Experimental Investigation And Design Method Of Cold-formed Ferritic Stainless Steel Square And Rectangular Hollow Section Member Under Compression

Stainless steel has many excellent characteristics: good corrosion resistance and durability;good plasticity and impact resistance;good processing performance;good high temperature resistance;easy to meet the requirements of architecture and aesthetics;100% recycling;ideal life cycle cost.However,the high initial cost of commonly used austenitic stainless steel hinders its application and promotion in the field of structure.Ferritic stainless steel,without or almost without Nickel,is cheaper and more stable.Although ductility and corrosion resistance are reduced,it is better than common carbon steel and has broad application prospects in the field of building structures.In 2012,the International Stainless Steel Forum(ISSF)decided to vigorously promote the use of ferritic stainless steel.Although ferritic stainless steel has so many attractive characteristics,it is still not widely used in the field of structure,because there is still a lack of relevant research and specifications on structural design of ferritic stainless steel.At present,most of the international cold-formed hollow section stainless steel tests are about austenitic and duplex stainless steel,and the research on ferritic stainless steel is also rising gradually in recent years.Domestic research on the structure of ferritic stainless steel has just started.The Chinese code CECS410 does not include ferritic stainless steel because of its less experience and engineering data in China.The Second National Symposium On Stainless Steel Structure Technology pointed out that it is necessary to speed up the relevant research on ferritic stainless steel structure and expand the scope of the specification.Based on the current situation of insufficient research on the structure of ferritic stainless steel,and the urgency of research on the structure of ferritic stainless steel.In this paper,the research on cold-formed ferritic stainless steel square and rectangular hollow section members under compression is carried out.The main research contents are as follows:1.For the first time in China,the experimental study of members under compression with ferritic stainless steel square and rectangular hollow section has been carried out.A total of 8 short columns and 8 long columns with hinged ends have been carried out.The basic dimensions and initial geometric imperfections of the components are measured accurately.At the same time,relevant tensile coupon tests were carried out:tensile coupon tests of 9 original steel plates,tensile coupon tests of 8 columns column cut flats,and tensile coupon tests of 8 column cut corners.2.The constitutive model of stainless steel is analyzed and discussed through the test results of tensile properties.The problems in stress-strain fitting are discussed,and the fitting methods of other researchers are used for reference.The optimum fitting method of strain hardening parameter n is proposed.At the same time,the material strengthening effect caused by cold working is analyzed and compared.3.Based on the test results and a large number of statistical data obtained in this paper,combined with the four commonly used codes(European Code,American Code,Australian/New Zealand Code,Chinese Code),the accuracy of the code for predicting the bearing capacity of members under compression is studied.At the same time,the sources and problems of design formulas in the code are discussed,and suggestions for updating and revising the code are put forward.4.In order to better predict the bearing capacity of members under compression,a large number of test data are obtained based on the test results and statistics in this paper.In this paper,a new width-thickness ratio limit is proposed.Meanwhile,the design formulas of section bearing capacity based on effective width method and the design formulas of overall stability bearing capacity based on Ayrton-Perry formula are put forward.Among them,the method of considering local buckling in the design formula of overall stability bearing capacity is the same as that in the code,while the local buckling calculation is based on the European code,the Chinese code and the new section bearing capacity design formula proposed in this paper.