矩形钢管混凝土受弯构件材料本构关系与失效判据研究

为了正确评估矩形钢管混凝土(CFST)受弯构件的承载力,提出钢管和核心混凝土材料本构关系的修正模型,建立CFST受弯构件的承载力失效判据。首先,考虑受拉区钢管双轴受拉有利应力状态及受压区钢管双轴拉压不利应力状态,并基于矩形CFST轴压短柱试验数据库,通过回归分析建立约束混凝土峰值应力表达式,在此基础上建立矩形钢管混凝土材料本构关系的修正模型。其次,基于构件承载能力极限状态,并合理考虑受拉区钢管的应变强化段,提出矩形CFST受弯构件的承载力失效判据。最后依据纤维模型法和试验数据库对比分析CFST受弯构件的不同材料本构关系和失效判据的精度及适用性。结果表明,所建立的CFST构件材料本构关系和承载力失效判据能够更加准确地反映矩形CFST构件的抗弯能力,具有更高的计算精度和广泛的适用性。     

隧道钢管混凝土支护构件承载力对比研究

钢管混凝土拱架支护作为地下工程的高强支护形式,具有广阔的应用前景。故应明确钢管混凝土支护构件与传统支护构件承载机制及承载力大小进行工程类比设计,但目前少有针对该领域的研究。为对比钢管混凝土(CFST)与工字钢构件承载力,基于钢管约束效应,建立了钢管混凝土构件简化计算模型,推导了构件承载力计算公式;进行了CFST构件、工字钢构件轴压室内试验和数值试验,深入分析了不同构件变形过程及破坏形态,基于构件承载力,验证了上述计算方法的合理性。在超大断面隧道开展了CFST拱架现场应用试验,提出了CFST构件在地下工程中应用的类比设计方法,研究结果可为相关工程设计提供理论依据。     

横向冲击荷载下高强钢管混凝土构件的性能

介绍一组新的关于横向冲击荷载下钢管高强混凝土构件的试验数据。对总共12个圆型钢管混凝土样本和用于对照的中空钢管进行测试。所用的钢管混凝土构件的混凝土强度达到75 MPa。建立一个有限元分析(FEA)模型来预测钢管高强混凝土构件的冲击性能,试验结果验证了这个模型的准确性。使用有限元分析模型对冲击荷载下钢管混凝土构件的性能进行全过程分析,从而了解受力状态、内力分布和抗弯承载力。最后,根据参数分析得到一个简化模型,从而计算冲击荷载下钢管混凝土构件的抗弯承载力。     

圆钢管混凝土柱侧向偏心冲击的动力仿真分析

通过对不同钢壁厚度的钢管混凝土构件以及对同直径混凝土构件的冲击模拟,分析了钢管约束效应系数对构件变形和冲击抗力的影响,比较了钢管混凝土与混凝土两种材料构件在抗冲击能力方面的差异,表明有限元分析软件在模拟复杂问题尤其是对钢管混凝土这种不易看到内部破坏过程材料的模拟方面具有极大的优越性。     

局部荷载作用下圆钢管混凝土有限元分析

对与构件垂直或成45°角的局部荷载作用下的圆钢管混凝土(CFST)进行有限元分析(FEA)。利用已发表在国际期刊上的试验结果对建立的有限元模型进行了验证。采用该有限元模型对局部荷载作用下的CFST进行有限元分析,研究其典型的失效模式和荷载-变形曲线。最后,给出计算局部荷载作用下CFST强度的简单计算公式。所提出的建议公式可避免支撑构件过早屈曲以及弦杆过早断裂。     

带球冠形脱空缺陷的钢管混凝土构件抗弯性能研究

在合理地选择材料本构模型和接触模型并考虑材料和几何非线性的基础上,建立了带球冠形脱空缺陷的钢管混凝土受弯构件的有限元模型,并利用试验结果验证了有限元模型的可靠性。利用数值模型对带脱空缺陷的钢管混凝土构件在纯弯作用下的全过程工作机理进行了细致剖析,明晰了球冠形脱空缺陷对构件抗弯性能的影响机理。结果表明球冠形脱空缺陷的存在降低了钢管对混凝土的约束效应,使混凝土开裂严重以及加剧了钢管的局部屈曲从而降低了构件的抗弯承载力。基于以上分析,研究了影响约束效应的相关参数对带缺陷的钢管混凝土构件的抗弯承载力以及弯矩-挠度关系曲线的影响规律,并在此基础上提出了考虑脱空缺陷影响的钢管混凝土抗弯极限承载力的简化计算公式,可为相关工程实践提供参考。     

矩形钢管混凝土构件抗弯性能研究

为研究厚实、非厚实和薄柔截面矩形钢管混凝土(CFST)构件的抗弯性能,提出一种有限元分析(FEA)模型。使用70组试验结果对有限元模型进行验证。有限元分析得到的复合构件极限抗弯承载力和弯矩-跨中挠度关系曲线与试验结果相符。利用有限元模型研究核心混凝土的破坏模式、外钢管典型的残余变形以及整个加载过程中组合结构的应力-应变分布。分析结果表明,组合梁中钢材和混凝土的相互作用使其产生了应力重分布,从而提高了矩形钢管混凝土梁的抗弯承载力和延性。最后,使用可靠性分析方法对欧洲规范EC 4(2004)、美国AISC(2010)和中国规范DBJ/T 13-51-2010中组合梁的现有设计公式进行了评估,结果发现,设计公式的可靠性指标较好。     

圆钢管混凝土受压短柱试验研究及有限元仿真分析

通过对基于不同长细比的圆钢管混凝土短柱的受压力学试验,对其破坏现象及机理进行了分析;探讨了长细比对该类构件力学性能的影响规律,同时分析了该类构件中钢管对核心混凝土的约束作用。建立三维精细有限元模型,比较分析了数值模拟结果和试验结果,并确定了钢管及混凝土的破坏准则和其本构关系的合理性,从而为该类构件的设计提供了可靠的理论依据。     

内钢板中空方形钢管混凝土叠合柱轴压力学性能研究

为研究中内钢板中空方形钢管混凝土（CFST）叠合柱的轴压力学性能,以内钢板与钢管的强度和壁厚为参数对8个叠合短柱进行轴压试验,以截面尺寸、钢管内外混凝土强度、钢材强度、纵筋与钢管用钢量分配为参数对81个叠合短柱进行有限元分析,对典型构件受力全过程、各部分接触作用以及承载力进行研究。在美国结构设计规范ANSI/AISC 360-16、欧洲钢结构设计规范BS EN 1994-1-1、GB 50936—2014《钢管混凝土结构技术规范》和T/CECS 663—2020《钢管混凝土加劲混合结构技术规程》的组合柱承载力计算公式中增加内钢板承载力项,得到内钢板中空方形CFST叠合构件的轴压承载力计算式。结果表明：轴压荷载作用下,内钢板中空方形CFST叠合柱钢管外混凝土、内钢板、钢管、纵筋以及核心混凝土能协同工作;内钢板强度与壁厚对构件承载力、延性和刚度影响均较小;截面尺寸和混凝土强度对构件承载力贡献最大,但构件延性随着混凝土强度的增大而降低。在T/CECS 663—2020和ANSI/AISC 360-16的组合柱承载力计算公式中增加内钢板贡献项计算得到的承载力值与试验和有限元结果最为接近。     

GFRP管-钢管双壁约束混凝土组合柱轴压性能与承载力实用计算方法研究

通过4根实心和中空的GFRP管-钢管双壁约束混凝土组合短柱轴压试验,对比分析了该组合柱的工作机理、破坏模式、复合材料管的约束效应、核心混凝土本构关系及其影响因素。研究发现,在其他条件相同的情况下,内钢管空心的构件变形能力超过实心构件,极限承载力小于实心构件,GFRP管对混凝土的约束程度低于实心构件;GFRP管径厚比越小,其对混凝土的约束效应越好。GFRP管径厚比相同的情况下,实心构件混凝土峰值应力比空心构件大,而极限应变比空心构件小。通过试验分析了约束混凝土强度模型,并采用极限平衡法推导了可用于计算实心和空心双壁约束混凝土组合柱轴压承载力的计算公式,理论计算与试验结果吻合较好。     

Performance of CFST column to steel beam joints subjected to simulated fire including the cooling phase

This paper presents the experimental results of three concrete filled steel tube (CFST) column to steel beam joints with reinforced concrete (RC) slabs under combined loading and fire including the heating and cooling phases. The test parameters include heating time and thickness of the fire protection material. Temperatures and deformations of the joint specimens during the heating, cooling and post-fire phases were measured. A finite element analysis (FEA) model to simulate the action of a CFST column to steel beam joint under combined loading and fire is developed. The FEM model was verified by the experimental results. The FEA model is then used to analyse the temperature distribution in the heating and cooling phases. The moment versus relative rotation angle between the CFST column and the beam under combined loading and fire including the heating and cooling phases is also discussed.     

Flexural performance of rectangular CFST members

This paper presents a finite element analysis (FEA) modeling to study the flexural performance of rectangular concrete filled steel tubular (CFST) members with compact, non-compact or slender element sections. Seventy test results are used to verify the FEA modeling. Generally good agreements were achieved in the ultimate bending capacity and the curvilinear trends of the moment versus mid-span deflection relations of the composite member between the experimental results and the FEA results. The FEA modeling is then used to investigate the residual failure patterns of the core concrete, the typical residual deformations of outer steel tube and the stress and strain distributions across the composite section in the whole loading procedure. Analysis results show that interaction of steel and concrete in the composite beam offers stress redistribution in steel and concrete which makes the rectangular CFST beam have high flexural capacity and ductility. Finally, the reliability analysis method is used to calibrate the existing design formulae on composite beam in EC4 (2004), AISC (2010) and DBJ/T13-51-2010 (2010). It was found that all the design formulae achieved adequate reliability index.     

钢管混凝土柱-钢梁节点在具有冷却过程的模拟火灾中的性能分析

对3个带有钢筋混凝土楼板的钢管混凝土柱与钢梁的节点进行了试验,这些节点承受组合荷载、同时具有加热和冷却的火荷载的共同作用。试验参数包括加热时间和防火材料厚度。测量了节点在加热、冷却和灾后的温度和变形。采用有限元模型模拟了节点在组合荷载和火灾下的反应。通过试验结果证实了有限元模型的有效性。随后采用有限元模型分析加热和冷却过程各自引起的节点温度变化。另外,给出此类节点在组合荷载和加热冷却火荷载作用下的弯矩-转角关系。     

Performance and calculations of concrete filled steel tubes (CFST) under axial tension

This paper reports the behavior of concrete filled steel tubes (CFST) under axial tension. A total of 18 specimens were tested. The main parameters were steel ratio, concrete type and bond or unbonded between the steel tube and its core concrete. A finite element model (FEM) was developed to perform mechanism analysis and parametric studies for CFST under axial tension. It was found that the tensile strength of steel tube can be increased due to the existence of the core concrete in CFST. Finally, a simplified formula that can predict the tensile strength was proposed.     

钢管混凝土框架中的空钢管施工受力分析

基于文献[1]钢管混凝土结构施工安全性的研究思路,建立了多层钢管混凝土框架中的空钢管结构施工受力分析的有限元模型。以一12层钢管混凝土框架结构为例,分析框架结构中的空钢管在施工荷载作用下的受力特点,研究了钢管应力和变形的发展规律,在此基础上初步探讨了不同施工方案的影响。     

温度和荷载共同作用下钢管混凝土短柱的性能分析

采用有限元模型研究温度与荷载共同作用下的钢管混凝土短柱的荷载-变形关系。该模型用来模拟一系列各种温度和力学加载条件下的钢管混凝土短柱试验,包括高温测试、常温下构件残余强度测试,以及无初始荷载的ISO-834标准温度下的构件测试。预测结果以及试验结果的对比表明:模型可以准确预测构件的荷载-变形关系。然后采用该有限元模型分析在具有初始荷载、加热和制冷条件下完全加载过程中的钢管混凝土短柱的性能,以观察构件横截面的应力分布和各个加载阶段的应力发展情况。所有构件在制冷过程之后都加载至极限强度,利用一系列参数对其残余应力进行了分析。结果发现:在温度和荷载共同作用下的构件极限强度,要比只有温度作用而无初始荷载的构件极限强度略低,但是在极限强度时,前者的最大应变显著增加。     

新型钢管混凝土柱-钢筋混凝土梁节点的有限元分析

本文研究一种新型的钢管混凝土柱与钢筋混凝土梁节点,即在钢筋混凝土梁与钢管混凝土柱连接区,钢管局部开矩形孔、节点区域钢管加强,使钢筋混凝土梁中的纵向钢筋直接伸入节点,节点混凝土与梁中混凝土成为整体,方便施工且保证了节点刚度。本文在选择了合理的钢材和混凝土的本构关系模型的基础上,利用通用有限元软件ABAQUS对这类新型的钢管混凝土柱-钢筋混凝土梁节点的受力性能进行了较为深入的研究,研究结果表明,这类节点可以实现"强节点弱构件"的抗震设计要求。本文的研究成果可为相关研究和工程实践提供参考。     

火灾后椭圆钢管混凝土界面黏结性能研究

近年来,椭圆钢管混凝土结构日益受到建筑师与结构工程人员的青睐,与传统的圆形和方形钢管混凝土柱相比,椭圆钢管混凝土柱具有流线型外观和较高的抗扭刚度,在高层和大跨等建筑结构中具有较广泛的应用前景。研究者已对圆形和方形钢管混凝土的火灾后界面黏结性能展开试验与理论研究,但尚缺少对椭圆钢管混凝土火灾后界面黏结性能的相关研究。文章采用弹簧单元模拟钢管-混凝土界面的滑移,建立可分析椭圆钢管混凝土火灾后界面性能的有限元模型,并与具有相同界面接触面积的圆形和方形钢管混凝土进行比较,深入分析椭圆、圆形和方形钢管混凝土的温度分布、火灾后界面黏结应力-滑移关系和火灾后黏结强度。最后,在建立的有限元模型基础上,对影响椭圆钢管混凝土火灾后黏结强度的重要参数进行分析,研究参数包括:目标温度(20℃、600℃和800℃)、恒高温时间(30min、90min、120min和180min)、混凝土强度(30MPa、40MPa、50MPa和60MPa)、截面周长(388mm、484mm、630mm和727mm)和纵横比(1.25、1.50、2.00和2.25),研究发现:混凝土强度和截面周长对椭圆钢管混凝土的火灾后界面黏结...     

Experimental study on shear resistance of self-stressing concrete filled circular steel tubes

This paper presents the results of shear tests on 27 self-stressing concrete filled steel tube (SSCFST) specimens and 8 conventional concrete filled steel tube (CFST) specimens. The main parameters in the tests were the self-stress and shear span to depth ratio. The experimental results indicate that the shear capacity of the CFST specimen is lower than that of the SSCFST specimen when 28-day cube strength of concrete core, shear span to depth ratio, yield strength and geometrical dimension of the steel tube are kept the same. The CFST/SSCFST specimen failed in shear when the shear span to depth ratio was smaller than 0.5 and failed in flexure when the shear span to depth ratio was 0.5 or higher. The bond between concrete core and steel tube also affected the shear capacities. Finally, an empirical equation for predicting the shear capacity of a SSCFST short beam is proposed.     

Time-dependent in-plane behaviour and buckling of concrete-filled steel tubular arches

This paper presents a theoretical analysis for the time-dependent behaviour and buckling of concrete-filled steel tubular (CFST) circular arches due to shrinkage and creep of the concrete core under a sustained uniform radial load. The algebraically tractable age-adjusted effective modulus method is used to model the time-dependent behaviour of the concrete core, based on which the differential equations of equilibrium for the time-dependent analysis of CFST arches are derived and analytical solutions for the long-term displacements, stresses and internal forces of CFST arches under the sustained load are obtained. It is shown that the visco-elastic effects of creep and shrinkage of the concrete core have significant long-term effects on the in-plane structural behaviour of CFST arches. The long-term radial and axial displacements, as well as the bending moment, increase substantially with time. For a CFST arch with a low area ratio of the steel tube to the concrete core, the long-term deformations may be excessive and affect the serviceability of the CFST arch. The increases of the long-term stresses in the steel tube with time are significant, while the long-term stresses in the concrete core decrease with time and may change from compressive to tensile if the time is sufficiently long. It is demonstrated that the time-dependent change of the equilibrium configuration of the CFST arch can lead to a buckling configuration being attained in the time domain under a sustained load, which is lower than the buckling loads of the CFST arch under short-term loading. The solution for the possible prebuckling structural life for time-dependent creep buckling of deep CFST arches is derived and can be used to determine the effects of various parameters on the creep buckling of a CFST arch.