Comparative Studies on Calculation Methods of Shear Behavior of Reinforced Concrete Beams of Chinese Modern Reinforced Concrete Buildings

In order to study the calculation methods of shear behavior of reinforced concrete beams of Chinese modern reinforced concrete buildings,this paper carried out tests on the concrete compressive strength of 12 Chinese modern concrete buildings,the mechanical properties of 66 rebars from different Chinese modern concrete buildings,and the concrete cover thickness of 9 Chinese modern concrete buildings,and the actual material properties and structural configurations have been obtained. Then,the comparison on calculation methods include the Chinese original calculation method,the Chinese present calculation method,the American present calculation method and the European present calculation method is studied with case analysis method.The results show that the Chinese original calculation method of shear behavior of reinforced concrete beams is based on the allowable stress calculation method,and the design safety factors are 3. 55- 4. 00. The standard value of the compressive strength of concrete cubes is 8. 48 MPa,the standard value of the concrete tensile strength is 1.20 MPa,the standard value of the yield strength of rectangular rebars is 229. 56 MPa,and the standard value of the yield strength of round rebars is 276. 82 MPa. The average value of the concrete cover thickness of beams and columns is 35.96 mm. In term of calculation area of hoop rebars of reinforced concrete beams,without considering earthquake loads,the Chinese original structural calculation method is safer than the Chinese present structural calculation method,but is more unsafe than the American present structural calculation method and the European present structural calculation method. The results can provide the support for structural safety assessments and repair designs of Chinese modern reinforced concrete buildings.

Erratum to:“An Approximate Method for Calculating the Fluid Force and Response of A Circular Cylinder at Lock-in” [China Ocean Engineering,22(3),2008,371-384]

Because of my carelessness,Eq.（1）in the paper "An approximate method for calculating the fluid force and response of a circular cylinder at lock-in"(China Ocean Engineering,22（3）,2008,pp.373)should be f’-1.0/U’-5.0=f’;-1.0/5.75f’;-5.0,not f’=U’/5.75. My apology is hereby given.

Elastoplastic analysis for infinite plate with centric crack loaded by two pairs of point shear forces

The near crack line analysis method was used to investigate a crack loaded by two pairs of point shear forces in an infinite plate in an elastic-perfectly plastic solid, and the analytical solution was obtained. The solutions include: the unit normal vector of the elastic-plastic boundary near the crack line, the elastic-plastic stress fields near crack line, law that the length of the plastic zone along the crack line is varied with an external loads, and the bearing capacity of an infinite plate with a center crack loaded by two pairs of point shear forces. The results are sufficiently precise near the crack line because the assumptions of the small scale yielding theory have not been made and no other assumption have been taken.

Elastic-plastic analytical solution for centric crack loaded by two pairs of point shear forces in finite plate

The near crack line analysis method was used to investigate a centric crack loaded by two pairs of point shear forces in a finite plate, and the analytical solution was obtained. The solution includes the unit normal vector of the elastic-plastic boundary near the crack line, the elastic-plastic stress fields near the crack line, the variations of the length of the plastic zone along the crack line with an external load, and the bearing capacity of a finite plate with a centric crack loaded by two pairs of point shear forces. The results are sufficiently precise near the crack line because the assumptions of small scale yielding theory have not been made and no other assumptions are taken.

Distinct element method investigation on mechanical behavior within shear bands in granulates under the Earth and the Moon conditions

This letter mainly aims to investigate the mechanical behavior within shear bands in regolith both under the Earth and the Moon conditions via the distinct element method, in which a novel contact model considering interparticle van der Waals forces and rolling resistance is employed. The results show that for regolith under both conditions the stress paths are almost identical inside and outside the shear bands but void ratio, average pure rotation rate, and strain paths are rather distinct with dilation, particle rotation and the second invariant of strain tensor mainly occurring within the bands. However, the regolith under the Moon condition has higher peak strength and more significant strain localization than those under the Earth condition.

THE MODEL TEST RESEARCH OF HORIZONTAL FORCE ON RIGID SHAFT FURNITURE IN DEEP MINE

The state of deep mine rigid shaft fUrniture horizontal force calculation in China is introduced and the calculating model of horizontal force is determined. Based on the interaction between hoisting vessel and shaft furniture, the vertical mobel test device is built and a large number of model tests and analyses are carried out. At last, the relationship between horizontal force and hoisting end load, hoisting speed or bunton level interval is gained. The three parameters horizontal force calculating equation of beep mine rigid shaft furniture is given and it can guide the design and calculation of shaft engineering.

A force control high-order single-step-β method (HSM) for substructure pseudo-dynamic testing

This paper proposes a new technique which introduces the high-order single-step-β method(HSM)into the experimental study on the substructure pseudo-dynamic testing(SPDT).The technique is based on the proposed concept of equivalent shear stiffness which can meet the requirement of the HSM algorithm.A study is done to theoretically validate the technique by the numerical analysis of two-storey shear building structure,in comparison of the proposed substructure pseudo-dynamic testing algorithm with the central difference method(CDM).Then,a full-scale SPDT model,the three-storey frame-supported reinforced concrete short-limb masonry shear wall structure,is designed and tested to simulate the seismic response of the corresponding six-storey structure and verify the proposed force control HSM technique.Meanwhile,the techniques of both stiffness correction and force control are suggested to control algorithmic error,control error and measurement error.The results indicate that the force control HSM can be used in the full-scale multi-degree-of-freedom(MDOF)substructure pseudo-dynamic testing before descent segment of structure restoring force properties.

近冰面航行潜体受力及操纵仿真研究

冰层可以为潜体提供良好的隐蔽性,为潜体作战效能发挥提供极大帮助。研究潜体在冰层下航行时的受力及操纵方法,可以为潜体更好地履行使命任务提供有力支撑。以美国SUBOFF潜艇模型为研究对象,采用STAR-CCM+流体计算软件,对不同航速下的潜体近冰面运动进行数值计算分析,计算潜体受力及力矩。将潜体所受力及力矩与潜体空间六自由度方程结合,模拟潜体近冰面航行运动趋势,给出操纵方法。研究表明,近冰面航行会影响潜体航行深度及姿态保持,及时采用降速、首尾舵操舵、纵倾平衡水舱调水等操纵措施可有效控制潜体航行深度及姿态,避免触冰情况发生。

组合桥面板切应力分布规律及横向剪力钉布置

根据组合桥面板截面的切应力、剪力流分布规律,在混凝土板和钢顶板完全连接的条件下,理论推导出混凝土板和钢顶板的剪力流承担比例,证明组合桥面板层间纵向剪力小于采用组合梁公式得到的计算值.层间完全连接和通过弹簧单元模拟剪力钉离散连接开展的有限元计算均支持这一观点,验证了组合桥面板截面的竖向剪力主要由腹板承担的观点的正确性.探究横向上剪力钉的布置方式.结果表明,组合桥面板应沿横向全宽布置剪力钉,在腹板两侧进行加密,腹板正上方不宜布设剪力钉.

薄钢板机械咬合螺栓抗剪连接试验与计算方法

为探究薄钢板机械咬合螺栓抗剪连接的受力性能,设计了12个具有不同垫圈形状和预拉力的机械咬合螺栓连接试件和普通螺栓连接试件,并开展了受剪破坏试验。试验结果表明机械咬合螺栓连接试件的薄钢板在咬合部位发生受拉破坏,而普通螺栓连接试件的薄钢板出现孔壁承压破坏,且机械咬合螺栓连接的受剪承载力显著高于普通螺栓连接的受剪承载力。分别建立了机械咬合螺栓连接和普通螺栓连接的精细有限元模型,根据受剪试验结果验证了模型的准确性,进一步探究了垫圈直径、螺栓直径、钢板厚度和咬合深度对机械咬合螺栓连接受剪承载力的影响规律。最后开展了机械咬合螺栓连接的受剪承载机理分析,提出了能够准确预测其受剪承载力的计算公式。

自攻螺钉与拉铆钉混合连接受剪承载性能试验

为改善自攻螺钉连接的构件在地震作用下易发生拉脱导致结构严重破坏的缺点,提升冷弯薄壁型钢组合墙体抗破坏能力,分析了组合墙体层间连接处的传力机理,针对自攻螺钉的破坏模式,提出拉铆钉与自攻螺钉混合连接。为研究混合连接的抗剪性能,共进行了48组连接接头抗剪性能试验,包含冷弯薄壁型钢结构常用的5种连接板厚度,不同搭接板厚比(变化范围1.0~2.0),包含纯自攻螺钉连接、纯拉铆钉连接及混合连接的连接方式。观察混合连接的破坏模式,自攻螺钉未发现拉脱破坏,其破坏模式主要表现为:板承压破坏与螺钉倾斜组合破坏、铆钉剪断破坏及板承压与铆钉部分剪断组合破坏3种;相较单一连接方式,混合连接荷载–位移曲线表现出更长的塑性阶段;当板厚比大于1.5且组合板厚小于3.0mm,混合连接的承载力及延性较单一连接增长明显;利用现有计算方法对混合连接的承载力进行累加计算,与试验结果对比,计算结果偏保守。研究发现:混合连接能较好地弥补拉铆钉和自攻螺钉受剪过程中的缺陷,有效改善自攻螺钉拉脱破坏,从而提升连接的承载力及延性;板厚和板厚比是影响混合连接破坏模式及承载力的重要因素,与单一连接相比,板厚比越大,承载力提升越大;排布方式对混合连接的力学性能及破坏机理影响有限;在本文试验工况下,结合混合连接的破坏模式,在现有计算方法的基础上,提出改善后的计算方法,其计算结果更合理。

研磨抛光颗粒流剪切膨胀及力链演变的力学机制

将研磨抛光作为后处理可以提高工件的表面质量,如何将研磨抛光工艺价值最大化是本文首要解决的问题。由于颗粒流润滑既适用于极端环境又具有环保作用,因此本文将颗粒流用于研磨抛光。通过离散单元法建立平行板结构模型,将颗粒流作为第三体填充至摩擦副间隙,将工件表面与刀具作为第一体对颗粒流体系施加法向力和剪切力,对研磨抛光过程进行数值模拟。研究结果表明:单个颗粒剪切膨胀过程可以分为上升阶段、最高点阶段和下降阶段,不同阶段的弱力链方向都偏向于x轴,其中上升阶段强弱力链方向稳定,可提高工件的加工效率以及表面质量。当载荷的较大,会使强弱力链的分布律与承载率稳定,当载荷较大及较小时,剪切膨胀率降低,强力链方向更偏向于x轴。通过本研究,可以将不易检测的力链和剪切膨胀现象进行数值模拟,为研磨抛光条件下使用颗粒流提供了理论基础。

基于差分法的双排抗滑桩结构内力计算

为研究有连梁双排抗滑桩快速有效的内力计算模型,在对有连梁双排桩进行受力分析的基础上,将有连梁双排抗滑桩结构简化为在桩顶连系梁零弯矩处断开的2根单桩结构,通过对双排桩受力进行叠加得到前后排桩桩顶连梁传递的弯矩与剪力,基于有限差分法建立了有连梁双排抗滑桩受荷段、嵌固段全桩内力计算模型,进而对有连梁双排抗滑桩桩体内力进行了计算。同时,通过大型室内模型试验内力实测结果对所计算结果进行了对比验证。结果表明:(1)模型试验结果与所建计算模型得到的桩顶位移与桩身弯矩值吻合较好,说明简化计算模型具有一定的适用性;(2)二者的后排桩最大弯矩出现位置略有偏差,计算得到的最大弯矩位置更接近实际桩体破坏位置,进一步验证了全桩内力计算模型的可靠性;(3)所建有限差分计算模型避免了将受荷段与嵌固段利用连续条件进行迭代的复杂运算过程,大大提升了计算效率,为实际工程提供了一种快速高效的有连梁双排桩内力计算方法。

结构强度试验惯性力计算方法研究

为验证基于作动筒运动位移数据的加载点惯性力计算方法,设计位控作动筒高频推动测力传感器及质量块往复运动的验证试验,同时在控制系统中引入位移数据FIR滤波算法及加速度计算算法。试验结果表明,试验过程中惯性力计算方法与实际测力传感器反馈数据量级一致,初步证明了算法的可行性。

考虑套筒灌浆随机缺陷的装配式剪力墙结构可靠度评估

在装配整体式剪力墙结构中,由于套筒灌浆连接的质量具有一定的随机性,势必影响结构的竖向连接性能和结构抗震性能。根据不同缺陷程度的套筒灌浆拉拔试验,建立了一套等效套筒灌浆缺陷连接承载力模型,并基于某实际工程结构,建立了装配整体式剪力墙结构有限元模型。通过考虑灌浆缺陷的随机性,赋予连接接头相应缺陷程度的力学连接性能,来反映套筒灌浆中可能存在的缺陷。通过非线性有限元分析并结合概率密度演化方法(probability density evolution method,PDEM)进行了结构随机非线性反应分析和可靠度评估。结果表明:在动力作用下,结构非线性与随机性具有明显的耦合效应;缺陷的随机性会随着时间的推移,逐渐放大对结构响应的影响;在不同的安全域内,结构的整体可靠度将存在较大的差异。

基于多层框架结构的楼层阻尼比修正的仿真研究

附加有效阻尼比的确定是消能减震结构设计的关键。为探究布置消能器楼层数的不同对结构设计安全性的影响,以新疆地区某多层钢筋混凝土框架结构为研究对象,采用非线性时程分析方法和等效结构模型的振型分解反应谱分析方法,基于各楼层剪力计算结果,引入楼层阻尼比修正系数k mn,对等效结构模型的附加有效阻尼比进行迭代修正。结果表明:采用小震时程分析阻尼比的等效结构模型,其楼层阻尼比修正系数随着阻尼器布置楼层数的逐渐增加呈现出先增后减的趋势,当阻尼器布置层数为楼层总数的3/5时折减率最低;采用中震时程分析阻尼比的等效结构模型,当阻尼器布置楼层数不少于2/5时,可满足设防要求;对于多层框架结构,考虑综合成本,黏滞阻尼器的布置楼层数可不采用满布的形式。

《港口工程荷载规范》船舶水流力计算公式的修正方法

随着船舶大型化和停泊水域动力环境复杂化,利用现行JTS 144-1—2010《港口工程荷载规范》附录F计算船舶水流力时,发现公式中存在诸多缺陷,主要为:1)相对水深适用范围窄;2)水流流向角分区段计算方法不统一;3)纵、横向水流分力的作用点不明确;4)引用相关数据缺陷等。严重制约标准规范的推广应用。因此,基于标准修正专项的研究,通过收集比对国外标准和规范等资料,以及结合笔者前期所开展大量船舶物理模型试验结果等方法,得到了将现行规范水流力计算公式中相对水深适用条件由1.5扩大至6.0;提出了以船舶中心为力作用点的新坐标系下,采用横向分力、纵向分力和偏心力矩3部分组成的水流力计算修正方法,满足了规范修正目的。

大型梁式承台模型试验及跨中挠度简化计算方法研究

为了解大型梁式承台的力学性能,以某快速化改造工程的大型梁式承台为背景,按照缩尺比1∶10制作梁式承台模型进行力学性能试验,结合有限元计算,分析梁式承台结构受力、破坏模式、开裂情况等,并研究不同跨高比条件下梁式承台的受力特性。结果表明:在跨中荷载作用下,梁式承台受力大致可以分为线弹性阶段、裂缝发展阶段和屈服阶段3个阶段;线弹性阶段截面应力分布已不满足平截面假定,剪切效应对结构变形的影响不可忽略;模型最终破坏模式为弯曲破坏;裂缝主要表现为跨中弯曲裂缝和斜裂缝;跨高比越小,梁式承台剪切刚度越大。为考虑剪切效应对梁式承台变形的影响,拟合得出梁式承台跨中挠度的简化计算方法,将该方法计算值及规范计算值与试验值进行对比,可得在裂缝发展阶段,规范计算值与试验值偏差较大,所提方法计算值与试验值偏差较小,该方法可用于线弹性阶段及裂缝发展阶段梁式承台跨中挠度的初步估算。

预制节段桥梁钢榫键干接缝抗剪机理及计算方法

接缝是节段预制拼装桥梁的薄弱部位,为确保节段间的定位和传力,设计了钢榫键接缝。为充分完整掌握钢榫键接缝局部剪切性能,基于试验研究,结合理论分析对钢榫键接缝的抗剪机理和计算方法进行深入研究。研究结果表明:在侧限压力的作用下钢榫键接缝借助榫键和混凝土的接触受压来传递接缝间的剪力,接缝具有较高的抗剪承载力和良好的延性。结合钢榫键接缝的传力机制,构建了适用于钢榫键接缝的力学模型,揭示了钢榫键接缝的抗剪机理及破坏模式,包括:榫键剪切破坏、混凝土局部受压破坏(接触面压碎、接触面端部膨胀、劈裂破坏)、混凝土撕裂破坏。最后,建议采用钢榫键剪切破坏作为钢榫键接缝抗力设计的依据,同时应对钢榫键周围混凝土强度进行验算。

微孔的磨料水射流抛光CFD模拟及试验

为解决飞秒激光微孔难以抛光的问题,结合磨料水射流去除函数稳定、自适应性强等特点,采用磨料水射流抛光方法提高飞秒激光微孔质量。利用Fluent软件对不同工艺参数下的磨料水射流微孔抛光过程进行计算流体力学(computational fluid dynamics,CFD)模拟,分析不同参数下的流场分布、侵蚀速率及壁面剪切力作用规律;然后通过响应面法对射流靶距、射流压力及磨料粒径等3因素进行优化试验,以微孔内壁面剪切力均方差为响应值,建立其响应面方程,获得最佳抛光参数组合并进行试验验证。结果表明:射流压力对微孔内壁面剪切力的影响最大,当射流压力从0.80 MPa增至1.50 MPa时,微孔内壁面剪切力增大2倍以上。射流的不同结构段因性质不同可适用于不同工况。利用响应面法分析得到水射流微孔抛光的最佳工艺参数组合是:射流冲击角,90°;射流靶距,3.5 mm;射流压力,1.10 MPa;磨料粒径,15.0μm。在该条件下抛光微孔内壁面的表面粗糙度R_a降至0.354μm。磨料水射流抛光可显著改善微孔壁面质量,且响应面法预测的数据模型有较高准确性。