My question is related to STAADPRO. I'm searching for a feature of StaadPro (that might not exist) that would allow the evaluation of the forces present in a cross-section comprising more solid elements. For example, imagine a solid model representing a concrete slab supported by concrete beams monolithically connected to the slab. For the purpose of a manual design of the beams, how can one extract the Moment, Shear, Torsion and Axial of a beam cross section (rectangular or T-section). I'm asking this question because I found out in other programs it is possible to inquire these forces (for example in ANSYS).
Thank you,
Tibi.
Currently, the facility of concrete design of a structure modeled with solid elements is not available in Staad.pro.
To perform the concrete design of a simple structural element like beam or column, you could use the member entity .
However, you may want to use the solid element to model the special structure like the bracket, T-beam, culvert abutment, dam, T.G foundation, etc.
Structurally these elements behave more like a solid element than a member element .
Click on the following link to know more about the general criteria to select solid, plate or member entity in Staad.
http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/8445.aspx
Now, regarding your T-beam modeling in Staad by solid element, the stress value could be extracted from post-processing table and converted them to the forces required to design the structure.
But one needs to consider an important point here.
As the stress-strain relation is considered purely elastic, it is suggested adopting the working-stress approach of design.
The idea of neutral could be approximately determined from the solid stress result .
See the Sxx stress contour of a sample T-beam section with the solid stress interpretation below.
The neutral axis lies somewhere in the yellow coloured band where the Sxx stress changes its sign.
Now, assuming the linear stress-strain curve, using modular ratio and the equilibrium of the section (Total Compression=Total Tension), the required steel could be approximately calculated.
If the maximum SXX developed at the extreme lamina (under compression) of the section reaches the allowable compressive stress of concrete, then the reinforcement computed would be in the balanced condition.
Similarly, one may also check the design for the shear condition by the shear stress like Sxy,Sxz or Syz.
Although, conventionally we take forces correspond to the stresses developed along geometric axis of beam members for designing, but in some special structures like bracket, corbel or machine foundation, considering the brittle nature of concrete, the concrete failure plane is ideally considered as the principal plane of the element (plane normal to the principal tensile stress). So, accordingly you need to know if the structure needs to be designed to address the critical principal stress.
Staad reports the three principal stresses as S1,S2 and S3.