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Section 5.7
Weld Summary
Last Revised:
11/04/2014
Strength Limit States:
All strength limit states take the form:
LRFD |
ASD |
R_{u} < f_{t}R_{n} |
R_{a} < R_{n}/W_{t} |
Req'd R_{n} = R_{u}/f_{t}
< R_{n} |
Req'd R_{n} = R_{a}
W_{t} < R_{n} |
R_{u} / (f_{t}R_{n})
< 1.00 |
R_{a} / (R_{n}/W_{t})
< 1.00 |
Which is: FORCE on a weld < STRENGTH of a weld
The STRENGTH of a weld is computed by:
The nominal capacity of the weld, R_{n} = minimum[Strength of
Weld, Strength of Base Metal]
Limit State |
Specification |
Nominal Capacity, R_{n} |
Typical Design Variables |
f |
W |
Weld Tensile Rupture, Shear Rupture,
and Yielding |
J2.4 |
F_{w}A_{w} F_{w}
from SCM Table J2.5 |
t_{e}, L_{w},
Electrode, Weld Layout |
SCM Table J2.5 |
SCM Table J2.5 |
Base Metal |
J2.4 or J4 |
F_{BM}A_{BM} F_{BM}
from SCM Table J2.5 or SCM Section J4 |
L_{w}, Weld Layout |
SCM Table J2.5 or SCM J4 |
SCM Table J2.5 or SCM J4 |
The FORCE on a weld is computed by:
Forces Concentric with the Bolt Group at the Faying Surface:
- All welds are assumed to be equally stressed. The force per unit
length equals the stress times a unit length.
Eccentricity in the Plane of the Faying Surface:
- Elastic Vector Method: See SCM pg 8-12. Computes shear in the
weld. Direct method that is conservative and has an inconsistent
factor of safety.
- Instantaneous Center of Rotation Method:
See SCM pg 8-9.
Computes the relationship between the applied load and the shear load in the
worst case weld segment. Iterative method that is more consistent with test
results and not as conservative as the Elastic Method.
Eccentricity out of the Plane of the Faying Surface:
- See SCM pg 8-14. Basic mechanics (Mc/I) using
the compression contact area to find the tension in the worst case weld
segment. If the shear is concentric with the bolt group it causes
equal stress in plane in all the welds otherwise use either the elastic
vector or IC method to find the distribution of in-plane stress.
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