Splice Sleeve Research Articles

Study of mechanical behavior of grout sleeve splicing of rebars

Study of mechanical behavior of grout sleeve splicing of rebars

Flexural behaviour of bolted flange-plate with bonded sleeve splice connections for pultruded GFRP circular tubular hollow beams

The paper presents an experimental and finite element investigation of bolted flange-plate with bonded sleeve splice connections for joining pultruded glass fibre-reinforced polymer (GFRP) circular tubular beams. The moment-rotation behaviour was investigated in terms of initial rotational stiffness, moment capacity and rotation capacity for all the tested splice connections. The effect of the number of flange-plate bolts, flange-plate thickness and the length of the bonded sleeve were examined. Failure modes for the thinner flange-plates included opening, bending and yielding of the flange-plates in the tension zone. Thicker flange-plates and a higher number of bolts exhibited improved initial rotational stiffness with lower rotational capacity, which can be enhanced by higher bonded sleeve lengths. Available design codes for steel joints were used to classify the splice connections with regards to rigidity and strength. The failure modes from the finite element models were consistent with the experimental observations, which includes the plastic deformation of the flange-plate and the cohesive failure of the adhesive.

Grout sleeve splicing of steel-fiber reinforced polymer composite bars: Tensile behavior and bond mechanism

In reinforced concrete structures exposed to harsh environments, steel corrosion poses a significant problem. Ductile and durable steel-fiber reinforced polymer composite bars (SFCBs), which can effectively address this issue, are a perfect alternative to conventional steel bars. However, the lack of suitable connection methods for SFCB has hindered their widespread adoption in civil engineering. To address this limitation, this paper proposes the use of grout-filled steel sleeves as a solution for connecting SFCB. The study designed 120 specimens of grout sleeve splices for SFCB to investigate their performance under unidirectional tensile forces. The experimental variables included the ratio of grout thickness to SFCB diameter, SFCB diameter, anchorage length, and grout strength. The results revealed various failure modes and found that specimens with a smaller ratio of grout thickness to SFCB diameter and greater grout strength demonstrated higher peak stress. The peak stress first increases and then slowly declines with an increase in anchorage length. Additionally, the peak stress decreased with increasing SFCB diameter, and the peak slip remained constant. Meanwhile, the bond mechanism between SFCB and grout was revealed. Finally, the study derived a theoretical bond-slip curve between SFCB and grout, as well as the development anchorage length.

Performance of Grouted Splice Sleeve as A Connection for Wall Panels

A grouted sleeve is a mechanical coupler used to join steel bars. It can be used to join precast concrete walls. Most grouted sleeves are pricey proprietary products. This study investigated the behaviour of a grouted sleeve made of steel pipe sections. The grouted sleeve was used as a wall panel connection. The specimens were subjected to three types of loads: tensile, shear, and flexural. The performance of the specimens was evaluated based on the load-displacement responses. For satisfactory bond strength, a bar embedded length of 11 times the bar diameter was required. The grouted sleeve performed well in tension but poorly in shear load. The service shear load was just one-third of the total load capacity. Thus, the grouted sleeve was not recommended for resisting shear load without shear keys to strengthen the joint.

Lateral hysteretic behavior of precast concrete shear walls with unjointed vertical distribution bars and opening

Precast concrete shear walls with unjointed vertical distribution bars have desirable lateral resistance compared with cast in situ concrete shear walls and much less construction cost as no sleeve splicing joint is needed. However, the influence of opening in the precast panels on their lateral hysteretic behavior has not been fully investigated. This study presents the results of cyclic loading tests of three full size precast concrete shear walls with unjointed vertical bars and opening. The test results showed that these shear walls had similar failure modes as a cast in situ concrete shear wall, such as cracking in the corners of the opening and the concrete and steel bars crushing at the bottom corners of the shear walls. The peak load of the positive and negative loading cycles and the stiffness of the unjointed shear wall with a window opening were 14.6%, 4.3% and 1.3%, respectively, smaller and the ductility ratio was 37.6% higher, than an otherwise the same cast in situ shear wall. The lateral stiffness of the unjointed shear wall with a door opening was 35% smaller than that of the one with a window opening, due to the stiffness contribution of the wall segment underneath the window opening. The development of the longitudinal strains of concrete and steel strain along the height of the wall limbs generally met the plane section assumption. However, those next to the vertical joint interface were affected by the development length of the shear force after the bedding mortar cracked under tension. The determination of the development length needs to consider the influence of the stiffness of the link beam and the wall segment underneath the opening.

Research and Application of Key Technologies for Assembling Design and Construction of Reinforcement in Super High Concrete Bridge Tower

Concrete bridge towers are widely used in long-span bridges. Aiming at the reinforcement process which requires the largest labor force and has the highest safety risk during the construction of the super high concrete bridge tower. The key technology of assembling design and construction of super high concrete bridge tower reinforcement characterized by “industrialized production of mesh, rapid section forming and on-site assembling installation” is creatively proposed. In terms of design, the three-dimensional bridge tower reinforcement is discretized into planar or 3D mesh. In order to facilitate the reinforcement segment, a new flush lapping is used for the circumferential connection of stirrup, and the tapered sleeve splicing is used for the connection of the reinforcement parts between the segments, and the reliability of the connection is verified by experiments. In terms of construction, industrial assembly lines are used for the production of steel mesh and overall bending forming. The bridge tower reinforcement segments are assembled on the special jig, and finally installed on the tower by the tower crane. At present, this technology has been successfully applied to projects such as Lingdingyang Bridge, reducing labor intensity, improving construction efficiency by 30%, and ensuring project quality.

Experimental study on mechanical properties of corroded grouted sleeve splice

Grouted sleeve splices are widely used in precast-concrete (PC) structures. Although extensive tensile tests have been conducted on grouted sleeves, the force mechanism and changing rules of grouted sleeve connections as influenced by environmental corrosion have rarely been investigated. Accelerated corrosion and monotonic tensile tests were conducted on twenty-five grouted sleeves. The investigated variables of the sleeve splices were the degree of corrosion, rebar eccentricity, and geometrical sizes of the rebar and sleeve. Based on the test results, the three-dimensional corrosion characteristics of the sleeve were analyzed, and the influences of the corrosion distribution, rebar eccentricity, and sleeve size on the failure mode, force–displacement curve, and strain distribution of the sleeves were discussed. The results indicated that the surface roughness parameters Sz, Sa, and Sq of the sleeve increased with an increase in corrosion. As a result of sleeve corrosion, the failure mode of the grouted sleeve connection changed from rebar fracture to sleeve fracture, accompanied by an increase in the longitudinal and circumferential strains of the sleeve, and reductions in strength, deformation capacity, and energy dissipation ability. In addition, the rebar eccentricity led to an uneven strain distribution in the circumferential direction.

Cyclic shear loading test for grout-sleeve joints in precast concrete shear wall structure

The reinforcement sleeve splicing technique has been utilized extensively in precast concrete shear wall structures, as it allows for achieving similar lateral capacity and deformation ability with cast-in-place (CIP) walls. However, investigation on shear behavior of the horizontal joint using this vertical connection is limited. In this study, six specimens of grout-sleeve (GS) joints designed for precast shear wall structures with single-row distributed reinforcements were subjected to cyclic loading tests under pure shear conditions, accompanied by three companion concrete-to-concrete (CC) joint specimens. The study investigated the influence of interfacial reinforcement ratio and surface roughness on the seismic performance of GS joints with different design details, aiming to understand their shear failure mechanism. The joint behavior under cyclic shear loading, including transverse dilation, strain development, and energy dissipation, was analyzed. Experimental results indicated that all specimens exhibited a significant pinching effect and strength degradation in hysteretic curves. Two types of shear failure, sliding failure along the grout-concrete interface with minimal wall cracking and diagonal compression failure with extensive concrete crushing above the grouted layer, are observed due to the roughness of the grout-concrete interface. This roughness also affects the curvature profile of interfacial reinforcement. A larger interfacial reinforcement ratio or a roughened interface can significantly increase the shear strength of the horizontal joints. However, although the GS joint and CC joint have similar failure modes, the variation in cracking patterns resulted in a reduction of up to 10.6 % in shear strength for the grout-sleeve joint. Nonetheless, it exhibited relatively ductile shear behavior compared to the concrete-to-concrete joint. A comparison of shear strength evaluation between five existing codes shows that Eurocode 2 gives the closest result to the test values.

Seismic performance of corroded prefabricated column-footing joint with grouted splice sleeve connection: Experiment and simulation

Steel corrosion is a critical factor in the seismic performance degradation of prefabricated concrete structures. In this study, the constant current accelerated corrosion method was employed to achieve targeted corrosion levels in steel bars within prefabricated column-footing joints connected by a grouted splice sleeve (GSS). Following that, a quasi-static cyclic experiment and numerical simulation method were employed to investigate the seismic performance of the specimens under various corrosion levels. Seismic performance indicators of specimens including the hysteresis curves, skeleton curves, bearing capacity, ductility coefficient, stiffness, and cumulative energy dissipation are examined. The results demonstrate that the failure modes of all column-footing joints are flexural failures. Specimens with steel bar corrosion levels below 14.1 % show negligible impact on the seismic performance. However, as the corrosion level increases, both the bearing capacity and cumulative energy dissipation capacity of the specimens significantly decrease. The horizontal displacement and ultimate displacement corresponding to the maximum bearing capacity are only 50.5 % and 45.2 %, respectively, compared to the non-corroded specimen. Additionally, a refined finite element model of prefabricated column-footing joints with GSS connections under different corrosion levels is developed and the hysteresis and skeleton curves obtained by numerical simulation are verified to be in good agreement with the experimental results. The numerical simulation outcomes regarding peak load and corresponding horizontal displacement maintain a relative error within 15 % compared to the experimental results.

Emulation Evaluation of Interior Beam-Column Connections in PC and RC Moment-Resisting Frames.

Precast concrete (PC) structures have many advantages, but their use in the construction of middle- to high-rise buildings is limited. The construction of PC structures requires skills in various operations such as transportation, assembly, lifting, and structural soundness. In particular, regarding the seismic design of PC structures, it is necessary to clearly evaluate whether they have the same structural performance and usability as integral RC (cast-in-place) structures. In this paper, an experimental study was conducted to investigate whether PC members can achieve a seismic performance equivalent to that of RC members in beam-column joints, which are representative moment-resisting frames. The main variables are the two types of structural systems (intermediate and special moment-resisting frames) and the design flexural strength ratio of the columns and beams. The experimental and analytical results showed that the seismic performance of the PC specimens was equivalent to that of the RC specimens in terms of strength, stiffness, energy dissipation, and strain distribution, except for the specimen with splice sleeve bond failure of the column reinforcement (poor filling of the internal mortar). In addition, the I series satisfied the present emulation evaluation criteria for special moment-resisting frames of PC structures, confirming the possibility of applying intermediate moment-resisting frames.

Seismic performance of centrifugally prefabricated square hollow columns: Experimental and numerical study

In this study, five 1/2.8-scale centrifugally prefabricated square hollow column specimens are experimentally investigated under quasi-static cyclic test, to evaluate the seismic performance of such columns with different design details. The specimens include one cast-in-place (CIP) specimen and four precast specimens, which aims to study the influencing factors of grouted splice sleeve connection, concrete grade, filled concrete, and tie bars. Damage development, hysteretic behavior, ductility, effective stiffness, energy dissipation, and residual displacement are compared, analyzed and summarized. Finite element modeling is then conducted for all specimens, and improved modeling approach is proposed. The improved modeling approach has considered structural nonlinear behavior by incorporating a new way of material modeling, other than conventional types of material. Detailed parametric analysis is also performed, and reasonable ranges of each factor are proposed. The new approach will potentially provide references for numerical simulation of such centrifugally prefabricated square hollow columns, which balances modeling accuracy and computational efficiency.

Behavior of grouted splice sleeve connection using FRP sheet

Most existing studies on grouted splice connections have focused on the bond behavior between connected steel rebars and conventional steel or iron sleeves. These research findings cannot properly predict the bond behavior and performance of the grouted splice connections, particularly when a new splice device, such as fiber reinforced polymer (FRP) materials, are adopted. The main purpose of this study is to investigate the feasibility of the proposed grouted splice sleeve connection (GSSC) using sheet materials of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP). A total of 45 GSSC specimens with various rebar embedded lengths and different polymer sleeve materials were tested to failure under incremental axial pull-out load to evaluate the bond performance of the connected steel rebars in confined grout provided by the FRP sleeves. To evaluate the confinement effect of FRP sleeves on the tensile strength of the grouted connection, an analytical model was developed. The pull-out test results showed that the rebar embedded length was the major parameter affecting the average tensile strength of the GSSC. Also, the effects of mechanical properties of FRP sheets, such as the number of FRP layers and type of FRP sheets, contributed to the tensile strength of the GSSC sleeves that allow the transmission of tensile load between rebars through the medium of grout, aluminum tube, and FRP sheets. The analytical model that incorporates the confinement effects predicted well the experimental ultimate tensile strength of GSSC connections.

Experimental study of precast columns with a hybrid joint incorporating bolted couplers and grouted sleeves

The grouted sleeve (GS) splicing with mature technology is a favored wet-assembled connection in Chinese engineering. A technical interval is normally required to reach the design strength of the grouting material in the in-situ construction of GS splicing, increasing the demands of temporary bracing and reducing the on-site construction efficiency. In this paper, a hybrid joint was proposed by incorporating grouted sleeves and bolted couplers to improve the construction efficiency of GS splicing and reach a comparable performance to the joint with GS splicing. The bolted coupler was labeled CTB coupler, characterized by a combination of threaded connection and bolt fastening. Quasi-static tests were conducted to discuss the seismic performances of four columns, including two precast columns with a hybrid joint (labeled the hybrid column), one precast column using grouted sleeves, and one precast column using CTB couplers. The discussions illustrated that the hybrid column exhibited comparable stiffness degradation and strength to the precast concrete column with the GS splicing, while the former showed a decrease in inelastic deformation capacity and energy dissipated capacity compared to the latter. The energy dissipated capacity of the hybrid column can be improved in two feasible ways: increasing the distance from the hybrid joint to the foundation and using a higher strength rebar for the lower rebar (in the CTB coupler) with respect to its upper rebar. Finally, simplified numerical manners were proposed to consider the effects of CTB couplers and GS splicing. The experimental result of each specimen matched well with its numerical result, validating the effectiveness of the simplified manners.

Tensile behaviors and configurations of double-headed bar overlap connections for precast concrete members

The superiorities in construction time, cost, and quality of precast RC structures are accompanied by the challenges in connection, particularly in steel bars connections between RC components. The extensively used steel bar connections for either grouted sleeve splice connection or grouted spiral-confined lap connection requires on-site grouting, which is a concealed construction process with increased the risk of grouting defects, thereby impairing connection reliability. The confined headed bar connection (CHBC) with visible on-site construction has been proposed to address the unseen grouting defects concerns. However, modern structures that use large-diameter or high-strength rebars present higher demands for steel bar connection capacity. For CHBC, it is suggested to use either a long connection length or a large-size head to satisfy the capacity demand. However, the long connection length can increase field wet operation, which is disadvantage in precast concrete construction. The large-size head can help reduce the connection length, but it can cause inconvenience including construction congestion and the increased eccentric bending moment under tension. This paper presents the CHBC with double-head configuration, which can reduce the single head size. The proposed CHBC consists of confinement stirrups and two overlapped headed bars and the stirrup confining the core concrete can also improve the CHBC capacity. Experimental investigation on 21 CHBC specimens has been carried out. The failure modes, bearing capacity, and stirrup strain development have been studied. Effects of the double-head configuration and confinement stirrup ratio have been analyzed through experimental and numerical investigation. Results show that the double-head configuration has a minor impact on the tensile capacity of CHBC while the increase of confined stirrup ratio can improve the tensile capacity of CHBC. Configuration details of size and spacing for stirrup reinforcement in CHBC are proposed. Based on the test results, CHBC tensile capacity prediction method is suggested, which can take the head configuration into account.

Experimental study on the seismic performance of precast segmental unbonded post-tensioned frame piers

Prefabricated assembly technology offers significant benefits for the construction of urban bridges, including shortened construction periods and reduction of traffic congestion. It can be used to construct precast concrete structures that are capable of withstanding seismic loads. However, studies on the seismic performance of precast segmental unbonded post-tensioned frame concrete piers are lacking. Therefore, there is an urgent need to evaluate the seismic performance of piers under different prestressing degrees. In the study, three prefabricated frame concrete piers were designed and subjected to quasi-static tests: unbonded post-tensioned tendons (UPT) with the prestressing degrees of 0.5 and 0.7 combined with grouted splice sleeves (UPT-0.5 specimen, UPT-0.7 specimen); and grouted splice sleeve connection (a reference specimen PC-S). The seismic performance of the UPT-0.5, UPT-0.7, and PC-S specimens was evaluated based on various evaluation indexes such as bearing capacity, residual displacement, displacement ductility, displacement of column segments, stiffness degradation, and energy dissipation (ED) capacity. The test results showed that the three piers exhibited flexural failure; however, the damage to the UPT-0.5 specimen was the most severe. With the increase of prestressing force, the hysteresis curve of the UPT-0.7 specimen was greater, the yield load and peak load of UPT specimens both increased by more than 18%, the initial stiffness and failure stiffness increased by more than 10%, but the impact on the ductility, residual displacement, and displacement of column segments was relatively small. At the end of the test, the cumulative energy dissipation (ED) values of specimens UPT-0.5 and UPT-0.7 were 76% and 53% lower than those of the PC-S specimen, respectively. The combination of grouted splice sleeves and unbonded post-tensioned tendons endows precast segmental frame piers with the characteristics of rapid construction and excellent self-centring ability. These characteristics are particularly advantageous for the efficient post-earthquake rehabilitation of urban bridges in low-to-medium seismic areas.

Data-driven models for predicting tensile load capacity and failure mode of grouted splice sleeve connection

Grouted splice sleeve connection (GSSC) is an important connection technology in prefabricated structures, and the tensile load capacity and failure models of GSSC are very important to joint safety. In this study, two data-driven prediction methods (i.e., the machine learning (ML) method, and the threshold method) are proposed to predict the tensile load capacity and failure mode of GSSC. To this end, a database containing 418 existing GSSC experimental data is built. The database is used for eleven ML algorithms (i.e., linear prediction (LP), artificial neural network (ANN), support vector machine (SVM), k-nearest neighbors (KNN), decision tree (DT), random forest (RF), extremely randomized trees (ET), gradient boosting decision tree (GBDT), extreme gradient boosting (XGBoost), light gradient boosting machine (LightGBM), and categorical boosting (CatBoost)) to establish ML models interpreted by shapley additive explanations (SHAP) and partial dependence plot (PDP). Further, the database is applied to the genetic programming (GP) algorithm to generate a simplified equation for the bond strength between rebar and grouting materials, which is the key mechanical parameter for the threshold method. The results show that both of these methods can effectively predict the tensile load capacity and failure mode of GSSC with various common construction defects, and the predictive performance of ML is slightly greater than that of the threshold method.

Experimental study on the seismic performance of prefabricated frame piers

Prefabricated assembly technology can speed up the construction process and is widely used in the construction of urban bridges. However, research on the seismic performance of prefabricated frame concrete piers is scarce, and the seismic performance of prefabricated frame concrete piers with different connection forms must be urgently evaluated. In this study, three prefabricated frame concrete piers with different connection forms–namely cast-in-place (CIP), grouted splice sleeve connection (PC-S), and grouted corrugated duct connection (PC-C)–were designed and fabricated. Through quasi-static testing, the seismic performances of the CIP, PC-S, and PC-C specimens were evaluated using bearing capacity, displacement ductility, stiffness degradation, energy dissipation capacity, etc. as evaluation indexes. Based on the plastic damage theory of concrete, a finite element model was established. The test results showed that all the three specimens experienced flexural failure, and their load–displacement hysteretic curves were similar in shape (i.e., shuttle-shaped). The bearing capacity and ductility coefficient of the PC-S specimen were 95.7% and 77.5% of the CIP specimen, respectively, and those of the PC-C specimen were 93.0% and 92.5%, respectively. The stiffness degradation trends of the three specimens were similar, but the PC-S specimen exhibited the largest initial stiffness, and the stiffness of the PC-S and PC-C specimens at failure was 86.0% and 95.7% of that of the CIP specimen, respectively. When the CIP specimen failed, the cumulative energy dissipation values of the PC-S and PC-C specimens were 16.7% and 14.2% lower than that of the CIP specimen, respectively. The numerical simulation curves fitted well with the test curves, which verified the accuracy of the test results. The seismic performances of two kinds of the prefabricated bridge piers were close to the CIP specimen. When the strength of connectors and sealing material meet the requirements, prefabricated frame concrete piers can be preferentially selected for medium and low seismic areas.

Behavior of a novel corrugated grouted sleeve splice for prefabricated construction under uniaxial tensile loading

A corrugated grouted sleeve (CGS) made of a seamless tube, which is easy to produce at low cost, is presented. To investigate the connection behavior of CGS splices, a total of 33 specimens are manufactured and tested under monotonic loads. The effects of the corrugation number, groove depth, and steel bar diameter on the connection performance of the CGS are examined. The test results show that the proposed CGS is deemed an effective and reliable steel bar connector for precast structure buildings due to the groove in the corrugation, which plays a key role as a wedge to prevent bond failure of the steel bar splice and enhance the confinement action of the sleeve; one corrugation formed by the roll extrusion method at the end of the seamless tube is sufficient to provide a wedge action to ensure steel bar failure first; the depth of the groove is suggested to be more than 2 mm to ensure that the bond strength is sufficient before steel bar fracture. Finally, an analytical model is proposed to predict the tensile resistance of the CGS considering the influence of confinement caused by the corrugations, and the predictions are in good agreement with the experimental data.

Numerical Modeling of Column Piers with Recessed Spliced Sleeves and Intentional Debonding for Accelerated Bridge Construction

The grouted splice sleeve (GSS) connection is considered to be an effective bending moment–resisting connection between precast RC members. This connection type has been used extensively in nonseismic regions. The application of such a connection type in moderate or high seismic regions has been investigated and considered for multistory moment frame buildings and highway bridges. A computational modeling strategy is proposed at local and global levels for developing an appropriate computational model for such a connection type using a recessed GSS connection with intentional debonding. A computational model capable of predicting the structural response under cyclic loading was developed using established material models and a forced-based beam-column element considering low-cycle fatigue of reinforcing bars, bar-slip, intentional debonding of reinforcing bars, and plastic hinge length. The proposed model for recessed GSS connections with intentional debonding was experimentally validated. The proposed model was subsequently used to obtain the seismic response of a three-column bridge bent to near- and far-field earthquakes in terms of the overall maximum drift ratio and the drift ratio at the maximum seismic force.

Experimental investigation on the dynamic behavior of grouted splice sleeve connector under fast tensile loading

This paper presents an experimental program designed to investigate strain rate effects on the bond behavior of grouted splice sleeves connected with deformed steel bars. Thirty-six grouted splice sleeve specimens with different anchorage lengths were designed and tested under direct dynamic tensile loads with four loading strain rates (10−3, 10−1, 10° and 10+1 s−1). Strain gauges were employed to record the strain of the sleeve and rebar. The failure modes and the dynamic bond-slip relationships of specimens were obtained. The results show that the bond force capacity increases with an increase in the strain rate. However, the failure mode shifts from the steel bar fracture towards steel bar pullout as the strain rate increases. The mechanisms of a dynamic load transmission are described based on the experimental results. A dynamic analytical procedure incorporating the strain rate effects was developed to predict the bond force-slip relationships and was validated by comparing the experimental bond force-slip curves. The shifting of failure modes was attributed to the damage aggravation effects of the grouted mortar, which led to a reduced effective anchorage length and a steel bar pullout failure mode at high strain rates. In addition, based on the proposed analytical model, the required anchorage length of grouted splice sleeves at different strain rates was calculated and an empirical model was developed to determine the critical embedment length to facilitate engineering design.