Finite Element Modeling of Girders with Large Web Openings

In finite element modeling, the objective is to simulate the actual behavior of a loaded structure so that the resulting structural stress predictions are sufficient to make design decisions. Very often it is not economically viable to generate a single mathematical model able to accurately reflect all the phenomena related to the behavior of a particular structure. In such situations, it is necessary to consider multiple models, some or all of which are reasonable compromises of accuracy vs. cost. The final choice of the model depends on engineering judgment, and differing situations demand different considerations. The primary purpose of this paper is to discuss some of the tradeoffs involved for one particular type of structure. The structure considered here can be described as a multi-celled girder, which contains manholes placed in vertical plates called bulkheads. These access openings need to be provided for construction as well as for inspection. This type of structure is encountered in large mining and earthmoving equipment. The behavior of plate shear walls in buildings, and diaphragms in box girders that contain manholes, is similar to the bulkheads analyzed here. The primary interest here lay with the bulkheads containing the manholes. Many of these manholes exist in a given structure, hence an accurate, but economical model is sought to enable the designer to determine the extent of stress concentration for each configuration.