690MPa高强钢薄壁方形截面轴压构件承载力直接强度法研究

与有效宽度法和有效屈服强度法相比,直接强度法更简单.采用ANSYS有限元软件建立模型分析了名义屈服强度fv为690MPa高强钢薄壁方形截面轴压构件的极限承载力,并和直接强度法、修正的直接强度法相比较.主要参数:板件宽厚比b/t=23,30,40,50和60;构件长细比λ=20,30,40,50,60,70,80和90.研究结果表明:对fy=690MPa的薄壁方形截面(b/t＞20)轴压构件,采用直接强度法和修正直接强度法计算时,其稳定系数采用《钢结构设计标准》(GB 50017-2017)中的a类曲线;对长细比70≤λ≤90的构件,3种方法均偏保守;对长细比20≤λ＜70的构件,在大部分宽厚比范围内,Kwon等提出的修正直接强度法能较好地预测有限元计算结果,直接强度法偏于不安全,Shen Hongxia提出的修正直接强度法偏安全.     

L形截面部分包覆钢-混凝土组合柱弱轴压弯整体稳定

为了研究L形截面部分包覆钢-混凝土组合(PEC)柱的压弯稳定性能，对L形截面PEC柱进行了弱轴压弯试验和有限元分析。试验研究中设计并制作了3个L形PEC柱试件，变化参数为长细比和偏心距。试验结果表明：截面形状和主钢件分布的几何非对称性，以及混凝土材料拉压强度的非对等性，造成L形PEC柱在受力后截面中和轴的偏转，导致构件发生弯扭变形。有限元分析表明，L形截面的肢背或肢端受压对构件承载力有一定影响；长细比较小(即长细比为10～30)时，肢背受压的构件轴力-弯矩相关曲线具有大小偏心分界的特征，但长细比较大(即长细比大于60)时，整体失稳成为控制破坏模式，相关曲线向原点内凹。建议了L形PEC柱绕弱轴压弯时的整体稳定承载力计算公式，与试验和有限元参数分析结果对比表明：当长细比小于60时，建议公式可以适用，当长细比大于80时，建议公式偏不安全，需进一步改进后才能用于工程设计。     

冷弯箱形组合截面长细比的计算

根据AISIS100-2007规范D1.2对由2种截面组成的受压构件(其屈曲模式与连接处剪力大小有关)的有关规定,其抗压承载力必然降低,应用修正长细比(KL/r)m替代原长细比KL/r。修正长细比考虑了连接焊缝间距及组件最小回转半径的影响。基于D1.2截面规定,必须确定焊接箱形组合构件承载力的降低程度。进行了48组试验,研究不同焊缝间距下(100～900mm),刚性及柔性端约束时,由2个C形截面组成的箱形截面受压构件的性能。试件长度为900mm,截面尺寸为100mm×100mm。其中24个试件厚度为1.5mm,其余试件厚度均为2.0mm。试验表明:除焊缝间距为900mm及柔性端约束条件下,极限抗压承载力总体上都没有降低,AISIS100-2007中考虑的极限承载力降低不适用于这些杆件。     

GFRP管防屈曲加固槽钢构件轴压性能试验研究

基于传统防屈曲耗能支撑构件设计理念,通过对三种长细比、两种加固形式的槽钢单轴对称截面钢构件进行轴心受力性能试验研究,分别得到了9个试件的变形形态和失效模式。初步试验研究表明:相对于未加固的传统纯钢构件,GFRP管防屈曲加固槽钢构件明显改善了槽钢构件的延性和峰值变形能力,加固后试件抗压极限承载力提高了10%~62%。本文通过多种屈曲失稳理论公式对比,完善了FRP管防屈曲加固钢构件轴压稳定性能的计算公式。     

内配型钢圆钢管混凝土压扭构件工作机理研究

采用ABAQUS有限元软件建立了内配型钢圆钢管混凝土压扭构件的有限元模型,利用已有试验数据验证了模型的可靠性。在截面含钢率不变的情况下,分析了3组钢管混凝土与内配型钢圆钢管混凝土极限承载力及扭矩分配的对比情况。通过对典型试件的分析,研究了内配型钢圆钢管混凝土各部件之间的接触应力分布规律、各部件的破坏模态及型钢对混凝土的影响规律。最后分析了加载路径、长细比、型钢截面形式以及轴压比对构件荷载-位移曲线的影响规律。结果表明:内配型钢圆钢管混凝土中钢管、混凝土及型钢三者之间可以很好地协调工作。钢管含钢率是影响构件承载力最主要的因素,加载路径、长细比以及型钢的截面形式对构件的承载力几乎没有影响,构件的极限承载力随轴压比的增大而增大,当轴压比大于0.4~0.5(对应不同强度等级材料)时,构件的极限承载力随着轴压比的增大而降低。     

方钢管混凝土柱耐火极限影响因素分析

研究了方形截面钢管混凝土柱的耐火性能 ,分析了材料强度、构件截面含钢率、截面尺寸、构件长细比及荷载偏心距、保护层厚度等参数对构件耐火极限的影响。结果表明 ,材料强度、构件截面含钢率、荷载偏心距对方形截面钢管混凝土柱耐火极限的影响不大 ;截面尺寸、构件长细比对方形截面钢管混凝土柱耐火极限的影响较大 ,且截面尺寸越大 ,构件耐火极限越长 ,长细比越大 ,构件耐火极限越短。并指出可以通过涂以一定厚度的防火涂料保证方形截面钢管混凝土柱达到要求的耐火极限     

矩形钢管高强混凝土中长柱轴压构件的试验研究与理论分析

进行了 10根矩形截面钢管高强混凝土中长柱轴压构件的试验研究 ,目的是分析长细比、含钢率和截面长宽比对中长柱轴压构件的影响。同时 ,采用数值分析的方法 ,编制了适用于矩形钢管高强混凝土轴压构件的非线性计算程序 ,理论分析结果和试验结果进行了对比 ,两者吻合较好。在此基础上 ,利用所编制的非线性分析程序 ,分析了含钢率、钢材屈服强度、混凝土强度和截面长宽比等因素对轴压构件长细比 -稳定系数相关曲线的影响。研究结果表明 :构件的稳定承载力主要和长细比有关 ,随着长细比的增大迅速降低 ;截面长宽比在 1 0～ 1 6的范围内变化时 ,对稳定系数和相对跨中挠度的影响很小。     

钢管-型钢混凝土柱耐火性能有限元分析

随着建筑结构的发展,钢混结构作为现代装配式建筑的主要形式之一,其耐火性能对建筑结构的整体能力影响重大。根据已有的试验研究,利用有限元分析软件ABAQUS构建了钢管-型钢混凝土柱的热-力耦合本构模型,分析了在ISO-834标准升温曲线下不同轴压比、偏心率、长细比和截面边长对钢管-型钢混凝土柱耐火极限的影响。模拟结果表明：构件耐火极限随着轴压比、偏心率和长细比的增加而降低;而在相同受火和荷载条件下,构件耐火极限随着截面边长的增加而增加。     

方中空夹层钢管混凝土构件压扭性能试验研究

为研究方中空夹层钢管混凝土构件在压扭共同作用下的力学性能,以截面尺寸及轴压比为参数,对12根中空夹层钢管混凝土进行压扭静力试验,同时建立有限元模型分析材料强度及长细比对构件承载力的影响.结果 表明:当轴压比较小(n＜0.5)时,轴压比对抗扭承载力影响不大,进入塑性阶段后,扭矩-转角曲线出现明显的屈服平台,且承载力仍有小幅度的上升,构件具有良好的延性.当轴压比较大(n＞0.5)时,抗扭承载力随轴压比的增大而明显减小,当n=0.6时,抗扭承载力已减小为纯扭时抗扭承载力的70％,进入塑性阶段后,承载力急剧下降,构件延性较差,呈现出完全不同的破坏模式.此外,外钢管强度对构件抗扭承载力影响较大,混凝土强度对构件承载力影响较小.抗扭刚度随长细比的增大而明显降低,但承载力受长细比的影响并不明显.     

高强钢薄壁箱形截面压弯构件极限承载力研究

利用数值模拟方法分析了18Mn2Cr Mo BA高强钢薄壁箱形截面(由槽形钢板对焊而成)压弯构件的极限承载力,研究了长细比、翼缘宽厚比、截面边长比3个参数对薄壁箱形截面构件极限承载力的影响。在数值模拟计算和对轴心受力、受弯构件研究的基础上,提出了适用于18Mn2Cr Mo BA高强钢薄壁箱形截面压弯构件极限承载力的计算方法。研究结果表明:随着长细比的增大,弯矩-轴力相关曲线由上凸变为下凹,翼缘宽厚比、截面边长的增大都会降低构件极限承载力,各参数之间相互影响。提出的建议计算方法与有限元计算结果符合较好。     

Curved concrete filled steel tubular (CCFST) built-up members under axial compression: Experiments

A series of tests on curved concrete filled steel tubular (CCFST) built-up members subjected to axial compression is described in this paper. Twenty specimens, including 18 CCFST built-up members and 2 curved hollow tubular built-up columns, were tested to investigate the influence of variations in the tube shape (circular and square), initial curvature ratio (β_r, from 0 to 7.4%), nominal slenderness ratio (λ_n, from 9.9 to 18.9), section pattern (two main components, three main components and four main components), as well as brace pattern (battened and laced) on the performance of such composite built-up members. The experimental results showed that the ultimate strength and stiffness of CCFST built-up specimens decreased with increasing β_r or λ_n. Different load-bearing capacities and failure modes were obtained for the battened and laced built-up members. A simplified method using an equivalent slenderness ratio was suggested to calculate the strength of CCFST built-up members under axial compression.     

轴心受压钢管混凝土曲杆的试验研究

进行了18组轴心受压钢管混凝土曲杆的试验,研究了管截面形状(圆形、方形)、初始位移(0～30mm)及长细比(20和60)对曲杆性能的影响。分析钢管混凝土曲杆的性能和破坏模型,并与无初始应变的偏心受压普通钢管混凝土比较。采用有限元模型,分析了轴心受压下钢管混凝土曲杆的全范围荷载-位移曲线。最后,将试验结果与AIJ-2008、AISC-2005、BS5400-2005、DBJ/T13-51-2010、EC4-2005等现行规范进行对比分析。     

Effect of chord configuration and spacing on cyclic flexural response of built-up columns

As per the current codes of practice, the design of battens of a built-up steel column depends on the level of axial load. These columns may not reach their plastic moment capacities under the lateral loading due to the premature instability of main chords in the expected plastic hinge regions. In this study, the cyclic performance of built-up battened columns is analytically evaluated under the gradually-increasing lateral displacements and the constant axial loads using a finite element software ABAQUS. The main parameters varied are the chord spacing, the column slenderness ratio, the level of axial load, and the chord configuration. Ninety-eight FE models of battened columns are analysed in this study in which the hot-rolled steel channel or I-Sections are used as the main chords. The analytical results showed that the built-up columns made up from I-sections have better lateral strength and ductility as compared to the Channel sections for nearly same values of axial load and slenderness ratio. Based on the analytical results, the limiting values of chord spacing, slenderness ratio and level of axial loads are proposed in order to delay the effect of instability on their lateral load resistance. Further, the interaction between axial load-moment capacity of built-up columns is discussed for various types of chord configurations.     

四肢拼合冷弯薄壁型钢截面立柱轴压性能试验研究及数值分析

对不同长细比的8根四肢拼合冷弯薄壁型钢截面立柱的轴压性能进行试验研究,在试验研究的基础上建立考虑材料、几何和接触非线性的有限元模型,并通过对试验试件的数值模拟,验证有限元方法的正确性。采用数值方法分析长细比、连接螺钉间距、截面翼缘宽厚比对四肢拼合冷弯薄壁型钢截面立柱轴压性能的影响。结果表明:试件最终破坏均呈现局部屈曲和畸变屈曲的破坏模式;四肢拼合冷弯薄壁型钢截面立柱的轴压性能具有"1×4≥4"的拼合效应;随着长细比的增大,四肢拼合立柱的最大承载力和刚度逐渐降低;当螺钉间距在150～450mm之间变化时,四肢拼合立柱的最大承载力和刚度变化不大;减小四肢拼合立柱截面的翼缘宽厚比,可以显著提高其最大承载力。     

冷弯薄壁型钢四肢拼合立柱轴压承载力设计方法

建立了考虑材料、几何和接触非线性的有限元模型,在对冷弯薄壁型钢四肢拼舍截面立柱的轴压性能试验试件进行模拟分析,验证有限元方法正确性的基础上,对考虑长细比、截面翼缘宽厚比等因素的一系列试件进行了数值分析,并得到其轴压承载力.在相关规范“有效宽度法”和“直接强度法”的基础上,提出了冷弯薄壁型钢四肢拼合截面立柱轴压承载力的设...     

Analytical investigation of cyclic behavior of laced built-up columns

In this research, 18 laced built-up columns with various geometric specifications were analyzed under different levels of axial load and cyclic lateral load using the finite element method. This research was performed as a continuation of the experimental investigation on the cyclic behavior of the laced columns. This study evaluated the effects of column's geometrical parameters and various levels of axial loads on the cyclic behavior of laced columns. A compression of the results shows that there is generally good agreement between the experimental and analytical results. The analytical results showed that as the axial load increased, the ductility of the laced columns decreased significantly. Further, at high levels of axial load (i.e., loads higher than 50% of the columns' compressive capacity), ductility was very poor. It was found that during lateral loading there is a bending moment in addition to the axial force in the lacing bars and the main chords, which affects the columns' behavior. The slenderness ratio of the main chords between the connecters and the shape of the cross-section of the lacing bars (i.e., bending strength of the lacing bars) are the main geometrical parameters affecting the laced columns' ductility.     

带开孔损伤钢管混凝土轴压性能试验研究

为了研究开孔损伤钢管混凝土的力学性能,对14根开孔损伤钢管混凝土构件进行轴压试验研究,考虑开孔损伤率、混凝土强度等级、长细比等变化参数,观察试件的受力全过程及破坏形态,获取开孔损伤钢管混凝土的破坏机理、荷载-变形以及应力-应变曲线,分析开孔损伤率、混凝土强度等级、长细比等变化参数对开孔损伤钢管再生混凝土承载能力及变形性能的影响。研究结果表明:开孔损伤钢管混凝土构件加载后期延性较好,其破坏形式大多为钢管鼓曲后撕裂破坏,开孔损伤率对试件的破坏形态和极限承载力有着不同程度的影响。最后对带损伤钢管混凝土的承载能力计算方法进行探讨,利用现有普通钢管混凝土规范方法进行计算,结果表明,在开孔损伤率(小于0.8%)不大的情况下,现有钢管混凝土规范方法计算结果还是安全的。     

Ultimate capacity of battened columns composed of four equal slender angles

Cold-formed steel structural members play a great role in modern steel structures due to their high strength and light weight. The behavior and strength of battened column members composed of slender angle sections are mainly governed by local buckling of angle legs or torsional buckling of the angle between batten plates. Moreover, local buckling depends on the interaction between the width–thickness ratio of angle leg, overall slenderness ratio of angle between batten plates and overall slenderness of column. Theoretical study has been carried out by a nonlinear material and geometrical finite element model. Numerous cases of slender battened column sections having different width–thickness angle leg ratios, overall slenderness ratios between batten plates and overall slenderness ratios are chosen in this study. Complete ultimate strength curves are drawn and different failure modes are studied by taking different member lengths, which produce local or torsional buckling of single angles between batten plates or overall buckling of the member. Empirical equations for the effect of shear deformation factor and the ultimate axial load capacities of members formed of battened slender angle sections are proposed. Strengths of axially loaded battened members predicted using finite element as well as the proposed empirical equations is compared with the design strengths obtained using North American and European codes. It is concluded that the design strengths predicted by North American and European codes are generally conservative, and these design rules have been shown to be reliable using reliability analysis.     

四肢圆钢管混凝土格构柱恢复力模型研究

为了探究钢管混凝土格构柱的弹塑性地震反应以便进行构件非线性理论分析,对2根四肢圆钢管混凝土格构柱进行了低周反复加载试验,并收集了12根四肢圆钢管混凝土格构柱低周反复荷载作用下的试验资料。通过理论分析及试验结果回归分析,提出了钢管混凝土格构柱的退化三折线恢复力模型,确立了构件轴压比、等效长细比及材料比例系数等主要参数与模型之间的关系,并将模型计算结果与试验结果进行了对比分析。结果表明:计算结果和试验结果吻合较好,且该恢复力模型计算方法简单,便于进行结构地震反应分析及工程应用。     

Investigation on slenderness ratios of built-up compression members

This study provides a direct experimental verification of the AISC slenderness ratio formulas for built-up compressive members. The comparison on various code-specified slenderness ratios or provisions, which used in the AISC-ASD, AISC-LRFD, AS-4100, and CSA S16-01, are presented. The 0.75 rule, which states that the slenderness ratio of component element of built-up member should not exceed three-fourths times the governing slenderness ratio of built-up member, seems justified according to the tests. The governing slenderness ratio of built-up member could be either the modified or the unmodified one — as specified in the AISC Specifications. The test results indicate that the built-up members with component slenderness ratio of 0.75 to 1.0 times the governing slenderness ratio (modified or unmodified) could also furnish a quite encouraging design outcome. The use of separation ratio (α) in built-up compression members results in the decrease of design strength when compared to one with no use of separation ratio.