文档介绍：The Structural Engineer 88 (1) 5 January 2010 25 Synopsis This paper presents a model for the strength of inclined screws used as shear connectors in timber and posite floors. Experiments show that both the stiffness and strength of screwed timber to concrete shear connections can be increased if the screws are inclined in the direction of shear; this model predicts the enhanced strength. The model is an upper bound plastic collapse model that assumes that the timber and screws behave perfectly plastically and that the concrete remains undamaged. Six failure modes are considered: yield of the screw, in tension or shear, and four modes bine bending of the screw and timber. The bined modes allow screw withdrawal, lateral crushing of the timber and the development of plastic hinges in the screw. A design chart is proposed which shows the expected strength and failure mode. The model is validated parison to two sets of experimental tests. Notation A α Cross-sectional area of screw at interface between concrete and timber. F ax, α Withdrawal load of inclined screw from timber. M y Yield bending moment of screw. R i Shear strength of the inclined screw timber to concrete connection; in mode i . Non-dimensional shear strength ( = 4 R / f u π d 2 ) W E External work done. W I,i Internal work done in mode i . d Diameter of screw. deff Effective diameter of screw. f 1cube Mean concrete cube strength. f h, α Embedment strength of the timber, at an angle α to the grain ( = f h,0 / f u ). f a, α Withdrawal shear stress of screw inclined at an angle α to the vertical. f u Yield stress of screw. h Length of screw head cast in situ in concrete. i Failure mode. k 90 Embedment strength modification factor. l ef Effective length of screw. t Length of screw inserted into timber ( = t/d ). x i Location of point of zero lateral translation in mode i = 3 or 4. u Lateral displacement of screw tip. α Angle of inclination of the screw axis with the vertical. ? ax Axial displaceme