## Methods for calculating deflections

Two methods for calculating deflection are presented below, and these are based on the advice in TR58 Deflections in concrete slabs and beams8 The rigorous method for calculating deflections is the most appropriate method for determining a realistic estimate of deflection. However, it is only suitable for use with computer software. The Concrete Centre has produced a number of spreadsheets that use this method to carry out deflection calculations for a variety of slabs and beams9. These offer a...

## Variable actions snow loads

In persistent or transient situations, snow load on a roof, s, is defined as being lt bs EN 1991-1-3 5.2 3 gt For flat roofs, 0 - a with no higher structures close or abutting , P1 - P2 - 0.8 For shallow monopitch roofs, 0 lt a lt 30 with no higher structures close or abutting , p1 - 0.8, p2 - 0.8 1 a 30 For other forms of roof and local effects refer to BS EN 1991-1-3 Sections 5.3 and 6 thermal coefficient, Ct - 1.0 other than for some glass-covered roofs, or similar characteristic ground snow...

## Summary of design requirements

lt 9.4.3 1 9.4.3 2 gt lt Exp. 6.52 gt Column strip 10 no. H20 U-bars max. 200 mm from column in pairs where 200 x 200 hole use 8 H20 T1 in U-bars in pairs Column strip and middle strip H20 200 B Column strip centre for 750 mm either side of support H20 100 T1 Column strip outer H20 250 T1 Middle strip H16 200 T1 Column strip H16 200 B2 Middle strip H12 300 B2 Column strip centre 6 no. H20 175 T2 Column strip outer H12 175 T2 Middle strip H12 300 T2 Column strip H16 250 B2 Middle strip H10 200...

## Variable actions wind loads

The procedure for determining wind load to BS EN 1991-1-4 is presented below. This presentation is a very simple interpretation of the Code intended to provide a basic understanding of the Code with respect to rectangular-plan buildings with flat roofs. In general maximum values are given with more information a lower value might be used. The user should be careful to ensure that any information used is within the scope of the application envisaged. The user is referred to more specialist...

## Design for punching shear

Eurocode 2 provides specific guidance on the design of foundations for punching shear, and this varies from that given for slabs. In Eurocode 2 the shear perimeter has rounded corners and the forces directly resisted by the ground should be deducted to avoid unnecessarily conservative designs . The critical perimeter should be found iteratively, but it is generally acceptable to check at d and 2d. Alternatively, a spreadsheet could be used e.g. spreadsheet TCC81 from Spreadsheets for concrete...

## Column design resistance

For practical purposes the rectangular stress block used for the design of beams see Chapter 4, originally published as Beams9 may also be used for the design of columns see Figure 7 . However, the maximum compressive strain for concrete classes up to and including C50 60, when the whole section is in pure compression, is 0.00175 see Figure 8a . When the neutral axis falls outside the section Figure 8b , the maximum allowable strain is assumed to lie between 0.00175 and 0.0035, and may be...

## Spacing of punching shear reinforcement

Where punching shear reinforcement is required the following rules should be observed. It should be provided between the face of the column and kd inside the outer perimeter where shear reinforcement is no longer required. k is 1.5, unless the perimeter at which reinforcement is no longer required is less than 3d from the face of the column. In this case the reinforcement should be placed in the zone 0.3d to 1.5d from the face of the column. There should be at least two perimeters of shear...

## Minimum area of shear reinforcement

The minimum area of shear reinforcement in beams, Asw.min should be calculated from where Pwmm can be obtained from Table 9. Procedure for determining longitudinal shear capacity of flanged beams Calculate the longitudinal shear stress from VEd D Fd hf Dx see Figure 13 Calculate the longitudinal shear stress from VEd D Fd hf Dx see Figure 13 Determine the concrete strut capacity from Table 8 Determine the concrete strut capacity from Table 8 or from VRd 0.160 fck 1-fck 250 Determine the...

## Ribbed or waffle slabs

Current practices for determining forces in ribbed and waffle slabs may also be used for designs to Eurocode 2.Where a waffle slab is treated as a two-way slab refer to previous section, but note that their torsional stiffness is significantly less than for a two-way slab and the bending moment coefficients may not be appiicabie.Where it is treated as a flat slab reference may be made to Chapter 7, originally published as Flat slabs4 The position of the neutral axis in the rib should be...

## Continuous ribbed slabs

This 300 mm deep ribbed slab is required for an office to support a variable action of 5 kN m2 It is supported on wide beams that are the same depth as the slab, as shown in Figure 3.9. One hour fire resistance required internal environment. Ribs are 150 mm wide 900 mm cc. Links are required in span to facilitate prefabrication of reinforcement. Assume that partitions are liable to be damaged by excessive deflections. In order to reduce deformations yet maintain a shallow profile use ck 35 MPa...

## Design for biaxial bending

Check MEdz MRdz a MEdy MRdy a lt 1.0 For load case 2 where MRdy moment resistance. Using charts From chart 15.5d, for d2 h 0.20 and Aefyk bhfCk 9648 x 500 500 x 500 x 50 0.39 NEd bhfck 9000 x 103 5002 x 50 MRd 0.057 x 5003 x 50 356.3 kNm lt Concise EC2 Fig. 15.5d gt lt 5.8.3 4 gt Using design actions to Exp 6.10 would have resulted in a requirement for 8500 mm2 500 x 500 x 0.85 x 50 1.5 9648 x 500 1.15 7083 3216 10299 kN NEd NRd 9000 10299 0.87. Interpolating between values given for NEd NRd...