Project contact is Daniel Dowden at Michigan Technological University
Summary
This award will investigate a low-damage solution for cross-laminated timber (CLT) seismic force-resisting systems (SFRSs) using a novel uplift friction damper (UFD) device for seismically resilient mass-timber buildings. The UFD device will embrace the natural rocking wall behavior that is expected in tall CLT buildings, provide stable energy dissipation, and exhibit self-centering characteristics. Structural repair of buildings with these devices is expected to be minimal after a design level earthquake. Although CLT has emerged as a construction material that has revitalized the timber industry, there exists a lack of CLT-specific seismic energy dissipation devices that can integrate holistically with the natural kinematics of CLT-based SFRSs. CLT wall panels themselves do not provide any measurable seismic energy dissipation. As a payload to the large-scale, ten-story CLT building specimen to be tested on the Natural Hazards Engineering Research Infrastructure (NHERI) shake table at the University of California, San Diego, as part of NSF award 1636164, “Collaborative Research: A Resilience-based Seismic Design Methodology for Tall Wood Buildings,” this project will conduct a series of tests with the UFD devices installed on the CLT building specimen. These tests will bridge analytical and numerical models with the high fidelity test data collected with realistic boundary and earthquake loading conditions. The calibrated models will be incorporated in a probabilistic numerical framework to establish a design methodology for seismically resilient tall wood buildings, leading to a more diverse and eco-sustainable urban landscape. This project will provide local elementary school outreach activities, integrate participation of undergraduate minorities and underrepresented groups into the research activities, and foster graduate level curriculum innovations. Project data will be archived and made available publicly in the NSF-supported NHERI Data Depot (https://www.DesignSafe-CI.org). This award contributes to NSF's role in the National Earthquake Hazards Reduction Program (NEHRP).
The research objectives of this payload project are to: 1) bridge the fundamental mechanistic UFD models linking analytical and numerical models necessary for seismic response prediction of seismically resilient CLT-based SFRSs, 2) characterize the fundamental dynamic UFD behavior with validation and calibration through large-scale tests with realistic boundary conditions and earthquake loadings, and 3) integrate low-damage, friction-based damping system alternatives within a resilience-based seismic design methodology for tall wood buildings. To achieve these objectives, the test data collected will provide a critical pathway to reliably establish numerical and analytical models that extend the shake table test results to a broad range of archetype buildings. The seismic performance of mass-timber archetype building systems will be established through collapse risk assessment using incremental dynamic analyses. This will provide a first step in the longer term goal of establishing code-based seismic performance factors for CLT-based SFRSs.
This document outlines the basis of design for the performance-based design and nonlinear response history analysis of the Framework Project in Portland, OR. It is intended to be a living document that will be modified and revised as the project develops and in response to peer review comments.
Performance-based design is pursued for this project because the proposed lateral force-resisting system, consisting of post-tensioned rocking cross-laminated timber (CLT) walls is not included in ASCE/SEI 7-10 Table 12.2-1. Lateral force-resisting systems included in ASCE/SEI 7-10 Table 12.2-1 may be designed for earthquake effects using the prescriptive provisions in ASCE/SEI 7- 10. Lateral force-resisting systems not included are still permitted but must be demonstrated to have performance not less than that expected for included systems. This option is available via the performance-based procedures of ASCE/SEI 7-10 Section 1.3.1.3. Note that lateral forceresisting systems for wind effects are not restricted in ASCE/SEI 7-10. Therefore, design for wind effects will still be approached within the performance-based design framework but in a more state-of-the-practice manner.
Project contact is Thomas Miller at Oregon State University
Summary
Understanding how roof and floor systems (commonly called diaphragms by engineers) that are built from Pacific Northwest-sourced cross-laminated timber (CLT) panels perform in earthquake prone areas is a critical area of research. These building components are key to transferring normal and extreme event forces into walls and down to the foundation. The tests performed in this project will provide data on commonly used approaches to connecting CLT panels within a floor or roof space and the performance of associated screw fasteners. Structural engineers will directly benefit through improved modeling tools. A broader benefit may be increased confidence in the construction of taller wood buildings in communities at greater risk for earthquakes.
This paper describes the structural design of low-rise multi-storey timber buildings using a new and exciting structural system. This system, originally developed for use with pre-cast concrete, combines un-bonded post-tensioning and additional energy dissipaters, providing a recentering capability after the earthquake, while greatly reducing the structural damage. This new structural system can be used in multi-storey buildings, with large structural timber members made from laminated veneer lumber (LVL) or glulam timber, with lateral loads resisted by prestressed timber frames or walls, separately or in combination. A case study of a six storey timber office building in a moderate seismic area is analysed and a virtual design is carried out, allowing investigation of different methods of structural analysis, and development of many construction and connection details for rapid construction. Total building cost is compared to equivalent steel and reinforced concrete options.
Journal of Structural and Construction Engineering: Transactions of AIJ
Summary
In this paper, the new type of seismic retrofit method using CLT panels as shear walls is proposed. In this method, setting small CLT panels in RC frame and bonding each panel and panel to RC frame with epoxy resin, panels compose shear walls. The advantages of this technique are: There are less dust, noise, and vibration during construction; Light weight panels enable easy construction and short construction period; Light weight panels also cause small seismic force.
In this research, cyclic loading tests for 5 types of reinforced specimens and 2 types of plain RC frames as control were conducted.
The stress analysis showed that the bond strength between CLT and RC and shear modulus of CLT in these specimens match the result of element tests. So the specimen strength could be divided into the RC frame strength and the CLT strength until the initial deformation. As the bond strength between CLT and RC was smaller than the shear strength of CLT, the specimens can be stronger by increasing the adhesive area.
The construction materials used in the building tall structures are responsible for extremely high carbon emissions. Therefore, to address this issue building designers are constantly looking at alternative sustainable construction materials. A new type of timber called MassTimber as a material for construction is now attracting the building designers because of its sustainability advantages. Mass-timber is an innovative type of engineered timber with improved structural properties making it suitable for the construction of tall and heavy structures. This paper is intended to study the performance of tall mass-timber buildings under the most severe dynamic loading conditions of India. Three models of mass-timber buildings are analyzed in ETABS under the seismic and wind loads according to the demands of most severe earthquake zone-V and one of the windiest regions at Bhuj, India. It is observed that the mass participation during seismic activities is considerably low and the wind loads are considerably higher than the seismic loads. It is concluded that with a suitable lateral load resisting structural system mass-timber buildings can perform adequately.
