Sleeve Connection Research Articles

Experimental study of the shear behaviour of concrete-grout-concrete joints

Grouted sleeve connections are currently widely adopted in precast concrete structures. For this kind of connection, there exists a kind of multilayer concrete-grout-concrete joint whose the mechanical behaviour is quite different from that of the new and old concrete interface. Simply following the current bonding theories and conclusions of new and old concrete interfaces will cause uncertainties in the structural analysis and design. In this study, monotonic and cyclic loading tests were both employed to examine the influence of the grouting thickness and the interfacial shear reinforcement ratio on the shear behaviour of this new type of joint. The shear behaviour was also compared with that of the new and old concrete interface. The results showed that the shear capacity of the concrete-grout-concrete joint was lower than that of the new and old concrete interface. Specimens with a thinner grouting layer or with a larger ratio of shear reinforcement have a higher shear capacity. According to the experimental results, the shear transfer mechanism of the concrete-grout-concrete joint was proposed based on the extended friction shear model, and the modified shear capacity calculation model was then established. • Monotonic and cyclic loading tests were both employed to examine the shear capacity of concrete-grout-concrete joint. • The shear capacity of the concrete-grout-concrete joint was lower than that of the old and new concrete interface. • Shear transfer mechanism of the concrete-grout-concrete joint was proposed.

Numerical Investigation of Precast Grouted Sleeve Connection under Cyclic Loading Using ABAQUS

This paper deals with numerical investigation using finite element software, ABAQUS CAE, for the analysis of precast reinforced concrete (RC) column connected to the foundation containing protruding bar in grouted sleeve subjected to axial, and lateral loads, including the cyclic loading response. The monolithic connection of column and foundation is designed and the same has been used for the design of precast concrete column and foundation. The model focusses on the length of the protruding bar provided in the foundation that is connected to the column through the grouted sleeve. As there is lack of Indian standard codes in the design of precast concrete connections, an attempt has been made by varying the length of protruding bars. The model was subjected to quasi-static loading condition and parameters such as ultimate load carrying capacity, load-displacement hysteresis, ductility and plastic strain were studied and were compared with that of monolithic connection. The results proved that when the length of protruding bars provided was equal to development length of the bar provided, the results were comparable with that of monolithic connection.

Design of sleeve connections with cross-bolted on circular hollow sections under axial tension

This present paper evaluates the behavior and resistance capacity of cross-bolted sleeve connections with circular hollow sections (CHS) under axial tension. This connection allows harmony in the continuity of the tubes. The cross-bolted sleeve connection with CHS comprises outer tubes connected by an inner tube and cross bolts at 90°. Therefore, an experimental, numerical, and parametric study was conducted to identify the connection's possible failure modes. The experimental tests were developed with cross bolts at 90°, which enable the identification of fracture through the effective net area, bearing failure, and bolt bending. Finite element (FE) numerical models were developed and validated by Ansys software to provide a parametric study. Thus, such a parametric study was carried out using the verified FE models. The failure modes were evaluated considering the effects of geometric properties concerning their type and location; a relative slenderness limit for the design of connections was proposed, directing the occurrence of a failure in the outer tube. Normative prescriptions do not foresee the design of the sleeve. Therefore, new formulation methods for estimating the strength were proposed, allowing the design of these connections.

Seismic Performance of Precast Columns Connected with Two Different Connection Modes

The precast reinforced concrete building is made of precast components, which are connected at the joints via reliable connection approaches. Therefore, the study on the stability and reliability of the connections should be conducted to improve the safety and integrity of the precast structure. In this paper, experiments on two connection modes, i.e. corrugated pipe confined with spiral stirrup connection and steel sleeve connection, were carried out. The experimental tests consisted of six specimens, including one cast-in-situ specimen, three precast specimens using steel sleeve connection and two precast specimens using corrugated pipe confined with the spiral stirrup. The influence of artificially unbonded length at the connection joint is also studied. All specimens were tested under low-frequency cyclic repeated loading to analyse their seismic performance under different connection modes. The experimental results showed that the precast columns using the two proposed connections have a similar or even better seismic performance compared with the cast-in-situ column. The installation of proper unbonded treatment on the longitudinal reinforcement in the connection is beneficial in improving the seismic performance of precast columns and the length of 5 times of the longitudinal reinforcement’s diameter is recommended.

Experimental Study on Seismic Behavior of Precast Frame Columns with Vertical Reinforcement Spliced with Grouted Sleeve Lapping Connectors

Grouted splice connector is widely employed in precast concrete structures, but its utilization is still limited by shortcomings such as high construction cost, inconvenience in assemblage, and uncompacted grout caused by its small sleeve diameter. The grouted sleeve lapping connectors proposed by the authors can not only provide reasonable force transfer and convenient construction processing but also have the characteristics of low price and easy grouting. In this paper, the seismic performance of two full-scale precast concrete columns with two types of grouted sleeve lapping connectors was investigated, where type-I connector connected two lapped rebars and type-II connector connected four lapped rebars by a steel sleeve, respectively. A cast-in-situ column was also tested as a reference. All the specimens were tested under reversed cyclic horizontal load with a constant axial force. The distribution of cracks, failure modes, loading capacities, deformation abilities, stiffness, ductility, hysteresis loops, and energy dissipation of the specimens were studied. The type-I and type-II grouted sleeve lapping connectors satisfactorily transferred the stress of rebars when the columns reached their ultimate loads, and the seismic performance of the precast concrete columns was found to be comparable to that of the cast-in-situ column. Thus, the grouted sleeve lapping connector has a potential to replace the grouted splice connector in cast-in-situ 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.

Monotonic and cyclic behaviour of cuff beam-to-column connection system for tubular pultruded GFRP profiles

The use of glass-fibre reinforced polymer (GFRP) cuff parts to join GFRP beams and columns has been object of several experimental and numerical studies in the past, which showed their improved mechanical performance when compared to connection systems that mimic steel structures, such as connections with GFRP web and/or flange cleats. The main objective of the study presented in this paper is to propose and assess a connection system – for tubular GFRP profiles –with similar cuff geometry, but made of stainless steel, in order to achieve higher ductility due to its inherent strain hardening, while maintaining the non-corrodibility capabilities of GFRP. Full-scale tests were performed on four different beam-to-column connection series using stainless steel cuffs with varying geometry and plate thickness. The experimental campaign comprised: (i)monotonic tests for all series; and (ii)cyclic tests for the series with the best performance in the monotonic tests. The monotonic response of the different series varied considerably. As expected, by increasing the plate thickness of the cuff, the initial stiffness and strength of the connections were substantially improved; on the other hand, the moment vs. rotation behaviour of connections with thinner cuff parts was more markedly non-linear and GFRP damage was delayed. Nevertheless, all connection series presented significant ductility, successfully making use of the stainless steel mechanical properties. For both monotonic and cyclic loading, the cuff connection system presented herein provided better mechanical performance than stainless steel sleeve connections developed earlier by the authors, namely regarding initial stiffness, overall strength and energy dissipation.

Experimental research on the mechanical behavior of grouted sleeves with fiber-reinforced grouting material under cyclic loading

The normal grouting material which has been widely used in traditional grouted sleeve connections has high brittleness and it often burst when broken. Moreover, these grouted sleeve connections required larger anchorage length and exhibited a worse cyclic load capacity than the steel bar. In this research, three kinds of fibers, including polypropylene fiber, polyvinyl alcohol fiber and basalt fiber, were selected as mixing materials in the grouting material. Their performance was tested in three areas: basic mechanical properties, toughness, and the optimal content and length of each fiber. Then, a total of 120 grouted sleeve connections with three selected optimal fiber grouting materials and five different anchorage lengths were manufactured. The mechanical performance of the grouted sleeves connections was tested under two loading schemes: cyclic loading at high stress (CH) and cyclic loading at large strain (CL). The compression test results of grouting materials demonstrated that fiber was an ideal material for improving the toughness of the grouting material. The optimal content of each fiber in grouting material was 0.5% (PP), 0.3% (BF) and 0.1% (PVA) and the optimal length was 9 mm (PP), 3 mm (BF) and 3 mm (PVA), respectively. Meanwhile, the minimum anchorage length of rebar in the grouted sleeves could be reduced by at least 1 d (d: diameter of rebar) when the fiber reinforced grouting material was adopted. According to the load–deflection curves under cyclic loading, the fiber reinforced grouted sleeve connections exhibited better residual deformation and stiffness degradation. Test results demonstrated that the fiber could clearly enhance the residual bond strength and ductility of the reinforced section, and the residual bond strength of the connections with the fiber grouting material could be increased by 3.8% ~ 22.8% when the steel bar was pulled out.

Experimental research on anti-seismic reinforcement of fabricated concrete pier connected by grouting sleeve based on CFRP and PET materials

To establish an anti-seismic reinforcement method (ASRM) for fabricated concrete piers based on carbon fibre reinforced polymer (CFRP) and polyethylene terephthalate (PET) materials, two 1/6-scale prefabricated piers with grouted sleeve connections (SFPs) and grouted sleeve prestressing tendon composite connections (SSFPs) were designed and manufactured. Shaking table tests were carried out for the model piers. Then, an ASRM using CFRP/PET with anti-sway external metallic dissipaters (AS-EMD) was proposed. The design and implementation methods of the CFRP–AS-EMD and PET–AS-EMD were established. Under the same excitation, shaking table tests of the SFPs repaired with the CFRP–AS-EMD and the SSFPs repaired with PET–AS-EMD were conducted. And finite element analysis (FEA) verification of the reinforcement effect was also carried out. The results showed that the initial seismic damage of the SFPs and SSFPs included pier body cracking, concrete spalling or crushing, and seam cracking at the bottom of the pier. The CFRP-AS-EMD and PET-AS-EMD can evidently decrease the horizontal displacement of the specimens, demonstrate good anti-sway capacity, provide a certain energy consumption capacity, and effectively improve the ductility of the reinforced pier specimens.

Baofeng selects LyondellBasell process for new polypropylene plant in China

To establish an anti-seismic reinforcement method (ASRM) for fabricated concrete piers based on carbon fibre reinforced polymer (CFRP) and polyethylene terephthalate (PET) materials, two 1/6-scale prefabricated piers with grouted sleeve connections (SFPs) and grouted sleeve prestressing tendon composite connections (SSFPs) were designed and manufactured. Shaking table tests were carried out for the model piers. Then, an ASRM using CFRP/PET with anti-sway external metallic dissipaters (AS-EMD) was proposed. The design and implementation methods of the CFRP–AS-EMD and PET–AS-EMD were established. Under the same excitation, shaking table tests of the SFPs repaired with the CFRP–AS-EMD and the SSFPs repaired with PET–AS-EMD were conducted. And finite element analysis (FEA) verification of the reinforcement effect was also carried out. The results showed that the initial seismic damage of the SFPs and SSFPs included pier body cracking, concrete spalling or crushing, and seam cracking at the bottom of the pier. The CFRP-AS-EMD and PET-AS-EMD can evidently decrease the horizontal displacement of the specimens, demonstrate good anti-sway capacity, provide a certain energy consumption capacity, and effectively improve the ductility of the reinforced pier specimens.

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.

EXPERIMENTAL INVESTIGATION ON PERFORMANCE OF DEFECT DETECTABLE AND REPAIRABLE HALF GROUTED SLEEVE CONNECTION UNDER HIGH STRESS CYCLIC TENSION-COMPRESSION LOAD

To improve the unreliable connection performance of grouted sleeves caused by the filling defect, a defect detectable and repairable half grouted sleeve connection had been proposed by the authors. In order to identify the performance of this new connection under high stress cyclic tension-compression load, 26 specimens, with the consideration of two different diameters of rebar, four grouting defect ratios and two repair methods, were manufactured and tested. The failure modes, bearing and deformation capacities of the specimens without defection, with different defect ratio and the repaired specimens were compared and analyzed. The results indicate that the connection performance of the specimens with high defect ratio is significantly affected by the cyclic tension-compression load. Once the ratio reaches a threshold, a bar slip failure mode is observed for these specimens, and the tensile capacity as well as deformation capacity are significantly lower than those of the specimens without defection. The threshold decreases with the increase of the diameter of rebar. For the specimen with a diameter of 20 mm and a defect ratio of 60%, the bar slip failure is observed before the rebar yields. In contrast, the repaired specimens and specimens without defection both exhibit a tensile failure mode, and the bearing as well as deformation capacities are approximately identical for these specimens. In addition, grout-repaired and epoxy-repaired specimens both satisfy the requirements specified in the associated code, thus validating the rationality and reliability of this new type of half grouted sleeve.

Composition and Analysis of Domestic Patented Sleeve Grouting Material

In recent years, with the urgent need of the country to vigorously promote the transformation and upgrading of the construction industry and the modernization of the construction industry, it has been proposed to vigorously develop prefabricated buildings and increase the proportion of prefabricated buildings in new buildings. The prefabricated concrete building is a concrete structure with prefabricated components in the factory and processing and connection on the construction site. Because of its fast construction speed and good overall benefits, it is widely promoted. For prefabricated buildings, the key technology is the connection of structural nodes, and most of the component connections use concrete sleeve connections. The quality of the sleeve grouting material is very important. The basic formula of the grouting material leads to different and different mechanical properties. Conditions apply. This article starts with different sleeve grouting patents, summarizes different functions and characteristics, and provides a reference for the next development of sleeve grouting.

Experimental study of grouted sleeve connections under bending for steel modular buildings

In steel modular buildings, both inter- and intra-module connections can attract bending moment under the action of lateral loads. The moment is distributed in accordance with the relative stiffness ratios among the structural components and hence the connections should have sufficient flexural resistance and stiffness relative to the connecting members to be classified as a rigid connection. Typically, intra-module connections (beam-column joints within a module) are designed as full-strength rigid connections, while the inter-module connections are normally designed as pin-connected for fast-track construction. This paper proposes the use of grouted sleeve connection which does not require bolting or welding to achieve fast-track construction of modular buildings. An experimental programme is carried to investigate two types of inter-module connections, shear-keyed grouted sleeve versus slot-hole grouted sleeve, under flexural loading to evaluate their structural performance in terms of strength, stiffness, and ductility. The results showed that both connections have adequate moment resistance and ductility to resist bending and they can be classified as partial strength rigid connection for use in braced steel modular buildings. An analytical model, based on EN1992-1-1, is proposed to predict the moment resistance of the connection for the purpose of design.

Effects of grout sleeve defects and their repair on the seismic performance of precast concrete frame structures

Precast concrete frame structures with grouted sleeve connections are widely used. An experimental study was conducted investigating the seismic performance of precast concrete frame structures having backflow defects in their grout sleeves. Repair of such defects is also demonstrated using a simple grout injection technique. Four two-storey precast concrete frame structures having grout sleeve connections in their columns were designed and tested under reversed cyclic loading. The performance of frames having no grout defects and those with defects and repaired defects is described in terms of failure modes, hysteresis characteristics, load-carrying capacity, ductility and energy dissipation capacity. The results indicate that the plastic collapse mechanism of the frames remains unchanged, the performance is affected by the presence of the grout sleeve defects. Despite the defects only reducing the capacity of one of three columns in the frame either 6% or 19%, the effect on the global behavior of the frame was evident in terms of reduced capacity, stiffness, ductility and energy absorption. Injecting grout into defective grout sleeves restored their capacity, and that of the frames, to a defect-free condition.

Experimental study on the mechanical properties of grouted sleeve joint with the fiber-reinforced grouting material

In recent years, more and more attention has been paid to the grouting material and technology of sleeve connection due to the wide application of prefabricated construction. The performance of sleeve connection, normally determined by the grouting material and technology of sleeves, has a significant influence on the seismic performance of prefabricated concrete structures. This paper presented an experimental study on the mechanical properties of the fiber-reinforced grouting materials and grouted sleeve joints, and the experimental parameters included the fiber type, fiber volume fraction, and fiber length. The main properties of the grouting materials were investigated, including fluidity, compressive strength, and flexural strength. The test results showed that the incorporation of fibers with different types, volume fractions, and lengths had different effects on the mechanical properties of the grouting material. Based on the grouting material tests, the sleeve splice test was conducted to investigate the influence of different anchorage lengths on the sleeve splice under the uniaxial loading, which indicated that substantial improvement could be observed for the mechanical properties and residual bond strength of the splices with fiber-reinforced grouting materials.

Static bearing capacity investigation of grouted square hollow section sleeve connection

As a pilot research for an aimed beam-column joint of steel prefabricated prefinished volumetric construction (PPVC) buildings, this study investigates the axial static bearing capacity of grouted square hollow section (SHS) sleeve connections via carrying out experimental tests. Ten specimens with different dimensions were tested to failure under monotonic axial compressive loading and their loading-displacement curves were measured and recorded. The effect of the grouted length, the shear-key spacing, and the grout strength to the bearing capacity of the grouted SHS sleeve connections are investigated in this study. It is found that the axial static bearing capacity of the specimens tested increases approximately in a linear manner with the grouted length increases and can reach the bearing capacity of the outer tube’s cross-section when the grouted length is sufficient. Besides, the benefits brought by the increment of the grout strength to the axial bearing capacity of the grouted SHS sleeve connection may depend on other parameters such as the shear-key size and spacing, the gap between two tubes, and the thickness of the outer tube. Therefore, more experimental tests are required to understand the effect of the grout strength comprehensively.

Seismic performance of fabricated concrete piers with grouted sleeve joints and bearing-capacity estimation method

The seismic performance and design method of fabricated concrete bridge piers limit their applications in complex and harsh environments. In this study, a continuous bridge pier in an 8-degree seismic fortification intensity area was considered as a prototype. Two 1/3-scale models were designed and manufactured. The specimens were connected via a grouted sleeve connections (SFP) and a grouted sleeve prestressing tendon composite connections (SSFP), respectively. Moreover, a cast-in-place 1/3-scale model (reinforcement concrete pier, RCP) was designed as a comparison specimen. Quasi-static experiments were performed on these three specimens. The seismic performance of the specimens was analysed according to the failure phenomena, bearing capacity, displacement ductility, stiffness, energy-dissipation capacity, and residual deformation. On these basis, a bearing-capacity estimation method for SFP (including SSFP) was developed and validated. The results indicated that the damage to the SFP and SSFP mainly accumulated along the top and bottom of the sleeves. The plastic hinge area of the SFP and SSFP moved up or down. Thus, the damage to the SFP and SSFP was concentrated at the joints. Cracks first occurred at the seam of the two fabricated specimens when the loading drift was relatively small. Then, the concrete at the loading edge of the joints was crushed. Furthermore, the longitudinal bars yielded and broke. Finally, the specimens failed. Compared with the RCP, the SFP and the SSFP had larger yield and ultimate displacements. The bearing capacities of the RCP and the SFP were similar. However, the bearing capacity of the SSFP was significantly higher. The bearing capacities of the SFP and SSFP did not decrease significantly before the specimens failed. Compared with the RCP, the SFP had a lower initial stiffness, a lower stiffness degradation rate, similar displacement ductility, smaller residual displacement, and less cumulative energy dissipation. The SSFP was better than the SFP with regard to the displacement ductility, initial stiffness, and cumulative energy dissipation. Thus, the SFP and SSFP can satisfy the seismic requirements of high-intensity areas. The proposed bearing-capacity estimation method can be used for the seismic design and evaluation of SFPs and SSFPs.

Behaviour of Precast Column Foundation Connection under Reverse Cyclic Loading

Precast column foundation connection is one of the critical connections under reverse cyclic loading, and the present study focuses on this connection. Three types of connections were considered, such as (i) base plate connection, (ii) pocket connection, and (iii) grouted sleeve connection. All the above connections were designed, and experimental investigation was carried out on 1 : 2 scaled models by subjecting the column to lateral reverse cyclic loading. Displacement-controlled loading pattern has been adopted for the testing of the specimens. The structural response of the connection was studied for their (i) load-displacement hysteresis behaviour, (ii) stiffness degradation, (iii) energy dissipation, and (iv) ductility. The results were then compared with that of the monolithic connection. The precast connection was more ductile, and the energy dissipated by the pocket connection was high compared to the base plate and grouted sleeve connection. The ductility and the load-carrying of grouted sleeve connection were small compared to other connections. The results of the study showed the precast column foundation can be used in seismic prone areas.

Mechanical behaviours of heat-damaged grouted sleeve connections

An experimental study with 72 specimens was conducted to determine the effects of various factors on the mechanical behaviours of grouted sleeve connections, including an increase in temperature from 20 °C to 600 °C, the loading regime (uniaxial tensile loading or cyclic loading), and the grout compressive strength (83.1–91.1 MPa). After the specimens were exposed to elevated temperatures of up to 600 °C and then uniaxial tensile loading or cyclic loadings, the experimental results indicated that the sleeve was still elastic and the grout had a compressive strength of more than 83.1 MPa, which was beneficial for maintaining the mechanical behaviours of the specimens. In this study, the sleeve region was equal to the gauge length, which consisted of the length of the sleeve and three times the diameter of the rebar from each end of the sleeve. Moreover, a bilinear model was formulated to calculate the yield and ultimate loads of the heat-damaged grouted sleeve connections after different loading regimes. Finally, the constitutive relationship of the heat-damaged grouted sleeve connection was investigated. These findings will be helpful in the fire safety design of precast concrete structures.