An innovative multi-layer (3 and 5) composite laminated panel (CLP) with various layups were developed using sawn lumber and structural composite lumber (SCL) to address the rolling shear and gap issues of cross laminated timber (CLT). The bending properties including apparent and effective bending stiffness, shear stiffness, moment capacities and failure modes of CLPs were evaluated by a combination of modal tests and third-point bending tests of beam specimens cut from the panels. The static bending test results showed that the apparent bending stiffness values of 3-layer and 5-layer CLPs were up to 20% and 43% higher than the corresponding values of 3-layer and 5-layer generic CLT, respectively. The bending moment capacity values of 3-layer and 5-layer CLPs were up to 37% and 87% higher than the corresponding values of 3-layer and 5-layer generic CLT, respectively. The use of SCL in transverse layers eliminated the potential rolling shear failure in CLT and increased the stiffness properties. The apparent and effective bending stiffness predicted by shear analogy method had a good agreement with corresponding values measured by bending tests and/or modal tests. The prediction of bending moment capacity using shear analogy method cannot be validated due to the rolling shear failure and tension failure modes observed in certain groups.
An experimental and analytical study on rotational behaviour of glulam beam-column moment connections with self-drilling dowels (SDD) was conducted. Connection properties including strength, stiffness, ductility and energy dissipation were experimentally evaluated by testing seven full-scale connection specimens with and without self-tapping screw (STS) reinforcement along timber perpendicular to grain. All the connections showed high initial stiffness and high moment capacity when compared with the test results of bolted connections reported in literature. The unreinforced connections had relatively low ductility due to timber splitting despite the increased fastener edge distance. The STS reinforcement effectively reduced timber splitting tendency and encouraged the yielding of more SDD, leading to slightly increased moment capacity, but significantly improved ductility. A modified analytical model (MAM) was then proposed to predict strength and rotation of the SDD moment connections based on force and moment equilibrium of the glulam members. Improved prediction accuracy was achieved for the SDD moment connections when compared with the past analytical methods.
The outcomes of an experimental study aimed to investigate the structural behaviour of wood-steel-wood glulam frame moment-resisting connections that were subjected to static bending are presented in this paper. Each frame test assembly was consisted of two glulam beams simply supported at their far ends and were connected to an inverselyloaded glulam column in the centre using two steel T-stub connectors. Two test variables including bolt’s end distance and number of bolt rows were investigated in eight full-size glulam beam-column assemblies. Test results revealed that increasing the number of bolt rows from two to three, with each row included two bolts, significantly increased the connection moment capacity with much greater increments compared to those added by increasing the bolt’s end distance from four- to five-times bolt diameter. However, brittle failure modes were found to be more pronounced in the connections with three rows compared to the connections with two rows of bolts.
An experimental study of four full-scale cruciform sub-assemblages of beam-to-column steel-timber composite joints with extended end plates was conducted to simulate the behaviour of an internal joint in a semi-rigid steel-timber frame. In this system, the Cross-Laminated Timber (CLT) panels were attached compositely to the steel beam using coach screws to achieve the shear connection and the steel-CLT composite beams were connected to the steel columns by bolted extended end plates. In addition, one specimen without a CLT slab was constructed and tested as a control with which to assess the influence of the CLT panels on the performance of the joint. The structural behaviour of this type of joint which requires the connection of the two juxtaposed CLT panels subjected to tension near the column was explored. The test results show that these novel composite joints have credible rotation and moment capacities and provide a viable alternative to their steel-concrete counterparts within a paradigm of reduced carbonemissions in the construction sector.
This paper presents a research study about timber connections in moment resisting frames, with materials commercially available in Costa Rica. With new developments in engineered timber, the Costa Rican Seismic Code included a chapter on timber structures, defining moment resisting timber frames with several values of structural global ductility, depending on the local ductility of the connections. A research study was then carried out, with the objective of determining the structural behaviour and static ductility factor of a beam to column connection. Twelve specimens were constructed and tested, varying the geometric characteristics, wood species and type of bolts. The specimens consisted of a glulam beam and column segment connected with a different bolt pattern. The beam segment was loaded at its free end to induce a moment in the connection, and the ends of the column segment were simply supported. The rotation of the connection was measured by placing two LVDTs in the beam and two LVDTs in the column. It was found that the ductility factors achieved by the test specimens ranged from 2.0 to 2.7 in average. The moment capacity of the connections can be safely estimated using the nominal values of bending yield strength of the bolts and the dowel bearing stresses. These results are an important input for the Costa Rican Seismic Code and for the development of engineered timber in Costa Rica.