Abstract
This paper presents a comprehensive assessment method of the fragility of low-rise cold-formed steel (CFS) framed wall structures subjected to wind hazards considering the fragility of both the main structure and the cladding system. The effects of wind directions on the fragility of CFS framed wall structures were also studied. For the main structure, the fragility curve is established using the maximum interstory drift ratio (ISDRmax) as the performance index for assessing the wind fragility of the structure. For the cladding system, the probabilistic models of the wind load and the cladding component resistance are established based on Monte Carlo simulation, and then methods for the fragility assessment of single cladding components and the cladding system under wind hazards considering the influence of the number and arrangement of the cladding components are proposed. The results indicated that, under strong wind, the cladding system may be damaged before the required wind resistance capacity of the main structure is exhausted. In particular, the roof sheathing is the most prone to damage, followed by the stud wall. That is, before the main structure is severely damaged or collapses, the cladding systems may be severely damaged, rendering the structure unusable. Therefore, the comprehensive assessment of the fragility of this type of structure subjected to wind hazard considering the fragility of both the main structure and the cladding system is more accurate. This study is of great significance for the improvement of the wind resistance performance of CFS structures and the popularization of this type of structure.
Highlights
Low-rise cold-formed steel (CFS) framed wall structures evolved from wood-frame structures and are mostly used in low-rise residential buildings
The wind fragilities of the main structure and the cladding system of a two-story CFS framed wall structure were separately investigated. e analysis processes and results were presented, and the wind fragility of the structure was comprehensively assessed based on those of the main structure and the cladding system. e main conclusions drawn are as follows: (1) A composite wall made of a combination of section steel stud and oriented strand boards (OSB) and gypsum board cladding in the structure has satisfactory in-plane stiffness and loadbearing capacity under wind load, resulting in small responses of the main structure to the wind and good wind resistance performance
(2) For the cladding components, the probabilistic wind load model and resistance model of the cladding component are developed based on component-level analysis, and the wind fragility analyses of the roof panel and cladding wall are performed using Monte Carlo simulation. e results show that the cladding components at the edges are more prone to windinduced damage than those in the intermediate position and that the wind resistance performance of roof panels is markedly lower than that of cladding walls. e fragility of single cladding components differs from that of the corresponding cladding system; the use of the fragility of single cladding components alone is insufficient for assessing the fragility of the whole cladding system
Summary
Low-rise cold-formed steel (CFS) framed wall structures evolved from wood-frame structures and are mostly used in low-rise residential buildings. E results from previous wind disaster investigations have shown that, despite the low probability of low-rise buildings collapsing under strong winds, the cladding components and systems are highly susceptible to severe damage even though the main framing structure remains safe, resulting in the loss of functionality of the structure [28] For this reason, the research on the wind performance of low-rise buildings has recently focused on cladding components such as the roof and wall sheathings, etc. Lee and Rosowsky [29] developed a fragility model for roof sheathing under wind load considering uplift (suction) based on the results of load-bearing tests on the roof connections for cladding components in lightweight wood-frame construction; they proposed a method for the wind fragility analysis of the roofing system of a wood structure. The fragility of this type of structural system subjected to wind hazard is comprehensively assessed based on the results of the fragility analysis of the main structures and the cladding system. e present study is of great theoretical significance for improving the wind-resistant design and performance of CFS structures
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