Search

The use of composite beams made with traditional concrete and bio-based materials (such as timber and bamboo) is a valuable solution to reduce the environmental impact of the building sector. Timber-Concrete Composite (TCC) beams have been used for decades in structural applications such as new buildings, refurbishment of old timber structures, and bridges. Recently, different researchers suggested composite beams based on engineered bamboo, commonly named Bamboo-Concrete Composite (BCC) beams. This study presents a systematic comparison of structural performances and connection behavior of TCC and BCC beams under short-term static load. TCCs beams are compared to BCC ones using similar shear connectors. The most important aspects of the two composite systems are compared: mechanical behavior of connectors and structural behaviors of full-scale composite beams (e.g., failure modes, connection stiffness, connection shear strength, ultimate load-carrying capacity, maximum deflection and composite efficiency). This comprehensive review indicates that BCC beams have similar or even better structural performances compared with TCC.

The subject of the article is to monitor the changes of moisture on the contact surface concrete and timber part of the composite timber-concrete beam. The moisture directly affects the properties of timber and causes its volume changes and degradation processes. These effects reduce of durability and load capacity of the structures. The beam was placed at the exterior. The observed contacts of the beam are often critical on real structures, as it is difficult to repair and maintenance in the case of increasing moisture or intrusion of dirt. The experiment was used to monitor and evaluate the dependence of changing moisture in contacts depending on ambient environmental conditions. Web of Science 65 6 924 917

This paper presents results of the laboratory tests of timber-concrete structural connectors applicable (but not limited to) road/pedestrian bridges. The tested elements are discrete circular hollow section connectors installed in the pre-drilled slots of a glulam. Symmetrical push-out tests are conducted for two groups of connectors: 1) with wood core not removed; no interlayer between wood and concrete; 2) concrete in-fill core instead of the wood core; waterproofing membrane interlayer between concrete and timber elements. Main structural parameters of the connectors are established including ultimate shear capacity and slip modulus. Relationship between the connector’s stiffness and ultimate shear capacity is established and failure mechanisms are briefly discussed.

The paper reports the results of a comprehensive experimental test performed on a 6 m span timber-concrete composite beam with glued re-bar connection. The beam had first been subjected to sustained load in unsheltered outdoor conditions for 5 years. Eventually a ramp loading test up to failure was performed. The long-term test showed an increase in deflection mainly during the first two years, while the slip rose during the whole testing period. Thermo-hygrometric variations of environment caused an important fluctuation of all quantities on both yearly and daily scale. By comparing experimental and analytical results, it is highlighted that composite beams in outdoor conditions should be assigned to the 3rd service class according to the Eurocode 5 (EC5). Analytical predictions based on approximate formulae suggested by such regulation are found to be not conservative for the long-term behaviour and fairly accurate for the collapse behaviour. Since the simplified formulae proposed by the latest versions of the EC5-Parts 1.1 and 2 largely underestimate the actual connection stiffness and strength, it is recommended that realistic values of these properties, such as those obtained through push-out tests, be used when designing timber-concrete composite beams.

The paper presents the structural solution to the joisted floor when the timber joist of composite cross‐section and the concrete slab are interconnected via a special semi‐rigid connection and form a timber‐concrete joisted floor composite element. Tensioned bottom flange is formed of a solid timber joist, the web is of oriented strand boards (OSB) and the compressive top flange is of a concrete slab into which a part of the web is let in. Studies were carried out on the “sleeved” connector in this part of the web between OSB and concrete slabs that should increase the stiffness of this connection. Theoretical and experimental researches on inter‐behaviour of connection of the sub‐components of composite timber I beam‐concrete were carried out, the obtained results are presented and evaluated. Kompozitinių medinių-betoninių perdangų „įvorinių“ jungių laikysenos tyrimas Santrauka.Aptariamas sijinės perdangos konstrukcinis sprendimas, kai sudėtinio skerspjūvio medinė sija ir betono plokštė tarpusavyje sujungiamos per specialią iš dalies standžią jungtį ir sudaro kompozitinį medinės‐betoninės sijinės perdangos elementą. Šio elemento tempiamoji apatinė juosta padaryta iš vientisos medienos lentų, sienelė – iš orientuotųjų skiedrų plokštės (OSB), gniuždomoji viršutinė juosta – iš betono plokštės, į kurią įleista sienelės dalis. Tirta šioje sienelės dalyje tarp OSB ir betono plokščių esanti “įvorinė” jungtis, skirta šios jungties standumui padidinti. Atlikti kompozitinės medinės‐betoninės sijinės perdangos sudėtinių dalių tarpusavio jungčių laikysenos teoriniai ir eksperimentiniai tyrimai, pateikti ir įvertinti gauti rezultatai. Reikšminiai žodžiai:kompozitinė medinė‐betoninė konstrukcija,medinė plonasienė sija,slinktis,iš dalies standi jungtis,slankumo modulis,šlyties jungė,išstumiamasis bandymas. First Published Online: 14 Oct 2010

In the field of timber bridges progressive static structural solution is if the timber bearing members of the bridge deck are combined with concrete layer applying a shear connection to receive their composite action. The composite timber-concrete bridge deck comparing to the standard timber bridge deck has a higher rigidity, is more resistant to dynamic effects and has protected wooden part from external mechanical actions. The behavior of timber–concrete bridge deck is significantly influenced by the conditions of surrounding environment. In the presented paper, results of theoretical and experimental investigation of the effect of temperature and humidity changes of environment on the timber-concrete composite bridge deck will be presented. The applied analytical calculation model developed for analysis of long term behavior of timber-concrete elements influenced by the environment temperature and humidity will be introduced. In the experimental program, timber–concrete members with different timber structural parts and various composite connections under short and long term loading were investigated. The environmental conditions, temperature and humidity, during the 5 year long test were continually registered. Comparison of theoretical and experimental results and some practical conclusions for design of timber–concrete bridge deck will be finally presented.

Wood and concrete are materials with different time dependent behaviour and both have different reactions to thermal and humidity environmental changes. In timber-concrete composite beams, it results in generation of inelastic strains and redistribution of stress in cross-section. It is possible to determine load carrying capacity of composite wood-concrete elements according to Additions B of EN 1995-1-1, Design of Timber Structures. This calculation technique, however, does not consider the influence of the rheological properties of composite materials such as shrinkage, the eventual bulking of materials, the influence of composite on creep coefficient, and the influence of environmental changes. In this paper, the analytical calculation model of long term behavior of the timber-concrete composite beams is presented, which considers the most significant rheological phenomena such as: viscous-elastic creep of concrete and wood, mechano-sorptive creep of wood, creep of shear connection, concrete shrinkage, and strains due to thermal and relative humidity changes of environment. This model is applicable for simple beams with linear material properties and allows determining the final deflection in the middle span and stressing distribution in the middle cross-section of the composite beams affected by long term loading. Applying the presented calculation model and results of experimental tests, the analysis of rheological behavior influence on long term load carrying capacity of timber-concrete beams is described as well.