Experimental study of moment sharing in multi-joist timber-concrete composite floors from zero load up to failure

Abstract

The critical T-sections of multi-joist timber concrete composite (TCC) floors must be designed at ultimate for support shear force and midspan moment, both of which are influenced by transverse sharing, but to different extents. Prior experimental work has investigated only support reaction sharing and only up to serviceability loads. The present experimental study builds on that status quo by quantifying also moment sharing, via strain gauge layouts at quarter-span and mid-span, along with reaction sharing via load cells at the supports of a multi-joist TCC specimen, over the entire load range up to failure. Use of steel mesh connectors bonded into hardwood laminated veneer lumber joists, and near geometric resemblance to a real building TCC floor recently built in London, were novel features of the specimen. The results show that midspan moment and reaction sharing both vary nonlinearly with load, but in distinctly different ways from each other (with up to almost 20% difference observed between them), in the progression between the uncracked, cracked and connection ductility regimes. In this approach reliable assessment of moment sharing depends on the quality of the recorded strains. Accordingly, the strain data were shown to be of high quality by converting these data to internal stress resultants that were then found to satisfy longitudinal equilibrium. It is concluded that this strain gauge layout is useful for future work aimed at building a database of transverse sharing of moments in TCCs.

Bending performance of cross-laminated timber-concrete composite slabs according to the composite method

“…Thus, it has been verified that the bending performance of TCC is highest when the connector insertion angle is 45°. Besides the frequently used screws, steel plates such as mesh plates (Mudie et al 2019) and hot-galvanized steel plates (Estévez-Cimadevila et al 2020) have been developed. Furthermore, Lukaszewska et al (2010) performed various composite fabrication processes, such as insertion of screws in a steel tube, use of ring-shaped nails in steel plates, and insertion of screws in the notch joint and the steel tube.…”

Structural Performance of Prefabricated Timber-Concrete Composite Floor Constructed Using Open Web Truss Joist Made of LVL Paraserianthes Falctaria

“…This kind of construction offers several advantages, as it is lighter compared with concrete beams and possesses higher timber durability than timber bridges because the timber joist does not experience any direct contact with rain and wind [6]. Previous research focused mainly on the evaluation of the system performance using different timber products as components, such as glulam [7] [8], solid timber [9], laminated veneer lumber (LVL) [10], [11] [12], cross-laminated timber (CLT) [13], and built-up joists. To connect the timber to the concrete part, the following are commonly used: adhesives [8], screws [7] [13] [14], punched metal plates [9], notched connections [10], steel mesh connections [11], or a combination of these connections (hybrid systems) [12].…”

“…Previous research focused mainly on the evaluation of the system performance using different timber products as components, such as glulam [7] [8], solid timber [9], laminated veneer lumber (LVL) [10], [11] [12], cross-laminated timber (CLT) [13], and built-up joists. To connect the timber to the concrete part, the following are commonly used: adhesives [8], screws [7] [13] [14], punched metal plates [9], notched connections [10], steel mesh connections [11], or a combination of these connections (hybrid systems) [12]. In about 45% of previous studies, metal dowel-type fastener connections were used [15].…”

Variations of moisture content in manufacturing CLT-concrete composite slab using wet construction method

“…Furthermore, it improves the ease of bonding a CLT floor with pillars, walls, or beams in the field. Therefore, with regard to the CCC manufacture method, between pouring concrete over a CLT floor structure in the field (wet construction method) or pre-fabricating CCC in a factory, the former is predominant (Kanócz and Bajzecerová 2015;Bajzecerová 2017;Thilén 2017;Jiang and Crocetti 2019;Mudie et al 2019;Teguedy et al 2019;Fu et al 2020). When CCC is manufactured through the wet construction method, the CLT plays the subgrade role of concrete.…”