Monotonic Tests on Beam-To-Column Joint with Steel Link for Timber Seismic Resistant Structures (original) (raw)
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COMPDYN Proceedings, 2021
For the design of dissipative heavy timber frame structures, in the context of modern seismic design approach based on the mechanical triad of strength, stiffness and ductility, brittle timber failure modes can be avoided by integrating hybrid timber-steel system into modern timber connection technology. Thus, the overall seismic performance of timber structures can be improved, entrusting the dissipation function to ad hoc conceived devices, like steel links. With reference to the structural type of Moment Resisting Frames (MRF), steel links located at the ends of the beams are able to provide a significant dissipative capacity, by means of cycles of plastic deformations, while timber members and steel connections, to be designed with an adequate overstrength as respect to the link, behave in elastic field. In this regards, the paper presents the capacity design and the mechanical characterization through monotonic numerical analyses of two different timber beam-to-column joint with steel link for MRF structures, consisting of a timber beam and a steel link connected each other by means of a stiffened end-plate and glued-in steel rods. The proposed design criteria of the joint are validated through the evaluation of performance, by means of nonlinear pushover analyses on the joint refined FEM models, in terms of key parameters, such as ultimate resistance, stiffness, rotation capacity and failure modes. The numerical results confirm the plastic deformation of the link, which large dissipative capacity of the joint corresponds to.
Ductile Moment-Resisting Timber Connections: A Review
Buildings, 2022
In the last two decades, high-rise timber buildings have been built using the glulam truss system, even with limited openings. Moment-resisting timber frames (MRTF) with semi-rigid beam-to-column connections can be an architecture-friendly way to provide a load-carrying system to vertical and horizontal loads for timber buildings. In these structures, connections of adequate ductility are crucial to ensure robustness and energy dissipation. This paper presents a review of the main types of timber beam–column moment connections with improved ductility and proposes to carry out a ductility assessment of these connections based on the most relevant ductility factors. Joints have a significant influence on the global performance of MRTF, and the application of ductile connections have improved the mechanical parameters of the timber frame. The reinforced bolted slotted-in steel plate and glued-in rods connections have similar mechanical performance, with high rotation capacity and good ...
2018
The use of engineered timber for Moment Resisting Frames (MRF) has undergone a significant evolution in the past years. In particular, the use of post-tensioned cables has allowed the development of moment-resisting jointed ductile connections for multi-story concrete, steel or timber frames in seismic areas. Post-tensioned cables/bars passing through the beam-column connections allow the self-centering of the frames after a seismic event. Also, the use of dissipative devices adds damping and ductility at the connection, developing a peculiar “flag-shape” hysteretic behavior. From the combination of these two features arises a connection referred to as "Hybrid System" using the term adopted in the 1990s as part of the PRESSS (PREcast Seismic Structural Systems) program. This technology concentrates inelastic demand at the connection level (gap opening) allowing damage control. A significant enhancement in the potentiality of this technology has been the extension to engine...
Engineering Structures, 2009
We present a new and alternative proposition for the traditional Asian timber column-and-beam connection, using the Kusabi-Nageshi (K-N) joint system. The mechanical behaviour is complex and relies on the embedment strength of the timber, pre-stress, friction, and elastic energy storage. Using a systematic comparative analysis, the advantages of the K-N joint over more traditional joints can be made clear. The comparison of the hysteresis from cyclic loaded cross-joint tests with varied pre-stress clarifies the enhanced mechanical behaviour of the K-N joint system.
Static and dynamic behavior of bolted timber joints with steel splice plates
2008
In timber structures, the earthquake energy is dissipated under several mechanisms such as internal friction, friction between structural and nonstructural elements, and inelastic deformation of structural members. However, large amount of this energy dissipation is mainly contributed through nonlinear load-deformation of their connections where the lateral loads are transmitted via bearing stress developed between the steel fasteners and the wood members. An effort to increase damping capacity of timber joints would greatly enhance the safety margin of wooden constructions especially that are placed in very active seismic zones. This increase can be carried out, for instance, by means of fastener pre-tensioning. This paper summarizes the experimental and analytical studies that are performed to examine both static and dynamic behavior of timber joints with pre-tensioned bolts. In addition, one-year stress relaxation measurement of the joints exposed to indoor environment condition ...
A Proposal for the Mechanical Classification of Beam-To-Column Joints for Timber Structures
2023
The performance of timber structures is greatly influenced by the capacity of the connections, in terms of both strength and stiffness, as well as ductility. Reliable estimations of the structural behaviour of timber buildings is possible through a full understanding of the joint behaviour. At present there is not a standard method that allows to identify the mechanical behaviour of timber connections. To fill this gap, in this paper, a procedure for the classification in terms of strength and stiffness of beam-to-column joints in timber structures is presented. The method is inspired to that one related to steel connections according to Eurocode 3. Then, with reference to a number of experimental studies available in the scientific literature on several timber beam-to-column joints, the proposed classification method is applied on typical configurations, evidencing that common joints can be classified as pinned or semi-rigid.
Seismic performance of connections in heavy timber construction
Canadian Journal of Civil Engineering, 2002
Results from monotonic and quasi-static cyclic tests on connections used in heavy timber construction are presented for two types of fasteners: steel bolts and glulam rivets. Bolted connections with three different diameter bolts, arranged in several configurations, as well as two different configurations of glulam rivet connections were tested. All configurations included a main glulam member and two steel side plates. For bolted connections, the seismic behaviour was found to be primarily dependent on the bolt slenderness ratio. Bolted connections with higher slenderness ratios (smaller diameter bolts) exhibited more ductile behaviour with considerable steel yielding and wood crushing before failure. Glulam riveted connections, which were designed in rivet failure mode, showed superior seismic performance when compared to bolted connections for similar design load levels. Riveted connections were also able to dissipate the highest amount of input energy before the failure was reac...
Ductility of timber joints under static and cyclic loads
Proceedings of the ICE - Structures and Buildings, 2011
The paper illustrates recent research on timber joints assembled with traditional and innovative dowel-type connectors. The experimental results are presented in terms of force–displacement relationships for specimens tested under a monotonic procedure and hysteretic diagrams for specimens tested under the cyclic procedure. The aim is to determine some quantitative values from the experimental data in order to characterise the ductility and dissipation capability of timber joints while taking account of design standards for earthquake-resistant structures. The paper presents and discusses procedures for the analysis of experimental data proposed in test standards and the scientific literature, the purpose being to evaluate the ability of current procedures to mechanically characterise a joint's behaviour as a function of different kinds of connector – traditional dowel-type systems or innovative self-tapping screws inserted with different inclinations with respect to the shear p...
Canadian Journal of Civil Engineering
Recent developments in novel engineered mass timber products and connection systems have created the possibility to design and construct tall timber-based buildings. This research presents the experiments conducted on the steel-wood connection as main energy dissipating part of a novel steel–timber hybrid system labelled Finding the Forest Through the Trees (FFTT). The performance was investigated using quasi-static monotonic and reversed cyclic tests. The influence of different steel beam profiles (wide flange I-sections and hollow rectangular sections) and the embedment approaches (partial and full embedment) was investigated. The test results demonstrated that appropriate connection layouts can lead to the desired failure mechanism while avoiding excessive crushing of the mass timber panels. The research can serve as a precursor for developing design guidelines for the FFTT system as an option for tall wood-hybrid building systems in seismic regions.