What is the relationship of initial deflection and camber?

The Criteria - Camber and Criteria - Deflection criteria together determine if beams will get cambered in the program design. Refer to the Ram Steel Beam manual, section 10.13 for details on exactly how this is done, below is an example for the most common case, Unshored, Composite Construction.

This example uses default camber and deflection criteria:

Which means that beams will be cambered if and only if, the deflection caused from 80% of the applied Construction Dead load is greater than 0.25".

The beam in question is a 20' long girder and the CDL stems from the beam and deck self weight. With 100% of that load considered acting on the pre-composite unshored beam, the deflection is 1.061" downward at mid-span. The deflection due to 80% of the CDL is therefore 0.8 * 1.061 = 0.85". Thus the program cambers 0.75" which is 3 times the 0.25" camber increment.

The Live load deflection is calculated using the composite properties (Ieff) and is therefore a smaller total deflection even though the applied loads may be more than the CDL. This Live load may already be reduced if the beam tributary area is large enough. Construction live loads are used in the Pre-composite strength check of the beam only, not in the initial deflection check.

The Post Composite value is also based on the composite beam effective inertia. The Post Composite load considered is any dead load above and beyond the CDL plus the Live Load. This is often referred to as the superimposed load. 

Thus the Net Total load can be calculated using the formula:

Net Total deflection = Initial defl + Post Composite delf - Camber

In the case above that is 

0.759 = 1.061 + 0.448 - 0.75

It's also worth noting that the initial deflection in this case is large enough to surpass the common L/240 deflection limits for dead loads, but that's OK because there is no limit on initial deflections (using our default deflection criteria). So long as the Live load deflection and Net Total deflection limits are OK, no warning will be given.

It is also worth noting that even with camber, this beam theoretically deflects 1.061 " - 075" = 0.311 inches during construction. The program does not increase the construction dead load to account for the additional topping concrete that might occur from such ponding. The applied loads should manually be increased where this is a concern.

Does the program check the cumulative deflection of a beam and the supporting beam?

No, Ram Steel beam only checks the local deflection of the beams, not the cumulative deflection of the beams plus the deflection of the supports. 

Can I turn off Camber on specific beams?

The Criteria - Camber controls whether to camber or not camber composite beams or non-composite beams for the whole model. In cases where you want no camber on specific beams consider adding a special deflection criteria with an initial deflection limit equal or less than the minimum camber and assign that deflection criteria to the beam in question: 

Are transfer loads from columns or hangers affecting composite beams considered pre-composite or post-composite?

All transfer dead and live loads affecting composite beams are part of the post-composite design. For transfer columns, that typically makes sense since the lower level composite beam should be hardened by the time the upper level is loaded. For hanging columns it's not so clear cut, but the transfer load is still only considered in the post-composite design in Ram Steel.

Transfer loads do not include the column self-weight since column design typically takes place after beam design. A point load for the estimated column self-weight is advised.

I have input a composite beam but it is designed with 0 studs, which deflection criteria are used?

In the case where a composite beam is designed non-compositely (i.e. with 0 studs), the deflection checks are performed using the non-composite deflection criteria. For more on reasons why composite beam are design without any studs, refer to Ram Steel Beams FAQ.

See Also

RAMSS Beams [FAQ]

Product TechNotes and FAQs

Structural Product TechNotes And FAQs