Lagscrewbolt (LSB) has been used widely for composing glulam moment resisting column-leg as well as beam-column joints for constructing semi-rigid wooden frame structures. A serious problem on the existing LSB joint, however, was its brittle failure mode. In order to avoid this characteristic, Slotted Bolted Connection (SBC) systems, which is a kind of the friction damper for steel truss structure, was introduced to the existing glulam LSB joint system serially. Experiments on full-scale column-leg joint and beam-column joint, which were intended to be used in a three storey glulam school building, showed satisfactory performance on the requirements for the stiffness, yielding and ultimate performance. By this innovative investigation, a glulam semi-rigid portal frame, which has high initial stiffness, clear yielding capacity, rich ductility, and free from glulam brittle fractures, might be possible to be realized.
International Journal of Advanced Structural Engineering
Summary
This paper presents analytical and numerical models for semirigid timber frame with Lagscrewbolt (LSB) connections. A series of static and reverse cyclic experimental tests were carried out for different beam sizes (400, 500, and 600 mm depth) and column–base connections with different numbers of LSBs (4, 5, 8). For the beam–column connections, with increase in beam depth, moment resistance and stiffness values increased, and ductility factor reduced. For the column–base connection, with increase in the number of LSBs, the strength, stiffness, and ductility values increased. A material model available in OpenSees, Pinching4 hysteretic model, was calibrated for all connection test results. Finally, analytical model of the portal frame was developed and compared with the experimental test results. Overall, there was good agreement with the experimental test results, and the Pinching4 hysteretic model can readily be used for full-scale structural model.
Moment resisting joint with lagscrewbolts shows good mechanical performance and aesthetic. However, beam and column joints rarely showed a brittle shear failure in a panel zone of a column in previous studies. Therefore, a joint system reinforced by long screws was developed to prevent from the failure in this research. The maximum shear strength of the joint increased with increasing the number of long screws. However, the average of six screws specimens was lower than that of four screws, because the glulam and some of the screws were damaged due to the narrow space between the screws during an inserting process of the screws.
