A Unique New-Build Family Home: Advanced Structural Engineering Workflows

MARTYN SHEARD: Hello, everyone. Thank you for joining our presentation today. And we're going to be presenting a case study of what we regard as a unique new-build family home, and we're going to be talking about the structural engineering workflows that we use to deliver it.

So here's a brief overview of what we'll be talking about today. As I mentioned before, this is a case study on a project that we've been working on over the last two years. And we have an image of it in the top left here. It's a single family custom built residential project on Martha's Vineyard in Massachusetts, USA. And we'll be getting a little more into that.

And just to continue the overview going clockwise here in the top right. We're going to be diving into the workflow that we use through this project, going into a little bit of detail on the various tools we used, how we link them together, and the benefits of doing so, continuing around in the bottom right, this is the real sort of focus of this project, which is the connection design, so the sort of culmination of the workflow that I just mentioned ended up with us arriving at these custom pretty special timber hybrid steel connections. And in unison with that and continuing around the bottom left, you'll see the IDEA StatiCa logo. So the guys at IDEA StatiCa have worked with us very closely on this throughout various stages of the project assisted as in using their software in some non-standard atypical ways. So we're very grateful to them for that.

Let's move on. And a little bit about ourselves to start with, we are craft engineering studio. My name is Martin Sheard. I'm a senior project engineer here, and I'm presenting today with my colleague Trevor, who introduced himself in a moment. And a little bit about the studio, we are a specialist structural engineering, design consultancy. We are based in New York City. We also have additional national and international offices, which we'll explain a little bit about in a moment.

And we are a 14-person studio all with a common thread in structural engineering. But we also draw upon sort of diverse backgrounds from architecture, mechanical engineering, elements of product design. And we were able to use these tools and apply them to disrupt the traditional notion of what structural engineering means and how that can feed into the delivery of projects. We have three main areas of focus, which are architecture-- in addition to that, we get very involved with specialist fabrication, so everything from custom staircases to furniture and other kinds of installations.

And then the third route that we follow is in art and sculpture. And the images on the right here hopefully give you an indication of that, OK. So as I said, Martin Sheard, Senior Project Engineer. I'm originally from the UK. I have been over in New York getting on for 3 and 1/2 years now. And I will ask very briefly to Trevor to provide an introduction.

TREVOR CHOU: Hi, everyone. My name is Trevor originally from Taiwan. I started working mostly in New York City for Craft as a project engineer.

MARTYN SHEARD: OK. And let's move on. Great. And then the final point of introduction about our practice, as I said, we're based in New York City. We also have a Boulder, Colorado office and now have an office in Athens, Greece, with a view to expanding that number as well as we go forward.

Our main practice where the majority of us are based is shown in the bottom right, which is our space in Manhattan, in New York as is hopefully obvious from that. And we're very keen on transparency, openness, collaboration, which we apply to our own internal practices as well as those external and how we approach our work. And as you can see from the other images when we're not in the studio, we like to get out on sites. We like to be meeting people. We like to really get under the skin of projects, understand how things are put together and constructed.

So, yeah, that's a little bit about us. And if we move on-- and so further to the point I mentioned before, we've worked very closely with the team at IDEA StatiCa on this project throughout. They've been a great resource and help on this. They also pushed us or encouraged us I should say to enter the engineering excellence awards, which we're very happy to say that we actually won in the category of small scale structures, which was an amazing accolade.

And we're very honored to be able to be presented with that. And they also suggested to us that we put together this presentation, which we're sharing with you today. So many thanks to the team there, very grateful.

OK. And so that was the intro, and we'll get into a bit more of the detail of the actual project itself. So as, I think, I briefly mentioned, a project that we're looking at or have looked at over the last two years is on the island of Martha's Vineyard in Massachusetts in the Northeast of the USA.

As you can see from the images on the left, it's one of the two major islands off of Massachusetts here, the other being Nantucket. The image to the right is our Revit model of all of the structure that we've modeled on the site in general. You can see made out here three main buildings, the main building in the lower right being the main house, which is the focus of this presentation.

But just for everyone's info, we also have a pool house to the top, a garage studio to the bottom left. And they're all linked by a custom designed hardwood timber pergola. We've been involved as the engineer of record throughout the process and for all structural design.

A key feature I'll draw your attention to although it's probably apparent is the steep and significantly high bluff, which you can see on the bottom right here. And you can see that there's this major elevation to the main house, which looks over the bluff down onto the ocean below, which is down at the lower level. And we'll come back to that aspect as it's had a significant impact on the design approach.

So if we move forward-- so we have been working very closely with Selldorf Architects throughout this process. I think the major aspect I want to draw people's attention to here-- and this is specifically the main house as I mentioned in the last slide. So the image in the top right here, which is very nice render from Selldorf--

I think one of the major aspects you can pick out here is the soft story in the lowest story for the full width of this building. You can see that there's an enormous amount of glass in here. You also have sliding doors. And one of the cruxes this is we've got no opportunities for sheer walls, also no opportunities for any kind of steel bracing.

And as you can also see from the render on the left, which gives us this beautiful, unobstructed view out onto the ocean, I think you can just make out a mass of yacht just poking over the horizon or down the bluff I should say. So that's been a major design driver from the architects throughout to have this completely unobstructed soft story, we'll call it from the structural perspective on this ocean side. And another aspect I'll just pick out is cantilevered balcony, second floor, which is also facing onto us as we look at this image on the top right.

This went through various design iterations, you can see from the render on the left, which is an old render that actually had an edge beam, which you might be able to make out there. That element was emitted as we went through the design process and we went through various stages to try and slim that balcony down as much as possible. So, yeah, that would be a good overview of the architecture.

And then to jump into our response to that in terms of a structural overview-- so the image on the top left, sort of a repeat of our structural Revit model for all of these buildings. You can see pretty traditional standard concrete substructures, single story basement on the main house and also on the poolhouse at the top and just frost walls for the garage. There's a few images here given to just indicate the kind of iterations that we typically go through and have very much made use of in this process with Selldorf to try and auctioneer, come up with alternatives, vet things out.

The images to the top right and bottom left are hopefully pretty typical of the level of detail that we like to get into at a very early stage so that all the implications of these decisions are understood. And, yeah, I would say, I think one of the big themes behind this project, which is pretty apparent from the image on the top left, is one of wood, quite obviously. We've tried for a variety of reasons to utilize the use of wood framing as far as possible for this project in general.

And that came from a number of drivers, one of which was the sustainability aspects of wanting to distill the project as much as possible. Another, it was more of a sort of philosophical stance from the client and architect of wanting this building to be in keeping with its neighbors and in keeping with more traditional building techniques, which are typical of the island and of this part of the states. I guess the final one being purely practical is one of the fact that we are simply on an island.

And so the ability to bring in large heavy steel sections to have those fabricated chopped and changed is limited. So as a result of those three drivers, three levers if you like, we've designed this entire structure as one of lumber. So engineered lumber, elements of glulam, and then traditional simple wood framing as far as possible.

The aspect that Trevor will really dive into, which is in connection with the point I was saying before about the soft story to the main house is that maybe the traditional approach to that would be to do that in steel. And certainly that was our initial take on it when we started looking at this project. And so when we get into the bones of this, Trevor will take you through how we were able to adapt that turn it into an all wood system. So I will now pass you over to Trevor. And I'll jump back in just towards the end to wrap up. So thank you.

TREVOR CHOU: All right, thank you, Martin. So next we'll be talking about the workflow of this project. So I think this diagram the full story of the workflow of this project, which shows the great communication between various kinds of software and how easily we can transfer different file types throughout each softwares. And I'll be going step by step [INAUDIBLE] in the following slides.

So starting with the first step, typically at Craft, we usually start building our Revit model based on the Revit model provided by the architect. However, Selldorf Architects, which is the architect for this project mainly worked in AutoCAD environment. So we had to come up with a typical solution for creating all geometry. And there is a feature called external reference in AutoCAD, which essentially will do-- is to create a container file. Then you can link all the different kinds of CAD drawings into it.

And as you can see in the diagram, on the right hand side, it kind of creates a semi-3D model in CAD. And one of the advantage of doing so is that you can then upload this file to Revit model as only one file because the traditional way to do it might be linking drawings into a specific view in Revit, which is going to take a lot of time by doing so. So I think this X ramps features in AutoCAD really help us to save a lot more time as a project process.

And it also helps us throughout the design information. Maybe a beam needs to be relocated. Or anything that changes in the background, we can easily just be updated the link in the [INAUDIBLE] powder and then hit the reload link and the Revit model, and the background will be automatically updated in our backgrounds, which is very handy for our project.

Next, we'll be talking about the MP coordination. So we also work very closely with the engineers on this project mostly through the Autodesk Construction Cloud, which is formally known as BIM 360. So it kind of creates a really nice platform for us to share our model to that platform. And we can easily review if there's any clashes between the ductwork or pipeline with our structure framings, no matter it's an excellent view or 3D view or plan.

And we can also issue design packages to switch essentially, just issue drawings to the other team. And they can also do the same process to review if anything comes out at hand and needs to be notified. If we follow the traditional way, which is issue official drawings and then review it on a computer without sharing a model, that could take us-- I don't know-- a lot of time, more than once than we expected. So I'll say BIM 360 really creates a really nice platform for us to review all the MEP coordinations.

Moving to the next slide, we'll be talking about the analysis overview of this project. So as Martin mentioned before, the design of the moment frame, which is the anterolateral system of the main house, is quite challenging because from the architecture standpoint, they want to assure open space and an uninterrupted space throughout the balcony and that resulting in a soft story at the first floor. And by looking at this initially, we think still might be the perfect solution because it has to take a lot of forces, not to mention the lateral force coming from the window.

And, however, the architect was trying to keep the harmony with the surroundings by using a wood solution. So we then turn to engineering wood members for our design. So in this diagram, you can see we imported the Revit model into Robot Analysis software. And one thing I do want to mention throughout this process is they really crazily smooth geometry transition.

So they save us time to try to recreate the geometries and define loadings in Robot Analysis, which is very handy because as you may know throughout the project process, there's going to be a lot of design integration, design changes. We shifted that column or anywhere. And it's really helpful to have this outlet that you can just instantly update the geometry in different software. And one thing to mention, you can also update geometry through Robot, which is very hand to us.

Moving on to the next slide, we'll be jumping into the actual framing design. But just to mention a bit more on the moment frame, so the two story moment frame, in the span on the left hand side, it's 25 feet. And the span on the right hand side is 14 feet. So it's a really long span. And if you look at the force diagram on top left, you can see in the joint at the second floor, it's taking forces from all different kind of direction, which we think might be the focal point for our connection design.

So we then turn to IDEA StatiCa for connection design by using the link fixture developed by their team in Robot. So in this way, we can-- again, like saving the time for us to try to recreate the geometry and by boundary condition and internal forces and all that stuff. So we can just really focus in on time just to figure out what's the right solution for the connection itself.

And then, next we'll be talking about the actual connection design. So as I previously mentioned, the force is quite large at the steel point. So we turn to a steel joint solution. At the beginning, we're trying to think of we should put more like stiffness so that we can able to resist the load coming for all directions.

So we started with the whole section. If you can see the right image, which is the top view of the connection model, the whole section stands in the middle and then all the other framing members connected to the hub. However, when we try to do the analysis, the results gives us a really high stress concentration at the top and bottom of the whole section.

And we're trying to rethink the design because this is not really a really smooth transition. So we rethink the geometry of the steel heart to be more like a Y flat shape. As you can see from this diagram, the stress diagram makes more sense now because we carry off the high stress concentration at the top and bottom and now since the force transition direction is more straightforward-- so you don't see any hiccups in terms of geometry, sudden changes.

So the force we're able to transmit to other members-- and this is the final design for our connection. I'll be talking about things-- even though the connection was carried out in the IDEA StatiCa design, however, the software actually doesn't support the codified design for [INAUDIBLE] members. So we have came up with in-house especially for first moment force distribution for moment connection and also for cell type faster with connections.

And if you look at the diagram in the middle, try to visualize how the force being distributed throughout the moment connection. It's purely based on the central moment of inertia and then the distance between the center of the boat to the location where you apply the force. So generally speaking, the forces that's at far distance from the center of the force will experience that really high magnitude of forces as you can see in the diagram. So once we develop that kind of in house specialty, we then compare the result with the shear force output from IDEA StatiCa to verify our calculation and also to finalize our connection design.

And this is my favorite site. It's just shows you how model become reality. And if you look at the diagram on the left hand side, we actually went back into Revit to try to recreate the geometry up there of the connection and create some really nice rendering. And looking at those two images on the right hand side, this first one at the top is the visualization of the steel joint.

We've started modeling and analyzing it in the software, and what it looks like on site-- it's really exciting. And the bottom there is the full image of the real connection. You see this layout of the bow pattern. It's exciting because when you try to analyze it and you start wondering, oh, does this makes sense or anything? But once it comes to sight, it's just a nice image there.

MARTYN SHEARD: So that was a bit of a wrap up. I have some nice images here from the site, which have been taken over the past 6 to 9 months. The image in the top left was at the early days of construction of the main house. You can see this soft story going in with some temporary lateral shores on those members.

The image in the top right is a view on the underside of the cantilevered balcony, which was all done in a hardwood with exposed stainless joist hangers. The image on the bottom right, this main house at a much more advanced stage, this is a recent photo. Cantilevered balcony complete, all soft story framing, sorry, completes glazing in. And the image on the left is everything that we've been talking about. But you can see it in harmony in unison with the architectural finishes and the cladding.

Yeah, another point to add in here is that as previously mentioned, we're right on the ocean. It's a very aggressive environment from a corrosion perspective. So there were several hoops we had to jump through with designing any penetrations through the facade in steel. Lots of stainless has been used lots of hot bed galvanizing and lots of careful detailing and working with the architects in order to achieve that.

And another aspect to that is, of course, as soon as we penetrate through the facade, there's a thermal question. So another element to the connection that we've been describing to you is that it's actually firmly broken for the cantilever dimension, which has a thermal brake pad inserted into it, which essentially is hidden behind the cladding in these photos. So a few extra points there.

And if we move on-- so that's an overall summary of the process described. To begin with, we would say that the tools we've employed along with this workflow has resulted in a number of pretty significant benefits of this project, the first of which definitely being that we've been able to put forward a non-standard structural system. So we've been able to take a building typology that really lends itself to steel and being able to adapt that and offer to the client and design team as we said before something, something more in-keeping with traditional house construction on the island and not having to ask GCs to be bringing in huge steel sections in order to deal with those spans and with deal with this soft story.

The other aspect to this is the ability to iterate. So I think as we've alluded to in the early stages of this project, there were multiple feedback loops, both from ourselves and from the architect in order to arrive at where we were. So the image card onto the right there, which is that final round trip back, really was born out through this.

And it meant that when there were significant design changes, we were never back to the drawing board. We were only ever feeding information back into the process, which then made its way through again and ultimately resulted in the connection design that we've been describing. But, yeah, there are a number of alternate routes that were explored before we arrived at the final one.

Further aspect is just-- yeah, we'll keep going. Close collaboration with the other disciplines, the image and the bottom right hopefully being pretty typical of that. As we mentioned before, we worked very closely with the MEP engineer as well as the other consultants on this project to a point where we were essentially using what we regard as more commercial level workflows, I would say, and the kind of tools they were using, more typical of larger buildings. But we're applying them to a much smaller, residential context partly because it's required for this type of building. The architecture doesn't have any wriggle room really around the structure, if it's very tight to it.

As I said before, we don't have any opportunities for bracing or share walls. And also all of the MEP lived within the sandwich of the floors. We didn't have any ceiling zones anywhere. So that level of understanding of the requirements of the other disciplines and understanding what it means for our structure and how to put forward a solution that's going to work for those was almost entirely based on having this workflow.

And if we weren't working in 3D, we didn't make the use of BIM 360, I don't think we would ever have got there. So I think that sets us apart in this context from a lot of other people that would be approaching these kinds of projects, which I think is a valuable thing.

And the final point in summing up would definitely be that I think we're able, I would say, to push the boundaries of what you can do in traditional wood frame construction here. And another key point to note is that this building was schemed in several different ways, the final stage of that really was that all of the wood members on this oceanfront were going to be in glulam, so it's all going to be solid glulam.

That coincided with the heights of the pandemic, which meant that supply for those members was significantly restricted, made even worse by the fact that we were on an island. So we were able to pretty rapidly swap those out for more standard engineered lumber members such as LVLs, which we lag together into great depths. So, yeah, I think that's a pretty-- I think that typifies this approach really in that we're using bigger, more commercial, more major types of engineering approach but being able to apply them to a much smaller scale and being able to put forward drawings to a contractor that they can readily understand and know they can source.

So that would I say with the summary. And then as I look ahead where we would want to take this and where we plan to take this is-- for one thing we want to try and automate this workflow as much as possible. And we want to try and make sure that these feedback loops are as intelligent as they can be.

It's a slightly difficult thing on these projects because they are so custom. Every project is very different. They don't tend to have too many similarities to each other. But there are definitely common themes to them.

And so the little bits of friction that exist in the workflow right now are essentially between the softwares. This was also going back 18 months, two years now as well. So we know that there are tools in place which can help us with that.

So that's one point. Another is standardization of connection design. So whilst a lot of the projects we do are atypical, and there aren't all that many similarities, there's definitely a case for standardizing connection design that can then be rolled out into these other projects. And in the hope that on these other ones we can have that same message of being able to come in and say, we can take what was traditionally thought of as a steel frame and substitute out at least parts of it in a much more traditional low cost efficient way of doing things.

But to that, we would really make use of the interoperability tools between software. We may consider trying to script the interfaces between them with APIs. Again, slight difficulties because everyone's different. But there are definitely some similar threads to it. And I guess a final point on it as well, which is something of intense interest to us-- and I'd be very keen to hear from the community as well whether there are any developments that have been made on this but essentially a customizable timber connection design tool in FEA.

So where we're all sort of hoping to get to in the hopefully near future is a tool that is akin to IDEA StatiCa and has all the benefits of allowing you to be fully customizable and rapidly prototype different options. But they may not apply that to actual codified timber checks as well. SO that final step as Trevor mentioned, we had to come up with our own in-house spreadsheets in order to bridge that gap but hopefully in the not too distant future, maybe something native in the software, whether that's IDEA StatiCa or a third party. We'll wait and see. But, yeah, we'd be pretty excited about that. And fingers crossed we would love to be a part of trying to develop that as well. Thank you very much.

TREVOR CHOU: Thank you for listening.