| In order to promote the development of China’s industrialization,respond to the state’s call for fabricated buildings,maintain the strategy of sustainable development and promote ecological balance,the future development of fabricated buildings in our country will enter a white-hot stage.Prefabricated components,as the basic components of prefabricated concrete structures,will be mass-produced with the rapid development of prefabricated buildings,which is different from the on-site operation of cast-in-situ structures.The prefabricated components need to be produced in the factory and transported to the site install.Therefore,the prefabricated components in the pouring of concrete after molding,demoulding,lifting,transportation and installation in place require the use of inserts.The application of a large number of inserts must ensure the safety,but the relevant norms and standards for inserts in our country are still in a blank state,which will make the use of inserts have a lot of uncertainties and potential safety problems.In the hoisting process of prefabricated components,the inserts will encounter a lot of shear forces.Therefore,it is necessary to further study the mechanical properties of inserts under the shear force.In order to determine the feasible shear test methods and reliable safety factor provided basis.The main research contents of this paper are as follows:According to the influence of 100mm and 150mm two different edge distance,a total of 47 inserts of F series in foreign country and D series in China were tested by shear in the same strength in concrete.Observe the mechanical properties of prestressed hanger,calculate the angle of wedge failure mode,analyze the relationship between load-displacement curve,study the relationship between the ultimate bearing capacity of concrete wedge failure and the physical properties of inserts.The results show that all the inserts eventually appear the concrete wedge failure,and the angle is in good agreement with the destructive angle in the ideal state.The diameter of the inserts,the depth of the inserts in concrete,the distance between the axis of inserts and the vertical edge of the shear force is Positive correlation related to the size of the shear strength,so it is feasible to confirm this loading test method.The calculation method of the ultimate bearing capacity of the concrete wedge failure of the inserts is summarized.Compare the theoretical calculation value obtained in China’s Specification for post-installed,the American Standard "ACI318" Chapter 17 and the British Standard "CEN/TR 15728" with the ultimate bearing capacity obtained in the test.The results of the comparison are as follows:the ultimate bearing capacity of the test is larger than the theoretical values of the three theoretical calculations,of which the theoretical value of Chapter 17 of American Standard"ACI318" is close to the theoretical value of British Standard "CEN/TR 15728",the theoretical value of "Technical specification for post-installed fastenings in concrete structures" in our country is smaller,all of these provide the theoretical basis for determining the range of values of effective safety factor.Comparing the safety factor of the relevant norms at home and abroad,the recommended value of China’s safety factor is given,and carry on the checking calculation of the lifting process of the prefabricated wallboard in the engineering example,the results show that the safety factor suggests values in line with China’s habits and requirements. |
