Seismic Coefficient Method

•Seismic coefficient method

The seismic coefficient method is one of the static procedures for earthquake resistant design of structures.

•Horizontal and/or vertical forces, which are calculated as products of the seismic coefficients H K , V K and the weight of the structures are applied to the structures.

•This approach is also known as "pushover" analysis.

•Three basic methods are available for analyzing the responses of a structure subjected to seismic ground wave: Static analysis. Response spectra analysis. Time history analysis.

Steps for seismic coefficient method

•Step-I Calculation Design base shear

VB=Ah*W

Ah –Design horizontal acceleration coefficient

Ah=Z*I*Sa

2*R*g

VB-Base shear

W-Seismic weight of building

Z-Zone factor (Annex E pg no. 36,37 IS 1893-2016)

I-Importance factor (Table 8, pg no.-19 IS 1893-2016

Important service and community building or structures (e.g. critical governance building, school) signature building, monument building, lifeline and emergency building (hospital , telephone exchange building, television station building, bus station, radio station, airport, food storage building, fuel station, fire station, large community hall like cinema hall, shopping malls, assembly hall)-1.5

Residential or commercial building (other than those listed in sr. 1) with occupancy more than 200 persons-1.2

All other building-1

R-Response reduction factor (Table 9, pg no.-20 IS 1893-2016

Lateral load resisting system

Moment frame system

RC building with ordinary moment resisting frame (OMRF)-3

RC building with special moment resisting frame (SMRF)-5

Steel building with ordinary moment resisting frame (OMRF)-3

Steel building with special moment resisting frame (OMRF)-5

Sa/g-Design acceleration coefficient for different soil type ,normalized with peak ground acceleration corresponding to natural period T of structure (pg no.-9 IS 1893-2016)

T-Natural time period of oscillation (pg no.-21 IS 1893-2016)

•Moment resisting frame (without any masonry infill wall)

Ta-0.075 h0.75 (for RC MRF building)

Ta-0.080 h0.75 (for RC steel composite MRF building)

Ta-0.085 h0.75 (for steel MRF building)

•Moment resisting frame (with any masonry infill wall)

Ta=0.09h/Γd

Step II- Calculation Seismic weight of building

•Seismic load=Dead load + live load + floor finish

Ø Dead load-sum of dead load of all floor

Ø Live/Imposed load-Percentage of Imposed load to be considered in calculation of seismic weight

Step III-Calculate Base shear

•VB=Ah*W

Step IV Determine lateral force

•lateral force

•Q= VB * wihi2

€wihi2

• wi seismic weight of floor

hi height of floor I measure from base