平缀管式等截面钢管混凝土格构柱荷载-位移骨架曲线计算方法

基于平缀管式等截面钢管混凝土格构柱在水平低周往复荷载作用下的拟静力试验结果,采用OpenSees建立纤维单元杆系计算模型,对影响此类结构水平荷载-位移骨架曲线的主要因素进行参数分析。采用三折线简化模型模拟水平荷载-位移骨架曲线,通过理论推导或数据统计分析得到了平缀管式等截面钢管混凝土格构柱相关骨架曲线控制参数的简化计算公式,包括:考虑柱肢与缀管剪切变形的弹性阶段刚度的计算公式;基于塑性铰破坏并考虑轴力-弯矩相关曲线的水平峰值荷载的计算公式;基于数据统计分析并考虑实际工程需要的位移延性系数的峰值位移与极限位移的简化计算公式。与拟静力试验、有限元参数分析以及模拟实际结构尺寸扩大参数分析的结果进行的比较表明,三折线简化模型可以有效地模拟平缀管式等截面钢管混凝土格构柱的骨架曲线,相关骨架曲线控制参数的简化计算公式具有较高精度。     

平缀管式等截面钢管混凝土格构柱抗震性能试验与有限元分析

为研究低周反复荷载下平缀管式等截面钢管混凝土格构柱的抗震性能,进行共计7根试件的拟静力试验,重点考察不同柱肢混凝土强度、柱肢纵向间距、缀管竖向间距对此类构件刚度、强度和延性的影响。同时,基于OpenSees平台建立了采用纤维单元的有限元计算模型,对此类钢管混凝土格构柱试件的滞回性能进行数值模拟,模拟结果与试验数据吻合良好。通过对试件破坏过程、荷载位移滞回曲线和骨架曲线等结果的分析表明:钢管混凝土格构柱试件具有良好的抗震性能,破坏形态均以整体压弯破坏为主,得到的水平荷载-位移滞回曲线饱满无捏缩;柱肢混凝土强度主要影响格构柱的承载力,随着混凝土强度等级从C40增加到C60,试件的承载力提高了5.7%;柱肢纵向间距由250 mm加大到650 mm,试件的承载力和位移延性系数分别提高了14.5%和6.8%;缀管竖向间距由200 mm增加到313 mm,试件的承载力和位移延性系数分别降低了12.9%和12.0%。     

圆钢管再生混凝土柱抗震性能与影响因素分析

为了研究圆钢管再生混凝土柱的抗震性能,以再生粗骨料取代率、长细比、轴压比和含钢率为变化参数,设计10个圆钢管再生混凝土柱试件进行低周反复加载试验,观察了其破坏过程及形态,获取其荷载-位移滞回曲线。基于试验实测数据基础,深入分析了各变化参数对强度、刚度、位移延性和耗能系数等抗震性能指标的影响规律。研究结果表明:在破坏形态上,钢管再生混凝土柱与普通钢管混凝土柱相似,均表现为底部钢管鼓曲、混凝土被压碎。钢管再生混凝土柱的滞回曲线饱满,其形状从梭形发展到弓形。钢管再生混凝土柱的各项抗震性能指标能满足现有抗震规范要求,在地震区推广应用钢管再生混凝土柱可行。随着长细比的减小,试件耗能系数减小,而其他抗震性能指标增加。除刚度随轴压比的减小而减小外,其他抗震性能指标对现有的设计参数变化范围并不敏感。试件壁厚优势在强度、弹性阶段刚度和破坏点耗能系数等方面表现较为显著。     

往复荷载作用下钢管混凝土格构式柱地震损伤模型及试验研究

为了解巨型组合结构体系中钢管混凝土格构式柱的地震损伤情况,通过对4根四肢钢管混凝土格构柱低周往复荷载试验,得出了四肢钢管混凝土格构柱在低周往复荷载下的破坏形态和构件损伤特征。在试验分析基础上,对经典的Park-Ang损伤模型进行了修正,提出了适用于四肢钢管混凝土格构柱的损伤指数和耗能因子计算公式;并根据试验现象和各阶段特征,选取了经典的Park-Ang损伤模型、基于能量的损伤模型和改进的Park-Ang模型进行对比研究。结果表明：改进的Park-Ang模型能较好的判断四肢钢管混凝土格构柱的损伤程度,且通过损伤值可将构件损伤划分为是否可修、不可修但未破坏和不可修且将破坏三个阶段,并以损伤值0.4作为划分试件是否可修的界限。     

往复荷载作用下钢管混凝土格构式柱地震损伤模型及试验研究EI北大核心CSCD

为了解巨型组合结构体系中钢管混凝土格构式柱的地震损伤情况,通过对4根四肢钢管混凝土格构柱低周往复荷载试验,得出了四肢钢管混凝土格构柱在低周往复荷载下的破坏形态和构件损伤特征。在试验分析基础上,对经典的Park-Ang损伤模型进行了修正,提出了适用于四肢钢管混凝土格构柱的损伤指数和耗能因子计算公式;并根据试验现象和各阶段特征,选取了经典的Park-Ang损伤模型、基于能量的损伤模型和改进的Park-Ang模型进行对比研究。结果表明:改进的Park-Ang模型能较好的判断四肢钢管混凝土格构柱的损伤程度,且通过损伤值可将构件损伤划分为是否可修、不可修但未破坏和不可修且将破坏三个阶段,并以损伤值0.4作为划分试件是否可修的界限。     

标准火灾作用后矩形钢管混凝土柱剩余承载力的研究

通过对6个矩形截面钢管混凝土柱按ISO-834标准升温曲线升温作用后的试验，研究火灾作用后矩形钢管混凝土柱的力学性能和剩余承载力。结果表明，在本次试验参数范围内，火灾后裸钢管混凝土柱的承载力损失严重。在确定了钢材和混凝土在高温作用后应力~应变关系模型的基础上，本文计算了火灾作用后矩形钢管混凝土压弯构件荷载~变形关系曲线，理论计算结果得到试验结果的验证。在分析了各参数，如火灾持续时间、构件截面含钢率、钢材种类、混凝土强度等级、荷载偏心率、构件长细比、截面高宽比和构件截面尺寸等影响的基础上，本文提出火灾作用后矩形钢管混凝土柱承载力实用计算方法。     

钢管混凝土哑铃形偏压长柱极限承载力研究

以长细比和偏心率为参数,进行了共16根钢管混凝土哑铃形偏压柱的试验。介绍了试验过程和试件的破坏形态,对试件的荷载-变形曲线、极限承载力等进行了分析。试验结果表明:钢管混凝土哑铃形偏压长柱属整体破坏,其极限承载能力和弹塑性阶段的切向刚度随着构件长细比和偏心率的增加而降低。建立了有限元模型,对哑铃形偏压长柱进行了受力全过程和极限承载力分析。分析表明:长细比和偏心率两个参数对钢管混凝土哑铃形偏压柱极限承载力的影响基本上是独立的,可以采用分项系数相乘来考虑二者的共同影响。稳定系数的计算公式可采取与哑铃形轴压长柱相同的计算公式。偏心率折减系数可采用本文通过对试验数据和有限元计算数据的回归拟合出的计算公式。     

钢管混凝土柱火灾后剩余承载力的试验研究

通过对6个圆形截面和6个方形截面钢管混凝土柱按ISO-834和GB9978-88规定的标准升温曲线升温作用后承载力的试验研究,研究钢管混凝土柱在标准升温曲线作用后力学性能和剩余承载力的变化规律。考察了构件长细比和荷载偏心率等因素对承载力损失率的影响。研究结果表明:在本次试验参数范围内,火灾后裸钢管混凝土柱的承载力损失严重,带护保护层的构件次之。在其它条件相同的情况下,与常温下的承载力相比,长细比越大,构件火灾后承载力的损失率越高。荷载偏心率则对火灾后构件承载力的损失率影响不大。本文的研究成果可为有关钢管混凝土工程进行火灾后修复加固时提供参考。     

STS管幕结构抗弯性能试验研究及参数优化

沈阳地铁某车站采用STS（Steel Tube Slab）管幕结构作为初期支护,在施工阶段需承受上覆土压力和路面荷载,其横向承载力对整个工程的安全尤为重要。该文基于6榀STS管幕简支梁的对称集中荷载抗弯试验,研究了STS管幕构件的破坏过程、裂缝开展模式及破坏机理,并对比分析了混凝土强度、钢管间距以及管间横向连接方式对承载力的影响规律。基于ABAQUS建立数值计算模型,进一步研究了钢管壁厚、翼缘板厚度等参数对STS管幕构件承载力的影响规律,并根据计算结果提供了翼缘板厚度与钢管壁厚之比的合理取值范围。研究成果将为STS管幕构件的设计提供参考依据。     

平缀管式钢管混凝土格构柱拟动力试验研究

在平缀管式钢管混凝土格构柱拟静力试验研究的基础上,进行了2个1∶8缩尺模型的拟动力试验,分别采用2008年汶川大地震和1995年日本阪神大地震的地震动时程记录作为输入地震波,研究在不同强度地震和主余震作用下此类结构的变形、强度、刚度、耗能等抗震性能。研究结果表明:平缀管式钢管混凝土格构柱具有良好的抗震性能,在8度多遇、基本、罕遇、极罕遇地震作用下,结构处于弹性工作状态;在9度罕遇地震作用下,钢管混凝土柱肢发生屈服,结构进入弹塑性工作状态;随着地震动峰值加速度的增加,柱底钢管应变急剧增加,柱顶最大响应位移非线性增长;直至试验加载结束,柱肢底部塑性铰区域未形成屈服环,结构无明显破坏。主余震作用加剧了结构的累积损伤,结构的刚度退化现象比较明显,在经历1次9度罕遇主震和2次同等强度的余震作用后,结构弹性阶段刚度相比初始弹性刚度减小约50.0%,最大位移增大约41%。通过钢管混凝土格构柱在各地震工况下的强度与变形的验算,进一步表明此类结构具有足够的强度储备和良好的变形能力,在经历多次强震后仍能保持一定的承载能力,在我国高烈度地区的桥梁工程中具有极大的应用前景。     

仓壁柱承钢筒仓结构行为的研究

仓筒壁直接支承于支柱是小型钢筒仓一种简单、经济的支承方式。采用数值分析方法,包括线性应力分析、线性特征值屈曲分析及几何非线性分析,对这类仓壁柱承钢筒仓的结构行为、特别对其稳定性能进行了系统研究。分析了仓筒径厚比、支柱伸入仓筒的高度、支柱宽度等几何参数对结构性能的影响。研究表明,支柱伸入高度是影响仓壁柱承筒仓屈曲强度的主要因素,屈曲模态也与之密切相关。为提高仓壁柱承筒仓的承载能力,支柱应尽可能地延伸至仓筒的顶部,这种支柱伸至仓顶檐梁的构造可用于大中型筒仓结构。     

Dynamic buckling of elastic–plastic square tubes under axial impact—II: structural response

Dynamic elastic–plastic buckling of thin-walled square tubes is studied from the viewpoint of elastic–plastic stress wave propagation, which originates from an axial impact loading. The influence of the impact velocity and the striking mass on the development of the buckling shape is discussed when considering the transient deformation process. It is shown that the maximum load, which results from a high velocity impact load and occurs at t=0, is a function of the impact velocity and is related to the speed of the elastic–plastic stress waves propagating along the tube. The predictions for the initiation of buckling based on a numerical simulation of the axial impact of strain rate insensitive square tubes using the FE code ABAQUS show good agreement with the results from experiments on aluminium alloy tubes impacted at various initial velocities. A comparison between the buckling initiation in square tubes and geometrically equivalent circular tubes reveals differences in the response, which are attributed to the stress wave propagation phenomena and to the structural differences between the two structures.     

超高模板支架的极限承载能力研究

近年来超高模板支架坍塌事故经常发生,承载力不足是主要原因,该文对模板支架的初始缺陷进行实测,统计分析测量数据,考虑较大的初始弯曲率和不足的钢管壁厚,提出一个新的极限承载力公式;通过非线性有限元理论计算,给出了初始弯曲率和钢管壁厚对极限承载力的影响系数;通过弹性稳定性分析,找出了不同立杆超出顶层水平杆长度下超高模板支架的临界荷载及失稳模态的变化规律,为今后的深入研究打下基础。     

Strength and Failure Modes of Hoop Wound CFRP Tubes Under Compressive High Rates of Loading

A study was undertaken to investigate the response of hoop wound carbon fibre reinforced plastic (CFRP) tubes to dynamic compressive loading at strain rates in the range of 5–200/sec. An experimental rig was designed and built to test short tubular specimens under external radial pressure with minimum end constraints. The load was applied by detonating a small explosive charge inside a water filled, steel, cylindrical chamber enclosing the test specimen. For each test the external pressure and the strains, in both circumferential and longitudinal directions, were recorded on suitable digital processing equipment. Two distinct modes of failure were identified; material and structural (buckling). The mode of failure was dependent on the rate of loading and the tube diameter/thickness ratio. For 100 mm diameter tubes with diameter/thickness=40, buckling failure dominated at strain rates below 10/s. However, at higher strain rates, material failure and a considerable enhancement in burst strength was observed. For 100 mm diameter tubes, with diameter/thickness=80, a buckling mode of failure was in evidence in all the tests, irrespective of the rate of loading.R. Ahmad: Presently at School of Mechanical Engineering, University Sains Malaysia, Pulau Pinang, Malaysia.     

Stimulating Equivalent Geometric Imperfections for the Numerical Buckling Strength Verification of Axially Compressed Cylindrical Steel Shells

A geometrically and materially nonlinear analysis with imperfections included (GMNIA) is currently the most sophisticated and perspectively the most accurate method of a numerical buckling strength verification. By this way, equivalent geometric imperfections, which have to cover the influence of all deviations from the nominal data of the resistance parameters, are fundamental. The problem of consistent equivalent geometric imperfections includes the problems of their shape and size. It is recommended to start from the failure modes of the perfect structure in order to get imperfection patterns, which are unfavourable with respect to buckling resistance, relevant referring to manufacture and easy to use. The influence of the imperfection length is not sufficiently attended in the present design codes. It is proposed to use the full wave length of the ideal ring buckling mode as the imperfection length of the equivalent geometric imperfection for the basic buckling case of the axially compressed cylindrical shell. Finally, proposals are made for consistent equivalent geometric imperfection amplitudes of this buckling case.     

横肋波纹钢板-方钢管混凝土组合柱双向偏压力学性能研究及承载力计算

为研究横肋波纹钢板-方钢管混凝土组合柱的双向偏压力学性能,对两根横肋波纹钢板-方钢管混凝土组合柱试件展开了双向偏压加载试验,探究了不同偏心距对试件在双向偏压荷载下的荷载-变形曲线、破坏模态和截面应变发展状况的影响,分析了波纹板与钢管、混凝土之间的相互作用机理.在试验基础上运用有限元模拟,分析了偏心距、加载角度、钢管厚度...     

Q420焊接圆钢管轴心受压稳定性能试验和设计方法研究

该文进行了15个Q420高强度钢材埋弧焊接圆钢管柱轴心受压试验研究,基于试验结果总结了其失稳变形特征,分析比较了15个试件的稳定系数与我国规范柱子曲线计算值的关系,并验证了有限元模型的可靠性。基于有限元参数分析计算结果,对比60个试件的稳定系数与我国规范柱子曲线计算值的关系,对Q420高强度钢材埋弧焊接圆钢管的整体稳定设计方法提出两种建议:一是对于我国规范柱子曲线选择的建议,即对于Q420埋弧焊接圆钢管可以按a类截面计算其稳定承载力;二是更新我国柱子曲线整体稳定系数φ的计算参数α₁、α₂、α₃,建议了一条新的设计曲线。     

Stochastic simulations of square aluminium tubes subjected to axial loading

Stochastic simulations of square aluminium tubes of 6060 T6 aluminium alloy subjected to axial crushing have been performed and compared to an experimental program carried out previously at SIMLab. The main variables during testing were the extrusion length, the wall thickness of the extrusions and the impact velocity of the impactor. Three different buckling modes were observed: progressive buckling, transition from progressive to global buckling and global buckling. Progressive buckling was primarily observed in the short specimens, while increasing the length a transition mode took place. However, for the thick-walled tubes a direct global buckling mode was found. In the present study, it has been investigated if geometric imperfections modelled by assumed Gaussian random fields could explain the experimentally observed behaviour. Variation of the random field parameters by use of a factorial design resulted in variations in especially the buckling modes and consequently the average force, and the same buckling modes found in the experiments were obtained in the simulations. For the chosen model, the shape of the geometric imperfections seemed to be more important than the amplitude. Further, simulations of profiles with three different lengths subjected to impacts at two different velocities were performed. The estimated probability for progressive buckling to appear decreased as the length increased, while the change in velocity had minor effects for the chosen parameter range.     

Q420高强度等边角钢轴压构件整体稳定性能设计方法研究

为研究Q420高强度等边角钢轴压构件的整体稳定受力性能与设计方法, 该文采用有限元软件ANSYS建立数值模型, 并经与试验结果对比验证后进行了大量参数分析, 研究了构件几何初始缺陷、残余应力和钢材屈强比对该类轴压构件整体稳定性能的影响, 分析了已有设计方法的适用性。结果表明, 构件初始缺陷对其稳定性能的影响与构件长细比及失稳模态有关, 残余应力的影响与构件长细比有关, 钢材屈强比的影响较小。基于数值计算结果建议了Q420高强度等边角钢轴压构件考虑板件局部屈曲相关作用的整体稳定设计方法, 为补充和完善我国钢结构设计规范提供了参考, 同时也有利于促进高强度钢材在我国钢结构工程中的应用。     

Energy absorption of an axially crushed square tube with a buckling initiator

Axially crushed thin-walled square tubes have been widely used as energy absorbers because of their high specific energy absorption capacity and long stroke. However, they render extremely high initial peak forces which may cause serious injury or damage to the people or structures being protected. This paper proposes a novel idea that by installing a buckling initiator near the impact end which is composed of a pre-hit column and pulling strips, the initial peak force of the square tube could be greatly reduced while its deformation mode and excellent energy absorption are retained. Both experimental and numerical investigations are conducted on aluminum alloy square tubes. The peak force, mean force and half-length of a fold of the tested specimens are examined. The results show that the mean crushing force and deformation mode are not affected by the buckling initiator, while the reduction of the peak force strongly depends on the pre-hit height. It is also found that the buckling initiator can ensure the deformation more stable and uniform. Finally, a simplified analytical model is developed to study the relationship between the reduction of the peak force and the geometric imperfections; and the model can successfully predict the effectiveness of the buckling initiator.