Recently more and more buildings of light structures have been built in Lithuania as well as in other European and world countries. Nevertheless, timber products are not widely used for floors in this share of construction market. Traditional light timber frame floors are characterized by vibrations, acoustic transmission and low fire resistance. The above-mentioned problems can be rationally solved by using timber-concrete composite (hereinafter TCC) floors. In comparison with entirely timber floors such type of floors are characterised not only by increased strength and stiffness but also by increased fire resistance and better sound insulation. In comparison with reinforced concrete floors manufactured of non-regenerative sources TCC floors are lighter and more economic. These characteristics stimulate usage of TCC floors in newly built buildings. It should also be noted that usage of timber in building structures instead of concrete or steel could substantially decrease energy demand and emission of carbon dioxide during production. In this work author presents TCC structural solution when thin-webbed beams (I-joists) used for timber floor beams instead of solid or glued rectangular beams. Thin-webbed beams are without upper flange of structural timber. Embedding in concrete a part of web of oriented strand board (hereinafter OSB) connects the OSB web and the concrete slab. This concept allows to save structural materials and production costs. Nevertheless, not so many... [to full text]

As vigas mistas de madeira e concreto são formadas pela união de vigas de madeira a lajes de concreto armado por meio de conectores de cisalhamento. Quando os pisos mistos de madeira e concreto são comparados aos pisos construídos unicamente em madeira ou àqueles confeccionados somente em concreto armado é possível destacar algumas vantagens, incluindo o bom desempenho em situações de incêndio. Os elementos estruturais quando submetidos a ações térmicas sofrem redução de resistência e rigidez, sendo, desta forma, necessário conhecer as modificações sofridas por cada um de seus componentes, que para o caso estudado são: a madeira, o concreto e os conectores de cisalhamento. Desta forma, foi elaborada uma estratégia de modelagem numérica para o estudo de vigas mistas de madeira e concreto em situação de incêndio, utilizando o programa computacional ABAQUS, o qual é baseado no método dos elementos finitos. Em uma primeira etapa da pesquisa foram realizadas modelagens numéricas de vigas de madeira e mistas de madeira e concreto em temperatura ambiente, encontrando-se boa correlação entre as curvas força versus deslocamento no meio do vão obtida numericamente e por meio de ensaios disponíveis na literatura. Em seguida procedeu-se a calibração das propriedades térmicas e mecânicas da madeira brasileira, alcançando-se resultados numéricos próximos aos experimentais, seja em relação às temperaturas do elemento analisado seja em relação à curva de deslocamento vertical em função do tempo de incêndio. Por fim, a estratégia de modelagem termoestrutural desenvolvida para a viga mista de madeira e concreto forneceu curva de deslocamento vertical em função do tempo de incêndio semelhante à curva obtida por meio de modelo analítico disponível na literatura. Por meio do modelo elaborado foi possível observar que a elevação do nível de carregamento reduz o tempo de resistência do elemento estrutural e que a proteção térmica do concreto é essencial para aumentar o tempo até a ruptura da viga. / Timber-concrete composite beams are formed by the union of timber beams to reinforced concrete slabs through of shear connectors. When timber-concrete composite floors are compared to timber floors or reinforced concrete floors it is possible to highlight some advantages, including good performance in fire situations. When subjected to thermal actions, structural elements suffer strength and stiffness reductions, being, therefore, necessary to know the modifications suffered by each of its components, which for the case studied are: timber, concrete and shear connectors. Thus, it is developed a numerical modeling strategy using the computational program ABAQUS, which is based on the finite element method, for the study of timber-concrete composite beams in fire situation. In the first stage of the research it was carried out a numerical modeling of timber beam and timber-concrete composite beam at room temperature, finding good correlation between the force versus displacement curves in the middle of the span obtained numerically and through tests available in the literature. Then, it was carried out the calibration of the thermal and mechanical properties of the Brazilian wood, reaching numerical results close to the experimental ones, either in relation to the temperatures of the analyzed element or in relation to the vertical displacement curve as a function of the fire time. Finally, the thermo-structural modeling strategy developed for the timber-concrete composite beam provided a vertical displacement curve as a function of the fire time similar to the curve obtained through an analytical model available in the literature. Through of the elaborated model it was possible to observe that the load level increase reduces the resistance fire time of the structural element and that the thermal protection of the concrete is essential to increase the rupture time of the beam.

As vigas mistas de madeira e concreto são formadas pela união de vigas de madeira a lajes de concreto armado por meio de conectores de cisalhamento. Quando os pisos mistos de madeira e concreto são comparados aos pisos construídos unicamente em madeira ou àqueles confeccionados somente em concreto armado é possível destacar algumas vantagens, incluindo o bom desempenho em situações de incêndio. Os elementos estruturais quando submetidos a ações térmicas sofrem redução de resistência e rigidez, sendo, desta forma, necessário conhecer as modificações sofridas por cada um de seus componentes, que para o caso estudado são: a madeira, o concreto e os conectores de cisalhamento. Desta forma, foi elaborada uma estratégia de modelagem numérica para o estudo de vigas mistas de madeira e concreto em situação de incêndio, utilizando o programa computacional ABAQUS, o qual é baseado no método dos elementos finitos. Em uma primeira etapa da pesquisa foram realizadas modelagens numéricas de vigas de madeira e mistas de madeira e concreto em temperatura ambiente, encontrando-se boa correlação entre as curvas força versus deslocamento no meio do vão obtida numericamente e por meio de ensaios disponíveis na literatura. Em seguida procedeu-se a calibração das propriedades térmicas e mecânicas da madeira brasileira, alcançando-se resultados numéricos próximos aos experimentais, seja em relação às temperaturas do elemento analisado seja em relação à curva de deslocamento vertical em função do tempo de incêndio. Por fim, a estratégia de modelagem termoestrutural desenvolvida para a viga mista de madeira e concreto forneceu curva de deslocamento vertical em função do tempo de incêndio semelhante à curva obtida por meio de modelo analítico disponível na literatura. Por meio do modelo elaborado foi possível observar que a elevação do nível de carregamento reduz o tempo de resistência do elemento estrutural e que a proteção térmica do concreto é essencial para aumentar o tempo até a ruptura da viga. / Timber-concrete composite beams are formed by the union of timber beams to reinforced concrete slabs through of shear connectors. When timber-concrete composite floors are compared to timber floors or reinforced concrete floors it is possible to highlight some advantages, including good performance in fire situations. When subjected to thermal actions, structural elements suffer strength and stiffness reductions, being, therefore, necessary to know the modifications suffered by each of its components, which for the case studied are: timber, concrete and shear connectors. Thus, it is developed a numerical modeling strategy using the computational program ABAQUS, which is based on the finite element method, for the study of timber-concrete composite beams in fire situation. In the first stage of the research it was carried out a numerical modeling of timber beam and timber-concrete composite beam at room temperature, finding good correlation between the force versus displacement curves in the middle of the span obtained numerically and through tests available in the literature. Then, it was carried out the calibration of the thermal and mechanical properties of the Brazilian wood, reaching numerical results close to the experimental ones, either in relation to the temperatures of the analyzed element or in relation to the vertical displacement curve as a function of the fire time. Finally, the thermo-structural modeling strategy developed for the timber-concrete composite beam provided a vertical displacement curve as a function of the fire time similar to the curve obtained through an analytical model available in the literature. Through of the elaborated model it was possible to observe that the load level increase reduces the resistance fire time of the structural element and that the thermal protection of the concrete is essential to increase the rupture time of the beam.

Purpose: The purpose of this study was to investigate whether timber-concrete composite (TCC) floors made of a CLT-deck and casted concrete could be used as a method for increasing the use of wood as a building material. Method: The methods used in this degree project were a literature study, in which a number of laws of construction and different connector systems were studied, as well as an experiment consisting of bending tests on CLT-decks with casted concrete where SFS VB-screws were used as shear connectors. Results: The TCC-beams in the experiment behaved as expected and went to bending failure. The beams displayed an almost invisible slip between the materials despite the low composite action of 40,2 %. In addition, the beams had a higher bending stiffness on average than CLT-beams of the same height would have. Conclusions: Compared to floors made entirely of wood, TCC-floors with CLT add extra mass, stiffness, and better acoustic properties to the construction while maintaining a low floor height. The three main types of connectors used in TCC floors are mechanical, notched and glued-in connectors, where the latter two generates higher composite action and stiffness. Adhesive connection is another method with great potential, but there is still more research needed for this type of connection to be used.

The dissertation investigates the behaviour of timber-concrete connections with inclined screws – the load carrying capacity and deformability. The essen¬tial objects of investigation are the load carrying capacity of inclined screws; the modules of connection slip deformation, and the mechanical properties of mate¬rials and ware of which the connection is made. The load-carrying capacity of the connection depends on the properties of the material of connected member and the connectors, on which depends the strength and stiffness of the composite member. The main aim of dissertation is to create the connection load carrying capacity predicting model, based on the more realistic behaviour of the material of connected members; to prepare the simplified approach for load-carrying capacity predicting model for composite timber-concrete connections within at any angle in respect to timber grain in¬clined crews. The paper approaches a few major tasks such as the choice of suitable load-carrying capacity predicting base model; preparing it to composite timber-con¬crete connections with inclined screws; the experimental investigation of con¬nection with inclined screws under long- and short term loading; the experi¬mental investigation of properties of connected materials and type of used con¬nectors; the evaluation of created predictive model based on results also of other researchers experimental investigations. / Disertacijoje nagrinėjama kompozitinės medinės-betoninės jungties su įžambiai šlyties plokštumai orientuotais medsraigčiais elgsena – laikomoji galia ir deformacinės savybės. Pagrindiniai tyrimų objektai yra įžambiai medienos pluoštui orientuotų medsraigčių laikomoji galia, slinkties deformacijų moduliai ir mechaninės jungtį sudarančių elementų savybės, veikiančios jungties elgseną. Nuo medsraigčio ašies posvyrio kampo, deformacinių po medsraigčiu glemžiamos ir ištraukiamos medienos ir lenkiamo medsraigčio savybių priklauso ir jungties irties pobūdis, laikomoji galia ir slinkties deformacijų moduliai, o nuo pastarųjų – kompozitinio elemento stiprumas ir standumas. Pagrindinis disertacijos tikslas yra sukurti skaičiavimo modelį tokių jungčių laikomajai galiai nuspėti, kuo tiksliau atsižvelgiant į medžiagų ir elementų mechanines savybes; pateikti supaprastintą skaičiuojamąjį modelį, skirtą bet kokiu kampu medienos pluošto atžvilgiu įsriegtų medsraigčių laikomajai galiai nuspėti. Darbe sprendžiami keli pagrindiniai uždaviniai: tinkamo pamatinio jungties laikomąją galią vertinančio skaičiuojamojo modelio parinkimas, jo pritaikymas įžambiai medienos pluoštui orientuotiems medsraigčiams; trumpalaikis ir ilgalaikis eksperimentinis įžambinės medsraigtinės jungties laikomosios galios tyrimas ir vertinimas; kitų autorių eksperimentinių rezultatų vertinimas sukurtajam jungties laikomąją galią vertinančiam modeliui pagrįsti.

Disertacijoje nagrinėjama kompozitinės medinės-betoninės jungties su įžambiai šlyties plokštumai orientuotais medsraigčiais elgsena – laikomoji galia ir deformacinės savybės. Pagrindiniai tyrimų objektai yra įžambiai medienos pluoštui orientuotų medsraigčių laikomoji galia, slinkties deformacijų moduliai ir mechaninės jungtį sudarančių elementų savybės, veikiančios jungties elgseną. Nuo medsraigčio ašies posvyrio kampo, deformacinių po medsraigčiu glemžiamos ir ištraukiamos medienos ir lenkiamo medsraigčio savybių priklauso ir jungties irties pobūdis, laikomoji galia ir slinkties deformacijų moduliai, o nuo pastarųjų – kompozitinio elemento stiprumas ir standumas. Pagrindinis disertacijos tikslas yra sukurti skaičiavimo modelį tokių jungčių laikomajai galiai nuspėti, kuo tiksliau atsižvelgiant į medžiagų ir elementų mechanines savybes; pateikti supaprastintą skaičiuojamąjį modelį, skirtą bet kokiu kampu medienos pluošto atžvilgiu įsriegtų medsraigčių laikomajai galiai nuspėti. Darbe sprendžiami keli pagrindiniai uždaviniai: tinkamo pamatinio jungties laikomąją galią vertinančio skaičiuojamojo modelio parinkimas, jo pritaikymas įžambiai medienos pluoštui orientuotiems medsraigčiams; trumpalaikis ir ilgalaikis eksperimentinis įžambinės medsraigtinės jungties laikomosios galios tyrimas ir vertinimas; kitų autorių eksperimentinių rezultatų vertinimas sukurtajam jungties laikomąją galią vertinančiam modeliui pagrįsti. / The dissertation investigates the behaviour of timber-concrete connections with inclined screws – the load carrying capacity and deformability. The essen¬tial objects of investigation are the load carrying capacity of inclined screws; the modules of connection slip deformation, and the mechanical properties of mate¬rials and ware of which the connection is made. The load-carrying capacity of the connection depends on the properties of the material of connected member and the connectors, on which depends the strength and stiffness of the composite member. The main aim of dissertation is to create the connection load carrying capacity predicting model, based on the more realistic behaviour of the material of connected members; to prepare the simplified approach for load-carrying capacity predicting model for composite timber-concrete connections within at any angle in respect to timber grain in¬clined crews. The paper approaches a few major tasks such as the choice of suitable load-carrying capacity predicting base model; preparing it to composite timber-con¬crete connections with inclined screws; the experimental investigation of con¬nection with inclined screws under long- and short term loading; the experi¬mental investigation of properties of connected materials and type of used con¬nectors; the evaluation of created predictive model based on results also of other researchers experimental investigations.

Ninety percent of all single-family houses and smaller residential buildings in Sweden are built with timber frames. Though, this figure is different for higher buildings, about twenty percent in timber frames and eighty percent in concrete and steel. However, the knowledge and experience about tall timber houses is limited today and it needs to be developed over the time, both technically and architecturally. Purpose: The wood has a lower E-module than concrete and steel, which cause an additional problem in high-rise buildings of more than eight floors, stability. The measures for this problem can be costly and reduce the living space of the building due to large dimensions of the wooden structure. This project work is based on the challenges that exist around the construction of tall wooden buildings and tries to present a beneficial hybrid solution for the construction of tall houses in wood and concrete. Method: The study object is a multi-story building on ten floors where wood is used in combination with concrete for the frame system. The vertical loads such as self-weight, payload and snow load are carried by the wooden frame. On the other hand, concrete has the task of taking care of the horizontal forces caused by wind loads. The frame system is dimensioned according to the Eurocodes and standard dimensions to ensure the load-bearing capacity of the building. Results: The result reports that two concrete cores in the hybrid building absorb all horizontal forces and loads down to the foundation. These cores can also be used as stair/elevator shafts and will not affect the building's living area. A timber-concrete composite with a thickness of 300 mm, replaced the wooden composite which normally reaches a thickness of 400 to 500 mm. This means a height gain of one to two meters. The columns will get smaller dimensions because of the cores and give more living space. The concrete utilization in that hybrid building decreases by 57 percent, which is a large saving from an environmental perspective. In addition, life cycle analysis, LCA shows that carbon dioxide equivalents, CO2e are 43 percent less in the hybrid framework. Conclusion: The hybrid multi-stories houses of concrete and wood can be a useful alternative for increasing construction of wooden houses. A concrete core in the middle of building helps the construction to become more stable and the swaying due to wind loads be minimized. Furthermore, the columns can have smaller dimensions, which increases the living space in the building. The timber-concrete composite gives the building more weight and solves the step sound problem that arises due to low E-module on the wooden flooring. Additionally, the height of the building decreases, which in turn leads to buildings being able to have more stories and more living space. Moreover, through hybrid solutions in buildings, the environmental benefits of wood can be utilized to build environmentally friendly buildings. The ten-stories hybrid framework in this study, saves 43 percent CO2e compared to the corresponding framework in concrete.

This thesis examines the development of a superstructure for a slab-on-girder wood-concrete composite highway bridge. Wood-concrete composite bridges have existed since the 1930's. Historically, they have been limited to spans of less than 10 m. Renewed research interest over the past two decades has shown great potential for longer span capabilities. Through composite action and suitable detailing, improvements in strength, stiffness, and durability can be achieved versus conventional wood bridges. The bridge makes use of a slender ultra-high performance fibre-reinforced concrete (UHPFRC) deck made partially-composite in longitudinal bending with glued-laminated wood girders. Longitudinal external unbonded post-tensioning is utilized to increase span capabilities. Prefabrication using double-T modules minimizes the need for cast-in-place concrete on-site. Durability is realized through the highly impermeable deck slab that protects the girders from moisture. Results show that the system can span up to 30 m while achieving span-to-depth ratios equivalent or better than competing slab-on-girder bridges.

This thesis examines the development of a superstructure for a slab-on-girder wood-concrete composite highway bridge. Wood-concrete composite bridges have existed since the 1930's. Historically, they have been limited to spans of less than 10 m. Renewed research interest over the past two decades has shown great potential for longer span capabilities. Through composite action and suitable detailing, improvements in strength, stiffness, and durability can be achieved versus conventional wood bridges. The bridge makes use of a slender ultra-high performance fibre-reinforced concrete (UHPFRC) deck made partially-composite in longitudinal bending with glued-laminated wood girders. Longitudinal external unbonded post-tensioning is utilized to increase span capabilities. Prefabrication using double-T modules minimizes the need for cast-in-place concrete on-site. Durability is realized through the highly impermeable deck slab that protects the girders from moisture. Results show that the system can span up to 30 m while achieving span-to-depth ratios equivalent or better than competing slab-on-girder bridges.