Answer Happy

The four-bay, four-story frame shown in Figure 1 is to be designed. All members are oriented for strong-axis bending in the plane of the frame. Columns are laterally braced in the out-of-plane direction at the top and bottom ends such that K₁=1.0. All beams are W30×108 of A992 steel. All braces are 2L8x8x½ double angle members of A572 Gr. 50 steel. As shown in Figure 1(b), braces (double-angle members) are welded to the web of a WT12×47 bracket of A992 steel. The bracket is then bolted with sixteen 7/8 inch A325-N bolts to the beam. The brace length is 20 ft. B 50 kips 12 ft 50 kips D 12 ft 40 kips 12 ft 20 kips-> 12 ft Detail Brace A 32 ft WT12x47 (A992) TYP 7@4 B -30 ft- (a) Elevation -30 ft- W30x108 (A992) Bolts A325-N 7/8" diam. Stiches, тур. -30 ft- W30x108 B 12" Holes STD Gage 5" -Cross Section- 2L8x8x% (A572 Gr.50) D=15 k D=20 k L=60 k -Side View- L=80 k (b) Second-floor Brace Detail between Grids A and B Figure 1: Braced Frame WT12x47

Department of Civil Engineering Istanbul Kultur University Spring 2021 Instructor: Gulen Ozkula Problem 1: Assume columns in grid line D are W12×58 in every story. Check if column DE has an adequate strength. Use P₁ = 1200 kips which is the sum of factored loads on all columns in the top story and each column carries the same amount of axial force. Results from a first-order structural analysis for the factored loads which include the notional loads are given for column DE in Figure 2. Use H= 105.4 kips and A=0.58 in. for the top story. Axial, NT Moment, NT -7.4 k-ft -300 kips 13.7 k-ft (a) The structure is restrained against lateral translation Axial, LT Moment, LT -104.5 k-ft -9.6 kips 52 k-ft (b) Due to lateral translation of the structure Figure 2: First-order Structural Analysis Results

Problem 2: Brace A shown in Figure 1(a) is a built-up section formed by 2L8×8×½ shapes. Intermediate connectors are snug tight bolts and the distance between them is 5 ft., along the length of the brace. See Figure 1(b). Braces can be subjected to either tensile or compressive axial force under the earthquake forces. (a) Compute the design tensile strength of Brace A. (b) Compute the design compressive strength of the member. Hint: Brace is a built-up member.