Abstract: [Objective] The formula for calculating the shear stress of the cross laminated timber (CLT) rectangular beam was explored to provide a theoretical basis for testing the interlaminar shear strength of CLT.[Method] Interlaminar shear strength of three-,five-and seven-layers CLT beams and glulam beams was calculated by Hooke's law and on the basis of the differential relationship between beam's bending moment and shear stress.Shear stress calculation formula of CLT beams was developed,and its distribution characteristics of CLT beams and glulam beams were also compared.[Result] Interlaminar normal stress of CLT beam was interrupted,and shear stress between layers was continuous.Shear stress for rectangular section CLT beams along the height of the section tended to equalize and no longer followed the parabolic distribution.In center-point bending loading for short-span CLT beams,rolling shear failure in vertical layer,interlaminar shear failure and bending failure in parallel layer occurred in turn.The maximum load of the center-point bending load-displacement curve for CLT short-span beams was the interlaminar shear failure load,it was stable and easy to read.Interlaminar shear strength of Hemlock CLT was positively correlated with elastic modulus of parallel layer.[Conclusion] Interlaminar shear stress and the maximum shear stress of CLT beams were related to the number of CLT layers and the ratio of elastic modulus of parallel and vertical layers E_L/E_T(or E_L/E_R).The maximum shear stresses of three-,five-and seven-layers CLT rectangular beams occurred on the neutral axis of the beam section,and their values were 92.8%,86.7%,and 92.6% of the 1.5 times section average shear stress,respectively.Short-span beam three-point bending method was an effective method of testing the interlaminar shear strength of short-span CLT beams.

Key words: cross laminated timber(CLT), interlayer shear stress, interlaminar shear strength, test