اثرات مختلف دال های کامپوزیتی فولاد و بتن تحت طرح حذف ستون
Abstract
1- Introduction
2- Experimental scheme
3- Experimental results
4- Discussion of experimental results
5- Conclusions
References
Abstract
Trapezoidal and Reentrant are two ordinary deck profiles in modern steel-concrete composite floor system in China. The progressive collapse resistance of rigid steel beam-column connections with these two different composite deck profiles was experimentally investigated. This research addressed progressive collapse behavior of components evaluated by removing columns through the alternate load path method where the connections simulated the behavior of connections from a multi-bay steel moment-resisting frame. Also, collapse resistance of the connection above the removed column and the adjacent connection was considered. The results were compared with a bare steel subassembly, which has the same configuration but without composite slab, the load carrying capacity of the specimen with trapezoidal steel deck is improved by 28% and the specimen with reentrant steel deck is improved by 44%. The type of steel decks influenced the degree of restraint to the beam top flange and resistance of the connection. The specimen with trapezoidal steel deck had a higher plastic rotation capacity than the reentrant one, but the specimen with reentrant steel deck had improved composite behavior in the large deformation range and, therefore, developed more catenary action than the specimens with trapezoidal steel deck. Overall, the specimens with reentrant steel deck had a better performance under the progressive collapse situation, however, some constructional measures must be made to delay the bottom beam flange fracture.
Introduction
Progressive collapse of structures begins with the failure of a few structural elements and then spreads to adjacent elements until substantial or complete collapse of a structure [1]. Potential causes of progressive collapse include design and construction flaws, explosion, bomb attack or some other extreme events. Design methods to prevent progressive collapse are found in the Unified Facilities Criteria, DoD [2] and the General Services Administration publication, GSA [3]. Both documents use the alternate load path method, which considers column removal as the initial damage state, and subsequently analyzes and designs the structural system to resist the demands resulting from the column removal. When a column is removed, an alternative load path capable of withstanding the full demands must be formed by the beams and slabs to redistribute the load initially supported by the removed column. Under this scenario, the response of the beam-column connections next to the removed column is crucial in sustaining and redistributing the gravity loads [4]. Prior research has investigated the behavior of steel beam-column connections under column-loss scenarios. Sadek et al. [5] conducted a coordinated experimental and numerical assessment of the performance of the intermediate steel moment frames and the special moment frames (with reduced beam section connections) under the middle column removal scenario. Compared with the intermediate steel moment frames, both ultimate resistance and failure displacement had been improved in the special moment frames, which was benefited from the contributions of reduced beam section connections. Yang et al. [6,7] compared the performance of bolted angle, shear tab and flush end plate connections under the middle column removal scenario. The bolted web angle connection had the best performance among the tested simple-connections, while the double flange and web angle connection had the highest load and rotation capacities among the tested semi-rigid connections. Li et al. [8,9], Qin et al.