Inertial Force Limiting Floor Anchorage Systems for Seismic-Resistant Building Structures
Project Overview
The objective of the proposed research is to develop new knowledge of the dynamic behavior of building structures with an innovative floor anchorage system that reduces inertial forces while maintaining a centered floor. With this knowledge, the research will determine the appropriate design parameters for this system to produce optimal seismic performance for a variety of building geometries and properties. The ultimate goal of the research is to produce feasible prototype designs for one or more candidate structures that can be used in dissemination of the concept to the practice.
The concept is an inertial force-limiting self-centering floor anchorage system for seismic resistant building systems. In this system, different than floor isolation systems as have been proposed previously, the connection to the primary lateral force resisting system (LFRS) is initially stiff and strong, and intended to transfer the ground motion excitation to the structure without relative movement of the floor. However, at a predefined force level, the primary transfer mechanism “cuts-off”. At this point, the anchorage dissipates energy through the relative motion of the floor to the primary LFRS elements (e.g. walls, frames). The relative movement of the floor is limited (targeted at ~10cm) and ultimately removed through an elastic restoring force in parallel with the ductile connection, along with the inherent resistance of the gravity load resisting system columns.
The system has the potential to:
- Reduce structural damage by lowering the seismic forces acting on the building
- Reduce non-structural damage to contents and equipment by lowering floor accelerations
- Eliminate the potential for non-ductile shear failure in core walls and shear walls
- Mitigate the potential for floor diaphragm failures
The trade-off occurs as increased relative motion of the floors, which will require seismic joints, special architectural details, and attention to stability of the gravity system. The performance targets are:
- Reduce floor accelerations from~4X to no PGA amplification
- Reduce LFRS damage tominimal or none
- Floor relative movement within an acceptable range (2”-4”) in the DBE and MCE
- Gravity system drift demands within 2% drift in DBE; 3% drift in MCE
Phase |
Position of Shear Wall |
Loading |
Energy Dissipation Devices |
Ia |
Fixed Vertical |
One direction cyclic dynamic in plane |
BRB + Rubber Bearings |
IIa |
Rotated out of plane 0.02 rad |
One direction cyclic dynamic in plane |
BRB + Rubber Bearings |
Ib |
Fixed Vertical |
One direction cyclic dynamic in plane |
LFD + Rubber Bearings |
IIb |
Rotated out of plane 0.02 rad |
One direction cyclic dynamic in plane |
LFD + Rubber Bearings |
IIIb |
Free to rotate out of plane – dynamic motion |
Two directions cyclic dynamic in plane and out of plane |
LFD + Rubber Bearings |
Ic |
Vertical |
Hybrid Simulation Test – One direction cyclic dynamic in plane |
LFD + Rubber Bearings |
Participants
Principal Investigator
- Robert B Fleischman – University of Arizona
Co-Principal Investigators
- Jose Restrepo – University of California – San Diego
- Richard Sause – Lehigh University
Research Staff
- Dichuan Zhang – University of Arizona
Design Consultants
- Joseph Maffei – Rutherford & Chekene
- David Mar – Tipping Mar
International Collaborators
- Giorgio Monti – University of Rome, La Sapienza
- Alessandro Scodeggio – University of Rome, La Sapienza
- Giuseppe Marano – Tech. University of Bari
Graduated Students
- Georgios Tsampras – Lehigh University
- Zhi Zhang – University of Arizona
- Steve Mintz – University of California – San Diego
- Arpit Nema – University of California – San Diego