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While the use of cross-laminated timber (CLT) panels for building construction has increased over the last several decades, current standards and existing literature provide limited information regarding the design of CLT diaphragms or the prediction of their deflections when subjected to wind and strong earthquake motions. This paper presents the design and assessment of a CLT diaphragm that was part of a full-scale two-story structure subjected to shake-table testing. An analytical model is proposed for diaphragm deflection accounting for in-plane shear and bending stiffness, as well as the stiffness of various connections. Moreover, a refined numerical modeling strategy is proposed in order to consider phenomena such as panel-to-panel gap closure. Results indicate that the analytical model yields conservative results both in terms of deflections and forces when compared to the numerical model that simulates similar sources of strength and stiffness. The analytical model is suitable for the design of symmetric diaphragms with regular shapes, whereas the numerical model can also be used to model asymmetric diaphragms with irregular shapes. [ABSTRACT FROM AUTHOR]

Displacement-based seismic design often requires nonlinear time history simulation of building responses which is computationally intensive. This technical note presents an artificial neural network (ANN) designed to generate max inter-story drift for buildings with post-tensioned mass timber (MT) rocking walls systems. This particular lateral system was selected because it is an innovative system with limited physical design parameters, making it an ideal candidate for ANN. The proposed model achieved significantly higher computational efficiency than time history simulation, while maintaining similar level of accuracy. The proposed method could potentially be used for automated design of MT rocking wall lateral systems. [ABSTRACT FROM AUTHOR]

A full-scale 2-story mass timber building was tested on the University of California San Diego Natural Hazards Engineering Research Infrastructure (UCSD-NHERI) uniaxial shake table during the period from June 2017 to September 2017. The main objective of the experimental program was to test the performance of mass timber building designs with different seismic lateral force–resisting systems. The focus of this study is on a building configuration designed using self-centering post-tensioned cross-laminated timber (CLT) rocking walls with U-shaped steel flexural plate energy dissipators. The shake-table tests were designed to subject the building to a series of earthquake ground motions of increasing intensity, ranging from a service-level earthquake to 1.20 times the maximum considered earthquake intensity. Between each ground motion, low-amplitude white-noise excitations were applied to the building, which responded as a quasilinear system. In this paper, two output-only operational modal analysis methods are used to estimate the modal parameters (frequency, damping, and mode shapes) based on acceleration data collected during the white-noise shake-table tests. The correlations of observed damage and repairs performed during the experimental program with changes in estimated modal features are reported. The modal parameters estimated from the testing program are also compared with a linear finite-element model that is used to validate the modal identification results and study the performance of the two system identification methods for CLT rocking structures. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) is a wood construction technology that has been utilized in Europe for several decades and has become even more popular recently. Although the technology has been in existence for approximately 20 years, its seismic performance has been explored only recently by a handful of researchers. Interest in bringing CLT to the North American construction market necessitates a full understanding of the seismic behavior of CLT systems and the development of a response-modification factor, known as the R-factor, for use in force-based seismic design codes. In this paper, a nonlinear, load-resistance model for CLT shear walls is developed based on reversed-cyclic test data and explained. An estimation of a possible R-factor is obtained by developing a design for a 6-story CLT apartment building, based on computed peak interstory drifts, to achieve good performance in a high seismic region of the United States. It is concluded that using the equivalent lateral force procedure with an R-factor close to 4.5 likely will provide an 80% probability of not exceeding 4% peak interstory drift during a maximum credible earthquake (MCE) near Los Angeles, CA (i.e., an earthquake with a return period of 2,500 years). [ABSTRACT FROM AUTHOR]

With two producers in operation and over 20 buildings already constructed or in planning process, use of cross-laminated timber (CLT) is gaining popularity in Canada. Since CLT as a structural system is currently not included in the National Building Code of Canada (NBCC), one of the most important issues are the values for the force modification factors for seismic design of CLT structures when NBCC equivalent static force procedure is used. In this study, a test-calibrated numerical model for CLT shear walls was applied to develop the design resistances for typical CLT wall configurations. An estimation of a possible range of Rd-factors was obtained by developing design variations for three multi-storey CLT apartment buildings. By specifying the desired seismic performance in terms of inter-storey drift, it is concluded that an Rd-factor of 2.0 will likely provide desirable building performance during the design earthquake level event in Vancouver, B.C. [ABSTRACT FROM AUTHOR]

The understanding of, and ability to predict, the seismic behavior of woodframe structures has improved immensely in the last 10 years. Two notable projects occurred in succession, the Consortium of Universities for Research in Earthquake Engineering (CUREE) and California Institute of Technology (Caltech) CUREE-Caltech Woodframe Project, and the Network for Earthquake Engineering Simulation (NEES) NEESWood Project, which provided greater understanding, improved analytical modeling, and advances in force- and performance-based seismic design (PBSD) of woodframe buildings, respectively. The NEESWood project focused on the development of a PBSD philosophy (and procedures) for midrise woodframe buildings and included full-scale system-level validation. To date, the complete design procedure has not been systematically explained, which serves as the impetus for this paper. While the method was shown to be quite viable, some challenges remain, including identifying a format that would facilitate widespread adoption and use by engineers. Thus, this paper examines the progress, current state, and challenges for PBSD of midrise woodframe buildings. [ABSTRACT FROM AUTHOR]

In July 2009, a full-scale midrise light-frame wood apartment building was subjected to a series of earthquakes at the world's largest shake table in Miki, Japan. This article focuses on the test results of that full-scale six-story light-frame wood building. The objectives of the testing program were to (1) demonstrate that the performance-based seismic design procedure developed as part of the NEESWood project worked on the full-scale building, i.e., validate the design philosophy to the extent one test can and (2) gain a better understanding of how midrise light-frame wood buildings respond, in general, to a major earthquake while providing a landmark data set to the seismic engineering research community. The building consisted of 1,350 m2(14,000 ft2) of living space and had 23 apartment units; approximately one-half one-bedroom units and one-half two-bedroom units. The building was subjected to three earthquakes ranging from seismic intensities corresponding to the 72-year event to the 2,500-year event for Los Angeles. In this paper, the construction of the NEESWood Capstone Building is explained and the resulting seismic response in terms of base shears, selected wall drifts, global interstory drifts, accelerations, hold-down forces, and roof drifts are presented. Detailed damage inspection was performed following each test and those results are summarized also. The building performed excellently with little damage even following the 2,500-year earthquake. The global drift at roof level was approximately 0.25 m and maximum interstory drifts were approximately 2% for the floor average with individual wall drifts reaching just over 3% in one corner of the building at the fifth story. [ABSTRACT FROM AUTHOR]

In July 2009, a full-scale six-storey platform wood frame apartment building was subjected to a series of earthquakes at the world's largest shake table in Miki, Japan. Two double-midply shear wall stacks were installed in the building from the first storey through to the fifth storey. A continuous anchor tie-down system (ATS) was used to prevent overturning and allow the shear walls to develop their full lateral load capacities. This paper focuses on the behavior of the stacked double-midply shear wall in a full-scale midrise building during a series of triaxial shakes scaled for the city of Los Angeles, California. The stacked midply shear wall achieved a maximum interstorey deformation of 40.4 mm (equivalent to 1.64% drift). The uplift forces measured at the bottom storey of the stacked wall exceeded 760 kN, indicating the need for substantial tie-down systems for this type of wall when utilized in a midrise platform wood frame building. En juillet 2009, un immeuble résidentiel à charpente en bois à plateforme de six étages à plein échelle a été soumis à une série de séismes sur la plus grande table de vibration au monde à Miki, au Japon. Deux empilements de murs de contreventement à doubles contreplaqués au centre ont été installés dans l'immeuble du premier jusqu'au cinquième étage. Un système d'ancrage à fixation continue (« ATS ») a été utilisé pour prévenir le renversement et permettre aux murs de contreventement de développer leur pleine capacité de porter la charge latérale. Le présent article porte sur le comportement d'un mur de contreventement empilé à doubles contreplaqués dans un immeuble de hauteur moyenne à pleine échelle durant une série de secousses triaxiales mises à l'échelle pour la Ville de Los Angeles, Californie. Le mur empilé de contreventement à doubles contreplaqués au centre a atteint une déformation maximale de 40,4 mm entre les étages (équivalent à une dérive de 1,64 %). Les forces de soulèvement mesurées à l'étage inférieur du mur empilé ont dépassé 760 kN, indiquant le besoin d'avoir des systèmes de fixation importants pour ce type de mur lorsqu'il est utilisé dans un immeuble de hauteur moyenne à charpente de bois à plateforme. [ABSTRACT FROM AUTHOR]

Performance-based seismic design (PBSD) of wood frame structures has been only preliminarily investigated by a handful of researchers around the world and is currently under development in the United States as well as other countries worldwide. This paper presents the basic concept of applying system identification logic as one alternative for PBSD of wood frame structures. In PBSD of wood frame structures, one prescribes combinations of hazard level and corresponding performance, and “designs” the system such that these performance metrics are met. For wood frame buildings this procedure fits the definition of a system identification problem, i.e., the input and output are known and the nonlinear system between them is sought. In most cases the shearwall locations, i.e., geometry, are known, and only the wall design is sought. In this paper, the concept is presented and a procedure to apply it within a PBSD framework is proposed. The validity of the procedure is confirmed through two illustrative examples, namely the design for a two-story wood shearwall and a two-story wood frame building. An existing ten-parameter hysteresis model commonly used for seismic analysis of wood frame structures was used in both examples to represent the nonlinear system to be identified. The “design” is then checked by applying a suite of ordinary ground motion records and comparing the multirecord incremental dynamic analysis of the peak deformation response to the target (performance) curve. The approach was found to work well for the example structures and shows promise for extension to more complicated structures and performance measures. [ABSTRACT FROM AUTHOR]

• The limits of traditional PBSD requirements for mass timber building is presented. • The process to combine traditional design and GA optimization is illustrated. • Two examples are designed and were shown to result in different designs. This paper presents a rational procedure to optimize design for mass timber rocking wall systems utilizing a genetic algorithm (GA) beyond typical displacement-based design metrics for wood buildings. Traditional displacement-based design is limited to simple displacement targets, with optimization techniques (GA), it is feasibly to consider more performance chrematistics (e.g. costs, serviceability, etc.). By formulating drift targets and other structural design limit states within an elimination step of the GA optimization process, the method proposed here optimizes rocking wall design with multiple criteria that factor much more than lateral displacement targets in the seismic analysis. This type of optimization is difficult to perform using traditional manual trial-and-error approaches. An existing simplified nonlinear time-history simulation model (validated through full-scale shake table test data) of a wood rocking wall is employed in this process. The design for an example building in Seattle with a six-story rocking wall is presented using the proposed procedure. The results revealed that the optimization of the mass timber rocking wall lateral system can be achieved in a reasonable time frame using the proposed method. Even though the same drift limits were applied, final designs produced by GA varied, depending on the other optimization objectives. This demonstrates how the seismic design of wood rocking wall systems could be readily improved with computerized optimization tools that factor in other aspects of the design including cost. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an empirical seismic loss analysis procedure for woodframe buildings and examines how it can be utilized to provide input for the development of seismic performance objectives for woodframe buildings in terms of economic loss. This type of performance measure is more directly useful to building owners than qualitative performance levels such as “Life Safety” proposed in first generation performance-based seismic design documents. The procedure combines the PEER loss estimation methodology with the most up-to-date seismic numerical structural models for woodframe buildings and experimental data from full-scale shake table tests. The resulting loss estimates are quite reasonable when compared to observations from the 1994 Northridge, CA earthquake. The procedure is applied to two-story, single-family residential structures to estimate losses as a function of ground motion intensity and building design, and the results are discussed to illustrate how they can be used to help: (1) characterize estimated losses, (2) define performance objectives, and (3) guide design to meet those performance objectives. The study provides the first fully comprehensive application of the PEER methodology to woodframe buildings. [Copyright &y& Elsevier]

In the US, codified seismic design procedure requires the use of seismic performance factors which are currently not available for CLT shear wall systems. The study presented herein focuses on the determination of seismic design factors for CLT shear walls in platform type construction using the FEMA P-695 process. Results from the study will be proposed for implementation in the seismic design codes in the US. The project approach is outlined and selected results of full-scale shear wall testing are presented and discussed. Archetype development, which is required as part of the FEMA P-695 process, is briefly explained with an example. Quasi-static cyclic tests were conducted on CLT shear walls to systematically investigate the effects of various parameters. The key aspect of these tests is that they systematically investigate each potential modelling attribute that is judged within the FEMA P-695 uncertainty quantification process. Boundary constraints and gravity loading were both found to have a beneficial effect on the wall performance, i.e. higher strength and deformation capacity. Higher aspect ratio panels (4:1) demonstrated lower stiffness and substantially larger deformation capacity compared to moderate aspect ratio panels (2:1). However, based on the test results there is likely a lower bound for aspect ratio (at 2:1) where it ceases to benefit deformation capacity of the wall. This is due to the transition of the wall behaviour from rocking to sliding. Phenomenological models were used in modelling CLT shear walls. Archetype selection and analysis procedure was demonstrated and nonlinear time history analysis was conducted using different wall configurations. [ABSTRACT FROM AUTHOR]