Topology optimization of steel girders subjected to thermal and mechanical loads

Topology optimization is a load path based design method that optimizes material distribution by finding the optimum number, location and shape of the hole/opening within a given design space subjected to given loading and boundary conditions. It improves the weight to stiffness ratio and aesthetic appeal of specific structural forms. This work, perhaps, describes the first successful application of structural topology optimization of steel I section beam subjected to a thermal gradient. ANSYS is used to perform transient thermal analysis of the beam subjected to ISO 834 fire and temperature profile of the beam is captured with respect to time. The software package HyperWorks Student Edition V14.0 is utilized to perform topology optimization. The effect of thermal loading is considered through thermal strain and degradation in material properties. Due to different material properties at different temperatures, the beam is treated as a composite beam having different Young’s Modulus, thermal conductivity and thermal expansion coefficient with respect to corresponding temperature. The optimization is performed on the web of the beam considering geometric nonlinear effects. The compliance of the structure is minimized with respect to its volume fraction with a constraint on the overall deflection of the beam (to ensure serviceability limit states are satisfied) using the solid isotropic material with penalization (SIMP) technique. Manufacturing constraints are also applied on the design so that design results can be manufactured economically. Geometry of the optimized beam is extracted and remeshed and then a Finite Element analysis is performed on the optimized beam to ascertain the performance in comparison to the original solid beam in terms of deflections, load carrying capacities and stress intensities. It is found that the optimized beam satisfies the entire serviceability criterion according to IS 800:2007 while it is more economical compared to a tradition design.by Satya ShrivastavM.Tech