STATIX Free calculators
Learn · worked example

Column base plate design to SANS 10162-1

A 203 × 203 × 46 H-column on a 400 × 400 × 25 plate with 4 M20 class 8.8 holding-down bolts, carrying 500 kN, 60 kNm and 60 kN: the EN 1993-1-8 component method for the base moment (concrete in bearing under the compression flange, the T-stub and anchors on the tension side), the SANS 10162-1 clause 25 checks for the holding-down bolts and the welds, and the EN 1992-4 anchor checks in the concrete. Every number below comes from the STATIX base plate calculator and was checked by hand.

1. The problem

InputValue
Column203 × 203 × 46 H-section (d 203.2, b 203.6, tf 11.0, tw 7.2 mm)
Base plate400 × 400 × 25 mm, S355 (fy 355 MPa)
Holding-down bolts4 × M20 class 8.8 (fu 830 MPa), 60 mm from the plate edge, cast-in headed, embedment 300 mm
Concretegrade 30: fcu = 30 MPa (cube), non-cracked, grouted bearing
Design loads (factored)N = 500 kN compression, M = 60 kNm, V = 60 kN
Column endsawn, in full contact bearing on the plate

SANS 10162-1 clause 25 covers holding-down bolts and the shear at a base, but it gives no method for the moment a base plate can carry. For that the calculator uses the component method of EN 1993-1-8 (clause 6.2.8) and says so on every row. The anchors in the concrete are checked to EN 1992-4, because clause 25.2.2.2 sends pull-out to SANS 10100-1, which has no anchor rules.

2. Concrete and grout in bearing (EN 1993-1-8 6.2.5)

The page asks for the cube strength. The calculator takes fck = 0,8 fcu = 24 MPa, so fcd = 24 / 1,5 = 16 MPa. With the grout and a foundation no wider than the plate, the joint bearing strength is two thirds of that. The plate spreads the load a distance c beyond the flange.

fjd = βj fcd = 2/3 × 16 = 10,67 MPa c = t √(fy / (3 fjd γM0)) = 25 × √(345 / (3 × 10,67)) = 82,1 mm (fy = 345 MPa for a 25 mm plate) Bearing area under the compression flange = (203,6 + 2c)(11,0 + 2c) = 367,8 × 175,2 = 64 440 mm² FC,Rd = 10,67 × 64 440 = 687,9 kN

3. The lever arm and the forces (EN 1993-1-8 6.2.8.3)

The compression acts at the centre of the compression flange, the tension at the bolt line on the other side.

zC = (203,2 − 11,0) / 2 = 96,1 mm zT = 400/2 − 60 = 140 mm z = 236 mm e = M / N = 60 / (−500) = −0,120 m (compression, beyond zC: one side in tension) Ft = (M − |N| zC) / z = (60 − 500 × 0,0961) / 0,236 = 50,6 kN (two bolts) Fc = |N| + Ft = 550,8 kN

4. Moment resistance Mj,Rd (Table 6.7)

Tension side: FT,Rd z / (zC/e + 1) = 272,3 × 0,236 / (1 − 0,801) = 322,6 kNm Compression side: −FC,Rd z / (zT/e − 1) = 687,9 × 0,236 / 2,167 = 74,9 kNm Mj,Rd = 74,9 kNm ≥ 60 kNm OK (80%)

The tension side is strong: the T-stub of the plate and two bolts carries 272,3 kN (mode 3, the anchors themselves, with no prying). It is the concrete under the compression flange that limits the moment. The same 80% shows as the bearing check: Fc = 550,8 ≤ FC,Rd = 687,9 kN.

5. The column, the plate and the welds

Column flange and web in compression: 550,8 ≤ 918,9 kN (60%) Column web in tension: 50,8 ≤ 413,6 kN (12%) Base plate in bending (T-stub): 50,8 ≤ 272,3 kN (19%) Flange weld (SANS 13.13.2.2): 133,7 ≤ 1 687,9 N/mm (8%) Web weld (Vz): 186,8 ≤ 1 218,9 N/mm (15%) Flange weld not weaker than FT,Rd: 272,3 ≤ 642,1 kN (42%)

6. Shear and the holding-down bolts (SANS 10162-1 cl. 25.2.3, 25.2.4)

Shear: friction 0,20 × Fc + 4 × min(Vr, Br) = 261,3 kN ≥ 60 kN OK (23%) Bolt tension + shear: Vu/Vr + Tu/Tr = 0,19 ≤ 1,4 OK

SANS gives no friction coefficient for a grouted base; the calculator takes 0,20 from EN 1993-1-8 6.2.2(6).

7. The anchors in the concrete (EN 1992-4)

Anchor steel tension: 50,8 ≤ 261,3 kN (19%) Concrete cone breakout: 50,8 ≤ 282,6 kN (18%) Pull-out (head bearing): 50,8 ≤ 131,9 kN (39%) Anchor steel shear: 30,0 ≤ 156,8 kN (19%) Pryout: 30,0 ≤ 565,2 kN (5%) N + V, concrete (eq. 7.55): 0,40 ≤ 1 (40%)

No free edge was declared, so edge breakout and splitting are not checked. If the base sits on a pedestal or near a slab edge, enter the edge distance: edge breakout usually governs there.

8. Result

CheckResult
Moment resistance Mj,Rd60 ≤ 74,9 kNm (80%)
Concrete and grout in bearing550,8 ≤ 687,9 kN (80%), governs
Column flange and web in compression60%
Anchor pull-out (EN 1992-4)50,8 ≤ 131,9 kN (39%)
Shear, 25.2.360 ≤ 261,3 kN (23%)
Bolt shear + tension, 25.2.40,19 ≤ 1,4
Welds42% or less

The base passes at 80%, governed by the concrete and grout in bearing under the compression flange. A thicker plate (a larger c) or a stronger grout and concrete raise it most.

Run this example yourselfThe STATIX base plate calculator opens with the inputs of step 1 and checks to SANS 10162-1 by default, with the EN component method where SANS has no rule. Every number above appears, with each clause and a printable calc sheet.
Open the free base plate calculator

A worked example for learning, not a design. Check every value against the current code and your own project, and have the design checked and signed by a registered professional engineer.

Early access

Be first to use STATIX 3D and STATIX 2D.

Leave your email and we will tell you when each part is ready for testing. One confirmation now, one message then. A short monthly update only if you tick the box.