Seismic behavior study on RC-beam to CFST-column non-welding joints in ﬁeld construction Xiaoxiong Zha ⁎, Chengyong Wan, Hang Yu, Jean-Baptiste Mawulé Dassekpo Department of Civil and Environmental Engineering, Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China abstract article info Article history: Received 12 October 2013 Received in revised form 10 July 2015 Accepted 14 July 2015 Available online xxxx Keywords: RC beam to CFST column joint Joint without welding Seismic behavior Skeleton curve Theoretical model Finite element analysis A newly developed reinforced concrete (RC) beam to concrete-ﬁlled steel tube (CFST) column joint without welding in the construction ﬁeld is introduced in this paper. The seismic experiment is conducted on the joint, and the hysteretic curve of the specimen under cyclic loading on the top of the column is obtained. By analyzing the mechanical characteristics and the failure mode of the joint, a three-stage skeleton curve model is presented. In the elastic stage, the initial stiffness is evaluated by solving the stiffness matrix. In the perfect plastic stage and strength degradation stage, the ultimate strength and the degradation stiffness of the joint can be obtained with the limit equilibrium method. Moreover, the test is also simulated with FEM, and the results agree well with the skeleton curves obtained from the test. So this joint shows good ductility and the ability to dissipate energy, and it can be used to replace the joints welded with reinforcement on the outer annular plate. And the ﬁnite element analysis results are compared with the theoretical results, which veriﬁes the theoretical model presented above. It is suggested that the three-stage skeleton curve model can be used to depict the mechanical behavior and bearing capacity of this new type of joint. In addition, Parametric analysis is conducted on this joint, with the consideration of different designs of beams, columns and steel brackets, and failure mode is discussed. © 2015 Elsevier Ltd. All rights reserved. 1. Preface The concrete-ﬁlled steel tube column is considered as a composite structure style, which has many excellent mechanical behaviors and bearing capacity. For RC beam to CFST column joint, the response to di- saster loads has a very important impact on such a structure. Generally, due to the form of beam members, CFST beam to column joints can be divided into steel beam-CFST column joint and RC beam-CFST column joint. Among them, the current reinforced concrete beam-CFST column joint types usually include rigid joints with interior and exterior rein- forced loop, anchor and cross-core, etc. Based on the needs of this pro- ject, the related research and the improvement of the joints are more focused in China. Where, Xu et al. [1] analyzed the working mechanism and seismic behavior of beam-column joints of CFST frames systemati- cally, based on some results from experimental research and engineer- ing application. The formation suited in the frame structure system, calculation methods and several design suggestions are presented and discussed. Nie et al. [2–3] carried out fourteen connection specimens composed of concrete-ﬁlled square steel tubular columns (CFSSTCs) and steel-concrete composite beams with interior diaphragms, exterior diaphragms, or anchored studs in order to investigate the seismic be- havior were tested, and the strength, deformation, and energy dissipa- tion capacity of these composite connections were analyzed; 3-D nonlinear ﬁnite element models were established to analyze the me- chanical properties of these three types of connection using ANSYS. Fi- nite element analyses were conducted under both monotonic loading and cyclic loading. Han et al. [4] conducted an experiment on eight thin-walled steel tube conﬁned concrete (TWSTCC) columns to rein- forced concrete (RC) beam joints subjected to cyclic loading, where the level of axial load in the column and the type of column cross- section were selected as test parameters. In addition, two concrete- ﬁlled thin-walled steel tubular columns to RC beam joints were also tested for comparison. Qu et al. [5] tested eight reinforced concrete (RC) beams to concrete-ﬁlled steel tubular (CFST) column joints enclosed by rebar under reversal horizontal displacement with constant axial load in order to study their seismic behavior. The test parameters are the axial load level and the section type of CFST column. In this study, the failure model, hysteretic characteristic, ductility and energy dissipation were investigated. Wang et al. [6] studied the semi-rigid joint of steel-concrete composite beam to CFST column with stiffening rings. Two specimens were tested by incremental loading and cyclic loading. The ﬁnite element package ABAQUS was used to study the non- linear behavior of such specimens. Li et al. [7–8] researched the seismic behavior of the joint of gangue concrete-ﬁlled steel tubular column- beam with ring stiffeners and steel corbels, and the quasi-static tests on the interior joint of gangue concrete-ﬁlled steel tubular column- ring beam joints in the low cycle reverse load by which the failure pat- terns, hysteretic characteristics, ductility and energy dissipation were studied. Liu et al. [9] carried out ﬁnite element analysis on the aseismatic Journal of Constructional Steel Research 116 (2016) 204–217 ⁎ Corresponding author. E-mail address: zhahero@126.com (X. Zha). http://dx.doi.org/10.1016/j.jcsr.2015.07.017 0143-974X/© 2015 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Journal of Constructional Steel Research