tag:blogger.com,1999:blog-20631961816836254292024-02-19T01:20:49.443-08:00Wood Design and ConstructionJasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.comBlogger51125tag:blogger.com,1999:blog-2063196181683625429.post-42611702803426010002012-06-01T10:52:00.001-07:002012-06-01T10:52:49.811-07:00New Southern Pine Design ValuesToday is the day. June 1, 2012 is the effective date for the new design values for No. 2 Dense and lower grades of visually graded Southern Pine lumber. The changes are for lumber that is 2"-4" thick and 2"-4" wide. The Addendum to the National Design Specification for Wood Construction by the American Wood Council can be found <a href="http://www.awc.org/publications/update/2012NDS-Addendum-March2012.pdf" target="_blank">here</a>. Please note that this is only for visually graded lumber and does not affect machine stress rated lumber. <br />
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For engineers, the severity of the change in design values for 2x4's will have less impact than what may be expected. (Not true for truss manufacturers.) We typically only use 2x4's as wall studs; and for many projects we are using 2x6 wall studs as directed by an Architect. This results in 2x4's being a small portion of a typical project. <br />
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Moving forward, is it only a matter of time before the other grades and sizes of Southern Pine have reduced design values. If you want to see what those other design values may look like, click <a href="http://www.spib.org/pdfs/Information-on-Proposed-Design-Values-for-Visually-Graded-Dimension-Lumber.pdf" target="_blank">here</a> for information from the Southern Pine Inspection Bureau. <br />
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I have already been asked the question of changing from Southern Pine to Spruce Pine since the new design values have changed. If you allow the change, you will need to make adjustments to all of the connection designs to account for the lower specific gravity of Spruce Pine. This makes a change much more complicated than just checking the stud strength. <br />
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<br />Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-83919270231077419542012-05-11T11:27:00.002-07:002012-05-11T11:27:51.702-07:00Deck Design Do's and Don'ts: Part 3<div class="separator" style="clear: both; text-align: left;">
Sawn lumber, unless protected, is highly susceptible to shrinkage, swelling, twisting, and bending when exposed to moisture. For an outdoor deck, lumber is exposed to rain and changes in humidity, the latter of which can be a nightmare in Alabama. The deck in the picture below shows signs of joist failure. One saving grace for the deck is the fact that the two test stations that have toppled over are constructed of thin, hollow metal and are much lighter than they may appear. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjg_F-g7QCWtjAY88STGwqkT6ueDDFQDH_lJLFqgBmFBIxAK43SMLPvRwPIIJPXBs5ojVwmjRPOhax5jq-EomQH2tIcrJwrk-AaixRI9IZ3AUU21dp06gyDsDDnPQnLkxXXt8T20spEm0mR/s1600/P6210040.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" rba="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjg_F-g7QCWtjAY88STGwqkT6ueDDFQDH_lJLFqgBmFBIxAK43SMLPvRwPIIJPXBs5ojVwmjRPOhax5jq-EomQH2tIcrJwrk-AaixRI9IZ3AUU21dp06gyDsDDnPQnLkxXXt8T20spEm0mR/s400/P6210040.JPG" width="400" /></a></div>
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The second picture, shown below, shows how the joists are being held up by the deck. The 1x ledger board used to support the joists is still in place. Unfortuntaly, the beam has rotated away from the deck, allowing the ledger to slide out from under the joists. The beam's rotation and deflection were exacerbated by the effects of weather exposure. The few nails that connected the beam to the joists were nailed from the beam and into the end grain of the joist, leaving very little resistance to lateral separation. The beam's lack of resistance to moving laterally allowed the effects of loading and weather to combine; ultimately causing failure of the deck without failure of the beam or joists. <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAaC8YTE2LLQElB1ZRCaTFEEIEBlVtlg2oY1HRFDXEnHAAIk7jYyBk_43fpyG5pxHQMddsUV6GwFENTyvyUdUvjhNAA0nV3u_BjslJ6_d-g29QZjRxd8OOnJh4efMG1GCV7Cc4vU5h_pu4/s1600/P6210030.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" rba="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAaC8YTE2LLQElB1ZRCaTFEEIEBlVtlg2oY1HRFDXEnHAAIk7jYyBk_43fpyG5pxHQMddsUV6GwFENTyvyUdUvjhNAA0nV3u_BjslJ6_d-g29QZjRxd8OOnJh4efMG1GCV7Cc4vU5h_pu4/s400/P6210030.JPG" width="400" /></a></div>
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Small changes in the construction of the above deck, such as toe nails or joist hangers, could have made a big impact on the decks performance. Thankfully, the employees working at the facility were unharmed. </div>
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Statistically, deck collapses are responsible for more people being injured or killed than any other part of their residence. Taking the time to consider low cost, high impact changes in all aspects of construction should be at the forefront of every builder. </div>
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Click <a href="http://www.myconstructionfinds.blogspot.com/2011/07/deck-design-dos-and-donts-part-2.html">here</a> for Deck Design Do's and Don'ts Part 2 and <a href="http://myconstructionfinds.blogspot.com/2011/06/deck-design-dos-and-donts-part-1.html">here</a> for Part 1. </div>
<br />Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com1tag:blogger.com,1999:blog-2063196181683625429.post-44992882997536571462012-05-03T13:32:00.000-07:002012-05-03T13:32:06.343-07:00Design Considerations for Sawn Lumber Wood StudsI am excited to say that my first publication for <em>Structure Magazine</em> just came out in the May issue. I wrote the article about wood stud design after seeing inconsistencies in the way that different engineers perform their analysis. I know of several engineers that use Enercalc's wood column feature for stud design. Using a column analysis for wood studs tends to alter the way adjustment factors are applied, specifically the repetitive member factor. <br />
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Another point of contention between some engineers is the allowable deflection for wood studs supporting brick veneer. While the L/600 limit is applicable to cold formed steel stud framing, the same limit is not applied to wood studs. <br />
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The article can be found <a href="http://www.structuremag.org/article.aspx?articleID=1459">here</a> if you would like to read it and learn more about the design of sawn lumber wood studs. <br />Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com2tag:blogger.com,1999:blog-2063196181683625429.post-52119090103484787122012-04-17T07:47:00.000-07:002012-04-17T07:47:15.185-07:00Possible World Record Log Truss<a href="http://www.bhpioneer.com/local_news/article_797bc38e-85be-11e1-ae56-001a4bcf887a.html#.T42BLBHCv8Y.blogger"><em>Nothing tops this truss - Black Hills Pioneer: Local News</em></a><em>: DEADWOOD — There are log trusses and then, well, there's the 80-foot behemoth log truss recently handmade over a 10-week period by the blood, …</em><br />
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Very interesting project for both log cabin folks and structural building component folks. I would be interested to know the amount of design load the truss will carry and what type of support reaction it will produce. Following the load path for that monster would be a fun task.Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-50181378226813497602012-03-12T08:52:00.001-07:002012-03-12T08:52:59.468-07:00HABIFRAME Storm Shelters-Texas Tech Debris Impact Test<iframe allowfullscreen="" frameborder="0" height="344" src="http://www.youtube.com/embed/i5MnO0EG2Zs?fs=1" width="459"></iframe><br />
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Pretty cool above ground, wood framed residential tornado shelter. Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com1tag:blogger.com,1999:blog-2063196181683625429.post-31838320820370402022012-02-06T13:50:00.000-08:002012-02-06T13:50:28.057-08:00Kerfing a Bowed StudWood studs are not perfect and never will be. Neither will any other material, plant, etc. that is made in nature. Through experience, science, and understanding, we learn how to manipulate natural materials to be suitable for our needs. Trees, which have branches in many aspects of our lives (pun intended!), are a top renewable resource. After centuries of harvesting tress, and thus lumber, to build shelters, etc., you would think our understanding of the material would be very thorough. But as some say, it can be hard to see the forest through the trees. In other words, sometimes you need to see the big picture. Below is an example of an instance where the big picture reveals much more than what is in front of you <br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhERpZO_b0yC8B-K6zzbzEeTc-nZttJuW174mNLzqlZWmGVLJ3GcqMUKyKMafu_pXwfNM2Ka7nWFzq7mOOQn8tuD7kNSLN-gyoCHUox71Pa9z2c4HP361RmXSjfSMVxTNbaSuxoWEEPMIwm/s1600/P1010034.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" sda="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhERpZO_b0yC8B-K6zzbzEeTc-nZttJuW174mNLzqlZWmGVLJ3GcqMUKyKMafu_pXwfNM2Ka7nWFzq7mOOQn8tuD7kNSLN-gyoCHUox71Pa9z2c4HP361RmXSjfSMVxTNbaSuxoWEEPMIwm/s400/P1010034.JPG" width="300" /></a></div><div class="separator" style="clear: both; text-align: center;"><br />
</div><div class="separator" style="clear: both; text-align: left;">It is common for carpenters to kerf a wood stud to remove a bow in the stud to allow for the wall finish to be flat. Depending on the function of the wall, such as load bearing, the kerf in the stud may be reinforced with a section of 2x material lapped and fastened to the full height stud. Regardless of how the stud is kerfed, reinforced, etc. the most important piece of knowledge involved is the function of the stud. Knowing what the stud supports can result in an appropriate repair solution. </div><div class="separator" style="clear: both; text-align: left;"><br />
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</div><div class="separator" style="clear: both; text-align: center;"><em>These 2x6 studs have a kerf that leaves just over an inch of solid material.</em> </div><div class="separator" style="clear: both; text-align: center;"><br />
</div><div class="separator" style="clear: both; text-align: left;">Now, back to that forest and tree stuff. The worker who cut these studs could only see the bowed stud (tree) in front of him. Had he looked at the big picture (forest), he might have realized that kerfing a first floor stud in a four story building might not be a good idea. And yes, this wall does carry floor trusses from each floor above. </div><div class="separator" style="clear: both; text-align: left;"><br />
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</div><div align="center"></div>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-24916188596036221662012-01-17T14:37:00.000-08:002012-01-17T14:37:54.778-08:00Southern Pine: Status UpdateClick <a href="http://sbcmag.info/news/2012/jan/alsc-approves-only-sp-no-2-2x4-design-values-effective-june-1">here</a> for a summary of the current status of the proposed changes to southern pine design values. I imagine that within the next 5 1/2 months (prior to implementation of new values) there will still be much debating on this issue. The primary point of concern boils down to this: change the lumber design values or change the lumber grading process. Timber Products Inspection has stepped up to the plate to develop a revised lumber grading process. Click <a href="http://sbcmag.info/news/2012/jan/timber-products-offers-revised-lumber-grading-approach-0">here</a> for more information from TPI. Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-55136036261589894402011-11-15T06:39:00.000-08:002011-11-15T06:39:14.910-08:00Southern Pine Span Tables - ProposalThe Southern Forest Products Association (SFPA) is kind of like a customer service department for Southern Pine. They provide assistance to end users in understanding Southern Pine grading rules and design values while also marketing lumber products. The SFPA website at <a href="http://www.southernpine.com/">http://www.southernpine.com/</a> provides information for end users regarding green building, pressure treatment, and product applications in addition to providing span tables for joists, rafters, headers and beams. <br />
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The SFPA is closely involved with the Southern Pine Inspection Bureau's (SPIB) proposal of new Southern Pine design values. While SFPA is not directly involved with testing of lumber or the establishment of design values, they will be the group that helps end users understand and adapt to any changes in Southern Pine use. The SFPA has published a sample span table for joists and rafters based on the proposed design values. You can find the tables <a href="http://www.southernpine.com/new-design-values.asp">here</a>. Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-89772663401614830772011-11-05T05:48:00.000-07:002011-11-05T05:48:29.499-07:00USDA Study of the Environmental Benefits of WoodThe USDA recently released a study of the science of the environmental benefits of using wood and wood products in construction. In a previous post <a href="http://myconstructionfinds.blogspot.com/2011/04/usda-to-support-wood-construction.html">here,</a> I wrote about the USDA's decision to support wood construction. This recent study is a continuation of the USDA's path to officially supporting wood construction for public entity structures. <br />
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<a href="http://www.fs.fed.us/news/2011/releases/09/green-building-report.pdf"><em>USDA Report</em></a><br />
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<a href="http://www.prnewswire.com/news-releases/usda-study-shows-economic-and-environmental-benefits-of-wood-as-green-building-material-130811963.html"><em>Comments from SFI</em></a><br />
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<a href="http://constructionadvisortoday.com/2011/10/agriculture-secretary-urges-us-builders-to-prioritize-wood-in-green-buildings.html"><em>Q&A with the President of AISC</em></a>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-7223561522391687482011-10-31T15:15:00.000-07:002011-10-31T15:15:15.751-07:00Southern Pine Design Values: CommentsNow that some of the dust has settled after ALSC's decision to postpone its ruling on proposed southern pine design values, the debate can begin with all sides in the mix. While the debate continues about the need for new design values, what does the industry do in the mean time to protect itself from inadequate design? An engineer from Florida recently asked me this question and it definitely bears some consideration. An edited version of my response is as follows: <br />
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<em>At this time, I am not sure how I will design wood while waiting on the possible new design values. There are several issues to consider before making this decision. </em><br />
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<em>First, I have yet to see the actual proposed new design values. While I do not doubt the testing, I would like to see the test data. Researchers at <place w:st="on"><placename w:st="on">Mississippi</placename> <placetype w:st="on">State</placetype></place> have conducted some tests that show a decrease in lumber strength but not enough to justify the amount of design value reduction proposed by SPIB. </em><br />
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<em>Second, while the proposed new values cover each size of southern pine, only 2x4's have been tested. I do not think we can assume a correlation between the design values of each size based on the In-Grade testing performed 20 years ago. Too much has changed in the timber industry. </em><br />
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<em>I think the easiest thing to do is limit the stress ratio of members we design to maybe 0.80 instead of 1.0. This would be easier than trying to adjust design values at this time and it may not make a significant difference in the overall design. </em></blockquote>
This was a short and quick answer to a complex problem. I have two new wood projects on my desk, including a multi-story apartment building, that will give me a chance to create and implement solutions for ensuring an appropriate design. I will post about my findings in the next few weeks as I complete the projects. <br />
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Also, I have requested a copy of the SPIB proposal. The recent comments from the <a href="http://sbcmag.info/news/2011/oct/slmas-take-60-day-delay-design-value-changes">SLMA</a> has a link to request the proposal for those who are interested. <br />
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Another good commentary regarding the industry's stance (or lack thereof) on what to do between now and January 5th when the ALSC rules on the design changes is <a href="http://sbcmag.info/news/2011/oct/syp-call-go-public">here</a>. Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-80396771076693269372011-10-28T09:56:00.000-07:002011-10-28T09:56:31.643-07:00Southern Pine Design Values: UpdatesWhile it may be difficult to navigate the different sources of information regarding the proposed southern pine design values, one source I have found continually provides excellent coverage. Just remember that the coverage is from the perspective of a group that does have a stake in the outcome. <br />
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<a href="http://www.sbcindustry.com/lumber.php">SBCA Lumber News</a><br />
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I would also like to add that I receive weekly emails from SBCA regarding news that affects the lumber industry as a whole. I recommend anyone with an interest in the lumber and housing market to sign up for the emails. <br />
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<a href="http://sbcmag.info/news">SBCA Magazine News</a><br />
<br />Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-26152776705349471662011-10-20T04:12:00.000-07:002011-10-20T04:16:40.586-07:00Southern Pine Design Values: UpdateAccording to a memo sent out by the American Lumber Standards Committee, the Board of Review has postponed making a decision regarding the SPIB's proposed changes to Southern Pine design values for 60 days. This postponement is to allow interested parties to review and comment on the technical aspects of SPIB's proposal. See the link below for the memo.
<a href="http://sbcmag.info/sites/sbcmag.info/files/ind_news/2011/10/111020_alsc_delay_memo_pdf_13414.pdf">ALSC Memo</a>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-38437914811346767932011-10-18T06:43:00.000-07:002011-10-18T06:43:34.405-07:00Southern Pine Design ValuesAs some of you may already be aware, on October 20th, 2011 the Southern Pine Inspection Bureau will be proposing new allowable design values for southern pine lumber to the Board of Review of the American Lumber Standard Committee. The proposal will lower design values for all grades and sizes of visually graded southern pine by approximately 25-30%. This will have a major impact on all aspects of the lumber industry. <br />
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While the testing for these changes began in 2010, it appears as though many groups have only recently become aware of the proposed changes. One point of contention for many industry representatives is the limited sample size of testing performed to provide the basis for the changes. To my knowledge, approximately 400 southern pine #2 2x4 were tested. No other sizes or grades were tested. Further contention lies in the lack of collaboration with other industry groups to insure that everyone affected has a chance to aid in the process of determining the new design values. <br />
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Much more information can be found in the following links:<br />
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<a href="http://www.sbcindustry.com/lumber.php">SBCA News Page</a><br />
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<a href="http://www.spib.org/important-notice.shtml">Southern Pine Inspection Bureau Updates</a><br />
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<a href="http://www.anthonyforest.com/design-value-news.shtml">Anthony Forest Products News Page</a><br />
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Another Note: While there appear to be several written items about the changes, I have not found a table of the proposed design values to compare with the current design values. <br />
<br />Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-64088069176961891112011-08-09T06:51:00.000-07:002011-08-09T06:51:09.211-07:00Building Codes change in Joplin and Pennsylvania<a href="http://www.koamtv.com/story/15190246/building-codes-change-in-joplin-aimed-at-creating-safer-homes#.TkE3S6BRCuY.blogger"><em>Building Codes change in Joplin aimed at creating safer homes - KOAM TV 7 Joplin and Pittsburg</em></a><em> </em><br />
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<a href="http://www.toolsofthetrade.net/industry-news.asp?sectionID=2123&articleID=1611976&cid=TOTTU%3A080211#.TkE3gZAekEI.blogger"><em>Build It Right: Bracing Walls for Wind</em></a><em> </em><br />
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It is interesting that as one City increases the requirements of the Building Code one State is decreasing its requirements. Decreasing the wall bracing requirements could have a negative impact on a homes resistance to a tornado. That may be the difference between a City that has seen first hand the damaging effects from a tornado and a State that has not. <br />
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The article below highlights findings by a National Science Foundation sponsored research team. Code Authorities should look to studies such as this to aid in decision making when planning for code changes, especially when reducing code requirements. <br />
<h1><span style="font-size: small;"><span style="font-family: inherit;"> </span></span><h1><a href="http://uanews.ua.edu/2011/08/structures-on-storms-edge-could-benefit-greatly-from-improved-engineering-according-to-ua-involved-study/"><em><span style="font-size: small;">Structures on Storm’s Edge Could Benefit Greatly from Improved Engineering, According to UA-Involved Study</span></em></a></h1></h1>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-83625080059537213452011-07-15T09:32:00.000-07:002011-07-15T12:42:29.060-07:00Deck Design Do's and Don't's: Part 2<div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;">For Part 2 (click <a href="http://myconstructionfinds.blogspot.com/2011/06/deck-design-dos-and-donts-part-1.html">here</a> for Part 1) of Deck Design Do's and Don't's, I want to address guard post attachments. Based on research at Virginia Tech, we now know that typical attachments used in deck construction do not meet code required design loads. One such instance can be seen in the picture below. </div><div style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none;"><br />
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</div><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: left;">The 4x4 post has been notched and nailed to the exterior rimboard of the deck. As you can see, the nails in the thin portion of the member have created a split in the wood along the grain. Similar notched and un-notched connections with bolts also fail to meet the code design loads. </div><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: left;"><br />
</div><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: left;">Use of hold-down anchor brackets, as shown in the picture below, are required to be installed at guard posts to meet the design loads. The primary method of failure for typical bolted connections stems from the rotation created in the rimboard. The rimboard attachment to the joists must support that rotation. Hold-down anchors provide a means of transferring the load out of the rimboard and into the floor system. </div><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: left;"><br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPHevutNtZNwMxdLlhupOoFQ6JfDbXlVz-aSFCtbg9WFCeZf0yrnqdy5bsuoOt3qSoT6xYoMtmnzWmU8pp879nCbGxLw2Tmfc_IjEGEpAFZIZu0apxUiWY4ycWokPR3a3C3nLWrUFgD9_Z/s1600/DTT2Z_install+blocking.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="381" m$="true" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPHevutNtZNwMxdLlhupOoFQ6JfDbXlVz-aSFCtbg9WFCeZf0yrnqdy5bsuoOt3qSoT6xYoMtmnzWmU8pp879nCbGxLw2Tmfc_IjEGEpAFZIZu0apxUiWY4ycWokPR3a3C3nLWrUFgD9_Z/s400/DTT2Z_install+blocking.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><em>Photo Courtesy of Simpson Strong-tie.</em></td></tr>
</tbody></table><div class="separator" style="border-bottom: medium none; border-left: medium none; border-right: medium none; border-top: medium none; clear: both; text-align: left;">For more information on deck design, including links to deck design guides, you can look at my previous post <a href="http://myconstructionfinds.blogspot.com/2011/06/residential-deck-design.html">here</a>. For more information about guard post connections you can look <a href="http://www.deckmagazine.com/pdf/2011/1105/1105code.pdf">here</a> for details and <a href="http://www.deckmagazine.com/article/385.html?cid=PRD110711002">here</a> for design. </div>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com1tag:blogger.com,1999:blog-2063196181683625429.post-63680153663030432392011-07-06T14:18:00.000-07:002011-07-06T14:18:19.993-07:002010 Wood HandbookThe Forest Products Laboratory (FPL) has recently released the printed edition of the 2010 Wood Handbook: Wood as an Engineering Material. While you can download the entire book from the FPL website (see below), I encourage anyone serious about wood design to buy the printed edition as a desk reference. At a cost of $60, this may be one of the least expensive engineering reference books you will find. <br />
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If you are looking for a textbook on wood design, such as how to design beams, etc., this is not the book for you. (I would recommend Design of Wood Structures by Breyer, Fridley, et.al.) This book focuses on the physical and mechanical properties of wood and wood composites and provides information on wood preservation, fastening, finishing, and adhesives. <br />
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This is taken from the FPL website:<br />
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<em><blockquote><em>The Wood Handbook is one of the most widely used documents in the wood literature. The 2010 edition is the first update of the 21st century and includes several new chapters. The original handbook was first published in 1935 by the USDA Forest Products Laboratory (FPL). </em><br />
<em>The Forest Products Society (FPS) is pleased to cooperate with the FPL to present this newly updated edition in hard copy. This 2010 edition is your one-stop source for information on wood as an engineering material and offers content such as:</em><br />
<em><br />
• Properties of wood and wood-based products <br />
• Design information for architects and engineers <br />
• Wood and non-wood composites <br />
• Wood-moisture relationships and wood durability<br />
<br />
<em><strong>...plus NEW CONTENT on:</strong><br />
• Wood as an environmentally responsible, sustainable building material <br />
• Heat-treating and sterilization procedures for wood infected by invasive insect species <br />
• A special COLOR chapter on low-magnification micrographs of cross sections of commercial wood species</em></em> </blockquote></em><br />
You can order your hard copy of the 2010 Wood Handbook <a href="http://www.forestprod.org/handbook/">here</a> or you can download content or sample the material that is in the book <a href="http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=100&header_id=p">here</a>.Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com3tag:blogger.com,1999:blog-2063196181683625429.post-70907528153880770902011-06-28T15:09:00.000-07:002011-07-15T12:42:43.958-07:00Deck Design Do's and Don't's: Part 1I recently visited a wood framed observation platform that I am replacing with new designs. The owner wants to keep a small section of the platform that is newer while replacing the older portion that is failing in some areas. I will post some of the failure items over the next few weeks so as not to show everything at once.<br />
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For Part 1, we can discuss the importance of post caps when bearing a girder on a beam. See the photograph above. Reasons to use a post cap for this condition include:<br />
<ol><li>Increases lateral strength of the connection.</li>
<li>Eliminates use of toe-nails, which when improperly installed can split the top of the post.</li>
<li>Contains movement of the wood girders relative to the top of post that results from the shrinking, swelling and twisting of wood as it reaches its equilibrium. </li>
</ol>Ultimately, you do not want the condition in the photograph to result in the photograph below. <br />
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For more information about deck design, please see my previous post <a href="http://myconstructionfinds.blogspot.com/2011/06/residential-deck-design.html">here</a>.Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com1tag:blogger.com,1999:blog-2063196181683625429.post-54260838029414078252011-06-10T08:41:00.000-07:002011-06-10T08:41:41.847-07:00Residential Deck DesignIn the last 6 weeks I have been researching and reading about deck and guardrail design and construction. I am currently working on a project to develop two observation platforms for air monitoring equipment. These platforms are stand-alone wood frames structures. While they are not residential decks, they are very similar in many ways with the exception of design loads. <br />
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For an introduction to deck design, I recommend <a href="http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf">Design for Code Acceptance-6: Prescriptive Residential Wood Deck Construction Guide</a> published by the American Wood Council. This guide covers design and detailing for several conditions including deck-ledger attachment, post-beam connections, and guard post attachments.<br />
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The guard post attachments are interesting because recent testing shows the inadequacy of many standard connections. The International Residential Code requires that residential deck railings be designed for a live load of a 200lb concentrated load in any direction located at any point along the rail.<span style="mso-spacerun: yes;"> </span>Upon reviewing local construction practices of guard-post attachments, many of which appeared questionable for meeting code requirements, researchers at Virginia Tech began testing these connections.<span style="mso-spacerun: yes;"> </span>The results, which have been published in Wood Design Focus and the Journal of Light Construction, were somewhat surprising.<span style="mso-spacerun: yes;"> </span>Typical bolted and lapped/bolted connections were unable to meet the code requirements.<span style="mso-spacerun: yes;"> </span><br />
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</div><div class="MsoNormal" style="margin: 0in 0in 0pt;">After attempts to redistribute load using typical connections were unsuccessful, the Researchers began testing Simpson HD2A anchors attached to deck joists.<span style="mso-spacerun: yes;"> </span>This method of connection for guard-posts has subsequently been included in DCA-6.<span style="mso-spacerun: yes;"> </span>While the 200lb concentrated load has been a code requirement for some time, until now there have been no prescriptive guidelines for meeting the code.<span style="mso-spacerun: yes;"> Further details for guard post attachment can be found <a href="http://www.deckmagazine.com/pdf/2011/1105/1105code.pdf">here</a>. </span></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><br />
</div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="mso-spacerun: yes;">Further Reading:</span></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="mso-spacerun: yes;"><a href="http://www.coastalcontractor.net/pdf/2008/0803/0803safe.pdf">Safe and Durable Coastal Decks</a></span></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><br />
</div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><span style="mso-spacerun: yes;"><a href="http://www.deckmagazine.com/filereader/1.html">Professional Deck Builder</a></span></div><div class="MsoNormal" style="margin: 0in 0in 0pt;"><br />
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</div>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com1tag:blogger.com,1999:blog-2063196181683625429.post-88320901016722223672011-05-27T08:33:00.000-07:002011-05-27T08:33:59.423-07:00Repetitive Member Factor: An Introduction<div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><span style="font-family: inherit;">An increase in the reliability of wood members when placed into assemblies with repetitive use components has been recognized for many years by the wood industry.<span style="mso-spacerun: yes;"> </span>The term assembly is typically defined as 3 or more members spaced at 24” on center or less and attached with load distributing elements capable of supporting the design loads.<span style="mso-spacerun: yes;"> </span>Examples include floors, walls, roofs and three-ply beams with load distributing elements of wood structural sheathing or transverse mechanical fasteners.<span style="mso-spacerun: yes;"> </span></span></div><div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><br />
</div><div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><span style="font-family: inherit;">Floors and walls are typically solid-sawn members attached with plywood or OSB sheathing.<span style="mso-spacerun: yes;"> </span>Roofs, however, are solid-sawn members or prefabricated trusses that have the top chord and/or bottom chord connected with structural wood sheathing.<span style="mso-spacerun: yes;"> </span>The sheathing creates load sharing between the members of the assembly.<span style="mso-spacerun: yes;"> </span>Three-ply beams share load through the mechanical fastening system used to build the member.<span style="mso-spacerun: yes;"> </span></span></div><div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><br />
</div><div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><span style="font-family: inherit;">The capacity of the assembly benefits from an increase in lateral stability of the members, partial composite action where the load is distributed lengthwise along the member, and load sharing where the load is distributed across parallel members that have different stiffnesses.<span style="mso-spacerun: yes;"> </span>The parallel members having different stiffnesses result in varying amounts of deflection under uniform loads.<span style="mso-spacerun: yes;"> </span>The load distributing element reduces the effects of various deflections by distributing the load away from more flexible members to stiffer members.<span style="mso-spacerun: yes;"> </span>Members that are more flexible tend to be weaker than stiffer members, resulting in load being distributed away from weaker members and into stronger members.</span></div><div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><br />
</div><div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><span style="font-family: inherit;">Load sharing is accounted for through the use of repetitive member factors.<span style="mso-spacerun: yes;"> </span>Since 1968, the National Design Specification for Wood Construction (NDS) has specified a repetitive member factor of 1.15 for bending design values of dimension lumber.<span style="mso-spacerun: yes;"> </span>Also, since 1970, ASTM D245 has recommended a load sharing factor of 1.15 for bending stresses in multiple member systems.</span></div><div class="MsoNormal" style="margin: 0in 0in 0pt; text-indent: 0.5in;"><br />
</div>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-56712230861073437432011-05-17T06:35:00.000-07:002011-05-17T06:35:01.104-07:00Lessons from a TornadoThe April 27 tornadoes left many opportunities to study structural performance of both commercial and residential buildings. One area that I have observed was a residential development located just out of the path of an EF3 tornado that made its trail not far from my home. With the exception of one building's collapse, damage to each home generally consisted of a portion of roof missing, as seen in the photo below. <br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTPtyk7WCsZma2iWA110DhXzY5keACm0wpC17b1abhIKiZsHhDNdrpzq86JkUJfDObqQPvdmWB6XUJ1jSc_dq5WVpRUMywWk1YulPIPtnrex9I2qO1qZbNhQ_YmHfjk6AVRRRXEWn_o0qk/s1600/P5040072.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTPtyk7WCsZma2iWA110DhXzY5keACm0wpC17b1abhIKiZsHhDNdrpzq86JkUJfDObqQPvdmWB6XUJ1jSc_dq5WVpRUMywWk1YulPIPtnrex9I2qO1qZbNhQ_YmHfjk6AVRRRXEWn_o0qk/s400/P5040072.JPG" width="400" /></a></div><br />
A close up inspection of the rafter heel condition at the top plate highlighted the failure of the roof system. A birds-mouthed rafter with (3) toe-nails into the wall top plate is a common framing detail used in residential structures. This detail was used throughout this development. There appear to be two realistic modes of failure for this detail as highlighted in the pictures below. The first mode is failure of the 2x rafter at the birds-mouth. This failure mode occurred in a small portion of rafters witnessed. <br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9An3nIuDpY5RtxvXSIzfOGkdVzoVI9S1_HwkpYb0z6WKTGczvySmeAQf8cizMNzh1r66raL2uF0hG2akZvj7xoe7Lax9YetkEaXTLFt4B-PgGQnumXKf9SSy_mSiQeri3c3d9CrGvs9TT/s1600/P5040077.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9An3nIuDpY5RtxvXSIzfOGkdVzoVI9S1_HwkpYb0z6WKTGczvySmeAQf8cizMNzh1r66raL2uF0hG2akZvj7xoe7Lax9YetkEaXTLFt4B-PgGQnumXKf9SSy_mSiQeri3c3d9CrGvs9TT/s400/P5040077.JPG" width="400" /></a></div><br />
The second mode of failure is at the toe-nail connection. Although this connection works reasonably well for lateral shear, the typical limit state for uplift loading is nail withdrawal from the wall top plate. The nails in the picture below appear to have seen very little stress during failure. <br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0v-E8yYeV_XzLnUyvMb1GJACR_kvUC0h0Y_NSNWKAvQ29RSgpKfx1RU901oNDRJYzbehy3cocdwrYi6RzDawJPjzMi5m7suA4Cu3gntFO9Vl3Qsr6xA6a-eAMGiKATra1HnP1QHCmCqSO/s1600/P5040084.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0v-E8yYeV_XzLnUyvMb1GJACR_kvUC0h0Y_NSNWKAvQ29RSgpKfx1RU901oNDRJYzbehy3cocdwrYi6RzDawJPjzMi5m7suA4Cu3gntFO9Vl3Qsr6xA6a-eAMGiKATra1HnP1QHCmCqSO/s400/P5040084.JPG" width="400" /></a></div><br />
Athough this is a common detail, I avoid detailing a rafter/truss to top plate connection with toe-nails. A Simpson H2.5A anchor, available at local hardware stores, is inexpensive and provides a significantly improved connection capacity. This syle of clip results in a more consistent installation and brings a different connection failure mode that does not include nail withdrawal. For a small home with a simple framed roof, such as homes in this development, a small investment in H2.5A clips can have a major impact on structural performance.Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-4984240387643787962011-05-10T07:19:00.000-07:002011-05-10T07:19:05.357-07:00Cross-Laminated Timber News<a href="http://techniker.oi-dev.org/blog/view/cross-laminated-timber-construction-for-schools"><em>Techniker Blog - Cross-Laminated Timber Construction for Schools</em></a><br />
<br />
<a href="http://www.structurlam.com/news/"><em>Structurlam Brings CrossLam to North America</em></a><br />
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<a href="http://www.storaenso.com/media-centre/press-releases/2011/01/Pages/stora-enso-continues-to-grow.aspx"><em>Investment in CLT Lumber in Europe Continues</em></a>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-70100491092904104942011-05-03T15:28:00.000-07:002011-05-03T15:28:08.021-07:00Tuscaloosa, Alabama Tornado Meets Wood TrussI pulled the picture below from The Birmingham Business Journal's coverage of the April 27, 2011 tornado damage. I have been slow to look at online pictures and videos of the event for a myriad of reasons. I lived in Tuscaloosa for several years while studying for my BS and MS. Even though many people have seen the devestation via TV, Web, or first hand, I could not resist sharing this picture here on the blog. <br />
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</div><div class="separator" style="clear: both; text-align: left;">A close look at the stick of wood embedded in the bumper of this car, and the wood lying on the ground in front of the car, reveals that this "stick" is actually from a metal plate connected wood truss. I do not know the context of this picture to understand how this may have happened or the location of adjacent buildings from where this truss may have lived. Whatever the process, the end result is amazing. </div>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-4261962507610320132011-04-29T05:11:00.000-07:002011-05-10T07:07:14.698-07:00Tornadoes and Home Construction<a href="http://www.usatoday.com/money/economy/housing/2011-04-20-tornado-home-construction.htm"><em><i>USA Today - Making a tornado-proof home is tough</i></em></a><br />
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I saved this post to publish this week. Not sure how it feels now. Thankfully, my family has made it through yesterday's tornadoes. Many families have not been as fortunate. Our thoughts and prayers are very important, but please don't forget to volunteer if possible or send supplies.Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0tag:blogger.com,1999:blog-2063196181683625429.post-23680973791112574772011-04-29T04:49:00.000-07:002011-04-29T04:49:45.193-07:00China Timber Deficit<a href="http://www.woodbusiness.ca/News/new-risi-study-forecasts-chinas-timber-supply-deficit-to-increase-by-55-by-2015.html"><em><i>Forecasts for China's Timber Supply Deficit</i></em></a>Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com2tag:blogger.com,1999:blog-2063196181683625429.post-50172875629408110642011-04-26T04:07:00.000-07:002011-04-26T04:07:04.911-07:00Hebei, China - A Growing Market<a href="http://www.bclocalnews.com/bc_thompson_nicola/clearwatertimes/business/119091714.html"><i>Clearwater Times - Hebei gets third truss plant, wood-frame research centre</i></a><br />
Further growth in the Asian markets for wood construction.Jasonhttp://www.blogger.com/profile/18086511467826948549noreply@blogger.com0