Structural Steel Detailing N5

[Macedonio Heninger]

TheAISC Steel Solutions Center is proud to release our Structural Steel Dimensioning Tool. Your interactive one-stop-shop, either at your desk or on-the-go, for detailing dimensions for all rolled sections in the 2017 printing of the 15th Edition AISC Steel Construction Manual. For more great tools and resources to make your life easier when using steel, contact the AISC Steel Solutions Center.

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Steel detailing is extremely competitive, and with labor costs varying extensively across the world, some companies can afford to absorb "doing things twice for free" better than others. However, it doesn't matter whether you are in India, Thailand, Australia, Canada, Wyoming, or New York City, you make your money as a detailer based on the hours you work and making sure they come in under what you originally bid. Same as the architect and engineers that offer their services as the design team. So why does the industry expect detailing professionals to work more hours, on a compressed schedule, from late changes and information, without properly being compensated for the difference? How does this end up not only negatively impacting the steel contract, but the entire project?

Steel detailing is around 6% to 10% of the overall cost of the steel contract on a commercial construction project. However, I like to quote a vice president of a large fabricator in California,

Steel detailing is at the center of every step in the steel design, procurement, fabrication, and construction process. It is a process that provides "detailed" instructions, quantities, and organization of all the structural steel components in order to eliminate waste and ensure productivity in the shop and field where the big costs are. Spending an extra $1 in detailing, saves $9 dollars potentially being lost on the rest of the project.

When detailers estimate and price work, they price it based on a "single pass flow of work" assuming the design is complete and little to no RFI's could hold them up. A wise detailing manager once told me,

What often ends up happening though, is missing information or late stage designs can completely disrupt this single pass flow and cause detailing productivity to drop, schedules to be delayed, costs to shoot up, and detailers looking for change orders to help recoup. If they can't get those, they pull shortcuts on the job to stay alive which opens up risk downstream for the other 90% of the cost in the steel contract.

Like steel detailing, steel construction is also highly competitive. 5% savings here and there can mean the difference of winning a bid. A fabricator might take the lowest detailing price into bid without any extra to cover the changes that will inevitably come, so they can win the job. Some fabricators see detailing as an overhead vs. a value added service and want to eliminate it as much as possible. Some project managers get paid bonuses when they bring projects in under budget and reducing detailing, a variable cost they can somewhat dictate, is the first place they go.

When you strain the schedule and budget of a steel detailer, you force their focus away from de-risking your project to only how fast they can throw things together. When a detailer is reduced to just putting sticks in a model, matching connection values from design, and rapidly pumping out semi automated shop drawings without getting time to properly review them, here is what you are doing:

I am not just saying throw more money at detailing and everything will magically get better. There is bad inexperienced detailing out there. You definitely need to have a vetting process to find the good detailers and you should go out and get competitive prices. But instead of going to market looking for just the cheapest sub-contractor, look for good valued partners. Go to bat to get your partner's hours and services compensated for when there are legitimate changes or missing information that has impacted their budget. Also try to keep some extra in your budget to cover a good detailer when you know there are things that should be paid, even if you will have a hard time getting the contractor to understand.

Today most detailers use 3D modeling software which is a completely different process than 2D detailing. 2D drafting production was much more isolated to each drawing and some late dimensional or material changes had a smaller impact than it does in a 3D process. In 3D detailing, you are working with an interconnected database. Pieces connect to each other, and the system automatically compares parts and assemblies to identify marks and quantities ("Numbering"). A lot more information, deliverables, and value is digitally extracted from this 3D database vs 2D drawings. Most of this added value has been realized by the steel fabricator without a change in price from the steel detailer.

Notice how this is a lot like an assembly line. You are doing specialized operations in a specific order and the next step in the line adds more complexity and is building off of the work from the previous. Think about this in relation to the fabrication shop. Every time you have to send something backwards in the line because of a change or disruption, your labor, material, and handling costs not only go up for that piece, but it adds to the cost of the other pieces coming down the line. You won't put up with that without charging for a change, so neither can the detailer. This is why you see detailers put clauses like below in their contracts:

Let's create a base unit of 1 to measure the level of impact to a detailer when information or changes come at different stages of a project. At each stage, the same change can begin to have a greater impact. When you understand this, a good project manager can set expectations on information flow to the entire project team and can prevent sending the detailer down a rabbit hole of having to redo things more than once.

This is the fastest part of a job typically for the detailer. They are laying out grids, inputting beams and columns, and getting the job ready to submit an advance bill of material list ("ABM"). If design changes or RFI responses on dimensions, profile sizes, elevation changes come in at this stage, the detailer can often do this at no additional charge. The exceptions to that would be for extremely complex sloped / skewed framing or if the quantity of pieces on the project change over 3 to 5% as that will have an overall cost impact to connections and creating drawings.

The detailer might also justify a framing change order if the revised design isn't clearly clouded or marked up, and they have to do a full line by line estimate of the new set of design drawings compared to the old. This can be anywhere from an additional 4 hours to days if its a big job. I personally can get a lot of sticks modeled in 4 hours. The other thing that can kill detailers is if they have to process and submit ABM revisions for a "trickle" of multiple design framing changes. This is unproductive and increases detailing costs.

If the connections are clearly designed, the framing is fairly simple and perpendicular, the impact of changing a connection on the ends of a few beams is almost at the same scale as changing stick framing. The 3D detailing software automatically updates the connection to the changed framing and in some software automatically updates the design.

However, the same rule of quantity applies here, just like in framing. If you start changing the fundamental design of connections across the whole job after connections have been applied then you are getting into an impact scale of 1.5 to 2x+ framing level costs and will likely see a change order.

Skewed Framing, Elevation Changes, Bracing, and Moment Connections cost detailers the most time to change and check. This is especially true if they have to manually model them and the 3D detailing software's system components don't just automatically create or design the connections. So if you are a project manager on the job and you see a lot of complexity, its good to ask the detailer some questions about how much effort is involved in these and what kind of impact it would be if late changes or information comes in.

For example, a moment connection RFI with missing information that affects 40 connections on the job isn't answered until 1 week before Issue For Approval. They need to be manually modeled as the detailing software doesn't automatically do them. The detailer won't make the submittal. Those are high labor connections and they will have already needed to be in the drawing production stage at that point. If they still need to make the schedule, they will have to work overtime which wasn't in their budget, and they will start to rush through the checking. Expect a change order on this even though it isn't a design change. It's the impact of late information in a labor intense process. A smart detailer will try to hold off on guessing and modeling while the RFI is out because if they are wrong and they have to go back and fix it, they just lost a lot of hours that they can't come back to the fabricator for. This happens all the time.

Architectural features, safety and erection aids, or steel connection materials that interact with other trades are the most expensive thing to model and change. These items aren't as automatic as connections. They may only comprise 10-20% of the tonnage but they can be up to 40% of the modeling cost and they take more manual dimensioning on the drawings.

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