Reinforced concrete solid slab bridges are often skewed to cross underlying objects, which increases the shear stress concentration at the obtuse corner. Limited experimental evidence on skewed slabs is available, so that both the shear capacity and failure mode in skewed slab bridges are subject to discussion. Therefore, an experimental program at Delft University of Technology investigated the capacity and failure modes in skewed slabs under concentrated loads near the edge. Results from 15 tests on five 1:2-scale slab members result in shear failures and show a decreasing capacity with increasing skew angles. The obtuse corner is found to be critical; the reinforcement layout did not influence the capacity significantly. Comparisons with calculation methods showed reasonable accuracy. A proposed method using a larger integration length around the peak shear stress obtained from linear finite element modeling may be recommended for assessment.

As infrastructure continues to age and traffic levels intensify, there is a growing need for efficient methods to verify the reliability of many existing structures. Field testing offers the possibility to assess the current condition of a structure. Specifically, in a proof load test, substantial loads are applied to evaluate the structure's resistance to future loads that could compromise structural safety. However, to prevent excessive test loads and their potential damage, it is desirable to assess structural reliability by monitoring the response under more moderate loads. This study merges laboratory and in-situ testing results through a Bayesian update of the structural reliability after each successful load application. Two case studies are presented where laboratory testing on structurally similar elements and analytical modelling provide ample evidence to justify test load reductions of 20 % and 25 %. The proposed method offers a systematic framework to link the structure's response during testing to structural reliability and address the uncertainties in resistance, loads and measurements. Nonetheless, the representativeness of the data in terms of structural similarity and uncertainties related to measurements continue to be significant factors. Despite these challenges, incorporating monitoring data during proof load testing is expected to reduce target loads in most cases.

Tunnel fires are relatively rare, but the consequences of damage can be large. This paper addresses the influence of tunnel fires on the ensuing damage to the concrete lining. To address this question, the existing literature is reviewed. This review focuses on different methodologies to get a well-rounded insight into the problem: relevant aspects of tunnel fire dynamics, theoretical considerations on the relation between the fire source and the resulting damage to the concrete, experimental evidences from testing concrete elements subjected to fire as well as data from tunnel fires that have taken place in the past, and insights from numerical analysis. The result is a comprehensive overview of what is currently known about the relation between a tunnel fire and the ensuing damage in the concrete, as well as guidance for the assessment of concrete tunnel linings under fire hazard and recommendations for future research to address the remaining open questions on this topic. To conclude, this paper gives a valuable overview based on different methodologies from the literature to give researchers, engineers, and asset owners a better insight in how fires can affect the concrete tunnel structure.

Despite the low probability of occurrence, fire events are a major hazard for structures, which can lead to severe socio-economic impact. Although reinforced concrete (RC) tunnels are an important component in transportation infrastructure, their structural behaviour under high temperatures is not yet fully understood. This study investigates the thermo-mechanical response of tunnels subjected to fire using nonlinear finite element analysis (NLFEA). For this purpose, recent experimental tests of large-scale reinforced concrete tunnels with and without fire protection are simulated. Different modelling strategies are discussed, and a detailed description of the constitutive model employed is presented. Then, model-to-model and model-to-experiment comparisons are conducted to identify the advantages and limitations of each approach. The analyses demonstrate the relevance of proper spalling modelling on the tunnel’s temperature distribution. The models also show a good agreement with the experimentally observed damage patterns. Finally, recommendations regarding modelling choices and further research topics are discussed.

Work–life balance (WLB) in academia remains a challenge as a result of increasing workloads, precarious employment, and expectations of constant availability. The COVID-19 pandemic exposed these structural barriers to work–life balance in academia and also clearly showed the inequities related to hybrid and remote work for women, caregivers, and underrepresented minorities. This paper highlights the key factors that pose challenges to WLB in academia, how these challenges have been worsened by COVID-19, and what we can learn from pandemic times solutions to devise inclusive practices for long-term structural change. The methodology used in this paper is a critical review of 298 published articles. This review is structured as follows: The structural barriers, inequities, and workplace policies that impact academic WLB are first inventoried. Then, the lessons learned from the pandemic are studied by dividing the short-term disruptions from the permanent shifts. Finally, inclusive solutions, focusing on institutional boundary-setting, workload redistribution, hybrid work policies, and mental health support are presented. This paper makes three key contributions: (1) it provides an intersectional understanding of WLB, accounting for gender, caregiving, ethnicity, migration, and social class; (2) it frames COVID-19 as a driver for structural reform, rather than an anomaly; (3) it bridges WLB research and policy design, proposing actionable strategies for universities and policymakers. By placing equity and inclusion at the core of the analysis, this work advocates for systemic solutions that promote a sustainable academic environment aligned with principles of social justice.

Concrete is strong in compression andweak in tension,which results in a lowtoughness and ductility in plain concretemembers under flexure. The traditional solution is to use steel reinforcement bars, but other solutions can include the use of distributed fibers in the concrete mix. To transition to a bio-based circular economy, natural fibers such as abaca and coconut are currently being explored. Proper design requires understanding their tensile behavior under flexural loading. Experiments on concrete prisms with natural fibers under third-point loading have been carried out. These are compared and fitted with an analytical moment-curvature response incorporating a quad-linear tension model, enabling strain compatibility analysis for structural design. While experiments on larger scale and on reinforced concrete members have not been carried out yet, the current results provide a foundation for the analytical modelling of members with natural fibers in bending.

As the construction industry shifts toward more sustainable solutions, bio-based materials are emerging as promising alternatives to conventional building components. This work explores two primary categories: supplementary cementitious materials (SCMs) derived from agricultural byproducts, and natural fibers used to reinforce cement-based composites. Materials such as rice husk ash and sugarcane bagasse ash can partially replace Portland cement, lowering carbon emissions while maintaining structural performance. At the same time, plant and animal-based fibers like jute, sisal, coconut, and wool enhance mechanical properties such as tensile strength and crack resistance. The use of renewable biopolymers and bio-based phase-change materials further improves workability, insulation, and energy efficiency. While challenges such as durability and material variability remain, bio-based materials offer a compelling pathway toward greener, eco-efficient construction.

Proof load testing (PLT) offers a valuable and sustainable alternative to analytical approaches for improving knowledge on the safety level of existing bridges, providing an in-situ measurement of structural bearing capacity under actual traffic loads by reducing resistance uncertainties and associated probability of failure if the test is passed. The present paper investigates the influence of the PLT on the structural reliability of prestressed concrete I-type simply-supported decks representing the most common type of existing bridges in Italy. By supplying data on the lower-bound of the capacity distribution, the PLT turns into an updated estimation of the bridge reliability. A fully-probabilistic analysis is developed combining random uncertainties on both materials and load effects with epistemic uncertainties. A traffic load model variable based on Eurocode Load Model 1 effects is calibrated to provide consistent modelling with code-prescribed safety levels. Structural capacity of the edge girder is considered both in terms of ultimate limit state for flexure and shear and serviceability limit state in terms of cracking load which could affect long-term bridge durability. The manuscript main contribution lies in developing a reliability-based approach to PLT that accounts for both prior (before test) and posterior (after test) structural reliability, incorporating conditioning on the success of the test. A sensitivity analysis according to the partial safety factor method is presented to investigate the impact of different proof loads assuming different Capacity-to-Demand Ratios (CDR). A case-study bridge is investigated where a proof load was executed recently demonstrating the benefit of the PLT in case of CDR lower than unit. The case study also showcases the possibility to significantly reduce the failure probability during the test when the target level is imposed with a number of intermediate levels of load steps.

This study explores UAV-based 3D modeling for bridge damage assessment. UAVs with highresolution cameras captured images of two bridges at different life cycle stages and locations. These images were processed into detailed 3Dmodels, offeringmore accurate evaluations than traditional visual inspections (VI). The models provided precise damage localization, geometric data information, and identified areas requiring urgent maintenance, reducing repair costs and time. Despite the advantages, challenges such as model accuracy and flight planning precision were noted. The results showed that larger and more complex bridges require significantly greater resources for 3D modeling, including longer flight and processing times, higher data volumes, and increased detail in the models, as reflected in the differences between the two case studies. Future research should focus on optimizing data acquisition, enhancing algorithms, and integrating augmented reality (AR) to improve collaboration and decision-making in bridge inspections.

Reinforced concrete structures (RCSs) face increasing vulnerability due to aging, deterioration, and climate change, compounded by seismic events. This paper proposes a framework that integrates time-dependent deterioration mechanisms, climate projections, and seismic vulnerability analyses. The methodology develops deterioration profiles using site-specific data while employing Performance-Based Earthquake Engineering (PBEE) to evaluate seismic risks. Climate scenarios from the IPCC address non-stationary climate impacts, such as accelerated corrosion. This research represents a first step toward defining a systematic process for assessing these combined effects. The proposed framework addresses critical gaps in traditional vulnerability assessments and contributes to improving the resilience of aging infrastructure under combined environmental and seismic hazards.

The field of proof-loading has expanded over the last decade with excellent examples of successful collaborations and multidisciplinary approaches. Advanced testing has, as one of the essential subjects in an interdisciplinary assessment, brought significant value to further understanding of structural responses and failure mechanisms related to concrete bridges. This paper presents laboratory and field collapse testing examples in the Netherlands and Denmark, and related investigations of the response of non-shear reinforced slabs until failure. A special focus is dedicated to load application, examples of test approaches, some practical insights and test result comparison. Considerations of the laboratory and field test planning in synergy will be discussed based on the results and experiences obtained. A substantial margin to ultimate failure was found from crack identification or other measurable warnings in all tests. These observations suggests that it is possible to get sufficient warning even for non-shear reinforced concrete slabs structures.

The accelerated population growth in Guayaquil has increased the demand for pedestrian infrastructure, emphasizing the need for sustainable, cost-effective materials. This study evaluates three alternatives for pedestrian bridges: A36 structural steel, conventional concrete (OPC), and geopolymer concrete (GPC). These solutions are compared using structural analysis in SAP2000, life cycle assessment (LCA), and cost evaluation through BIM modelling in Revit. Both A36 steel and Ordinary Portland Concrete (OPC) demonstrated superior structural performance, whereas GPC displayed increased deflections due to a lower modulus of elasticity. However, GPC offered significant environmental advantages, with CO₂ emissions up to 67% lower than OPC and potential cost savings of up to 11% at higher strengths. The findings underscore GPC’s promise as a sustainable alternative, offering reduced carbon footprint and competitive costs.

During a proof load test on a bridge, high magnitude loads are applied. To avoid causing irreversible damage, thresholds to the structural responses, the so-called stop criteria, need to be defined. This paper proposes to categorize stop criteria into three levels: green light (related to the serviceability limit state), yellow light (related to potential irreversible damage) and red light (related to potential local collapse). For the Ultimate Limit State, stop criteria for shear and flexure are defined. Shear stop criteria are derived from mechanical models, using traditional strain measurements and acoustic emission measurements. These stop criteria are validated with experiments on reinforced concrete slab strips, straight slabs, and skewed slabs. The resulting traffic light system gives the bridge engineer a tool to make decisions during a proof load test. This approach is a step forward in the interpretation of structural responses during proof load testing.

Structural assessment of existing bridges becomes a challenging process in the presence of deterioration phenomena and outdated design action and resistance models. This paper explores the potentiality and effectiveness of reliability-based methods in the structural evaluation of existing PC I-girder bridges, highlighting scenarios where conventional methods, such as Partial Safety Factor Method, may underestimate structural capacity. Based on detailed visual inspection, in-situ data of deterioration phenomena is introduced in the probabilistic analysis and a Eurocodebased traffic model is adopted for the traffic load effect characterization. A case study is discussed emphasizing the advantages of adopting a reliability-focused assessment strategy and demonstrates that most of the investigated girders do not require intervention, even though considered inadequate, enhancing the efficiency and sustainability of infrastructure maintenance.

In the Netherlands, approximately 70 prestressed slab-between-girder bridges are present, built between the 1950s and 1970s. These bridges typically do not fulfil the requirements for shear in an assessment, but show no signs of distress upon inspection. Additional load-carrying mechanisms and effects of global bridge behaviour, such as compressive membrane action, compressive arch action, load (re)distribution, and the influence of the crossbeams, which could significantly enhance the structural capacity, are typically not considered in the assessment calculations. This paper studies the global structural behaviour experimentally of the full slab-between-girder bridge system as compared to the isolated T-girder. For this purpose, two spans of an existing multi-span T-girder bridge, the Vecht Bridge, built in 1962 were tested. In total, three experiments were carried out in span 4 (full system), and four experiments in span 2 (after applying saw cuts in the deck to create isolated girders). This paper reviews the state-of-the-art regarding collapse testing, global bridge behaviour, and slab-between-girder bridges in the Netherlands. Then, the results of the experiments are presented and analysed. It is expected that these experimental results will form the basis of improved assessment methods for slab-between-girder bridges in the Netherlands and beyond.

Safe proof loading of concrete bridges requires reliable stop criteria. Such criteria must ensure sufficient margin to the ultimate resistance and may be based on observations from advanced testing. In particular, the identification of thresholds related to pre-stressed and non-shearreinforced slab structures is currently ongoing with an addition of specific focus on potentially brittle failure modes of such structures. This paper presents representative examples of identifying stop criteria and target load thresholds using a combination of laboratory- and in-situ testing. Responses from recently tested structures and structural elements will be presented to enable discussion and perspectivation. The presented test results show measurable warning with sufficient margin from crack initiation to stop criterion. It was additionally seen that the target load often may be the governing threshold when proof load testing.

In the more than sixty years of experience in forensic structural engineering of Adviesbureau Hageman, damages in concrete parking structures in The Netherlands repeatedly passed by. In a study on these damages,mainly based on the comprehensive archive of Adviesbureau Hageman, an overview of the various damages that can be distinguished is made. Furthermore, one category of damages, that is not limited to only parking structures, but generally occurring in concrete structures, is damage to concrete corbels. In order to investigate the behaviour of such corbels under load imposed by the concrete elements that they support, finite element analyses (FEA) are performed with the FE Code ATENA. It was found that damage only occurred in case the bearing material was situated at the edge of the corbel or with an additional horizontal load. In both cases the corbel withstood a rather significant load. In the paper the basic findings of the overview of damages in concrete parking structures and the study on corbel behaviour are presented.

As the bridge stock in many countries is ageing, the topic of bridge assessment is gaining more importance. Bridge load testing is one of the tools that can be used to assess existing bridges. Over the past decade, assessment, and by extent, bridge load testing, have been applied, studied, and improved in various countries. This paper provides an international overview of bridge assessment practices, load testing practices, and recent research insights. Moreover, synergies in the research activities, collaboration efforts via technical committees, and recently published codes and guidelines are highlighted. The major topics of importance identified are linking load testing to global and element structural behaviour, improved on-site sensing techniques, incorporating load testing with structural monitoring, non-destructive evaluation, numerical modelling, probabilistic analysis, and leveraging the use of digital tools for embedding detailed load testing insights into modern bridge management systems. It can be concluded that bridge load testing is a dynamic field of application and research, for which international collaboration and comparing best practices is essential.

The authors regret that the original publication of this paper did not assign the correct affiliations to R.D.J.M. Steenbergen. The authors would like to apologise for any inconvenience caused.

Proof load testing for assessment can involve a large risk due to the high loads. Stop criteria can reduce this risk. Stop criteria are necessary for shear, which is a brittle failure mode. This paper describes the development of shear stop criteria for slab strips. The shear stop criteria are developed by combining theoretical concepts related to cracking, as well the relationship between bending- and shear-critical regions, along with insights from the Critical Shear Crack Theory and the Critical Shear Displacement Theory. The shear stop criteria are validated with fourteen beam tests. The result is a set of shear stop criteria in a “traffic light system” with a green light level related to serviceability, and yellow and red light related to the ultimate limit state for shear. These stop criteria serve as the basis for a global approach for proof load testing of reinforced concrete bridges.