Grouted Splice Sleeve Research Articles

Determination of grout compactness in rebar grouted splice sleeves using frequency domain characteristics of the excitation process

Grouted splice sleeves are widely used in assembly building connections. However, void defects within the sleeve directly affect the load-bearing capacity of the building structure. This paper presents a new method for detecting void defects inside a grouted splice sleeve based on the frequency domain characteristics of mechanical vibration waves. This method analyses the grouted spliced casing containing void defects as a gas-liquid two-phase flow system. To confirm the validity of the method, this paper builds a test setup for testing. The results showed that the test method can effectively detect the void defects and the volume of the defects inside the grouted splice sleeves when the grout is not solidified.

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.

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.

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.

Quasi-Static Cyclic Tests of Precast Two-Column Bent Connected with Both Grouted Splice Sleeves and Grouted Central Tenon

Owing to the advantages of accelerated construction, reduced traffic disturbance, and enhanced quality control, precast segmental two-column bents are extensively utilized in urban and highway bridges, particularly in areas of low-to-medium seismicity. However, the application of this technique in high-seismicity regions is limited owing to insufficient knowledge about the seismic performance of such precast bents. To address this, the present study investigates the seismic performance of precast segmental two-column bents, focusing on the connection of “grouted splice sleeves and grouted central tenon”, namely the proposed GSS-GCT connection. For this purpose, three large-scale two-column bent specimens were fabricated and subjected to quasi-static cyclic tests: one cast-in-place bent, one precast two-column bent with conventional grouted splice sleeves, and another with the GSS-GCT connection. The benefits of the GSS-GCT connection under high seismic activities were demonstrated regarding lateral load-carrying capacity, displacement ductility, energy dissipation capacity, and residual displacement. Moreover, five levels of damage states were qualitatively and quantitatively divided based on experimental observation, which can be evaluated with lateral displacements. Furthermore, seismic assessments of the two-column bents were obtained using the capacity spectrum method. The proposed GSS-GCT connection could significantly improve the seismic performance of precast segmental two-column bents under high-level earthquakes.

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.

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.

A practical multiscale modeling strategy to model wet-type beam–column connections for seismic analysis of precast RC frame structures

Numerical models of beam–column connections are widely used in the seismic analysis of wet-type precast concrete frame structures. However, because of the trade-off between computational accuracy and efficiency, it is difficult to appropriately consider wet-type precast features by using existing numerical approaches. Therefore, this paper presents a multiscale modeling strategy based on OpenSees software, in which frame and solid elements are adopted to model the flexural behavior of precast members (beams/columns) and cast-in-place joint panels, respectively. Moreover, a multiscale interface is developed and implemented in OpenSees to establish the displacement compatibility and force equilibrium conditions of the interface between the frame and solid elements. The proposed strategy can capture the features of wet-type precast beam–column connections, including grouted splice sleeves, bond–slip, pre- and postcast concrete interfaces and shear deformations in the joint panel. The strategy is validated by experimental results on both the member and structural levels. Finally, an inelastic seismic analysis case study is developed to assess the computational efficiency of the proposed strategy.

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.

Review of experimental investigations on seismic performance of precast segmental bridge columns in seismic regions

Due to the fast construction and low interference, precast segmental bridge columns have gained increasing attention for use in non-seismic regions. However, their applications in seismic areas remain scarce due to their ambiguous dynamic performance. To estimate the seismic performance of PSBCs, existing quasi-static cyclic tests and shaking table tests are gathered and reviewed in this study. According to the structural details and material property at the joints, the PSBCs are categorized as 11 types based on the connection type, namely grouted splice sleeve couplers (GSSCs), grouted corrugated duct connections (GCDCs), wet joint connections (WJCs), mechanical bar splice connections, socket connections (SCs), unbonded post-tensioned tendon connections (UPTCs), partial precast columns (PPCs), hybrid connections (HCs), high-strength steel bars (HSBs), high-performance concrete (HPC), and external dissipators (EXDs). Based on the experimental results, the failure reason of each connection types are discussed and the effective structural details are suggested. And also, the PSBCs are divided into those with ductile and resilient connections according to the damage levels, residual drift ratios, displacement ductility coefficients, equivalent viscous damping ratios and effective stiffness parameters. With the achievements in this research, the application of PSBCs is expected to be promoted in medium-to-high seismic regions.

Seismic performance of short precast bridge columns with grouted splice sleeve (GSS) connectors for shear study: Quasi-static cyclic test and analytical estimation

In this study, shear damage development of four precast bridge columns with different connection design details are first examined via quasi-static test. The short columns are of identical dimension and reinforcement arrangement for both pier and footing segments, and the span-to-depth ratio is 0.85 for shear study. The connection utilizes grouted splice sleeve (GSS) couplers for all four specimens. Different bonding materials are compared, effectiveness of shear keys is investigated, and variation of steel rebar grades is carried out. It is found that epoxy retain lower bond strength than high strength mortar, lower grade of longitudinal rebar significantly reduces shear strength of bridge column, and shear keys are of limited effectiveness on the overall shear damage development. An analytical method for shear strength calculation is then proposed and calibrated based on different test results, which incorporates possible influencing factors for shear strength estimation. Maximum difference between the test results and estimated strength values are less than 10%, and it indicates that the proposed method can be used as a reference for shear strength estimation of short precast bridge columns for seismic strength estimation.

Experimental study and theoretic analysis of shear failure mechanism for short precast bridge columns with grouted splice sleeve (GSS) connectors under direct shear load

Precast bridge structures have been increasingly applied in recent civil engineering applications, which shortens construction time, lowers cost, improves structure quality, decreases traffic interruption, and reduces environment pollution. However, studies regarding to the shear behavior of short precast columns are limited. In this study, five short precast bridge columns, with span-to-depth ratio of 0.43, are tested under direct shear load. This is to understand shear failure mechanism of precast bridge columns with different design details. Two types of shear failure are found due to different embedment location of grouted splice sleeve (GSS) connectors. Different design details (e.g. steel grade of rebar, bonding material of joint interface, and existence of shear keys) also have certain impact on the shear strength of precast columns. Based on the test results, a new theoretic method is proposed to estimate shear strength of tested precast column specimens. The proposed method incorporates possible influencing factors of shear strength along with different failure stages and types. The parameters and formulas are calibrated and adjusted accordingly. It is found that, for short precast columns with GSS connectors, the theoretic solutions are within 5% in difference compared with test results, which shows better accuracy than other methods. This indicates that the proposed method is effective for the estimation of shear strength in this case.

Fragility-informed seismic design of multi-column bridge bents with post-tensioned concrete columns for accelerated bridge construction

Accelerated Bridge Construction (ABC) is playing an increasingly large role in bridge construction within urban centers due to faster installation, improved quality and lower cost. Concrete columns are prefabricated and connected together with footings and cap beams using either grouted splice sleeves, socket connections, or through post-tensioning. Precast unbonded post-tensioned (PT) concrete columns are protected from damage due to their ability to mitigate seismic demand through rocking. A numerical model is developed for rocking columns which is validated using published data. Seismic assessment of a two-column bridge bent constructed with precast PT concrete columns is carried out; column height-to-width ratio and ratio of initial posttensioning force to axial column capacity are selected as the assessment parameters. Performance limits are defined for the bridge model using non-linear pushover analysis. Probabilistic seismic hazard analysis is carried out using nonlinear time-history analysis for a set of eighty ground motions. The results show that PT concrete columns provide sufficient re-centering to the bridge bent so that it remains serviceable after a large earthquake. An ABC bridge bent with unbonded PT concrete columns is designed using the outcome of seismic fragility analysis. The seismic performance of the fragility-designed PT bridge bent is compared to that of a bent with conventional cast-in-place (CIP) concrete columns using nonlinear time-history analysis. The seismic performance of the ABC PT bridge bent using fragility analysis satisfied performance objectives similar to a monolithic CIP bent designed according to the latest seismic design codes; in addition, the residual drift of the PT bent was practically zero. The fragility-informed approach for designing ABC bridge bents constructed with unbonded PT concrete columns presented is expected to promote post-earthquake serviceability and functional recovery after a large earthquake.

Experimental test on precast concrete reinforcement connector technology based on strong lapping concept

Experimental test on precast concrete reinforcement connector technology based on strong lapping concept

Experimental Study on UHPC-Based Grouting Materials and Mechanical Performance of Grouted Splice Sleeve Joints

The prefabricated concrete structure is regarded as the main body of the green construction technology, while the joint connection of the prefabricated components is the weak link of force. In addition, the grouting sleeve connection is a widely used connection method in the prefabricated component joints. The effective anchorage of reinforcement is realized by the implementation of a mechanical bite force, friction force and bonding force between reinforcement, grouting material and sleeve inner wall, respectively. Along these lines, in this work, a UHPC-based grouting material was prepared, and its main technical performance was tested. The influence of the grouting mix proportion and anchorage length on the stress performance was thoroughly investigated by carrying out a unidirectional tension test of eight grout-filled splice sleeves. The acquired results show that UHPC grouting containing micro and particles possess high mechanical strength and durability. The incorporation of UHPC grouting containing steel fibers can further improve the compressive and flexural strength. However, its fluidity will be reduced and grouting difficulties will be induced. For that reason, the utilization of UHPC-based grouting material without steel fibers is recommended. The grout-filled splice sleeve joints with UHPC meet also the strength requirements, and the sleeve can be found in the elastic stage in the test, indicating that sleeve joints possess a higher safety margin.

Effects of Grout Compactness on the Tensile Behavior of Grouted Splice Sleeve Connectors

The quality of grouted sleeve has a significant influence on the performance of the sleeve splice. Incompactness of the infilled grout is inevitable in sleeve grouting. To investigate the tensile behavior of grouted splice sleeves due to different grout compactness, monotonic tensile tests on grouted splice sleeve connectors were performed at grout compactness of 100%, 90%, 70%, and 50%, respectively. The bond-slip analytical model of rebar-grout was deduced by fitting the tensile test data, and the formula for the tensile capacity of the grouted splice sleeve was proposed in the paper. The results show that the tensile strength of the splice sleeve reduces as the grout compactness decreases. It was found from the experiment that the calculated values of tensile capacity are in good agreement with the experimental values. The proposed formula can be adopted in determining whether reinforcing remedies or re-grouting should be taken in the case of incompact grout in grouted splice sleeve connectors.

Cracking analysis of members connected by grouted splice sleeves under axial tension

Precast bridge columns (PBCs) connected by grouted splice sleeves (GSSs) are important in accelerated bridge construction. To determine the specific crack mechanism of GSS joints and to ensure the serviceability and durability of PBCs, 13 specimens, each divided into two segments and connected by GSSs, were designed and subjected to axial tension. Owing to the presence of GSSs, each specimen could be divided into three regions—respective joint, sleeve, and no-sleeve regions—with different axial tensile stiffness. Consequently, four critical sections (joint, no-sleeve, bar stop, and GSS top sections) cracked successively in sequence from the smallest axial tensile stiffness to the largest. After analysing the cracking process and internal force redistribution laws of the specimens, the crack mechanisms of the critical sections were examined separately, and further used to deduce the formulae for calculating the crack widths of the critical sections. The predictions from the calculation results of this study were compared with the test results and showed good agreement, which, in turn, confirmed the rationality of the proposed crack mechanisms.