BASE SHEAR: Example 2 STRUCTURE WITH BASEMENT

PROBLEM: A  public school is to be built in Baguio city. Due to lack of budget, there wasn't any soil test done on site. The building should consist of a basement for carpark. The following weight and height per floor is listed below:

	kN
Ground Flr	1500
Second Flr to 4th Flr (typical)	1800
Roof deck	1000

FLOOR HEIGHT	meters
Fndtn to Basement	2.50
Basement to Grnd Flr.	4.00
Ground Flr to Roof Deck	3.50

Determine the base shear.

SOLUTION:

Assuming the structure is a regular structure, the analysis to be used is static procedure with the following equations:

                                                      

1.  I = 1.50. For essential occupancy structures.
2. R = 8.50. For Special Reinforced Concrete Moment Frames.
3. For W: The building not being used as a warehouse, the total seismic load is the summation of the dead load above the Ground Floor.
             W= 3 (1800) + 1000  [For 3 levels of 1800 from 2Flr to 4Flr + Roof deck weight]
                = 6,400 kN
4. For T: The elastic fundamental period of the building uses the formula:
                  
              for reinforced concrete moment-resisting frames
                hn is taken from the base (gradeline) to the top [disregard stories under the gradeline].
          
             

5. For Cv:

• Baguio city is located at Zone 4.
• Lack of soil analysis, Sd

                              
              where:
                  Seismic source type = A
                  Distance to known seismic source <=2km [since location is not found on map, and many faults surround the city, it can be assumed that source is very near.]
                  
          Thus:
                 
                


Therefore:

CHECK WITH Vmax AND Vmin:

1.    

                    where:
                           with Zone 4 and Soil Profile Type Sd
                                      for <2km and Seismic source type A
                         

                                     
                                     
Thus:


 

  [Design V is ok]

2. 
      
              [Design V is ok]

3.   
         
             [Design V is ok]

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Design Base Shear