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Wind and Structures
  Volume 26, Number 1, January 2018 , pages 45-56

Wind-induced fragility assessment of urban trees with structural uncertainties
Yongbo Peng, Zhiheng Wang and Xiaoqiu Ai

    Wind damage of urban trees arises to be a serious issue especially in the typhoon-prone areas. As a family of tree species widely-planted in Southeast China, the structural behaviors of Plane tree is investigated. In order to accommodate the complexities of tree morphology, a fractal theory based finite element modeling method is proposed. On-site measurement of Plane trees is performed for physical definition of structural parameters. It is revealed that modal frequencies of Plane trees distribute in a manner of grouped dense-frequencies; bending is the main mode of structural failure. In conjunction with the probability density evolution method, the fragility assessment of urban trees subjected to wind excitations is then proceeded. Numerical results indicate that small-size segments such as secondary branches feature a relatively higher failure risk in a low wind level, and a relatively lower failure risk in a high wind level owing to windward shrinks. Besides, the trunk of Plane tree is the segment most likely to be damaged than other segments in case of high winds. The failure position tends to occur at the connection between trunk and primary branches, where the logical protections and reinforcement measures can be implemented for mitigating the wind damage.
Key Words
    finite element modeling; fractal theory; grouped dense-frequencies; fragility assessment; probability density evolution method; Plane tree
Yongbo Peng: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China;
Shanghai Institute of Disaster Prevention and Relief, Tongji University, Shanghai 200092, China
Zhiheng Wang: Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089, USA
Xiaoqiu Ai:Shanghai Institute of Disaster Prevention and Relief, Tongji University, Shanghai 200092, China

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