Preliminary analyses have shows that membrane materials play quite an important role in determining the structural responses of orthotropic steel deck bridges. This necessitates search for a realistic representation of the behaviour of the membrane material. For this purpose, a Desai type material model was selected to describe the response of the membrane material to any state of stress.
In this contribution, a procedure to determine the parameters of the material model using "the global model concept" from results of the four-point shear tests will be described. The constitutive model is verified by simulating laboratory tests. Some numerical examples of the application of the model are also given.