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RC Structural Design Tables

Durability CoverParticular Environmental conditions are classified as Exposure Classes and are given below:

Table 4.1 BS EN 1992-1-1:2004(EC2)

Other exposure classes include freeze/thaw attack & chemical attack.

Definitions of compressive strength class & nominal cover

Compressive strength class is a classification comprising the type of concrete (normal-weight orlightweight), the minimum characteristic 150 mm diameter by 300 mm cylinder strength and the minimumcharacteristic 150 mm cube strength.

eg ForC20/25, fck = 20 N/mm2 & fcu= 25N/mm2

Nominal coveris thedepth of cover to reinforcement shown on RC drawings comprising the minimum cover

plus an allowance in design for deviation, cdev, to accommodate for deviations during construction.An allowance of10 mm is normally used for buildings.

For concrete cast against prepared ground (including blinding), the nominal durability cover should be atleast 40 mm & at least 65mm for concrete cast directly against soil.

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Nominal Coverto reinforcement for the appropriate strength & exposure class are given below:Table NA.2 NA to BS EN 1992-1-1:2004(National Annex to EC2)

Use cdev= 10 mm

Fire Resistance CoverRequired Axis Distances to achieve specified Fire Resistance (from Table 5.2a of EC2 Part 1-2)

In addition to durability & fire cover considerations, the nominal cover must be greater than bar +10 mm toease placement in the formwork and to ensure adequate bond between the concrete and the steel.

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OPC

bmin& a

R60 Fire Resistance

Fire Resistance is unlikely to be critical.

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Cracking Control - Maximum Rebar Diameters & Spacings

Table 5.6 gives the max orthe max spacing for hi bond rebars for specified stress ranges.(Based on tables 7.2N & 7.3N of EC2.)

Table 5.6 from the ISE Manual for the design of concrete building structures to Eurocode 2

Service stress, s = 435 (Gk + 0.3Qk /1.35Gk + 1.5Qk) (As req /As prov)N/mm2

As req is the area of tension reinforcement required at the sectionconsidered for the ultimate limit state.As prov is the area of reinforcement actually provided.

Eg: if the service stress is 280 N/mm2 (MPa) then either bars of size H12 or smaller can be used at any spacing orbars of any size can be used at a spacing of 150 mm or less.

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SHEAR TABLES

Concise Eurocode EC2 Table 7.2

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DEFLECTION TABLES - All 3 from Concise Eurocode EC2

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