Hey everyone. I'm working on a method to optimise rebar usage on site using a structural model, but I think i've hit a wall with what revit can do out of the box and I can use some advice.
But first a little background. I've got a structural model full of rebar for which i've created a few schedules. The model has been split up into different levels and zones for ease of scheduling and planning. So the sequence of work on site would be Level 1 Zone 1, then L1-Z2, L1-Z3, L2-Z1, L2-Z2, etc. Every structural component from slab to beam to the rebar within is assigned to a zone parameter under identity data. It's also important to note that our manufacturer only supplies lengths of 12m for all bar types so we have to do our own cutting and bending on-site.
We have 4 main goals that we are trying to achieve with using these schedules.
First we have a purchasing schedule. This will determine the total length needed for each bar type in each zone. From this we can calculate how many bars we need to order with a simple formula (Total Bar length/12000mm) and pass it onto the QS team for costing.
Secondly, we have a fabrication schedule. This one has all the bar types, shapes, bending diameters, angles and dimensions needed to cut and bend our bars on site. First we had to go through the model and readjust all the bars to reflect the max length of 12m, adding extra bars with included lap lengths where required. For the other bars where the length is less than 12m, we have a calculated parameter that tells us the cut off length (12000mm - Bar Length). From these quantities our workers can fabricate the rebar much faster.
Thirdly, i've created a waste schedule. For each bar type, i've identified the smallest length in the model (E.g. 300mm for T10). So every cut off length less than 300mm = waste length. This way I can calculate the total waste for each bar type and send it to a recycler.
The last part i'm working on is the actual optimisation. When one zone gets completed, I want to identify where all the cut off lengths we have left over can be used for new bars in the next zone. For example, we have ten bars of T12's cut to a length of 7m, therefore we have ten 5 meter lengths left. Say in the next zone I have various areas requiring 4 meter lengths of T12's. They might be spread across 2 beams and a column.
- What parameters do I need to add to each bar to make this optimisation work?
- How do I link the cut off lengths from the previous zone to elements in the next zone? If I start off with a basic formula like if Cut Off Length Bar A > Bar Length B then.... then what?
- Is there a way to spread those cut off lengths into various other elements? So going back to that example, four of the 5 meter lengths will be used in one beam, another four in another beam and the last two in a column. How do you go about making that information presentable in the schedule?
- After these cut offs are used, there's still going to be another 1m cut off left of each bar. Can the process be repeated again and again until the cut off length = waste length?
- As the project progresses, i'm expecting the minimum lengths for each rebar type to change which will affect the calculations in the waste schedule. As I begin to mark components as complete, will the values of in all these formulas and schedules update automatically?
- After a cut off length is reused, it should no longer be available for use again in the zone after that. How do I take these lengths off the table? Do I just mark the component as complete and let everything update?
The main challenge i'm up against is that i'm dealing with cut off lengths i.e. bars that don't physically exist yet in the model, but are just represented by numbers and formulas in a schedule. I think I might be reaching the limits of what can be communicated in a revit schedule and frankly i'm starting to confuse myself. Are there plugins or dynamo scripts available that can achieve the optimisation i'm looking for? I've been learning the basics of Dynamo since the start of the year and i've successfully created some scripts that were able to implement the zoning for me. What if I exported the schedule into Excel and continued on there?
I can't be the first person who's thought of doing something like this so I would really appreciate any ideas or solutions anyone has to offer. Thanks in advance!
