51 research outputs found
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Study on collapse mechanism of steel frame with CFST-columns under column-removal scenario
The design of structure against progressive collapse has tended towards more quantitative design where utilizing catenary action becomes essential. In this paper, a single internal column removal test was conducted for a 1/3 scale 4-bay steel frame with concrete-filled steel tubular (CFST) columns. The anti-collapse mechanism of the frame under the scenario of column loss is discussed. Both FE model and simplified analytical model are developed to investigate the behavior of steel frame with CFST columns in resisting progressive collapse. The accuracy of the two models is verified through the experimental results. The anti-collapse measures of the proposed model are sensitive to the modeling techniques used to simulate the CFST columns. A method based on the energy equivalence is used to evaluate the dynamic behavior of the frame. The results show that the DAF (dynamic amplification factor) value of 2.0 which is recommended by DoD provision in linear static analysis is reasonable. However the mobilization of âcatenary actionâ which is not considered in DoD provision would increase the DAF value as currently given in DoD
Theoretical assessment of progressive collapse capacity of reinforced concrete structures
The progressive collapse behaviour of reinforced concrete (RC) structures requires consideration of material and
geometric non-linearity, concrete crushing and rebar fracture. Compressive arch action (CAA) and catenary action
(CTA) are the main resisting mechanisms against progressive collapse following a column loss. Hence, many studies
have concentrated on the development of CAA and CTA in RC beams, but without considering the effect of bar
fracture and the reduction in beam effective depth due to concrete crushing. Taking these additional factors into
account, an analytical model to predict the structural behaviour of RC beams under a column removal scenario was
developed. The proposed model was evaluated and validated with the available experimental results. The evaluation
and validation indicate that the proposed model can provide a reliable assessment of RC beam capacity against
progressive collapse
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Capacity of semi-rigid composite joints in accommodating column loss
In the scenario of column loss, joints would be subjected to bending moment combined with a tensile force due to large vertical displacement, where tensile force plays a critical role in resisting progressive collapse of structure by providing the catenary force. In order to study the effect of tensile force on the behavior of semi-rigid composite joints in structures in the case of column loss, six semi-rigid flush endplate connections tests were conducted, which include pure flexural tests, pure tensile tests and combined flexural and tensile tests. The experimental results indicate that under pure bending moment condition, the semi-rigid composite joint displays sufficient rotation capacity for forming âcatenary actionâ. It is characteristic of the semi-rigid composite joint that its moment capacity decreases in a linear manner together with the increase of tensile load. Also, the capacity of semi-rigid composite joints is compared with that of the full-welded rigid composite joints. The tensile strength of high-strength bolts would not exert any effect on the initial stiffness of semi-rigid joint, but bring about decline in the moment resistance and tensile resistance of semi-rigid joint. The joints tend to fail at âcatenary phaseâ under tensile force. A simplified M-N correlation formula for composite joint is proposed to describe the behavior of joint in structures under column loss. The finite element model with material failure criterion can predict the fracture of bolt in semi-rigid composite joint
Progressive Collapse Resistance of RC Frames under a Side Column Removal Scenario: The Mechanism Explained
Progressive collapse analysis of a steel building with pre-northridge moment connections
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