Force Reduction Factor Case Study

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2.4 Force Reduction Factor In most building codes, the reduction is accomplished by introducing force reduction factor (R) or alternatively called behavior factor (q) or response modification factor. This factor accounts mainly for ductility as well as the degree of redundancy in the structure and the strain hardening (Truby A. 2015).
Force reduction factor (R) in ECP 2012 is defined for five categories of basic structural systems with total twelve subsystems for different ductility classes of building according to the type of utilized structural system .While in the EC8:2004 behavior factor (q) values are given for various materials and structure systems according to the relevant ductility classes (high or medium or low). Table 4 shows the …show more content…

H≤ 60 m H≤ 40 m
Second Method
T_1=2п√((∑_(i=1)^n▒〖w_(i.) u_i^2 〗)/(g∑_(i=1)^n▒〖F_(i.) u_i 〗))

Where:
Wi: Is the design weight at the floor (i).
Fi: Is the lateral force at the floor (i). ui: Is the horizontal displacement at the floor (i) due to horizontal force (Fi). n: Is the number of stories. g: Is the ground acceleration.

The restriction of this method that T1 should not exceed 1.20 T1 that calculated from the first method. For structures with concrete or masonry shear walls the value of Ct in the first method may be taken as:
Ct = 0.075/ √(A_C )
Where:
Ac = Σ[Ai .(0.2 + lwi / H)2]
Ac: Is the total effective area of the shear walls in the first story of the building in (m2).
Ai: Is the effective cross-sectional area of shear wall (i) in the direction considered in the first story of the building in (m2). lwi: Is the length of the shear wall (i) in the first story in the direction parallel to the applied forces in (m).
H: Taken as in the first method.

The restriction of this method that lwi/H should not exceed 0.9.
Third
Method Using computer modeling with the restriction that T1 should not exceed 1.20 T1 that calculated from the first method. T1 = 2

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