Abstract
In order to provide the steel-concrete synthesis effect of composite beam,a method of welding steel angle shear connectors to hat-shaped cold-formed steel(CFS)section has recently been used.For the design of such composite beam system,Kang et al.[1]proposed the shear strength design equation of angle shear connector welded to hat-shaped CFS section(Eq.(1))based on AISC 360[2]design equation for channel shear connector welded to wide-flange section.The equation is adopted by AC495[3],which specifies the design,test method,and acceptance criteria for such composite beam system.
where Qn is nominal shear strength of each steel angle shear connector(N),tf is thickness of horizontal leg of steel angle(mm),tw is thickness of vertical leg of steel angle(mm),
is specified concrete compressive strength(MPa),Ec is modulus of elasticity of concrete(MPa),and la is CFS structural beam web-to-web clear distance(mm).
In this study,to validate the AC495 design equation,a series of push-out tests(Figure 1)and beam flexural tests(Figure 2)were carried out with the shear connector spacing and direction as the main variables.From the tested 10 pushout specimens,the measured angle shear connector strengths exceeded 2.5 to 4 times the nominal strength determined by the AC495 design equation(Table 1).In addition,shear connector related failure modes did not appear in the beam flexural specimen with shear connector spacing three times larger than the spacing determined by AC495 design equation,which verifies the push-out test results(Figure 3).The current shear connector design equation in AC495 was found to underestimate shear connector strength significantly,because the shear strength provided by concrete itself is not considered in the design equation.That conservative estimation on the shear connector strength can lead to excessively short shear connector spacing,which makes construction difficult and costly.Thus,it is necessary to improve the equation for more reasonable design of angle shear connectors.
Figure 1 Push-out test
Table 1 Push-out test results
Figure 2 Composite beam flexural test
Figure 3 CFS beam-concrete interface slip after the flexural test