PeterJ1982
Structural
- Jun 7, 2010
- 7
I am designing a composite steel decking consisting of secondary beams with heavy point loads, 150kN, primary beams and steel columns. Beams are tubular box sections, having shear studs for composite action. I have connected secondary beams to primary with fin plate connection. Primary beams are connected to steel columns just by plate without any mechanical connection, so primary beams are free to rotate and twist.
So the system works as secondary beam end reaction goes to primary beams bending and primary beams are "flexible" to twist freely at the support. Then one thing is unknown for me; how to evaluate bolt forces acting in fin plate connection beams?
I think it goes as follows:
1. Construction stage, unpropped construction: Because of no composite action, fin plate bolts has to handle torsion, so there will be significant horizontal force in bolts, because shear centre is in the middle of primary beam. All bolts will carry shear equally. For example 1 row 3 bolts connection, upper bolt have horizontal force V*e/z, V=shear force, e= eccentrity, z=bolts "shaft"...
2. Final stage: Bolts carry shear equally, but not anymore horizontal moment, because primary beam no is not anymore free to twist, because of shear studs. Still, does bolt still have horizontal force because of the twisting of primary beam? Some force is needed to balance twisting moment, otherwise the system collapses. I think balancing system can be so that bolt connection act as tension side and concrete as compression.
By the way, I have designed the fin plate connection so that it will handle the total moment V*e, but I think it may be too concervative solution, because of composite action. There is no good literature about how to connect beams in composite systems...
So the system works as secondary beam end reaction goes to primary beams bending and primary beams are "flexible" to twist freely at the support. Then one thing is unknown for me; how to evaluate bolt forces acting in fin plate connection beams?
I think it goes as follows:
1. Construction stage, unpropped construction: Because of no composite action, fin plate bolts has to handle torsion, so there will be significant horizontal force in bolts, because shear centre is in the middle of primary beam. All bolts will carry shear equally. For example 1 row 3 bolts connection, upper bolt have horizontal force V*e/z, V=shear force, e= eccentrity, z=bolts "shaft"...
2. Final stage: Bolts carry shear equally, but not anymore horizontal moment, because primary beam no is not anymore free to twist, because of shear studs. Still, does bolt still have horizontal force because of the twisting of primary beam? Some force is needed to balance twisting moment, otherwise the system collapses. I think balancing system can be so that bolt connection act as tension side and concrete as compression.
By the way, I have designed the fin plate connection so that it will handle the total moment V*e, but I think it may be too concervative solution, because of composite action. There is no good literature about how to connect beams in composite systems...
