Research On Static Behavior Of Big Eccentric Circular Hollow Section N-Joints

Tubular N-joints will appear easily that two braces overlap in practiceproject, this is to guarantee formula provides overlap rate must is greater than25%of limit; while, clearance node must guarantee two braces of clearancevalue is greater than two braces wall thick of and, however two bracesoverlap of exists and increased has welding construction engineering volumeand cannot guarantee within hidden part of welding quality, so in actualconstruction and design in the often making into full take received node orlarge clearance node and led to formed beyond currently both at home andabroad various specification[1-5]partial heart rate provides (0.25≥e/D≥-0.55, where e is the eccentricity, diameter of the D chord) form a largeeccentric N-joints steel tube connections. Current formula and literature athome and abroad for small eccentric circular steel tube with or withouteccentricity plane N-joints, there is little reported of the big eccentriccircular hollow section N-joints. It is necessary to conduct a comprehensivestudy on the static behavior of this joints.The background of this article to test, based on ANSYS software analysis,mainly visit eccentric mechanical properties of n-type joints, and failuremodes and ultimate bearing capacity of static as well as effects ofeccentricity on the ultimate bearing capacity of.To study the static behavior of hollow section N-joints with vertical braceunder compression in sym-metrical Pratt truss and vertical brace understretch in anti-symmetrical Pratt truss, nine vertical brace under compressionand nine vertical brace under stretch were tested under monotonic loading.Results of tests show that: firstly,When joint eccentricity ranges from bignegative to0.25（0）,the ultimate capacity of joints increases in proportion toeccentricity and culminates at0.25（0）eccentricity. When eccentricity rangesfrom0.25to1.00, the ultimate capacity of joints decreases；Secondly,In measuring the ultimate capacity of big negative joints, results calculated inaccordance with both Chinese code and Euro code are fixed values which donot correspond with experimental results and turn out unsafe. Thirdly: bigeccentric CHS N-joints can be regarded as rigid connection by comparingexperimental results with theoretical value; Thus, the ultimate capacity ofjoints in vertical brace under stretch which is higher than vertical brace undercompression when the joints is negative eccentric specimens,and the ultimatecapacity of joints in vertical brace under stretch which is less than verticalbrace under compression when the joints is negative eccentric specimens.Then this article on the mechanical properties of type node for nonlinearfinite element study on calibration and analysis. Based on tests on the basisof the establishment of an effective and accurate finite element analysismodel and ANYSA comparison of analysis results and test results, againverify the applicability of finite element models, and revealed the test cannotexpress a full range of understanding the mechanical properties of the classesnode.Whereafter, with reference to the ultimate capacity of the circular hollowsection K(N)-joints in the Eurocode3formula, by multiple regression iseccentric N-joints calculation formula of ultimate bearing capacity of circularsteel tube with nodes. and comparative analysis of the results of this test,verify that this formula with high accuracy and reliability.Finally, discuss the content of the next step is to research.