Research On Direct Strength Method Of Perforated Lipped Channel Axial Compression Bearing Capacity

In recent years,the cold-formed thin-walled steel are widely used in building structures.In order to reduce weight and meet the needs of the construction pipeline,more and more attentions are paid to perforated cold-formed thin-walled steel structures.However,it has produced a lot of new problems.The presence on cold-formed thin-walled steel web holes will lead to a stress redistribution on membrane unit of plates,affect buckling characteristic and load capacity and even change the buckling mode.The influence of perforating parameters to stability bearing capacity,buckling mode and stress distribution is what the related design and scientific researchers concern.Researches on cold-formed thin-walled steel without holes under axial compression have been relatively mature at home and abroad,but remain further researches on perforated members.Furthermore,researches on perforated members were usually focused on channels with common edge,there are few insight into channels with complex edge.At present,direct strength method of members without holes has been adopted into the revised draft of"cold-formed steel structure technical specification",but it requires a further improvement for calculating method of perforated cold-formed steel members.In view of the current research status,respectively channels with common edge and channels with complex edge with web holes under axial compression in forms of different cross-section parameters were studied by finite element analysis in this paper.The analysis method was verified by the test specimens in premenstrual subject.With engineering practice and the corresponding national standards as reference,the influence of perforating parameters,such as hole width,hole height,hole shape and hole spacing,to stability bearing capacity,buckling mode and stress distribution of the lipped channels were studied in this paper.It showed that the change of hole width,hole shape and hole spacing may change the buckling mode,but influences the ultimate bearing capacity little in a reasonable perforating range;However,it performed a obvious decline of stability ultimate bearing capacity with the increase of opening height.The changing trend of ultimate bearing capacity with opening height was studied in this paper.Net section carrying efficiency was defined an evaluation index to get a reasonable opening height scope.Taking all points above into consideration,reasonable suggestions on hole shape and hole sizes were put forward in this paper,to serve as a reference for researchers.In addition,direct strength method of perforating lipped channels(including common edged channels and complex edged channels)under axial compression was studied in this paper.The elastic critical stress was calculated according to the existing methods abroad,and the feasibility of this method has been verified through simulation data.By comparison,the best direct strength method stands out by a comprehensive compaction of the existed calculating methods of perforating channels with common edges abroad.And the method was extended to calculate perforating channels with complex edges under axial compression.Furthermore,practical calculating method of perforating lipped channels at home was put forward in this paper,according to the revised draft of the technical specification for cold-formed steel structure,which suits material mechanical properties in our country better.Applicability of the formula was verified good can be used as a reference for related design and research personnel.