Bar Connection Research Articles

Experimental Studies on Portal Frames made with Palm oil Shell Light Weight Fiber Reinforced Concrete

This present research mainly focused on the behaviour of monolithically and precast portal frames made with lightweight fiber reinforced concrete. The lightweight fiber reinforced concrete (LWFRC) is achieved with Palm oil shells (POS) and glass fibers (G.F). The POS is replaced with coarse aggregates and the G.F is added to the concrete to increase ductility parameters. To reduce the further density of the concrete, replaced cement with GGBS and Palm Oil Fuel Ash (POFA) individually. All these replacements are helping the reduction of solid waste and greenhouse gases from cement Industries. Portal frames are made with M30 Grade LWFRC through replacements. All the precast frames are connected with the Dowel bar connection through the grouting. All the LWFRC frames are compared with conventional concrete frames. The palm oil shells are replaced up to 50% in coarse aggregates to diminish the density of the concrete and also to decrease the greenhouse gases from the cement industry; cement is replacing with Ground Granulated Blast Furnace Slag (GGBS) and Palm Oil Fuel Ash (POFA).

Anchorage behaviour of headed bars as connection system for precast reinforced concrete structural components

Precast reinforced concrete (RC) structural joint is a critical region which demands appropriate connection system for adequate shear transfer. Prevalent dowel bars connection for precast components is prone to damage during the seismic motion. This paper proposes an innovative modified dowel bar connection, termed as headed bars, wherein the reinforcement bars are attached to the steel head anchor through welding and embedded into the concrete. To investigate the anchorage behaviour of headed bars, pull-out tests were conducted on a total of 144 specimens, which were differentiated on the parameters of head profile i.e., plain, grooved, ribbed and without head (representing dowel bar); varying length of the head and varying embedment depth into the concrete. The anchorage behaviour of headed bars was studied from the standpoint of failure mode, bond capacity and slip of bar. Dowel bars demonstrated pull-out failure with low bond capacity, whereas headed bars exhibited slip of bar and concrete failure along with higher bond capacity. Based on the experimental results, geometrical specifications for headed bars are recommended. A numerical analysis was carried out to evaluate the efficacy of headed bars as a connection system, where precast RC wall and columns connected using headed bars of proposed geometry were subjected to displacement controlled lateral loading and compared with the structural performance of connection using conventional dowel bars. Numerical analysis exhibited superior performance of precast RC wall-columns connected through headed bars in comparison to the dowel bar connection.

Enhancing the Seismic Performance of Precast RC Frames with Cladding Panels through Setting U-Shaped Dampers and Rocking Walls

An approach combining U-shaped dampers (USDs) and rocking walls is proposed in this paper to improve the seismic performance of traditional precast reinforced concrete (RC) frames with cladding panels (PRCFCPs): (1) the steel bar and USD connection methods are adopted at the top and bottom of the cladding panels to use the relative deformation between the cladding panels and the main structure and then dissipate the seismic energy and (2) rocking walls are added to the structure to control the structural deformation profiles. The USD numerical model is calibrated using the test data, and a series of nonlinear pushover analyses, dynamic time-history analyses, and incremental dynamic analyses are successively performed to compare the seismic performance and collapse capacity of the PRCFCP, PRCFCP with USDs (PRCFCP-USD), and PRCFCP with USDs and rocking walls (PRCFCP-USD-RW).The results show that the USDs in the PRCFCP-USD-RW undergo more uniform deformation along the structural height and higher energy dissipation efficiency and the PRCFCP-USD-RW exhibits enhanced seismic performance and collapse capacity, which verify the superiority of the proposed combined approach.

Dynamic load test on progressive collapse resistance of fully assembled precast concrete frame structures

The progressive collapse of reinforced concrete (RC) and precast concrete (PC) structures is one of the most critical failure scenarios and is consequently of great concern to the structural engineering community. In this study, two half-scale RC and PC moment sub-structures were designed to evaluate the progressive collapse performance under a sudden mid-column loss scenario. In the PC specimen, the beam-column connection was fully assembled using the dowel bars embedded in a corbel, and steel angle cleats were applied to the connection between the upper surface of the beam-end and column to further transmit the flexural moment. The beam-column joint was strengthened by horizontal hoops and U-shaped bars. The dynamic responses such as the load-carrying capacity, beam deflection, lateral displacement, failure modes, crack distribution, and rebar strains were evaluated. The test results showed that the load-carrying capacity of the PC specimen was 76.9% of that of the RC specimen, while the ultimate deflection of the mid-column in the PC specimen was 106.1% of that of the RC specimen. Ultimately, shear failure occurred in the dowel bar connection of the PC specimen. On the other hand, ductile failure occurred by fracture of beam rebars in the RC specimen. Under dynamic loading, compressive arch action (CAA) was developed in the both specimens, but the effective catenary action (CTA) was developed in the RC specimen only. Finite element analysis was performed, and the analysis results agreed well with the test results. The dynamic test results and analysis results showed that the RC specimen exhibited better progressive collapse performance than the PC specimen.

Stress-strain behaviour of steel bars with long nut connection

The reinforcement of reinforced concrete always needs a connector. In order to reduce the overlapping length, the long nuts are used as steel bar connector. The tensile experimental test was obtained to find out the value of yield stress, ultimate tensile strength, elongation and ductility which can be achieved by steel bar long nut connection. The test was using UTM machine instrument which connected to the computer, thus stress-strain curve is obtained. The curve shows the values of elastic, plastic, strain hardening until ultimate tensile strength region, value of yield stress Fy, and ultimate tensile strength Fu. The result of tensile tests how’s that the yield stress value of steel bar with long nut connection has the same value with the steel bar without connection. The steel bars with long nut connection can achieve yield stress about 330 MPa, ultimate tensile strength about 340 MPa and strain value about 5%-6%, it is lower than the steel bars without connection. It indicates that long nut can be used as a connector tool in overlapping steel bar connection.

Twin-box ITER joints under electromagnetic transient loads

The ITER Toroidal Field (TF) coil winding packs are designed to be wound in double-pancakes. The twin-box joint provides the electrical pancake-to-pancake connection between the two Nb3Sn 68kA conductors and electrical coil-to-bus bar connection between the TF coil terminations and NbTi 68kA bus bars conductors.The twin-box full size joint sample connecting two Nb3Sn conductors (pancake-to-pancake joint) was prepared in order to qualify the TF joint assembly in SULTAN Test Facility. The original goal of the test program was the measurement of joint resistance at different operating conditions. The accidental dump of the SULTAN background field caused a noticeable increase of resistance due to the induced electromagnetic transient load. The TF joint test was continued in order to investigate a change of joint resistance following electromagnetic transient loading which was triggered by intentional dump of the background field. Also, a dependence of the joint resistance on current was observed; in order to explore the origin of resistance change, additional experiments were performed with a modified (artificially degraded) TF twin-box joint.The test results of a TF twin-box joint after electromagnetic transient loading and performance of the joint after a modification are presented in this paper. The performance of Nb3Sn 68kA conductor observed during those tests is highlighted as well.

Constructing large-scale tensegrity structures with bar–bar connection using prismatic elementary cells

As a novel type of light-weight and reticulated structures, tensegrities have found many technologically important applications. In this paper, a facile method is developed to construct a class of large-scale tensegrities consisting of bar–bar connection using prismatic elementary cells. We tune the orientation of the structural axis of each cell by the affine transformation technique. Then, the cells can be assembled easily in any directions required by the structural design. The method proposed here allows us to construct various types of large-scale tensegrity structures satisfying the demands of sizes and topology. A number of representative examples are provided, including straight and curved beams, plates, shells, and three-dimensional large-scale tensegrities.

Based on the Principles of Mechanical and Electronic Multi-Function Love Gyro Design Research

based on the principle of mechanical and electrical design of multifunctional love gyro can be made by a support bar connection, have the function of barbell, two combined weight is moderate, can exercise and arm strength. Cixin gyro high-grade, durable, suitable weight, to a certain speed issued a similar to the sound of diabolo, due to the tuyere is stainless steel material, can the thrum gyro is more pleasant than other materials, suitable for adults whipped (especially middle-aged and old friends) can strengthen physical health treatment of periarthritis of shoulder, can lose weight again.

Characterization and Reliability of Sintered Nanosilver Joints by a Rapid Current-Assisted Method for Power Electronics Packaging

A rapid current-assisted sintering technology (CAST) was used to bond electronic devices with nanosilver paste, which is a promising alternative compared with traditional solders. Instead of using an external heating source, the specimen and bonding material of nanosilver paste were heated by the alternating current whose current direction is not constant. Die-shear testing and hardness measurement were used to evaluate the bonding strength. The bonding strength and hardness increase with increasing the current and/or current-on time. CAST was able to sinter nanosilver in a very short time, i.e., less than 1 s. Scanning electron microscopy was used to characterize the microstructures of sintered silver joints. The reliability of the sintered joints by CAST was also evaluated by cyclic shearing tests. The joint by CAST could survive much longer time than that by the conventional hot pressing way. The CAST was recommended to bond two pieces of bare copper with nanosilver paste in power electronic applications without any protective gas atmosphere, e.g., bus bar connection.

STATCOM and Capacitor Banks in a Fixed-speed Wind Farm

Wind Farms are the viable solution for delivering clean energy in near future. There are many difficulties in ensuring higher quality power into the grid, as demanded by the more and more stringent grid codes. The solution of these problems could be solved by Flexible Alternate Current Transmission Systems (FACTS) devices in the system and particularly the Statatic synchronous condenser (STATCOM). Which uses the principle reactive power (injection or absorption).One of the main causes of disconnection of wind network is the variation of voltage (drop voltage or over voltage) at the bus bar connection. The use of STATCOM, allows regulating the voltage and maintaining the grid connected wind even under certain severe conditions of disturbance.In this paper, we propose a study of the importance use of STATCOM when it installed in a wind farm and we will try to see the effect of injecting reactive power in order to maintain the voltage at the nominal value. This opportunity offers the possibility of connecting the wind farm to the grid. The choice of this study is justified by simulation in MATLAB.

The influence of desensitizing dentifrices on pain induced by in-office bleaching

The purpose of this study was to evaluate whether the use of desensitizing dentifrices used 15 days prior to and after in-office tooth bleaching could eliminate or reduce tooth sensitivity. After institutional review board approval and informed consent, 45 subjects were selected and divided into 3 groups according to the dentifrice selected: Colgate Total (CT), Colgate Sensitive Pro-Relief (CS) or Sensodyne ProNamel (SP). The subjects used toothpaste and a toothbrush provided to them for 15 days prior to bleaching. They were then submitted to two in-office bleaching sessions (Whiteness HP Blue Calcium). Their tooth sensitivity was assessed using the Visual Analog Scale (VAS) for a week after each session. Their tooth shade alteration was measured with a Vitapan Classical shade guide to determine if the dentifrices could influence the effectiveness of the bleaching agent. The data were submitted to Wilcoxon, Kruskal-Wallis and Mann-Whitney tests (α = 0.05). The use of desensitizing dentifrices did not affect the bleaching efficacy. In regard to tooth sensitivity, there was a statistically significant difference between the results of the Control Group and Group T2 after the first session (p = 0.048). There was no statistically significant difference in the results for the other groups after the first session. In regard to the second session, there was no statistically significant difference in the results for all the groups. The use of a desensitizing dentifrice containing nitrate potassium reduced tooth sensitivity during the bleaching regimen. Dentifrices containing arginine and calcium carbonate did not reduce tooth sensitivity. Color change was not influenced by the dentifrices used.

Quality of Life of Patients Treated With Implant-Supported Mandibular Overdentures Evaluated With the Oral Health Impact Profile (OHIP-14): a Survey of 58 Patients

ABSTRACTObjectivesThe purpose of this study was to evaluate the oral health-related quality of life of patients treated with implant-supported mandibular overdentures and to compare the attachment systems used.Material and MethodsAltogether 112 patients treated with implant-supported mandibular overdentures in 1985 - 2004 were invited to the follow-up; 58 of them attended and replied to the Oral Health Impact Profile (OHIP-14) -questionnaire. There were 48 overdentures with a bar connection and 10 with a ball connection, the total number of implants installed and still in use was 197. The mean follow-up time was 13.7 years. The associations between the OHIP-14 variables and the patient's age, gender as well as the number of implants supporting the overdenture and the type of attachment used were assessed.ResultsThe results showed that patients with implant-supported mandibular overdentures were satisfied with their oral health-related quality of life (OHRQoL). Older patients were more satisfied than younger ones in both genders. Neither the implant connection type nor the number of supporting implants seemed to have a significant influence on the OHRQoL.ConclusionsEspecially older patients with mandibular implant-supported overdentures were satisfied with their oral health-related quality of life. Attachment type or the number of supporting implants did not have a significant influence on the oral health-related quality of life.

Experimental study of telescopic steel bar connection technology in precast pier

Experimental study of telescopic steel bar connection technology in precast pier

Tensile Capacity of Mechanical Bar Connection Corresponding to Detail of Screw on Bar Surface for Construction

This study is intended to investigate the performance depending on the screw type at the end part of reinforcement in the mechanical connection of high strength reinforcement with screws. Three types of mechanical connection were designed and tensile test was performed for those. The results presented that, although the end part of reinforcement was processed with screws, the reinforcement’s yield and tensile strength sufficiently appeared. But, its plastic deformation capacity after yielding fell 17~26% more than reinforcement.

Test on Hybrid Connection for Steel Bars in Concrete

The steel bar connection is an important and inevitable work in civil engineering. The traditional overlapped connection method usually needs to place the transversal rebars in the overlapped splicing area to restrict the splitting cracks in concrete. The steel usage and labor cost are increased. An improved splice, which is the hybrid connection of welding and overlapping, was developed for mid-diameter bars, which is easy to install and has commendable mechanical behavior. A series of reinforcing rebar splice tests with steel-concrete interaction were conducted. The failure model of hybrid connection and the ultimate strength were acquired. Based on the tests, the failure mechanism of hybrid connections was analyzed. The results show that the ultimate load of the new splice is sufficient for the engineering application and the failure model is reasonable. The hybrid connection could be used in the engineering practice.

Outcome of implant‐supported overdenture treatment – a survey of 58 patients

The aim of this follow-up study was to evaluate the long-term outcome of implant-supported or implant-retained mandibular overdenture treatment. Altogether 112 patients treated with implant-supported overdentures between 1985 and 2004 were invited to the follow-up and 58 attended the clinical examination. The total amount of implants examined and still in use was 197. The average number of implants installed was three (range 2-4), and the mean length of the implants was 12 mm (range 8-21 mm). There were altogether 48 overdentures with a bar connection and 10 with a ball connection. The most frequent prosthetic complications were technical: loosening of the retentive mechanism (39.7%) and breakage of the matrices (5.2%). The most common peri-implant soft-tissue findings were bleeding and slight hyperplasia. The implant-supported overdentures of 19 patients (32.8%) had been renewed, while 39 patients (67.2%) still used their original overdentures, of which the oldest was 20 years old. The results of this long-term follow-up study show that the outcome of implant-supported mandibular overdenture treatment was excellent. The patients were satisfied with the treatment, regardless of the attachment type used. Removable overdentures are more easy to clean and can be cleaned outside the patient's mouth, whereas fixed-implant full-arch dentures in the edentulous mandible require much more time-consuming hygiene. This kind of overdenture treatment is suitable also in the elderly, even though their ability to practice appropriate oral hygiene might be decreased.

Experimental study on two types of new beam-to-column connections

The new structure consisting of continuous compound spiral hoop reinforced concrete (CCSHRC)column and steel concrete composite (SCC) beam has both the advantages of steel structures and concrete structures. Two types of beam-to-column connections applied in this structural system are presented in this paper. The connection details are as follows: the main bars in beam concrete pass through the core zone for both types of connections. For connecting bar connection, the steel I-beam webs are connected by bolts to a steel plate passing through the joint while the top and bottom flanges of the beams are connected by four straight and two X-shaped bars. For bolted end-plate connection, the steel I-beam webs are connected by stiffened extended end-plates and eight long shank bolts passing through the core zone. In order to study the seismic behaviour and failure mechanisms of the connections, quasi-static tests were conducted on both types of full-scale connection subassemblies and core zone specimens. The load-drift hysteresis loops show a plateau for the connecting bar connection while they are excellent plump for bolted end-plate connection. The shear capacity formulas of both types of connections are presented and the values calculated by the formula agree well with the test results.

Implant-Retained Mandibular Bar-Supported Overlay Dentures: A Finite Element Stress Analysis of Four Different Bar Heights

Proper stress distribution on dental implants is necessary in bar-retained implant overlay dentures. We aimed to comparatively assess this stress distribution according to different bar heights using finite element models. A three-dimensional (3D) computer model of mandible with 2 implants (ITI, 4.1 mm diameter and 12 mm length) in canine areas and an overlying implant-supported bar-retained overlay denture were simulated with 0-, 1-, 2-, and 3-mm bar heights using ABAQUS software. A vertical force was applied to the left first molar and gradually increased from 0 to 50 N. The resultant stress distribution was evaluated. Bars of 1 and 2 mm in height transferred the least stress to the implants (3.882 and 3.896 MPa, respectively). The 0-mm height of the bar connection transferred the highest stress value (4.277 MPa). The amount of stress transferred by 3-mm heights of the bar connection was greater than that of 1- and 2-mm bar connections and smaller than that of 0-mm bar connection (4.165 kgN). This 3D finite element analysis study suggested that the use of Dolder bar attachment with 1- and 2-mm heights could be associated with appropriate stress distribution for implant-retained overlay dentures.

Fatigue Crack Initiation and Growth in a High Loaded Bolted Bar Connection

The fatigue crack initiation and growth in a high loaded bolted bar connection made of high strength steel S1100Q is presented. The material parameters for the fatigue crack initiation f’, f’, b and c are determined using low cycle fatigue test according to ASTM E 606 standard. The fracture mechanics parameters C and m are determined according to ASTM E 647 standard. Based on low cycle fatigue parameters the computational analysis is performed to determine the number of stress cycles required for the fatigue crack initiation. The remain service life up to the final failure is than determined using the known parameters C and m and calculated stress intensity factor, where 3D numerical analysis is performed. The bolted bars are also experimentally tested. Comparison of computational and experimental results shows a reasonable agreement.

Fatigue Assessment of High Loaded Bolted Bar Connection Using Strain-Life Approach

The paper deals with the problem of service life evaluation of counterweight bar bolted connection by means of computational analysis and experimental testing. Computational analysis has been performed using the local strain-life approach (ε-N), where appropriate material properties for treated high strength steel S1100Q has been determined previously. Experimental fatigue tests of bars were carried out in a specially constructed hydraulic pulsation machine. Comparison of computational and experimental results shows a reasonable agreement.