Mohammad

Fire Performance of Timber Connections, Part 2: Thermal and Structural Modelling

This paper presents models for calculating the fire resistance ratings of bolted timber connections based on fire-resistance test results carried out recently. In the first phase of the work, a three-dimensional finite-element thermal model was employed to analyze heat transfer within bolted Wood-Steel-Wood (WSW) and Steel-Wood-Steel (SWS) connections. The thermal model was found to provide good predictions when comparing the calculated temperatures and residual cross-section dimensions of timber connections with the experiment results. In the next phase, an embedment strength reduction model was used to calculate the load-bearing capacity of WSW and SWS bolted connections by including the temperature profiles generated from the heat transfer model. Different relationships of wood embedding strength as a function of temperatures were used in the structural model. The comparisons with experimental results showed that Norens approach seemed to predict fire resistances of bolted timber connections in good a...

Fire Performance of Timber Connections, Part 1: Fire Resistance Tests on Bolted Wood-Steel-Wood and Steel-Wood-Steel Connections

This paper presents the results of a series of fire-resistance tests on bolted wood-steel-wood (WSW) connections and bolted steel-wood-steel (SWS) connections. In total, 16 WSW specimens and 6 SWS specimens were tested in accordance with the provisions of CAN/ULC-S101. All the specimens were subjected to a constant tensile load parallel to grain during the tests. The effects of load level, wood thickness, fastener diameter, number of fasteners, edge distance and protection were studied. The test results show that the fire-resistance ratings of all the tested WSW connections without protection were less than 45 minutes (a target rating for Canadian code compliance) and the fire-resistance ratings of all the tested SWS connections without protection were less than 25 minutes. Specimens with thicker wood side members were found to exhibit better fire resistances. Decreasing the load ratio increased the fire resistance. The test results on protected specimens show that the protection provided by a single-laye...

Effects of end-pressure on the finger-joint quality of black spruce lumber: a microscopic analysis

Efficiency of finger-joints in the Engineered Wood Products is key to the performance of these products. The aim of this research work was to evaluate, by scanning microscopic analysis, the effect of end pressure on the performance of horizontal finger-joint of black spruce (Picea mariana (Mill.) B.S.P) specimens. A feather joint configuration glued with an isocyanate type of adhesive cured at room-temperature was used. The finger-joints were machined at a feed rate of 18.3 m/min, rotational speed of 3500 rpm, and at a feed per knife (chip-load) of 0.86 mm. A single-face glueline application was used at a spread rate of 110 g/m 2 . The curing time was kept at 24 hours. Six end-pressure levels ranging from 1.38 MPa to 4.82 MPa applied for 20 seconds were investigated. Results showed that cell depth damage increased as end-pressure increased. Joints also showed formation of some air bubbles within the glueline which lead to a reduction in their tensile strength.

RACKING AND BENDING TESTS FOR PREFABRICATED WALL PANELS

El objetivo de este estudio fue evaluar y optimizar conexiones lineales “muro a muro” utilizadas en la instalacion de muros de madera prefabricados para casas. Los resultados de 6 tests de cizallamiento y 9 tests de flexion realizados en muros de 2.44 x 2.44 m son presentados a continuacion. Los muros fueron prefabricados a partir de dos segmentos de 1.22 x 2.44 m conectados con tres tipos de conexion. Los tests de cizallamiento fueron realizados de acuerdo a las indicaciones presentes en la norma ASTM, y dos conexiones diferentes a los cimientos fueron utilizadas. Los tests de flexion fueron llevados a cabo utilizando un protocolo de carga propuesto, ideado a partir del calculo de la presion de viento ejercida perpendicularmente a los muros. Para estos tests, tres tipos de conexion a los cimientos fueron utilizadas. En los tests de cizallamiento, los resultados demuestran que el tipo de conexion utilizada entre los muros no incide significativamente en la resistencia de los muros anclados a los cimientos, mientras que, para los muros clavados a los cimientos, la capacidad de resistencia no fue alcanzada. Respecto a los tests de flexion, los muros resistieron alta presion de viento, independiente del tipo de conexion muro a muro utilizada. Los resultados seran usados para validar un modelo preliminar de elementos finitos, desarrollado para predecir el comportamiento de muros prefabricados ante solicitaciones de cizallamiento y de flexion, con especial atencion en la optimizacion de la conexion muro a muro y del anclaje a los cimientos

Load Distribution in Timber Structures Consisting of Multiple Lateral Load Resisting Elements with Different Stiffnesses

It is well known that the stiffness properties of diaphragms and lateral load resisting elements (LLREs) influence the load distribution between LLREs under lateral load induced by earthquake or wind. Where a more sophisticated method of calculating the load distribution in a lateral load resisting system is used, often it is based on the concept of a beam on an elastic foundation. This approach could be tedious to apply in design when there are more than a few LLREs. A multiple-spring model (MSM), whereby the translational springs are used to model the diaphragm stiffnesses and the stiffnesses of the LLREs, is proposed. The model was validated with test and finite-element results of a particular benchmark building. The lateral load distribution between LLREs with various stiffness ratios of diaphragm to LLRE was also investigated. The results show that, contrary to common belief, the forces transferred by a semirigid diaphragm to supporting LLREs may be higher than those predicted by flexible and rigid-diaphragm assumptions. Therefore, using the envelope force approach may lead to underestimation of the design forces in the shear walls.

Effect of end pressure on performance of structural finger-joined lumber fabricated using a short joint profile

This study was to examine the effect of end pressure on the mechanical properties and delamination resistance of structural black spruce (Picea mariana) finger-joined lumber made of a short (12.7-mm-long) finger profile. End pressures used were 2.00, 3.43, 6.00 and 8.00xa0MPa. 8.00xa0MPa yielded the greatest 5th percentile ultimate tensile strength, but caused cracks at tips of a joint. It was recommended that 2.00xa0MPa be used as the optimized end pressure from the viewpoint of energy saving.

Influence of diaphragm flexibility on lateral load distribution between shear walls in light wood frame buildings

In light wood frame buildings, diaphragm flexibility influences the load distribution between shear walls under lateral load induced by earthquake or wind action, which is important for structural design. A multiple spring model with the ability to represent the load-transferring behaviour of this complex lateral load resisting system of light wood frame buildings was developed. The developed model was validated with results from the more sophisticated model, spring deep-beam model. The lateral load distribution between shear walls with various stiffness ratios of diaphragm to shear wall was also investigated. Based on preliminary findings from this study, contrary to common belief, the forces transferred by a semi-rigid diaphragm to the supporting shear walls, may be higher than those predicted by flexible and rigid diaphragm assumptions.

On the Fire Performance of Double-shear Timber Connections

In heavy timber structures, double-shear connections, including wood-wood-wood (WWW), wood-steelwood (WSW) and steel-wood-steel (SWS) connections with either bolts or dowels as fasteners, are widely used to assembly structural members and transfer loads. However, connections with metal fasteners and components are potentially venerable links in fire exposure. A number of efforts have been devoted to study the fire performance of timber connections in the last two decades. With the knowledge and experimental data generated, new attempts have been made in order to develop new calculation methods and improve design rules for timber connections in fire. In this paper, existing models are discussed and new correlations are presented for the calculation of the fire resistances of double-shear timber connections. Various factors, i.e. timber thickness, fastener diameter, and load ratio are considered in the correlations. Comparison between the predictions using the correlations and the measured results in fire resistance tests shows good agreement. For timber connections with protective membranes, the component additive method (CAM) can be used by adding the additive fire resistances of the protective membranes to the fire resistances of unprotected timber connections. Connections with concealed fasteners and intumescent paint are also discussed in this paper.