ASCE 113 Update 3

[799931]

Hello transmissiontowers, I was just checking in to see if we might get an updated ASCE 113 this year.

I copied a reply from an old thread below since they closed it:

We have a meeting in Feb 2018 to look over committee comments and after that we have a spot on the agenda of the ETS conference in November to give a status update at the pre-conference. After that we will send to peer review and then address the peer comments we get back. Probably sometime in 2019 to go to publication. Lots of loose ends to fix. I know ASCE has been after us to finish, but getting 25 Structural Engineers from all over the country to agree to technical details is like hearding cats.

Thanks!

 

[dauwerda]

joshab, I actually just asked him about this on May 9th in this thread: thread593-445268
His response was,

We are meeting next week to talk about it. Hopefully we will make some progress, but don't hold your breath. We still have to get it where all committee members agree and then on to peer review and address comments.

 

[799931]

Glad I didn't start holding my breath last time either!

 

[transmissiontowers]

I am Chair of the ASCE 113 revision committee. I don't get around to posting here very often since they reorganized the sections. We are getting closer and have a meeting scheduled for mid-November. Most of the issues have been argued to death and we still lack a examples section of worked examples. This meeting is supposed to be our last and it's good to have goals.

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I have been called "A storehouse of worthless information" many times.

 

[transmissiontowers]

A quick update. We are getting closer to finishing the revision to ASCE 113 for those that asked. We had a meeting in Houston in mid November 2019 and have started to wrap up with Skype meetings of a smaller editorial committee to put the chapters together. Then we go to peer review, and make changes as requested. Then onto publication.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[799931]

Thanks for the update. Very curious to see if there will be an update to load combinations which address compatibility with wind speeds specified in ASCE 7-10 and later.

 

[dauwerda]

transmissiontowers, is the peer review that you refer to the public comment period that ASCE standards go through or is it something else? Or to ask my question in a different way, will the new version go through public comment or is that only required/done for full blown standards?

 

[transmissiontowers]

I don't get by this forum often enough. I'm not sure why I do not get eMail notifications for this thread.

We had our Houston meeting and are trying to speed things along. To joshab; We have gone to ASCE 7-16 wind maps and have a couple of tables for load combinations. We have one for LRFD load combos and another for ASD loads. We recommend LRFD for most structures, but recognize ASD should be used for deflection cases and probably for foundation design. Deflection cases are done for less than extreme wind loads (if you want). Of course, you can check deflection at 140 mph if you want to, but realistically you probably want to check for winds where the equipment might be expected to operate like a disconnect switch. We have greatly expanded SCF equations and given the option for doing a full dynamic analysis (if you have the time and data) of a SCF case with forcing functions. Normally, we just use IEEE 605 type equations and use the max static load and combine with extreme wind or extreme ice. The simple steady state equation is given for those that wish to use it. The left coast guys have expanded the seismic equations and you have the option to do a full dynamic analysis of seismic cases. One key point is that even though we give load combinations and suggested factors, you do not have to consider every load. You probably do not need to combine a hurricane wind with SCF and a seismic load with an ice storm and do a full dynamic ANSYS run to find the force in a beam or column. Anchor bolt design has been revised for the case where the base plate is on leveling nuts.

To dauwerda; Once the committee has edited the chapters, we will select a few people to do a peer review and combine all the chapters into one PDF. Since we are still a Manual of Practice, there is no public comment phase. Once the peer reviewers return their review comments and suggest changes if any, we will vote as a committee for each change and if it should be done or not. The first edition of 113 had over 1000 comments and changes requested. Many were just grammatical, and some were substantial and we adopted most but not all.

One thing that we are trying to include is an Appendix for a Proposed Draft Pre-Standard of what 113 might look like if it were to become a Standard. I believe ASCE 74 did the same. The Appendix is just to get comments from users on how they like or dislike it.

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I have been called "A storehouse of worthless information" many times.

 

[799931]

Will the LRFD wind load factor match the ASCE 7 factor (1.0) or will it be something less like in the current version of ASCE 113 such as (1.2/1.6) ?

 

[transmissiontowers]

I found out that my Gmail had classified Eng-Tips as Span and notifications were in my Spam folder, so that is why I am late in responding to these threads.

I'll logon to my work PC and look into the factor question since I don't remember off the top of my head, but in general when you compare 113 or 74 or other T-Line ASCE documents, we generally do not have the loss of human life as a factor in our documents. ASCE 7 has to consider the building or bridge as a potential loss of life category. A substation structure or T-Line tower is less critical than a building and we use lower factors. There is a lot of research behind the wind and ice maps in ASCE 7 but they sometimes include factors that the T-Line industry does not use.

Electricity is becoming more important as technology depends on it and we may get to a point where regulators dictate that we use bigger factors to prevent wide blackouts. All it will take is for some US Senator's child not to be able to post a picture of their latest meal on Facebook or Insta-Whatever in a blackout, and we will be designing structures for a 3000 year return period wind storm that coincides with a 7000 year return period earthquake and a Short Circuit event with 3 inches of radial ice.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[transmissiontowers]

Here is a snip of the load combination table for LRFD or USD design from the proposed new guide (the subscripts like "a" and 300 and 100 did not come over ie. 1a means case 1 with a note a that means the Owner should determine if you need to combine SC with the other loads in the Case):




Table 3-18 Ultimate Strength Design (USD) Load Combinations


CASE COMBINATIONS (all 8 cases may not apply)
1a 1.1 D+1.0 W_300+0.75 SC+1.1 T_(WI-300)
2a 1.1 D+1.0 I_100+1.0 W_(WI-100)+0.75 SC+1.1 T_(WI-100)
3 1.1 D+1.0 SC+1.1 T_APP
4a 1.1 D+1.0 E+0.75 SC+1.1 T_EA
5a 0.9 D+1.0 W_300+0.75 SC+1.1 T_(WI-300)
6a 0.9 D+1.0 I_100+1.0 W_(WI-100)+0.75 SC+1.1 T_(WI-100)
7 0.9 D+1.0 SC+1.1 T_APP
8a 0.9 D+1.0 E+0.75 SC+1.1 T_EA

a The combination of SC loads with extreme events listed above should be determined by The Owner

Table 3-18 and Table 3-19 show suggested design load cases, combinations, and minimum load factors to be use for substation structures. For the load conditions that include ice, the effect of icing on the wire dead load and wind load concurrent with the ice formation should be included. The individual load components are the following:
D = Structure and equipment dead load;
W_300 = Extreme wind load (F, from Equation 3-1,) from 300yr MRI wind map;
I_100 = Extreme ice load from 100yr MRI Ice Map;
W_(WI-100) = Concurrent Wind load in combination with ice from the 100yr MRI ice map;
T_(WI-100) = wire tension resulting from the following loads acting simultaneously: weight of the wire; weight of ice corresponding to ice thickness in the 100yr MRI ice map; wind load on the iced wire corresponding to wind speed in the 100 MRI ice map and: wire temperature per Figure 3-3a through Figure 3-3e.
E = Seismic load as defined in Section 3.1.7.8;
T_(W-300)= wire tension due to wire weight acting simultaneously with the wind force corresponding to the wind speed from the 300yr MRI wind map at an ambient temperature determined by the Substation Owner;
SC = short circuit load;
T_APP = wire tension due to the wire weight acting simultaneously with any appropriate ice weight and temperature as determined by the Substation Owner (every day or normal operational conditions);
• T_EA= wire tension corresponding to wire dead load acting simultaneously with the seismic loading per Section 3.1.7.13, at an ambient temperature determined by the Substation Owner


The above text is very preliminary and subject to peer review and could change before it gets published but it is the current thinking of the Committee.


_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[dauwerda]

Thanks for the above information transmissiontowers, any chance we can get an update on the progress or a targeted publication month?

 

[transmissiontowers]

Working from home has been tough to get things going. We have been doing weekly 1 hour Zoom/Webex meetings between an editorial committee of about 6 folks. We are getting closer but still need to address the Appendix for the Draft Pre-Standard section. I hear ASCE 74 had one that was a "What-If" this MOP were to become a Standard to generate comments. The Examples also need some work. We are about to select the Peer Review committee and then will have to address all the Peer comments. IIRC, the 1st Edition had over 1000 comments that had to be addressed (I was Vice-Chair for the 1st edition)
Hopefully, sometime in 2020 will get it to ASCE.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[Trafo1982]

Hello transmissiontowers, thank you very much for the hard work and the updates!

I am currently reading ASCE 74-20, and well, many things change, I think for the good.

We are now reaching the end of 2020. Any news on the process for ASCE 113?

 

[transmissiontowers]

The ASCE definitely wants us to finish up soon and we are in the final stages of an Editorial Committee review of the chapters. The Peer Reviewers have been chosen and I told ASCE I would try to get a document to the Peer Reviewers by 1-31-2021.

I have gotten a PDF of ASCE 74 but have not gotten around to reading over it yet. IIRC, their wind maps are the same as 113's but the big change for my part of Texas is the hurricane prone regions are now in Exposure D according to ASCE 7-16 (we used to be in Exp C)

My other observation is the NESC-C2 that covers all things on T-Lines, still uses the wind maps from ASCE 7-05 and the NESC is very slow to change. The dilemma is, do I abide by NESC (not a design code, but a public safety code) or do I use MoP 74 and their wind maps?

I have a friend in Louisiana that was asked what the cost impact would be to design poles and towers for a 170 mph wind vs the 140 mph wind in the NESC (about a 50% increase in loads) because all the T-Lines went down in the hurricanes that hit them this season.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[StructureME]

My instinct would be to follow ASCE 74 and/or ASCE 7-16... Following NESC now is so out of date, and as you stated, just a safety code, not code. I think using a 200-year MRI would be reasonable for ultimate design, alone with a 25 yr MRI for deflection. Thanks @Transmissiontowers for keeping us posted! It's sad that it excites me to know an updated ASCE 113 is coming out... Please tell me their will be some new info on foundations and anchors (specially drilled piers)!

 

[transmissiontowers]

Hi StructureME;
The owner of the T-Line or Substation decides which codes to follow with input from the engineers. Historically the NESC with OLF's >1 on Rule 250C wind maps has served well in my Utility with few T-Line and Substation structure failures during hurricane events. IIRC, there is an exemption in 7-16 for electric utilities because we do have NESC and ASCE 74 to use for wind maps. Electric power is becoming a "can't do without" commodity and might get the attention of the regulators that could force us to be a Risk Category IV for new designs.

AFA the foundation, yes we will have a chapter on them but it is very generic to say what are the general types of foundations in a Sub. There are no equations in the chapter for what the capacity of a foundation is. We do have load combination tables to use with the foundation that are based on ASD. I do not do foundations myself and have always used a USD approach for the steel design, so designing foundations is very foreign to me. As long as you tell the Geotech the reactions and the OLF's that are included in them, they should be able to come up with a foundation that will withstand the ultimate loads.

On the anchor "rods", there is a new method based on a European ETAG code but the big change is for the base plate on levelling nuts, you will always have to include the bending moment in the bolt. ASCE 48 allows you to neglect the bending if the the gap is less than 2 bolt diameters, but 113 recommends to always use the bending, no matter the gap.

HTH

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[transmissiontowers]

I looked over my old eMails and came across this statement I put together for one of my many bosses:


The ASCE 7-16 applies to buildings and other inhabited structures. NESC C2-2017 recognizes that transmission lines, distribution lines, and substation structures are uninhabited in extreme events. ASCE 7-16 has a section in the previous edition ASCE 7-10 on Page 506, Section C26.1.2 Wind, where the electric utility industry has an exemption from the wind maps. I believe it is because we have developed a loading guide, ASCE 74, that applies to our structures plus the NESC.

These are my opinions and may not hold up in court.

_____________________________________
I have been called "A storehouse of worthless information" many times.

 

[StructureME]

Again, that is for all the info and insight, Transmissiontowers! I would love it if you were correct and the industry segregated from ASCE 7 and just used its own wind loading. Far too often than not, I have a client who's standards use ASCE 7-05, State building code uses 7-10, and NESC also needs to be considered - end up having hundreds of load combinations! As for foundations and anchors, ACI 318 is the industry standard, but fails to discuss anchors in drilled piers well, which are used all the time in our industry! That's really why I was hoping it would be addressed, but I guess we'll just continue as we've been doing it.

Thanks again!

 

[dauwerda]

StructureME, as far as designing anchors (and their supplementary reinforcement) in drilled piers are concerned one of the main references I have seen used (perhaps "adapted" would be a better term) is, "Design of Anchor Reinforcement in Concrete Pedestals" by Widianto. It can be downloaded here:

https://www.semanticscholar.org/pap...Owen/d31d19ed0c5c63c6efa7417ec60fdcd814e728ad

Another resource is ASCE's "Anchorage Design for Petrochemical Facilities"

https://ascelibrary.org/doi/book/10.1061/9780784412589

Unfortunately these do not address round piers, but I believe engineering judgement can be use to apply the same principals.