Hi thanks for the video, I have modelled a deck grillage and included a design beam of a prestress member. I didn’t utilise the line beam, however, I was able to define my DL and SIDL loading using the load ‘Generate’ tool. As part of the SIDL I included the Surfacing and other dead loads on my deck which I noticed you didn’t do as it acts on the full structure when its fully integral. I also modelled the live loading by transferring results from my grillage envelope analysis. My question is regarding my prestress beam deflections results which shows a sag of -4mm after the dead load increment has been added to the stresses at transfer. Is it not best to utilise the construction stage results instead and add up my deflections at erection (after shrinkage/relaxation losses etc) to my DL loads deflection increment (weight of wet slab only) to work out the deflection prior to the deck being integral with the rest of the structure? After this I would then use my grillage results to work out deflections of the rest of the load cases (i.e surfacing/ traffic, etc) when fully composite with the rest of the deck? I have assumed the SIDL and Live Load (LL) are crucial to the design stresses of the prestress beam, however, as the beam is composite with the rest of deck, the deflections should be taken from the grillage? Any help, clarification would be much appreciated.
Hi there, I am really sorry for the late reply. I assumed that the superimposed dead load includes the surfacing. As for live load, yes, I am intending to model them on the grillage first, so that it can be transferred to the beam, exactly as you said. 100%. As for the deflection, I see what you are planning. If I understood your correctly, you are planning to say: Deflection from construction + deflection from extra load due to erection (shrinkage, relaxation included) + deflection due to wet concrete Then yes, I agree. This makes sense. If you take the deflection from the grillage, you may run into the risk of misinterpreting your results. What I mean by this is: The beam itself (no composite action, wet slab) would have different deflection limits when compared to the full structure. I think I will keep this point on my notes and have it covered later. It is a good point and your suggestion is gold.
Hi thanks for the video,
I have modelled a deck grillage and included a design beam of a prestress member. I didn’t utilise the line beam, however, I was able to define my DL and SIDL loading using the load ‘Generate’ tool.
As part of the SIDL I included the Surfacing and other dead loads on my deck which I noticed you didn’t do as it acts on the full structure when its fully integral. I also modelled the live loading by transferring results from my grillage envelope analysis.
My question is regarding my prestress beam deflections results which shows a sag of -4mm after the dead load increment has been added to the stresses at transfer. Is it not best to utilise the construction stage results instead and add up my deflections at erection (after shrinkage/relaxation losses etc) to my DL loads deflection increment (weight of wet slab only) to work out the deflection prior to the deck being integral with the rest of the structure? After this I would then use my grillage results to work out deflections of the rest of the load cases (i.e surfacing/ traffic, etc) when fully composite with the rest of the deck?
I have assumed the SIDL and Live Load (LL) are crucial to the design stresses of the prestress beam, however, as the beam is composite with the rest of deck, the deflections should be taken from the grillage?
Any help, clarification would be much appreciated.
Hi there,
I am really sorry for the late reply.
I assumed that the superimposed dead load includes the surfacing.
As for live load, yes, I am intending to model them on the grillage first, so that it can be transferred to the beam, exactly as you said. 100%.
As for the deflection, I see what you are planning. If I understood your correctly, you are planning to say:
Deflection from construction + deflection from extra load due to erection (shrinkage, relaxation included) + deflection due to wet concrete
Then yes, I agree. This makes sense.
If you take the deflection from the grillage, you may run into the risk of misinterpreting your results.
What I mean by this is:
The beam itself (no composite action, wet slab) would have different deflection limits when compared to the full structure.
I think I will keep this point on my notes and have it covered later. It is a good point and your suggestion is gold.