K.M. Solberg

High-Force-to-Volume Seismic Dissipators Embedded in a Jointed Precast Concrete Frame

An experimental and computational study of an 80-percent scale precast concrete 3D beam-column joint subassembly designed with high force-to-volume (HF2V) dampers and damage-protected rocking connections is presented. A prestress system is implemented using high-alloy high-strength unbonded thread-bars through the beams and columns. The thread-bars are posttensioned and supplemental energy dissipation is provided by internally mounted lead-extrusion dampers. A multilevel seismic performance assessment (MSPA) is conducted considering three performance objectives related to occupant protection and collapse prevention. First, bidirectional quasi-static cyclic tests characterise the specimen’s performance. Results are used in a 3D nonlinear incremental dynamic analysis (IDA), to select critical earthquakes for further bidirectional experimental tests. Thus, quasi-earthquake displacement tests are performed by using the computationally predicted seismic demands corresponding to these ground motions. Resulting ...

Seismic Performance of Damage-Protected Beam-Column Joints

This paper presents an experimental and computational study on the bidirectional behavior of a precast concrete three-dimensional (3D) beam-column joint subassembly designed with damage-protected rocking connections. A prestress system is implemented in which high-alloy, high-strength, unbonded threaded bars running through the beams are coupled to rods within the columns. The threaded bars are posttensioned and supplemental energy dissipation devices are also installed. Both wet and dry joint solutions are considered. The authors conducted a multilevel seismic performance assessment considering three performance objectives related to immediate occupancy and collapse prevention. First, bidirectional quasistatic cyclic tests were conducted and the specimen’s performance was characterized. This data was then used in a 3D nonlinear incremental dynamic analysis (IDA). Results from the IDA were used to select three critical earthquakes for further experimental bidirectional testing. Thus, quasi-earthquake displacement tests were performed. Results indicate the tested specimen met all 3 seismic performance objectives. In precast rocking frames designed to damage-avoidance principles, a cast-in-place closure pour at one beam end helps to alleviate construction tolerance issues and ensures the face of the beam is aligned properly with the column. The performance of such joints was found to be satisfactory.