Esfuerzos Admisibles

ESFUERZOS ADMISIBLES

ESFUERZOS Y SOLICITACIONES ADMISIBLES

σAdm: Esfuerzo Admisible = σRotura ó Falla/ F.S

SAdm: Solicitación Admisible = Solicitación Rotura/ F.S

Ejemplo

f´m = 10 Mpa, t = 0.12 m, h = 2.4 m

Se arranca considerando el rango elástico.

σ

"σmax " "P" /" A " " ± " "Mc" /"I"

Mc/I=(Mx h/2)/((t x h^3)/12)= 6M/( th^2 )

σ_□((T+)/(C-)) " "= P/th ± 6M/(th^2 )

SON TRES METODOS

COMPRESION

TENSION

CORTANTE

POR COMPRESION

Fa = Resistencia Mamposteria

Fa = 0.2 f`m Re Re = Reduction de Esbeltez

Fa = 0.2 x 10 Mpa X 0.9 = 1.8 Mpa

Re= 〖(h`/40t)〗^3 h’ = Altura libre muro

Re= 〖(2.0/40(0.12))〗^3= 0.90

Fa ≥ fa

Resistencia Mamposteria Lo que está actuando

Fa = 1.8 Mpa ≥ fa = P/th

Fa=0.2 x 10 Mpa X 0.9=1.8 Mpa

fa=(540000 N)/(120 mm x 2400mm)=1.875 Mpa

Como no cumple, aumentamos el f’m

Aumentamos a 11 Mpa

Fa=0.2 x 11 Mpa X 0.9=1.99 Mpa ok

Fb ≥ fb

Fb = 0.33 f’m ≤ 14 Mpa

Fb=0.33 x 11 Mpa = 3.63 Mpa

fb=P/th+ 6M/〖th〗^2 = (540000 N)/(120mm 2400mm) X (6 x 280 X 〖10〗^6)/(120mm x 〖2400mm〗^2 )= 4.3 Mpa

Fb = 3.63 Mpa ≥ fb = 4.3 Mpa

Como no cumple aumentamos f’m

F’m = 14 mpa

Fb=0.33 x 14 Mpa = 4.62 Mpa

Fb= 4.62 Mpa ≥fb=4.3 Mpa Ok

σT=P/th- 6M/〖th〗^2

σT=540000N/(120mm x 2400mm)- (6 x 280 x 〖10〗^6)/〖120mm x 2400mm〗^2

σT= -0.55 Mpa

T = As x fs

fs = 0.5Fy ≤ 170 Mpa

Fy = 420 Mpa

fs = 210 Mpa

fs = 170 Mpa

(4.33+0.55)/(2.4)=(0.55)/x

x = (0.55 x 2.4)/(4.88) =0.27 m

T = (270mm x 0.55 Mpa)/2 x 120mm=8910N=8.9 KN

T = As x fs despejando

As = T/fs= (8910 N)/(170 Mpa )= 〖52.41mm〗^2=〖0.52cm〗^2

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