Building Designer

1–20 storey framed buildings · RC or steel · gravity, wind and seismic · foundations and quantities

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Presets

Structure and geometry

Structural systemBays in X (m), comma separatedBays in Z (m), comma separated

Storeys (1–20)Ground ht (m)Typical ht (m)

Use and loads

Occupancy

Floor superimposed dead (kN/m²)Roof dead (kN/m²)Roof live / snow (kN/m²)Cladding line load (kN/m)

Estimate cladding from wall typeOpenings %

For a full layout with real doors and windows use the Walls, Doors & Windows tool.

Materials

ConcreteRebar fyk (MPa)Column β (eff. length)

Lateral loads

Wind (EN 1991-1-4, simplified)

Basic speed vb,0 (m/s)Terrain

Earthquake (EN 1998-1, lateral force)

Shear walls / cores

Walls (count)Length (m)Thickness (mm)

Walls share the lateral load with the frames by stiffness. Set the count to 0 for a frame-only building.

Foundation and code

Allowable bearing (kPa)National Annex (partial factors)

All checks pass · 4 storeys · H = 13.2 m · plan 18.0 × 12.0 m · floor area 864 m²

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

Summary of 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

Floor slab (typical critical panel)

Thickness / type		220 mm, two-way
ULS floor load / roof load		13.13 / 10.35 kN/m²
Bottom steel (short span)		Ø8 @ 150 mm
Bottom steel (long span / distribution)		Ø8 @ 175 mm

Beams: 350 × 400 mm throughout (governing beam per storey)

Storey	Span	M sag	M hog	V	Bottom	Top	Links
4	6.0 m	82	140	139	5Ø12	5Ø16	Ø8@250	OK
3	6.0 m	93	168	168	4Ø16	4Ø20	Ø8@200	OK
2	6.0 m	93	176	169	4Ø16	5Ø20	Ø8@200	OK
1	6.0 m	97	187	172	4Ø16	5Ø20	Ø8@200	OK

Moments in kNm, shear in kN, from the envelope of all load cases on the critical frame. Reinforcement is for the governing beam of each storey; other beams are detailed from the same analysis.

Columns (per storey, worst column governs)

Storey	Size	NEd (kN)	M (kNm)	Bars	ρ	Links
4	350 × 350	269	91	4Ø20	1.03%	Ø8@350	OK
3	350 × 350	602	71	6Ø12	0.55%	Ø8@225	OK
2	350 × 350	935	82	4Ø12	0.37%	Ø8@225	OK
1	350 × 350	1270	63	4Ø12	0.37%	Ø8@225	OK

Floor-by-floor schedule

Floor	Level (m)	g / q (kN/m²)	Slab	Beams	Beam Msag / Mhog / V	Beam bars	Column	N / M (kN, kNm)	Column bars	Wind / seismic F (kN)	Drift (‰)
Roof	13.2	7.0 / 0.6	220 mm Ø8@150 + top Ø8@150	350 × 400	82 / 140 / 139	bot 5Ø12 top 5Ø16 links Ø8@250	350 × 350	269 / 91	4Ø20 links Ø8@350	18 / —	0.2 (≤ 2.0)	OK
Level 2	10.0	7.5 / 2.0	220 mm Ø8@150 + top Ø8@150	350 × 400	93 / 168 / 168	bot 4Ø16 top 4Ø20 links Ø8@200	350 × 350	602 / 71	6Ø12 links Ø8@225	33 / —	0.3 (≤ 2.0)	OK
Level 1	6.8	7.5 / 2.0	220 mm Ø8@150 + top Ø8@150	350 × 400	93 / 176 / 169	bot 4Ø16 top 5Ø20 links Ø8@200	350 × 350	935 / 82	4Ø12 links Ø8@225	28 / —	0.5 (≤ 2.0)	OK
Ground floor	3.6	7.5 / 2.0	220 mm Ø8@150 + top Ø8@150	350 × 400	97 / 187 / 172	bot 4Ø16 top 5Ø20 links Ø8@200	350 × 350	1270 / 63	4Ø12 links Ø8@225	26 / —	0.5 (≤ 2.0)	OK

Beam and column sizes are uniform per storey; bars are the governing member of each storey. Slab steel is for the critical panel.

Foundations (pad footings, critical frame)

Column	NEd	MEd	Size	Depth	Bars (each way)
Edge column (critical frame)	600 kN	51 kNm	1.8 × 1.8 m	400 mm	Ø10@150	OK
Interior column (critical frame)	1270 kN	32 kNm	2.3 × 2.3 m	450 mm	Ø10@100	OK

Whole-building raft (stability)

Raft plan (building + 1.0 m all round)		20.0 × 14.0 m, 500 mm thick (designed)
Permanent load G / variable Q		12440 / 1426 kN
Overturning moment (wind) / base shear		861 kNm / 106 kN
Eccentricity e (limit L/6)		0.06 m (3.33 m)
Bearing pressure max / min (allowable)		50 / 49 kPa (200)

Net ULS pressure under heaviest column panel		35 kPa
Effective depth d		434 mm
Bottom bars (each way)		Ø12 @ 125 mm
Top bars (each way)		Ø10 @ 100 mm
Reinforcement		27 kg/m²
Raft quantities (alternative to the pads)		140 m³ concrete, 7430 kg steel

✓ Raft slab: punching and flexure

✓ Raft: eccentricity (no uplift): e = 0.06 m ≤ L/6 = 3.33 m

✓ Raft: bearing pressure: q,max = 50 kPa ≤ 200 kPa

✓ Raft: overturning: 0.9GL/2 / M = 130.09 (≥ 1.5)

✓ Raft: sliding: μ·0.9G / H = 42.19 (≥ 1.0)

Rigid-raft assumption, friction μ = 0.4, characteristic loads. The slab is sized as an inverted flat slab under the heaviest column (punching, shear, flexure; top steel for the span moment). It does not model soil-structure interaction: confirm with a raft or finite-element analysis.

Lateral loads and stability

Wind base shear (whole building)		106 kN
Roof sway (SLS wind)		5.3 mm (limit 26 mm)

Wind (SLS, limit h/500)

Storey	Drift (mm)	Limit (mm)	θ
4	0.6	6.4	0.022	OK
3	1.1	6.4	0.030	OK
2	1.7	6.4	0.047	OK
1	1.8	7.2	0.045	OK

Quantities (estimate)

Concrete: slabs / beams / columns / footings		190 / 26 / 19 / 18 m³
Concrete total		253 m³
Reinforcement total		14.2 t
Steel per m³ concrete		56 kg/m³
Steel per m² floor		16.5 kg/m²

Preliminary quantities only: rebar excludes laps, wastage, stirrup hooks detail and non-critical members beyond the intensity extrapolated from the designed frame.

Scope: regular rectangular frame, critical 2D frame method (equal lateral share between frames), diaphragm assumed rigid, T-beam flange action ignored in beams, no shear walls or cores (use the Lateral tool for walls), pad footings on uniform soil, no basement or retaining walls. Results are an aid only and must be verified by a qualified, licensed engineer before use. National Annex presets are recommended values and must be checked against the official documents.