For formation of collapse mechanism in the following figure,

For formation of collapse mechanism in the following figure, the minimum value of P_u is cm_p /L. m_p and 3 m_p denote the plastic moment capacities of beam sections as shown in this figure. The value of c is________.

Mechanism I
3m_p .θ + m_p .(2 θ ) + m_p θ

P _u ×	L	× θ
	4

⇒ 6m_p .θ = P _u ×	L	× θ
	4

⇒ P _u = 24	m_p
	L

Mechanism II

1.Φ = 3θ
⇒ Φ = 3θ

= 13.33	m_p
	L

∴ c = 13.33