Abstracts

Fire Hazards in Bridges – A Current Review

Kenny Luu Manager – Structures

Laura Roberts Associate Engineer

The last two decades have seen a significant increase in fire incidents on bridges worldwide. Many of these fires have caused significant damage or total collapse of the structures. Based on recent studies, the biggest cause of fires in most of the bridges that collapsed or failed due to fire was from fuel leakage resulting from collision or spillage. Bridges collapses often lead to life and significant economic losses which need to factor in loss due to connectivity. In the US alone, the average annual fire loss for bridges is estimated to be $1.26bn. Despite the increase significance of fire hazards in bridges, current engineering practices lack comprehensive guidance for addressing fire hazards in the bridge structures, especially for existing bridges. This gap in knowledge poses significant challenges for ensuring the resilience and longevity of critical infrastructure which has the potential to significantly impact the safety of communities and result in significant economic impacts. This paper aims to provide a critical review of the current design standards and practices to deal with fire hazards in bridges in Australia. Through this review, the authors aim to identify the critical gaps in the current approach and provide recommendation to better enhance fire resilience in bridges in Australia.

Suggested Changes to AS5100 Bridge Design for Fire Design

Ross Pritchard Technical Principal Structures

Bridges are becoming wider in urban areas. Historic evidence shows that there is increased probability of fire under bridges in industrial areas or where heavy vehicles are queued due to traffic. Some modern bridge types, such as cable stayed bridges are more susceptible to damage due to fire on heavy vehicles or as a result of vehicle collision. AS 5100:2017 Bridge Design has clauses on fire design for the first time. The implementation of these new clauses has been challenging to bridge designers. The paper examines the history of fire at bridges to provide an insight into historical events as a base case. This paper explores if the standard adequately addresses fire design and proposes a number of changes so that the standard could be more easily adopted to fire design in the future. The relationship between fire engineering and structural engineering is developed.

Geotechnical Solution to Address Structural Challenges for a Bridge over a Creek with Compressible Soils

Michael Lee Senior Associate Engineer

Dr. Andrew Bradley Senior Engineer

Dr. Sam Doan Experienced Engineer

Simply supported bridge designs are often adopted for smaller bridges due to their relative cost and ease of construction. This can lead to complex design challenges in watercourse locations with compressible soils. Geotechnical design assessments demonstrated that exceedance of the project design criteria was anticipated without geotechnical ground treatment. The presentation will demonstrate a case study of the geotechnical solutions to overcome structural challenges to support road bridges on a project and validate the geotechnical design techniques and implemented prior to construction. 

Design Considerations of Accessible steel Box Girders Supporting Overhead Signage

Dr. Huy Binh Pham Technical Principal

Dr. Hasret Aydin Experienced Engineer

Box girders are gaining popularity for use in overhead sign structures. However, these wind-sensitive structures must accommodate increasingly larger spans due to wider carriageways and site constraints, while also providing maintenance access and meeting urban design and safety requirements. This presentation will focus on the key design considerations and challenges associated with box girder structures, emphasizing fatigue performance, the distortion effects of side-mounted attachments, and the need to adapt to evolving design guidelines and functional requirements. These factors support the case for box girders, which have been found to outperform conventional truss structures across a range of measures, offering benefits for longevity and adaptability with minimal maintenance cost for the client. 

Assessment of Slender Steel Flexural Members to AS5100-2017 with the use of Buckling Analysis  

Dave Huggett Principal Engineer

The lack of understanding and knowledge about buckling analysis often leads to designers adopting alternative methods and can lead to higher estimated structural capacity, which means less accuracy in performance limits. Sharing the results of a load rating assessment for a bridge superstructure with fabricated steel plate girders and precast deck planks. It compares the girder flexural capacity determined through buckling analysis with that calculated using simplified methods and outlines the process for calculating member capacity using buckling analysis. 

60M Span Spliced Super T Bridge Design   

Noritomo Maruo Senior Associate Engineer

In Australia, Super T girder bridges are preferred for spans up to 40m due to their cost-effectiveness, simplicity in casting, availability of molds, ease of construction, durability, and safety. This presentation will focus on the feasible study, including a review of related literature, trial designs of 3-span continuous (45+60+45), construction staging proposals and girder splice details. This will provide insights into how the Spliced Super T Girder Bridge design can offer a viable alternative to current solutions for longer spans, potentially providing cost savings and improved quality of bridge constructions. 

Design and Construction of Bridges Subjected to Mine Subsidence in New South Wales, Case Study

Michal Krotofil Technical Principal, SMEC Australia

Giammaria Gentile Engineering Manager, Fulton Hogan

The latest section of the Newcastle Bypass is in an area with complex topography and geology characterised by presence of carbonaceous materials and historical mining works. As a result of the possibility of mine subsidence bridges, like any other asset built above mining works, must be carefully designed to ensure safe and serviceable performance at an acceptable cost and environmental impacts. This case study highlights the key design and construction challenges and the innovative solutions and managing the risk associated with complex construction above mine subsidence areas.  

Elizabeth Avenue Pedestrian Overpass – Clontarf

Loïc Fields Senior Associate Engineer

BJ Byrnes Senior Engineer

Driven by pedestrian safety concerns near Clontarf Beach State High School, a coastal suburb in the Moreton Bay region, which has facilities on both sides of Elizabeth Street in Clontarf, the Department of Transport and Main Roads engaged SMEC to design an active transport overpass from concept through to detailed design and construction. This presentation discusses design considerations, bridge detailing, constructability challenges, and how the team incorporated a unique architectural structure to accommodate pedestrian traffic and bicycle riders in accordance with current accessibility standards. 

Breakfast Creek / Yowoggera Bridge

Paul Bradbury Principal Engineer

Alistair Smith Senior Associate Engineer

As part of Brisbane City Council’s vision to enhance the active transport link for pedestrians and cyclists between the inner city and northern suburbs of Brisbane, Breakfast Creek Green Bridge was constructed connecting Kingsford Smith Drive and Breakfast Creek Road through Newstead Park. It delivers an architectural structure complimenting the rich heritage of Newstead House and surrounding park grounds.

Through a rigorous Multi-Criteria Analysis process, various alignments and structural forms were assessed for the bridge taking into considerations some key aspects including the aesthetics, heritage impact, environment, ground conditions and public Utility Plant constraints. Being in a prominent location in close proximity to the Brisbane River, the preferred bridge form of the main span needed to be a light-weight elegant bridge form, that is aesthetically pleasing in its heritage environment. This led to selection of an asymmetrical steel tied arch structure with the span alignment running skewed across Breakfast Creek utilising a trapezoidal deck of approximately 85m in length. The paper discusses the various bridge forms considered, design development, construction challenges as well as key design aspects, which are largely dependent on the actual arch bridge construction staging and installation methods.