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App 1 - TODS - Bridge Certification
CD:JM 20507 14 February 2020 328 Upper Pinbarren Creek Road PINBARREN QLD 4568 ATTENTION: Property Owners RE: 328 UPPER PINBARREN CREEK ROAD, PINBARREN – PROPERTY BRIDGE – LEVEL 3 REPORT AND CERTIFICATION TOD Consulting were engaged by the property owners, at the time of inspection, to carry out a Level 3 investigation for the structural condition of an existing bridge, on the property of 328 Upper Pinbarren Creek Rd. TOD Consulting carried out a Level 3 inspection on 30 January 2020. Conclusion: Bridge to be load limited to 7.5 tonnes allowable gross vehicle mass (GVM) for a maximum of 2 years (until January 2022). If the bridge shows any concerning behaviour before this date, please contact a bridge engineer for advice immediately. The bridge shall be subjected to a Level 3 inspection and re-rated on/before 30 January 2022. Bridge Details: The timber girder bridge is comprised of two spans and is continuous over the middle pier support. The overall deck dimensions are 12.8 metres long (nominal) x 2.9 metres clear width between kerbs. Span 1 is 5.9 metres and Span 2 is 6.0 metres between the centre of supports. The two abutments and one pier are constructed in concrete, where the extents are unknown. The bridge carries two directional traffic with one lane of operation. Original Design Load: The original design load is assumed to have been 30 tonnes allowable GVM. It has dilapidated since then, as per the following paragraphs. Existing Risks: Several built-in risks were identified with the bridge superstructure, including: • Girder 1 (Span 2 midspan) is in Very Poor condition (Condition State 4) due to vertical crack at top of girder causing internal rotting/decay of component. • Girder 2 End 1 (at Abutment A) is in Poor condition (Condition State 3) due to 18% snipe. • Girder 3 End 1 (at Abutment A) is in Very Poor condition (Condition State 4) due to 23% snipe and 26% pipe. Please note that the timber girders were unable to be accessed to be drilled at either side of Pier 1. Therefore, the Condition States at these points are unknown. Condition State: In our opinion, the bridge Condition State is 4 (Very Poor).
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Current Capacity: Our calculations indicate that the current capacity of the bridge superstructure
is suitable to carry 7.5 tonnes allowable GVM (single axle load must not exceed 3.75 tonnes). The
nature of timber is such that it will continue to dilapidate and lose capacity as time passes.
It is essential to impose a 10km/hr speed limit using signs, to reduce the “bounce” effect of the
vehicle load on the bridge.
Please note that the substructure of the bridge was not assessed during this Level 3 investigation,
as the depth of these supports are not visible. An extensive investigation would be required to
assess the substructure.
Short-Term Recommendations: We strongly recommend the following:
• Installing and maintaining in-ground termite baits near each abutment.
• We consider it essential to install 10km/hr signs at both ends of the bridge.
• We consider it essential to install 7.5-tonne load limit signs at both ends of the bridge.
• We recommend that a Level 1 (visual inspection) be carried out every six months until the
next Level 3 inspection on/before 30 January 2022.
The Level 1 inspection shall be carried out by an experienced bridge technician/builder.
The Level 3 inspection shall be carried out by an experienced bridge engineer.
We are happy to provide detailed designs of repair/replacement works to allow for the bridge to
support a heavier vehicle load, under an extension to the original Agreement. At this preliminary
stage, the repair works is likely to include the installation of larger diameter replacement
girders/logs and load distribution boards under the decking.
Please note that due to the sizes and severity of defects of the existing girders, we suspect that it
would be more cost efficient to replace the existing superstructure rather than undertaking
maintenance on the bridge.
Yours faithfully,
Chris Dowding – R.P.E.Q. 8339
07 5449 9600 | [email protected]
TOD consulting engineers