Nonlinear analysis of composite beams with concrete-encased steel truss: Fid-Bau Portal

Nonlinear analysis of composite beams with concrete-encased steel truss

Tullini, N. / Minghini, F.

Abstract Composite beams constituted by a concrete-encased steel truss welded to a continuous steel plate are analyzed using a nonlinear finite element formulation based on Newmark's classical model. The web member of the steel truss is made by deformed or structural steel rebars and behaves like a deformable shear connection. In order to avoid slip locking, finite elements based on second-order interpolation of longitudinal displacements and flexural rotations are employed. Simply supported composite beams subjected to a uniformly distributed transverse load are considered. The bending capacity is evaluated for short up to long spans, taking the nonlinear behavior of concrete, steel and shear connection into account. The effects of the shear connection ductility are put in evidence, showing that, for short spans, the interfacial stress transfer resulting from the yielding of connection may be penalizing. In fact, the high slip gradient arising in sections near the supports may lead to a premature concrete failure. In this case, the exact solution to the linear elastic problem for steel–concrete composite beams can be used for design purposes.

Highlights • Beams with concrete-encased steel truss are analyzed using slip locking free elements. • The moment resistance is proportional to the span length for short up to medium spans. • The shear connection yielding near the supports leads to premature concrete failure. • The linear elastic model with cracked concrete-section stiffness is valid for short spans. • The ultimate moment for long spans can be computed as for RC sections.