Facade Structural Engineering

Today’s guest is Steven Sletten, a Licensed Professional Structural Engineer and Project Manager for Larson Engineering in New York. Steve has great experience in the Façade and Curtain Wall Industry and has licenses from New York and Minnesota states. Has been involved in many great projects such as Transbay Transit Center, the Star Statue at Mall of America, Lantern House on NYCs Highline, One Madison Ave in NYC and many more. Works for Larson, one of the biggest firms in the field with 11 offices across United States. Skyline: What are the important items in a Facade Structural Reports and where do you give the most attention?  Steven: There are many important aspects of a façade structural report that bear mentioning.  The most critical items that should never be overlooked or discounted, are those pertaining to design loads and applicable building codes/standards.  The codes used today are established to provide an appropriate level of safety factor, in order to ensures a design is safe.  There are aspects of the design and engineering that can be up to the engineer’s judgment, however the minimum standard of care should always be to meet or exceed load/building code requirements. The second most important aspect, in my opinion, is providing an efficient design that will meet the project specifications.  This includes working closely with the client (fabricator/glazier/etc) to determine any project specific design criteria or specification requirements, including serviceability limit states, that may impact the design. These are important as they impact the clients’ bottom line, as well as owner satisfaction with the end product.  If specifications are not met, there is potential for the owner rejection resulting in rework or potential back charges to the client. The engineer’s goal should be to have an efficient design.  The project may have high corner zone wind pressures, but may only occur on a small percentage of the building.  It may be possible to get by with reinforcing system(s) only in corner wind regions, or maybe the loading is high enough in all regions, such that a change to the system extrusions/depths is warranted. Additional engineering time spent may be well worth the effort in order to provide the most efficient design for the client. Considering the additional cost of labor and material resulting from an excessively conservative or quick engineering design, may far exceed the cost associated with a more thorough engineering design. Each aspect of the overall design, should be reviewed with respect to the project specifications, applicable codes, and consideration for both the engineering and client budget. Skyline: Are the specifications and wind loads getting over-designed? Steven: Wind and code loadings are an ever-changing topic in the structural engineering industry. As more testing is executed, and more information is learned by the code agencies, the more accurate the resulting requirements become. This is paired in the facade industry with the need to be as efficient in design as possible.  These factors combined have led to our current codes and results in wind loads being dependent on many project specific factors, including but not limited to:  project profile (Manhattan skyscraper versus two-story building in Iowa), project complexity (unique building footprint vs box building), project location (Suburban area in Pennsylvania vs the coast line of Florida), applicable building codes for the project location, and also overall building design/construction. Typically, if a project is a low profile, simple building, the design wind loading for the project, likely wouldn’t be much different from older to newer codes much from older building codes. Skyline: What software you use for Facade Structural Reports? Steven: Wind and code loadings are an ever-changing topic in the structural engineering industry. As more testing is executed, and more information is learned by the code agencies, the more accurate the resulting requirements become. This varies within in the industry, but typical software includes: – Mathcad or similar engineering math software which is used in the creation of many calculation templates. – Use of Microsoft excel sheets, can be used in similar fashion, but may not be as friendly to the reviewer. – RISA or other similar 2D/3D structural analysis software. – RFEM or other Finite Element Analysis software. – AutoCAD or similar drafting software. – Bluebeam Revu or similar pdf editing software. Depending on your firm / expertise, you may have other complimentary software as well, used to support thermal analysis, acoustic analysis, etc. Skyline: What is the typical academic background for a Facade Structural Engineer? Steven: It is standard that a Facade Structural Engineer will have at minimum a Bachelor’s degree in Civil Engineering – Structural emphasis.  It is also common for some firms to require a Master’s degree. Most engineers will have completed and passed the EIT exam, either prior to starting full-time, or during their first years as an engineer.  Most engineers will go on to take either the PE or SE exams for their respective state, and other states as required for the company/position. Skyline: What is the most challenging project you have worked and why? Steven: The most challenging project so far in my career, was a façade replacement for a high rise in New York City.  Due to damage on a portion of the elevation high up on the building, there was a need to remove and replace multiple bays of curtain wall system in an occupied building. The project was a testament to collaboration, as there were no drawings provided from the building owner, and also required to get an exact match to the adjacent existing curtain wall.  Careful consideration for site access and safety was maintained throughout the project, and the final product met all project requirements.  To this day, an unknowing eye, will most likely not be able to see that anything had been replaced. Overall, it was an exciting and challenging experience, as we spent more time than normal coordinating directly with members of the design team, the project building envelope consultant, and also a contracted façade designer that aided in all of

Today we have the honour to host in our blog John L. Wheaton, CEO and Co-Founder of Wheaton & Sprague Engineering in Ohio. John is a legendary figure in facade industry, having engineered, consulted or directed on thousands of exterior cladding projects.  Including custom and standard curtain-wall systems, panel systems, stone facades, architectural components and most other types of exterior wall systems across United States and Caribbean. He is Structural Engineer by discipline and Professional Engineer in multiple States. Additionally, John is the host of the fabulous podcast Creating Structures (https://creatingstructure.buzzsprout.com/) featuring interviews and discussions about life, business, architecture, construction and more. The podcast is available on all favorite podcasting platforms, I personally prefer to listen it through Apple podcasts. Skyline: John, you are in this business for almost 40 years now. During this period, we have experienced 5 or 6 downward economic cycles. What is the relation of construction cycles relative to those in general economy? JLW: In our space we are at the tail of recession cycles. It’s seen first in retail, consumer goods, and similar, then other things downstream like home purchases, new home construction, then on and on until it hits the commercial construction space. We have long lead times to assess and monitor what is happening in the markets by being at the tail end of the downturns, typically. Through the process it’s expressed in fewer RFP’s, more competition, less work over time. We typically have been 12 months to 18 months behind, since many projects, once started, have to go to completion. This isn’t always the case, since all cycles of downturn are unique, but construction and specialty subcontracting is at the back end however long it takes to get there. Skyline: Many of the businesses in our field are family ownership and management. How do you see the performance of those businesses over time. JLW: The truth is that most business are privately held in general. All privately held businesses are “family businesses” (private money put up by someone that is at risk). My view is that it runs from poorly managed to well managed depending on may factors. Privately held “family” businesses, whether simply financed by private ownership with a management team or owned and operated by private ownership with a management team supporting, can be well managed or poorly managed. It depends on the level of function or dysfunction in the leadership. All companies rise and fall on the strength of ownership, and how they think, conduct, operate, finance. Skyline: Do you predict that the use of Revit will replace traditional AutoCAD in the near future. JLW: I am not big on predictions, but I have been both in the forefront and the backend of this question about the shift to REVIT. The question is broad and the answer depends on what context we work within. REVIT has been and is replacing traditional AutoCAD at many architecture companies. However, it will not replace AutoCAD in near future in the glass, glazing, façade, curtain wall space. Professional services firms, contract glazing companies, and architectural fabricators all use their own approaches. I know some that use RHINO, some AutoCAD, some REVIT in part or in full, and some INVENTOR. Some use a combination of all or part of them. It just varies based on the application, people, training, processes, and other factors. No one software fits all applications. They are all just “tools in the toolbox.” Skyline: We see lately bigger and bigger openings in buildings, let it be cladding panels or glazing. What challenges does this imply for structural engineers?  JLW: Bigger openings, taller, wider, panel, glass, infill, cladding materials, just make more opportunity for structural engineers to help support and inform the process. The challenges can lie in various areas on how it influences required system depths, anchorages, connections, and performance criteria of the “panel” itself. Some clients don’t think through the cause-effect relationship of how the bigger opening or cladding material may affect the framing that supports it. I like that things are “pushing the envelope” with ever increasing measure and exploring the limits of materials. It creates opportunity and value for those brave enough to step into it. Skyline: What is the real value of PE stamp for engineering. JLW: Well many may be surprised to hear me, as a professional engineer (PE), say this but there is no intrinsic value to the PE stamp alone, but in the knowledge, approach and integrity of the PE overseeing or executing the work. Fundamentally, the PE stamp is supposed to have value to a project in validating that the work is engineered according to the appropriate standard of care, performance criteria for the systems, and for the benefit of the health and welfare of the occupants, public or users. There should be a strong risk mitigation component that brings confidence to the client and all constituents that engage touch or use the building or systems supported by the PE stamp. But the PE stamp is only as good as the PE behind it. PE’s do much to make the world a better place, much of which is not recognized. Approached properly, a client should receive not only the peace of mind that the PE’s stamp certifies the integrity of the system, but that they also provide client-centered or client-specific value that is expressed in the cost-to-value ratio. This can be manifested in various ways such as material or labor optimization, simplifying design, reducing complexity, communicating clearly, and more. Skyline: What is a project that you really feel proud of? JLW: I feel proud of every project we do and complete. Some notable projects include University of Baltimore Law Library in Baltimore, MD, Rainier Square in Seattle, AJ Celebreze Courthouse in Cleveland, Ohio, University of South Florida Judy Genshaft Honors Building in Tampa, Florida, the RUFUS (Amazon) HQ buildings in Seattle, and many, many others across the USA and in the Caribbean.