Cracking Methods and Cracking Behaviors

Cracking Methods 

ACI Table 6.6.3.1.1(b) was used in calculating the moments of inertia for elastic analysis. The stiffnesses provided in the table are applicable for all service and ultimate level of loading.

As an alternative, the Robert F. Mast’s procedure is a practical approach for analyzing the elastic behavior of cracked prestressed concrete sections. This iterative procedure consists of assuming a depth to the neutral axis, computing the section properties of the net cracked section, checking stresses at the assumed neutral axis location, and then revising this location as necessary to make the concrete stress equal to zero at the assumed neutral axis location. For more information see: Analysis of Cracked Prestressed Concrete Sections: A Practical Approach, Robert F. Mast, P.E..

Cracking Behaviors

No Cracks

• Description: Disables the cracking check, resulting in an elastic analysis.

• Behavior: The analysis assumes the concrete sections remain uncracked under all loading conditions.

Assume Cracked

• Description: All sections are assumed to crack regardless of the stress level in the concrete.

• Behavior: This approach results in a linear non-elastic response, as the analysis considers the concrete to be fully cracked from the start.

Crack at Rupture

• Description: A stress check will be performed to determine if the concrete approaches its modulus of rupture.

• Behavior: When the stress in the concrete approaches the modulus of rupture, the program will automatically switch to the cracked section properties (Icr).