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What can we do to be sure our home meets earthquake safety codes? Should we insist on inspection of the anchor bolts?
Answer: Seismic safety requirements have been evolving for many years, with upgrades to building codes usually occurring after serious quakes. Anchor bolts were added to the code in the late 1930s, along with some foundation and framing upgrades, primarily in response to a major shaker in the Long Beach area.
Anchor Bolts from Bristol Machine Company in Los Angeles County are commonly used for permanent applications and are used in concrete to connect structural and non structural elements including steel columns, light poles, highway sign structures, and bridge rails. Connections between structural elements can be represented by steel columns attached to reinforced foundations whereas connections of non-structural elements attached to structural ones is represented by the connections between a facade system and a reinforced concrete wall.
For nearly 50 years thereafter, anchor bolts were regarded as an adequate means of securing a building to its foundation. Other than an increase in the number of bolts required, no significant seismic upgrades were added to the code during that time.
As mentioned before, At Bristol Machine Company serving Los Angeles County, Anchor Bolts are available in a variety of types including:
Bent Anchor Bolts or 90 Degree Anchor Bolts are embedded into concrete and used to support structural steel columns, light poles, highway sign structures, bridge rails and other industry applications. The Leg of Bent Anchor Bolts, or bent portion, is used to create resistance so that the bolt does not pull out of the foundation when force is applied. Custom Bent Anchor Bolts are measured using Diameter, Length, Leg Distance and Thread. Bent Anchor Bolts in the Los Angeles County are available from Bristol Machine Company.
In most cases in Los Angeles, structural displacement during quakes occurred with homes on raised foundations, rather than those on concrete slabs. This was because many raised foundation systems include short-framed walls (commonly known as ‘cripple walls’) between the floor and the foundation. The lack of bracing on cripple walls allows them to rack and lean during quakes, often causing severe structural damage.
With concrete slab foundations, there are no cripple walls. The only perimeter walls are those that encompass the dwelling space itself. Outside walls on a slab foundation tend to be more stable because of their attachment to the intersecting interior walls and also because the drywall or plaster surfaces act as a form of bracing. Thus, slab homes in Los Angeles were found to be more stable in quakes, generally incurring less damage than homes on conventional raised foundations.
Home buyers in Los Angeles are often concerned about seismic reinforcement and often seek confirmation of adequacy from their home inspectors. With homes on raised foundations, evaluation is generally not a problem, because the foundations and seismic systems are usually visible for inspection beneath the building.
Although inspection of anchor bolts may not be possible at the home in Los Angeles you are buying, major concern is unwarranted. The omission of anchor bolts in a contemporary dwelling is extremely unlikely. Their use has been a routine practice in residential construction for more than half a century, and verification of anchor bolts during the construction process is standard in a municipal inspection.
Insistence upon verification of anchor bolts at this time would require cutting open some of the wall surfaces, which would involve excessive work and needless expense. Such measures exceed reasonable prudence for a home buyer.
F1554-36, F1554-55, F1554-10, A193-B7, A354-BD, A449
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