Print SiteFlexure
The design procedure for flexural design is
given in an accompanying flow
chart; this includes derived formulae based on the simplified rectangular stress block from Eurocode
2. The table below can be used to determine bending moments and
shear forces for beams, provided the notes to the table are
observed.
Table 3 - Bending moment and shear coefficients for beams
| Moment | Shear | |
| Outer support | 25% of span moment | 0.45 (G+Q) |
| Near middle of end span | 0.090 γ GG/ +0.100 Ql | |
| At first interior support | -0.094 (<gamma>GG+<gamma>QQ) l | 0.63 (G+Q)a |
| At middle of interior spans | 0.066 <gamma>GGl +0.086 <gamma>QQl | |
| At interior supports | -0.075 (<gamma>GG+<gamma>QQ) l | 0.50 (<gamma>GG+<gamma>QQ) |
|
Key
a 0.55 (G+Q) may be used adjacent to the interior span Notes
1 Redistribution of support moments by 15% has been included 2 Applicable to 3 or more spans only and where Qk<Gk 3 Minimum span is > 0.85 longest span 4 l is the span, G is the total of the ULS permanent actions. Q is the total of the ULS variable actions |
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Co-efficients for one-way spanning slabs are
available in 'Concise
Eurocode 2'.
Eurocode 2 offers various methods for
determining the stress-strain relationship of concrete. For
simplicity and familiarity the method presented here is the
simplified rectangular stress block, which is
similar to that found in BS 8110 (see Figure below).
similar to that found in BS 8110 (see Figure below).
Simplified rectangular stress block for concrete up to class
C50/60 from Eurocode 2
Eurocode 2 gives recommendations for the design of concrete up to class C90/105. However, for concrete greater than class C50/60, the stress block is modified. It is important to note that concrete strength is based on the cylinder strength and not the cube strength (i.e. for class C30/37 the cylinder strength ( fck) is 30 MPa, whereas the cube strength is 37 MPa).