The lack of guidelines and building codes for design and validation, uncertainty in static and dynamic performance after production, and unknown long-term performance, make the building application process of natural fiber-reinforced composites challenging. This paper addresses these challenges comprehensively by outlining essential procedures required for building application and offering effective solutions. For the design phase, a new approach is proposed based on material properties and the underlying elastic strain limit. The mechanical model is manufactured and tested to validate design assumptions. Consequently, the 15m span novel footbridge made of flax fibers and a partial bio-based resin was produced. Following the bridge's production, a load test was conducted to assess its static performance. Strain and deflection values obtained from FBG and LVDT sensors, respectively, were measured and compared with FEA. Modal analysis was performed to obtain natural frequencies. Bridge management was developed to guarantee safety during the long-term service of the footbridge by determining strain thresholds with a new approach based on first loading outputs and damage evaluation for this material. The paper offers guidelines for material selection, design, production quality, static and dynamic performance evaluation, and bridge management, providing a holistic framework for the successful application of NF in footbridge.

The paper explores the potential applications of adaptive components based on shape memory polymer (SMP) composites in vibration control of plate/shell structures and rigidization of inflatable structures. These components achieve stiffness and damping variation by thermally actuating SMP between its glassy and rubbery states. In CASE A, steel-SMP sandwich plates of a truss bridge are actuated to glass transition temperature (Tg), where material damping reaches the peak to mitigate dynamic responses. CASE B proposes a simple and reversible rigidization method for inflatable structures, creating high compaction ratio and design flexibility. Converting the SMP layer between its glassy and rubbery states, inflatable structures achieve multiple functions during transportation, construction, and service life. SMP-based adaptive components enhance structural performance and mitigate dynamic effects in demanding environments for various structures.

This study examines the influence of weathering aging on the mechanical properties and durability of flax fiber-reinforced polymer composites (FFRP) intended for outdoor applications. Employing an accelerated weathering environment replicating natural outdoor conditions, encompassing UV radiation, condensation, and water spray, the FFRP samples with 2 and 4 mm thicknesses underwent exposure durations of 0, 500, 1000, and 1500 h. Mechanical tests characterized tensile, flexural, and inner-plane shear properties, while a custom-made apparatus measured the long-term tensile creep behavior. Additionally, scanning electron microscopy allowed for the observation of microscopic changes in fiber and matrix. The findings illustrate a consistent decline in tensile and flexural properties with increased weathering exposure, resulting in reductions of 17% and 38% in the tensile strength and modulus, and 24% and 52% in the flexural strength and modulus after 1500 h. Intriguingly, inner-plane shear strength exhibited a slight increase after 500 h before a subsequent decrease. Furthermore, samples with the same thickness demonstrated an increased creep development with longer weathering durations. Despite this, the mechanical degradation rate induced by weathering was comparatively slower for thicker samples. Overall, the diminished mechanical properties of FFRP post-weathering can be attributed not only to the polymer but also to the substantial role played by flax fibers in this process.

As an environmental-friendly material with eligible mechanical properties, FFRP (Flax Fiber Reinforced Polymer) composites are being widely studied and used in the construction industry. This paper presents an investigation of the effect of environmental humidity on the viscoelastic properties of FFRP. Frequency sweep tests are conducted, and results are re-organized by the Time-Temperature Superposition Principle (TTSP). The Huet-Sayegh viscoelastic model is introduced to describe the relationship between viscoelastic properties and loading frequency. The fractional derivative is applied to the model for more accurate results. It is found both storage modulus and loss modulus decrease with the increase of relative humidity. However, the loss factor does not have a monotonical correlation with the relative humidity of the environment. In general, it can be concluded both the capacity of FFRP to store and dissipate the energy decreases over the hygroscopicity absorption in the air, but there is no specific relationship between the amount of their reduction.

Natural fiber-reinforced composites (NFRCs) are expected to find growing applications in near future, especially in Europe where stringent environmental codes are being legislated and public pressure for their enforcement is increasing. Study has shown that NFRCs are also gaining recognition among civil engineers as a viable alternative to traditional materials for use as concrete reinforcement in load-bearing structural members as in building frames and bridge decks. The present review strives to provide a brief overview of NFRCs, state-of-the-art developments in their manufacture, and examples of their structural applications. Another aspect of the review involves investigation of the challenges facing the use of fiber composite materials in civil engineering. These include the high manufacturing costs, difficulties associated with appraisal of its potential benefits, uncertainties about their properties, lack of understanding among civil engineers of the material and its service life, and the relatively small battery of standards developed for the composite industry. Finally, the study will conclude with the prospects of bio-composite applications and the emerging trends in novel bio-composites for future structural applications.

The present research is aimed at examining the changes in tensile and compressive properties of natural fiber-reinforced composites (NFRC) exposed to various humidity conditions; this is due to the fact that moisture content (MC) in fibers is generally assumed to be detrimental to composite performance. It was found that once moisture is exposed, compressive strength and strain of specimens would be higher than those of tensile, whereas modulus of elasticity would be lower. Due to increasing moisture content, although elongation in all tests was enhanced, tensile and compressive strength declined by 15% and modulus of elasticity decreased by 20%. In addition, Poisson's ratio for both compressive and tensile properties was nearly identical (0.33) in distinct moisture content. A new understanding of moisture's effects on mechanical behavior is presented in this study by finding an optimum point for exposing moisture to increase compressive and tensile strength.

This paper deals with the numerical and experimental analysis of a large-scale footbridge model made of flax fiber-reinforced polyester composite. The goal of this work was to support the design of the 15 m span flax -polyester footbridge installed at the Floriade Expo 2022 in Almere, the Netherlands. The model stacking sequence, thicknesses, material, and vacuum infusion technology are identical to those of the footbridge. For the numerical analysis, a multi-layered laminate was modeled using ABAQUS with a composite layup and continuous shell elements. The model was equipped with 16 embedded fiber-optic Bragg grating (FBG) sensors for strain sensing and mechanical evaluation. The specimen was subjected to monotonic loading and unloading. Numerical results were compared with those obtained from the load test. The good agreement revealed the correctness of the assumptions. This study provides a design methodology based on numerical and experimental investigation, to overcome uncertainties derived from the application of this innovative material for load-bearing applications in footbridges.

Flax fiber-reinforced polymer (FFRP) composites are getting more and more popular in the construction industry as an emerging environmental-friendly material. However, their obvious creep behavior makes it a design concern for the creep development of structures made from FFRP. Though the creep behavior of the FFRP is critical for the structural design, the creep tests before structure design is not common due to the tests can take a very long time. The Time-temperature superposition principle provides a good theoretical basis for the accelerated creep tests to shorten the testing time, but the specific application of the FFRP is not clear and needs to be further developed. This study is to investigate the application methods of the Time-Temperature Superposition Principle (TTSP) theory on the FFRP material with unidirectional fibers. The three most related methods are used for constructing the creep master curves during the TTSP application to determine the most efficient application process of TTSP. The results indicate that the creep of FFRP can be effectively analyzed by the TTSP accelerated creep testing method with the proper application process.

countries -work in progress at the time of writing -can help the construction sector to transition from a linear to a circular economy beyond the pilots themselves as well as beyond the borders of the project countries.The project and its approach are multi-, inter-, and transdisciplinary, covering not only construction and the related disciplines of architecture and civil engineering, but also the domains of demolition, materials science, environmental impact assessment, economics, the sociology of work, and regulation and public policy.This approach also allows the display and discussion of diverse technological, economical, and societal aspects that can catalyse the transition to a more circular modus operandi in the construction sector.Consequently, this chapter draws from various disciplinary vocabularies pertaining to the diverse disciplinary fields while still being positioned primarily within the construction sector research.This chapter considers CE catalysts as factors enabling the implementation of the reuse to advance circularity and CE principles in the construction sector.The definition follows that of Cabell and Valsiner (2011), proposing that catalysts are positive 'helpers' that initiate and facilitate change processes.Focal catalysts encompass feasible deconstruction technologies and work processes, robust protocols for verifying the deconstructed elements' properties and quality, remanufacturing processes turning the elements into ready-for-reuse construction products, and regulation that acknowledges their recertification.It is also noted that key persons in stakeholder organisations, willing and positioned to ease this transition, can be considered catalysts in their own right.Moreover, it is considered that an extractable urban mine of a sufficient volume and a functional circular value chain, consisting of separate but connected operators, are also crucial for realising the upscaling potential of reuse.In brief, a wide variety of interlinked catalysts are required to operate simultaneously to facilitate a transition to circularity.

Flax fiber-reinforced polymer (FFRP) composites are emerging popular environmental-friendly construction materials. However, their significant creep properties have been a major concern for using FFRP in load-bearing structures. This article presents an investigation of the effect of environmental humidity on the creep behavior of the FFRP. Samples with flax fiber in 0 degrees, 90 degrees, and +/- 45 degrees were manufactured, respectively, by the vacuum infusion method. Accelerated creep tests were conducted on samples in different relative humidities (RH), and the results were analyzed by the time-temperature superposition principle (TTSP). It is found the creep development of samples with 0 degrees and 90 degrees fiber increases with the RH, and their 30-year total strain in 97% RH is about 10 times higher than that in 11% RH. The samples with +/- 45 degrees fiber are found not obviously sensitive to the humidity change. The scanning electron microscope (SEM) check indicates the change in the fiber-matrix interface and cracks between microfibrils in a fiber bundle is the main reason for the change of creep behavior in high humidity. This study may benefit the design of structures made of natural fiber-reinforced polymer composites, especially for load-bearing structures working in high-humidity environments.

Abstract Natural plant fiber-reinforced polymer composites (PFRP) have emerged as an environmental-friendly material in the construction industry, but their creep behavior is a critical concern for load-bearing structures. This study investigates the creep behavior of flax fiber-reinforced polymer composites (FFRP) using the time–temperature superposition principle (TTSP). Due to the application of TTSP on the tensile creep behavior of FFRP is not fully understood, three potential methods for calculating the critical parameters during TTSP are compared to obtain an efficient application method to build the creep master curve. A 2,000-h long-term creep test is conducted parallelly on the same sample to validate the accuracy of the creep analysis results. The study proposes an ideal method to determine the key parameters in TTSP, providing valuable insights for the practical application of PFRP in the construction industry. Meanwhile, the research results in this study would be helpful in better understanding the creep behavior of FFRP via short-term accelerated tests.

This paper presents experimental testing of a new semi-active vibration control device comprising a shape memory polymer (SMP) core that is reinforced by an SMP-aramid composite skin. This control device works as a load-transfer component that can be integrated into truss and frame structures in the form of a joint. At the material level, thermal actuation from ambient (25 degrees C) to transition temperature (65 degrees C) causes a significant 40fold increase in damping due to viscoelastic effects. At the component level, uniaxial tensile and four-point bending tests have shown that tensile strength depends primarily on the bond strength between the reinforcement skin and the structural element while flexural strength depends on the strength of the reinforcement skin fibers. Through cyclic testing, it has been observed that material viscoelasticity is beneficial to ductility and energy dissipation. When the joint core is actuated to the SMP transition temperature, axial and flexural stiffness decrease by up to 50% and 90%, respectively. The property change at material and component levels enable tuning the frequency and damping ratio at the structure level, which has been successfully employed to mitigate the dynamic response of a 1/10 scale three-story prototype frame under resonance and earthquake loadings.

可再生的原材料提供给建筑行业一种减少资源消耗和建筑碳足迹的方法.除了木材之外,生物复合材料也备受人们的关注.亚麻和大麻这类快速生长的天然纤维兼具刚度和强度.生物树脂将这些纤维连接在一起,就创造出了一种坚固的轻质材料.

Building adaptation and re-use can contribute to a circular and sustainable built environment, as existing buildings are adapted and the need for new construction materials is reduced. The “adaptability” of buildings has been widely studied; however, few of these studies are quantitative. This paper uses Artificial Neural Networks (ANN) and Logistic Regression (LR) models to explore relationships between the physical features of buildings and their demolition or adaptation outcomes. Source data were taken from 59 buildings that were either demolished or adapted in the Netherlands. After the models were created and validated, a series of sensitivity studies were conducted to evaluate relationships between physical parameters and building outcomes. The physical parameter with the strongest relationship to adaptation outcomes was demountability (ease of removal) of building service elements. The quantitative results were then compared to results from an adjacent qualitative study. The relationships observed from the quantitative sensitivity studies align well with the qualitative observations.

This paper presents numerical and experimental studies on semi‐active seismic response control of structures equipped with variable stiffness and damping structural joints. Such adaptive joints, which are comprised of a shape memory polymer (SMP) core reinforced by an SMP‐aramid composite skin, function as load‐transfer components as well as semi‐active control devices. The SMP core material can transition from a glassy to a rubbery state through thermal actuation resulting in a shift of the structural natural frequencies and a parallel increase of damping ratio, which enables a new semi‐active control strategy. Control performance has been evaluated on a three‐story frame equipped with 12 adaptive joints and subjected to seismic excitations. Full‐transient analysis has shown that when the joints are thermally actuated to the transition temperature (65°C), acceleration and base shear are reduced by up to 62% and 65%, respectively. Shake‐table tests have been carried out on a 1/10‐scale prototype, confirming that through thermal actuation of the adaptive joints the structural damping ratio increases from 2.6% to 11.3% and the first natural frequency shifts by up to 37%. As the structure becomes more flexible, an increase of displacements and interstory drift might occur. However, depending on the seismic excitation, top‐story acceleration and base shear are significantly reduced in the range 43%–50% and 35%–51%, respectively. These results confirm that semi‐active control through thermal actuation of variable stiffness and damping structural joints is effective to mitigate the structure response under seismic excitation.