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Introduction. The paper discusses the advantages and features of the main existing methods of connecting wooden columns and crossbars.Materials and methods. It was proposed to increase the load-bearing capacity and reduce the deformability of joints by modifying the joints with the introduction of epoxy resin between the screw and the wood and between the overlay and the end of the wooden element to which it is attached and modifying the design of the overlays.Results. As a result, a constructive solution for connecting wooden columns and crossbars was developed, which has increased reliability compared to the studied connections and is free of their disadvantages. This result was achieved due to the presence of an adhesive layer between the screw and the wood, as well as between the overlay and the wooden element, the making of notches on the sides of the overlays attached to the wooden elements, the increased length of the screws screwed into the overlay with a groove, compared to the length of the screws screwed into an overlay with a tenon, placement of holes for screws at an angle of 90° to the surface of the overlay into which the screws are screwed.Conclusions. An urgent issue is the development of constructive solutions for connections of wooden elements, in particular the interfaces of columns and crossbars. The paper discusses the advantages and features of the main existing methods of connecting wooden columns and crossbars.

This study solves the following tasks: a comparative analysis of theoretical, computer, and experimental data on the bending of experimental beams is given, the influence of various forms of reinforcement on the strength and stability of beams with a corrugated web is determined; the deformability of a beam with a corrugated web with perforations and without perforations in the elastic and elastic-plastic stage is studied. Experimental studies of models have allowed establishing the main characteristics of the load-bearing capacity, the features of the loss of stability of shelves and corrugated webs with various methods of reinforcing perforations. The given test results showed the necessity and economic feasibility of the work carried out to identify the optimal ways of reinforcing perforations, to meet the requirements of technologists for passing equipment within the construction height of the beams, reducing the consumption of steel for their reinforcement and reducing the complexity of production. The conducted mathematical modeling, laboratory tests, and the performed dispersion analysis allow the study to draw conclusions about the effectiveness of the improved BGS-3 and BGS-5 models and about the need to develop recommendations for introducing two proposed options for reinforcing the perforations of the BGS-3 and BGS-5 models. [ABSTRACT FROM AUTHOR]

Beam–column connections with corbels supporting the beams and continuity reinforcement protruding from the columns, also known as composite connections, are often used in construction as an alternative to monolithic cast-in-place connections. Since they are halfway between fully rigid and pin connections, these semirigid composite systems require more in-depth investigation, especially concerning their behavior at high temperatures and in fire. Compared with fully rigid connections, the primary advantage of semirigid systems is that they allow the use of precast beams. Unlike pin connections, semirigid systems allow a certain degree of fixity at beam ends after the in-place casting of the top of the beams. This study focused on the designs of two full-size specimens representing the region of the connection comprising the column stub, corbel, and beam extremity cast and tested in ambient conditions and under standard fire exposure to compare their performance with two monolithic specimens tested under the same conditions. The study also develops a numerical model of the connection using a finite-element discretization (ANSYS software) to conduct a sequential analysis of the thermal and static behavior of the connection. The numerical results are shown to satisfactorily fit the deflection curves, crack patterns, and actual conditions of the specimen after failure. The semirigid connection is stiff at ambient and medium temperatures but behaves as a pin connection at high temperatures. Further, the moment redistribution with a decreasing hogging moment at the beam ends and higher sagging moment at the midspan shows that semirigid beam–column connections are more vulnerable at high temperatures than monolithic connections. [ABSTRACT FROM AUTHOR]

Nowadays, hybrid structures, which combine low‐density composites with low‐cost thin‐walled metals, have shown great effect in enhancing the performance of automotive body structures, especially the energy absorber components. This study focuses on the experimental and numerical investigation of the bending energy absorption behavior of CFRP/aluminum hybrid double hat‐section beams used in the side part of the car body. In the experimental section, two types of double hat‐section beams were fabricated: aluminum and Al/CFRP. These beams were then subjected to quasi‐static three‐point bending tests. The results demonstrated that the hybrid beam exhibited superior energy absorption capabilities compared to the single beam. Subsequently, a finite element model was developed using LS‐Dyna software and was validated by comparing the experimental and numerical load–displacement results. In‐depth numerical analyses were conducted to investigate the influence of various design parameters, including CFRP‐reinforcement configuration, numbers of CFRP layers, CFRP ply‐angle, CFRP reinforced length, and aluminum/CFRP mass, on crashworthiness indicators. The numerical findings indicate that the hybrid beam with 04, 45/−45s ply‐angles exhibited better crash force efficiency (CFE) and specific energy absorption (SEA) compared to other ply‐angles, respectively. Furthermore, increasing the number of CFRP layers within the total beam's mass improved its energy absorption capacity. It was also revealed that the CFRP length on the upper and lower hats could be considered as 42.5% of the total aluminum beam length, as opposed to the full CFRP length, providing enhanced energy absorption capabilities. Highlights: Bending behavior of the Al and Al/CFRP double hat section beams.Effects of variable thickness and identical mass on the double hat section beam.Effects of variable ply angle and number of CFRP layers on the hybrid beams.Discrete effect of CFRP reinforcement configurations and inner CFRP lengths. [ABSTRACT FROM AUTHOR]

Perforated beams can bring countless benefits compared to traditional plain-webbed beams. However, steel beams with sequential web openings are more susceptible to instabilities, and special care must be taken in a design concerning the failure modes these structures can present. The study presented herein explicitly dealt with the stability behavior of perforated beams with sinusoidal openings. This type of perforated member features smooth-lined openings constructed from a single thermal cut in conventional plain-webbed steel profiles. A broad study was carried out through numerical simulation using the ABAQUS software, in which perforated profiles manufactured with S600E high-strength stainless steel were studied. The use of high-strength steels in perforated profiles is a little explored topic in the literature, despite having a significant impact on the behavior of these elements. With the study carried out, a broad overview of the stability behavior of these members was obtained, especially concerning global stability. A total of 5940 FE models were developed, considering the application of different types of loads. In these models, linear buckling analysis (LBA) and geometrically and materially nonlinear analysis with imperfections (GMNIA) were performed. The results obtained were compared with international design codes, and it was found that some codes fail to represent the behavior of members that present lateral-distortional buckling (LDB) and interactions between local and global failure modes. This behavior is a significant design concern since the studied members had high yield strength, making them more susceptible to interaction-governed failure modes than usual-yield strength members. Additionally, the study found that some design codes do not accurately represent the behavior of members loaded outside the shear center due to the destabilizing effect of loading on these structures. [ABSTRACT FROM AUTHOR]

Over recent decades, various heritage institutions have utilized a multitude of materials to reinforce the painted layers of ancient Chinese wooden architecture. In this study, we conducted a comprehensive evaluation of the properties and durability of four widely used reinforcement agents, i.e., AC33, B72, FKM, and FEVE, using a series of techniques, including contact angle tests, water vapor permeability measurements, color difference evaluations, tensile strength tests, UV–vis spectrometry, and scanning electron microscopy (SEM). The results demonstrate that the transmittance rates of the films made from these four reinforcement agents are approximately 100% in the visible light range. Among them, the B72 film exhibits the highest hydrophobicity. The AC33 film has better permeability, fair tensile strength, and is more hydrophilic. FKM film is more hydrophobic but has lower permeability and tensile strength. Overall, the FEVE film presents the best comprehensive properties, including better hydrophobicity, higher permeability, and tensile strength. This research provides data evidence to guide heritage conservators and curators in decision-making when selecting appropriate reinforcement materials in practice. [ABSTRACT FROM AUTHOR]

On the load‐bearing behaviour of mechanical fasteners in steel‐timber‐composite floors In the context of a sustainable structural design, research on steel‐timber‐composite floors (STC) is currently being performed at the Technical University Dortmund. The performance of the ceiling system depends on the used materials and especially on the design of the composite joint. Accordingly, various joint configurations with reversible mechanical fasteners were experimentally tested at the beginning of the research. In the course of the performed push‐out tests, the advantages of wood screws (HS) installed perpendicular to the grain compared to self‐drilling metal screws (BS) and wood screws installed with an inclination angle could be detected. The vertically installed wood screws showed a comparatively high composite stiffness as well as a highly ductile failure mechanism combined with a low installation effort. Thus, in future experimental tests to determine the flexural behaviour of the STC ceiling system, vertically installed wood screws will be predominantly used for the composite joint. [ABSTRACT FROM AUTHOR]

Calculation of timber‐concrete composite ceiling connected only at a few discrete points by the force method This article demonstrates that timber‐concrete composite ceiling with discontinuously arranged connectors can be calculated using the force method with little computational effort. The calculation results match exactly when the framework‐model is applied, where the pendulum rods are always densely arranged and their tensile stiffness increases. The concept of transverse moment is introduced for calculating the unit states, and analytical solutions are derived. Through superimpositions, a good insight into the complex behavior of timber‐concrete composite ceiling is obtained. [ABSTRACT FROM AUTHOR]

In this study, a real plot of abandoned agricultural land overgrown with forest in Russia has been surveyed. The amount of future CO2 sequestration by this forest for the next 20 years has been calculated by means of a mathematical model. The unprofitability of the 20-years climatic reforestation project on this land has been proved, based on the current price of carbon units in Russia and China, because Russia cannot enter the European carbon units' market. To improve profitability, it was proposed to combine the reforestation with timber harvesting, charcoal, natural fertilisers and forage production. Thus, the wood cut for maintenance is used partially for sale, partially for production of charcoal and partially left as a fertiliser on the cleared stripes, where meadow plants will be replaced with alfalfa, using technologies of zero soil treatment. The economic feasibility study has been performed based on the real capital and current expenses of the combined reforestation project. The positive Net Present Value and a very high Internal Rate of Return of the joint project, calculated by the methods of financial mathematics have indicated its economic viability and attractiveness for investors. [ABSTRACT FROM AUTHOR]

The exterior beam-column joints (BCJs) in reinforced concrete (RC) structures are critical and often vulnerable elements, particularly under seismic conditions, with the potential for catastrophic structural failure. Achieving robust and ductile joint design is paramount. Although efforts have been made to establish design standards for strong and ductile joints, further research is needed, especially regarding the realization of a weak beam-strong column mechanism in moment frames. This study utilizes finite element modeling (FEM) to enhance BCJs performance by exploring various reinforcement configurations as alternatives to conventional shear stirrups in the joint area. The objective is to address the challenge of reinforcement congestion in the joint area during concrete placement, which can compromise earthquake resistance. Ten FEM models were developed for evaluation, one without additional reinforcement and nine with various reinforcement configurations. The primary focus was on assessing the effectiveness of these configurations in BCJs under monotonic loading by comparing damage–rotation curves, load–deflection curves, and damage distribution. The results show that in-plane diagonal bars outperformed their out-of-plane bars, reducing core damage by 22–37%. Among the configurations, the model with two X-shaped reinforcements, replacing conventional joint stirrups, emerged as the optimal solution. This configuration provided enhanced rotational stiffness, minimized core damage in tension and compression by about 83%, improved load-carrying capacity by 13.7%, and promoted the formation of plastic hinges away from the joint, achieving the sought-after weak beam-strong column mechanism. This research has significant implications for practical design and construction in RC structures, enhancing their resilience to seismic events and contributing to safer built environments. [ABSTRACT FROM AUTHOR]

Concerning preventive maintenance plans for heritage timber buildings, computational methods are pioneering knowledge for the implementation of new preservation approaches in heritage structure management. In this context, fuzzy logic and random forest methodologies manage both data obtained from professional experts and data obtained in situ from the buildings themselves. This kind of digital procedure can harmonize the outcomes of building assessments because slight variations in the evaluation of input parameters do not produce a significant dispersion over the model's output. Preventive conservation strategies require cooperation among qualified experts who examine multidisciplinary knowledge related to heritage properties. Thus, new digital protocols and procedures that help decision makers prioritize preventive interventions and avoid corrective actions are paramount in minimizing the irreparable loss of properties. The main aim of this research is a new approach to two computational management systems: fuzzy logic and random forest. The outcomes of this study will be useful to stakeholders who are responsible for the maintenance of heritage buildings, as this methodology reduces the probability of failure and uncertainty during decision-making. The instruments derived will establish mitigation strategies oriented toward proactive future maintenance programs for heritage timber buildings in southern Chile. [ABSTRACT FROM AUTHOR]

The fracture toughness in opening mode GIc for selected oil paints from Mecklenburg's Paint Reference Collection after approximately 30 years of natural ageing was determined using the procedure adopted from the ASTM D5528–13 standard in which double cantilever beam specimens are split in tensile tests. The careful reglueing procedure allowed multiple fracturing tests to be carried out that not only improved statistics of the measurements but also provided insight into the variation of the fracture toughness across the paint film observed for some paints. The latter was due to pigment sedimentation or chemical change of the oil binder as a result of the easier access of oxygen from the side open to the air. For the lead white paint, used over centuries both in paint films and oil grounds, the GIc values more than doubled from 18 to 39 J/m2 for three consecutive cracks formed at an increasing distance from one side of the paint film. The study demonstrated that fracture toughness corresponding to the first crack formation in aged oil paints ranged between 10 and 40 J/m2, relatively low values compared to the animal glue-based ground in paintings. In consequence, oil paints are more vulnerable to crack initiation and growth induced by tensile stress than the ground layer. The measurements filled the gap in the knowledge required for the analysis of fracturing or delamination processes in paintings. [ABSTRACT FROM AUTHOR]

Ultrasonic-guided waves (GWs) have shown a high potential to be applied to the structural integrity of timber utility poles to detect and assess distinct types of defects. Yet, there are many challenges associated with this method, which may hinder its application, including the orthotropic nature of the timber, the presence of natural cracking, and the effect of environmental factors such as temperature and moisture content (MC) on the propagation of GWs. This study aims to scrutinize the effect of MCs ranging from 0 to 24%, and temperatures between − 20 and 100 °C on the propagation characteristics of GWs (longitudinal and circumferential) in cylinder timber structures excited over a range of frequencies between 10 and 20 kHz, experimentally and numerically. The numerical analysis was carried out using COMSOL Multiphysics, and Macro Fiber Composites were used to excite and sense the GWs. The anisotropic nature of timber poles was modeled using a transversely isotropic behavior. The results showed that the effect of timber's temperature and MC on the GWs should be assessed simultaneously. Three-dimensional maps were generated to present the relationship between various wave modes, temperature, and MC. The work observed a larger critical role of MC than the temperature on the propagating GWs and timber's material properties. The effect of temperature is more critical when timber's MC increases above the fiber saturation point (FSP) due to high stiffness variations. This is seen as the group velocities of the longitudinal and flexural waves (as well as the bulk wave) shifted more at MCs above FSP than below FSP. When MC varies above FSP with no temperature variations the velocity difference is negligible with 1.5% due to complete timber saturation at all temperature values. The results showed that the change in the mode velocities in dry wood is not significant with varying temperatures, as the stiffness changes by 0.07%. Experimental validation, for the numerical results, showed low differences for the bulk wave, and flexural modes were within [7.1 15]% and [1.3 4.7]% for the 2nd flexural branch at 12.5 kHz, respectively. Based on the above results, the environmental conditions can highly impact the GWs characteristics in timber structures, hence this should be carefully considered in the application phase. [ABSTRACT FROM AUTHOR]

Forests contain substantial carbon stores, including above and belowground biomass and living and non-living biomass. Different management regimes produce different outcomes related to stored and sequestered carbon in forests. The geographic focus of this study is the Wabanaki-Acadian Forest of the Maritime Provinces of Canada (New Brunswick, Nova Scotia, and Prince Edward Island). This study reviews the literature to evaluate the carbon impacts of (1) intensive forest management for fiber products, (2) unharvested (or conservation) forest, and (3) climate-focused, ecological forestry. Each of these forest management strategies and concomitant silviculture regimes sequester and store carbon at varying rates and across different carbon pools in the forest. The literature suggests that unharvested (conservation) forests store and sequester the most carbon, and traditional, intensive fiber management stores and sequesters the least. Ecological forestry may provide the best balance between carbon sequestration and storage and climate adaptability, while also allowing for the provision of some timber/fiber products. This study also discusses the co-benefits offered by forests under each of the three management regimes. New research, in general and in the region, needs to examine further belowground carbon dynamics in soil as most efforts to document carbon focus on aboveground carbon pools. [ABSTRACT FROM AUTHOR]

This paper consists of the results of experimental and analytical studies carried out to determine the moment redistribution in reinforced concrete (RC) continuous beams realistically, which are frequently used structural forms in buildings. It was determined that the parameter affecting the moment redistribution the most was the reinforcement ratio, so six RC continuous beams were produced with different reinforcement ratios. In this study, the tensile reinforcement ratio (ρ), the compressive reinforcement ratio (ρ'), and the balanced reinforcement ratio (ρb) in the intermediate support sections are considered as the main variables, and the effects of two parameters on the moment redistribution capacities of the beams are investigated. While one of them is (ρ'/ρ), the other one is (ρ/ρb). Considering the experimental results obtained, a simple formulation has been proposed by taking into account the neutral axis depth factor (c/d), which is the parameter frequently used in the determination of moment redistribution in the literature and in the design code provisions. Moreover, a database was created by considering the experimental results of 80 beams collected from the literature and it was aimed to determine the effectiveness of this proposed formulation compared to the equations in the literature and in the design code provisions. According to the results, it was determined that the proposed formulation gave better statistical outcomes than the others. It is thought that the design codes statistically give more negative results than the results of this study, as they generally prefer to be on the safe side deliberately. In addition to moment redistribution, the general behaviors of RC continuous beams under concentrated loads, such as load-displacement relationships, ductility, energy dissipation, and moment-curvature relationships have also been investigated in detail. [ABSTRACT FROM AUTHOR]

The building industry requires the development of a ductile lateral force–resisting system made of mass timber to allow mass timber to continue to grow in popularity as the primary structural building material. A timber frame with mass ply lam (MPL) beams and columns with a timber buckling-restrained brace (TBRB) was subjected to a quasi-static cyclic loading protocol defined according to the qualification procedure of conventional buckling-restrained braces (BRBs). Two of the TBRBs in this study included a carbon fiber–reinforced polymer (CFRP) wrap to help confine the two ends of the mass ply panel (MPP) casing and improve the performance of the brace. The experiments showed that the TBRB without any CFRP wrap met the requirements for qualification of conventional BRBs, and the mass timber braced frame was able to reach a drift ratio of 3.0%. The TBRB with CFRP wraps met the requirements for qualification of conventional BRBs; the confinement provided by the CFRP wraps postponed failure of the TBRB by enabling the steel core to reach a maximum strain of 3.1% in both tension and compression and the mass timber braced frame to reach a maximum drift ratio of 4.5%. [ABSTRACT FROM AUTHOR]

The increasing availability of mass timber panels has expanded the possibilities for using timber-concrete-composite (TCC) flat floors beyond the traditional TCC T-beams. While TCC floors often easily satisfy ultimate limit state requirements, their stiffness, vibration characteristics, and long-term performance are critical design considerations. This research aimed to validate the bending, vibration, and long-term performance for nine different TCC floor systems through full-size tests with a span of 5.8 m. The tested floor systems used laminated-veneer-lumber, laminated-strand lumber, and cross-laminated-timber (CLT) panels connected to a concrete slab with and without an interlayer. Three types of shear connections were employed: self-tapping screws; glued-in steel mesh; and a combination of STS and adhesive bond. First, the shear connection properties were determined via 54 small-scale push-out tests. Then, 18 floors were tested in bending and vibration shortly after fabrication, and an additional nine floors were subjected to service loading for 32 months under variable climatic conditions, after which they were subjected to bending and vibration tests. The results confirmed that the calculations based on the γ -method accurately predict the stiffness, natural frequency, and governing failure modes of TCC floors. The long-term exposure to service loading had minimal effect (within 10%) on resistance, stiffness, and natural frequency of TCC floors, except for the TCC using CLT, which showed the highest creep deflection and stiffness reduction among the tested configurations. [ABSTRACT FROM AUTHOR]

The evolution of long-span timber structures during the last centuries has been driven by technological developments that are associated with materials, joints, and manufacturing. Many extraordinary structural solutions have been developed, some of which have been very advanced in their time and have been replaced by new ones, typically because of the advent of new manufacturing methods or, at times, due to new technological innovations. This study examines the Hilding Brosenius (HB) system, which was developed in the 1940s as a versatile wooden frame solution for medium-to-long spans. The HB system is based on an I-shaped cross section where the web consists of two diagonal board layers, and the flanges are assembled from boards by nailing and gluing. This study presents and discusses the main structural components of the system from the perspective of structural mechanics, current design requirements, and manufacturing technologies. As a practical application example, the structural system will be examined in the renovation project of an HB portal frame from the 1950s. The main findings of this study are: (1) the HB system has certain features that would make it worthwhile modernizing and reusing it more widely; and (2) the HB system design principles lead to a safe and robust yet light and optimal structure. [ABSTRACT FROM AUTHOR]

Removal of predators and creation of early seral habitat have, in many systems, caused substantial population growth of herbivores. Hyperabundant herbivores, in turn, induce cascading ecosystem effects, but few studies have investigated long-term browser density trends in relation to succession and stochastic climate events. Here, we use annual, empirical population estimates of a forest browser to relate forest succession to long-term decline of an herbivore that prefers early seral habitat. From 2007–2021, concurrent with reduced timber harvest, we used line-transect distance sampling to document annual changes in Columbian black-tailed deer (Odocoileus hemionus columbianus) density on a mid-sized (17.3km2) predator-free island. We documented successional changes associated with forest aggradation and decreased forage quality for deer: early successional shrub/scrub habitat declined 3.8%/year; timber volume increased 4.5%/year; and canopy coverage increased 2.5%. In 2007–2008, deer densities were the greatest observed (~44/km2), but then an historic snowstorm reduced deer density by 39%. From 2010–2021, as forests continued to mature, deer density decreased 4.0%/year, declining to 20 deer/km2. Using a multivariate approach to combine habitat variables (i.e., early seral coverage, timber volume, and canopy closure) into a measure of forest maturation, we found a significant negative relationship between deer density and forest aggradation. Thus, consistent with predictions for bottom-up limited browsers, we observed significant annual declines in a deer population throughout an extended period of forest regrowth. Despite declines, deer density on the island exceeds mainland densities, and overbrowsing likely continues to disrupt ecosystem processes. [ABSTRACT FROM AUTHOR]

There is a gap between mechanical measurement methods under laboratory conditions and those under real conditions of structural monitoring. This paper proposes a method that applies well-established computer vision developments to photomechanics in difficult conditions. It is therefore a technique that is flexible and versatile while maintaining satisfying accuracy. It consists in marker tracking using ArUco fiducial markers as measurement points. It allows locating markers in non-optimal conditions of camera orientation and position. A homography process was used to analyse pictures taken with a view angle. The accuracy of the method was estimated, especially in case of out-of-plane motions, and the impact of the view angle and of the distance between camera and markers on the location error was studied. The method was applied in creep tests to measure crack parameters as well as the transverse expansion of wooden beams. In the application example presented, it enabled to compute distances between markers with only 0.28% of relative error and hence to measure the crack parameters and the long-term shrinkage-swelling of the wooden beams. However, the impacts of brightness variations and camera parameters have not been estimated. This method is very promising when experimental conditions are variable and when multiple measurements are necessary. [ABSTRACT FROM AUTHOR]

The commercialization of modular timber products as cost-effective and lightweight components has resulted in innovative engineering products, e.g., glued laminated timber, laminated veneer lumber, I-beams, cross-laminated timber and solid timber joined with wedge joints. With the passage of time, timber structures can deteriorate, or new structural elements are required to increase the stiffness or load-bearing capacity in newly built structures, e.g., lintels over large-scale glazing or garages, or to reduce cross-sectional dimensions or save costly timber material while still achieving low weight. It is in such cases that repair or correct reinforcement is required. In this experimental and numerical study, the static performance of flexural timber beams reinforced with prestressed basalt BFRP, glass GFRP and hybrid glass–basalt fiber bars is shown. The experimental tests resulted in an increase in the load-carrying capacity of BFRP (44%), GFRP (33%) and hybrid bars (43%) and an increase in the stiffness of BFRP (28%), GFRP (24%) and hybrid bars (25%). In addition to this, glued laminated timber beams reinforced with prestressed basalt rods subjected to biological degradation, 7 years of weathering and prolonged exposure to various environmental conditions were examined, and an increase in the load-bearing capacity of 27% and an increase in stiffness of 28% were obtained. In addition, full-size laminated timber beams reinforced with prestressed basalt bars were investigated in the field as an exploratory test under fire conditions at elevated temperatures, and the effect of the physical–mechanical properties during the fire was examined via an analysis of these properties after the fire. In addition, a satisfactory correlation of the numerical simulations with the experimental studies was obtained. The differences were between 1.1% and 5.5%. The concordance was due to the fact that, in this study, the Young, Poisson and shear moduli were determined for all quality classes of sawn timber. Only a significant difference resulted in the numerical analysis for the beams exposed to fire under fire conditions. The experimental, theoretical and numerical analyses in this research were exploratory and will be expanded as directions for future research. [ABSTRACT FROM AUTHOR]

In the present study, a piecewise-integrated composite bumper beam for passenger cars is proposed, and the design innovation process for a composite bumper beam regarding a bumper test protocol suggested by the Insurance Institute for Highway Safety is carried out with the help of machine learning models. Several elements in the bumper FE model have been assigned to be references in order to collect training data, which allow the machine learning model to study the method of predicting loading types for each finite element. Two-dimensional and three-dimensional implementations are provided by machine learning models, which determine the stacking sequences of each finite element in the piecewise-integrated composite bumper beam. It was found that the piecewise-integrated composite bumper beam, which is designed by a machine learning model, is more effective for reducing the possibility of structural failure as well as increasing bending strength compared to the conventional composite bumper beam. Moreover, the three-dimensional implementation produces better results compared with results from the two-dimensional implementation since it is preferable to choose loading-type information, which is achieved from surroundings when the target elements are located either at corners or junctions of planes, instead of using information that comes from the identical plane of target elements. [ABSTRACT FROM AUTHOR]

The transition to a fossil-free society in Sweden is expected to cause an increased demand for forest-derived products which may intensify existing conflicts between forest ecosystem services. This study investigated the preferences among non-industrial private forest owners for maintaining multiple forest ecosystem services and their preferences for future forest development. The findings were related to their prioritizations for and knowledge of forest management. The study results were generated through the means of a survey which revealed a consistent high valuation among all respondents of ecosystem services relating to water quality, timber quality, recreation, and biodiversity. A majority of the respondents desired increasing proportions of mixed species and broadleaved stands within the future forest landscape. Certified forest owners who were members of a forest owner association (CMs) prioritized achieving high economic income through roundwood production with strong preferences for the ecosystem services high stand growth and high timber quality. For CMs, carbon substitution was the preferred means of mitigating climate change. Forest owners lacking both certification and membership in a forest owner association ranked the ecosystem services recreation and biodiversity significantly higher, and also preferred retaining more old forest within the landscape. The survey results revealed a higher management activity among CMs, resulting in a more frequent establishment of mixed and broadleaved stands. Forest owners with medium to large scale properties were well-represented within the CM category. The results indicated that while the CMs have stronger preferences for roundwood production compared to owners of small properties, they are also more likely to have taken adaptive measures favoring risk management and biodiversity. [ABSTRACT FROM AUTHOR]

In many buildings with wooden structures, the service life and comfort of the floor will be affected by the walking load of the human body. The vibration effect generated by the human walking on the floor will affect the comfort that the floor brings to people. This article primarily focuses on the study of the correlation between floor vibration and human walking load in wooden buildings. It provides an analysis and summary of research findings from both domestic and international sources. Furthermore, the data collected is utilized to establish a model for estimating human walking load. The advent of information technology has witnessed significant transformative changes spurred by shifts in societal needs. Notably, the establishment of wireless sensor networks stands as a significant milestone within the field of information technology, highlighting advancements in science and technology. The evolution of wireless sensor networks has proven instrumental in various sectors within China, including but not limited to the military, environmental monitoring, biological research and medical systems, disaster monitoring, and energy allocation. This paper uses deep learning algorithms to analyze the node deployment problems of wireless sensor networks, summarizes a reasonable node deployment plan through specific research and practice, and uses collaborative deep learning methods to improve the operating efficiency of the network. In addition, this article also tested the vibration effect of wood structure buildings, analyzed different influencing factors, and provided a good reference point for the formulation of wood structure comfort standards. [ABSTRACT FROM AUTHOR]

Topologically interlocked structures (TIS) are structural assemblies that achieve stability and carrying capacity through the geometric arrangement of interlocking blocks, relying solely on contact and friction forces for load transfer. Unlike beam-like TIS, whose deflection never exceeds the height of the blocks, the deflection of slab-like TIS often does. Yet, the upper limit of deflection of slab-like TIS, a key parameter defining their loading energy capacity, remains unexplored. Here, we establish a theoretical upper bound for the deflection capacity of slab-like TIS and outline a systematic design strategy to approach this upper bound. This strategy is based on engineering the contact interfaces such that the non-central blocks are more engaged in the structural response, leading to a more global and holistic deformation mode with higher deflections. We demonstrate the application of this strategy in a numerical case study on a typical slab-like TIS and show that it leads to an increase in deflection by a factor of 3.5, yielding a value closer to the upper bound than previously reported in the literature. We find that the resulting deflection mode engages all the blocks equally, avoids localized sliding modes, and resembles that of monolithic equivalents. Lastly, we show that the strategy not only maximizes TIS' deflection capacity but also their loading energy capacity. [ABSTRACT FROM AUTHOR]

Mass timber construction has seen a growing interest in North America and worldwide. In the US, code provisions allow mass timber buildings to be up to 82 m tall, but with floor slabs requiring a noncombustible, usually cementitious, topping over mass timber panels (MTPs). Designing the MTP and concrete topping to act compositely can increase the strength and stiffness compared to noncomposite MTP floors. Several connections are available to create composite action between an MTP and a concrete topping, with self-tapping screws being the most widely considered practice. A new test fixture and testing method were developed to characterize connection properties and facilitate the selection of fasteners most suitable for developing composite action. Three conventional self-tapping screws were experimentally investigated at the single-fastener scale. The screws were subjected to withdrawal at 90° and 45° orientations to the interface plane between the MTP and concrete. Withdrawal from both the MTP substrate and concrete topping was investigated. Three MTP materials were tested: cross-laminated timber (CLT) consisting of two different wood species and a mass ply panel (MPP). Results demonstrated that the pullout failure of the screwhead from the concrete was the limiting failure mode. Comparisons were made between the experimental results and analytical models for screw withdrawal to assess the applicability of available models to the different MTPs. These models underestimated the capacity of the tested fasteners for all samples except for the fully threaded screws. [ABSTRACT FROM AUTHOR]

In the presence of softening section constitutive relations, classical beam theories predict erroneous strain singularities, and the corresponding force/flexibility-based (FB) beam-column element formulations result in strain localization and loss of response objectivity, i.e., divergence, rather than convergence, with progressive mesh refinements. To address this challenge, various FB element formulations have been proposed in the literature. One of these formulations is the so-called "gradient inelastic" (GI) FB formulation, which is a two-node element formulation that eliminates the strain localization and achieves response objectivity through strain gradient nonlocality relations. Although a single two-node GI element can effectively simulate an entire beam or column, simulating such a member via multiple two-node GI elements in series (e.g., to apply intermediate point loads, to more accurately capture geometric nonlinearities, or to represent cross-section variation) would not lead to accurate response predictions. This is because, in a model with multiple two-node GI elements in series, the nonlocality relations are not enforced at the intermediate/connection nodes between adjacent elements. Instead, end member boundary conditions (BCs) are enforced at those connection nodes because the two-node GI formulation has been designed to simulate an entire member. To tackle this shortcoming, this paper proposes an innovative multinode GI FB element formulation. To enforce the nonlocality relations at the connection nodes, two different sets of mathematically admissible section strain compatibility conditions (CCs) are adopted. The multinode formulations using both sets of CCs are evaluated through several simulation examples, including beams and columns subjected to various loads. The evaluations demonstrate the ability of both element formulations to produce objective softening responses, while one set of CCs is found to more closely predict the responses of previously tested RC beams under midspan loading. [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation of the flexural behavior of timber beams externally strengthened with carbon-fiber-reinforced polymer (CFRP) sheets. At first, the accuracy of linear elastic and elastic-plastic models in predicting the behavior of bare timber beams was compared. Then, two modeling approaches (i.e., the perfect bond method and progressive damage technique using the cohesive zone model (CZM)) were considered to simulate the interfacial behavior between FRP and timber. The models were validated against published experimental data, and the most accurate numerical procedure was identified and subsequently used for a parametric study. The length of FRP sheets varied from 50% to 100% of the total length of the beam, while different FRP layers were considered. Moreover, the effects of two strengthening configurations (i.e., FRP attached in the tensile zone only and in both the tensile and compressive zones) on load-deflection response, flexural strength, and flexural rigidity were considered. The results showed that elastic-plastic models are more accurate than linear elastic models in predicting the flexural strength and failure patterns of bare timber beams. In addition, with increasing FRP length, the increase in flexural strength ranged from 10.3% to 52.9%, while no further increase in flexural strength could be achieved beyond an effective length of 80% of the total length of the beam. Attaching the FRP to both the tensile and compressive zone was more effective in enhancing the flexural properties of the timber beam than attaching the FRP to the tensile zone only. [ABSTRACT FROM AUTHOR]

This study is aimed at investigating those parameters related to timber flooring that can affect the acceptability of vibration behaviour of a timber floor in a residential building in view of the criteria stated in Eurocode EC5. The timber floor investigated is made of OSB/3 floorboards and timber joists. The parameters that are investigated in this study are thickness of flooring, floor joist span, joist spacing and connection of floorboards to the joists. In this context, two cases are considered. First: the flooring is nailed or screwed to the joists and no composite action or interaction is obtained between joists and floorboards. Second: the flooring is glued sufficiently to the joists and full interaction is obtained. The result suggests that glued floorboards perform much better with respect to natural frequency, static deflection and peak floor velocity than nailed or screwed floorboards. In almost all cases of glued floorboards, the result complies fully with the Eurocode 5 design vibration requirements. However, as floor lengths increase, the static deflection will increase beyond the allowable limit, especially for relatively thin floor panels and relatively widely spread joists. For both cases, increasing floorboards thickness and decreasing the joist span by adding more beams can yield even better results to satisfy the requirement of vibration comfort. [ABSTRACT FROM AUTHOR]

• Wood is always a top material for beams. • 40 million of slender young oak trees are available in French forest. • Round-wood squared at the minimum keeps the high resistance of trunks. • Using green wood is the fastest and most energy-saving method. • High tech modern techniques can be used for the best sorting of trees. During the fire of Notre-Dame de Paris, all timber frames coming from the Middle ages period, in the nave and choir, were burnt. It was decided to proceed as possible to an identical reconstruction, but many questions arise about the timber frame. Is wood outdated as a material for beams? Is oak wood the best solution for timber frame? Are we able to find similar long slender oak beams in today French forest? Is it safe to use green wood for the building? In fact, the forested area in France is the same today as in the Middle ages period, but two times higher than during the 19th century. Results from the forest inventory proves that 40 million slender oak trees are available in order to sort around 1500 trees for the restoration. Cathedral heritage provided a demonstration of the high efficiency of carpenter's know-how. Most of oak beams kept their functionality for more than 800 years. This is a nice experimental result for a very long mechanical testing. Wood, emerged as material 300 million years ago as a result of long time evolution, is used to build trees, which are a collection of wooden beams able to resist flexure forces, for a long time. Technical know-how about timber frame is old in human societies and was improved during the Middle ages, but scientific knowledge about wood as an anisotropic material is very recent. The background in mechanics for such material has been developed in early 20th century and observation tools for material structures at the nanometre scale appeared in late 20th century. Wood can be considered as an archetypal high-tech material using polymer-with-additive technology combined to nanostructured fibre-composite within a honeycomb-like micro-structured material. This explains why nature solution for tree beams is very efficient in terms of bending resistance per weight. The mechanical behaviour of wooden beams is highly sensitive to the orientation of the main direction of anisotropy (grain direction) relative to bending forces. Natural beams in trees are built by a kind of 3D printing process so that grain orientation at beam periphery is always optimum. Mechanical bending performance of these beams (round-wood), in spite of branching, is equivalent to the performance of standard clear-wood specimens documented in databases. Squaring at the minimum this round-wood should be done while keeping grain angle closest to zero-degree value, which is performed by specific axe-hewn log squaring. The result is "coarse" slightly curved beams much more resistant than "nicely" straight sawn beams with local grain angle above 10° Using directly green wood in the building process is effective for time of building and energy consumption. The drying of wood induces long deep longitudinal cracks and a reduction in beam section but a bigger increase in wood mechanical performance. If the green frame resists, the dried one will resist all the following years. Finally, today carpenters have kept the building know-how and there are many modern non-destructive techniques available for the best sorting of trees and mechanical evaluation of beams. [ABSTRACT FROM AUTHOR]

Selective logging is the most widespread driver of land‐use change in biodiverse and carbon‐rich tropical forests. However, the effects of selective logging on biodiversity are less than those associated with other drivers of forest degradation. A suite of recent research has shown that reduced‐impact logging (RIL) results in few or no changes to biological assemblages. But because this logging technique is relatively new, most studies have only considered short‐term impacts.We address this research gap by quantifying changes in biodiversity assemblage as a result of RIL over the longer term. We comprehensively sampled bird and bat assemblages pre‐logged, 1 year after, and 10 years after RIL in Guyana, using a before‐after control‐impact (BACI) sampling design. We compared bird and bat assemblages in each timeframe, and additionally appraised the impact of time since logging, and the number of trees harvested across the suite of species which we further divided between different feeding guilds, disturbance sensitivity and vertical stratification of forest use.We found that 1 year after logging only minor changes could be detected, but 10 years later richness had slightly declined in some groups, while others had shown complete recovery. Nectivorous and insectivorous birds, and carnivorous bats declined in richness, while carnivorous birds, showed a clear recovery to a state akin to pre‐logging. This indicates that for some niches a subtle, but long‐term relaxation effect may be occurring, whereby extinction debts are realized long after the initial disturbance, while other groups have either recovered or not changed after logging.Assemblage changes were also predicted by vertical stratification of forest use, with avian species using the understorey and mid–upper levels of the forest being most affected.Synthesis and applications: Our study demonstrates how best practice forestry and logging can maintain healthy vertebrate populations over the long term. Forestry concessions that adopt techniques of low‐harvest RIL and are managed for their long‐term timber provision through extension of regeneration times beyond 10 years after harvest, are likely to benefit from the ecosystem services provided by biodiversity, while also making a valuable contribution to the global conservation estate. [ABSTRACT FROM AUTHOR]

This paper presents a model-based probabilistic structural identification that uses the deflection of prestressed concrete bridges (PSCBs) as observational information to perform Bayesian inference on the state variables associated with creep, structural rigidity, dead loads, shrinkage and prestress. The creep development is modeled as a stochastic process, and the structural rigidity is modeled as a stochastic field using the Karhunen-Loeve transform. By incorporating the stochastic process/field into the inference frame, detailed information on structural states can be extracted. Considering the high dimension of the state variables, their posterior distributions are derived by the Hamiltonian Markov chain Monte Carlo (HMCMC) algorithm. As an illustrative example, two sets of deflection measurement of a case bridge are used to update the state variables in a sequential manner. Bayesian inference can calibrate the state variables, while the uncertainties associated with the state variables can be reduced. A K-means analysis can reveal the typical modes in the joint posterior distribution of the state variables, corresponding to the typical failure modes in the attributive analysis of the excessive deflection. The updated state variables are used in the probabilistic condition assessment associated with the deflection evolution. [ABSTRACT FROM AUTHOR]

The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate (GRL) layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact (LVI) are investigated. The current study aims to carry out a dynamic analysis on the sandwich beam when the impactor hits the top face sheet with an initial velocity. For the layer analysis, the high-order shear deformation theory (HSDT) and Frostig's second model for the displacement fields of the core layer are used. The classical non-adhesive elastic contact theory and Hunter's principle are used to calculate the dynamic responses in terms of time. In order to validate the analytical method, the outcomes of the current investigation are compared with those gained by the experimental tests carried out by other researchers for a rectangular composite plate subject to the LVI. Finite element (FE) simulations are conducted by means of the ABAQUS software. The effects of the parameters such as foam modulus, layer material, fiber angle, impactor mass, and its velocity on the generated voltage are reviewed. [ABSTRACT FROM AUTHOR]

This paper presents experimental investigations on the lateral performance of cross-laminated timber (CLT) shear walls with customized self-tapping screw (STS) connections. The panel-to-base (hold-downs and shear brackets) and panel-to-panel (spline) connections were tested under quasi-static monotonic and reversed cyclic loading to derive design values of STS, which were shown to be 2.8–3.6 times higher than those calculated using the current Canadian timber design standard. Then, a total of 26 CLT shear walls, including single-, double- and triple-panel configurations, were tested, again under quasi-static monotonic and reversed cyclic loading. The shear walls consisted of five-ply, 139-mm-thick and 3-m-high CLT panels with aspect ratio of either 2∶1 or 3∶1 , and different numbers of STS in the connections. The shear wall strength and corresponding displacements increased with the number of screws in hold-downs and spline joints; further, it increased with number of connected panels and decreased as a function of aspect ratio. The data can be used for developing and calibrating numerical models to investigate the lateral responses of CLT shear walls with different configurations. [ABSTRACT FROM AUTHOR]

We consider the inverse problem of determining transverse dynamic loads acting on a clamped plate stiffened by two sets of orthogonal beams. Under the assumption of infinitesimal deformation, in the sense that linear elasticity applies, homogeneous isotropic material and negligible beam torsional stiffness, we show that the measurement of the transverse response of the system in an open subset of the mid-plane, and for an arbitrarily small interval of time, is sufficient for the unique determination of the spatial component of the load. The uniqueness result holds for multiple asynchronous loads and suggests a reconstruction procedure, which is used for a numerical validation of the method. • Determination of dynamic loads over a clamped plate stiffened by sets of orthogonal beams from minimal data. • Uniqueness for the load identification is proved even in the presence of the stiffness. • Consideration of asynchronous loads. • A recovery method for the unknown asynchronous loads is proposed. [ABSTRACT FROM AUTHOR]

In a previous study, the authors demonstrated the steps necessary to determine the performance characteristics of a micromechanical mirror element. The mirror is made up of two bimorph structures consisting of aluminum and silicon dioxide, with a reflective element coated in aluminum attached to movable beams. By applying voltage to electrical heating elements within the beams, the structure can be manipulated due to uneven expansion of the materials. In this study, finite element analysis software is used to simulate the mirror and compare the results with analytical methods. The importance of accurate parameter calculation in designing micromechanical devices is emphasized. The study shows that the deflection sweep, overheating values, and heating/cooling times of the mirror beams align with previously calculated analytical expressions and experimental results. This suggests that the analytical method described in previous studies can be applied to designing micromechanical devices that rely on thermal principles and require precise temperature control for optimal performance. Also the package characteristics are considered and guidelines for it are given with consideration to mirror performance. [ABSTRACT FROM AUTHOR]

This study evaluated the impact of using different contents and sources of Reclaimed Asphalt Pavement (RAP) on the bottom-up fatigue cracking of asphalt mixtures and the return on investment (ROI). Two RAP sources were used that primarily provided a significant difference in RAP binder Performance Grade (PG): Source A was a PG 76-22 while Source B was a PG 94-10. Bottom-up fatigue cracking was predicted using Level 1 of the AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software. The ROI was then evaluated using FHWA RealCost. To increase the accuracies of the predictions, volumetric properties and blended binder properties were calculated based on the amount of RAP binder that actively blended with the virgin binder. The accuracies were also increased by determining the AASHTOWare PMED fatigue strength coefficients, $k_{\,f1}$ k f 1 , $k_{\,f2}$ k f 2 , and $k_{\,f3}$ k f 3 , using flexural bending beam fatigue tests rather than using the global defaults provided by this software. In conclusion, the ROI of the six RAP mixtures based on bottom-up fatigue cracking was found to be affected by both RAP content and RAP source, and because of the effect of RAP source, it could not be generalised that using either a higher or lower RAP content will always provide a higher ROI. [ABSTRACT FROM AUTHOR]