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Gaps in joist hangers

TimNY

TimNY

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Jan 13, 2010
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Charleston, SC
I just picked this up from Simpson: http://www.strongtie.com/ftp/bulletins/T-HANGERGAPS10.pdf?newsletter=Aug10

It addresses situations where there is a gap between the joist and the carrying member, including the reduced allowable load.

Since most hangers are Simpson brand, this should apply just about everywhere. I think this is one of the more useful bulletins Simpson has put out.

It provides a solution other than ripping everything out (provided the actual loads do not exceed the reduced table loads), which is a good thing™
 
TimNY,

Thanks for the information, how many times has a contractor ask'd the building inspector how to solve a joist hanger framing problem after you just wrote him up!

pc1
 
TimNY,

Thanks for the link.

To me; the recommendations for shim are for the use of the Truss Designer (not inspectors); and, I don't have a problem with the Truss Designer usint the "recommended actions" where gaps occur.

I do have a problem with the suggestion that "load allowances" be made for the gaps; and would not approve the recomended adjustment.

I also have a problem with "or another design professional" being used by the builder. I would not approve this; period.

The NOTE towards the bottom of page 6 is the most important information on that bulletin;

"Note:




Other options could work. The actual field remedy or repair must be designed and approved by the Truss Designer. All shims and scabs must be designed by the Truss Designer."

Uncle Bob

​
 
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And if there is no structural designer?.......About the only engineered plans I get here are logs or timbers...currently, I say rip it out or hire an engineer..might be nice to have an alternative...?
 
There is always a structural designer. That person could be the owner, contractor, framer or licenced professional. There is always a structural designer.
 
It is clear that if the gap is greater than 1/8” that the connection is on the surface non-compliant and the applicant needs to propose a resolution. This concern applies to both trusses and joists from sawn lumber.

If the gap occurs for a sawn lumber member and there is no engineer involved. The applicant either has to build it right or he needs to hire an engineer to justify a less disruptive fix.

If there was an engineer involved then the engineer needs to propose a fix if the contractor does not want to build it right.

While the building official has the right not to accept the non conforming work, I would suggest that the building official was being unreasonable if the engineer could show that the expected loads are less than the reduced capacities provided by Simpson.

Repairs involving other manufacturers products cannot make use of the Simpson data.

In many projects the structural engineer for the project, and not the truss designer, will specify the joist hanger to support the truss. In this context there is no reasonable reason for the building official to insist on the evaluation and repair being handled by the truss designer. While it may not be worth the fight by the applicant I believe that the building official would be acting illegally by refusing to accept a fix just because it was not approved by the truss designer.

It is my understanding that the wood truss industry promotes the idea that the truss designs can be performed by an unlicensed truss designer. It is my opinion that such practices would be inconsistent with the state laws related to the practice of engineering and architecture.
 
Interesting point Mark K: The bottom line is to make sure that the truss is installed per the manufacture. Most truss companies here have and create the design and the fix. I would settle for either the truss company or an outside engineer.
 
So allowing for either the truss company or an outside engineer to provide a fix, and not the original design engineer, what happens with a failure.

A liability providers dream. Everyone pointing the fingers at everyone.
 
There may be liability issues but those are not of concern to the building official who is concerned about code compliance and life safety.

The connections are not integral to the design of the truss. If I were to design a connection fix I do not see myself taking on responsibility for problems elsewhere in the truss nor would it relieve the truss manufacturer of liability for truss failure.

The dividing line between the work of the engineer of record for the project and a specialty engineer performing delegated designs is always a matter of negotiation.
 
It seems that the document deals with hanging trusses not hanging joists. I am not sure that matters.
 
I undestand Kansas City hyatt very well. The firm I worked for back then had been partially owned by the engineer who was forund liable. I attended presentations on the problem

The problems with the Hyatt disaster had to do with the fact that nobody took ownership of the connection. In addition the engineer of record and his staff did not deal with the problem when brought to their attention. If I design the connection for the trusses I accept reaponsibility for the connection design. In addition I do this with consideration of both the truss design and the design of the members supporting the truss. This is a world of difference.

Sure I may decide to accept responsibility for the truss support connection which was originally performed by the truss designer but there may be situations where this would help the project and where I decide it is worth it, especially if I am paid extra for the effort. This is a decision to be made by the design engineer and his client and is not something of concern for the building official.
 
Mark

You did not hear what I said. My point is that the liability issue is not a concern of the Building Official and thus he is not concerned about who does the work. The building official is concerned about compliance to the code and life safety and in that role he is concerned that somebody resolves the problem acceptably not who.

Because all of the attention on the Hyatt Kansas City not a lot of attention was paid to the influence of the building official. If changes after issuance of the permit were required to be approved by the building official he would have an opportunity to catch the problem. I believe that by requiring the changes be submitted that the engineer would have looked more carefully and would have likely found the problem.

In addtion some of the new special inspection provisions might have caught the change.
 
By allowing multiple structural designers you are asking for a failure.

A new structural designer, focused on one connection, disregarding the structure as a whole is a mistake.

If there is a structural designer of record, and the BO allows another structural designer to modify the design, I feel is negligence by the BO
 
There are already multiple engineers on many projects. For example when in addition to the engineer of record for the project there is an engineer hired by the truss supplier to design the trusses.

On the issue of joist hangers for trusses you will find situations where sometimes the EOR designs the hanger and other times the truss design engineer will. The critical point is that somebody addresses the problem.

I support the idea that there is one prime design professional responsible for assuring that all of the systems get coordinated. This is a concept that is reflected in Section 107.3.4.1 of the 2009 IBC and is supported by SEAOC. This is flexible enough to allow different engineers of record for seperate buildings built under a common permit and to allow a delegated engineer to design the building skin or a truss used in the building. Even DSA and OSHPD (two notorious agencies in California) allow this.

When there are multiple designers working on a project the interface must be coordinated. This is the primary role of the Design Professional in Responsible Charge (Section 107.3.4.1) who may look to his consultants to help.

There are also cases where another engineer is needed because the original engineer is not availible. In such situations the new enginer is responsible for that part of the work that he was involved with changing. This is similar to another engineer making modifictions to an existing building.

On structures where tey put 4 stories of wood over a concrete base podium structure housing parking it is not unheard of for one engineer to design the podium while another designs the superstructure.

Section 1710 of the IBC makes provisions for another engineer being engaged to perform structural observation.

I contend that the BO does not have any grounds for not allowing multiple engineers to work on the project as long as they comply with the code.
 
DSA and OSHPD Require the engineer of record to review others work

On podium structures, it is common for two permits one podium one superstructure.
 
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Section 107.3.4.1 of the 2009 IBC

The building official shall be notified in writing by the owner if the registered design professional in responsible charge is changed or is unable to continue to perform the duties.

The registered design professional in responsible charge shall be responsible for reviewing and coordinating submittal documents prepared by others, including phased and deferred submittal items, for compatibility with the design of the building.

It does not say you can have multiple EoR's at the same time,
 
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What DSA says up front is different from what they accept. Have handled a number of deferred submittals for delegated designs on school projects for things like precast skin. The statement we placed on the deferred delegated design submittal said that we had checked the interface and we had checked to make sure that the deferred submittal was compatible with the primary structural system. We did not check the details for the delegated design.

DSA and OSHPD also implies that the EOR needs to put his professional stamp on the ddelegated design. In reality the EOR signed a statement describing the nature of the review that was placed on each sheet of the delegated design.

Even if the podium is permitted seperately from the superstructure somebody needs to cordinate the two designs.

The registered design professional in responsible charge(DPRC) is the prime design professional, typically the architect. The DPRC can be working with multiple consultants. There can be multiple structural engineers and multiple mechanical engineers. This is common when there are requirements for local, small business, or minority participation and in these cases it is common for each structural consultant to sign for only his portion of the work. One could argue that if one individual had to stamp all of the structural work prepared by multiple offices that there would be a problem of overstamping, which could create conflicts with the professional licensing laws.

Sine the state reulates the practice of architecture and engineering the local building department and the building code can't say that there cannot be multiple EORs on a project.
 
Mark K: The code absolutely can and does say that the building official shall require the owner to hire a registered design professional in responsible charge, as stated in the section you guys previously referenced. As you have already noted, this in no way precludes multiple engineers. However, contrary to your statement above, the words " reviewing and coordinating" are far different from "stamping", and that does not create conflicts with licensing laws.

If a project falls under 107.3.4.1, 2009 IBC, requiring a design professional in responsible charge, and changes are made to the connection by the engineer that designed it, I have the resposibility to make sure it is reviewed by the registered design professional in responsible charge. The code says that he must "review and coordinate" that change. Does it mean that he must run that specific change by the truss designer? How about the column designer? Foundation designer? I don't think the code specifies. That's why the DPRC is required. It is my resposibility to make sure that there is a DPRC, and that he "reviews and coordinates". It is not my responsibility to tell him HOW to review and coordinate, unless I am made aware of an actual code violation.

A lot of this falls outside of the IRC, but it is still relevant to the subject of changes in structural design. Good discussion, and I agree with some of what each Mark has said.
 
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Texasbo: Well put and yes I have to agree with some points. As BCO the code does allow us and creates a path that all changes be review by the DP in charge. Just finished a health care expansion with five different addition. One principle DP and all issues past through him. If a changes was made by a Mechanical, Electrical or structural they all past back through him/her. I kinda like that type of flow system. It is much better then a half dozen Dp's & engineers running loose not knowing what the other is doing.
 
FWIW I wouldn't allow this for truss connections without the blessings of the truss designer. Typically these guys are more than happy to help out, so I don't see an issue with that. The truss system is a designed system, so any modification would also have to be designed. This bulletin gives the truss designer something to work with.

More importantly I find this useful for joists. For simple spans this bulletin creates another avenue of compliance. For every failure there is usually the question, "what do I do?" It is always nice to have a few options available. It is still the responsibility of the permit holder to be able to document compliance, but it would be nice to say, "well, you could remove it all and reinstall without gaps, or simpson has a tech bulletin you could use to prove compliance, or any other method that is approved"
 
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