Number Of Longitudinal Stiffeners Research Articles

Designing method for fire safety of steel box bridge girders

This paper presents a designing method for enhancing fire resistance of steel box bridge girders (closed steel box bridge girder supporting a thin concrete slab) through taking into account such parameters namely; fire severity, type of longitudinal stiffeners (I, L, and T shaped), and number of longitudinal stiffeners. A validated 3-D finite element model, developed through the computer program ANSYS, is utilized to go over the fire response of a typical steel box bridge girder using the transient thermo-structural analysis method. Results from the numerical analysis show that fire severity and type of longitudinal stiffeners welded on bottom flange have significant influence on fire resistance of steel box bridge girders. T shaped longitudinal stiffeners applied on bottom flange can highly prevent collapse of steel box bridge girders towards the end of fire exposure. Increase of longitudinal stiffeners on bottom flange and web can slightly enhance fire resistance of steel box bridge girders. Rate of deflection-based criterion can be reliable to evaluate fire resistance of steel box bridge girders in most fire exposure cases. Thus, T shaped longitudinal stiffeners on bottom flange incorporated into bridge fire-resistance design can significantly enhance fire resistance of steel box bridge girders.

A numerical model for evaluating fire performance of composite box bridge girders

This paper presents an approach for evaluating fire performance of composite box bridge girders exposed to fire. The model takes into account critical parameters, namely, fire scenario, fire exposure length, load level, numbers of longitudinal stiffeners in web and bottom flange and web pattern, that influence fire performance of bridges. A three dimensional finite element model, developed in the computer program ANSYS, is applied to model the fire response of composite box bridge girders. The finite element model is validated by comparing predicted sectional temperatures and deflections from the model with fire test data generated from a test on box bridge girder. The applicability of the numerical model in practical application is illustrated through numerical analysis on a composite box bridge girder subjected to simultaneous structural loading and fire exposure. Results from the numerical study clearly show that fire severity, fire exposure length, load level, number of longitudinal stiffeners and web slenderness have significant influence on the fire resistance of composite bridge girders. Provision of longitudinal stiffeners can result in lower deflections; thus enhancing fire resistance. Further, inclined web (configuration) incorporated into sectional shape can enhance fire resistance of composite box bridge girders.

Geometric Evaluation of Stiffened Steel Plates Subjected to Transverse Loading for Naval and Offshore Applications

This work searched for the optimal geometrical configuration of simply supported stiffened plates subjected to a transverse and uniformly distributed load. From a non-stiffened reference plate, different geometrical configurations of stiffened plates, with the same volume as the reference plate, were defined through the constructal design method. Thus, applying the exhaustive search technique and using the ANSYS software, the mechanical behaviors of all the suggested stiffened plates were compared to each other to find the geometrical configuration that provided the minimum deflection in the plate’s center when subjected to this loading. The optimum geometrical configuration of stiffeners is presented at the end of this work, allowing a reduction of 98.57% for the central deflection of the stiffened plate if compared to the reference plate. Furthermore, power equations were adjusted to describe the deflections for each combination of longitudinal and transverse stiffeners as a function of the ratio between the height and the thickness of the stiffeners. Finally, a unique equation for determining the central deflections of the studied stiffened plates based only on the number of longitudinal stiffeners without significantly losing accuracy has been proposed.

Ultimate strength of hull structural stiffened plate with pitting corrosion damage under unaxial compression

Pitting corrosion can cause the ultimate strength degradation of hull structure. This research aims at the development of ultimate strength calculation formula of pitted stiffened plates under unaxial compression. Firstly, the relative parameters (such as sizes of stiffened plates, sizes and shape of pits, initial geometric imperfection and residual stresses of stiffened plates, boundary condition and type and size of finite element) of pitted stiffened plates in the finite element analysis were analyzed and assumed. Secondly, the effects of a few factors (such as distribution status, depth and position of pits, number of longitudinal stiffeners and sizes of stiffened plates) on the ultimate strength with respect to the corroded volume loss were discussed. Lastly, the ultimate strength reduction formulae of pitted stiffened plates based on corroded volume loss were obtained by the data analysis from lots of nonlinear finite element analyses.

Stiffness requirement for flat-bar longitudinal stiffener of box-girder compression flanges

In this paper, the moment of inertia requirement of flat-bar longitudinal stiffener of bottom flange in steel box girder is investigated through finite element modeling. The required minimum stiffness for longitudinal stiffeners of box girder flange is given in the AASHTO LRFD Bridge Design Specification and is modified by Yoo. However, this requirement is adopted for T-shape stiffeners. Here, the effect of important parameters on the minimum required moment of inertia of flat-bar stiffener is numerically investigated by examining the anti-symmetric mode of buckling. This study presents the results that are based on 3D finite-element analysis of four hundred hypothetical compression flange models stiffened by varying numbers of flat-bar longitudinal stiffeners with realistic dimensions such as the height of stiffener, the thickness of the compression flange, the number of longitudinal stiffeners and the aspect ratio of plate panel. A new proposed equation for required minimum stiffness of the flat-bar longitudinal stiffeners is derived from nonlinear regression analyses. Beside that the study has taken into account the effect of boundary conditions and the effect of inelastic transition on the critical buckling stress of compression flange. Through the evaluation of a design example, the validity and reliability of the new proposed equation is demonstrated.

Stability of plates and plated structures: General Report

This paper is aimed at presenting two main aspects of the design rules of Part 1.5 of ENV 1993-3 (ENV 1993-1-5. Eurocode 3–Design of steel structures: part 1.5: Supplementary rules for planar plated structures without transverse loading. Brussels: CEN, 1997), which result from some research efforts conducted in the last decade. Also some background to these rules is given. First, the resistance of plates subjected to direct stresses is examined. It is based on the consideration of two types of behaviour (platelike and columnlike behaviour) with a possible interaction between both. The general procedure can be simplified a bit when there are a very few number of longitudinal stiffeners. Second, the resistance to shear stresses of an unstiffened plate as well as the effect of longitudinal stiffeners are commented on. The fatigue resistance to web breathing is a topic that is not satisfactorily covered by the codes. However, substantial progress was achieved in the field, and this is briefly commented on. When design rules are concerned, not only are they reported on, but also a critical evaluation is made and possibly some tracks are proposed in order to improve them.

剪断を受ける矩形ウェブ板縦方向スチフナの実用算式について

In recent years the research concerning the numerical solutions of the buckling strength of the stiffened web plates has been rapidly developed by use of I.B.M., and systematic stability coefficient's values have been published by K. Kloppel, J. Scheer and others. A method is herein developed for determining the stability of the longitudinally stiffened plates under shearing forces by proposing the simplified formulas applicable to the actural design. The basic equations of the stability coefficient taking out from datas up to this date is exhibited as following form. [numerical formula] where [numerical formula] [numerical formula] β=a/b, a=length of web plate, b=width of web plate q=(number of longitudinal stiffeners)+1, μ_L=EJ_L/N・b N=Et^3/12(l-v^2), t=thickness of plate, J_L=moment of inertia of longitudinal stiffener b_0=b/q, b_0'=minimum width of panel plate. The simplicity of the proposed formula has a tendency to give rather large safetyside errors in the case of large values of β or μ_L, but it does not bring out much errors to be methoned of in the range of applicable design. The formula can be applied to the transverse stiffeners such as vertical stiffeners of plate girders, and derived formula can be represented in the form. [numerical formula] where J_0=moment of inertia of vertical stiffeners a_0=spacing of vertical stiffeners.