# Deflection of beams

The structural frame
The construction
The reinforcement I
The reinforcement II
Quantity/Cost estimation
Detailing drawings
Introduction >

Wind and Seismic Forces >
Structural model and Analysis
Slabs
Seismic behavour of frames
Appendix A
Appendix B
Appendix C
Appendix D
Introduction >
Modelling slabs

Materials
To be continued >
Introduction

## Bending moments of joists supported on beams 300/1000

The traditional structural analysis considers beams as practically undeformed. Nowadays, with the accurate analysis using finite elements, it is possible to form structures of remarkably higher stiffness of beams than slabs.
The effect of vertical deformation of beams to the deformation of the slab is insignificant for beams with cross-section 300/1000 (deformations of beams practically zero).

## Bending moments of joists supported on beams 300/500

The effect of vertical deformation of beams to the deformation of the slab is moderate for beams with cross-section 300/500 (considerably smaller with respect to those of the slab).

## Bending moments of joists supported on beams 300/300

The effect of vertical deformation of beams to the deformation of the slab is significant for beams with cross-section 300/300.

## Bending moments of slab strips supported on beams 300/1000

In the two-dimensional finite element method, the secondary bending moments are always sig-nificant, while the moments in the main direction remain relatively constant.
In this case, like the modelling using members, the effect of vertical deformation of beams to the deformation of the slab is insignificant for beams with cross-section 300/1000 (deformations of beams practically zero).

## Bending moments of slab strips supported on beams 300/500

In both cases of modelling, the effect of vertical deformation of beams to the deformation of the slab is moderate for beams with cross-section 300/500.

## Bending moments of slab strips supported on beams 300/300

In both cases of modelling, the effect of vertical deformation of beams to the deformation of the slab is significant for beams with cross-section 300/300. In conclusion, the assumptions of frame elements being modelled with members and slab ele-ments being modelled with two-dimensional finite elements are considered to be both logical and successful. This success is greater the stronger the beams cross-section (mainly their depth), the smaller their span, and also the smaller the thickness of the slabs is.