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hello sesimosoft

i have question about confinement factor in mander et.al nonlinear model.
you have suggested this factor for concrete member between 1.2 to 1.3 in help .why have you limited between 1.2 to 1.3 ?
i assessed this factor base on mander model for a column 45 cm x 45 cm with 12 bar longitudinal reinforcing(1.6 cm diameter) and transverse reinforcing spacing 6 cm (1 cm diameter) but this factor was yielded by 1.8 (over range of 1.2-1.3).i check it for some member it is higher than 1.2-1.3 for most of them ,if i use confinement factor more than 1.2-1.3 in program i will lose negative stiffness after peak strain .is it correct to use this factor more than 1.2-1.3 considering that most of member i checked have more than this value (1.2-1.3)

thank you

Mohamad, I don’t believe that the Help system recommends a limit of 1.2-1.4 on confinement factors. That is simply the default and would correspond to a section with very light transverse reinforcing. In fact, if you will note on the con_ma material property tab, there is a button to the left of the confinement factor which will calculate the confinement factor for you. I plugged in your values and it calculated 1.74, very close to your 1.8 value. The difference could be the strengths used.

The issue with limiting strains is similar. The 0.008 is probably only a default value corresponding to a low confinement section. You can change the limiting strain in the Performance Criteria tab to a calculated value higher than 0.008. And yes, for well-confined sections the limiting strain should be increased from the 0.008 value and the confinement factor in excess of 1.3 is appropriate.

Regards,

huffte

thank you huffle

i can not receive in 1.74 for confinement factor could you send me file that you could receive to 1.74 ,i want to see how you fill out parameters in confinement factor calculation and have received to 1.74

this is my email

mohamad.akhavanpur@gmail.com

Rather than send the SeismoStruct file I am sending a screen shot of the input screen for confinement factor calculation.

The reason fo rthis is that once the dialogue is closed, and then reopened, the values in the fields revert to defaults. So, with the SeismoStruct file you would not be able to see my input.

i still believe that program calculate wrong this factor because program dose not get shape of hoops for calculating confinement factor .program simply consider that only single hoop on perimeter of section if you have single hoop + w/4 tie in inside of member can not consider it .if you want to be sure about that check the example of page 104 in this book (Seismic Design Of Reinforced Concrete And+Masonry Buildings T.Paulay M.Priestley (1992))which has found k factor for rectangular section and base on mander model .if you can find k factor same as this book in program please show me

This is entirely possible mohamad. So, in your case it is probably better to calculate k by hand as you have done and input it manually into the form.

Mohamed,

Whilst the confinement factor calculations currently carried out in SeismoStruct are not wrong, the corresponding input parameters dialog box does indeed not feature the flexibility needed to model all different possibilities and use cases. In the forthcoming release this will be addressed.

For what concerns the example found in Paulay & Priestley (1992), the book authors have decided to arbitrarily consider a Kc factor equal to 0.75, whereas the correct figure should have been around 0.57-0.60 (depending on the unknown longitudinal reinforcement), hence it will not be possible to obtain the confinement factor of 1.82 that they report in their book, even with the more complete confinement factor calculation model of the new release.

Thank you for brining this matter to our attention,

Seismosoft Support