Preventing seismic damage to floors in post-tensioned timber frame buildings

Post-tensioned rocking structures are known to perform well under seismic action, but as with most other structuralsystems, there is concern about possible damage to floor diaphragms. This is due to displacement incompatibilities,especially if frame elongation occurs due to gap opening at the beam-column-joints. This paper describes theexperimental behaviour of an engineered timber floor connected to a post-tensioned timber frame subjected tohorizontal seismic loading.A full scale two-bay post-tensioned frame was loaded with lateral loads, which were applied through a strip of floordiaphragm spanning perpendicular to the beams. Several different connection configurations between the floor portionson either side of the central column were tested. The diaphragm deformation demand adjacent to the beam-column-joint gap opening was accommodated through two mechanisms: a concentrated floor gap opening at the column or acombination of panel elongation and small gap openings over a number of floor elements. In all the tests, only elasticdeformations were observed and the diaphragm behaviour of the floor elements was fully maintained throughout thetesting.The results showed that design to allow flexibility of timber elements combined with proper connection detailing canprevent damage at high level of drift to the floor diaphragms in post-tensioned timber frame buildings.