Rebar Splicing Research Articles

Impact of incorporating parallel-threaded mechanical coupler splices on the seismic behaviour of reinforced concrete columns

This study compared the performance of reinforced concrete (RC) columns using mechanical couplers with that of traditional overlapping splices under axial and cyclic loading conditions. Splicing methods incorporating larger diameters are critical for ensuring the structural integrity of large structures, for which safety is of paramount importance. Overlapping splices often result in congestion and poor construction quality owing to the complex RC detailing in the joints. Mechanical couplers enable efficient installation and provide economic benefits. In this study, RC columns with different splicing configurations were tested using quasistatic cyclic lateral loading. The coupler properties, geometry, and position were analysed. The results demonstrate that mechanical couplers can maintain or slightly enhance the ductility, energy dissipation, and self-centring capacity while effectively maintaining the stiffness and strength. These findings suggest that mechanical couplers are superior alternatives to traditional rebar splicing methods for improving the overall performance and reliability of RC structures in large-scale construction projects.

Full-scale experimental study and mechanical model for beam-wall joints of prefabricated enclosure structure

Owing to long exposure to the urban environment, the construction technology of the enclosure structure is closely related to the urban low-carbon development. Shenzhen Metro has recently proposed a novel prefabricated enclosure structure and demonstrated its application. Among them, the mechanical properties of the beam-wall joint between precast diagram wall and precast beam are the core for the performance of the prefabricated enclosure structure. This study demonstrated foremost the application of prefabricated enclosure structure and its key joint mechanical model in Shenzhen Metro Phase V stations. First, this study conducted a full-scale bending experimental study on beam-wall joints and continuous joints. Second, the Joint Coordinating Contact Model (JCCM) of the beam-wall joint was proposed. Third, the model was validated and assessed by using the experiment data. The main conclusions include: (1) The beam-wall joint showed semi-rigid properties despite using reliable assembly. (2) The performance degradation of the beam-wall joint originated from the interface. The interface weak link changed the solid continuity of the joint. (3) With reasonable rebar splices (≥66%), the joint stiffness does not change substantially. However, the joint performance with too few rebar splice showed significant degradation (≤33%). (4) JCCM assessment suggested a rigid beam-wall joint by enlarging the joint height by 31.3% and using 44% rebar splice ratio. The research achievement provides a theoretical basis and application value for the assessment of beam-wall joints and the promotion of prefabricated enclosure structures.

Estimation of Failure Mode of Mortar-Filled Sleeve Rebar Splices

In order to establish a more rational structural design method for mortar-filled sleeve rebar splices, it is necessary to analyze and evaluate structural factors affecting the structural performance of these rebar splices. It is very desirable to be able to quantitatively estimate the failure mode of the splices at the design stage. A method for estimating the failure mode of mortar-filled sleeve rebar splices presented from the existing research is not clear because the boundary of failure mode is not expressed in formulas. There are also limitations using the methods because the research is based on limited number of test variables, insufficient number of test specimens, and the fact that only steel pipe sleeves were used. Therefore, to establish a more general and comprehensive failure mode estimation method, it needs to be presented in a more quantitative and explicit fashion and evaluated using more diverse variables. In this study, as part of an effort to generate basic data for the establishment of a more rational and quantitative structural design method for mortar-filled sleeve rebar splices, the failure mode estimation method is presented based on the existing bond strength equations of sleeve rebar splices. In addition, to examine the suitability of this failure mode estimation method, the failure modes of 303 sleeve rebar splices were evaluated. The evaluation results indicated that the failure mode estimation method for mortar-filled sleeve rebar splices proposed by this study would yield a failure mode estimation with a sufficiently practical accuracy.

Experimental study on mechanical behavior of thermally damaged grouted sleeve splice under cyclic loading

AbstractAn experimental program concerning 48 specimens of grouted sleeve splices, first heated up to 600°C and then subjected to cyclic loading was presented and discussed in this study. Similar rebar splices were often used in the precast concrete structures designed for seismic regions. The temperature of the splice and the compressive strength of the grout were the main variables considered in this study. It is found that the temperature mainly affected the peak bearing capacity of the grout and the failure pattern of the connection. In fact, the typical failure pattern at room temperature (rebar fracture outside the sleeve) turned to rebar pullout of the sleeve above 400°C, which indicated that below this temperature grout‐to‐rebar bond kept most of its original efficacy. On the contrary, bond failure occurred for all specimens at 600°C because of rebar slip. A calculation method was proposed as well to evaluate the peak bearing capacity of grouted sleeve splice, based on the load transferring mechanisms of the bond between grout‐to‐rebar and sleeve‐to‐grout. The conducted experimental study and analysis provide a better understanding on the bond mechanism of thermally damaged grouted sleeve splices subjected to cyclic loading.

Using nondestructive methods for determination types of rebar splices

The article considers the types of rebar splices in reinforced concrete building structures. Examples of couplers and lap splices of reinforcing bars with a diameter of 20 mm are given. The main task of the work is to analyze the results of tomographic studies of various concreted splices. The studies were performed using the MIRA A1040 low-frequency ultrasound tomograph. Conclusions about the possibility of using the ultrasonic method to determine the types of splices were made.

Experimental study of grout defect identification in precast column based on wavelet packet analysis

Grout defects always exist in sleeves of precast structures, but studies on grout defect identification are rarely performed. This article proposes a combination method of dynamic excitation technique and wavelet packet analysis for sleeve defect identification in the precast structure. Hammer excitation on a 1/2-scaled two-floor precast concrete frame structure with column rebar splicing by grout sleeves is conducted to collect column acceleration responses. Moreover, the corresponding energy spectrum is obtained by the wavelet packet analysis. Furthermore, three defect identification indices, that is, percentage of energy transfer, energy ratio variation deviation, and energy spectrum average deviation, are calculated and compared. Robustness analysis of the energy ratio variation deviation is carried out by adding white noise in the original acceleration response signals. The results show that (1) the percentage of energy transfer, the energy ratio variation deviation, and the energy spectrum average deviation are positively correlated with the grout defect degree where the energy ratio variation deviation is more sensitive in the identification of defects; (2) the energy ratio variation deviation robustness of the original signal with the inputted multiplicative white Gaussian noises is better than that with the inputted additive white Gaussian noise; and (3) the proposed defect identification method can characterize the sleeve grout defect degree in column.

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.

Seismic behavior of precast columns with large-spacing and high-strength longitudinal rebars spliced by epoxy mortar-filled threaded couplers

An innovative precast concrete column system, which is expected to be emulative to conventional cast-in-situ columns, is proposed in this paper. In this system, short novel epoxy mortar-filled threaded couplers (MTCs) provide column longitudinal reinforcement with continuity; large-spacing and high-strength longitudinal rebars are used to replace the conventional normal-strength rebars for simplified rebar splices; labor-saving spiral hoops combined with crossties provide core concrete with enhanced confinement. The effectiveness of the innovative construction details was investigated by individual connector tests and column tests. Test results showed that precast columns exhibited global behavior, damage state, cracking distribution, energy-dissipation, and deformation capacity comparable to those of cast-in-situ columns, validating the reliability of the innovative construction details. The short MTCs had little effect on the plastic hinge formation, and could enable precast columns to exhibit stable load-carrying capacity through extensive deformations. Eventually, an approximate method based on a modified plastic hinge length was developed to evaluate the deformation capacity of spliced columns, and the evaluated results agreed well with the measured ultimate drifts.

BARRIERS TO NEW TECHNOLOGY DISSEMINATION IN THE CONSTRUCTION INDUSTRY

Despite the common belief, there is a considerable amount of innovation that occurs in the construction industry. However, the construction industry has been relatively slow to embrace the full potential of many new technologies. Evidence suggests that there is a lag in the uptake and effective implementation of several new technologies such as mechanical rebar splicing system. The objective of this study is to identify the impediments or barriers to the implementation of innovative technologies such as mechanical rebar splicing systems in the construction industry. A comprehensive literature review is conducted to identify and classify the barriers to new technologies dissemination. The findings of this literature review are validated using interviews with the construction industry experts. This study contributes to the state of knowledge by identifying and classifying the barriers that generally hinder the dissemination of new technologies in the construction industry. The practitioners can utilize the findings of this study to design appropriate strategies to overcome the barriers for implementation of new construction technologies. As part of this study, the extent to which the identified barriers have hindered the adoption of rebar splices, a technology that has not been adapted to its full potential. A questionnaire was designed, which was categorized the identified barrier in five major categories of cost, society and regulation, knowledge, marketing, and technical matters. The findings of the survey it was concluded that the lack of knowledge has the highest level of impact.

Investigations and Non-destructive Testing in New Building Design

Mechanical rebar couplers are preferable in the advanced building construction and structural design of antiseismic elements. The paper presents destructive inspection techniques used to investigate stress fields (tensile and compressive) and deformation curves for mechanical rebar splicing. The properties of mechanical rebar splicing are investigated by the non-destructive testing digital radiography. The behavior of real connections (column-to- column, beam-to-column) is studied under static and dynamic loads. Investigation results allow the elaboration of recommendations on their application in the universal prefabricated antiseismic structural system developed at Tomsk State University of Architecture and Building, Tomsk, Russia.

Mechanical rebar splicing

Different mechanical rebar splicing systems are presented, and design situations where mechanical splicing has advantage over reinforcement splicing by overlapping and welding are defined in this paper. New international standards for testing and proof of systems for mechanical rebar splicing quality are considered. Mechanical splicing system for rebar and bolt connection, usable in steel and reinforced concrete structural elements connections, is presented in this paper. There are only few examples of mechanical rebar splicing in our country. The most significant one - the pylon and beam connection at Ada Bridge in Belgrade is presented in the paper. Intensive development of production and use of mechanical rebar splicing systems, research in this area, as well as the publication of international standards prescribing requirements for quality and procedures for proof of quality, represent very good base for development of the corresponding technical norms in Serbia. The legislation in this area would quicken proof of quality procedures, attest and approval issuing for individual products, leading to wider use of this system in all situations where it is in advantage over the classical reinforcement splicing.

Bond strength of glass fibre-reinforced polymer bars in unconfined concrete

Glass fibre-reinforced polymer (GFRP) bars can be used to avoid steel reinforcement corrosion in bridge decks, which usually have no transverse reinforcement. In this study, 35 flexural tests of beams and slabs were carried out to experimentally determine the bond strength of spliced GFRP bars with no transverse reinforcement. The test variables included splice length, cover thickness, and bar spacing. The splice lengths were relatively large to test realistic splice lengths used in the field (longer than 30 d b in most tests). In addition, four beams with conventional steel rebar splices were also tested to compare their bond strengths with those of the GFRP bars. Test results showed that the bond strengths of the specimens with GFRP bars were lower than those of the steel rebars. Although the average bond strength of the GFRP bars decreased with increasing splice length and decreasing cover thickness/bar spacing, the bond strength of the long splice increased when c/ d b ⩾ 2.5, in which c denotes the smaller of the minimum concrete cover and 1/2 of the bar clear spacing. Two equations for predicting the average bond strength of GFRP bars in unconfined concrete are proposed based on the regression analysis of the 33 test results from the beams and slabs that failed by concrete splitting.

SD600 철근의 B급 겹침 이음에 대한 현행설계기준의 적용성

이 연구에서는 SD600 철근 B급 이음에 대한 현행 설계기준의 적용성 평가를 위하여 실험적 연구가 수행되었다. 단순 지지된 12개의 B급 겹침 이음 실험체에 단순 증가 하중을 가하여 실험하였다. 주요 변수는 겹침 이음 철근 직경, 콘크리트 피복 두께, 콘크리트 강도, 횡보강 철근 간격이다. 콘크리트는 24 MPa의 보통 강도 콘크리트와 60 MPa의 고강도 콘크리트를 사용하였다. 대부분의 실험체는 현행 설계기준의 B급 이음 길이를 만족하도록 설계하였다. 실험에서 발현된 철근 응력의 평균을 현행 KCI설계기준의 예측 철근 응력과 비교하였으며, 그 결과를 통하여 SD600 철근에 대한 현행 설계기준의 적용성을 평가하였다. 현행 설계기준은 모든 D13 겹침 이음과 횡보강 철근이 배치된 D22, D32 겹침 이음에 대하여 안전측이었다. 직경 D22 이상 철근의 겹침 이음은 횡보강 철근의 사용이 권장되는 결과를 나타내었다. 고강도 콘크리트를 사용한 D22, D32 철근의 겹침 이음은 안전한 경향성을 보였으나, 확실한 검증을 위하여 추가적인 연구가 필요하다.

Behavior of reinforced concrete buildings during the Hyougoken-Nanbu earthquake

The Hyougoken-Nanbu earthquake caused serious damage to reinforced concrete building structures. Investigation results indicated that most buildings which suffered serious structural damage were built before 1981, i.e. new modern buildings behaved well, because the current seismic design provisions were enforced by the ministry of construction in 1981. Typical damage patterns of reinforced concrete building structures were: (1) collapse of soft first story construction; (2) collapse of a mid-height story; (3) torsional failure resulting from eccentricities of stiffness and mass; (4) inadequate spacing and anchorage of transverse reinforcement; (5) shear failure of short columns; (6) fracture of re-bar splices by gas-pressure welding; (7) damage to separation joints and elevated corridors; and (8) damage to non-structural members (Preliminary Reconnaissance Report of the 1995 Hyougoken-Nanbu earthquake, Architectural Institute of Japan, 1995 (English version)).