Questions and discussion for this lecture live here. Fire away by hitting Reply below 
Hi Sean. Wanted some clarity on the beam in question here. The second illustration (the one with the c/c span dimension) provided at the start makes it seem like an interior continuous beam, rather than a simply supported one. What’s going on there?
I would also like some clarity on how you managed to calculate M1. Didn’t quite catch that part.
Thanks.
Unrelated question:
Hypothetically, if some heavy additional loading (telco equipment, for example) was meant to be fit to the terrace slab of an existing structure and you were tasked with assessing the structure to ascertain that it will be able to accommodate the load, how would you go about this? What would be the full scope of your analysis?
Assuming some additional reinforcement would be deemed necessary (for example provision of additional I beams), How would this be installed to the existing structure and what would be the eventual load transfer path?
Hope my question makes sense.
The top image is a side elevation (showing the beam as simply supported) - the image below is a section of the same beam.
M1 is what I refer to in lecture 30 at about 04:50 as Delta M - the change in moment between the point of zero moment and half way up to the point of max moment. So, on a simply supported beam, that’s the bending moment at the quarter point - you’ll work it out from simple statics.
S
If I was in that situation I would really hope to have access to the original certified design of the structure so I could have some confidence as to what reinforcement was provided. I may even opt to do some exploratory testing and break out some of the slab to confirm the rebar.
Once I had an idea of the actual rebar in the slab and understood the load path (how loads make it from the surface of the slab all the way down to the foundations, I’d assess the new load against the reserve capacity.
If additional I-beams were required, I would analyse these working in parallel with the slab since the new load will be shared in proportion to the relative stiffnesses of the existing flexural member (the slab) and the new beams.
Not a very straightforward analysis but an interesting one to get your teeth into.
S