Wind speed

[Sifu]

This is for anybody who gets the wind speed better than me....so a whole bunch of you, but I am particularly interested in the opinions of any P.E.'s on the forum. (but please don't take it personally, this is an honest question)

Our adopted wind speeds are: 115 Vult (IRC) and 105 V (IBC)...straight off of the map.

Given the ever-changing wind speed designations in the IBC and ASCE-7, the IBC now uses V (basic design wind speed) and/or Vasd. The IRC uses Vult and Vasd. Without going too much into why and what the differences are I have a simple question.

Why do I continue to get engineers referencing Vult instead of V on commercial plans?

I get that they may not be accustomed to the 2018 IBC, but many times they will reference the 2018 IBC and then the very next line will have the Vult wind speed, sometimes the value is correct with the wrong designation (105 Vult), sometimes the value is from the IRC (115 Vult), occasionally I might even see 115V. (I recently spoke with an engineer about that one and he just said well I guess I over-engineered it, but I'll leave it alone) This is almost a daily occurrence. It really bites to have to send a plan back with that comment. How can I make it stop? Or am I just too particular? Is it not a big deal to them? What am I missing?

Sorry, bit of a rant, but I get frustrated when I can't tell if I am the one missing something so obvious, or they are.

 

[ADAguy]

HMMM?

 

[north star]

$ ~ $ ~ $

Sifu,

IMO, ...you will not get "it" to stop !......As you already
know, the Vult. is a calculation used for greater wind
speed, and thus, the engineer has covered themselves
with the greater requirements........Also, who's to say
that the wind stops at the calculated speed ?.......It
is certainly possible for the winds to "greatly exceed"
the calculated speeds [ RE: Hurricanes Camille, Katrina
and others have proved this ].

Also IMO, ...if you want to be exact in your comments
and in compliance with the `18 IBC, then you will need
to submit your comments back to the RDPs and request
a change to comply with the `18 IBC, most likely, ...every
time........I have not found an easy path \ method to have
the RDP's comply with what they are designing.......It
is indeed frustrating at times, but that is part of the Plans
Review process.......This is what good Plans Examiners
do !

Keep at it sir !

$ ~ $ ~ $

 

[Keystone]

When we foresee or do experience repetitive planning or inspection issues we generate a simple email and blast it out to all of our regular contractors and or RDP’s. Their contact info is requested and received at plan submission, we maintain those emails/contact info. This will lighten the rejection letters at least locally.

You may also want to consider adding the requirement to your permit application.

 

[Mark K]

The focus should be on whether the building complies with the regulations not whether the calculation are correct. If the building as designed exceeds the code requirement it complies with the code and thus the building official should not be concerned.

The IRC allows you to show code compliance by conforming to the provisions in the IBC. So if the engineer used the IBC wind speed and conformed with the IBC provisions for calculating the loads and the resistance then there is no problem.

In California and I would expect elsewhere engineers will, with rare exceptions, design residential buildings in accordance with the provisions in the IBC so it is not surprising that they might not be intimately familiar with the IRC provisions and as previously stated if the building complies with the IBC it is not a problem.

While the IBC may use V to denote the wind speed the fact that Vasd = V*0.77 infers that V is a factored or ultimate speedthus suggesting that instead referring to V as Vult is understandable.

I suspect that this is less of a concern when an engineer performs the structural plan check.

 

[Sifu]

The focus should be on whether the building complies with the regulations not whether the calculation are correct. If the building as designed exceeds the code requirement it complies with the code and thus the building official should not be concerned.

The IRC allows you to show code compliance by conforming to the provisions in the IBC. So if the engineer used the IBC wind speed and conformed with the IBC provisions for calculating the loads and the resistance then there is no problem.

In California and I would expect elsewhere engineers will, with rare exceptions, design residential buildings in accordance with the provisions in the IBC so it is not surprising that they might not be intimately familiar with the IRC provisions and as previously stated if the building complies with the IBC it is not a problem.

While the IBC may use V to denote the wind speed the fact that Vasd = V*0.77 infers that V is a factored or ultimate speedthus suggesting that instead referring to V as Vult is understandable.

I suspect that this is less of a concern when an engineer performs the structural plan check.

I don't take issue with a residential design to the IBC. What I am perplexed by is the continual mixing of terms. We have a legally adopted design criteria for residential-115 Vult. We have a legally adopted mapped wind speed for the IBC-105V. When I do a review I don't spend a lot of time checking their calculations, but I do want to know that they have used the legally adopted wind speeds as their base. It's kind of the low hanging fruit, shouldn't they use that at a minimum? If they used 115V on an IBC design, it is greater than code, thus allowed. But if they use 115 Vult for a commercial design they are not using the legally adopted wind speed. The most basic regulation would be to use the adopted wind speed terminology wouldn't it?

Both the IRC and the IBC offer a conversion chart, and they appear to line up. 115 Vult converts to 89 Vasd in the IRC. 89 Vasd converts to 115V in the IBC. So, if I can safely use those two conversion charts in that manner, it looks like a 115 Vult (IRC) would equal 115V (IBC), making it a more robust design. When they list the design criteria as 105 Vult on a commercial design, I need to extrapolate down (it's not listed in the IRC conversion chart) to find that they would then be providing a design to approximately 80 Vasd, which converts back to 105 V in the IBC. Is it safe to use this conversion method, basically Vult = V? Doing so would produce an IRC project designed to the IBC criteria of 105 V which would convert to 105 Vult, which would be less than the minimum.

Wouldn't it be easier if they just used the adopted design terminology....wouldn't it be easier if both books used the same #^%$ terminology? Doesn't the ASCE 7-16 use only one term?

I can't help but imagine a scenario where after a building defect or failure I am asked why I approved a design to the wrong design criteria.

Lawyer: "tell me Sifu, did you not read the code analysis and see the most basic error?"
Sifu: "well, yes but see, the code books use different terms, and I think if I go from the IBC to the IRC I can convert using this method, then go back to the IBC and convert back using the same method, and it looks like it was about the same"

Just makes me uncomfortable.

 

[steveray]

Have the engineer answer you in writing and put it in the file for reference...

My understanding is that it basically comes out the same, even though the "base number" went up, the way the calculations are performed has changed a bit and the end result didn't actually change that much...At least around here, and we are about 125Vult

 

[Paul Sweet]

I could understand the change from the old steady wind speed to the 3-second gust (about 30% faster), since the news usually mentions the gust (bigger numbers are scarier). The actual pressures came out about the same, but the engineers didn't have to defend themselves from charges of underdesign.

I'm not sure what the purpose for basing the code on ultimate windspeed is. When you put in the factors of safety the working stress pressures are still about the same. Maybe all the structural analysis programs are getting away from working stress, but it makes me wonder when live loads & snow loads might also go to ultimate figures.

 

[Mark K]

My understanding is that the perceived problem is the result of some sloppiness in the terminology. This is in part the result of the IBC and the IRC using different wind maps and because even though the primary code is the IRC many if not most engineers will perform the wind design in accordance with the IBC.

In response to the legal issues raised, it needs to be recognized that the building official has essentially no liability and is given great discretion as to the thoroughness of the plan review. From my perspective the concern about a lawyer asking some questions is a bogus concern.

The engineer of record is liable if the design does not comply with the code. If the building can be shown to comply with the building code the engineer has fulfilled that obligation even if some information on the construction documents noting the wind speed is wrong.

 

[Sifu]

I have had to answer questions from lawyers, fortunately not on a witness stand (I have colleagues who have), but I don't think the concern is bogus. It is my belief (right or wrong) that as long as I am not negligent I have some protection, but if I miss, skip or otherwise ignore the obvious I may be moving into the negligent realm. Isn't an adopted design criteria obvious? If they have the design criteria wrong, how can it be determined to comply with code?

 

[Paul Sweet]

Ultimate windspeed varies by the risk category of the building. Most buildings fall into risk category II which would be 115 MPH for most of the country. Risk category I, which would be 105 MPH, is limited to agricultural, temporary, and small storage buildings. Risk categories III & IV are for buildings with a high occupancy or buildings that have to remain functioning during a storm and require a 120 MPH ultimate velocity.

 

[Mark K]

Building officials may have to answer questions from lawyers but they essentially have no liability. If building officials had liability they would be named in most construction defect cases. This is not reality.

If you believe that you need to check the structural design then the plan check should be performed by a registered engineer. If all you are concerned with is whether the design criteria is correctly stated then I suggest you have really done nothing.

The reality is that in many jurisdictions the structural plan checks are more a formality than a reality and if building officials were subject to liability for negligence then it would be easy to show that these building officials were negligent. But again building officials have no liability. This is clearly stated in California law and I believe it is essentially the same in other states.

Sure you might question the wind speed reported but if the building complies with the code there is no problem. A plan checker who is an engineer could in many cases easily make the determination. Although the IRC is the primary code for many residential projects if the documents show the wind speed in the IBC and the design complied with the IBC requirements then the building complies. In these instances the worse you have is a problem with unclarity in the documentation not a code compliance problem.

 

[Mark K]

A slight clarification

The wind speed is defined by nature and with all natural phenomena the wind speed varies.

The risk categories are a way of saying that the chance of failure due to wind loads should not exceed a certain probability for certain buildings. The mapped wind speeds for a given risk category reflect the wind speeds associated with that target probability for a given location..

While designing for the wind speeds associated with Risk Category 4 should result in better performance in extreme situations the actual wind speed may exceed these the mapped values. When this happens there is a greater possibility that the building might not be functional after the extreme wind. There are no absolute guarantees.

 

[Sifu]

For the record so we are talking apples to apples: my question is why wind speed data on the commercial plans references the terminology from the IRC (or the criteria from a previous code version), not the current IBC. Given all technical differences between the two designations, and why they may or may not be converted, why is it seemingly so difficult to get the DP to make the correct reference? I also understand that a designer can design to the IBC if they choose, and that the IRC is an option for prescriptive design for SFD's and townhomes. So if they do I am fine with it. But the IRC isn't an option for a commercial building beyond that scope.

OK, I understand a building official might have limited legal liability. But lets take it to an extreme. Say the adopted design criteria via the wind speed map is 105V for a commercial project. The structural plans come in and they list a wind speed design criteria of 90V. Should I accept it and move on? Have I done my job if I do? How can the design meet code if it is designed to less than the code minimum? What if they design to a 78 Vasd? Is there a time when I should care?

I also agree, "structural" plan review by a non-engineer, is a formality, and I am the first to tell you I don't do it. I do a cursory review, I make sure the building is the same as the A pages, I make sure structural members are called out where they should be, I make sure building geometry matches supplemental documents (shops, trusses etc), and I check design criteria. Often, if I don't understand something I, with reverence and humility, call the engineer and have great discussions. When I call about the wind speed issue we are discussing I have never had one say, "oh, that doesn't matter". Usually they say "oops, we were using the 2012, we'll get that fixed". I'm just trying to figure out why it happens so often and find a way to make it an easier process.

Again, it isn't really an issue if they design to 115 Vult if Vult is equal to V. It would just mean they have designed to a higher wind speed than the code dictates. For instance I got one today: Vult 116 and right below it 90 Vasd. By using the conversion chart in the IBC 90 Vasd is equivalent to 105V, good to go if that conversion can be used, but why the use of Vult. It isn't in the 2018 IBC except for a single reference in the definitions for hurricane prone regions (artifact?).

 

[Mark K]

If you have a reason to believe that the design does not comply with the code you can make a comment and expect a response from the engineer.

I am not going to attempt to guess why it happens so often because I suspect that there are many reasons.

If you wish to create an easier process we would need to deal with issues beyond what can be solved on this forum. Changes will likely need to be made in the practices of both engineers and building departments. I suspect that the variations in practices among the different jurisdictions plays a role. The chaos introduced by owners and architects may be a factor.

 

[jar546]

If you have a reason to believe that the design does not comply with the code you can make a comment and expect a response from the engineer.

I am not going to attempt to guess why it happens so often because I suspect that there are many reasons.

If you wish to create an easier process we would need to deal with issues beyond what can be solved on this forum. Changes will likely need to be made in the practices of both engineers and building departments. I suspect that the variations in practices among the different jurisdictions plays a role. The chaos introduced by owners and architects may be a factor.

In our case in Florida, we are verifying that the correct design criteria was used and shown on the plans. Almost everything I have on the barrier island I take care of is 170 Vult, Risk Category II, Exposure D. I do have some Risk Category III & IV. I have a continual issue with RDPs using the wrong Exposure Category & often the wrong Design Pressure Zone for windows and doors and sometimes the wrong wind zone altogether. I can't just have a bland statement saying that they will comply with ASCE 7-10. We need more specifics, otherwise are are not doing our job, aka "formality" as some call it. We have windows specified that don't meet the minimum design pressures and find other issues on an almost regular basis.

So I take issue with calling plan review a "formality" as it exists for a reason. We are all fallible. Another level of verification is helpful and necessary under the laws of the state. I can also tell you of the times I just happened to look at the calculation for an LVL hip-rafter only to notice that the calculation was based on a 16' span when, in fact it was a 22' span. The very professional PE was thankful that I caught it.

If you are saying that the plan review is a formality then why would you promote only using a PE for plan review? Shouldn't the QC be done at the RDP's office before it's submitted as a permit set?

 

[jar546]

This is for anybody who gets the wind speed better than me....so a whole bunch of you, but I am particularly interested in the opinions of any P.E.'s on the forum. (but please don't take it personally, this is an honest question)

Our adopted wind speeds are: 115 Vult (IRC) and 105 V (IBC)...straight off of the map.

Given the ever-changing wind speed designations in the IBC and ASCE-7, the IBC now uses V (basic design wind speed) and/or Vasd. The IRC uses Vult and Vasd. Without going too much into why and what the differences are I have a simple question.

Why do I continue to get engineers referencing Vult instead of V on commercial plans?

I get that they may not be accustomed to the 2018 IBC, but many times they will reference the 2018 IBC and then the very next line will have the Vult wind speed, sometimes the value is correct with the wrong designation (105 Vult), sometimes the value is from the IRC (115 Vult), occasionally I might even see 115V. (I recently spoke with an engineer about that one and he just said well I guess I over-engineered it, but I'll leave it alone) This is almost a daily occurrence. It really bites to have to send a plan back with that comment. How can I make it stop? Or am I just too particular? Is it not a big deal to them? What am I missing?

Sorry, bit of a rant, but I get frustrated when I can't tell if I am the one missing something so obvious, or they are.

This brings me to one of the other threads that I started. If everyone is so worried about wind speed design criteria, then why do so many blow off doing plan review for the windows to ensure that they meet the design pressures? It seems the U-factor for energy compliance is looked at much more than the actual design pressures. Wouldn't you think that the design pressure was equally if not more important than the energy code requirement? Why worry about the nailing pattern when you have windows that don't meet minimum pressure requirements. The Swiss Cheese effect.

 

[Mark K]

I am not saying the review should be a formality but it is my observation that when engineers see documents approved with no comments or where the plan checker concentrates on one thing and ignores everything else it is hard to assume that the plan check is in effect nothing but a formality. This situation occurs more often than we would want. Engineers are not so dumb as to assume that a lack of comments means the design is perfect.

The design professional has a responsibility to get it right and some are better than others. Admittedly some problems can be identified by an individual who has no engineering training but lacking the training the reviewer is incapable of finding possibly more serious mistakes. So if the department makes a decision to have the structural aspect of the job checked by a non-licensed professional it sends a message that they do not think it is important.

The only place in the construction documents where it is acceptable to state that something needs to comply with ASCE 7 is when part of the design has been delegated to a contractor who will have a design professional design the component which is then submitted as a deferred approval.

You ask why does this happen. This is not to excuse mistakes but I suggest it is more likely because of the chaos of the design and permitting processes. Schedules are often tight and the engineer often does not get key information till late in the process. In order to meet schedule the engineer will focus on those issues that they believe have the potential to be the biggest problems. Bad habits tend to be perpetuated when there is no feedback. While this issue may be a big issue to you I will suspect that many other plan checkers are not as focused on these issues. If this was something that every plan checker focused on designers would respond to this feedback and this problem would rarely occur. But I suggest that building departments are inconsistent in the feedback they provide. People respond to consistent feedback.

With regards to wind loading on doors and windows I suspect that the problem is often aggravated by the fact that the Architect and not the engineer is responsible for specifying those components. The Architect should talk with the engineer to understand the wind loads but all too often that does not occur.

 

[tmurray]

In reference to the questions about liability, This isn't that the building inspector will be held as negligent for the structural design completed by a professional engineer, whom the building official (assuming in this case they are not a professional engineer) does not have the training to properly review, but that the building official missed obvious code violations, thus indicating that they were negligent in the discharge of their duties.

I think relying on immunities from prosecution for defending poor reviews or inspections is at best a poor excuse. Your assumption that you will always have this immunity. I'm sure the police thought this way as well, but this immunity is quickly eroding away. In Canada, the Supreme Court recognized that it makes no sense to provide this immunity. You cannot give government officials the power to perform public safety inspections, have a public that relies on the proper execution of these duties, but then not hold these officials responsible when they are negligent in discharging these duties.

I am always amazed that such protections exist for people who quite frankly, aren't doing their job.

 

[Sifu]

I am not saying the review should be a formality but it is my observation that when engineers see documents approved with no comments or where the plan checker concentrates on one thing and ignores everything else it is hard to assume that the plan check is in effect nothing but a formality. This situation occurs more often than we would want. Engineers are not so dumb as to assume that a lack of comments means the design is perfect.

The design professional has a responsibility to get it right and some are better than others. Admittedly some problems can be identified by an individual who has no engineering training but lacking the training the reviewer is incapable of finding possibly more serious mistakes. So if the department makes a decision to have the structural aspect of the job checked by a non-licensed professional it sends a message that they do not think it is important.

The only place in the construction documents where it is acceptable to state that something needs to comply with ASCE 7 is when part of the design has been delegated to a contractor who will have a design professional design the component which is then submitted as a deferred approval.

You ask why does this happen. This is not to excuse mistakes but I suggest it is more likely because of the chaos of the design and permitting processes. Schedules are often tight and the engineer often does not get key information till late in the process. In order to meet schedule the engineer will focus on those issues that they believe have the potential to be the biggest problems. Bad habits tend to be perpetuated when there is no feedback. While this issue may be a big issue to you I will suspect that many other plan checkers are not as focused on these issues. If this was something that every plan checker focused on designers would respond to this feedback and this problem would rarely occur. But I suggest that building departments are inconsistent in the feedback they provide. People respond to consistent feedback.

With regards to wind loading on doors and windows I suspect that the problem is often aggravated by the fact that the Architect and not the engineer is responsible for specifying those components. The Architect should talk with the engineer to understand the wind loads but all too often that does not occur.

I totally agree the chaos and inconsistencies are a big part of the issue. So to combat that I continue to try to work the code as it is written, including the design criteria. Inconsistencies erupt when we deviate from the code, or "interpret" the code or glean it's intent when not expressly written. I admit I do it at times, though I try very hard not to, I think at times I am forced to, either because I don't fully understand it, or because it is unclear or doesn't apply. I do so knowing that I could be accused of being part of the consistency problem. I truly believe as plans examiners and inspectors we have a pretty simple job. Compare what we observe to the adopted codes as written and report what we observe. The job gets more complicated when we deviate from the words as published.

I appreciate your perspective, and this thread was not meant in any way to impune the profession or those that are in it. It was meant more to find out how far off-base I was in asking for clarity in the design criteria since I see it so often.

 

[Sifu]

In reference to the questions about liability, This isn't that the building inspector will be held as negligent for the structural design completed by a professional engineer, whom the building official (assuming in this case they are not a professional engineer) does not have the training to properly review, but that the building official missed obvious code violations, thus indicating that they were negligent in the discharge of their duties.

I think relying on immunities from prosecution for defending poor reviews or inspections is at best a poor excuse. Your assumption that you will always have this immunity. I'm sure the police thought this way as well, but this immunity is quickly eroding away. In Canada, the Supreme Court recognized that it makes no sense to provide this immunity. You cannot give government officials the power to perform public safety inspections, have a public that relies on the proper execution of these duties, but then not hold these officials responsible when they are negligent in discharging these duties.

I am always amazed that such protections exist for people who quite frankly, aren't doing their job.

Agree, I have never sat back and thought, what I do doesn't matter because I am protected. First, I don't believe I am. Second, I feel a moral and ethical responsibility beyond the legal ramifications of what I do. Third, I feel a fiduciary responsibility to those that pay a fee for my services...whether they want to pay it or not. They are paying for a service, I can't just phone it in.

 

[Mark K]

In California the "public duty doctrine" holds that the duty of the public official is to the public not to individuals and that the immunity that they have does not apply when they have voluntarily taken on a duty to protect particular individuals. Thus by claiming that you have a fiduciary responsibility to the building owner you have accepted a duty not covered by state immunity laws.

Thus focus on enforcing the code and do not state that you have a fiduciary responsibility.

 

[ADAguy]

Within reason depending on the role you play and the limits of your E & O insurance.

 

[Sifu]

Well if you want to get technical I didn't say to the owner of the building, I said to those that pay a fee. I get your point, but my statement was about the fee paying public, even if my words didn't convey the message. By using the word "those" I am referring to them...the public. There is no special relationship with an individual that would negate any immunity, real or perceived.

From Merriam Webster: fiduciary:
: of, relating to, or involving a confidence or trust: such as
a: held or founded in trust or confidence, a fiduciary relationship

I believe there exists an expectation of trust and confidence between the public and myself that I do my best not to betray. I stand by the sentiment.