Determination of shear stiffness for headed-stud shear connectors using energy balance approach

Huawen Ye,Ruosen Huang,Shiqing Tang,Yu Zhou,Jilin Liu 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.4

The shear stiffness of headed-stud shear connectors has no unified definition due to the nonlinear characteristics of its load-slip relationship. A unified framework was firstly adopted to develop a general expression of shear load-slip equation for headed-stud shear connectors varying in a large parameter range based on both force and energy balance. The pre- and postyield shear stiffness were then determined through bilinear idealization of proposed shear load-slip equation. An updated and carefully selected push-out test database of 157 stud shear connectors, conducting on studs 13~30mm in diameter and on concretes 30~180 MPa in cubic compressive strength, was used for model regression and sensitivity analysis of shear stiffness. An empirical calculation model was also established for the stud shear stiffness. Compared with the previous models through statistical analysis, the proposed model demonstrates a better performance to predict the shear load-slip response and stiffness of the stud shear connectors.

Research on the Load-slip Properties of Corrugated rib connectors' Push-out Test

Shuqin Li,Lichao Su,Zhibin Sun 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.4

The failure characteristic and load-slip performance of corrugated rib connectors under static load were investigated usingthe push-out test combined with Finite Element Analysis (FEA). The results obtained from experiment and FEA indicate thatthe shear bearing capacity of the corrugated rib connectors are closely relate with the key factors including cubic strength ofconcrete (fcu), the open area of the steel plate (Ac1), perforated rebar tensile yield strength (fy) and Cross-sectional area (Ay),horizontal projection area of corrugated rib (= dwhw). In elastic stage, the overall shear stiffness of the corrugated rib connectorare mainly affected by the shear stiffness of the concrete bars. And in elastic-plastic stage, the shear stiffness of the concretebars and perforated rebar pronouncedly influence the overall shear stiffness of the corrugated rib connector. Finally, a linearmodel and a power law model for the load-slip behavior at elastic stage and elastic-plastic stage are provided based on theregression statistical analysis, respectively.

Static behaviour of lying multi-stud connectors in cable-pylon anchorage zone

Zhaofei Lin,Yuqing Liu,Jun He 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.6

In order to investigate the behaviour of lying multi-stud connectors in cable-pylon anchorage zone, twenty-four push-out tests are carried out with different stud numbers and diameters. The effect of concrete block width and tensile force on shear strength is investigated using the developed and verified finite element model. The results show that the shear strength of the lying multi-stud connectors is reduced in comparison with the lying single-stud connector. The reduction increases with the increasing of the number of studs in the vertical direction. The influence of the stud number on the strength reduction of the lying multi-stud connectors is decreased under combined shear and tension loads compared with under pure shear. Yet, due to multi-stud effect, they still can't be ignored. The concrete block width has a non-negligible effect on the shear strength of the lying multi-stud connectors and therefore should be chosen properly when designing push-out specimens. No obvious difference is observed between the strength reductions of the studs with 22 mm and 25 mm diameters. The shear strengths obtained from the tests are compared with those predicted by AASHTO LRFD and Eurocode 4. Eurocode 4 generally gives conservative predictions of the shear strength, while AASHTO LRFD overestimates the shear strength. In addition, the lying multi-stud connectors with the diameters of 22 m and 25 mm both exhibit adequate ductility according to Eurocode 4. An expression of load-slip curve is proposed for the lying multi-stud connectors and shows good agreement with the test results.

Evaluation of nonlinear behavior and resisting capacity of reinforced concrete columns subjected to blast loads

Park, Gang-Kyu,Kwak, Hyo-Gyoung,Filippou, Filip C. Elsevier 2018 Engineering failure analysis Vol.93 No.-

<P><B>Abstract</B></P> <P>A numerical method to estimate the dynamic response of reinforced concrete (RC) columns subjected to axial and blast loads is introduced in this paper. Upon adopting Timoshenko's beam theory, both the flexural and direct shear behaviors are incorporated into the numerical formulation. The moment-curvature relationship of a reinforced concrete (RC) section is based on the construction of the bending stiffness and, in advance, a dynamic increase factor (DIF), usually defined in the stress-strain relations of concrete and steel, is newly designed to be defined in the moment-curvature relation. In addition to the description of the dynamic characteristics in the RC section, additional modification of the moment-curvature relation is also performed to exactly simulate the large plastic deformation concentrated at the mid-span or beam-column joint due to the bond-slip or anchorage slip after yielding of the main reinforcement. Finally, the validity of the proposed method is verified by comparing the analytical results with the experimental data, and then the pressure-impulse (P–I) diagrams are constructed and compared to review the change in the resisting capacity of a RC column according to the variation of the axial force and slenderness ratio.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A numerical model incorporating the flexural behavior and the direct shear behavior is proposed. </LI> <LI> A dynamic increase factor (DIF) for the moment-curvature relationship is newly designed. </LI> <LI> The verification of the numerical model is performed through comparison with experimental data. </LI> <LI> A parametric study of RC column is performed to review the influence of the parameters. </LI> </UL> </P>

Nonlinear dynamic analysis of RC frames using cyclic moment-curvature relation

Kwak, Hyo-Gyoung,Kim, Sun-Pil,Kim, Ji-Eun Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.3

Nonlinear dynamic analysis of a reinforced concrete (RC) frame under earthquake loading is performed in this paper on the basis of a hysteretic moment-curvature relation. Unlike previous analytical moment-curvature relations which take into account the flexural deformation only with the perfect-bond assumption, by introducing an equivalent flexural stiffness, the proposed relation considers the rigid-body-motion due to anchorage slip at the fixed end, which accounts for more than 50% of the total deformation. The advantage of the proposed relation, compared with both the layered section approach and the multi-component model, may be the ease of its application to a complex structure composed of many elements and on the reduction in calculation time and memory space. Describing the structural response more exactly becomes possible through the use of curved unloading and reloading branches inferred from the stress-strain relation of steel and consideration of the pinching effect caused by axial force. Finally, the applicability of the proposed model to the nonlinear dynamic analysis of RC structures is established through correlation studies between analytical and experimental results.

Numerical analysis of channel connectors under fire and a comparison of performance with different types of shear connectors subjected to fire

S.E.M. Shahabi,N.H. Ramli Sulong,M. Shariati,M. Mohammadhassani,S.N.R. Shah 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.20 No.3

The behavior of shear connectors plays a significant role in maintaining the required strength of a composite beam in normal and hazardous conditions. Various types of shear connectors are available and being utilized in the construction industry according to their use. Channel connectors are a suitable replacement for conventional shear connectors. These connectors have been tested under different types of loading at ambient temperature; however, the behavior of these connectors at elevated temperatures has not been studied. This investigation proposes a numerical analysis approach to estimate the behavior of channel connectors under fire andcompare it with the numerical analysis performed in headed stud and Perfobond shear connectors subjected to fire. This paper first reviews the mechanism of various types of shear connectors and then proposes a non-linear thermomechanical finite element (FE) model of channel shear connectors embedded in high-strength concrete (HSC) subjected to fire. Initially, an accurate nonlinear FE model of the specimens tested at ambient temperature was developed to investigate the strength of the channel-type connectors embedded in an HSC slab. The outcomes were verified with the experimental study performed on the testing of channel connectors at ambient temperature by Shariati <i>et al</i>. (2012). The FE model at ambient temperature was extended to identify the behavior of channel connectors subjected to fire. A comparative study is performed to evaluate the performance of channel connectors against headed stud and Perfobond shear connectors. The channel connectors were found to be a more economical and easy-to-apply alternative to conventional shear connectors.