American Society of Civil Engineers


Time-Dependent Analysis of Shear-Lag Effect in Composite Beams


by Luigino Dezi, (Prof. of Struct. Engrg., Inst. of Struct. Engrg., Univ. of Ancona, via Brecce Bianche, Monte D’Ago, 60131, Ancona, Italy. E-mail: dezi@popcsi.unian.it), Fabrizio Gara, (Grad. Engr., Inst. of Struct. Engrg., Univ. of Ancona, via Brecce Bianche, Monte D’Ago, 60131, Ancona, Italy), Graziano Leoni, (Postdoct. Res., Inst. of Struct. Engrg., Univ. of Ancona, via Brecce Bianche, Monte D’Ago, 60131, Ancona, Italy), and Angelo Marcello Tarantino, (Assoc. Prof., Dept. of Engrg. Sci., Univ. of Modena, via Campi 213/B, 41100, Modena, Italy. E-mail: tarantino@unimo.it)

Journal of Engineering Mechanics, Vol. 127, No. 1, January 2001, pp. 71-79, (doi:  http://dx.doi.org/10.1061/(ASCE)0733-9399(2001)127:1(71))

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Document type: Journal Paper
Abstract: Taking into account the long-term behavior of the concrete, a model for analyzing the shear-lag effect in composite beams with flexible shear connection is proposed. By assuming the slab loss of planarity described by a fixed warping function, the linear kinematics of the composite beam is expressed by means of four unknown functions: the vertical displacement of the whole cross section; the axial displacements of the concrete slab and of the steel beam, and the intensity of the warping (shear-lag function). A variational balance condition is imposed by the virtual work theorem for three-dimensional bodies, from which the local formulation of the problem, which involves four equilibrium equations with the relevant boundary conditions, is achieved. The assumptions of linear elastic behavior for the steel beam and the shear connection and of linear viscoelastic behavior for the concrete slab lead to an integral-differential type system, which is numerically integrated. The numerical procedure, based on the step-by-step general method and the finite-difference method, is illustrated and applied to an example of practical interest.


ASCE Subject Headings:
Composite beams
Finite difference method
Flexible connections
Numerical analysis
Shear lag
Time dependence