Wood Fibre Insulation Boards as Load-Carrying Sheathing Material of Wall Panels

Transcription

1 irst published in: Wood ibre Insulation Boards as Load-Carrying Sheathing Material o Wall Panels Gunnar Gebhardt 1, Hans Joachim Blaß ABSTRACT: To date wood ibre insulation boards (WIB) are used as thermal and acoustic insulation in timber construction. As wood-based panels, WIB are also suited or the transer o loads caused by wind and earthquakes in timber rame construction, they may replace plywood, particle boards or OSB. This new ield o application o WIB has been analysed in a research project at Karlsruhe Institute o Technology. In order to calculate the load-carrying capacity o wall and roo panels the characteristics o WIB as well as those o joints with WIB and dowel-type asteners need to be known. In tests these characteristics were determined. A proposal is made or the calculation o timber-wib-joints with dowel type asteners. urthermore the stiness properties o timber-wib-joints were determined. In this paper the results o the tests are presented. KEYWORDS: Wood ibre insulation board, wall panel, sheathing material INTRODUCTION AND CHARACTERISTICS O WIB 1 Wood-based sheathing materials in timber rame construction normally are plywood, particle boards or OSB. A urther possibility is sheathing made o gypsum plasterboards. These panels have a relatively high density caused by the compression and adhesion o the dierent raw materials. The heat insulation properties do not equal those o typical insulation materials like mineral or wood ibre. or the heat insulation o outer walls thereore additional insulation material is required. Due to the increasing demands regarding energy and CO saving the insulation thickness increases. Wood ibre insulation materials produced as panels are thereore suited or the use in shear walls in timber rame construction i they are able to carry the shear loads in the panel itsel and i the connections between WIB and timber members have a suicient strength and stiness. This new ield o application o WIB was analysed in a research project at Karlsruhe Institute o Technology. In this paper a proposal is given to calculate the load-carrying capacity o timber-wib-joints with dowel-type asteners. or this purpose the load-carrying capacity o joints in timber and WIB is determined according to Johansen s yield theory and an extension o this theory. Tests were carried out to evaluate the 1 Gunnar Gebhardt, Timber structures and building construction, Karlsruhe Institute o Technology, R.- Baumeister-Platz 1, Karlsruhe, Germany. gunnar.gebhardt@kit.edu Hans Joachim Blaß, Timber structures and building construction, Karlsruhe Institute o Technology, R.- Baumeister-Platz 1, Karlsruhe, Germany. blass@kit.edu embedding strength o nails in WIB and the crown pull-through resistance o wide-crown staples in WIB. The test results veriied the calculation model and the stiness properties o timber-wib-joints were evaluated. urthermore the shear strength and the shear modulus o WIB were determined. The raw material o WIB is wood chips. WIB are abricated in two dierent manuacturing processes. In both the wood chips are irst thermo-mechanically pulped. In the wet process the wood ibres are mixed with water and urther aggregate into a suspension. Aterwards the boards are ormed and dried. or the bonding o the wood ibres only the wood s own cohesiveness (predominantly lignin resin) is used. Due to the high use o energy or the drying process, boards with higher thicknesses are manuactured by gluing raw single-layer boards to multilayer boards, also dierent density boards may be combined. In the dry process the wood ibres are dried and sprayed with resin. Aterwards the boards are ormed and the resin hardens. In this process boards with thicknesses up to 4 mm are manuactured as single-ply boards. WIB are used in dierent parts o buildings. In roos, rain-tight sub plates are ixed as sub decking. A urther insulation is possible as above-rater or interim-rater insulation with universal insulation boards. In walls, plaster baseboards may be used in composite thermal insulation systems. 11 dierent WIB o three dierent manuacturers were selected to analyse the characteristics needed or the use as sheathing in shear walls. The nominal density range was between 11 kg/m 3 and 7 kg/m 3. The densities and moisture contents o the tested boards were determined. The measured moisture content was 7.3% to 1.3%. EVA-STAR (Elektronisches Volltextarchiv Scientiic Articles Repository)

2 ANALYSIS O WALL PANELS In analysis methods the load-carrying capacity o the connection between timber member and sheathing panel is required. The analysis according to German design code DIN 15 in addition requires the shear strength o the sheathing panel. The connection s load-carrying capacity is calculated according to Johansen s yield theory considering the dierent ailure mechanisms. In joints with asteners driven in through a counter batten the inclination o the astener in ailure modes 1a and b involves embedding resistances in the counter batten. Hence the related equations or these ailure mechanisms are extended. The load path is rom the stud into the sheathing panel. There is no resulting load in the counter batten. orce and moment equilibrium, considering the existing embedding strength distribution and the yield moment, result in equations or the extended ailure mode 1a and or the extended ailure mode b. The load-carrying capacity increases with increasing axial load-carrying capacity o the astener. I the astener is driven in directly into the sheathing panel the axial load-carrying capacity depends on the withdrawal parameter o the astener in the timber member and the head/crown pull-through resistance in the sheathing panel or a counter batten, i the astener is driven in through a counter batten BASIC PARAMETERS O DOWEL-TYPE ASTENERS IN WIB About 6 embedment tests with nails were perormed according to EN 383 in order to evaluate the embedding strength o dowel-type asteners in WIB. The test results or the embedding strength correlate with the measured densities o the test specimens and the astener diameter. By means o a multiple regression analysis an equation was derived or the embedding strength o WIB. In order to calculate the rope eect the crown pull-through resistance o wide-crown staples in WIB was examined. According to EN 1383 about 1 tests with and were carried out. The displacement at maximum load correlates with the thickness o the WIB. By means o a multiple regression analysis an equation was derived to estimate the crown pull-through resistance o staples in WIB. LOAD-CARRYING CAPACITY AND STINESS O TIMBER-WIB-JOINTS In order to veriy the results obtained in tests and to examine the stiness o joints, urther tests were perormed. In tests with joints the calculated values considering the determined parameters are checked. urthermore the stiness o timber-wib-joints was evaluated. Rain-tight sub plates o three manuacturers in three thicknesses, respectively, and plaster baseboards were used as sheathing panel. Nails and staples were driven in through a counter batten. Wide-crown staples were driven in directly. The load-carrying capacity may be obtained according to Johansen s yield theory considering the test results and the extended calculation model. The yield moments o the asteners were evaluated according to EN 49. The embedding strength o staples in WIB was calculated assuming the validity or diameters smaller than the tested ones. The embedding strength o nails in WIB was determined in tests and used or the calculation. The embedding strength o the astener in the timber member was calculated according to DIN 15 considering the specimen densities. The withdrawal resistance and the pull-through resistance were calculated according to DIN 15 or nails and staples. The crown pull-through resistance or wide-crown staples was determined in tests. The tests were carried out according to EN The maximum load was reached at a displacement o 15 mm. Although ailure mode 1b was governing in the calculation or nails, ailure mode 3 was observed in the tests. This may be explained by riction between the joint members. The relative deormations between WIB and stud were measured at each o the our asteners. The analysis o the joint stiness considers a linear loaddisplacement behaviour up to 4% o the maximum load. Due to a non-linear load-displacement behaviour the analysis o the stiness was calculated or a constant displacement o.3 mm. By means o a multiple regression analysis an equation was derived to calculate the stiness o timber-wib-joints. SHEAR STRENGTH AND SHEAR MODULUS O WIB The shear strength and the shear modulus o WIB were determined according to EN 789. The WIB specimens were reinorced by our lateral timber boards connected with the WIB test specimen by ive pre-stressed bolts. The correlation between shear strength, density and board thickness was analysed. The correlation coeicient between shear strength and board thickness is r = -.544, while the correlation coeicient between shear strength and density is r =.847 and between density and board thickness is r = urthermore the correlation coeicient between shear modulus and density is r =.894. CONCLUSIONS To date wood ibre insulation boards are used as acoustic and thermal insulation. As wood-based panels they can also be used or the load transer in wall panels. The load transer requires a suicient load-carrying capacity o the joint between studs and sheathing and suicient shear strength o the WIB. In order to calculate the load carrying capacity o joints between timber and WIB the embedding strength o nails in WIB and the crown pull-through resistance o wide-crown staples in WIB were determined. Johansen s yield theory was extended to consider the inluence o a counter batten on the load carrying capacity. The stiness o joints between timber and WIB was evaluated in urther tests. The shear strength and shear modulus o WIB were also determined in tests. The results serve as a basis or the analysis o wood ibre insulation boards as sheathing panel in timber rame construction.

3 Wood ibre Insulation Boards as Load-Carrying Sheathing Material o Wall Panels Gunnar Gebhardt 1, Hans Joachim Blaß ABSTRACT: To date wood ibre insulation boards (WIB) are used as thermal and acoustic insulation in timber construction. As wood-based panels, WIB are also suited or the transer o loads caused by wind and earthquakes in timber rame construction, they may replace plywood, particle boards or OSB. This new ield o application o WIB has been analysed in a research project at Karlsruhe Institute o Technology. In order to calculate the load-carrying capacity o wall and roo panels the characteristics o WIB as well as those o joints with WIB and dowel-type asteners need to be known. In tests these characteristics were determined. A proposal is made or the calculation o timber-wib-joints with dowel type asteners. urthermore the stiness properties o timber-wib-joints were determined. In this paper the results o the tests are presented. KEYWORDS: Wood ibre insulation board, wall panel, sheathing material 1 INTRODUCTION 1 Wood-based sheathing materials in timber rame construction normally are plywood, particle boards or OSB. A urther possibility is sheathing made o gypsum plasterboards. These panels have a relatively high density caused by the compression and adhesion o the dierent raw materials. The heat insulation properties do not equal those o typical insulation materials like mineral or wood ibre. or the heat insulation o outer walls thereore additional insulation material is required. Due to the increasing demands regarding energy and CO saving the insulation thickness increases. Wood ibre insulation materials produced as panels are thereore suited or the use in shear walls in timber rame construction i they are able to carry the shear loads in the panel itsel and i the connections between WIB and timber members have a suicient strength and stiness. This new ield o application o WIB was analysed in a research project at Karlsruhe Institute o Technology. In this paper a proposal is given to calculate the loadcarrying capacity o timber-wib-joints with dowel type asteners. or this purpose the load-carrying capacity o joints in timber and WIB is determined according to 1 Gunnar Gebhardt, Timber structures and building construction, Karlsruhe Institute o Technology, R.- Baumeister-Platz 1, Karlsruhe, Germany. gunnar.gebhardt@kit.edu Hans Joachim Blaß, Timber structures and building construction, Karlsruhe Institute o Technology, R.- Baumeister-Platz 1, Karlsruhe, Germany. blass@kit.edu Johansen s yield theory and an extension o this theory. Tests were carried out to evaluate the embedding strength o nails in WIB and the crown pull-through resistance o wide-crown staples in WIB. The test results veriied the calculation model and the stiness properties o timber-wib-joints were evaluated. urthermore the shear strength and the shear modulus o WIB were determined. CHARACTERISTICS O WIB The raw material o WIB is wood chips. WIB are abricated in two dierent manuacturing processes. In both the wood chips are irst thermo-mechanically pulped. In the wet process the wood ibres are mixed with water and urther aggregate into a suspension. Aterwards the boards are ormed and dried. or the bonding o the wood ibres only the wood s own cohesiveness (predominantly lignin resin) is used. Due to the high use o energy or the drying process, boards with higher thicknesses are manuactured by gluing raw single-layer boards to multilayer boards (igure ), also dierent density boards may be combined. In the dry process the wood ibres are dried and sprayed with resin. Aterwards the boards are ormed and the resin hardens. In this process boards with thicknesses up to 4 mm are manuactured as single-ply boards (see igure 1).

4 wall plaster baseboard and insulation igure 3 (cont.): Applications o WIB igure 1: WIB single-ply boards 11 dierent WIB o three dierent manuacturers were selected to analyse the characteristics needed or the use as sheathing in shear walls. The nominal density range was between 11 kg/m3 and 7 kg/m3. The densities and moisture contents o the tested boards were determined. The measured moisture content was 7.3% to 1.3%. Characteristic densities or the dierent types o WIB are given in table 1. Table 1: Proposed characteristic density o WIB WIB type Characteristic density in kg/m3 Rain-tight sub plate (RTSB) Plaster baseboard () 15 Universal insulation board (UIB) ANALYSIS O WALL PANELS igure : WIB multilayer boards 3.1 ANALYSIS ACCORDING TO GERMAN DESIGN CODE DIN 15:8-1 WIB are used in dierent parts o buildings. In roos, rain-tight sub plates () are ixed as sub decking. A urther insulation is possible as above-rater or interimrater insulation with universal insulation boards (UIB). In walls, plaster baseboards () may be used in composite thermal insulation systems. In igure 3 the dierent applications are shown. The analysis according to German design code DIN 15 [1] is a simpliied analysis or wall and roo panels. Three dierent ailure modes are considered. Beside the ailure o the connection between timber and sheathing material, shear ailure and buckling ailure o the sheathing panel are considered. The shear low per wall panel length is obtained using Equation (1): sv,, d = v,d = roo rain-tight sub plate () = v, d (1) design value o horizontal load acting on wall panel and length o wall panel. The shear strength per wall panel length is calculated according to Equation (): roo rain-tight sub plate () and interim rater insulation v,, d kv1 = roo rain-tight sub plate () and above rater insulation igure 3: Applications o WIB kv = R kv1 d a v = min kv1 kv v, d t kv1 kv v, d 35 t ar () actor considering the joints at the panel boundaries (kv1 = 1, i panel boundaries ixed at all sides, else kv1 =.66), actor considering i the sheathing is one-sided (kv =.33) or both-sided (kv =.5),

5 R d = design value o load-carrying capacity o the joint between sheathing and timber rame, a v = spacing o asteners, v,d = design value o shear strength o sheathing panel, t = thickness o sheathing panel and a r = spacing o vertical studs. 3. ANALYSIS ACCORDING TO EN The analysis according to EN [] is a simpliied analysis or wall and roo panels similar to the analysis in DIN 15. However, the analysis only considers the ailure o the connection between timber and sheathing material. The load-carrying capacity o a wall panel is obtained using Equation (3): b c,,, = Rd i i ivrd,rd = design value o the load-carrying capacity o a single astener, b i = length o wall panel, s = spacing o asteners. s (3) involves embedding resistances in the counter batten. Hence the related equations or these ailure mechanisms are extended. 4 EMBEDDING STRENGTH O WIB Tests with nails were perormed according to EN 383 [3] to evaluate the embedding strength o mechanical asteners in WIB. The test set-up is shown in igure 4. In preliminary tests an inluence o the angle between orce and production direction could not be identiied. About 6 embedment tests with ive dierent diameters (d = 3.1/3.4/3.8/4.6/5. mm) were carried out. The test results or the embedding strength correlate with the measured densities o the test specimens. In igure 5 the embedding strength is plotted vs. the density. The correlation coeicient is r =.88. urthermore, the analysis considers the geometry o the wall panel by a actor c i, see Equation (4): 1 or b1 b ci = bi or b1 < b b b = h/, h = height o wall panel. (4) 3.3 NECESSARY TESTS AND ANALYSIS In both analysis methods the load-carrying capacity o the connection between timber member and sheathing panel is required. The analysis according to DIN 15:8-1 in addition requires the shear strength o the sheathing panel. The connection s load-carrying capacity is calculated according to Johansen s yield theory in both standards and depends on the geometry o the connection (thicknesses o the jointed members and diameter o the astener), the yield moment o the astener and the embedding strengths o the jointed members. The load-carrying capacity may be increased i the astener can be loaded axially apart rom loading laterally. I the astener is driven in directly into the sheathing panel the axial load-carrying capacity depends on the withdrawal parameter o the astener in the timber member and the head/crown pull-through resistance in the sheathing panel or a counter batten, i the astener is driven in through a counter batten. Johansen s theory considers six dierent ailure mechanisms or single shear joints. In the irst three ailure mechanisms the embedding strength o one or both o the jointed members is reached. In ailure modes our and ive in addition one plastic hinge appears. In ailure mode six two plastic hinges are ormed. In joints with asteners driven in through a counter batten the inclination o the astener in ailure modes 1a and b igure 4: Test - embedding strength o nails in WIB There is a less pronounced correlation between the embedding strength and the thickness o the boards. A negative correlation exists between the embedding strength and the astener diameter. Due to a correlation between the density and the thickness and the higher correlation between embedding strength and thickness, the parameters diameter and density are considered in a regression model or the embedding strength. By means o a multiple regression analysis, equation (5) was derived or the embedding strength h o WIB = d in N/mm (5) h ρ ρ = density o the WIB in kg/m 3 and d = diameter o the astener in mm. In igure 6 the embedding strength values rom the tests are plotted vs. the calculated embedding strength values. The correlation coeicient is r =.916. The slope o the regression straight is m = 1. and the y-intercept is b = -.9.

6 Embedding strength in N/mm y =.368x r =.88 n = 68 UIB Density in kg/m 3 WIB was examined. The test set-up is shown in igure 7. igure 5: Embedding strength vs. density Tested embedding strength in N/mm y = 1.x -.9 r =.916 n = 68 UIB Calculated embedding strength in N/mm igure 6: Embedding strength rom tests vs. calculated embedding strength Characteristic values o the embedding strength may be calculated considering the proposed characteristic densities or the dierent types o WIB (table ). Table : Characteristic embedding strength in N/mm WIB Characteristic density in kg/m 3 15 UIB 15 UIB 1 Characteristic embedding strength in N/mm.75 h,k = 8.88 d.75 h,k = 4.5 d.75 h,k = 3.53 d.75 h,k = 1.57 d 5 CROWN PULL-THROUGH RESISTANCE O WIDE-CROWN STAPLES IN WIB The load-carrying capacity according to Johansen s yield theory depends on the geometry o the connection (thicknesses o the connected members and diameter o the astener), the embedding strengths o the members (or WIB presented in chapter 4) and the yield moment o the astener. The load-carrying capacity increases with increasing axial load-carrying capacity o the astener. The rope eect depends on the withdrawal strength o the astener in the irst member and the head/crown pullthrough resistance in the second member. Hence the crown pull-through resistance o wide-crown staples in igure 7: Test Crown pull-through resistance o widecrown staples in WIB According to EN 1383 [4] about 1 tests with and were carried out. or each o the 15 dierent WIB at least our tests were perormed. The displacement at maximum load correlates with the thickness o the WIB. In igure 8 the displacement at maximum load is plotted vs. the thickness o the WIB. Displacement at maximum load in mm y =.5x r =.893 n = Thickness in mm igure 8: Displacement at maximum load vs. thickness By means o a multiple regression analysis, equation (6) was derived to estimate the crown pull-through resistance R ax, o staples in WIB Rax, =.4 ρ t in N (6) ρ = density o the WIB in kg/m 3 and t = thickness o the WIB in mm. In igure 9 the crown pull-through resistance values rom tests are plotted vs. the calculated values. The correlation coeicient is r =.814. The slope o the regression straight is m = 1.1 and the y-intercept is b = -.1. The test results o a with relatively high thickness and density cannot be explained by the regression model, the test values are higher than the calculated values. Here, urther tests are needed.

7 Tested crown pull-through resistance in kn,5, 1,5 1,,5, y = 1.1x -.1 r =.814 n = 97,,5,5,75 1, 1,5 1,5 Calculated crown pull-through resistance in kn ( + β ) 4β 1 M y β ( 1+ β) + + h 1 d t h,1 t d R = 1+ β t 3 β β3( 1+ β) t β t 3 = thickness o the counter batten, h,3 = embedding strength o the counter batten and h, β = h,1 (9) igure 9: Crown pull-through resistance rom tests vs. calculated crown pull-through resistance Characteristic values o the crown pull-through resistance may be calculated considering the proposed characteristic densities or the dierent types o WIB (equation (7)). h,3 β 3 = h,1 R =.3 ρ t in N (7) ax,,k k ρ k = density o the WIB in kg/m 3. 6 CALCULATION O JOINTS BETWEEN TIMBER AND SHEATHING PANEL The load-carrying capacity may be calculated according to Johansen s yield theory considering the dierent ailure mechanisms. I the astener is driven in through a counter batten, in ailure modes 1a and b an extension o the existing equations is necessary. In ailure modes 1a and b the embedding strength in the counter batten is reached and this eect increases the load-carrying capacity. The load path is rom the stud into the sheathing board. There is no resulting load in the counter batten. orce and moment equilibrium, considering the existing embedding strength distribution and the yield moment, result in equation (8) or the extended ailure mode 1a and equation (9) or the extended ailure mode b. The ailure modes with the inluence o the counter batten are shown in igure 1 and igure 11. h,1 h, h,3 igure 1: Consideration o the counter batten in ailure mode 1a t t β + β t1 t1 h,1 t1 d R = 3 t t 3 1 β β + β β3( 1+ β) + t 1 t1 t β 1+ t1 (8) M h,1 h, h,3 igure 11: Consideration o the counter batten in ailure mode b

8 7 LOAD-CARRYING CAPACITY AND STINESS O TIMBER-WIB- JOINTS WITH NAILS AND STAPLES In order to veriy the results obtained in the tests presented in chapter 4 and 5 and to examine the stiness o joints, urther tests were perormed. In the previous paragraphs the basic parameters (embedding strength and crown pull-through resistance) or the calculation o the load-carrying capacity o timber-wib-joints were determined. The calculation method according to Johansen s yield theory was extended or asteners driven in through a counter batten. In tests with joints the calculated values considering the determined parameters are checked. urthermore the stiness o timber-wib-joints was evaluated. o three manuacturers in three thicknesses, respectively, and were used as sheathing panel. Nails and staples were driven in through a counter batten. Wide-crown staples were driven in directly. In igure 1 and igure 13 the test specimens or the tests with nails and staples are shown. In igure 14 the test set-up is shown. The load-carrying capacity may be obtained according to Johansen s yield theory considering the test results and the extended calculation model. The yield moments o the asteners were evaluated according to EN 49 [5]. The embedding strength o staples in WIB was calculated according to equation (1) assuming the validity or diameters smaller than the tested ones. The embedding strength o nails in WIB was determined in tests and used or the calculation. The embedding strength o the astener in the timber member was calculated according to DIN 15 [1] considering the specimen densities. The withdrawal resistance and the pull-through resistance were calculated according to DIN 15 [1] or nails and staples. The crown pull-through resistance or wide-crown staples was determined in tests. 4 1 t 3/ t igure 13: Test specimen or test o timber-wib-joints with wide-crown staples driven in directly igure 14: Test specimen or test o timber-wib-joints The tests were carried out according to EN 6891 [6]. The maximum load was reached at a displacement o 15 mm. Although ailure mode 1b was governing in the calculation or nails, ailure mode 3 was observed in the tests. This may be explained by riction between the joint members. The relative deormations between WIB and stud were measured at each o the our asteners. The analysis o the joint stiness considers a linear loaddisplacement behaviour up to 4% o the maximum load. In the tests non-linear load-displacement behaviour was observed. Due to this the analysis o the stiness was calculated or a constant displacement o.3 mm. The load-carrying capacity rom tests is plotted vs. the calculated load-carrying capacity in igure 15 or nails, in igure 16 or staples and in igure 17 or wide-crown staples. igure 1: Test specimen or test o timber-wib-joints with nails and staples driven in through a counter batten

9 Tested load-carrying capacity in N n = 7 4 d = 3.8 d = Calculated load-carrying capacity in N igure 15: Load-carrying capacity rom tests vs. calculated load-carrying capacity or nails driven in through a counter batten Tested load-carrying capacity in N n = 7 t = 18 mm t = mm t = 35 mm Calculated load-carrying capacity in N igure 16: Load-carrying capacity rom tests vs. calculated load-carrying capacity or staples driven in through a counter batten Tested load-carrying capacity in N n = 36 4, t = 18 mm, t = mm, t = 35 mm Calculated load-carrying capacity in N Tested stiness in N/mm k s,test = 1. k s,cal r =.898 n = 9 Staple 1 mm Staple 7 mm Nail 3.8 mm Nail 4.6 mm Calculated stiness in N/mm igure 18: Stiness rom tests vs. calculated stiness 8 SHEAR STRENGTH AND SHEAR MODULUS O WIB The shear strength and the shear modulus o WIB were determined according to EN 789 [7]. The geometry o the test specimens and the test set-up are shown in igure 19 and igure. The WIB specimens were reinorced by our lateral timber boards connected with the WIB test specimen by ive pre-stressed bolts R = 15 mm R = 15 mm igure 19: Geometry o test specimen and test set-up 5 5 igure 17: Load-carrying capacity rom tests vs. calculated load-carrying capacity or wide-crown staples By means o a multiple regression analysis, equation (1) was derived to calculate the stiness o a timber- WIB-joint. In igure 18 the stiness rom tests is plotted vs. the calculated stiness. The correlation coeicient is r =.898. K = 1.5 ρ ρ t d in N/mm (1) ser WIB ρ WIB = density o the WIB in kg/m 3, ρ = density o timber in kg/m 3, t = thickness o WIB in mm and d = diameter o astener in mm. igure : Test specimen during test

10 The correlation between shear strength, density and panel thickness was analysed. The correlation coeicient between shear strength and board thickness is r = -.544, while the correlation coeicient between shear strength and density is r =.847 and between density and board thickness is r = The shear strength may be assessed by Equation (11). igure 1 shows the shear strength vs. the density = in N/mm (11) v ρ ρ = density o the WIB in kg/m 3. Shear strength rom tests in N/mm 1,6 1,4 1, 1,,8,6,4,, r =.847 n = 91 UIB Density in kg/m 3 igure 1: Shear strength rom tests vs. density The shear modulus is plotted vs. the density in igure. The correlation coeicient between shear modulus and density is r =.894. The shear strength may be assessed by Equation (1) G = ρ in N/mm (1) carrying capacity o joints between timber and WIB the embedding strength o nails in WIB and the crown pull-through resistance o wide-crown staples in WIB were determined. Johansen s theory was extended to consider the inluence o a counter batten on the load carrying capacity. The stiness o joints between timber and WIB was evaluated in urther tests. The shear strength and shear modulus o WIB were also determined in tests. The results serve as a basis or the analysis o wood ibre insulation boards as sheathing panel in timber rame construction. REERENCES [1] DIN 15:8-1 Design o timber structures General rules and rules or buildings [] EN Eurocode 5: Design o timber structures Part 1-1: General Common rules and rules or buildings [3] EN 383: Timber structures; Test methods; Determination o embedding strength and oundation values or dowel type asteners [4] EN 1383:-3 Timber structures Test methods Pull through resistance o timber asteners [5] EN 49: Timber structures; Test methods; Determination o the yield moment o dowel type asteners; Nails [6] EN 6891: Timber structures; Joints made with mechanical asteners; General principles or the determination o strength and deormation characteristics (ISO 6891:1983) [7] EN 789:5-1 Timber structures Test methods Determination o mechanical properties o woodbased panels ρ = density o the WIB in kg/m 3. Shear modulus rom tests in N/mm 5 15 r =.894 n = UIB Density in kg/m 3 igure : Shear modulus rom tests vs. density 9 CONCLUSIONS To date wood ibre insulation boards are used as acoustic and thermal insulation. As wood-based panels they can also be used or the load transer in wall panels. The load transer requires a suicient load-carrying capacity o the joint between studs and sheathing and suicient shear strength o the WIB. In order to calculate the load