Experimental Study On Tensile And Tensile Shear Mechanical Properties Of Inserts

The development of assembly architecture leads to the widespread application of the inserts.In the process of prefabricated components hoisting,the inserts play an important role.With the rapid increase of the demand for inserts in China,our country is in urgent need of further research on the safety performance of the inserts being used in production,especially for the tensile and tensile shear mechanical properties often occurred in practical engineering.The main research work of this paper is as follows:Referring to the relevant standards at home and abroad,according to the transmission way,the structural form and the applicable scope of the inserts,the existing inserts are divided into six categories:Extender inserts,Anchors with additional rebar,Anchor systems with threaded sockets,Short versions of Extender inserts,Short versions of spread anchors,and Plate sockets.In this paper,the tensile and tensile shear mechanical properties of the above six kinds of inserts are studied in depth.Combing the domestic standard "Technical Specification for Post-Anchorage of Concrete Structures",American Standard "ACI 318",and British Standard "CEN/TR 15728",the classification of failure modes of tension and shear and the calculation formulas of tensile and tensile shear bearing capacity under different failure modes are enumerated.The formulas for calculating of the bearing capacity in each standard are compared and analyzed in terms of application scope,cone failure formula influence coefficient and partial coefficient,and the influencing factors of bearing capacity are summarized.In order to further study the tensile mechanical properties of the inserts,a total of 54 inserts of six categories and seven species are selected in this experiment.According to the product specifications and standards,18 groups of 54 base material concrete specimens are designed.In order to study the influence of buried depth on bearing capacity,9 sets of comparative tests are designed.In order to study the influence of edge distance on bearing capacity,4 groups of comparative tests are designed.Based on the test phenomenon,the main failure mode is concrete cone failure occurred in the test,only the DEHA Combi anchor occurres steel failure in the case of large edge distance,test failure angles were slightly smaller than the ideal angle of 35 degrees,to verify the feasibility of the test plan;According to the analysis of test data and load-displacement curve,the greater the embedment depth of the same insert is,the greater the tensile bearing capacity of the insert is.Under the same embedment depth,the larger the margin is,the larger the tensile bearing capacity of the insert is;Comparing the ultimate bearing capacity of the tensile test with the theoretical value calculated according to the specifications at home and abroad,the ratio between the experimental value and the theoretical value of each standard is respectively 1.1-2.8,1.3-3.0,1.5-3.6,and the larger values occur in the two types of' inserts,namely DEHA Plate anchor and DEHA Plain anchor,it shows that these two types of inserts are more safe to use.The ratio of' minimum occurrs in the two types of Dimensions of spherical head anchors for slabs and Spread Anchor TPA-FS,indicating that the safety of this insert is poorer when compared with other inserts.When selecting,it is necessary to increase the buried depth or increase the number to increase the safety.Through the comparison and analysis of the standards,it is found that the calculation formula of the tensile carrying capacity of "CEN/TR 15728" is more suitable for the calculation of practical engineering.In order to further study the tensile shear mechanical properties of the inserts,a total of 18 inserts of three categories and three species are selected in this experiment.According to the product specifications and standards,3 groups of 9 base material concrete specimens are designed.Through the analysis of the test phenomenon,we can see that nine concrete specimens occurres concrete failure.By analyzing the experimental datas and the load-displacement curves,the ultimate bearing capacity of each precast suspension can be calculated,and the feasibility of the experimental scheme is verified;The test results were substituted into the three standards for checking the calculation formulas for the coupling of tensile shear.The results show that the calculation method specified in "ACI 318" is more secure when calculating the tensile d shear force,which can be used to guide the caleulation of the force of the domestic inserts in the actual project.