| Summary: | 碩士 === 國立雲林科技大學 === 營建工程系碩士班 === 93 === During building construction, the collapse of construction structures often causes enormous loss of lives and properties. In terms of construction engineering, the construction structure is mainly composed of formwork support and scaffolding, while in the field of bridge engineering, the construction structure consists of temporary shoring structure and other professional shoring methods, such as advancing shoring method, incremental launching method and balanced cantilever method. Presently, because of the lack of related reference regulations for design and practice of construction structure in our country, the establishment of construction structures on the construction site generally relies on the experience of the master worker. Due to the limitation of experience-based construction and lack of reference material for designing construction structure, incidents of construction structure collapse occur from time to time in our country.
The results of the study show that only increasing the number of “leaning columns” in the shoring system does not help with the critical load of the system. When the total number of shores in the shoring system is fixed, increasing the number of strong shores or equivalent strong shores is able to effectively improve the total critical load of the system. There is a linear relationship between the increase of the number of strong shores and the improvement of the total critical load of the shoring system. Furthermore, the locations of strong shores do not obviously affect the total critical load of the system. Besides, the locations of strong shores or equivalent strong shores are not recommended to be in the outmost side. Instead, it is favorable for the system critical load to put the strong shores as close to the central area of the floor and the beams as possible. It can also reduce the slab formwork settlement in the central area to do so. In a double-layer shoring system, if horizontal displacement of the horizontal planks in the central area happens, leaning column effect will occur in spite of the fact that the upper and lower edges are both fixed. Reducing the horizontal displacement of the planks can improve the total critical load of the system.
The findings of the study show that the collapse of the outer-wall scaffolding usually happens at the “outer-wall external formwork assembly stage” of formwork assembly operation and “plastering and whitewashing stage” of the finishing operation. At the construction site, when assembling the external formwork of outer-wall, the scaffolds are often connected with wooden braces, leading to the collapse of scaffolding when the external formwork of outer-wall is blown off by the strong wind. When plastering and whitewashing the outer wall, construction workers tend to tear down the wall-fixing braces and make way for laying ceramic tiles, which brings about the collapse of the scaffolding structure due to the significant reduction of its load-carrying capacity. At the “elevator room walls finishing stage”, workers also tear down the wall-fixing braces to facilitate the whitewashing process, which brings about the collapse of the scaffolding structure due to the reduction of its load-carrying capacity.
When calculating the strength of the temporary shoring structure of the bridge engineering, the designer easily overestimates the load-carrying capacity of the shoring system if the one only focuses on the design of “elements” and overlooks the calculating critical load of the shoring system. Temporary connections such as ordinary bolts and alligator clips are used for connection and fixing between steel shores and scaffolds. Since this kind of connection method is unable to bear the flexural moment when the unbalanced settlement happens on the supporting bottom layer soil, the joints connected by alligator clips might break and bring about a domino type collapse of the whole structure.
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