Seismic performance of connections in heavy timber construction

Abstract

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 reached.Key words: timber connections, glulam rivets, bolts, ductility, timber, wood, braced frames, seismic performance, heavy timber construction.

Ductile Behavior of Timber Structures under Strong Dynamic Loads

“…The mechanical causes of it have been discussed in Section 2.2.1. This effect has been documented by many authors, as for instance [48][49][50][51][52]. It was found, in particular, that for a given displacement level, the highest resistance and widest hysteresis loop was attained at the first load cycle, whilst the subsequent cycles were narrowed and achieved lower resistance, stabilizing after about three cycles (see Figures 9a and 9b).…”

“…On the other hand, while different protocols are available to carry out cyclic loading tests on timber structures, for example, EN 12512 [30], CUREE-Caltech standard [33], UBC protocol [11], a consensus on the best protocol to be assumed as standard has not been yet reached [48]. Many experimental findings proved, however, the influence of the load history on the final results.…”

“…[48] that a connection usually reaches its maximum load at a lower deformation under cyclic loads than under monotonic loading. In Ref.…”

“…[50], it was found that the ductility ratio of timber shear walls may be much higher when measured under static monotonic tests than when measured under dynamic tests. These experimental findings indicate that results from monotonic tests tend to overestimate the load-deformation behavior of connections with respect to cyclic loading tests, and therefore should be avoided when determining the seismic performance of timber buildings [48]. Dynamic tests are surely the best choice to capture the behavior of timber structures under seismic or wind loads, also in view of the fact that the failure modes may be very different in static and dynamic conditions [50].…”

Cross Laminated Timber (CLT) as an Alternative Form of Construction Wood

“…This range corresponds to the density of softwood species intended for structural purposes. Thereby, the weight of typical CLT in a wall panel of a thickness of 103 or145 mm ranges from 67 to 72 kg/m 2 or 49 to 52 kg/m 2 , respectively, (Ceccotti, 2010;Popovski, 2010;FPInnovations, 2010).…”