A prestressed concrete bridge was built in 1963 with BBRV cables. It has three spans and a total length of 134.8 m. Due to mining activities the bridge was loaded with trucks with a total weight of 90 ton during 2012-2014 and from 2019. Crack development has been monitored manually and from 2020 with strain gauges and LVDTs.

Cracks normally vary between 0.1 to 0.3 mm in width and grow in length with time. In November 2020 some of the strain gauges on the concrete showed alarming growth and the bridge was closed for traffic. Additional strain gauges were installed on vertical reinforcement bars and an assessment was carried out of the fatigue capacity of the bridge. It was found that the new strain gauges did not indicate any growth in strain and that the fatigue capacity was sufficient. The bridge could be opened again for traffic after being closed for five weeks. Monitoring drift in the strain gauges and fatigue are discussed.

The backbone of European infrastructure was built after the end of the second World War and has reached, or is near to, the end of its nominal design life. This issue urges the development of structural assessment procedures that can provide infrastructure managers the information to make decisions for repairing, upgrading, or replacement. In this paper, a methodology based on load testing and Structural Health Monitoring (SHM) for the assessment of a 65- year-old prestressed concrete bridge located in Northern Sweden is presented. The retrieved data is used to develop and calibrate structural models with different levels of data completeness. The SHM procedure includes the evaluation of material properties by diagnostics, definition of the layout and installation of the instrumentation, test execution, and data analysis. A preliminary structural model is developed based only on the original design parameters, and it is sequentially updated with monitoring data retrieved during a performed proof loading test of the bridge.

The reduction of the structural capacity and eventual collapse of existing concrete bridges is often related to the loss of the initial prestressing forces. This loss can be associated to immediate or time dependent factors such as elastic shortening, creep, relaxation, loading, and cracking, among others. In addition, environmental factors can lead to corrosion of the strands with the subsequent reduction of their area, loss of bond with the concrete and additional cracking which in turn will influence the value of the residual prestress force and the bridge capacity. Therefore, the evaluation of such losses is critical in the decision-making process of defining a financial and environmental cost optimized intervention strategies (e.g., strengthening or replacement). In this paper, a detailed literature review regarding destructive and non-destructive methods for measuring the residual force in prestressed concrete bridges is carried out and used to develop a database of existing experimental tests.

Over the last decades, economic growth and sustained development have enforced the need to ensure reliable and long-lasting infrastructure network to guarantee serviceability and safety. Nevertheless, detrimental effects can lead over time to insufficient structural performance under increasing service loadings and extreme events. Hence, Structural Health Monitoring (SHM) arises as a solution to cope with the need of having timely and continuous data to assess the state of crucial structural assets, such as prestressed concrete bridges. On this matter, the validation of the retrieved data becomes essential for the risk-based decision making in the assessment of bridges, where selecting the most suitable monitoring system could allow to addressed main causes to the right phenomena of deterioration during the service life of the bridge. Consistently with these efforts, this paper deals with a comparative study between the data acquired by different strain-based sensors such as Fiber optic systems (FOS) and strain gauges that were installed to monitor a proof loading test developed on a 65-year-old balanced cantilever prestressed concrete bridge located in Northern Sweden. The monitored data led to establish main differences between emerging types of monitoring systems such as FOS to the well-based strain gauges when exposed to low temperature conditions. Conclusions regarding the influencing parameters between both retrieved data are drawn when evaluating the structural response under serviceability loading conditions is performed, supporting decision makers when different levels of structural assessment are required.

The transport infrastructure consists of roads, bridges, and tunnel networks. Among these, bridges, viaducts, and tunnels are particularly vulnerable due to structural degrad-ation caused by environmental conditions, overloading, and other factors. Ensuring the safety of these assets, especially at the network level, is a significant challenge. The emergence of Bridge Management Systems (BMS) addresses the need for comprehensive information in managing inspections, condition assessments, and optimizing investments in bridge maintenance. Despite the benefits, many countries face challenges in identifying high-risk bridges. Issues include the lack of high-quality data, mixed ownership of assets, diverse management system platforms, varying condition rating schemes, and the absence of a risk-based assessment. This review aims to highlight current practices and research efforts in evaluating bridge condition indices/ratings (BCI) for existing bridges. The identified knowledge gaps emphasize the need for national authorities to develop policies leading to a unified and functional approach for condition rating.

The direct socio-economic consequences of the deterioration of aging infrastructure systems have triggered a continuous process of revising and updating current design standards and guidelines for critical network components. Specifically, long-term degradation processes demand the analysis and evaluation of vital structural assets such as prestressed concrete bridges. It is crucial to develop theoretically consistent, user-friendly, and non-destructive methodologies that engineering professionals can employ to prevent and mitigate potential catastrophic outcomes during the service life of these bridges. This study provides a thorough review of the available testing methods employed over the years for prestressed concrete bridges and introduces a comprehensive framework for evaluating existing methods for residual prestress force assessment. Through a multi-criteria selection process, the three most feasible tests were designed and carried out on an existing 66-year-old balanced cantilever box girder bridge exposed to freezing temperatures that affected the instrumentation plan and test execution. Finally, predictive models compliant with standard codes were calibrated based on the experimental results and the life cycle loss of prestress forces was evaluated to assess relevant bounding intervals. Findings reveal limited on-site testing and discrepancies between calculated residual forces and predictions by standard codes. The saw cut method showed a 18% difference from the initial applied prestress according to the prestress protocol, suggesting the use of a cover meter and concrete modulus evaluation for improved accuracy. The strand cutting method resulted in a 14% difference, emphasizing the need for stress redistribution assessment. The second-order deflection method showed a 6% difference, indicating a focus on enhanced boundary conditions and thorough sensitivity analysis for future investigations.

The present study is aimed at investigating the effect of hybridisation on Kevlar/E-Glass based epoxy composite laminate structures. Composites with 4 mm thickness and 16 layers of fibre (14 layers of E-glass centred and 2 outer layers of Kevlar) were fabricated using compression moulding technique. The fibre orientation of the Kevlar layers had 3 variations (0, 45 and 60°), whereas the E-glass fibre layers were maintained at 0° orientation. Tensile, flexural, impact (Charpy and Izod), interlaminar shear strength and ballistic impact tests were conducted. The ballistic test was performed using a gas gun with spherical hard body projectiles at the projectile velocity of 170 m/s. The pre-and post-impact velocities of the projectiles were measured using a high-speed camera. The energy absorbed by the composite laminates was further reported during the ballistic test, and a computerised tomographic scan was used to analyse the impact damage. The composites with 45° fibre orientation of Kevlar fibres showed better tensile strength, flexural strength, Charpy impact strength, and energy absorption. The energy absorbed by the composites with 45° fibre orientation was 58.68 J, which was 14% and 22% higher than the 0° and 60° oriented composites. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

As emission regulations in the EU are becoming stricter, the reduction of greenhouse gas emissions from the construction industry has become a pressing need. As part of the efforts related to this issue, it has been found that Environmental Life Cycle Analysis (LCA) approaches are required to optimize the design, construction, operation, and maintenance of buildings and infrastructure assets. In this paper, The Institution of Structural Engineers guidance on how to calculate the embodied carbon in structures is used as LCA model and evaluated in a case study. The guidance divides the structure´s life cycle into five stages (A1-A3: Product, A4-A5: Construction process, B1-B7: Use, C1-C4: End of live and D: Benefits and loads beyond the system boundary) and the environmental impact is measured in terms of carbon dioxide equivalent emissions (kgCo2e) or global warming potential (GWP). The model was applied to an existing reinforced concrete trough bridge, which is a structure type commonly used in Swedish railways. Results show that that the model was effective and simple for investigating the environmental impact of the studied structure. 

Having in mind the topic of industrialised construction and the benefits of modular construction, sandwich panels are investigated to be utilised as load-bearing wall elements. To assess its full potential, the present paper tackles the linear elastic buckling response of axially loaded angle sandwich panels, by means of numerical and analytical calculations, as the upper bound of its load bearing capacity. The failures modes are obtained and framed for concentrically loaded angle panels with fixed and pin-ended supports. A parametric study of the angle panel comprising a series of finite element models is undertaken where responses are compared with analytical calculations based on the theory of sandwich panels. Boundaries for local and global buckling are identified and framed.

3D printing or additive manufacturing (AM) is considered as a flexible manufacturing method with the potential for substantial innovations in fabricating geometrically complicated structured polymers, metals, and ceramics parts. Among them, polymeric composites show versatility for applications in various fields, such as constructions, microelectronics and biomedical. However, the poor resistance of these materials against fire must be considered due to their direct relation to human life conservation and safety. In this article, the recent advances in the fire behavior of 3D-printed polymeric composites are reviewed. The article describes the recently developed methods for improving the flame retardancy of 3D-printed polymeric composites. Consequently, the improvements in the fire behavior of 3D-printed polymeric materials through the change in formulation of the composites are discussed. The article is novel in the sense that it is one of the first studies to provide an overview regarding the flammability characteristics of 3D-printed polymeric materials, which will further incite research interests to render AM-based materials fire-resistant.

To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests areplanned for a 50 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden.Both non-destructive and destructive full-scale tests will be performed. This paper summarisesthe test programme, which comprises evaluation of the structural behaviour of the bridge, theresidual forces in the prestressed steel, methods for strengthening using carbon fibre reinforcedpolymers (CFRP) and the shear resistance of the bridge slab.

Three Swedish concrete bridges have been tested to failure and the results have been compared to assessment using standard code models and advanced numerical methods.

The three tested and assessed bridges were:

1. (1)

   Lautajokk, a 29 year old one span (7 m) concrete trough bridge tested in fatigue to check the concrete shear capacity.

    
2. (2)

   Ӧrnskldsvik, a 50 year old two span trough bridge (12 + 12 m) strengthened to avoid a bending failure.

    
3. (3)

   Kiruna Mine Bridge, a 55 year old five span prestressed concrete road bridge (18 + 21 + 23 + 24 + 20 m) tested in shear and bending of the beams and punching of the slab.

    

The main results in the paper are the experiences of the real failure types, the robustness/weakness of the bridges, and the accuracy of different codes and models. In all three cases the bridges had a considerable hidden capacity.

In this paper, experiences on the development of an assessment method for existing bridges are presented. The method is calibrated using the results of full-scale testing to failure of a prestressed bridge in Sweden. To evaluate the key parameters for the structural response, measured by deflections, strains in tendons and stirrups and crack openings, a sensitivity study based on the concept of fractional factorial design is incorporated to the assessment. Results showed that the most significant parameters are related to the tensile properties of the concrete (tensile strength and fracture energy) and the boundary conditions. A finite element (FE) model in which the results of the sensitivity analysis were applied, was able to predict accurately the load-carrying capacity of the bridge and its failure mode. Two additional existing prestressed concrete bridges, that will be used to improve further the method, are also described, and discussed.

To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests were carried out on a 55 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden. Both non-destructive and destructive full-scale tests were performed. This paper presents results regarding methods for assessment of the structural capacity of concrete bridges.

In order to provide relevant data for calibration and development of methods for assessment ofexisting bridges, a 55 year old posttensioned concrete bridge has been subjected to non-destructiveand destructive tests. The bridge, located in Kiruna, Sweden, was a 121 m long girder bridgecontinuous in five spans. The test programme included failure loading of the girders and slab,respectively, condition assessment of the post-tensioned cables and material tests. Moreover, twostrengthening systems, using carbon fibre reinforcing polymer (CFRP), were evaluated. In this paperthe experimental programme and some preliminary results are presented to give an insight to researchproject.

To calibrate methods for condition assessment of prestressed concrete (PC) bridges, tests were carried out on a 55 year old five-span bridge with a length of 121 m in Kiruna in northern Sweden. Both non-destructive and destructive full-scale tests were performed. This paper presents results regarding the residual forces in the prestressed reinforcement.

Twenty years ago, in 2003, a European project was started to increase the sustainability of existing railway bridges. This paper summarises what was achieved and looks ahead. Nine Working Packages were organized: (1) Background material; (2) Guidance by stakeholders; (3) Condition Assessment and Inspection Guidelines; (4) Loads, Capacity and Resistance Guidelines; (5) Monitoring Guidelines; (6) Repair and Strengthening Guidelines; (7) Demonstration with Field testing of Bridges; (8) Demonstration on Monitoring on Bridges; and (9) Training and Dissemination.

Some of the main results (from 4 Guidelines and 47 Background documents) are highlighted and some experiences, conclusions and thoughts about the future are given. Hidden strengths and weaknesses are discussed, analyses and codes for assessment can be improved, new monitoring and strengthening methods are available and life length can be prolonged. 

When assessing the sliding stability of a concrete dam, the influence of large-scale asperities in the sliding plane is often ignored due to limitations of the analytical rigid body assessment methods provided by current dam assessment guidelines. However, these asperities can potentially improve the load capacity of a concrete dam in terms of sliding stability. Although their influence in a sliding plane has been thoroughly studied for direct shear, their influence under eccentric loading, as in the case of dams, is unknown. This paper presents the results of a parametric study that used finite element analysis (FEA) to investigate the influence of large-scale asperities on the load capacity of small buttress dams. By varying the inclination and location of an asperity located in the concrete-rock interface along with the strength of the rock foundation material, transitions between different failure modes and correlations between the load capacity and the varied parameters were observed. The results indicated that the inclination of the asperity had a significant impact on the failure mode. When the inclination was 30° and greater, interlocking occurred between the dam and foundation and the governing failure modes were either rupture of the dam body or asperity. When the asperity inclination was significant enough to provide interlocking, the load capacity of the dam was impacted by the strength of the rock in the foundation through influencing the load capacity of the asperity. The location of the asperity along the concrete-rock interface did not affect the failure mode, except for when the asperity was located at the toe of the dam, but had an influence on the load capacity when the failure occurred by rupture of the buttress or by sliding. By accounting for a single large-scale asperity in the concrete-rock interface of the analysed dam, a horizontal load capacity increase of 30%–160% was obtained, depending on the inclination and location of the asperity and the strength of the foundation material.

During the last two decades, strengthening concrete structures with epoxy bonded carbon fiber reinforced polymers (CFRP) has shown excellent results in increasing bearing capacity. However, there are some limitations with epoxy coated concrete surfaces, e.g.; low permeability which may provoke freeze/thaw problems, poor thermal compatibility to the concrete substrate which makes epoxy coating more sensitive to the surrounding temperature and regulations when it comes to the security and health (allergic reactions) of applicators and third party users. In this respect, using mineral based composites (MBC) may overcome some of these challenges associated with epoxy bonded strengthening systems. MBC, in this context, refers to high strength fibers bonded to the surface using a mineral based bonding agent. This study examines the cracking behavior and strain development of shear MBC strengthened RC beams. The results show that using MBC as shear strengthening postpones the formation of macro-cracks and that a considerable strengthening effect is achieved by using MBC.

During the last two decades, strengthening concrete structures with epoxy bonded carbon fibre reinforced polymers (CFRP) have shown excellent results in increasing bearing capacity. However, there are some limitations with epoxy coated concrete surfaces, e.g.; low permeability which may provoke freeze/thaw problems, poor thermal compatibility to the concrete substrate which makes epoxy coating more sensitive to the surrounding temperature and regulations when it comes to the safety and health (allergic reactions) of applicators and third party users. In this respect, using mineral based composites (MBC) may overcome some of these challenges associated with epoxy bonded strengthening systems. MBC, in this context, refers to high strength fibres bonded to the surface using a mineral based bonding agent. This study is examining the cracking behaviour and strain development of shear MBC strengthened RC beams. The results show that using MBC as shear strengthening postpones the formation of macro-cracks and that a considerable strengthening effect is achieved by using MBC.

Chloride salts can cause severe corrosion damage to reinforcing steel bars in cement-based materials whereas nitrite salts inhibit corrosion. The storage and release of these two anions in cement materials occurs mainly at the interface of monosulfoaluminate (AFm) hydrates. In this paper, molecular dynamics are used to analyze the interaction between anions and AFm phases and clarify the competitive relationships between the anions at adsorption sites on the AFm surface. It was found that the ordered structure of the [Ca2Al(OH)6]+ layers of the AFm plays a key role in anion adsorption and that the mobility of ions desorbed from AFm layers decreases linearly with increasing proximity to the AFm surfaces.

Corrosion of steel reinforcement in concrete is a significant cause of structural failure, particularly in environments exposed to chloride ions and mechanical stress. The passivation film on steel reinforcement, composed of hematite or magnetite, plays a crucial role in protecting the steel from further corrosion. However, the intrusion of harmful ions or mechanical stress can compromise the film’s integrity, transforming it into a loose structure and accelerating the corrosion process, leading to structural failure. This study investigates the mechanical behaviors at the interfaces between corrosion products (hematite and magnetite) and C-S-H using reactive molecular dynamics. C-S-H and interfacial models incorporating hematite and magnetite were developed, with stress–strain analysis refined by filtering raw data and using true strain rather than engineering strain to improve the precision of the stress–strain responses. The results indicate that the Magnetite-CSH interface is more prone to loosening under external forces compared to the Hematite-CSH interface, thereby reducing its corrosion resistance. Structural evolution analysis under uniaxial tension highlights the detrimental effects of passivation film degradation on interfacial mechanical properties. This study contributes to improving the precision of stress–strain responses in MD models and facilitates comparison of mechanical properties at the nanoscale with results from other scales. The findings provide valuable guidance for improving the durability and performance of construction materials in corrosive environments, helping to bridge the gap between molecular-level simulations and macroscopic experimental data.

This paper investigates the current landscape of multiscale studies in concrete composites incorporating molecular dynamics (MD) methods. Through a thorough literature analysis, it was determined that finite element, discrete element, homogenization, microphysical characterization, and machine learning methods are better suited for integration with MD in multiscale studies of concrete composites. The paper delves into MD's application characteristics and the selection of force fields in multiscale studies and provides a summary of the combined applications between MD and various methods. Challenges identified include the optimization of MD simulations and the appropriate selection of combined methods. The conclusions underscore the growing recognition of MD's significance, advocating for rational multi-method integration in multiscale approaches to effectively advance research on concrete composites.

The durability and compressive strength of concrete will vary with the material components, ambient temperature, external intrusion. Using molecular dynamics (MD) methods to study the dynamic behavior of particles in cement-based materials can help us understand the underlying mechanism of property changes in concrete caused by above factors at the atomic level. So far, MD methods have been widely used to analyze the physical and chemical properties of concrete materials and the interaction mechanism between different interfaces at the nanoscale. However, too much complexity in the models will reduce the result accuracy and increase the computational cost. A suitable neural network structure can not only ensure the accuracy of analysis results, but also reduce the computational cost. In this work, MD methods are applied to build the models to explore the diffusivity of Na+ and Cl− in the calcium silicate hydrate (C-S-H) gel pores at different concentration and temperatures. In the process of running models, part of the MD models’ fidelity is reduced to save the computational cost, then the trained multi-fidelity physics informed neural network framework was used to obtain more accurate analysis results. The combination of MD simulations and deep learning methods expands the application range of MD in the field of concrete structure, has good development prospect and application value.

The Iron Ore Railway Line was built around 1900 and has more than 100 bridges. It has a length of ca 500 km and runs from Kiruna and Malmberget in northern Sweden to the ice-free harbour in Narvik in Norway on the Atlantic and to Luleå in Sweden on the Baltic. The original axle load was 14 ton. The axle load has gradually been increased to 25 ton in 1955, to 30 ton in 1998 and to 32,5 ton in 2017.

The increases in axle loads have been preceded by monitoring and assessment studies of the bridges. The capacity and need for strengthening or replacement of the bridges have been evaluated. Many of the bridges could carry a higher load than what it was designed for. Experiences from studies before the axle load was increased in 1998 and 2017 are presented and discussed.

Prestressed concrete bridges experience complex load scenarios throughout their lifespan, which impacts their load capacity and overall performance. To ensure opyimal functionality and safety it is crucial to understand the diverse responses from the structure under varying load. By deploying sensors in strategically placed locations, a numerical representation of varying responses can be attained during operation. Variation in temperature can affect the reading of a sensor. This can lead to false positive structural damage responses. Thus, it is important to differentiate between variations in structural properties induced by temperature fluctuations, and variations from structural damage. This paper presents a novel approach for mapping the temperature effect in structural responses. By employing an artificial neural network (ANN) and measurement data from a prestressed concrete bridge located in northern Sweden, a correlation between temperature and the sensor values is achieved.

A new bridge was built in Kalix, northern Sweden, to replace an existing prestressed concrete box-girder bridge that had been in service for over 60 years. The old bridge had a total length of 283.6 m divided into five spans: 43.9 m, 47.0 m, 94.0 m, 47.0 m, and 43.9 m. It was constructed using the balanced cantilever method with segments having lengths of around 3.0 m. The need for replacement arose from recommendations extracted from an assessment of the old bridge's state and capacity. In addition to the construction of the new bridge, its replacement necessitated the creation and evaluation of demolition procedure for the existing bridge. This procedure had to be carefully designed to avoid damaging the new bridge and stability-related issues but also to prevent debris from falling into the Kalix River, which is part of a Natura 2000 protected area. This paper discusses various issues considered while developing the demolition strategy, including the use of bed-rock anchored tendons, intermediate support fixing at specific locations, and proper evaluation of position of the demolition equipment supported by the bridge, among others. The problem of disposing of the demolished material is also discussed.

By-products management from industrial and natural (agriculture, aviculture, and others) activities and products are critical for promoting sustainability, reducing pollution, increasing storage space, minimising landfills, reducing energy consumption, and facilitating a circular economy. One of the sustainable waste management approaches is utilising them in developing biocomposites. Biocomposites are eco-friendly materials because of their sustainability and environmental benefits that have comparable performance properties to the synthetic counterparts. Biocomposites can be developed from both renewable and industrial waste, making them both energy efficient and sustainable. Because of their low weight and high strength, biocomposite materials in applications such as automobiles can minimise fuel consumption and conserve energy. Furthermore, biocomposites in energy-based applications could lead to savings in both the economy and energy consumption. Herein, a review of biocomposites made from various wastes and their related key properties (e.g. mechanical and fire) are provided. The article systematically highlights the individual wastes/by-products from agriculture and materials processing industries for composites manufacturing in terms of their waste components (materials), modifications, resultant properties, applications and energy efficiency. Finally, a perspective for the future of biowastes and industrial wastes in polymer composites is discussed.

The effect of pyrolysis reactors on the properties of biochars (with a focus on flammability and mechanical characteristics) were investigated by keeping factors such as feedstock, carbonisation temperature, heating rate and residence time constant. The reactors employed were hydrothermal, fixed-bed batch vertical and fixed-bed batch horizontal-tube reactors. The vertical and tube reactors, at the same temperature, produced biochars having comparable elemental carbon content, surface functionalities, thermal degradation pattern and peak heat release rates. The hydrothermal reactor, although, a low-temperature process, produced biochar with high fire resistance because the formed tarry volatiles sealed water inside the pores, which hindered combustion. However, the biochar from hydrothermal reactor had the lowest nanoindentation properties whereas the tube reactor-produced biochar at 300 °C had the highest nanoindentation-hardness (290 Megapascal) and modulus (ca. 4 Gigapascal) amongst the other tested samples. Based on the inherent flammability and mechanical properties of biochars, polymeric composites’ properties can be predicted that can include them as constituents.

The present study was conceived in order to investigate the shear behaviour of the Precast Reinforced Concrete Wall Panels (PRCWP) with cut-out openings subjected to in-plane seismic loading conditions and to assess the shear capacity gain obtained using Fiber Reinforced Polymer (FRP) composites as retrofit solution. The structural system of Precast Reinforced Concrete Large Panels (PRCLP) was extensively used in Romania, from 1950 to 1990, for housing buildings with 5 and 9 stories. Cut-out openings are often required to facilitate direct access from outside or between adjacent apartments, predominantly at the ground floor, where both gravity and seismic capacity demand is maximum. However, cut-out openings performed in structural walls results in the modification of the internal force flow paths, loss of load bearing capacity and reduced structural safety. Similar experimental researches are scarce in the literature. The earthquake resisting behaviour of Reinforced Concrete (RC) structural walls with openings, strengthened by Carbon FRP (CFRP) sheets and grids, was investigated in the post-damage repair and strengthening case. The shear and flexural strengthening effect of differently oriented CFRP sheets was examined on cantilever type RC shear walls in both prior-to-damage and post-damage situations. Experimental research was performed on high slenderness RC walls with door openings distributed on four height levels, strengthened with CFRP sheets.

This paper designed a 1/20 scaled two-segment 19-story mega-frame suspended structure. The seismic behaviors of the structure equipped with viscous dampers (named damping suspended structure, DSS) or rigid connecting rods (named normal suspended structure, NSS) were studied and evaluated by a series of shaking table tests, where three seismic ground motions with two intensities were selected as input motions. Both acceleration and displacement responses of the primary and suspended structures were recorded. The results revealed that the mega-frame suspended system showed good seismic behaviors and viscous dampers could effectively improve its energy dissipation capacities. For DSS, the maximal acceleration and displacement reduction of suspended structures were 75.4% and 39.8% while those of the primary structure were 29.4% and 35.3% respectively. White noise tests showed all models were at the elastic stage under all cases. Evident relative displacements between the primary and subordinate structures were observed for DSS, in this case, the suspended floors were considered as the additional mass of the primary structure and the energy could be dissipated by the swing of suspended floors. The energy dissipation mechanism of DSS was theoretically analyzed while the effect of connection forms on vibration reduction was discussed.

Load testing is a way to control the capacity and function of a bridge. Methods and recommendations for load testing are described and examples are given form tests carried out in Croatia and Sweden. In order not to damage the bridge being tested, the load must be limited, often to be within the serviceability limit state (SLS). Numerical models can be calibrated by load tests and then be used to check the carrying capacity for higher loads than what has been tested. Need for further work and recommendations are discussed. By effective planning, costs can be saved and a more sustainable use of bridges can be obtained.

This document presents the work related to the assessment of the effectiveness of strengthening reinforced concrete (RC) dapped-end beams using carbon fiber reinforced polymers (CFRP). Several non-linear finite element analyses were performed using different strengthening configurations, from the simplest solutions to the more complex ones in which different application schemes were overlapped. The work is focused on evaluating the strengthening systems, considering the ultimate capacities they can lead to and the failure modes involved. There were modeled 17 different strengthening configurations. While some of them provided a marginal in the ultimate load that can be applied, several of them provided important load bearing capacity increase. The observed failure modes ranged from a sudden failure of the whole strengthening system up to the desired progressive failure of the individual components of each strengthening system.

Load testing is a way to control the capacity and function of a bridge. Methods and recommendations for load testing are described and examples are given form tests carried out. In order not to damage the bridge being tested, the load must be limited, often to be within the serviceability limit state (SLS). Numerical models can be calibrated by load tests and then be used to check the carrying capacity for higher loads than what has been tested. Need for further work and recommendations are discussed. By effective planning costs can be saved and a more sustainable use of bridges can be obtained.

Dam failures are catastrophic events and in order to improve safety, engineers must have good tools for analysis and an understanding of the failure process. Since there are few cases of real failures in concrete dams, which can work as validation, physical model tests are a good way of improving numerical models and the understanding of the failure process. In this article, a physical model test of the buttress from a concrete Ambursen type dam is used as a benchmark for calibrating a FE-model. The dam failure is thereafter simulated using the concept of safety commonly used in the design codes. The advantages and drawbacks of performing load- and displacement-controlled simulations are compared. A new method for performing displacement-controlled simulations, using nonlinear springs to introduce the hydrostatic pressure and ice load is thereafter suggested and tested. The proposed method gives results which corresponds to the classical methods of analysis but has some advantages. Primarily, the new method is stable and does not suffer from convergence issues as was the case with the other methods. It is also simple to introduce in most commercial software compared to classical displacement-controlled simulations.

A significant portion of the reinforced concrete railway bridges in Sweden is reaching its designed lifespan and is scheduled to be demolished and replaced in the upcoming years. To limit the economic and environmental impact related to the replacement of this existing railway infrastructure, a comprehensive evaluation of their capacity is required with the aim of extending its lifespan. Experimental evidence has shown that some of these bridges may have a higher capacity than previously determined due to the conservative assumptions used during their design. The proper stress distribution pattern at the ballast-concrete interface is among the factors that need to be studied, as research on the topic has shown that some of the available guidelines to calculate it can produce conservative results. In this paper, available analytical models for computing the forces in concrete bridges due to train axle loads are compared to numerical models calibrated using the experimental results obtained from the test of ballasted reinforced concrete trough bridge, a typical structural type found in Sweden. As a first step, a literature review of existing numerical modeling strategies for ballasted concrete railway structures (e.g., finite element models, discrete element models, and their combination) is conducted. Then, appropriate numerical modelling strategies are identified and used to develop the numerical model of the bridge, including the ballast. Finally, results of contact pressure and vertical stresses in the numerical models are compared to those obtained analytically.

Reactive molecular dynamics was applied in this study to construct the sodium aluminosilicate hydrate (N-A-S-H) and tensile fracture models with various crack angles. The impact of crack angle on the behavior of N-A-S-H fractures was explored while considering structural mechanical properties and energy evolution. Furthermore, the fracture toughness and brittleness index for various crack angle models were calculated. The findings indicated that the ultimate strength and elastic modulus of the fracture models grew linearly with the increase in crack angle. The fracture toughness value progressively grew while the model’s elastic energy efficiency and new surface energy efficiency decreased simultaneously. The 45° crack model possessed the largest oblique crack development surface in the fracture process due to the coupling effect of tensile and shear stress. Its elastic energy efficiency decreased as well the most, while the new surface energy efficiency increased and the fracture toughness value dropped sharply. It is crucial to place a stronger emphasis on spotting cracks both in the in-service structures or structures being demolished. This ensures optimal performance and safety by enabling more effective adjustments to the direction of external forces and energy input.

This paper presents the results of experimental investigations on reinforced concrete slabs strengthened using fibre-reinforced polymers (FRP). Eight tests were carried out on four two-way slabs, with and without cut-out openings. Investigations on slabs with cut-outs revealed that the FRP can be placed only around the edges of the cut-out when retrofitting the slabs whereas, in the situation of inserting cut-outs combined with increased demands of capacity, it is necessary to apply FRP components on most of the soffit of the slab. The proposed strengthening system enabled the load and deflection capacities of the FRP-strengthened slabs, in relation to their un-strengthened reference slabs, to be enhanced by up to 121% and 57% for slabs with and without cut-outs respectively.

Natural fibre-based composites are replacing traditional materials in a wide range of structural applications that are used in different environments. Natural fibres suffer from thermal shocks, which affects the use of these composites in cold environment. Considering these, a goal was set in the present research to investigate the impact of cryogenic conditions on natural fibre composites. Composites were developed using polyester as matrix and jute-fibre and waste Teak saw-dust as reinforcement and filler, respectively. The effects of six parameters, viz., density of saw-dust, weight ratio of saw-dust, grade of woven-jute, number of jute layers, duration of cryogenic treatment of composite and duration of alkaline treatment of fibres on the mechanical properties of the composite was evaluated with an objective to maximise hardness, tensile, impact and flexural strengths. Taguchi method was used to design the experiments and response-surface methodology was used to model, predict and plot interactive surface plots. Results indicated that the duration of cryogenic treatment had a significant effect on mechanical properties, which was better only up to 60 min. The models were found to be statistically significant. The study concluded that saw-dust of density 300 kg/m(3) used as a filler with a weight ratio of 13 wt.% and a reinforcement of a single layer of woven-jute-fibre mat of grade 250 gsm subjected to alkaline treatment for 4 h in a composite that has undergone 45 min of cryogenic treatment presented an improvement of 64% in impact strength, ca. 21% in flexural strength, ca. 158% in tensile strength and ca. 28% in hardness.

The issue of sustainability is a growing concern and has led to many environmentally friendly chemical productions through a great intensification of the use of biomass conversion processes. Thermal conversion of biomass is one of the most attractive tools currently used, and pyrolytic treatments represent the most flexible approach to biomass conversion. In this scenario, microwave-assisted pyrolysis could be a solid choice for the production of multi-chemical mixtures known as bio-oils. Bio-oils could represent a promising new source of high-value species ranging from bioactive chemicals to green solvents. In this review, we have summarized the most recent developments regarding bio-oil production through microwave-induced pyrolytic degradation of biomasses.

This paper presents the results of an experimental campaign carried out to investigate the behavior of reinforcedconcrete (RC) beams strengthened in shear using externally bonded advanced composite materials. In order tocompare their performance, two different types of composite materials were used to strengthen the beams: fiberreinforced polymer (FRP) and fiber reinforced cementitious matrix (FRCM) composites. The beams were thentested in four-point bending scheme, and measurements regarding applied load and mid-span displacements wereacquired. Observations regarding the gain in shear strength, influence on mid-span deflection and ductility, andcomparison of the performance of the two strengthening systems are provided. For specimens strengthened withFRCM composite, the contribution to the shear strength provided by the FRCM strengthening system is comparedwith the value predicted by an analytical model found in the available literature.

Shear failure of reinforced concrete (RC) beams is an undesirable mode of failure due to its sudden and brittlenature and thus needs to be carefully evaluated when planning a strengthening intervention. The use of fiberreinforced polymer (FRP) composites has shown to be capable of providing an adequate increase in shear strength.However, in recent years, there is interest in developing new techniques in which the positive attributes of FRPare utilized but some of its drawbacks are overcome. Among these techniques, fiber reinforced cementitious matrix(FRCM) composites, in which the organic resins are replaced by inorganic mortars, have shown promising results.In this paper, a bibliographical review of the available literature on FRCM shear strengthening of RC beams iscarried out. Two available design models are evaluated using a database compiled by the authors. The reviewshows that FRCM is able to provide an increase in strength and performance comparable to RC beams strengthenedwith FRP. However, the models are not able to accurately predict the behavior of FRCM strengthened beams.

Fiber-reinforced cementitious matrix (FRCM) composites have shown promising results as shear strengthening of reinforced concrete (RC) beams. However, due to the limited available experimental evidence, further research is needed to develop accurate and reliable design formulations. In this paper, the results of an experimental campaign previously carried out by the authors on RC beams strengthened in shear with FRCM composites are used to identify the shear strength contributions of the concrete, internal transverse reinforcement, i.e., stirrups, and external transverse reinforcement, i.e., FRCM jacket. Two approaches are used. In the first, the concrete contribution is calculated as the difference between the strengthened beam capacity and the internal and external reinforcement contributions, computed based on experimental strains. In the second, the concrete contribution is estimated from the control (unstrengthened) beam and then combined with the internal reinforcement contribution obtained from the experimental strains to estimate the FRCM contribution. Results show that the concrete and stirrup contributions to the shear strength of strengthened beams are lower than those of corresponding control beams. This conflicts with the assumptions of available design guidelines that compute the shear strength of FRCM-strengthened beams as the summation of the maximum contributions by concrete, internal reinforcement, and FRCM.