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Marine Bollard Calculations 2
- Thread starter garo213
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MikeHalloran
Mechanical
The anchor bolts on a bollard are largely decorative.
Not to put too sharp a point on it, but you are in over your head.
Mike Halloran
Pembroke Pines, FL, USA
Not to put too sharp a point on it, but you are in over your head.
Mike Halloran
Pembroke Pines, FL, USA
That is a sharp point Mike!
I'm just a civil engineer, looking to learn new things. A quick look at marine bollards makes me think the anchor bolts serve a function, unless the bollard is held in place by weight. Is that the case?
Garo, I'd ask folks who sell the bollards, for instance. Let us know what you find out, it's an interesting question>
I'm just a civil engineer, looking to learn new things. A quick look at marine bollards makes me think the anchor bolts serve a function, unless the bollard is held in place by weight. Is that the case?
Garo, I'd ask folks who sell the bollards, for instance. Let us know what you find out, it's an interesting question>
- Thread starter
- #4
atook, you are correct! Without the anchor bolt/ stud, the bollard would simply slide right the dock. The anchors are embedded in the concrete to match the bolt pattern on the base of the bollard. Usually the anchor material would be A449, although, I just quoted a job in Jax FL, asking for F1554.BTW..Maritime is our competitor.....they ain't giving us @#%$. I was hoping that somewhere there may be a program that could spit out the calculations.Many spec will ask for the bollard to withstand its rating from 0 deg. to 60 deg. in one plane and 0 deg. to 180 deg. in another plane, with a safety factor of 2.
MikeHalloran
Mechanical
Uh, no, they're not held down by weight, but stationary bollards seem to rely a lot on chance.
Tugboat bollards extend far down into the hull structure, and have to, because they're actually used.
The bollards on a dock are statistically unlikely to be pulled on really hard, which is probably why their anchor bolt holes are relatively small, given the overturning moment that could be produced before modern cordage would even stretch, much less fail. I assume the bollard makers just blame the anchor supplier when the occasional bollard gets uprooted.
Garo, I'm sure your competitors wouldn't answer the questions you want answered, for obvious commercial reasons, and quite possibly because they don't know the answers anyway. An engineer could answer the questions for you, and maybe give you a competitive advantage. Rent one for a while.
Mike Halloran
Pembroke Pines, FL, USA
Tugboat bollards extend far down into the hull structure, and have to, because they're actually used.
The bollards on a dock are statistically unlikely to be pulled on really hard, which is probably why their anchor bolt holes are relatively small, given the overturning moment that could be produced before modern cordage would even stretch, much less fail. I assume the bollard makers just blame the anchor supplier when the occasional bollard gets uprooted.
Garo, I'm sure your competitors wouldn't answer the questions you want answered, for obvious commercial reasons, and quite possibly because they don't know the answers anyway. An engineer could answer the questions for you, and maybe give you a competitive advantage. Rent one for a while.
Mike Halloran
Pembroke Pines, FL, USA
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The bolts I have seen are not 'decorative' as was suggested. I have not seen many break but what I have seen is the whole bollard along with a substantial piece of the dock or deck get torn off with it. The dock/deck seems to be the weak point not the bolts. The only exception was when it was obvious the bolts on the far side of the load were loose and the bollard bent over before breaking the near bolts.
That 2-1 safety factor seems a little low when you consider that the bollard takes some awful abuse. Idiot Captains will test their engines on them (ok that was me), scour the bottom with their props to give them a little more depth at the dock while tied to them (me again), test their windlass on them (yep me), forget to untie one line when leaving the dock (not my fault), trucks will back into them (not me), and all this will happen over a period of maybe 50 years while they receive zero maintanance and sit in a corrosive environment. Not to mention the obvious hurricanes etc.
My point is that most boat captains never think twice about them and consider them as fixed as a mountain until they see them fly past the wheelhouse window so use the biggest bolts possible - please.
That 2-1 safety factor seems a little low when you consider that the bollard takes some awful abuse. Idiot Captains will test their engines on them (ok that was me), scour the bottom with their props to give them a little more depth at the dock while tied to them (me again), test their windlass on them (yep me), forget to untie one line when leaving the dock (not my fault), trucks will back into them (not me), and all this will happen over a period of maybe 50 years while they receive zero maintanance and sit in a corrosive environment. Not to mention the obvious hurricanes etc.
My point is that most boat captains never think twice about them and consider them as fixed as a mountain until they see them fly past the wheelhouse window so use the biggest bolts possible - please.
MikeHalloran
Mechanical
I admit, "decorative" was not a great choice of words, but it does describe the relative strength of a stationary flanged bollard vs. a tugboat's bollard.
In a former life my fab shop made some t-bar bollards for a yacht's deck, from our best stainless tube, to a customer's design. They looked so nice that the boss asked if we should be making them as a standard product.
The boss said he wanted them strong enough to break any rope that could be bent on to them. Nobody makes them that strong, and if they did, they'd have to be tied to the keel, not the deck. I couldn't find a standard for how strong they should be, and I couldn't find a manufacturer who published a load rating. Some of them go so far as to quote specs for the material or the fasteners they use, but no farther.
Maybe they just flat don't know. More likely they do, and also figured out that if they make the bolt holes small enough and provide no other means for transferring loads to the substrate, they force the inevitable failure into someone else's backyard, and someone else will get yelled at when a bollard goes whistling by the wheelhouse.
Mike Halloran
Pembroke Pines, FL, USA
In a former life my fab shop made some t-bar bollards for a yacht's deck, from our best stainless tube, to a customer's design. They looked so nice that the boss asked if we should be making them as a standard product.
The boss said he wanted them strong enough to break any rope that could be bent on to them. Nobody makes them that strong, and if they did, they'd have to be tied to the keel, not the deck. I couldn't find a standard for how strong they should be, and I couldn't find a manufacturer who published a load rating. Some of them go so far as to quote specs for the material or the fasteners they use, but no farther.
Maybe they just flat don't know. More likely they do, and also figured out that if they make the bolt holes small enough and provide no other means for transferring loads to the substrate, they force the inevitable failure into someone else's backyard, and someone else will get yelled at when a bollard goes whistling by the wheelhouse.
Mike Halloran
Pembroke Pines, FL, USA
davidgao800
Mechanical
FEA software such as PTC-MECHANICA or ansys-workbench
Can do it easy
Finite Element Analysis (FEA), also known as the Finite Element Method (FEM), is probably the
most important tool added to the mechanical design engineer's toolkit this century. The development of FEA has been driven by the desire for more accurate design computations in more complex situations, allowing improvements in both the design procedure and products.
mooring equipments such as marine bollards and anchor are "small systems",so FEA(Finite Element
Method) is not difficult for them.
I am come from china ,we calculate the mooring equipments by FEA software for years.
Can do it easy
Finite Element Analysis (FEA), also known as the Finite Element Method (FEM), is probably the
most important tool added to the mechanical design engineer's toolkit this century. The development of FEA has been driven by the desire for more accurate design computations in more complex situations, allowing improvements in both the design procedure and products.
mooring equipments such as marine bollards and anchor are "small systems",so FEA(Finite Element
Method) is not difficult for them.
I am come from china ,we calculate the mooring equipments by FEA software for years.
DaveVikingPE
Structural
Mooring forces are surprisingly complex. What you really need, maybe, is a program like OPTIMOOR to calculate all the forces - FROM EVERY POSSIBLE DIRECTION - and apply the maximums accordingly to your mooring bollards. ...and then figure out how many lines your design vessel will need vs. how many they really have, etc.
Pauljohn had some good clues for determination of potential loadings. i.e. potential thrust of the largest vessel you expect to be tied to the bollard. Assume the thrust is taken by one bollard. Other sources for the load, absorbing the kinetic energy of the largest vessel to be tied to the bollard i.e. stopping it. Wind force from the vessel being blown away from the bollard assume the worst case wind.... The mind boggles for the number of potential load cases the bollard may see!
My personal favorite is trucks using them as guides along the pier!
Cheers
Mark Hutton
My personal favorite is trucks using them as guides along the pier!
Cheers
Mark Hutton
Garo
The new hurricane in the atlantic got me thinking that by far the biggest load that I would think a bollard would see is from storm surge (although this load is not limited to hurricanes- i.e. tides, regular storms etc.). This load would also be relatively easy to compute, buoyancy and angle.
Is this something a 'bollard designer' would add to their calculations or is it too unreasonable to think a bollard should take such a load.
BTW I do not intend to test any bollards this hurricane season. (but you never know!!)
The new hurricane in the atlantic got me thinking that by far the biggest load that I would think a bollard would see is from storm surge (although this load is not limited to hurricanes- i.e. tides, regular storms etc.). This load would also be relatively easy to compute, buoyancy and angle.
Is this something a 'bollard designer' would add to their calculations or is it too unreasonable to think a bollard should take such a load.
BTW I do not intend to test any bollards this hurricane season. (but you never know!!)
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