Performance based wind design and optimization of tall buildings considering the nonlinearity in building response
Date
2022-12
Authors
Preetha Hareendran, Smrithi
Major Professor
Advisor
Alipour, Alice
Behrouz, Shafei
Cho, In-Ho
Pratim Sarkar, Partha
Hsu, Ming-Chen
Committee Member
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Abstract
Progressive research and increased computational efficiency over the past couple of decades has produced elegant solutions to the analysis and design of tall buildings such as Performance-Based Design (PBD). PBD has become a mainstream approach to assess and reduce the risks in rehabilitation of existing structures. Application of PBD philosophy for design of tall buildings and other structures excited by wind loads has received much attention over the past few decades. The main objective of Performance Based Wind Design (PBWD) is to assess the adequacy of a structure in terms of the decision variables set forth by the stake holders. The performance levels are defined based on acceptable levels of strength and serviceability requirements of both structural and non-structural components. They also reflect the probable levels of damage, casualties, downtime, and costs of repair. Despite the extensive work that has been conducted by these researchers in formulations and development of PBWD, most of these studies focus on the elastic response of the structures. However, understanding the post-elastic response of structures under wind loads is critical to the PBWD.
This dissertation is written based on identifying the requirement for improved nonlinear modeling techniques and more detailed wind load models and to aid the advancement of Performance Based Wind Design as a mainstream approach for the design of tall buildings. The work consists of novel analysis and design methodologies to predict the nonlinear structural response of tall buildings under sustained durations of wind loads. The dissertation is divided into five chapters based on four major studies conducted on PBWD of tall buildings. The studies presented in the dissertation implements the PBWD methodology by following the true nature of the PBD philosophy considering the nonlinearity in response of buildings and associated uncertainties in the wind loading. The first study presented in Chapter 2 makes contributions to the field of PBWD by providing prediction of turbulent wind loads at each level of the building and by developing the formulation to account for along-, across-, and torsional- wind loading along the height of the building. The methodology of PBWD is validated using a case study of a 44-story steel frame building subjected to wind loads. This study is then expanded in Chapter 3 by exploring the interaction of building with environment characterized by self-excited forces which can result in flutter instability and amplification of response due to modification of structural damping and stiffness along all degrees of freedom. The performance objective focused in the study is occupant comfort and the structural parameters used in the evaluations are displacements and accelerations.
The nonlinear 3D model of any tall building contains thousands of connections and structural members making it a complex finite element model. Dynamic time history analysis of such a model under sustained wind loads can be computationally expensive and often fail to achieve convergence. An alternative approach to the nonlinear dynamic time history analysis is explored in Chapter 4 by implementing data driven techniques using limited numerical and field data to predict nonlinear structural response in tall buildings under long duration wind loads. The study aims to predict the nonlinear structural response of tall buildings under sustained durations of wind loads using deep learning model of Long Short Term Memory (LSTM).
Chapter 5 explores the challenges to the design optimization of tall buildings in the context of PBWD. The study evaluates the performance of a novel smart, morphing façade module system in mitigating building vibrations. The façade is capable of dynamically modifying the aerodynamic shape of the building surface in real time considering the variations in wind speed and wind directions to limit wind-induced vibrations. The Smart Morphing Façade or Smorphacade is evaluated for its performance in the acceleration control of tall buildings using nonlinear dynamic time history analysis. Chapter 6 provides the general conclusions from the research.
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