Design crane bridge with CMAA #70

[jonlogar]

Hello, I am designing a crane bridge(OVerhead traveling crane multigirder) with the standard CMAA #70, and I have a question, in the structural design,Do I have to consider the design fatigue?, so in this standard showme only a allowable stresses for example: allowable tension stress is equal to 0.6 of yield stres. and I don't know if this stress is the static stress, If this is correct then I have no fatigue design stress.

please someone who has previously worked with this standard and can help

thank you

 

[dik]

For a start, when designing a crane system, I usually obtain/determine the following:

HOISTING EQUIPMENT
CMAA CRANE CLASS [A (INFREQUENT SERVICE | B (LIGHT SERVICE | C (MODERATE SERVICE|
D (HEAVY SERVICE | E (SEVERE SERVICE |
F (CONTINUOUS SEVERE SERVICE])
HMI CRANE USE [H2 (INFREQUENT USE) | H3 (AVERAGE DUTY) | H4 (HEAVY DUTY)]
CRANE SPAN (APPROX) 30'-0"
CRANE WHEEL BASE 7' 2-5/8"
CRANE HOOK HEIGHT 15'-0"
MAX DEFLECTION 0.5 in

MAXIMUM CRANE CAPACITY 10000 LBS
WEIGHT OF BRIDGE 3600 LBS
WEIGHT OF HOIST AND TROLLEY 730 LBS
WEIGHT OF END CARRIAGE 700 LBS
TOTAL CRANE WT + CAPACITY 14330 LBS
MAXIMUM STATIC WHEEL LOAD 6000 LBS
MAXIMUM DYNAMIC WHEEL LOAD 6800 LBS
END STOP BUFFER FORCE 2500 LBS
LONG BREAKING FORCE (MANU) 600 LBS
LONG BREAKING FORCE (CODE) 1000 LBS
LAT FRICTION FORCE (MANU) 1700 LBS
LAT FRICTION FORCE (CODE) 2100 LBS

BRIDGE SPEED 100 FT/MIN
HOIST SPEED 65 FT/MIN (TRANSVERSE)
HOISTING SPEED 20/3.3 FT/MIN (2 SPEED UPWARDS)

CRANE SHALL BE DESIGNED FOR A DUTY CYCLE OF 10 LIFTS PER DAY, FOR 250 DAYS / YEAR FOR A PERIOD OF 20 YEARS (50,000 LIFTING OPERATIONS)

% CAPACITY LOAD (LBS) % USEAGE No. OF LIFTS
100 10000 5 2500
80 8000 50 25000
50 5000 30 15000
20 2000 10 5000
10 1000 5 2500

and I use the last bit of information to determine fatigue loading if necessary

 

[dik]

It formats with non-proportional fonts...

Dik

 

[dhengr]

Jonlogar:
I don’t have a copy of CMAA Spec. #70, so I don’t know exactly what it covers or how it covers it. I would think the latest edition of that would be your primary design guide and spec. ASME probably has some standards which might be helpful. AISC has some Specs., Codes and standards which should be helpful in understanding steel design and fabrication and various critical details and stress conditions. AWS has some Specs., Codes and standards which should be helpful in understanding welding. Both AISC and AWS have some material on fatigue design. Dik’s listing is a good list of basic questions that you must have answers for to really get started. Then you do basically do a static design, with some impact load factors for various load conditions. Then based on the number of load cycles and the various stress ranges, you adjust your details to stay below an allowable stress for that load and number of cycles.

 

[jonlogar]

Thank you.