In the past five decades, man-made and synthetic fibers have dominated the market and have been used to strengthen masonry structures. This study explores the feasibility of using natural fibers, specifically jute fiber-based materials, to improve masonry walls’ structural and thermal performance through integrated upgrading/retrofitting. It thoroughly examines the application of jute nets (with mesh dimensions of 2.5 cm × 1.25 cm), jute fiber diatons, and jute fiber-reinforced composite mortar (containing 1% jute fiber by dry mortar weight) in masonry strengthening. The research assesses the impact of these materials on both the structural integrity and thermal efficiency of upgraded masonry walls. Remarkably, the use of Natural Fiber Textile Reinforced Mortar (NFTRM) led to an increase of more than 500% in the walls’ load-bearing capacity and improved insulation by 36%. Additionally, the study incorporates detailed crack pattern analysis under in-plane cyclic loading using advanced DIC techniques. Therefore, integrated upgrading/retrofitting has been demonstrated to be an ideal solution against seismic action while enhancing the energy efficiency of a building.

The search for sustainable, low-carbon construction materials has drawn attention to bamboo due to its renewability, fast growth, and favorable mechanical properties. This study investigates the bond behavior of bamboo strips used as reinforcement in bio-concretes, focusing on the influence of surface treatments with castor oil resin and sand. Pull-out tests were conducted to evaluate bond strength and fracture energy, and a simplified bilinear bond-slip model was applied for analytical validation. The results demonstrated that the resin-sand treatment increased the bond strength by up to 3.9 times compared to untreated bamboo, significantly improving interfacial performance. The analytical model showed good agreement with the experimental curves, especially for the reference condition (REF), and reasonably captured the behavior of treated samples (CR and CRS), despite their higher variability. The study confirms the potential of castor oil resin as an effective, bio-based treatment for improving the interface between bamboo and cementitious matrices, contributing to the development of more sustainable reinforcement systems.

Structural Health Monitoring (SHM) plays a crucial role in the assessment and management of ageing infrastructure and enables the continuous observation of structural behaviour and early detection of anomalies. Among SHM techniques, Operational Modal Analysis (OMA) is particularly effective for in-service bridges, as it allows the identification of modal parameters without requiring controlled excitation, with a minimum intrusiveness and a high global assessment capability. The present work focuses on the dynamic identification of a road bridge located in central Italy and composed by four spans featuring six Gerber-type half-joints. Over time, the bridge has undergone major structural alterations, such as reinforcement and potential stiffening of half-joints, which have modified its global dynamic behaviour. The dynamic response of the structure was analysed over several months by using a continuous vibration-based monitoring system, which includes almost 30 MEMS accelerometric channels analysed via advanced OMA techniques implemented through the “P3P” software suite. This work presents the proposed monitoring strategy and analyses the collected monitoring data with the aim of identifying the main effects of the structural interventions and the outcomes of long-term dynamic response tracking.

Growing environmental awareness is increasingly justifying the development and adoption of sustainable solutions in various industrial sectors. The civil engineering sector is no exception: new materials sourced from renewable, locally available resources are being developed and explored worldwide. Alongside this widespread effort, a class of emerging materials is receiving particular attention: bio-based composite systems. This study investigates the mechanical response of a textile-reinforced mortar (TRM) system that incorporates two layers of flax and jute fabric into a hydraulic lime-based mortar matrix. Specifically, the bond interaction between the natural fabrics and the mortar matrix is analysed using direct pull-out tests, as well as by examining cracking patterns observed in tensile tests on natural TRM systems. These analyses reveal the substantial mechanical response in both cases, offering insights into the potential application of natural textile reinforcement in restoring and reinforcing existing masonry elements and structures.

ABSTRACT Considering the needs for reducing carbon emissions and except for extreme cases of very degraded existing structures, research on technologies allowing continued use or upgrading of older buildings has become a priority topic. Generally, research on upgrading of reinforced concrete frame structures certainly has a prominent role, because of the large number of buildings of this type. Particularly, seismic upgrading is a common request to structural engineers in earthquake‐prone regions, where structure‐level techniques, such as exterior steel bracing systems (“exoskeletons”), can help enhance safety of existing structures without disrupting occupancy and, possibly, allowing integration with other interventions intended at improving the energy efficiency. Usually, seismic analysis neglects the contribution of masonry infills, although their lateral stiffness and resistance could be detrimental to the efficiency of the new bracing system and there could be interactions in the inelastic range impairing the original bare frame design. To investigate this issue, a numerical analysis was carried out considering an archetype existing frame structure located in a high seismic hazard zone, which was meant to be seismically upgraded by the addition of newly designed steel exoskeletons. More specifically, two possible retrofit designs were compared, considering two different performance levels either to ensure the structure serviceability or to prevent its collapse. Based on results from both static and dynamic non‐linear analyses, this paper discusses the role and effects of masonry infill panels on the effectiveness of the steel bracing system, emphasising the most relevant performance indicators characterizing both the bare frame structure and the infilled frame structure.

The use of industrial bamboo residues as bio-aggregates in cementitious composites offers a sustainable approach to reducing the environmental impact of conventional concrete. However, there is still limited knowledge regarding the compressive behaviour of mixtures in which bamboo particles fully replace traditional coarse aggregates. This study investigates the mechanical performance of bamboo bio-concretes (BBCs) with total replacement of coarse aggregates, using bio-aggregate volume fractions of 15%, 20%, 25%, and 30%. After 28 days, compressive strength decreased from 31.5 MPa (BBC-15) to 17.9 MPa (BBC-30), while the elastic modulus declined from 15.08 GPa to 8.57 GPa. Higher bamboo contents improved post-peak ductility, with BBC-30 sustaining up to 52% of the peak load at 8000 mu epsilon, compared to 39% for BBC-15. Poisson's ratio values (0.36-0.43) indicated significantly greater lateral deformability than that of conventional concretes, and statistical analysis showed that this parameter is governed mainly by the low stiffness of bamboo particles rather than by the bio-aggregate fraction itself. Existing theoretical models (Model Code 2010 and Eurocode 5) did not accurately represent the ductile post-peak behaviour, whereas Popovics' equation produced better fits. The results highlight the distinct mechanical features of bamboo bio-concretes and support their suitability for low-load-bearing structural elements.

The increasing demand for sustainable and resilient construction practices in seismic areas calls for innovative retrofitting solutions utilizing renewable resources. This study presents an experimental investigation on the structural performance of masonry walls upgraded using a Natural Fiber Textile Reinforced Mortar (NFTRM) system based on jute fibers. Hollow brick masonry walls were strengthened through the application of jute fiber nets, jute-based diatons (transverse connectors), and a composite mortar incorporating 1% jute fibers by weight. In-plane cyclic shear tests were performed under constant vertical loads to evaluate the improvement in shear strength ultimate capacity. The results show that the NFTRM system significantly enhances the load-bearing performance compared to unreinforced walls, reaching an ultimate shear strength of approximately 2.7–2.9 MPa. The outcomes highlight the potential of bio-based reinforcement systems to provide an eco-friendly and effective alternative for masonry strengthening in seismic regions, promoting both sustainability and resilience.

Masonry buildings constructed in past centuries were generally built without seismic design provisions. Commonly, Fiber Reinforced Polymers (FRP) or Textile Reinforced Mortar (TRM) systems are used for masonry retrofitting/upgrading. TRM systems are generally considered more suitable for masonry upgrading applications. In this work, an experimental campaign has been developed to retrofit/upgrade masonry walls with a Natural Fiber (NF) TRM system configured with two jute fiber nets (mesh types: 2.5 cm & times;2.5 cm and 2.5 cm & times;1.25 cm), four jute fiber made diatons and/or jute fiber (1% fiber (30 mm) with respective to the mortar mass) composite Structural Mortar (SM). This paper reports the improved strength of masonry walls upgraded with the proposed NFTRM system. Constant vertical load has been applied on these upgraded walls, and the shear strength capacity and ultimate strength of these walls have been evaluated through in-plane cyclic shear tests. It has been found that the ultimate strength of the NFTRM system is found to be very close to each other and ranging between 2.7 (MPa) to 3.1 (MPa). The overall load-carrying capacity of the strengthened masonry walls increased by more than 455%. This study shows that jute-based NFTRM systems improve masonry performance while advancing sustainable, circular construction practices aligned with the United Nations Sustainable Development Goals.

In recent years there is a growing interest in Textile-Reinforced Mortar (TRM) systems as a convenient solution for seismic strengthening of masonry buildings. Moreover, TRM systems based on the use of natural fibers (hereafter referred to as nTRM) are emerging as a sustainable alternative to the currently available composite systems. However, predicting the cracking evolution in nTRM is still an open issue, as this process is significantly affected by several geometric and mechanical properties whose direct evaluation is not straightforward in the case of textiles made natural fibers. In this context, starting from the experimental results obtained from tensile tests on nTRM specimens, this study aims to formulate and apply a novel methodology intended at understanding the mechanisms behind the cracks formation process in nTRM systems and making their behavior more predictable and controllable at the design stage. The proposed model is based on the use of one-dimensional spring-like elements, which can lead to a reasonable balance between computational cost and simulation accuracy. The nonlinear analysis algorithm adopted in the implemented numerical code is based on a classical incremental-iterative procedure, which includes the various relevant mechanical phenomena and physical quantities (e.g. mortar matrix cracking, mortar-textile slippage and bond interaction). The model is validated by comparing the numerical results with the corresponding experimental ones, both in terms of nominal stress-strain and force-average-crack-spacing relationships. The promising results obtained in this preliminary application of the proposed model can inspire future experimental research to further investigate the role of the fundamental parameters related to geometry and mechanical properties of mortar and textile with the aim to improve the composite behavior of nTRM systems.

Several existing reinforced concrete (RC) structures are unable to fulfil the current structural safety standards with respect to seismic actions, owing to their inadequate structural detailing. However, recent Government policies tend to favour the reuse of older buildings, thus making the seismic retrofit of RC structures an increasingly common request to structural engineers. In this context, structure-level techniques, such as exterior steel bracing systems (“exoskeletons”), can help enhance the safety of existing structures without causing occupancy disruption. The development of an accurate numerical model, reproducing the nonlinear response of brace elements, existing RC members and infill panels, is fundamental to evaluate properly the capacity of the retrofitted structure, especially when damage to non-structural components needs to be prevented. Hence, the present paper outlines the performance assessment of an archetype existing RC structure (ideally located in a high seismic risk zone) equipped with steel exoskeletons. In particular, two possible retrofit designs are compared, considering two different performance levels either to ensure the structure serviceability or to prevent its collapse. The paper focuses on discussing the role and effects of masonry infill panels on the effectiveness of the steel bracing system. To this end, nonlinear static analyses were carried out, emphasizing the most relevant performance indicators characterizing both the bare frame structure and the infilled frame structure.

The Externally Bonded Reinforcement on Groove (EBROG) is an innovative technique for strengthening concrete structures using CFRP strips, that has enabled the development of a fully composite solution for prestressed strips. This study presents the results of a large-scale experimental campaign on six reinforced concrete slab strips, each 6 m long, tested using a six-point bending setup and strengthened with both non-prestressed and prestressed, EBR and EBROG techniques. The research aimed to validate the effectiveness and reliability of the EBROG technique coupled with a recently developed anchorage system and to investigate the performance of a novel strengthening approach that combines both EBR and EBROG techniques. In this latter solution, the EBROG technique is applied in the anchorage zones, while the EBR technique is used over the remaining slab length. The approach was considered to simplify the application process without compromising the effectiveness of the strengthening. The test results showed that the EBROG solution can increase load carrying capacity by more than 32 % compared to a non-prestressed EBR solution. By combining EBROG and EBR, similar loading behaviour was observed, demonstrating that it is a valid alternative for slabs and beams where intermediate debonding is not the dominant failure mode. The experimental results are supported by the numerical study, which, through the simulation of interface slips between the FRP and the concrete substrate, allows for an accurate understanding of the load transfer mechanism between concrete and CFRP in the different strengthened systems.

In recent years, the development of alternative and more sustainable technologies for reinforced concrete structures has been attracting more and more interest, given the increasing need to reduce the impact that the construction sector has on the environment. Furthermore, 3D concrete printing (3DCP) technology falls into this context, allowing the optimization of the quantities of employed raw material to be used while at the same time allowing the possibility to design more complex elements’ shapes. In the view of improving the sustainability of construction sector, the present study aims at experimentally investigating the characteristics of the fresh and hardened states of concrete mixtures incorporating different percentages of replacement of the fine aggregate with recycled aggregates of different nature. As such, the key innovative aspect of the present study is the possible investigation of cement-based mixtures produced with 100% recycled fine aggregates (both derived from concrete waste and brick elements) without affecting either the fresh or hardened mechanical properties of the resulting Recycled Aggregate Concrete (RAC) mixtures. Furthermore, in order to make this study linked to 3D printing technology, extruded concrete elements were realized and tested through a process designed to simulate the automated 3D concrete printing process: in fact, the RAC mixtures were designed in order to obtain an adequate workability and compressive strength typically adopted for ordinary 3D printed mixtures. Although some adjustments and further analyses are required in order to optimize the shape retention and stability, as well as the well-known problem of the 3D mixtures being linked to anisotropic behavior, the obtained results unveil that it was possible to observe promising characteristics for the mixes containing recycled aggregates (i.e., consistency index at the fresh state above 150 mm and compressive strength at 28 days above 50 MPa), which were in any case suitable for the creation of 3D printed structural concrete elements and can be further confirmed with future studies in order to validate their possible buildability.

Predicting the development of cracking processes in structural elements made of reinforced concrete (RC) or other cementitious composites is still a challenging task. Although well-established experimental procedures are widely adopted with the aim to gain empirical knowledge of the aforementioned processes, no similar consensus has been reached about mechanical modeling. Actually, the simulation approaches available in the literature are based either on computationally demanding 3D finite element models or on simplified 1D solutions obtained through alternative numerical strategies, such as finite difference schemes. The present paper proposes a simplified FEM model based on 1D spring elements, which aims at obtaining a reasonable balance between simulation accuracy and computational effort. The incremental-iterative scheme driving the nonlinear solution procedure is described in detail and some comparisons with experimental results on RC tensile members are proposed with the aim of validating the proposed model. Moreover, the promising results obtained in this paper inspire the future developments of the research towards the numerical simulation of the cracking behavior of other inorganic-matrix composites, like textile reinforced mortars (TRM), subjected to tensile actions.

Sustainability in the construction and building sector with the use of greener and more eco-friendly building materials can minimize carbon footprint, which is one of the prime goals of the twenty-first century. The use of natural fibers in ancient and traditional buildings and structures is not new, but in the last fifty years, only man-made fibers have predominantly occupied the market for structural retrofitting or upgrading. This research investigated the potential of utilizing natural fibers, particularly jute fiber products, to enhance masonry’s thermal and structural characteristics. The study meticulously investigated the utilization of materials such as jute net (with a mesh size of 2.5 cm × 1.25 cm), jute fiber diatons, and jute fiber composite mortar (with 1% jute fiber with respect to the dry mortar mass) in the context of masonry upgrading. The research evaluated the structural and thermal performance of these upgraded walls. Notably, the implementation of natural fiber textile-reinforced mortar (NFTRM) resulted in an astounding increase of over 500% in the load-bearing capacity of the walls, while simultaneously enhancing insulation by more than 36%. Furthermore, the study involved a meticulous analysis of crack patterns during in-plane cyclic testing utilizing the advanced Digital Image Correlation (DIC) tool. The upgraded/retrofitted wall exhibited a maximum crack width of approximately 7.84 mm, primarily along the diagonal region.

This article examines the structural behavior of a paradigmatic case in the cement industry: an existing reinforced concrete (RC) Preheater Tower (PT). The study focuses on assessing the degradation caused by the severe operational conditions of these industrial facilities and evaluating the consequent impact on structural safety. PTs are defined by their considerable total and inter-platform heights, substantial live loads on all platforms and prolonged exposure to high temperatures from the clinker preheating process. These factors pose significant structural challenges in ensuring long-term safety. Unlike previous studies, this research provides a more comprehensive analysis by investigating scenarios that are likely to occur throughout the lifecycle of critical industrial structures like PTs. Through in situ non-destructive dynamic tests conducted on all platforms and detailed finite element (FE) modeling, a rigorous calibration process was carried out to match observed vibration frequencies at different levels. The obtained parameters were then compared with the mechanical properties of concrete after long-term exposure to elevated temperatures. The analysis reveals that PTs in the cement industry undergo significant degradation due to prolonged exposure to medium and high temperatures. This concern is particularly critical in high-seismic-risk zones and in cases where inadequate maintenance results in the loss of necessary thermal insulation in cyclones and ducts—especially the platform over the kiln, which is the most vulnerable to high temperature exposure. Overall, this study establishes a reliable methodology for evaluating PTs safety by integrating on-site vibration analysis, FE structural modeling, and predictive modeling for PT under frequent seismic events.

El presente artículo tiene como objetivo examinar el comportamiento estructural de un caso paradigmático en la industria cementera: una Torre de Precalentamiento (TP) existente de hormigón armado (HA). Se evalúa la degradación inducida por condiciones operativas severas y su impacto en la seguridad estructural. Las TPs presentan grandes alturas, cargas vivas sustanciales en las plataformas, y una exposición prolongada a altas temperaturas, lo que plantea desafíos relevantes para su integridad a largo plazo. En contraste con investigaciones previas, en este trabajo se realiza un análisis más exhaustivo considerando escenarios probables a lo largo de su ciclo de vida. Se describe una metodología que combina ensayos dinámicos no destructivos in situ y modelado por elementos finitos (EF), calibrando frecuencias medidas y propiedades mecánicas del hormigón degradado. Los resultados evidencian una degradación significativa, especialmente crítica en zonas sísmicas con mantenimiento deficiente y pérdida de aislamiento térmico, destacando la vulnerabilidad de la plataforma sobre el horno. Este estudio propone una metodología fiable para evaluar la seguridad de las TPs mediante la integración de análisis de vibraciones in situ, modelado estructural EF y modelado predictivo en eventos sísmicos frecuentes.

The use of natural reinforcement as a substitute for conventional reinforcing fabrics within Textile Reinforced Mortar (TRM) technology is an increasingly addressed topic in research. This choice was made to improve the sustainability of such reinforcement interventions on structures. The main problems encountered with respect to this solution are inherent to the characteristics of the natural fabric itself: in fact, the latter presents on the one hand mechanical characteristics suitable for structural use, in particular for masonry; on the other hand, aspects such as variability in physical and mechanical characteristics and durability represent “weak” points to be investigated and addressed. The study carried out deal with these issues, applying the polymer coating technique to the natural fabric/yarns. However, to avoid compromising the sustainability of the intervention, rather than using conventional polymers (mainly epoxy resin), bio-polymer (Poly-Lactic Acid, PLA) has been chosen. As a matter of fact, although coating/impregnation is a commonly used technique in TRM to improve the characteristics of the reinforcement, the possibility of using bio-polymers has not been effectively addressed yet in the literature. The physical and mechanical characterization of the fabric elements thus treated was then carried out. One of the analyses concerned the study of the bond behaviour between the impregnated fabric-yarns and the lime-based mortar with which the latter will have to interact. Two phases of pull-out tests were then carried out, designing specific test configurations for the required needs, and in these the bond between the fabric and the matrix was recorded by varying different parameters (different impregnation concentrations, different anchoring lengths, different type of natural yarns). The results obtained represented a failure mechanism between impregnated cord and mortar mainly related to the interaction between the matrix and the PLA present on the surface of the cord. In general, however, the behaviour of the fabric presents promising characteristics for use within TRM systems.

The growing demand for sustainable construction has encouraged the use of composite beams combining timber or bamboo with concrete to optimize structural performance and reduce environmental impact. These hybrid systems, widely used in new constructions and retrofits, present modeling challenges due to the nonlinear interaction between materials and their mechanical connections. This study aims to develop and validate a finite element model to simulate the nonlinear flexural behavior of these composite beams. The model is based on an exact solution for two-layer elastic systems and incorporates nonlinear constitutive laws for concrete and timber/bamboo, along with a trilinear shear–slip law to represent interface behavior. Unlike most models, it is applicable to different connector types and a range of materials—including bamboo, timber, and both conventional and lightweight concrete. An incremental–iterative solution captures progressive deformations and failure mechanisms. Validation against 16 experimental beams showed accurate predictions of linear load capacity, mid-span deflection, and initial stiffness. Over 80% of the results showed deviations below 30%, and 50% were within 20%. The model also correctly captured the experimental failure mode in all cases. This approach provides a reliable and versatile tool for the structural analysis and design of composite beams.

A significant number of existing buildings worldwide are made of masonry and, as they were built in the past, they do not generally meet the current standards in terms of structural/seismic safety and energy efficiency. Moreover, buildings, including masonry ones, are responsible for a significant share of energy demand and Green-House-Gas (GHG) emissions. Therefore, there is an urgent need to come up with efficient and effective techniques capable of enhancing both structural safety and thermal insulation of existing buildings. Besides some isolated attempts to come up with a integrated approach to target both aspects, the scientific community generally addresses seismic safety and thermal insulation as two separated and this is also the case of practitioners. In this context, the present paper summarizes the preliminary results of the IntegraTRM project which aims at formulating an efficient and sustainable solution for coupled thermal and seismic upgrading of existing constructions. More specifically, it aims at formulating the composition of a composite Textile Reinforced Mortar (TRM) system characterized by an “optimized” performance in terms of both structural strengthening and thermal insulation. The formulation of the TRM system under consideration is based on the use of “environmentally-friendly” constituents: a significant fraction of recycled aggregates, coming from construction and demolition waste, are considered for the mixture proportioning of the mortar matrix; vegetable fibers and fabrics are being employed to achieve both mechanical resistance and thermal insulation potential.