15 Nov 2024
The demands on Aotearoa’s bridges and road structures are ever rising, with increased vehicle weights, extreme weather and climatic events, and heightened expectations of resilience under accidental loadings such as vessel and vehicle impacts.
While modern design standards have made infrastructure more resilient with minimal instances of failure, a large portion of our ageing bridges stem from the late 1930s construction boom. In benign environments with low traffic use, these bridges have performed well. Yet those subjected to harsh environmental conditions, increased loadings and perennial deferred maintenance are fast approaching the end of their service life, or are no longer able to meet expected levels of service and resilience. Most of these aged assets fall short of today’s design standards, having been designed for hazards and loads much lighter than current demands. These factors of aged asset portfolios and increasing demands put the country’s road structures at a critical junction.
Criticality of asset management
Long-life assets such as bridges have for many years been an easy target for “sweating the asset” strategies. Unlike potholes, which are conspicuous in the road surface, structural deterioration generally occurs out of the public view. Relatively benign effects such as corrosion of reinforcing and structural steel, or waterway degradation, if left unattended progressively consume asset life and increase vulnerability. This can lead to life-safety threats, early asset replacement or costly unplanned interventions. Unfortunately, this scenario has become increasingly common among asset owners.
Rising freight loads, traffic volumes and major weather events are exposing the deteriorating conditions and inherent vulnerabilities in our existing structures. Addressing the vulnerabilities that have reached a critical state is consuming an increasing portion of investment in network operations, often at the expense of proactive and preventative maintenance.
Time for asset managers to shine
Asset managers serve as the safety net for the general public, entrusted with identifying threats to asset performance, managing these vulnerabilities and prioritising necessary interventions for the lowest whole-of-life cost. The ethos of maximising the use of existing assets resonates strongly within the asset management community, promoting sustainable resource use and efficient use of taxpayer and ratepayer contributions.
Leading asset owners of Aotearoa’s transport structures, in collaboration with diligent structures managers, have proactively screened their asset portfolios for failure risks not normally captured during condition inspections. Instances like load-deficient bridge halving joints, exposed truss members above deck, or bridges susceptible to vessel impact have been pinpointed through meticulous scrutiny. Through proactive and strategic interventions to address these vulnerabilities, the integrity and safety of critical transport infrastructure can still be protected. However, the growing cost of delivering these treatments presents a barrier to progress.
A pathway forward
The role of asset managers grows increasingly pivotal, albeit with their safety nets wearing thin with growing backlogs of deferred maintenance, arising from decades of insufficient maintenance or asset renewals to maintain a steady state. On top of this, uncertain climate change dynamics, eco-conscious road network operations and enduring fiscal limitations magnify the challenges faced.
Embracing proactive maintenance and targeted improvements is essential for aged assets to achieve their design life, or better still, remain in service indefinitely. This approach requires that asset owners have a thorough understanding of their portfolios, built up on individual asset condition, vulnerabilities and documented management strategies that make best use of these assets. Decisions made on a whole-of-life optimisation approach would put an end to a “throwaway” era. It would also allow the delivery of greater financial and resource operational efficiency through reduced premature asset renewal and reduced need for emergency works.
Reducing levels of service may provide relief where the funding constraints prevent intervention. This trade-off of efficiency for reliability is a necessary consideration for communities residing in sparsely populated regions.
The good news is that good asset managers already have a thorough understanding of the condition, threats and vulnerabilities of the portfolios that they manage. Our design standards have continued to evolve to enable justified replacements to be longer lasting and more resilient now. We must work together to ensure the urgent threats facing the country’s bridges are well understood, and to emphasise the importance of adequate funding and investment to keep these critical community assets safe and serviceable into the future.
Andrew Ball CMEngNZ CPEng IntPE(NZ) is the Transport Structures Asset Management Director at Beca, with more than 20 years’ experience in the life cycle of transport structures from concept design through to end-of-life planning and everything in between.
This article was first published in the September 2024 issue of EG magazine.
