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.

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.

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.

四肢钢管混凝土格构柱试验研究及参数分析

为研究四肢钢管混凝土格构柱的受力机理及抗震性能,对4根四肢格构柱进行拟静力试验研究及有限元分析。通过试验得到四肢钢管混凝土格构在低周往复荷载作用下的滞回曲线和骨架曲线,分析了试件破坏过程。研究结果表明:格构柱的耗能能力及延性都较好;轴压比对试件的影响主要体现在破坏阶段,轴压比越大承载力下降段的斜率越大;长细比对试件受力性能有较大影响,随着长细比增大,试件的屈服位移和极限位移会增大,但水平承载力和破坏段的斜率会降低。建立了数值计算模型,并与试验结果进行对比,验证其正确性。并对不同高宽比、节间距与柱肢外径比等参数对试件弹性刚度和承载力的影响进行分析,结果表明:减小格构柱的高宽比和节间距与柱肢外径比对格构柱的受力性能有很大提升。建议实际工程中格构柱的高宽比不宜大于4.8;节间距与柱肢外径比低不宜大于7.0。

四肢和两肢钢管混凝土柱框架的用钢量对比

以实际工程石横特钢1780热连轧绿色智能产品结构调整项目热轧主车间为实例,选取热轧主车间框架为研究对象,对框架格构柱分别为两肢、四肢钢管混凝土柱的情况下,框架的整体耗钢量进行了分析。对比框架为两跨、三跨、四跨的不同情况时,采用四肢钢管混凝土柱和采用两肢钢管混凝土时,主车间框架的用钢量和混凝土用量,为类似的工程设计提供一定的参考和借鉴。

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.

青浦题学平和学校综合馆结构设计

青浦题学平和学校综合馆由游泳馆和篮球馆组成,下部两层采用钢框架结构,上部屋盖采用格构柱-空间管桁架屋盖体系。对屋盖抗侧力体系及截面选取、格构柱与下部结构连接方式等关键技术进行研究。采用SAP2000软件分别建立屋盖单体模型和结构整体模型,并对两种模型在水平和竖向荷载作用下屋盖的内力和变形进行分析比较;同时针对本项目的受力特点,对屋盖整体稳定及关键节点应力等进行多方面的分析。分析结果表明:关键构件应力比不应大于0.85,屋盖其他构件应力比不大于0.90,屋盖在竖向荷载下挠度及风荷载、地震作用下的位移均满足规范要求,屋盖结构体系安全可行,节点连接可靠,现行的设计能够满足设计目标。

内置L-CFRST十字形短柱耐火性能有限元分析

目的 研究内置格构式圆钢管混凝土十字形短柱四处阴角受火下轴压耐火性能。方法 基于ABAQUS有限元软件建立81种不同工况的耐火极限模型,分析火灾荷载比、钢管内混凝土强度、含钢率和钢管强度对耐火极限的影响变化规律,通过正交试验分析得出不同因素对耐火极限的敏感程度,最后提出试件耐火极限简化计算公式。结果 试件耐火极限随火灾荷载比增加呈负相关并且显著降低,其他影响因素均呈正相关,钢管强度对耐火极限影响程度最低;耐火极限理论计算结果与有限元结果符合较好。结论 钢管的约束效应对于试件耐火极限有一定影响,在工程设计时尽量保证约束效应系数大于1.12;选用火灾荷载比为0.4、钢管内混凝土强度为60 MPa、含钢率为0.067 9、钢管强度为390 MPa的组合耐火性能最好。

内置格构式钢管混凝土十字形短柱轴压力学性能试验研究

提出一种新型的内置格构式钢管混凝土异形柱,对3根内置格构式钢管混凝土和2根等强度换算的钢筋混凝土十字形短柱进行了轴向受压试验,分析短轴的力学性能、荷载-位移曲线以及破坏规律。研究表明:内置格构式钢管混凝土十字形短柱发生斜向剪切破坏;与钢筋混凝土十字形柱相比,内置格构式钢管混凝土十字形柱的承载能力、屈服位移、峰值位移、破坏位移以及试件延性有较大的提高,峰值荷载后荷载-位移曲线下降平缓,从而为结构构建第二道防线。

四肢钢管混凝土格构柱极限承载力的试验研究与理论分析

进行共计20根缀条为K形布置的四肢钢管混凝土格构柱偏压及轴压极限承载力试验,重点考察偏心率与长细比对钢管混凝土偏压构件受力性能的影响。试验结果表明,长细比对试件承载力有一定影响,偏心率对承载力影响明显,两者对承载力的影响接近独立,试件的斜缀条在试验过程中始终保持弹性状态,近载一侧钢管在试件进入非线性阶段后,泊松比明显增大,钢管开始发生套箍作用,远载一侧,套箍作用不明显,除个别短柱外,试件破坏均为整体失稳破坏。同时,采用半波正弦曲线模拟杆件的变形曲线,在考虑紧箍效应的钢管混凝土应力-应变关系和剪切变形影响的基础上,建立杆件中截面的平衡方程,提出钢管混凝土格构柱弹塑性极限承载力数值方法,该方法不仅适用于两端偏心相等的偏压构件,而且适用于两端偏心不等的偏压构件的弹塑性极限承载力的计算;理论分析结果与试验研究结果对比表明,提出的钢管混凝土格构柱弹塑性极限承载力计算方法具有相当高的精度。

钢管混凝土格构柱极限承载力计算方法研究

提出钢管混凝土格构柱有限元分析方法,应用ANSYS通用程序对试件的分析结果与试验结果吻合良好。对钢管混凝土格构柱极限承载力,进行偏心率、长细比和构造参数的影响分析。对国内CECS 28∶90、JCJ 01-89和DL/T 5085-1999 3个钢管混凝土设计规程计算结果与有限元数值计算结果进行比较分析。分析结果表明CECS28∶90规程的偏心率折减系数计算公式较合理。柱肢的钢材种类和混凝土强度对稳定系数的影响较大,通过算例数值分析,提出换算长细比的材料修正系数γ的计算方法。斜缀条交角等构造参数对钢管混凝土格构柱整体承载力的影响均很小,验证了换算长细比的放大系数简化算法的合理性,并对国内3个规程中换算长细比的计算方法提出修正建议。最后,给出四肢钢管混凝土格构柱极限承载力的合理实用的计算方法。

钢管混凝土格构柱偏压承载能力分析的数值方法

采用泰勒级数作为分段插值函数,在考虑多个截面的平衡条件和紧箍效应钢管混凝土应力-应变关系基础上,提出了钢管混凝土格构柱弹塑性极限承载力数值方法,并编制了相应的计算程序。与现有的分段合成法相比,该方法考虑了剪力对柱变形的影响,不仅适用于两端偏心相等的偏压构件,而且适用于两端偏心不等的偏压构件的弹塑性极限承载力的计算。利用提出的计算方法和编制的程序对国内已有两端偏心相同的四肢钢管混凝土格构偏压长柱的试验结果进行了计算,并与现有规程进行了比较,结果表明:现有计算方法结果偏于保守,计算误差大,本文提出的计算结果与试验结果吻合良好。

华润中心结构设计中的关键技术

深圳华润中心结构复杂,存在大量的转换构件,且结构长度远远超过规范要求分缝的限值。结合工程本身的特性,设计采取了分层钢管芯混凝土组合柱、半空心型钢混凝土转换梁、格构式空腹箱形钢梁、抗剪型钢混凝土转换梁等多种结构体系相结合的措施。结构体系的刚度、延性和稳定性良好,确保了工程的安全性和经济性,满足了建筑方案对空间的要求。主要介绍工程结构关键技术的设计和应用特点,并对工程中应用的33m跨格构式空腹箱形钢梁组作为中庭转换梁的设计及构造作出分析。

海口市侨中路隧道设计关键技术分析

研究目的:海口市侨中路隧道工程具有外部环境复杂、工期紧张、结构埋深浅等特点,根据工程特点和工期要求确定了盖挖顺作的施工方法。本文结合该工程,研究盖挖顺作法隧道中常用的三种立柱——钢格构立柱、钢管混凝土立柱和钢筋混凝土钻孔灌注桩立柱的特点、计算方法和适用性。研究结论:(1)基于该工程特殊的工期要求、浅埋层地质条件和基坑深度,确立了盖挖顺作的施工方法;(2)钢格构立柱、钢管混凝土立柱和钢筋混凝土钻孔灌注桩立柱型式均可应用于该隧道工程,钢格构立柱具有施工和底板防水处理简单且造价低的优势,但竖向承载能力相对较差;(3)钢管混凝土立柱具有承载能力高、底板防水处理简单但施工精度要求高的特点;(4)钻孔灌注桩立柱具有承载能力高、施工简单的特点,但底板防水处理困难;(5)根据本工程实际情况和施工工艺水平选定了钢管混凝土立柱;(6)相关结论可应用于采用盖挖顺作法施工的地下工程领域。

三肢圆钢管格构柱抗震性能试验研究

为了研究三肢圆钢管格构柱的抗震性能,进行了两个试件在低周反复荷载作用下力学性能的试验研究,考察了肢件钢管壁厚度对低周反复荷载作用下三肢圆钢管格构柱破坏形态、荷载-位移曲线、荷载-应变曲线、刚度退化、耗能能力和延性的影响。结果表明,试件肢件的钢管壁越厚,其水平承载力、初始刚度、累积耗能和位移延性系数越大,同时刚度退化越慢。最后,通过《钢结构设计规范》(GB 50017—2003)计算得到的三肢圆钢管格构压弯构件承载力与试验结果的比较,探讨了反复荷载作用下三肢圆钢管格构柱承载力的计算方法。研究成果可为有关工程实践提供参考。

大型炼钢厂房格构柱及吊车梁优化设计

主厂房的柱和吊车梁在大型炼钢厂房中占有较大比重,其合理设计对厂房的安全性和经济性至关重要。分别对相同吊车荷载作用下,不同结构形式厂房柱及不同强度、跨度吊车梁的经济、技术等指标进行对比分析。结果表明:在大型炼钢厂房中采用多肢钢管混凝土格构柱既可满足结构安全的需要,又可降低成本、缩短工期;对吊车梁而言,当跨度在27 m及以下时,采用Q345钢材比较经济,而当跨度增大时,采用Q390钢材经济效益更加显著。

钢管混凝土组合格构柱高墩偏压试验研究

雅泸高速公路黑石沟特大桥在国内首次提出并采用了钢管混凝土组合格构柱高墩。为研究这种结构形式高墩的组合性能,进行了偏压试验和破坏试验,考察了钢管混凝土柱肢、钢管外包混凝土及腹板剪力墙的受力性能。试验结构表明:正常使用极限状态下,钢管混凝土组合格构柱处于小偏心受压,结构处于弹性状态。