LRFD Load Combinations
Choose the combination that results in the highest U, use U in your calculations.
$$U = 1.4(D+F)$$
$$U = 1.2(D+F+T) + 1.6(L+H) + 0.5(L_r or S or R)$$
$$ U = 1.2D + 1.6(L_r or S or R) + (1.0L or 0.8W)$$
$$ U = 1.2D + 1.6W + 1.0L + 0.5(L_r or S or R)$$
$$ U = 1.2DL + 1.0E + 1.0L + 0.2S$$
$$U = 0.9D + (1.6W or 1.0E) + 1.6H$$
D = Dead Load, L = Live Load, T = self-straining, H = earth pressure, \(L_r\) = roof live load, S = Snow Load, R = rain load, E = earthquake load
Dead Loads and Live Loads
Structural loads are placed into two main categories, dead loads and live loads.
Dead loads are loads on a structure due to the structure’s own weight.
Live loads are loads on the structure due to objects that are not permanent like people, furniture, and vehicles.
The goal of structural design is to accurately tally up the projected loads in a structure, convert them to stress, and compare that stress to what the structure can handle (the designed strength). There are two camps on how this is to be done: