Stiffness and Concrete Pier Bent Moments

[curvbridger]

[Morning]

All,
I am using a new (state-mandated) software package which gives me the option of applying a ratio of gross to cracked stiffness (Ig/Icr) for the columns of the concrete pier bent I am analyzing. No factor is available to apply to the cap.

Is it realistic to analyze this frame with a cracked stiffness for the columns and a gross stiffness for the cap? The Ig/Icr ratio for the columns will be about 3.5.

The pier bent in question is a conventional three column highway overpass 60 feet long, 20 feet high, and having approximately 3.5' x 3.5' columns and cap.

Peace,

Curvbridger

 

[JAE]

What's the ratio of the span of the cap to the length of the columns. Many times the columns tend to be longer and have a much higher influence on the lateral displacement of the bent than the horizontal "beam" has.

You could also contact the program authors and ask for the reason.