Development and testing of an alternative dissipative posttensioned rocking timber wall with boundary columns

The unbonded posttensioned rocking and dissipative technology was first developed as the main outcome of the PREcast seismic structural systems (PRESSS) Program in the United States. After the first developments and significant refinement, the technology was extended to steel and, more recently, timber structures. The timber version, referred to as prestressed laminated (Pres-Lam) system can be either implemented for timber walls (single or coupled) or frames or a combination of the above, with unbonded posttensioning and supplemental dissipation devices. In unbonded posttensioned dissipative wall systems a combination of recentering capacity and energy dissipation leads to a controlled rocking mechanism, which develops a gap opening at the wall base. This generates an uplift displacement that is transferred to the floor diaphragm. This vertical displacement incompatibility can represent a potential issue if the connection detailing between floor and lateral resisting system is not designed properly. The same issue can be mitigated by adopting an alternative configuration of the rocking/dissipative wall system, based on the use of a column-wall-column posttensioned connection. This concept, originally proposed for precast concrete walls and referred to as prestressed wall with end column (PreWEC), has been extended and adapted to posttensioned timber structures and validated through experimental testing. The paper presents the design, detailing, and experimental testing of a two-thirds scale wall specimen of this alternative configuration. Different wall configurations are considered in terms of posttensioning initial force as well as dissipation devices layout. The experimental results confirm the excellent seismic performance of the system with the possibility to adopt multiple alternative configurations.