4.6 PROBLEMS FOR SOLUTION 4.6 Problems for Solution 125 For all these problems, select sizes with LRFD expressions and check the selected sections with both the LRFD and the ASD expressions. 4-1 to 4-8. Select sections for the conditions described, using F, 50 ksi and F₁ = 65 ksi, unless otherwise noted, and neglecting block shear. 4-1. Select the lightest W12 section available to support working tensile loads of Pp = 120 k and Pw 288 k. The member is to be 20 ft long and is assumed to have two lines of holes for 3/4-in 0 bolts in each flange. There will be at least three holes in each line 3 in on center. (Ans. W12 x 45 LRFD and ASD) 4-2. Repeat Prob. 4-1 selecting a W10 section. 4-3. Select the lightest WT7 available to support a factored tensile load P, 250 k, P = 160 k. Assume there are two lines of 7/8-in bolts in the flange (at least three bolts in each line 4 in on center). The member is to be 30 ft long. (Ans. WT7 x 26.5 LRFD. WT7 x 24 ASD) 4-4. Select the lightest S section that will safely support the service tensile loads Pp = 75 k and P-40 k. The member is to be 20 ft long and is assumed to have one line of holes for 3/4-in bolts in each flange. Assume that there are at least three holes in each line 4 in on center. Use A36 steel. 4-5. Select the lightest C section that will safely support the service tensile loads Pp = 65 k and P = 50 k. The member is to be 14 ft long and is assumed to have two lines of holes for 3/4-in bolts in the web. Assume that there are at least three holes in each line 3 in on center. Use A36 steel. (Ans. C8 x 18.75 LRFD and ASD) 4-6. Select the lightest W10 section that will resist a service tensile load, Pp 175 k and PL-210 k. The member is to be 25 ft long and is assumed to have two lines of holes in each flange and two lines of holes in the web. Assume there are four bolts in each line 3 in on center. All holes are for 7/8-in Ø bolts. Use A992 - Grade 50 steel. 4-7. Select the lightest C section that will safely support the service tensile loads Pp = 20 k and P = 34 k. The member is to be 12 ft long and is assumed to have only a transverse weld at the end of the channel. A36 steel is used. (Ans. C6 x 10.5 LRFD and ASD) 4-8. Select the lightest MC12 section that will resist a total factored load of 372 kips and a total service load of 248 kips. The member is to be 20 ft long and is assumed to be welded on the end as well as to each flange for a distance of 6 in along the length of the channel. A36 steel is used. 4-9 to 4-16. Select the lightest section for each of the situations described in Table 4.1. Assume that bolts are 3 in on center (unless noted otherwise). Do not consider block shear. Determine U from Table 3.2 of this text (except if given). TABLE 4.1 Prob. PD no. Section PL Length (kips) (kips) (ft) Steel End Connection Answer 4-9 W8 75 100 24 24 A992 Two lines of 5/8-in 0 bolts (3 in a line 2 1/2 in on center) each flange W8 x 28 LRFD and ASD (Continued)