Y-type Perfobond Rib Shear Connectors Research Articles

Shear Resistance Assessment of the Y-Type Perfobond Rib Shear Connector under Repeated Loadings

The steel–concrete composite structures consist of two different material parts, which are connected with reliable shear connectors to enable the combined action of the steel and concrete members. The shear connectors may experience either one-directional repeated cyclic loadings or fully reversed cyclic loadings depending on the structural functions and acting loadings. It is essential for structural engineers to estimate the residual shear strength of the shear connectors after action of repeated loads. The characteristics of deteriorating shear capacities of Y-type perfobond rib shear connectors under repeated loads were investigated to estimate the energy dissipating capacity as well as the residual shear strength after repeated loads. To perform the repeated load experiments four different intensities of repeated loads were selected based on the monotonic push-out tests which were performed with 15 specimens with five different design variables. The selected load levels range from 35% to 65% of the representative ultimate shear strength under the monotonic load. In total, 12 specimens were tested under five different repeated load types which were applied to observe the energy dissipating characteristics under various load intensities. It was found that the dissipated energy per cycle becomes stable and converges with the increasing number of cycles. A design formula to estimate the residual shear strength after the repeated loads was proposed, which is based on the residual shear strength factor and the nominal ultimate shear strength of the fresh Y-type perfobond rib shear connectors. The design residual shear strength was computed from the number of repeated loads and the energy dissipation amount per cycle. The reduction factor for the design residual shear strength was also proposed considering the target reliability level. The various reduction factors for the design residual shear strength were derived based on the probabilistic characteristics of the residual shear strength as well as the energy dissipation due to repeated loads.

Development of Shear Resistance Formula for the Y-Type Perfobond Rib Shear Connector Considering Probabilistic Characteristics

A design shear resistance formula for Y-type perfobond rib shear connectors is proposed with the various reduction factors, which can be selected depending on the target safety level. The nominal shear resistance formula is improved based on the systematic sensitivity analysis as well as the regression fit test based on 84 push-out test results, including 15 additional push-out tests to extend the application ranges and reduce the estimation errors, compared to the formula proposed in previous studies. Some design variables are additionally included in the proposed design formula: the yield strengths of rebar and rib plate. The basic design variables in the proposed design formula are (1) number of ribs and transverse rebars, (2) concrete compressive strength, (3) rebar diameter and yield strength, and (4) rib thickness, width, height, and yield strength. The application ranges of the basic design variables are recommended for the proposed design formula. The various shear resistance reduction factors are proposed based on the probabilistic ultimate shear resistance model of Y-type perfobond rib shear connectors. The proposed procedure may be recommended to develop the design formula for shear connectors with various shapes.

Behavior of Y-type perfobond rib shear connection under different cyclic loading conditions

A cyclic loading test is a simple method to determine the behavior of shear connection between steel and concrete. Tests using different cases of cyclic loading is necessary since most experimental programs considered limited loading conditions during reversed cyclic loading test. Various cyclic loading cases should be applied during cyclic tests in order to consider different situations. This study applied various cyclic loading cases to analyze and verify the effect of cyclic behavior on shear connection using stubby Y-type perfobond rib shear connectors. Our result show that the shear strength under cyclic loads was lower than that under monotonic load. Furthermore, plastic slip occurred after cyclic loads in each test.

Hysteretic model of Y-type perfobond rib connectors with large number of ribs

This study analyzes the shear and hysteresis behavior of Y-type perfobond rib shear connector and suggests a hysteretic model. Y-type perfobond rib shear connectors with different number of ribs (4 ribs, 6 ribs, and 8 ribs) are considered to evaluate energy dissipation. The aim of this study is to do estimation on hysteretic behavior for large number of ribs, as the size of large number of ribs makes it difficult to proceed with an experiment.Numerical analysis and experimental study are conducted to compare the shear strength and energy dissipation of the specimens. In the experimental study, monotonic loading test and cyclic loading test are performed to investigate the hysteresis behavior of Y-type perfobond rib shear connectors. Cyclic loading test is performed in accordance with European Convention for Constructional Steelwork (ECCS) reference which is a procedure of test for assessing the behavior of structural elements under cyclic loadings. Numerical analysis is conducted since the authentication of Y-type perfobond rib shear connector should be modelled to find the shear resistance of each specimen. For hysteretic model of Y-type perfobond rib shear connector, Bouc-Wen-Baber-Noori (BWBN) model is adopted. Finally, the BWBN model parameters are predicted for shear connectors with large number of ribs based on the experimental data of shear connectors with small number of ribs. The slip amplitude is separated into small slips (1–4 mm) and large slips (over 4 mm) in order to improve the accuracy of the energy dissipation prediction.

Numerical simulation of Y-type perfobond rib shear connectors using finite element analysis

This study presents finite element analysis (FEA) on a Y-type perfobond rib shear connection using Abaqus software. The performance of a shear connection is evaluated by conducting a push-out test. However, in practice, it is inefficient to verify the performance by conducting a push-out test with regard to all design variables pertaining to a shear connector. To overcome this problem, FEA is conducted on various shear connectors to accurately estimate the shear strength of the Y-type perfobond rib shear connection. Previous push-out test results for 14 typical push-out test specimens and those obtained through FEA are compared to analyze the shear behavior including consideration of the design variables. The results show that the developed finite element model successfully reflects the effects of changes in the design variables. In addition, using the developed FEA model, the shear resistance of a stubby Y-type perfobond rib shear connector is evaluated based on the concrete strength and transverse rebar size variables. Then, the existing shear resistance formula is upgraded based on the FEA results.

Hysteretic performance of stubby Y-type perfobond rib shear connectors depending on transverse rebar

The shear behavior of stubby Y-type perfobond rib shear connectors differs according to the diameter of the transverse rebar used for composite action. Pull-push test specimens with transverse rebar of different diameters (D10, D13, D16) were manufactured for monotonic and cyclic loading tests to investigate the effects on not only the shear resistance but also the hysteretic performance. The energy dissipation capacity, shear strength, and ductility increased with the diameter of the transverse rebar, while the stiffness degradation appeared comparable. The specimens with D16 transverse rebar had high ductility, while those with D10 and D13 transverse rebar had moderate ductility.

Experimental behavior of double-row Y-type perfobond rib shear connectors

Although existing studies have only analyzed Y-type perfobond rib shear connectors arranged in a single row, practical applications can apply numerous such connectors to beams with narrow spaces between them. The present study aimed to evaluate the structural behavior of double-row Y-type perfobond rib shear connectors, and thus describe grouped Y-type perfobond rib shear connectors. Push-out tests were conducted in accordance with Eurocode-4, and the relative slip, shear resistance, and ductility were measured. There were two primary variables (spacing and number of Y-type perfobond rib shear connectors) and three types of test specimens: single row, double rows (120 mm spacing), and double rows (300 mm spacing). The representative single-row specimen was used to validate the push-out test results by providing a comparison with previous tests, and provided a shear resistance reference value. The other two specimen types consisted of multiple Y-type perfobond rib shear connectors attached in parallel to an H-beam. Test results revealed that shear resistance increased as the number of shear connectors increased; however, the structural behavior depended on the shear connector spacing. The specimen with wider spacing demonstrated a better ultimate load and ductility relative to the specimen with narrower spacing. Wider shear connector spacing thus leads to better structural behavior retention.

Influence of transverse rebar on shear behavior of Y-type perfobond rib shear connection

This study experimentally investigated the effects of transverse rebar on the shear behavior of Y-type perfobond rib shear connectors. Push-out tests were performed on 12 specimens for which the strength and diameter of transverse rebar were utilized as variables. Test results from a previous study were used to confirm the shear strength and ductility of the Y-type perfobond rib shear connectors, along with the initial cracking and failure modes of the concrete. The results showed that shear strength increased as the diameter of the transverse rebar increased, and this effect was amplified in concrete with lower compressive strength.

Analysis of the Shear Behavior of Stubby Y-Type Perfobond Rib Shear Connectors for a Composite Frame Structure.

Shear connectors are used in steel beam–concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13.

Comparison of hysteretic performance of stubby Y-type perfobond rib and stud shear connectors

Abstract In the composite frame of a building structure in an earthquake-prone area, the shear connection between a concrete slab and a steel beam plays a very important role in distributing the load of the structure and preventing collapse. A shear connection with high stiffness evenly disperses the inertial force created by an earthquake load throughout a pillar to increase the resisting capacity of the structure. In addition, after receiving the seismic loading, the residual strength of the shear connection delays separation of the slab from the beam, thus preventing secondary accidents. However, a beam–slab shear connection of a composite structure that is subjected to frequent seismic excitation receives repeated loadings far exceeding design loadings, thereby greatly reducing its resisting capacity from the level in the original design. The Y-type perfobond-rib shear connector belongs to the new generation of shear connectors developed to overcome the disadvantages of the conventional stud shear connector and the perfobond-rib shear connector. In order to analyze the behavior of the shear connection, fully reversed cyclic loading tests were carried out on a stubby Y-type perfobond rib shear connection and a stud shear connection. Using the test results, the amount of energy absorbed by the connections and changes in their stiffness were verified, which also showed that the former exhibited better hysteretic performance.

Generalized formulation for shear resistance on Y-type perfobond rib shear connectors

This study investigates the performances of Y-type perfobond rib shear connectors subjected to shear forces and vertical separations in steel–concrete composite girders through an experimental and numerical method. In previous studies, a series of push-out test specimens was used to investigate the effect of various parameters on the connector performance. Empirical formulas were proposed based on a regression analysis of various test results to estimate the ultimate shear resistance of the connector. However, the validity of these formulas has been verified for only the limited variables considered in the experimental program. Push-out tests covering wider ranges of design variables than previous studies are conducted in this study, and the numerical simulation model is adopted to evaluate the performance of various additional specimens as well, especially larger specimens with up to ten ribs. The effect of the hole diameter, transverse rebar diameter, and edge distance is also evaluated numerically. The changes in increasing rates of the ultimate shear resistance owing to the additional one-pair of ribs are found to converge to 44%p from a two- to a four-, six-, eight-, and ten-rib system. A formula to predict the ultimate shear resistance, which is a function of the rib shape dimensions, reduction factor due to an increase in the number of ribs, and concrete strength, is newly proposed based on the experimental and numerical results obtained from many different design variable combinations. With some additional refinements, the proposed formula may yield consistently reliable results. The proposed formula shows wider validity than existing formulas and is more applicable to various steel–concrete composite girders.

Y-type perfobond rib shear connectors subjected to fatigue loading on highway bridges

This study evaluated the structural performance of Y-type perfobond rib shear connectors under cyclic loading; the plastic slip, stiffness ratio, and residual strength were also measured. Cyclic loading tests were conducted on each specimen for 650,000cycles, and the specimen with the maximum plastic slip was subjected to 1300,000cycles to investigate the long-term behavior. After the cyclic loading test, push-out tests were conducted to evaluate the residual strength. Under repeated loading, the Y-type perfobond rib shear connectors experienced a slightly larger permanent plastic slip than the puzzle-shaped dowels and stud shear connectors in the early stage. However, this maintained the slip level between the other shear connections after 500,000cycles. The residual strength and stiffness ratio of the Y-type perfobond rib shear connectors remained unchanged even if the system experienced an initial plastic slip. To evaluate the applicability of the Y-type perfobond rib shear connector to highway bridges, the structural performances of plate and steel box girders using these connectors were analyzed numerically. The numerical simulation results for the bridge examples showed that the additional deflections and bending stresses due to the early-stage plastic slip were negligible.

Shear resistance characteristic and ductility of Y-type perfobond rib shear connector

This study evaluates behavior of the Y-type perfobond rib shear connector proposed by Kim et al. (2013). In addition, an empirical shear resistance formula is developed based on push-out tests. Various types of the proposed Y-type perfobond rib shear connectors are examined to evaluate the effects of design variables such as concrete strength, number of transverse rebars, and thickness of rib. It is verified that higher concrete strength increases shear resistance but decreases ductility. Placing transverse rebars significantly increases both the shear resistance and ductility. As the thickness of the ribs increases, the shear resistance increases but the ductility decreases. The experimental results indicate that a Y-type perfobond rib shear connector has higher shear resistance and ductility than the conventional stud shear connector. The effects of the end bearing resistance, resistance by transverse rebars, concrete dowel resistance by holes, and concrete dowel resistance by Y-shape ribs on the shear resistance are estimated empirically based on the push-out test results and the additional push-out test results by Kim et al. (2013). An empirical shear resistance formula is suggested to estimate the shear resistance of a Y-type perfobond shear connector for design purposes. The newly developed shear resistance formula is in reasonable agreement with the experimental results because the average ratio of measured shear resistance to estimated shear resistance is 1.024.

Behavior of composite girder with Y-type perfobond rib shear connectors

A Y-type perfobond rib shear connector is a new type of perfobond rib shear connector which has a Y-shape. This study evaluates the behavior of the Y-type perfobond rib shear connector which is installed in a composite girder. An analytical model of the proposed Y-type perfobond rib shear connector in a composite girder considering the partial composite behavior is developed to evaluate the structural behaviors of the girder. The validity of the analytical model is verified through a loading test on the sample girder. Through analytical and experimental evaluations of a composite girder with either the proposed Y-type perfobond shear connectors or the conventional stud shear connectors, it is confirmed that the adoption of the Y-type perfobond rib shear connector increases the load-carrying capacity of a composite beam as the composite interaction increases; resulting in about 17% increase in both the yield load and the ultimate load. Considering the advantages over the conventional shear connectors, such as the shear resistance, the ductility, the increased load-carrying capacity of composite girder, and the improved workability of rebar, the proposed Y-type perfobond rib shear connector can be applied to the various types of composite structures.

End-bearing resistance of Y-type perfobond rib according to rib width–height ratio

A Y-type perfobond rib shear connector has a higher shear resistance and ductility than a conventional perfobond rib shear connector, and can address the issues of low vertical resistance and the constructability of transverse rebars. This study focuses on push-out tests for verifying the performance of Y-type perfobond rib shear connectors. These tests are conducted according to the guidance provided in Eurocode-4. Previous studies on Y-type perfobond rib shear connectors aimed to verify their shear performance using parameters such as the concrete strength, the presence of transverse rebar, the thickness of the rib, and the Y-shaped bending angle of the ribs. However, there are scant attempts to clarify the effects from different rib widths and heights. The end-bearing resistance of the Y-type perfobond rib shear connector may be determined by the sizes of the rib width and rib height. Therefore, the end-bearing resistance is comparatively analyzed in this study according to the rib widths and rib heights. On the basis of the push-out test results, the shear resistance equation presented by Kim et al. [14,15] are improved. The improved equation is able to more rationally consider the effects from various rib shape factors and compressive strengths of concrete.

Experimental shear resistance evaluation of Y-type perfobond rib shear connector

Recently due to the increase in the construction of the steel–concrete composite structures, researches on shear connector which is capable of composite behavior of two members have been widely studied. This study evaluated the behavior of Y-type perfobond rib shear connector which is superior in shear resistance and ductility than conventional perfobond rib shear connector. Also, it suggested a shear resistance equation based on the push-out test. Firstly, various types of the proposed Y-type perfobond rib shear connectors have been examined to evaluate the effect on design variables such as strength of concrete, transverse rebar, thickness of rib, and Y-shape angle. As a result, the experiment showed that the higher the concrete strength, the shear resistance increased, while ductility decreased. In addition, transverse rebar significantly impacted both shear resistance and ductility to increase. Moreover, as thickness of ribs increased, shear resistance increased and ductility decreased. It was also proven that Y-shape angle has an effect on shear resistance and ductility to grow. Furthermore, it was indicated that Y-type perfobond rib shear connector has higher shear resistance and ductility than the conventional perfobond rib shear connector by comparing and estimating the experimental results. Lastly, the effect of bearing resistance, transverse rebar, dowel resistance by holes, and dowel resistance by Y-shape ribs on shear resistance was estimated by regression analysis. Through the result, the shear resistance equation was suggested to predict shear resistance of Y-type perfobond shear connector.

F152. Estimation of shear stress distribution in the vicinity of a mechanical heart valve prosthesis in vitro

A Y-type perfobond rib shear connector is a new type of perfobond rib shear connector which has a Y-shape. This study evaluates the behavior of the Y-type perfobond rib shear connector which is installed in a composite girder. An analytical model of the proposed Y-type perfobond rib shear connector in a composite girder considering the partial composite behavior is developed to evaluate the structural behaviors of the girder. The validity of the analytical model is verified through a loading test on the sample girder. Through analytical and experimental evaluations of a composite girder with either the proposed Y-type perfobond shear connectors or the conventional stud shear connectors, it is confirmed that the adoption of the Y-type perfobond rib shear connector increases the load-carrying capacity of a composite beam as the composite interaction increases; resulting in about 17% increase in both the yield load and the ultimate load. Considering the advantages over the conventional shear connectors, such as the shear resistance, the ductility, the increased load-carrying capacity of composite girder, and the improved workability of rebar, the proposed Y-type perfobond rib shear connector can be applied to the various types of composite structures.