回曲线比较饱满,弹塑性变形能力大;梁柱纵向钢筋配筋率以及柱的钢管含钢率与实际高层建筑工程基本一致的试件为梁受弯破坏,实现了强柱强核心区弱梁的抗震设计要求;洞口周围设置加劲板或加厚钢管壁能有效改善钢管壁开洞核心区的抗剪性能,提高核心区的受剪承载力.

L形钢管混凝土芯柱正截面承载力研究

目的研究L形钢管混凝土芯柱的承载力变化规律以及影响因素,为钢管混凝土在工程中的应用提供参考依据.方法根据L形钢管混凝土芯柱的工作机理和有限元计算原理,编写MATLAB程序求其承载力,通过改变加载角、偏心距、钢管直径以及钢管厚度等参数研究其对L形钢管混凝土受力性能的影响,并与有限元模拟值进行对比.结果偏心距一定时,加载角在0～45°内变化,L形钢管混凝土芯柱的承载力随加载角的增大而逐渐减小;当钢管厚度不变直径增加,或者钢管直径不变厚度增加时,试件承载力随含钢率的增加而逐渐增大.结论数值模拟结果与有限元模拟结果吻合良好,验证了程序的可行性.可以利用本套程序对L形钢管混凝土芯柱进行进一步的研究,得出不同参数变化下试件承载力的变化规律.

约束边缘区域不同构造的带钢板暗支撑高阻尼混凝土核心筒抗震性能研究

针对带钢板暗支撑高阻尼混凝土核心筒结构,探讨约束边缘区域不同构造措施对其抗震性能的影响,共完成了3个核心筒的低周反复加载试验。试验结果表明:带钢板暗支撑高阻尼混凝土核心筒结构具有良好的变形能力,约束边缘区域配置型钢能提高试件的强度和延性;在角部设置叠合柱的试件,其抗侧刚度和耗能能力有显著提高;带钢板暗支撑高阻尼混凝土核心筒翼墙存在剪力滞后效应,角部叠合柱的设置能降低剪力滞后系数,进一步发挥核心筒的整体空间作用。通过与试验结果的对比与校验,应用OpenSees有限元软件建立高阻尼混凝土带钢板暗支撑组合核心筒试件非线性分析模型,以此非线性分析模型为基础,考察了轴压比对高阻尼带钢板暗支撑混凝土核心筒抗震性能的影响,结果表明即使在试验轴压比为0.6的情况下,这种核心筒的延性与变形指标仍能满足规范要求。