Codes

• EN 1990: Basis of structural design
• EN 1991-1-1: Densities, self-weight and imposed loads
• EN 1991-1-3: Snow loads (simplified)
• EN 1991-1-4: Wind actions (simplified)
• EN 1992-1-1: Design of concrete structures
• EN 1997-1: Geotechnical design (bearing pressure, simplified)

Slab checks

• OKFlexure lx 335 ≥ 288 mm²/m
• OKFlexure ly 287 ≥ 276 mm²/m
• OKMain bar spacing 150 ≤ min(3h, 400) = 400 mm [9.3.1.1(3)]
• OKShear (VEd ≤ VRd,c) 22.4 ≤ 103.6 kN/m
• OKDeflection (l/d) 31.4 ≤ 333.4
• OKAspect ratio ly/lx = 1.00 ≤ 2

• Structural concrete C30/37 to EN 206 (frame exposure XC1: maximum w/c 0.65, minimum cement 260 kg/m³; foundations XC2: maximum w/c 0.6, minimum cement 280 kg/m³).
• Blinding C10/12, 75 mm. Maximum aggregate size 20 mm unless the bar spacing needs smaller.
• Slump 100 to 150 mm at the point of placing (S3). Vibrate all concrete; do not add water on site.
• Test cubes or cylinders: one set for every 50 m³ or every day's pour for each grade; strike formwork only on the strengths and ages below.
• Curing: keep exposed surfaces damp or covered for at least 7 days (10 days in hot or dry weather).

• High-yield ribbed bars B500B (fyk = 500 MPa) to EN 10080, with a mill certificate for each delivery.
• Nominal cover: beams 25 mm, columns 30 mm, slabs 25 mm, foundations 50 mm (to links where links are used). Use plastic or concrete spacers at not more than 1 m centres in each direction.
• Lap lengths and anchorages as scheduled; stagger laps so that no more than half the bars are lapped in one section where possible.
• Bends to the minimum mandrel diameters of EN 1992-1-1 Table 8.1N (4 φ up to Ø16, 7 φ above); no re-bending of partly bent bars.
• Remove loose rust and mill scale before concreting; keep bars clear of oil, mud and release agent.

• Design and prop formwork for the wet concrete and the construction loads; use the cambers on the drawings. Set out to the tolerances of EN 13670 (± 10 mm on dimensions, ± 5 mm on level).
• Typical striking times for ordinary Portland cement at 15 °C or more: vertical faces of columns and walls 1 to 2 days; beam and slab sides 2 days; slab soffits 7 to 10 days with props kept 21 days (longer for spans over 6 m or in cold weather).
• Re-prop at once after striking soffit forms where the floor above is to be cast within 14 days.

• Blocks: minimum compressive strength 3.5 N/mm² (non-loadbearing partitions) and 7 N/mm² (external walls), to EN 771; mortar 1:5 cement to sand by volume.
• Provide damp-proof course at the base of ground-floor walls; tie masonry to the frame with ties at 450 mm vertically; break joints in alternate courses.
• Plaster 12 mm in two coats on prepared, damp surfaces; external render 15 mm with a weatherproof coat; paint after the plaster has dried for 28 days.
• Bathroom, kitchen and WC floors: waterproof membrane turned up 150 mm, falls to the drains, tiles on bedding.

• Set out from the structural grid on the drawings; check diagonals of the building plan and the levels of every floor before casting.
• Fire resistance R60: do not reduce the cover or the member sizes shown on the drawings.
• Inspect reinforcement (size, spacing, cover, laps) and formwork before every pour; keep a record signed by the engineer.
• All design values are preliminary: they must be checked and approved by a qualified engineer before construction.

Design checks

• OKSlab 220 mm, two-way panel 6 × 6 m
• OKBeams 350 × 400 mm, 0 of 12 failing
• OKColumns 0 of 4 storeys failing
• OKDrift: Wind (SLS, limit h/500) max drift 0.05% of storey height
• OKP-Δ sensitivity θ (Wind) max θ = 0.047 (limit 0.1)
• OKRoof sway (wind) ≤ H/500 5.3 ≤ 26 mm
• OKFooting: Edge column (critical frame) 1.8 × 1.8 m, h = 400 mm, NEd = 600 kN
• OKFooting: Interior column (critical frame) 2.3 × 2.3 m, h = 450 mm, NEd = 1270 kN
• OKConcrete class for frame (XC1) C30 ≥ C20/25; limits w/c ≤ 0.65, cement ≥ 260 kg/m³
• OKConcrete class for foundations (XC2) C30 ≥ C25/30; limits w/c ≤ 0.6, cement ≥ 280 kg/m³
• OKFire R60: slab axis distance 29 mm ≥ 20 mm required for 220 mm section
• OKFire R60: beams axis distance 41 mm ≥ 25 mm required for 350 mm section
• OKFire R60: columns axis distance 48 mm ≥ 40 mm required for 350 mm section
• OKRaft: eccentricity (no uplift) e = 0.06 m ≤ L/6 = 3.33 m
• OKRaft: bearing pressure q,max = 50 kPa ≤ 200 kPa
• OKRaft: overturning 0.9GL/2 / M = 130.09 (≥ 1.5)
• OKRaft: sliding μ·0.9G / H = 42.19 (≥ 1.0)
• OKRaft slab: punching and flexure 500 mm thick, bottom Ø12@125, top Ø10@100 each way

Warnings

• Critical 2D frame method: torsion, 3D effects, diaphragm flexibility and foundation interaction are not modelled. Verify with a full 3D model for final design.

Limitations

• Preliminary design: member sizes and reinforcement come from a critical two-dimensional frame analysis. Torsion, three-dimensional effects, flexible diaphragms and foundation interaction are not modelled.
• Eurocode recommended values are used. National Annex parameters in this report were entered from memory and must be checked against the official National Annex before use.
• Wind and snow actions use the simplified methods of EN 1991-1-4 and EN 1991-1-3. Seismic actions use the lateral force method of EN 1998-1 and no ductility detailing beyond minimum reinforcement.
• Foundations are isolated pad footings on a uniform soil with an assumed allowable bearing pressure; a geotechnical investigation and foundation design are required.
• Quantities are preliminary estimates and exclude laps, wastage, non-critical members and non-structural elements.
• This report is an aid only. All results must be verified, and the design taken responsibility for, by a qualified, licensed engineer.