The paper presents a numerical study conducted on a seven storey cross-laminated (X-lam) buildings equipped with translational Tuned Mass Dampers (TMD’s), as a technique for reducing the notoriously high drifts and maximum seismic accelerations of these types of structures. The building was modelled in the finite element software package Abaqus using 2D elastic shell elements and non-linear springs, which were implemented as an external user subroutine and properly calibrated to simulate the cyclic behavior of connectors in X-lam buildings. The used TMD device is linear, and placed on the top of the building. Time-history dynamic analyses were carried out under natural earthquake ground motions. Several comparisons between the response of the structure with and without TMD are presented, and the effectiveness and limits of these devices to improve the seismic performance of X-lam buildings are critically discussed.
This paper presents the results of an experimental study whose objective was to investigate the behavior of a hybrid wood shear-wall system defined herein as a combination of traditional light-frame wood shear walls with post-tensioned rocking Cross-Laminated Timber (CLT) panels. The post-tensioned CLT panels in the hybrid system offer both vertical and lateral load resistance and self-centering capacities. The traditional Light-Frame Wood Systems (LiFS) provide additional lateral load resistance along with a large amount of energy dissipation through the friction of nail connections. Thus, a combination of these two types of structures, in which traditional light-frame wood shearwalls are utilized as structural partition walls, may provide an excellent structural solution for mid-rise to tall wood buildings for apartments/condos, where there is a need for resisting large lateral and vertical loads as well as structural stability. In this study, a real-time hybrid testing algorithm using a combination of time-delay updating and Newmark-Beta feed forward to reduce the undesirable effects of time delay was introduced. The top two-stories of a three-story building were modeled as a numerical substructure with the first story as the experimental CLT-LiFS substructure. The experimental results of the hybrid wall are presented and discussed in this paper.
Cross laminated timber (CLT) is a new panelized mass timber product that is suitable for building tall wood buildings (higher than eight stories) because of its structural robustness and superior fire resistance as compared with traditional light-framed ...
Project contact is Daniel Dowden at Michigan Technological University
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 paper presents the preliminary design of a rocking Cross-laminated Timber (CLT) wall using a displacement-based design procedure. The CLT wall was designed to meet three performance expectations: immediate occupancy (IO), life safety (LS), and collapse prevention (CP). Each performance expectation is defined in terms of an inter-story drift limit with a predefined non-exceedance probability at a given hazard level. U-shape flexural plates were used to connect the vertical joint between the CLT panels to obtain a ductile behavior and adequate energy dissipation during seismic motion. A design method for ensuring self-centering mechanism is also presented.
In this project, a conceptual but realistic 20-storey building of hybrid construction incorporating massive timber panels and other structural materials was identified. The project team, consisting of three practicing consultants and 6 graduate student and post-doctoral researchers from NEWBuildS, undertook an analysis and engineering design of the demonstration building. An advisory group that includes FPInnovations scientists, NEWBuildS supervisors of the graduate students and Post Doctoral Fellows, provides technical support to the project team. The performance attributes addressed in the project were structural performance under seismic and wind load, fire resistance and building envelope. . This publication documents the analysis and design of the demonstration building, and identifies technical issues that require further study.
Project contact is Mark Fretz at the University of Oregon
University of Oregon and Oregon State University are collaborating through TallWood Design Institute (TDI) to upgrade aging, energy inefficient and seismically unprepared multifamily housing by developing a mass plywood (MPP) retrofit panel assembly that employs digital workflows and small diameter logs (down to 5") to create an economically viable energy/seismic retrofit model for the West Coast and beyond. The project has broad potential to support forested federal land management agencies and private forestry by proving a new market for small diameter logs.