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fasteners spacing (which is not true). The important and safety relevant property ductility has even not found recognition in the Codes; fasteners spacings may highly affect the ductility of a joint. The weak points in a timber structure are often the joints. Generally the joint presents a lower load-carrying capacity than the two parts to be jointed. Highest performance is linked to an undisturbed (smooth) flux of forces in direction of the fibres. This is achieved the nearest by finger-jointing. More indicated – since a rather smooth flux of forces is possible – are glued in rods. A near steady flow of shear forces is originated around the rod. Conclusion In view of the great importance of a correct formulation of the spacing requirements for the performance of connections with axially loaded screws and glued-in rods inserted parallel to the grain the actual Codes have to be adapted. 43-21-2 T Uibel, H J Blass A new method to determine suitable spacings and distances for selftapping screws Introduction In recent years self-tapping screws have been increasingly used for connections or reinforcements in timber engineering. Most self-tapping screws can be arranged maintaining only small spacings and distances without risking a consequential splitting failure of the timber member. To avoid significant crack growth and splitting failure minimum values for spacings, end and edge distances as well as for the corresponding minimum timber thickness have to be determined. These requirements are important for the design of joints with self-tapping screws and have to be defined in technical approvals or to be examined regarding structural design codes [1] [2]. Fig. 1 shows typical splitting failure due to too small spacings and distances. The determination of spacing, edge and end distance requirements for self-tapping screws requires numerous and comprehensive insertion tests. Yet the results of such tests cannot be transferred to other types of screws or even to screws of different diameter because of differences in shape or geometry. To reduce the effort of insertion tests a new method was developed which allows the estimation of required spacings, distances and timber thickness. Fig. 1: Typical splitting failure caused by the insertion of self-tapping screws Conclusions To estimate the splitting behaviour of timber during the insertion process a new calculation method was developed. It represents a combination of a FE calculation and a new test method. The FE model allows the calculation of the resulting crack area for screws in different end distances as well as for different cross-sections of timber. In the Finite Element model the tensile strength perpendicular to the grain that represents a relevant factor for splitting was simulated by using non-linear spring-elements whose material behaviour was determined on the basis of tests using CT specimens. In order to determine the fastener-specific influences on the splitting behaviour a new test method was developed for measuring forces affecting the member perpendicular to the grain during the insertion process. This method also allows a direct evaluation of a screw’s effect on the splitting behaviour by comparing it with the results of parallel tests involving reference screws whose influence on the splitting behaviour has already been established. For the calibration and verification of the model the crack area was visualized in insertion tests by means of dyeing the relevant areas. CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.86
The simulated crack areas mostly proved to correspond with the test results. Using the new method reduces the effort of conventional insertion tests and offers a basis for a realistic calculation of the load carrying capacity of joints in the case of failure by splitting. In the continuation of the research project the parameters influencing the splitting behaviour like e.g. the angle between screw axis and tangent to the annual rings will be determined in greater detail. Besides the influences of the angle between screw axis and grain direction will be examined. In addition, parameters to facilitate the evaluation of the splitting behaviour and their limits (e.g. limits for the dimension of split areas) will be derived. CIB-W18 Timber Structures – A review of meeting 1-43 4 CONNECTIONS page 4.87
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CONTENT 4.1 BLOCK SHEAR ...........
Page 3 and 4:
41-7-2 P Quenneville, J Jensen Vali
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4.9 LOAD DURATION 66 22-7-4 A J M L
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4.1 BLOCK SHEAR 30-7-2 J Kangas, A
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Schematic plug shear failure Conclu
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Conclusion With the new LVL-D struc
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4.2 CONNECTORS 25-7-6 H J Blass, J
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for determination of the load-carry
Page 17 and 18:
4.3 DOWEL-TYPE FASTENERS LOADED PAR
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carrying capacity of steel bolts in
Page 21 and 22:
carrying capacity on condition that
Page 23 and 24:
- shear failure of a group of rows
Page 25 and 26:
32-7-4 I Smith, P Quennevile Predic
Page 27 and 28:
tion of the yield capacity of dowel
Page 29 and 30:
General discussion Moment carrying
Page 31 and 32:
4.4 DOWEL-TYPE FASTENERS LOADED PER
Page 33 and 34:
- the results given by the two SIF
Page 35 and 36: positive effects on the load-carryi
Page 37 and 38: 37-7-5 M Ballerini A new prediction
Page 39 and 40: on the fracture mechanics and on th
Page 41 and 42: - Through identification of applica
Page 43 and 44: tee on Adhesives (D14.30) for adopt
Page 45 and 46: and numerical results were found to
Page 47 and 48: 4.6 GLUED-IN RODS 19-7-2 H Riberhol
Page 49 and 50: 30-7-1 K Komatsu, A Koizumi, T Sasa
Page 51 and 52: have been varied. Minimum values of
Page 53 and 54: Within the GIROD-project the work i
Page 55 and 56: - spacing rules between rods and be
Page 57 and 58: 4.7 JOINTS IN TIMBER PANELS 39-7-5
Page 59 and 60: 4.8 LOAD DISTRIBUTION 23-7-2 H J Bl
Page 61 and 62: The results of the evaluation are c
Page 63 and 64: small fabrication tolerances lead t
Page 65 and 66: 39-7-1 P Quenneville, M Bickerdike
Page 67 and 68: 36-7-6 S Nakajima Evaluation and es
Page 69 and 70: The amount of testing is considerab
Page 71 and 72: Conclusions In addition to the semi
Page 73 and 74: nents and jointed structures under
Page 75 and 76: perimental data to characterize the
Page 77 and 78: 4.13 SCREWS 42-7-1 G Pirnbacher, R
Page 79 and 80: with nef = 0.9 · n · m with the n
Page 81 and 82: 4.14 SLOTTED-IN STEEL PLATES 30-7-3
Page 83 and 84: 38-7-7 B Murty, I Smith, A Asiz Des
Page 85: Conclusions Splitting sensitivity o
Page 89: 4.17 TRADITIONAL JOINTS 41-7-4 C Fa
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