Effects of notching on timber girder performance

Dewey, Justin, Tuladhar, Rabin, Mullamphy, Lara, and McCormack, Lucy (2017) Effects of notching on timber girder performance. In: [Presented at the 3rd International Conference on Timber Bridges]. From: ICTB 2017: 3rd International Conference on Timber Bridges, 26-29 June 2017, Skelleftea, Sweden.

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Abstract

With the advent of modern construction materials such as concrete and steel, the use of timber in bridge construction in Australia has significantly decreased. However, many aging timber bridges, with an average age of more than 60 years, are still in operation around the country. Maintenance and repair of these aging timber bridges thus poses a growing challenge for the asset owners. One of the major concerns while managing the existing timber bridges is determining the capacity of the girders with notches. Notching is where a section of a beam is cut to allow for its placement on supports. Notching, however, causes stress concentration at the notch corner, which may initiate crack opening at the notch corner and lead to the ultimate failure of the girder. This research is focused on the experimental study on rectangular and circular timber girders to identify the effect of notch on their shear capacities and determining the critical notch angle. While there are design standards available for notching on rectangular timber beams, there is currently no standardized equations for notching on circular timber breams. Twelve small-scale rectangular and circular timber members with three different types of notch angles were tested under three point bending. Three notch angles tested were 1:0, 1:2 and 1:4. Experimental study showed that a notch angle of 1:0 had the lowest capacity for both rectangular and circular members. For notch angle 1:0, notch crack initiation and notch failure loads were much smaller compared to the ultimate failure load. Whereas for notch angle 1:4, notch crack initiation and crack propagation were very similar to the ultimate failure load, which indicated that full shear capacity of the beam could be achieved with the notch angle of 1:4. The shear capacity of the beams from the experimental study were also compared with the existing Australian design standards for rectangular notched beams. The experimental results showed that the existing design equation for notched beams in the Australian design standards are very conservative. Comparison with design equations found in Australian standards showed that existing design provisions for notched beams are very conservative when applied to round sections.

Item ID: 51461
Item Type: Conference Item (Non-Refereed Research Paper)
ISSN: 0284-5172
Keywords: snipe, notch, round girders, timber girders
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Date Deposited: 09 Nov 2017 02:12
FoR Codes: 09 ENGINEERING > 0905 Civil Engineering > 090506 Structural Engineering @ 80%
09 ENGINEERING > 0905 Civil Engineering > 090503 Construction Materials @ 20%
SEO Codes: 87 CONSTRUCTION > 8703 Construction Materials Performance and Processes > 870305 Timber Materials @ 60%
87 CONSTRUCTION > 8704 Construction Processes > 870401 Civil Construction Processes @ 20%
87 CONSTRUCTION > 8702 Construction Design > 870202 Commercial Construction Design @ 20%
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