Seismic loading to ASCE code 3

[EdClymer]

Greetings from England

A specification document from American Society of Civil Engineers (ASCE) gives seismic loading for proposed GRP (FRP) composite tanks as;

Aa = 0.2 and Av = 0.2

Can anyone give the units for Aa and Av

Are they already factored?

If not can anyone suggest factors?

And the context in which they would be used.

Many thanks




Ed Clymer
Resinfab & Associates
England

 

[Qshake]

They are coefficients derived from proportion to vertical gravity acceleration.

The accelerations read from an accelogram are typically reported in units of cm/s/s.



Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[IFRs]

I thought they were in % units ie % of gravity acceleration

 

[Taro]

The units are g's, not % of g. The 0.2 coefficient is multiplied by the gravitational constant to determine the ground acceleration. Then additional factors are incorporated to account for local soil amplification effects. Finally, factors representing structure's dynamic and hysteretic properties are included to determine the design forces.

It should be noted that these accelerations are based on a 475-year return period earthquake. More modern U.S. codes use a 2,500-year return period to account for substantially larger earthquakes than can occur. Make sure that you were not given an outdated specification.