Finite element analysis on the collapse of infill walls with holes and different length-to-height ratios

Wenchuan earthquake damage survey displayed the major structures of buildings suffered only small damages,but it was common that infill walls suffered heavy damages or even collapse. To study the failure forms and collapse mechanism of infill walls in an earthquake,the influence of opening or length-to-height ratio on shake-resisting capability of filling walls was analyzed,and measures to improve the anti-collapse ability of infill walls were put forwaed. The numerical simulations on collapse process in earthquake were carried out by using ABAQUS software. We used 5 single story and single span models. It is revealed that the rigidity and compressive capacity of infill walls are reduced because of the infill walls with holes and the increases of length-to-height ratios. Adding constructional columns and horizontal beams can ensure structural integrity and improve the anti-collapse ability of the wall.

Change of the mode of failure by interface friction and width-to-height ratio of coal specimens

Bumps in coal mines have been recognized as a major hazard for many years. These sudden and violent failures around mine openings have compromised safety, ventilation and access to mine workings.Previous studies showed that the violence of coal specimen failure depends on both the interface friction and width-to-height（W/H） ratio of coal specimen. The mode of failure for a uniaxially loaded coal specimen or a coal pillar is a combination of both shear failure along the interface and compressive failure in the coal. The shear failure along the interface triggered the compressive failure in coal. The compressive failure of a coal specimen or a coal pillar can be controlled by changing its W/H ratio. As the W/H ratio increases, the ultimate strength increases. Hence, with a proper combination of interface friction and the W/H ratio of pillar or coal specimen, the mode of failure will change from sudden violent failure which is brittle failure to non-violent failure which is ductile failure. The main objective of this paper is to determine at what W/H ratio and interface friction the mode of failure changes from violent to non-violent. In this research, coal specimens of W/H ratio ranging from 1 to 10 were uniaxially tested under two interface frictions of 0.1 and 0.25, and the results are presented and discussed.

An Experimental and Numerical Thermal Flow Analysis in a Solar Air Collector with Different Delta Wing Height Ratios

This study conducts both numerical and empirical assessments of thermal transfer and fluid flow characteristics in a Solar Air Collector(SAC)using a Delta Wing Vortex Generator(DWVG),and the effects of different height ratios(Rh=0.6,0.8,1,1.2 and 1.4)in delta wing vortex generators,which were not considered in the earlier studies,are investigated.Energy and exergy analyses are performed to gain maximum efficiency.The Reynolds number based on the outlet velocity and hydraulic diameter falls between 4400 and 22000,corresponding to the volume flow rate of 5.21–26.07 m^(3)/h.It is observed that the delta wing vortex generators with a higher height ratio yield maximum heat transfer enhancement and overall enhancement ratio.The empirical and numerical findings demonstrate that the exergy and thermal efficiencies decline in a specific range.TheNusselt number,pressure drop,energy,and exergy efficiencies enhance with rising Reynolds number,although the friction coefficient diminishes.The maximum heat transfer enhancement is 57%.According to the evaluation of exergy efficiency,the greatest efficiency of 31.2%is obtained at Rh=1.4 and Reynolds number 22000.

Stress-strain-acoustic responses in failure process of coal rock with different height to diameter ratios under uniaxial compression

Residual coal pillars play an important role in mining the adjacent coal seam safely,managing the gobs and maintaining the stability of abandoned coal mines.The height to diameter ratio(H/D)affects the stability of residual coal pillars.In this study,uniaxial compressive tests of coal specimens with five H/D(2.0,1.5,1.0,0.8 and 0.6)were performed,and the stress,strain and acoustic emission(AE)were monitored.Results show that the uniaxial compressive strength(UCS)and peak strain increase with H/D decreasing.An empirical equation is proposed to calculate the UCS based on the H/D.The AE activities during coal failure process can be separated into four periods.The span of quiet period and rapid decline period shorten with H/D decreasing.The smaller the H/D is,the more complicated the failure characteristics of coal will be.The failure form of coal with H/D of 2.0,1.5,and 1.0 is primarily shear failure,while splitting failure along the axial direction is the mainly mode when H/D is 0.8 or 0.6.The initiation,expansion,aggregation and connection of micro-cracks can be reflected by the real-time spatial evolution of AE event points.

Rational cutting height for large cutting height fully mechanized top-coal caving

Large cutting height fully mechanized top-coal caving is a new mining method that improves recovery ratio and single-pass production. It also allows safe and efficient mining. A rational cutting height is one key parameter of this technique. Numerical simulation and a granular-media model experiment were used to analyze the effect of cutting height on the rock pressure of a fully mechanized top-coal caving work face. The recovery ratio was also studied. As the cutting height increases the top-coal thickness is reduced. Changing the ratio of cutting to drawing height intensifies the face pressure and the top-coal shattering. A maximum cutting height exists under a given set of conditions due to issues with surrounding rock-mass control. An increase in cutting height makes the top-coal cave better and the recovery ratio when drawing top-coal is then improved. A method of adjusting the face rock pressure is presented. Changing the cutting to drawing height ratio is the technique used to control face rock pressure. The recovery ratio when cutting coal exceeds that when caving top-coal so the face recovery ratio may be improved by over sizing the cutting height and increasing the top-coal drawing ratio. An optimum ratio of cutting to drawing height exists that maximizes the face recovery ratio. A rational cutting height is determined by comprehensively considering the surrounding rock-mass control and the recovery ratio. At the same time increasing the cutting height can improve single pass mining during fully mechanized top-coal caving.

Dynamics and Wheel's Slip Ratio of a Wheel-legged Robot in Wheeled Motion Considering the Change of Height

The existing research on dynamics and slip ratio of wheeled mobile robot （WMR） are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS- Ⅱ. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS- Ⅱ in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified, Moreover, the relative horizontal motion between fore/hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore/hind wheels become larger/smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.

Research on the squeeze cast technology of the castings with large ratio of height to thickness

The squeeze cast technology is only applicable, at present, to the castings with a ratio of height to thickness less than 3.5. Researching the squeeze cast technology for castings with a large ratio of height to thickness will broaden the applicable range of the advanced casting technology. This paper describes a study of the temperature distribution during solidification for castings with a ratio of height to thickness of 7 by the methods of experiment and computer simulation. The shrinkage porosity distribution in the castings and the mechanical properties of the castings were also researched. The experimental and simulated results show that increasing squeeze force, or enhancing mold temperature, cannot reduce the shrinkage porosities in the castings. When castings solidify in a sequential manner and the squeeze force effectively acts on the surface of the liquid metal, the shrinkage porosities in the castings are eliminated and mechanical properties are clearly improved.

宽高比对煤柱型冲击地压影响规律的实验研究

我国深部煤炭开采日趋复杂,区段煤柱在采动、构造或坚硬顶底板影响下极易诱发煤柱型冲击地压,煤柱型冲击地压的防治已成为煤矿安全高效开采的难题,研究不同宽高比条件下区段煤柱的力学性能及冲击破坏特性对煤柱型冲击地压防治具有积极意义。采用不同宽高比煤样的“岩-煤-岩”组合体进行了单轴压缩实验,通过分析煤岩组合体的冲击倾向性、动态破坏特征、分形维数和声发射特征参数等,研究了宽高比对煤柱冲击破坏的影响规律。结果发现:①煤柱的宽高比对煤岩组合体的冲击倾向性具有显著影响,宽高比不小于2∶1时,其冲击能量指数K_(E)为1.82~2.65,冲击倾向性无明显变化;小于2∶1时冲击倾向性呈先升高后降低的趋势,1∶1时K_(E)最大,达到了15.43。②随宽高比减小,煤岩组合体破坏特征依次表现为:拉压破坏—压剪破坏—拉剪破坏。煤柱宽高比为5∶1~3∶1时,煤岩组合体破坏较为缓慢;宽高比为2∶1时开始出现片状煤屑弹出,冲击破坏剧烈程度较低;宽高比为1∶1和0.75∶1时,具有明显的冲击破坏特性;宽高比为0.5∶1时,煤岩组合体整体稳定性下降,相对0.75∶1煤岩组合体煤柱破坏的剧烈程度降低。③峰后声发射能量释放率与分形维数D变化规律相似,均随宽高比减小呈先升高后降低的趋势。宽高比不小于2∶1时,煤岩组合体破坏过程中能量持续释放时间较长,煤柱破坏平缓;宽高比为1∶1时,能量释放率和D值明显增大,相较宽高比不小于2∶1煤岩组合体的能量释放率增大了约4倍,D值增大了0.18~0.23,煤柱冲击破坏最为剧烈;宽高比0.75∶1煤岩组合体能量释放率与D值分别降低了约10%和0.01,破坏剧烈程度与1∶1煤岩组合体相近;宽高比减小至0.5∶1时,相关参数的降低幅度约为0.75∶1煤岩组合体的6倍,破坏剧烈程度相对较小。研究表明:宽高比对煤柱的冲击破坏具有显著影响,整体上,煤柱冲击破坏剧烈程度随宽高比减小(5∶1~0.5∶1)呈先升高后逐渐降低的趋势;煤柱宽高比大于3∶1时,煤柱冲击危险性相对较小,煤柱宽高比为1∶1和0.75∶1时冲击危险性较大,0.5∶1次之。

老年高血压人群腰围身高比与新发脑梗死的关系

目的研究腰围身高比(WHtR)与老年人新发脑梗死的相关性。方法纳入开滦地区研究人群9096例老年高血压患者,以首次发生脑梗死为终点事件,采取前瞻性队列研究方法进行研究,依据观察对象WHtR值以0.05为间距等距分为四组,分别为G1组(WHtR<0.45)、G2组(0.45≤WHtR<0.50)、G3组(0.50≤WHtR<0.55)及G4组(WHtR≥0.55),用寿命表方法统计各人群的累积终点事件发生率,采用Cox比例风险分析方法,探讨WHtR在新发脑梗死中的作用。模型一为单一因子Cox比例风险分析模式,只考察WHtR对脑梗死发生风险的作用;在此基础上,模型二为校正性别、年龄、体重及血清超敏C反应蛋白、收缩压、血清甘油三酯、抽烟史、血清空腹血糖、饮酒情况、高密度脂蛋白胆固醇、舒张压、体育运动、低密度脂蛋白胆固醇、文化程度、服降压药史后观察WHtR对新发脑梗死的作用。结果随访时间为(9.3±2.7)年,期间共新发脑梗死848例。以G2组为对照,单因素Cox比例风险回归模型分析显示G1组、G3组和G4各组发生脑梗死的HR(95%CI)分别为1.00(0.67~1.50)、1.29(1.05~1.60)、1.36(1.12~1.66);多因素Cox比例风险回归模型分析显示G1组、G3组和G4各组发生脑梗死的HR(95%CI)分别为1.09(0.72~1.65)、1.24(0.99~1.54)、1.31(1.05~1.62)。结论老年高血压人群当0.45≤WHtR<0.50时脑卒中发病风险最低,WHtR≥0.55与新发脑梗死风险增加相关。

水稻秸秆拆解工艺参数优化及纤维自交织结构

大尺寸高长径比纤维是影响非织造秸秆纤维生态毯质量的关键。机械揉搓是获得高长径比纤维的最佳处理技术工艺。该研究探究了揉丝机主轴转速和锤齿间隙对不同含水率秸秆纤维拆解揉丝的影响,其工艺参数为主轴转速、锤齿间隙及物料含水率,指标输出为秸秆丝化率与标定单位生产率,并对纤维自交织结构特性进行评价。结果表明,采用Box-Behnken响应面法(response surface method,RSM)开发了一个可确定输入和输出参数间的函数,2种评价指标模型均具有较高的可信度,决定系数分别为R^(2)>0.95,R^(2)>0.84。优化数学模型工艺参数:含水率41.2%,主轴转速2498 r/min,锤齿间隙12.84 mm组合下秸秆丝化率达96.93%,标定单位功率生产率为29.33 kg/(kW?h)。大尺寸高长径比秸秆纤维长度>70 mm和长宽比>80比例增幅分别达120.55%和16.01%,有效改善纤维自交织能力,所开发的RSM模型秸秆的实际揉搓拆解丝化率达96.27%,加工成本降低27.50元/t,可广泛应用于生产大尺寸纤维秸秆基高值农用制品。该研究为生物质秸秆的有效循环利用和高值化材料产业的绿色可持续发展提供重要依据和技术支撑。

木屑颗粒堆积参数对液体渗流特性的影响规律

为了探究木屑颗粒堆积参数对液体渗流特性的影响规律,参照达西渗流实验,设计开发了渗流实验系统,选取颗粒床层湿度、渗流速度、床层储水量及透水率作为评价颗粒床层内液体渗流特性的指标,在对各因素进行初步筛选的基础上,实验研究木屑颗粒堆积床层的粒径分布、压缩高度比以及渗透压力(注水量)对液体渗流特性的影响.实验结果表明,相同粒径分布,注水量为1500 mL时,压缩高度比从0.80降到0.50,木屑颗粒床层湿度变化幅值为3.32%;相同粒径分布,压缩高度比为0.50,注水量从1500 mL增加到3000 mL时,木屑颗粒床层湿度变化幅值为2.30%;相同压缩高度比和注水量,全粒径分布、不同级配粒径分布及小粒径分布时木屑颗粒床层最大湿度分别为54.4%、54.0%及53.7%,变化幅值为0.7%.在本文研究范围内,压缩高度比对颗粒床层湿度影响最大,初始注水量次之,颗粒级配影响最小.相同粒径分布,注水量为2000 mL时,压缩高度比从0.80降到0.50,木屑颗粒床层渗流速度变化幅值为18.92×10^(-4) m/s;相同粒径分布,压缩高度比为0.50,注水量从1500 mL增加到3000 mL时,木屑颗粒床层渗流速度变化幅值为1.08×10^(-4) m/s;相同压缩高度比和注水量,全粒径分布、不同级配粒径分布及小粒径分布时木屑颗粒床层最大渗流速度分别为20.7×10^(-4) m/s、15.4×10^(-4) m/s及18.2×10^(-4) m/s,变化幅值为5.3×10^(-4) m/s.在本文研究范围内,压缩高度比对颗粒床层渗流速度影响最大,颗粒级配次之,初始注水量影响最小.综合各类因素考虑,不同粒径级配的木屑颗粒床层,压缩高度比为0.70、注水量为2000 mL时木屑颗粒床层中的液体渗流特性较好,此时,床层湿度为52.5%,平均渗流速度为9.86×10^(-4) m/s,床层储水量为1149 mL,床层透水率为42.56%.相关结果可为后续可压缩性颗粒堆积物的存放以及水基灭火剂开发需要关注的参数提供指导.

分体式三箱主梁气动特性数值模拟

为研究分体式三箱主梁气动特性,基于某公铁两用斜拉悬索协作体系桥梁分体式三箱主梁,采用FLUENT软件开展了不同槽高比(G/D)、不同风攻角下分体式三箱主梁气动特性二维数值模拟。所述主梁气动特性主要包括气动力系数、涡量场、平均压力系数以及压力系数标准差分布。数值模拟结果表明:在研究参数范围内,不同风攻角下,阻力系数总体随槽高比增大而增大,升力系数和力矩系数未随槽高比单调变化,且力矩系数对槽高比变化更敏感。各槽高比下升力系数随风攻角变化斜率均为正值,这表明该分体式三箱主梁颤振性能良好;0°风攻角下,G/D=0时,仅在箱梁尾流区存在周期性漩涡脱落。G/D=1.61时,0°风攻角下箱梁开槽处及中间箱体和下游箱体表面漩涡脱落显著,相较于0°风攻角,±10°风攻角下中间箱体与下游箱体开槽处及下游箱体表面漩涡脱落减弱;主梁开槽使得中间箱体上表面负的平均压力系数幅值增大,并导致箱梁表面压力系数标准差增大。G/D=1.61时,相较于0°风攻角,±10°风攻角下箱梁表面压力脉动减弱,尤其下游箱体表面压力系数标准差显著减小;该分体式三箱主梁临界槽高比为G/D=2.08。

岩石类材料直接拉伸破坏的FDEM数值模拟

有限元-离散元耦合算法(FDEM)在岩石裂纹扩展模拟中广泛应用,尤其在直接拉伸模拟中用于参数校核。然而,模拟结果通常受到拉伸速率和网格尺寸的影响。本文首先阐述FDEM基本原理;然后,建立直接拉伸数值计算模型,探究拉伸速率、网格尺寸及高径比对破坏模式和力学参数的影响;最后,给出直接拉伸模拟中建议采用的拉伸速率和网格尺寸。研究结果表明:随着拉伸速率增加,试样抗拉强度、破坏程度和峰值应变率增加,而平均弹性模量减小;在较低拉伸速率下(v≤0.01 m/s),试样仅产生1条主拉伸裂缝;当拉伸速率较高时,有分支裂缝出现在主拉伸裂缝上侧。网格尺寸对抗拉强度、峰值应变率和平均弹性模量的影响较小,但对破坏模式和破坏程度的影响较显著。随着高径比增加,试样的抗拉强度、破坏程度和峰值应变率增大,但平均弹性模量呈相反趋势,并且高径比对破坏程度的影响较为显著。建议在直接拉伸模拟中使用0.01 m/s的拉伸速率,并将网格尺寸限制在1.5 mm以内。

多因素影响下巷道围岩稳定性分析及优化设计研究

针对深部煤层巷道矿压显现剧烈且巷道变形难以控制的问题,基于Kastner公式对巷道高宽比、侧压系数、埋深、断面形状、围岩强度5种影响巷道围岩稳定性的因素展开正交数值模拟实验,通过方差和直观分析图法研究了各因素对巷道变形破坏的敏感性。采用平面弹性复变函数理论分析了不同侧压系数与巷道高宽比下椭圆和矩形巷道围岩的应力分布规律,对椭圆形和矩形巷道宽高比和形状进行了优化设计。研究结果表明:围岩强度与侧压系数是影响巷道围岩稳定性的主要因素,埋深、断面形状、巷道高宽比为次要因素;椭圆形巷道在等轴应力比下围岩应力差值最小;矩形巷道宽度为5 m、高宽比为0.6左右时,应力集中程度较小;针对矩形巷道应力快速增高区,在考虑承压特性和断面利用率的基础上设计了圆角矩形优化巷道,确立了圆角半径的计算公式,通过数值模拟验证了其良好的性能。

山西省白榆优良速生家系的选育

在山西省各地共采集46个白榆优良家系进行播种育苗,对其生长指标进行测定分析,以筛选出苗高、基径和高径比表现较好的家系。结果表明,白榆不同家系间的苗高、基径和高径比均存在极显著差异。根据多重比较和变异系数可知,以苗高为标准进行筛选时,家系26为最优家系;以基径为标准进行筛选时,家系29为最优家系;以高径比为选择标准时,家系4为较优家系。

凹槽叶顶的气膜冷却特性

涡轮工作时,叶顶间隙内高速高温的间隙泄露流会直接冲刷动叶顶部,产生局部高温区域,因此控制间隙泄露流至关重要。基于压敏漆涂料(PSP)实验,研究了密度比、吹风比和间隙高度对凹槽叶顶气膜冷却特性的影响。研究结果表明:密度比增大,凹槽叶顶气膜冷却效果逐渐提高,尤其是大间隙下冷效提高较为明显,叶顶面平均冷效增加了35%;间隙高度和吹风比对叶顶表面冷效的作用不是单一的,小间隙条件下,叶顶表面气膜冷效随着吹风比增大而增大,大间隙条件下,吹风比的增加使得叶顶表面气膜冷效先减小后增加,同时小吹风比时,间隙高度增加提高了叶顶尾缘区域和孔周围的气膜冷效,叶顶面平均冷效提高了6.85%。

大荷载矿石堆场中深厚吹填软土的地基处理及后评价

吹填淤泥形成陆域是资源利用和环境保护方面的优质解决方案,但当前吹填软土形成陆域的工程中,多数为荷载较小的堆场、工业园区道路、绿化区等。以青岛港董家口港区矿石码头工程20万吨级散货泊位后方预留堆场区的地基处理工程为例,对该工程的设计、施工及使用后6年的情况进行详细阐述,从多个角度展示深厚吹填软土的演变情况,详细介绍土体含水量、孔隙比、抗剪强度等指标在不同时期的变化,对比施工期沉降计算和监测数据,分析不同时期抗剪强度指标下矿石堆存的高度。结果表明,在大荷载矿石堆场中采用吹填软土形成陆域是可行的,通过合理的地基处理方式和有序增加堆存荷载,最终可使矿石堆场达到满载堆存。

考虑作物冠层高度的屋脊形大棚形状优化

为提高屋脊形大棚太阳辐射利用率,增强保温蓄热能力。该研究依据大棚内部作物对采光和蓄热保温的需求,提出了基于冠层高度和恒定体积约束的屋脊形大棚形状优化模型,设置大棚采光面捕获太阳辐射量大及有效种植面积尽可能大的约束条件,在内部能量需求恒定的条件下分析大棚高度比及方位角对太阳辐射捕获量的影响规律,并优选出不同脊位比大棚在不同地区下的最优参数组合。结果表明:1)大棚所捕获的太阳辐射量大多随高度比减小而逐渐减小,在高度比k=5时为最大值;相同高度比下,脊位比越大,大棚所捕获的太阳辐射量越大;当高度比k=5时,沈阳地区脊位比为0.65、0.75和0.85的大棚相对于脊位比为0.50时的增长率分别为2.67%、4.42%和6.17%。2)大棚太阳辐射捕获量大多随方位角增加呈先减小后增加趋势,在方位角0°~90°的范围内,脊位比越大,大棚所捕获的太阳辐射量越多,在90°~180°的范围内相反;当大棚脊位比为0.65、0.75和0.85时,随着地区纬度的增加,大棚太阳辐射捕获量最低值点所对应的方位角值逐渐减小,不同脊位比之间的差异逐渐减小。3)大棚在不同地区优选得到的高度比值仅与作物冠层高度有关;地区纬度越高,脊位比及高度比越大,大棚优选得到的方位角相对于南北走向偏转的角度越大。该研究可依据作物冠层高度大小在大棚捕获太阳辐射量尽可能多的前提下减少大棚供热成本,为推进塑料大棚的整体规划发展提供理论依据。

基于声发射特征的不同高径比矸石胶结充填柱单轴压缩损伤演化

为研究高径比对矸石胶结充填柱单轴压缩性能的影响,本实验制备了高径比为0.5~4.0的5组圆柱体试件进行单轴压缩试验,同时利用数字图像相关技术(DIC)和声发射进行监测,探讨了不同高径比充填柱的破坏特征.研究表明:矸石胶结充填柱的峰值应力和峰值应变都会随着高径比的增大而减小,并与高径比呈指数关系;充填柱的破坏形式在高径比大于2.0后从整体破坏转为局部破坏,局部应变大于16%可以导致充填柱整体失稳;充填柱的高径比从1.0升高到4.0,损伤程度下降到11%;充填柱在累计振铃计数快速上升区中的破坏占总破坏的比例随高径比的增大从22.6%增加到72.3%,高径比大于2.0时该比例达到40.9%且上升速度加快,破坏的集中程度较高;声发射最终累积振铃计数先随着高径比增大而增大,在高径比为2.0以后开始减小,且高径比对振铃集中出现的位置有较大影响;用声发射能量与振铃计数的比值(E/C)反应能量释放剧烈程度,平均E/C随高径比增大从1.26增大到2.76,高径比大于2.0时峰后能量释放较为剧烈.试验结果可以为结构充填开采中充填柱高径比的选取提供参考.

小高宽比框架结构爆破拆除数值模拟研究

为研究小高宽比框架结构爆破拆除的倒塌过程,利用ANSYS/LS-DYNA有限元软件建立分离式共节点模型,对其倒塌过程进行数值模拟研究,分析该结构钢筋混凝土柱的受力特点。通过对比实际工程与模拟结果,发现两者在倒塌时间、倒塌历程、爆堆范围等方面高度一致,由此可见数值模拟是可靠的。研究发现:在倒塌过程中,各排立柱达到截面抵抗弯矩后会在梁柱节点处产生塑性铰,上部结构以塑性铰作定轴转动,前倾过程中对后排立柱产生向后的反力,以致产生明显的后坐。倒塌前期钢筋与混凝土单元共同受力,混凝土单元失效后,与其共节点的钢筋单元应力发生突变,随后在拉压状态下不断变换,直至倒塌结束,爆破切口处的钢筋对上部结构的自由落体有一定的阻碍作用。