Study On Working Performance Of Umbrella-Shaped Girder With Anchor Machine In Static Load Test

According to investigate the foundation of the huge project and important structure, load test is the most reliable method among varies of original test, it has many advantages, such as direct, visual and accurate. Now as a major method of original test, load test has been used widely. In China, plate-load test is often used to test the bearing capacity of the natural foundation, compound foundation and pile. To the whole test, load-on system and reactive system are also important. The load-on system usually adopt gravity load or lifting jack;There are varies of reactive implement in plane-load test, such as support-wall, anchor pile cross beam and so on.. In 《The Standard of Architecture Pile Foundation》 JGJ 94-94,there are three experiment reactive device: Anchor pile cross beam reactive device, Pressure platform reactive device and Anchor pile pressure combination reactive device. There are some disadvantages during the there methods, such as high fee, long period, form and well equipped test yard, safety and so on. To improve these disadvantages, the plane load test machine with umbrella pirder and anchor has come true, it divided into two parts: overground and underground. The overground part is the space girder structure, it is used to deliver load and restrain deforming;The overground part is made of metallic spiral anchor block, mainly supplying anti-pulling out force that needed for the experiment, the plane load test machine with umbrella pirder and anchor is convenient for disassembly and assembly department, flexible for arrangement ,safe and reliable. It has short cyclic of experiment, low outlay ,and better social and economic efficiency.By constructing the finite element mode ,the writer has analogued the working status of the plate load test machine with umbrella pirder and anchor and calculated the endogon and displacement of the whole structure. By analyzing the member bars position , stress and distortion, the writer had figured out the conclusion of safely design and proper layout. By analyzing the spiral anchor blocks position\stress and distortion, the writer has made the conclusion that the association of anchor block is a chief balance system for testing load. In addition, the vertical stress on every anchor block is identical the same. That is to say , when the external force is balanced, because the upper part of the space truss distribute it on all the anchor block, every one sufficiency display the ability of anti-pulling out. At the same time, author analyse the bearing force of system. The bearing force is determined by the amount of anchor and the capability of single anchor. Now the plane load test machine can work under 200t load.From comparing the anchor deformation and stress status under different elastic-module, depth and radius, we get the main influence factor of reaction force. Finally, through case history, verify system s feasibility, make comparison with other method on fee.