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 can be used to directly assess bridges. Over the past six years, fundamental research has been carried out at Delft University of Technology to derive mechanics-based shear stop criteria and to enable structural reliability updating via Bayesian methods. To translate these research findings into recommendations for practice, aspects related to determining the target load, location of the load, location of the sensors, and practical implementation steps have been addressed. This paper illustrates these recommendations with a hypothetical case study showing the influence on the preparation and execution of proof load tests. The result is practical guidance for proof load testing, demonstrating how information sources can be combined to achieve minimal target loads. While application via a full-scale test is pending, these recommendations reflect the latest research insights into proof load testing and its implementation strategies.

This work presents a concrete-specific analytical framework for modelling body-wave scattering by explicitly tailoring multiple-scattering theory to the microstructural characteristics of concrete. Instead of treating scattering parameters as abstract statistical quantities, the framework parameterizes the key inputs of scattering theory in terms of physically measurable concrete attributes, including coarse aggregate size, volume fraction, and the material property contrast between the matrix and the dominant scattering phase, whether coarse aggregates or the interfacial transition zone. By embedding these microstructure-informed parameters into a two-phase spatial statistical formulation, closed-form expressions for total and transport scattering cross-sections are derived and directly linked to ultrasonic diffusivity through diffuse wave theory. Experimental validation using geopolymer concrete members and published data for ordinary concrete demonstrates consistent agreement between theoretical predictions and experimental measurements across a broad frequency range. The proposed framework therefore renders body-wave scattering in concrete quantitatively computable from material composition, providing a physically grounded basis for quantitative interpretation of diffuse wave transport, energy equilibration, and coda-wave velocity changes without reliance on ad hoc fitting parameters.

Submerged floating tunnels are more and more considered as a suitable solution to cross water channels limiting environmental impact on the visual landscape and ensuring large ship passage while crossing large distances between coasts. The design of this kind of strategical infrastructures must deal not only with live loads and particular loading condition coming from the floating situation but needs also to carefully consider accidental actions that concur to the global safety of the infrastructure. The construction of the new E39 highway along the Norwegian coast asks for crossing several fjords and this solution is seriously taken into consideration. For this reason, a comprehensive research programme was aimed at the analysis of accidental load design of the infrastructure. This paper aims to present a comprehensive overview of an ad-hoc experimental investigation on the behaviour of reinforced concrete (RC) circular slabs (60 cm diameter) under exposure to fire, blast, or a combination of both actions. Additionally, it seeks to draw design-driven conclusions that could be valuable for the design of critical infrastructure in scenarios involving fire and blast. The presented experimental campaign was intended to provide a benchmark for assessing the reliability of the design approaches to be adopted in the design of the global infrastructure. First, the concrete mechanical characterisation at normal condition and at high temperatures was performed referring both to the uniaxial compression and uniaxial tension. The structural behaviour of simply supported RC slab has been also investigated by considering slabs exposed to a hydrocarbon fire curve at different exposure times and by considering the post-fire application of static or dynamic loading condition. In particular, the fire curve was applied by a gas burner while the dynamic load was reproduced by a shock tube equipment that was used to apply two different blast-like pressure histories.

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.

Bridges are among the most important infrastructure assets, especially reinforced concrete slab bridges. Many were built with a skew angle instead of straight due to the limited space available. The skewness affects the internal shear force distribution of the slabs and causes shear stress concentration at the obtuse corner. Most of the shear design methods are developed based on straight slabs. Whether these methods apply to skewed slabs is unclear. On the other hand, experiments on skewed slabs are quite limited. Therefore, an experimental programme of skewed slabs was conducted at Delft University of Technology. The slabs have a height of 300 mm, representing a half-scale model of representative solid slab bridges in the Netherlands. A concentrated load was applied close to the edge of the slabs to induce a one-way shear failure. Both the top and bottom surfaces of the slabs were measured using stereo Digital Image Correlation (DIC). This paper presents the design and the results of the experiment. By using the stereo DIC from both surfaces, the internal shear crack propagation is captured. All specimens failed in shear and the results demonstrate that the shear capacity of the slabs decreases as the skewness increases. Moreover, the experiment confirmed that the shear stress concentration is more significant in the obtuse corner than in the acute corner. An evaluation method is proposed to calculate the shear capacity of the skewed slab combined with the Linear Finite Element Analysis. The calculated shear capacity given by the proposed method shows a good alignment with the experimental results.

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.

The next generation of acoustic emission (AE) applications in concrete structural health monitoring (SHM) relies upon a reliable and quantitative relationship between AE measurements and corresponding AE sources. To achieve this, it is a prerequisite to accurately model the whole AE process that is a multiscale coupling process between local material fracturing and induced elastic wave propagation at structural level. Such a complex process, however, cannot be well addressed in currently available modelling methods. To fill this research gap, this study proposes a lattice modelling approach that achieves for the first time the explicit simulation of complete waveforms of transient AE signals induced by concrete fracture. The proposed approach incorporates an explicit time integration technique with a novel proportional-integral-derivative (PID) control algorithm for reducing spurious oscillations and a Rayleigh damping-based calculation and calibration method for the attenuation of AE waves. In this paper, the proposed lattice modelling approach is implemented to simulate the concrete Mode-I fracturing process in a three-point bending test. Besides the mechanical behaviors and AE hit number, a comparison was conducted between numerically and experimentally obtained AE waveforms. The AE waveforms and their attenuation characteristics simulated by the proposed lattice modelling method turn out to be comparable to experimental results. The proposed approach is of significance for a deep understanding of AE-related fracture mechanisms and a more reliable application of AE technique.