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RE: Lag screws in withdrawal from end grain[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Lag screws in withdrawal from end grain
- From: "Dennis S. Wish PE" <wish(--nospam--at)cwia.com>
- Date: Wed, 9 Sep 1998 00:43:51 -0700
As my good friend, Bill Allen, knows - I need to get the last word in :>). Seriously, in the case that Bill described his opinion is valid - whether you can defend yourself and prove your innocence is a separate issue. In my practice, I will provide a level of design that I feel is appropriate for my clients needs. I tend not to be intimidated by the prospects of being sued. Before I discuss why let me say that if I choose to accomodate the clients desire, the design will meet the aesthetics that he wants but the cost may be higher than he anticipated. In this case I would need to add a sufficient level of conservatism into the design to insure that I am comfortable with the connection. In this case the mathmatical proof is only a starting point. In one project I did, the great room was surrounded by four blocks. I had the option of desiging each block independently and distributing the hear created by the greatroom diaphragm equally into the surrounding blocks. Instead, I analyzed the structure from four directions in put the full shear (in that direction) into each outside block which essentially doubled the shear into that block. I started with an Rw of 6 since the structure was all plywood shearwalls. It was overly conservative, but provided the greatest level of security I could afford my client considering the creativity of the architect and the need to tie everything together. Litigation is like a rolling freight train. Once it gets moving, little can stop it. The winner of a suit is not determined by right or wrong - just as many cases that follow code are found guilty as those that are negligent. Most cases end up settling out of court determined by who has the better credential and evidence. Personally, the idea of litigation is very distastful since rarely is truth the deciding issue. The law has made a science out of manipulating fact that truth is of little value in a decision. It is, in most cases, determined by who have the most compelling expert witness and most persuasive hired guns. In a recent case, the plantif's expert witness manipulated the facts significantly to win his clients case. He argued that the design engineer, if competent in retrofit work, should have been aware of the debates being held by the code creating committee of SEAOSC that resulted in changes in the code two years later. Although I was a member of this committee, only about ten or twelve practicing engineers participated in the code creation. The rest were too busy earning a living to attend and acted upon the letter of the code in force at the time the design was created. I was appalled by the fact that the plantif's expert, whom I had admired for years as a competent engineer, would stoop to present facts that were not in evidence at the time the design was done. The moral is that nothing can stop an angry building owner from seeking revenge. As these discussions have indicated, there are grey areas in the code that needs interpretation. There are also sections of the code that are being revised as this post is written. The revisions may prove that the code we follow today is inadequate. In addition, there may be an Errata issued to the code to correct an error that you may not have caught. Or the Erratta may never be issued since the next code provision no longer supports the current code as in the case of the IBC. In this case, who becomes liable for an error published in the code? You do of course! Therefore, I can only recommend that you follow your own judgment and err on the side of conservatism. This is off the path from what Nels proposed. Nels solution to introduce perpendicular locking rods is, in my opinion, a creative and excellent solution that resists the pullout problems and satisfies the design limitations. Assuming that the locking pins are machine bolts recessed into the beam to hide their appearance, they will work in shear parallel to grain with steel sideplates (washers on both sides) much better than the threaded rod working strictly in tension. If he wants to use only an embedded rod, I would suggest going in 1.5 to 2 times the calculated depth and adding epoxy into the conncection regardless of what the calcs prove to be sufficient. On the issue of what code is appropriate I believe that you should stick with that which the building offical uses. This may sound obvious but I had a situation where the City of Santa Monica issued an ordinance for Open Front Retrofit design. Some time later the City of Los Angeles initiated their Open Front code. After reviewing the methodolgies, I decided to use the City of Los Angeles code rather than Santa Monica's ordinance. I received a correction notice citing that I used the wrong code. I simply wrote a letter to the plan check engineer explaining how the L. A. code was more conservative and that I felt it was appropriate for the project I designed. This was enough justification for Santa Monica and they permited the work. I am not sure how others feel on this issue, but I believe that if you *can* deviate from an established code if you justify your methodology with supportive analysis and possibly submit a letter citing the codes or methodologies which you used. I would believe that if you obtained the approval of the building official on using an alternative design, you would have sufficient strength to initially avoid a suit. However, once the suite is started then it becomes a "pissing contest" of who has the better credentials and powerful hired guns. Most of us would feel stiffled if all we thought about was the propects of being litigated against for our professional judgement. We are potentially impaired by having this hanging over our heads. Therefore, I can only suggest that you use reason combined with conservatism when dealing with creativity and maintain a record of your justification. I can't urge engineers enough to avoid intimidation and remember that engineering is a creative field and our clients hire us to create a solution for the illusions they wish to create. Regards Dennis -----Original Message----- From: Bill Allen, S.E. [mailto:bill(--nospam--at)allendesigns.com] Sent: Tuesday, September 08, 1998 7:18 PM To: seaint(--nospam--at)seaint.org Subject: RE: Lag screws in withdrawal from end grain Ernie- Allow me to pose a scenario for you. Say you design this connection with lags in withdrawal in end grain. Later, it fails. You are dragged into court. An expert witness testifies that several recognized published documents state that this condition "should not" be used in design. The expert witness also cites behavioral properties of wood such as shrinkage, fiber fracture, etc. Now it's your turn to take the stand. My questions are: 1. What would you offer as a defense? 2. Why take this chance? I know my good friend Dennis Wish recommends using "creativity" when interpreting the code and I agree to a significant degree. However, you need to pick and choose your places and ensure you have a defensible position if ever you have to defend your design in a court of law. I have a difficult time visualizing that a connection, although probably more straightforward if lagged end grain, cannot be achieved by lagging side grain with some sort of bracket. Regards, Bill Allen -----Original Message----- From: ErnieNSE(--nospam--at)aol.com [mailto:ErnieNSE(--nospam--at)aol.com] Sent: Tuesday, September 08, 1998 3:04 PM To: seaint(--nospam--at)seaint.org Subject: Re: Lag screws in withdrawal from end grain Ed, How do we define "when it cannot be avoided"? When it is absolutely impossible to do any other kind of connection? When it is impractical to do another type of connection, although possible? When it is uneconomical? When it is already existing? Ernie Natividad
- RE: Lag screws in withdrawal from end grain
- From: Bill Allen, S.E.
- RE: Lag screws in withdrawal from end grain
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