The viaduct Zijlweg, a reinforced concrete bridge with cracking caused by an alkali-silica reaction, is the subject of a case study that is examined in this chapter. The preparation, execution, and postprocessing of the load test serve as the chapter’s primary focus. The load test and analysis of measurements showed that the viaduct’s capacity is adequate for the code-prescribed live loads and that no structural strengthening is necessary. The second topic is a discussion of the economic, environmental, and social cost savings gained from this procedure as opposed to replacing the superstructure.@en

As the existing bridge stock is aging, assessment of existing bridges becomes increasingly important. In the Netherlands, the shear capacity of reinforced concrete slab bridges is found to be insufficient. In particular, the shear and punching shear capacity of reinforced concrete slab bridges subjected to concentrated loads from the design tandem or truck is subject to discussion, as the shear behavior is situated in between oneway and two-way shear. Currently, an experimental program is being conducted at Delft University of Technology to determine the shear capacity of straight and skewed reinforced concrete slabs under point loads near to the support. This paper presents the results of the 25 tests conducted on six straight slabs of 5m × 2.5 m × 0.3 m subjected to a proof load testing loading protocol. The failure load and modes of the slabs are described in detail. Reinforced concrete slabs under concentrated loads can fail in shear, punching, and flexure, as well as a combination of these failure modes. The results of the experiments are compared to strength predictions obtained by using current design models and current methods for assessment. These experiments demonstrated that the Dutch guidelines, which are based on previous slab experiments, are an improvement as compared to the Eurocode for the assessment of existing reinforced concrete slab bridges. Ultimately, this work provides recommendations for bridge engineers tasked to assess reinforced concrete skewed slab bridges.

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Bridges, essential for economic and social development, face significant deterioration due to aging and environmental factors. Consequently, assessing the condition of reinforced concrete bridges is essential to anticipate their future performance and optimize maintenance, rehabilitation, and replacement needs. While traditional visual inspections are widely used, the integration of unmanned aerial vehicles (UAVs) presents a more efficient approach, particularly in inaccessible areas. This article presents a comprehensive evaluation of the condition of a bridge over a decade through a case study in Ecuador. The assessment revealed significant deterioration in several structural elements, especially the substructure and road elements. These findings underscore the urgent need to improve maintenance practices and integrate advanced inspection techniques to ensure the safety and longevity of bridges in Ecuador.@en

Structural assessment of existing bridges is one of the most challenging aspects for the correct and sustainable management of civil infrastructures that emerged in the last few years. Specifically, Italy has a substantial number of bridges over 50 years old, mainly represented by simply supported prestressed concrete I-girder-type with a cast-in-situ deck. Proof load testing represents an empirical alternative to the standard calculation methods commonly adopted for safety assessment of existing structures. This article investigates the reliability of a bridge in different configurations including damaged and undamaged scenario through sitespecific traffic data collected by Weigh-In-Motion (WIM) systems in the Netherlands. Assuming a target load corresponding to characteristic load combination according to Eurocode provisions, the proof load test resulted into slightly reduced reliability indexes during the test while achieving higher values under successful completion. Preliminary results contribute to demonstrate proof load test can represent a valuable method for assessment of existing bridges.

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Natural fibers are becoming a key point for the development of new concrete mixes because these fibers are recovered from residual biomass. In this paper, we focus on the natural fib‘ers found in the Metropolitan District of Quito, Ecuador. For this purpose, we searched for materials (fibers) available in the Chemical Engineering laboratory at Universidad San Francisco de Quito USFQ. In this paper, we analyze different literature on how the use of fibers influences the mechanical properties of concrete. Based on this analysis and the materials at the laboratory, we have developed recommendations on which natural fibers are of interest for further experimental research. Furthermore, this paper provides an understanding of how natural fibers influence the mechanical properties of concrete. It also proposes a process for the selection and study of any type of natural fiber for further replicability in mix analysis.@en

In various parts of the world, seismic events happen regularly. While engineers have gained an understanding on the behaviour of bridges under seismic loading, this knowledge is still under development as more methods and devices for building seismically-resistant bridges become available. This paper reports on the observed damages from recent events, with a focus on recent earthquakes in Ecuador, Chile, and Turkey. To report the damage that has occurred, this paper presents descriptions of a number of cases of observed damage to bridges after earthquakes. The various types and locations of damage are then analyzed to develop broad categories of problems that can be identified from these cases. This insight then leads to a summary of lessons learned from the presented case studies. The information provided in this work can be used for the assessment of existing bridges and the improvement of the design of new bridges.@en

As the existing bridge stock is ageing in various parts of the world, the topic of how to assess, maintain and/or improve, and manage existing bridges becomes increasingly important. Existing bridges may be designed according to outdated codes with requirements that may be considered unsafe nowadays, and for loads that are significantly different than those used nowadays. For those bridges, an accurate assessment leads to more efficient management of the bridge stock. This paper outlines various strategies that lead to an improvement of the assessment, and potentially to the extension of the service life of existing concrete bridges. This paper provides a selected examples that engineers who are faced with the assessment of ageing bridge can use. Ultimately, the presented insights can serve to support countries with a younger bridge stock in the development of an assessment strategy.@en

Given the ageing infrastructure, verifying the reliability of existing structures is crucial. Field testing presents a viable approach to evaluating a structure’s current condition, particularly proof load testing. In a proof load test, a large load is applied to assess its reliability. Structures in sound condition are expected to display satisfactory behaviour under average load intensities. Can good structural performance under moderate load levels already prove sufficient structural reliability? The proposed method utilises data from laboratory tests on similar structural elements. A case study was conducted on a bridge to illustrate the effectiveness of the method. Data acquired from laboratory tests were pre-processed to provide the required input for the reliability updating. It reveals that sufficient reliability can be demonstrated without excessive load levels by incorporating laboratory data. However, the actual capacity of the bridge and the uncertainty associated with the laboratory data remain important factors.

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At ACI Avances en Ciencias e Ingenierias, we care deeply about open science. After all, we are an open access journal that does not charge an article processing charge, and all editors are volunteers who support open science practices. Our hosting and administrative costs are funded by Universidad San Francisco de Quito.

In a new effort to strengthen our open science practices, we have launched a Preprints server, named Preprints ACI. Authors who send an article to ACI Avances en Ciencias e Ingenierias are encouraged to deposit their article as a preprint on the server. Authors from within and outside the community of Universidad San Francisco de Quito are also welcome to use our preprint server.@en

Load testing of bridges is commonly used to verify the performance of a bridge prior to opening as well as for the assessment of existing bridges. This paper reports on recent advances in the field of bridge load testing, based on experimental work carried out in Europe as well as international collaboration efforts. The experimental, numerical and analytical work that has been carried out in these past years is summarized. The main findings are: 1) modern instrumentation techniques (such as acoustic emission measurements and digital image correlation) can be combined with traditional measurements to gain more in-depth insights during and after the test; 2) for load testing to be fully compliant with current codes, a probabilistic substantiation of the methodology is needed; and 3) international collaboration is key in order to successfully update current codes and guidelines and develop recommendations and sets of best practices. The recent advances in North America and Europe have also resulted in improvements to the practice of bridge load testing in Latin America (in particular in Costa Rica and Colombia). To conclude, load testing is an important tool for engineers faced with the task of assessing existing bridges. The aforementioned efforts will result in improved recommendations for the assessment of concrete bridges by load testing to be included in codes and guidelines in Ecuador and other countries in Latin America@en

In the Netherlands, there are about 70 prestressed T-girder bridges with cast-inbetween decks, constructed post-WorldWar II.While they have low ratings upon assessment, inspections reveal no distress. This research aims to understand the structural behavior of the full system compared to isolated T-girders. Experiments were conducted on the original structure, as well as on the structure with the deck sawn to test individual girder behavior. The main insight is that the system behavior at the ultimate limit state is driven by compressive membrane action in the deck as well as compressive arching action in the girders, and that simplified distribution factors for shear derived from linear elastic behavior do not properly reflect the distribution and load path at the ultimate. These results can be used for a better assessment of the existing pre- stressed T-girder bridges.

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Bridge deck slabs are members on which one-way reinforced concrete slabs are found frequently loaded by concentrated loads. Although the one-way shear failure mechanism has gathered more attention in the past years, both one-way shear and two-way shear mechanisms may be critical for such loading conditions. This paper addressed the ultimate capacity of thin one-way reinforced concrete slabs subjected to concentrated loads and yielding of the flexural reinforcement. In practice, the test setup studied was devised to represent short-span rural bridges frequently found in Brazil. The experimental program included 12 tests performed on 6 slabs applying the concentrated loads at varied positions. All tests started to fail by punching shear. Nevertheless, both one-way shear and punching shear cracks were observed at ultimate states after shear redistribution. The reinforcement yielding followed by excessive flexural cracking hampered the arching action activation for loads closer to the support. The comparison of experimental and calculated resistances using standard code-based expressions suggests that improvements in unitary shear capacity could be supported as a result of slabs' transverse load distribution capacity. Alternatively, increasing the effective shear width can help estimate one-way shear capacity for loads near to the support.@en

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.

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Major fire events in tunnels have shown severe consequences in their structural performance, as reported in several incidents in the last decades. Particularly, due to the enclos-ure geometry of tunnels, intense thermal loading may develop in comparison to typical fires in buildings, which may result in more damage. Even though tunnel linings are an important com-ponent in transportation infrastructure, the understanding of their behaviour under high tem-peratures is limited. This paper aims to study 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 approaches and strategies are discussed, and a detailed descrip-tion of the constitutive model employed is presented. The results obtained in the simulations indicated that the numerical analysis can be used to investigate the thermo-mechanical behav-iour of concrete structures.

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Bridge load testing is one of the tools engineers are using for the assessment of existing bridges, which is becoming increasingly important to manage the existing bridge stock in a sustainable manner. Over the past years, various research groups have worked on theoretical and practical research regarding load testing. Moreover, various international committee work on load testing recommendations. This paper provides an overview of recent research efforts in Denmark, the Netherlands, and Sweden. The way in which recent research efforts are implemented in new committee reports and guidelines is highlighted. Overall, the efforts have focused on combining load testing with insights in structural behavior, applying improved instrumentation techniques, combining with numerical analyses, and providing a probabilistic substantiation. In conclusion: bridge load testing is a dynamic field of research that benefits from international collaboration. Further improvements to existing codes and guidelines will be forthcoming in the next years.

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To meet the sustainable development goals, novel concrete mixes are necessary. Natural fibers are becoming an interesting new element for concrete mixes, because these fibers are biomaterials recovered from residual biomass and fit in the concept of the circular bioeconomy. In this paper, we catalog research insights on concrete mixes with natural fibers and pay special attention to natural fibers that are available in the Metropolitan District of Quito, Ecuador, to use local bio-based materials. We focus on examining information from the literature on how natural fibers influence the mechanical properties of concrete, namely the tensile, compressive, and flexural strength. Based on this analysis, we have developed recommendations on which natural fibers are of interest for further experimental research, with the aim to develop sustainable concrete mixes for Quito. Moreover, this paper gives insights in how natural fibers influence the mechanical properties of concrete and proposes a framework that translates to other regions and cities for the selection of local and adequate natural fibers.@en

In design, the sectional depth of reinforced concrete spread footings is usually governed by design code provisions for punching shear, which are derived primarily from experiments on slab-column connections. Previous experiments have shown that the punching behavior of concentrically loaded spread footings differs from that of slab-column connections. This paper describes punching of a concentrically loaded spread footing by combining conventional strut and tie modeling with the concept of an arch strip, part of the Strip Model. By itself, the Strip Model describes the behavior of slab-column connections under a variety of loading conditions. For spread footings, Strip Model concepts need to be combined with conventional strut and tie modeling to adequately describe load transfer in a concentrically loaded spread footing. Two methods are explored, each producing closed-form expressions for the footing capacity that agree well with experimental results (112 tests from the literature). The analyses make it possible to estimate the fraction of footing load that is carried by conventional strut and tie behavior. The experimental results are also compared to punching shear capacities in accordance with ACI 318-19. The Strip Model produces results with roughly the same average test-to-predicted ratio (in the order of 1.3) as ACI 318-19 but with a lower coefficient of variation (10.3% compared to 15.8%). This work shows how a lower-bound plasticity-based model can be used for the practical case of determining the capacity of reinforced concrete spread footings failing in punching shear.

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One-way slabs under concentrated loads may fail by one-way shear, two-way shear, flexure, or a combination of these modes. This paper reviews shear and punching shear-failure mechanisms of one-way slabs under concentrated loads tested from the literature and investigates the accuracy of different approaches to predict the ultimate capacity for such slabs using the ACI code expressions. A database with 160 test results was evaluated. Shear and concentrated loads measured at failure were reviewed according to parameters such as the load position, slab width, and reinforcement ratios. The load position and slab width play a marked influence on the failure mechanism and tested loads. The analyses improved the understanding of the main parameters influencing the behavior of one-way slabs under concentrated loads. Finally, the proposed effective shear width expression enables accurate shear capacity predictions using the ACI code expressions.

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One-way slabs under concentrated loads may fail by one-way shear, punching, flexure or a mixed-mode between them. This study examines the benefits of using Linear Elastic Finite Element Analyses (LEFEA) combined with analytical expressions to predict the shear and punching capacities of such slabs. Besides, the determination of the most critical shear failure mechanism is also addressed. A simplified approach is proposed to predict the shear and punching capacity without numerical models. Forty-eight tests of simply supported slabs under concentrated loads were evaluated. The LEFEA was conducted with ABAQUS. The analytical expressions are based on the Critical Shear Crack Theory (CSCT). The coupling of the CSCT-expressions with the LEFEA accurately predicts the governing shear failure mechanism and the shear capacity of most test results. In this study, it was also found that the punching capacity predictions may be improved by considering the influence of the slab width and load size on the governing failure mechanism. A similar level of precision was achieved using only analytical expressions when properly calibrated. Therefore, the CSCT expressions can be used at different stages of design and assessment of existing structures according to the Level of Approximation required.

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