## Design principles reinforced concrete

The loads to be used in calculations are Characteristic permanent action (dead load), Gk the weight of the structure complete with finishes, fixtures and fixed partitions. The characteristic variable actions (live loads) Q where variable actions act simultaneously a leading variable action is chosen Qk1, and the other actions are reduced by the appropriate combination factor. Where it is not obvious which should be the leading variable action, each action should be checked in turn and the worse...

## 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...