THE USE OF ENCASEP TIMEBER BEAMS AS ALTERNATIVE TO REINFORCED CONCRETE BEAMS

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Department of Engineering

ABSTRACT
The project investigates the possibility of adopting a composite beam consisting of concrete and timber, and consequently comparing the structural performance and the economical implications of this beam to a normal reinforced concrete beam. The idea to do this is borne out of the need to discover alternative(s) to reinforced concrete beams which are otherwise expensive and therefore unaffordable to the majority of our people. To achieve these objectives, two beams are designed (one as reinforced concrete and the other as timber encased in concrete) to satisfy the same conditions of loading and serviceability requirements, the prototype beams so obtained are modelled down mathematically to smaller and manageable sizes, which are tested in flexure till failure while observing and recording their respective deflections, strains, crack developments, mode of failure and failure loads. The cost comparative analysis is a very important aspect of this research, this is based on the actual (prototype) beams. It includes the production as well as materials cost of each beam. Finally, the experimental data obtained are analysed and the following conclusions made. i) That there was a 10% decrease in the production cost of the encased timber beam. ii) There is also a 40% increase in collapse load for the encased timber beam over that for the reinforced concrete beam. iii) The reinforced concrete beam being more rigid deflected far less in comparison with encased timber beam. V I I iv) The encased timber is viable for spans not exceeding 6m. Beyond this the encased timber beam ceases to be economical as the timber section required to satisfy the deflection clause would be too large. v) The slope of the load-deflection graph of the plain timber beam tested (timber without concrete encasement) showed a greater deflection per load compared to the encased timber beam, indicating that a composite action does occur and that the concrete contributes to the stiffness of the encased timber beam.