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CSI SAFE : How To Check Slab Deflection
SAFE can use user-defined reinforcement to compute cracked-slab deflection. For this option, select Run > Reinforcing Option for Cracking Analysis, then select User Specified Rebars in Reinforcement Source. Select Draw Slab Rebar from the vertical menu on the left. Note that rebar must be added in both the tension and compression regions for the entire slab since the software will only use the user-defined reinforcement, and not use the reinforcement design.
Cracked-section analysis is run in SAFE using either of the following two methods ;
1) All load patterns are applied in a single load case which uses either immediate or long-term cracked deflection
2) A single load pattern is applied in a load case, then another case is set to continue From State at End of Nonlinear Case.
In SAFE, Two types of cracked-section analysis are available, including ;
1) Immediate cracked deflection
2) Long-term cracked deflection accounting for creep and shrinkage
Long-term cracked deflection, in which analysis is divided into the following two categories:
1) Non-sustained portion, in which cracked-section analysis considers only the non-sustained portion of LIVE load, solving for incremental deflection.
b) Sustained portion, in which long-term cracked analysis considers the sustained loading from DEAD, SDEAD, and a portion of the LIVE load. Creep and shrinkage are included only in this sustained portion of analysis because these effects are only applicable under sustained loading.
Most engineers simply check this values against ACI 318 Table 9.5(b), since this will always result in safe and conservative design.
