ERI: Developing Ductility through Replaceable Concrete Anchorage Connections for Improved Seismic Performance of Mass Timber Structures

This Engineering Research Initiation (ERI) award supports research to develop an improved seismic resistant timber-concrete connection using replaceable ductile-anchor rods for rapid post-earthquake repair. Of growing interest in the United States, mass timber buildings hold a relevant place in the history of world architecture and construction. To meet the modern design philosophy in regions vulnerable to seismic hazards, mass timber buildings are designed to remain safe during large earthquakes by focusing damage, ductility, and seismic energy dissipation in the connections. However, these mechanisms inevitably induce building damage and affect the overall building post-earthquake occupancy, functionality, and repairability, ultimately impacting community resiliency. The improved timber-concrete connection will mitigate the impact of seismic damage in timber structural components and enhance seismic resiliency by enabling a reliable ductile mechanism to dissipate energy in the anchor connecting timber components to the concrete footing and allowing replacement of the stretched anchor rod after damage. Component testing will investigate the seismic behavior of timber-concrete connections and a numerical study will expand these findings to evaluate additional design parameters toward the development of design suggestions and modeling recommendations suitable for engineering practice. The research activities will be incorporated into an in-class course module in structural engineering and will engage underrepresented groups in engineering through outreach programs. Project data will be archived and made publicly available in the Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (https://www.DesignSafe-ci.org). The main mechanisms of failure observed in timber-concrete connections include plastic deformations of the small diameter fasteners connecting the steel plates to the timber component and plasticization of the steel plate itself, with consequent damage in the attached timber element. The improved ductile-anchor connection focuses on the concept of anchor deformation to promote overall enhanced structural robustness, ductility, and strength, limiting the damage in the plate and in the connected timber component and accelerating the repair of timber buildings in post-earthquake scenarios. The project research objectives include exploring (1) the seismic behavior of the ductile-anchor connection and its residual capacity after repair, and (2) analytical methods relating the overall structural seismic demand to the connection capacity. Simulated seismic tests of timber-concrete connection prototypes with ductile anchor and replaceable thread rod will be conducted to investigate the new connection design and the effect of anchor stretch length on the overall performance of the connection. The response of a broader range of connection configurations will be studied using experimentally validated finite-element analysis to inform design and modeling guidelines for practicing engineers. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.