This study investigates the alterations in the ratios of components such as class C fly ash (FA), blast furnace slag (BFS), and waste stone powder (WSP) types of limestone powder (LP) used in the production of geopolymer concrete. These components are meticulously examined concerning the physical and mechanical attributes of geopolymer concrete. Using the mixture-design method, 10 different mixing ratios were determined using FA, BFS, and LP, and experimental research on the mechanical attributes and workability of geopolymer mortar is presented. A series of experimental tests, including tests for compressive strength, impact strength, setting time, flow table, flexural strength, and water absorption, were carried out on the geopolymer mortars that were made using FA, BFS, and LP, to investigate and enhance their overall performance. The experimental study aimed to ascertain the extent to which variations in the materials used in the formation of geopolymer mortar affected its mechanical and physical properties. To achieve this objective, certain parameters for geopolymer mortar formulation were fixed, according to the literature (molarity: 10; aggregate/binder ratio: 2.5; plasticizer ratio: 2%; sodium silicate (SS)/sodium hydroxide (SH): 1.5; additional water content: 14.5%; alkali activators/binder: 0.5). Subsequently, mortars were produced according to the 10 different mixing ratios determined by the mixture-design method, and the experiments were completed. The samples of the 10 different mixes were subjected to air curing at an ambient temperature (23 °C ± 2 °C) for 28 days. Following the curing period, the tests revealed that mix No. 9 exhibited the best compressive, flexural, and impact strengths, while mix No. 10 demonstrated superior workability of geopolymer mortar. It was shown that impact, compressive, and flexural strength values decreased as the ratios of FA and LP increased. In contrast, the increases in the ratios of FA and LP positively influenced the workability of geopolymer mortar.

A pre-design guide for cantilever retaining walls and a detail parametric study of such walls is presented here. Mathematical models based on statistical methods were improved for calculating safety factors of sliding, overturning, and slope stability of those walls. The harmony search algorithm (HSA)-a metaheuristic optimization method-was employed to realize reasonable results of the pre-design guide from all distinct cases. Through the design algorithm, the optimal design was determined for varied soil types differently from suggestions of design codes. Thus, an optimal pre-design guide for safe and economic wall design was realized in a shorter time compared to the conventional method.

In this paper, discrete design optimization of a cantilever retaining wall has been submitted associated with a detailed parametric study of the wall. In optimal design, the minimum wall weight is treated as the objective function. Through design algorithm, the optimal design variables (base width, toe width, thickness of base slab and angle of front face) yielded minimum structural weight of the wall and satisfied stability conditions have been determined for different soil parameter values. At the end, a detail parametric study searching the effect of change of soil parameters on the retaining wall design has been conducted with 120 optimized wall designs for different values; eight values of the angle of internal friction, three values of the unit volume weight and five values of wall heights. The obtained results from optimization analyses indicate that change of the angle of internal friction more effective than change of the unit volume weight on the optimal wall weight. Economic wall design with optimization analysis is achieved in a shorter time than the traditional method.

In this study, earthquake performance of the structures was tested which were modeled according to the minimum criteria of simplified analysis approach proposed in TBEC-2019. For this purpose, 144 reinforced-concrete building models were designed according to parameters such as earthquake design class, building height (number of storey), number of spans, soil type and three different simplified formulas suggested in the code. The level of structural performance of buildings models was determined by the linear (L) and nonlinear performance analysis (NL) methods that given in TBEC-2019. The base shear force, top displacements and over-strength factor (Ω) of each structural model were obtained, and performance analysis was performed by comparatively. As a result of the structural analyses, it was seen that some of the buildings model designed according to minimum column sectional criteria given in simplified methods could not meet the suggested seismic performance level. While the number of structural models that provide the controlled damage (CD) level in the L analysis method is 44 (30.55%), it is 107 (74.3%) in the NL analysis method. The insufficient performance was obtained in both L and NL methods in models which have over-strength values below 3. It has been observed that multi-criteria of building performance are not met with the weakening of local soil conditions. It was also seen that the L method chosen in the performance analysis gave more conservative results with this study.

Regarding the behavior of reinforced concrete structures under seismic loads, the interaction between structure and soil is as important as the load-bearing system and foundation type. This study was designed to assess the effect of structural types and soil–structure interactions (SSIs) on the responses of reinforced concrete (RC) buildings to earthquakes. Therefore, nonlinear time history analyses were performed on 20-storey RC buildings. In this analysis, three different structural system types and three different foundation types were considered for the parametric study. The numerical results obtained from the nonlinear dynamic analysis were criticized in terms of base shear force and roof displacement. Based on the obtained numerical results, utilizing SSI in the nonlinear time history analysis of the RC buildings improved the overall structural integrity by delaying plastic hinge formation and preventing the total failure of structural elements. Base shear forces increased up to 20% for the same structural system and different SSI situations, and up to 60% for different structural systems and the same SSI situation. Roof displacements increased up to 17% for the same structural system and different SSI situations, and up to 24% for different structural systems and the same SSI situation. All of the behavioral differences showed the importance of considering the SSI in the design stage of the buildings.