Analytical Model for Determining Electric Overhead Traveling Crane Skewing Forces on Crane Runways

Abstract

A generalized model that can be used to determine service level electric overhead traveling (EOT) crane skewing forces for the design of crane runways is proposed. The model has various characteristics that address deficiencies in current skewing force guidance. These characteristics include the ability to model any common EOT crane configuration; direct output of skewing force magnitudes and directions at the bridge wheel tractive surfaces; incorporation of the runway girder and its lateral stiffness to enable evaluation of skewing forces at any crane bridge location; inclusion of rational crane inertial forces; and quantification of service level bridge drive forces. Two existing cranes were experimentally investigated, and finite element analyses performed to validate the model, which showed that the proposed approach performed significantly better overall than the current Association for Iron and Steel Technology guidance for developing skewing forces. Using the model, a parametric analysis was conducted to determine skewing force coefficients for ten common crane configurations. The proposed model improves the accuracy of the approach suggested by current design guidance, which may not accurately specify service level crane skewing force magnitudes and directions. Overhead cranes produce skewing forces on the runway that act perpendicular to the direction of crane travel and cause fatigue stresses. As North American design codes do not quantify crane skewing forces in detail, a model of the combined crane and runway system is proposed that can be used to determine detailed crane skewing forces with any three-dimensional frame analysis program. For normal crane operating conditions, current design guidance for crane skewing forces generally underestimates service level skewing force magnitudes and does not correctly specify skewing force directions for all types of overhead cranes. This affects crane runway member and connection fatigue design. A more accurate determination of crane skewing forces results in more reliable crane runway designs.