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RE: Concrete Masonry Load Bearing Buildings[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
- Subject: RE: Concrete Masonry Load Bearing Buildings
- From: William Keil <WJK(--nospam--at)brph.com>
- Date: Thu, 7 Oct 1999 11:15:49 -0400
< Does anyone have any thoughts on masonry load bearing vs steel? - Cost, steel vs masonry? > In general, I believe load-bearing masonry is cheaper; however, it requires more labor and affects the construction schedule. For example, once a steel frame and deck are completed, work can happen simultaneously on all floors. A load bearing masonry structure requires the first floor walls to be built, then the slab poured, then the second floor walls, then the slab, etc. My experience in the NE taught me that labor must be minimized because it usually controlled the budget. In the SE, cheap labor floats in on a raft everyday so material costs control the budget. < - Resistance to seismic and wind loads? > Ductility is needed to survive a seismic event, which in my opinion, masonry is not very ductile. Masonry is prone to shrinkage and movement cracks. This means putting in several control joints, a potential source of water infiltration. Good masonry detailing is essential for a quality structure. Pay particular attention to the masonry piers between windows/doors. < - Quality control of construction? > Good masons are required for a masonry bearing wall project. This cannot be stressed enough because the structural integrity of the wall and aesthetic qualities both suffer when substandard practices (or cheap, inexperienced labor) are used. I still haven't been able to quantify the structural contribution of aluminum cans, newspaper and plastic wrap dumped in the masonry cells. < - Anything to look out for? > Differential settlement due to poor foundations/soil compaction. One project had a huge crack develop in the corner of the building. Floor and roof loads were not on yet so the wall was only subjected to its' own weight. The contractor said we had better review our design. We insisted the contractor expose the footing so we could assess the whole problem. Probably because the contractor knew it was a foundation bearing stratum problem, they refused to expose the footing and quickly offered to "repair and monitor the crack for no additional charge." < - etc etc > I share your preference for a frame over bearing walls. I prefer to have redundancy in the structure and combining the structural and cladding systems into one element does not offer much redundancy. If the masonry is cladding only and it fails, then you just have minor repairs to local areas. If the masonry is the structure and the cladding and it fails (structurally or aesthetically), then major repairs are required. William J. Keil, P.E.
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