(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 = q_ref C_e (Z_e) C_pe – q_ref C_e (Z_i) C_pi

where

q_refCeZeCpe - external pressure

q_refCeZiCpi - internal pressure

 q_ref - the reference velocity pressure

       = rV_ref² /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:

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

           V_ref = C_DIR  C_TEM C_ALT V_ref,o

           Where

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

C_DIR is the direction factor to be taken as 1.0

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

C_ALT 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 + g_p (s/m)