Analyzing shear strength of steel-concrete composite beam with angle connectors at elevated temperature using finite element method

Abstract

Steel- concrete composite beams are widely used in the construction of tall building with steel floors. In these floors, the bearing capacity of beams in which the performance of concrete and steel is composite is more than 30% of the same beams with non-composite performance. Fire, especially in buildings, has a devastating effect on the components of the structure including the columns, beams, floors, etc. Also, fire indirectly affects the shear connectors buried in floor concrete and reduces their strength, thus reducing the overall strength of the floor. In this research, the behavior of angle shear connectors as a type of shear connectors used in the steel-concrete composite floor due to temperature increase was investigated numerically. Thermo-mechanical finite element modeling was performed using Abaqus software on push-out samples, and the results have been compared with the results obtained from the laboratory tests. Similar to the laboratory conditions, samples with different dimensions of angle shear connectors were modeled at different temperatures including 25, 550, 700 and 850 degrees Celsius. According to the laboratory process, 24 samples were modeled in Abaqus software thermally. The research results showed that the models made in the software were able to accurately predict the laboratory results including shear strength and slip. It was found that the maximum shear force error between analytical and laboratory results is 21.6% and the minimum shear force error in some samples is near to zero. As the temperature increases, the error rate between the laboratory and analytical results increases. Also, shear connector dimensions, concrete strength and temperature value have direct effect on the final strength of steel-concrete composite floors and load slip diagrams. It was also concluded that increasing the angle height to a certain extent could increase the final shear strength of the steel-concrete floor and increasing the angle height after a certain limit had no effect on increasing the shear strength and results in material loss and uneconomical design. Moreover, results indicated that increasing the temperature up to 850C leads to reducing the shear strength of the samples by approximately 56%.