Section properties for calculation of member capacity with haunch

[kiran.narsey]

Hi,

I have noticed a potential error with the design module for steel beams to AS4100 and was just seeking some clarification. The scenario is as follows:

• I have a portal frame building with haunches each end of rafters between columns.
• Columns are on a 25m grid
• I have defined a complex member to encompass all rafter members between 2 columns (multiple smaller segments make up the rafter length)
• I have defined parameters in the code parameters to reflect the 25m rafter length. I have defined parameters to force a failure at midspan of the rafter, which is a 460UB74.6

The issue is as follows:

• When I select a sway frame through user defined parameters with points in the adjoining compression buckling "Y" direction (refer figure 1), the section elastic and plastic modulus are defined to be equal in the calculations (refer figure 2) and are also greater than the actual member properties (refer figure 3).
• When I alter the definition of the "Y" compression buckling to not have "at adjoining elements", the calculations are performed correctly (correct plastic and elastic section modulus as per Figure 3). I have noticed that these parameters allow the design module to run significantly quicker as well.
• Theoretically, there is no difference between each of the above scenarios as there are no other members joining the rafter midspan.

I have attached a copy of my model for reference.

Regards

Kiran

Figure 1

User defined parameters

Figure 2

Equivalent plastic and elastic section properties for bending

Figure 3

Section Properties

[kiran.narsey]

Unfortunately I cannot attach the model at this instance. Will attempt later.

[kiran.narsey]

@Artur.Kosakowski

Hi Artur,

I have tried uploading the model numerous times to no success. Is there an email I can send the model to?