What are the pressures on the underside of an open foundation structure?

There are currently no provisions for calculating pressures for the underside of open foundation structures in ASCE7-10 or FEMA documents. Wind could cause a positive or negative pressure depending on the make-up of the substructure space that breaks the wind and flood water.

The following FAQ is based on the presentation of STD310 – Part 1 of the 2012 WFCM Webinar Series: Wind Speed and Design Pressure Determination According to ASCE 7-10.