Shear performance of grouted stud connections for steel-cross laminated timber composite beams
To study the shear performance of steel-cross-laminated-timber(CLT)composite beams with grouted stud connections(GSC),eight groups of GSC specimens and two groups of bolt connectors in grout pockets(BCGP)specimens were designed for push-out tests.Test parameters included stud diameter(16-22 mm),row of studs(single and double),slotting mode(single-way and double-way),angle of groove surfaces(0°-30°),connection type(studs and bolts)and whether steel fibers were added to the grout or not.The test results indicate that the GSC fail primarily by bending or shear failure of studs combining with cracking and rotation of grout blocks,while the main failure modes of BCGP include bolt shearing failure and grout blocks crushed at the root of studs.The shear strength and shear stiffness of GSC increase linearly with the stud diameter increasing from 16 mm to 22 mm.Compared with the rectangular notch,the bearing capacity of the connections with wedge-shaped(WS)notch decreases,while the stiffness of the connections with WS notch increases with the number of sloping surfaces of the notch increasing.As the angle of the sloping surfaces of the WS notch increasing from 0° to 30°,the shear capacity decreases initially and then increases,while the shear stiffness increases at first and then decreases.Compared with the rectangular notch,the rotation of grout blocks in the WS notch is more obvious.Due to the group effect of studs,the total shear capacity and the total shear stiffness of double-row stud connections are not in a linear relationship with the number of stud rows.A shear capacity formula is proposed for the GSC in case of local crushing of the CLT panel,and the calculation results are in good agreement with the experimental results.Finally,for the shear failure of stud,the predictions from exiting formulas for shear capacity in relevant specifications differs from experimental results with a maximum difference up to more than 50％.
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