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4.7 PROBLEMS
4.1 An angle L9 x 4 x ½ made of A441 steel (Fy = 42 ksi) is used as a
tension member. Connection of the angle is through 7/8-in.-diameter bolts.
The pattern of holes in the angle is as shown in Figure 4.15 (with two
lines of holes in the long leg and a single line of holes in the short
leg). Find the allowable tensile force for this member.
4.2 Two main plates 12 in. x 1 in. subjected to tension T have been connected to each other
by two splice plates 12 in. x 7/16 in. and
one-inch-diameter bolts as shown in Figure 4.16(a). The plates are made of
A441 steel with yield stress of 40 ksi and ultimate stress of 60 ksi.
Assuming that the bolts do not control the design of connections, determine
the maximum tension capacity of the connection. Next, in order to increase
the efficiency of the connection, holes are staggered as shown in Figure
4.16(b). For what spacing s of
the holes and bolts will the tension capacity of the connection be the
largest? For this spacing find the percentage increase in the capacity of
the connection due to staggering of the bolts. (Note. You should refer to ASD B3 and J3.8).
4.3 The
fatigue-critical member of a bridge truss consists of 2L8 x 6 x 1 connected to a gusset
plate by fillet welds, as shown in Figure 4.17. Angles are made of A36
steel (Fy = 36 ksi).
The member is subjected to a dead load tensile force of 50 K and a live
load varying from 30 K in compression to 178 K in tension. Find the design
lifetime of the bridge. The average daily number of standard vehicles
passing over the bridge and producing the above-mentioned live load
variation is 182. (Note. Refer to
Appendix K of ASD.)
4.4 Design the members of the bottom chord of the
truss of Figure 4.18. Each member shall consist of two angles with a
spacing of ½ in. to be filled by gusset plates at joints. The two angles
shall be connected to the gusset plate with two 1-in. bolts in the vertical
leg of the angles. Use A36 steel (Fy
= 36 ksi).
4.5 Find the size of the main cables and the
cross-sectional dimensions of the rectangular concrete compression ring for
a circular suspension roof covering an area of diameter 305.6 ft.
supporting a combined dead and live load of 60 psf. Allowable tensile
stress of cable steel is 65 ksi. Compressive strength of concrete is 4 ksi.
Use a sag-to-span ratio of 0.2 for the cables and a width-to-depth ratio of
½ for the cross section of the compression ring. Solve the problem for
three different cable spacing at the compression ring of about 8 ft., 12
ft., and 15ft.
4.6 Solve Problem 4.5 with a
sag-to-span ratio of 0.25 for the cables.
4.7 Solve Example 2 of this chapter, assuming that
the diameter of the structure is 60 ft., the dead load is 70 psf, and the
live load 75 psf. Select the lightest channel (C section) available in the
ASD for the hangers.
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