I don't know what it is but I swear woman are always the best teachers as they are more detailed and don't rush over material for us students. Just an observation 😮 . Thank you Tanya and God bless
How do you deal with load combinations that have both gravity loads and lateral loads? for example: 1.2D +1.0W + L + 0.5(Lr or S or R)? When designing your gravity resisting system, we would neglect the W in our calculations and then designing our lateral load resisiting system, we would only deal with the wind, correct?
Excellent explanation! Quick question how I add flood loads if the building will be designed to resist hydrostatic ,hydrodynamic and projectile? To which of the combinations. Thanks
Hello Tanya. Thank you very much for the fantastic video. I am a civil engineer in Europe and I am supposed to do a dimensioning of a facade mullion for a project in the USA. In Europe, the area moment of inertia of the mullion is determined from the allowable deflection. The deflection is calculated from the serviceability limit state (SLS) combinations. The section modulus, in turn, is calculated from the ultimate limit state combinations (ULS). Is there a standard that lists the serviceability combinations? Best regards and again, great videos.
In light of the anticipated advancements in artificial intelligence within the next couple of years, I am seeking your expert guidance on the strategic considerations associated with pursuing a Ph.D. in structural engineering. Given the potential integration of AI in design processes, what insights can you provide regarding the long-term relevance and opportunities for specialization within the field of structural engineering? Your professional perspective on the evolving landscape and the intersection of AI with structural engineering would be highly valued in informing my decision-making process. Thank you for your time and expertise
Sure. A few thoughts. First, keep in mind, existing generative AI models are trained on existing datasets. Someone involved in original research is by definition working outside of existing knowledge. For example, a PhD student might devote their work to designing, testing, and validating a new type of connection. But an AI would not be capable of that, as that connection has never existed before. AI can only churn out remixed copies of things that already exist; it can't make anything new. Another issue of completely replacing structural engineers with AI is that every structure is unique. You can't just copy the design of a structure intended for one location and paste it in some other location. Our existing AI models rely on huge sets of training data. You feed the whole public internet into a big training model and create ChatGPT out of it. You use that huge volume of text to teach the computer how to write. But it's hard to see how you would create such a dataset with structural design. You can't just feed a bunch of structural blueprints into an AI model and expect to train a structural engineer from that. Often beams or columns are at the location they are not because of mechanics, but because of the needs of the client. A column on a set of blueprints might be where it is because of some weird reason known only to the client. Or consider foundations. Foundations are designed to site soil conditions, and the location and design of columns are affected by this. Your site may have weak soils on just a part of it, or some soil you don't want to disturb, and this is reflected in the design drawings. But all that nuance is lost on a training model that is trying to derive all of structural engineering from just a set of plans. Really, I am not optimistic of generative AI replacing structural engineers any time soon. We already have software that can automate some functions of structural engineering in a limited, well-defined concept. For example, software exists that uses evolutionary algorithms to optimize the design of parts using stress analysis. It is not remotely possible today to feed an AI an architect's blueprints and a soil report and have it spit out a set of structural drawings. There simply isn't enough training data to capture all the permutations. And even if these get better, keep in mind that the demand for engineers and architects is not a fixed quantity. For example, today in the US, only the most expensive homes are custom designed by architects. Most people buy mass produced tract homes. For most, the first step in buying a new house is not contacting an architect. Most just go buy a tract home. But what if the architecture and structural engineering could be automated enough to lower the cost of those services? What if an architect can design a house in 1/10th the time, and a structural engineer can design the structure in 1/10th the time? They could cut the price they charge accordingly. Suddenly, the amount of people who can afford such services increases. The artistically designed custom home goes from being a luxury of the wealthy to the norm everyone can afford. I look to history, and the example I think of is clothing. In the early industrial revolution, people were poor and typically only owned 2-3 outfits that they likely handmade themselves. With automation, people worried that we wouldn't need weavers anymore. In the end, the demand for weavers actually went up. Instead of owning only a handful of outfits, people now own entire walk-in closets full of clothes. Instead of wearing the same outfit for weeks at a time, many wear multiple outfits in a single day. Technology made it easier to make clothes, but that also meant people could buy more of them. That's the perspective to keep in mind in discussions about tech-related job losses. Yes, technology will automate some of the services that structural engineers currently do. But in turn, structural engineers will be able to do more jobs in a day and will be able to charge less for each job. More people will be able to afford the services of structural engineers, and we all end up better off for it. Now, in theory, sure, you could imagine a computer far better than any bot that exists today. You can imagine a truly general artificial intelligence that can communicate with clients, operate some robot drone that can perform site visits, and monitor construction progress. But to truly replace everything a structural engineer does, you would need to have software that can literally do everything a human can. And even if you have a computer that is fully as intelligent and capable as a person, I still don't think the profession is doomed. Even if you've can mass produce Lt. Commander Data, I don't think the structural engineering profession is doomed. Why? Because I would argue that a machine that is fully capable of performing every task that a human can, that can do so in a way that is indistinguishable from a person, that can operate in our society like any other person...simply IS a person. An AI that advanced likely has its own thoughts, desires, and goals. At that point, you really have to start worrying about the ethics of forcing such entities to do your bidding. In short, if your computer is so advanced that it can completely replace a structural engineer, forcing that computer to work for you is probably slavery at that point. And we really shouldn't be creating a slave race of intelligent robots. Read either a sci fi or a history book to learn how that ends. And if you need to pay the new structural engineer AI you just created, there's no reason to create that AI in the first place. You might as well just hire an actual human.
My smooth brain thinks that for load combo #5, D should be the dead load of the roof only and not of the entire building since the only weight that's counteracting the roof blowing off is the weight of the roof. Can you please explain why I'm wrong? Thanks!
Sorry for the question, still a bit confused. ASCE 7-10 and 16 gives FACTORED Wind speeds which gives factored wind pressures. If I’m designing a masonry curtain wall (cladding), this means I should NOT use ASD load combinations? But if I’m checking a roof membrane capacity, then I CAN use ASD? What about for components, such as roof purlins, also no ASD? Should we match ASD/LRFD load combinations with ASD/LRFD methods for steel/masonry design or should this NOT matter? Thank you.
If ASCE 7 shows that the wind speeds they are using is factored, then an ASD equivalent should be provided based on a factor (in IBC, I remember seeing sqrt(.6), but a similar factor might be in ASCE as well). If that’s the case, I would use the final wind pressure calculated with Vasd in the asd load combos if that’s needed.
Interesting approach, but the idea that LC 5 (ASD) and 7 (LRFD) are accounting for vertical forces is completely wrong. If you look at the first building code requirements from 1945 (ASA 58.1-1945), you can see that there were no established combinations, but there was a requirement for the overturning moment due to wind shall not be more than 66% (2/3) of the moment of stability (5-9.a). This is the origin of the infamous 1.5 overturning factor requirement that is often incorrectly applied today. In later ASCE 7 editions, this requirement was baked into specific load combinations for both ASD and LRFD. in ASCE 7-05 which implemented allowable level wind, we has 0.6D+1.0W. Later on these load combinations were adjusted to account for ultimate level wind, but the purpose of the combination remained the same. If you dig into both wind and seismic chapters, you will find detailed considerations for vertical forces and or uplift that must be considered during the design. For seismic there are even additional load combinations.
If case 7 in LRFD, 0.9D is reducing Dead due to vertical loads, why include Ev in the combination. Why doesn't case 5 have a Wv load in the combination? I was under the impression that a reduced Dead load accounts for the opposite of case 1, over estimated dead loads. These cases are overturning cases where the dead load is overestimated and the horizontal loads are at full capacity. These cases produce an overturning factor of 1.5. If under estimated loads are possible, then overestimated loads are also most certainly possible. For me it doesn't make sense that 0.9 is intended to account for vertical loads. It just doesn't add up. There is still judgment needed when applying loads, the load cases are not intended to be blindly applied.
Uplift is an interesting case. Imagine a simple structure, say a pergola or a simple rectangular frame. Normally the columns carry a downward load. The weight of the columns and the structure above is added to the external loads. To add some margin of safety, you would want to overestimate your dead load, for example by designing for 1.2D. But what about uplift? Now the columns of that structure are being put into tension. Maybe there's a large wind over the structure generating a huge upward force on it. But how does gravity relate to this uplift? Think about the relative directions. Uplift wants to pull the structure into the air. Gravity meanwhile is still acting as it always does, pulling the structure downward. In this case, gravity is acting in opposition to the applied force. If the columns are in tension, the dead load will actually be decreasing the maximum tension on the columns. In other words, in the case of uplift, dead load will actually HELP you, not hurt you. Thus, to provide a margin of safety, we have to reduce our dead load, not magnify it in the case of uplift.
