This paper addresses to the development of a simulated annealing (SA) based solution algorithm which is automated to achieve the simultaneous optimum design of truss type structures with respect to size, shape and topology design variables. The proposed algorithm is designed in such a way that together with applicability to practical design problems, it is also aimed at producing efficient and improved design solutions for the problems of interest. From the practicality point of view, the task is chosen as minimising the weight of the structures under a set of particular constraints imposed by national design code specifications on nodal displacement. member stress and stability. Concerning the efficiency of the algorithm, SA is adapted to be able to work fruitfully in the design spaces of complex problems occupied by many regions of highly different characteristics. The proposed algorithm is tested on two large design example problems taken from the literature for comparison purposes and the results are fully discussed.