| Author: | Chen, Wenfeng |
| Title: | Direct analysis for building structures subjected to wind loads considering direct sheltering effects |
| Advisors: | Chan, S. L. (CEE) |
| Degree: | Ph.D. |
| Year: | 2023 |
| Subject: | Buildings -- China -- Hong Kong -- Aerodynamics Wind-pressure Buildings -- China -- Hong Kong Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xvi, 313 pages : color illustrations |
| Language: | English |
| Abstract: | The design of building structures in Hong Kong is generally governed by strong wind. Typhoon causes significant loss and damage in the South of China and the other countries in East Asia every year. Recently, a new Hong Kong wind code was issued, which provides an advanced method for determination of the wind actions on the building structures and the building elements. However, the method is tedious and only valid for some structures with regular shapes. Thus, this thesis aims to propose a comprehensive solution for the design of new building structures and the safety assessment of existing building structures based on the new wind code by using a cloud-based system. To achieve the above-mentioned objectives, the research works will be divided into two main parts: (1) refined methods on direct analysis for more accurate prediction of structural behaviours of buildings; (2) cloud-based system incorporated with deep learning for calculation of wind actions on building structures with consideration of direct sheltering effects. The structural members in buildings are commonly subjected to distributed loads rather than concentrated loads. Hence, a new consistent co-rotational formulation for both Euler-Bernoulli and Timoshenko beam-column elements under distributed loads is proposed in the first part of work. The co-rotational technique is widely adopted in the geometrically nonlinear analysis because of simpler element formulations and higher numerical efficiency. The conventional co-rotational formulations assume that the finite element is only subjected to nodal loads, leading to inaccurate analysis results when the members exhibit large deflections. To this, an element-independent co-rotational formulation considering uniformly distributed loads for beam-column elements is derived here based on updated geometrical relationship of rigid body movement and pure deformation to improve the accuracy of second-order direct analysis of frame structures. In this thesis, a new flexibility-based beam-column tapered element with direct modelling of both initial geometrical imperfection and residual stress at the element level is proposed for the direct analysis of structures with non-prismatic sections allowing for both symmetric and asymmetric variations. To account for the influence of varied tapering ratios on the member behavior, a new initial geometrical imperfection pattern is introduced for both prismatic and non-prismatic members. Apart from that, residual stress is explicitly considered through a fiber section method in the proposed beam-column element. Therefore, there is no need to consider the effective length as both of geometrical imperfections and residual stress have been incorporated into the proposed element. The progressive yielding behavior of tapered members is also taken into account through the fiber section with nonlinear stress-strain relationships. From the above, the proposed beam-column element will be equipped with the proposed consistent co-rotational formulation for second-order direct analysis of building structures with significant improvement of accuracy and numerical efficiency. The proposed element is validated via a series of practical structural cases, closed-form equations, and refined solid finite-element analysis methods. Wind loads are most common distributed loads for the design of buildings and govern the design of buildings in Hong Kong. Hence, the Code of Practice on Wind Effects in Hong Kong 2019 HKWC (2019) was issued for accurate calculation of the wind actions on building structures with consideration of direct sheltering effects of obstructing buildings. However, it is difficult to perform the computation of wind loads based on HKWC (2019) by hand calculation method, which will induce many human errors and are time-consuming. This thesis employed artificial intelligence techniques to meet the requirements of HKWC (2019) such as the identification of arbitrary building shapes. Most of wind codes such as HKWC (2019) have limitations when adopting the equivalent rectangular building shape and other simplified strategies, which cannot reflect the real system response of building structures and will considerably lead to inaccuracy of calculating wind loads on building structures and building elements. Therefore, computational fluid dynamic (CFD) simulation method is adopted by using a free, open-source CFD toolbox (OpenFOAM) to accurately evaluate the wind pressure distribution on the buildings with arbitrary shapes. Besides, a deep learning-based technology is present to perform the fast evaluation of stress distribution of building elements such as glass panels for numerous buildings in a region. Finally, a cloud-based system is developed to implement analysis and design of building structures with irregular plan shapes subjected to wind loads considering direct sheltering effects and incorporating the proposed new co-rotational framework and the proposed tapered element with new imperfection pattern. |
| Rights: | All rights reserved |
| Access: | open access |
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