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2020-12-07

VE0019 | Flessione plastica - Carico del momento

Descrizione

Uno sbalzo è completamente fissato all'estremità sinistra e caricato da un momento flettente secondo il seguente schizzo. The problem is described by the following set of parameters. Small deformations are considered and the self-weight is neglected in this example. Determine the maximum deflection u_z,max.

Material	Elastic-Plastic	Modulo E	E	210000.000	MPa
		deformazione trasversale	ν	0.000	-
		Modulo di taglio	G	105000.000	MPa
		Plastic Strength	f_y	240.000	MPa
Geometry	Cantilever	Durata	L	2.000	m
		Larghezza	w	0.005	m
		spessore	t	0.005	m
Load		Momento flettente	M	6.000	Nm

Flessione plastica - Carico del momento

Soluzione analitica

The cantilever is loaded by the bending moment M. The quantities of this load are discussed at first. The moment M_e when the first yield occurs and the ultimate moment M_p when the structure becomes plastic hinge are calculated as follows:

M_{e} = 2 \int_{0}^{t / 2} σ (z) z w d z = 2 \int_{0}^{t / 2} \frac{2 f_{y}}{t} z^{2} w d z = \frac{f_{y} w t^{2}}{6}

Momento elastico

M_{p} = 2 \int_{0}^{t / 2} σ (z) z w d z = 2 \int_{0}^{t / 2} f_{y} z w d z = \frac{f_{y} w t^{2}}{4}

Momento plastico

The bending moment M causes the elastic-plastic state. The cross-section in the elastic-plastic state is divided into the elastic core and the plastic surface, which is described by the parameter z_p according to the following diagram.

Distribuzione della tensione di flessione

z_{p} = \frac{f_{y}}{κ (x) E}

Parametro z_p

The elastic-plastic moment M_ep in the cross-section has to equal to the bending moment M. The curvature κ results from this equality.

κ = \frac{f_{y}}{E} \sqrt{\frac{1}{3 (\frac{t^{2}}{4} - \frac{M}{f_{y} w})}}

curvatura

The total deflection of the structure u_z,max is calculated using the Mohr's integral.

u_{z, \max} = \int_{0}^{L} κ (L - x) d x

Inflessione totale dello sbalzo

RFEM Settings

Modeled in RFEM 5.16 and RRFEM 6.01
The element size is l_FE= 0.020 m
Geometrically linear analysis is considered
The number of increments is 5
Shear stiffness of the members is neglected

Risultati

Material Model	Soluzione analitica	RFEM 5		RFEM 6
Material Model	u_z,max [m]	u_z,max [m]	Ratio [-]	u_z,max [m]	Ratio [-]
Plastica ortotropa 2D	1.180	1.190	1.008	1.190	1.008
Isotropic Plastic 2D/3D, Plate		1.173	0.994	1.173	0.994
Plastico isotropo 1D		1.180	1.000	1.180	1.000
Isotropic Nonlinear Elastic 2D/3D, Plate, Mises		1.190	1.008	1.190	1.008
Isotropic Nonlinear Elastic 2D/3D, Plate, Tresca		1.190	1.008	1.190	1.008
Plastico isotropo 1D		1.180	1.000	1.180	1.000

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Esempio di verifica 0019 | 1 | Parete | Plastica ortotropa 2D | Tsai-Wu

Bibliografia

Lublino, J. (1990). Teoria della plasticità. New York: Macmillan.

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