Utilização de madeira de eucalipto de pequenas dimensões na fabricação de uma ponte protendida com madeira laminada colada / Use of small-sized eucalyptus wood to build a pre-stressed bridge with glued-laminated timber

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This study aimed to build and evaluate the behavior of a highway stress-laminated timber bridge deck measuring 6m in length, 3.5 m width and 0.24 m thickness submitted to a load of 13 t. The deck was built with laminations made from eucalyptus logs of various thinning-originated specimens, with a mean diameter of 2.5 m and ages ranging between 8 and 19. To build the deck, the constructive system stress-laminated timber was adopted in which 100 laminations previously selected and tested for rigidity and perforated along their neutral lines at calculated distances received tensioning steel bars. During stressing, the number of bars used provided perpendicular interlaminar compression equivalent to 0.7 MPa, sufficient to make the deck rigid. The 0.035 m thick, 0.24 m wide and 6 m long laminations were produced by applying resorcinol-formaldehyde adhesive at a rate of 300 g/m2 on three 0.035 m thick and 0.08 m wide laminations. After the cure of the adhesive, the timber was assayed to determine rigidity in flexure and eliminate timber that failed when submitted to a central load in a 5.8 m span. Maximum load was calculated as being double that necessary to produce a central deflection equal to the allowable, considered as being L/350. Load and deflection loads were determined conventionally, using deflectometers. Mean elasticity module reached 14.874 MPa, with standard deviation of 1.985 MPa and coefficient of variation of only 13%. The deck thus obtained was built on a supporting structure constituted of two square timber blocks representing the bridge approaches. Low angle ramps were also built to allow vehicle traffic. Deflectometers were installed under and along the bridge. The former allowed determining the magnitude of transversal deflection after vehicle traffic; the latter supplied the magnitude of longitudinal deflection. Transversal deflection, which reached maximum values in two points under the vehicle wheels, did not surpass 3.7 mm at these points. Longitudinal deflection, whose maximum value occurred at half the deck length, reached a value of 3.2 mm. These two values are quite inferior to the admissible ones, leading to the conclusion that the value adopted for stressing was sufficient for the deck to acquire a stable and rigid configuration.

ASSUNTO(S)

pre-stressed bridge pontes protendidas eucalyptus madeira laminada colada eucalipto glued-laminated timber tecnologia e utilizacao de produtos florestais

ACESSO AO ARTIGO

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