06-11-2010, 11:09 AM
The articles in EC8 refer to primary and secondary members. For further information about the formation of plastic hinges in columns go to: Seismic Design of Reinforced Concrete and Masonry Buildings by T.Paulay&N.Priestley. By choosing some structural members as secondary members, they can be designed without considering the requirements given in EC8. So, in my opinion, this solution can be applied if you have beams with very large dimensions, compared to the columns.
Comment:-
Like I had sounded several times before now, this requirement has nothing to do with seismic design (which is a different topic). Please refer to my previous posts.
Your last post reads and I quote: -
...Codes do not require non-linear analysis, so if you design a building using any type of linear analysis you won't be able to see if hinges appear in columns. Only nonlinear analysis can tell you this. How can you design a building so as not to have plastic hinges in columns without the use of nonlinear analysis?.....
Comment: -
Please read: -
“As result, work started on plastic theory and plastic method of design was first permitted in the country in 1948 when a clause was inserted in the new edition of BS 449”. -Quoted from the “Steel Designers Manual” (page 531)(Note: - as far back as 1948!!!!! that plastic design was included in the BS).
Pushover analysis is a non-linear analysis and it is used in the analysis and design of most non-simple structures.
Ultimate limit state method of design is a non-linear design. Is it true that the codes do not require ultimate limit state method of design in structural design and/or forbids Pushover analysis? If not, then which codes are you talking about; which articles in Euro code 8 are you talking about. Please cite them. You wrote:-
".... I have never said that it is OK to have plastic hinges in columns". . . In line with this, please refer to POST #2 (that arrived in your name) and I quote you verbatim. "....But, you must take into consideration the fact that the building will not fail if a plastic hinge forms in a column, rather than in a beam (it is necessary to have plastic hinges in all the columns). Further more the plastic hinges must form in all the columns both at the top part and at the bottom part.." . Also refer to Post # 6 and I quote you line for line:-
...."3. If you do a non-linear dynamic analysis you will see that hinges can appear in columns. If this is the case the overall stability of the building is not jeopardized. Also, plastic hinges can form in the top story columns (the codes allow the situation). The formation of plastic hinges in columns will lead to story mechanisms (any form of brittle failure is excluded)..
Or am I quoting another person?. Again:-
"....but this situation can occur and this does not mean that you will have a structural collapse....". "the codes allow the situation" when you said before now that "the Codes do not require non-linear analysis." Reasoning along the lines, are these statements not contradicting themselves? Or are you talking of a none engineering code here?
I quote you again:-
".....What do you mean by brittle collapse?
The formation of plastic hinges in columns is due to the bending moment..."
Comment: -
Yes it is assume that the formation of plastic hinges in columns is due to the bending moment, but this is not the actual fact as in the analysis and design of columns, the dominant action is axial force and not bending and for this fact, adjustments have to be made to the results obtained in assuming that the plastic hinges are due to bending. Please read that part again and confirm.
regards
Teddy
Comment:-
Like I had sounded several times before now, this requirement has nothing to do with seismic design (which is a different topic). Please refer to my previous posts.
Your last post reads and I quote: -
...Codes do not require non-linear analysis, so if you design a building using any type of linear analysis you won't be able to see if hinges appear in columns. Only nonlinear analysis can tell you this. How can you design a building so as not to have plastic hinges in columns without the use of nonlinear analysis?.....
Comment: -
Please read: -
“As result, work started on plastic theory and plastic method of design was first permitted in the country in 1948 when a clause was inserted in the new edition of BS 449”. -Quoted from the “Steel Designers Manual” (page 531)(Note: - as far back as 1948!!!!! that plastic design was included in the BS).
Pushover analysis is a non-linear analysis and it is used in the analysis and design of most non-simple structures.
Ultimate limit state method of design is a non-linear design. Is it true that the codes do not require ultimate limit state method of design in structural design and/or forbids Pushover analysis? If not, then which codes are you talking about; which articles in Euro code 8 are you talking about. Please cite them. You wrote:-
".... I have never said that it is OK to have plastic hinges in columns". . . In line with this, please refer to POST #2 (that arrived in your name) and I quote you verbatim. "....But, you must take into consideration the fact that the building will not fail if a plastic hinge forms in a column, rather than in a beam (it is necessary to have plastic hinges in all the columns). Further more the plastic hinges must form in all the columns both at the top part and at the bottom part.." . Also refer to Post # 6 and I quote you line for line:-
...."3. If you do a non-linear dynamic analysis you will see that hinges can appear in columns. If this is the case the overall stability of the building is not jeopardized. Also, plastic hinges can form in the top story columns (the codes allow the situation). The formation of plastic hinges in columns will lead to story mechanisms (any form of brittle failure is excluded)..
Or am I quoting another person?. Again:-
"....but this situation can occur and this does not mean that you will have a structural collapse....". "the codes allow the situation" when you said before now that "the Codes do not require non-linear analysis." Reasoning along the lines, are these statements not contradicting themselves? Or are you talking of a none engineering code here?
I quote you again:-
".....What do you mean by brittle collapse?
The formation of plastic hinges in columns is due to the bending moment..."
Comment: -
Yes it is assume that the formation of plastic hinges in columns is due to the bending moment, but this is not the actual fact as in the analysis and design of columns, the dominant action is axial force and not bending and for this fact, adjustments have to be made to the results obtained in assuming that the plastic hinges are due to bending. Please read that part again and confirm.
regards
Teddy