BASE SHEAR: Example 1 BASE SHEAR FROM GROUND FLOOR

PROBLEM: A commercial building is to be constructed in Iloilo city where soil profile type is very dense soil and soft rock profile. The structure will be concrete with the weight of each floor as listed:

	kN
Ground Flr	1500
Second Flr to 7th Flr (typical)	1800
Roof deck	1700

Dead load weight for each floor are as follows:

FLOOR HEIGHT	meters
Fndtn to Ground Flr	2.50
Ground Flr to 2nd Flr	4.00
2nd Flr to Roof Deck (typical)	3.20

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 = 1.00. For special 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= 6 (1800) + 1700  [For 6 levels of 1800 from 2Flr to 7Flr + Roof deck weight]
                = 12,500 kN
4. For T: The elastic fundamental period of the building uses the formula:
                  
              for reinforced concrete moment-resisting frames
          
             

5. For Cv:

• Iloilo city is located at Zone 4.
• Very dense soil and soft rock profile, Sc

                              
              where:
                  Seismic source type = A
                  Distance to known seismic source >=15km
                  
          Thus:
                 
                


Therefore:

CHECK FOR Vmin AND Vmax.

1.    

                    where:
                           with Zone 4 and Soil Profile Type Sc
                                      for >10km and Seismic source type A
                         

                                     
                                     
Thus:


 

  [Design V is ok]

2. 
        
              [Design V is ok]

3.   
           
             [Design V is ok]

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