Assessment of time-dependent structural resistance of RC bridges in the Barak valley region, Assam, India

The reinforced concrete (RC) bridges deteriorate essentially due to strength loss induced by aging of the structure, extreme weathering conditions, and unplanned increased service loads. However, these load variations and aging factors equally could compromise structural reliability, and service life for continuous satisfactory operation of service bridges for future performance. A reasonable model of bridge strength and applied loads becomes the basis of accurate prediction of bridge functionality. Hence, time-dependent reliability approaches could be used efficiently to gain a reliable understanding of issues facing by the bridges in the study area for appropriate solutions. In this paper, the reliability of bridges under harsh conditions studied using time-variant and time-invariant reliability models in which both load and resistance considered as a time-dependent parameter. A combination of condition rating (CR) and time-dependent load employed to attain accurate insights about the degradation of structural resistance of the existing bridges. The result shows the significant impact of aging as well as traffic loads influence in the service life of both national highways (NH) and rural road service bridges. These observations might be used to adopt appropriate planning strategies as well as rational decisions to ensure the safety of the bridges for future operation.

Multi-Temporal InSAR for transport infrastructure monitoring: Recent trends and challenges

Worldwide, transport infrastructure is increasingly vulnerable to ageing-induced deterioration and climate-related hazards. Oftentimes inspection and maintenance costs far exceed available resources, and numerous assets lack any rigorous structural evaluation. Space-borne Synthetic Aperture Radar Interferometry (InSAR) is a powerful remote-sensing technology, which can provide cheaper deformation measurements for bridges and other transport infrastructure with short revisit times, while scaling from the local to the global scale. As recent studies have shown the InSAR accuracy to be comparable with traditional monitoring instruments, InSAR could offer a cost-effective tool for long-term, near-continuous deformation monitoring, with the possibility to support inspection planning and maintenance prioritisation, while maximising functionality and increasing the resilience of infrastructure networks. However, despite the high potential of InSAR for structural monitoring, some important limitations need to be considered when applying it in reality. This paper identifies and discusses the challenges of using InSAR for the purpose of structural monitoring, with a specific focus on bridges and transport networks. Examples are presented to illustrate current practical limitations of InSAR; possible solutions and promising research directions are identified. The aim of this study is to motivate future action in this area and highlight the InSAR advances needed to overcome current challenges.

Optimal strengthening by steel truss arches in prestressed girder bridges

This work focuses on the proposal and the evaluation of a new consolidation system for prestressed reinforced concrete (PRC) beams of girder bridges. The system consists of two arch-shaped steel trusses placed alongside the lateral faces of the beam to beconsolidated. The arches develop longitudinally along the entire span of the beam and in elevation using the available height of the PRC cross section. The consolidation system is characterized by its own external constraints, independent from those serving the pre-existing element. The efficiency of the system with respect to parameters variability is described also focusing on the ratio between the load discharged by the consolidation system and the total applied load. Referring to a case study, the consolidation of a PRC beam is presented adopting the proposed system with respect to the usually adopted external prestressing technique. The cross sections properties of the steel arch shaped trusses are defined by means of a structural optimization process using a genetic algorithm, identifying the minimum steel consumption. Finally, a preliminary cost-benefit analysis is performed for the proposed solution for a comparison with other commonly adopted techniques.

Assessing and mitigating risks to bridges from large wood using satellite imagery

The transport and accumulation of floating large wood (LW) debris at bridges can pose a major risk to their structural integrity. The impact forces arising from collisions of LW can cause significant damage to piers, and accumulations can constrict the flow and exacerbate scour at piers and abutments. Furthermore, LW accumulations increase afflux upstream of bridges, heightening flood risk for adjoining areas. Consequently, there is a need for a practical and rapid approach to identify bridges prone to LW-related hazards and to prevent the formation of LW accumulations. This paper proposes an approach based on satellite imagery to (i) quantify the risk of LW at a bridge structure and (ii) locate a LW-trapping system upstream of the identified vulnerable bridges to dramatically reduce risks of LW-related damage. This methodology is applied to major rivers in Devon (UK). 26 bridges were identified as at risk to LW with the majority prone to LW jams. Furthermore, satellite imagery was used to identify 12 locations for the potential installation of LW trapping systems for bridge protection. The results reported in this paper show that satellite imagery is a powerful tool for the rapid assessment and plan of mitigation measures for bridges at risk to LW.

Resilience metrics for transport networks: a review and practical examples for bridges

Climate change, diverse geohazards and structural deterioration pose major challenges in planning, maintenance and emergency response for transport infrastructure operators. Hence, to manage these risks and adapt to changing conditions, well-informed resilience assessment and decision-making tools are required. These tools are commonly associated with resilience metrics, which quantify the capacity of transport networks to withstand and absorb damage, recover after a disruption and adapt to future changes. Several resilience metrics have been proposed in the literature, however, there is lack of practical applications and worked examples. This paper attempts to fill this gap and provide engineers and novice researchers with a review of available metrics on the basis of the main properties of resilience, i.e. robustness, redundancy, resourcefulness and rapidity. The main steps of resilience assessment for transport infrastructure such as bridges are discussed and the use of fragility and restoration functions to assess the robustness and rapidity of recovery is demonstrated. Practical examples are provided using a bridge exposed to scour effects as a benchmark. Also, an illustrative example of a systems of assets is provided and different aspects of resilience-based decision making are discussed, aiming to provide a comprehensive, yet straightforward, understanding of resilience.

Seismic resilience for recovery investments of bridges methodology

Bridges are fundamental links for the movement of goods and people and bridge damage can thus have significant impacts on society and the economy. Earthquakes can be extremely destructive and can compromise bridge functionality, which is essential for communities. Evaluation of bridge functionality is thus fundamental in the planning of emergency responses and socioeconomic recovery procedures. It is especially useful to define parameters to assess investments in bridge infrastructure. Resilience is a key parameter that can identify decision making procedures necessary for recovery investments. In this regard, resilience can be defined as the rapidity of a system to return to pre-disaster levels of functionality. This aim of this work was to assess the lack of robust analytical procedures for quantifying systematic restoration for earthquake-damaged bridges, to provide a link between the assessment of resilience and its application in decision making approaches. The proposed methodology (called seismic resilience for recovery investments of bridges) uses functionality–time curves that allow quantification of resilience along with readable findings for a wider range of stakeholders. The results presented in this paper should be of interest to multi-sectorial actors (i.e. bridge owners, transportation authorities and public administrators) and could drive interdisciplinary applications such as the assessment of recovery techniques and solutions.

Kincardine Bridge – An engineering triumph 85 years on

When construction of Kincardine Bridge was completed in 1936, it was the longest road bridge in Scotland and the largest swing-span bridge in Europe. 85 years on, the Historic Environment Scotland Category A listed bridge remains in service and carries approximately 12,000 vehicles daily across the Forth Estuary. On occasions when the Queensferry Crossing and Forth Road Bridge are closed simultaneously, the Kincardine Bridge offers the shortest available diversion route across the estuary for unrestricted traffic. A 2019 principal inspection highlighted deterioration to some structural elements and in 2020 DMRB bridge assessment standards were revised. As a result, a quantitative assessment was undertaken to provide confidence that the bridge remains safe for use and fit for purpose and to inform future maintenance requirements. This paper focuses on the multitude of structural forms that comprise the overall bridge and how they: - have comparably performed relating to durability over the past 85 years - have been quantitatively assessed - have comparably withstood present-day traffic loading criteria - will be maintained in future.

Simulating the Role of Transportation Infrastructure for Community Disaster Recovery

Functional recovery of transportation infrastructure after a disaster is essential for community disaster resilience as the recovery of damaged community components depends on their accessibility for repair. This paper presents a community disaster recovery simulation that accounts for community component's accessibility for repair using a demand-supply framework. Considered components of a community are viewed as suppliers and/or users of various resources and services essential for community functionality, reflected in components’ supply and demand properties. Whenever the demand of a component is not met, that component ceases to operate, simulating interdependency effects. Similarly, recovery demand is attributed to damaged components, representing the amounts of resources and services (e.g., workers, machinery and transportation services) these components need to recover. The proposed framework is illustrated on a virtual community with 3600 inhabitants supported by several interdependent infrastructure systems. The results show that the transportation network damage slows down the recovery of the virtual community by preventing access to damaged components and reducing the ability of the community to mobilize available repair resources. Furthermore, the effect of such prolonged transportation system recovery on the damage-free infrastructure systems whose functionality was decreased due to their dependency on the affected infrastructure systems, is quantified.