Cross-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 conducted and the monotonic load-displacement curves and hysteretic loops were obtained. In this paper, an energy-based cumulative damage assessment model was calibrated with the CLT connection test data. Finally, a correlation between the damage index and physical damage is provided.
Wood-frame is the most common construction type for residential buildings in North America. However, there is a limit to the height of the building using a traditional wood-frame structure. Cross-laminated timber (CLT) provides possible solutions to mid-...
International Specialty Conference on Behaviour of Steel Structures in Seismic Areas
January 9-11, 2012, Santiago, Chile
A steel-wood hybrid system furnishes not only aesthetically pleasing and sustainable hybrid structures but is superior in seismic applications due to the light weight, high resistance, and adjustable ductility. Such hybrid structural systems are not covered by any material and structural design standards that hinder the general implementation. For light structures, a builder’s guide to hybrid wood and steel connection details already exists in North America. Despite the obvious advantages, however, today’s applications of steel-wood hybrid structures have been limited. Rare hybrid buildings with a concentrically braced frame used for lateral load resistance with a glulam timber floor slab have been built as prototypes. The use of glulam floor slab led to a substantially reduced self-weight, compared with the reinforced concrete slab option. The lighter structure behaves superior in seismic events and has made wind loads the governing design case. The next generation steel-wood hybrid structures should optimally utilize each material. This paper describes a research program of the next generation wood-steel hybrid structures should optimally utilize each material. In detail the following development issues will be addressed: innovative hybrid steel-wood building systems, technical tools to predict structural responses of hybrid systems, design principles underpinning the definition of key code provisions related to strength and serviceability performance of hybrid buildings. It will be highlighted that potential structural problems at the design stage result from material incompatibilities. The constitutive properties of each material, hybrid-material, and joint properties reported in the literature will be used, or supplemented by findings from experimental work.
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 3-, 6-, and 9-story hybrid buildings with three bays and CLT infilled middle bay. Nonlinear time history analysis, using twenty 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.
Provincial code changes have been made to allow construction of light wood-frame buildings up to 6 storeys in order to satisfy the urban housing demand in western Canadian cities. It started in 2009 when the BC Building Code was amended to increase the height limit for wood-frame structures from four to six. Recently, provinces of Quebec, Ontario and Alberta followed suit. While wood-frame construction is limited to six storeys, some innovative wood-hybrid systems can go to greater heights. In this report, a feasibility study of timber-based hybrid buildings is described as carried out by The University of British Columbia (UBC) in collaboration with FPInnovations. This project, funded through BC Forestry Innovation Investment's (FII) Wood First Program, had an objective to develop design guidelines for a new steel-timber hybrid structural system that can be used as part of the next generation "steel-timber hybrid structures" that is limited in scope to 20 storey office or residential buildings. ...
International Journal of Advanced Structural Engineering
This paper presents analytical and numerical models for semirigid timber frame with Lagscrewbolt (LSB) connections. A series of static and reverse cyclic experimental tests were carried out for different beam sizes (400, 500, and 600 mm depth) and column–base connections with different numbers of LSBs (4, 5, 8). For the beam–column connections, with increase in beam depth, moment resistance and stiffness values increased, and ductility factor reduced. For the column–base connection, with increase in the number of LSBs, the strength, stiffness, and ductility values increased. A material model available in OpenSees, Pinching4 hysteretic model, was calibrated for all connection test results. Finally, analytical model of the portal frame was developed and compared with the experimental test results. Overall, there was good agreement with the experimental test results, and the Pinching4 hysteretic model can readily be used for full-scale structural model.
In 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 using a collapse risk assessment approach. The hybrid structure incorporates cross-laminated timber (CLT) infill walls within steel moment resisting frames. Following the FEMA P695 procedure, archetype buildings of 3-story, 6-story, and 9-story height with middle bay infilled with CLT were developed. Subsequently, a nonlinear static pushover analysis was performed to quantify the actual over-strength factors of the hybrid archetype buildings. To check the FEMA P695 acceptable collapse probabilities and adjusted collapse margin ratios (ACMRs), incremental dynamic analysis was carried out using 60 ground motion records that were selected to regional seismic hazard characteristics in southwestern British Columbia, Canada. Considering the total system uncertainty, comparison of the calculated ACMRs with the FEMA P695 requirement indicates the acceptability of the proposed over-strength and ductility factors
In this paper, over-strength and ductility-related force modification factors are developed and validated using a collapse risk assessment approach for a timber-steel hybrid structure. The hybrid structure incorporates Cross Laminated Timber (CLT) infill walls within steel moment resisting frames. Following the FEMA P695 procedure, initially, archetype buildings of 3-, 6-, and 9-storey height with middle bay infilled with CLT were developed. Subsequently, a nonlinear static pushover analysis is performed to quantify the actual over-strength factors of the hybrid archetype buildings. To check the FEMA P695 acceptable collapse probabilities and Adjusted Collapse Margin Ratios (ACMRs), Incremental Dynamic Analysis is carried out using 60 ground motion records that are selected to regional seismic hazard characteristics in southwestern British Columbia, Canada. Considering the total system uncertainty, comparison of the calculated ACMRs with the FEMA P695 requirement indicates the acceptability of the proposed overstrength and ductility factors.