Truss design for private structure in Mexico 1

[Prestressed Guy]

I have been asked to design a set of 50' span steel trusses for a church in Mexico that will be built by a US mission team. Anyone have experience with this type of project?

 

[Prestressed Guy]

My understanding is that there are no building permits or inspections required in the town where the building is located.

 

[BAretired]

Sounds like a good time to say "no thanks".

BA

 

[Prestressed Guy]

This project will get built with or without design input. The thinking is that it will be stronger than the surrounding buildings.

 

[SlideRuleEra]

The truss should be designed to match the skills of the team performing the work.

Bolting? or Welding?

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[msquared48]

Not only the skills, but the materials too.

Car or truck frame steel will not work.

Mike McCann, PE, SE (WA)

 

[dhengr]

Haydenwse:
I don’t think that a church is a private structure, just because it is not owned by the state. “The thinking is that it will be stronger than the surrounding buildings.” In many locations, that sets a pretty darn low standard. You better be designing and detailing to a standard which you can defend, which protects public safety, health and well being. You are a Structural Engineer (Registered /licenced?) and are/can be held to a much higher std. than some guy driving nails and claiming to be a very religious, know-it-all builder. Most builders claim to know everything, and will argue at great length to try to prove it, religious builders also have God on their side, blessing all they do and think. At least, so they think. The fact that there are no local codes, permits, AHJ watching over construction, actually may not make things easier for you; rather, it might allow the builder to think he can use just any old mat’ls. and do things any way he wants. We’ve all heard the argument..., damn the code, this is the way we’ve always done it, my Grandpa showed me. Do you know about how they do thing locally and what materials they use? Also, don’t forget, Mexico is starting to wake up to the existence of EQ’s and the fact that stacked mud bricks don’t make for resistant structures. Almost everything you detail may look like much more work and effort than they are accustomed to. This is a tough situation to be in, you do want to be helpful in furtherance of a project like this, but as SlideRuleEra suggests, you have little knowledge of the abilities of the workers, and they may not have much local knowledgeable overseeing either, so you better design and detail accordingly. You may be doing this gratis, but you still better have a real clear contract/understanding with the mission team (its church, etc.) about the limits of your responsibilities and liability. Everyone wants to help with charity, and they certainly appreciate the free help, until something goes wrong. Then they start looking for the deepest pockets and for the guy who should have know better than to do that detail, which they then built wrong. I’m not suggesting don’t do it, I am suggesting keep your eyes open and protect yourself. It’s a darn shame, that in today’s world we are forced to think and act this way. Remember the old saw..., no good deed goes unpunished.

 

[Prestressed Guy]

The team that will be doing the work consists of a group of journeymen masons to layup the CMU and a couple of iron workers / certified welders to build the trusses. I got involved with this project after all of the materials were on site so have a pile of A36 angle iron in several sizes and CFMF “S” sections for purlins. When they purchased the building materials the plan was to build a prototypical design they have used before, but the foundation was already in place which required the span to increase from 35’ to 52’. Change the 2’ deep scissor trusses to a 7’ deep 10-panel Pratt gabled truss and the on-hand materials work just fine.
Project is located 100 miles inland from the gulf coast, so wind will not be hurricane and seismic will be low. Project team consists of mostly professional construction workers who are seeking details and have the experience to construct accordingly.

 

[JLNJ]

https://www.theguardian.com/world/2...llapse-kills-more-than-60-worshippers-reports

Be careful.

Mexico City has a building code (they are 100+ miles inland and a seismic nightmare), beyond that it's pretty loose at best.

 

[thaidavid40]

I worked for ten years in Thailand as an evangelist, but I also participated in many building projects. I would have never even begun to think about designing ANYTHING there until I first saw how such items were built in the particular local area. As many have said here, the building means and methods, and skills, vary widely across the entire spectrum, from good to pitiful - even within the same country. If you are not a long-time resident of those parts, with intimate knowledge of these aspects, then you are probably in over your head. Even having short-term mission personnel who are somewhat familiar with the area is likely not sufficient. Will you be there to oversee the fabrication and installation of these trusses? Think carefully about this task, as your assumptions and understandings of the task may push the craftsmen to solutions with which they are unfamiliar. That could make their end result worse, not better, even though you tried to design them to a better standard.
Good luck,
Dave

Thaidavid

 

[Lomarandil]

Haydenwse -- get in touch with Engineering Ministries Intl. Nicaragua (

http://www.emilatina.org).

EMI is a Christian non-profit, so they're very familiar with these types of projects.

They have a network of local engineers throughout Latin America who will be able to help you through the questions of local details, means and methods, maybe even provide a connection for on-site oversight/coordination.

If for whatever reason going through EMI doesn't work out, let me know. I have a connection with a fantastic structural engineer working as a church planter in Nicaragua -- geographically not ideal, but better than nothing.

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The name is a long story -- just call me Lo.