Load Of Girders Research Articles

Challenges and possible solutions of the time-variant reliability of ship's hull girder

The main theme of the paper centres on the use of probabilistic methods to assess the hull girder bending capacity to be used in a risk-based inspection planning framework. The effect of corrosion wear on hull girder geometric properties is also discussed, and the annual probabilistic distributions and the probabilistic distributions for given time period are built. A new procedure is then proposed for the probabilistic presentation of the still water and wave-induced hull girder hogging and sagging loads as a single phenomenon. Lastly, the rules of the composition law of the constituent variables are used to build the probabilistic distribution of the total hull girder load and the corresponding total hull girder bending stresses. Thus, it becomes possible to calculate the probability of exceeding any given limit of the total hull girder stresses.

Assessment of the Total Ship’s Hull Girder Bending Stresses for Unified Model of Sagging and Hogging Bending Moments

A method is proposed for calculating the hull girder bending stresses following the procedure in the class rules but in probabilistic terms. The total hull girder bending moment, section modulus and bending stresses are treated as random variables with corresponding probabilistic distributions. The still water and wave-induced hull girder hogging and sagging loads are presented in probabilistic format as one phenomenon, using bi-modal probability density functions. The probabilistic distribution of the total hull girder load is calculated using the rules of the composition of the distribution laws of the constituent variables. After that, the hull girder geometric properties are presented in probabilistic format as annual distributions and distributions for any given life-span. An example is given for 25000 tdw bulk carrier.

Sensitivity analysis of the effect of initial imperfections on the (i) ultimate load and (ii) fatigue behaviour of steel plate girders

Abstract The study is divided into two parts: (i) in the first one, the plate girder (Fig 1) is considered to be exposed to quasi‐constant loading (ie to loads which are either constant or repeated in a very small number of cycles), while (ii) in the other one, the girder is assumed to be subjected to repeated loading. Then it is understandable that the objective of the first part should be to look into the influence of initial imperfections on the static ultimate load of the girder related to the formation of a plastic failure mechanism in it, while that of the second part was to study the effect of imperfections on the stress state under considerably lesser loads, viz under such as to correspond to the development of fatigue cracks in the girder and, consequently, to its fatigue limit state. In this case the state of stress was measured by bending stresses developing in the crack‐prone areas (Fig 4) of the web “breathing” under the repeated loads, which ‐as demonstrated by the Prague experiments ‐ occur...

Structural Characteristics and Applicability of Four-Span Suspension Bridge

A four-span suspension bridge which has two main 2,000 m spans is investigated with respect to the deformation characteristics. Generally, deformation behavior of the four-span suspension bridge is mainly influenced by rigidity of the center tower. This study is focused on properties such as bending and torsional rigidity of the girder, sag ratio, and dead load. The result of this investigation clarified that the lower rigidity under live load than the three-span bridge is caused by the smaller cable spring coefficient of the main span, which is 1/6 of the side span. Nevertheless, the tendency is stable and can be assisted by stiffened rigidity of the center tower. Live load deflection of the girder can be reduced to less than 1/200 of the main span length, which is useful and economical, by stiffening the bending coefficient of the center tower. Moreover, relatively lower rigidity of the center tower is sufficient for the 2,000 m span suspension bridge than for the 1,000 m span case, keeping the same deflection ratio. Three-dimensional sag geometry of the main cable is effective in limiting the torsional deformation, which is an especially important issue for the four-span suspension bridge caused by twist of the center tower.

Load-capacity estimation and collapse analysis of thin-walled beams and columns—recent advances

The present paper is devoted to the recent results of research in the area of load-capacity and post-failure behaviour of thin-walled beams and columns (among them thin-walled cold-formed profiles). It deals with ultimate load and collapse of box-section girders (tubes) of different cross-sections under bending, as well as of lipped and plain channel-section beam-columns. The paper contains the presentation of theoretical analysis and experimental investigation of plastic mechanisms of failure and collapse behaviour of these thin-walled sections. The short review of results obtained in recent years in general precedes those obtained by the Department of Strength of Materials and Structures, TUL. The problem of post-failure behaviour is solved using the rigid-plastic theory adopted and modified for the purposes of the solution taking into consideration strain-hardening of the member’s material. On the basis of experimental investigations theoretical models of plastic mechanisms of failure are produced for different sections. Theoretical analysis is based on the principle of virtual velocities. The problem is solved in an analytical–numerical way. The particular attention has been paid to the influence of the strain-hardening of the material after yielding upon the collapse structural behaviour and also to the influence of cross-section shape and dimensions on the character of collapse. The upper-bound estimation of the load-carrying capacity of analysed thin-walled sections by combining results of non-linear, elastic post-buckling analysis with the results of plastic mechanism analysis is carried out. Results are presented in diagrams showing post-failure curves as well as curves representing structural behaviour in the whole range of loading up to and beyond the ultimate load. Some results are compared with experimental results and those obtained from FE analysis. A comparison of lower- and upper-bound estimation of the load-carrying capacity is discussed and illustrated in diagrams. Conclusions dealing with the influence of strain-hardening phenomenon displayed by the material upon the load-carrying capacity and collapse behaviour of examined sections are derived. Also conclusions concerning different upper- and lower-bound estimations of the load-carrying capacity of analysed sections are presented.

Finite element modelling of plate girders with web openings

This paper is concerned with a finite element model to predict the behaviour and ultimate load of plate girders with web openings. The finite element package ABAQUS is used to model the plate girders with web openings. Accuracy of the model is assessed by applying it to plate girders tested earlier by other researchers. Comparison of analytical results with the available experimental results for yielding patterns, ultimate load values and load–deflection relationships show good agreement between the finite element and experimental results thus validating the accuracy of the proposed model. The proposed finite element method was extended to carry out a parametric study. The study covered parameters such as web slenderness and flange stiffness.

Initial shape of cable-stayed bridges

A finite element computation procedure for determining the initial shape of cable-stayed bridges under the action of dead load of girders and pretension in inclined cables is presented. The system equation of cable-stayed bridges including the nonlinearities due to large displacement, beam-column, and cable sag effects is first set up and then solved using the Newton-Raphson method on increment-iterationwise. Based on a reference configuration and an assumed cable pretension force, the equilibrium configuration under dead load is found. Further, by adjusting cable forces, a ‘shape iteration’ is carried out and a new equilibrium configuration, i.e., a more reasonable initial shape, can be determined. The shape iteration is repeated until the desired tolerance is achieved. Numerical results show that a more accurate initial shape having reasonable prestress distribution and less deflection of girders can easily be determined by the proposed procedure.

Initial shape of cable-stayed bridges

A finite element computation procedure for determining the initial shape of cable-stayed bridges under the action of the dead load of girders and pretension in inclined cables is presented. The system equation of cable-stayed bridges including the nonlinearities due to large displacement, beam-column, and cable sag effects is first set up and then solved using the Newton-Raphson method in an increment-iterationwise approach. Based on a reference configuration and an assumed cable pretension force, the equilibrium configuration under dead load is found. Further, by adjusting cable forces, a ‘shape iteration’ is carried out and a new equilibrium configuration, i.e., a more reasonable initial shape, can be determined. The shape iteration is repeated until the desired tolerance is achieved. Numerical results show that a more accurate initial shape having reasonable prestress distribution and less deflection of girders can easily be determined by the proposed procedure.

Parametric Study of Continuous Prestressed Composite Girders

The technique of prestressing has been used successfully to improve the performance of existing concrete structures. However, very few applications of this technique can be found in steel structures. Prestressing by means of high‐strength cable or bar can be used to effectively increase the working load and the ultimate capacity of composite steel‐concrete girders. The benefits of prestressing the steel wide flange section in composite construction can be achieved in strengthening of existing structures as well as in the design of new structures. In this paper, the elastic behavior of continuous, prestressed, composite girders with straight and draped tendon profiles is examined. The effects of design variables such as the prestress force, tendon eccentricity, and tendon length on the working load and deflection of girders are studied. The results show that the allowable load of girder increases proportionally with increase in prestress force and eccentricity. The effect of load pattern on the change in t...

Plastic Collapse Load of Continuous Composite Plate Girders

Composite beams and girders with a reinforced concrete slab have different moment-curvature characteristics, depending on whether the moment is positive or negative. It is usually assumed for the maximum strength of the negative moment section that the concrete slab does not carry tensile stresses, but the reinforcing steel bars are considered to act compositely with the steel section. In the Load Factor Design (LFD) method of the AASHTO Standard Specifications for Highway Bridges, the maximum strength of laterally braced I-shaped sections is determined based on the provision of compact or noncompact sections. A compact section is defined as a section that can reach the plastic moment and rotate inelastically at this constant plastic moment. Recently (1986), the AASHTO Guide Specification for Alternate Load Factor Design Procedures was published for the design of steel beam bridges using braced compact sections. This procedure was adopted as a logical extension of the existing LFD method and it is based on the Autostress Design (ASD) procedures. The resistance of continuous beam bridges is determined by the plastic-mechanism method. In this method, a considerable amount of plastic rotation is required at the negative moment sections of intermediate supports, and so the concept of an effective plastic moment was applied. The ultimate load was assumed to be reached when a composite section in positive bending reached the plastic moment. The usefulness of this method was confirmed by design examples and loading tests of an actual bridge.

Interactive computer-aided load and resistance factor design of plate girders

Based on the newly proposed load and resistance factor design specification for steel buildings, an interactive microcomputer program is presented for design of welded stiffened steel plate girders. The program is capable of designing hybrid girders and takes into account the tension-field action of the web. The loading on the girder may consist of a uniformly distributed load plus any number of concentrated loads. Single or double plates may be used as transverse stiffeners. For flangeto-web connections, either continuous or intermittent fillet weld may be specified. The program rounds off the thickness and width of the flange plates and stiffeners and the thickness of the web plate to practical sizes according to the increments specified by the user/designer. This program demonstrates the effectiveness of microcomputers in practical design of structures.

A Method for the Estimation of Collapse Loads of Corner Girders and Struts

The equivalent thickness of deflected panels under compression and bending moment are estimated by the energy method. The effective flexural rigidity of columns with rather small slenderness ratio are estimated by using Johnson's and Euler's formula. Using these equivalent thickness and effective flexural rigidity, the collapse load of corner girders and struts are calculated by elastic finite element method. The collapse load and collapse mechanism are compared with experimental results. This method will be usefull at the initial design stage for the simplicity.

A MECHANISM SOLUTION FOR PREDICTING THE COLLAPSE LOADS OF SLENDER PLATE GIRDERS WHEN SUBJECTED TO IN-PLANE PATCH LOADING.

Keywords CARDIFF UNIVERSITY COLLEGE MECHANISMS, COLLAPSE, PLATES, PATCH, EXPERIMENTS, CALCULATIONS, HINGES, DESIGN, INTERACTION, BENDING, BEHAVIOUR, SOLUTIONS, LOADS, GIRDERS, PLASTIC, PLANE, DATA, UPPER BOUNDS, FLANGES, FORMULAE, STRESS, STOCKY, PREDICTION, SLENDER, IN PLANE, FAILURES, WEBS, METHODS, THEORY, YIELD LINE, THICK... Show All

A DESIGN METHOD FOR PREDICTING THE COLLAPSE BEHAVIOUR OF PLATE GIRDERS.

A simple design method is presented which is capable of predicting the collapse load of plate girders to a high degree of accuracy. It can be applied to both symmetrical and asymmetrical plate girders, reinforced by both transverse and longitudinal stiffeners, when subjected to the combined action of shear and bending. Detailed comparison is presented between the predicted failure loads obtained using the proposed design method and all relevant available experimental data.(a) /TRRL/

Minimum Weight Design of Structures Based on Buckling Strength and Plastic Collapse 2 nd Report

In the Previous report the authors showed a method of plastic analysis of plate girders in postbuckling subjected to shear force.Herein we present a simplified method to determine the collapsing load of plate girders in postbuckling under pure bending.Namelymu=mcr+β(1-mcr) where, mu=Mu/MY, mcr= Mcr/MYMu : Ultimate bending moment Mcr : Web buckling moment.MY : Flange yielding moment.β : Effectiveness of section modulus in postbuckling.The results of tests carried out by the authors, as well as the other research organizations are compared with the theory which showed a good agreement.A modified interaction curve for collapsing in postbuckling under bending moment and shearing force was introduced.

Minimum weight design of structures based on buckling strength and plastic collapse

A study on the plastic design method of plate girders whose webs buckled in shear is presented. Local buckling of flanges and shear buckling of webs set limitations to the plastic design of plate girders, and it is recommended that the dimensions of cross section shoule be so designed as to prevent various types of buckling from taking place up to the strain hardening range.The web hight, however, is regarded as the most important factor when we aim at the minimum weight, and girders are able to carry shear force by tension field action after buckling occurs in their webs. So it is necessary to introduce the concept of incomplete tension field into the plastic design method. The problem was studied by K. Basler, but the interaction curve he proposed seemed to be unsafe and the theoretical direction of tension field does not coincide with our experiments.The authors tried a different approach based on the lower bound theory and the assumption that the compressive principal stress after web's shear buckling maintains the value at buckling in the same direction. Conclusions are as follows.(1) There are two types of shear collapsing modes. One is that the web yields uniformly along the tension field and deforms in rhomic. The other is that the yielded band grows nearly in diagonal direction and the adjacent flanges are pulled into the web finally.(2) Interaction curve between bending moment and shearing force including the web buckling in shear is introduced. It is showed that the maximum carring moment is reduced by not only the shearing stress in web, but also the compressive stress in flanges caused by the tension field action.(3) The generalized method to decide the collapsing load of indeterminate girders using the linear programming method is showed.(4) Tests were carried out on 2 span continuous girders subjected to concentrated loads, and the tests results showed a good agreement with the theory.

On the buckling of a girder, elastically supported and elastically clamped in a number of equidistant points

Lately the authors have been engaged in an inquiry with respect to the safety of scaffolding constructions, as used in the erection and the repair of large buildings. A question of detail was presented by the determination of the buckling load of a prismatic girder, elastically supported and elastically clampled in a number of equidistant points. The present paper gives an answer to this problem with the understanding that the endpoints of the girder — though elastically clamped — are fixedly supported.