<p>Timber railway bridges are an important aspect of Canada’s heritage. In this study, the mechanical properties of 12 decommissioned creosote-treated Douglas fir beams from a railway bridge were investigated. Longitudinal and transverse stress-wave analysis, vibration testing, resistance drilling, and destructive testing were employed. Resistance drilling identified localized density variations but showed no direct correlation with global density. The stress-wave analysis yielded an average modulus of elasticity (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$E_{sw}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mrow> <mi mathvariant="italic">sw</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>) of 15,090 MPa, and vibration testing yielded a dynamic apparent MOE (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$E_{app,v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mrow> <mi>a</mi> <mi>p</mi> <mi>p</mi> <mo>,</mo> <mi>v</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>) of 12,102 MPa and a true MOE (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$E_{true,v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>E</mi> <mrow> <mi>t</mi> <mi>r</mi> <mi>u</mi> <mi>e</mi> <mo>,</mo> <mi>v</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>) of 17,046 MPa. Finally, destructive bending tests produced static MOE values ranging from 8,564 MPa to 11,722 MPa. The beams exhibited failure primarily in shear, at an average maximum shear stress of 3.7 MPa and an average maximum bending stress of 29.6 MPa. Two beams were subjected to fatigue testing: one beam endured 80,000 loading cycles without degradation, while the second exhibited shear failure after 28,000 cycles. The findings emphasize the complexity of accurately assessing the mechanical properties of timber using non-destructive methods in the conservation of historical timber structures.</p>

Non-destructive, semi-destructive and destructive tests on decommissioned beams of historical timber bridge

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2025年12月26日

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Amir Ghavidel,
Brendan Fitzgerald,
Jianhui Zhou,
Thomas Tannert

摘要

Timber railway bridges are an important aspect of Canada’s heritage. In this study, the mechanical properties of 12 decommissioned creosote-treated Douglas fir beams from a railway bridge were investigated. Longitudinal and transverse stress-wave analysis, vibration testing, resistance drilling, and destructive testing were employed. Resistance drilling identified localized density variations but showed no direct correlation with global density. The stress-wave analysis yielded an average modulus of elasticity ( $E_{sw}$ $E_{sw}$ ) of 15,090 MPa, and vibration testing yielded a dynamic apparent MOE ( $E_{app,v}$ $E_{a p p, v}$ ) of 12,102 MPa and a true MOE ( $E_{true,v}$ $E_{t r u e, v}$ ) of 17,046 MPa. Finally, destructive bending tests produced static MOE values ranging from 8,564 MPa to 11,722 MPa. The beams exhibited failure primarily in shear, at an average maximum shear stress of 3.7 MPa and an average maximum bending stress of 29.6 MPa. Two beams were subjected to fatigue testing: one beam endured 80,000 loading cycles without degradation, while the second exhibited shear failure after 28,000 cycles. The findings emphasize the complexity of accurately assessing the mechanical properties of timber using non-destructive methods in the conservation of historical timber structures.