Mechanical Splices Research Articles

An experimental comparison of RC beam-column joints incorporating different splice methods in the beam

Reinforcement ratio and bar splice methods have an indubitable effect on the behavior of RC beam-column joints. The present experimental study is focused on evaluating the influence of parameters including reinforcement ratio of beams, method and number of splices on the performance of RC beam-column joints under dynamic loads. To aim this goal, four RC beam-column joints with different numbers of forging (GPW) or mechanical splices (threaded couplers) in the longitudinal bars of beams were tested under cyclic and axial loads applied to beams and columns, respectively. Force-drift hysteresis curves are provided and seismic parameters including displacement ductility, absorbed energy and stiffness are investigated and discussed. More importantly, the results of this study are compared to the results of other specimens available in the literature with similar splice methods but different reinforcement ratio examined under the same loads in order to figure out the effect of reinforcement ratio on the performance of joints with bar splices. Results indicated that the joints incorporating forging method exhibited more appropriate response in comparison to those with threaded couplers by showing more ductility, absorbed energy and stiffness. Moreover, it was observed that reinforcement ratio does not significantly affect stiffness of the specimens with different numbers and types of splices whereas ductility and absorbed energy changes remarkably by changing types and numbers of spliced bars when reinforcement ratio alters.

Non-contact lap splice connections for steel-plate composite walls - to - reinforced concrete structures

Non-contact lap splices may be considered for connecting steel-plate composite (SC) walls to conventional reinforced concrete (RC) structures. This connection type is preferred over mechanical splice connections because of perceived construction efficiency. The primary components of the non-contact lap splice connection are the steel rebars, which are fully developed in the RC structure and extended and embedded in SC walls to transfer tensile stresses to the steel faceplates. The structural performance of a non-contact lap splice connection depends on the detailing of rebars (embedment length and location relative of stud anchors) embedded in SC walls, and the design of stud anchors (spacing and size) along the rebar length. This paper presents the results of experimental investigations conducted on SC-to-RC non-contact lap splice connections to evaluate the influence of various design and detailing parameters on structural performance, failure modes, and the ability to develop full-strength connection design. Design recommendations developed previously for SC-to-RC non-contact lap splice connections were reviewed and modified based on the results of experimental investigations.

Reflective fiber fault detection and characterization using long short-term memory

To reduce operation-and-maintenance expenses (OPEX) and to ensure optical network survivability, optical network operators need to detect and diagnose faults in a timely manner and with high accuracy. With the rapid advancement of telemetry technology and data analysis techniques, data-driven approaches leveraging telemetry data to tackle the fault diagnosis problem have been gaining popularity due to their quick implementation and deployment. In this paper, we propose a novel multitask learning model based on long short-term memory to detect, locate, and estimate the reflectance of fiber reflective faults (events) including the connectors and the mechanical splices by extracting insights from monitored data obtained by the optical time-domain reflectometry principle commonly used for troubleshooting of fiber optic cables or links. The experimental results prove that the proposed method (i) achieves a good detection capability and high localization accuracy within a short measurement time even for low SNR values and (ii) outperforms conventionally employed techniques.

Cyclic performance of RC beam-column joints with mechanical or forging (GPW) splices; an experimental study

Beam-column joints affect the performance of structures remarkably, therefore, finding an appropriate method for their construction has always been one of the major concerns of researchers. In the present study, the influence of incorporating mechanical and forging (gas pressure welding) splices in longitudinal reinforcement bars of beams on the cyclic performance of RC beam-column joints is evaluated experimentally. Totally five RC joints with non-spliced, mechanically (threaded couplers) spliced and forging spliced bars were examined under axial and cyclic loads applied to columns and beams, respectively. Crack propagation of specimens are analyzed and load-drift hysteresis curves are provided as test outputs. Moreover, the influence of the splice method and number of spliced bars on joints’ behavior is assessed in terms of seismic parameters including displacement ductility, stiffness and cumulative absorbed energy. Results showed that forging splices can be considered as an efficient and reliable method for bar splicing and mechanical splices might affect joints’ behavior significantly.

Integrated Ammonia Sensor Using a Telecom Photonic Integrated Circuit and a Hollow Core Fiber

We present a fully integrated optical ammonia sensor, based on a photonic integrated circuit (PIC) with a tunable laser source and a hollow-core fiber (HCF) as gas interaction cell. The PIC also contains a photodetector that can be used to record the absorption signal with the same device. The sensor targets an ammonia absorption line at 1522.45 nm, which can be reached with indium phosphide-based telecom compatible PICs. A 1.65-m long HCF is connected on both ends to a single-mode fiber (SMF) with a mechanical splice that allows filling and purging of the fiber within a few minutes. We show the detection of a 5% ammonia gas concentration, as a proof of principle of our sensor and we show the potential to even detect much lower concentrations. This work paves the way towards a low-cost, integrated and portable gas sensor with potential applications in environmental gas sensing.

Mechanical bar splices for incorporation in plastic hinge regions of RC members

Mechanical devices are incorporated in reinforced concrete (RC) structures in lieu of conventional lap splicing mainly to reduce bar congestion in joints. Mechanical bar splices, which are also referred to as bar couplers, might also be used to connect precast members to accelerate construction. Nevertheless, current codes prohibit the use of bar couplers in plastic hinge regions of RC special moment-resisting frames and RC bridge columns in high seismic zones preventing the use of couplers as precast connections. This may be because of a lack of systematic test data on the coupler performance, limited experimental studies on mechanically spliced RC members, and engineering precautions. All bar couplers available in the U.S. market were evaluated as part of this study and 10 products from six different manufacturers were identified as potential couplers to be used in precast members. New standard test methods for mechanical bar splices were developed and more than 160 bar couplers were tested under uniaxial monotonic and cyclic loading to failure to generate the first-of-its-kind systematic database of the coupler performance. Mechanical properties of these splices were established, and a coupler material model adopted from the literature was found to be viable in producing the splice stress–strain behavior. Furthermore, a parametric study was carried out to investigate the seismic performance of mechanically spliced bridge columns utilizing the verified coupler models. More than 240 pushover analyses were performed. It was found that mechanically spliced bridge columns may exhibit up to 43% lower displacement ductility capacity compared to conventional RC columns and the force capacity of these columns may be up to 10% higher than that for RC columns. Columns spliced with rigid and long couplers will show the lowest displacement capacities. Based on the research findings, a new standard testing method was prepared for seismic couplers and was submitted to the American Association of State Highway Transportation Officials (AASHTO) for possible adoption.

Cyclic Loading Tests of Slab-Wall Connections Using Removable Rail Mechanical Splices

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Seismic behaviour of flat connections between steel-plate composite (SC) walls and reinforced concrete (RC) walls

The steel-plate composite (SC) wall has been a competitive substitute for reinforced concrete (RC) wall in nuclear power plants and small modular reactors. As essential parts of the structures, the joints and connections in various shapes deserve attentions, in which the seismic behavior of flat connection between SC wall and RC wall has not been adequately studied. In this paper, four large-scale flat connections with longitudinal rebars of RC walls inserted into SC walls were tested under cyclic out-of-plane loading. Test parameters involved shear-span ratios and construction details. For specimens with small shear-span ratios, the role of shear lugs passing through the interface between SC wall and RC wall was studied. For specimens with large shear-span ratios, the necessity of mechanical splices at the ends of the inserted longitudinal rebars was concerned. The failure modes, load-strain curves and load-displacement responses of test specimens were documented. A finite element model (FEM) simulating the behavior of the test specimens using ABAQUS was established for additional insights. Based on the results, the effects of the test parameters were analyzed in detail, the load-transfer mechanism of out-of-plane bending moment was illustrated. Since the shear or flexural failure on RC wall was observed in the specimens, the design equations for the nominal shear and flexural strength of RC walls were evaluated.

Use of an international experience of mechanical reinforcement bars splicing in Ukraine

The problematic of reinforcement bars splicing by overlap tying and by the way of welding is described, as well as alternative splicing by the mechanical compression couplers as a way of its solution. Lap splicing showed good results in structures with small nominal dimensions of steel bars, low rate yield strength and in buildings not higher than 15 floors. Welding is the more flexible method of steel bars splicing but its use brings to rising costs and complicity of construction work. The quality of welded splices depends on many factors mainly on the existing problems in welding process. The analysis of world construction practice shows a more reliable, technological and effective way of splicing reinforcement bars it means the use of connecting couplers i.e. mechanical rebar coupling. Successful international experience of applying mechanical steel bars splicing in USA, Japan, China, Kazakhstan, UAE, etc. is described. It must be noted that with the advance of the enactment of DBN V 2.6-98 and DSTU B V.2.6-156, standard acceptable methods of steel bars splicing in Ukraine are lap splicing, welded connections and mechanical splicing. General technical requirements of the connections of reinforcement were analyzed and systematized, as well as general advantages of mechanical splices were proved. Analysis of international and native regulations showed that in Ukraine it should be taken more strict requirements for mechanical splices. Methodology and test results of mechanical splices were covered. A number of regulation documents were developed as a result of large scale theoretical and experimental research of mechanical connections. The technology of coupling of reinforcement bars was applied at many construction projects as well as in seismic regions.

Use of an international experience of mechanical reinforcement bars splicing in Ukraine

The problematic of reinforcement bars splicing by overlap tying and by the way of welding is described, as well as alternative splicing by the mechanical compression couplers as a way of its solution. Lap splicing showed good results in structures with small nominal dimensions of steel bars, low rate yield strength and in buildings not higher than 15 floors. Welding is the more flexible method of steel bars splicing but its use brings to rising costs and complicity of construction work. The quality of welded splices depends on many factors mainly on the existing problems in welding process. The analysis of world construction practice shows a more reliable, technological and effective way of splicing reinforcement bars it means the use of connecting couplers i.e. mechanical rebar coupling. Successful international experience of applying mechanical steel bars splicing in USA, Japan, China, Kazakhstan, UAE, etc. is described. It must be noted that with the advance of the enactment of DBN V 2.6-98 and DSTU B V.2.6-156, standard acceptable methods of steel bars splicing in Ukraine are lap splicing, welded connections and mechanical splicing. General technical requirements of the connections of reinforcement were analyzed and systematized, as well as general advantages of mechanical splices were proved. Analysis of international and native regulations showed that in Ukraine it should be taken more strict requirements for mechanical splices. Methodology and test results of mechanical splices were covered. A number of regulation documents were developed as a result of large scale theoretical and experimental research of mechanical connections. The technology of coupling of reinforcement bars was applied at many construction projects as well as in seismic regions.

Experimental investigation of using mechanical splices on the cyclic performance of RC columns

In this study, the influence of using mechanical splices on the cyclic performance of RC columns under axial and cyclic loads was investigated experimentally. Totally six specimens were fabricated and examined; the first one was fabricated by non-spliced reinforcement bars which was considered as reference specimen. Overlap splice in the middle of the column was used in the second specimen. Threaded mechanical splices were used for the all of the longitudinal bars at 50 mm above the column-foundation interface in the third column. The fourth column was fabricated the same as the third one but half of the couplers were staggered at 600 mm above the bottom couplers. The fifth and sixth specimens were fabricated similar to the third and fourth column but shear screw-threaded couplers were incorporated instead of threaded couplers. Force-displacement hysteresis loops were presented as the output and parameters including lateral load bearing capacity, ductility, absorbed energy and stiffness are considered and discussed. Based on the obtained results, it was concluded that mechanical splices can considerably affect cyclic behavior of RC columns.

Mechanical Splices for Seismic Retrofitting of Concrete Structures

Mechanical Splices for Seismic Retrofitting of Concrete Structures

Mechanical Splices for Seismic Retrofitting of Concrete Structures

As an alternative to lap splicing, mechanical splices can be used for retrofit purposes. They are generally most economical than traditional lap splices when available spacing or length makes laps difficult to utilize. Mechanical splices are frequently used in new construction. However, their use is limited and not practical for use in retrofitted structures. However, if the bars to be joined do not need to be threaded in order to be connected with a special mechanical splice, such mechanical splices can be useful. It is presented a proposal of using two types of mechanical splices for retrofit purposes. Cycle Tension and cycle tension-compression tests are presented and discussed. It was found that mechanical splices are suitable and have acceptable response under seismic loads.

Seismic behaviour of RC columns with welded rebars or mechanical splices of reinforcement

The extension of existing RC buildings is a challenging process, which requires efficient connection between existing and new materials to guarantee load transferring between the lap-spliced longitudinal columns\' reinforcement. Therefore, the length of the columns\' starter bars is a crucial factor, which decisively affects the seismic response of the new columns. In particular, when the length of the starter bars is short, then the length of the lap splices of reinforcement is inadequate to ensure load transfer between steel bars and concrete, with an indisputable detrimental impact on the seismic behaviour of the columns. Moreover, in most of the existing RC buildings the column starter bars are of particularly short length, while they have probably been bent, cut or corroded. In the present study, the effectiveness of both welded rebar and mechanical splices of reinforcement in ensuring load transferring between the starter bars and the longitudinal reinforcement of the new column was experimentally evaluated. Four cantilever column subassemblages were constructed and subjected to earthquaketype loading. Three of the specimens were used to examine different types of shielded metal arc welding (SMAW), while in the fourth subassemblage mechanical splices were tested. The hysteretic response of the columns was evaluated and compared to the behaviour of a fifth specimen with continuous reinforcement, tested by Kalogeropoulos and Tsonos (2019). Test results clearly demonstrated that the examined types of SMAW were equally satisfactory in ensuring the ductile seismic performance of the columns, while the mechanical splices found to be more susceptible to exhibit slipping of the bars.

Experimental evaluation of coupler behavior for mechanical rebar splices in reinforced concrete structures

Abstract The use of mechanical splices to connect steel bars is an important solution in many infrastructure projects worldwide. In Brazil, this system is rarely used. The Brazilian standards regarding this subject are old and out of date; particularly with regard to the performance evaluation test methods for these splices in the laboratory. This paper presents and discusses the test procedure proposed in the international standard ISO 15835 [1] in light of the current procedure defined by Brazilian Standard ABNT NBR 8548 [2], applied to types of mechanical splices commonly used in Brazil: taper threaded and bolted couplers. Performance parameters for these mechanical splicing systems related to structural integrity in reinforced concrete structures are evaluated on the basis of the results obtained in these tests. In the end, it is intended that this paper provide support for discussion of design procedures and laboratory performance evaluation of couplers for mechanical splices of steel bars in reinforced concrete structures in future reviews of Brazilian standard ABNT NBR 8548 [2].

Inelastic cyclic behaviour of RC members incorporating threaded reinforcement couplers

This paper describes an experimental investigation into the inelastic cyclic performance of reinforced concrete members incorporating mechanical reinforcement splices. Based on a survey of available mechanical splicing forms, two types of threaded couplers with different geometric configurations, namely ‘parallel threaded couplers’ and ‘parallel threaded sleeve couplers’ are selected for detailed experimental assessment. The fundamental uniaxial monotonic and cyclic response of reinforcement bars connected with threaded mechanical splices is firstly examined through bare (in-air) and embedded (in-concrete) tests, and their response is compared with that of their non-spliced counterparts. This is followed by an experimental study on four large scale reinforced concrete specimens subjected to lateral inelastic cyclic displacements, which provides a direct comparison between the performance of members with or without the two types of reinforcement couplers as well with or without a co-existing axial load. The test results enable a direct comparative assessment of the key response characteristics of the specimens including stiffness, strength, ductility and energy dissipation. Overall, the results show that members incorporating reinforcement bars connected through threaded mechanical couplers can provide considerable ductility and energy dissipation. However, the coupler-concrete interaction behaviour, which depends primarily on the geometry and location of the threaded coupler, has a significant influence on the inelastic cyclic response and ductility levels exhibited by reinforced concrete members. The experimental results indicate that the presence of the slender coupler alters the plastic hinge behaviour by localising the curvatures between the coupler and interface, reducing the rotational capacity. In contrast, the response of members with compact couplers, and without axial load, is virtually identical to that of the specimen with continuous reinforcement. The axial load enhances the stiffness and lateral capacity yet reduces the ductility performance due to a response strongly characterised by crushing. It is shown that whilst uniaxial in-air reinforcement performance may be adopted as a basis for selecting suitable mechanical couplers for use in dissipative members, the expected levels of ductility implied in current codified seismic procedures need to be carefully and explicitly evaluated when relatively non-compact couplers are employed.

Connecting to Eurocode 2: an investigation of reinforcement continuity connections for construction joints

As the local market moves away from cheaper foreign labour and focusses on higher productivity, we should use every possible avenue and technique to ensure that this does not result in a ballooning in construction costs. One such way is to take advantage of the move away from BS 8110 to EN 1992-1-1; there are a number of subtle changes between the standards that can result in reduction of materials, providing we know where to look. The move has not been seamless as there are a number of omissions from Eurocode 2 that has caused confusion, for example, there are no longer any requirements for mechanical splices as this is deemed to fall outside the scope of a design standard. However, there are equally some new areas that are covered in much more detail and it is these we should focus on. This paper will look specifically at the design provisions of construction joint continuity and show how they can be utilised to both improve productivity and reduce the amount of steel required across the joint. This not only saves the contractor time and money due to lower material costs, but will also reduce the amount of embodied CO2 present in the structure as less steel will result in a “greener” solution. It will address the differences between current practices and new technologies that will enable smarter connections while staying firmly within the scope of MS EN 1992-1-1.

철근 기계적 이음 모듈을 적용한 벽-슬래브 접합부의 반복하중에 대한 구조 성능

철근 기계적 이음 모듈을 적용한 벽-슬래브 접합부의 반복하중에 대한 구조 성능

Numerical study on mechanical and adhesive splices for ribbed GFRP plates used in concrete beams

A new concrete beam design, comprising concrete core and glass fiber reinforced polymer (GFRP) ribbed side plates has been developed. Plate splicing is made by using a mechanically fastened or adhesively bonded spliced form through end ribs. This paper presents the development, calibration, and application of comprehensive finite element models for the hybrid beam. The models incorporate material and geometric nonlinearities along with bond-slip interfacial relations. Interfacial behavior at the plate-to-plate splice, whether adhesively bonded or mechanically fastened, as well as plate-concrete interface are considered. Parametric study was performed to examine the effects of fastener spacing and adhesive coverage length of the 4 mm thick GFRP plates. It was shown that the ultimate strength of beams with adhesively bonded splices was 28% higher than the beams with unbonded splice (i.e. without any adhesive or fasteners). Decreasing fastener spacing from 47 to 3.8 times the fastener diameter resulted in increasing ultimate load by about 20%. No further reduction in load occurs beyond fastener spacing larger than 47 times the diameter. The beam stiffness at service load is not affected by the fastener spacing or the adhesive coverage length.

Parametric study on a novel grouted rolling pipe splice for precast concrete construction

Grout-filled mechanical splice system, with its remarkable ability to connect precast elements, is one of the most important technologies for precast concrete construction. However, for the time being, its high cost has hindered the implementation of precast concrete structures to a certain degree in developing countries. This paper presents a new type of grouted sleeve which can be easily and economically fabricated with a standard seamless steel pipe through cold rolling techniques. Utilizing this sleeve, 69 sets of coupler specimens were prepared considering parameters of inner cavity structure and cross-sectional dimension of sleeve, grout strength, and diameter and embedded length of steel bar. Through direct pullout test, it is shown that the proposed splice is capable of developing of 100% of ultimate strength of the bar providing an embedded length of 6 times bar diameter. Increasing the number and height of inner concentric rib which rolled on the sleeve only in inelastic segment is an effective technique to improve the bond strength of the splice. With the increment of the ribs, clearly different effects of sleeve dimension and grout cylinder thickness on the bond strength can be observed due to different confining mechanism. Finally, a design method for the novel deformed grouted splice sleeve is proposed.