Effective Stiffness Values for Linear Analysis.

Table 3.1.2.1. Effective Stiffness Values for Linear Analysis.

Component	Flexural rigidity	Shear rigidity	Axial rigidity
Beams – nonprestressed ^a	0.3E_cEI_g	0.4E_cEA_w	1.0E_cEA_g
Beams – prestressed ^a	E_cEI_g	0.4E_cEA_w	1.0E_cEA_g
Columns with compression caused by design gravity loads ≥ 0.5 $A_{g} f_{c E}^{'}$ ^b	0.7E_cEI_g	0.4E_cEA_w	1.0E_cEA_g
Columns with compression caused by design gravity loads ≤ 0.1 $A_{g} f_{c E}^{'}$ or with tension^b	0.3E_cEI_g	0.4E_cEA_w	1.0E_cEA_g(compression)1.0E_sA_s(tension)
Beam-column joints	Refer to 4.2.2.1		1.0E_cEA_g
Flat slabs – nonprestressed	Refer to 4.4.2	0.4E_cEA_g	—
Flat slabs – prestressed	Refer to 4.4.2	0.4E_cEA_g	—
Diaphragms (in-plane) – nonprestressed ^e	0.25E_cEI_g	0.25E_cEA_g	0.25E_cEA_g
Diaphragms (in-plane) – prestressed ^e	0.5E_cEI_g	0.4E_cEA_g	0.5E_cEA_g
Walls – uncracked with compression caused by design gravity loads ≥ 0.3 $A_{g} f_{c E}^{'}$ ^b^,^c	1.0E_cEI_g	0.3E_cEA_w	1.0E_cEA_g
Walls – uncracked with compression caused by design gravity loads ≤ 0.05 $A_{g} f_{c E}^{'}$ or with tension^b^,^c	0.5E_cEI_g	0.3E_cEA_w	1.0E_cEA_g
Walls – cracked ^c ^, ^d	0.25E_cEI_g	0.15E_cEA_w	1.0E_cEA_g(compression)1.0E_sA_s(tension)
Coupling beams with longitudinal or diagonal reinforcement	0.05 (l_n/h) E_cEI_g ≤ 0.20E_cEI_g	0.2E_cEA_w	1.0E_cEA_g

^a For T-beams, I _g can be taken as twice the value of I _g of the web alone. Otherwise, I _g shall be based on the effective width as defined in Section 3.1.3.

^b For columns and walls with axial compression falling between the limits provided, flexural rigidity shall be determined by linear interpolation. If interpolation is not performed, the more conservative effective stiffnesses shall be used. An imposed axial load N _UG is permitted to be used for stiffness evaluations.

^c Walls are permitted to be considered cracked due to earthquake demands in flexural actions where flexural demands exceed M _crE and/or in shear actions where shear force demands exceed the cracking shear strength defined in Section 7.2.2. It shall be permitted to assume all walls to be cracked.

^d Alternative stiffness values dependent on axial load and boundary longitudinal reinforcement ratio shall be permitted in accordance with Section 7.3.

^e In-plane diaphragm effective stiffness values apply where diaphragm flexibility is considered in accordance with Section 10.2.2.