The Maximum Value of DLF (dynamic load factor) ????

Dear All,

i studied in CAESAR help file and other books.. In that they stated that DLF cant be greater than 2(TWO)

BUT In my case, DLF SPECTRUM GENERATOR it is showing GREATER THAN 2. NEARLY 6.

IS CAESAR HAS ANY LIMITATIONS FOR DOING SLUG ANALYSIS ???

Thanks,
Durga

DLF is the quotient dynamic answer/static answer with the same exicite load.
DLF = 2 ( max) will be at short impuls load.
General DLF can be bigher as 2.
This is a resonanz question ( natural frequency to exicite frequency)

Thank you Ohliger for ur reply,

Can you please tell me for slug case

I observed value DLF=6 in slug case, what is the reason...??

If your slug case more as one event , then you have a force/time exicite
(maybe harmonic).
And then you become higher DLF, because your system go in Resonanz.
For a harmonic damped system :
DLF = 1/ SQRT (( 1- fe/fn)*(1-fe/fn)+ 4 D*D * fe/fn)

fe ==> your ecitite frequency
fn ==> natural frequency
D ==> Damping (%)

I think its a good idea you visit a dyn. Caesar2 seminar

Hello Ohlinger

SO, what you are saying is, DLF can be greater than 2.

can u give path to know more about that case where DLF greater than 2.

Thanks Ohliger, TAKE CARE

I observed that ...

In user defined time vs force spectrum, If Time duration is more, then DLF crossing 2..

means for short period DLF less than 2

for higher time period DLF can be greater than 2

IS my statements are Correct???

Caesar transfer the force over time input to DLF over frequency.
DLF over frequency is the same as acceleration over frequency.
Means DLF 2 is 2g.
The calculation is spectrum method.
If your time in your input longer then you get more DLF frequency points.
If you see no chnging DLF (higher) at greater frequencys then it is ok.
And the last DLF will get for missing mass calculation.

Time duration in dyn Parameter input is for modal Time history method.

Ohlinger,

DLF CAN BE GREATER THAN 2,

YES OR NO.

yes when??
no why??

reference please....

Ohliger already answered to your questions.

A reference: Humar, Dynamics of Structures, second edn
Chapter 6, Forced harmonic vibrations: single-degree-of-freedom system, 6.3. Undamped harmonic vibration, (6.13) expression of the dynamic load factor - pag 249; 6.3. Damped harmonic vibration, (6.32) expression of the dynamic load factor for steady state response - pag 256,; Chapter 7, 7.4 Response to a step function load (for a single-degree-of-freedom system) pag 320; 7.6 Response to a step function load with rise time, expression (7.28) pag 326 and Figure 7.8 Response for a step function load with rise time, pag 327

DLF has max of 2.0 for a single application of an impulse load.

Thank you Dave & Mariog,

so why in my case it is greater than 2 ??

iam Doing slug analysis (Impluse loading)

Can you please Eloberate..

and you say without mentioning the word "single".


Maybe you would progress analyzing the discussions in these threads:
http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=80
and
http://65.57.255.42/ubbthreads/ubbthreads.php?ubb=showflat&Number=43370
and in many others that you can find/ by searching through this forum.

Iam Fresher to this Field,

iam very Thankful marioq, for ur Help

I will go through it once..

Thanks,
Durga

thank you Marioq,

Every thing is clear..

THANK YOU ONCE AGAIN