Capacity Of Connections Research Articles

Enhancing progressive collapse resistance of steel structures using a new bolt sleeve device

In the present study, frame robustness is enhanced by improving the contribution of the bolts to the rotational capacity of connections; the higher the bolts' elongation, the higher the rotational capacity that can be achieved. The proposed method comprises a hollow steel sleeve, with a predetermined wall curvature, that is inserted between the washer and the end plate interrupting the load path in the connection thus enabling a more ductile response. In order to demonstrate the efficacy of the proposed method, end plate connections with varying sleeve parameters are numerically examined using verified FE models. The proposed system significantly increases the ductility and strength of the connection by up to 2.6 and 2.5 times that of the standard connection, respectively. Additionally, different ductile responses can be achieved based on the sleeve parameters without changing the configuration of the connection.

Abstract TMP72: Multimodal Prediction Of Stroke Severity

Introduction: Predicting individual outcomes post-stroke with the highest possible accuracy is a crucial steppingstone in the realization of precision medicine. We here evaluated various types of lesion information in their capacity to predict stroke severity in a large cohort of patients with acute ischemic stroke. Methods: A total of 1,075 patients of the MRI-GENIE study [age: 64.2(14.7), 38% women] contributed to analyses (N=792 as train and N=283 as test sample). We employed ridge regression with hyperparameter optimization and nested five-fold cross-validation to predict acute NIHSS-based stroke severity. Our baseline model considered DWI lesion volume. Further models tested structural lesion location, indirect structural and functional lesion connectivity, individually and combined with lesion volume. Data was preprocessed by principal component analysis (PCA), retaining 95% of the variance of the original data. Model performance was compared in terms of explained variance (R-squared) and 95% confidence intervals in the outer loop of the training set and the test set. Results: Structural lesion connectivity enabled the highest prediction performance in the test set ( Figure 1 ). Prediction performance did not change notably with inclusion of lesion volume information. This contrasted with the combination of functional lesion connectivity and lesion volume that achieved a substantially higher prediction performance compared to functional lesion connectivity or lesion volume in isolation. Lesion location resulted in a prediction performance that was in the range of lesion volume alone and significantly lower than the ones of structural or functional connectivity with lesion volume. Conclusions: Structural connectivity facilitated the most convincing prediction of stroke severity. The capacity of functional lesion connectivity was substantially improved by the inclusion of lesion volume, indicating both represent complementary information.

Design Approach for Tuning the Hybrid Region of 3D-Printed Heterogeneous Structures: Modulating Mechanics and Energy Absorption Capacity

The functional hierarchical structures of the triply periodic minimal surface are receiving much attention in tissue engineering applications due to their lightweight and multifunctionality. However, current functionally graded structure design methods are not friendly to heterogeneous structures containing different orientations and different unit types and often face the problems of insufficient connection in the hybrid regions and low local stiffness. In this paper, an improved gradient structure design method was proposed, which solves the problem of insufficient connection between substructures by constructing hybrid region transition functions. Three improved heterogeneous structures were constructed using Primitive and Gyroid lattices and compared with the unimproved heterogeneous structure. Their mechanical properties, deformation mechanism, and energy absorption capacity were examined by finite element analysis and experiments. The results showed that the proposed design method can effectively solve the problems of insufficient connection and poor bearing capacity in the hybrid region between substructures. This method can not only ensure the full connection of the hybrid regions but also flexibly adjust the mechanical properties and energy absorption capacity as well as effectively expand the application range of the energy absorption. Overall, these findings provide valuable guidelines for designing gradient structures with disordered and hybrid features.

The Role of Extra-motor Networks in Upper Limb Motor Performance Post-stroke

Background: Motor improvement post-stroke may happen even if resting state functional connectivity between the ipsilesional and contralesional components of the sensorimotor network is not fully recovered. Therefore, we investigated which extra-motor networks might support upper limb motor gains in response to treatment post-stroke. Methods: Both resting state functional connectivity and upper limb capacity were measured prior to and after an 8-week intervention of task-specific training in 29 human participants [59.24 ± (SD) 10.40 yrs., 12 females and 17 males] with chronic stroke. The sensorimotor and five extra-motor networks were defined: default mode, frontoparietal, cingulo-opercular, dorsal attention network, and salience networks. The Network Level Analysis toolbox was used to identify network pairs whose connectivities were enriched in connectome-behavior relationships. Results: Mean upper limb capacity score increased 5.45 ± (SD) 5.55 following treatment. Baseline connectivity of some motor but mostly extra-motor network interactions of cingulo-opercular and default-mode networks were predictive of upper limb capacity following treatment. Also, changes in connectivity for extra-motor interactions of salience with default mode, cingulo-opercular, and dorsal attention networks were correlated with gains in upper limb capacity. Conclusions: These connectome-behavior patterns suggest larger involvement of cingulo-opercular networks in prediction of treatment response and of salience networks in maintenance of improved skilled behavior. These results support our hypothesis that cognitive networks may contribute to recovery of motor performance after stroke and provide additional insights into the neural correlates of intensive training.

IMPROVING THE DYNAMIC COMPETITIVENESS OF ENTERPRISES: RESEARCH IN THE FIELD OF TOURISM

Enterprises are now facing fierce competition under the pressure of global economic integration. For sustainable development, businesses must improve their competitiveness. In that context, identifying, nurturing, and developing resources to increase competitiveness is an urgent requirement of enterprises. The article focuses on determining factors affecting dynamic competitiveness. Empirical research in the field of tourism has shown that absorptive capacity, adaptive capacity, creative capacity, connectivity capacity, cognitive capacity, and market orientation are the basic components of tourism competence dynamic competition. The article suggests implications for building and improving the dynamic competitiveness of enterprises.

Rehabilitation of defective connections between two precast concrete segments (experimental and analytical study)

Connections in precast concrete elements are essential for improving the structures' utilization, cost, and quality control. Moment connection in beams was one of the easiest ways to achieve good performance of the structures by eliminating the plastic hinges zone. Due to constructing precast elements, some of them can be defective. This paper presents an experimental and analytical study to rehabilitate defective connections between two precast concrete segments. Six simply supported beams with beam-to-beam connections and one simply supported beam without connections, each with dimensions of 200 × 400 × 1600 mm, were fabricated and loaded to failure with a four-point load. The main variables parameters were a) the type of concrete mix in the splice region, two types of concrete were employed: Normal Strength Concrete (NSC) and High Strength Concrete (HSC) b) effect of rehabilitation techniques with using NSC in the connection zone such as; using warped fiber sheets around splice region or Carbon Fiber Reinforcement Polymer CFRP laminates at the tension surface of the tested beams c) effect of rehabilitation techniques with using HSC in the connection zone. Also, a new model was proposed based on some codes and guidelines of beams strengthened with Externally Bonded FRP Systems to calculate the flexure capacity for rehabilitating the beam-to-beam connections. The results indicate that neither casting NSC nor the HSC at the connection region has any effect on increasing the beam's capacity and cannot be used only as a rehabilitation technique in beam-to-beam connection. The fiber sheet warped around the splice region constructed from either NSC or HSC did not significantly increase the beam's capacity compared to rehabilitated beams with casting concrete only in the connection region. The load capacity of the rehabilitated beam with CFRP laminates and warped fiber sheets is increased significantly by about 122 % and 209 % compared to rehabilitated beams with splice regions constructed from NSC and HSC, respectively. The proposed model based on CNR-DT 200 R1/2013 equation gave a good prediction of the capacity of the rehabilitation connection for rehabilitated beams with CFRP laminates and warped fiber sheets.

Sharing the network infrastructure between renewable sources with different technologies as a way to increase the connection possibilities of the power system

The article considers the possibility of gaining access to the grid for new renewable energy sources (mainly photovoltaic farms) by sharing the grid infrastructure with existing wind farms. Due to the negative correlation of the generation capabilities of wind farms and photovoltaic farms, it is possible to use lines, transformers and other devices by both technologies, without the need to adapt this infrastructure to the power that results from the algebraic summation of nominal powers. As shown by the calcu-lations, the control of the power of a photovoltaic farm allows the use of the connection capacity reserved for the wind farm with very slight curtailment of the annual energy production.

Experimental and theoretical investigation on shear performances of glued-in perforated steel plate connections for prefabricated timber–concrete composite beams

Glued-in perforated steel plate (GIPSP) connections demonstrate significant shear strength and high slip modulus. Consequently, they indicate substantial potential for application in timber–concrete composite (TCC) structures according to the emerging tendencies in high-storey and large-span buildings. However, the application pattern in prefabricated TCC structures and the theoretical analysis of the shear performances of GIPSP connections are highly deficient. This hinders the application of this type of shear connection. In this study, the shear performances of GIPSP connections were evaluated using push-out tests. Ten groups of push-out specimens with different steel plate numbers, steel plate lengths, and concrete slab types were tested. The concrete slab types investigated in the experiments included a prefabricated concrete slab and cast-in-situ concrete slab. The experimental results were discussed in terms of the failure mode, load-carrying capacity, and slip modulus. The theoretical models for the load-carrying capacity related to the associate failure mode were discussed based on an analysis of the failure mechanisms. In addition, design proposals with regard to the load-carrying capacity and slip modulus of the GIPSP connection were presented. The research results can provide design guidance for TCC beams using GIPSP connections and prefabricated concrete slabs.

A Collapse Strength Model for a 7” Crescent-Worn Casing Connection Considering Sealing Integrity

Collapse failure under external pressure is one of the common failure forms of casing. Much research has been performed on the casing body, but few on the threaded connection, in view of the general belief that the threaded connection has a thicker wall and larger collapse strength than the casing body. However, under external pressure, the sealing capacity of a worn casing connection will decrease due to deformation of the sealing structure, so the influence of sealing ability should be considered to determine the collapse strength of casing. In this paper, we established a three-dimensional finite element model of a 7” crescent-worn casing connection and calculated the collapse strength of the connection under different wear depths. Meanwhile, the stress distribution characteristics on the sealing surface were obtained and the influence of wear on the sealing performance of the casing connection under external pressure was analyzed. The results showed that when the wear rate exceeds a certain value, the collapse strength of the connection based on sealing integrity was lower than that of the casing body. Based on these, a collapse strength model for a 7” crescent-worn casing connection considering sealing integrity was developed and a safety evaluation method of the collapse strength of the worn casing string was proposed.

Experimental study on flexural capacity and fire resistance of high strength Q690 steel flush end-plate connections

High-strength steel is widely used in building structures, but fire-induced damage and collapse of high-strength steel structures cause huge economic losses. As a primary part of the structure, the reliability of beam–column joints is essential for the structure’s fire safety. This paper presents an experimental study on high-strength Q690 steel flush end-plate connections (Q690-FEC) at ambient and elevated temperatures. Ultimate bending capacity tests were conducted at ambient temperature to investigate its structural performance, where initial rotational stiffness, bending capacity, and ultimate rotation were obtained. Numerical models were developed to reproduce the tests, and parametric analyses were performed to investigate the influence of load ratio, end-plate thickness, and bolt diameter. Transient fire-resistance tests were performed on specimens with different end-plate thicknesses, where specimen temperature, furnace temperature, and joint rotation were measured. The test results indicate that increasing end-plate thickness has little influence on the critical temperature and fire resistance. Finally, a rotation-temperature relationship model was proposed to predict the fire behavior of Q690-FEC and validated against the experimental data.

Experimental and numerical evaluation on the behavior of single-shear timber connections using lag screw

In current design procedures, the capacities of single-shear timber connections with lag screws are determined based on their governing failure modes, which are assumed to occur independently. In this study, the capacity and failure modes of single-shear timber connections with lag screws are evaluated experimentally and numerically. Six specimens of Red Meranti wood and lag screws with different penetration lengths are tested to obtain their lateral load capacities and failure modes. Nonlinear 3D finite element analyses using Abaqus are conducted to simulate the test condition. The experimental and numerical results are evaluated in terms of connection failure modes and capacities. Moreover, the result will be compared with NDS 2018 predictions. The study results show that the connection capacities between experimental tests and numerical analysis are similar if the minimum penetration requirement of NDS 2018 is satisfied. It can also be seen that the dominant failure modes, both from experimental and numerical results, match with those predicted using NDS 2018, although they are slightly combined with the other failure modes.

Experimental research of the bearing capacity of the pin load connection of a composite shaft with flange

Experimental research of the bearing capacity of the pin load connection of a composite shaft with flange

Nonlinear Analysis of Punching Behavior of Flat Slab at Corner Column Under Effect of Vertical Load

In this study, anon-linear 3D numerical analysis using ANSYS was performed to investigate the influence of slab and column dimension on the punching shear capacity of the corner slab-column connection. Most research studied the punching shear stress, but none of them studied the distribution of punching shear stress, which was assumed to be linear in different codes. Verification models have been used to simulate existing experimental data. Two factors were taken into consideration for their influence on the punching shear strength of the concrete: the slab aspect ratio, column aspect ratio, and other factors are constant. Therefore, twenty-one models of different slab and column dimensions were investigated, and a comparison between the results obtained by the finite element analysis and the numerical results was made. Also, a comparison between shear stresses computed using two different methods in the Egyptian code, the simplified method, and the detailed method, and compare them with the Ansys models.

NUMERICAL INVESTIGATION OF PUNCHING SHEAR STRENGTH OF SLAB-COLUMN CONNECTIONS

Flat slab system is commonly used because of aesthetic appearance and flexibility of architecture. The punching shear is the major drawback of this structural system. The punching shear causes sudden failure lead to total collapse in the structure. In this paper 3D models that follow the method of applied element (AEM) to analyze the behavior of interior column-slab connections exposed to vertical displacement. The aim of this paper to show the importance of providing various types of punching shear reinforcement in the connection and improve the capacity of column-slab connection to prevent the local failure. The numerical study involved twenty six full-scale interior column- slab connections. This study is divided into two groups in addition to a control model where this model has no punching shear strengthening. The first group has thirteen models with additional punching strengthening such as closed stirrups around the column. The second group contains thirteen models with additional punching strengthening such as multi leg stirrups. The ultimate load is compared among several models. The simulated results display that shear strengthening improve both of strength.

Impact of changes in river network structure on hydrological connectivity of watersheds

River network connectivity is a key factor affecting watershed ecosystems and an important criterion for evaluating the health of river. The river network structure of the basin has changed dramatically in recent years due to human activity, but the response of connectivity to changes in physical structure is still poorly understood. In this paper, a dynamic index (connectivity index) based on daily-scale flow and probability density function is proposed to characterize the connectivity capacity of river networks. The Haihe River basin in China is selected as the study area, and a graphic model is constructed to assess the evolutionary structure of the river network. The 54 sections were classified into Low human impact (LHI) and High human impact (HHI), and the trends and causes of connectivity changes of the sections with the evolution of the network were analyzed. The results reveal that the river network degree and clustering coefficient keep increasing, the path length decreases and becomes more dense downstream, and the river network gradually evolves into a “small-world” network. The “small-world” characteristics improve the potential efficiency and specific functionality of the river network, but make the physical structure mismatch with the hydraulic gradient, and the network flow disperses severely, leading to a significant decrease in connectivity (HHI connectivity index is lower than LHI 52.1%). Moreover, the structural changes enhance the spatial and temporal differences in hydrological connectivity, which further restricts the function of the river system. “Small-world” and connectivity indicators (duration, start time, and intermittency) show strong correlations. Therefore, physical structure is an important factor influencing connectivity capacity of river networks. The planning and management of the watershed should consider the changes in hydrological connectivity caused by the structural modifications of the river network.

Future Technologies for Train Communication: The Role of LEO HTS Satellites in the Adaptable Communication System.

The railway sector has been characterized by important innovations regarding digital technologies for train-to-ground communications. The actual GSM-R system is considered an obsolescent technology expected to be dismissed by 2030. The future communication systems in the rail sectors, such as Adaptable Communication Systems (ACS) and Future Railway Mobile Communication Systems (FRMCS), can manage different bearers as 4G/5G terrestrial technologies and satellites. In this environment, the new High Throughput Satellite (HTS) Low-Earth Orbit (LEO) constellations promise very interesting performances from data rate and coverage points of view. The paper analyzes the LEO constellations of Starlink and OneWeb using public data. The Rome-Florence railway line is considered for simulations. The results evidence the LEO satellite can provide interesting performance in terms of visibility, service connectivity, and traffic capacities (up to 1 Gbps). This feature enables the LEO to fully manage a high amount of data, especially in the railway scenarios of the next years when video data applications will be more present.

KEKUATAN SAMBUNGAN DUA TAMPANG PADA MDF DENGAN ALAT SAMBUNG PASAK WPC

MDF (Medium Density Fiberboard) and WPC (Wood Plastic Composite) are innovative results of using sawdust waste to overcome the problem of wood scarcity. This study used a WPC Teak dowel because it has high shear strength and does not cause rust marks. This study was conducted to determine the value of the MDF connection capacity using WPC Teak dowel connectors and to determine the connection failure mode based on the EYM (European Yield Model) theory. This study used a WPC Teak dowel with a diameter of 6 mm, 8 mm, 10 mm, and 12 mm. The type of connection is a double-shear wooden joint using MDF. The test was carried out at the Structural Laboratory, Civil Engineering Department, Tidar University using a Compression Testing Machine to get the value of the connection capacity and test failure mode based on the MDF bearing strength and WPC Teak post failure referring to ASTM D764-97a. The test results obtained an average connection capacity value WPC dowel with a diameter of 6 mm, 8 mm, 10 mm, and 12 mm, respectively, which was 1094 N; 1870 N; 2439 N; and 3462. The highest average connection capacity value at 12 mm diameter was 3462 N, and the lowest at 6 mm was 1094 N.

Moment Rotation behavior of Top and Seat Angle Connection with Angle Stiffeners

The design specifications for seven commonly used semi-rigid steel connections have been embodied in Indian Standard Code of Practice for General Construction in Steel (IS800:2007). Bolted connections are proved to be efficient by several researchers for its energy dissipating capability under reversal of loading; among them top and seat angle (TSA) connection has higher capacity. An attempt has been made to investigate the behaviour of stiffened TSA connection by finite element analysis in this research. Previously published experimental specimens of TSA connection (RAMAN 2005) semi-rigid TSA bolted connection and their results have been considered to develop 3D Non-linear Finite Element (FE) model and analyses have been executed using the general purpose FE software. The M-?r behavior of numerical analyses are compared with that of the experimental results and thus, the FE model is validated. Further studies are carried out on TSA with all angles stiffened and TSA with angles subjected to tension alone are stiffened. The FE analysis results showed that TSA connection with only tension angles stiffened behave similar to that of TSA connection with all angles stiffened i.e., the stiffeners provided in compression angles does not contribute to the stiffness and connection capacity. The plastic flexural resistance of stiffened TSA connection has enhanced by 30% to that of TSA connection and the ratio of initial stiffness of stiffened TSA to the unstiffened TSA is found to be 1.25. So, the stiffened TSA connection is proved to be efficient in terms of both capacity and failure. The further studies have been carried out to investigate the influence of stiffener properties on the M-?r mechanism of the connection and the results showed that thickness of stiffener equal to the beam web thickness is more efficient.

Flexural properties of wooden nail friction welding of laminated timber

The properties of single shear specimens connected by wooden nail frictional welding and twist nails were studied. The single shear properties of the specimens connected by wooden nail welding were lower than that of the twist nail specimens. The single shear capacity of the wooden nail welding specimen was determined by calculating the method of design value of the bearing capacity of the pin connection. Furthermore, the flexural properties of the wooden nail welding laminated timber were analyzed. Due to the larger diameter of the wooden nails compared with the twist nails, the wooden nail welding laminated timber in the elastic phase had higher stiffness. The elastic modulus of the wooden nail welding laminated timber exceeded the average elastic modulus of the constituent lumber pieces by 9.46%. The number of wood lumbers in wooden nail welding laminated timber had little effect on the elastic modulus of laminated timber, but the nail spacing had a certain effect. Therefore, in future research, it is recommended to use the construction method of twist nail connection to design the wooden nail welding laminated timber. In addition, the nail spacing should refer to the GB 50005 (2003) standard and the wood structure design manual.

Towards hydrological connectivity in the karst hillslope critical zone: Insight from using water isotope signals

Hydrologic connectivity along the hillslope critical zone is essential for the transmission of water, solutes, and nutrients to streams. However, the influences of critical zone structure on hydrological connectivity are not adequately understood, especially for hillslopes with complex topography. We investigated the hydrological connectivity along different topographical positions of two adjacent dolomite hillslope plots in southwest China: a deep soil plot (average value: 66 cm) and shallow soil plot (average value: 35 cm). We characterized the dynamics of multiple-interface runoff and soil water based on observations of stable isotopes (δ18O and δD) and hydrometric monitoring, and computed the lc-excess, young water fraction (yw), and hydrograph separation from June 2020 to July 2021. On both hillslopes, soil depth gradually increased from up-slope to down-slope, and the contribution of event water and yw to soil water gradually decreased (100 % to 69 %). In the vertical depth, a sudden decrease in the contribution of yw (98 % to 47 %) and event water (44 % to 11 %) in the down-slope of the soil-epikarst interface was observed. These results indicate that the infiltration of rainwater from up-slope to down-slope was altered by vertical flow to lateral flow, which was connected through the soil-epikarst interface and finally converged in the low-lying area. Contrary to expectations, the contribution of yw at the soil-epikarst interface was lower in the shallow soil plot (43 %) than in the deep soil plot (71 %). As a supplement, moisture at the soil-epikarst interface was significantly higher in the shallow soil plot. This indicates that the renewal cycle of groundwater was slower in shallow soil-covered hillslopes not only because almost all rainwater (∼98 %) entered the soil-epikarst to redistribute as well as the higher water storage area in the soil-epikarst interface. Accordingly, the soil-epikarst structure, which is differentiated by soil depth, controls hillslope hydrological connectivity and groundwater storage capacity in the karst region of southwest China.