Monitoring Dynamic Properties of a Pres-Lam Structure: Trimble Navigation Office

Abstract

Pres-Lam technology relies on unbonded post-tensioning tendons to provide moment capacity to timber beam-column, wall-foundation, or column-foundation connections. When designing buildings for high-seismic-risk areas, additional energy dissipation can be introduced by mild steel bars or replaceable damping devices. After a comprehensive testing program started in 2005, Pres-Lam technology was implemented in several buildings in New Zealand and worldwide. Although extensive information regarding test results is present in the literature, little information is available about the actual behavior of buildings in practice. This paper shows how an operative Pres-Lam structure performed as monitored over a 3-year period. Results show that the natural properties of the building are independent of the average post-tensioning loss, which was found to be equal to 5% in 3 years. Due to the natural torsional behavior of the building, the accelerations recorded were found to be around 25% higher than the spectral ones. Despite this fact, the building responded elastically to a moderate seismic event, as per design.