Abstract Racking Performance Of

ABSTRACT

RACKING PERFORMANCE OF PAPERBOARD AND WOOD BASED SHEATHING MATERIALS

By Benjamin Ong

A small scale (16 x 16 inch) racking tester was used to evaluate the racking performance of the paperboard and wood based sheathing materials. In this study it was shown that the staple spacing, staple size and caliper of the paperboard affect racking performance. It was established in this study that extending staples length beyond 1 inch has no advantage for the paperboard and wood based sheathing materials. Similarly, using nails for fasteners has no advantage both for paperboard and wood based sheathing materials. This finding is limited to the present set up and does not represent other racking testers. The racking performance improved when adhesive was used in combination with staples to attach the sheathing to the wood frame. It was observed after the racking test, the physical state of the paperboard sheathings indicate that staples have a higher withdrawal resistance and less tear through when compared to the nails. The stretching of the paperboards during the racking test slightly affects the tensile properties and further study is needed. The hardboard was evaluated to have better racking stiffness and strength than that of plywood and oriented strand board. The comparison of staples and nails as fasteners based on the racking stiffness and strength show that nail will be preferred for hardboard but for plywood and oriented strand board, either nails or staples could be used as fasteners. The basis weight and racking strength have an inverse relationship for the wood based sheathing.

THE RACKING PERFORMANCE OF PAPERBOARD AND WOOD BASED SHEATHING MATERIALS

A thesis

Submitted to the Faculty of Miami University

in partial fulfillment of

the requirements for the degree of

Masters of Science

Department of Paper and Chemical Engineering

Benjamin Ong

Miami University

Oxford, Ohio

2006

Approved by:

Advisor ______Dr. Douglas W. Coffin

Reader ______Dr. Catherine Almquist

Reader ______Dr. Robert C. Peterson

Table of Contents

Introduction………………………………………………………...... 1 Literature Review…………………………………………………………..3 Objectives…………………………………………………………………...9 Test Specimens, Equipment, and Procedures…………………………...10 1. Materials…………………………………………………………...10 2. Paperboard Characterization………………………………………10 3. Wood Board Characterization……………………………………..11 4. Simplified Small Scale Racking Tester……………………………12 5. Experimental Procedure…………………………………………...14 6. Method of Analysis………………………………………………..18 Discussion of Results……………………………………………………...19 I. Paperboard……………………………………………………………..19 1. Paperboard Characterization………………………………………19 2. Experimental Program……………………………………………..20 (1) Effect of Staple Spacing on the Racking Performance of the Paperboard Sheathing…………………….21 (2) Effect of Staple Size on the Racking Performance of the Paperboard Sheathing…………………….25 (3) Effect of Caliper (thickness) on the Racking Performance of the Paperboard Sheathing…………………….28 (4) Comparison of Racking Performance of the Paperboard Sheathing using Staples and Nails………………..30 (5) Effect of Stretching during Racking Test on the Tensile Properties………………………………………35

ii (6) Racking Stiffness as a Function of Geometric Mean Modulus ……………………………………………………….36

II. Wood-Based Board……………………………………………………38 (1) Effect of Staple Size and Thickness on the Racking Performance of Hardboard……………………………………38 (2) Comparison of Racking Performance of the Three Wood Boards using Staples……………………………39 (3) Comparison of Racking Performance of the Three Wood Boards using Nails……………………………………..41 (4) Comparison of Racking Performance of the Three Wood Boards using Both Staples and Nails…………………..42 (5) Comparison of Racking Performance of Wood Boards and Paperboards……………………………………………....44 (6) Effect of Basis Weight on the Racking Performance of the Wood Boards…………………………….46

III. Comparison of Calculated and Actual Racking Load……………..47 IV. Metal Sheathing...... 48 Summary and Conclusion…………………………………………...... 51 Recommendation………………………………………………………….56 Literature Cited…………………………………………………………...57 Appendix…………………………………………………………………..60 Appendix 1a: Effect of spacing on the racking performance of the Paperboard……………………………..60 Appendix 1b: Effect of spacing on the racking performance of the paperboard……………………………..61 Appendix 2: Effect of staple size on the racking

iii performance of the paperboard……………………………...62 Appendix 3: Effect of caliper (thickness) on the racking performance of the paperboard……………………..65 Appendix 4: Comparison of racking performance of the paperboards using both staples and nails…………….68 Appendix 5: Comparison of racking performance of the wood boards using both staples and nails……………69

iv List of Tables

Table 1a: Characterization data of the three grades of paperboard...... 19 Table 1b: Characterization data of the Dark Gray and Dirty White paperboard.………………………………………………………………...... 19 Table 2: Results of the reproducibility test of small scale racking tester…………………………………………………………………..20 Table 3: Comparison of racking performance of the nailed and stapled paperboards……………………………………………………………………33 Table 4: Comparison of elastic modulus of the paperboards before and after racking test…………………………………………………………...... 36 Table 5: Properties of the wood boards……...... 38 Table 6: Comparison of racking performance of 2/16 and 3/16 inch hardboard……………………………………………………………………...39 Table 7: Comparison of racking performance of the three types of wood board…………………………………………………………………….41 Table 8: Comparison of racking performance of the three wood boards using nails as fastener………………………………………………...... 42 Table 9: Comparison of racking performance of the wood boards using nails and staples……………………………………………………………….43 Table 10: Effect of basis weight on the racking strength of the three wood boards…………………………………………………………………...47 Table 11: Comparison of calculated and actual load……………………………………48 Table 12: Comparison of racking performance of the aluminum sheathing using staples and screws………………………………………………………49

v List of Figures

Figure 1: Component of a timber shea wall……………………………………………..3 Figure 2: Distortion of frame when panel is subjected to racking load…………………4 Figure 3: Set up of small scale (16 x 16 inch) racking tester………………………...... 12 Figure 4: Close up of small scale racking tester...... 13 Figure 5: The directional force of 16 x 16 inch racking tester…………………………13 Figure 6: The directional force of racking load of standard tester……………………..14 Figure 7: The edge wood and the metal frame……………………………………...... 15 Figure 8a: The metal frame and wood inserts…………………………………………..16 Figure 8b: The woods were inserted into the metal frame……………………………...16 Figure 9: Alignment of the test frame with a template………………………………...17 Figure 10a: The paperboard as stapled to the edge wood using the markings of the template………………………………………………………………17 Figure 10b: The installed racking test assembly………………………………………...18 Figure 11: Reproducibility test of the small scale racking tester……………………….21 Figure 12: Effect of spacing on the racking stiffness…………………………………..22 Figure 13: Effect of spacing on the displacement……………………………………...22 Figure 14: Effect of spacing on the peak load………………………………………….23 Figure 15: Effect of spacing on the peak load (with glue)……………………………..24 Figure 16: Effect of staple size on the racking stiffness………………………………. 26 Figure 17: Effect of staple size on the displacement…………………………………...26 Figure 18: Effect of staple size on the racking stiffness………………………………..27 Figure 19: Effect of staple size on the displacement…………………………………...27 Figure 20: Effect of caliper (thickness) on the peak load………………………………29 Figure 21: Effect of caliper (thickness) on the racking stiffness……………………… 29 Figure 22: Effect of caliper (thickness) on the displacement…………………………..30 Figure 23: Load displacement curves of 1 inch staple and nail………………………...31 Figure 24: Load displacement curves of 1-1/4 inch nail and staple……………………32

vi Figure 25: Comparison of physical state of nailed and stapled paperboards using fastener size of 1 inch and 2 inch spacing……………...34 Figure 26: Nails withdrawal and nail torn through on paperboard using 1 inch nail and 3 inch spacing……………………………………………....34 Figure 27: Nails torn through on paperboard and displacement of paperboard from the wood frame…………………………………………...35 Figure 28: Plot of racking stiffness with geometric mean modulus...... 37 Figure 29: Load displacement curves of 2/16 and 3/16 inch hardboard………………..38 Figure 30: Load displacement curves of the three wood boards using 1-1/4 inch staple…………………………………………………………….40 Figure 31: Load displacement curves of the three wood boards using 1-1/4 inch nail………………………………………………………………42 Figure 32: Comparison of racking strength of plywood………………………………..44 Figure 33: Comparison of racking performance of the wood boards with paperboards using 1-1/4 inch staple and nail……………………………….45 Figure 34: Comparison of racking performance of the wood boards with paperboards using 1 inch staple…………………………………………….46 Figure 35: Load displacement curves of the aluminum sheathing……………………..49 Figure 36: Comparison of racking performance of the aluminum sheathing with paperboards…………………………………………………50

vii ACKNOWLEDGEMENT

I would like to thank Dr Douglas Coffin, my thesis advisor and committee chair, for his patience, support and guidance throughout this project. Mr. Douglas Hart, senior research staff of Paper and Chemical Engineering Department also contributed to the success of this project in guiding me at the start of the experimental program and for preparing the testing materials.

I would like also to thank Mr. Ramanathan Somasuntaram of Computer Science Department for his valuable assistance in guidance and assisting in preparing the data for analysis using Excel.

Finally I dedicate this thesis to my wife, Ellen for her undying love and support despite we are far apart by half way around the world.

viii Introduction

In the United States, single family dwellings and low rise residential buildings are usually constructed of wood. In such structures, shear walls play an important role of resisting loads induced by wind and earthquake. Modern shear walls consist of light frame (usually 38 x 89 mm or 38 x 140 mm of nominal lumber) covered with a sheathing made of plywood, oriented strand board (OSB), fiberboard or other panel material. The sheathing is connected to the framing by nails. More recently, staples or screws are used. These connections typically are ductile and therefore the wall as a whole can fail if the fasteners yield. Shear wall utilize the high racking strength of the sheathing to provide rigidity against shear forces. Without the sheathing, the framing would easily rack under. shear. Through this composite action, a shear wall system is able to effectively transfer loads to the foundation of a building. Most of the studies (9, 11-17, 21, 23-24, 27, 30) conducted in the past years used plywood, oriented strand board, gypsum (interior wall), fiberboard, flakeboard, particle board as sheathing materials. The standard racking test according to ASTM E72 and ASTM E564 used an 8x8 ft shear wall that represents a typical wall in a residential home. Sherwood and Moody (24) have made a comparison of the two standard tests where ASTM E72 is intended to provide a common basis for comparison of sheathing materials and ASTM E564 is for measuring the shear resistance of framed wall. ASTM E564 has received limited recognition, it is intended for the evaluation of wall performance rather than performance of the sheathing materials and permit variations in the hold down mechanism and wall configuration which closely approximates actual wall performance. The question that arises is how well the monotonic laboratory tests of shear walls relate to the behavior of full size shear walls subjected to reversed cyclic loads. Skaggs and Rose (25) had made an evaluation of the two standard test methods together with a modified version of ASTM E564 (cyclic loading) that was developed by Structural Engineers Association of Southern California in 1994. Even though there were small scale racking tests with a height of two feet and varying length conducted in the past (15,16), Bi (32) used two small scale racking testers (16 and 32 inches in dimension) for the evaluation of the racking strength of the paperboards. The small scale racking test may provide an easy, quick, and inexpensive method of determining the racking strength

1 of sheathing materials. Bi (32) in his studies of the three grades of commercial paperboard as sheathing materials had not concluded as to its suitability in the application as a component of a wall panel in a residential dwelling. It is the scope of this thesis to examine also the racking performance of wood based sheathing such as plywood, oriented strand board and hardboard other than the commercial grade paperboards as sheathing materials. The wood based sheathing materials or panels are used as building materials either for structural and nonstructural applications. Plywood and OSB are used primarily as the sheathing material for shear wall.

2 Literature Review Conventional light frame housing is the largest form of residential construction in the United States. As a major lateral load resisting system in most houses and small buildings, timber shear walls have been the focus of numerous studies and research projects. Timber shear walls are one of the most important components of the light frame house, and the performance of shear walls need to be fully understood to make the most efficient use of light frame construction. Timber shear walls provide resistance to lateral loads, such as wind or seismic loading, in many low rise building. A typical timber shear wall consists of four primary components: the framing, sheathing, connectors joining the sheathing to the framing, and hold-downs as shown in Figure 1.

Figure 1: Components of a timber shear wall

The framing consists of studs, top plates, bottom plates, and headers if openings are present. Studs are oriented vertically and have a typical cross section measuring 38 mm x 89 mm (2 x 4 in nominal) or 38 mm x 140 mm (2 in x 6 in nominal). Top plates and bottom plates are oriented horizontally and help to keep the studs in place in the wall. Framing provides the bending resistance of the wall. Sheathing is attached to the framing

3 of shear walls and helps to provide strength, stiffness, and stability to the walls. The sheathing provides most of the resistance to shearing forces. As shown in Figure 2, when a load is applied along the top plate of a shear wall, the framing distorts (d) in a manner resembling to a parallelogram while the sheathing remains rectangular and rotate slightly, with one side of the panel rising slightly and the opposite side sinking slightly.

Undeformed Panel d Distortion Under Load R

H x

R L Frame Sheathing

Figure 2: Distortion of frame when panel is subjected to racking load (R)

Early research focused on the monotonic testing, which is a one directional loading used to obtain the ultimate strength of a wall. The monotonic testing was the standard method for testing shear wall because it gives a better indication of the performance under one-directional loading or wind loading. Earlier tests have considered many variables. The contribution of various sheathing materials has been studied extensively by Patton-Mallory et al (16) and Price and Gromala (18). Patton-Mallory et al (16) also studied the effect of opening and wall length in a wall panel. Small scale racking tests were also conducted by both Patton-Mallory (16) and Price (18). Patton-Mallory,

Gutkowski, et al (15) compared the racking load resisted by double sided wall to the sum of loads resisted by the two single sided walls tested individually.

4 In addition to experimental studies, mathematical models were also developed to help understand the performance of shear walls. Numerous studies (4, 6, 9, 17, 27) have evaluated and predicted the performance of shear walls when subjected to racking load. Patton-Mallory and McCutcheon (17) used four models to predict the wall load displacement behavior of doubled sheathed walls with dissimilar materials and compared the predicted results to the small scale racking test experimental data. They found that the asymptotic fastener curves give the best predictions of shear wall performance. Tuomi and McCutcheon (27) presented a mathematical model for calculating the racking strength of timber-framed shear walls. The mathematical model is expressed as follows:

2 n2 – 1 m2 – 1 2 2 P1 = s sinα [ n + m - — ( −−−− cos α + −−−−− sin α ) ] ………….....(1) 3 n m

where P1 = racking strength of the panel (full scale racking tester), lbs s = lateral nail strength of single fastener, lbs α = angle whose tangent is base/height of sheet (tan α = L/H) m = number of nail spaces along the vertical edges n = number of nail spaces along the horizontal edges

The model was derived based on the assumptions that when a wall is subjected to a racking load, the nail connectors are deformed and the stud frame distorts from a rectangular shape to a parallelogram while the sheathing remains rectangular. The external load is resisted by the energy absorbed by the nails as they distort. A model of this phenomenon is shown in Figure 2 and formed the basis of developing the mathematical model for predicting racking strength. The mathematical model gives the racking strength of a panel with perimeter nailing in terms of the individual nail resistance (s), the width/height ratio (tan α), and the number of nail spaces along the vertical and horizontal edges (m and n, respectively).

Tuomi and McCutcheon (27) verified the validity of the model by comparing the calculated results from Equation (1) with the experimental data. The variables examined

5 were panel geometry, the number and spacing of nails and the lateral resistance of single nail. The model considers only the resistance contributed by the sheathing and assume that from the timber frame can be neglected. Different types of sheathing materials including several grades and thickness of fiberboards were used for testing. In addition to standard full scale test, experimental results from small scale test such as 2 x 2 ft panel were also used. The agreement between the predicted and actual loads is very good. The model is good for small deformation since the load distortion relationship for a single nail was assumed to be linear. Bi (32) related the racking load to the small scale diagonal load. _ P2 = 2/(√2 ) (P1) ………………………………….....(2)

P1 = shear load in small scale racking tester, lbs

P2 = racking diagonal strength of the small scale racking tester, lbs

Easley et al. (4) developed formulas for analyzing shear walls. The formulas can be used for various types of sheathing panels attached with nails or other types of fasteners. The formulas derived include the sheathing fastener forces, the linear shear stiffness of a wall, and the non-linear shear load-strain behavior of a wall. Good agreement was observed between the formulas and actual load test and finite element analysis. Gutkowski and Castillo (6) developed a mathematical model to analyze light-frame shear walls subjected to racking load. The nonlinear analysis includes single and double- sided sheathed wall using plywood or gypsum. They used other researchers’ data to confirm the validity of the model. Close agreement between the model and the actual load-displacement curves of shear wall was demonstrated in their studies. Connections between the sheathing and the framing members are one of the most important factors influencing the performance of a shear wall. Shear strength and load deflection characteristics of a connection are of greatest concern when analyzing a shear wall subjected to monotonic loading. McCutcheon (9) presented a theory to predict the racking performance of wood-stud shear walls. McCutcheon took into account the nonlinear behavior of nails. The energy method used defines the wall performance in terms of the lateral non-linear load slip behavior of the nails which fasten the sheathing to

6 the frame. The theory also includes linear deformation due to shear distortion of the sheathing material, and provides accurate estimation of wall performance up to moderate load levels. The small scale racking tests (2 x2 ft panel) were generally very good predictors of full scale racking performance. Gupta and Kuo (5) presented new mathematical models to represent the behavior of the shear walls. Even though the nail force-slip characteristics mainly governed the behavior of shear walls, the bending stiffness of the stud and the shear stiffness of the sheathing also contributed to the stiffness of the system, but played a secondary role in defining the load deformation properties. The proposed model is comparable to the finite element model and gave results which were in good agreement with those from tests. Since the proposed models are simpler than the finite element model they are more suitable for such application as in a repetitive nonlinear dynamic analysis. Itani et al. (8) presented a methodology for calculating the racking performance of sheathed wood-stud walls. A simplified model was introduced to analyze the response of walls, with and without door and window openings, to racking forces. The analysis reduces a wall sheathing system to a simpler structure that can be analyzed by available computer programs. In fact the procedure used for estimating racking resistance is by simulating each panel of sheathing by a pair of diagonal spring. Stiffness of the spring is based on the stiffness of an individual nail used to fasten the sheathing. Results from the model analysis indicate that forces and displacement are significantly influenced by the presence of openings. In addition to predicting racking strength of full size shear wall through using lateral nail resistance test as shown by Neisel (12,13), small scale wall racking tests (9, 15,16, 18) have been utilized to evaluate sheathing materials and predict full scale racking performance. As shown in the past the small scale racking test is very convenient and relatively inexpensive compared to that of a full scale racking test. It was shown in the past that the small scale tacking test could well predict the racking performance of a sheathing material in the full scale racking test. The research work done on the small scale racking test was limited and it seems to discontinue after the 1980s. Currently no small scale racking test standard is available. Most of the racking tests are more focused on ASTM E564. ASTM E564 is an assembly test and ASTM E72 is a panel test.

7 Dolan and White (3) observed that the use of adhesives to attach the sheathing to the framing of a wall would increase the stiffness and reduce the ductility of the wall. A wall that incorporates both adhesives and nails has significantly different properties than wall to which the sheathing is attached with nails only. Similarly, the wall that used adhesive and nails have higher racking resistance and less ductility than walls with nails alone. Their studies show that the displacement of standard nailed wall was larger than the corresponding displacement for the adhesive walls. Pellicane (18) conducted studies on the nail/glue joints in wood and showed that the use of glue in conjunction with a nail greatly enhanced the load carrying capacity of the joint. The average ratio of nail/glue to nail only joint strength was approximately 3.7. This study was initiated to quantify the effect of elastomeric construction adhesives on nailed joints in wood members subjected to lateral loading. In recent years commercial grade paperboards have been introduced to the construction industry as sheathing materials for framed wall. Information regarding their racking performance in shear wall is limited. Bi (32) was first to evaluate these commercial grades of paperboards in a small scale racking tester and used staples as a fastener. Bi (32) findings in summary are that 1) the initial paperboard racking stiffness correlated to elastic modulus and caliper but the response was insensitive to paperboard orientation or test dimension; 2) both panel buckling and paperboard cutting at the staples affected the response; 3) the major factor in influencing the racking response was the load transfer to the frame through the staples. Yet information on the properties and structures of the commercial grade paperboards are also limited. These factors are, to a certain extent, related to the performance of the paperboard.

8 Objectives The main objectives of this study are as follows: 1. Investigate the effect of staple spacing on the racking performance of the paperboard as a sheathing material. 2. Investigate the effect of staple size on the racking performance of the paperboard as a sheathing material. 3. Investigate the effect of structural grade changes on the racking performance of the paperboard as a sheathing material. 4. Investigate the effect of using combined staple/adhesive on the racking performance of the paperboard. 5. Investigate the effect of stretching on the tensile properties of the paperboard after subjecting to racking test. 6. Compare the racking performance of the paperboard sheathing using both staple and nail. 7. Investigate the racking performance of the wood based sheathing using both staple and nail. 8. Compare the racking performance of the aluminum sheathing with paperboards.

9 Test Specimens, Equipment and Procedures (1) Materials Five different commercial grade paperboards were tested in this study. Three of the tested sheathing materials came from Bi’s (32) research work, the Green color (standard grade) and the Red color (structural grade) and the Blue color (super structural grade). Bi (32) labeled A for the Green color, B for the Red color and C for the Blue color in his works. One other sheathing material was Dark Gray in color and the last was a Dirty White color labeled as grade B. The two sheathing materials were labeled as Dark Gray and Dirty White for differentiation through out the study. The wood based sheathing materials (wood board) used for this study such as plywood, OSB, hardboard were purchased from a local supplier (Ace Hardware). The thickness for plywood and OSB is 1/4 inch and the hardboard has 2/16 and 3/16 inch thickness. Staples used for this study are U-shaped wire fasteners with two same size pointless legs connected by a common crown. They are designed to be driven by manual strike, pneumatic, electric, or spring tools and to hold two or more pieces together. The length of the staples are 3/4, 1, and 1-1/4 inch and the length of the common crown is 1 inch.

(2) Paperboard Characterization (a) Caliper (inch) - Paperboard caliper for each specimen was measured using a Mitutoyo Dial Caliper gage. A total of 8 measurements taken around the edges with two readings per edge were recorded and the average was calculated. (b) Basis Weight (lb/1000ft2) – To determine the basis weight, 5 samples with a dimension of 5 x 5 inch were used and the mass of each sample was determined using a top loading balance. The basis weight was calculated using the following equation: B.W. (lb/1000ft2) = Weight (g)*(2.204lb/1000g)*(144 in2/ft2)*1000/(25in2) (c) Moisture Content (%) – The moisture content of the samples (5 x 5 inches) were determined after conditioning at 50 % relative humidity and 23 degree Celsius for three days in paper testing laboratory. To ensure that the sample was dried,

10 the drying time was 72 hours at 103 degree Celsius in an oven. The weights were taken before and after drying. The moisture content of the paperboard was calculated with the following formula: Moisture Content % = [(Initial Weight – Dried Weight)/(Initial Weight)] x 100

(d) Elastic Modulus (lbf/in) – MD and CD strips with dimension of 0.5 x 10 inch were used to determine the elastic modulus of the paperboard. The clamp length was 7 inches. The sample size was 4 to 5 pieces each for MD and CD and were tested for Elastic Modulus using Instrom 3344 series EM Test Instrument. The Merlin software calculated the Elastic Modulus and the results are presented in average values. (e) Density (lb/ft3) – the density is calculated by the weight and the volume of the 5 x 5 inch sample. Density (lbs/ft3) = Weight (gm) * (2.204lb)/(1000gm) * (69.12) /(t ft3) t = caliper of the paperboard in inch

(3) Woodboard Characterization (a) Moisture Content (%) - same procedure as in paperboard testing procedure and the sample dimension is 4 x 4 inch and the drying time is 48 hours at 103 degree Celsius. The moisture content is calculated using the same equation as in paperboard. (b) Basis Weight (lb/1000 ft2) – 8 samples of 4 x 4 inch wood board were used in the basis weight determination. B.W. (lb/1000 ft2) = Weight (g)*(2.204lb/1000g)*(144 in2/ft2)*1000/ (16 in2) (c) Density (lb/ft3) - the density is calculated using the oven dried weight and the volume. Density (lb/ft3) = Weight (gm) * (2.204 lb/1000 gm) * (108)/(t ft3) t = thickness of the wood board in inch

11 (4) Simplified Small Scale Racking Tester (16 inch) Figure 3 and 4 shows the set up of the 16 inch racking tester. The racking tester is

Load Cell

MTS model 1122 Test Frame

Figure 3: Set up of small scale (16 x 16 inch) racking tester designed to induce shear in the panel. There is a similarity to the standard tester as specified in ASTM. One of basic differences from the standard tester is the direction of the application of the racking load. The direction of the racking force for both type of testers are shown in Figure 5 and 6. The racking tester records the racking

12 Load Cell

Test Frame

Figure 4: Close up of small scale (16 x 16 inch) racking tester

P = Load

displacement

16 x 16 inch Racking Tester

Hold Down

Figure 5: The directional force of 16 x 16 inch racking tester

13 P = Load

8 x 8 ft Standard Tester

Figure 6: The directional force of racking load of standard tester load and deformation. The racking tester provides a testing frame to which the sheathing material is fastened and is designed to contribute minimal resistance to the racking deformation. The racking load is considered carried by the sheathing. The tester instrument is the MTS model 1122 and its software (Test Works Version 3.07) controls the tester and records both the load and displacement or deformation. The limit of the load that can be applied is 1200 lbs and it is also the cut off point. The testing frame used in this study is the same as the one used by Bi (32) and was described in full details in his thesis. The aspect ratio is one. The additional feature for the present study was the template used as a guide in the stapling of sheathing materials to the edge wood of the testing frame.

(5) Experimental Procedure For the small scale racking test, the following test procedure should be followed: a) The paperboard and frame inserts were cut according to the specified dimension. The paperboard was cut at the four corners with 2.5 inches from the corner to the two sides. The paperboard was conditioned at least 1 to 2 days whereas the

14 frame or edge wood only one day. For wood based sheathings, 3 to 4 days of conditioning was employed. b) The racking load cell (1200 lb capacity) was calibrated according to the specified procedure by the testing software (TestWorks). Once calibrated, there was no need to repeat the calibration before each test. c) The wood inserts were cut into a shape as shown in Figure 7. The shorter side was for insertion into the metal frame and the longer side was for attaching the sheathing.

Figure 7: The edge wood and the metal frame d) The four sides of the metal frame were connected by four hatch pins and for lay out on a table counter. The wood inserts were inserted into the metal frame as shown in Figure 8a and 8b. The metal frame was turned over and the dry wall screws (three per side) were drilled into the edge wood through the holes on the backside of the metal frame. It is important that the attachment of the edge wood to the metal frame was tight. The screw should be driven perpendicular to the wood. e) The metal frame with inserted edge wood was turned over and the template was inserted into the pins that were located at the four corners for alignment purpose as shown in Figure 9.

Figure 8a: The metal frame and wood inserts

Figure 8b: The woods were inserted into the metal frame

f) After the paperboard was set on the top of the wood (the other side was inserted into the metal frame) the template was inserted again into the pins at the four corners. With the insertion of the template, the test frame is aligned. The template has a marking to guide to the location where the staples will be positioned as shown in Figure 9. Two templates were provided, one has the marking for one and two inch spacing and the other one for 3 inch spacing. A staple gun was used to attach the sheathing to the test frame. The staple has three sizes, 3/4, 1, and 1 1/4 inch. The template is removed and the racking test frame is then attached through the top and bottom hatch pins to the test assembly as shown in Figure 10a and 10b. g) Start the TestWorks and the loading speed was set at 0.1 inch/min. Zero the extension and load meters. The experiment to be conducted will be assigned a testing name for record and reference purposes.

Figure 9: Alignment of the test frame with a template h) Run the test until stopped by the cut-off load (1200 lbs) or earlier that is, the failure load has been attained (the load is going down whereas the displacement keep increasing) and the test is manually shut down. i) Remove the test frame from the test assembly and make note of the sheathings as to its surface condition after subjecting to the racking load. j) Repeat from d) to i) for any new experiment to be conducted.

Figure 10 (a): The paperboard as stapled to the edge wood using the markings of the template

Figure 10 (b): The installed racking test frame

(6) Method of Analysis The raw data from the TestWorks was copied and converted into a form where it can be used in Excel. The two parameters being measured in this study are the racking strength and stiffness. The racking strength was determined from the results of measurement made by TestWorks where it is presented as peak load. The corresponding displacement for the peak load was also determined from the data. The term peak load is used interchangeably with the racking strength in this thesis. The racking stiffness was determined from the maximum slope of the racking load displacement curve. The range of the racking load where the maximum slope is being searched covers from the origin up to 30-35 % of the maximum load. The determination of the maximum slope was done using Excel. There are a few runs where it shows dead load and this was corrected by shifting it to zero or origin through adjustment by subtracting the dead load where the load starts to increase. The modulus of MD and CD strips that were obtained from Instrom Tensile Tester were used in the comparison of fresh and stretched paperboards. The stretched paperboards were those subjected to racking load in the small scale racking tester. This will determine the extent of changes that may have occurred in their internal structures and properties.

18 Discussion of Results

I. Paperboard

Paperboard Characterization

Table 1 presents the testing results of the paperboard. The data shows that the basis

Table 1a: Characterization data of the three grades of paperboard Paper Properties Standard Structural Super Structural (Green) (Red) (Blue) Ave S. D. Ave S. D. Ave S. D. Basis Weight, lbs/1000 ft2 282.13 4.05 377.50 4.12 459.15 7.81 Caliper (thickness), (t, in) 0.070 0.0004 0.099 0.0025 0.126 0.0020 Moisture Content (%) 7.156 0.040 7.385 0.068 5.972 0.052 Density (lbs/ft3) 48.36 45.76 43.73 Elastic Machine Direction 34000 1000 39400 3300 45800 1600 Modulus Cross Direction 13600 370 16000 2200 14500 750 (lb/in) 3 21.503 25.108 25.770 EMD ECD , x 10

Table 1b: Characterization data of the other paperboard Paper Properties Dark Gray Dirty White Grade B Ave S. D. Ave S. D. Basis Weight, lbs/1000 ft2 411.36 5.01 545.65 12.20 Caliper (thickness), (t, in) 0.104 0.0006 0.142 0.0014 Moisture Content (%) 7.148 0.088 7.447 0.090 Density (lbs/ft3) 47.47 46.10 Elastic Machine Direction 37200 1260 45600 2500 Modulus Cross Direction 18000 570 19200 170 (lb/in) 3 25.877 29.589 EMD ECD , x 10

weight and caliper of the three paperboards are different and increases from standard (Green) to super structural grade (Blue). The elastic modulus in the machine direction has an increasing trend but the difference between the structural and super-structural grades is small compared to the difference between the standard and structural grades. The irregularity of the modulus in the cross direction is in the difference between the

19 structural and super-structural grades. The structural grade shows an unexpectedly higher modulus than that of super-structural grade. Note that two sets of structural grade samples were tested separately and the reported figure is the average of the two sets. The two sets of data show a wide difference and may reflect variability of the product quality. The basis weight and caliper are very close to the testing results of Bi (32). The moisture contents of the present result are slightly lower than that of Bi (32). There is a similarity in trend for elastic modulus in machine direction and but not in cross direction. Note that the present study has a clamp length of 7 inches whereas Bi (32) has 6 inches. The Table 1b presents the testing results of the other two paperboards that were obtained from different sources.

Experimental Program Prior to the implementation of the experimental program, the small scale racking tester was subjected to reproducibility test. The purpose of the reproducibility test is to determine the variability of the racking tester. Five experimental runs using Dark Gray paperboard were conducted under the same conditions (1 inch staple and 1-1/2 inch spacing) and show a very reasonable reproducibility as shown in Figure (11). The racking stiffness and displacements at the peak load are reasonably close ( ± 7% using one standard deviation) for the five runs. The detailed results are presented in Table 2.

Table 2: Results of the reproducibility test of small scale racking tester Test No. Specimen No. Stiffness, lb/in Peak Load, lbs Displacement, inch ben1 1 6195 1136 0.3714 2 6151 1109 0.3567 3 6380 1034 0.3410 4 5777 998 0.3053 5 5545 1082 0.3516 Average 6010 1072 0.3452 S.D. 340 56 0.0248

Racking Load versus Displacement

1200

1000

800

600 Racking Load, lbs Load, Racking

400

200

0 0 0.1 0.2 0.3 0.4 0.5 0.6 Displacement, inches

Figure 11: Reproducibility test of the small scale racking tester

(1) Effect of Staple Spacing on the Racking performance of the Paperboard Sheathing

It has been shown in the past studies (4, 11, 14, 20, 21, 27) that the spacing of nail affects the racking strength of the shear wall. The present study covers three spacing, namely, 1, 2, and 3 inch. The staple sizes are 3/4, 1 and 1-1/4 inch in length. As shown in Figure 12, the racking stiffness has an inverse relationship and is nearly linear with the staple spacing for all the staple sizes tested. Figure 13 shows the displacement (diagonal elongation) increases with the staple spacing. When the paperboard is glued to the edge wood prior to stapling, both the stiffness and displacement increased. The 3 inch spacing was used for this special test due to its poor performance among the three staple spacing. The racking stiffness is significantly higher than that of 3 inch staple spacing without glue and either comparable to or slightly lower than that of 1 inch staple spacing.

Racking Stiffness versus Spacing

7000

6000 with glue

5000

4000 Staple Size - 1 inch DW Board Staple Size - 1 1/4 inch DW Board Staple Size - 3/4 inch DW Board 3000 Racking Stiffness, lbs/in

2000

1000

Dirty White Paperboard

0 00.511.522.533.5 Spacing, inches

Figure 12: Effect of spacing on the racking stiffness

Displacement versus Spacing

1.2

1 with glue

0.8

Staple Size 1 inch DW Board 0.6 Staple Size 1 1/4 inch DW Board Staple Size 3/4 inch DW Board Displacement, inches 0.4

0.2

Dirty White Paperboard

0 00.511.522.533.5 Spacing, inches

Figure 13: Effect of spacing on the displacement

22 The effect of spacing on peak load was demonstrated by using the data of color coded Green paperboard that has a peak load of less than 1200 lbs or that does not exceed the cut off point. As shown in Figure (14), the peak load decreases as the spacing increases. The effect of using combined adhesive/staple on peak load is shown in Figure (15) using the color coded Red paperboard. The peak load decreases with increasing spacing and with the combination of glue and staple, the peak load increases. The tests with glue were conducted using 3 inch staple spacing and all the staple sizes. In reality, the shape of the curves for staple sizes of 1 and 1-1/4 inch as shown in Figure 15 should follow the shape of the curve for 3/4 inch staple from 2 inch to 1 inch spacing. From 2 inch to 3 inch spacing all the staple sizes have similar curves. Note that if the actual load is higher than the cut off load which is 1200 lbs, the software (TestWorks version 3.07) will report it at the cut off load. This is the reason why the peak loads of 1 and 1-1/4 inch staple converge at 1200 lbs.

Peak Load versus Spacing

1200

1000

800

Staple Size 1 inch Green Board Staple Size 1 1/4 inch Green Board 600 Staple Size 1 1/4 inch Green Board Staple Size 3/4 inch Green Board Peak Load, lbs

400

200

Green Paperboard

0 00.511.522.533.5 Spacing, inches

Figure 14: Effect of spacing on the peak load

Peak Load versus Spacing

1400

1200 with glue

1000

800 Staple Size 1 inch Red Board Staple Size 1 1/4 inch Red Board Staple Size 3/4 inch Red Board 600 Peak Load, lbs

400

200 Red Paperboard

0 0 0.5 1 1.5 2 2.5 3 3.5 Spacing, inches

Figure 15: Effect of spacing on the peak load

In summary, the racking stiffness and peak load decrease as the spacing increases. The displacement increases as the spacing increases. The combined staple/adhesive has increased the peak load and racking stiffness whereas the displacement decreased considerably when compared to the same paperboard without glue. The finding in this study on the effect of spacing on the racking performance in terms of peak load and stiffness are in agreement with the results of NAHB Research Center (11), Robertson (20) and Robertson and Griffith (21). Similarly, the studies on the contribution of glue to the racking performance of the paperboard sheathing are in agreement with the results of Dolan and White (3). They found that 1) the walls with adhesives were stronger, stiffer, and less ductile than the standard nailed walls; 2) the standard nailed wall has an average displacement at peak load larger than the corresponding displacement for the adhesive walls. Bi (32) concluded in his study that using Liquid Nail glue as a

24 sheathing method greatly improved the paperboard racking stiffness and strength at the medium and large deformation in 16 inch racking tester. The racking stiffness is also comparable to those racking tests of using two and five times staples in 32 inch racking tester.

(2) Effect of Staple Size on the Racking Performance of Paperboard Sheathing Figure 16 and 18 show the relationship of the stiffness of paperboard based sheathing (color coded Dark Gray and Dirty White) with different sizes of staples at a given staple spacing. The graphs show a bell shape trend for the relationship of the staple size with the stiffness. The stiffness increases from 3/4 to 1 inch staple to be followed by the decreases from 1 inch to 1-1/4 inch staple. From the graphs one may conclude that using staples longer than 1 inch has no additional advantage. The results of other paperboards also indicate that using staple longer than 1 inch has no advantages in terms of racking resistance. The results from this study are in agreement with Urquhart (28) where he found that extending beyond the optimum length of penetration of nail did not improve the load capacity of the nailed joints. The other paperboards color coded Green, Red, and Blue are not consistent in terms of racking performance as the paperboards in the figures. As shown in Figure 17 and 19, the relationship of staple size with the displacement is of reverse trend when compared to Figure 16 and 18. The displacement at 1-1/4 inch staple is higher than that at 1 inch staple which indicate that staples longer than 1 inch has no advantages in terms of racking performance. For other paperboards (color coded Green, Red, and Blue), even though that there is a difference in the displacement relative to the staple size, the plots of displacement with the staple size are not discernable as the ones in Figure 17 and 19.

25 Stiffness versus Staple Size

7000

6000

5000

4000 DW 1 inch spacing DW 2 inch spacing DW 3 inch spacing 3000 Stiffness, lbs/in

2000

1000 Dirty White Paperboard

0 0 1/5 2/5 3/5 4/5 1 1 1/5 1 2/5 Staple Size, inch

Figure 16: Effect of staple size on the racking stiffness

Displacement versus Staple Size

0.8

0.7

0.6

0.5

DW 1 inch Spacing 0.4 DW 2 inch Spacing DW 3 inch Spacing

Displacement, inch 0.3

0.2

0.1 Dirty White Paperboard

0 0 1/5 2/5 3/5 4/5 1 1 1/5 1 2/5 Staple Size, inch

Figure 17: Effect of staple size on the displacement

26 Stiffness versus Staple Size

7000

6000

5000

4000 DG 1 inch Spacing DG 2 inch Spacing DG 3 inch Spacing 3000 Stiffness, lbs/in

2000

1000

Dark Gray Paperboard

0 0 1/5 2/5 3/5 4/5 1 1 1/5 1 2/5 Staple Size, inch

Figure 18: Effect of staple size on the racking stiffness

Displacement versus Staple Size

0.6

0.5

0.4

1 inch spacing 0.3 2 inch spacing 3 inch spacing Displacement, inch 0.2

0.1

Dark Gray Paperboard

0 0 1/5 2/5 3/5 4/5 1 1 1/5 1 2/5 Staple Size, inch

Figure 19: Effect of staple size on the displacement

27 (3) Effect of Caliper (thickness) on the Racking Performance of Paperboard Sheathing

The only set of paperboard that has different calipers was from Fibre Converters (Constantine, Michigan). The caliper (or thickness) of paperboard with its corresponding grade and color coding are 0.0696 inch for standard grade and Green color, 0.0991 inch for structural grade and Red color and 0.126 inch for Super Structural grade and Blue color. Bi (32) used the paperboards from Fibre Converter. Figure 20 shows the relationship of peak load with the caliper of the paperboard. The graph covers the 3 inch staple spacing with different staple sizes. The 1 and 2 inch staple spacing could not be represented in the graph since its peak loads are higher than the cut-off point (1200 lbs) of the machine. The peak load increases with the caliper in almost a linear fashion. The graph also shows that 1 and 1-1/4 inch staple has very small difference in terms of racking strength. This confirms the earlier finding about the racking performance of 1 and 1-1/4 inch staple. Figure 21 shows the relationship of the caliper with the stiffness using 1 inch staple spacing with different staple sizes. The general trend of the curves shows that the stiffness increases with the paperboard caliper. The 1-1/4 inch staple has an irregular pattern at the low end of the thickness (0.0696 inch) when compared to 1 and 3/4 inch staple. Figure 22 shows the effect of caliper on the displacement. The graph shows an inverse relationship between caliper and displacement. This shows that the thinner board has a weaker strength compared to the thicker one. This is also reflected in the results obtained for the caliper and the peak load where it shows a direct relationship between the two parameters. The details of the results are presented in the Appendix 3.

28 Peak Load versus Thickness of the Paperboard

1400

1200

1000

800 3/4 inch staple 1 inch staple 1 1/4 inch staple 600 Peak Load, lbs

400

200 Fibre Converter Paperboard 3 inch spacing

0 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 Thickness, inch

Figure 20: Effect of caliper (thickness) on the peak load

Stiffness versus Thickness of the Paperboard

6000

5000

4000

3/4 inch staple 3000 1 inch staple 1 1/4 inch staple Stiffness, lbs/inch

2000

1000

Fibre Converter Paperboard 1 inch spacing

0 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 Thickness, inch

Figure 21: Effect of caliper (thickness) on the racking stiffness

Displacement versus Thickness

0.8

0.7

0.6

0.5

3/4 inch staple 0.4 1 inch staple 1 1/4 inch staple

Displacement, inch 0.3

0.2

0.1 Fibre Converter Paperboard 1 inch spacing 0 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 Thickness, inch

Figure 22: Effect of caliper (thickness) on the displacement

(4) Comparison of Racking Performance of Paperboards using Staples and Nails

Color coded Dirty White paperboard was used as the test specimen for this study. Two fasteners spacing were used, namely 2 and 3 inch. The nails were hand driven thru the sheathing whereas an air staple gun was used for the staples. The fastener (nails and staples) sizes were 1 and 1-1/4 inch. One special test where 1-1/4 inch screw was used as fastener and to see how it compared to nails and staples. Figure 23 and 24 show the comparison of the load displacement curves of nails and staples. Figure 23 compares the racking performance of paperboard using 1 inch nail and staple. Although the stiffness is reasonably close for 1 inch staple and 1 inch nail, it does not relate to the racking strength. The stapled paperboard (DW) has a strength higher than that of nailed paperboard as shown in Table 3. Although the maximum displacement may not seem to be significantly different, it is emphasized here that for a meaningful

30 comparison, displacement for 1 inch nail and staple should be compared at 775 lbs which is the peak load of the nailed paperboard at 3 inch spacing. The displacement for 1 inch staple decreases considerably when compared to 1 inch nail after this adjustment. Visual examination of the physical state of the test specimens, the 1 inch nailed paperboard has nail withdrawal at the sides of the marks top and bottom of the paperboard. The top refers to that corner of the test frame where it is attached to the cross head and the bottom is the opposite corner where it is attached thru its hatch pin to the base of the test assembly. Note that the test frame is attached to the test assembly diagonally. It is also observed that other nails had their heads pulled up a little bit. The nails tore through the sheathing. One would notice that the attachment of paperboard to the wood frame loosened up. The 2 inch spacing has less nail withdrawal when compared to 3 inch spacing. The nails that torn through the paperboard at 2 inch spacing were less when compared to 3 inch spacing. The displacement of the paperboard from the wood frame is larger for 3 inch spacing as compared to 2 inch spacing.

Racking Load versus Displacement

1200 1 inch staple 1 inch staple 1 inch nail 3 inch spacing 2 inch spacing 2 inch spacing 1000

1 inch nail 3 inch spacing

800

nail1 spe1 nail1 spe2 600 ben12xyz spe2 ben12xyz spe3 Racking Load, lbs

400

200

Dirty White Paperboard

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Displacement, inches

Figure 23: Load displacement curves of 1 inch staple and nail

31 The 3 inch spacing has a lower strength when compared to that of 2 inch spacing. For 1-1/4 inch fastener, the stapled paperboard has a higher stiffness than that of nailed paperboard at 2 inch spacing whereas at 3 inch spacing the difference in stiffness is small. The displacements of 1-1/4 inch nailed paperboard are higher than that of stapled paperboard. Again this is in agreement with the observation made in 1 inch nailed paperboard sheathing. The physical state of the nailed paperboard with 1-1/4 inch nail at 2 inch spacing has a very small displacement from the wood frame (edge wood) when compared to 3 inch spacing. For 3 inch spacing, almost all the nails were torn through the sheathing whereas for 2 inch spacing the nails are intact. Figure 24 shows the load displacement curves for 1-1/4 inch nail and staple.

Racking Load versus Displacement

1400

1 1/4 inch nail 1 1/4 inch staple 2 inch spacing 1200 2 inch spacing 1 1/4 inch nail 1 1/4 inch staple 3 inch spacing 3 inch spacing 1000

nail1 1/4 spe1 800 nail1 1/4 spe2 ben14xyz spe2 ben14xyz spe3 600 screw1 1/4 spe1

Racking Load, lbs Load, Racking 1 1/4 inch screw 3 inch spacing

400

200

Dirty White Paperboard

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Displacement, inches

Figure 24: Load displacement curves of 1-1/4 inch staple and nail

Using 1-1/4 inch wood screw as fastener, the paperboard has a stiffness higher than that of 1-1/4 inch staple and nail as shown in Table 3. From the graphs in Figure 24, the racking load decreases as the displacement

32 increases which indicate that the screws has given way as could be seen in the physical state of the paperboard after the run was done. Note that one edge wood of the test specimen separated from the paperboard. The screws tore through on the paperboard and the paperboard was displaced half an inch at one end of the of the wood frame after the test. Figures 25 to 27 show the physical state of the nailed paperboard.

Table 3: Comparison of racking performance of the nailed and stapled paperboards Testing Specimen Fastener Spacing Stiffness Peak Displacement Number Number Size, in. inch lbs/in Load, lbs inch ben12xyz 2 staple 1 2 4704 >1165 0.384; 0.311 nail1 1 nail 1 2 4692 985 0.632 ben12xyz 3 staple 1 3 3504 >1162 0.964;0.411 nail1 2 nail 1 3 3721 775 1.033 ben14xyz 2 s 1-1/4 2 3719 >1179 0.439 nail1 1/4 1 n 1-1/4 2 3138 >1191 0.512 ben14xyz 3 s 1-1/4 3 3333 >1172 0.748;0.511 nail1 1/4 2 n 1-1/4 3 3120 1053 1.312

Screw1 1/4 1 sc 1-1/4 3 3629 860 0.441

Note: The second value on the displacement of stapled paperboard was taken at the peak load value of the nailed paperboard.

Lastly, Table 3 shows that the 1 inch nailed paperboard has a better racking stiffness and strength than that of 1-1/4 inch nailed paperboard at 2 and 3 inch spacing just as well as the stapled paperboard.

Figure 25: Comparison of physical state of nailed (left) and (right) stapled paperboards using fastener size of 1 inch and 2 inch spacing

Figure 26: Nail withdrawal, nail torn through on paperboard and paperboard displacement from the wood frame (1 inch nail and 3 inch spacing)

Figure 27: Nail torn through on paperboard and displacement of paperboard from the wood frame (1-1/4 inch nail and 3 inch spacing)

(5) Effect of Stretching on the Tensile Properties of Paperboard Only the color coded Red, Blue, Dark Gray and Dirty White (XYZ) paperboard were used in this study. In reality, the racking test subjected the paperboard to stretching. The cross head pull up the racking test frame with sheathed paperboard while the connecting pin at the base of the test assembly where the hatch pin of the test frame is attached is countering the pull up action of the cross head. The paperboards after racking test are cut into strips of 0.5 x 10 inch. Only the good portion of the tested paperboard is selected, that is devoid of crease mark or buckled areas. The testing results as presented in Table 4 show that the color coded Dirty White B grade paperboard was affected by the stretching process during the racking test. This is indicated by the decrease of elastic modulus in MD direction. This was confirmed by conducting a t-test on the data before and after the racking test where it shows a significant difference at 95 % confidence level. For the elastic modulus in CD direction, basically there is no difference between the untested (fresh) and racking tested (RT) samples. The color coded Dark Gray, Red, Blue paperboards have elastic modulus both in MD and CD directions the same as samples from the paperboard that has not been tested in the racking tester.

35 Therefore it appears safe to conclude that there is no change in the tensile properties after the paperboards were subjected to stretching process during the racking test except for color coded Dirty White paperboard. It is emphasized here that even though the elastic modulus in CD direction for racking tested (RT) sample is higher than that of untested (Fresh) sample, it is unlikely that the tensile properties improved after subjecting the paperboard to a stretching process. It appears that they are the same.

Table 4: Comparison of elastic modulus of the paperboard before (Fresh) and after (RT) racking test Paperboard Grade Condition and Elastic Modulus (color coded) Direction lbf/in

Red Standard Fresh - MD 39400 RT - MD 41000

Fresh - CD 16000 RT - CD 19200

Blue Super Structural Fresh - MD 46000 RT - MD 47000

Fresh - CD 14500 RT - CD 17000

Dark Gray Fresh - MD 37200 RT - MD 38200

Fresh - CD 18000 RT - CD 17450

Dirty White B Fresh - MD 45600 RT - MD 42500

Fresh - CD 19200 RT - CD 18550

36 (6) Racking Stiffness as a Function of Geometric Modulus ( EMD ECD )

From the results of Table 1a, the geometric mean modulus increases with the the caliper of the paperboard. The results are in agreement with Bi (32). Since it has been established that racking stiffness increases with the caliper, it is expected that it will also increase with the geometric mean modulus as confirmed by Figure 28. This also confirmed the equation published in BI (32) where it relates the stiffness or slope (P / δ, lb/in ) to paperboard thickness (t) and geometric mean modulus.

P / δ = 0.78 t EMD ECD ………………………………. (3)

where P = racking load, lbs δ = displacement, inch 2 EMD = elastic modulus in machine direction, lbs/in 2 ECD = elastic modulus in cross direction, lbs/in t = thickness, inch

Racking Stiffness versus Geometric Mean Modulus

6000

5000

4000

3/4 inch staple 3000 1 inch staple 1-1/4 inch staple

Racking Stiffness, lbs/in 2000

1000

Fibre Converter Paperboard 1 inch spacing

0 0 5 10 15 20 25 30 Geometric Mean Modulus, X 1000 lb/in

Figure 28: Plot of racking stiffness with geometric mean modulus

37 II. Wood-Based Boards

Table 5 presents the results of the moisture content, density based on the oven dry weight and volume, and the basis weight of wood boards.

Table 5: Properties of the wood boards Type of Wood Boards Hardboard Plywood Oriented Strand Board Moisture Content, % 4.951 7.522 5.196 Basis Weight, lb/1000ft2 1005 923 859 Density, lb/ft3 67.34 38.35 44 Caliper, inch 0.170 0.267 0.222

Experimental Program

(1) Effect of Staple Size and Thickness on the Racking Performance of the Hardboard

Figure 29 shows the load displacement curves of hardboard for 2/16 and 3/16 inch thick. The graph shows that only 2/16 inch thick hardboard with 3/4 inch staple

Racking Load versus Displacement

1400 3/16 inch thick 3/16 inch thick 3/4 inch staple 1 1/4 inch staple 3/16 inch thick 1200 1 inch staple 2/16 inch thick 2/16 inch thick 3/4 inch staple 1 inch staple 1000

2/16 inch thick 1 1/4 inch staple hb3/16 spe3 800 hb-1 spe3 hb3/16 spe1 hb-1 sp2 hb3/16 spe2 600 hb-1 spe1 Racking Load, lbs Load, Racking

400

200

hardboard

0 0 0.2 0.4 0.6 0.8 1 1.2 Displacement, inch

Figure 29: Load displacement curves for 2/16 and 3/16 inch hardboard

has a peak load less than 1200 lbs. Other hardboards have more than 1200 lbs for peak load. Table 6 presents the data for the racking performance of the 2/16 and 3/16 inch hardboard. The tabulated results show that the staple size affects the

Table 6: Comparison of racking performance of 2/16 and 3/16 inch hardboard Test Specimen Thickness Staple Stiffness Peak Displacement Number Number inch Size, inch lbs/in Load, lbs inch

hb-1 3 2/16 3/4 3083 1102 0.709 2 2/16 1 5074 >1189 0.408 1 2/16 1-1/4 3761 >1197 0.500

hb-3/16 3 3/16 3/4 3917 >1188 0.478 1 3/16 1 5227 >1197 0.435 2 3/16 1-1/4 4050 >1222 0.429

Note: All the runs have 3 inch spacing.

racking performance of the hardboard. The stiffness of stapled wood board increases from 3/4 to 1 inch and followed by a decrease to 1-1/4 inch staple. This trend is observed both for 2/16 and 3/16 inch hardboard and in the stapled paperboard. Similarly, the trend of the displacement with staple size for 2/16 inch hardboard is similar to the stapled paperboard where 1 inch has the minimum displacement among the three staple sizes. The variation of displacement with staple size for 3/16 inch hardboard is not significant for 1 and 1-1/4 inch staple but the difference between 3/4 and 1 inch staple shows the effect of staple size on the displacement. From the above results, one would conclude that there is no additional advantage from going beyond 1 inch in length for staple fasteners.

(2) Comparison of Racking Performance of the Three Wood Boards using Staple

Comparing the racking performance of the three types of wood boards that were

39 used in this study are shown in Figure 30 and Table 7. The hardboard used for this comparison has a thickness of 3/16 inch whereas for plywood and oriented strand board, the thickness is 1/4 inch.

Racking Load versus Displacement

1400

oriented strand board 1200 hardboard

1000

plywood 800

OSB-1 spe1 600 ply-1 spe1 hb3/16 spe2

Racking Load, lbs Load, Racking 400

200 1 1/4 inch staple 3 inch staple spacing 0 0 0.1 0.2 0.3 0.4 0.5 0.6

-200 Displacement, inch

Figure 30: Load displacement curves for the three wood boards using 1-1/4 inch staple

The graph shows that the hardboard has a better racking performance than that of plywood and oriented strand board. The displacement at the cutoff load (1200 lbs) for hardboard is lower than that of plywood and oriented strand board despite the thickness is 3/16 inch. The racking strength between the plywood and oriented strand board show differences only at the high end of the racking load, from 800 lbs to cut off load (1200 lbs). Therefore the racking strength for the three wood boards could be ranked as hardboard > plywood > oriented strand board.

Table 7: Comparison of racking performance of the three types of wood boards

Test Specimen Type of Wood Staple Stiffness Peak Displacement Number Number Boards Size, inch Lbs/in Load, lbs inch hb-3/16 1 hardboard 1 5227 >1197 0.435 2 1-1/4 4050 >1222 0.429 ply-1 2 plywood 1 3772 >1202 0.469 1 1-1/4 3166 >1179 0.453

OSB-1 2 oriented 1 4675 >1206 0.539 1 strand board 1-1/4 3875 >1165 0.534 Note: 3 inch spacing was used for all the test runs

The tabulated results in the above table show again that stapled wood boards with 1 inch staple has a higher stiffness than that of 1-1/4 inch staple. This just confirm the earlier finding that there is no advantage for using longer staples. The racking stiffness could be ranked as hardwood > OSB > plywood.

(3) Comparison of Racking Performances of the Three Wood Boards using Nails

Figure 31 shows the load displacement curves of the three wood boards using 1-1/4 inch nail as fastener. The graph shows that the hardboard has a lower displacement at cut off load when compared to plywood and oriented strand board. The oriented strand board has a better racking strength from 200 lbs to 900 lbs range when compared to plywood. From 900 lbs to cut off load there is a shift in the racking strength where plywood shows a better strength than that of oriented strand board. The three wood boards in terms of racking strength could be ranked as hardboard > plywood > oriented strand board. Similarly, the racking stiffness could be ranked as hardboard > oriented strand board > plywood.

Racking Load versus Displacement

1200

3/16 inch hardboard

1000

1/4 inch OSB

800

hbnail1 1/4 spe1 600 osbnail1 1/4 spe1 plynail1 1/4 spe1 1/4 inch plywood Racking Load, lbs 400

200

1-1/4 inch nail and 3 inch spacing 3i h i 0 0 0.10.20.30.40.50.60.7 Displacement, inches

Figure 31: Load displacement curves of the three wood boards using 1-1/4 inch nail

Table 8: Comparison of racking performance of the wood boards using nails as fastener Test Number Specimen Nail size Spacing Stiffness Peak Displacement Number inch inch lbs/in Load, lbs inch

hbnail1 1/4 1 1-1/4 3 5258 >1200 0.321

plynail1 1/4 1 1-1/4 3 3220 >1167 0.531

osbnail1 1/4 1 1-1/4 3 3746 >1152 0.601

(4) Comparison of Racking Performance of the Three Wood Boards using Staples and Nails

Table 8 summarizes the racking performance of the three wood boards that used both the staples and nails. The hardboard has a thickness of 3/16 inch and both

42 the plywood and oriented strand board have thickness of 1/4 inch.

Table 9: Comparison of racking performance of the wood boards using nails and staples Test Number hb-3/16 hbnail ply-1 Plynail OSB -1 OSBnail

Wood Board hardboard hardboard plywood plywood oriented strand board

Fastener Size S-1-1/4 in N-1-1/4in S –1-1/4 in N-1-1/4 in S-1-1/4 in N-1-1/4 in Staple Nail Staple Nail Staple Staple Stiffness, 4050 5258 3166 3220 3875 3746 lbs/in Peak Load, >1222 >1200 >1179 >1167 >1165 >1152 lbs Displacement 0.429 0.321 0.453 0.531 0.534 0.601 inch Note: All the runs in the table used 3 inch spacing. The fastener size is 1-1/4 inch.

The above data shows that only the hardboard with nail as fastener has a higher stiffness and a lower displacement when compared to the same hardboard that used staple. For oriented strand board and plywood, it did not seem to improve the stiffness nor the displacement when nails were used as fasteners relative to a staple. The racking strength of the plywood used in the current study was

compared with the study made by Mallory et al (15) using a small scale racking tester (2 x 2 ft). The 2 x 2 ft racking tester has a middle stud and the plywood sheathing has 1/2 inch thickness. The nail spacing was 5-1/4 inches vertically, and ranged 5-1/2 to 6 inches horizontally. The nail used in their study is 8d common wire nail. The nail size used in the current study is 1-1/4 inch in length with 3 inch spacing. Staple size of 1-1/4 inch is also included for comparison purpose. The thickness of the plywood is 1/4 inch. Figure 32 shows a comparison of racking strength of the plywood. There is a similarity in the slope of the lines from Mallory (15) and the current studies. The racking load of Mallory (15) data is several order of magnitudes higher than that of current study. This could be explained that the set up of the racking tester, the nail dimension, and the thickness of the plywood used is different from the current study. The slope of the line with staple as fastener also run parallel with the nail and nearly overlapped

43 with each other. This also shows that both the nailed and stapled plywood sheathings have nearly the same racking strength.

Comparison of Racking Strength of Plywood

1200

1/2 inch plywood from 22 x 24 inch racking tester (Mallory data) 1000

800

plywood 1/2 inch 600 ply-1 spe1 present study plynail spe1 1/4 inch plywood with

Racking Load, lbs Load, Racking staple as fastener 400

200 present study 1/4 inch plywood with nail as fastener

0 0 0.05 0.1 0.15 0.2 0.25 0.3 Displacement, inches

Figure 32: Comparison of racking strength of plywood

(5) Comparison of Racking Performance of Wood Boards with Paperboards Figure 33 compares the racking performance of wood board with paperboard (color coded Dirty White) using fastener size of 1-1/4 inch. The wood boards (plywood, hardboard, and oriented strand board) have a 3 inch spacing and used 1-1/4 inch nail whereas the paperboard used 1, 2, 3 inch spacing and 1-1/4 inch staple as fastener. From the graph, the 2 inch spacing of paperboard has a racking strength better than that of plywood and oriented strand board simply based on the displacement and the slope of the load displacement curve at the high load end which is steeper than that of plywood and oriented strand board. No significant difference in racking strength between hardboard and paperboard with 1 inch spacing was observed. The paperboard with 3 inch spacing has a poorer

44 racking strength when compared to the three wood boards.

Racking Load versus Displacement

1400 Drity White Paperboard Dirty White Paperboard 2 inch spacing 3 inch spacing 3/16 inch hardboard 1/4 inch OSB 1200

Dirty White Paperboard 1 inch spacing 1000

hbnail1 1/4 spe1 800 osbnail1 1/4 spe1 plynail1 1/4 spe1 1/4 inch plywood ben14xyz spe3 ben14xyz spe2 600 ben14xyz spe1 Racking Load, lbs Load, Racking

400 Dirty White Paperboard 1-1/4 inch staple

200 wood board -- 1-1/4 inch nail and 3 inch spacing 3i h i 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Displacement, inches

Figure 33: Comparison of racking performance of the wood boards with paperboards using 1-1/4 inch staple and nail

The racking performances of the wood boards were also compared to paperboard using 1 inch staple. Figure 34 shows the comparison of the racking performance of wood boards using 3 inch spacing with paperboard that used 1 and 2 inch spacing. The paperboard with 2 inch spacing has a slightly better racking strength than that of wood board. For paperboard with 1 inch spacing, the racking strength is considerably better than the wood boards. For paperboard with 3 inch spacing, although not included in Figure 34, the racking strength is not expected to be better than the wood boards simply based on the racking performance of paperboard with 2 inch spacing.

45 Racking Load versus Displacement

1400

Dirty White Paperboard 2 inch spacing 1200 Dirty White Paperboard 1 inch spacing

1000

3/16 inch hardboard OSB-1 spe3 800 ply-1 spe2 1/4 inch oriented hb3/16 spe1 strand board ben12xyz spe2 600 ben12xyz spe1

Racking Load, lbs 1/4 inch plywood

400 Dirty White Paperboard 1 inch staple 200 wood board 1 inch staple 3 inch staple spacing

0 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 Displacement, inch

Figure 34: Comparison of racking performance of the wood boards with paperboard both using 1 inch staple

(6) Effect of Basis Weight on the Racking Strength of Wood Boards Table 10 presents the data of basis weight of wood boards with the racking strength. The fastener sizes are 1-1/4 inch for staple and 1-1/4 inch for nail. From the tabulated results, the basis weight appears to have an affect on the racking strength in terms of displacement at the peak (cut off) load. The ranking (from high to low) in the basis weight for the wood boards is also followed in the racking strength of the wood boards using either 1-1/4 inch nail or staple. The data shows an inverse relationship between the basis weight and displacement at the peak load.

46 Table 10: Effect of basis weight on the racking strength of the wood boards Test Number hb-3/16 ply-1 OSB-1 hbnail plynail OSBnail Wood Board hardboard plywood OSB* hardboard plywood OSB Basis Weight, 1005 923 859 1005 923 859 lbs/1000ft2 Fastener staple staple staple nail nail nail Fastener Size, in 1-1/4 1-1/4 1-1/4 1-1/4 1-1/4 1-1/4 Displacement 0.429 0.453 0.534 0.321 0.534 0.601 at Peak Load, in * OSB – oriented strand board

III. Comparison of Calculated and Actual Racking Load Equation (1) and (2) were used to calculate the racking load of the paperboard with the lateral strength of an individual nail being replaced with a staple. Bi (32) conducted lateral staple resistant test where maximum lateral cutting forces were obtained for the three grade of paperboards. The selected staple maximum cutting forces were from the perpendicular CD samples, namely 105 lbs for standard grade(Green), 148 lbs for structural grade (Red) and 158 lbs for super structural grade (Blue). Equation (1) is reduced to a final form where you just feed in the lateral cutting force according to the grade of the paperboard. The angle in the equation is 45 degree since the 16 x 16 inch racking tester is a square. The number of staples depend on the spacing you used for the calculation of racking strength. The calculated load is then compared to the actual load. Note that only those runs where the actual peak load did not exceed the cut off load (1200 lbs) were used for comparison. Table 11 summarizes the results of the calculation together with the actual load. Note that the equation calculates only the racking strength of the sheathing panel (wood frame is assumed to have zero or negligible strength).

47 Table 11: Comparison of calculated and actual Load Paperboard Grade Standard Structural Super- Structural Color Code Green Red Blue Spacing, in 2 3 2 3 3 No. of Staple 6 4 6 4 4 Calculated Load 851 577 1200 814 869 Actual Load 744 605 1099 899 1113 (Cal/Act)*100 114 % 95 % 109 % 91 % 78 % Note: The load has a unit of lbs.

The ratio of calculated load to actual load for the Standard and Structural grades are within the reasonable level. The super-structural grade has a calculated load quite different from the actual load. The data of staple lateral cutting force for super structural grade may not be accurate since the difference between the structural and super structural grades is very small. Between these two grades there is another grade which is the structural plus. It is likely that the staple lateral cutting force of the super structural grade is higher than 158 lbs.

IV. Metal Sheathing Two special runs with aluminum sheet (thickness of 0.018 inch) as sheathing and using fastener of 1-1/4 inch staple and screw were made to determine its racking performance. The physical state of the aluminum sheathing after the racking test show buckling almost over on the entire surface using either 1-1/4 inch staple or screw. Figure 35 shows the load displacement curves for the two runs and the differences in racking strength begin to show from 600 lbs up to their corresponding peak load. The graph shows that the screws as fastener has more strength than that of staples. Table 12 shows the comparison of racking performance of aluminum sheathing using screws and staples. The stiffness of the two aluminum sheathings using different fasteners are nearly the same. The peak load and displacement for the aluminum sheathing using screws as fastener are higher and lower, respectively than that of aluminum sheathing using staples

48 as fastener.

Table 12: Comparison of racking performance of the aluminum sheathings using screws and staples Test Specimen Staple Spacing Stiffness Peak Displacement Number Number Size, in inch lbs/in Load, lbs inch

Alum 1 1-1/4 inch 3 inch 3808 961 0.6557 screw 2 1-1/4 inch 3 inch 3764 827 0.6958 staple

Racking Load versus Displacement

1000 1-1/4 inch screw 900

800

700 1-1/4 inch staple 600

alumspe1 500 alumspe2

400 Racking Load, lbs

300

200

100 3 inch spacing

0 0 0.2 0.4 0.6 0.8 1 1.2 Displacement, inches

Figure 35: Load Displacement Curves of Aluminum Sheathing

49 Racking Load versus Displacement

1400

Dirty White Paperboard Blue Paperboard

1200 1-1/4 inch screw Aluminum 1000 1-1/4 inch staple Dark Gray Paperboard

800

1-1/4 inch staple Aluminum 600 alumspe1 Racking Load,lbs 1-1/4 inch staple alumspe2 Dark Gray Red Paperboard Red 400 Green Blue 1-1/4 inch staple Dirty White Green Paperboard 200

3 inch spacing

0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Displacement, inches

Figure 36: Comparison of aluminum sheathing with paperboards

Figure 36 shows that the color coded Dirty White paperboard has a better racking performance than other paperboards as its racking load is higher than 1200 lbs, which is the cutoff load for the present small scale racking tester. The physical state of all the paperboards except for color coded Dirty White have crack marks, crease marks (buckled up) diagonally, displacement at top and bottom portion of the test frame, and staples tore through the paperboards. The 3 inch staple spacing gives a better picture of the racking performance of the paperboards. The aluminum sheathings have entire surface crumpled up and the load displacement curves are very similar to the color coded Red and Dark Gray paperboard. The aluminum sheathings have racking stiffness the same as the paperboard at the lower end (up to 500 lbs). Based on Figure 36, the ranking in terms of racking strength is as follows: DW (Dirty White) > Blue > aluminum sheathing (screws) > Dark Gray and Red > aluminum sheathing (staples) > Green.

Summary and Conclusions A total of 71 experimental runs were conducted for this study. The objectives of the test were to determine the racking performance of various sheathing materials such as paperboard and wood board. Based on the results of this study, the following findings are presented below:

Reproducibility Test Five runs were made to establish the reproducibility of the small scale racking tester. The test conditions of the five runs were identical and using the same grade of paperboard. The test results showed a reasonable reproducibility (± 7 %).

Effect of Staple Spacing on the Racking Performance of the Paperboard Sheathing

The staple spacing has pronounced effect on the racking performance of the paperboard sheathings. (a) The racking stiffness decreases with increased spacing. (b) The displacement at peak load increases as the staple spacing increases. (c) The peak load decreases as the staple spacing increases.

Effect of Staple Size on the Racking performance of Paperboard and Hard- board Sheathings

(a) The effect of staple size on the racking stiffness showed a maximum of stiffness at 1 inch staple. (b) The effect of staple size on the displacement at peak load showed the reverse trend of its effect on the racking stiffness where 1 inch staple has a lower displacement than that of 3/4 and 1-1/4 inch staple. (c) The pattern observed between the racking performance and staple size showed that no advantage will be derived for using longer than 1 inch staple.

51 Adhesive as a Sheathing Method (a) An adhesive (Liquid Nail) that was used to glue the paperboard to the wood frame in combination with staples contributed to the improvement of the racking performance in terms of increasing the stiffness and decreasing the displacement. The tests were conducted on those runs using a 3 inch staple spacing. The resulting racking performance was comparable to 1 inch staple spacing. (b) The peak load of those runs with color coded Red paperboard and using 3 inch spacing also increased when adhesive was used in combination with staples. The extent of improvement was not as good as that of 1 inch spacing of 3/4 and 1-1/4 inch staple.

Comparison of Paperboards Racking Performance of using Staples and Nails (a) Using the staples as fastener has generally a better racking strength than that of nails. (b) The 1-1/4 inch staple has a higher racking stiffness than that of 1-1/4 inch nail. The 1 inch staple and nail have nearly the same racking stiffness. (c) Nails withdrawal were observed on those paperboards using 1 inch nail as fastener and 3 inch nail spacing and showed the most severe. Nail torn through was also observed on these paperboards. (d) No nail withdrawal was observed on the paperboard using 1-1/4 inch nail as fastener with 2 and 3 inch nail spacing. This shows that 1-1/4 inch nail has a higher withdrawal resistance than that of 1 inch nail. (e) The 3 inch nail spacing shows nails torn through on paperboard. (f) The staples as fastener for the color coded Dirty White paperboard did not have staple removal or pullout and torn through on paperboard. This shows that the staples has a better withdrawal resistance than nails.

Effect of Stretching during Racking Test on the Tensile Properties (a) Of the 4 paperboards studied for stretching effect during racking test, only one (color coded Dirty White) paperboard shows the elastic modulus in

52 machine direction was affected by the stretching process during racking test. The elastic modulus in cross direction is the same for all the paperboards before and after racking test.

Comparison of Racking Performance of the Wood Boards (a) The three wood boards using staples (1 and 1-1/4 inch) as fastener have ranked as hardboard > plywood > oriented strand board in terms of racking strength. (b) For the racking stiffness, the ranking is hardboard > oriented strand board > plywood for the three wood boards using staple (1 and 1-1/4 inch) fasteners. (c) The wood boards using 1-1/4 inch nail as fastener exhibits the same ranking sequence for racking strength and stiffness as with the staples. The oriented strand board has consistently shown to have a better stiffness than plywood using either staples or nails as the fastener. Similarly the hardboard has a better racking strength when compared to oriented strand board and plywood using either staples or nails as the fastener. (d) The hardboard using 1-1/4 inch nail as the fastener has better racking stiffness and strength than that same hardboard using staples as the fastener. (e) The plywood using either1-1/4 inch nail or staple as the fastener has the same racking stiffness. Similarly the oriented strand board has also the same racking stiffness using either nails or staples as fastener. (f) Both the plywood and oriented strand board have a better racking strength using staples as fastener when compared to the same wood board using nails as fastener.

Comparison of Racking Performance of Wood Boards with Paperboards (a) The paperboard with 2 inch spacing and using 1-1/4 inch staple has a racking strength better than that of plywood and oriented strand board. (b) No significant difference in racking strength between the hardboard and paperboard was observed.

53 (c) The racking strength of paperboard with 3 inch spacing was lower when compared to the three wood boards. (d) The paperboards using 1 inch staple with 1 and 2 inch spacing have a better racking strength than that of the wood boards using 1 inch staple and 3 inch spacing.

Comparison of Actual and Calculated Load using Mathematical Equation Using the data of lateral staple resistance, the racking load was predicted using mathematical equation (1) and (2) with reasonable accuracy when compared to the actual loads of both the standard and structural grades paperboards. The super structural grade may have data on lateral staple resistance lower than the actual value which contributes to the wide gap between the predicted and actual load.

Comparison of Racking Performance of Metal Sheathing with Paperboards. (a) The aluminum sheathing has shown that using screws as fastener has a better racking strength than that of staples. The stiffness is the same using either screws or staples as fastener. (b) The physical state of the aluminum sheathing has the entire surface crumbled up using either screws or staples as fastener during racking test. (c) The aluminum sheathing has the same racking stiffness at the lower load end (up to 500 lbs) as the paperboards. (d) The racking strength of aluminum sheathing in comparison with the paperboards has the following ranking: DW (Dirty White) > Blue > aluminum sheathing (screws) > Dark Gray and Red > aluminum sheathing (staples) > Green.

Final Conclusions

Based on the above findings, the staple size and spacing, and the caliper have an effect on the racking performance of the paperboard. Using staples longer than 1 inch has no advantage in terms of racking performance. The staple has a higher withdrawal

54 resistance than the nail when both are used as fasteners of paperboard. It was observed from the physical state of the paperboard after the test that size and spacing have an influence on the withdrawal resistance of the nail. Definitely it was shown in this study that staples are better fasteners than nails. Screws did not improve the racking performance of the paperboard when compared to staples. The racking test on 2/16 and 3/16 inch thick hardboard, shows that using staples longer than 1 inch has no additional advantage in racking performance. Test results from the hardboard also show that the thickness (2/16 and 3/16 inch) has an effect on the racking performance. It was found that the hardboard has a better racking performance than the plywood and oriented strand board using either staples or nails as fastener. Oriented strand board (OSB) has a higher racking stiffness and a slightly lower racking strength when compared to plywood using either nails or staples as fastener. The paperboard (color coded Dirty White) during the racking test has demonstrated to have a racking strength better than or comparable to, that is dependent on the staple spacing when compared to the wood based sheathing materials such as hardboard, plywood and oriented strand board. The racking test on the aluminum sheathing is preliminary at this stage. The physical state after the racking test showed its crumpled surface. This indicated poor strength that could be attributed to its thickness (0.018 inch.).

55 Recommendation

1. The orientation (MD and CD directions) of the paperboard on the test frame should be evaluated for its influence on racking performance. 2. Lateral staple and nail resistance test on the wood board sheathings such as hardboard, plywood and oriented strand board should be conducted after racking test. The data obtained will be used in calculating the racking load through existing equation. 3. To determine if the density of the wood frame (edge wood) has bearing on the racking performance of the paperboard. 4. To evaluate the racking performance of 1 inch staple and nail on wood based sheathing materials and compare with full scale racking test. 5. To adopt and apply the shear wall property definitions such as wall capacity, wall failure, energy dissipation and EEEP parameters (elastic stiffness, yield load and displacement and ductility) to the load displacement curves of paperboards. 6. To compare the testing results from 16 x 16 inch racking tester with the full scale racking tester.

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59 Appendix

Appendix 1a: Effect of staple spacing on the racking performance of the paperboard Test Specimen Staple Spacing Stiffness, Peak Displacement Number Number Color Size, in inch lbs/in Load, lbs inch

ben2 1 Dark Gray 1 1 6620 1117 0.2716 2 1 2 5723 1118 0.4122 3 1 3 4800 840 0.4618

ben3 1 Dark Gray 1 1/4 1 5938 1161 0.4197 2 1 1/4 2 6156 1071 0.4471 3 1 1/4 3 4406 894 0.6605

ben4 4 Dark Gray 3/4 1 4624 1201 0.3143 2 3/4 2 4458 1012 0.5371 1 3/4 3 3356 875 0.7081 w/glue 5 3/4 3 5249 897 0.2172 ben5r 1 Red 1 1 4217 1183 0.3611 2 1 2 4809 1099 0.4715 3 1 3 3932 889 0.7108 w/glue 4 1 3 3707 1174 0.3513 ben6r 1 Red 1 1/4 1 4186 1183 0.4411 2 1 1/4 2 4706 1120 0.5883 3 1 1/4 3 4271 857 0.7221

ben7r 4 Red 3/4 1 4594 1186 0.3975 2 3/4 2 4450 973 0.4502 3 3/4 3 3294 795 0.7462 w/glue 5 3/4 3 3295 841 0.6617 ben8g 4 Green 1-1/4 1 4524 1129 0.7066 2 1-1/4 2 3418 717 0.6511 3 1-1/4 3 4342 589 0.4779 ben9g 1 Green 1-1/4 1 2790 1024 0.6869 2 1-1/4 2 2846 709 0.4104 3 1-1/4 3 2390 600 0.4482

60 Appendix 1b: Effect of staple spacing on the racking performance of the paperboard Test Specimen Staple Spacing, Stiffness, Peak Displacement Number Number Color Size, in inch lbs/in Load, lbs inch

ben10g 1 Green 3/4 1 3355 1105 0.7297 2 3/4 2 3402 679 0.6251 3 3/4 3 2724 552 0.4558

ben11g 1 Green 1 1 3487 1000 0.6444 2 1 2 2685 744 0.3827 3 1 3 3121 605 0.4483

ben12xyz 1 DW 1 1 5968 1214 0.2285 2 1 2 4704 1165 0.3843 3 1 3 3504 1162 0.9643 w/glue 4 1 3 6028 1177 0.2502

ben13xyz 1 DW 3/4 1 3873 1196 0.3339 2 3/4 2 3052 1183 0.5739 3 3/4 3 2900 879 0.6901 w/glue 4 3/4 3 5895 1052 0.2928

ben14xyz 1 DW 1 1/4 1 4447 1184 0.2899 2 1 1/4 2 3719 1179 0.4389 3 1 1/4 3 3333 1172 0.7482 w/glue 4 1 1/4 3 5440 1185 0.2278

Note: DW - Dirty White Color

61 Appendix 2: Effect of staple size on the racking performance of the paperboard sheathing Specimen Test No Number Color Staple size Spacing Stiffness Load, lbs Displacement Peak Load Displacement inch inch lbs/in inch lbs inch ben4 4 Dark Gray 3/4 1 4624 1056 0.3143 1201 0.3143 ben2 1 1 1 6620 1056 0.2716 1117 0.2716 ben3 1 1 1/4 1 5938 1056 0.3621 1161 0.4197 ben4 2 Dark Gray 3/4 2 4458 970 0.5371 1012 0.5371 ben2 2 1 2 5723 970 0.3234 1118 0.4122 ben3 2 1 1/4 2 5733 970 0.3866 1071 0.4471 ben4 1 Dark Gray 3/4 3 3356 807 0.5711 875 0.7081 w/glue 5 3/4 3 5249 897 0.2172 ben2 3 1 3 4800 807 0.4618 840 0.4618 w/glue 4 1 3 4369 869 0.7702 ben3 3 1 1/4 3 4406 807 0.5148 894 0.6605 w/glue 4 1 1/4 3 3775 851 0.7982

ben13xyz 1 Dirty White 3/4 1 3873 1196 0.3339 ben12xyz 1 1 1 5968 1214 0.2285 ben14xyz 1 1 1/4 1 4447 1184 0.2899 ben13xyz 2 Dirty White 3/4 2 3052 1183 0.5739 ben12xyz 2 1 2 4704 1165 0.3843 ben14xyz 2 1 1/4 2 3719 1179 0.4389

Appendix 2: Continuation Test No Specimen Color Staple Spacing Stiffness Load, lbs Displacement Peak Load Displacement Number Size inch lbs/in inch lbs Inch ben13xyz 3 Dirty White 3/4 3 2900 862 0.6901 879 0.6901 w/glue 4 3/4 3 5895 1052 0.2928 ben12xyz 3 1 3 3504 862 0.5051 1162 0.9643 w/glue 4 1 3 6028 1177 0.2502 ben14xyz 3 1 1/4 3 3333 862 0.4031 1172 0.7482 w/glue 4 1 1/4 3 5440 1185 0.2278

ben10g 1 Green 3/4 1 3355 969 0.5489 1105 0.7297 ben11g 1 1 1 3487 969 0.6444 1000 0.6444 ben8g 4 1 1/4 1 4524 969 0.4488 1129 0.7066 ben10g 2 Green 3/4 2 3260 652 0.6341 679 0.6341 ben11g 2 1 2 2685 652 0.3191 744 0.3827 ben8g 2 1 1/4 2 3418 652 0.3721 717 0.6511 ben10g 3 Green 3/4 3 2724 534 0.4558 552 0.4558 ben11g 3 1 3 3121 534 0.3411 605 0.4483 ben8g 3 1 1/4 3 4342 534 0.3531 589 0.4779

ben7r 4 Red 3/4 1 4594 1186 0.3975 ben5r 1 1 1 4217 1183 0.3611 ben6r 1 1 1/4 1 4186 1183 0.4411

Appendix2:Continuation Test No Specimen Color Code Staple Size Spacing Stiffness Load, lbs Displacement Peak Load Displacement Number inch inch lbs/in inch lbs inch ben7r 2 Red 3/4 2 4450 923 0.4502 973 0.4502 ben5r 2 1 2 4809 923 0.3456 1099 0.4715 ben6r 2 1 1/4 2 4706 923 0.3363 1120 0.5883 ben7r 3 Red 3/4 3 3294 760 0.7426 795 0.7426 w/glue 5 3/4 3 3295 841 0.6617 ben5r 3 1 3 3932 760 0.4701 889 0.7108 w/glue 4 1 3 3707 1174 0.3513 benblue2 1 Blue 3/4 1 5166 1215 0.3071 benblue1 1 1 1 5353 1185 0.2488 benblue 1 1 1/4 1 5659 1203 0.2321 benblue2 2 Blue 3/4 2 5198 1167 0.4955 benblue1 2 1 2 4385 1174 0.4039 benblue 2 1 1/4 2 4584 1169 0.4135 benblue2 3 Blue 3/4 3 4188 867 0.9068 890 0.9068 benblue1 3 1 3 4194 867 0.4201 1113 1.0901 benblue 3 1 1/4 3 3773 867 0.4601 1143 1.0704

Appendix 3: Effect of thickness on the racking performance of the paperboard Test No. Specimen Color Thickness Staple Spacing Stiffness Peak Load Displacement Number in. Size, in. in. lbs/in lbs ben11g 1 Green 0.0696 1 1 3487 1000 0.6444 ben5r 1 Red 0.0991 1 4217 1183 0.3611 benblue1 1 Blue 0.1251 1 5353 1185 0.2488 ben2 1 Dark Gray 0.1035 1 6620 1117 0.2716 ben12xyz 1 Dirty White 0.1418 1 5968 1214 0.2285

ben11g 2 Green 1 2 2685 744 0.3827 ben5r 2 Red 2 4809 1099 0.4715 benblue1 2 Blue 2 4385 1174 0.4041 ben2 2 Dark Gray 2 5723 1118 0.4122 ben12xyz 2 Dirty White 2 4704 1165 0.3843

ben11g 3 Green 1 3 3121 605 0.4483 ben5r 3 Red 3 3932 889 0.7108 benblue1 3 Blue 3 4194 1113 1.0901 ben2 3 Dark Gray 3 4800 840 0.4618 ben12xyz 3 Dirty White 3 3504 1162 0.9643

ben8g 1 Green 1 1/4 1 4524 1129 0.7066 ben6r 1 Red 1 4186 1183 0.4411 benblue 1 Blue 1 5659 1203 0.2321 ben3 1 Dark Gray 1 5938 1161 0.4197 ben14xyz 1 Dirty White 1 4447 1184 0.2899

Appendix 3: Continuation Test No. Specimen Color Thickness Staple Spacing Stiffness Peak Load Displacement Number inch Size, in. inch lbs/in lbs inch ben8g 2 Green 1 1/4 2 3418 717 0.6511 ben6r 2 Red 2 4706 1120 0.5888 benblue 2 Blue 2 4584 1169 0.4131 ben3 2 Dark Gray 2 6156 1071 0.4471 ben14xyz 2 Dirty White 2 3719 1179 0.4389

ben8g 3 Green 1 1/4 3 4342 589 0.4779 ben6r 3 Red 3 4271 857 0.7221 benblue 3 Blue 3 3773 1143 1.0461 ben3 3 Dark Gray 3 4406 894 0.6605 ben14xyz 3 Dirty White 3 3333 1172 0.7482

ben10g 1 Green 3/4 1 3355 1105 0.7297 ben7r 4 Red 1 4594 1186 0.3975 benblue2 1 Blue 1 5166 1215 0.3071 ben4 4 Dark Gray 1 4624 1201 0.3143 ben13xyz 1 Dirty White 1 3873 1196 0.3339

ben10g Green 3/4 2 3260 679 0.6341 ben7r Red 2 4450 973 0.4502 benblue3 Blue 2 5198 1167 0.4951 ben5 Dark Gray 2 4458 1012 0.5371 ben13xyz Dirty White 2 3052 1183 0.5739

Appendix 3: Continuation Test No. Specimen Color Thickness Staple Spacing Stiffness Peak Load Displacement Number inch Size, in. inch lbs/in lbs inch

Ben10g 3 Green 3/4 3 2724 552 0.4558 Ben7r 3 Red 3 3294 795 0.7426 Benblue2 3 Blue 3 4188 890 0.9071 Ben4 1 Dark Gray 3 3356 875 0.7081 ben13xyz 3 Dirty White 3 2900 879 0.6901

Appendix 4: Data for comparison of racking performance of the paperboard using staple and nail Testing Specimen Color Fastener Spacing Stiffness Peak Displacement No. Number Size, inch inch lbs/in Load lbs inch

nail1 1/4 1 DW N - 1 1/4 2 3138 1191 0.5122 2 3 3120 1053 1.3121

ben14xyz 2 DW S - 1 1/4 2 3719 1179 0.4389 3 3 3333 1172 0.7482

nail1 1 DW N - 1 2 4692 985 0.6318 2 3 3721 775 1.0332

ben12xyz 2 DW S - 1 2 4704 1165 0.3843 3 3 3504 1162 0.9643

screw1 1/4 1 DW Sc - 1 1/4 3 3629 860 0.4406

Sc - Screw S - Staple N - Nail

68 Appendix 5: Comparison of racking performance of the wood boards using staple and nail Test Number Specimen Thickness Staple Stiffness Peak Displacement Number inch Size, inch lbs/in Load, lbs inch hb-1 3 2/16 3/4 3083 1102 0.709 2 1 5074 >1189 0.408 1 1-1/4 3761 >1197 0.501 hb-3/16 3 3/16 3/4 3917 >1188 0.478 2 1 5227 >1197 0.435 1 1-1/4 4050 >1222 0.429

OSB-1 2 1/4 1 4675 >1206 0.539 1 1-1/4 3875 >1165 0.534 ply-1 2 1/4 1 3772 >1202 0.469 1 1-1/4 3166 >1179 0.453

Note: The spacing is 3 inch

Test Number Specimen Thickness Nail Size Stiffness Peak Load Displacement Number inch inch lbs/in lbs inch hbnail1 1/4 1 3/16 1-1/4 5258 >1200 0.321 plynail1 1/4 1 1/4 1-1/4 3220 >1167 0.531

OSBnail1 1/4 1 1/4 1-1/4 3746 >1152 0.601

Note: The spacing is 3 inch

Test Number Specimen Thickness Fastener Stiffness Peak Load Displacement Number inch Type lbs/in lbs inch

Alum 1 0.018 Screw 3808 961 0.656 2 Staple 3764 827 0.696

Note: The spacing is 3 inch