Numerical simulation of a progressive collapse of structures using computer has a very actual apprehension for structural engineers due to their interest in structures veracity estimation. This simulation helps engineers to develop methods for increasing or decreasing the progressive failure. Finite Element Method (FEM) is the most computer simulation analysis currently used to perform a structural vulnerability assessment. Unfortunately, FEM is not able to automatically analyze a structure after element separation and collision which has a great effect on a structure's performance during collapse. For instances, a bombing load can cause damage to a main supporting column in a structure, which will cause debris flying at a very high velocity from the damaged column. This debris can cause another local failure in another column upon impact and lead to the progressive collapse of the whole structure. A new simulation technique, which was developed in 1995 as part of Tagel-Din's doctoral research, called Applied Element Method (AEM) can simulate the structure's behaviour from zero loading until collapse, through the elastic phase, opening and propagation of cracks, yielding of reinforcement bars and separation and collision of elements. This method is used in Extreme Loading for Structures software (ELS) by Applied Science International (ASI). In the current paper, a brief description of the AEM is given. Also, numerical modelling based on two experimental studies available in the literature conducted by Ahmadi et al. [1] and Yi et al. [2] are generated using ELS. These models are used to confirm the capability of AEM in simulation the progressive collapse behaviour of structures. Also, the models are utilized to examine and measure the structural resisting mechanisms of reinforced concrete structures against progressive collapse. The obtained numerical results indicated that, ELS can accurately model all structural behaviour stages up to collapse. A better agreement between the experimental and numerical results is observed. Moreover, the results obtained with ELS indicated an enhanced agreement with other software packages such as; OpenSees, Ansys, Abacus, and MSC Marc.
The Finite Element Method (FEM) and the other numerical strategies are viably actualized in linear and non-linear analysis of structures. Recently, a new displacement based on Applied Element Method (AEM) has been developed. It is applicable for static and dynamic for both linear and non-linear analysis of framed and continuum structures. In AEM, the structural member is partitioned into virtual elements connected through normal and shear springs representing stresses and strains of certain portion of structure. FEM assumes the material as continuous and can indicate highly stressed region of structure, however it is difficult to model separation of element unless crack location is known. The main advantage of AEM is that it can track the structural collapse behavior going through all phases of the application of loads.In the current research, the application of AEM is illustrated through a non-linear dynamic analysis. Progressive collapse simulation is conducted using Extreme Loading for Structures software (ELS), which follows the AEM. The experimental and analytical works carried by Park et al. [17 and 28] for 1/5 scaled 3 and 5 stories reinforced concrete structures are used for verification. Good matching between the experimental and numerical results has been obtained using ELS. Therefore, it can be confirmed that ELS is capable in simulating the structures' behavior up to collapse.Furthermore, a study has been made to investigate the effect of considering the floor slabs on progressive collapse. The results show that considering slab in progressive collapse analysis of multistory buildings is important as neglecting the slabs' contribution leads to incorrect simulation and uneconomic design.
The objective of this paper is to investigate the Structural behavior of the damaged steel B.F.I. Beam (No. 10) under fatigue load (repeated load by 40% the value that produces a static failure) and make a comparison with the static loads for the same specimen. Which repaired and reinforced by Carbon fiber polymers strips (CFRP) (3*10cm * 100cm), fixed at the center of the tension flange and 8 strips (8*8mm*10mm) were distributed and fixed to the two faces of the web. The damage is created by notching (4mm) in the center of the tension flange for the six beams and two beams were damaged by the failure test of the two control beams. We have ten B.F.I. Beams, five beams were tested under static load and the other five beams under fatigue load with different ways of reinforcing by the layers of CFRP. We make an experimental comparison between the behavior for the ten beams under static and fatigue loads. We noticed that CFRP patching resulted in improvement in fatigue life of the damaged beams of up to 6.4 times over that of unrepaired beams, and to 1.8 % for static load cases, CFRP strips moderate fatigue crack propagation. The reinforcing to the web work as a stiffeners improve the shear failure and the deflection.
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