In this paper, an optimization approach was presented for the flexural strength and stiffness design of reinforced concrete beams. Surrogate modeling based on machine learning was applied to predict the responses of the structural system in three-point flexure tests. Three design input variables, the area of steel bars in the compression zone, the area of steel bars in the tension zone, and the area of steel bars in the shear zone, were adopted for the dataset and arranged by the Box-Behnken design method. The dataset was composed of thirteen specimens of reinforced concrete beams. The specimens were tested under three-point flexure loading at the age of 28 days and both the failure load and the maximum deflection values were recorded. Compression and tension tests were conducted to obtain the concrete data for the analysis and numerical modeling. Afterward, finite element modeling was performed for all the specimens using the ATENA program to verify the experimental tests. Subsequently, the surrogate models for the flexural strength and the stiffness were constructed. Finally, optimization was conducted supporting on the factorial method for the predicted responses. The adopted approach proved to be an excellent tool to optimize the design of reinforced concrete beams for flexure and stiffness. In addition, experimental and numerical results were in very good agreement in terms of both the failure type and the cracking pattern.

Cable stayed Bridges are highly vulnerable to strong wind load induced vibrations which are responsible of generating aerodynamic instability and in a critical situation lead to structural failure. This paper focuses on buffeting response and flutter instability in a cable stayed Bridge. A strong fluctuating wind is assigned to a cable stayed Bridge model in ABAQUS FE program to onset optimization and global sensitivity analysis through considering three aerodynamic parameters (wind attack angle, deck streamlined length and stay cables viscous damping) by targeting the vertical and torsional vibrations of the deck. The numerical simulations results in conjunction with the frequency analysis results emphasized the existence of such vibrations. Model validation performed by comparing the results of lift and moment coefficients between the present FE model and two benchmarks from the literature (flat plate theory and flat plate by Xavier et al., 2015), which resulted in good agreements between them. Optimum values of the adopted aerodynamic parameters have been identified and discussed. Global sensitivity analysis based on Monte Carlo sampling method was utilized to formulate the surrogate models and the sensitivity indices so that to identify rational effect and role of each parameter on the aerodynamic stability of the structure.

Reusing waste is one of the most recent topics and one of the main contributors to sustainability. It is known that concrete is one of the most common materials to produce different types of construction members around the world. That is due to mainly its low cost, availability, long period of durability, and ability to withstand harsh environments. On the other hand, due to the rapid changes that have happened in the last few decades in the production of decorative materials, some material types of cladding are used for decoration purposes, such as Styrofoam (EPS) (trade name “Astropol”), which is developed from disposal materials. Discovering and implementing a method of reusing these wastes in concrete is beneficial for the environment to reduce waste around the globe. In the current study, Styrofoam (Astropol) waste was used as a replacement for fine aggregate since concrete structures contain this material in their composition. It is important to test these materials for fire resistance and expose them to an elevated temperature in order to discover the post-fire mechanical properties of the composite material. The experimental result showed that the post-fire compressive strength of concrete containing different ratios of EPS (Astropol) increases compared to conventional concrete. The compressive strengths were 19.94 MPa, 19.295 MPa, 16.806 MPa, and 17.66 MPa for 0%, 15%, 25%, and 50%, respectively, while the post-fire indirect tensile strength for all specimens containing EPS reduced as the fire duration and temperature increased.