fundamentals of engineering supplied-reference handbook - Ventech!

STEEL STRUCTURES
LOAD COMBINATIONS (LRFD)
References: AISC LRFD Manual, 3rd Edition
AISC ASD Manual, 9th Edition
Floor systems: 1.4D
Roof systems: 1.2D + 1.6(Lr or S or R) + 0.8W
1.2D + 1.6L
1.2D + 0.5(Lr or S or R) + 1.3W
0.9D ± 1.3W
where: D = dead load due to the weight of the structure and permanent features
L = live load due to occupancy and moveable equipment
L r = roof live load
S = snow load
R = load due to initial rainwater (excluding ponding) or ice
W = wind load
TENSION MEMBERS: flat plates, angles (bolted or welded)
Gross area: Ag = bg t (use tabulated value for angles)
Net area:
2
s
An = (bg − ΣDh + ) t across critical chain of holes
4g
where: bg = gross width
t = thickness
s = longitudinal center-to-center spacing (pitch) of two consecutive holes
g = transverse center-to-center spacing (gage) between fastener gage lines
Dh = bolt-hole diameter
Effective area (bolted members):
U = 1.0 (flat bars)
Ae = UAn U = 0.85 (angles with ≥ 3 bolts in line)
U = 0.75 (angles with 2 bolts in line)
LRFD
Yielding: φTn = φy Ag Fy = 0.9 Ag Fy
Fracture: φTn = φf Ae Fu = 0.75 Ae Fu
Block shear rupture (bolted tension members):
Agt =gross tension area
Agv =gross shear area
Ant =net tension area
Anv=net shear area
When FuAnt ≥ 0.6 FuAnv:
φRn =
When FuAnt < 0.6 FuAnv:
φRn =
smaller
smaller
0.75 [0.6 Fy Agv + Fu Ant]
0.75 [0.6 Fu Anv + Fu Ant]
0.75 [0.6 Fu Anv + Fy Agt]
0.75 [0.6 Fu Anv + Fu Ant]
121
CIVIL ENGINEERING (continued)
Effective area (welded members):
U = 1.0 (flat bars, L ≥ 2w)
Ae = UAg U = 0.87 (flat bars, 2w > L ≥ 1.5w)
U = 0.75 (flat bars, 1.5w > L ≥ w)
U = 0.85 (angles)
0
ASD
Yielding: Ta = Ag Ft = Ag (0.6 Fy)
Fracture: Ta = Ae Ft = Ae (0.5 Fu)
Block shear rupture (bolted tension members):
Ta = (0.30 Fu) Anv + (0.5 Fu) Ant
Ant = net tension area
Anv = net shear area