Negative Moment Zone Research Articles

Numerical and Theoretical Study on Flexural Performance and Reasonable Structural Parameters of New Steel Grating–UHPFRC Composite Bridge Deck in Negative Moment Zone

As the bridge’s structural component is directly subjected to vehicle loads, the stress performance of the bridge deck has a significant impact on the safety, durability, and driving comfort of the bridge. In order to improve the bending performance of the bridge deck in the negative moment zone, a new type of steel grating–UHPFRC composite bridge deck was proposed in this paper. Firstly, structural details and advantages of the new steel grating-UHPFRC composite bridge deck were introduced. Secondly, the finite element program ABAQUS was used to establish a refined solid finite element model of the new bridge deck. The mathematical program MATLAB (PYTHON) was also used to analyze the effects of the structural parameters on bending bearing capacity and put forward reasonable structural parameters of the new bridge deck, considering the technical and economic indexes. Thirdly, the simplified plasticity theory was applied to analyze the bending bearing capacity of the new bridge deck, and the corresponding formula for bending bearing capacity calculation was derived and verified by numerical model results. In addition, the cost–benefit analysis and environmental impact assessment of the new bridge deck were also conducted. The results show that the bending bearing capacity of the new bridge deck in the negative moment zone increases with the increase of the width of the bridge deck, the thickness of the wing plate, and the height of the web plate, with a trend of increasing and then decreasing when the horizontal inclination of the web plate decreases. The bridge deck width does not have a significant effect on improving the bearing capacity. The bearing capacity calculated by theoretical formulas is close to that calculated by numerical models and the maximum relative deviation is 9.1%. The new steel grating-UHPFRC composite bridge deck proposed in this paper is superior to conventional steel-UHPC composite bridge deck in terms of cost-benefit and environmental impact.

Flexural strengthening of reinforced concrete cantilever beams having insufficient splice length

Structural systems often undergo changes due to variations in the usage, the loading conditions, or the presence of defects in their elements. The problem can be exacerbated when there is insufficient overlap between reinforcing bars in critical moment zones. This article investigates the behavior of reinforced concrete cantilever beams exhibiting insufficient overlap between bars that used as main reinforcing steel bars in the negative moment zone. Various strengthening techniques were employed in order to improve these defected cantilever beams. Eleven beams underwent flexural testing until reaching failure. The experimental parameters encompassed the strengthening scenarios and the bonded length. Three strategies were used: the application of stainless-steel plates (SSPs) as externally bonded reinforcement, near surface mounted (NSM) reinforcement in which additional deformed steel bars were bonded utilizing engineering cementitious composites, and externally pre-stressing technique. The anchorage length was examined at 40, 50, and 60 times the internal bar diameter. It was noted that the most substantial improvement achieved with the NSM method, followed by the externally pre-stressing method. It is worth mentioning that most of the beams failed in a flexural manner, with partial debonding occurring in beams strengthened using external strengthening. Moreover, this article includes the development of a numerical model employing the finite element method to replicate the response observed from the experimentally tested beams. The accuracy of the model was confirmed through the comparison of its outcomes with the experimental data, demonstrating an acceptable level of accuracy with deviations of less than 4.4 %. This successful numerical investigation was also used to conduct a parametric study. From this study it is evident that the effect of debonding on SSPs can be reduced by adding steel anchors at the ends of these plates. Finally, an analytical method was proposed to calculate the ultimate load capacity of strengthened reinforced concrete beams.

Research Progress on Shear Characteristics and Rapid Post-Disaster Construction of Narrow-Width Steel Box–UHPC Composite Beams

The narrow-width steel box girder is an important type of steel–concrete composite bridge structure, which is usually composed of reinforced concrete wing plates, narrow steel boxes partially injected with concrete, and shear connectors that promote shear force transfer. The utilization of narrow-width steel box girders, augmented by partially filled concrete, embodies the synthesis of steel and concrete elements, fostering structural efficiency. Moreover, its attributes, including reduced structural weight, diminished vertical profile, enhanced load-bearing capacity, and augmented stiffness, have prompted its gradual integration into bridge engineering applications. In this study, the calculated values of shear strength under three current design codes were reviewed, and the shear failure phenomena and its determinants of narrow-width steel box–ultra-high-performance concrete (UHPC) composite beams under negative bending moment conditions were investigated, which were mainly determined by shear span ratio, concrete wing plate, UHPC steel fiber content, UHPC plate thickness, and transverse partition inside the box. Concurrently, this paper evaluates two innovative structural designs, including a double-narrow steel box girder and a three-narrow steel box girder. In addition, strategies to reduce crack formation under the negative bending moment of long-span continuous narrow and wide box girder abutments are discussed, and we show that this measure can effectively control the formation of cracks to support the negative bending moment zone. At the same time, the scope of the application of a narrow-width steel box girder composite bridge is reviewed, and the conclusion is that a narrow-width steel box girder is mainly used in small-radius flat-curved bridges or widened-ramp bridges with a span of 30 m or more in interworking areas and in the main line with a 60–100 m span in mountainous or urban areas. Finally, the research direction of the shear resistance of the UHPC–narrow steel box girder under negative bending moments is proposed.

Mechanical behavior improving study of concrete deck of main beam at pylon root of composite beam cable-stayed bridge

Steel-concrete composite beam has been increasingly applied to large span cable-stayed bridges. It takes full advantage of the material properties of steel and concrete. However, the concrete deck bears tension in the negative moment zone, such as zero block, which is disadvantageous to structures. Aiming at this problem, a finite element model of the zero block in the negative moment zone of a semi-floating cable-stayed bridge is built, and the local mechanical performance of the bridge deck under completed status is studied. Based on the analysis results, three improvement measures have been proposed. The improvement effect of each method and composed of three methods has been studied. The numerical results show that the whole zero block zone is in the compressed state under the combined action of the bending moment and axial force of the stay cable. However, the local negative moment effect in the zero block zone is very prominent under the support of the diaphragm plate. Removing parts of the diaphragm plate at the bearing position can significantly improve local mechanical behavior in the concrete deck, which transfers the local support to the adjacent two diaphragm plates. The composed improvement effect is prominent when the three measures are adopted simultaneously.

Bending performance of wet joints in negative moment zone of prefabricated small-box girder bridges: Experimental and numerical study

The prefabricated small-box girder (PSBG) structure adopts the construction method of simple supporting beam transforming to continuous beam, which results in negative bending moment on the box girder supports and large tensile stress on the top of the longitudinal wet joints. Due to the relatively low tensile strength of concrete, the top plate of the bridge in the negative bending moment zone is susceptible to cracking under the load of vehicles, as well as due to the shrinkage and creep of concrete. This poses a risk to the safety, applicability, and durability of the bridge structure and may lead to a reduction in these aspects. Ultra-high performance concrete (UHPC) has excellent tensile performance and stronger crack control capability, which can effectively improve the anti-cracking and durability of the wet joints of the PSBG. In the present study, the research focused on the negative bending moment zone of a three-span continuous small–box girder bridges. This zone was selected as the research object and served as the basis for designing a stepped wet joint girder, where UHPC is partially cast on the top plate. By conducting three-point bending tests, we compared the bending mechanical properties of the joint girders when poured with normal concrete (NC) and UHPC in the joint top area. Further, the key factors affecting the anti-cracking performance and bearing capacity, including the length and thickness of the UHPC layer and the width of the wet joint, were analyzed by finite element simulation. The results show that the contribution of the top plate UHPC to tensile stress cannot be ignored. Compared with the NC joint girder, the UHPC joint girder has better toughness and plasticity, and the cracking load and bearing capacity increased by 28.6% and 9.7%, respectively. According to the simulation results, as the increase of the length and thickness of the UHPC layer and the width of wet joint, the anti-cracking and bearing capacities of the PSBG with the wet joint were enhanced. The thickness and length of the UHPC layer had a significant effect on improving the anti-cracking performance of the wet joint, and the joint width only needed to meet the transfer length of rebar bond stress.

Rational prediction of moment redistribution in continuous concrete beams reinforced with FRP bars

In continuous fiber reinforced polymer (FRP) reinforced concrete (RC) beams, moment redistribution is typically not allowed in the design owing to the lack of ductility of FRP bars. However, this simplification cannot be justified as moment redistribution depends primarily upon the difference in stiffness along the beam length. This study aims at improving the current state-of-the-art redistribution quantification in continuous FRP RC beams. Redistribution behavior against neutral axis depth (c/d) of continuous FRP RC beams are numerically assessed, focusing on the impact of ρr1/ρr2 (ρr1, ρr2= tensile reinforcement ratios at positive, negative moment zones). It is shown that continuous FRP RC beams may experience marked positive or negative redistribution of moments, depending on ρr1/ρr2. However, the importance of ρr1/ρr2 is neglected in c/d-based code models (EC2, BSI and CSA). A modified BSI model is proposed to estimate the moment redistribution in continuous FRP RC beams. By introducing ρr1/ρr2, the proposed simplified model accounts for the structural characteristic and demonstrates a rational prediction of moment redistribution in these beams.

Bearing capacity of UHPC‐NC connection structure in negative moment zone of PC beam bridges

AbstractA new type of UHPC‐NC (normal concrete) structure in the negative moment zone was proposed to improve the bearing capacity of the connection structure in the negative moment zone of prefabricated prestressed concrete (PC) beam bridges. First, the distribution characteristics of the crack, cracking load, ultimate moment, and ductility coefficient of the new structure were obtained by the 1:4 scale model tests. The feasibility of the connection structure is verified. Then, the value ranges of critical structural parameters affecting the bearing capacity of the connection structure based on the plane section assumption analysis, including the reasonable thickness of the UHPC layer, the reinforcement ratio of the longitudinal tensile reinforcement, and the diameter of the reinforcement, are obtained. At the same time, based on the verification of the finite element model, the influence of crucial research parameters on the bending capacity of the connection structure is obtained by using the finite element method. Finally, a theoretical method for the bending moment capacity of the connection structure of the UHPC‐NC structure is proposed, considering the high ductility characteristics of UHPC materials. The average relative error between the calculation results and the finite element method is within 7.2%, which verifies the reliability of the calculation method in this paper and provides a reference for its design and engineering application.

Mechanical properties of composite beams with web openings under negative bending moments

Experimental research and nonlinear finite element parameter analysis were performed to study the mechanical properties and ultimate bearing capacity of composite beams with web holes under a negative bending moment, and the mechanical properties of composite beams reinforced around the holes. The results indicate that, after the holes were opened, the stiffness and bearing capacity of the composite beams in the negative moment zone were significantly reduced. The stress–strain distribution in the section of the cave entrance no longer accords with the hypothesis of the plain section and shows an S-shaped distribution. The thicknesses of the concrete slab and steel beam web significantly affected the ultimate bearing capacity. The concrete wing slab significantly contributed to the shear capacity of the composite beams with web holes in the negative-moment zone. The interface slip value of the hole area increased significantly, indicating that the stud exhibited plastic deformation. Based on the serious problem that the load-bearing capacity and deformation capacity of composite beams after web holes are weakened, and combined with current mainstream reinforcement measures, a new reinforcement measure is proposed to change the shear distribution around the holes and improve the ductility and bearing capacity of composite beams with holes in the negative bending moment area.

Comparative study on flexural behavior of steel-UHPC composite beams and steel-ordinary concrete composite beams in the negative moment zone

To compare the flexural behavior of steel-UHPC (ultra-high performance concrete) composite beams and steel-ordinary concrete composite beams under a negative bending moment, 4 steel–concrete composite beams were tested under a negative bending moment. The effects of slab materials and stud number on flexural failure mode, crack development, stiffness ductility, cracking load and ultimate flexural capacity of composite beams were investigated. The results show that the UHPC can significantly improve the flexural behavior of steel–concrete composite beams under a negative bending moment. For the steel-UHPC composite beams with a single row, the cracking load is 135 % higher than that of steel-ordinary concrete composite beams, and the overall stiffness increased by 108 %, the yield stiffness increased by 40 %, the ultimate flexural capacity increased by 9 %, and the ductility increased by 133 %; for the steel-UHPC composite beams with double row, the cracking load is 102 % higher than that of the steel-normal concrete composite beam, the overall stiffness is increased by 34 %, the yield stiffness is increased by 44 %, the ultimate flexural capacity is increased by 6 %, and the ductility is increased by 75 %. Increasing the number of studs can significantly improve the overall ductility of composite beams, while the improvement of cracking load, overall stiffness, and ultimate flexural capacity of composite beams is not significant. The cracking load, overall stiffness, yield stiffness, ultimate load, and ductility of double-row stud steel–concrete composite beams are 23 %, 53 %, 13.2 %, 12 %, and 115 % higher than those of single-row stud steel–concrete composite beams, respectively; while those of double-row steel-UHPC composite beams increases by 6 %, 8 %, 16 %, 8 % and 62 % higher than those of single-row stud steel–concrete composite beams, respectively. A simplified calculation model for the flexural capacity of steel-UHPC composite beams in a negative moment zone was established.

Influence of longitudinal prestress on the shear resistance of prefabricated shear stud connectors

In order to meet the requirements of accelerated bridge construction (ABC), the structure of steel–concrete composite bridges presents a development trend of the entire assembly. A Prefabricated Composite Shear Studs (PCSS) is proposed to speed up the assembly efficiency of traditional steel–concrete composite beams and improve the effectiveness of the prestress of prefabricated concrete decks in the negative moment zone. A finite element model (FEM) of the PCSS shear connector is established by considering the stress characteristics of different assemblies, thirty different steel tendon quantities, and relative arrangements are selected to analyse the impact of longitudinal prestress on the shear resistance of PCSS, the effectiveness of finite element model is verified this through test results. It is revealed that the steel tendon arrangement and quantity will change the shear resistance of the PCSS shear connectors. However, the magnitude, positive and negative effects are related to the position of the steel tendon along the deck height. When the steel tendon deviates downward from the neutral axis of the deck, the shear bearing capacity and shear stiffness increase; in addition, its force transfer mechanism is that the longitudinal prestress changes the lateral restraint effect of the PCSS on the concrete. Under the combined action of prestressing and transverse restraint of steel plate, the cooperative working ability of the stud and surrounding concrete can be enhanced or weakened. Thus, the yielding of stud and concrete damage can be delayed or accelerated, significantly affecting the shear bearing capacity and stiffness.

Experimental study of continuous T-beams with negative bending moment using UHPC instead of prestressed tendons under flexure

In order to explore the flexural performance of the two-span simply supported to continuous T-beam using UHPC material instead of prestressed tendons in the negative bending moment zone and the effect of the UHPC material connection length on the bearing capacity of the test beam, the flexural tests of three beams with different UHPC connection lengths were carried out. The results show that by using UHPC material instead of prestressed tendons to make continuous beams in the negative bending moment region, the tensile properties and high elastic modulus characteristics of UHPC material can be better exerted. The three test beams were all resistant to bending failure, and the cracks were distributed in the two positive and negative bending moment sections. Increasing the connection length of the UHPC material will increase the distribution range of cracks and the number of cracks in the positive moment section and the cracking load in the negative moment section. The ductility was reduced. When the connection length was increased from 300 mm to 2200 mm and 2300 mm, respectively, the bearing capacity of the test beam was increased by 4% and 6%, respectively, and the mid-span ultimate displacement was reduced by 7% and 12%, respectively. The flexural performance of the test beam was improved.

Investigations on influences of Engineered Cementitious Composites (ECC) on pull-out properties of studs in steel-concrete composite bridge

Stud plays an important role in the connection of steel-concrete composite bridge (SCCB). The stud is under pull-out load in the negative moment zone of SCCB. Engineered Cementitious Composites (ECC) are a new type of materials with tensile strain hardening and multiple cracking behavior to strengthen SCCBs. In this study, the cyclic pull-out effect on the ECC-stud connection was studied through pull-out tests. The stud diameter (d=13/16 mm) and the embedment depth (hef=40/60/80 mm) are included as design parameters, resulting in a total of 18 specimens of six scenarios. The failure mode, load-bearing capacity, and ductility factor of the specimens under cyclic loading are compared with those under monotonic loading, and the stiffness, energy dissipation capacity, and residual displacement of the specimens under cyclic loading are analyzed. Based on the experimental results, under cyclic loading, the concrete cone failure and splitting failure occur, and the threshold of hef/d between the two failure modes is 3.75–4.62, which is smaller than the threshold of the monotonic scenarios. Both concrete and splitting failure modes show ductile failure characteristics because of the bridging effect of fibers in ECC. The load-bearing capacity and ductility factor under cyclic loading are lower than those under monotonic load. This is because, under cyclic loading, the specimens show cumulative damage, which, however, is weakened due to the strengthening effect of ECC. As d and hef increase, the load-bearing capacity, ductility factor, stiffness, and energy dissipation capacity increase correspondingly, and the residual displacement decreases. The stud with a larger d shows a more obvious ductility holding stage.

Fatigue Experiment Study on Internal Force Redistribution in the Negative Moment Zone of Steel–Concrete Continuous Composite Box Beams

Due to the accumulated fatigue damage in steel-concrete continuous composite box beams, a plastic hinge forms in the negative moment zone, leading to significant internal force redistribution. To investigate the internal force redistribution in the negative moment zone and confirm structural safety under fatigue loading, experimental tests were conducted on nine steel-concrete continuous composite box beams: eight of them under fatigue testing, one of them under static testing. The test results showed that the moment modification coefficient at the middle support increases during the fatigue process. When approaching fatigue failure, an increase of 1.0% in the reinforcement ratio or 0.27% in the stirrup ratio results in a reduction of 13% in the moment modification coefficient. Furthermore, a quadratic function model was proposed to calculate the moment modification coefficient of a steel-concrete continuous composite box beam during the fatigue process, which exhibited good agreement with the experimental results. Finally, we verified the applicability of the plastic hinge rotation theory for steel-concrete continuous composite box beams under fatigue loading.

Behavior of Damaged Continuous Reinforced Concrete Beams Repaired by CFRP Sheets

Despite the widespread use of RC continuous beams, the performance of these beams, when repaired via Fiber Reinforced Polymer (FRP) composite material, has received less attention. Furthermore, several features of the flexural aspect of repaired RC continuous beams still demand experimental and analytical evaluation. However, many anchoring methods have been developed to delay premature failure in the RC beams, which are strengthened with FRP composite materials. The plan of this experimental study consists of eight continuous beams cast with dimensions (150*250*2800) mm considering the length of the clear span is 1300mm. Except for one, all specimens were attached via Carbon FRP sheets about 70% of the span length in negative and positive moment zones beyond a predetermined damage level. Moreover, this study suggested modifying the end-anchor technique and adding CFRP layers with (45, 65, and 95) % as damage ratios. According to the results, the optimal percentage of restored ultimate capacity was 108.8% with peeling-off concrete cover failure mode, which was obtained from using an end-anchor and two layers of the sheet. Also, increasing the damage ratio leads to a decline in toughness and ductility values. In addition, it is possible to repair the structure with a 95% damage ratio rather than remove it.

Experiment Analysis on Crack Resistance in Negative Moment Zone of Steel–Concrete Composite Continuous Girder Improved by Interfacial Slip

Due to the strong interface effect of continuous steel-concrete composite beams with conventional shear connectors, the efficiency of applying pre-stress in the negative moment zone is greatly reduced, which leads to a difficulty of anti-cracking design in the negative moment zone of pre-stressed steel-concrete composite box girder. In order to study the feasibility and the working mechanism of improving the crack resistance of continuous steel-concrete composite bridges by releasing the interfacial slip effect within the negative bending moment region, two groups of model tests were carried out in the paper. Two steel-concrete composite beams were used for model test, one of them using the conventional stud shear connectors, another one using the new shear connectors, named uplift-restricted and slip-permitted shear connectors. The results show that, compared with the composite beam with conventional shear studs, the composite beams with uplift-restricted and slip-permitted shear connectors have a higher pre-stress application efficiency, and the new connector could release the interface slip, which can make the tensile stress distribution in concrete slab more uniform within the negative moment zone, thus increasing the cracking load of concrete slab and reducing the subsequent crack width effectively. This study is helpful to understand the relationship between the interface slip and the anti-crack characteristics in negative moment zones, and a new anti-crack design method is proposed for the design of continuous composite girder.

Study on mechanical behavior of steel-UHPC-NC composite beams under negative bending moment

To investigate the negative moment region flexural performance of a steel-ultrahigh performance concrete (UHPC)-normal concrete (NC) composite beam, steel-UHPC-NC composite beams with a uniform and cluster arrangement of studs and three push-out specimens were designed and fabricated. Based on the test results, the finite element model of steel-UHPC-NC composite beams was established and verified. The results of the study show that in the push-out test, the failure mode of the specimens is the shear failure of the stud, and the specimens with the NC-UHPC composite slab and UHPC slab are crushed and spalled at the root of the studs, but the damage extent and damage range of the specimens with UHPC slabs were significantly smaller than the NC-UHPC composite slab specimens. The load-slip response of the push-out specimen is obviously affected by the concrete slab material. The ultimate bearing capacity of the single stud of the steel-UHPC specimen, the steel-UHPC-NC stud single layer arrangement and the double-layer arrangement specimens were 249 kN, 158 kN and 192 kN, respectively. In the negative bending moment zone loading test, the development trend of the mid-span load–displacement curves of steel-UHPC-NC composite beams with uniform and cluster studs is consistent, with the cracks in the former concentrated at the mid-span position and the cracks in the latter concentrated near the nearest group of shear studs in the mid-span. The load–displacement curves of composite beams that studs are evenly distributed and studs are cluster type are consistent, with ultimate displacements in the span of 65.8 mm and 68.5 mm, respectively, and ultimate bearing capacities of 723.8 kN and 712.3 kN, respectively. The calculation results obtained by the simulation method are in good agreement with the test results, which could effectively predict the load–displacement response of the steel-UHPC-NC composite beam.

Design formulae for Long-Term responses of continuous Steel-Recycled aggregate concrete composite slabs

The steel-recycled aggregate concrete (RAC) composite slab is a low-carbon structural member with higher constructional efficiency. However, no design method has been established for the serviceability limit state evaluation of such members accounting for long-term effects. The non-uniform shrinkage peculiar to composite slabs significantly deteriorates the long-term responses of slabs, which would be more significant when using RAC. Previous studies only focused on the long-term responses of simply-supported composite slabs using NAC. The investigated responses include member deflection and stress in steel decking. No research attention has been paid to the continuous composite slabs, in which non-uniform shrinkage further induces possible yielding of the negative reinforcement and the limit exceeding of concrete crack width in the negative moment zone. Furthermore, the recycled aggregate influence has not been accounted for in the long-term design of the composite RAC slabs. In this context, this study aims to establish simplified explicit design formulae for the long-term responses of continuous RAC composite slabs accounting for the non-uniform shrinkage effects and the recycled aggregate influence. The target long-term responses include deflection, steel decking stress, negative reinforcement stress, and the concrete crack width in the negative moment zone. The simplified explicit formulae were derived from cross-sectional analysis results with some variables reasonably simplified into constant values based on collected data from real applications. The validation results have shown that the proposed formulae are capable of predicting the long-term responses of continuous RAC composite slabs, with the prediction accuracy similar to the code formulae for reinforced concrete slabs.

Cracking Resistance of UHPC-NC Structure in Negative Moment Zone of Prestressed Concrete Beam Bridges

Cracking Resistance of UHPC-NC Structure in Negative Moment Zone of Prestressed Concrete Beam Bridges

Design method of serviceability limit states of BFRP bar reinforced ecological high ductility concrete beam: Experimental and theoretical analysis

Ecological high ductility concrete (Eco-HDC) has a larger tensile deformation than normal concrete, and Eco-HDC can be used to cast bridge deck link slab in negative moment zone. To acquire the flexural design method of bridge deck link slab made by BFRP (basalt fiber reinforced polymer) bar reinforced Eco-HDC, serviceability limit states of beam containing crack width and deflection are studied through the experimental and theoretical analysis. Test variables are diameter of BFRP bar, cover thickness and loading regime. Increasing the BFRP bar diameter or decreasing the cover thickness is an efficient method to decrease the maximum crack width. Cyclic loading type is also beneficial to reduce the maximum crack width. Besides, as the diameter increases, the peak deflection increases within a diameter of 8 mm ∼ 12 mm, and then decreases. Beam with a larger cover thickness has a lower peak deflection. Peak deflection is independent on the loading regime. Formulas in design codes are adopted to predict the maximum crack width and peak deflection, and the formulas are proposed to evaluate the test results. In addition, maximum crack width limit, maximum limit of stress and strain in Eco-HDC and BFRP bar are the governing parameters to compute the reinforcement ratio of BFRP bar in the design of bridge deck link slab.

Experimental study of earthquake-resilient prefabricated composite joint with T-shape connector

Based on the idea of damage control, a new type of earthquake-resilient prefabricated composite joint (ERPCJ) with the T-shape connector has been proposed. On the premise of considering the composite action of concrete slab and beam-column joint, the seismic behavior, post-earthquake recoverability and failure mode of concrete slab under different loading protocols are studied. By changing the connection mode between flange cover plate (FCP) and beam, the influence of the relative slip between FCP and beam on the bearing capacity and energy dissipation capacity of the specimen are also studied. The low frequency cyclic loading tests and low cyclic fatigue tests of six specimens show that the basic and repaired specimens of the prefabricated composite joints with recoverable functions show good seismic behavior. The plastic damage of steel joint is concentrated on FCP, while the main structural members such as beam and column still maintain elasticity. The collaborative work of T-shape connector with foams, concrete slab and the gaps between concrete slab and column can reduce the plastic damage of concrete slab. The main reason of concrete slab damage is the strong squeezing effect between concrete slab and T-shape connector in negative moment zone. Whether FCP can slip or not can make a great difference in the bearing capacity and energy dissipation capacity of the joint. The damage and deformation of FCP are small when FCP and beam can slide relatively, but the bearing capacity and energy dissipation capacity of the joint are low. The bearing capacity and energy dissipation capacity of the joint are high when FCP and the beam cannot slip relatively, but FCP will cause serious plastic damage and even fracture.