Civil 313 Earthquake Homework Problems 2A – 2F
See the followingfloor plan sketches and elevation of the proposed new 3 story classroom building on campus at CSU Chico.
The gravity framing consists of the following:
Roof: Plywood on 2×12’s spanning to wood trusses, which span to the exterior walls.
3rd Floor: Concrete-filled metal deck spanning between wide-flange steel beams which span to wide-flange steel girders or columns in the perimeter walls.
2nd Floor: 8″ concrete slab spanning to 24″ x 24″ square concrete columns below.
The lateral force resisting system consists of concrete shear walls extending the full height of the building (these walls are not shown on the framing plans). See the attached sketches for floor plans and framing details, an elevation, and shear wall layout.
2A. Calculate the following (see the additional information below):
A. The seismic weight tributary to each floor, wx.
B. The seismic weight of the entire building, W.
C. The coordinates of the center of mass at the roof only.
2B. Calculate the total building seismic base shear, V, in the north-south direction only. Assume the total seismic weights of each floor are: Roof = 150 kips, 3rd Floor = 700 kips, 2nd Floor 900 kips (note these are not the answers to 2A!). Use Ss = 0.616, Sl = 0.274. The lateral force resisting system is a Building Frame System with special reinforced concrete shear walls. The building capacity is more than 500 students (Risk Category Ill) and the soil site class is D.
Additional Information and Simplifying Assumptions
- Assume the exterior walls weigh 20 pounds per square foot (psf).
- Neglect the weight of the shear walls (you wouldn’t do this in real life!).
- Use the unit weights on the Material Weights handout.
- Add a uniform partition seismic mass of 10 psf for interior walls over the entire area on each floor.
- Provide an additional 5 psf at the roof and at each floor for weights of mechanical and electrical systems, sprinklers, etc.
- Wide flange beams and columns are designated “W14x90”, where 14 stands for the nominal depth of the “I” beam in inches and the “90” indicates its weight in pounds per lineal foot.
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