Grouted Sleeve Connectors Research Articles

A Literature Review Paper on Experimental Study on the Properties of Precast Concrete in Beam-Column Joints Using Polyvinyl Alcohol Fibres and Aramid Fibres with Half Grouted Sleeve Connectors

A Literature Review Paper on Experimental Study on the Properties of Precast Concrete in Beam-Column Joints Using Polyvinyl Alcohol Fibres and Aramid Fibres with Half Grouted Sleeve Connectors

Rebar-concrete bond behaviour in grouted sleeve connectors

Grouted sleeve connectors (GSCs) are commonly used in precast/prefabricated concrete structures. To ensure force transfer, connectors tend to be overdesigned, and this has a detrimental effect on the plastic deformation capacity of the connection region and the displacement ductility of the precast structure. To enable improvements in the design of precast RC connections involving GSCs, an accurate analysis of the bond behaviour of GSCs is required. This paper presents an analytical model for the local bond behaviour under the particular sleeve confinement. A representative cross-section of a GSC is treated as interconnected hollow circular tubes. Three stages are identified according to the state of the grout, namely elastic, partially cracked, and fully cracked. The confining pressure is formulated within the cross-section, and the bond stress is subsequently evaluated by a modified bond stress-slip law accounting explicitly for the confinement. Compared with traditional bond-slip laws, the model is capable of representing the evolution of confining stress in the loading process. Comparison with relevant experimental results show good agreement. A subsequent parametric study demonstrates the trends of influence of various parameters, and notably, within allowable limits, a reduction of the grout thickness tends to increase the bond strength in the connectors.

Detection of grout sleeve defects based on the time domain dimensionless indicators of component signals

In recent years, precast concrete structures have been widely used in building and bridge engineering. Grouted sleeve connectors (GSC) are extensively applied to connect vertical rebars between precast concrete members. In practical construction, defects, such as no grouting, insufficient grouting, and missing rebar, often exist in the GSC, which reduces the load-bearing capacity. Therefore, detecting GSC defects is important for the safety of precast concrete structures. In this paper, a numerical model of meso-scale GSC concrete was developed. The model was verified by test data from existing literature. The ultrasonic wave signals in the GSC with and without defects were compared in detail. The signals were decomposed based on wavelet packet transform and empirical mode decomposition. Then the time domain dimensionless indicators were extracted to examine the GSC defects. The proposed method was shown to be superior in detecting the GSC defects with high sensitivity.

Evaluation of common defects of grouted sleeve connectors

Grouted sleeve connectors have been widely used in vertical connections of prefabricated reinforced concrete structures. However, the quality of grouted sleeve connections are likely affected by adverse factors during winter construction such as grouting operation error, adverse environmental change, and management negligence. Some defects in winter construction are difficult to check including insufficient strength of grouting material, insufficient anchorage length of connecting reinforcement bars and adverse impact of low-temperature grouting. Although research has been carried out on the connection performance of grouted sleeves with defects, few are on the comprehensive evaluation of the connection performance of grouted sleeves with different defects caused in winter construction. In this paper, 25 groups (75 sleeves) of semi-grouted sleeve connectors with various defects are designed and manufactured. The effects of insufficient anchorage (i.e. insufficient length of reinforcement bar extending into the sleeve), insufficient strength of grouting materials and low-temperature grouting on the tensile properties of semi-grouted sleeve connectors are experimentally studied. On the basis of the test, finite element analysis is performed on extended defect conditions to comprehensively evaluate the safety control indicators. This research provides reference for the safety evaluation of grouted sleeve connections for prefabricated structures.

Deformation Behavior of Grouted Sleeve Wall Connector Under Shear Load in Precast Process of Concrete Wall

This study investigated the behaviour of grouted sleeve connectors under shear loads. Tapered Head Sleeve (THS) connectors were fabricated from mild steel pipes. Five test specimens and a control specimen were produced. Each test specimen comprised two walls, which were connected by THS. An incremental shear load was applied at the joint until the specimen failed. The behaviour of the specimens was analyzed based on the load-displacement response. The feasibility of THS as a wall connection was determined based on ductility ratio, failure mode, performance ratio, and serviceability ratio. THS required an embedded length of 8 times the bar diameter to generate sufficient bond strength. The specimens experienced bar dowel action, which led to a significant horizontal displacement with a ductility ratio of 27.5 to 55.9. The test specimens offered shear capacities comparable to the control specimen, with performance ratios close to 1.0. The service load was only 1/3 of the ultimate capacity, and thus THS was ineffective in resisting shear load. Shear keys would be required to strengthen the joint of the specimen.

Experimental investigation on seismic behaviors of precast concrete shear walls with sleeve grouting defects

The grouted sleeve connector is one of the most widely used connections in precast concrete shear wall structures. Due to the technology limit of the assembly workers, the sleeve grouting often has defects, which could significantly weaken their practical performance. Only considering the effect of defects on the bearing capacity of the sleeve connector cannot simulate the effect of defects in actual engineering. To this end, an experiment was carried out to investigate the seismic performance of precast concrete shear walls with sleeve grouting defects. Four full-scale precast concrete shear walls with different defect levels of insufficient grouting were designed and tested under cyclic loads. The development of concrete cracking, failure mode, hysteresis features, load-bearing capacity, stiffness degradation, structural ductility and energy-dissipation capacity are analyzed to reveal the influence of the sleeve grouting defects on precast concrete shear walls. The test results indicated that with the increase of the defect level, the opening gap between the bottom of the wall and the top of the foundation beam widened, and the failure mode changed from tensile fracture of reinforcing steel bar to anchorage failure of the tensile reinforcement on the defective side. Meanwhile, as the level of grouting defects increased, the bearing capacity decreased, and the specimen failed prematurely. The effect of the grouting defects on cracking load was minor, while they had a significant influence on the yield bearing capacity, peak bearing capacity and ultimate bearing capacity. The experimental results also indicated that the grouting defects caused the weakening of the stiffness, ductility and energy dissipation of the precast concrete shear walls. The presented work could be used for defect prevention and evaluation of precast concrete shear walls with sleeve grouting defects.

STUDY ON THE INFLUENCE OF THE CONFINEMENT EFFECT ON THE BOND STRENGTH RECOVERY IN THE DEFECTIVE GROUTED SLEEVE CONNECTION

Defects emanating from the onsite operation of the grouted sleeve connector have a significant impact on the ultimate tensile capacity of the connector. In this research, an experiment on the capacity of the fully grouted sleeve connector considering different configurations of defects was carried out. The experiment results indicated that the connector is highly sensitive to the location of the defects, which engenders a drop of 15% in the ultimate capacity of the connector. Based on the accurate simulation of the experiment model, a series of parametric analyses were conducted to evaluate the interaction of defects with other mechanical properties of the connector. It was found that the different values of the ratio of the sleeve diameter to that of the bar within the design recommended interval significantly influence the connection's performance. The lowest ratio value engenders approximately 10% to 16% of tensile strength recovery in the weakened configuration, while a bigger ratio value engenders a decline in the capacity. This work proposes the incorporation of a safety constant in the average bond expression.

Analytical model of grouted sleeve connector and its solution based on the state space method

The grouted sleeve connector has wide application in assembly construction to connect the prefabricated structure members. Based on the experimental observation, an analytical model is established for the mechanical behaviors of grouted sleeve connections. The state space method is then introduced to simulate the pull-out test of grouted sleeve connectors theoretically. The predicted results agree well with both of the results from tests and the results form finite element analysis. The bond-slip relationship between the reinforcement and the grout is discussed. Finally, parametric study and parameter optimizing of the grouted sleeve connector are carried out.

Experimental investigation on connection performance of fully-grouted sleeve connectors with various grouting defects

Grouted sleeve connector is one of the most widely used connections in precast concrete structures. However, various defects may be introduced in the grouted sleeve connectors due to construction errors, which could significantly weaken their practical performance. In this study, 42 connectors were manufactured and tested under uniaxial tensile loading, where multiple grouting defects were considered (i.e. end defect, middle defect, anchor length defect, uniform defect, grouting density defect, thickness defect, horizontal defect, eccentric defect and grouting strength defect). First, the defect fabrication is examined by using the cone-beam computed tomography (CT) inspection system. Based on the tensile testing results, three failure modes including tensile fracture of reinforcing bar, anchor failure of the top reinforcing bar and anchor failure of the bottom reinforcing bar, could be observed. Besides, the decrease of the total effective anchor lengths of the bottom reinforcing bars could significantly lead to deterioration of the anchor properties and change the failure mode from fracture failure to anchor failure. For the specimens with end defect, when the defect length was longer than 42 mm, the connection performance deteriorated and the failure mode shifted from the tensile fracture of reinforcing bar to the anchor failure of reinforcing bar. Meanwhile, there was a significant correlation between the ultimate displacement and the failure mode, that is, the ultimate displacement of the anchorage failure specimens was generally less than that of the tensile fracture failure specimens. For connectors with the same total effective anchor lengths, discrete defects resulted in lower bearing capacity than concentrate defects, and when defects were farther away from the sleeve end, the bearing capacity is lower. That is, the lowest ultimate anchor strength was found in specimens with uniform defect, followed by specimens with middle defect and specimens with end defect. The presented work could be used for defect prevention and evaluation of grouted sleeve connectors.

The Feasibility Study of Quantitative Flaw Detection of Grouted Sleeve Connection by Ultrasonics

Grouted sleeve connection has been widely used to connect rebars in prefabricated concrete (PC) structures. Due to the complexities of materials and internal configurations, the flaws or defects are inevitable, which may cause the negative impact on the mechanical properties of reinforcement sleeve connection, ultimately leading to the hidden risk in the PC structures. It is challenging to explore a reliable and efficient flaw detection method for the grouting sleeve. In this paper, an active grout defects detection approach for grouted sleeve connectors using UT wave measurement is proposed, where piezoelectric-lead-zirconate-titanate (PZT) transducer are mounted on surface of the sleeve as transmitter and receivers; and experimental study is carried out to validate the feasibility of the proposed method. In order to investigate the effect of grout defects on UT wave measurement, five grouted sleeve specimens with different degrees of the artificial grout defects are designed and analysis on the PZT transducer was used for measurement. By comparing the PZT transducers measurement of different specimens with different grout defects under an identical impulse excitation signal, the grout defect is detected. Experimental results indicate grout defect leads to decrease in PZT transducers measurement UT energy, the relationship between the UT energy ratio and the internal grouting flaws is established: the UT energy decreases with the increment of flaw size. Therefore, the UT method provides a feasible option to evaluate the internal flaws of grouted sleeve connection.

Numerical study on the influence of defects in grouting on the mechanical properties of a full grouted sleeve connector

ABSTRACT The present article analyses the influence of defects in the bonding zone between the reinforcement bar and the grout on the mechanical performance of the full-grouted sleeve connector. Grouted sleeve connections are widely used for horizontal and vertical connections of precast concrete members. This work establishes a friction-based interfacial model to simulate the bond between the reinforcement and the grouting materials when the connection is subjected to tensile loading and conducts a Parametric Analysis to study how the confinement effect and contact surface interact with defects in various mechanical and geometric configurations of the connector on 50 different setups of the models in Abaqus. It is found that the influence of defects is non-homogeneous and additional partial grouting improves the bond strength, which increases the tensile capacity of the connector by up to 70% in some specimens. The effect of the sleeve diameter’s reduction is proven to improve the performance of the connector due to the confinement effect, and the safe minimum anchorage of the bar required for adequate bonding in the weakest configuration is eight times the diameter of the bar.

Study on tensile properties of semi grouted sleeve connectors after high temperature

In this paper, the uniaxial tensile tests of semi grouted sleeve connectors at normal temperature, 200 ℃, 300 ℃, 400 ℃ and 600 ℃ were carried out. The influence of temperature and anchorage length on the tensile properties of semi grouted sleeve connectors after high temperature was studied, and the transition process of failure mode of connection with the increasing of temperature was analyzed. The results showed that with the increasing of temperature, the failure mode of the grouted sleeve connectors changed from tension failure after steel bar yield to the pull-out failure after steel bar yield, and finally to pull-out failure before steel bar yield. The ultimate bearing capacity of the semi grouted sleeve connector decreased with the increasing of temperature. When the temperature was lower than 400 ℃, the best anchorage length of the specimen was 110 mm. The temperature was higher than 400 ℃(including 400 ℃), increasing the anchorage length can effectively increase the ultimate bearing capacity of the specimen. Finally, based on the test results, the calculation formula of the ultimate tensile force of the semi grouted sleeve connectors with the change of temperature and anchorage length was given, which provides a reference for related specification design and engineering construction.

Structural Performance of Grouted Sleeve Splice Connectors with Grooves Under Axial Tensile Load for Precast Concrete Structure

This study explains the performance of the proposed grouted sleeve connector with internal Grooves within the sleeve beneath incremental tensile load until failure. In this study, a series of twelve grouted sleeve splice with grooves (GSSG) were tested experimentally beneath incremental tensile load until failure to determine their feasibilities. The connector utilized mild steel pipe as sleeve where the sleeve comprises internal grooves with differing height and width .The mild steel pipe and the grooves are utilized to confine and strengthen the grout and the two dis continued bars joined end-to-end configuration within the sleeve. The specimens are studied and evaluated based on two major aspects; (a) ultimate tensile capacities, whether it is higher than 125% of the specified yield strength, (b) failure modes, The test shows up that, there are two modes of failure which were bar to grout failure and bar broken outside the sleeve. Sex examples out of twelve shows up palatable comes about since it failed due to bar broken outside the sleeve and fulfill palatable ultimate tensile capacity. The stiffness and the ductility of the connectors additionally fulfill. It is found that the grooves on the sleeves are essential to interlock with the confined grout, resisting it from slipping out of the sleeve. The test appears that the performance of the grouted sleeve connector with grooves was represented by grout-bar bond, anchorage length and control action given by the sleeve and the grooves . Possibility consider for tried grouted sleeves detailing their adequacy in agreement with the code arrangements of ACI 318-14 and ECP 203-2018 is displayed. Besides, design equations capturing the parameters influencing the bond strength, the confining pressure, grooves , and the specified embedment length are determined.

Seismic performance of precast column connected with grouted sleeve connectors

Connections using grouted sleeves remain a popular option for precast elements because of their relative ease of construction, but existing knowledge about the seismic performance of such connections is incomplete and poorly understood. In particular, the effects of the grouted splices are intensively studied in this paper. The main objectives of this study are to examine the influence of axial compression ratio on the strain distribution and shearing deformation in the plastic hinge zones based on full-scale experimental results, as well as to discover the flexural strengths of local grouted sleeve and normal cross-section and evaluate the deformation of precast columns based on modified plastic hinge models. Analysis results demonstrated the following: (1) strain and shearing deformation exhibited that the grouted sleeve has good connection performance, but the existing grouted sleeve was of crucial importance for shearing deformation of precast column; (2) flexural strength of the grouted sleeve cross-section was higher than that of the normal cross-section, which expressed that the compressive strength of a grouted sleeve in the cross-section should be considered; (3) a simplified analysis model based on modified plastic hinge length was presented to evaluate the deformation capacity of a precast column connected by a grouted sleeve, and the decreasing trend of displacement ductility compared favorably with experimental values, but the calculated ductility coefficient expressed smaller results when the axial compressive ratio was 0.5 and 0.85.

Study on properties of carbon fibre reinforced cement-based grouting materials

As an efficient, eco-friendly and economical solution for connecting precast concrete components, grouted sleeve connectors aroused widespread interest in engineering site. However, as the key material of grouted sleeve connection, grouting material needs to provide enough good performance to meet the engineering requirements. In order to better design the mix proportion of grouting materials, this paper studies the influence of water binder ratio, carbon fibre content, expansion agent addition and other factors on the performance of grouting materials, and optimizes the mixture ratio of grouting materials by analyzing the workability, compressive strength and expansibility, and analyzes the bonding performance of grouting materials by using the half-grouting steel sleeve connector.

Mechanical performance for defective and repaired grouted sleeve connections under uniaxial and cyclic loadings

Grouted sleeve connectors provide a convenient and economical solution for connecting precast concrete elements in engineering site. However, sleeve connections may include insufficient grouting defects at certain conditions which may significantly decrease the bearing capacity and increase the failure risk of connection joints. In order to better understand the influence of insufficient grouting defects, the mechanical performance of insufficiently grouted sleeve connections with predesigned vertical grouting defects is investigated in this study by considering three loadings: uniaxial tensile loading, cyclic loading at high stress and cyclic loading at large strain. Comparatively, the repaired sleeve connections by refilling grout material to the sleeve enclosing insufficient grout material are considered as well. Total 24 sleeve connection specimens are tested and the correlation of failure mode, force-displacement response and the defect level is analyzed and discussed. It is revealed that the failure mode of defective specimens may shift from the tensile fracture of reinforcing steel bar to the interfacial bond-slip failure of rebar with the decrease of the anchorage length of reinforcing steel bar. Additionally, it is found that the loading condition affects the failure mode too. Moreover, the repaired sleeve connections show similar mechanical performance to the fully grouted sleeve connection except deformation. This indicates that the regrouting operation to repair the grouting defect in the sleeve is effective in engineering applications.

Structural Performance of Grouted Sleeve Connectors with and without Transverse Reinforcement for Precast Concrete Structure

This paper presents the performance of the proposed grouted sleeve connector with and without steel spiral as transverse reinforcement under incremental tensile load until failure. The connector utilized mild steel pipe as sleeve where the sleeve consists of external and internal sleeve with the diameter of the external sleeve is larger than internal sleeve. The mild steel pipe and the steel spiral are used to confine and reinforce the grout and the two discontinued bars spliced end-to-end configuration in the sleeve. The test shows that, there are two modes of failure which were bar slipped and bar fractured outside the sleeve. Eleven specimens out of fourteen shows satisfactory results as it failed due to bar fractured outside the sleeve and achieve satisfactory ultimate tensile capacity. The stiffness and the ductility of the connectors also satisfy. Grouted sleeve connectors with steel spiral perform better compared to connectors without a steel spiral. The test shows that the performance of the grouted sleeve connector with or without steel spiral was governed by grout-bar bond, anchorage length and confinement action provided by the sleeve and the steel spiral. The connectors have a potential to be used in connecting precast concrete structure.