Does STAAD.Pro account for cracking of concrete section ?
STAAD.Pro does not automatically account for cracking of concrete. However there are ways to account for that as described below
For beams and columns, there are a couple of ways to handle this. You may use any one
Method 1 : Specifying the cracked section properties directly
When analyzing a structure, STAAD uses the properties specified by the user under MEMBER PROPERTIES. In other words, whatever values are specified by the user for AX, IZ, IY etc. will be used exactly the way the user enters them. Here is a sample input
3 TO 10 PR YD 12.0 ZD 12.0 IZ 864. IY 864. IX 1279
If the user ONLY enters the section dimensions YD and ZD, the properties are going to be calculated based on these dimensions ( YD=depth ZD=width ). In such cases, properties will be based on the gross section dimensions. However when one specifies the values like AX, IY, IZ etc. the software does not calculate the section properties anymore from YD and ZD and simply uses the values provided. It only calculates those terms among AX, IY, IZ etc. which the user has not entered and in such cases these would be based on overall dimensions ( gross section ).
So to account for cracked concrete sections, one can specify reduced values for these section properties. These can be done using the command file as shown above OR using the Graphic user interface as shown next
Method 2 : Specifying the cracked section properties through Property Reduction Factors
From STAAD.Pro 2007 onwards, STAAD has an option to define reduction factors for member properties like cross sectional area and moment of inertia. These reduction factors can be specified from the General - Specs - Beam page of the program, as shown next
The corresponding properties are multiplied by these reduction factors for analysis purposes. Please note that design of the member will still be based on the gross section dimensions.
For plates, the user may account for the cracking by specifying a reduced thickness for the plate elements, or by specifying an E value (modulus of elasticity) which is lower than the value for the grade of concrete used for the slab or wall.