Behavior of Steel Plate Girders with Deep Section under Dynamic Effect

Having a minimum mass, equal-sized flanges and no web stiffeners is the most economical plate girder to fabricate. As with rolled I-sections, for a given section modulus a section with a greater depth will have a lower mass than one with a smaller depth, except in some instances where a thicker web is required in the deeper section. A wider flange plate to resist the buckling tendency may be necessary to use, when the compression flange is laterally unrestrained, but this will add to the cost because of the more difficult assembly procedure. In order to arrive at a minimum-mass cross section as much as possible of the material should be located in the flanges and as little as possible in the web, consistent with shear requirements. There is usually an advantage, however, in using a somewhat thicker web in order to reduce welding distortion, or to avoid the use of or number of stiffeners. It can be shown that for a given web depth to thickness ratio the minimum-mass cross section is that in which the area of the two flanges combined equals that of the web, i.e. 2Af = Aw.An important consideration in cost reduction is the use of preferred plate widths and thicknesses for the flange and web elements.