## A A

Figure 4.7 Ribbed slab spanning between beams For a dry environment, exposure class is 1. Minimum concrete strength grade is C25 30. For cement content and w c ratio, refer to ENV 206 Table 3. Assume nominal aggregate size 20 mm Assume maximum bar size 20 mm 20 mm nominal cover is sufficient to meet the NAD requirements in all respects. Table 3 Check requirements for fire resistance to BS 8110 Part 2. NAD 6.1(a) Type 2 deformed reinforcement, f 460 N mm2 f - 400 N mm2 2.2.3.2P(1) C25 30...

## Basic method

The conditions in the section are shown in Figure 5.4. It is assumed that EC2(1) Section 4.2.1.3.3(12) implies that a should be taken Table 3 as 0.8 for biaxial bending but the NAD(1) would allow 0.85. It can be seen from the diagram that the axial force provided by the concrete is given by The moments about the centroid of the concrete section are given by

## Check by calculation

10.2.3.1 Calculation of steel stress and strain A area of reinforcement within the tensile zone area of concrete within tensile zone 1000 x 200 200 x 103 mm2 a coefficient taking account of stress distribution 1.0 for pure tension a coefficient allowing for the effect of non-uniform self-equilibrating stresses 0.8 for tensile stresses due to restraint of intrinsic deformations (h < 300 mm) tensile strength of concrete effective at first cracking 3.8 N mm2 (taking fctk Q95 but see Section...

## Check for bending in z direction

This check uses the full section dimensions 2 x 460 x 106 K2 1.15 x 0.9 x 340 x 0.2 0.1 x 82 x 106 x 13.01K2 x 10 6 83.7K2 mm As in the previous example, iterate using the design chart in Section 13 Figure 13.2(c) to find the appropriate value for K2 and hence AJ Ibhf , starting with K2 1. This procedure results in

## Column B support moments

Analysis moment 198 kNm in both directions Column strip WSdcs 0.75 x 198 149 kNm BS 8110 Use 13T16 (2613 mm2) top in column strip. Provide 9T16 150 mm crs. in central 1.3 m and 2T16 300 mm crs. on either side Check whether minimum moment required for punching shear has been met. With -0.125 This is to be carried over a width of 0.3 . Since V includes for a loaded width of 5.2 m, it is assumed that the larger panel width may be used. By inspection reinforcement (9T16 in central 1.3 m) is...

## For The Design Of Concrete Buildings

Based on BSI publication DDENV1992-1-1 1992. Eurocode 2 Design of concrete structures. Part 1. General rules and rules for buildings. Published by the British Cement Association in conjunction with Ove Arup & Partners 13 Fitzroy Street London W1P 6BQ Tel 071-636 1531 S.B. Tietz & Partners 14 Clerkenwell Close Clerkenwell London EC1R OPQ Tel 071-490 5050 Environment 2 Marsham Street London SW1P 3EB Tel 071-276 3000

## Info

Bars mark 8, which are located outside the web, must extend a further 150 mm - refer to Figure 2.8. Curtailment of the main reinforcement and arrangement of the link reinforcement are shown in Figures 2.6 and 2.7. Reinforcement details are shown in Figure 2.8 and given in Table 2.4. Figure 2.6 Curtailment diagram of main reinforcement Figure 2.6 Curtailment diagram of main reinforcement

## Introduction And Symbols

1.1 Introduction 5 1.2 Symbols 5 2.1 Introduction 15 2.2 Basic details of structure, materials and loading 15 2.3 Floor slab 17 2.4 Main beam 20 2.5 Edge beam (interior span) 30 2.6 Columns 34 2.7 Foundation 39 2.8 Shear wall 43 2.9 Staircase 49 3.1 Introduction 53 3.2 Design methods for shear 53 3.3 Shear resistance with concentrated loads close to support 63 3.4 Design method for torsion 70 3.5 Slenderness limits 81 4.1 Solid and ribbed slabs 82 4.2 Flat slabs 109 5.1 Introduction 132 5.2...

## Load cases example

Fundamental load combination to be used is 2.3.2.2P(2) For beams without cantilevers the same value of self-weight may be applied 2.3.2.3(4) to all spans, i.e., 1.35Gk. The load cases to be considered for the imposed loads are 2.5.1.2(4) (a) alternate spans loaded and The various load arrangements are shown in Figure 12.8. Note Load cose A above should be combined with cases B-J below as necessary

## Maximum concrete stresses

As the beam is a T-section, the values of Wx and Wb are not equal. By calculation it can be shown that I 6.79 x 109 mm4 and that the centroid of the section is at a height of 196 mm from the soffit. The calculation of the stresses under each load combination is not shown here. The method follows that given in the Post tensioned concrete floors Design handbook. The top and bottom concrete stress for transfer conditions are given in Table 9.3 and those after all losses are given in Table 9.4.

## Minimum longitudinal steel

CIRIA Guide 2 refers to the British Standard CP 110, and EC2 will be slightly more onerous. Aa < 0.6fc> tcWyk < 0.0015bp 5.4.2.1.1 Basing the flexural steel on the active height assumed for the beam design A 0.0015 x 300 x 5750 2588 mm2 Deep beams should normally be provided with a distributed reinforcement near 5.4.5(2) both sides, the effect of each being equivalent to that of an orthogonal mesh with a reinforcement ratio of at least 0.15 in both directions. This reinforcement should...

## Shear resistance

Shear will be taken as acting on the web of the section only. When combined shear and torsion effects are to be considered, shear is to be checked using the variable strut inclination method. The angle 0 of the equivalent concrete struts is to be the same for both torsion and shear design. The design shear resistance, V , with zero axial load is given by 1.6 - d 1.6 - 1.44 0.16 < 1.0 Assuming 0.25 o tensile reinforcement, p 0.0025 > 0.02 i Rd1 0.34 x 1(1.2 + 40 x 0.0025) x 250 x 1440 x 103...

## Limit state of cracking

No check is required at transfer since beam is totally in compression. Design crack width for post-tensioned member under frequent load combinations The method adopted to determine the minimum reinforcement required is to 4.4.1.2. 5 carry out a rigorous calculation of the crack width where the flexural tensile stress 4.4.1.2 7 under rare loads exceeds 3 N mm2. If the calculated crack width under 4.4.2.4 frequent loads does not exceed 0.2 mm then further bonded reinforcement is not required....

## Combined footing

Design a combined footing supporting one exterior and one interior column. An exterior column, 600 mm x 450 mm, with service loads of 760 kN dead and 580 kN imposed and an interior column, 600 mm x 600 mm, with service loads of 1110 kN dead and 890 kN imposed are to be supported on a rectangular footing that cannot protrude beyond the outer face of the exterior column. The columns are spaced at 5.5 m centres and positioned as shown in Figure 7.2. The allowable bearing pressure is 175 kN m2, and...

## Pilecap design example using truss analogy

A four-pile group supports a 500 mm square column which carries a factored load of 2800 kN. The piles are 450 mm in diameter and spaced at 1350 mm centres. Assume a pilecap depth of 800 mm. Allow the pilecap to extend 150 mm beyond the edge of the piles, to give a base 2.1 m square as shown in Figure 7.7. Use 2.1 m x 2.1 m x 0.8 m deep pilecap For components in non-aggressive soil and or water, exposure class is 2 a . Minimum concrete strength grade is C30 37. For cement content and w c ratio...

## Twoway spanning solid slabs

EC2 1 permits the use of elastic analysis, with or without redistribution, or plastic analysis for ultimate limit state design. Elastic analyses are commonly employed for one-way spanning slabs and for two-way spanning slabs without adequate provision to resist torsion at the corners of the slab and prevent the corners from lifting. Plastic analyses are commonly used in other situations. Tabulated results for moments and shears from both types of analysis are widely available. Care is necessary...

## Concrete Nib Design

lt 0.0015 x 1000 x 81 122 mm2 Check minimum area of reinforcement for crack control 0.4 x 0.8 x 3.0 x 52.5 x 103 460 110 mm2 No further check for crack control Is necessary as h 105 lt 200 mm. Maximum bar spacing 3h 315 lt 500 mm The reinforcement details are shown in Figure 8.5. Figure 8.5 Nib reinforcement details Figure 8.5 Nib reinforcement details Check shear in nib, taking into account the proximity of the concentrated load 4.3.2.3 to the support. 0 2.5dlx 2 5 X 81 1.69 Eqn 4.17

## Symmetrically reinforced rectangular columns

Figures 13.2 a to e give non-dimensional design charts for symmetrically reinforced columns where the reinforcement can be assumed to be concentrated in the corners. The broken lines give values of K in Eqn 4.73 of EC2. Eqn 4.73 Where the reinforcement is not concentrated in the corners, a conservative approach is to calculate an effective value of d' as illustrated in Figure 13.3.

## Comparison with spaneffective depth ratio

The procedure for limiting deflections by use of span effective depth ratios is set out in EC2 Section 4.4.3. 100 4 100 x 2410 o _ UU 0.37 Therefore the concrete is lightly stressed, p lt 0.5 The NAD 1 introduces a category of nominally reinforced concrete corresponding to p 0.15 Basic span effective depth ratio for a simply supported beam, interpolating for p 0.37 For flanged beams where M gt w gt 3.0 the basic span effective depth ratio should be multiplied by a factor of 0.8 The span...