Explain the principles of structural optimization and their applications in designing efficient and cost$-$effective civil engineering structures. How do optimization techniques, such as genetic algorithms, simulated annealing, and gradient$-$based methods, help engineers achieve optimal designs that meet performance criteria and constraints? Discuss the factors that influence structural optimization, including material properties, geometric configurations, and loading conditions, and explain how advanced optimization tools and software are used in practice to improve the design and efficiency of bridges, buildings, and other civil engineering structures.