Contents lists available at ScienceDirect Journal of Constructional Steel Research journal homepage: www.elsevier.com/locate/jcsr Bearing capacity of the cast-steel joint with branches under eccentric load Wenfeng Du a , Yun Sun a , Mijia Yang b,⁎ a Institute of Steel and Spatial Structures, School of Civil Engineering and Architecture, Henan University, Kaifeng, 475004, China b Department of Civil and Environmental Engineering, North Dakota State University, Fargo, ND, 58108-6050, United States ARTICLE INFO Keywords: The three-branch cast-steel joint Numerical simulation Experiment Failure mode Bearing capacity ABSTRACT Bearing capacity of cast-steel joint with branches in a tree-like column structure is important when adopted, since failure of the joint will surely lead to the collapse of its whole superstructure. In this paper, by using the means of numerical simulation and experimental verification, mechanical behavior of three-branch cast-steel joints in the tree-like column structure under eccentric load was studied. A typical full-scale cast-steel joint with three branches was first tested under eccentric loads. Numerical analysis of the cast-steel joint with three branches under eccentric load was then carried out through ANSYS and SolidWorks. Failure mechanisms of this kind of joint were analyzed and the main failure mode was summarized. Finally, the formula for predicting load- carrying capacity of the cast-steel joint with branches under eccentric forces was proposed. The results showed that the failure mode of the joint under eccentric load is the buckling failure at the end of the compression side of the main pipe, and the formula based on the main failure mode is applicable in engineering and building designs. 1. Introduction Tree-like column based on the principle of bionics is more and more widely used in long-span spatial structures because of its novel and beautiful structural configuration, excellent bearing performance, and magnificent ability of wide coverage [1–2]. The representative projects include the Stuttgart Airport in Germany (1991), the Detroit Airport in USA (1996), the Portugal East Station in Lisbon (1998), the Stansted Airport in London (1999), the Shenzhen Cultural Center “Golden Tree” in China (2006), the ION Orchard Mall in Singapore (2009), Shenzhen North Station (2011), and Tianjin International Airport terminal building in China (2014). Joint is the key part of the tree-like column structure. In order to realize the smooth transition among the main pipe and all branches, the joint in the tree-like column is generally made of the cast-steel joint with branches [3–4]. On the one hand, the welding location between the joint and components can be moved out of the joint area. On the other hand it can reduce construction difficulty and improve safety. However, the tree-like column structure is connected through a single joint at each level branch. The failure of the joint will surely lead to the collapse of its superstructure. It is therefore important to study the bearing capacity of this type of joint. Theoretical analysis of the cast-steel joint with three branches was carried out by Sun [5]. Finite element analysis of the joint using the software of SolidWorks and ANSYS was conducted and the mechanical responses of the joint under axial load were obtained. Construction of the tree-like column structure was studied by Tan [6], in which selection of materials and dimensions, fabrication, installation and other technical problems about the joint were discussed. A summary of research and application of connections of structural steel casting was published in 2010 [7], in which important issues on structural design of cast steel connections including material properties, design criteria, theoretical and experimental analysis were addressed. Recently, more researches were geared to local yielding, fracture, and fatigue of cast steel joint connections, such as [8–11]. Loading analysis of the cast- steel joint with three branches was studied by Wu et al. [8]. Influencing factors on the performance of the joints were analyzed and the formula predicting capacity of the cast-steel joint with three branches was derived. Yielding in the cast steel yielding brace system for concen- trically braced frames were discussed in [9]. Balanced fatigue design of cast steel nodes in tubular steel structures was discussed in [10], in which the allowable initial crack size was obtained. Stiffness require- ment was discussed in [11], in which the method to correctly evaluate the joint stiffness was suggested. However, these studies are purely on theoretical analysis or purely on experimental results of cast-steel joints with branches, which have no relevant experiment verification or no connection between the theoretical and the experimental results. Moreover, in practical en- gineering applications, it is difficult to achieve that the joints only bear the axial forces under the action of various load conditions. Therefore, in this paper, loading test of a typical full-scale cast-steel joint with three branches under eccentric load was first carried out. Mechanical http://dx.doi.org/10.1016/j.jcsr.2017.04.005 Received 3 October 2016; Received in revised form 29 March 2017; Accepted 8 April 2017 ⁎ Corresponding author. E-mail address: mijia.yang@ndsu.edu (M. Yang). Journal of Constructional Steel Research 135 (2017) 285–291 0143-974X/ © 2017 Elsevier Ltd. 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