Experimental investigation on the pull-out force of modified purlin to rafter connections

In Malaysia, almost all houses in rural area are non-engineered structures. The roof of these houses is susceptible to failure and many types if roofing failure can be expected. This study examines the pull-out capacity of several simple connections meant for tying the timber purlin to rafter. The types of connections are single nail, double nail, nail plus metal strap and nail plus rope. The tests were conducted on timber type Damar Minyak (Araucariaceae), commonly used for the purlin and rafter assembly of rural houses. The wind load was applied in the form of pull-out force generated via in-house frame and Universal Testing Machine. The results from the pull-out force versus nail displacement exhibited unique features for each type of connection. In the case of a single nail connection, the graph showed two phases. When the single nail is combined with another nail or metal strap or rope, the responses exhibited in three distinct phases. The first phase for every type of connections showed linear relationship. The failure pattern for nail only (single and double) showed gentle degradation of the connection strength. However, for nail and metal strap connection, the strength degradation was abrupt due to the yielding of the metal strap. On the other hand, for nail and rope connection, the failure phase was cascaded due to the progressive snapping of the jute fibre. The highest the pull-out resistance based on the maximum pull-out force was shown by the nail and metal strap connection.