Study On The Mechanical Property Of K-Joints In Truss-Arch Plastic Greenhouse

Trussed arch lightweight steel skeletons of greenhouse has been widely used in many areas of our country due to its advantages, such as simple structure, easy methods of production and high cost-effective,The values of wind pressure and snow pressure are high in the north of China, The common phenomenon is that trussed arch lightweight steel skeletons of greenhouse can be collapsed by the action of a storm. The reason is that the characteristics of skeletons is in small section, large span, insufficient bearing capacity and poor stability. K-joints are the main form of trussed arch lightweight steel skeletons of greenhouse.Thus,the damage of the skeleton started from the destruction of K-joints, This paper did the following research work for K-joints that were made by steel pipe and rebar:1. 21 hollow K-joints were designed on the basis of three factors include the ratio of the diameter of main steel pipe diameter and the strut β,the gap of two welding the strut g,and axis angle of main steel tube and pipe θ,The static loading tests of hollow K-joints were carried out by using a self-made reflexive force loading device of K-joints.It got the load-sag displacement curve and the load-stress curve of K-joints when the main steel pipe was pressured.One strut was pressured and the other strut was pulled.Compared with the the ultimate bearing capacity of test value of K-joints and the calculated value of the of formula in 《Design code of steel structure》GB 50017-2003.According to the actual situation of deformation tests of the K-joints,the axial force of the pressured strut was defined as the ultimate bearing capacity of K-joints of trussed arch lightweight steel skeletons of greenhouse when the ratio of the main pipe sag displacement and its diameter is 10%.By Modifing standard formula with the experimental value, the suitable formula of ultimate bearing capacity of K-joints of trussed arch lightweight steel skeletons of greenhouse was obtained.2. 21 Grouting K-joints was designed on the basis of the three factors same with 21 hollow K-joints.The static loading tests of grouting K-joints were carried out by the same form with 21 hollow K-joints.The results of test of grouting K-joints showed that the sag displacement of main steel pipe was smaller than hollow K-joints’, and the form of destroy of grouting K-joints was that steel pipe is torn. It greatly reduced the pressure of main steel pipe by grouting in the pipe.The value of the bearing capacity of K-joints has improved by 150%3. Before the static behavior of grouting K-joints and hollow K-joints were analyzed by software ANSYS. Meanwhile, the static loading tests of grouting K-joints and hollow K-joints were carried out in order to prove the veracity of FEA results.