32 oakley street 39 - revised calcs

8/3/2019 32 Oakley Street 39 - Revised Calcs

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N.B. Nominal cover 20mm to the slab, C30 concrete

STRUCTURAL CALCULATIONSSite: 32 Oakley Street, London SW3 5NT

Job: Basement Courtyard Extension

Job Ref: 1004-528 REV A

Web: www.sts-se.co.uk Email: [email protected]

Winner of2007 Camden Council Building Quality-Small Commercial Development Award

58 Crossway, Welwyn Garden City, Herts, AL8 7EE Tel: 01707 695466 Fax: 01707 692006


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Site: 32 Oakley Street, London SW3 5NT Made By: MN

Job: Basement Courtyard Extension Checked: SS

Job No. 1004-528 Page:

Design PhilosophyN.B. Nominal cover 20mm to the slab, C30 concrete

STS Structural Engineering

Tel: 01707 695466 Fax: 01707 692006, www.sts-se.co.uk, 58 Crossway, Welwyn Garden City, Herts AL8 7EE

1. Overview

The existing property occupies the ground floor/basement floors of a converted Victoriantownhouse. The existing building is spread over 6storeys (basement, ground and four aboveground floors), and is of traditional loadbearing masonry construction with suspended timberfloors and a timber framed mansard roof.

The proposal is to construct the new basement extension. The basement walls are mostly to beformed in contiguous piling supporting. The upper basement slab is to rest onto the perimeterpiles and is to support the 1m soil replanting zone over. The lower slab is to be groundbearing.Please see the drawings and the construction method statement for further information.

2. Loading and the Structural Model

The structure is subject to dead, imposed and wind loading. All loading is listed and alsographically shown in the analysis.

All steel sizing was done in accordance with BS5950, all concrete sizing to BS8110. Therelevant load combination for sizing was 1.4*Dead+1.6*Imposed load. The deflections werechecked for unfactored combinations of loading.

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Load Analysis for the upper basement slab


The upper basement slab is to be analysed as a grillage using a FE software.

Only direct loading is to be inputed. Selfweight of the slab assigned automatically.

Excluding selfweight, the loading onto the slab is as follows:

DL, 1.3x18=23.4kN/m2 - allow for 1.3m of soil, screed, tiles etc.

LL, 2.5 kN/m2 - car parking space

N.B. Construction loadcase is less honerous ince the soil is to be

placed towards the end of construction

3D representation of the slab and loading:



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Upper Slab Analysis Results REV A




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Job No. 1004-528

RC Sizing to BS8110 - Upper Basement RC Slab REV AN.B. Nominal cover 20mm to the slab, C30 concrete

250mm dp. Upper Basement Reinforced Concrete slab:Nominal cover 40mm on all sides

Find Moment Capacity for different areas of reinforcementd = 200 mm d' = 35 mm

fy = 460 N/mm2

fcu = 30 N/mm2 K' = 0.156

Table 25 Min. reinforc. For slabs 0.1% 200 mm2/m

3.4.4.4 K = M/bd2fcu =

formulae: for KK'; As = K'fcubd/0.95fyz) + As'

M K z x As' As bar dia bar dia

kNm mm mm mm2 mm2 @200c/c @100c/c

5 0.004 190.0 22.2 N/A 60 T6 T6

10 0.008 190.0 22.2 N/A 120 T6 T6

15 0.013 190.0 22.2 N/A 181 T8 T6

20 0.017 190.0 22.2 N/A 241 T8 T6

25 0.021 190.0 22.2 N/A 301 T10 T8

30 0.025 190.0 22.2 N/A 361 T10 T8

35 0.029 190.0 22.2 N/A 422 T12 T8

40 0.033 190.0 22.2 N/A 482 T12 T8

50 0.042 190.0 22.2 N/A 602 T16 T10

60 0.050 188.2 26.2 N/A 730 T16 T10

70 0.058 186.1 31.0 N/A 861 T16 T12

80 0.067 183.9 35.8 N/A 996 T16 T12

90 0.075 181.6 40.8 N/A 1134 T20 T16

100 0.083 179.3 45.9 N/A 1276 T20 T16

110 0.092 177.0 51.2 N/A 1422 T20 T16

120 0.100 174.5 56.6 N/A 1573 T25 T16

130 0.108 172.0 62.2 N/A 1729 T25 T16

140 0.117 169.4 68.0 N/A 1891 T25 T16

150 0.125 166.7 74.1 N/A 2059 T25 T20

160 0.133 163.8 80.4 N/A 2235 T25 T20180 0.150 157.7 93.9 N/A 2611 T32 T20

200 0.167 155.4 99.2 178 2935 T32 T20



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Job No. 1004-528

RC Sizing to BS8110 - Upper Basement RC Slab REV A



RC Beam Between piles 65 and 66 (b/d = 250/1250mm)N.B. beam required to prevent punching shear over the corner piles

From Slab Maximum factored moment: Mu = 186 kNm

FE analysis Maximum factored shear force Vu = 144 kN

Member properties:

b = 250 mm d = 1150 mm

fy = 460 N/mm2 d' = 50 mm

fcu = 30 N/mm2 K' = 0.156

3.4.4.4 K = M/bd2fcu = 0.0188

z = d {0.5+(0.25-K/0.9)} (an 1093 mm

x = (d-z)/0.45 = 128 mm

As = M/0.95fyz = 390 mm2

Compression reinforcement not requireTable 25 Min. reinforc. for rect. beams 575 mm2

Use min. 3T16 bars top and bottom (As = 603mm2)

3.4.5.2 Shear stress v = V/bvd = 0.501 N/mm2

sv = 200 mm fyv = 460 N/mm2

vc = 0.356 N/mm2

v


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Job No. 1004-528

BS8110 - Punching Shear over the central piles REV AN.B. Nominal cover 40mm to the slab, C30 concrete

N.B. Firstly check piles that are set away from the edges of the slab, therefore

punching shear to be considered for an 'internal' column support.

Veff = 1.15*V to allow for moment transfer, nominally.

Maximal reaction is onto pile 52, V = 178kN, therefore

BS8110,Pt1 consider this support as most critical for punching shear

3.7.6.2 Veff = l*1.15*V = 1.5*1.15*178=307kN (factored)

The perimeter of the pile = 300*pi=942mm; d = 210mm

Check maximum shear at pile face:

3.7.6.4 vmax = Veff/uod = 307*1000/942/200 = 1.55 N/mm2

Max allowable shear stress vall = 0.8 fcu = 0.830 = 4.38 N/mm2

and not exceeding 5.0N/mm2. OK

3.7.7.4 Check shear at crit ical section, 1.5d from the face of the column:

u = 4D+8lp, where lp=0.75d=150mm, hence u = 2400mm

v = V/ud = 307*1000/2400/200 = 0.61 N/mm2

Slab reinforcement over the piles to be T20s+T10s@200c/c

in both directions over the columns, therefore 100As/bd =

(100*5*10^2*3.14/4+100*5*20^2*3.14/4)/210/1000 = 0.93

Table 3.8 hence vc = (30/25)^(1/3)*0.5 = 0.70 N/mm2

Therefore, punching shear reinforcement not required as v

32 oakley street 39 - revised calcs

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