Optimal versions of braced girder used in civil engineering, by Finite Element Method MIHAI NEGRU, VILCU ROSCA, ADRIANA IONESCU Faculty of Mechanics University of Craiova ROMANIA , . Abstract:  This paper presents two optimized versions of a steel structure used in civil engineering obtained thru a process of structural optimization using Finite Element Method. The main advantage of these optimized structures is the cost which is 50% smaller then the cost of a standard version of this steel structure. The optimization process was made using Finite Element Method and Ansys program. The paper presents the results of structural optimization process and the static analysis of these optimized steel structures in two load cases: the snow weight and the seism simulation. KeyWords:  Finite Elements Method, Steel Structure, Civil Engineering, Structural Optimization, Ansys 1 Introduction Steel offers much better compression and tension than concrete and enables lighter construction. Steel structures use threedimensional trusses, so they can be larger than reinforced concrete counterparts. Computerized, highprecision stress analysis and innovative jointing allow an array of structures and shapes. Steel frame construction now predominates. Examples include the 200meter Astro/Dome and Super Dome in the United States and Japan's Fukuoka and Nagoya domes. This paper analyze the steel structures used for manufacturing buildings. These buildings are made from I section beams with large dimensions of the I section (78cm x 26cm), as in figure 1. Fig.1 The present version of the steel structure This kind of structure has multiple disadvantages because the weight of the steel is bigger and the welding process is difficult. So, the costs of these types of structures are bigger then it should be. Basically the optimization process, in this case, consists in improving a initial shape of the braced girder and the columns which sustain it. This searching was made by making different types of structural modifications of shapes and improving those which had a good behavior at snow and seismic loads. These behaviors were determined using linear structural static analysis in Ansys program. The initial shape of the braced girder, which was subjected to the process of structural optimization is presented in fig.2. Fig.2 The initial shape of the braced girder Proceedings of the 10th WSEAS International Conference on MATHEMATICAL and COMPUTATIONAL METHODS in SCIENCE and ENGINEERING (MACMESE'08) ISSN: 1790-2769 364 ISBN: 978-960-474-019-2