Types Of Connections Research Articles

Analysis of Progressive Collapse Resistance in Precast Concrete Frame with a Novel Connection Method

The configuration of beam–column joints in precast concrete (PC) building structures varies widely, and different connection methods significantly affect the progressive collapse resistance of the structure. This study investigates the progressive collapse resistance of an innovative beam–column connection node frame. Finite element models of four-story, two-span space frame structures made of reinforced concrete (RC) and PC were developed using ANSYS 14.0/LS-DYNA R5.x software, employing nonlinear dynamic and static analysis to examine structural collapse behavior under bottom middle or corner column damage. Numerical results indicate that following the failure of the middle or corner column due to explosion loading, the vertical displacement and collapse rate of the PC structure with the novel connection method are less than those of the RC structure during collapse progression. Furthermore, upon removal of the middle or corner column, the residual load-carrying capacity of the PC structure with the innovative connection increased by 7% and 3.7%, respectively, compared to the RC structure. This suggests that PC structures with this type of connection demonstrate superior performance in resisting progressive collapse, offering valuable insights for future engineering applications.

Long-Term Behavior of Timber–Concrete Composite Structures: A Literature Review on Experimental and Numerical Investigations

Timber–concrete composite structure is a type of efficient combination form composed of concrete floors and timber beams or floors through shear connectors, and shows good application potential in the floor system of timber buildings. The long-term performance of the timber–concrete composite structures is complex and is affected by the creep of timber and concrete, as well as the long-term slip of the shear connectors. This article presents a comprehensive overview of the research status on the long-term behavior of timber–concrete composite members and different shear connectors. For the shear connectors, the effects of loading levels, environments, and component materials on their creep coefficients are summarized. As to the timber–concrete composite members, both the experimental and numerical investigations are gathered into discussions: the connection types, component materials, loading conditions, and durations in the long-term tests are also discussed; various models for describing long-term behavior of timber, concrete, and connection systems are provided, and then a comprehensive description of the progress of numerical investigations over the last decades is made. In addition, the suggestions for future research are proposed to reach a clearer understanding of the bending mechanisms and mechanical characteristics of timber–concrete composite structures.

The dance of neurons: Exploring nonlinear dynamics in brain networks

The brain is a complex, nonlinear system, exhibiting ever-evolving patterns of activities, whether in the presence or absence of external stimuli or task demands. Nonlinearity can notably obscure the link between structural constraints enforced on the interaction and its dynamical consequences. Suitable nonlinear dynamical models and their analysis serve as essential tools not only for bridging structural and functional understanding of the brain but also for predictably altering the complex dynamical organization of the brain. Here, starting from a large-scale network of threshold Hodgkin–Huxley style neurons, we formulate the average nonlinear dynamics implicitly following from the Wilson–Cowan assumptions. We investigate the influence of biophysical and structural properties on the complexity of neural dynamics at the microscale level and its relationship with the macroscopic Wilson–Cowan model. Incorporating the elements in the model can help identify more realistic regimes of activity and connect the mathematical prediction of increasing nonlinearity to physical manipulations. Our simulations of the temporal profiles reveal dependency on the binary state of interacting subpopulations and the random property of structural network at the transition points, when different synaptic weights are considered. For substantial configurations of stimulus intensity, our model provides further estimates of the neural population’s dynamics, ranging from simple-periodic to aperiodic patterns and phase transition regimes. This reflects the potential contribution of the microscopic nonlinear scheme to the mean-field approximation in studying the collective behaviour of individual neurons with particularly concentrating on the occurrence of critical phenomena. We show that finite-size effects kick the system in a state of irregular modes to evolve differently from predictions of the original Wilson–Cowan reference. Additionally, we report that the complexity and temporal diversity of neural dynamics, especially in terms of limit cycle trajectory, and synchronization can be induced by either small heterogeneity in the degree of various types of local excitatory connectivity or considerable diversity in the external drive to the excitatory pool.

Ансамбль онтологических моделей для обеспечения интеллектуальной поддержки лазерных аддитивных технологических процессов

Barriers hindering the use of additive manufacturing processes for metal parts production are discussed. The necessity of integrating an intelligent decision support system (DSS) into the professional activities of laser additive manufactur-ing engineers is substantiated. The advantages of the developed ontological two-level approach for forming semantic information are highlighted. This approach's peculiarity lies in separating ontological models from the databases and knowledge formed on their basis—target information. The ontology dictates the rules for the structured formation and interpretation of target information. An ensemble of ontological models, forming the foundation of the developed intel-ligent system, is presented. The composition of the ensemble, the purpose of its individual components, and possible types of connections between them are described. The ensemble includes ontologies for reference databases on equip-ment and materials for laser additive manufacturing, an archive of protocols for technological operations of laser pro-cessing, a knowledge base about settings for laser processing modes, and a database of mathematical models. The en-semble of ontological models is implemented on the IACPaaS cloud platform using its tools. Ontologies, databases, knowledge bases, and a decision support system are part of the Laser Additive Manufacturing Knowledge Portal. Ac-cumulating and using the knowledge and experience from different technologists in the portal will reduce the number of preliminary experiments needed to identify suitable technological modes and lower the qualification requirements for users of technological equipment.

Strengthening of glass fiber sheets for multi-bolted pultruded GFRP connections: Effects of connection type and bolt-tightening force

This study investigated the effects of bolt-tightening forces on the connection strengths of non-strengthened and glass fiber sheet (GFS)-strengthened pultruded glass fiber reinforced polymer (PGFRP) connections through a series of experiments using double-lap and single-lap specimens. A total of 96 specimens (3 specimens for each parameter), half of which were non-strengthened, were tested under tensile loads and four bolt-tightening forces: 0, 5 N.m, 10 N.m, and 20 N.m. The (0°/90°)/chopped strand mat/(0°/90°) lamination was bonded to both PGFRP plates’ outside surfaces and improved the connection strengths. The results indicated that maximum failure loads increased with an increase in bolt-tightening forces. However, there were different trends in the maximum failure load changes, depending on the specimen type (non-strengthened or GFS-strengthened specimens; double-lap or single-lap specimens) and bolt-tightening forces. In addition, GFSs could effectively improve PGFRP’s connection strengths and ductility performances.

Thermal response of timber connections using densified wood dowels under fire

A new type of timber connection using densified wood dowels is being developed and tested. The procedure involves inserting these densified dowels into pre-drilled holes. As this connection technique is in its early stages, a unique design approach is necessary, considering the impact of temperature variations. The primary goal is to characterize the thermal behaviour of these connections under elevated temperatures. The study employs an experimental approach, complemented by numerical analysis, innovatively applying kinetic models, commonly used for investigating heat-related biomass characteristics, to wood. The method requires the use of thermogravimetric analysis to identify the kinetic parameters. The proposed pyrolysis kinetic model has been implemented in the Abaqus/Implicit code via a user subroutine UMATHT. The study concludes that using kinetic models enhances accuracy by considering mass loss, a key factor influencing thermal properties. Simulation successfully replicates temperature distribution and charred layer thickness, crucial for designing timber structures.

Flexural behaviour of built-up I-shaped bamboo scrimber beams: experimental tests and design method

ABSTRACT This paper presents the flexural behaviour of built-up I-shaped bamboo scrimber beams under four-point bending. Ten bamboo scrimber beams were tested, employing different types of connections between the web and flanges. The load-deflection relationship, failure mode and load-slip relationship of beams were obtained through experimental tests. Besides, the measured strains of bamboo scrimber in various regions were used to analyse the flexural mechanisms of I-shaped beams. Test results showed that the beam with a glued connection exhibited debonding at the web-flange interface, hindering the development of flexural capacity of the beam. By using self-tapping screws or bolted steel angles to strengthen the connection, the slip between the web and flanges was considerably reduced, resulting in the increased flexural capacity of beams. The rupture of the bottom flange near the concentrated point load led to the final failure of strengthened beams. The design method for mechanical fastened glulam beams in Eurocode 5 was adopted to assess the flexural capacity of bamboo scrimber beams. Comparisons between experimental results and calculated results per Eurocode 5 indicate that the method is capable of predicting the flexural resistances of I-shaped bamboo scrimber beams with reasonably good accuracy.

People with sensory processing sensitivity connect strongly to nature across five dimensions

Human connections to nature are critical to the sustainability of life on Earth. Nature connections are often linked with pro-environmental behaviors. Therefore, a better understanding of the nuances of human-nature connections can help inform policies and practices to advance sustainability. Connections to nature research has rarely investigated nuances like the nature connections of subpopulations or distinguished between types of nature connections. This article reports on an investigation of the subpopulation of highly sensitive individuals (HSPs), a group comprising about one-third of the general population thatexhibits higher levels of sensitivity to stimuli, greater depth of processing, and stronger emotional and physiological reactivity to both positive and negative stimuli than the general population, a suite of traits known as “sensory processing sensitivity” or “environmental sensitivity.” We assessed the nature connections of this group across five nature-connection types: material, experiential, cognitive, emotional, and philosophical. We found that HSPs hold deeper nature connections than less sensitive individuals with respect to all five connection types. Additionally, variability in nature-connection scores decreased as sensitivity increased, showing a significant trend. Future research can investigate links between nature connections and pro-environmental behavior in this population and the potential mediating role of specific psychological characteristics. We also recommend that researchers consider including sensitivity in future connections to nature assessments.

Investigating the efficiency and reliability of different lap-splice configurations in NSM BFRP rods for strengthening RC beams

The use of near-surface mounted (NSM) fiber-reinforced polymer (FRP) reinforcement has shown great promise for flexural and shear strengthening of reinforced concrete (RC) members. However, the continuity of NSM FRP rods is often interrupted due to length constraints, necessitating lap splices to transfer forces between spliced rods. The performance of lap splices depends on design configuration factors, including anchorage shape, splice length, and connection method. This research describes an experimental investigation into the bond behaviour and failure mechanisms of various lap splice designs for NSM basalt FRP (BFRP) rods in RC beams. The parameters investigated were end anchorage shape (straight or Embedded Through-Section (ETS) anchors), and connection type (overlay rods or face-to-face with FRP sheet wrap). A total of 8 simply supported RC beams strengthened with different NSM BFRP lap splice configurations were tested under four-point bending. The load-deflection response, strain distribution, and failure modes were evaluated. Test results showed that beams with NSM FRP rods with ETS anchors exhibited higher bond strength and ductility than face-to-face connections. The outcomes of this study can help optimize lap splice design and detail provisions for NSM FRP systems in future strengthening applications.

In-plane shear performance and damage evolution of FRP connectors for composite sandwich panels

This study investigated the in-plane shear responses of four types of connectors (single-strand truss, double-strand truss, grid-type, and I-shaped) in precast concrete sandwich panels (PCSPs). The influence of connector type, connector arrangement, and wythe material on the shear performance was discussed through in-plane shear tests and finite element analysis. The failure modes and test results of the four types of connectors were closely related to their shear resistance mechanisms. Changing the connector arrangement method from continuous along the length to discrete arrangement improved connector damage extent and toughness index (TI). The substitution of ordinary concrete with ECC or UHPC in wythes can prevent the wythes failure and enhance peak load (Pm). The finite element (FE) model using the Hashin damage model and randomly generated fibers can accurately capture the shear response of the connectors within PCSP. The damage factor was introduced for quantitative analysis of the damage processes in connectors and wythes and corresponding damage evolution model was developed. Furthermore, the damage evolution model was applied to characterize the degradation of shear stiffness in the load-slip curve, and a load-slip theoretical model that accounted for the progressive development of damage was established.

Thermal imaging control of electrical equipment of industrial enterprises

RELEVANCE. Thermal imaging control is used to monitor the technical condition of electrical equipment, as well as contacts and contact connections of switching devices, which allows to increase the efficiency of work.OBJECT. Timely detection of defects of contacts and contact connections of low-voltage switching devices to prevent emergencies.METHODS. Determination and control of technical condition of electrical equipment, contacts and contact connections of apparatuses in real time by means of indicators and thermal imaging control.RESULTS. The values of contact heating temperatures from material and type of contact connections were analysed. The criteria for estimation of the state of contacts of switching devices with the help of indicators of their state have been determined. The optimum values of loading coefficients of the circuit breaker in moulded case VA04 and contactors KMI and KTI are obtained. Emergency cases at the industrial object are shown, which prove the necessity of application of indicators and thermal imaging control as one of the tools of automation of technical condition control of low-voltage electrical equipment.CONCLUSIONS. The offered noncontact method of estimation and control of technical condition of electrical equipment, contacts and contact connections of devices in real time with the help of indicators and thermal imaging control allows both to receive data in real time mode and to increase inter-repair periods for power equipment and to increase reliability of operation of the whole system.

Influence of shear connector type and degree on semi-rigid joints of composite cold-formed steel beam-to-column connections

Influence of shear connector type and degree on semi-rigid joints of composite cold-formed steel beam-to-column connections

The Cyclic Performance and Macro-Simplified Analytical Model of Internal Joints in RC-Assembled Frame Structures Connected by Unbonded Prestressed Strands and Mortise-Tenon Based on Numerical Studies

This paper introduces a novel type of connection that integrates unbonded prestressed strands (UPS) and mortise-tenon in an assembly frame structure (UPS-MTF). First, the damage process and failure modes of the joints under reciprocating horizontal loads were systematically analyzed using refined numerical models. The recommended values of the design parameters of the joints were derived from the parametric analysis results. Refined numerical modeling results reveal the diagonal compression strut mechanism within the core region of the joint. The diagonal compression struts model assists in establishing the theoretical calculation formula for the skeleton curve of shear stress–strain in the core region. Second, a genetic algorithm (GA) parameter was identified for the restoring force model of the core region to determine the parameters of the hysteresis rules. Finally, a macro-simplified analytical model of the joint was created based on the restoring force model of the core region, and parameter analysis was conducted to verify the applicability of this macro-simplified analytical model. The research results prove that the damaged form of the joint proposed in this paper originates from the shear and relative slip damage between the components in the core region. The axial compression ratio significantly affects the hysteretic performance of the joints, and the upper and lower limit values were identified for the axial compression ratio of the joints. The area and initial effective stress of the UPS exert a minimal effect on the hysteretic performance of the joint. Based on the method proposed in this paper for determining the restoring force model in the core region of the joints, the hysteresis curves obtained from the macro-simplified analytical model closely match the refined numerical analysis model results. This correspondence verifies the applicability of the macro-simplified analytical model.

Research programs and the progress of theory in sociology: the post-positivist conception of J. Berger, M. Zelditch Jr. and D. Wagner

The article presents an explanation of the post-positivist conception of the progress of sociological theories in research programs, which was developed by J. Berger, M. Zelditch Jr. and D. Wagner. Their conception specified related types of theoretical structure and dynamics of research programs, as well as their functions in sociological theorizing. Structural and dynamic differences of research programs represent different types of conceptual connections between theories and their corresponding basic modes of theoretical growth. In particular, the elaboration of theories of certain explanatory domains by increasing their scope, rigor, precision, or empirical relevance is a mode of progress of linear programs. The proliferation of theories into new explanatory domains and the expansion of the subject range of their applicability is the mode of development of branching programs. The competition of theories in a certain explained domain for the best conceptual representation of its problems is a mode of progress of competing programs. Special types of conceptual connections and modes of theoretical progress may also emerge between theories in linear, branching, and competing research programs: variation of theories as a result of deepening them into their established subject domains due to increased conceptual insight, sophistication and detail; integration of theories. The theoretical development of research programs is provided by their functions, which are analogous to the functions of paradigms in mature sciences: determination of theoretical significance and doability of sociological problems; evaluation and cognitive-based selection of competing theoretical formulations of their solutions; ensuring synergy of the consequences of performing the above-mentioned functions.

Navigating the Present and Future Dynamics of Electric Vehicle Fast Charging and its Impact on Grid

As electric vehicle (EV) adoption surges worldwide, the need for fast charging infrastructure becomes paramount. Fast charging technology alleviates range anxiety and bolsters EV practicality. This comprehensive analysis delves into current challenges and future prospects surrounding EV fast charging and its grid impact. Examining the state of fast charging technology, it scrutinizes charging standards, connector types, and power levels across global regions. Emphasis is placed on key market players and the imperative for interoperability and standardization to seamlessly integrate EVs into the power grid. Voltage fluctuations, harmonics, and power factor issues stemming from rapid, high-power charging pose technical hurdles. Solutions like advanced power electronics, grid management tactics, and enhanced communication between EVs and the grid are explored to uphold stability and power quality. Consideration is given to energy sources fueling fast chargers, including renewable integration and environmental repercussions. Economic facets, encompassing infrastructure deployment costs and grid upgrade analyses, are examined amidst escalating electricity demand and potential grid expansion needs. A forward-looking perspective addresses future challenges and opportunities. This includes advancements in battery tech, smart grid solutions, and bidirectional power flow potential between EVs and the grid. Index Terms: Battery electric vehicles (BEVs), Grid, Fast Charging, plug-in hybrid electric vehicles (PHEVs).

Experimental Study of Angle Type Connectors in Steel and Concrete Composite Beams

Esta investigación técnico experimental tiene como objetivo analizar la resistencia a corte, considerando que para los perfiles laminados tipo ángulo no se cuenta con una fórmula de cálculo normalizada al emplearse como conectores de corte y que pueden ser usados en secciones compuestas. El estudio consistió en el análisis de 16 especímenes; 8 con un ángulo de 3 mm de espesor y otras 8 con 4 mm de espesor; cada grupo de 8 especímenes se dividió en dos subgrupos de 4, que se diferencian entre sí por la posición del conector a 45 y 90 grados. Al comparar los resultados con estudios de otros autores, se evidencia que el modo de falla está relacionado con la forma de la probeta, lo cual resulta en una falla prematura del concreto sobre las nervaduras. El análisis de estos ensayos resultó en la obtención de parámetros como: resistencia, ductilidad, deslizamiento y rigidez del material; independientemente de la orientación del conector, y se concluyó que el conector orientado a 90 grados es el que mayor carga resiste. En cuanto a la rigidez, los valores obtenidos son similares con investigaciones previas, lo que lleva a la conclusión que el conector orientado a 45 grados tiene una mayor rigidez característica que el orientado a 90 grados. Los mismos, según la norma establecida, tienen una ductilidad moderada y según las gráficas carga-deslizamiento los de 3 mm de espesor tienen un mayor desplazamiento que los de 4 mm, independientemente de su orientación.

A Comprehensive Review of Developments in Electric Vehicles Fast Charging Technology

Electric vehicle (EV) fast charging systems are rapidly evolving to meet the demands of a growing electric mobility landscape. This paper provides a comprehensive overview of various fast charging techniques, advanced infrastructure, control strategies, and emerging challenges and future trends in EV fast charging. It discusses various fast charging techniques, including inductive charging, ultra-fast charging (UFC), DC fast charging (DCFC), Tesla Superchargers, bidirectional charging integration, and battery swapping, analysing their advantages and limitations. Advanced infrastructure for DC fast charging is explored, covering charging standards, connector types, communication protocols, power levels, and charging modes control strategies. Electric vehicle battery chargers are categorized into on-board and off-board systems, with detailed functionalities provided. The status of DC fast charging station DC-DC converters classification is presented, emphasizing their role in optimizing charging efficiency. Control strategies for EV systems are analysed, focusing on effective charging management while ensuring safety and performance. Challenges and future trends in EV fast charging are thoroughly explored, highlighting infrastructure limitations, standardization efforts, battery technology advancements, and energy optimization through smart grid solutions and bidirectional chargers. The paper advocates for global collaboration to establish universal standards and interoperability among charging systems to facilitate widespread EV adoption. Future research areas include faster charging, infrastructure improvements, standardization, and energy optimization. Encouragement is given for advancements in battery technology, wireless charging, battery swapping, and user experience enhancement to further advance the EV fast charging ecosystem. In summary, this paper offers valuable insights into the current state, challenges, and future directions of EV fast charging, providing a comprehensive examination of technological advancements and emerging trends in the field.

Investigation of triaxial cables and microdetectors in small field dosimetry

Background. Small field dosimetry presents unique challenges with source occlusion, lateral charged particle equilibrium and detector size. As detector volume decreases, signal strength declines while noise increases, deteriorating the signal-to-noise ratio (SNR). This issue may be compounded by triaxial cables connecting detectors to electrometers. However, effects of cables, critical for precision dosimetry, are often overlooked. There is a need to evaluate triaxial cable and detector impacts on SNR in small fields. The purpose of this study is to evaluate the influence of triaxial cables and microdetectors on signal-to-noise ratios in small-field dosimetry. This study also aims to establish the importance of cable quality assurance for measurement accuracy. Methods. Six 9.1 m length triaxial cables from different manufacturers were tested with six microdetectors (microDiamond, PinPoint, EDGE, Plastic scintillator, microSilicon, SRS-Diode). A 6 MV photon beam (TrueBeam) was used, with a water phantom at 5 cm depth with 0.5 × 0.5 cm2 to 10 × 10 cm2 fields at 600 MU min−1. Readings were acquired using cable-detector permutations with a dedicated electrometer (except the scintillator which has its own). Cables had differing connector types, conductor materials, insulation, and diameters. Detectors had various sensitive volumes, materials, typical signals, and bias voltages. Results. Normalized field output correction factors (FOFs) relative differences of 13.4% and 4.6% between the highest and lowest values across triaxial cables for 0.5 × 0.5 cm2 and 1 × 1 cm2 fields, respectively. The maximum difference in FOF between any cable-detector combinations was 0.2% for the smallest field size. No consistent FOF trend was observed across all detectors when increasing cable diameter. Additionally, the non-normalized FOF differences of 0.9% and 0.3% were observed between cables for 0.5 × 0.5 cm2 and 1 × 1 cm2 fields, respectively. Conclusions. Regular triaxial cable quality assurance is critical for precision small field dosimetry. A national protocol is needed to standardize cable evaluations/calibrations, particularly for small signals (<pC) from modern detectors. This could enhance measurement accuracy and treatment delivery with advanced small-field radiotherapy techniques that promise improved patient outcomes. Further studies should expand detector and cable models tested across institutions to establish robust quality control guidelines.

Experimental research on pull-out behavior of steel-UHPC composite beams with new composite dowels connectors

In order to study a new type of steel-UHPC composite connector, a total of 16 steel-UHPC composite connectors with steel dowels and studs and steel-UHPC composite connectors with steel dowels without studs were designed and manufactured, and the pull-out test, finite element simulation and theoretical analysis were carried out. The load-slip curve, ultimate pull-out bearing capacity, crack development law of the UHPC layer and crack growth trend of the steel-UHPC interface were experimentally studied. The influence of the type of connector, the height of the steel dowel and the inclination angle of the steel dowel on the ultimate pull-out bearing capacity and failure mode of the specimens were compared by parameter analysis. The test results are compared with the finite element analysis results to verify the accuracy of the finite element model. A simplified calculation formula for the pull-out bearing capacity was proposed. The results showed that the failure modes of 16 specimens were the shear failure and axial tensile failure of the UHPC, both of which were ductile failures. The bearing capacity in the elastic stage and ultimate bearing capacity of the steel dowel connector with headed studs were higher than those of the steel dowel connector. After adding headed studs, the pull-out bearing capacity of the specimens could be increased by about 49% ∼ 84%. When the longitudinal steel bars were added to the bottom of the steel dowel connector with headed studs, the ductility in the loading stage and ultimate bearing capacity of the specimen could be improved. The steel dowel composite connector with headed studs with a steel dowel height of 100 mm and an inclination angle of 65° had better pull-out resistance.

Some Properties of Kenmotsu Manifolds Admitting a New Type of Semi-Symmetric Non-Metric Connection

Some Properties of Kenmotsu Manifolds Admitting a New Type of Semi-Symmetric Non-Metric Connection