Wind Comparison

 

ASCE7 - 10 

NSCP 2015

3-second peak gust wind speed measured at 10-meter height (above ground) over open and flat terrain

 

300/V25 = V300/V50 / V25/V50 = 1.26 = sqrt(1.6) = conversion factor of service level wind velocity to strength design wind velocity.

(V10/V50)^2 / (V1700/V50)^2 = 0.7/1.83 = 0.3825 <= conversion factor of MRI 1700 years wind load to MRI 10 years wind load.

(V10/V50)^2 / (V700/V50)^2 = 0.7/1.6 <= the 1/1.6 factor is conversion of design wind load to service load & 0.7 factor is the conversion of MRI 50 years to MRI 10 years (considered for wind drift check).

Understanding Wind Velocity Map of PAGASA and NSCP 2015

PAGASA 3-second peak gust wind speed measured at 10-meter height (above ground) over open and flat terrain with various return periods were derived in the study such as 20, 50, 100, 200 and 500 year return periods (MRI).

PAGASA Severe Wind Map link

For comparison with the NSCP 2015, please consider PAGASA maps as service level wind (ASD) speed. Note that NSCP is a strength design (LRFD) windspeed. Thus, to convert service level (ASD) wind speed to strength design (LRFD) wind, use factor of sqrt (1.6) or sqrt(1/0.6). 

ASD wind speed with MRI 20 year * sqrt(1.6)= LRFD wind speed with MRI ~200 years. 

ASD wind speed with MRI 25 year * sqrt(1.6) = LRFD wind speed with MRI ~300 years. (comparable to NSCP 2015 Category IV and V) 

ASD wind speed with MRI 50 year * sqrt(1.6)= LRFD wind speed with MRI ~700 years. (comparable to NSCP 2015 Category III) 

ASD wind speed with MRI 100 year * sqrt(1.6)= LRFD wind speed with MRI ~1700 years. (comparable to NSCP 2015 Category I and II) 

ASD wind speed with MRI 200 year * sqrt(1.6)= LRFD wind speed with MRI ~4000 years. 

For wind serviceability checks, which are short-term loadings, considers wind speed of MRI 10 years. Wind speed of MRI 10 years, V20 is 0.8387 time wind speed of MRI 50 years, V50. Thus, the wind velocity pressure factor is (V10)^2 / (V50)^2 = 0.8387^2 = 0.7 

Reference: 

1) ASCE 7-10 Minimum Design Loads for Building and other Structure. 

2) McAllister, T, Wang, N, Ellingwood, B (2018). "Risk-Informed Mean Recurrence Intervals for Updated Wind Maps in ASCE 7-16". Volume 144, Issue 5, Journal of Structural Engineering. 

3) National Structural Code of the Philippines (NSCP) 2015, 7th edition 2nd Printing. 

4) https://bagong.pagasa.dost.gov.ph/ 

Disclaimer: For academic purpose only.