Prediction of Buckling Load in Plate Girders Subjected to Pure Bending Moment

The design of plate girders, like any other structures, is linked with many important

parameters. One of these important aspect is the interaction between the flange and web

which determines the capacity of the girder under loadings . In this paper a theoretical

analysis was carried out to investigate the buckling behavior of the web plate in plate girders

in the portion of the pure bending moment, i.e. in the case of simply supported beam subject

to symmetric concentrated loads.

The theoretical analysis is performed using the finite element program (ANSYS 5.4).Three

hundred dimensional finite element models ware examined to clarify the influence of

sectional compactness , aspect ratios of web panel and initial imperfections of webs on the

estimation of the critical load of plate girder under pure moment. An empirical formula to

estimate the critical load of plate girder under pure moment from load- lateral displacement

data is also proposed. The critical loads of such girders computed from the present prediction

equation were compared with those according to different methods .

The procedure adopted in the paper in directed to suggest some accurate and simple

procedures from which a fairly good estimate for the critical moment can be obtained, taking

into account the real boundary conditions between the web and the flanges. Thus, two

different suggestions were undertaken. The first formula can be used to determine the critical

moment from practical or theoretical data concerning the relationship between applied loads

and web out-of plane deformations. The second approach is concerned with the estimation of

the critical moment from a reasonably accurate and simple stress distribution on the cross

section.