This paper presents an investigation of possible disproportionate collapse for a nine-storey flat-plate timber building, designed for gravity and lateral loads. The alternate load-path analysis method is used to understand the structural response under various removal speeds. The loss of the corner and penultimate ground floor columns are the two cases selected to investigate the contribution of the cross-laminated timber (CLT) panels and their connections, towards disproportionate collapse prevention. The results show that the proposed building is safe for both cases, if the structural elements are removed at a speed slower than 1 sec. Disproportionate collapse is observed for sudden element loss, as quicker removal speed require higher moments resistance, especially at the longitudinal and transverse CLT floor-to-floor connections. The investigation also emphasises the need for strong and stiff column-to-column structural detailing as the magnitude of the vertical downward forces, at the location of the removed columns, increases for quicker removal.
March 29-31, 2012, Chicago, Illinois, United States
This paper describes initial experimental testing to investigate feasible sources of passive damping for the seismic design of post-tensioned glue laminated timber structures. These innovative high performance structural systems extend precast concrete PRESSS technology to engineered wood structures, combining the use of post-tensioning bars or cables with large post-tensioned timber members. The combination of these two elements provides elastic recentering to the structure while the addition of damping using a specialised energy dissipation system gives the desirable `flag shaped' hysteretic response under lateral loading. Testing has been performed on a full scale beam-column joint at the University of Basilicata in Italy in a collaborative project with the University of Canterbury, New Zealand. The experimental testing uses engineered wood products, extending the use of laminated veneer lumber (LVL) structures tested in New Zealand to testing of glue laminated timber (glulam) structures in Italy. Current testing is aimed at further improvement of the system through additional energy dissipation systems.