Mass Timber Research Workshop Held at FPL

The Forest Products Laboratory (FPL) hosted the inaugural Mass Timber Research Workshop this week in cooperation with Woodworks – Wood Products Council.  During the two-day event, more than 120 national and international attendees, including 26 presenters, gathered to learn about cross laminated timber (CLT) and how its design and use can further green building efforts while also aiding in forest restoration activities. Tom Williamson of Timber Engineering, LLC, facilitated the workshop, and the Softwood Lumber Board generously provided support.

CLT offers outstanding structural, thermal, and acoustic performance.

CLT offers outstanding structural, thermal, and acoustic performance.

Experts discussed past and current research on CLT and how the material can be used in conjunction with underutilized and high-quality wood to construct a variety of multi-story buildings.  While CLT has been used in Europe for nearly 20 years, it is only recently catching on in North America.  Multi-story buildings using CLT are popping up around the United States and Canada, and in fact, the first large-scale commercial installation of CLT in the United States (using CLT manufactured in North America) was built right here in Madison, Wis., for Promega Corporation.  Construction is slated to begin shortly on what will be the tallest wood building in North America, a 12-story residential structure in Quebec City, Quebec.

In addition to CLT construction and design, other topics discussed at the workshop included information on fire safety, seismic conditions, architectural design, and the Forest Service budget outlook for 2016 and beyond. According to FPL Assistant Director for Wood Products Research Mike Ritter, the Forest Service firefighting budget is expected to continue to increase in the years ahead, making CLTs and other value-added wood products a critical component in maintaining the health of our Nation’s forests.

Contributed by Steve Schmieding and Francesca Yracheta

FPL Partner Procures Patent: Better Building With BioSIPS

Whether serving as a bookshelf, tabletop, or wall panel, the composite board is a ubiquitous construction material found in furniture and homes alike. Traditional composite boards use mankind’s most trusted building resource, wood, as a base — but a new patented process using waste products stands to revolutionize the familiar building material, making it even more sustainable and environmentally friendly.

FPL-2011-24

BioSIPS use low-value recycled material to make high-value structural materials.

Julee Herdt, a professor at the University of Colorado – Denver, and Kellen Schauermann, a former graduate student, were recently awarded a patent for their Bio-Structural Insulated Panels (BioSIPS) system. BioSIPS are structural boards comprised of waste material such as recycled paper, noxious weeds, industrial hemp, and forest debris.

Herdt, the CEO and president of BioSIPS Inc., hopes that her product will help ease the environmental and energy concerns of tomorrow.

Although wood-based Structural Insulated Panels (SIPS) have been around for some time, Herdt’s BioSIPS, made from 100% recycled material, could replace their conventional wood counterparts. BioSIPS wall, floor, and roof panels even surpass conventional SIPS in some strength-testing areas (especially compressive and transverse loading) as well as exhibit superior thermal characteristics — which is important, as thermally-efficient structures go hand-in-hand with decreased energy usage.

Herdt’s accomplishment comes on the heels of a long legacy of research and collaboration with the Forest Products Laboratory (FPL). In 1995, she was part of a project that researched and tested GRIDCORE (FPL’s Spaceboard) panels — three-dimensional, molded structural panels comprised of recycled corrugated containers, old newsprint, and kenaf, a plant native to southern Asia. The name “spaceboard” referred to the spaces afforded by the waffle-like design of the GRIDCORE panels, which allowed for increased strength and decreased weight and material usage.

Nearly 20 years later, BioSIPS, like GRIDCORE panels before them, carry on the tradition of turning society’s low-grade waste into high-value products that have proven utility in real-world construction projects. Along with her personal office, Herdt and her team built entire houses with BioSIPS, winning first prize at the U.S. Department of Energy’s Solar Decathlon in 2002 and 2005.

biosips

Herdt, Schauermann and Hunt await another patent for new methods of creating complex three-dimensional shapes with fiber boards.

Herdt and Schauermann, along with FPL Research General Engineer John Hunt, are awaiting the award of a second patent, Cut-Fold Shape Technology for Engineered Molded Fiber Boards, which relates to a new process of folding fiber boards into three-dimensional shapes to maximize their utility and strength.

In a world of increased environmental awareness, BioSIPS promise to offer designers, engineers, and industry professionals new ways to build strong, energy-efficient structures and provide another avenue for society to make better use of its waste products. Through technologies like these, we will better be able to tackle the construction challenges of tomorrow in an environmentally responsible way.

 

 

Exploring Construction Using Whole Trees

wholetreestruss-(2)Researchers at the Forest Products Laboratory (FPL) are testing trusses, which provide structural support for buildings, made from whole trees.  One such truss, pictured above, had a clear span of 55 feet and was made from low-value red pine logs. Similar trusses will be installed in a commercial retail building this spring.

This work, which is a cooperative effort between FPL and Whole Trees, LLC, is being conducted to demonstrate the technical feasibility of using tree stems, in their original form, as structural members in commercial structures.

“We’re engineering the tree into structural assemblies which make use of the tree’s superior strength in bending when compared with milled wood. This will lead to stronger buildings while adding value to forests,” said Roald Gundersen, co-founder and project lead at Whole Trees. “We couldn’t achieve these goals without the Small Business Innovation Research Grant Program and the partnership of FPL and lead research engineer Doug Rammer and his team.”

Evaluation of Extended Wall OSB Sheathing Connection: Summary and Conclusions

Fig.2

Specimen used for research.

The new study, Evaluation of Extended Wall OSB Sheathing Connection under Combined Uplift and Shear Loading for 24-inch Heel Trusses, leaves us with the following conclusions:

This testing program was designed to further evaluate the performance of OSB wall sheathing panels extended over the roof heel in resisting combined uplift and shear forces. The results of this study provide guidance towards further expanding prescriptive solutions for high-heel truss attachment optimized for performance from the standpoint of structure, energy, and ease of construction. The following is a summary of the conclusions based on the results of this testing program:

  1. The tested system using extended wood structural panel as the primary connecting element (without additional connecting hardware) at the roof-to-wall interface of energy trusses can provide a continuous load path in both the shear and uplift directions and can be considered a viable option for residential construction in most areas of the country.
  2. The uplift-shear capacity interaction curve for the energy truss heel connection system is nonlinear, with capacities for all uplift to shear ratios measured in this testing program exceeding the capacities predicted based on a linear interaction. In design applications, a linear relationship may be a simplified and conservative representation of the response under combined loading for energy truss heel connection system using extended wood structural panel sheathing.
  3. The uplift-shear capacity interaction curve for the energy truss heel connection system is nonlinear, with capacities for all uplift to shear ratios measured in this testing program exceeding the capacities predicted based on a linear interaction. In design applications, a linear relationship may be a simplified and conservative representation of the response under combined loading for energy truss heel connection system using extended wood structural panel sheathing.

Evaluation of Extended Wall OSB Sheathing Connection: Combined Uplift and Shear Loading for 24-inch Heel Trusses

A new study has been published, Evaluation of Extended Wall OSB Sheathing Connection under Combined Uplift and Shear Loading for 24-inch Heel Trusses, by Vladimir Kochkin and Andrew DeRenzis from the Home Innovation Research Labs, Upper Marlboro, Maryland, and FPL’s Xiping Wang.

According to Norbord, Inc. (Toronto, Ontario), home builders in high-wind areas are increasingly frustrated by the large number of metal hold down devices (hurricane straps) required between floors on exterior walls. In addition to the expense and additional labor required to install such devices, they often experience nailing interference problems with the wood structural panel sheathing or siding, or both. Wood structural panels can be used to resist both shear and uplift.

The present study was designed to evaluate the performance of the extended wall structural panel connection in resisting combined uplift and shear forces at the roof-to-wall interface with a focus on a truss heel height of 24 inches to address the expected increases in the depth of attic insulation used in Climate Zones 5 and higher. Five full-size roof–wall assemblies were constructed with extended oriented strandboard (OSB) wall sheathing and each was tested under a different loading combination.

fig_01

Test specimen and setup.

The test results indicate that using extended wood structural panel wall sheathing as the primary connecting element (without additional connecting hardware) at the roof-to-wall interface of energy trusses can provide a continuous load path in both the shear and uplift directions and can be considered a viable option for residential construction in most areas of the country. The overturning effects caused by increased truss heel heights up to 24 inches can be offset by additional face nails that attach the extended wood structural panel wall sheathing to the energy truss heel.

This study was Phase 3 of a test program that responds to the new requirements for roof-to-wall connections in the 2012 International Residential Code (IRC) and expands upon the previous phases that evaluated innovative roof-to-wall connection systems. The new IRC provisions specify complex details for attachment of rafters and trusses to the supporting walls. These new requirements, which apply to high-heel energy trusses even in the low-wind areas, are labor intensive and add cost to construction of light-frame wood buildings. A previous testing project conducted to evaluate optimized structural roof-to-wall attachment solutions demonstrated the effectiveness of wood structural panels in restraining high heel (i.e., energy) trusses against rotation. Further testing in Phase 2 confirmed the ability of oriented strandboard (OSB) wall sheathing panels extended over the roof heel to resist combined uplift and shear forces without additional roof-to-wall hardware.

Phase 3 builds upon previous testing by evaluating the performance of the extended wall structural panel connection in resisting combined uplift and shear forces at the roof-to-wall interface with a focus on a truss heel height of 24 inches to address the expected increases in the depth of attic insulation used in Climate Zones 5 and higher. The results of this study are expected to further expand prescriptive construction solutions optimized for performance from the standpoint of structure, energy, and ease of construction.

The specific objective of the Kochkin and others study was to develop an uplift-shear capacity interaction curve for extended wood structural panel wall sheathing used as the primary connecting element at the roof-to-wall interface with 24-inch-high energy truss heels.

Curve

This figure shows the uplift versus shear capacity interaction curve based on the test results. For comparison, the figure also includes a linear interaction.