Abstract: Fiber-reinforced materials are characterized by macro-anisotropy. Bridges ore formed when cracks appear. Up to now, almost all the research efforts on bridges have been limited to static analysis. In this paper, a dynamic model for bridges is set up to study the dynamic fracture behavior of the bridges. In the model, loads are substituted for the bridge segments and the fibers continue to rip off when the cracks start propagating. An analytical solution on the crack propagation in an orthotropic body under a point force Pt/x is developed in this paper. The solution is utilized to obtain various solutions of the model by means of super position.