Modelling existing buildings, how to capture contribution from rein. in deflec. calc. using SAP2000?

[Kristene]

Hello, I am trying to model an existing RC building. My intention is to predict the deflections of the existing member under a load test. I am using SAP2000 to model elements using "Section Designer" so that we can capture contribution from reinforcement. I notice that the deflection calculation performed by SAP is based on concrete section only, it does not consider the assistance from reinforcement.

My question is how can we capture the influence of reinforcement in reducing deflection. Following are the few method that I can think of, please provide your valuable suggestions,

1. I understand that we can tweak structural properties using stiffness modifiers.
2. May be we can model concrete with equivalent transformed section properties.
3. We can use the section assigned using "Section Designer" to check the adequacy of the design. But does SAP recalculate the deflection under the provided section.

Any help or suggestion is highly appreciated.

Thanks

 

[PicoStruc]

1. Yes - Complete freedom
2. No, reinforcement are used only for check/design purpose in SAP, In my knoledge, SAP2000 only use gross section for properties.
3. Not sure.

Except for very specific analysis, Concrete Code usually recommands to calculate deflection considering cracked section, usually neglecting reinforcement.

 

[IDS]

Except for very specific analysis, Concrete Code usually recommands to calculate deflection considering cracked section, usually neglecting reinforcement.

?? Deflections with a cracked section neglecting reinforcement would be rather large!

Different codes have different provisions for calculating deflections, but all simplified methods have the potential to greatly underestimate deflections under some circumstances.

If deflections are critical they should be checked from first principles, including all significant factors, such as creep, shrinkage, loss of tension stiffening, cracking due to differential temperature, etc.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/