creep analysis

[hakimi]

In the case of a steel structure (30 stories) with a concrete core in the middle how can we consider the creep effect of central core on the structure?

my email: hakooo@yahoo.com

thank you

 

[ishvaaag]

A good, clear reference on design for time-dependent effects I have to find yet (sure there's some there). For the problem of an axially loaded column (which more or less is your core to the effects of shortening) I have a Mathcad sheet giving what occurs from shrinkage and creep in one column element and if you want I can send to you, (or a word 97 doc) since I think I haven't posted it to the Collaboratory site. For the core is just then a matter of tabulating it starting at the respective construction time.

mom@arrakis.es

 

[RiBeneke]

Estimates of concrete creep over long periods are just 'estimates' and precise calculation is not possible.
Your best estimates should perhaps be compared with laboratory tests on the concrete mix you will be using.
After this, you will probably still need to design the structure with hinge/flexibility etc that can cope with some variation from the calculated values.

 

[chandr]

As an estimate during design: If it's a new building, you have to assume a construction sequence and assign different creep functions (eg. CEB-FIP MC90) to each floor. With the cross-section of the wall, steel contents, and each floor load, the floor level variation can be calculated. If the beam-end is shear-connection type (the trend in my country), the calculation is simple and the creep effects might not be serious to the structure. We really got creep problems with a 60-storey RC building having an eccentric core and frame setbacks, even they're on the same thick pile-mat foundation.