01-05-2011, 05:13 PM
Each problem has its focus.
For telecommunications towers, with three or four supports or legs, the most critical load is the traction, not the soil capacity of the land, which is the secondary verification.
In my country, and in coastal areas where wind loads are significant (without going to extremes of hurricanes), it is verified that the structure is sufficiently anchored in the ground, assuming a load in tension or uplift equal to the weight itself structure plus an additional factor. This verification is done for each leg, and then to the slab, considering the maximum resulting on the first analysis and their situation over the slab.
After verifying the stability uplift loads, it performs the analysis of ultimate bearing capacity; probable settlement are verified at the end.
Normally, for purposes of initial analysis, it neglects the weight of the earth over the foundation, for incorporate it into the subsequent analysis. Now, if the slab can not "embedded" in the field, and should be flat with the surrounding land, the weight of the foundation slab must be equal to or greater than the probable maximum tensile load (maximum load plus an uplift factor additionally, it can be seen between 1.10 and 1.30).
It is a common practice (in my Country) that the first calculation and verification is done manually (you determine the weight of the tower, estimates the maximum uplift load, is applied to the foundation, placing the burden on the position of each of the legs, one at one time, and recess is verified on the ground. Subsequent verifications (allowable capacity and settlements) can be done with software. Personally, I do all the calculations by hand, and then verified using software later, to avoid mistakes.
RegardsFor telecommunications towers, with three or four supports or legs, the most critical load is the traction, not the soil capacity of the land, which is the secondary verification.
In my country, and in coastal areas where wind loads are significant (without going to extremes of hurricanes), it is verified that the structure is sufficiently anchored in the ground, assuming a load in tension or uplift equal to the weight itself structure plus an additional factor. This verification is done for each leg, and then to the slab, considering the maximum resulting on the first analysis and their situation over the slab.
After verifying the stability uplift loads, it performs the analysis of ultimate bearing capacity; probable settlement are verified at the end.
Normally, for purposes of initial analysis, it neglects the weight of the earth over the foundation, for incorporate it into the subsequent analysis. Now, if the slab can not "embedded" in the field, and should be flat with the surrounding land, the weight of the foundation slab must be equal to or greater than the probable maximum tensile load (maximum load plus an uplift factor additionally, it can be seen between 1.10 and 1.30).
It is a common practice (in my Country) that the first calculation and verification is done manually (you determine the weight of the tower, estimates the maximum uplift load, is applied to the foundation, placing the burden on the position of each of the legs, one at one time, and recess is verified on the ground. Subsequent verifications (allowable capacity and settlements) can be done with software. Personally, I do all the calculations by hand, and then verified using software later, to avoid mistakes.
oanm2000