The increasing population, limited residential space, and scarcity of suitable land for construction have led to a rise in the construction of high-rise buildings (HRBs) as a means to provide additional housing. The increase in human activities (such as excavations for geothermal resources) has led to an increase in seismic activity, making HRBs more vulnerable to earthquakes. Structural analysis of HRBs that are exposed to seismic loadings depends on one of the most important factors that judge the stability and resistance to seismic waves which is the stiffness of the buildings. Various methods that reduce flexibility and enhance stiffness for HRBs are the subject of this numerical investigation, and they were applied to a high-rise building (HRB) of 20 floors, considering soil–structure interaction (SSI). The stiffening methods adopted herein are steel or concrete shear walls (SWs) in specific arrangements, and different bracings in specific arrangements. Moreover, in this study, tuned mass dampers (TMDs) are used, as a damping method of the HRB seismic response, also considering SSI, and the results are compared with the stiffening methods results to judge how the applied methods enhance the seismic resistance of HRBs. These methods, which were used to influence the stiffness or the damping of the building, had different positive effects on the seismic response of the HRBs, which appeared in the results through the base shears, the base moments, the maximum top displacement, and the fundamental period of the building.

Various cases of two adjacent multi-story buildings with different numbers of floors and equal or unequal foundation levels under earthquake loading and considering soil-structure interaction (SSI) are investigated. A two-dimensional model for each case of the two adjacent unequal buildings without separation distance is used and a special arrangement of contact elements in the contact zone is employed to fulfil all possible deformation contact modes which take place under seismic loading. The soil is modelled by two-dimensional 4-node elements which are in contact with the foundations of the two adjacent buildings. This paper studies the earthquake-induced double pounding that takes place between the two adjacent unequal height buildings in some upper points at superstructure in the contact zone and also at foundation level, considering soil-structure interaction (SSI). The double pounding and the soil-structure interaction (SSI) effects should be taken into consideration in the seismic analysis of adjacent buildings especially those with different heights and different foundation levels.

The architectural requirements imposed on the structural design of buildings sometimes necessitate vertical and horizontal irregularities with their possibly dangerous effects when these structures are subjected to earthquakes. One of the greatest challenges in structural engineering is the design of a steel high-rise building (HRB) with vertical and horizontal irregularities. In this research, two irregular steel high-rise buildings (HRBs) were seismically analyzed as 3D models considering soil–structure interaction (SSI) and tuned mass damper (TMD) systems were used to mitigate their seismic response under different earthquakes. The two studied HRBs were a vertically irregular (step-pyramid-shaped) steel HRB, and a both vertically and horizontally irregular (L-shaped in-plan, stadium-shaped) steel HRB. The SSI provides the actual response of the tall buildings subjected to earthquake, and mitigation schemes using TMDs were suggested with arrangements of the TMDs on the top plan and along the elevation of the steel high-rise buildings to achieve seismic control of these structures. The present study has shown that the best efficiency in the mitigation of the effect of earthquakes on vertically and horizontally irregular steel high-rise buildings is obtained by implementing TMDs at the corners of the HRB plan on the top of the HRB and also at different floor levels along the upper half-height of the HRB.

A steel high-rise building (HRB) with plan irregularity is a major challenge in engineering design, especially under seismic loads. Soil–structure interaction (SSI) is one of the most important factors in designing steel high-rise structures. Herein, a T-shape in plan steel HRB subjected to four different earthquakes will mitigate the vibration and control the displacements and base straining actions resulting from earthquakes by using tuned mass dampers (TMDs) systems, and the most controlling arrangement of TMDs, in the fixed base HRB model and in the SSI HRB model, will be examined. Three-dimensional models of the steel high-rise building (HRB) with a T-shape in the plan subjected to four different earthquakes fixed or with the SSI effect were analyzed to investigate the seismic mitigation effect of six different plan arrangements of TMDs applied on the top plan of the fixed HRB model, while for the SSI HRB model, these TMDs distributions were applied on the top plan and additionally on two intermediate plans along the HRB height. The TMDs for the T-shape in plan steel HRB are more effective in the SSI model than in the fixed base model. In the SSI effect model, the distributions of the TMDs not only on the top plan of the model but also through the model (on two additional plan levels along the height) further reduced the HRB seismic response and this three-level TMDs distribution was required for the plan arrangement of 2 or 4 TMDs.

The study of a monopile offshore wind turbine with the soil–structure interaction effect is most challenging in structural design under multiple hazards, i.e., the combined wind, sea wave, and earthquake excitations. Different arrangements of passive tuned mass dampers (TMDs) were used to mitigate the service and seismic loads affecting an offshore wind turbine (OWT) including the pile–soil–structure interaction (PSSI) effect. Different schemes of passive TMDs, placed at the top of the OWT tower or also at the center of gravity (CG) of the OWT tower or at the connection between the OWT tower and monopile, were tested. Various arrangements of TMDs including the proposed herein top radial TMDs arrangements have been investigated to determine their validity in resisting vibrations resulting from service and earthquake loads. The lateral displacements, shear forces and bending moments in both horizontal directions and the axial forces all over the OWT tower and monopile heights were recorded to compare the performance of each mitigation scheme of TMDs. The comparison results showed that the TMDs placement should be at the top of the OWT tower and the top radial 6 TMDs arrangement was found to be the most effective mitigation scheme for all straining actions in the tower and the monopile of the OWT subjected to service and earthquake loads.

An existing riverine platform in Egypt, together with its pile group foundation, is analyzed under environmental loads using 3D FEM structural analysis software incorporating soil-pile interaction. The interaction between the transfer plate and the piles supporting the platform is investigated. Two connection conditions were studied assuming fixed or hinged connection between the piles and the reinforced concrete platform for the purpose of comparison of the structural behavior. The analysis showed that the fixed or hinged connection condition between the piles and the platform altered the values and distribution of displacements, normal force, bending moments, and shear forces along the length of each pile. The distribution of piles in the pile group affects the stress distribution on both the soil and platform. The piles were found to suffer from displacement failure rather than force failure. Moreover, the resulting bending stresses on the reinforced concrete plate in the case of a fixed connection between the piles and the platform were almost doubled and much higher than the allowable reinforced concrete stress and even exceeded the ultimate design strength and thus the environmental loads acting on a pile-supported riverine offshore platform may cause collapse if they are not properly considered in the structural analysis and design.