Abstract
Abstract In the region of negative bending moments of continuous and semi-continuous steel and concrete composite beams, the inferior portion of the steel section is subjected to compression while the top flange is restricted by the slab, which may cause a global instability limit state know as lateral distortional buckling (LDB) characterized by a lateral displacement and rotation of the bottom flange with a distortion of the section’s web when it doesn’t have enough flexural rigidity. The ABNT NBR 8800:2008 provides an approximate procedure for the verification of this limit state, in which the resistant moment to LDB is obtained from the elastic critical moment in the negative moment region. One of the essential parameters for the evaluation of the critical moment is the composite beam’s rotational rigidity. This procedure is restricted only to to steel and concrete composite beams with sections that have plane webs. In this paper, an equation for the calculation of the rotational rigidity of cellular sections was developed in order to determine the LDB elastic critical moment. The formulation was verified by numerical analyses performed in ANSYS and its efficiency was confirmed. Finally, the procedure described in ABNT NBR 8800:2008 for the calculation of the critical LDB moment was expanded to composite beams with cellular sections in a numerical example with the appropriate modifications in geometric properties and rotational rigidity.
Highlights
A steel and concrete composite beam, according to Brazilian Standard ABNT NBR 8800:2008 [1], consists of a steel component symmetric with respect to the flexure axis, which can be an I profile of a truss, with a concrete slab on top of its superior flange
In the region of negative bending moments of continuous and semi-continuous steel and concrete composite beams, the inferior portion of the steel section is subjected to compression while the top flange is restricted by the slab, which may cause a global instability limit state know as lateral distortional buckling (LDB) characterized by a lateral displacement and rotation of the bottom flange with a distortion of the section’s web when it doesn’t have enough flexural rigidity
The ABNT NBR 8800:2008 provides an approximate procedure for the verification of this limit state, in which the resistant moment to LDB is obtained from the elastic critical moment in the negative moment region
Summary
A steel and concrete composite beam, according to Brazilian Standard ABNT NBR 8800:2008 [1], consists of a steel component symmetric with respect to the flexure axis, which can be an I profile of a truss, with a concrete slab on top of its superior flange. The Brazilian Standard ABNT NBR 8800:2008 [1] provides and approximate procedure for the verification of the limit state for lateral-torsional buckling (LTB), similar to the European Standard EN 1994-1-1:2004 [2], based on the behavior of the inverted U-frame mechanism, from which the resisting flexural moment to LTB is obtained from the critical elastic moment of the hogging moment region. A fundamental parameter to compute the critical elastic moment is the rotational stiffness of the composite beam. This procedure from the standard is restricted to composite beams of continuous plane webs. Research on lateral-torsional buckling of composite beams with cellular profiles is still recent
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
