考虑支承位移的钢筋混凝土楼板受力有限元分析

采用有限元分析程序ANSYS对一双轴对称的剪力墙结构建立一两层1/4平面的模型,分析竖向荷载作用下楼板的内力,并与基于传统方法的PMCAD的计算结果对比。指出由于不能考虑支承的竖向位移,传统方法计算的楼板弯矩比有限元方法的结果偏大或者偏小,甚至反号,从而导致不适当的钢筋配置,既浪费又不安全。     

Modelling and analysis of two-way composite slabs

The paper deals with the modeling and analysis of the ultimate behavior of two-way composite slabs. A software package of COSMOS/M 2.6 is used. Non-linear material properties are considered. The proposed finite element model is validated by making a comparison with full-scale tests published in literature for one and two-way composite slabs. Many parameters are studied, such as slab aspect ratio and slab slenderness ratio. The effect of embossments flattening is considered. The effect of cold steel straps which are fixed to the bottom steel deck flange perpendicular to corrugation direction is studied, including the variation of its thickness and distribution. Also the effect of shear studs is considered. The effect of all previous parameters on the ultimate capacity, distribution of reactions into both weak and strong directions, and slab deflection are investigated. The results are also recorded at the serviceability limit state. The analytical results of the two-way composite slabs are compared with the corresponding results of one-way composite slabs. A dramatic increase occurs on slab loads and distribution of reactions into the weak direction. A considerable decrease occurs on slab deflection as a result of using steel straps and studs.     

Reliability analysis of reinforced concrete slabs under explosive loading

Inherent in every material is the uncertainty of strength parameters, be it uncertainty in distribution type or distribution variables. In the case of structures subjected to explosive loading, the load itself is very much uncertain, as it is widely accepted that explosive experiment is difficult to predict. With these random effects associated with material, geometry and loading, it is necessary to incorporate them into the analysis in order to have a more realistic estimation of the structural response. This paper presents results from a parametric investigation of the reliability of reinforced concrete slabs under blast loading. Performance functions are set up based on displacement ductility and maximum strain limit-states for reliability estimation. Monte Carlo simulation is used to verify the adequacy of the SDOF representation of the structural slab.     

现浇钢筋混凝土单向板经济性分析

采用PKPM软件建立了现浇钢筋混凝土楼板结构模型,统计了现浇钢筋混凝土单向板的用钢量和混凝土用量,得到了该结构单向板板厚、混凝土强度等级和跨度的经济组合规律,为单向板的经济设计提供了参考。     

地下室底板受力分析的FLAC数值模拟

介绍了FLAC数值模拟的基本原理,针对成都某高层建筑地下室底板变形开裂事故,利用FLAC数值模拟地下室底板在无顶板、有顶板无覆土、有顶板加覆土条件下的受力变形情况,揭示了该高层建筑地下室底板开裂的原因,并提出了合理的加固处理措施。     

爆炸荷载作用下钢筋混凝土板破坏评定方法

压力-冲量(P-I)曲线是结构构件在爆炸荷载作用下的初始设计及在爆炸荷载作用后的破坏评定的有效工具。目前,确定结构构件的P-I曲线采用的方法均是基于单自由度结构体系假定的,并且多以结构构件的中点位移作为破坏指标。然而在爆炸荷载作用下,结构构件大多因高阶响应而发生局部破坏,且可能发生弯剪破坏。因此,通过将结构构件简化为单自由度体系模型并且选择结构构件中点位移为单一破坏指标获得的结构构件的P-I曲线,不能准确评定其破坏程度。利用LS-DYNA有限元动力分析软件,建立了典型钢筋混凝土板在爆炸荷载作用下响应和破坏的分析方法,提出了基于钢筋混凝土板跨中截面受弯剩余承载力的破坏指标以及利用数值方法确定钢筋混凝土板跨中截面受弯剩余承载力的步骤。同时,综合分析数值模拟结果,拟合了钢筋混凝土板P-I曲线的数学表达式,提出了一种简化了的确定钢筋混凝土板P-I曲线的方法,采用该方法确定的P-I曲线可用来对任意爆炸荷载作用后钢筋混凝土板的破坏进行评定。     

预应力混凝土叠合双向板叠合后的刚度分析

对预应力混凝土叠合双向板的抗弯刚度进行了分析研究,提出了预应力混凝土叠合双向板叠合后的刚度理论计算公式,为进一步研究预应力混凝土叠合双向板叠合后的刚度提供了理论依据。     

双重抗侧力体系的弹性稳定分析

采用连续的悬臂梁模型,对弯曲型支撑-框架体系的弹性稳定进行研究,得出了体系有侧移失稳的临界荷载公式。在此基础上分析并提出了弯剪型支撑双重抗侧力体系的临界荷载公式,并与有限元方法结果进行对比,所得公式精度良好。提出的公式对工程实际应用具有参考意义。     

索网结构的弹性冗余度分析

主要介绍索网结构弹性冗余度的定义及其理论分析过程.冗余度的定义为可用的方程个数比求解时所必需的方程个数多出来的个数.索网结构属于柔性张力结构,不同于传统刚性结构,柔性张力结构的刚度主要由预应力提供,其刚度可分为弹性刚度和几何刚度,预应力主要影响几何刚度.索网的冗余度可分为弹性冗余度和几何冗余度,分别对应它的弹性刚度和几何刚度.本文通过对势能方程求解微分,得到索网结构的平衡方程、物理方程和几何协调方程,再将几何协调方程线性化,代入平衡方程和物理方程,推导弹性冗余度的计算公式,并采用MAT-LAB编程实现这一算法.最后通过算例,分析索网弹性冗余度的特性,得出一些有用的结论,对工程应用有一定的指导意义.     

边支承双向板与柱支承双向板的界定条件

建立了考虑板、梁、柱协同工作的楼盖结构三维有限元分析模型;对具有不同梁板刚度比、板区格跨度比的31个现浇混凝土楼盖结构模型进行了弹性有限元分析,同时用弹性薄板理论计算了这些楼盖结构模型中板的内力和挠度;将两种方法的计算结果进行比较,研究了梁、板刚度比变化对板内力和变形的影响。研究结果表明,梁板刚度比变化对板内力和变形有较大的影响;综合比较弯矩和挠度计算结果,提出将αl2/l1≥5作为弹性内力计算时边支承双向板与柱支承双向板的界定条件。     

Curling of concrete slabs on grade: experimental versus theoretical analysis

Bridge structures are very critical elements within a complex transportation system, and movable bridges are especially important because they provide an effective way for traffic to cross an active waterway granting passage to ships that would otherwise be blocked by the infrastructure. As a consequence, reliability assessment as well as health monitoring of movable bridge structures are challenging issues that deserve significant attention because structural failures or temporary out-of-service may have a tremendous socio-economic impact. In this perspective, the structural monitoring of movable bridge structures can support more reliable numerical simulations, thus increasing the consistency of the whole assessment process. Moving from these considerations, the present paper addresses the optimal sensor placement (OSP) for monitoring a historic swing bridge in Taranto (Italy) by means of dynamic measurements. First, the bridge structure and the structural model are briefly illustrated. Subsequently, the considered strategies for sensor positioning are presented. Comparative analyses are finally performed to support the experimental design for this special infrastructure.     

预应力混凝土简支板抗火性能试验与分析

完成了9块无粘结和1块有粘结预应力混凝土单向简支板的抗火试验。各试验板内的热电偶在火灾下的实测结果表明,温度由迎火面至背火面逐渐递减,由迎火面至背火面的温度变化梯度随离迎火面距离的增大而减小。布置于无粘结预应力筋锚固端的力传感器和试验板上的位移传感器的测试结果表明,受火初期试验板挠曲变形增长较快,无粘结预应力筋应力呈增长趋势;受火一段时间之后试验板变形增长速度有所减缓,无粘结预应力筋应力呈减小趋势,且这种趋势一直延续到停火后一段时间;停火一段时间之后,试验板有变形恢复趋势,无粘结预应力筋应力水平又有所恢复。在受火过程中试验板背火面经历了水分溢出、水蒸气形成和发展、溢出水干涸及水蒸气消失的过程。在试验炉两侧壁的观察孔观测到有6块试验板发生了爆裂,爆裂发生在预应力度较高、荷载作用水平较低的试验板的邻近支座区域。基于试验结果,试算确定了对流换热系数、辐射换热相当发射率系数、混凝土导热系数和比热的取值,应用ANSYS     

Finite difference analysis of simply supported RC slabs for blast loadings

A finite difference procedure that can account for strain-rate effects, both shear and flexural deformations, permits variations in cross-section geometry and strength and loading over the length of a component is proposed to accurately and efficiently analyze the dynamic response of a simply supported structural member under blast loads. A section-based layered analysis model that accommodates varying strain rates across a member’s cross-section is used to derive sectional moment–curvature relationships. A formula is derived to estimate the distribution of strain rate over the depth of a cross-section along the length of the member, and the corresponding strain rate effects are incorporated into the section-based layered analysis model. The Timoshenko beam equations that include both shear deformations and rotational inertia are solved numerically using an explicit finite difference scheme. The accuracy of the proposed finite difference analysis model is part validated using results of blast testing of reinforced concrete slabs with combinations of explosive weights and standoff distances. The results are also compared with those obtained by conventional single-degree-of-freedom (SDOF) analysis and finite element (FE) analysis using solid elements. The finite difference analysis procedure is both fast-running and accurate and most suitable for design office application, combining the speed of SDOF analysis and the detail and accuracy of FE analysis.     

闭口型压型钢板-混凝土组合板数值模态分析研究

目前,压型钢板-混凝土组合板结构在工业厂房和电厂中得到广泛应用,其组合板振动特性也日渐为业主和设计人员所关注。利用ANSYS有限元分析程序对闭口型压型钢板-混凝土组合板进行数值模态分析,得到组合板各阶自振频率及振型。对模态分析过程中所涉及到的材料模型定义、单元划分以及建模技术等问题进行了详细介绍,数值模拟结果与组合板模态试验结果比较吻合,表明所采用的有限元模态分析方法能较准确模拟组合板的振动特征。进一步运用ANSYS程序对一系列不同跨度和边界条件下的组合板进行数值模态分析,得到不同跨度和边界条件下组合板的振型和自振频率,为组合板的振动设计提供有益的参考和依据。     

Dynamic analysis of composite systems made of concrete slabs and steel beams

Structural engineers have long been trying to develop solutions using the full potential of its composing materials. At this point there is no doubt that the structural solution progress is directly related to an increase in materials science knowledge. These efforts in conjunction with up-to-date modern construction techniques have led to an extensive use of composite floors in large span structures. On the other hand, the competitive trends of the world market have long been forcing structural engineers to develop minimum weight and labour cost solutions. A direct consequence of this new design trend is a considerable increase in problems related to unwanted floor vibrations. For this reason, the structural floors systems become vulnerable to excessive vibrations produced by impacts such as human rhythmic activities. The main objective of this paper is to present an analysis methodology for the evaluation of the composite floors human comfort. This procedure takes into account a more realistic loading model developed to incorporate the dynamic effects induced by human walking. The investigated structural models were based on various composite floors, with main spans varying from 5 to 10 m. Based on an extensive parametric study the composite floors dynamic response, in terms of peak accelerations, was obtained and compared to the limiting values proposed by several authors and design standards. This strategy was adopted to provide a more realistic evaluation for this type of structure when subjected to vibration due to human walking.     

Elastic analysis of asymmetric tall building structures

A simplified elastic hand method for estimating forces in asymmetric multi‐bent structures subjected to horizontal loading is presented. The structures may consist of combinations of coupled walls, rigid frames, braced frames and wall‐frames with shear walls. Results for structures that are uniform in height compare closely with results from stiffness matrix analysis. The method is developed from coupled‐wall deflection theory, which is expressed in nondimensional structural parameters. It accounts for bending deformations in all individual members as well as for axial deformations in the vertical members and is, therefore, more accurate for very tall structures. A closed solution of coupled differential equations for deflection and rotation gives the deflected shape along the height of the building. The proposed method of analysis offers a relatively simple and rapid means of comparing the shear forces and bending moments of different stability systems for a proposed tall building. The derivation of equations for analysis shown in this paper are for unisymmetric stability systems only, but the method is also applicable to general asymmetric structures. Copyright © 2001 John Wiley & Sons, Ltd.     

水泥路面脱空原因分析及评价探讨

论述了水泥路面脱空形成的原因,介绍了水泥路面脱空的检测方法,探讨了脱空识别原理,通过对检测结果的分析,提出了具体的处治养护建议,以延长水泥混凝土道路的使用寿命。     

爆炸荷载作用下梁板结构反弹机理分析

基于等效单自由度体系和分布参数体系研究了爆炸荷载作用下梁板结构在弹性阶段的反弹机理,给出了5种常用荷载作用下的单自由度弹性反弹曲线,进一步建立了典型加劲肋钢板有限元模型,对其在塑性阶段的反弹机理进行了数值模拟。研究结果表明：荷载作用时间越短,反弹越严重,相反,荷载作用时间越长,反弹越小;当荷载作用时间无穷大时,反弹抗力约为正向抗力的50%;荷载形式的改变对反弹影响较大;阻尼对结构的反弹影响显著,设计时建议按30%折减;当结构进入塑性阶段后,反弹效应减弱,反弹规律与弹性阶段类似。     

Wall-clamping of floor slabs

In design of floor slabs, insufficient allowance is made at present for the wall-clamping effect. The paper deals with determination of bending moments in different systems, with joint deformability taken into account and structural safety ensured by covering all possible modes of failure. By this means, significant saving can be effected in large-span structures.     

浅析25 m预应力空心板施工技术

针对25m预应力空心板在施工中容易出现的问题，结合大运高速平遥惠济河大桥施工实践，从预应力锚具、锚板、夹片、钢绞线等材料的选用和生产工序的控制，预应力张拉等几方面介绍了施工中采取的措施、方法，并进行了探讨，使生产的产品能量大可能地满足设计要求。