Finger jointing

from Wikipedia, the free encyclopedia
Different finger joint profiles for different types of wood

A method of longitudinally connecting two components made of solid wood or wood-based material is referred to as finger-jointing or finger-jointing .

purpose

This type of wood connection is used to produce very long wooden components or to cut out unsightly knots and cracks that reduce strength. With finger joint connections, it is possible to join short pieces of wood to form a theoretically endless strand of wood. In addition to lengthening workpieces, finger jointing is also used to miter components at any angle .

It is an applied longitudinal dovetailing and an evolution of since prehistoric applied scarf joint . The finger joint is usually also glued. Their tensile strength is based on the multiplication of the area of ​​the glued joint, which is inclined to the grain of the wood. Due to the constant transition between the two connected parts, it also has a relatively high flexural strength . With regard to these properties, it is superior to steel-wood connections and other wood-wood connections. Finger-jointed components can, under optimal conditions in production and quality assurance, almost achieve the load-bearing capacity of components grown in one piece.

In the additionally glued connection, which is joined together with longitudinal forces, material, force and form-fit connections are created. The wedge prongs stuck in the transverse direction form fit into each other. Frictional connection is created between the wedge surfaces of the prongs, as the latter are elastically "thinned" when they are joined together. With a sufficiently small flank angle of the prongs, the elastic reaction forces are large enough to cause self-locking against slipping apart. The adhesive on the tine flanks creates a bond between them. However, this material connection is generally more effective than the self-locking force connection. Thus, the finger-joint connection, when pulled in the longitudinal direction, is primarily a materially bonded connection produced by gluing. It is superimposed by the form fit of the adhesive layer with the fibrous-porous surface of almost all types of wood. The action of intermolecular forces has also been proven.

definition

In the standard literature, the finger joint is defined as a “longitudinal connection of two solid pieces of wood, e.g. B. boards, planks, squared timber, the ends of which interlock with wedge-shaped prongs of the same pitch and the same profile and are glued to one another. ”There are other product-specific definitions of terms with similar but slightly different wording. This standard definition is binding for structural timber components. In some non-load-bearing applications, such as furniture construction, there are finger joints that differ from this and that do not conform to the standard.

history

The building materials scientists Otto Graf and Karl Egner provided fundamental knowledge for the development of the finger joint connection . The systematic investigation of glued tab connections was started by Graf in 1933. In an article published jointly by Graf and Egner in 1938, constructive proposals for improving glued tab connections were presented. By means of beveled straps and correspondingly pointed wood, a significant increase in load-bearing capacity has been achieved compared to the previously common design. In the tensile test, the new type of plate connection withstood an average of 75% higher breaking loads than the connection with straight plates. This series of tests marks the beginning of the finger joint connection. Initially, the term shift joint was used for the new bracket connection.

In the years 1937 to 1942 Egner researched shift jointing further into finger jointing. He dealt with the tine geometry in terms of load-bearing capacity and machine production and was involved in the development of appropriate processing machines and tools. This created the prerequisites for a wide range of applications in timber construction: On the one hand, through the possibility of mechanical and thus reproducible and economical production of the finger joints, and on the other hand, this new connection is suitable for a wide range of uses due to its high strength, including in load-bearing structures.

The geometry developed by Egner and his fundamental findings found their way into standardization in 1958 with DIN 68140. This standard regulates the requirements for finger joint connections for load-bearing timber components. In the 1960s, the finger joint connection became the subject of numerous research work, including in the areas of adhesives, areas of application, joint geometries and tool technology. In terms of geometry, the trend was towards shorter tine lengths in order to increase the wood yield. The tine length proposed by Egner in 1944 was 40 millimeters. Investigations under the direction of Joseph-Eric Marian led in the second half of the 1960s to the development of mini tines with a tine length of 7.5 millimeters and around 1970 to the development of micro tines with a tine length of 4 millimeters. At present, shorter tine lengths are generally preferred. In industrial production, tine lengths of 4 or 10 millimeters are common for non-load-bearing components. Tine lengths of 10, 15 or 20 millimeters are the rule for load-bearing components.

Manufacturing

There are essentially three process steps required for production: the production of the prong geometry, the application of the adhesive to the prongs and the subsequent pressing of the surfaces wetted with adhesive. Finger joint profiles are produced almost exclusively by milling , rarely by sawing (for example with Trigonit beams). In the manual sector, the tines are manufactured on table milling machines or routers , while industrial production takes place on special finger joint milling machines . The tine contour is mapped by removing chips in the wood using a tine milling tool. Depending on the machine concept, the feed movement occurs through the workpiece or the tool. The tooth feed , the tool condition, the type of wood and the nature of the workpiece have an influence on the work result . The adhesive is applied shortly after the tine milling. In general, the adhesive is applied automatically; manual application is only common in manual production. The automated application of the adhesive is most often done by counter-profile rollers or combs immediately after milling, in some systems by brushing or contactless by spraying. The adhesive is usually applied on both sides for safety reasons. Since 2008, a method for one-sided adhesive application has also been approved in load-bearing timber construction, in which the adhesive application is continuously monitored with regard to the amount and distribution of the adhesive. The application of longitudinal compression to produce the adhesive connection is crucial for the subsequent strength of the connection. The pressing time and the pressure in the adhesive joint have an influence on the quality of the bond.

Processes with finger-joint profiles pressed in by forming have not yet established themselves.

Types of wood used

In principle, any type of wood can be processed using the finger jointing method. The actual use of the various types of wood as a building material is largely determined by their material, processing and usage properties. Machinability and bondability are among the significant processing properties. The material properties include bulk density, modulus of elasticity, hardness, tensile, compressive, flexural and torsional strength as well as splitting strength and thermal conductivity. Swelling and shrinking behavior, durability, knottiness, color, fiber flow, gloss and smell are among the properties of use.

The regional distribution and availability of a wood species plays just as important a role as the preference of the user and consumer.

Load-bearing components

Softwoods are currently the predominantly used wood in the construction sector. Among other things, this is related to the requirements of the current standards. For any products made from hardwood, there is no information on production-relevant properties such as strength or adhesion. In structural timber construction, only approved types of wood may be used for load-bearing components. In Germany these are spruce, fir, pine, Douglas fir, Laricio pine and black pine, larch, sea pine as well as poplar, radiata pine, sitka pine, hemlock and Canadian red cedar. Thus, in addition to twelve softwoods, only poplar is permitted as the only hardwood. In Switzerland, hardwood is generally permitted as construction timber for load-bearing purposes, but a lack of strength classification and information on adhesive strength limit its usability. The economically most important native wood species for structural timber construction is spruce, followed by fir. Spruce is common for glued laminated timber, fir, pine, larch and Douglas fir are more rarely used.

In 2005, hardwoods accounted for 1 percent of the production volume for rod-shaped solid wood materials such as glued laminated timber, cross beams, duo and trio beams in Germany, Austria and Switzerland. The most common type of wood was oak, followed by beech and ash. In order to establish hardwoods for load-bearing purposes, a number of research projects have been pushed. Beech in particular, the most common type of hardwood felled in Germany, has been intensively investigated with regard to its suitability for the production of glued laminated timber. In October 2009, the German Institute for Building Technology (DIBt) granted building authority approval for glued laminated timber and hybrid beams made of beech. Structures with glued laminated timber made of ash and oak have also already been realized.

Non-structural components

Glued wood panels for indoor use as semi-finished products for tables, kitchen tops, steps and furniture bodies are often made of hard deciduous woods such as beech, oak, birch, alder, cherry or walnut, ash, maple, robinia and hornbeam. Beech wood glue boards are also used for worktops and workbenches. But softwoods such as spruce and pine are also processed into glued wood panels.

Adhesives used

Only adhesives that have passed the test according to DIN EN 301 or DIN EN 302 Part 1 to 4 or are regulated by the German Institute for Building Technology may be used to bond load-bearing components. A test according to DIN 68141 is still required with regard to the performance properties. A regularly updated list of approved adhesives is publicly available.

Tine geometry

Typical finger joint
typical profile of a finger joint a, b Joining parts
c Adhesive surface on the tine surfaces
b Width of the tine base
b s Wide tine tip
G Tine base
l sp Prong play
l z Tine length
p Tine division
s Tine tip
x Axis of symmetry of the tine
α Pitch angle

The essential properties of the finger joint are determined by the length of the teeth l z , the angle of inclination α, the width of the base of the teeth b and the pitch of the teeth p. Furthermore, the connection is determined by the degree of weakening

as well as the relative tine clearance

described in more detail. The degree of weakening describes the relative proportion of the width of the tine tip in relation to the tine division. Since the area of ​​the tine tip does not contribute to the strength of the bond, it has a weakening effect on the connection.

The length of the tines is not essential for the strength of the connection, but the angle of inclination. As the flank inclination angle becomes smaller, both the flexural strength and the tensile strength of the connection increase significantly.

Load-bearing components

In the case of finger joints for load-bearing components, the length of the teeth, the pitch of the teeth and the degree of weakening must be in the following relationship:

  • with tine lengths l z = 10 mm: and
  • for zinc lengths l z > 10 mm .

The slope angle must

  • with tine lengths l z = 10 mm: respectively
  • for tine lengths l z > 10 mm: be.

The degree of weakening must always be.

In the case of load-bearing connections, a distinction is made between finger joint connections for individual timbers and universal finger joint joints for glued laminated timber (glulam) . By finger-jointing individual pieces of wood, the single lamella of a glued-laminated timber can be manufactured, while the universal finger-jointing connects two glued-laminated timbers. The axis of symmetry of the finger joints must always run parallel to the direction of the wood grain. The presence of the so-called tine play, i.e. the distance between the tip of the tine and the base of the tine, is essential for the resilience of a finger joint. The play of the tines ensures that, as a result of the longitudinal compression pressure to be applied during the gluing, the tine flanks sit snugly. The tine flanks represent the adhesive surfaces.

Universal finger joint connections allow highly stressed connections to be glued at any angle to beams and frame corners made of glulam. Glulam components can also be glued to corner pieces made from laminated veneer lumber and construction veneer plywood (made from softwood or poplar wood).

Glue errors are difficult to detect afterwards and can have more serious consequences than errors with mechanical fasteners. In the case of load-bearing components within the meaning of DIN 1052, the manufacturer must therefore be certified by an independent monitoring body. With the certification, the manufacturer acquires a "certificate for the proof of suitability for bonding load-bearing wooden components". This ensures that the company has the technical and organizational requirements to produce fault-free bonds.

Non-structural components

In the area of ​​non-load-bearing components, there are no restrictions with regard to the tine geometry. Accordingly, there are tine geometries and arrangements for which other requirements for the finger joint connection are in the foreground. These requirements relate primarily to economic and aesthetic aspects of the product.

Forms of the finger joint

If the workpieces to be connected do not have a square cross-section, a fundamental distinguishing feature is the direction of the prong connection with respect to the cross-sectional dimension of the wood. The prongs can be made at right angles or parallel to the broad side of the wood.

Horizontal finger jointing

The prong profile is visible on the narrow side of the workpiece. Horizontal finger jointing is mainly used for workpieces in the visible area, for example for furniture panels and parquet made of solid wood.

A special form of horizontal jointing is the crown joint, which is used in the craft sector. It always has two prongs. In contrast to the finger joint - in which the teeth are arranged on the face of the workpiece - the crown joint is a joint joint. The prongs are inserted into the long side of the workpiece.

  • Horizontal tines, positive-negative profile with edge tines

  • Horizontal tine, half-shoulder profile with edge tines

  • Horizontal tine, interchangeable shoulder profile with edge tines

  • Horizontal tines, trapezoidal profile without edge tines

Vertical finger jointing

The tine profile is visible over the entire broad side of the workpiece. Vertical finger-jointing is mainly used in structural timber construction, for example for the production of solid structural timber (KVH) , glued laminated timber and cross laminated timber (CLT) .

  • Vertical jointing

Edge tines

Another distinguishing feature with regard to the shape of the tine connection is the presence of edge tines. They are present when the external prongs are followed by a flat surface that forms the end of the visible surface. The production of the edge teeth requires an additional work step using a separate tool during the production of the finger joints. Edge prongs ensure that the butt joint of the connected timber is straight. This results in a more pleasing appearance of the visible surface. Edge teeth are not permitted on load-bearing components. The butt joint can therefore run unevenly depending on the geometry of the wood surface. Load-bearing components generally have no visible surfaces or the aesthetic requirements take a back seat to the strength properties.

Edge joints are used for both vertical and horizontal finger joints.

application

The finger joint is used in a variety of different products made of solid wood and wood-based materials. Glued laminated timber, solid structural timber, cross-laminated timber, cross beams, DUO and TRIO beams are primarily produced by finger-jointing in constructive glued wood construction. Also, square timbers , planks and boards are often dovetailed. Finger-jointing is used several times in the manufacture of formwork beams . Belts and webs are finger-jointed to the required length. The joining of belt and web can also be done by finger jointing. All of these preliminary products are used in a variety of ways in engineering structures such as houses, halls, bridges, towers and other structures . In interior design, window and door elements, strips, stairs and railings as well as solid wood floors are typical applications. In furniture construction, finger-joint connections can be found in worktops and furniture wood panels for the production of solid wood furniture. Picture frames and clothes hangers are also manufactured by finger-jointing.

Remarks

  1. ↑ The term `` Schiftzinkung '' was presumably chosen based on the shaft , as the geometry of the pointed wood corresponds to two mutually stacked shafted wood.
  2. ↑ Notwithstanding this, the first edition of DIN 68140-1 is dated June 1960.

literature

  • Vanessa Angst, Manfred Augustin u. a .: Handbook 1 - Structures made of wood. (PDF; 7 MB) In: Course materials for the design and construction of wooden structures - TEMTIS. December 2008, accessed June 8, 2012 .
  • Fördergesellschaft Holzbau und Aufbau mbH (Ed.): 100 Years of the Association of German Carpenters . 1st edition. Bruder, Karlsruhe 2003, ISBN 3-87104-143-2 .
  • Peter Glos, Dietger Grosser, Borimir Radovic, Wolfgang Rug: Wood construction manual, series 4 building materials, part 1 general, part 1 wood as a structural building material . 2008, ISSN  0446-2114 ( mh-massivholz.de ( Memento from August 13, 2012 in the Internet Archive ) [PDF; 7.0 MB ; accessed on June 25, 2012]).
  • Otto Graf, Karl Egner: Experiments with glued strap connections made of wood . In: Wood as a raw material . tape 1 , no. 12 , 1938, pp. 460-464 , doi : 10.1007 / BF02608801 .
  • Elmar Josten, Thomas Reiche, Bernd Wittchen: Holzfachkunde - A teaching, learning and workbook for carpenters / joiners, wood mechanics and specialists for furniture, kitchen and moving services . 5th edition. Vieweg + Teubner, Wiesbaden 2009, ISBN 978-3-8348-0530-0 .
  • Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues . In: ETH Zurich, Institute for Building Materials - Wood Physics (Ed.): Research Collection of the ETH Zurich . July 15, 2010, doi : 10.3929 / ethz-a-006113078 .
  • Karin Lißner, Ansgar Felkel, Klaus Hemmer, Borimir Radovic, Wolfgang Rug, Dieter Steinmetz: DIN 1052 - Praxishandbuch Holzbau . 2nd Edition. Beuth Verlag, Berlin 2010, ISBN 978-3-410-17176-8 ( limited preview in Google book search).
  • Ulf Lohmann: Wood Lexicon . 4th edition. tape 1 : A-K . DRW-Verlag, Leinfelden-Echterdingen 2003, ISBN 3-87181-355-9 .
  • Joseph-Eric Marian: A new process for finger-jointing wood and its basics . In: Wood as a raw material . tape 26 , no. 2 , 1968, p. 41–45 , doi : 10.1007 / BF02615808 ( diva-portal.org [PDF; 12.0 MB ; accessed on March 12, 2012]).
  • José Luis Moro: Building construction - from principle to detail . tape 3 implementation. Springer, Berlin 2009, ISBN 978-3-540-85913-0 , doi : 10.1007 / 978-3-540-85914-7 .
  • Hans-Wolf Reinhardt: In memory of Otto Graf, universal building researcher in Stuttgart . Univ., Stuttgart 2006, ISBN 3-926269-71-5 ( uni-stuttgart.de [PDF; 5.0 MB ; accessed on March 7, 2012]).
  • Wolfgang Rug: Innovations in Timber Construction - The Hetzerbauze (Part 2) . In: Bautechnik: Journal for all civil engineering . tape 72 , no. 4 , 1995, ISSN  0932-8351 , p. 231–241 ( page no longer available , search in web archives: holzbau-statik.de [accessed on March 7, 2012]).@1@ 2Template: Toter Link / www.holzbau-statik.de
  • Kurt Rügge: State of the art in finger jointing wood . In: Wood as a raw material . tape 34 , no. 11 , 1976, p. 403-411 , doi : 10.1007 / BF02608006 .
  • André Wagenführ, Frieder Scholz (Ed.): Pocket book of wood technology . Fachbuchverlag Leipzig in Carl Hanser Verlag, Munich 2008, ISBN 3-446-22852-7 .

Norms

  • German Institute for Standardization e. V. (Hrsg.): DIN 68140-1 Finger joint connections of softwood for load-bearing components . February 1998 (withdrawn).
  • German Institute for Standardization V. (Ed.): DIN EN 385 Finger joint connections in construction timber - performance requirements and minimum requirements for manufacture; German version EN 385: 2001 . November 2007.
  • German Institute for Standardization V. (Ed.): DIN EN 387 universal finger joint connections - performance requirements and minimum requirements for manufacture; German version EN 387: 2001 . April 2002.
  • German Institute for Standardization V. (Ed.): DIN EN 15497 Finger joint connections in construction timber - Performance requirements and minimum requirements for manufacture; German version prEN 15497: 2011 . September 2011 (draft standard).

Web links

  • Finger joint - Forms of finger joint. Höchsmann GmbH, accessed on March 9, 2012 (information on standardization, areas of application and forms of finger joint connections).
  • Directory of recognized glue construction companies and directory of approved adhesives. MaterialsTesting InstituteUniversity of Stuttgart, accessed on March 9, 2012 (list of companies that have provided proof of suitability for gluing load-bearing wooden components in accordance with DIN 1052; list of tested adhesives in the scope of DIN 1052 and general building authority approval; list of adhesives used for gluing glued laminated timber according to DIN EN 14080: 2005 are suitable).

Individual evidence

  1. ↑ a b c German Institute for Standardization e. V. (Ed.): DIN EN 387 universal finger joint connections - performance requirements and minimum requirements for manufacture; German version EN 387: 2001. 2002, p. 4.
  2. ↑ Elmar Josten, Thomas Reiche, Bernd Wittchen: Holzfachkunde - A teaching, learning and workbook for joiners / joiners, wood mechanics and specialists for furniture, kitchen and moving services. 2009, p. 318, p. 481.
  3. ↑ a b José Luis Moro: Building construction - from principle to detail. 2009, pp. 262-263.
  4. ↑ Vanessa Angst, Manfred Augustin a. a .: Handbook 1 - Structures made of wood. 2008, p. 150 f., P. 164.
  5. ^ André Wagenführ, Frieder Scholz (ed.): Pocket book of wood technology. 2008, p. 135.
  6. ↑ Gerd habenicht: Gluing - Basics, Technologies, Applications . 6th edition. Springer-Verlag, Berlin 2009, ISBN 978-3-540-85264-3 , pp. 927 ( limited preview in Google Book search).
  7. ↑ a b German Institute for Standardization e. V. (Hrsg.): DIN 68140-1 Finger joint connections of softwood for load-bearing components. 1998, p. 2.
  8. ↑ German Institute for Standardization e. V. (Ed.): DIN EN 385 Finger joint connections in construction timber - performance requirements and minimum requirements for manufacture; German version EN 385: 2001. 2007, p. 4.
  9. ↑ Fördergesellschaft Holzbau und Aufbau mbH (Ed.): 100 Years of the Bund Deutscher Zimmermeister. 2003, p. 370.
  10. ^ Otto Graf, Karl Egner: Experiments with glued tab connections made of wood. 1938, p. 464.
  11. ↑ Hans-Wolf Reinhardt: In memory of Otto Graf, universal building researcher in Stuttgart. 2006, pp. 30-32.
  12. ↑ a b c d Ulf Lohmann: Wood Lexicon. 2003, pp. 666-667.
  13. ↑ Hans-Wolf Reinhardt: In memory of Otto Graf, universal building researcher in Stuttgart. 2006, pp. 35-37.
  14. ^ Wolfgang Rug: Innovations in timber construction - The Hetzerbauweise (part 2). 1995, p. 239.
  15. ↑ Fördergesellschaft Holzbau und Aufbau mbH (Ed.): 100 Years of the Bund Deutscher Zimmermeister. 2003, p. 371.
  16. ↑ Kurt Rügge: State of the art in finger jointing wood. 1976, p. 403.
  17. ↑ Hans-Wolf Reinhardt: In memory of Otto Graf, universal building researcher in Stuttgart. 2006, p. 36.
  18. ↑ Joseph-Eric Marian: A new method for finger-jointing wood and its basics. 1968, p. 43.
  19. ↑ José Luis Moro: Building construction - from principle to detail. 2009, p. 262.
  20. ↑ Peter Niemz, Fritz Bächle, Walter Sonderegger, Kristin Junghans, Yvonne Herbers: Basics of wood working and processing. (PDF; 14 MB) In: Research Collection of the ETH Zurich. ETH, Eidgenössische Technische Hochschule Zürich, Institute for Building Materials IfB, 2007, pp. 2–15 , accessed on August 10, 2012 ( doi: 10.3929 / ethz-a-005433202 ).
  21. ↑ a b Karin Lißner, Ansgar Felkel, Klaus Hemmer, Borimir Radovic, Wolfgang Rug, Dieter Steinmetz: DIN 1052 - Praxishandbuch Holzbau. 2010, pp. 62–64, p. 103.
  22. ↑ Walter Stampfli, Thomas Meyer: Contactless adhesive application on finger joints . In: Adhesion Gluing & Sealing . No. 10 . Springer Vieweg, 2008, ISSN  0001-8198 ( page no longer available , search in web archives: purbond.com [accessed August 20, 2012]).@1@ 2Template: Dead Link / www.purbond.com
  23. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 64.
  24. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 22.
  25. ↑ German Institute for Standardization e. V. (Ed.): DIN EN 15497 Finger joint connections in construction timber - Performance requirements and minimum requirements for manufacture; German version prEN 15497: 2011. 2011, p. 9.
  26. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 23.
  27. ↑ Peter Glos, Dietger Grosser, Borimir Radovic, Wolfgang Rug: Timber Construction Manual, Series 4 Building Materials, Part 1 General, Part 1 Wood as a structural building material. 2008, pp. 45-48.
  28. ↑ Glulam. (No longer available online.) WECOBIS ecological building material information system, archived from the original on December 30, 2011 ; Retrieved June 20, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.wecobis.de
  29. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 66.
  30. ↑ Holzmarktbericht 2010. (PDF; 1 MB) Federal Ministry of Food, Agriculture and Consumer Protection (BMELV), August 2011, p. 5 , accessed on June 19, 2012 .
  31. ↑ A. Frühwald, JB Ressel, A. Bernasconi: High-quality glued laminated timber made from beech wood. (PDF; 5 MB) July 2003, archived from the original on April 25, 2012 ; Retrieved June 19, 2012 .
  32. ↑ Hans Joachim Blaß, J. Denzler, Matthias Frese, Peter Glos, P. Linsemann: Flexural strength of glued laminated timber made of beech . Universitätsverlag Karlsruhe, Karlsruhe 2005, ISBN 3-937300-40-6 , doi : 10.5445 / KSP / 1000001371 ( digbib.ubka.uni-karlsruhe.de [PDF; 12.0 MB ; accessed on June 19, 2012]).
  33. ↑ Matthias Frese: Flexural strength of glued laminated timber made of beech - experimental and numerical investigations on the lamination effect . Universitätsverlag Karlsruhe, Karlsruhe 2006, ISBN 3-86644-043-X , doi : 10.5445 / KSP / 1000004599 ( digbib.ubka.uni-karlsruhe.de [PDF; 13.0 MB ; accessed on June 19, 2012]).
  34. ↑ Hans Joachim Blaß, Matthias Frese: Flexural strength of glulam hybrid girders with edge lamellas made of beech wood and core lamellas made of softwood . Universitätsverlag Karlsruhe, Karlsruhe 2006, ISBN 3-86644-072-3 , doi : 10.5445 / KSP / 1000005148 ( digbib.ubka.uni-karlsruhe.de [PDF; 7.0 MB ; accessed on June 20, 2012]).
  35. ↑ Glulam made of beech and glulam beech hybrid beams. (PDF; 2 MB) German Institute for Structural Engineering, October 7, 2009, accessed on June 20, 2012 .
  36. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 67.
  37. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 65.
  38. ↑ Solid wood panel (1-layer / multi-layer). (No longer available online.) WECOBIS ecological building material information system, archived from the original on February 21, 2012 ; Retrieved June 20, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.wecobis.de
  39. ↑ Karin Lißner, Ansgar Felkel, Klaus Hemmer, Borimir Radovic, Wolfgang Rug, Dieter Steinmetz: DIN 1052 - Praxishandbuch Holzbau. 2010, p. 103.
  40. ↑ List of adhesives I of the MPA University of Stuttgart regarding tested adhesives in the scope of DIN 1052 and general building authority approvals. (PDF; 100 kB) (No longer available online.) Materials Testing Institute University of Stuttgart, February 28, 2013, formerly in the original ; Retrieved May 13, 2013 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. @1@ 2Template: Toter Link / www.mpa.uni-stuttgart.de  
  41. ^ André Wagenführ, Frieder Scholz (ed.): Pocket book of wood technology. 2008, pp. 135, pp. 517-518.
  42. ↑ German Institute for Standardization e. V. (Hrsg.): DIN 68140-1 Finger joint connections of softwood for load-bearing components. 1998, p. 3.
  43. ↑ Karin Lißner, Ansgar Felkel, Klaus Hemmer, Borimir Radovic, Wolfgang Rug, Dieter Steinmetz: DIN 1052 - Praxishandbuch Holzbau. 2010, pp. 62–64, p. 102.
  44. ↑ finger joint. Höchsmann GmbH, 2013, accessed on July 13, 2014 .
  45. ↑ Elmar Josten, Thomas Reiche, Bernd Wittchen: Holzfachkunde - A teaching, learning and workbook for joiners / joiners, wood mechanics and specialists for furniture, kitchen and moving services. 2009, p. 296.
  46. ↑ Andreas Kalweit, Christof Paul, Sascha Peters, Reiner Wallbaum: Handbook for Technical Product Design - Material and Manufacturing - Decision-making basis for designers and engineers . 2nd Edition. Springer-Verlag, Berlin 2012, ISBN 978-3-642-02641-6 , pp. 177 , doi : 10.1007 / 978-3-642-02642-3 ( limited preview in Google Book search).
  47. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 67, p. 71, p. 74 f.
  48. ↑ Peter Glos, Dietger Grosser, Borimir Radovic, Wolfgang Rug: Timber Construction Manual, Series 4 Building Materials, Part 1 General, Part 1 Wood as a structural building material. 2008, p. 71.
  49. ↑ Patent DE10121522C1 : formwork beams. Registered on May 3, 2001 , published on October 31, 2002 , applicant: Doka Industrie GmbH, Amstetten, AT, inventor: request for non-naming. ‌
  50. ↑ Elmar Josten, Thomas Reiche, Bernd Wittchen: Holzfachkunde - A teaching, learning and workbook for joiners / joiners, wood mechanics and specialists for furniture, kitchen and moving services. 2009, p. 297, p. 481.
  51. ↑ Verena Krackler, Daniel Keunecke, Peter Niemz: Processing and uses of hardwood and hardwood residues. 2010, p. 65.
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