Considering the effect of soil–structure interaction in dynamic analysis of structures can change their responses. It is generally assumed that the structure is located on a rigid foundation and the flexibility effect of the soil is not considered. Researches on the soil–structure interaction show that the dynamic response of the structures located on a soft and flexible soil is completely different from the dynamic response of the same structure located on a stiff soil. In this paper, the effect of the soil–structure interaction on the response of a single-degree-of-freedom system (Nagasaki airport tower) that is controlled by a modified tuned liquid damper is investigated. The soil effect is modeled using an approximate cone method based on the semi-infinite boundary conditions. First, the governing equations for describing the fluid sloshing obtained with shallow water wave theory are solved by Lax’s finite-difference scheme. Then, the dynamic equilibrium equations for a structure controlled with a modified tuned liquid damper are obtained by considering the effect of soil–structure interaction using Lagrange’s method. These equations are solved numerically by Newmark’s method. The controlled structural responses are calculated in different time steps and compared with the responses of the uncontrolled structure. Results show that the seismic design of the modified tuned liquid damper system can be more effective to reduce the structural responses. Also, this system can reduce efficiently the maximum responses of the structures considering soil–structure interaction effect during a near-fault earthquake.

Modified Tuned Liquid Dampers for Seismic Protection of Buildings Considering Soil–Structure Interaction Effects

The focus of this study is to investigate the seismic behavior of outrigger-braced building considering the soil–structure interaction based on finding the best location of outrigger and belt truss system. For this purpose, a central outrigger-braced frame of a steel tall building is considered. A layered soil deposit underlied this frame and the resulting soil–structure system is subjected to seismic excitation. To analyze this system, direct method is employed in OpenSees. Also, elastic and in-elastic analyses are both considered and a comparison is made between current results and the results related to the system with fixed base. The best location of outrigger–belt truss system is determined by considering the maximum roof displacement, base moment and base shear with and without soil–structure interaction. It is shown that considering SSI affects the location of outrigger–belt truss system. Elastic analysis of both systems, namely with fixed base and with soil–structure interaction, showed that locating the belt truss at higher stories caused lower amounts of roof displacement.

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Seismic performance of outrigger–belt truss system considering soil–structure interaction

The main goal of this paper is to investigate the effect of blast phenomenon on structures to determine the best location of belt truss system in tall buildings. For this purpose, one of the exterior frames of a tall steel building, in which the belt truss is located, is considered. The steel frame model is subjected to two different charges of equivalent weight which are applied in two different standoff distances. In this research, the best location of the belt truss system is determined using OpenSees software based on the nonlinear dynamic analysis. The best location of the belt truss system for different types of loading is investigated both with and without considering the post-buckling effect for all members of the belt truss system. The results show that when blast charges are located in a 5-meter range from the building (R=5), post buckling effect of truss elements are more obvious than the case in which blast charges are located in a 10-meter range (R=10); this, in turn, causes the amount of base moment to be completely different when the belt truss is located in the first storey in comparison to the cases where the belt truss is located in any other stories. In addition, if the explosion occurs near the building when the base moment is considered as a criterion, the post buckling effect has a significant role.

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The Best Location of Belt Truss System in Tall Buildings Using Multiple Criteria Subjected to Blast Loading

Minimum‐weight design of high‐rise structures subjected to flexural vibration at a desired natural frequency

A comprehensive introduction to outrigger and belt-truss system in skyscrapers

In this paper, a continuous–discrete approach based on the concept of lumped mass and equivalent continuous approach is proposed for free vibration analysis of combined system of framed tube, shear core and outrigger-belt truss in high-rise buildings. This system is treated as a continuous system (i.e., discrete beams and columns are replaced with equivalent continuous membranes) and a discrete system (or lumped mass system) at different stages of dynamic analysis. The structure is discretized at each floor of the building as a series of lumped masses placed at the center of shear core. Each mass has two transitional degrees of freedom (lateral and axial( and one rotational. The effect of shear core and outrigger-belt truss on framed tube system is modeled as a rotational spring placed at the location of outrigger-belt truss system along structure’s height. By solving the resulting eigen problem, natural frequencies and mode-shapes are obtained. Numerical examples are presented to show acceptable accuracy of the procedure in estimating the fundamental frequencies and corresponding mode shapes of the combined system as compared to finite element analysis of the complete structure. The simplified proposed method is much faster and should be more suitable for rapid interactive design.

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Ali Malekinejad

Papers

A continuous–discrete approach for evaluation of natural frequencies and mode shapes of high-rise buildings