Experimental Study On Mechanical Properties Of Special Embedded Steel Strand Loops Parts

With the rapid development of prefabricated construction,the project is more and more big,the demand for a string of traditional rings can not meet the requirements,be badly in need of a kind of economic and crane product with high bearing capacity,steel strand strength,made in Europe and the United States and other countries have extensive use of steel strand hanging pieces,for not related research in our country,its application has been curbed,so in this paper,the mechanical properties of the steel strand hanging piece was studied,the test made 2 group of steel strand anchor conditions,six straight steel strand hanging pieces and 1 kind of round steel rings.The main research work of this paper is as follows:(1)steel strand and concrete bond anchorage strength test:diameter 15.2mm steel strand and concrete bond anchorage strength test,determine the bond anchorage strength of steel strand in the state of direct anchor.(2)drawing capacity test of steel strand lifting parts of strip sleeve.The steel sleeve sleeve,which can make the steel strand line bear uniform force,is bent on the steel strand line and made into the lifting ring of the steel strand line.The relationship between bearing capacity of lifting ring and anchorage length was found by designing lifting ring with different anchorage lengths.(3)different bending Angle of steel wire lifting ring drawing bearing capacity test.Find the relationship between the bearing capacity of lifting ring and bending Angle.(4)the end of the treatment of steel strand lifting parts drawing capacity test.In order to change the failure mode of the steel wire sling,the end of the steel wire sling is treated by two treatment methods,that is,dispersing and bending hook,and the different failure modes formed by different treatment methods are tested.(5)16mm round steel lifting ring test,find its failure form and bearing capacity,and steel strand lifting ring for comparison.Find out the advantages and disadvantages of the steel wire sling ring relative to the round steel sling ring.Combing the specification design-faced and the specification for steel wire rings in the CEN/TR 15728 rules,according to the CEN/TR 15728 British code regulate the design-faced,with the United States of prestressed steel strand production rings as well as the relevant provisions of the test data from analysis,give advice about steel wire rings used in China and the regulations,fill the blank of the our country without specification and provide reference for prefabricated factory use,make them more specification when use and safety.Comparing the value of safety coefficient of relevant codes at home and abroad,the recommended value of safety coefficient of steel strand sling ring in China is given as 8.4,and the force checking calculation of double T plate lifting process in an engineering example is carried out.The results show that the recommended value of safety coefficient is 8.4,which is in line with the usage habits and requirements of China.The following Suggestions are put forward for the use of suspension rings of steel strand in China through tests and referring to the American standard " PCI Design Handbook" and the British standard "CEN/TR 15728"1.The embedded lifting parts of steel strand shall be made of steel strand with a strength design value of 1860MPa and a nominal diameter of 12.7mm or 15.2mm.The performance of steel strand shall meet the requirements of GB/T 5224.2.In order to make the steel strand embedded lifting parts bear uniform force,the bending part of the lifting parts shall be covered with galvanized pipe,and the wall thickness of galvanized pipe shall not be less than 4mm.3.The steel strand embedded hung a bending Angle should be greater than or equal to 30°,the bending radius should be greater than 4 d.The depth of embedded concrete in the pre-embedded lifting parts of the steel strand shall not be less than 40d and the larger value in 600mm.D is the nominal diameter of the steel strand.Steel wire tail should be broken or made into bending hook.4.Each strand wire embedded lifting member can be calculated according to two sections,and the stress of the strand wire in the lifting member shall not be greater than 150N/mm2.5.Necessary measures should be taken to ensure that 4 lifting rings are stressed at the same time.When there is reliable experience,8 lifting rings can be used.6.Lifting angle,namely the sling with the direction of the vertical Angle should not be greater than 30°.When lifting angle must be greater than 30°,each hanging pieces should be calculated according to a cross section.7.The bearing capacity of double-stiffened lifting members is 1.7 times that of single-stiffened lifting members.Lifting rings with three or more stiffened members should not be used without reliable experience.8.The surface of the steel wire used to make lifting parts shall be clean without oil,sand or rust.No tensioned steel strand shall be used to make lifting rings.