Title

Active control of pendulum tuned mass dampers for tall buildings subject to wind load

Date of Award

2017

Degree Name

Ph.D. in Mechanical Engineering

Department

Department of Mechanical and Aerospace Engineering

Advisor/Chair

Advisor: Reza Kashani

Abstract

Wind induced vibration in tall structures is an important problem that needs effective and practical solutions. TMDs in either passive, active or semi-active form are the most common devices used to reduce wind-induced vibration. The objective of this research is to investigate and develop an effective model of a single multi degree of freedom (MDOF) active pendulum tuned mass damper (APTMD) controlled by hydraulic system in order to mitigate the dynamic response of the proposed tall building perturbed by wind loads in different directions. The proposed APTMD can be tuned to the first three dominant frequencies of the targeted structure in three directions (X, Y, γ) simultaneously and add damping to the corresponding modes. Another design requirement of the APTMD is the capability of adjusting its properties (stiffness and damping) to compensate for the detuning occurred due to the varying operating conditions such as an environment, or imposed loading. These supplemental damping devices offer attractive means to protect tall buildings against natural hazards and make a genuine contribution to the building sway, which has such a great economic and social effects. The targeted structure for the proposed approach in this work is a MDOF model representing a full scale concrete tall building. This building is a modern high-rise building designed as a flexible and slender structure, asymmetric geometry, excited by wind loads in multiple directions. The building has 41 stories above the ground where each floor has three degrees of freedom, two in x,y directions (planar) and one around the axis perpendicular to x-y plane γ (rotational). The first 15 modes of the building will be included in this study, five modes in each direction. The innovative idea of this work is involving the Stewart Platform, was originally designed in 1965 as a flight simulator, and it is still commonly used for that purpose. It is controlled by hydraulic system that is used for motion control (position control) of the pendulum TMD relative to the building. The pendulum itself is a passive device but as it is comprised with active-controlled hydraulic actuators, the legs of the Stewart Platform in our case, it becomes an active system. The electrohydraulic servo valve is used to control the hydraulic system of the proposed active PTMD because it can offer more responsive and accurate control tasks in a timely manner. By combining the muscle of the hydraulic power and the accuracy of electrical control, electrohydraulic control valves can control hydraulic systems precisely and efficiently. The desired control force is calculated from the acceleration, velocity, and displacement feedbacks of the MDOF system and active PTMD in order to achieve the different tuning frequencies and damping effects. The proposed tasks for the conduct of `Multi Tuning-frequency Passive/on demand Active Pendulum Tuned Mass Damper’ research are: To synthesize the control scheme for active Pendulum TMD that can be tuned simultaneously to multiple directions replacing multiple more massive PTMDs. Such attributes lowers the cost, weight and space requirement associated with dampening multiple modes using multiple TMDs. To increase the effectiveness of the proposed active PTMD, which leads to lowering its weight (50% less) without degrading its performance. With its small size and multi-frequency tuning capacity, the proposed APTMD is as effective as a passive TMD many times more massive. To obtain a high fidelity model of the structure targeted for damping The synthesis and analysis of the proposed passive/on-demand active PTMD is presented. The effectiveness of the proposed tuned mass damper is numerically demonstrated, by interfacing its model with that of a high-rise building.

Keywords

Tuned mass dampers Design and construction, Pendulum, Damping (Mechanics), Skyscrapers Vibration, Mechanical Engineering, multi tuning frequency, passive on demand active, pendulum TMD, tuned mass damper, structural damping

Rights Statement

Copyright © 2017, author

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