xsec example
Eurocode 2: example 6.1-1
Accompanying this are files para_a.xsf and para_b.xsf that are both in metric units with
small dimensions.
Designers’ guide to EN 1992-2, Eurocode 2: Design of concrete structures, Part 2:
Concrete Bridges by C. R. Hendy and D. A. Smith, published by Thomas Telford
Publishing, London 2007 included a “Worked example 6.1-1: Reinforced concrete deck
slab”.
The accompanying file para_b.xsf demonstrates that the application computations are
consistent with that worked example. The accompanying file para_a.xsf uses the same
example to illustrate the use of the application with reinforcing steel that has a strain limit
although this is not in accordance with the worked example.
The file Para_b.xsf represents an analysis using the parabolic-rectangular stress block for
concrete and the horizontal top branch described in clause 3.2.7 (2) b) for the reinforcing
steel.
The worked example computations show the required area of steel is 1936 mm²/m and
the design has bars at 150 mm centres. This implies the required area of each bar is
290.40 mm². The file Para_b.xsf represents a 150 mm width of the deck slab having one
bar of that area. Also details in the worked example indicate that the depth of the bar, d =
200 mm.
Ultimate strength computations with the application result in a bending moment of
22.493 kNm on a 150 mm width of deck slab. That is equivalent to 150 kNm/m and is
consistent with the worked example computations.
The file Para_a.xsf represents an analysis also using the parabolic-rectangular stress
block for concrete but uses the inclined top branch and a strain limit described in clause
3.2.7 (2) a) for the reinforcing steel. This produced a bending moment slightly higher
than the worked example. It is included here to illustrate how the application can cope
with reinforcing steel that has a strain limit. In such cases the Ultimate Bending Moments
“method” in the application might not work. In such cases the Yield Bending Moments
“method” might help.
Use the Yield Bending Moments “method” and increased the strain in the bar from the
yield strain 0.002174 to a strain slightly less than the strain limit; 0.004500. This can be
done on the “choose a bar” dialog. Uncheck the check box indicating that the yield tensile
strain is to be used and a text edit box will appear where a strain can be input. The value
of the strain limit is available in the stress – strain table revealed by the “Display as text”
button on the material edit dialog for the steel. It is the strain value on the last line in the
table.
The computations with the application result in a bending moment of 23.563 kNm on a
150 mm width of deck slab. That is equivalent to 157.1 kNm/m; slightly higher than the
150 kNm/m.
Eurocode2: example 6.1-1
September 2016
page 1 of 2
These computation use a steel cross-section area equivalent to the minimum determined
in the worked example. The same computation could be repeated using the cross-section
area of a standard bar size that is available.
Eurocode2: example 6.1-1
September 2016
page 2 of 2