(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
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)
Vref is the reference wind velocity as defined in Section 3.7.2. i.e.,
Vref = CDIR CTEM CALT Vref,o
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
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 22.214.171.124) (ranges from 0.9 - 2.0)
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)