Innovative bridge assessment for a sustainable future
Dr. Pierre van der Spuy, Zutari, and Department of Civil Engineering, Stellenbosch University
Across the world, bridges form the backbone of national transport networks, connecting people, supporting economies, and sustaining growth. Yet many of these structures are ageing. In South Africa, as in much of the developing world, thousands of bridges are nearing the end of their design lives. Assessing whether they can safely continue to carry modern traffic loads has become a pressing and costly challenge.
Traditionally, South Africa’s bridge assessments treat existing structures as if they were newly built, often decades after construction. This overly conservative approach can result in expensive rehabilitation works or, in extreme cases, unnecessary demolitions. As budgets for maintenance and replacement tighten, engineers need smarter, data-driven assessment methods that extend the life of existing infrastructure without compromising safety.
Rethinking Bridge Assessment
Bridge assessment determines a structure’s ability to continue carrying load safely. In South Africa, assessments are typically based on the design standards for new bridges, assuming a 100-year service life and modern traffic loading conditions. However, the actual traffic loads on many bridges are far lower than these design assumptions, and the structures themselves may perform better than expected.
By applying reliability-based bridge assessment methods, common practice in countries such as Canada, the USA, the UK, Denmark, and Switzerland, engineers can quantify design parameters more accurately using real-world data. This allows for less conservative, more cost-effective decisions about rehabilitation, strengthening, or replacement.
A Tiered, Reliability-Based Approach
In developed countries, bridge assessment has evolved into a structured, multi-tier process that gradually refines understanding of a bridge’s true performance. Each level adds accuracy and reduces uncertainty:
- Tier 1 – Initial Assessment:
The bridge is assessed as if new, using standard code-based methods. If the structure fails to meet the safety margins required for new bridges, further analysis follows. - Tier 2 – Reducing Uncertainty:
Engineers collect in-situ data, measuring self-weight and material properties, to replace assumptions with actual measurements. Partial safety factors for permanent loads may be reduced, while those for traffic loads remain unchanged. - Tier 3 – Measuring Behaviour Under Load:
The deformation of the structure under service loads is recorded to better understand its load deformation behaviour. - Tier 4 – Advanced Computational and Testing Methods:
Non-linear finite element analysis and other advanced modelling tools are used to more accurately calculate load capacity.
Further refinements include measuring actual traffic loads on the bridge, testing in-situ material strength, and, ultimately, proof loading, subjecting the bridge to a controlled test to verify its real load-carrying capacity.
Each tier provides additional confidence in the bridge’s performance, enabling engineers to make evidence-based decisions that balance safety and cost.
Why It Matters for Developing Countries
In South Africa and many other developing countries, bridge assessment typically stops at the first tier. This limited approach is understandable, as resources for testing and rehabilitation are constrained, but it can lead to unnecessary expenditure. By integrating even a few additional levels of assessment, substantial cost savings can be achieved through reduced strengthening requirements or by avoiding premature replacement.
For a nation facing growing infrastructure demands and constrained budgets, the implications are significant. A data-driven, reliability-based assessment strategy allows more bridges to be safely maintained for the same investment, an essential consideration for long-term sustainability and economic growth.
Learning from Global Best Practice
European and North American standards provide valuable lessons for countries like South Africa. The Austrian, Swiss, and German codes, for instance, apply the same process: start with a new-bridge assessment, then progressively reduce uncertainty through measurements and testing. Each step refines the assessment, replacing assumptions with verified data, and resulting in more efficient use of limited maintenance budgets.
Applying these principles locally can transform how South Africa manages its bridge network. By focusing on actual performance rather than theoretical design life, engineers can make informed decisions that extend the usability of infrastructure assets while ensuring public safety.
Towards a South African Reliability Framework
The methodologies described above are readily adaptable to the South African context. What remains is to define an acceptable safety margin, one that reflects local materials, traffic conditions, and budget realities. Ongoing research at Stellenbosch University aims to establish this framework, setting out locally relevant reliability targets based on global best practice.
Such a framework will not only improve bridge assessment accuracy but also strengthen the foundation for sustainable asset management and long-term infrastructure resilience.
Smarter Engineering for the Future
Reliability-based bridge assessment is not just a technical upgrade; it represents a shift in thinking. For developing countries, it offers a practical pathway to extend the life of critical infrastructure through better data, smarter analysis, and a more balanced approach to risk.
As the research shows, embracing these innovative assessment techniques can yield tangible savings, reduce unnecessary interventions, and ensure that South Africa’s bridges continue to serve communities safely for decades to come.
Through its commitment to applied research, Zutari is helping redefine what sustainable engineering looks like in the African context, bridging the gap between theory and practice, and between today’s challenges and tomorrow’s resilient infrastructure.