First Character, Material

A, ALUMINUM
C, CORRUGATED METAL
F, FIBER REINFORCED POLYMER
I, WROUGHT IRON
L, LIGHTWEIGHT CONCRETE
M, STONE MASONRY
P, PRESTRESSED CONCRETE
R, REINFORCED CONCRETE
S, STEEL
T, TIMBER
W, WETHERING STEEL
X, POST-TENSIONED CONCRETE
Y, PRECAST CONCRETE

Second & Third Characters, Type

AR, ARCH
BC, BOX GIRDER COMPOSITE DESIGN
BM, BEAM
CB, BOX CULVERT
CS, SLAB
DG, DECK T-GIRDER OR ORTHOTROPIC
DT, DECK TRUSS
FA, FILLED SPANDREL ARCH
FB, RIGID FRAME BOX
FC, GIRDER FLOORBEAM COMPOSITE DESIGN
FG, GIRDER FLOORBEAM SYSTEM
GC, RIGID FRAME COMPOSTIE DESIGN
HT, HIGH TRUSS
IS, ILLINOIS BULLETIN SLAB
IT, INVERTED T-GIRDER
LP, LONG SPAN PIPE
LT, LOW TRUSS
LW, LOW-WATER CROSSING
MC, BEAM COMPOSITE DESIGN
MP, PIPE
OA, OPEN SPANDREL ARCH
RC, RIVETED PLATE GIRDER COMPOSITE DESIGN
RF, RIGID FRAME
RG, RIVETED PLATE GIRDER
SC, GIRDER STRINGER FLOORBEAM COMPOSITE
SG, GIRDER STRINGER FLOORBEAM SYSTEM
SP, STRUCTURAL PLATE PIPE
SS, STRUCTURAL SLAB
TA, THROUGH ARCH
TG, THROUGH GIRDER
TU, TUNNEL
VS, VOIDED SLAB
WC, WELDED PLATE GIRDER COMPOSITE DESIGN
WG, WELDED PLATE GIRDER

Fourth Character, Feature

0, NOT APPLICABLE
C, CONTINUOUS
D, DROP-PANEL
F, FIXED
H, CONTINUOUS & PARABOLIC HAUNCH
L, LINEAR HAUNCH
P, SPANS WITH BEAMS ENCASED IN CONCRETE
R, CIRCULAR HAUNCH
S, SIMPLE UNSRESTRAINING SUPPORT AT EACH SPAN END
T, TIED

Example: RCSH - Reinforced Concrete Haunched Slab
   R = Reinforced Concrete
   CS = Slab
   H = Haunched