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.

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.

Inverted T precast girders with a cast-in-situ topping layer, recognized as precast composite girders, are commonly used in Dutch bridge construction. Notably, the bridges built before 1974 often lacked sufficient shear reinforcement, raising concerns about their shear capacity under increasing traffic loads. However, how to assess these composite girders under the scope of the second-generation Eurocode remains challenging, as the shear formulations were originally developed for monolithic structural members. Consequently, their direct applicability to precast composite systems, due to the distinctive stress distribution in the web of the composite structural members, lacks theoretical substantiation and experimental validation. This study first presents the three alternative failure criteria equations based on the same theory, and after that, an experimental investigation of the shear behaviour of precast composite girders through two full-scale tests is discussed. The test data is later used to compare the alternative failure criteria.

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.

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.

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.

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.

The cracking of the pre-/post-casting UHPC joint in the steel-UHPC composite bridge deck system can lead to continuous tensile damage in the UHPC layer, reducing its ability to stiffen the steel deck. This study aims to clarify the cracking mechanism of the segmented-casting UHPC joint, and to provide design recommendations for cracking control. Axial tension tests on full-scale composite deck specimens were conducted, in which the influence of with and without joint, and varying reinforcement ratios on cracking response were identified. Moreover, the nonlinear numerical model for the composite deck, where the UHPC-UHPC interface was simulated in three methods, i.e. unbonded case, cohesive zone model (CZM), and perfectly bonded case, was developed and validated to simulate the crack initiation and propagation of the UHPC layer. Based on the validated numerical model incorporating CZM, improving the bond strength of CZM is more effective in controlling crack opening at the interface than increasing the failure displacement. Finally, optimized reinforcement arrangement and joint shape recommendations were provided to enhance construction convenience, minimize stress concentration, and limit crack opening.