3D numerical analysis of reinforced concrete beams exposed to elevated temperature

2014 ◽  
Vol 58 ◽  
pp. 166-174 ◽  
Author(s):  
Joško Ožbolt ◽  
Josipa Bošnjak ◽  
Goran Periškić ◽  
Akanshu Sharma
Author(s):  
Amr H. Badawy ◽  
Ahmed Hassan ◽  
Hala El-Kady ◽  
L.M. Abd-El Hafez

The behavior of unbounded post tension and reinforced concrete beams under elevated temperature was presented. The experimental work was consisted of two major phases. In the first phase, the objective was studying the mechanical performance of prestressed beam, prestressed beam with steel addition and reinforced concrete beams respectively were studied. In the second phase, the residual mechanical performance of prestressed beam, prestressed beam with steel addition and reinforced concrete beams under elevated 400oC, for 120 minutes durations. The failure mechanisms, ultimate load capacity, and deflection at critical sections were monitored. The numerical prediction of the flexural behavior of the tested specimens is presented in this paper. This includes a comparison between the numerical and experimental test results according to ANSYS models. The results indicate that the prestressed beam with steel addition and reinforced concrete beams had higher resistance to beams under elevated 400oC than that of prestressed concrete beam in terms of ultimate capacity. It is also shown that the reinforced concrete beams have higher resistance to beams under elevated temperature than that of prestressed beam, prestressed beam with steel addition.


Author(s):  
Mykolas Daugevičius ◽  
Juozas Valivonis ◽  
Tomas Skuturna

The numerical analysis of the reinforced concrete beams strengthened with CFRP is presented. The beams previously tested experimentally under long-term loading are selected for numerical simulation. The numerical modelling is performed by evaluating the beam’s work at various stages: the work stage before the long-term loading period, the work stage under the long-term load action, the work stage when the external load is removed and the work stage until failure. The work stages of all modelled beams are described in more detail. To analyse the behaviour of beams at different work stages, the numerical modelling using the phase analysis is performed. Different finite element groups are evaluated in each phase of analysis. The external load is increased, maintained and reduced. The finite elements of the CFRP layer are activated at a certain work stage for evaluating the strengthening effect. To assess the accuracy of the numerical analysis, each beam is modelled from the finite elements of various sizes. The paper presents the process of the numerical modelling and the predicted deflections. The numerically predicted deflections are compared with the deflections of the experimental study. The modelling of the behaviour of the strengthened beams has shown that the nature of the long-term deflection differs from that obtained in the experiment. The increment of the numerically predicted deflection decreases gradually over the long-term period. Meanwhile, the experimental long-term deflection increment is characterised by the sharp increase and decrease at the start of the long-term period. This contradiction shows that the experimental long-term deflections are greater. However, over time, the numerical model deflections may reach and exceed the experimental deflections due to steady increase. The smaller size of the finite elements causes the increase in the cracking moment and the higher moment when the yielding of the tensioned reinforcement occurs. However, the cracking moment obtained by the numerical modelling is much higher than that obtained by the experimental modelling. However, when the yielding strength of the tensile reinforcement is reached, the considered moment is smaller than the experimental one.


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