Connection Configurations Research Articles

Observations from opening of a novel geotextile tube connection in field test site

A novel connection configuration for geotextile tubes was proposed, involving the insertion of an auxiliary tube between two main tubes, to ensure proper alignment and leveling when connecting them in a series, thus consolidating individual tubes into a unified structure while maintaining a consistent horizontal level. The novel connection was implemented at a test bed site in the Saemangeum reclaimed area, South Korea, to test exposure to the marine environment including sea waves, sun light exposure and reclamation process. This study presents the observations made upon opening the connection tube after 8 years. The observation shows that the connected geotextile tubes using the proposed auxiliary tube are suitable for use in long-term reclamation projects.

Behavior of Extended Single-Plate Shear Connections Subjected to Combined Shear and Compression Forces Using Finite Element Analysis

Extended single-plate shear connections can be subjected to compression loads in addition to shear loads during extreme events like wind and earthquakes. However, the existing interaction equations found in the AISC Steel Construction Manual, in literature, and in design examples—which are being used in design for combined loading cases—have not been formally validated for use by experimental testing or finite element analysis. This research aims to study the behavior of these connections when subjected to combined loading of shear and compression force by performing a nonlinear finite element analysis in ABAQUS. The variables considered in the study are column web stiffness, connection configurations, and different bracing conditions of the beam. The results from these analyses were compared to the available interaction equations in the AISC Manual and in literature to assess their applicability under different conditions. Shear-compression interaction plots were generated from the results that show the shear strength decreases with an increase in compression force in the connection. The effect of the compression force on the shear strength depends on the column web’s rigidity and the bracing condition of the beam.

Seismic fragility analysis of three-tower cable-stayed bridges with different connection configurations

Seismic fragility analysis of three-tower cable-stayed bridges with different connection configurations

Geotagging accuracy in smartphone photography

After a decade of technological advancements, digital forensic science is under increasing pressure to deliver investigative findings with a high degree of scientific rigor. The judicial community has voiced growing concerns regarding digital traces and their interpretation. This research focuses on assessing the significance of geolocation information embedded within the metadata of photographs captured using a mobile phone. In order to examine the variability in the accuracy of this geolocation metadata and identify potential external influences, images were taken at 29 different locations distributed along three distinct paths. The photographs were captured using two Samsung Galaxy S8 SM-G950F devices running on Android 8.0. Various configurations of GNSS and mobile network connections were tested, and their potential impact on the accuracy of geolocation metadata was investigated. The findings show the dependency of geolocation accuracy on the specific measurement location. This research ultimately highlights the imperative for evaluative approaches to take into account the specific characteristics of each point of interest, as opposed to leaning on broad statements about the reliability of geolocation processes in general.

Behaviour of large-diameter high-strength bolted shear connections for prefabricated composite beams

This paper presents an experimental investigation into the structural behaviour of a new proposed shear connection incorporating high-strength large-diameter steel bolts in conjunction with steel fibre reinforced concrete blocks. A detailed account of fourteen large-scale push-out tests is provided with the aim of examining and quantifying the full deformational characteristics of these shear connections. The results include the load-slippage responses, shear resistances, and failure modes for the various specimens. It is shown that the proposed connection configuration is suitable for prefabricated composite beams in highway bridges and can be detailed to provide high stiffness over 1500 kN/mm, large shear resistance exceeding 1000 kN, and slippage at failure greater than 6.0 mm. The proposed connection can also be easily assembled on site and provides significant resistance against pull-out forces. Based on the experimental results, complementary design procedures are proposed to enable a prediction of the shear resistance of the connections. A simplified load-slippage relationship for the shear connections is also suggested and shown to represent closely the full deformation characteristics. Overall, the proposed shear connection configuration is shown to offer considerable stiffness, resistance, and ductility, and can be readily installed on site for joining steel beams and precast slabs in combination with high performance in-situ concrete. This connection form contributes to an enabling construction technology for promoting effective prefabrication of composite bridge structures.

Constrained multi-scale dense connections for biomedical image segmentation

Multi-scale dense connection has been widely used in the biomedical image community to enhance the segmentation performance. In this way, features from all or most scales are aggregated or iteratively fused. However, by analyzing the details, we discover that some connections involving distant scales may not contribute to, or even harm, the performance, while they always introduce a noticeable increase in computational cost. In this paper, we propose constrained multi-scale dense connections (CMDC) for biomedical image segmentation. In contrast to current general lightweight approaches, we first introduce two methods, a naive method and a network architecture search (NAS)-based method, to remove redundant connections and verify the optimal connection configuration, thereby improving overall efficiency and accuracy. The results demonstrate that the two approaches obtain a similar optimal configuration in which most features at the adjacent scales are connected. Then, we applied the optimal configuration to various backbone networks to build constrained multi-scale dense networks (CMD-Net). Experimental results evaluated on eight image segmentation datasets covering biomedical images and natural images demonstrate the effectiveness of CMD-Net across a variety of backbone networks (FCN, U-Net, DeepLabV3, SegNet, FCNsa, ConvUNeXt) with a much lower increase in computational cost. Furthermore, CMD-Net achieves state-of-the-art performance on four publicly available datasets. We believe that the CMDC method can offer valuable insight for ways to engage in dense connectivity at multiple scales within communities. The source code has been made available at https://github.com/JerRuy/CMD-Net.

Finite Element Modeling of Beam-to-Column Steel Timber Composite Joints with Different Parameters

This study presents a comprehensive three-dimensional finite element modeling and parametric analysis of composite beam-to-column joints in steel–timber composite structures. The investigation encompassed a variety of shear connector configurations, end plate designs, and bolt dimensions, aiming to elucidate their respective influences on the structural performance and behavior of these joints. Through meticulous numerical simulation, this research sought to enhance the understanding of the interactions and load transfer mechanisms within composite connections, thereby contributing to the optimization of design practices in the field of structural engineering. The load–displacement relationship for timber–steel composite joints subjected to monotonic loading was investigated using ABAQUS 6.14 software. This study systematically analyzed the effects of various parameters, including different configurations of shear connectors, end plate thicknesses, and bolt dimensions, on the overall performance of the joints. Through this comprehensive numerical analysis, the research aimed to provide deeper insights into the mechanical behavior and structural integrity of these composite connections under the applied loading conditions. A non-linear finite element model of timber was developed and verified with the results of the experiment in this study. The findings are discussed in detail, highlighting the intricate relationships between the selected parameters and their respective effects on the performance and overall stability of the composite connections. This thorough evaluation aimed to enhance the understanding of how these variables interact within the context of composite joint design and behavior. Finally, design recommendations for composite structures, such as the dimensions of the bolt, end plate thickness, and different sizes of shear connectors are provided.

The Efficacy of Modified Ilizarov Distraction-Tension Device on Limb Wound Difficult to Cover with Skin Flaps.

Closure of complex limb wounds poses challenges and requires innovative approaches. This research aimed to evaluate the effectiveness of a modified distraction-tension device using Ilizarov external fixation for wound closure in challenging cases. A retrospective analysis was conducted on 43 patients with extremity wounds that were difficult to cover with skin flaps between January 2019 and December 2022. Tension-relieving traction was applied using the Ilizarovexternal fixator apparatus, tailored to individual wound characteristics. Three types of wire-pin connections were used in this study. The distraction begins on the third postoperative day, with a speed of 0.5mm/d. Clinical wound healing scores were evaluated at 5 and 30 days postoperatively. Complications were documented following the Paley classification system. Traction using modified Ilizarovexternal fixation promoted a significant reduction in wound size. The mean traction period was 11.2 ± 7.3 days, and the mean healing duration was 17.0 ± 3.7 days. The clinical wound healing score improved from 3.7 ± 2.9 at 5 days to 1.7 ± 0.7 at 30 days postoperatively (p < 0.05). Complications were minimal, with no significant obstacles or sequelae observed. Direct closure healing was achieved in 21 cases, skin graft healing in 13 cases, and suture healing in 9 cases. No recurrences were reported. Using Paley's classified complications, there were 17 problems, 9 obstacles, and 0 sequelae. The Ilizarov tension-relieving traction shows promise in facilitating wound closure that is challenging to manage with skin flaps. The modified three types of pin-skin connection configuration could satisfy various types of wound closure.

Watershed landscape characteristics and connectivity drive river water quality under seasonal dynamics

Landscape characteristics and connectivity are pivotal determinants of river water quality within the context of water quality management. They play particularly important roles in the spread of non-point source pollution. However, previous research has not investigated their combined effects, especially in the topographically and ecologically volatile Loess Plateau, China. This study applied machine learning and positive matrix factorization techniques to water quality monitoring data for the Wuding River basin, China, from 2017 to 2021 to assess the seasonal impacts of environmental factors on river water quality. The results showed that there were spatial and seasonal variations in pollution sources, and specific thresholds for the key landscape indices that influence water quality were identified. Landscape composition and configuration have the greatest influence on the water quality parameters during the dry season, whereas connectivity and landscape configuration are more critical during the wet season. The connectivity contributions to chemical oxygen demand, the potassium permanganate index, and total phosphorus in the wet season were 19.07%, 27.47%, and 5.08% greater than in the dry season, respectively. Connectivity also made a significant contribution to the composite water quality index, accounting for 33.46% in the dry season and 36.22% in the wet season. The positive matrix factorization model identified agricultural non-point sources and mixed pollutants as the main factors affecting water quality during the dry season, whereas erosion and mixed pollution sources dominated the wet season. Critical thresholds were established for the landscape indices that affected water quality, such as a landscape shape index below 18.5 and a grassland proportion above 65%. The results can be used to develop more effective water quality management strategies and illustrate the essential role played by connectivity when tailoring water quality management strategies to seasonal variations.

Glubam roof truss with riveted glubam connections adopting thin-walled steel tube: Experiment, modeling, and model-updating

Bio-based laminated structures offer a timely solution to meet the pressing demand for resource-efficient and environmentally responsible construction practices in civil engineering. Riveted connections are a kind of commonly used joint and significantly impact the mechanical behaviors of global structure. However, existing studies on the complex behavior of such joints for bamboo-based structures are insufficient. This study investigated the hysteretic behavior of riveted Glued Laminated Bamboo (glubam) connections using thin-walled steel tube and corresponding planar roof truss with thin-walled steel tube connections by experimental and numerical methods. Firstly, cyclic tests were conducted on the riveted glubam connections with thin-walled steel tube to investigate their hysteretic behavior. The test matrix encompasses four distinct connection configurations, carefully selected to assess the connection behavior of glubam. After the investigation of connection behavior, cyclic tests were further conducted on glubam planar roof truss structures to evaluate their global and local hysteretic behavior. Subsequently, the numerical hysteretic models for joints and hybrid roof trusses were developed within the OpenSeesPy framework. To accurately and efficiently calibrate the model parameters, a novel parallel genetic algorithm (PGA) was proposed to carry out an initial calibration on model parameters. Based on PGA, a more comprehensive model updating framework combining the neural network, prior knowledge and PGA was developed to obtain optimal parameters. Finally, the numerical models were successfully validated against the experimental data, demonstrating the effectiveness of the established numerical model and model-updating framework.

Introduction to a novel geotextile tube connection construction method: A case study of test site and field application

One particular challenge in constructing geotextile tubes is ensuring proper alignment and leveling, especially when connecting them in a series. This study introduces a novel connection configuration to address this challenge by inserting an auxiliary tube between two main tubes. The proposed connection method offers the advantage of consolidating individual geotextile tubes into a unified structure while maintaining a consistent horizontal level. The proposed connection technique was successfully applied both at test site and on dry construction platform for bridge construction. This study is beneficial for practicing engineers as it presents a new and effective method for connecting geotextile tubes, offering valuable insights into its practical application.

Towards scaling up of the electrochemical production of Caro’s acid: Electrode size and/or stacking?

This work focuses on very important aspects associated with the scale up of electrochemical devices by facing a 4-times increase in the electrochemical production of the Caro’s acid, starting from a very efficient electrochemical cell that was developed and evaluated in previous works for this process. Thus, the effect is compared of (a) increasing the size of the electrodes by four by resizing, adapting, and manufacturing the cell prototype using 3-D printing technology and (b) that of stacking four cells to reach the same surface area, using different hydraulic connection configurations. Results demonstrate that the resizing of the electrochemical cell is more successful than stacking four cells. Resizing allows to obtain not only results that are comparable to those obtained by the lower scale cell but even to improve those results, because of the lower impact of edge effects. Regarding hydraulic connection, it was found that it is better to use parallel than series configuration. A simple phenomenological model is used to conclude that scavenging effects are higher when the series configuration is used. The resized cell was fully evaluated from the fluid dynamic behavior, pointing out its outstanding behavior.

Experimental and Numerical Investigation on Stress Concentration Factors of Offshore Steel Tubular Column-to-Steel Beam (STCSB) Connections

Steel tubular column-to-steel beam (STCSB) connections are critical parts in offshore structures, where complex component connections and the stress concentration are of significant concern. This study conducted stress concentration tests on welded STCSB connections and subsequently developed a finite element (FE) model for the connections, with the experimental results validating the accuracy of the model. The discussion focused on the influence of parameters such as the width-to-diameter ratio of the beam to the column, the diameter-to-thickness ratio of the column, the diameter-to-thickness ratio of the column to the beam, and the height-to-thickness ratio of the beam web on the fatigue performance. The study proposed optimization methods including the addition of stiffeners and outer flange plates. The findings indicate that optimized connection configurations can effectively mitigate stress concentration in the connected areas, thereby enhancing the structural stability and fatigue life. The width-to-diameter ratio of the beam to the column and the diameter-to-thickness ratio of the column significantly affect the fatigue performance of welded STCSB connections, with an increased width-to-diameter ratio of the beam to the column or a reduced diameter-to-thickness ratio of the column leading to a substantial decrease in the maximum stress concentration factors (SCFs). The addition of stiffeners and adjustment of the outer flange plate can improve stress concentration effects in the connection area.

Discussion on ultimate resistance formulas of high-strength bolts under tensile-shear coupling loading

Bolted connections are one of the key connection configurations in steel structures. The ductile fracture prediction is one of the challenges in the structural integrity evaluating of steel structures. To guarantee the safety of steel bridge in connections, an accurate assessment of the ultimate resistance of high-strength bolts under combined tensile-shear loads is necessary. However, the impacts of various parameters on high-strength bolts under combined tensile-shear loads are not sufficiently analysed in the existing references. Hence, in this paper, the validated mesoscale critical equivalent plastic strain (MCEPS) method is used to evaluate the ultimate resistance of high-strength bolts with different bolt grades, bolt diameters, bolt types, hole clearance, and preload force when the bolts are exposed to combined tensile-shear loading. The simulation results are compared to existing design specifications. Finally, the formula modifications in the existing design standards are proposed based on statistical analysis on numerical parametric results.

Experimental study on seismic performance of spatial and planar hoop-head mortise and tenon timber joints in historical architecture

This paper aims to present an experimental study investigating the seismic behaviour of spatial and planar hoop-head mortise and tenon (MT) timber joints in traditional Guangfu Ancestral Halls. The unique design of the external hoop head provides additional restraints for the tenon and mortise in these joints, endowing them with enhanced pull-out resistance and increased structural integrity compared to other types of MT connections commonly used in traditional timber-framed structures. The research commenced with material testing to determine the mechanical properties of Merbau wood used in this timber frame construction. Reversed cyclic loading tests were then performed on two planar and two spatial hoop-head MT timber joints. The experimental results demonstrated the favourable seismic performance of the hoop-head MT joints. All specimens failed within the MT joint area, exhibiting different failure modes based on varying connection configurations and tenon sizes. Furthermore, the spatial MT joints showed lower stiffness and bearing capacities compared to the planar MT joints of equivalent size. Their hysteresis curves, envelope curves, and cyclic stiffness degradation curves displayed greater asymmetry. These discrepancies can be attributed to the reduction in tenon sections necessary to accommodate the overlapping beams within the spatial joint core area.

Prefabricated bolted PEC beam-to-CFST column joints: Development and its seismic behavior

This paper developed a novel bolted connection of prefabricated partially encased composite (PEC) beam to concrete-filled steel tubular (CFST) column by end-plates or π-connectors, and two joints with varying design details were tested subjected to cyclic loading. The seismic performance of the developed connections was investigated by experimental and finite element (FE) analysis. It was observed that both the two type connections exhibited concrete crushing within the PEC beam, accompanied by localized buckling and eventual fracture of the flanges in the main steel component of the beam. At the same time, other components were essentially in the elastic phase, such as end-plates, π-connectors, high-strength bolts, and column steel tubes. The bolted end-plate connections demonstrated excellent hysteretic performance, exhibiting high ductility factors. The stiffness, ductility, and energy dissipation capacity of the bolted π-connector connections were significantly diminished due to the influence of relative slippage between the π-connectors and the beams, in stark contrast to the bolted end-plate connection. According to Eurocode 3, the suggested connection configurations exhibited semi-rigid behavior and full-strength characteristics for non-sway frames.

Structural impacts on the degradation behaviors of Ir-based electrocatalysts during water oxidation in acid

Large-scale hydrogen production by electrocatalytic water splitting still remains as a critical challenge due to the severe catalyst degradation during the oxygen evolution reaction (OER) in acidic media. In this study, we investigate the structural impacts on catalyst degradation behaviors using three iridium-based oxides, namely SrIrO3, Sr2IrO4, and Sr4IrO6 as model catalysts. These Ir oxides possess different connection configurations of [IrO6] octahedra units in their structure. Stable OER performance is observed on SrIrO3 and attributed to the edge-linked [IrO6] structure and rapid formation of a continuous IrOx layer on its surface, which functions not only as the “real” catalyst but also a shield preventing continuous cation leaching (with <1.0 at.% of Ir leaching). In comparison, both Sr2IrO4 and Sr4IrO6 catalysts demonstrate quick current fading with structure transformation to rutile IrO2 and formation of inconducive SrSO4 precipitates on surface, blocking the reactive sites. Nevertheless, over 60 at.% of Ir leaching is detected from the Sr4IrO6 catalyst due to its isolated [IrO6] structure configuration. Results of this work highlight the structural impacts on the catalyst stability in acidic OER conditions.

Applications of Spatial Timber Structures in China and Research on the Performance of Their Typical Connections

Timber, being a versatile and sustainable material, has been used for residential and public buildings throughout history. In recent years, advancements in engineering and construction technology have resulted in the development of innovative timber spatial structures that push the boundaries of traditional timber construction. Especially, numerous spatial timber structures have been constructed in China in recent years. This study aims to provide an overview of notable examples of spatial timber structures in China, including their architectural features, structure arrangement and construction method. Additionally, the configuration of some timber connections utilized in the Taiyuan Botanical Garden project are analyzed and the mechanical behavior of connections are investigated by a brief introduction of experimental tests. The research will provide a reference for engineering design of spatial timber structures in the future.

Experimental and numerical investigations of the impact resistance of socket and pocket connections for precast bridge columns

This study investigates the dynamic performance of precast bridge columns under pendulum impact testing, including socket connection, pocket connection, and cast-in-place (CIP) columns. The study focuses on comparing the impact behavior of CIP and precast columns regarding failure modes, impact force-time, and deflection-time histories. Furthermore, the mechanism by which the socket or pocket connection configurations affect the impact resistance of the precast columns is discussed. The results indicate that the development of cracks in the precast and CIP columns is consistent under the same impact conditions. Notably, the shear resistance mechanisms and failure modes vary significantly at the bottom of the two columns. For the precast specimens, substantial local damage occurs at the connections with consecutive impacts. Specifically, punching shear failure is observed at the pocket connections, whereas the connection sections of the socket columns may pull out from the grooves. Local damage to the column-footing connections reduces the global stiffness of precast columns, leading to higher deformation, greater residual displacements, and lower impact forces than those of CIP columns. A simplified finite element modelling method is proposed to simulate the characteristics of precast column connections, and its accuracy is verified using the test results. The numerical findings show that increasing the friction coefficient at the connection interface promotes the formation of diagonal compression struts within the connection, effectively resisting impact loads and preventing excessive shear stress produced by sliding at the interface. Furthermore, amplifying the minimum embedment depth of the socket-connected precast column to 1.0 D is recommended to ensure safe performance under impact loading.

Impact of string connection and contact defects on electrical current distribution in solar cells and modules: A model validated by magnetic field imaging

AbstractModeling of solar modules and their components is essential to quantify geometrical, optical, and electrical losses and to improve the designs and technologies in terms of performance. In most loss analysis models, the current share among the busbars of the solar cell is assumed to be equal since a symmetrical distribution of the metallization is given. The impact of string terminal connection on the current distribution among the ribbons and the resulting changes in ohmic losses has not been studied yet. In this study, a MATLAB model is developed to consider the impact of the string connector terminal position on the current distribution and the ohmic losses in the ribbons and in string connector. The model allows for the analysis of the impact of contact defects scenarios in ribbons and string connectors on the current distribution. Results show that the highest current flows at the closest busbar to the string connector terminal while the current decreases at the busbars farther away from the terminal due to higher ohmic resistance of the current path. The higher the ohmic resistance of the string connector, the more inhomogeneous the current share at busbars. Simulating a 9 busbar M6 half‐cell with 1 × 0.08 mm2 string connector, positioning the string connector terminal at the leftmost or rightmost ribbon results in 0.4 W less power compared to center connection configuration, where the string connector terminal is positioned at the center ribbon. Furthermore, simulation results show that inhomogeneity of current causes about 2.1% reduction in module power compared to the case of evenly distributed cell current, considering a 120‐haf‐cell module with the same string connector. Regarding contact defect analysis, exemplary simulations show the impact of the position of detached ribbons on the power or efficiency loss. Considering left or right connection configuration, detaching the leftmost or rightmost ribbon results in higher power loss compared to other ribbons. Detaching one cell ribbon completely from the string connector results in about 0.2%abs decrease in cell efficiency, while detaching the outer ribbon along all strings of a 120‐half‐cell module results in power loss of about 0.8%. The developed model is validated by performing magnetic field imaging (MFI) measurements, in which the magnetic flux density induced by the current carried by the ribbons is measured.