Optimum design of cross-sectional profiles of pultruded box beams with high ultimate strength

Pultruded box beams under bending may be subjected to local buckling which causes premature failure of the beams. As such it is important to design pultruded box beams with high local buckling resistance to increase their ultimate strength. This paper presents an optimum design approach for cross-sectional profiles of pultruded box beams of (approximately) the same mass with emphasis on accomplishment of high local buckling resistance through finite element analysis. Five different sectional profiles have been designed by stiffening a simple box, and finite element analysis is used to study linear buckling and postbuckling of the beams. Results for the critical loads of linear buckling and local buckling judged by stress variation, stresses and deformations in postbuckling are presented. The computational results show one of the proposed sectional profiles does not develop local buckling and produces much smaller stresses and deformations within the load range of interest.