A series of numerical simulations were carried out on two types of superstructures and six types of piled raft foundations to investigate the effects of seismic soil–pile–structure interaction (SSPSI) on the seismic responses of the superstructures. In this research, the effectiveness of a piled raft application was assessed; the pile optimum numbers, locations, and configurations were estimated; and finally, a comparison was made between the nonlinear structural responses of the obtained two-dimensional (2D) and three-dimensional (3D) models. Parametric studies were conducted to achieve strategies for optimized designs of piled raft foundations subjected to the low-to-high intensities of real earthquake records as the input motions. The numerical results represented a reasonable correlation between the shaking intensity rates (SIRs) and maximum interstory drifts of the structures. It was discovered that the performance levels of the structures on a softened ground were a function of the area replacement ratios, lengths, diameters, and spaces between the piles; ground motion features; and height/width ratios of the structures. These important aspects had to be regarded to achieve a reliable design. The aim of this investigation was to ameliorate the characteristics of a system of long–short combined piled raft foundations based on an understanding of the interaction mechanics.

This study addresses the experimental behavior of octagonal partially encased composite column under axial and bending load conditions. The complementary study on axial and combined axial–torsional behavior is done through finite element analysis. The main parameters for the experiment part are reinforcement details and failure modes. The six parameters of this analytical analysis include width-to-thickness ratio of flange, transverse links spacing and diameter, welding line arrangements, and different types of retrofit of cross-shaped steel (concrete encasement, use of stiffener plates and transverse links). To verify accuracy of the proposed three-dimensional finite element model, the axial behavior of the numerical models was compared with test specimens. Experimental results of the axial study show that concrete crushing phenomena and local buckling behavior occurred for all specimens under ultimate stage of loading. It should be noted that local buckling behavior occurred after crushing phenomena. The analysis of bending assessment demonstrated that the use of stirrups has no remarkable effect on increasing the effective bending moment strength of octagonal partially encased composite columns. Meanwhile, an equation was developed based on comprehensive parametric study of octagonal partially encased composite column using detailed finite element analyses. Under axial–torsional load conditions, one could conclude that steel shear plates should be placed at the end zones of column to heighten torsional resistance of member. Meanwhile, transverse links were found to exert marginal effect on torsional behavior of octagonal partially encased composite column.

The main purpose of this study is to investigate the effect of wastes, namely plastic wastes, iron wire, and cast-iron powder, as a potential substitute material on the behavior of environmental-friendly sintered clay bricks to reduce environmental pollution and production cost. Twenty groups of mixtures were tested to obtain precise results for the compressive strength, flexural strength, weight per unit area, apparent porosity, freeze-thaw resistance, ultrasonic pulse velocity (UPV), water absorption, and initial rate of absorption tests. The results indicated that no single trend could be identified to measure the effect of additional materials on the improvement or deterioration of mechanical and durability properties. The results revealed that an increment in the content of plastic particles up to 4% by weight resulted in a decline in water absorption, whereas an increase in the content of coarse plastic particles raised water absorption. It was found that specimens including regular iron wire and cast-iron powder demonstrated higher compressive strength rather than the specimens with plastic and irregular. The results of the freeze-thaw test revealed that most of the specimens satisfied the requirement of ASTM, and those incorporating cast-iron powder had the best results. Due to the low specific gravity of plastic wastes, the weight per unit area of specimens mixed with them was lower than that of specimens with iron wire and cast-iron powder, leading toward a reduction in the seismic weight of buildings. It concludes that the best improvement in the flexural strength of bricks was achieved by a 40% replacement of cast-iron powder, compared with the reference specimen.

In the present experimental study, 12 specimens were tested to assess and quantify the effects of bolt tightness on the overall behavior of a bolt-ball joint under uniaxial loading. A three-dimensional (3D) nonlinear finite-element (NFE) model with all geometrical complexities, including the threads, was developed to examine the significance of bolt tightness on overall behavior. Three types of parameters were studied, namely, tightness torque, material properties, and friction coefficients. The tests showed that the tightness torque moments had a significant effect on the axial stiffness of the specimens under compressive loading. Observations during the tests indicated that the bolt and sleeve had important roles in the load transferring mechanism. Based on the results of the current experimental study, the finite-element model (FEM) was verified against the test specimens. An acceptable qualitative agreement was observed between the FE models and the experiments for the axial behavior of the joint. It was found that the material properties had a significant role in changing the failure mode and load-bearing capacity. Based on experimental tests and NFE analyses, the present study provides a nonlinear model for determining the relationship between the torque and the preload using gene expression programming. It was concluded that the simplified formulation proposed in this study can calculate the relationship between the torque and the initial load against the bolt tightness database with good accuracy.