Deep foundation definition and seismic foundation ties questions

[AaronMcD]

1) What is the definition of deep vs shallow foundation for IBC (CBC specifically)? I couldn't find one. Is it base on type, total depth, or ratio?

2) designing seismic ties for 0.1Sds x factored gravity loads:
a) Must one restrain all piers at once for this load, or check each individually?
b) Is it acceptable to use soil as buckling restraint for very long ties in compression, or does one need to use intermediate "bracing" ties for very long compression ties?

http://www.hellodwell.design

 

[HTURKAK]

1) The following para. copy und paste from IBC Illustrated handbook ;

Section 1810 Deep Foundations
1810.1 General. Foundations are divided into two major categories of shallow foundations and deep foundations. Shallow foundations are the individual or strip footings,
the bottom of which is typically close to the surface such as mat foundations, slab on grade, or similar foundation types. Deep foundations are those that are not classified as shallow foundations. Deep found ations are regulated in Sections 1810.1 through 1810.4 and are those typically referred to as piles, piers, or caissons that transfer load from a superstructure such as a building to the underlying soils or rock that provides support for the superstructure.

2)The ties shall be capable of transmitting a nominal force equal to the larger footing 0.1Sds x factored gravity loads ..

a) The code ( for your zone ) states the use of larger footing factored gravity loads for each ftg. You may simplify by using the largest column load keeping in mind economy and simplicity as necessary.

b) Refer to ASCE 7 Items 12.13.9 ...( All ties shall have a design strength in tension or compression at least equal to a force
equal to 10% of SDS times factored gravity loads ..) Refer to ACI 318 Section 18.13.4; ... the smallest cross-sectional dimension of the tie beam must not be less than the clear spacing between pile caps divided by 20...