Comprehensive Examinations- Spring DESIGN Question

Transcription

1 Universit of California, Berkele Department of Civil and Environmental Engineering Structural Engineering, Mechanics and Materials Comprehensive Eaminations- Spring 2014 DESIGN Question Consider ONLY one of the steel or reinforced concrete beam-columns shown below loaded aiall and laterall. The cross section of the beam-column is shown in the figures. The aial factored load is 500 kips. Calculate the factored lateral load Q that can be applied to this beamcolumn. Check all bending and shear failure modes and indicate whether or not the beam-column is adequate to carr the loads. The steel beam is sufficientl braced and lateral-torsional buckling is not a consideration. All the information ou need for this problem are given below, still, if ou feel ou need a piece of information that is not given, make a reasonable assumption and continue the problem. No questions can be asked during the eam. You can use approimate equations if ou do not remember eact equation, but, ou have to eplain the approimation and how that approimation might affect our answer. STEEL 500 kips Q kips or CONCRETE 500 kips Q kips 500 kips 500 kips PL 1 20 (both flanges) PL 3/ R/C Beam 8 # 10 rebars (diameter=1.25 ) Continuous Welds # 4 8 c/c Steel : F=36 ksi, Fu=58ksi Steel rebars : F=60ksi, Concrete: f c=6,000 psi

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3 Universit of California at Berkele Structural Engineering Mechanics and Materials Department of Civil and Environmental Engineering You onl need to do either steel or reinforced concrete design of the core wall and the columns but not both! M.S. Comprehensive Eam - Spring 2012 Design The 8-stor building shown in Figures (a) and (b) is considered. The structural sstem of this building consists of a core wall coupled through the floor slab with columns. Our aim is to design part of the double-c-shape core wall of the building under the combined effect of earthquake loading in the North- South direction and gravit loads. Assume that the lateral seismic forces are resisted entirel b the core walls. The walls are fied at their base. Assume that the walls have adequate capacit against buckling. The uniforml distributed factored seismic weight of each floor is w = 0.3 kips / ft 2 and includes the self weight of the structural components, partitions, permanent equipments, as well as the live load contributing to the seismic weight. The design lateral seismic force is F s = 0.1W total where W total is the total seismic weight of the building. The profile of the lateral seismic forces has an inverted triangle shape, see Figure (b). The ield strength of steel used is f = 60 ksi and the concrete compressive strength is f c = 6 ksi. Consider the reinforced concrete sections well confined. (1) Determine the length of the core walls L in order to have adequate fleural strength at their base. The longitudinal (fleural) steel ratio of the reinforced concrete (RC) walls is L = 1.2%. The longitudinal steel ratio is defined as the total area of longitudinal steel used divided b the gross section area. (2) For the length L ou determined check if the core wall has adequate shear strength. For the RC wall the shear reinforcement of each segment of the wall consists of two No. 6 bars ever 8 inches, see Figure (d). (3) Describe b means of a short narrative the main objectives of the design of the gravit columns. What is the minimum column section area ou would use? 1

4 gravit column floor slab core wall floor slab North core wall gravit column L L/2 L/2 60 ft Lateral seismic forces 810 =80 ft East 60 ft (a) Building floor plan view ground (b) Building elevation view and profile of lateral seismic forces t = 6 inches t=20 inches No. 8 L t = 6 inches L Uniforml distributed longitudinal steel with L = 1.2% t = 20 inches L/2 L/2 (c) Steel design core wall section L/2 L/2 (d) Reinforced concrete design core wall section 2

5 UNIVERSITY OF CALIFORNIA, BERKELEY SPRING SEMESTER 2009 Department of Civil and Environmental Engineering Structural engineering, Mechanics and Materials Name: M.S. Comprehensive Eam Design Consider the frame shown below. Consider onl one of the Steel or Reinforced Concrete cross sections shown below to be the member section for both members of the frame and calculate maimum factored horizontal seismic force H that can be applied to the frame. Notice that ou need to do the problem considering it to be steel or R/C but not both. The frame has lateral bracings at Points A, B and C bracing it in out of plane direction at these locations. For either case of Steel or Reinforced Concrete frame, both members (i.e. the column and the diagonal brace) have the same cross section as shown. Use the beam-column interaction equation: P/P cr + (M/M p ) for both steel and concrete members. For buckling capacit ou can use Euler s equation: P cr = (π 2 EA)/ (KL/r) 2 P ma where P ma is equal to A g F for steel and equal to 0.8[0.85f c (A c -A r ) +F r A r ] for concrete section. Consider all applicable strength-related limit states (i.e. failure modes). Deflection limit states are not part of this problem. Make assumptions on an information that is not given, such as concrete cover on rebars, and eplain our assumptions. Show all our calculations and ignore the self-weight of the structure in our calculations. Use the following properties for material: Steel plates: F =50 ksi, F u =65 ksi, E s = 29,000 ksi Concrete: f c = 8,000 psi, E c = 9,500 ksi Rebars: F r = 60 ksi. B P=500 kips (Factored load) H=? kips You need to do either Steel or R/C frame but not both! 16 #11 rebars ( dia.=1.41 inch) # 5 ties@ 12 c/c (dia=0.625 inch) Cross Section of Members for R/C frame 2626 inch 1.5 in. 14 in. 1.5 in. A Roller C Pin Steel Plates 1.5 i 14 in. 1.5 in. View of the Frame Cross Section of Members for Steel frame

6 Universit of California, Berkele Department of Civil and Environmental Engineering Structural Engineering, Mechanics and Materials Name: 500 kips Comprehensive Eaminations- Spring 2008 DESIGN Question Consider ONLY one of the steel or reinforced concrete beam-columns shown below loaded aiall and laterall. The cross section of the beam-column is shown in the figures. The aial factored load is 500 kips. Check all bending and shear failure modes and calculate the factored lateral load Q that can be applied to this beam-column. Concrete cover over rebars is 2. The steel beam is sufficientl braced and lateral-torsional buckling is not a consideration. All the information ou need for this problem are given below, still, if ou feel ou need a piece of information that is not given, make a reasonable assumption and continue the problem. No questions can be asked during the eam. You can use approimate equations if ou do not remember eact equation, but, ou have to eplain the approimation and how that approimation might affect our answer. STEEL Q kips or 700 kips CONCRETE Q kips 500 kips 15 ft 15 ft 700 kips PL 1 20 (both PL 3/4 30 Continuous Welds R/C Beam 8 # 10 rebars (diameter=1.25 ) # 4 8 c/c Steel : F=36 ksi, Fu=58ksi Steel rebars : F=60ksi, Concrete: f c=6,000 psi

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