Proof load testing on bridges requires high magnitude loads. Stop criteria are used to avoid irreversible damage or failure during proof load testing. These stop criteria are thresholds to measurable parameters during the test. After reaching a stop criterion, the proof load test needs to be terminated. While in the past, stop criteria have been identified as a single level, this research proposes to use a traffic light system for stop criteria: green light (related to the serviceability limit state), yellow light (as an intermediate level) and red light (further testing is not permitted). The green light relates to the development of cracking, whereas the yellow and red light relate to the failure modes of flexure and shear. To develop stop criteria for the brittle failure mode of shear, thresholds are derived from mechanical models, based on strain measurements and crack widths, as well as using acoustic emission measurements. To validate the stop criteria, three series of experiments are analyzed: reinforced concrete slab strips, straight slabs, and skewed slabs. While field validation of the traffic light system is pending, the developed tool is a step forward to safely test concrete bridges without shear reinforcement.

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.

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.

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.

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.

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.