## Combination of actions

Quasi-permanent combination of actions The combination of permanent and variable loads which is most likely to be present most of the time during the design working life of the structure. Frequent combination of actions The most likely highest combination of permanent and variable loads which is likely to occur during the design working life of the structure.

## Latin upper case letters AAccidental action

Ac Cross sectional area of concrete Ap Area of a prestressing tendon or reinforcement As min minimum cross sectional area of reinforcement Asw Cross sectional area of shear reinforcement Diameter of mandrel Fatigue damage factor Effect of action Tangent modulus of elasticity of normal weight concrete at a stress of vc 0 and at 28 days Effective modulus of elasticity of concrete elasticity of concrete Ecm Secant modulus of elasticity of concrete Ec(t) Tangent modulus of elasticity of normal...

## Secretary to the Task Group B Chan BScHons AMIMechE

Published by The Institution of Structural Engineers 11 Upper Belgrave Street, London SW1X 8BH, United Kingdom Telephone +44(0)20 7235 4535 Fax +44(0)20 7235 4294 Email mail istructe.org.uk Website www.istructe.org.uk 2006 The Institution of Structural Engineers The Institution of Structural Engineers and the members who served on the Task Group which produced this report have endeavoured to ensure the accuracy of its contents. However, the guidance and recommendations given should always be...

## Fig Redistribution procedures for frames

The effective span of a simply supported beam should normally be taken as the clear distance between the faces of supports plus one-third of the beam seating width at each end. However, where a bearing pad is provided between the slab and the support, the effective span should be taken as the distance between the centres of the bearing pads. The effective span of a beam continuous over its supports should normally be taken as the distance between the centres of the supports. The effective...

## Sizes and reinforcement of columns

Where possible it will generally be best to use 'stocky columns' i.e. generally for typical columns for which the ratio of the effective height to the least lateral dimension does not exceed 15 as this will avoid the necessity of designing for the effects of slenderness. Slenderness effects can normally be neglected in non-sway structures where the ratio of the effective height to the least lateral dimension of the column is less than 15. For the purpose of initial design, the effective height...

## Division of moments between column and middle strips

The design moments obtained from analysis of the frames or from Table 5.4 should be divided between the column and middle strips in the proportions given in Table 5.5. Table 5.5 Distribution of design moments of flat slabs For the case where the width of column strip is taken as equal to that of the drop and the middle strip is thereby increased in width, the design moments to be resisted by the middle strip should be increased in proportion to its increased width. The design moments to be...

## Section design ribbed and coffered slabs

Ribbed or waffle slabs need not be treated as discrete elements for the purposes of analysis, provided that the flange or structural topping and transverse ribs have sufficient torsional stiffness. This may be assumed provided that the rib spacing does not exceed 1500mm the depth of the rib below the flange does not exceed 4 times its width the depth of the flange is at least 1 10 of the clear distance between ribs or 50mm, whichever is the greater transverse ribs are provided at a clear...

## Twoway spanning slabs on linear supports

Bending moments in two-way slabs may be calculated by any valid method provided the ratio between support and span moments are similar to those obtained by the use of elastic theory with appropriate redistribution. In slabs where the corners are prevented from lifting, the coefficients in Table 5.3 may be used to obtain bending moments per unit width msx and msy in the two directions for various edge conditions, i.e. Where bsx and bsy are the coefficients given in Table 5.3 n is the total...

## Initial design reinforced concrete

In the initial stages of the design of building structures it is necessary, often at short notice, to produce alternative schemes that can be assessed for architectural and functional suitability and which can be compared for cost. They will usually be based on vague and limited information on matters affecting the structure such as imposed loads and nature of finishes, and without dimensions, but it is nevertheless expected that viable schemes be produced on which reliable cost estimates can...