Examining fire response of unilaterally concrete-reinforced web prestressed composite beams with corrugated webs

Prestressed steel-concrete composite beams with concreted and corrugated webs are a novel system that have been attracting attention lately. Unfortunately, there has been little research with regard to the fire performance of such beams. To overcome this knowledge gap and in the hope of exploring attractive solutions to improve the fire resistance of these beams, a testing campaign was conducted to examine the potential of reinforcing the webs of such beams via concrete. In this pursuit, three different prestressed steel-concrete composite beams (PCBCWs) were examined under fire conditions. The first beam was conventional PCBCW, the second PCBCW was unilaterally concreted between flanges and the third PCBCW was bilaterally concreted between flanges. These PCBCWs were exposed to the standard ISO834 fire and mechanical loading. The results of the fire tests revealed that PCBCWs without encased concrete suffer from the buckling of the web, but beams reinforced with concreted webs did not. Moreover, the vertical deformations were significantly influenced by the concreting of webs or the absence of such reinforcement. PCBCW with one-sided concrete between the flanges also underwent horizontal deflection during the test. To complement the conducted fire tests, finite element models (FEM) were developed to further explore the fire response of PCBCWs. The FE simulations show that, for PCBCW with one-sided encased concrete between flanges, there is horizontal deflection due to asymmetrical tension of the cable strands, horizontal temperature gradient, and torque around the longitudinal axis of the beam. Further, the shear center of PCBCW with one-sided encased concrete moves towards the coldest side with temperature rise. Finally, the FE analysis indicates signs of rupture of the cable strands inside the encased concrete triggers the failure and corresponding horizontal deflection of PCBCW with one-sided encased concrete between the flanges at high temperatures.

Automated summary

Prestressed steel-concrete composite beams can improve their fire resistance by reinforcing the webs with concrete, preventing buckling and horizontal deflection. Finite element models further revealed the mechanisms of fire response.