Structural assessment of current steel design models for transmission and telecommunication towers

The usual methods of structural analysis involved in the design of steel telecommunication and transmission towers tend to assume a simple truss behaviour where all the steel element connections are considered hinged. Despite this fact, the most commonly used tower geometries possess structural mechanisms that could compromise the assumed structural behaviour. A possible explanation for the structure stability is related to the actual behaviour being close to semi-rigid connections instead of the assumed hinged connections. This paper proposes an alternative structural analysis modelling strategy for the steel tower design considering all the actual structural forces and moments combining three-dimensional beam and truss finite elements. Comparisons of the two above-mentioned design methods with a third method based on the use of spatial beam finite elements to model the main structure and the bracing system on two actually built steel telecommunication towers (40 and 75 m high steel towers) are described. The comparison is based on an extensive parametric study of the tower geometry in order to access the structural tower ultimate and serviceability limit states.     

A model for warping transmission through joints of steel frames

A simple approach is developed in this paper which considers the effect of partial warping continuity through the joints of thin-walled steel frames when using beam finite element analysis. Using a condensed stiffness matrix for the joint generated by the substructuring technique, warping springs are introduced to represent the condition of partial warping restraint at intersections between members. The performance of the proposed model is demonstrated through a number of numerical examples. Excellent agreement is achieved between the results of beam finite element analysis using the suggested joint model and accurate shell finite element analysis.     

Nonlinear finite element analysis of behaviors of steel beam–continuous compound spiral stirrups reinforced concrete column frame structures

Many tests and numerical research for RCS frame consisted of reinforced concrete (RC) column and steel (S) beam have been conducted in the USA and Japan over the past decades; they showed that the performance of the RCS system is superior to traditional concrete frame and steel frame. Up to the present, no research reports on composite CCSHRCS frame structure consisted of high‐strength concrete columns confined with continuous compound spiral stirrups (CCSHRC) and steel (S) beam. Herein, an accurate finite element model of composite CCSHRCS frame is developed; the finite element model is investigated in order to fully include important factors such as local buckling of steel beam and nonlinear behavior of confined concrete; the validity of the proposed models is examined by comparing with the results of cyclic loading experiments on the RCS frame in reference. With the proposed model, the effect of composite CCSHRCS frame is discussed in detail. Copyright © 2012 John Wiley & Sons, Ltd.     

Interface behavior of grouted connection on monopile wind turbine offshore structure

The interface behavior of a concrete grouted connection is studied in a monopile wind turbine offshore structure. The grouted connection between transition piece and monopile is fixed by filling it with grout materials made of high-strength concrete. We observe a nonlinear equilibrium path from the grouted connection in experiments. For comparison with the experimental results, nonlinear finite element analysis of the grouted connection is performed, taking the effects of both material and geometrical nonlinearities into consideration. A finite element model of the grouted connection between the steel and concrete materials is realistically simulated using an interface element. The finite element results compares well with the experimental results. Thus, the finite element analysis showed that the numerical model based on the interface element is a good method for investigating the behavior of grouted connections of monopile offshore structures.     

An Accurate Analysis for Sandwich Steel Beams with Graded Corrugated Core Under Dynamic Impulse

This paper addresses the dynamic loading characteristics of the shock tube onto sandwich steel beams as an efficient and accurate alternative to time consuming and complicated fluid structure interaction using finite element modeling. The corrugated sandwich steel beam consists of top and bottom flat substrates of steel 1018 and corrugated cores of steel 1008. The corrugated core layers are arranged with non-uniform thicknesses thus making sandwich beam graded. This sandwich beam is analogous to a steel beam with web and flanges. Substrates correspond to flanges and cores to web. The stress–strain relations of steel 1018 at high strain rates are measured using the split-Hopkinson pressure. Both carbon steels are assumed to follow bilinear strain hardening and strain rate-dependence. The present finite element modeling procedure with an improved dynamic impulse loading assumption is validated with a set of shock tube experiments, and it provides excellent correlation based on Russell error estimation with the test results. Four corrugated graded steel core arrangements are taken into account for core design parameters in order to maximize mitigation of blast load effects onto the structure. In addition, numerical study of four corrugated steel core placed in a reverse order is done using the validated finite element model. The dynamic behavior of the reversed steel core arrangement is compared with the normal core arrangement for deflections, contact force between support and specimen and plastic energy absorption.     

望京国际广场巨型斜交网格节点有限元分析

北京保利望京国际广场1号塔楼高160 m,由巨型斜交网格外框筒＋钢筋混凝土内筒组成,其中网格外筒为钢管混凝土斜柱交叉组成.由于钢管混凝土柱斜向交叉相贯,导致相交节点几何构造复杂,其受力也较为复杂.采用大型通用有限元软件ABAQUS对节点进行有限元分析,分析出节点的极限承载力,与试验结果进行对比,验证了数值仿真分析的可行性,并对节点的安全性进行了评价,依据试验与数值分析的结果,优化了节点几何构造.有限元分析可为节点设计提供有益参考数据.     

粘钢加固混凝土框架节点的有限元分析

通过模拟地震作用,对受低周循环荷载的混凝土框架中节点做粘钢加固前后的ANSYS有限元数值模拟分析,并将数值模拟结果与实验数据进行对比分析,在验证了有限元模型正确的基础上,通过改变加固钢材的厚度,建立了M1,M2,M3,M4四个模型,讨论了加固不同厚度柱部角钢、梁上钢板、梁柱核心区箍板对节点受力的影响,以及加固板厚对节点滞回曲线的影响,得出结论。     

塔式起重机结构有限元分析技术研究

以某平头塔式起重机为研究对象，对其进行结构有限元分析，分别采用杆单元和梁单元构建模型，对比分析两种方案的优劣，得出塔机腹杆宜选用杆单元、弦杆选用梁单元建模的结论。依此方案建立塔式起重机有限元模型并进行应力分析，利用ANSYS的列表功能将应力数据提取后，导入EXCEL软件对塔机杆件的稳定性进行自动计算，使计算效率得到提高，为进一步完善塔式起重机有限元分析的理论提供参考。     

型钢再生混凝土柱-钢梁组合框架节点受力性能非线性分析

在型钢再生混凝土柱-钢梁组合框架节点拟静力试验基础上,采用ABAQUS有限元软件建立了组合框架节点的数值计算模型,对该组合框架节点在水平荷载作用下的受力非线性行为进行了有限元分析,获取了组合框架节点的破坏过程、破坏形态、应力云图、荷载-位移曲线及荷载特征值,并对节点的承载力计算值与试验值进行了比较,验证了有限元计算模型的合理性,进而分析了有限元拓展参数对组合框架节点受力性能的影响规律。结果表明:有限元计算结果与试验结果吻合较好,该有限元模型能较好地模拟该组合框架节点在水平荷载作用下的受力性能;另外,提高再生混凝土强度或者箍筋强度对组合框架节点的抗剪承载力是有利的,但节点的延性变形能力有所降低;组合框架节点的抗剪承载力随着型钢强度的提高而显著增加,但节点的变形能力变化不大;增加体积配箍率或型钢配钢率可以明显提高组合框架节点的抗剪承载力和变形能力。     

蓟运河某斜拉桥钢锚箱局部应力分析

本文采用子结构法选取钢塔和钢梁中的钢锚箱,使用ANSYS有限元软件建立蓟运河某斜拉桥钢锚箱有限元模型,计算了地震作用下最大索力对应的钢锚箱局部应力。     

钢筋混凝土双肢剪力墙非线性静力有限元分析

利用有限元软件ABAQUS中的混凝土损伤塑性模型,采用分离式方法建立有限元模型,对钢筋混凝土双肢剪力墙进行了非线性分析;在与试验结果进行对比分析的基础上,选取了用于钢筋混凝土剪力墙非线性有限元分析的材料破坏准则和本构关系进行建模;通过数值计算,分析了轴压比、墙连梁跨高比、墙分布钢筋配筋率、边缘构件配筋率对钢筋混凝土双肢剪力墙的承载能力、延性、破坏形态等的影响。结果表明:轴压比、分布钢筋配筋率和连梁跨高比对钢筋混凝土双肢剪力墙的受力性能影响较为明显;边缘约束构件配筋率对墙体的影响较小。     

脱排一体式钢塔设置TMD对减轻风致振动的 控制研究

为了减轻脱排一体式钢塔的风致振动,采用调谐质量阻尼器(TMD)控制装置,对其进行风振控制研究。利用ADINA有限元软件,进行脱排一体式钢塔的风洞数值模拟与时程分析,并对脱排一体式钢塔结构进行现场实测,现场实测结果与数值模拟结果误差在15%之内,验证了数值模拟方法的准确性。根据脱排一体式钢塔的结构特性,合理设计了TMD控制装置。进行风荷载作用下设置TMD的脱排一体式钢塔时程分析,结果表明,TMD控制装置可以增加脱排一体式钢塔的等效阻尼比,有效降低脱排一体式钢塔的整体位移、加速度响应与结构底部应力响应,但会增大结构上部与中部的应力响应。TMD与主体结构相对位移较小,可对TMD控制装置进行优化设计。     

Performance of shear connection in composite beams with profiled steel sheeting

This paper describes the structural performance of shear connection in composite beams with profiled steel sheeting. An accurate and efficient nonlinear finite element model was developed to study the behaviour of headed stud shear connectors welded through-deck. The profiled steel sheeting had transverse ribs perpendicular to the steel beam. The material nonlinearities of concrete, headed stud, profiled steel sheeting, reinforcement and steel beam were included in the finite element model. The capacity of shear connection, load-slip behaviour of the headed stud, and failure modes were predicted. The results obtained from the finite element analysis were verified against experimental results. An extensive parametric study was conducted to study the effects on the capacity and behaviour of shear connection by changing the profiled steel sheeting geometries, the diameter and height of the headed stud, as well as the strength of concrete. The capacities of shear connection obtained from the finite element analysis were compared with the design strengths calculated using the American Specification, British Standard and European Code for headed stud shear connectors in composite slabs with profiled steel sheeting perpendicular to the steel beam. It is found that the design rules specified in the American and British specifications overestimated the capacity of shear connection, but the design rules specified in the European Code were generally conservative.     

钢管组合大跨越输电塔线体系简化模型研究

利用有限元分析软件ANSYS建立了钢管组合大跨越输电塔线体系有限元分析模型,采用子空间迭代法得到了单塔结构的前18阶模态和体系的前600阶模态,通过对比分析,定性地得到了导地线在侧向(X向)和纵向(Y向)施加给铁塔的刚度耦合效应。同时推导了塔线体系的理论简化计算公式,得到了比较实用、直观的等效刚度模型。最后通过引入适当的等效刚度系数,分析了输电塔线体系简化模型的动力特性,一定程度上验证了简化模型的合理性。分析研究进一步揭示了导、地线对输电塔的耦合作用规律,对输电塔的抗震、抗风设计有一定参考意义。     

基于有限元方法的QTZ40塔机模态分析与试验

指出在塔武起重机结构轻量化设计中,采用中高强度结构钢来代替普通Q235碳素结构钢,可以减轻塔机重量,应用有限单元法程序ANSYS对QTZ40塔机进行了动态特性分析,建立了塔机的有限元分析模型,计算并探讨了塔机前六阶模态的固有频率和振型,以完善塔机动态设计.     

火灾下钢结构的性能与高等分析

本提出了一种改进的模型用于真实火灾下结构的性能分析。其主要特点是用非线性有限元模拟构件，反映结构整体非线性的影响。对真实火灾采用多区域及热辐射模型进行了模拟，对瞬态热传导采用有限元法进行了计算。采用边界面理论来考虑塑性沿构件截面的连续性。对承受局部火灾的半连续框架、多高层及大跨拱形析架采用了基于性能的分析方法。其中对梁跨度，火源位置对火势的蔓延对结构的影响进行了分析。最后对大跨屋面结构在非对称热力作用下的权限状态进行了分析。     

Behaviour of embedded steel plate in composite coupling beams

Plate-reinforced composite (PRC) coupling beam is fabricated by embedding a vertical steel plate into a conventional-reinforced concrete coupling beam to enhance its strength and ductility. Shear studs are welded on the steel plate surfaces to allow for proper load transfer between the concrete and steel plate. The present study focuses on the evaluation of internal load distributions and load sharing on the embedded steel plate as well as at the shear studs in composite coupling beams using the nonlinear finite element package ATENA. The proposed two-dimensional finite element model is able to simulate the overall load-deflection behaviour and internal load distributions of coupling beams subjected to bending and shear forces. The reliability of the model is demonstrated by comparisons with the available experimental results. This is followed by an extensive and carefully planned parametric study using the calibrated finite element model. Numerical results on the effects of steel plate geometry, span-depth ratio of beams and steel reinforcement ratios at beam spans and in wall regions are presented and discussed in this paper. The finite element model provides a better understanding of the behaviour of shear studs as well as plate anchorage in the wall regions and embedded beam region. Based on the numerical results, equations for quantifying the shear stud forces are established and a set of non-dimensional design charts for determining the internal forces of the embedded steel plates is constructed. Both of them are useful for engineers to design PRC coupling beams.     

基于有限元的分层空间桁架法计算精度分析

通过分析分层空间桁架法与有限元法之间的计算差别来讨论分层空间桁架法的计算精度;对某电视塔分别用分层空间桁架法及有限元法在相同荷载条件下进行计算,认为有限元方法为精确解,并以此来分析分层空间桁架法的计算结果。分析结果如下:分层空间桁架法在结构截面形状及截面尺寸没有突变时误差较小,内力及位移计算误差基本可以控制在20%以内,内力较小的斜撑计算误差较大,但不影响设计,截面形状及截面尺寸发生突变时斜撑内力及层间侧移计算误差可达50%以上,此时分层空间桁架法不适用;在上下分布较为均匀的实际结构中,分层空间桁架法误差较小,可以用于结构初步设计以及与有限元计算结果相互校核。     

A Numerical Study on the Thermo-mechanical Response of a Composite Beam Exposed to Fire

This study presents an analytical framework for estimating the thermo-mechanical behavior of a composite beam exposed to fire. The framework involves: a fire simulation from which the evolution of temperature on the structure surface is obtained; data transfer by an interface model, whereby the surface temperature is assigned to the finite element model of the structure for thermo-mechanical analysis; and nonlinear thermo-mechanical analysis for predicting the structural response under high temperatures. We use a plastic-damage model for calculating the response of concrete slabs, and propose a method to determine the stiffness degradation parameter of the plastic-damage model by a nonlinear regression of concrete cylinder test data. To validate simulation results, structural fire experiments have been performed on a real-scale steel–concrete composite beam using the fire load prescribed by ASTM E119 standard fire curve. The calculated evolution of deflection at the center of the beam shows good agreement with experimental results. The local test results as well as the effective plastic strain distribution and section rotation of the composite beam at elevated temperatures are also investigated.     

预应力装配式高耸风电塔架受力性能研究

预应力装配式高耸风电塔架下部为预制装配式混凝土塔筒,上部为钢塔筒,上端锚固于法兰环,下部锚固于基础内部。在风电塔架体内沿环向均匀布置竖向预应力拉索,张拉后将上部钢塔筒和下部装配式混凝土若干塔筒连接为整体。针对中间转换部分,采用转换段法兰环、变截面混凝土、预制混凝土竖向缝以及水平缝等连接构造。为研究该结构及各连接构造的受力性能,开展精细化有限元分析、拉索107次高周疲劳性能试验以及1∶3大比例尺模型试验,得到了结构关键部位的力学响应和破坏模式等。结果表明：设计荷载作用下,预应力装配式混凝土塔筒表现出弹性特征,可以安全地承受设计荷载;极限荷载作用下,预应力装配式混凝土塔筒段承载力储备充足,且上部钢塔筒先于混凝土塔筒段出现屈曲破坏,混凝土塔筒与钢塔的承载力比例设置合理,避免了混凝土塔筒先于钢塔筒破坏,验证了结构体系和连接构造设计的可行性;疲劳试验及有限元分析结果表明拉索能承受107次的疲劳次数,满足抗疲劳安全性要求。