Empirical formulations for estimation of ultimate strength of continuous stiffened aluminium plates under combined in-plane compression and lateral pressure

The present research was undertaken based on the results obtained by the same authors in a sensitivity study on the buckling and ultimate strength of continuous stiffened aluminium plates. Empirical expressions are developed for predicting ultimate compressive strength of welded stiffened aluminium plates used in marine applications under combined in-plane axial compression and different levels of lateral pressure. Existing data of the ultimate compressive strength for stiffened aluminium plates numerically obtained by the authors through the previously performed sensitivity analysis are used for deriving formulations that are expressed as functions of two parameters, namely the plate slenderness ratio and the column (stiffener) slenderness ratio. Regression analysis is used in order to derive the empirical formulations. The formulae implicitly include effects of the weld on initial imperfections, and the heat-affected zone.     

Numerical analysis of piping elbows for in-plane bending and internal pressure

This work presents the development of two different finite piping elbow elements with two nodal tubular sections for mechanical analysis. The formulation is based on thin shell displacement theory, where the displacement is based on high-order polynomial or trigonometric functions for rigid-beam displacement, and uses Fourier series to model warping and ovalization phenomena of cross-tubular section. To model the internal pressure effect an additional formulation is used in the elementary stiffness matrix definition. Elbows attached to nozzle or straight pipes produce a stiffening effect due to the restraint of ovalization provided by the adjacent components. When submitted to any efforts, the excessive oval shape may reduce the structural resistance and can lead to structural collapse. For design tubular systems it is also important to consider the internal-pressure effect, given its effect on the reduction of the pipe flexibility. Some conclusions and examples are compared with results produced by other authors.     

Ultimate strength formulations for stiffened panels under combined axial load, in-plane bending and lateral pressure: a benchmark study

This paper develops advanced, yet design-oriented ultimate strength expressions for stiffened panels subject to combined axial load, in-plane bending and lateral pressure. The collapse patterns of a stiffened panel are classified into six groups. It is considered that the collapse of the stiffened panel occurs at the lowest value among the various ultimate loads calculated for each of the collapse patterns. The panel ultimate strengths for all potential collapse modes are calculated separately, and are then compared to find the minimum value which is then taken to correspond to the real panel ultimate strength. The post-weld initial imperfections (initial deflection and residual stress) are included in the developed panel ultimate strength formulations as parameters of influence. The validity of the developed formula is confirmed by comparing with the mechanical collapse tests and nonlinear FEA. A comparison of the present method is also made with theoretical solutions from the Det Norske Veritas classification society design guideline. Important insights developed are summarized.     

A simple but exact method for vibration analysis of composite laminated plates with all edges simply supported and under lateral and in-plane loading

A simple but exact method of calculating the natural frequencies of vibration for some structural members with all edges simply supported and under lateral and in-plane loading, is presented herein. This method uses the deflection influence surfaces which can be obtained by any method for vibration analysis and consists of determining the deflected mode shape of the member due to the inertia force under resonance condition. Beginning with initially guessed mode shape, exact mode shape is obtained by the process similar to iteration. In this paper, equations are given for the case of special orthotropic laminates. However, the same equations can be used for any laminate as long as B₁₆, B₂₆, D₁₆, and D₂₆ are negligible as the number of plies increases and some laminates having such properties are presented.     

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.     

Compressive strength of rectangular plates under biaxial load and lateral pressure

Equations are derived to assess the strength of plates subjected to biaxial compressive loads, including the effect of initial distortions and residual stresses. These equations are then extended to the case of simultaneous lateral pressure loads.In calibrating the proposed methods and in assessing their model uncertainty published results of experiments and of numerical calculations have been used.The proposed methods were shown to be unbiased as regards plate slenderness and aspect ratio. The model uncertainty of each method was quantified and thus can be used to derive design formulations with the desired level of safety.     

工字型铝合金轴心受压构件中美设计规范对比

对比GB50429-2007《铝合金结构设计规范》、DGJ08-95-2001《铝合金格构结构技术规程》（试行）、美国铝合金设计规范中6061-T6工字型铝合金构件的整体稳定系数,求出了铝合金板材不同宽厚比下弹性屈曲允许应力,得到了铝合金构件不同长细比与宽厚比之间的关系.工程设计中应综合考虑整体稳定、局部稳定及局部屈曲的影响,以确定最合理的截面形式.     

A new stiffened plate element for the analysis of arbitrary plates

In spite of the large number of finite elements developed so far, most of these lack in generality, and are found to be inadequate and inefficient in some way or other, when it comes to analyzing plates of arbitrary geometrical configurations. So far the isoparametric element has been the most successful among available elements because of its ability to model a curved boundary successfully. However, the shear-locking problem inherent in the isoparametric element makes it unsuitable for analyzing thin plates of arbitrary shapes. Though research has been conducted using reduced integration and stabilization to overcome the problem, the formulations either do not converge to the correct solution in the thin-plate limit or they make the stiffness matrix a singular one. In this paper, a four-noded stiffened plate element is developed. This has the advantages and elegance of an isoparametric element in modelling arbitrary shaped plates, but without the disadvantage of shear-locking phenomena. Though this element is a high-order element, only the usual degrees of freedom have been considered, and performance is superior to that of the low-order ones. The stiffened plate element has the feature of accommodating the arbitrary shape of the plate geometry, and the stiffener modelling has been done in a general manner, with the stiffener lying anywhere with arbitrary orientation, and not necessarily following the nodal lines. The new element has been successfully used for the static, free vibration and stability analyses of arbitrary bare and stiffened plates. The results are found to agree quite satisfactorily with those of previous investigators.     

Non-linear plastic analysis of steel arches under lateral buckling

Curved graphs are proposed that relate the shape of the box cross-section of an arch to the real ultimate lateral strength for various values of length, support conditions and of height of the cross-section.The real ultimate lateral strength of a series of arches is determined and the results obtained are then compared to those provided by Sakimoto and Komatsu [1].Elastic–plastic steel material and geometric non-linearity hypotheses, residual stresses, and initial lateral deflection are all taken into consideration with respect to the real ultimate lateral strength.     

Modelling and analysis of retrofitted and un-retrofitted masonry-infilled RC frames under in-plane lateral loading

In the context of various developing countries where many old structures require retrofitting or strengthening work to mitigate earthquake hazards, a cost-effective method is the retrofitting of damaged masonry-infilled reinforced concrete (RC) frames using ferrocement overlays, and the strengthening of existing infilled RC frames with ferrocement. However, no reliable mathematical or computational tool is accessible in the open literature to estimate the effect of such a retrofitting technique quantitatively. The present study is a numerical investigation of the retrofitting effect of masonry-infilled RC frames using ferrocement. A finite element technique has been used effectively to develop a computational model for analysing bare RC frames, together with un-retrofitted and retrofitted masonry-infilled RC frames. The proposed model accounts for the material nonlinearities of both concrete and masonry, and the yielding of reinforcing steel. It is shown that the proposed model can be used effectively in predicting the load carrying capacity of existing RC frames, as well as the required degree of strengthening when ferrocement overlays are applied as a retrofitting scheme. A parametric study was performed using the proposed model on bare and infilled frames to quantify the effects of different parameters. This enabled the development of a simplified equation for predicting the ultimate load carrying capacity of masonry-infilled RC frames, which proved to be reasonably accurate and which was validated by both experimental and numerical results.     

Buckling of cracked functionally graded plates under tension

Buckling of functionally graded cracked plates under tension has not been investigated so far. In this paper critical buckling load of functionally graded plates containing a crack has been obtained using classical plate theory through the finite element method. Displacement in vicinity of crack tips has been approximated using previous solutions related to bending of cracked plates. Effect on buckling of plate under uni-axial and bi-axial tension of different parameters, such as plate dimensions and material properties, are studied. Results show that the critical load decreases as material gradient index increases, while bi-axial loading leads to higher critical loads compared to uni-axial case.     

Numerical study on the permissible gap of intermittent fillet welds of longitudinally stiffened plates under in plane axial compression

Intermittent fillet welding of stiffeners to plates and its influence on the collapse behaviour of stiffened plates is investigated applying the finite element method. Special attention is paid to the modelling of the fillet welds at the plate-to-stiffener junction. Some available experimental results are simulated in order to obtain reliable numerical results. A series of numerical analyses of stiffened steel plates subjected to an in plane axial compressive load has been performed. Stiffened plates are selected from the deck structure of real sea-going ships and inland waterway vessels. Complete equilibrium paths are traced up to collapse for the non-linear elastoplastic response of stiffened plates. Finally a proposal is presented for the permissible gap of welds in intermittent fillet welding of stiffened plates.     

低周反复荷载作用下钢筋混凝土异形柱受力性能试验研究

通过对13根钢筋混凝土异形柱的低周反复加载试验,分析了不同肢长、轴压比、配箍率及纵筋不同配置形式等因素对异形柱承载力及抗震性能的影响。结果分析表明,试件的承载力随着轴压比的增大而提高,但延性降低明显;异形柱腹板的增大提高了试件的承载力,但变形能力及延性有所降低;增大配箍率及端部加强纵筋对试件的延性有一定的改善。     

均布条形荷载作用下支护结构上的侧压力计算

从布辛尼斯克（Ｂｏｕｓｓｉｎｅｓｑ）解出发,推导了均布条形荷载作用下支护结构上的侧压力计算公式,并给出了计算参数表,利用此公式和表格进行侧压力计算,比较方便、简单。     

Ultimate strength of longitudinally stiffened I-girder webs subjected to combined patch loading and bending

A numerical study is performed to investigate the ultimate strength of I-girder webs subjected to the combined action of patch loading and bending moment. The study was conducted by means of nonlinear finite element analysis. Initial geometrical imperfections, plastic material behaviour and large deflection effects were considered in the model. The finite element model was validated against experimental results taken from the literature. A parametric study was carried out in order to investigate the influence of the magnitude of the bending moment and the relative location of the stiffener on the ultimate strength to patch loading. Furthermore, diagrams showing the interaction between the aforementioned parameters are presented.     

Numerical and experimental investigations on the compression behaviour of stiffened plates

The main objective of this paper is to present the results of the finite element method for non-linear analysis of stiffened plates subjected to axial compression load considering post-buckling behaviour up to collapse. For this purpose two series of well executed experimental data on longitudinally stiffened steel plates with and without transversal stiffeners subjected to uniform axial in-plane load carried out to study the buckling and post-buckling up to final failure have been chosen. The first series are those of Ghavami where the influences of stiffener cross-section of the type rectangular (R), L and T, their spacing and the presence of rigid transversal stiffeners have been studied. The second series of Tanaka & Endo, where the behaviour of stiffened plates having three and two flat bars for longitudinal and transversal stiffeners respectively were analysed. For the purpose a well-established commercially available Finite Element program ANSYS has been chosen. The selected element was SHELL43, which can trace the full-range, elastic-plastic behaviour of the stiffened plates. It is seen that the simulated results of FEM are in good consistency with the test results.     

Strength assessment of steel plates subjected to compressive load and dent deformation

This work presents an assessment of the ultimate compressive strength of damaged steel plates with a local dent. Extensive non-linear finite element analyses are performed, where three groups of analyses are considered. In the first group, the effect of the dent orientation (longitudinal and transverse) is studied for three plate thicknesses. For the second group, the direction of the dent depth (upward and downward) with respect to the global initial imperfection is explored. In the third group, the variation of the dent size for several plate thicknesses and its influence on ultimate compressive strength is investigated. The post-collapse behaviours are discussed and the inflection plate slenderness with and without dent is observed, at which the behaviour of the plate changed. A certain dent breadth to the plate breadth ratio is established, revealing the different plate response. Based on the performed analyses, a generalised expression of the ultimate strength reduction factor due to dent is developed.     

四肢钢管混凝土格构柱极限承载力试验研究

进行共计22根四肢钢管混凝土格构柱的极限承载力试验,试验参数为长细比和偏心率。介绍试验过程和试件的破坏形态,对试件的荷载-挠度曲线、极限承载力及组成构件的受力等进行了分析。试验结果表明,格构柱的柱肢以受压为主,缀管受力较小且处于弹性阶段。近载侧柱肢在试件进入非线性后紧箍效应开始发生作用且不断增大。格构柱破坏时有较明显的面内弯曲,属整体破坏。随着长细比和偏心率的增大,构件整体侧向挠度增大、极限承载力降低。长细比和偏心率对极限承载力的影响基本上是独立的,格构柱总体承载力的折减系数可采用分离的偏心率折减系数和长细比折减系数相乘来计算。研究结果表明,偏心率折减系数可采用与单圆管钢管混凝土偏压柱相似的公式计算;长细比折减系数计算中,换算长细比可应采用简化的放大系数法。     

Lower bound buckling strength of axially loaded sandwich cylindrical shell under lateral pressure

Effects of the lateral pressure on the FEM and reduced stiffness lower bound buckling strength of axially loaded sandwich cylindrical shell are examined. Further, a reduced stiffness lower bound buckling strength for the axially loaded sandwich cylindrical shell under lateral pressure is proposed. The effect of the lateral pressure on the FEM and reduced stiffness lower bounds are corresponding; it causes them to reduce slightly. However, reduced stiffness buckling mode shape remains the same. In addition, the proposed reduced stiffness lower bound buckling strength is shown to provide effective and valid for cores having different shear stiffness. It provides comparatively close lower bounds to short axially loaded sandwich cylindrical shells under lateral pressure. Further, it provides a safe lower bound that does not depend on precise geometrical imperfection spectra and lateral pressure and it is simple and easy to employ.     

Experimental and numerical investigations of axially loaded RC walls restrained on three sides

Axially loaded reinforced concrete (RC) walls in tilt‐up structures can be supported top and bottom only by floors or roof structures. However, RC walls are often combined to form I‐, C‐, T‐, and L‐shapes to make efficient use of the building area in multi‐storey buildings. With these configurations, walls may also be laterally supported on either or both sides by interconnecting walls. While many researchers have investigated the behaviours of RC walls, either in one‐way action or two‐way action supported on four sides with and without openings, limited research has been conducted on two‐way action walls supported on three sides (TW3S). As such, this paper experimentally and numerically investigates the behaviour of TW3S walls. Details of the 12 half‐scale walls tested, including experimental setup, failure loads, crack patterns, and load‐deflection characteristics, are reported. In addition, the Finite Element Method using ABAQUS software for investigating the behaviour of TW3S walls is described in detail. Finally, due to the conservative nature of code design equations and there being limited available methods for predicting the ultimate load of TW3S walls with openings, a rigid‐plastic approach has been proposed in this study to evaluate the failure load of TW3S walls.