支撑布置对钢结构影响的试验及数值研究

进行试验及数值研究,分析支撑布置对钢结构动力特性的影响。土耳其工业大学土木工程实验室对某缩尺为1:2的3层钢结构模型,进行一系列环境振动试验,研究无支撑及有支撑框架的模态。分析了4种支撑形式:交叉型,倒V字型,V字型,K字型支撑。通过频域分解法,确定各阶自振频率、振型及阻尼比。建立有限元模型,对结构动力性能进行数值模拟。对比无支撑框架与有支撑框架动力特性的不同,分析支撑布置的影响。以试验结果为标准,揭示了试验及有限元结果的不同。研究表明:通过设置支撑,可提高钢结构刚度,支撑的影响大小取决于支撑布置,交叉型支撑对刚度的提高作用最大。数值结果比试验结果偏大,故必须对初始有限元模型进行一定改进。     

Experimental and numerical investigation of high strength stainless steel structures

The paper summarises research on high strength stainless steel tubular structures conducted at the University of Hong Kong, and the Hong Kong University of Science and Technology. Square and rectangular hollow sections were investigated. The test specimens were cold-rolled from high strength austenitic and duplex stainless steel sheets. The material properties of the test specimens were determined by tensile coupon tests at normal room and elevated temperatures. The initial geometric imperfection and residual stress of the specimens were measured. The experimental and numerical investigation focused on the design and behaviour of cold-formed high strength stainless steel structural members. The results were compared with design strengths calculated using the American, Australian/New Zealand and European specifications for cold-formed stainless steel structures.     

Experimental and numerical assessment of stayed steel columns

Stayed steel columns may be used as compression-resisting members of a structure presenting high slenderness ratios and fast erection requirements. The system is able to sustain a wide range of load levels and lengths with economic and reliable structural solutions. Although this structural solution dates back from the 1960s its structural behaviour is not fully understood. This fact motivated a study of the system structural behaviour by means of an experimental program followed by finite element simulations aiming to determine the most efficient structural geometries and the corresponding steel ties pre-stress force magnitudes. A series of full-scale tests were executed in 12 m pre-stressed steel columns with a 90 mm diameter. Some of the main contributions of the current study are related to the conception, development and execution of new tri-dimensional full-scale tests and the development of a finite element model calibrated against these experiments. An extensive parametric analysis based on the calibrated finite element simulation was also performed focusing on the most significant parameters that could affect the structural response, i.e., column length and diameter, pre-stress force magnitude, among others. The test and numerical results will certainly contribute to the development of updated design procedures and formulae to be introduced in future structural design codes.     

A numerical investigation of dynamic plastic buckling behaviour of thin-walled cylindrical structures with several geometries

In this study dynamic buckling behaviors of an aluminum alloy cylindrical shell with axial linear variable thickness, discontinuity and conical shaped have been numerically investigated for high velocity impact by means of finite element method. The validation of finite element model was provided by the results of previous studies in literature. Throughout study commerce finite element package program LS-DYNA3D was used and all simulations were fulfilled as explicitly. According to results obtained, the minor changes in the geometry are able to convert the dynamic plastic buckling into dynamic progressive buckling behavior. This study indicates that which of the dynamic buckling or progressive buckling mechanism will be dominant is sensitive to geometrical properties for cylindrical aluminum alloy shells under the high velocity impact.     

Experimental and numerical investigation of cold-formed lean duplex stainless steel flexural members

Experimental and numerical investigation of cold-formed lean duplex stainless steel flexural members is presented in this paper. The test specimens were cold-rolled from flat plates of lean duplex stainless steel with the nominal 0.2% proof stress of 450 MPa. Specimens of square and rectangular hollow sections subjected to both major and minor axes bending were tested. A finite element model has been created and verified against the test results using the material properties obtained from coupon tests. It is shown that the model can accurately predict the behaviour of lean duplex stainless steel flexural members. An extensive parametric study was carried out using the verified finite element model. The test and numerical results as well as the available data on lean duplex beams are compared with design strengths predicted by various existing design rules, such as the American Specification, Australian/New Zealand Standard, European Code and direct strength method for cold-formed stainless steel. Reliability analysis was performed to evaluate the reliability of the design rules. It is shown that these current design rules provide conservative predictions to the design strengths of lean duplex stainless steel flexural members. In this study, modified design rules on the American Specification, Australian/New Zealand Standard, European Code and direct strength method are proposed, which are shown to improve the accuracy of these design rules in a reliable manner.     

Experimental and numerical studies of lean duplex stainless steel beams

Stainless steel is well suited to a range of engineering applications owing to its durability and favourable mechanical properties. The most widely used grades of stainless steel are from the austenitic family and typically contain around 18% chromium and 8%-11% nickel — these grades have a relatively high initial material cost, due, in part, to their high nickel content, and a nominal yield strength (in the annealed condition) of around 220 N/mm². A new, low nickel grade of stainless steel (UNS 32101/EN 1.4162), commonly referred to as ‘lean duplex’, has been developed, that offers over two times the strength of the familiar austenitic grades and at approximately half the initial cost — this lean duplex stainless steel appears well suited to load-bearing applications in construction. This paper reports material and 3-point bending tests on lean duplex stainless steel hollow sections. The 3-point bending tests were replicated by finite element (FE) analysis and, upon validation of the numerical models, parametric studies were conducted to assess the effect of key parameters such as cross-section aspect ratio, cross-section slenderness and moment gradient on the strength and deformation capacity of lean duplex stainless steel beams. Based on both the experimental and numerical results, appropriate slenderness limits and design rules, suitable for incorporation into structural stainless steel design standards, have been proposed.     

Seismic response of box-type tunnels in soft soil: Experimental and numerical investigation

A series of dynamic centrifuge tests were carried out at the geotechnical centrifuge facility of IFSTTAR in Nantes, to investigate the response of box-type tunnels embedded in dry sand under sinusoidal and seismic excitation, as affected by soil-tunnel relative flexibility and soil-structure interface rugosity. The system under investigation was analyzed by means of full dynamic time history analyses, implementing rigorous finite element models. The numerical models were calibrated on the basis of back analysis of tests, while the numerical predictions were compared with experimental data, in terms of soil and tunnel horizontal acceleration, soil shear strains and tunnel deformations. The validated numerical models were then employed to further investigate several aspects of the system seismic response. Results indicate a rocking deformation mode coupled with the well-known racking distortion of box-type tunnels under seismic shaking. The effect of the soil-tunnel interface characteristics and soil yielding on the racking deformation of the tunnel, the dynamic earth pressures and shear stresses around the tunnel, as well as on dynamic lining forces is also reported. Soil yielding leads to post-shaking, residual, dynamic earth pressures, shear stresses and lining forces, especially in the case of flexible tunnels, while interface characteristics affect the distributions of these response parameters around the perimeter of the tunnel section. The ability of simplified seismic design methods for tunnels to predict the response is finally discussed, by comparing their predictions with the recorded data and the numerical results.     

大跨钢拱结构动力特性分析

本文以某高校钢拱结构体育馆为背景,基于动力有限元理论,采用SAP2000软件建立了结构有限元模型,对模型进行模态分析,得到该结构的动力特性。同时,通过改变结构模型相关参数(跨度,矢跨比,支座条件等)分析其对此结构动力特性的影响,为进一步深入研究此类钢拱结构的地震响应提供了基础性资料。     

钢结构残余应力测定中应力释放系数的有限元分析

盲孔法是测量钢结构残余应力的高效简单的方法,应力释放系数A、B对盲孔法测量结果的精确性有重要意义。应用有限元分析软件ANSYS,建立带盲孔的板件的有限元模型,施加单向均匀拉伸应力场,对盲孔法应力释放系数A、B的测定进行有限元分析计算。通过对测量距离D、孔径、孔深、等参数的分析,发现盲孔附近应力释放大致在D/d<5范围内,在此范围内,A、B随着D/d的增大而减小,同时孔径的变化对于A、B的影响很小,而孔深的增大时A、B的绝对值有所增大,但幅度很小。通过对不同板厚的分析,发现应力释放系数A随板厚增大而增大,B则相反。     

Finite element analysis under different boundary conditions of the filling of cylindrical steel silos having an eccentric hopper

A three-dimensional finite element analysis was made of the filling of cylindrical silos having an eccentric hopper, using different boundary conditions—silos supported at the transition or on discrete columns. The analysis included the options of the presence or absence of reinforcement in the transition and walls. The results for the pressures on the wall for a flexible wall and all the boundary conditions were compared with those for a silo with a rigid wall. The membrane stresses and meridional and circumferential bending moments were then evaluated in the silo wall and in the reinforcing elements. Lastly, the influence of the eccentricity of the hopper in a silo of intermediate eccentricity was analysed, and conclusions were drawn for the optimal design of these structures.     

Experimental and analytical studies on a streamlined steel box girder

A new type of streamlined girder (lenticular cross-section) bridge with a thin-walled steel box girder is proposed. In order to deal with the problem of increasing traffic congestion, this bridge is designed with a large width-to-span ratio, which results in significant shear lag effects and causes non-uniform stress distribution in the three-cell thin-walled box girder, especially along the flanges of the girder. The aim of this study is to investigate the effect of shear lag in thin-walled box girder bridges with large width-to-span ratios through both experimental and numerical studies. A large-scale Plexiglas model is tested under different loading cases. The material parameters are obtained from physical characteristics tests and tensile tests. In addition, a computational model is presented for a comprehensive simulation of a girder bridge including the orthotropic top/bottom/web plates and their ribs, which leads to accurate modeling of structural properties of the girder. The simulation of the computation results compared well with the experimental results. It is illustrated that the finite element analysis is an effective method to predict properties of this class of bridges.     

Experimental and finite element study of profiled steel sheet dry board folded plate structures

Folded plate structures constructed with profiled steel sheeting connected to dry boards by self drilling, self tapping screws (known as the PSSDB system) are being proposed as an alternative to traditional forms of roof construction. This paper describes the analysis, testing, and the structural behaviour of such kind of structures. The proposed efficient and load bearing structural system consists of an assembly of individual PSSDB panels connected by steel angle plates at the ridges, formed to the required shape, width and span. An analytical model using finite element method has been proposed. The profiled steel sheeting was idealised as an equivalent homogeneous orthotropic thin shell plate elements of constant thickness. Two directional plate elements were proposed in modelling the connection between profiled steel sheeting and dry board to include biaxial shear deformation. The proposed analytical method has been used to analyse the results of full-scale folded plate PSSDB tests and is found to give good results.     

有限元模型对输电塔架结构动力特性分析的影响

本文较全面地分析讨论了节点构造和节点刚度等因素对塔架动力性能的影响及在有限元建模中的处理方法。本文选取一个 5 0 0kV输电线路中常见的猫头型塔架 ,建立了 1个空间桁架模型、1个空间刚架模型和 3个由杆单元和梁单元组成的混合有限元模型 ,对输电塔架结构进行了模态分析 ,系统研究讨论了不同有限元模型、连接偏心对模态分析结果的影响 ,指出了各种有限元模型在塔架动力特性分析中的特点和适用范围 ,对输电塔架结构的动力特性研究具有实用意义。     

不规则有侧移钢框架二阶弹性分析

对几类典型的不规则有侧移钢框架进行了一阶和二阶弹性分析,采用有限元方法得到了框架的二阶精确分析结果,并与现行《钢结构设计规范》(GB50017-2003)给出的二阶分析近似方法的计算结果进行了比较,分析了不规则钢框架的二阶效应以及规范近似方法对不规则框架的适用性,分析结果可供设计人员参考。     

Experimental and numerical analysis on the structural behaviour of cold-formed steel beams

A research study on the structural behaviour of cold formed steel beams with C-, I-, R- and 2R-shaped cross-sections at ambient temperature is presented, based on the results of a large programme of experimental tests and numerical simulations. Firstly, several four-point bending tests were carried out in order to assess mainly the failure loads and failure modes of the beams. Secondly, a suitable finite element model was developed to compare with the experimental results, and finally, a parametric study was undertaken in order to investigate the influence of the thickness, height and length of the beams on its structural behaviour.     

Experimental investigation of lightweight residential floors supported by cold-formed steel C-shape joists

Presented in this paper are the experimental results of a recent study carried out at the University of Waterloo on vibration characteristics of cold-formed steel-supported lightweight residential floor systems. Laboratory tests were conducted for floors with different spans and assemblies to identify the critical parameters that contribute to the control of floor vibration. Both static and dynamic tests were carried out on the floor systems. On-site tests were also conducted in this study to substantiate the results obtained in the laboratory tests and evaluate the actual vibration performance of cold-formed steel-supported lightweight residential floor systems.     

Experimental and numerical analysis of beam to column joints in steel structures

The behaviors such as extreme non-elastic response, constant changes in roughness and resistance, as well as formability under extreme loads such as earthquakes are the primary challenges in the modeling of beam-to-column connections. In this research, two modeling methods including mechanical and neural network methods have been presented in order to model the complex hysteresis behavior of beam-to-column connections with flange plate. First, the component-based mechanical model will be introduced in which every source of transformation has been shown only with geometrical and material properties. This is followed by the investigation of a neural network method for direct extraction of information out of experimental data. For the validation of behavioral curves as well as training of the neural network, the experiments were carried out on samples with real dimensions of beam-to-column connections with flange plate in the laboratory. At the end, the combinational modeling framework is presented. The comparisons reveal that the combinational modeling is able to display the complex narrowed hysteresis behavior of the beam-to-column connections with flange plate. This model has also been successfully employed for the prediction of the behavior of a newly designed connection.     

Elastic local buckling of perforated webs of steel cellular beam-column elements

In this study, the finite element method is employed to determine the critical in-plane longitudinal load at which elastic local buckling of the web of cellular beam-column elements occurs. To simplify the simulation of the problem, the interaction between the flanges and perforated web is approximated by modelling the web only as a long plate having aspect ratio (L/h_w≥10) with multiple circular perforations. The utilized model incorporates restrained out-of-plane displacements along the four edges of the plate. Analyzed plates are subjected to linearly varying in-plane loads to simulate various combinations of axial and flexural stresses. The effect of different geometrical parameters on the elastic buckling load of perforated web plate is investigated. These geometrical parameters include the plate’s length and width, and the perforations’ diameter and spacing. Comprehensive finite element analyses are conducted to identify the behaviour of wide spectrum of perforated web plates at buckling under various combinations of axial compressive load and bending moment. Outcomes of the study are expected to enhance the understanding of the elastic local buckling of web plates of cellular beam-column elements.     

Experimental and analytical investigation of steel column bases

The present work is devoted to the experimental and analytical investigation of the steel column bases. Therefore, eight sets of tests, simulating the column to concrete foundation joint, were carried out. Beside, three-dimensional FEM models of the test specimens were constructed and analysed. Finally, the results of these experimental and FEM analyses were correlated with those obtained from an analytical formula proposed by the authors in a previous work, describing the relation among bending moment and angle of rotation (M-φ) of the column base. The verification among the results seems to be satisfactory.     

Simplified nonlinear progressive collapse analysis of welded steel moment frames

In this study, two nonlinear analysis methods are proposed that can be used for a simplified but accurate evaluation of progressive collapse potential in welded steel moment frames. To this end, the load-resisting mechanism of the column-removed double-span beams in welded steel moment frames was first investigated based on material and geometric nonlinear parametric finite element analysis. A simplified tri-linear model for the vertical resistance versus chord rotation relationship of the double-span beams was developed. The application of the developed model to energy-based nonlinear static progressive collapse analysis was then proposed. The relationship between the gravity loading and the maximum dynamic chord rotation or the concept of collapse spectrum was also established for a quick assessment of the maximum deformation demands.