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Keywords: ribbed plates, building slabs, rib to plate eccentricity, finite element method, reinforced concrete.

Summary

It is usual practice in the structural analysis of buildings to assume the concentricity between plates and beams. Previous studies showed that in waffle-slabs, where the distance between beams is small, the eccentricity of the beam to the plate results in a reduction of stress and displacements of system, however a similar study concerning the eccentricity influence in slabs with few beams is not available.

The way to include the plate to beam eccentricity is to transfer its contribution to the stiffness matrix of the beam and then link it to the shell finite element. There are various ways to consider the eccentricity in the finite element method, one of them is the use of offsets, which was adopted in this work. With this, the effects of the eccentricity can be included by modifying the rigidity matrix of the beam finite element.

To represent the beam-plate connexion three models were idealized. The first model has the beams concentric with the plates, in the second model the beam is assumed to be fixed to the bottom of the plate and in the third the beam is taken as extending up to the top surface of the plate.

The model studied here consists of a rectangular ribbed floor slab with corners supported by columns clamped at its lower ends. Little by little ribs were removed to arrive at a model where the slab has only beams at its boundary, simulating several building slab problems. The analyses of the eccentric models are compared with the concentric ones, which are usually used in reinforced concrete floors, to evaluate errors in the formulations used. All slabs were analysed using the ANSYS program with beam and plate elements that suited the structure modelled.

The models are discretized with beam elements of two nodes with six degrees of freedom each and the plates are discretized with shell elements with four nodes each with six degrees of freedom.

The results for the rectangular slabs models show that the displacements in the concentric models are up to one hundred and ten percent greater than the eccentric ones.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 93 PROCEEDINGS OF THE TENTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: Paper 100 Numerical Study on the Influence of the Plate to Beam Eccentricity in Usual Building Slabs H.B.S. Silva, J.B. Paiva and J.S. Giongo Engineering Structures Department, São Carlos Engineering School, University of São Paulo, Brazil doi:10.4203/ccp.93.100 purchase the full-text of this paper Full Bibliographic Reference for this paper H.B.S. Silva, J.B. Paiva, J.S. Giongo, "Numerical Study on the Influence of the Plate to Beam Eccentricity in Usual Building Slabs", in , (Editors), "Proceedings of the Tenth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 100, 2010. doi:10.4203/ccp.93.100 Keywords: ribbed plates, building slabs, rib to plate eccentricity, finite element method, reinforced concrete. Summary It is usual practice in the structural analysis of buildings to assume the concentricity between plates and beams. Previous studies showed that in waffle-slabs, where the distance between beams is small, the eccentricity of the beam to the plate results in a reduction of stress and displacements of system, however a similar study concerning the eccentricity influence in slabs with few beams is not available. The way to include the plate to beam eccentricity is to transfer its contribution to the stiffness matrix of the beam and then link it to the shell finite element. There are various ways to consider the eccentricity in the finite element method, one of them is the use of offsets, which was adopted in this work. With this, the effects of the eccentricity can be included by modifying the rigidity matrix of the beam finite element. To represent the beam-plate connexion three models were idealized. The first model has the beams concentric with the plates, in the second model the beam is assumed to be fixed to the bottom of the plate and in the third the beam is taken as extending up to the top surface of the plate. The model studied here consists of a rectangular ribbed floor slab with corners supported by columns clamped at its lower ends. Little by little ribs were removed to arrive at a model where the slab has only beams at its boundary, simulating several building slab problems. The analyses of the eccentric models are compared with the concentric ones, which are usually used in reinforced concrete floors, to evaluate errors in the formulations used. All slabs were analysed using the ANSYS program with beam and plate elements that suited the structure modelled. The models are discretized with beam elements of two nodes with six degrees of freedom each and the plates are discretized with shell elements with four nodes each with six degrees of freedom. The results for the rectangular slabs models show that the displacements in the concentric models are up to one hundred and ten percent greater than the eccentric ones. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £145 +P&P)
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