11:50 it is tension in the bolt but it is because of "compression" that the crack developed... The bolt "head" is similar to a compressive load, this developed the "cone failure"... This anchor failure is because of concrete compression failure from the point loading of the bolt head (using tension as the loading force)... Hope that makes sense... A deeper embedded head would resist more and a larger head /"plate" would distribute the load also. Overlapping cones of course are always an issue and wind loads create a shock force greater than non-shock loads. Deeper concrete footers and embedding of bars are superior to the smaller surface bolts. Your fracture implied surface tension was not shared in the concrete resistance... Loading was from bolt head and this cone failure is typical (38-45 degrees )... Typical of the fractures from the edge of the bolt head "edges" and of course this would be circular from top view / visual. The question is, how much force to create this fracture in this concrete and embedment? Again, this is an an internal compression load from the bolt head and I can get results from drilling a hole in a core and loading head of bolt to duplicate this failure (of course I would drill a hole to point load the embedded head , this will allow for the surrounding concrete to preticapate to some degree. My theory is of "stirrups" and this allows for "trapping" exploding concrete, this is not a deflection failure but an "bursting failure" and strapping does a great job on trapping that buckling failure. Confine the cone, do not allow it to "displace"... I hope I did not confuse you and I hope you do take offense.
“A deeper embedded head would resist more and a larger head /"plate" would distribute the load also.” Agreed. It would have cost very little to increase the embedded bolt length to, say, 20 times the major diameter. Also, the embedded washer (if we can call it that) is too small in diameter and curiously over-thick. Better would have been a diameter of 2.5 to 3.0 times the major diameter of the threaded rod. But notice, though, on the low-resolution photo what appears to be a plastic sheath over the embedded portion of the threaded rod above the “washer.” This is smart. It prevented concrete from bonding to the rod above the washer. Two factors to consider. One, concrete is strong in compression, but weak in tension. Two, the rod, like any elastic object, will elongate as load is applied. If the concrete had bonded to the upper part of the rod (which, as I stated, was not the case), as the rod elongated under tension, part of the tensile load would have been shared by the concrete bonded to it. Since concrete is weak in tension, a local concrete failure would have occurred near the surface with a proportionally smaller cone of failure compared to that shown in the photo. The immediate result would have been less remaining intact material to support the tensile load. One can imagine a cascading effect, especially under cyclical loading, where supporting material would be progressively lost until ultimate failure. The load required for said hypothetical failure, we may reasonably speculate, would be significantly less than was the case of the failure shown in the photo, where concrete bonding above the washer was prevented. Your thoughts?
Thank you so much for providing good information. Please make a video on topic how steel base plate transfer load on concrete pedestal. Most of the book cover directly base plate to concrete pedestal uniform load type. But in practical most of time I see steel base plate is elevated over pedestal through bolt even no any grouting has provided. Will it transfer load as point load through bolt on pedestal.
It's very simple..in main structural bolt we consider yield and rupture but in anchor bolts we only consider ultimate strength. Isn't it ? And as ultimate strength is much higher than yield strength, even if we use lesser strength material our purpose is solved
Hello sir, I have a question if the base is pinned connected and the upper frame is moment connected how does the flange carry loads from column to the base plate and to the foundation …. Your explanation on this would be very helpful
such great tutorial, helped me with my assignment. Very clear and straight forward explanation.
Glad you like it
11:50 it is tension in the bolt but it is because of "compression" that the crack developed...
The bolt "head" is similar to a compressive load, this developed the "cone failure"...
This anchor failure is because of concrete compression failure from the point loading of the bolt head (using tension as the loading force)...
Hope that makes sense...
A deeper embedded head would resist more and a larger head /"plate" would distribute the load also.
Overlapping cones of course are always an issue and wind loads create a shock force greater than non-shock loads.
Deeper concrete footers and embedding of bars are superior to the smaller surface bolts.
Your fracture implied surface tension was not shared in the concrete resistance... Loading was from bolt head and this cone failure is typical (38-45 degrees )... Typical of the fractures from the edge of the bolt head "edges" and of course this would be circular from top view / visual.
The question is, how much force to create this fracture in this concrete and embedment?
Again, this is an an internal compression load from the bolt head and I can get results from drilling a hole in a core and loading head of bolt to duplicate this failure (of course I would drill a hole to point load the embedded head , this will allow for the surrounding concrete to preticapate to some degree.
My theory is of "stirrups" and this allows for "trapping" exploding concrete, this is not a deflection failure but an "bursting failure" and strapping does a great job on trapping that buckling failure.
Confine the cone, do not allow it to "displace"...
I hope I did not confuse you and I hope you do take offense.
“A deeper embedded head would resist more and a larger head /"plate" would distribute the load also.” Agreed. It would have cost very little to increase the embedded bolt length to, say, 20 times the major diameter. Also, the embedded washer (if we can call it that) is too small in diameter and curiously over-thick. Better would have been a diameter of 2.5 to 3.0 times the major diameter of the threaded rod.
But notice, though, on the low-resolution photo what appears to be a plastic sheath over the embedded portion of the threaded rod above the “washer.” This is smart. It prevented concrete from bonding to the rod above the washer. Two factors to consider. One, concrete is strong in compression, but weak in tension. Two, the rod, like any elastic object, will elongate as load is applied. If the concrete had bonded to the upper part of the rod (which, as I stated, was not the case), as the rod elongated under tension, part of the tensile load would have been shared by the concrete bonded to it. Since concrete is weak in tension, a local concrete failure would have occurred near the surface with a proportionally smaller cone of failure compared to that shown in the photo. The immediate result would have been less remaining intact material to support the tensile load. One can imagine a cascading effect, especially under cyclical loading, where supporting material would be progressively lost until ultimate failure. The load required for said hypothetical failure, we may reasonably speculate, would be significantly less than was the case of the failure shown in the photo, where concrete bonding above the washer was prevented.
Your thoughts?
Explained very well. Thanks for video.
Glad you like it
Excellent explanation
Thank you so much for providing good information. Please make a video on topic how steel base plate transfer load on concrete pedestal. Most of the book cover directly base plate to concrete pedestal uniform load type. But in practical most of time I see steel base plate is elevated over pedestal through bolt even no any grouting has provided. Will it transfer load as point load through bolt on pedestal.
Ok soon
Your approch is very good
Thank you 💗
Very nice explanation, sir could you explain us why we use lesser strength material for anchor bolts when compared to main structure bolts
It's very simple..in main structural bolt we consider yield and rupture but in anchor bolts we only consider ultimate strength. Isn't it ? And as ultimate strength is much higher than yield strength, even if we use lesser strength material our purpose is solved
Keep it up !
Always!
Sir
Theory very clear now. Can you add a problem on anchor bolt
I will try
Very nice
Thank you for your appreciation.
Please provide how to calculate reinforement to avoid crack due to shear force & tension....
Excellent Dear Maity
Glad you like it
how about value of torque anchorbolt. how to calculate?
Hello sir, I have a question if the base is pinned connected and the upper frame is moment connected how does the flange carry loads from column to the base plate and to the foundation …. Your explanation on this would be very helpful
This needs a video explanation. I will put it as soon as possible.
Hats off
Glad you like it
Plz tell about double connection in column in next video bro
Ok
Thanks for the video. When modelling anchor bolts in ABAQUS, is it necessary to include bolt pretension?
You can if your code allows
Why is sometimes Base plate kept on nuts and later grouting is done below base plate . Why base is not kept directly over Concrete surface.?
To ensure uniform surface contact
The bolt will never be stronger than the concrete. Before the concrete cracks, the bolt will crack first
yes right 50 mpa vs 415 mpa
Are bhai Hindi boll
don't be selfish...it's for everyone..not only for Hindi medium students
i missed your point