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

United States Department of Agriculture

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

Vladimir Kochkin Andrew DeRenzis Xiping Wang

Forest Forest Products General Technical Report August Service Laboratory FPL–GTR–233 2014 Abstract Contents This study was designed to evaluate the performance of Introduction ...... 1 the extended wall structural panel connection in resisting Objective ...... 1 combined uplift and shear forces at the roof-to-wall interface with a focus on a truss heel height of 24 in. to address Materials and Methods...... 1 the expected increases in the depth of attic insulation used General...... 1 in Climate Zones 5 and higher. Five full-size roof-wall as- semblies were constructed with extended oriented strand- Specimen Construction...... 1 board (OSB) wall sheathing and each was tested under a Test Setup and Protocol...... 3 different loading combination. Our test results indicate that using extended wood structural panel wall sheathing as the Results...... 7 primary connecting element (without additional connect- Summary and Conclusions...... 10 ing hardware) at the roof-to-wall interface of energy trusses can provide a continuous load path in both the shear and References...... 10 uplift directions and can be considered a viable option for Appendix—Summary of the Shear Load versus residential construction in most areas of the country. The Horizontal Displacement Curves for Tests B overturning effects caused by increased truss heel heights up Through E...... 12 to 24 in. can be offset by additional face nails that attach the extended wood structural panel wall sheathing to the energy truss heel. Conversion Table Keywords: High-heel truss, lateral performance, extended OSB wall sheathing, roof-to-wall connection, uplift force, English unit Conversion factor SI unit shear force. inch (in.) 25.4 millimeter (mm) foot (ft) 0.3048 meter (m) Acknowledgments pound (lb) 0.45359 kilogram (kg) This project was funded through a cooperative research miles (m) 1.6093 kilometers (km) agreement between the Home Innovation Research Labs and the USDA Forest Service Forest Products Laboratory. This research was supported in part by funds provided by Nor- bord, Inc., Toronto, Ontario, Canada.

August 2014

Kochkin, Vladimir; DeRenzis, Andrew; Wang, Xiping. 2014. Evaluation of extended wall OSB sheathing connection under combined uplift and shear loading for 24-inch heel trusses. General Technical Report FPL-GTR-233. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Prod- ucts Laboratory. 12 p. A limited number of free copies of this publication are available to the public from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI 53726–2398. This publication is also available online at www.fpl.fs.fed.us. Laboratory publications are sent to hundreds of libraries in the United States and elsewhere. The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. The use of trade or firm names in this publication is for reader information and does not imply endorsement by the United States Department of Agriculture (USDA) of any product or service. The USDA prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orienta- tion, genetic information, political beliefs, reprisal, or because all or a part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720–2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250–9410, or call (800) 795–3272 (voice) or (202) 720–6382 (TDD). USDA is an equal opportunity provider and employer. Evaluation of Extended Wall OSB Sheathing Connection under Combined Uplift and Shear Loading for 24-inch Heel Trusses

Vladimir Kochkin, Director Andrew DeRenzis, Structural Engineer Home Innovation Research Labs, Upper Marlboro, Maryland

Xiping Wang, Research Forest Products Technologist Forest Products Laboratory, Madison, Wisconsin

Introduction Materials and Methods This study is Phase 3 of a test program that responds to the General new requirements for roof-to-wall connections in the 2012 International Residential Code (IRC) and expands upon the Testing was conducted at the Home Innovation Research previous phases that evaluated innovative roof-to-wall con- Labs located in Upper Marlboro, Maryland. All specimens Conversion Table nection systems (DeRenzis and others 2012, 2013). The were constructed in the laboratory and all construction materials were purchased from local suppliers. The Norbord English unit Conversion factor SI unit new IRC provisions specify complex details for attachment TallWall/Windstorm OSB product used for the wall sheath- inch (in.) 25.4 millimeter (mm) of rafters and trusses to the supporting walls (ICC 2012). These new requirements, which apply to high-heel energy ing was donated by Norbord, Inc., Toronto, Canada. foot (ft) 0.3048 meter (m) trusses even in the low-wind areas, are labor intensive and A total of five laboratory tests of a roof–wall assembly with pound (lb) 0.45359 kilogram (kg) add cost to construction of light-frame wood buildings. A extended OSB wall sheathing were conducted, each under a miles (m) 1.6093 kilometers (km) previous testing project conducted to evaluate optimized different loading combination. Table 1 provides a test matrix structural roof-to-wall attachment solutions demonstrated summarizing all uplift-shear loading combinations. A com- the effectiveness of wood structural panels in restraining pletely new specimen was constructed for each test. high heel (i.e., energy) trusses against rotation (NAHBRC 2011; DeRenzis and others 2012). Further testing in Test A (100% uplift, no shear load) and Test E (100% shear Phase 2 confirmed the ability of oriented strandboard (OSB) load, no uplift load) were conducted to anchor the combined wall sheathing panels extended over the roof heel to resist loading interaction curve by establishing capacities under a combined uplift and shear forces without additional roof-to- single direction loading. The uplift load levels by percent- wall hardware (NAHBRC 2012; DeRenzis and others 2013). age of total uplift capacity were selected to provide system performance at realistic combined load combinations (Tests Phase 3 builds upon our previous testing by evaluating the B, C, and D) for a low-rise residential building. Combined performance of the extended wall structural panel connec- loading scenarios for residential construction are typically tion in resisting combined uplift and shear forces at the above a 2:1 uplift to shear loading ratio. Therefore, two roof-to-wall interface with a focus on a truss heel height of of the three combined loading tests used the loading ratio 24 in. to address the expected increases in the depth of attic above 2:1. insulation used in Climate Zones 5 and higher. The results of this study are expected to further expand prescriptive Specimen Construction construction solutions optimized for performance from the Figure 1 shows a photo of a roof–wall assembly speci- structural, energy, and constructability standpoint. men in a laboratory setup. Each specimen was constructed with five 24-ft span wood trusses with a 24-in. heel height, Objective spaced at 24 in. on center. The overall size of the full roof The specific objective of this study is to develop an uplift- system was 8-ft deep by 24-ft wide with additional 16-in. shear capacity interaction curve for extended wood struc- long overhangs on each side. Trusses were supported at the tural panel wall sheathing used as the primary connecting heel by 4-ft high by 8-ft long light-frame wood walls. The element at the roof-to-wall interface with 24-in.-high energy supporting walls were constructed with 24-in. on center truss heels. framing and sheathed on the exterior with 4-ft wide OSB panels extending up past the top plate of the wall to capture General Technical Report FPL–GTR–233

Table 1—Test matrix Test Uplift loada Uplift to shear ratiob Shear load Purpose A 100 NA None Establish peak uplift load capacity of the specimen B 85 5.7:1 Max load at 85% uplift Develop uplift versus shear load capacity C 70 2.3:1 Max load interaction relationship at various combined at 70% uplift loading ratios D 40 0.7:1 Max load

at 40% uplift } E 0 NA Max load Establish peak shear load capacity of the specimen at 0% uplift aAs percentage of peak uplift capacity. bAssuming linear relationship.

testing. The shear/rotational restraint limit state was used as the basis because a higher heel height creates higher demand on the shear/rotational resistance of the connection (without changing the uplift demand). Therefore, maintaining the same nail spacing was expected to provide the resistance to combined loading equal or better than observed in Phase 2. No other connection hardware was installed between the wall and the roof. Sheathing was attached to the wall framing (Fig. 3 and Table 3) in general accordance with the provisions developed by American Wood Council (AWC) for the use of wood structural panels to resist combined uplift and shear (Coats and Douglas 2011) that specify additional nails along the top and bottom plates of a shear wall to resist the uplift component in a combined loading scenario. One exception Figure 1. Test specimen and setup. in the tested specimen attachment details was the 4-in. on center nail spacing at the top plate (increased from the 3-in. spacing specified in the AWC provisions) on account of the the energy truss heel. The heel height is the distance from additional roof-to-wall load path through the sheathing-to- the top of the wall to the top of the rafters (underside of the truss heel fasteners. roof sheathing) measured along the line of the wall framing exterior. The supporting walls were anchored to the laboratory strong floor using ½-in.-diameter bolts at 16 in. on center with 3-in. Tables 2 and 3 provide summaries of the materials and by 3-in. by 0.229-in. square plate washers and Simpson HD methods used in construction of the specimens and the hold downs at each wall’s end. fastening schedule for the wall sheathing, respectively. Figures 2 and 3 show the typical test specimen and 7/16-in.-thick OSB roof sheathing was installed perpen- fastening detail, respectively. dicular to the truss top chord members with a staggered panel layout. Metal sheathing clips were installed on the The 7/16-in.-thick TallWall/Windstorm OSB sheathing was unblocked edges of each panel at 24 in. on center between fastened to the truss heel with seven 8d common nails the framing members. A 2-in.-wide roof vent was provided (2½ in. by 0.131 in.) (Fig. 3, Table 3). A total of seven nails at the ridge (1 in. each side of the ridge) such that bearing of were used for the current study (with only one of the seven panel edges did not occur during testing. The ceiling gyp- nails installed into the end grain of the bottom chord of the sum panels were installed perpendicular to the truss bottom truss). This number of nails is based on approximately the chord members and the first rows of fasteners was located same nail spacing that was used in Phase 2 of this testing approximately 8 in. from the supporting walls (i.e., program. It is also the minimum number of nails necessary floating edges) in accordance with the Gypsum Associa- based on preliminary analysis to provide a shear/rotational tion’s Application and Finishing of Gypsum Panel Products performance similar to that exhibited in the Phase 2 (GA-216-2010, Gypsum Association 2010). A single

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

Table 2—Construction of specimens Materials Methods Roof dimensions 24-ft roof span (plus 1-ft 4-in. overhang on each end) 8 ft deep (a total of five trusses) Truss heel height 24 in. measured from the top of wall to the top of the truss (underside of roof sheathing). Measured along the exterior of the wall framing. Roof pitch 7=12

Roof framing members Metal plate connected wood trusses fabricated with No. 2 SPF lumber

Truss spacing 24 in. on center

Truss-to-wall plate connection Trusses toe-nailed to top plate of wall with two 16d box (3¼-in. × 0.131-in.) nails

Fascia board 1 by 6 nominal lumber face-nailed to each truss end with two 8d common (2½-in. × 0.131-in.) nails Roof sheathing materials 7/16-in-thick OSB sheathing installed perpendicular to framing member with steel edge clips and unblocked edges parallel to the ridge. No boundary fastening to the roof diaphragm. Roof sheathing fasteners 8d common (2½-in. × 0.131-in.) at 6 in. on center on panel perimeter and 12 in. on center in the panel field Ceiling material 1/2-in.-thick gypsum panels installed perpendicular to truss bottom chord members, joints in the panel field taped and mudded Ceiling fasteners 1-5/8 in. Type W drywall screws at 8 in. on center with first rows of fasteners 8 in. from side walls (i.e., floating edges) Supporting wall dimensions 8 ft long by 4 ft high

Supporting wall framing 2 by 4 nominal SPF stud or No. 2 grade lumber (including top plates) Supporting wall sheathing 7/16-in.-thick Norbord TallWall/Windstorm OSB sheathing attached with 8d common (2½-in. by 0.131-in.) nails

Table 3—Wall sheathing fastening schedule Location/Connection Fastener schedule Extended wall sheathing to energy truss Face-nailed with seven 8d common (2½ in. by heel 0.131 in.) Wall sheathing to vertical wall framing 8d common (2½ in.by 0.131 in.) at 6 in. on center (Nailing for shear) around perimeter, 12 in. on center in the field Wall sheathing to top plate (Increased 8d common (2½ in. by 0.131 in.) at 4 in. on center nailing for additional uplift load) along top plate Wall sheathing to bottom plate (Increased 8d common (2½ in.by 0.131 in.) at 3 in. on center nailing for additional uplift load) along bottom plate

2× boundary member and 2× nailing member were installed of the Test E specimen (100% shear load, no uplift load) at the front and back trusses to simulate the presence of sup- was further reinforced with additional bracing of the truss porting gable-end walls by providing the bearing surface bottom chord members to force the failure at the energy for the exterior edges of the gypsum as the gypsum panels truss heel connection. All interior gypsum panel joints for rotate under the shear loading. Figure 4 shows a schematic all specimens were taped and mudded; however, no finish- of this boundary detail. ing was done at the interface of the ceiling and the supporting bearing walls. Because the objective of the study is to evaluate the performance of the wall sheathing to energy truss heel connection, Test Setup and Protocol gypsum panels were attached to bottom truss chords using Figure 5 provides the American Society of Civil Engineers screws at 8 in. on center to simulate the upper bound capac- (ASCE) 7–10 lateral wind load profile in the direction paral- ity of residential ceiling diaphragms. The ceiling diaphragm lel to the ridge. Wind pressures are transferred to the roof

3 General Technical Report FPL–GTR–233

Figure 2. Specimen construction.

Figure 3. OSB sheathing connection detail. and ceiling diaphragms through the framing of the gable DeRenzis and others (2012) for a more in-depth explanation end wall and wall below the roof. Figure 6 illustrates the of the distribution of forces and derivation of the loading tributary area associated with each of the diaphragms, in- methodology. cluding the additional load into the ceiling diaphragm from Figure 7 shows a schematic of the test setup including the the wall framing below. The location of lateral loading brace specimen, loading apparatus, and instrumentation, and Fig- was chosen to most closely replicate this ratio of forces in ure 8 provides a photo of the uplift/shear loading apparatus. the roof and ceiling diaphragms by a wind load. Refer to

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

monomer (EPDM) rubber and placed on a support structure underneath the test specimen (Fig. 8, Fig. 9). The support structure also isolated the air bag from the test specimen walls to prevent any restraint of the walls due to friction with the bag. The top of the air bag was isolated from the gypsum ceiling diaphragm by a translatable bearing surface constructed of a series of bearing plate rollers sandwiched between two layers of OSB panels; the rollers allowed the specimen to move independently of the air bag in the lateral direction under combined loading. Figure 9 provides a detail of the translatable bearing surface. The lateral load was applied in tension using a computer- controlled hydraulic cylinder mounted to a steel reaction Figure 4. Ceiling diaphragm boundary detail at front and frame. The reaction frame was attached to the laboratory back trusses. structural floor. Uplift loading via inflation of the air bag was achieved using a computer controlled Pressure Load Lateral load was applied to the specimen using the same Actuator (PLA). methodology developed and used during Phase 1 and For Test A, uplift loading was applied continuously at a rate Phase 2 testing of this project (DeRenzis and others 2012; targeting failure to occur at approximately 5 min. For all DeRenzis and others 2013). Specifically, load was applied subsequent combined loading tests, uplift load was ramped through permanent truss bracing (2 × 6 nominal Southern up to a value determined in accordance with Table 1 as a Pine, No. 2 Grade lumber) attached at the center vertical percentage of the peak uplift pressure achieved in Test A web member of each truss approximately 2 ft, 8 in. up from and then held constant throughout the remainder of the test. the bottom. The intent of using a pair of typical permanent After the target uplift load was achieved, lateral load was truss braces was to minimize the restraints imposed on the ramped up monotonically at a constant displacement rate of specimen by the loading apparatus by applying the load 0.06 in. per minute to allow for sufficient visual observa- through members that are typically present in truss roof as- tions throughout the test. Testing was continued until failure, semblies. defined as a 20% drop from the peak lateral load. Each center vertical truss web member was reinforced with Several displacements were measured using electronic linear a double 2 × 8 vertical member to prevent weak-axis bend- motion position transducers (LMPTs) as shown in Figure 7, ing failure of the web. Each permanent bracing member was including the following: attached to the vertical reinforcing member with a single 4½-in. by ½-in. lag bolt to provide sufficient load transfer • Lateral displacement of the top of the heel (TOH) on the with minimal rotational restraint. first/front truss (T1) at both ends; Uplift loading was applied uniformly to the ceiling dia- • Lateral displacement at the top of the supporting walls phragm through a pressurized rectangular air bag. The air (TOW); bag was constructed of flexible ethylene propylene diene • Lateral displacement of the ceiling diaphragm;

Figure 5. ASCE 7-10 wind loading profile.

5 General Technical Report FPL–GTR–233

Figure 6. Tributary area of wind loads.

• Lateral slip at the bottom of the supporting walls; • Uplift at the end stud of the supporting walls;

• Compression at the end stud of the supporting walls; Figure 8. Translatable bearing surface. • Relative uplift between the supporting wall and the heel of the first/front truss at both ends; and the uplift load calculated from the pressure measurements • Relative uplift between the supporting wall and the heel to the uplift reaction load measured using load cells placed of the last/back truss at both ends. at the bottom of the supporting walls. Uplift load based on pressure measurements was calculated as the pressure read- Lateral loading was measured using an electronic load cell ing inside the air bladder multiplied by the area of loading installed between the cylinder and the loading bracket. Up- (i.e., the translatable bearing surface) and then adjusted lift loading was measured via an electronic pressure trans- down to account for the weight of the specimen and the ducer located within the pressurized bladder. All load and setup. For direct measurement of uplift load (rather than displacement measurements were recorded using an elec- pressure), each anchor bolt was fitted with a 5,000-lb load tronic data acquisition system. cell that measured the uplift force between the anchor bolt A series of calibrations were conducted as part of Phase 2 and the specimen (oversized holes were drilled at each testing on a full-size specimen to verify the correlation of of the anchor bolt locations in the bottom plates of the

Figure 7. Test setup and instrumentation (LMPT is linear motion position transducers).

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

Figure 9. Specimen uplift and lateral load apparatus.

1,000 Calibration was also conducted as part of Phase 2 testing to quantify the amount of lateral resistance of the translatable 900 bearing surface imparted onto the specimen through friction 800 Test results effects. A full-size test specimen was constructed without Linear roof or ceiling sheathing and subjected to incrementally in- 700 creased uplift load. At each load increment, the uplift force 600 was held constant while the specimen was laterally loaded lb/ft )

( to a set displacement and then allowed to return to its origi-

f t 500 i

l nal position. Lateral load measurements during this calibra- p

U 400 tion showed that the contribution of the frictional forces to the lateral load was negligible. 300

200 Results

100 The results of the testing are summarized in Table 4 including the unit uplift capacity and corresponding unit shear capacity for each specimen. Figure 10 shows the uplift versus 0 200 400 600 800 1,000 shear capacity interaction curve based on the test results. Shear (lb/ft) For comparison, Figure 10 also includes a linear interaction. Figure 10. Uplift versus shear interaction curve from testing. Appendix A provides a summary of the shear load versus horizontal displacement curves for Tests B through E, measured at various locations on the specimen, including the supporting walls to prevent friction). The results of the cali- midpoint of the bottom chord of the first truss, the TOH of bration showed that the uplift load based on the pressure the first truss, and the TOW at both ends of the specimen. measurements and the reaction load measurements were within 6.5% of each other, with the pressure-based uplift Test A (100% uplift) provided a benchmark uplift capacity loads being the higher of the two. Subsequent uplift capaci- for the 24-in. energy truss heel connection system. Test A ties calculated from uniform pressure load measurements reached a unit uplift capacity of 890 lb/ft. The primary fail- during testing were adjusted down accordingly. ure mode in Test A was a Mode 3m yielding followed by nail head pull-through at the OSB wall sheathing-to-truss heel

7 General Technical Report FPL–GTR–233

Table 4—Test results Uplift load Unit shear (as % of peak Unit uplift capacity Test uplift capacity) capacity (lb/ft) (lb/ft) A 100 890 — B 85 760 390 C 72 640 385 D 45 396 555 E 0 — 620

Figure 12. Fastener yield and pull-through failure mode of Test B.

Figure 11. Primary failure mode of Test A. connection and a withdrawal of the toenails from the top plate (Fig. 11) (ANSI/AWC 2011). Tests B, C, and D evaluated the shear load capacity of the connection system at various levels of uplift loading. The primary failure modes of Test B (85% uplift) were similar to those seen in Test A. The majority of the OSB to heel nail Figure 13. Fastener pull-through failure mode of Test C and Test D. connections exhibited the Mode 3m. Yield failure followed by nail pull-through (Fig. 12), with the back trusses (trusses under tension from global overturning) reaching capacity to achieve failure at the energy truss heel connection. Test E first. reached a unit shear capacity of 620 lb/ft, and also exhibited The primary failure mode of Test C (70% uplift) and Test D nail pull-through at the OSB-to-wall bottom plate connec- (45% uplift) was nail pull-through at the connection of the tion as its primary failure mode (Fig. 14). OSB wall sheathing to the wall bottom plates at the uplift Evaluation of the combined uplift and shear capacity inter- ends of the supporting walls (Fig. 13). action curve indicates a nonlinear relationship with all of Test E (0% uplift load) benchmarked the shear capacity the tested capacities greater than those predicted by a linear of the energy truss heel connection system. The ceiling relationship. Therefore, a linear relationship may be a sim- diaphragm of the Test E specimen was reinforced with ad- plified and conservative representation of the response under ditional sheathing on the top face of the truss bottom chords combined loading for design of 24-in. energy truss heel

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

magnitude of the increase, however, is slightly greater than expected, with only a 40% increase in capacity predicted by the ratio of nails used in the two phases. This degree of difference between the predicted and observed performance overall is within the expected range of variability in the density of wood products: the lumber used in the high-heel energy truss construction and the OSB sheathing panels. Comparison of the results from two phases also suggests a greater degree of nonlinear interaction between the uplift and shear forces for the trusses with the greater heel (Phase 3). This observation suggests that the impact of shear load on the uplift capacity is lower for trusses with a higher heel (Phase 3) relative to trusses with a lower heel (Phase 2). The potential reasons for the increased nonlinearity are the added nails at the heel and the greater heel height area resulting in a greater moment resistance. The shear capacities from the lateral load only scenario of the two phases of testing were nearly equal, indicating that the additional nails offsets the greater overturning effects caused by the increased truss heel height. The controlling failure mode in the lateral load only tests changed from a Figure 14. Fastener pull-through failure mode of Test E. roof-to-wall connection failure in Phase 2 to a bottom of wall sheathing-to- plate connection failure in Phase 3. Both of these facts indicate a balanced system that is not adverse- 1,000 ly affected by the increase in heel height. Phase II 900 Test A The increased capacity of Phase 3 Tests B, C, and D, along Phase III 800 with the change in failure location from the roof-to-wall Test B connection to the sheathing-to-bottom plate connection 700 further indicates that the additional nailing in the truss heel Test C 600 connection offsets the greater overturning moment caused lb/ft ) ( Test A by the increase in heel height. f t

i 500 l

p Test B Figures 16 and 17 compare the combined uplift and shear U 400 Test C Test D interaction curve based on testing to design wind load sce- 300 narios for several typical house roof sizes. The roof sizes 200 Test D (24 ft by 50 ft, 36 ft by 50 ft, and 48 ft by 50 ft) were selected to bracket the majority of the building dimensions 100 and roof length to width aspect ratios present in residential Test E Test E construction. The wind loads were determined using Ta- 0 200 400 600 800 1,000 bles 2.2A and 2.5B from Wood Frame Construction Manual Shear (lb/ft) (WFCM) for One- and Two-Family Dwellings—2012 Edi- tion (AWC 2012) assuming a mean roof height of 30 ft, a Figure 15. Comparison of Phase II and Phase III results. 7:12 roof pitch, and the truss span in the short direction. Note that the 2012 edition of the WFCM is based upon ASCE/SEI 7-10 Minimum Design Loads for Buildings and connection systems using extended wood structural panel Other Structures (ASCE 2010) basic wind speeds for a sheathing. 3-second gust and 700-year return period. Design wind Figure 15 provides a comparison between the results of loads were adjusted up by assuming a factor of safety of 2.0 Phase 2 and Phase 3 of this testing program. The uplift ca- to provide a direct comparison to the uplift and shear capacity in Test A of the Phase 3 testing was approximately pacities of the system measured from testing. 60% greater than the capacity of the similar uplift test from Analysis presented in Figures 16 and 17 shows that the Phase 2. This increase of capacity over the Phase 2 results capacity of the energy truss heel connection exceeds the was expected because of the increased number of nails in adjusted design values in Exposure B wind regions for all the wall sheathing-to-truss heel connection (seven nails analyzed building configurations at basic wind speeds up in Phase 3 testing vs. five nails in Phase 2 testing). The

9 General Technical Report FPL–GTR–233

States, excluding only the coastal regions in the eastern half 1,000 195 mph exp. B 170 mph exp. B of the country. 900 150 mph exp. B 800 160 mph exp. B Summary and Conclusions 180 mph exp. B This testing program was designed to further evaluate the 700

f t ) performance of OSB wall sheathing panels extended over / 140 mph exp. B b

l 600 the roof heel in resisting combined uplift and shear forces. (

f t The results of this study provide guidance towards further i l 500 p expanding prescriptive solutions for high-heel truss attach- U 400 ment optimized for performance from the structural, energy, Test results and constructability standpoint. The following is a summary 300 Linear relationship of the conclusions based on the results of this testing 200 24- by 50-ft house, exp. B program: 36- by 50-ft house, exp. B 100 48- by 50-ft house, exp. B 1) The tested system using extended wood structural panel as the primary connecting element (without additional 0 connecting hardware) at the roof-to-wall interface of en- 50 150 250 350 450 550 650 ergy trusses can provide a continuous load path in both Shear capacity (lb/ft) the shear and uplift directions and can be considered a Figure 16. Comparison of tested capacity to typical wind viable option for residential construction in most areas of loading scenarios (Exposure B regions). the country. 2) The overturning effects caused by increased energy truss 1,000 heel heights can be offset by additional face nails attach- 160 mph exp. C ing the extended wood structural panel wall sheathing to 900 140 mph exp. C energy truss heel. This conclusion has been validated for 800 150 mph exp. C trusses with heel heights up to 24 in. (Results of Phase 2 testing validated performance for trusses with heel heights 700 120 mph exp.C up to 15¼ in.). The number of nails used in these testing 130 mph exp. C 600 programs for attaching wall sheathing to the truss heel is based on a maximum nail spacing of 4 in. on center at the 500 heel member.

Uplift (lb/ft) 400 3) The uplift-shear capacity interaction curve for the energy 300 Test results truss heel connection system is nonlinear, with capacities Linear relationship for all uplift to shear ratios measured in this testing pro- 200 24- by 50-ft house, exp C gram exceeding the capacities predicted based on a linear 36- by 50-ft house, exp C 100 interaction. In design applications, a linear relationship 48- by 50-ft house, exp C may be a simplified and conservative representation of the 0 response under combined loading for energy truss heel 50 150 250 350 450 550 650 connection system using extended wood structural panel Shear capacity (lb/ft) sheathing. Figure 17. Comparison of tested capacity to typical wind loading scenarios (Exposure C regions). References ANSI/AWC 2011. NDS-2012 National design specification (NDS) for wood construction. Washington, D.C.: American to 140 mph, and in the case of the shorter roof spans at ba- National Standards Institute and Leesburg, VA: American sic wind speeds up to 180 mph. Accordingly, the analysis Wood Council. indicates that the tested energy truss heel connection can provide a factor of safety of 2.0 in Exposure B wind regions ASCE 2010. Minimum design loads for buildings and other for nearly all typical building layouts across the majority structures (ASCE/SEI 7-10). Reston, VA: American Society of the country. The applicability of the tested system is also of Civil Engineers. extensive when comparing peak capacities to design values AWC. 2012. Woodframe construction manual for one and in Exposure C wind regions (Fig. 17); the system capac- two family dwellings (2012 Edition). Leesburg, VA: Ameri- ity yields a factor of safety of 2.0 or greater at basic wind can Wood Council. speeds of up to 120 mph. A basic wind speed of 120 mph encompasses the greater majority of the continental United

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

Coats, P.; Douglas, B. 2011. Use of wood structural panels to resist combined shear and uplift from wind. Structure Magazine. June 2011:16–19. DeRenzis, A.; Kochkin, V.; Wang, X. 2012. Evaluation of the lateral performance of roof truss-to-wall connections in light-frame wood systems. General Technical Report FPL– GTR–214. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 25 p. DeRenzis, A.; Kochkin, V.; Wang, X. 2013. Evaluation of the high-heel roof-to-wall connection with extended OSB wall sheathing. General Technical Report FPL–GTR–222. Madison, WI: U.S. Department of Agriculture, Forest Ser- vice, Forest Products Laboratory. 11 p. Gypsum Association. 2010. Application and finishing of gypsum panel products (GA-216-2010). Hyattsville, MD: Gypsum Association. ICC. 2012. International residential code for one and two family dwellings. Country Club Hills, IL: International Code Council. NAHBRC. 2011. Evaluation of the lateral performance of roof truss-to-wall connections in light-frame wood systems. Upper Marlboro, MD: National Association of Home Build- ers Research Center. NAHBRC. 2012. High heel roof-to-wall connection testing–Phase 2: Evaluation of extended wall OSB sheathing connection under combined uplift and shear loading. NAH- BRC. Upper Marlboro, MD: National Association of Home Builders Research Center.

11 General Technical Report FPL–GTR–233

Appendix—Summary of the Shear Load versus Horizontal Displacement Curves for Tests B Through E

Test B Test D 800 800 800 800 700 700 700 700 ) ) ) ) t t t t f f 600 f f / / 600 600 / / 600 b b b b l l l l ( ( ( (

500

500 500 500 a d a d a d 400 400 a d 400 l o l o 400 l o l o

t t f f i a r 300 i a r 300 l 300 l e 300 e h h U p S 200 200 U p S 200 200 100 100 100 100 0 0 0 0 -0.1 0.4 0.9 1.4 1.9 2.4 2.9 –0.1 0.4 0.9 1.4 1.9 2.4 2.9 Displacement (in.) Displacement (in.) Shear Top of wall: N end Shear Top of wall: N end Top of wall: S end Top of heel: N end Top of wall: S end Top of heel: N end Top of heel: S end Uplift Top of heel: S end Uplift

Test C Test E 800 800 800 700 700 700 ) ) t t f f 600 / ) / 600

t 600 b b f l l / ( (

500 500 b l

( 500

a d a d 400 400 l o l o a d

t 400 f l o i

a r 300 300 l e a r

h 300 e U p

S 200

200 h

S 200 100 100 0 0 100 –0.1 0.4 0.9 1.4 1.9 2.4 2.9 0 Displacement (in.) –0.1 0.4 0.9 1.4 1.9 2.4 2.9 Displacement (in.) Shear Top of wall: N end Top of wall: S end Top of heel: N end Top of heel: S end Uplift Shear Top of wall: N end Top of wall: S end Top of heel: N end Top of heel: S end