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.
This paper investigates the risk of disproportionate collapse following extreme loading events. The methodology mimics a sudden removal of a loadbearing wall of a twelve-storey CLT building. The ductility-demand from the dynamic simulation is checked against the ductility supplied by the structural components and their connections. The analyses focus on rotational stiffness (k) of the joints by considering three different sub-structural idealisations according to the required modelling details and the feasibility of model reductions. To resist the imposed dynamic forces, the required k-values may be too large to be practically achieved by means of off-the-shelf brackets and screw connections. Improved structural detailing as well as adequate thickness of structural elements need to be considered in order to reduce the probability of disproportionate collapse.
Timber-concrete-composite (TCC) floors, composed of timber and concrete layers connected by a shear connector are a successful example of hybrid structural components and are commonly used in practical applications.The connection of the two components is usually achieved with mechanical fasteners where relative slip cannot be prevented and the connection cannot be considered rigid. The growing availability of panel-type engineered wood products (EWPs) offers versatility in terms of architectural expression and structural and building physics performance. Preceding research determined the properties for a range of TCC connector systems in several EWPs using full-scale short-term bending tests. In the research presented herein, nine TCC floor segments (one specimens of each previously investigated configuration) were exposed to serviceability loads for approximately 2.5 years. During this time, the environmental conditions and the deflections of each floor were monitored. After having been long-term loaded, the floor segments were tested to failure. The results show an increase of deflection over time but neither bending stiffness,load-carrying capacity nor vibration performance were impacted by the long-term loading. This research provides input data to develop design guidance for TCC floors.