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Reference

The Sri Lanka National Annex to Eurocode 2: every value that differs from the recommended

Every value of NA to SLS EN 1992-1-1:2013 that differs from the CEN recommended values, from the 0.85 concrete factor to bar spacing and column steel.

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A reinforced concrete house frame under construction in a Sri Lankan suburb, column bars standing up from the roof slab
Reading time
5 minutes
Standard
EN 1992-1-1 with the Sri Lanka NA
Calculator
Slab
Updated
On this page 8 sections
  1. Materials
  2. Analysis
  3. Serviceability
  4. Detailing of slabs and beams
  5. Columns
  6. Punching and footings
  7. What stays at the recommended values
  8. Other National Annexes

Eurocode 2 leaves a number of values for each country to decide: the Nationally Determined Parameters (NDPs). Each country publishes them in a National Annex. In Sri Lanka that is the NA to SLS EN 1992-1-1:2013, amended by AMD 522:2019.

Most of its values are the ones EN 1992-1-1 recommends. This page lists the ones that are different, as the calculator applies them, with the clause each belongs to. Every value the calculator takes from an annex is marked NDP on the calculation sheet, with the row of the annex it comes from.

The changes that matter most

Concrete strength factor
0.85
αcc, against 1.0 recommended: every fcd is 15 % lower
Crack width limit
0.3 mm
wmax for every exposure class
Slab bar spacing
3h ≤ 300 mm
main bars, against 3h ≤ 400 mm
Column minimum steel
0.004 Ac
twice the recommended 0.002 Ac

Materials

ClauseParameterRecommendedSri Lanka
3.1.6(1)P, long-term factor on the concrete strength1.00.85
3.2.2(3)Pupper limit of 600 MPa500 MPa

The factor reduces the design strength of the concrete, . With 0.85, C30/37 concrete has = 17.00 MPa instead of 20 MPa. The partial factors themselves, and , are the recommended ones.

The cut is the same share for every class, so it is largest in absolute terms for the strongest concretes. Both sets of values, as the calculator's material step works them out:

Design compressive strength for each class

fcd = αcc fck / γC with γC = 1.5. The National Annex choice of αcc changes every concrete calculation that follows.

  • Recommended, αcc = 1.00
  • Sri Lanka, αcc = 0.85
0 10 20 30 40 fcd (MPa) C20/25 C25/30 C30/37 C35/45 C40/50 C45/55 C50/60 0 10 20 30 40 fcd (MPa) C20 C25 C30 C35 C40 C45 C50
Show the numbers
Recommended, αcc = 1.00 (MPa)Sri Lanka, αcc = 0.85 (MPa)
C20/2513.3311.33
C25/3016.6714.17
C30/3720.0017.00
C35/4523.3319.83
C40/5026.6722.67
C45/5530.0025.50
C50/6033.3328.33

Analysis

ClauseParameterRecommendedSri Lanka
5.5(4) in the redistribution limit, 0.440.4
5.5(4), for concrete above C50/600.540.4
5.1.3(1)Pload arrangements for continuous membersalternate and adjacent spans loadedthe same, or all spans loaded with a 20 % cut in the support moments where the annex's conditions are met

The smaller allows a little more redistribution of moment, and a slightly deeper neutral axis, before compression steel is needed. The simplified load arrangement for slabs is a welcome short cut; the calculator checks its conditions (one of them is the area of the bay, which is why it asks for the slab width) and says which arrangement it used.

Serviceability

ClauseParameterRecommendedSri Lanka
7.3.1(5), crack width limit0.4 mm (X0, XC1), 0.3 mm (others)0.3 mm for every class
7.4.2(2)cap on the factor none1.5

Detailing of slabs and beams

ClauseParameterRecommendedSri Lanka
9.3.1.1(3)largest spacing, main bars in slabs mm mm
9.3.1.1(3)largest spacing, secondary bars mm mm
9.3.1.1(3)near concentrated loads, secondary bars mm mm
9.2.1.2(1), top steel at end supports for partial fixity0.150.3
9.2.1.4(1), bottom steel continued to end supports0.250.3
9.2.2(8)spacing of the legs of links across a beam mmalso, no tension bar more than 150 mm from a leg

The tighter slab spacings matter in practice: a 200 mm slab may not use bars wider apart than 300 mm under the Sri Lanka annex, against 400 mm in the recommended values.

Columns

ClauseParameterRecommendedSri Lanka
9.5.2(1)smallest longitudinal bar8 mm12 mm
9.5.2(2)minimum steel, as a share of 0.0020.004
9.5.2(3)maximum steel, away from laps0.040.06
9.5.2(3)maximum steel, at laps0.080.10

Punching and footings

ClauseParameterRecommendedSri Lanka
6.4.5(3) at the column face
9.8.2.1(1)smallest bar in a footing8 mm10 mm

The Sri Lanka annex prints the column face limit as , the form the recommendation took before the 2010 corrigendum to EN 1992-1-1; the corrected recommended value is . The calculator uses the annex as printed for Sri Lanka designs, and the corrected value for the recommended set.

Everything else is the same as the recommended values, including the partial factors, the shear constants , and , the cover allowances, the strut angle range, and the span to depth factors .

Other National Annexes

The calculator also offers the UK annex (the first edition, 2005, of the UK National Annex to BS EN 1992-1-1). The Sri Lanka annex follows it closely: the same α_cc of 0.85, the same redistribution constants, the same load arrangement options word for word, the same 0.3 mm crack width and the same cap of 1.5 on A_s,prov/A_s,req. The main differences are that the UK keeps the recommended slab bar spacings and column steel limits, sets β₁ = 0.25, allows 65 mm (not 75 mm) for concrete cast against soil, and takes the cover for durability from BS 8500, where a stronger concrete allows a smaller cover.

There are also the CEN recommended values, used in countries without an annex of their own, and an Another National Annex option where you type the values of any annex yourself; they are then printed on the calculation and the PDF under the name you give. More annexes will be added as the published documents are checked value by value.

Open the calculator and switch the annex between Sri Lanka and the recommended values to see which steps change.