LONG TERM DEFLECTION

[SAYATTIA]

DEAR ALL :
HOW TO CALCULATE SLAB LONG TERM DEFLECTION BY SAFE ?
SND WHAT IS THE ALLOWABLE LONG TERM DEFLECTION VALUES?

 

[handex]

go in to load cases and add a new case, by choosing long term with cracking on the right. specify the shrinkage and creep coefficients. How accurate safe computes this, I dont know.

As for allowable deflections, there is no hard set rule here. Depends on the sensitivity of the structure to deflections. For instance if there is brittle masonry being supported by the slab then deflections must be tighter than if it was say a stud wall over

 

[StrPerson]

go to the CSI FAQ (frequently asked questions). you can easily find the way to calculate the long term deflections for slabs.

 

[allam84]

Dear Colleagues This is to share with you my findings regarding this issue:In order to find the long term deflection according to ACI318-08 considering the Creep and Shrinkage effects the following tips have to be followed using the SAFE v12: 1- Define Load Patterns for Dead Load (DL), Super Imposed Dead Load (SIDL) and Live Load (LL). 2- Define Load Cases as following: i) Case 1, to be Load Case type: Static, to be initial conditions: Zero Initial Conditions, to be Analysis Type: Nonlinear (Cracked), to be Loads Applied: DL (1) and SIDL (1). ii) Case 2, to be Load Case type: Static, to be initial conditions: Zero Initial Conditions, to be Analysis Type: Nonlinear (Cracked), to be Loads Applied: DL (1), SIDL (1) and LL (1). iii) Case 3, to be Load Case type: Static, to be initial conditions: Zero Initial Conditions, to be Analysis Type: Nonlinear (Long Term Cracked), to be Loads Applied: DL (1), SIDL (1) and LL (0.25), for example.According to the ACI318-08 (R9.5.2.5) and reference to ACI Committee 435 (2.3.5) ,It is Recommended to use Creep Coefficient as 1.60 and Shrinkage Strain 0.0004. 3- Define Load Combination (Long Term) Case 3 (+1.0), Case 2 (+1.0) and Case 1 (-1.0).I am looking for your helpful feedback in order to use the right method.