Issue 14

B. M. Chiaia et

alii, Frattura ed

Integrità Strutt

urale, 14 (2010)

45-51; DOI: 10

.3221/IGF-ESIS.

14.05

(3.b) k are unive red to specim een K I and

)( g G t 

)0()( G v G (0) are th ck speed v . ce G = K 2 / E

ctively, g and small compa tionship betw

wh fun dim the

ere K I (0) and ctions of cra ensions. Sin form:

e static stres Eq. 3.a is va , it is possib

s intensity fa lid as long a le to combin

ctor and the s the length e Eqns. 3.a a

energy relea of crack pr nd 3.b, obtai

se rate, respe opagation is ning the rela

rsal en G in

2

E tKv I

)( )(

(4)

A t )(  G

ere :

wh

 1      v assuming th che depend

   

1   

 

v

 1

(5) e the expres and basal sh

)(  vA th the same a width of dr ngth).

 h



c

r pproach and y slab avalan

sion ear

e arrest of fra ing on slab

cture propag parameters

ation, Jamies (slab thickne

on and John ss, slab tens

ston [7] deriv ile strength

Wi of stre

N U

MERICAL S

IMULATION

OF DYNAM

IC FRACTU

RE ARREST

IN DRY SNO

W AVALAN

CHES

rack arr stress c possibil nsidering som n advantage uces the stre f stringer ele nearest rivet beneficial e tain geometri th the use of pagation, sev sidered like ording to Ta

est can be a oncentration ity is to redu e experimen ous that the ss intensity f ment betwee s are very clo ffect of a sin cal arrangem the FEM so eral paths o a linear–elast b. 1 [2].

ttained in th and introdu ce the stress tal results fo crack passes actor. The st n the two clo se to the cra gle hole itse ent of holes. ftware FRA f crown frac ic square she angle: α slab height: H layer height: slab density: slab elastic slab Poisson layer shear w layer peak st II fracture Paramete r

ree different ction of resi intensity fact r riveted she between riv ringer is mo sest rivets te ck. Then the lf is negligib NC 2D [3], ture propaga et (100m x 10

ways: reduc dual compre or by forcing et structures, et holes: th re effective in nds to keep t stringer is ve le, the best r based on the tion and the 0m), with un Typical valu 38° 0.5 m 10 mm 200 kg m -3 1 MPa 0.2 0.1 MPa 2 kPa 0.2 J m -2

tion of the c ssive stresses the crack to we know tha e stringer tak doing so w he crack clo ry effective i esults are ob maximum c ir stability h it thickness

rack tip stre [8]. In the runs into a t if stringers es load from hen the rive sed. If the cr n the reducti tained when ircumferentia ave been inv (1m), and wit

ss intensity, case of snow weaker part o are attached the cracke ts are closer ack passes be on of crack t the crack p l stress crite estigated. Th h physical pa

reduction of avalanches, f the snowp to the plate, d skin and t to the crack: tween two h ip stresses. S asses betwee rion for frac e snow cove rameters cho

the the ack. it is hus the oles ince n a ture r is sen

Co eve red stif the the cer Wi pro con acc

e

Ran 30-4 0.3-1

ge

Ref

erence [9] [9] [9] [9] [9] [9]

Slope Snow Weak Snow Snow E Snow Weak G Weak Mode IIc

5°

m mm

h ρ modulus:

1-15 100-300 0.5-10 0.1 0.1-0.6 0.3-6 0.1-0.3

kg m -3 MPa

’s ratio: ν

0.4

modulus:

MPa

[1

0, 11] 0, 11] [12]

rength: τ p energy: G

kPa

[1

J m -2

Tabl

e 1 : Typical va

lues for snow

slab and weak

layer [2].

47