The braced frame shown below resists lateral loads at the second floor and roof levels. Shear in the each story is resisted by two square HSS braces and a buckling-restrained brace (BRB). The HSS braces are steel (E=29000 ksi) and their cross-sectional area, A, can be found in Table 1-12 of the Steel Manual or online via Google. According to the manufacturer's specifications, the BRBs in both stories each have an effective modulus E=45000 ksi and effective cross-sectional area A=5 in. 500 kip BRB HSS6x6x1/2 12 ft 650 kip BRB HSS8x8x3/8 15 ft 24 ft 15 ft Assume that the girders act as rigid diaphragms and that the columns do not resist any lateral load. For all problems, report stiffness as kip/inch and force as kip. 1. Calculate the lateral stiffness of the HSS braces and the BRB in the second (upper) story. 2. Determine the magnitude of the axial force in the second story HSS braces. 3. Determine the magnitude of the axial force in the second story BRB. Answer: PBRB=192 kip The braced frame shown below resists lateral loads at the second floor and roof levels. Shear in the each story is resisted by two square HSS braces and a buckling-restrained brace (BRB). The HSS braces are steel (E=29000 ksi) and their cross-sectional area, A, can be found in Table 1-12 of the Steel Manual or online via Google. According to the manufacturer's specifications, the BRBs in both stories each have an effective modulus E=45000 ksi and effective cross-sectional area A=5 in. 500 kip BRB HSS6x6x1/2 12 ft 650 kip BRB HSS8x8x3/8 15 ft 24 ft 15 ft Assume that the girders act as rigid diaphragms and that the columns do not resist any lateral load. For all problems, report stiffness as kip/inch and force as kip. 1. Calculate the lateral stiffness of the HSS braces and the BRB in the second (upper) story. 2. Determine the magnitude of the axial force in the second story HSS braces. 3. Determine the magnitude of the axial force in the second story BRB. Answer: PBRB=192 kip