Marjan Popovski

Approximate R-Factor for Cross-Laminated Timber Walls in Multistory Buildings

AbstractCross-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 ...

Damage Assessment of Connections Used in Cross-Laminated Timber Subject to Cyclic Loads

AbstractCross-laminated timber (CLT) products are gaining popularity in the North American market and are being used in midrise wood buildings, in particular, in shearwall applications. Shearwalls provide resistance to lateral loads such as wind and earthquake loads, and therefore it is important to gain a better understanding of the behavior of CLT shearwall systems during earthquake events. This paper is focused on the seismic performance of connections between CLT shearwall panels and the foundation. CLT panels are very stiff and energy dissipation is accomplished by the connections. A literature review on previous research work related to damage prediction and assessment for wood frame structures was performed. Furthermore, a test program was conducted to investigate the performance of CLT connections subjected to simulated earthquake loads. Two different brackets in combination with five types of fasteners were tested under monotonic and cyclic loading protocols. In total, 98 connection tests were co...

Force Modification Factors for CLT Structures for NBCC

Cross-laminated timber (CLT) as a structural system is not introduced in European or North American building codes, and there is limited information available on the seismic factors for design of such structures. The objective of the study was to derive suitable ductility-based force modification factors (Rd-factors) for seismic design of CLT buildings in the National Building Code of Canada (NBCC). For that purpose, the well-known six-storey NEESWood Capstone wood-frame building was redesigned as a CLT structure. Non-linear analytical models of the building designed with different Rd-factors were developed using the SAPWood program. CLT walls were modeled using the output from mechanics models developed in Matlab that were verified against CLT wall tests conducted at FPInnovations. Each of the 48 building models was subjected to a series of 22 bi-axial input earthquake motions suggested in the FEMA P-695 pro cedure. Results showed that an Rd-factor of 2.0 is appropriate for the building studied.

Behaviour of Cross-Laminated Timber Panels under Cyclic Loads

In this paper, the behaviour of cross-lam (CLT) wall systems under cyclic loads is examined. Experimental investigations of single walls and adjacent wall panels (coupled walls) in terms of cyclic behaviour under lateral loading carried out in Italy at IVALSA Trees and Timber Institute and in Canada at FPInnovations are presented. Different classifications of the global behaviour of CLT wall systems are introduced. Typical failure mechanisms are discussed and provisions for a proper CLT wall seismic design are given. The influences of different types of global behaviour on mechanical properties and energy dissipation of the CLT wall systems are critically discussed. The outcomes of this experimental study provides better understanding of the seismic behaviour and energy dissipation capacities of CLT wall systems.

Direct Displacement-Based Design of a Novel Hybrid Structure: Steel Moment-Resisting Frames with Cross-Laminated Timber Infill Walls

This study proposes an iterative direct displacement based design method for a novel steel-timber hybrid structure. The hybrid structure incorporates cross-laminated timber (CLT) shear panels as an infill in steel moment-resisting frames. The proposed design method is applied to design three-, six-, and nine-story hybrid buildings, each with three bays and a CLT-infilled middle bay. Nonlinear time history analysis, using 20 earthquake ground motion records, is carried out to validate the performance of the design method. The results indicate that the proposed method effectively controls the displacements due to seismic excitation of the hybrid structure.

Seismic Base Shear Modification Factors for Timber-Steel Hybrid Structure: Collapse Risk Assessment Approach

AbstractIn this paper, to supplement the Canadian building code for a timber-steel hybrid structure, over-strength, and ductility-related force modification factors are developed and validated usin...

Overview of a Project to Quantify Seismic Performance Factors for Cross Laminated Timber Structures in the United States

Cross-laminated Timber (CLT) has been extensively used in Europe and is now gaining momentum in North America; both Canada and more recently the U.S. Construction projects have shown that CLT can effectively be used as an alternative construction material in mid-rise structures and has significant potential in commercial and industrial buildings. In the United States, the CLT system is not currently recognized in seismic design codes and therefore a seismic design can only be performed through alternative methods specified in the codes. The FEMA P695 report published in 2009 presents a methodology to determine seismic performance factors namely the response modification factor, overstrength factor, and deflection amplification factor for a proposed seismic resisting system. The methodology consists of a number of steps to characterize system behavior and evaluate its performance under seismic loading. The additional benefit of the methodology is that it considers variability in ground motions and uncertainties in tests, design, and modeling. This paper presents an overview of the P695 methodology and more specifically the approach adopted to apply the methodology to Cross Laminated Timber (cross lam) systems in the United States. The type of tests and testing configurations conducted as part of this study and development of the CLT archetypes are discussed. Nonlinear models used to simulate CLT behavior at the connection, wall, and system levels are presented and the procedure to determine collapse margin ratio is explained.

Nonlinear Time-History Analysis of a Six-Story Wood Platform Frame Buildings in Vancouver, British Columbia

In 2009, the British Columbia Building Code was amended to increase the allowable height of wood-frame residential buildings to six stories from four stories. This paper presents the details of a numerical study undertaken to understand the seismic performance of six-story wood-frame buildings designed in accordance with the 2006 British Columbia Building Code. To investigate the seismic behavior, a four-story building was used to represent the benchmark seismic performance prior to the amendment. Two independent analyses using computer programs DRAIN-3DX and SAPWood were carried out on representative buildings located in the city of Vancouver, BC, using a suite of 20 earthquake records scaled to the design seismic hazard level for the site. The analyses showed that six-story wood-frame buildings had similar performance to four-story wood-frame buildings.