Capacity Of Connections Research Articles

Bi-level planning model of distributed PV-energy storage system connected to distribution network under the coordinated operation of electricity-carbon market

The disordered connection of Distributed PV-Energy Storage Systems (DPVES) in the Distribution Network (DN) will have negative impacts, such as voltage deviation and increased standby costs, which will affect the demand of urban consumers for reliable and sustainable power consumption. Therefore, reasonable planning of the location and capacity of the DPVES in the DN is one of the key measures to reduce these negative impacts, while promoting the consumption of renewable energy and protecting the income of the DPVES. In this paper, under the background of coordinated operation of China's electricity market and carbon market, considering the uncertainty of distributed photovoltaic (DPV) output power and the demand response (DR) behavior of users, a bi-level planning model of DPVES in DN is established. The upper-level model aims at the maximum revenue of the DPVES in the DN and the highest local consumption rate of DPV, and the decision variables are the connection location and capacity of the DPVES. The lower-level model aims at the minimum average voltage deviation of the DN nodes, and the decision variables are the implementation of load-side DR and the output power of the DPVES. Then, the solution method and process of the model are given. Finally, four planning scenarios are set up in the IEEE-33 node distribution system, and the planning results of different scenarios are analyzed and discussed. The research results show that the bi-level planning model proposed in this paper can reduce the average voltage deviation of DN nodes while effectively increasing the average return of the DPVES and improving the local consumption rate of DPV.

Interfacial shear performance of UHPC-strengthened RC structures using post-installed rebar connections: Experiments and analyses

The reliable bonding effect between the ultra-high performance concrete (UHPC) layer and the existing reinforced concrete (RC) components is always expected when UHPC is used to rehabilitate deteriorated RC structures. The post-installed rebar connection has been demonstrated to possess robust mechanical performance. However, no research to date clarifies how to design the post-installed rebar connection in engineering practice. To this end, this study conducted 34 push-out tests to investigate the interfacial shear performance of UHPC-strengthened RC structures using post-installed rebar connections. The primary variables in the tests included strengthening form, embedded depth of rebar, rebar diameter, rebar spacing, and substrate type. Based on the test results, three different failure modes were identified. The analytical results indicate that the embedded depth of the rebar has a significant influence on the performance of the post-installed connection. A formula was proposed to determine the minimum embedded depth, and its accuracy was validated by the physical experiments. The load-bearing mechanisms were revealed based on the experimentally measured force–displacement curves. The shear capacity of the connection mainly comprises the adhesive effect, rebar shearing, and friction. The connection capacity can be approximated by the rebar shear capacity due to its robust shear resistance. Also, a formula was proposed to estimate the shear capacity of the rebar. The experimental and theoretical results facilitate the design and application of post-installed rebar connections in UHPC-strengthened RC structures.

Progressive collapse resistance of reinforced concrete beam-column connection under fire conditions

To reveal the reinforced concrete (RC) structural response under fire-induced progressive collapse scenarios, 3D finite element (FE) models were developed to investigate the effect of high temperatures on the collapse resisting mechanisms of RC beam-column connections. To describe the behavior of RC connections at elevated temperatures, temperature-dependent thermal and mechanical properties of concrete and reinforcing steel were adopted in the 3D FE model. The sequentially coupled thermal–mechanical analysis was performed with the explicit solver in a quasi-static manner. The concrete damaged plasticity (CDP) and ductile damage for metals (DDM) were adopted to better describe the failure of concrete and steel rebar, respectively. The proposed numerical model was validated by experimental data at different temperatures from literature. To understand better the collapse resistance of RC beam-column connections, a new loading scheme was adopted in the developed model. The load capacity of RC connection under fire conditions was investigated analytically and numerically. The effects of top and bottom reinforcement ratios, concrete strength, beam depth and fire severity on the collapse resisting mechanisms were investigated. The regulated chord rotation failure criteria recommended by the U.S. Department of Defense (DoD) were utilized and showed to be conservative on the collapse identification of RC structures under fire conditions.

Effect of additional constraints of push-out test on the mechanical properties of perfobond shear connectors

Perfobond shear connector is widely used in steel–concrete composite structures due to its high ultimate shear capacity, large shear stiffness, and excellent fatigue resistance. The mechanical properties of perfobond connectors are mainly studied by the push-out test. However, the confinement effect caused by the contact friction at the bottom of push-out specimens does not exist in the actual structures. There is also a significant difference in the confinement effect caused by the restrained rebar in the actual structures and push-out specimens. This confinement effect on perfobond connectors may overestimate the shear capacity based on the conventional push-out test. To accurately evaluate the shear capacity of perfobond connectors, four groups of push-out tests are carried out. The effect of the restrained rebar and contact friction on the mechanical properties of perfobond connectors is studied. The test results indicate that the shear capacity of the connectors increase by 19 % under the effect of restrained rebar. However, the improvement of shear stiffness and ductility is slight. Under the effect of contact friction, the shear capacity, the representative slip S0.9U, and representative shear stiffness K0.5U are increased by 24%, 136%, and 31%, respectively. This indicates that the friction force can significantly improve the shear capacity, shear stiffness, and ductility of connectors. The influencing mechanism of the restrained rebar and contact friction on the mechanical properties of connectors is clarified, and a simplified mechanical model of the perfobond connectors is proposed. Finally, an empirical formulae is proposed for the shear capacity of perfobond connectors considering the effect of additional confinement, based on the simplified mechanical model. The shear capacity of the perfobond connectors was predicted well by the proposed formulae.

Single-side yielding precast concrete slotted beam-column connection with replaceable energy dissipation bars: Experimental investigation and finite element analysis

A new type of rebar coupler, non-slipping combined threaded sleeve (NCTS), is proposed, and based on this, replaceable energy dissipation (ED) connector is assembled. An innovative single-side yielding slotted beam-column connection with replaceable ED bars (SYSC-REDB) was developed by placing the ED connector in the beam end bottom of prefabricated concrete frame. Four quasi-static tests were conducted to evaluate the seismic behavior, such as the damage distribution, failure characteristics, hysteretic response, ED capacity, and deformation pattern. The hysteretic curves were stable and full without pinching, indicating excellent seismic performance. The deformation pattern of single-side yielding can enhance the ED capacity of connectors, concentrate damage and failure on the ED bars, and significantly reduce the deformation of the top beam and beam elongation. The joint could be repaired by replacing the ED bars via the inner space of the NCTS. The seismic behavior of the repaired specimens was similar to those of the original specimens. In addition, the finite element models of ED connector and SYSC-REDB joint were established by ABAQUS respectively, and their accuracy were verified by comparing with the test phenomena and results. Furthermore, parametric finite element analysis was executed for some key factors, including the top-hinge area depth, ED bar area, and top longitudinal reinforcement bar area. Theoretical and parametric study of bending moment capacity is also performed.

On Navigating Paranoia, Repair, and Ambivalence as Crip Pandemic Affects, Or, I’m So Paranoid, I Think Your COVID Test Is About Me

How do my 'hermeneutics of suspicion' color this current crisis? In this auto-theoretical essay, I reflect upon the blend of judgment, suspicion, and paranoia that have settled into my body-mind this past year, and how these feelings shape my engagement with people, institutions, and systems. I have been taught that 'judgment' is an essential aspect of immigrant and crip safety. Recently, it has become my (crip)epistemology, and I cannot decide whether this is for better or worse. On the one hand, suspicion is productive. It has kept me and my loved ones alive in a time of deliberate death. On the other, it frustrates, disrupting my capacity for connection. I check my temperature constantly, I hear the guilt in my voice when my family in India tell me they have not left the apartment in months, I spend precious time with friends calculating their risk relative to mine, I go to protests but am afraid of the consequences of my solidarity. Drawing on Eve Sedgwick's essay on paranoid reading practices, Patricia Stuelke's Ruse of Repair, Sianne Ngai's work on ugly feelings, Nikolas Rose's analyses of somatic ethics, and Mel Chen's theory of racialized toxins, I explore the modalities that paranoia has both enabled and disabled for me. I examine my ambivalent relationship with repair—some reparative practices like mutual aid sustain queer/crip/immigrant community while others like cure constrict our lives. This piece aims to tease out the tensions latent in crip worldmaking between suspicion and generosity, public health and communal care, and paranoia and repair.

Review: The Post-Screen Through Virtual Reality, Holograms and Light Projections: Where Screen Boundaries Lie, by Jenna Ng

Review: <i>The Post-Screen Through Virtual Reality, Holograms and Light Projections: Where Screen Boundaries Lie</i>, by Jenna Ng

Bolt-bearing strength parallel and perpendicular to the grain of four Indonesian hardwoods

Bearing strength is an important factor in determining the load-carrying capacity of a bolt-timber connection besides the bolt-bending yield strength. This study aims to determine the bolt-bearing strength parallel and perpendicular to the grain using three bolt diameters (6, 9 and 12 mm) in four hardwoods species with different specific gravities, namely terap (Artocarpus odoratissimus), durian (Durio zibethinus), mindi (Melia azedarach L) and rubberwood (Hevea brasiliensis Muell. Arg). The bolt-bearing strength was determined as described in ASTM D5764 using half-hole testing. The moisture contents ranged from 13.49–14.77% and specific gravities were 0.33–0.60. The higher the specific gravity, the higher the bearing strength. The bearing strength values parallel to the grain were higher than those perpendicular to the grain. The bearing strengths parallel to the grain were 3–18% and 2–24% lower than those based on the Indonesian National Standard (SNI) 7973 and National Design Specification (NDS) for Wood Construction 2015, respectively. In contrast, the experimental bearing strength of mindi was 8% higher than the SNI. Except for mindi, which was 22% exceed SNI and 9% above NDS, bearing strengths perpendicular to the grain were 3-32% and 14-41% less than values based on SNI and NDS, respectively.

Seismic performance of self-centering concrete-filled square steel tubular column-to-steel beam connection equipped with SMA bolts

This study demonstrates the considerable potential of the combined application of superelastic NiTi shape memory alloy (SMA) bolts and brass friction energy dissipation devices for self-centering connections to effectively deal with both the large residual drift and lower energy dissipation of traditional connections after an earthquake. Cyclic tests were conducted on eight 1/2 scaled concrete-filled square steel tubular (CFSST) column-to-steel beam connections, including seven T-stub steel connections with SMA bolts and one conventional T-stub steel connection with normal high-strength bolts. The mechanical behavior of the connection was analyzed considering the effect of the pre-strain of the SMA bolt and the pretension force in the friction bolts through web friction devices (WFDs). The results showed that the SMA connection specimen exhibited recognizable double-flag-shaped hysteretic responses with excellent recentering ability and moderate energy dissipation capability, and the primary structural components remained elastic after each cyclic loading. The self-centering capacity of the SMA connection increases with an increase in the pre-strain of the SMA bolt, and the energy dissipation capacity of the SMA connection increases with an increase in the pre-tension force in the friction bolts. Moreover, the SMA self-centering connection has good shock resistance and repairability. After an earthquake, the seismic performance of the SMA connection can be quickly restored by replacing the T-stub steel.

Numerical analysis on corrosion and mechanical performance of shear stud connector in concrete

Geometric shape of shear stud connector plays an important role on its connecting capacity in steel-composite structures. Recent application of steel–concrete structures showed the degradation of structural performance due to aggressive medium from environment. Available research indicated that the presence of chloride ions in concrete induced depassivation on the surface of steel shear stud connector and resulted in its corrosion accordingly. Thus, it is essential to obtain the corroded shape of shear stud connector for further accurate assessing structural performance of steel–concrete composite structure. As the focus of this paper, based on Fick's second law and Butler-Volmer equation, a quantitative simulation method for reaction of corrosion in steel–concrete composite structures was introduced and discussed. Wherein, two steps of this approach were listed. Firstly, mass transportations of chloride ion, oxygen and hydroxide were simulated for their concentration for preparation of electrochemical reaction. Secondly, electrochemical reaction of Ferrum with presence of oxygen and water, catalyzed by chloride ion, was numerically simulated. Furthermore, two cases of ingression of chloride ion into concrete were discussed for the influence of boundary condition on structural characteristics of steel–concrete composite structure. Random distribution of aggregate in concrete was considered. Result of numerical simulation indicated that, corrode shape of shear stud connector was related to configuration of boundary condition and different pull-out performance were obtained by finite element analysis. Moreover, degradation of mechanical properties of shear stud during its service life were provided.

Uncovering university students’ communication patterns and limiting factors in an Indonesian online learning context using WhatsApp

WhatsApp group is one of the most widely used online learning media. Communication patterns in the online teaching and learning processes are influenced by this media. This platform affects communication patterns in the online learning process. However, some students felt they did not enjoy teaching and learning using WhatsApp group. This qualitative study explored WhatsApp group as a communication pattern in teaching and learning process in a university, using observation and semi-structured interviews analyzed by using the concept from Tubbs, to gather data from five higher education students and a lecturer. Study findings expose that WhatsApp groups gave freely for higher education students to communicate. However, the social media showed weaknesses during the teaching and learning process, including poor internet connection and low phone memory capacity. The students seemed to be not disciplined. They could not regulate their time to learn. They could cheat the answer of their peers. In this regard, the lecturer had to be creative to encourage students’ participation. Therefore, the lecturer had some strategies to overcome it. The lecturer should be able to provide feedback to all students, create a fun class, and control students to be involved in class.

Effect of Interlayer and Inclined Screw Arrangements on the Load-Bearing Capacity of Timber-Concrete Composite Connections

The solution of timber-to-concrete composite (TCC) floors represents a well-established construction technique, which is consistently used for both the retrofitting of existing timber floors and the realization of new diaphragms. The success of TCC floors relies on the intrinsic effectiveness in increasing both the in-plane (for lateral loads) and the out-of-plane (for gravity loads) performance of existing timber floors. As a widespread retrofit intervention, it is common to use existing floorboards as a permanent formwork for the concrete pouring. Rather few research studies of literature, in this regard, highlighted an overall reduction of load capacity and slip modulus due to the presence of such an interposed interlayer. In this regard, the present paper focuses on the use of screws as efficient mechanical connectors and analyses different configurations and inclination angles for their arrangement. This main goal is achieved by performing parametric Finite Element (FE) numerical analyses, validated on previous experimental tests, in order to specifically investigate the influence of the in-between interlayer, as well as the role of friction phenomena and the influence of the test setup and experimental protocol to achieve the basic mechanical performance indicators.

Strengthening of slab-column connections using ultra high-performance fiber concrete

This experimental work intends to assess the efficiency of employing ultra-high-performance fiber concrete (UHPFC) as a strengthening system for improving the punching shear capacity of slab-column connections (SCCs). Seven reinforced concrete SCCs were constructed and tested under axial load. One of them was retained as a control slab (un-strengthened), and the other six were strengthened with different strengthening schemes. The results revealed that the strengthening scheme is effective in improving the punching shear capacity of slab-column connections significantly. Strengthened slabs achieved increases in punching shear capacity, pre cracking stiffness, post-cracking stiffness, and toughness of up to 172.68 %, 235.70 %, 300 %, and 233.59 %, respectively. It turns out that it is important to use UHPFC with longitudinal reinforcement (R-UHPFC) to enhance the strength and toughness. Finally, the punching shear capacities of the tested specimens were compared to those predicted by the existing theoretical approach.

Behavior of horizontal steel plate + studs connectors in a glulam-UHPC composite system: Experiment and analysis

Compared with conventional timber–concrete composite structures, glued laminated timber (glulam)–ultrahigh–performance concrete (UHPC) composite (GUCC) structures can remarkably reduce the deadweight and have small long-term deflection, good durability, and improved span capacity. Thus, this work designed a horizontal steel plate + stud (HS) connector with high stiffness and high shear capacity to ensure a reliable connection in the designed glulam–UHPC composite system and then investigated the structural behavior of the HS connector in the GUCC. In total, fifteen push–out specimens (in five groups with three replicates of each group) were fabricated and conducted a static load test. Effect of size of steel plate, the height-diameter ratio of stud, size of slab, and slab type (UHPC or NC) on the load-slip rules, shear stiffness, failure mode, and the shear capacity of HS connectors in GUCC were evaluated experimentally. The experimental results show that the average slip modulus and shear capacity of the HS connection ranges from 134.9 to 165.6 kN/mm and from 167.6 to 200.3 kN respectively. The primary failure mode of the structure comprises the shear failure of the glulam along the grain and the studs. Lastly, the empirical formula for calculating the load–slip relationship and the design formula for the shear capacity of the HS connection of GUCC systems are proposed. A comparison between the theoretical and experimental results reveals that the developed method has reasonable accuracy and can be used to guide the design of GUCC structures.

Examining the Use of Mobile Technology to Deliver Tailored Sexual Assault Prevention in a Classroom Environment in the Military: Development and Usability Study.

Advances in mobile technology over the last 10 years have expanded its use in scientific research. However, there are challenges in creating a reliable system for intervention content delivery and data collection in an environment with limited internet connectivity and limited staffing capacity. The Sexual Communication and Consent (SCC) study used tablets to provide individualized Sexual Assault Prevention and Response training in a classroom environment that was both technologically and support staff limited. We developed the SCC Basic Military Training app and a separate Sexual Assault Response Coordinator app to support individualized training within the new SCC program. This paper presents the functionality, protocols, challenges, and feasibility of deploying mobile technology in an educational environment in the military with limited resources. We developed both mobile apps targeting the Apple iOS ecosystem. The Basic Military Training app provided a screening instrument that routed the trainee into 1 of 5 specific intervention programs. Over 2 days of basic military training set 2 weeks apart, trainees received a combined 6 hours of program-specific tablet training, combined with universal, interactive classroom training, led by qualified instructors. The Sexual Assault Response Coordinator app, used to deliver supplemental content to a subgroup of trainees, was made available for voluntary and private use at the Sexual Assault Response Coordinator's office on base. All anonymous data were manually transferred onto laptops, where the data were aggregated into files and securely transferred to the project staff for analysis. The study was conducted at the Lackland Air Force Base, Joint Base San Antonio, with 9196 trainees providing the data. A total of 7742 trainees completed both the sessions of the SCC program and a series of evaluative assessments. Some trainees did not receive day 2 training, and only received day 1 training because the COVID-19 pandemic shortened the study period. Of the 190 SCC classes taught, only one class was unable to complete tablet training because of Apple licensing-related technology failure. The 360 study tablets were distributed across 3 classrooms (120 per classroom) and were handled at least 16,938 times with no reports of breakage or requiring replacement. Wi-Fi access limitations exacerbated the complexity of Apple licensing revalidation and the secure transfer of data from the classroom to project personnel. The instructor staff's limited technical knowledge to perform certain technical tasks was challenging. The results demonstrated the feasibility of deploying a mobile app for tablet-based training in a military educational environment. Although successful, the study was not without technical challenges. This paper gives examples of technical lessons learned and recommendations for conducting the study differently, with the aim that the knowledge gained may be helpful to other researchers encountering similar requirements.

Research on non-communication protection of distribution line considering new energy access

The large-scale access to new energy sources turns the traditional single-power radiation distribution line into a complex network. At the same time, the fault characteristics of new energy sources will also cause the change in the magnitude, direction and distribution of short-circuit current in the distribution network. It leads to the misoperation or refusal of the traditional three-stage. Scholars at home and abroad have researched distribution network protection considering new energy access. On the one hand, the impact of new energy access on current protection can be reduced by limiting the grid connection capacity of new energy sources or using short-circuit current limiter. On the other hand, improving the protection performance by changing the protection scheme. This paper begins with a brief analysis of a two-phase fault in a distribution line connected to a DG. Then proposes a new protection scheme based on non-communication protection. Set the grid connection point as the protection segment point, and detect the tide direction and fault direction. If it is determined to be the source side, overcurrent protection will be activated. If it is determined to be the load side, undervoltage protection will be activated. Cooperate with other protection segment points on the distribution line to realize accurate and selective fault isolation. Finally, the correctness of the proposed protection scheme is verified by simulation.

Cyclic behavior of column-to-column connections in novel prefabricated H-shaped steel beam to CFST column joint

This paper presents a novel form of prefabricated H-shaped steel beam to concrete-filled steel tubular (CFST) column joints. The behavior of such novel beam-to-column joints was investigated through cyclic loading tests on four joint specimens. The examined parameters included the thickness and the yield stress of the column steel tube, and the distance between the transfer sleeve and the flange of the steel beam. The hysteretic behavior, failure modes, flexural stiffness and capacity, and energy consumption of the joint specimens were discussed in detail. Particularly, the effectiveness of the proposed column-to-column connections, which are critical sections of the proposed joints, in transferring bending moments between column segments was evaluated. The test results indicated that the proposed beam-to-column joints exhibited great flexural capacity and energy dissipation capacity. It was also found that the thickness and yield stress of the steel column tube significantly affect the flexural capacity of the column-column connection and the shear deformation of the panel zone. Finally, accurate finite element model was developed for the prediction of main mechanical properties, such as initial stiffness, yield strength, and maximum strength.

An Optimized and Energy-Efficient Ad-Hoc On-Demand Distance Vector Routing Protocol Based on Dynamic Forwarding Probability (AODVI)

MANET (mobile ad-hoc network) is a wireless ad-hoc network made up of mobile devices that use peer-to-peer routing to provide network access instead of using a preexisting network infrastructure. Despite the network infrastructure’s simplicity, it faces issues such as changeable connection capacity, dynamic topology, node battery power exhaustion, and inadequate physical security. Broadcasting is a standard MANET approach for sending messages from a source node to all other nodes in the network. Flooding is a frequent method for broadcasting route request (RREQ) packets, which is susceptible to broadcast storms. The high retransmission rate is caused by the standard flooding technique, which causes media congestion and packet collisions, which can drastically reduce throughput and network performance. In a mobile ad-hoc network, efficient broadcasting focuses on selecting a compact forward node set while assuring broadcast coverage. The goal is to find a limited number of forward nodes that will provide complete coverage. In this paper, we propose an optimized and energy-efficient routing protocol for MANET (mobile ad-hoc network) based on dynamic forwarding probability in general and AODV (ad hoc on-demand distance vector) in particular, in which the route request packets are randomly controlled to increase the network lifetime and reduce packet loss in the flooding algorithm. We tested and assessed the results of our proposed solution using various network performance factors after implementing and integrating it into NS-2. According to simulation findings, our proposed technique effectively reduced route request propagation messages (RREQ). The suggested technique is more efficient, has a longer network lifetime, and uniformly utilizes node residual energy, enhancing network throughput and minimizing routing overhead when compared to regular and modified AODV protocols.

Experimental and analytical investigation of innovative wing plate headed stud shear connector in composite structures

The most widely employed components in concrete-steel composite constructions to achieve composite action are headed stud shear connectors. Although headed studs are widely employed, their behaviour causes shank failure at the interface, and incomplete composite action is unfair due to unused residual concrete strength. This study intended to enhance the shear capacity of the stud by enlarging its bearing area by introducing triangular-shaped steel wing plates at the base of the stud on either side of it. The effectiveness of integrating wing plates to the headed stud on the shear carrying capacity of composite connection was evaluated using experimental testing on ten pushout specimens. Ultimate shear capacity, ductility, stiffness, and modes of failure were investigated. Furthermore, the ABAQUS dynamic-explicit has been used to analyse the pushout specimens. A proposed modelling strategy used for further parametric analysis was validated with the test results. For the parametric research, two different grades of concrete and wing plate sizes were evaluated. The innovative stud's performance was compared with the traditional stud, demonstrating that the suggested studs give 34–74 per cent greater shear capacity, increased stiffness, and slip with superior ductility. Finally, based on the FE parametric and regression analysis, two equations for predicting the shear strength of the wing plate headed stud shear connector was developed and proposed for composite constructions.

Hydroelectric operation for hybridization with a floating photovoltaic plant: A case of study

Hybrid renewable systems increase electricity production by reducing the randomness of sources without greenhouse gas emissions. Literature indicates that further research is still required for large systems connected to the grid. The energy storage capability of hydroelectric plants provides an opportunity to develop new renewable energy generation.This work presents the results of a hybrid preliminary design between an existing hydropower plant (HPP) in Brazil, Santa Branca, and a simulated floating photovoltaic plant (FPV), occupying only 2.8% of reservoir's surface. The study analyzed 20 years of HPP historical data, the methodology proposed the injection of the FPV full power into the system during daytime and the HPP adjusting the production. As this process changed the HPP generation profile, operational limits such as reservoir level needed to be verified.In the period, while HPP generated about 4 TWh, the FPV could add 2 TWh without significantly changing the daily generation of HPP. This increase of 50% in production was possible since there was space available in the reservoir to store water during the day and use it during the night, working as a free virtual battery for the FPV. A 50% increase of the grid connection capacity factor was also observed.