huangyhg

existing brick foundation wall
i have a job with an existing 50 to 100 year old brick foundation wall, that the owner wants to keep in place, and build 4 stories on top of.
how can this be evaluated. what physical testing should be done to see if mortar and brick can handle the new load.
a couple of questions here...
what seismic area are we talking about?
is there a concrete strip footing under the brick, or is it brick only?
mike mccann
mccann engineering
question; how many wythes or how thick is the wall?
what kind of structure? - loadbearing masonry walls or concentrated loads.
if you stick with a compatible masonry structural system, you may have to trouble.
do not try to take "prism" samples out of the existing walls. you could remove some brick units and correlate the compressive strength with code tables using an assumed mortar strength (mortar is not really the major strength factor for a wall).
if it is a solid bonded brick wall, 4 stories may not be much of a problem with loadbearing masonry/ columns and concentrated loads could be a different story.
dick
location is new york city seismic zone 2a
will there be a way to deal with seismic requirements?
if not, then this idea is dead!
regarding load no columns to be added, just cmu units
regarding footing below,
i am assuming there is a concrete footing, but this still has to be verified, likewise width still to be verified.
with an old brick foundation wall - there are usually some unknowns to deal with:
1. masonry brick strength f'm
this can usually be visually verified (not numerically, just general order of magnitude) in terms of general quality of the masonry.
2. width of the brick foundation below it.
this can be verified by a series of local excavations to determine the width. many old brick foundations were formed by corbelling out the brick at each course until some determined width was acquired.
3. voids in the foundation wall...i.e. spaces between wythes.
again, local destructive investigations can be performed to verify the interior nature of the wall. cutting and removing only small areas to see "inside" are required.
some possible actions to take in your design:
1. if you place a new, rigid element, like a concrete gradewall on top of the brick, then brick wall could then be considered just a more rigid portion of the subgrade. the brick is most likely more competent than the soil beneath it and the new gradewall will spread out any irregularities in loading on the brick and also help tie the brick together.
2. verify the soil bearing capacity directly near/adjacent to the wall. this will allow you means to compare the existing footing width with the proposed new loads.

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