(Ethiopian Building Code Standard - 1995)

Summary of EBCS-1-95 Wind Actions on Structures


Refer to Chapter 3 of ECBS-1 (Ethiopian Building Code Standards) – Wind Actions

Design Wind Pressure:

We = qref Ce (Ze) Cpe – qref Ce (Zi) Cpi

where

qrefCeZeCpe - external pressure

qrefCeZiCpi - internal pressure

 qref - the reference velocity pressure

       = rVref2 /2  where

r is the air density. For Ethiopian conditions, a temperature of 20oc  is used with the variation of the atmospheric pressure with altitude defined in Table 3.1 given below:

 

Site altitude in meters (ASL)

r (kg/m3)

0

500

1000

1500

2000

1.2

1.12

1.06

1.00

0.94

           Vref  is the reference wind velocity as defined in Section 3.7.2. i.e.,

           Vref = CDIR  CTEM CALT Vref,o

           Where

Vref,o is the basic value of the reference wind velocity to be taken as 22m/sec.

 

CDIR is the direction factor to be taken as 1.0

CTEM is the temporary (seasonal) factor to be taken as 1.0.

CALT is the altitude factor to be taken as 1.0.

Cpe - external pressure coefficient derived from Appendix A.

Cpi  - internal pressure coefficient obtained from Appendix A.

        For windward wall:

        Cp = 0.8 for the entire height

        Leeward wall:

        Cp = -0.5 (suction) - use H/2 for calculation of Ce

Cpi - internal pressure coefficient (Figure B-14 of Commentary, P.29)

Ce - exposure factor

        Simple Procedure - use (Table 4.1.8.1) (ranges from 0.9 - 2.0)

        Detailed Procedure:

Exposure A - Ce = (Z/10)**0.28, Ce >= 1.0

Exposure B - Ce = 0.5*(Z/12.7)**0.50, Ce >= 0.5

Exposure C - Ce = 0.4*(Z/30)**0.72, Ce >= 0.4

         (Z is in meters)

 

Cg - gust effect factor determined using simple procedure or detailed procedure.

       Calculating Cg (Gust Effect Factor) - is defined as the ratio of the maximum effect 

       of the loading to the mean effect of the loading.

 

        Simple Procedure (Page 13 of Commentary)

Cg = 2.0 for structural systems

        Detailed Procedure (Page 13 of Commentary)

Cg = 1.0 + gp (s/m)