Investigation of conjugation nodes of a structure's loadbearing elements in the nonlinear formulation

21st International Scientific Conference on Advanced in Civil Engineering "Construction - The Formation of Living Environment"

土木建筑工程

Mkrtychev, Oleg^1 ; Sidorov, Dmitriy^1 ; Bulushev, Sergey^1

Moscow State University of Civil Engineering, Yaroslavskoe shosse 26, Moscow

129337, Russia^1

关键词: hinged beam;    hinged node;    Implicit finite element methods;    Load-bearing elements;    Loadbearing structure;    Nonlinear formulation;    Nonlinear statics;    Steel beams;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/365/4/042039/pdf
DOI  :  10.1088/1757-899X/365/4/042039

学科分类：土木及结构工程学

来源: IOP

【 摘 要 】

When designing beam grids and frameworks for industrial and public buildings, contemporary engineering makes use of finite-element complexes. Loadbearing structures are usually modeled with beam-type finite elements. The joints between elements are typically modeled as perfect hinges or entirely rigid. Nodes are designed separately depending on the previously obtained loads aided by different tools, ad-hoc software among others. The actual behavior of nodes is different from that of a perfect model. This necessitates a research on the effect the assumptions and simplifications make on the stress (strained) condition of loadbearing structures and nodes. The paper scrutinizes the behavior of hinged nodes. The research is centered around a welded steel I-beam hinged on both sides. The beam was modeled in two ways: using rod finite elements supported with perfect hinges on both sides and via dimensional finite elements, where modeling in its own right was performed for the hinged nodes located on the welds. The structure was stressed evenly with a distributed one-parameter load increasing from zero to a certain finite value at which the beam collapses. The beam is considered to fail as soon as fiber yielding behavior arises in the flanges of the welded I-beam. The calculation was run in the multipurpose software complex LS-DYNA employing explicit and implicit finite element methods as well as nonlinear static techniques. The research has revealed that the actual hinged node is not a perfect hinge and has a certain finite rigidity. Thus, the actual beam, as opposed to a perfect beam, will exhibit a bending moment, while the moment will have a smaller value across the span. Since the node was designed for a transverse force only, the real behavior of the weld exhibits plastic deformations driven by the bending moment. Moreover, deformations arise in the gusset plates and in the web of the welded I-beam where the maximum strain caused by bending moments manifests itself. Research has discovered that failure does not happen due to the minuteness of such deformations. Thus, the conclusion can be made that a hinged beam can be designed as a beam with perfect hinges, but it will at the same time modeled with a surplus. The results obtained are backed up by the data given in various sources.