Progress 09/01/12 to 08/31/13
Target Audience: Phase II results will allow for the scaling of round timber manufacturing through the following Technical Objectives: 1) Continue axial mechanical testing of branched timbers in Ash and in Aspen. 2) Further develop and test novel sub-assembly connection methods for branched column-truss assemblies to best utilize the strength of branched timbers. 3) Test prototype column-truss assemblies for axial loading the field. 4) Use test data to establish design values for the connections, the Y-branched columns and trusses to assist in grading timbers and engineered framing systems for Phase III commercialization. In its first year's efforts toward these technical objectives, the project team reached the following target audiences: Construction Industry Leaders: In order to eventually commercialize the products developed under this grant, WholeTrees has engaged leaders in commercial construction through out the development of this truss system, its branched tree members, its steel connections, and its assemblies. Market research has occured during the development of these tests and products to establish what building dimensions will allow for these products, which early adopters in the industry will likely purchase these products, and for what types of commercial construction. Forestry Operations: By seeking convenient sources for its branched timbers destined for testing, WholeTrees reached out to forest owners, municipalities and rural land owners, to connect with their foresters, their timber cruisers, and the end-users for small diameter branched timbers (pulp mills, urban stagin grounds and chipping centers, as well as occassional structural timber builders). This outreach built awareness for the growing use of timber as structural members. WholeTrees is now a central connector and leader for Upper Midwest forest stakeholders seeking higher value markets for their management thinnings. Timber Engineers: The increased use of small diameter round timber in construction implies a larger network of structural engineers comfortable with timber. As WholeTrees drew together experts on structural steel connections and timber assemblies for this project, we began to create a database of structural engineers accross the country interested in increasing the use of timber in construction, and willing to innovate and advocate for this. Changes/Problems: The problems and challenges encountered in our first year fell under the following project tasks: TASK Complete Structural Engineering of 36’ long column-truss assembly, as well as second, pre-tensioned truss assembly: PROBLEM: These values are for a normal duration and wet service condition. If dry condition is required, the following increases ASTM D245 increases to 19% MC. WholeTrees needed to decide whether the testing of this assembly demanded kiln drying, or whether strength values for seasoned wood might be suffi cient. Certainly, on our path to commercialization, seasoning is far more cost effective than kiln drying. The team has yet to conclude the best method moving forward, so WholeTrees assumes its Red Pine cords will be kiln dried. TASK Complete analysis of structural forces for each connection point on truss: PROBLEM: The forces transferring from steel web to steel and wood connection are very high at the edges of each girder truss (less in the middle), and the design solution for a connection that can withstand such high tension and compression loads is very challenging. The team has spent many iterations of connections exploring this problem, and one is certain yet whether the proposed designs will handles the necessary force during sub-assembly tests. TASK A brainstorm of connection ideas are shared by the project team, and three distinct connection concepts are chosen. PROBLEM: The performance to cost analysis ratio of each proposed connection type is proving more relevant than originally assumed, and needs exploration prior to proceeding-- an unfunded cost to WholeTrees. This is slowing down the eventual sub assembly tests. TASK Final selection criteria established for columns to-be-tested, as well as for column-truss assembly sizes, lengths, geometry, and moisture level. PROBLEM: Harvest criteria was established in Autumn, which is a less ideal season for peeling timber, and added time and money to the acquisition of text-specimens. Then, the South West Wisconsin forest floor did not freeze until late in winter, delaying the harvest of felled and peeled trees to a landing ground for further seasoning. TASK Harvest, peeling and storage of 60 columns for destructive testing (25 Ash, 35 Aspen); and 10 red pine cutoffs for sub assembly connections. PROBLEM: Matching the established chord size for red pine (14” width at mid span for lower chord, and 12” width at mid span for upper chord) proved more challenging than expected. This width, though abundant in larger scale production, is less available in quantities of 15 or 20, as this research project requires. WholeTrees finally located two sources for this size of red pine thinning, but the search was time consuming. What opportunities for training and professional development has the project provided? The first year of this project has allowed WholeTrees staff training and professional development in the following areas: Collaboration and Mentoring by Structural Engineers nationally: The work plan required WholeTrees to network with the nation's most experienced timber structural engineers. Sharing our research problems with this cohort, under NDA's, WholeTrees was able to develop a much more substantial body of knowledge regarding existing engineering for timber structures, as well as undeveloped research. This collaboration also helped WholeTrees identify entire areas of research required to scale up the use of small diameter timber internationally. Non-Destructive Evaluation (NDE) collaborations: The USDA Forest Products Laboratory hosted an international NDE convention, which WholeTrees partipated in as a sponsor. This network of researchers has built our staff's understanding of what is already possible in non-destructive evaluation of round timber, and what areas of research need further pursuit. How have the results been disseminated to communities of interest? Year two of this project has and will include dissemination of project results. WholeTrees will be sure to report on these events in its final report. What do you plan to do during the next reporting period to accomplish the goals? The work thus far accomplished within this Phase 2 research project prepares the team for destructive testing of a) subassembly connection tests, b) branched column axial load tests; c)full assembly load tests of column/truss prototype. These tests are scheduled at the Forest Products Laboratory for Spring-Summer 2014. Prior to these destructive tests, all branched columns will undergo a 30-dimensional scan with appropriate laser devices to collect digital point clouds that will later be paired with information on breakage, strength, and structural failure. This process is scheduled for August-September, 2013, and WholeTrees has connected to researchers at MIT and internationally involved in tangential uses of lasers in forest products metrics. Finally, all data from destructive testing will be analyzed, and correlations will be drawn between structural failure and 3-dimensional geometric characteristics of branched timber columns.
What was accomplished under these goals?
WholeTrees has reached its mid-phase goals for three of the four stated objectives, with the fourth objective scheduled for Year Two of this project. All specimens for continued axial mechanical testing have been harvested and are seasoning until Spring, 2014; and axial tests have been designed, with preparations made at the USDA Forest Products Laboratory, Madison, WI. Data from Phase 1 has infl uenced the selection criteria for these specimens, as has ongoing dialogue about ideal product heights, lengths, and load capacity for commercialization. A diverse team of architects, engineers, and business professionals have brainstormed innovative steel connections that will enable the cost-effective use of branched timber in commercial construction settings, and the top three designs have been fabricated by a steel fabricator, in preparationg for sub assembly load tests in May-June, 2013. Extensive structural analysis has been completed for the prototype column-truss assembly described in this grant proposal, with load requirements influencing the design of steel connections and webbing, as well as the species of round timber selected for the project. All inventory for assembling these prototypes has been harvested and is seasoning through Summer, 2013. If need be, all inventory will be kiln dried in September, 2013.