Abstract:A new smoothed elastic bimodular constitutive relationship is presented, therefore the sensitivity of stiffness matrix with respect to displacement and the sensitivity of displacement with respect to elastic modulus can be obtained conveniently. A FEM and sensitivity analysis based numerical model is developed to solve direct problems of truss structures with dual extensional/compressive modulus, and Newton-Raphson algorithm is employed in the solution process. By utilizing the solutions of direct problems, a two level sensitivity analysis based algorithm is presented for the identification of bimodulus, Gauss—Newton algorithms is used in the identification. Numerical verification with noisy data is provided with satisfactory results.