Topic Thread

  • 1.  Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-07-2022 04:57 PM
    Following a discussion on wind loads, I was reminded of the early stages of my education/career and how I viewed ASCE 7 "Minimum Design Loads for Buildings and Other Structures". ASCE 7 reminds us throughout the text with the use of the terms "Minimum", "Basic", and "In the absence of ...", that there is or may be more to consider.

    There is a difference between assessing an existing structure and designing a new structure. For an existing structure, the minimum load and design requirements are great for checking to ensure that is "Adequate for the minimum". For designing a new structure or renovating an existing structure, the more questions you ask the stakeholders and end-users, the better.

    Of course, minimum design loads and requirements are most often directly related or proportional to time, cost, and weight; however, they may also be inversely proportional to performance. For example, the plans for the renovation and the addition to a martial arts building undoubtedly addressed the minimum requirements of the local and statewide building code (including ASCE 7), as a structural engineer and a member of the dojang, I realized, rather quickly, that it clearly did not address the noise and vibration associated with the activity (running, jumping and yelling) on a floor above.

    Did the designer ask questions? Did they miss the clue that it was a martial arts building in the drawing title? Was the potential cost increase too much for the owner? Did the designers miss information during the site visit? Did the individual performing the design perform the site visit?

    My questions when designing any type of structure include how, what, when, where and why. Once had a project manager deem a load case associated with machinery failure to be excessive when the machinery was constantly failing. I am quite sure I do not get it right all the time, but I strive to provide sound engineering judgement based on having contemplated the specifics of the project. I want my failings to be on the conservative side of analysis and not associated with the structure or structural elements.

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    James Williams P.E., M.ASCE
    Principal/Owner
    POA&M Structural Engineering, PLC
    Yorktown, VA
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  • 2.  RE: Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-08-2022 10:14 AM
    You make a great observation and pose some great questions. I also applaud your approach, i.e. asking how, what, when, where and why. This is also tantamount in my view to understanding and elucidating value - or what's important. You and others might be interested in the article that recently ran in Source on decision making. Having clear values and tradeoffs are essential if one is to take a good decision.

    Minimum standards also make me think about residential design practice to mitigate flooding. For example, the City of Houston (where I live) post Harvey requires that all new residential structures be at least 2 feet above the 500-year floodplain elevation. This is a minimum requirement and what developers and most homeowners would build to. However, what if the floodplain maps are wrong or are at risk of being made obsolete by adjacent development? If I were building a home - and a top value was to avoid structural flooding - I would take a cue from safety and design for ALARP (As Low as Reasonably Practicable). This would entail looking at the incremental cost of building above the minimum and finding a happy medium between additional elevation and not blowing up the foundation cost. ALARP in this case is As High as Reasonably Practicable.


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    Mitch Winkler P.E., M.ASCE
    Houston, TX
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  • 3.  RE: Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-09-2022 10:05 AM
    I will have to check out the article. I still use the approach taught in school that starts with "Defining the Problem". It was the start of every homework assignment & problem in several classes.

    I like the thought of AHARP when paired with common sense. Flood Hazards remain a challenge given the ever changing environment including ground and sea. I took the online ASCE course "Flood Design for a Changing Climate" back in 2019 using my membership credit (Thank you ASCE). I spent a lot of time studying the FIS (Flood Insurance Study), sea level rise (SLR) and ground subsidence for a client looking to raise their home. I used a variety of systems to view SLR data. One of which gave me a variety of scenarios where you could control level of rise or year (i.e., 2020, 2040, 2060). Of course, the county had their own freeboard or factor of safety which seemed to cover the SLR and ground subsidence. More studying and more questions. I believe we settled on a time frame the clients were comfortable with.

    If I recall correctly, in one area of Virginia the houses were raised to the level required by local code and FEMA only to see new guidance years later that place them below the revised Base Flood Elevation (BFE). My understanding was that this created a challenge when trying to sell the houses. My initial solution was that in lieu of stating that a home does not meet code requirements simply identify the Flood Hazard MRI (10-year, 30-year, 50-year, 100-year or 500 -year) or Annual Probability (10%, 3%, 2%, 1%  or 0.2%) for the home and let the home buyer decide.


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    James Williams P.E., M.ASCE
    Principal/Owner
    POA&M Structural Engineering, PLC
    Yorktown, VA
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  • 4.  RE: Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-11-2022 09:14 AM
    The engineer is only one stakeholder in the design. Other stake holders include: building officials, architects, owners, contractors, and most notably the insurer.  Depending on the project, these voices may be strong or week.  I have designed rails and partitions for dance studios in the past... simple right?  Well the floor slab was isolated with springs and the services of an acoustic engineer were enlisted.  The budget and expertise was available for the project based on the owner's position - a major university.  Seeing how the local dojang does not have these sort of resources... there are likely more economical ways like a thick slab on grade that could achieve the same results.  In the case you describe the engineer fulfilled the job specifications, but did the other stakeholders participate?  Does the engineer have the duty to speak up on responsibilities outside their scope?

    Is this an environmental concern or serviceability concern?  Serviceability is not always dictated by the code, but it could be by the owner.  The owner received the services as requested in the contract.  In some cases the serviceability is limited by the architectural design or constructability which the owner may prioritize at their own discretion.  Noise levels may be limited by local ordinances... beyond that, what is the engineer expected to achieve?

    I don't know that this a shortfall of the code or application of it, but poor design can often be attributed to too much specialization of the parties involved.  Each contributor is responsible for their own part of the project, but no one is responsible for overseeing the general function of the building.  As engineers, we may perform side work that is not submitted... the deflection and vibration may have been checked, but not owed to the owner.  Control of vibration was not requested and would have resulted in additional cost to all.  The engineer would be wise to address this concern with the owner.  As the owner may not understand the concept of serviceability and may seek to hold the engineer and contractor accountable regardless of the contract terms.  The owner may not have a concern, but patrons may.  All leads back to the definition of failure... which is harder to define than one may think.  If the patrons do not like to use the dojang, is that not a failure of the building?

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    Chad Morrison P.E., F.ASCE
    Professional Engineer
    Greenville RI
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  • 5.  RE: Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-11-2022 10:36 AM
    You make some great points. Picking up on your last point about failure, I think this an area that many too narrowly define. Failure is much more than structural failure. It's also more than meeting stated objectives. Failure includes not having an agreed set of objectives. For me, it comes back to proper Front End Loading and application of a proper decision making process. Here's a another great resource on this topic from the UK Government. The fact that many projects do not get it right is a failure to learn in my opinion.

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    Mitch Winkler P.E., M.ASCE
    Houston, TX
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  • 6.  RE: Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-11-2022 01:55 PM
    Chad, definitely agree regarding the importance of stakeholder input. As an engineering designer, I believe getting the input of the stakeholders is part of defining the design requirements. Building codes are "prescriptive" minimums. As most codes state, deviation from the code requires a design professional. In my opinion, one of the greatest challenges is getting folks to define the constraints, limits and/or criteria of their request or as some would say having folks identify what they do not or may not know. That is where consulting comes in.

    You raise an interesting question about an engineer's duty to speak up. While I cannot speak for others, if it is outside of my scope of work and I see or recognize an issue (not my preference), I provide written "opinion based" notification, particularly if it is an issue of safety. This, of course, gets into the importance of documenting the scope of work on products one may seal.

    Chad, when it comes to overseeing the general function of the building, does that not fall on the general contractor, project manager or architect?  You perception is probably my reality, on some projects I have been given a specific task and perform that duty only. Of course, I still ask questions.

    Speaking of outside the scope, it just reminds me of project where I was developing temporary slabs to support temporary safety scaffolding. In receiving the technical dwgs, I saw what I believed to be odd loading and an undesirable eccentricity at a joint of the temporary scaffolding. I raised the questions, had a few email exchanges and I let the issue go and went about designing a slab. Once I received any technical documents (field related) and view them for my specific purpose, I feel a responsibility or an obligation to provide feedback if I come across something interesting. If you have ever worked where your presence and silence may constitute any form of approval, you learn to speak up; even if just to say "I'm not sure about that", "Do I need to check that for your?" or "Is someone looking at that?". Because if something goes wrong, someone will undoubtedly say, "The engineer was just here, _(fill in the blank)___!". This of course leads to that whole issue E&O insurance companies raise of limiting what you photograph when on a site for liability purposes. [Sorry if this reply has devolved. Blame it on lack of sleep.]


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    James Williams P.E., M.ASCE
    Principal/Owner
    POA&M Structural Engineering, PLC
    Yorktown, VA
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  • 7.  RE: Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-13-2022 11:22 AM
    You have done an excellent commentary James!! you bring to us some perspectives on "how experience might play a role in the field" (The Engineer/to/The Profession) Can AND Will help in order to "built a Strong Sense to deal with uncertainties to repair buildings" that sometimes we need to see to repair the real structure, get a vision and form better patterns to solve it, (today they are expanding this operations with drones/automotive process/ data..).  One of my experienced professors during CE Education in the field of: topography, remote sensing and aerophotogrammetry- once said: there is no perfect camera than the Human Eye. yet - maybe the same is with our minds [there is other machine so advanced as we are . . . (yet)]. Old structures maybe more sensitive because their lifetime span has already evolved, even more when failure occurs in recent years because the climate changes are accelerating the degradation of the redundancy regions compromised, so additional attention is required by the Engineer while Advanced Machines are not being use in every possible scenario.  Congratulations and thank you for your contribution , and for this insight!! Let's try to achieve the best results for the future, sharing our experiences!

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    Andre Newinski S.E., A.M.ASCE
    Engenheiro Estrutural
    AN
    Santo Angelo
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  • 8.  RE: Contemplating the terms "MINIMUM" and "BASIC" in ASCE 7's and other standards

    Posted 04-21-2022 02:20 PM
    Thank you Andre!

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    James Williams P.E., M.ASCE
    Principal/Owner
    POA&M Structural Engineering, PLC
    Yorktown, VA
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