Bolted Timber Connections: Part II. Bolt Bending and Associated Wood Deformation


  • Philip E. Humphrey
  • Larry J. Ostman


Bolted joints, bolt deflection, X-ray scanning, wood-deformation mechanisms


Complete double-shear joints with a single bolt were tested in tension. Approximately 10 X-ray scans were made of each joint as it was progressively loaded to failure; in this way, bending and overall displacement of the bolts within the members could be quantified. Combining the above data with measured joint-slip values enables the penetration of the bolt into the surrounding wood to be calculated for all positions along the length of the bolt. In a preceding related study, the authors observed the mechanisms of deformation that occur in thin wood wafers around a round steel pin of a diameter identical to that of the bolts used in the present work. By combining this information on behavior mechanisms in the plane at right angles to the pin axis with the X-ray data for whole joints, wood behavior throughout the joint and reactions against the bolt along its length can be estimated. The above analysis is applied principally to joints with 75- x 75-mm wood main members, 75- x 37.5-mm wood side members, and a single 12.5-mm diameter bolt an an end-distance of seven diameters. Representative X-ray scans of joints manufactured with a range of steel side-member thicknesses and bolt diameters are also included. The techniques presented complement theoretical model predictions and thus may be used to aid in optimizing joint design.


Foschi, R. O. 1977. Load-slip characteristics for connections with common nails. Wood Sci. 9(3): 118-123.nHetenyi, M. 1939. Analysis of bars on elastic foundations. Int. Assoc. Bridge Struct. Eng. Second Congress, Wilhelm Ernst and John, Berlin-Munich.nHetenyi, M. 1946. Beams on elastic foundations. University of Michigan Press, Ann Arbor, MI.nHumphrey, P. E., and L. J. Ostman. 1989. Bolted timber connections: Part I. A wafer technique to model wood deformation around bolts. Wood Fiber Sci. 21(3):239-251.nJansson, G. B. I. 1955. Effect of nail characteristics on load-carrying capacity of a nailed joint. M.S. thesis, Iowa State College, Ames, IA.nJohansen, K. W. 1949. Theory of timber connections. Int. Assoc. Bridge Struct. Eng. 9:249-262.nKuenzi, E. W. 1955. Theoretical design of a nailed or bolted joint under lateral load. USDA For. Serv. Rep. No. D1951. For. Prod. Lab., Madison, WI.nMcLain, T. E., and S. Thangjitham. 1983. Bolted wood joint yield model. J. Struct. Div. ASCE 109(8):1820-1835.nNoren, B. 1961. Nailed joints—a contribution to the analysis of yield and strength. Proceedings-First International Conference on Timber Engineering, Southampton, UK.nSmith, I. 1982. Analysis of mechanical timber joints with dowel type connectors subjected to short term lateral loading—by finite element approximation. Res. Rep. 282. Timber Research and Development Association, Hughenden Valley, Buckinghamshire, UK.nStluka, R. T. 1960. Theoretical design of a nailed or bolted joint under lateral load. M.S. Thesis, Dept. of Civil Engineering, University of Wisconsin, Madison, WI.nTokuda, M. 1977. Studies on the nailed wood joint. I. Measurements of the nail shear deformation by Softex. Mokuzai Gakkaishi 23(1): 17-24.nWilkinson, T. L. 1978. Strength of bolted wood joints with various ratios of member thicknesses. USDA For. Serv. Res. Pap. FPL 314. For. Prod. Lab., Madison, WI.nWong, C. M. S., and F. L. Matthews. 1981. A finite element analysis of single and two-hole bolted joints in fiber reinforced plastic. J. Compos. Mater. 15:481-491.n






Research Contributions