1,603 research outputs found
Time-dependent behaviour of timber–concrete composite floors with prefabricated concrete slabs
No full textThis paper presents the results of long-term experimental tests performed on prefabricated timber–concrete composite beams intended for use in a proposed floor system, in which the concrete slab is prefabricated off-site and connected to the timber beam using one of two novel connection systems (either steel tubes inserted into the concrete slab and coach screws, or metal plates embedded in the concrete slab and nailed to the timber beams). In the experimental progra mme two beam specimens representing strips of
composite floor were subjected to sustained (quasi-permanent service) loading for almost a year in an
indoor, unheated and unconditioned environment. Throughout the test, mid-span deflection, relative slips at various connector locations, strains in the concrete slab and timber beam, and the ambient relative humidity and temperature, were continuously monitored. Both specimens showed only minor
increases in deflection, slips and strains over time, demonstrating excellent overall long-term behaviour.
The findings are consistent with a major advantage of prefabrication in this context; the concrete cures
and can thus freely shrink before the slab is connected to the timber beam, thereby minimising stresses and deflection in the composite beam. Results of accompanying numerical analyses are also presented. A rigorous uniaxial finite element model was first validated against experimental results, and then used to predict the total deflection at the end of the 50-year service life of the specimens tested and of other specimens with different connection system not tested. The total deflection was found to be in the range of 3.5–4 times the elastic deflection due to the quasi-permanent load condition (excluding the self-weight of the beam). This value was always lower than the acceptable limit of span length over 200, with better
predicted performance from stiffer connection systems such as notches cut in timber and glued-in dowels
"Static and dynamic (vibration) performance of composite beams with prefabricated concrete slab"
No full text
Influence of the construction method on the long-term behavior of timber-concrete composite beams
No full textDevelopment of prefabricated timber–concrete composite floor systems
No full text The timber–concrete composite structure consists of timber joists or beams effectively interconnected to a concrete slab cast on top of the timber members. This type of structure is finding new applications in multi-storey buildings and short-span bridges. Most of the research performed to date has focused on systems where ‘wet' concrete is cast on top of timber beams with mounted connectors. This paper presents a novel composite system where the concrete slab is prefabricated off-site with connectors already embedded and then connected to the timber joists on site. The advantages of this method include reduced cost and better quality control of the materials, absence of ‘wet' components on site during building erection and reduced concrete shrinkage effects on the composite beam. The paper reports an overview of a pilot research project conducted at Luleå University of Technology, Sweden, which includes direct shear tests to failure of different connection systems, bending tests to failure, dynamic (vibration) tests and long-term tests under sustained load of full-scale composite beams. The paper also reports the mechanical properties of the connection, which can be used within a simple design method given in Eurocode 5. The economic advantages of prefabrication and the possibility of demounting the structure make the proposed floor system very promising. </jats:p
“Performance of connections for prefabricated timber-concrete composite floors.”
No full textTimber–concrete composite beams and slabs require interlayer connectors, which provide composite action in the cross-section. A range of
mechanical connectors is available on the market
with an extensive variety of stiffness and strength properties, which are fundamental design parameters
for the composite structure. Another crucial parameter
is the cost of the connector, including the labour cost, that if too high may prevent the use of the composite system. In order to reduce the construction cost and make timber–concrete structures more widespread on the market, it is believed that a high degree of prefabrication should be achieved. For a simple and cost effective construction process, the use of ‘‘dry’’ connections, which do not require the pouring and curing of concrete on site, may represent a possible solution. This paper reports the outcomes of an experimental programme aimed to investigate a number of different mechanical ‘‘dry–dry’’ connectors previously embedded into a prefabricated
concrete slab. Direct shear tests on small blocks made
of a glulam segment connected with a prefabricated concrete slab were performed. The shear force relative
slip relationships were measured and all the
relevant mechanical properties such as slip moduli
and shear strengths were calculated. It was found that
some of the new developed connection systems for
prefabricated concrete slab can perform as satisfactorily
as those for cast-in-situ slabs, with the additional benefit of being relatively inexpensive
Evaluation of the slip modulus for ultimate limit state verifications of timber-concrete composite structures
No full text"Laboratory tests and numerical analyses of prefabricated timber-concrete composite floors."
No full textThis paper describes tests on a novel composite floor system constructed by connecting prefabricated concrete slabs to timber
joists. Seven types of shear connectors have been developed and tested: lag screws, either alone or combined with a notch cut from each timber joist; metal plates embedded in the concrete slab and either nailed or glued to the joists; dowels embedded in the concrete and glued to the timber; and toothed metal plates embedded in the concrete and pressed into the timber. Four-point bending tests to failure were performed on five, full-scale, 4.8 m long specimens connected with lag screws or metal plates nailed to the timber. Values of deflection and relative slip between the concrete slab and the timber obtained in these tests showed high correspondence with values obtained from a uniaxial finite element model developed for nonlinear analyses of composite beams. The model was also used to perform a numerical analysis to failure of composite beams with the other four connection systems that were developed but not tested on full-scale specimens. The outcomes of the experimental tests and numerical analyses show that the newly developed system can provide good
structural performance, especially if connections with coach screws and notches in the timber are used. The economic advantages of
prefabrication and the possibility to disassemble the structure and reuse the timber beams and concrete panels at the end of the service life make the proposed floor system very promising
Strutture in acciaio e composte acciaio-calcestruzzo. Sviluppi recenti e nuove sfide. Contributi in ricordo del Prof. Ing. Claudio Amadio
No full textQuesto volume è dedicato in particolare alle ricerche sul comportamento delle strutture in acciaio e composte acciaio-calcestruzzo, che hanno rappresentato una costante nelle tematiche affrontate da diversi Progetti Esecutivi del DPC - ReLUIS. È l’occasione per ricordare, anche tramite una selezione di contributi scientifici che vengono riproposti a testimonianza del costante e rigoroso impegno, l’intensa attività scientifica del Prof. Ing. Claudio Amadio, già coordinatore dell’Unità di Ricerca dell’Università degli Studi di Trieste
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