Method of constructing structures with seismically-isolated base

Abstract

A seismically isolated structure and a method of constructing same provide a rigid diaphragm, a plurality of footings each positioned at least partially under the rigid diaphragm, and a plurality of base isolation devices each positioned between a footing and the rigid diaphragm, wherein the rigid diaphragm was constructed in situ above the footings generally below its final elevation. A barrier is positioned between the rigid diaphragm and at least the footings to prevent bonding between the rigid diaphragm and the footings. The barrier, which may be structural or chemical or a combination thereof, may also span between the footings if appropriate.

Description

FIELD OF INVENTION [0001] This invention relates generally to a method of constructing structures with a seismically-isolated base, in particular, a method of constructing structures supported on base-isolation devices. BACKGROUND OF INVENTION [0002] The building codes used in the U.S. were based on one of three model codes: the Building Officials and Code Administrators International, Inc. (BOCA) National Building Code (NBC); the Southern Building Code Congress International, Inc. (SBCCI) Standard Building Code (SBC); and International Conference of Building Official's Uniform Building Code (ICBO's UBC). However, BOCA, ICBO and SBCCI recently formed the International Code Council® (ICC) and produced the International Building Code® (IBC), a single, unified family of building codes, for use throughout the U.S. The three model codes were merged into one in an effort to integrate the most current earthquake knowledge and seismic design technology into the building codes. [0003] Scient...

AI Technical Summary

Benefits of technology

[0013] The present invention offers many advantages, including general adherence to known construction methods, costs and timelines for structures of comparable size and complexity, but provides for a structure that incorporates base-isolation devices for better adaptation against earthquakes or other types of seismic activity or ground vibrations.

Problems solved by technology

Scientists began studying earthquakes as early as 1880, but gathering meaningful and accurate seismic activity data proved difficult due to the irregularity of earthquake events and long intervals of inactivity therebetween.

According to research by National Earthquake Hazards Reduction Program (NEHRP), the costs of providing seismic-resistant features for the protection of life rarely exceed two percent of the construction costs for new buildings.

Similarly, the 1997 NEHRP indicates that its design earthquake ground motion levels could result in both nonstructural and structural damage.

In fact, engineers recognize that new buildings could sustain so much damage in a severe earthquake that they may have to be demolished and rebuilt, yet still not collapse.

While there is no question that there exist the necessary engineering expertise and technology to design and build highly earthquake-resistant structures, the cost would be prohibitive.

Most BIDs also damp the movement.

However, the use of BIDS has often been limited to “critical structures” such as hospitals and selected government facilities, leaving most single family homes, low rise apartments and condominiums, particularly those of light wood frame construction in the Western United States, vulnerable to earthquake damage.

This problem is compounded by the fact that construction methods for light wood frame structures follow generally similar formats.

Since construction budgets and schedules are often closely monitored, the construction industry disfavors disruptions or deviations from those methods that would increase cost or prolong construction schedules even if they render the structure safer and more earthquake-proof.

Thus, while elevating a structure, such as a single family home, low rise apartments and condominiums, is known, the process can be expensive and dangerous.

Moreover, since a popular guideline allows for lifting a house no more than 1 / 16 inch per day, the process can also be extremely time-consuming.

As such, lifting an older house or building or one after construction has been completed for purposes of earthquake retrofitting, even if the house or building is smaller, can be logistically and / or economically prohibitive for the owner.

As such, the construction of basement or subbasement has often precluded the use of BIDS in almost all by the most crucial of newly constructed buildings.

While the installation of BIDS in a new construction having a basement is possible, there is usually a significant increase in construction time and expenses stemming from the additional excavation and construction materials, such as for a subbasement to provide space and continued access to the BIDS and falsework to provide temporary support to the basement floor during construction.

Images