REVIEW OF AS SCOPE AND GENERAL PRINCIPLES

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1 REVIEW OF AS SCOPE AND GENERAL PRINCIPLES Nigel Powers, VicRoads, Australia Frank Rapattoni, Parsons Brinckerhoff, Australia ABSTRACT AS5100, the Australian Bridge Design Code, is currently under review. AS5100.1, Scope and General Principles, sets out the requirements for the design of new bridges, using limit states principles for bridges associated with roads, rail, tramways, pedestrian traffic and cycleways. It also sets out the design requirements for other structures that support road and rail traffic such as culverts, retaining structures, deflection walls, crash walls and sign gantries. The review of AS5100 and Part 1 commenced in late Overall Part 1 has been updated to reflect current technology and philosophy and to address any recent feedback from industry. The more significant changes include the addition of guidance on safety in design and sustainability and climate change, further guidance on collision protection and utilities and clarification on special studies. This paper provides an overview of the proposed changes and discusses in greater detail the more significant changes. INTRODUCTION AS has 7 parts with AS being Part 1: Scope and General Principles. AS sets out the requirements for the design of new bridges, using limit state principles for bridges associated with roads, rail, tramways, pedestrian traffic and cycleways. It also sets out the design requirements for other structures that support road and rail traffic such as culverts, retaining structures, deflection walls, crash walls and sign gantries (Standards Australia 2004). The review of AS Bridge Design Code was originally proposed by Transport and Main Roads, Queensland in mid This was subsequently approved by Standards Australia in late 2011 and the review of the AS5100 commenced. Once approved, Standards Australia called a meeting of the AS5100 main committee BD-090. This committee consists of industry representatives that have been nominated by Nominating Organisations such as Austroads and Engineers Australia. At the initial meeting the committee decided on the scope of the review and then agreed on how the review would proceed. Working groups were set up to undertake the reviews with one working group to review Parts 1, 2 & 7. The working group tasked with reviewing AS was chaired by Nigel Powers, VicRoads and Austroads, and consisted of members from the road and rail industries, public organisations and private companies. Work started on the review in early 2012 with the initial scope of generally updating to current technology and methodologies. During the review, the scope developed to include feedback from industry and developments within and outside of Australia. The following sections of this paper will broadly cover the changes to AS with more emphasis put on the major changes. The intent of this paper is to inform industry of the changes and highlight the more significant changes whilst facilitating discussion at the Austroads Bridge Conference MINOR CHANGES Overall there have been numerous changes made in AS but many sections have been left largely untouched such as the design philosophy. Some of the more minor changes are as follows: ARRB Group Ltd and Authors

2 Clarification on the use of the standard for new and existing structures, Several definitions added such as relevant authority, crash wall and deflection wall for greater clarity and to update for new content, Clause references have been removed from Section 4 Notation to enable easy revision and future updates, The addition of urban debris based on the recent flood events in Queensland, Greater linkages into the Austroads Guide to Road Design to define the requirements for aspects such as geometry, vertical clearance and pedestrian and cycleway bridges. Further guidance on the use of special performance level barriers, and General updating to align with changes within the overall AS5100 and the inclusion of AS Rehabilitation and Strengthening of Existing Structures and AS Timber. MAJOR CHANGES A number of significant changes were made to AS in the process of the review. These include: The addition of guidance on safety in design and sustainability and climate change, Further guidance on collision protection and utilities, and Clarification on special studies. The following section of this paper highlights and discusses these changes. Safety in Design Safety in design is a principle that has significantly developed in profile across the industry in recent times. In the last decade, safety in design has been mandated in some State and Territory legislation across Australia and must be incorporated into all designs. Even though it is in State legislation, the working group considered it important and necessary to further highlight it to ensure designers are aware and take this into account in their designs. There are many and varied definitions for safety in design. The working group reviewing AS adopted the definition of the identification, assessment and minimisation as low as reasonably practicable of risks to persons during construction, future operations, in-service maintenance and eventual decommissioning of an asset. In the review, the working group also highlighted the importance of documentation of risks and actions. There are two main reasons for this. Firstly to highlight the risks associated with a design, such as hazardous features or materials that might be realised during the life of an asset. Secondly, it is important to document the risk assessment, the mitigation of risks and also highlight risks that cannot be eliminated during the design phase and need to be managed at a later stage. Sustainability and Climate Change Sustainability and climate change are buzz words used across the industry and across the world currently. The exact nature and impact of climate change is uncertain and whether it actually exists is a point of much debate. Sustainability seems to be more widely accepted although the drive for it can vary across the industry and community. The concept of sustainability for bridges includes many particular factors not normally affecting buildings. To quote Daniel Whittemore (2010): Many fellow bridge engineers, when faced with the term "Sustainable Bridge", conjure up images in their minds of picturesque glued-laminated structures blending in harmoniously with their surroundings deep in a national park. Or, their imagery may stop at a vegetated wildlife crossing over a perilous section of interstate. Notably, both of these images would seem to have ARRB Group Ltd and Authors

3 very little applicability to the real world problems faced by either the bridge owner or bridge professional, and would be quickly dismissed as something unpractical or of limited usefulness. In reality, such images and the basic assumptions behind them are off the mark. To reframe the discussion, sustainable design is commonly defined as "development that meets the needs of the present without compromising the ability of future generations to meet their own needs." Extrapolating from this basic definition, a sustainable engineering project such as a bridge can therefore be defined as one that is conceived, designed, constructed, operated, maintained, and eventually put out of service in such a fashion that these activities demand as little as possible from the natural, material and energy resources of the surrounding supporting community. So, in practice, sustainable bridge design is not about strictly environmental concerns, or only about energy conservation. Instead, it is a more holistic - top to bottom review and evaluation of a bridge project s merit and compatibility with the indigenous human and wildlife populations on both the micro and macro scale. As such, it has the potential to be a useful tool to quantify and determine the true scale of even indirect or unintended deterioration done to our environment, society and the community at large. The working group reviewing AS thought it was important to include this subject in the review. Acknowledging the above, it was seen as important that our designs are conceived with this in mind to ensure sustainability into the future. It is much easier and more cost effective to address these now than in the future and often any changes are cost neutral. The working group acknowledge that many relevant authorities have their own policy on sustainability and climate change and this should be referred to in undertaking a design. Where this is not the case, several points have been provided to guide the designer. Also, AS : Climate change adaptation for settlements and infrastructure A risk based approach was referenced for additional guidance on the topic. Collision Protection The appropriate level of collision protection is often a topic of debate across the industry. The decision is often a challenging balance of safety versus cost with other aspects such as amenity, aesthetics and geometry also coming into account. In the review, the working group focussed on providing additional guidance on the collision from railway traffic as this area is often an area of conflict and uncertainty. In A an approach is defined where bridges over railways shall have a clear span between abutments unless the relevant authority determines this is not achievable. If a clear span is not achievable then (in order or preference): Alternative loads paths shall be provided to safeguard against collapse of the bridge superstructure, or Heavy construction piers must be provided with provisions to avoid head-on impact by a derailed train. In the opinion of the working group, it appears that a clear span and alternative load paths are rarely adopted and heavy construction piers are common practice. This is not the intention of the clause as heavy pier construction increases the risk of a major incident and loss of life for railway users unless head-on impact by a derailed train with the pier can be avoided. To address the above, the working group have provided additional guidance and information in the draft AS Included is the alternative of a risk analysis and to ensure the risk to loss of life is as low as reasonably practicable. Additional guidance is given on the risk analysis, in particular on the bridge type and hazard level. Also, guidance has been provided on designing for collision including scenario prediction, literature review and collision simulation. Finally, frangible piers have been more clearly defined to assist designers when designing a bridge with alternative load paths. Even though the working group have taken the above steps, it is important for designers and asset managers to carefully consider all options with collision protection of bridges over ARRB Group Ltd and Authors

4 railways. The best solution for the reduction of risk is always to have a clear span even with the mitigation actions associated with the other possible options. The collision protection of bridges over railways is comprehensively covered in the Austroads Bridge Conference 2014 paper by Frank Rapattoni and Joe Muscat who are members of the AS working group. Utilities Road and rail bridges are often the most cost effective and convenient way for utility service authorities to carry their services from one side of an obstacle to another. In AS some guidance was provided on conditions for attachment of utilities to bridges and this has been greatly expanded in the draft of AS The clause on utilities now better addresses risks to ensure the design life of the bridge and the utility. This has been influenced by the recent flood events in Australia with emphasis put on protection of utilities from flood debris as well as from other forms of damage such as vehicle impact and vandalism. Also addressed were the risks associated with utilities inside closed cells. Utilities conveying dangerous substances have been banned from closed cells and if liquids are to be conveyed within closed cells then appropriate level of drainage shall be provided in case of leaking or bursting utilities. Special Studies The industry as a whole is moving at tremendous speed with technology developing and prospering on a daily basis. All areas are progressing, with the adoption of the latest materials, methods and techniques for the advancement of the industry and in some cases competitive advantage over other consultants, contractors and suppliers. The working group acknowledge this and at the same time acknowledge that it is often not possible and not viable to keep up with or ahead of this progress. Rather than restrict or limit it, the working group considered it appropriate to include an appendix that allows for it and allows the industry to embrace technology. Now included is Appendix D Special Studies which states that Where changes are made to a part or all of the design processes detailed in AS5100 or new information or methods are introduced, they should be established by special studies. Special studies can be used to establish information or methods not defined in AS5100 and define more accurately information and methods in AS5100. Also, special studies can be used to evaluate loads or other actions than those specified in AS5100. It is important that special studies have the appropriate level of rigour and are well documented. Examples of special studies are bridge specific live loading used in recent years for the West Gate Bridge, Victoria, ANZAC bridge, New South Wales, and Gateway Bridge, Queensland. CONCLUSION The working group reviewing AS have taken on feedback from industry and adopted or improved on advancements within and outside of Australia ensuring the progression of the Standard and the industry as a whole. The major changes made address topics including safety in design, sustainability and climate change, collision protection, utilities and special studies. The changes made to items such as collision protection will ensure that the bridges we design now will be safe for all road and rail users for the 100 year life of the bridge. The inclusions of mandatory safety in design and consideration of sustainability and climate change ensure that these important aspects will be incorporated into designs and reduce the risk of occupational health and safety issues and level of service issues of the structures we design. There will always be the need to undertake further review, refinement and development but this version of AS has taken significant steps forward from the 2004 version. ARRB Group Ltd and Authors

5 ACKNOWLEDGEMENT I would sincerely like to thank the AS working group for the significant time and effort they have put in over the past 3 years. The review of a Standard can be a quite difficult task often with a significant workload, frequent travel, complex issues and conflicting views and opinions. Many members volunteer their time and all members will often work on the Standard on their own time which is an incredible effort considering significant work and family commitments. REFERENCES Daniel Whittemore 2010, P.E., LEED AP, Sustainable Structures for the Bridge Engineer, Structure Magazine Standards Australia 2004, Bridge Design Part 1: Scope and General Principles AS , Standards Australia, NSW Standards Australia 2014, Draft Bridge Design Part 1: Scope and General Principles DR AS5100.1, Standards Australia, NSW AUTHOR BIOGRAPHIES Nigel Powers has been working with VicRoads since graduating from RMIT University in At VicRoads he has successfully fulfilled roles in numerous areas related to bridges including design, construction, maintenance, inspection and management. Currently Nigel is the Manager Technology and Assets in the Structures Group where he is responsible for standards, policy and guidelines for the design, construction, maintenance and management of structures across VicRoads. Nigel is the VicRoads representative on the Austroads Bridge Task Force, the Austroads representative on the Standards Australia committee BD-090 and the chair of the working group reviewing Parts 1, 2 & 7 of AS5100. Frank Rapattoni s career spans some 43 years and includes key positions at VicRoads, BlueScope Steel and Cardno. His experience includes bridge design and construction, flood studies, road design and construction, geotechnical investigations, planning, traffic engineering, road safety audits and market development. He is accredited as a Proof Engineer by VicRoads. Frank has a successful track record of key innovations. He led the development of PSC T-slabs and Super-T beams which changed the way short to medium span bridges are built in Australasia. At BlueScope Steel, Frank actively developed innovative steel bridging systems and was responsible for publications on steel bridges, design aids and concept designs of a number of bridges in cooperation with contractors and consultants. He has also published 21 technical papers on bridge engineering. Frank is a member of Australian Standards Committee BD/90 responsible for the Australian Bridge Design Code AS Copyright Licence Agreement The Author allows ARRB Group Ltd to publish the work/s submitted for the 9 th Austroads Bridge Conference, granting ARRB the non-exclusive right to: publish the work in printed format publish the work in electronic format publish the work online. The Author retains the right to use their work, illustrations (line art, photographs, figures, plates) and research data in their own future works The Author warrants that they are entitled to deal with the Intellectual Property Rights in the works submitted, including clearing all third party intellectual property rights and obtaining formal permission from their respective institutions or employers before submission, where necessary. ARRB Group Ltd and Authors