Flood resistant building structure

Details Flood resistant building structure Flood resistant building structure

2000-08-16

2002-02-19

Friedman, Carl D. (Department: 3635)

Static structures (e.g., buildings)

Controlled by condition responsive means

C052S064000, C052S169900, C405S229000

Reexamination Certificate

active

06347487

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to flood resistant building structures, and more particularly to building structures that are floatable such that damage is reduced in the event of a flood.
The invention has been developed primarily for use with residential structures in relatively flood-prone areas, and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to use in this field.
Historically waterways have been useful for transportation of goods and people, and as a water supply for industry and agriculture. Land near waterways, lakes and the like also tends to be aesthetically pleasing. For these and other reasons, early human settlements tended to be built relatively close to waterways, and rivers in particular. This pattern has been repeated over time, notwithstanding improvements in land-based transport and water distribution networks.
Unfortunately, land adjacent waterways and in low-lying areas is relatively prone to flooding. Flooding can cause tremendous emotional and financial damage as structures and businesses are damaged, and personal property destroyed. Worldwide, the annual cost of flood damage and displacement runs into many billions of dollars every year. For building occupants and owners this is a particularly pressing problem as it is frequently difficult or at least expensive to obtain insurance cover against flooding. Naturally, the more prone to flooding an area is, the more difficult it will be to obtain such insurance.
One of the difficulties of planning for buildings in flood prone areas is that floods occur at irregular intervals and that the magnitude of less common floods can be substantially greater than those floods that occur over a typical human lifetime.
Conventional buildings, such as the house
200
shown in
FIG. 1
, are built with a floor level
205
at or near ground level
125
. Clearly this is an undesirable form of construction for use in flood-prone areas, simply because flood waters of any substantial depth can advance higher than the floor level. Further, such buildings can obstruct the flow and egress of flood waters, potentially exacerbating flooding problems. Regulatory bodies may therefore require an “above-grade” construction.
An example of the usual approach to above-grade construction is shown in FIG.
2
. A conventional building
100
includes a superstructure
105
constructed atop piers
115
that are fixed into foundations in the underlying ground. This arrangement is used to permanently maintain the building superstructure
105
and its associated floor structure
110
at a predetermined height above grade level
125
. The piers
115
are often braced
120
to reduce lateral movement in, for example, high winds. This arrangement allows low level floodwater to pass beneath the building without actually flooding the superstructure
105
or floor structure
110
. This arrangement has been used since early civilisation, without fundamental changes other than in building materials and construction methods.
However, there are a number of specific disadvantages with the arrangement of
FIG. 2
, such as:
(a) flood waters may advance higher than the raised floor level
110
;
(b) the fixed piers
115
may be unsightly, especially if they are relatively high to deal with correspondingly high potential flood water situations;
(c) building regulations may place restrictions on maximum roof or floor heights, which can prevent sufficiently long piers being used;
(d) in very low-lying areas or areas prone to deep flooding the required pier height can be considerably higher than is desirable given the need for day-to-day access for residents.
In an effort to mitigate some of the problems with fixed elevated structures, various techniques have been proposed for constructing floatable buildings at grade level on dry land.
One such technique is disclosed in U.S. Pat. No. 5,347,949 by Paul K. Winston (hereinafter referred to as “Winston”). As shown in
FIG. 3
, Winston discloses a prefabricated modular housing unit
300
for use in flood prone areas. In particular, there is shown a cross section of a floatable housing unit
300
floating on floodwater
305
. The housing unit
300
uses flotation elements
310
formed from plastic liners
320
filled with foam
315
. The flotation elements
310
are seated underneath a foundation
325
of wooden beams fastened to a conventional floor joist system.
The housing unit
300
is anchored to the building site through a series of telescopically extendible piers
330
, in combination with a series of wooden pilings
340
that serve as a fixed dry-land foundation.
During a flood, the flotation elements
310
displace water until the entire weight of the building's superstructure is supported by them. As the flood waters continue to rise, the housing unit
300
is raised by the flotation elements
310
, which act as pontoons. The building is maintained in a substantially constant lateral position by the extendible piers, which slide telescopically from their submerged recesses as the housing unit
300
is raised by the flotation elements
310
.
The Winston arrangement suffers from a number of disadvantages. For example, the extendable telescopic piers
330
are exposed even in the retracted position, and can be subject to ingress of moisture and dirt over time. Moreover, the exposed portions of the piers
330
can corrode, inhibiting their subsequent extension. Additional corrosion can occur as floodwater rises and the telescopic piers
330
extend. Water even fills the extended telescopic piers
330
, apparently to provide a damping effect. However, this also washes away protective lubricants, further accelerating corrosion.
In addition the foam filed plastic liners are potentially prone to degradation over the long term. Under normal conditions, access for inspection and maintenance to these units is limited. The foam liners also provide a ready means of ingress for termites to the building structure in regions where termites are active.
In addition, the Winston housing unit
300
is unstable when it floats and requires careful balancing of loads. On the heavy portion of the housing unit
300
, larger foam flotation elements
310
are required. The load distribution in the housing unit
300
shifts as the building is furnished. To compensate for shifting loads, air bladders
350
at each corner of the housing unit
300
are required. The air bladders
350
are filled with proper amounts of air to provide a stable and level flotation. This is complex, inefficient and time consuming as it requires a compressor, a level measuring device and fine tuning (i.e. repeated inflation and deflation) of each air bladder to achieve a level flotation. For example, inflating a first air bladder often requires re-adjusting the air in the remaining three air bladders
350
, which in turn can necessitate further re-adjustment of the first air bladder.
Furthermore the Winston disclosure does not reveal a manner whereby the additional buoyancy forces applied to the floor structure
325
from the bladders
350
can be transmitted laterally to support movable loads, such as people and furniture that are not directly over the bladders
350
. Thus, with the disclosed floor joist system, it is likely that there will be relative movement within, and hence physical distress to, the housing unit
300
.
Furthermore, the potential for a low pressure region between the ground, pontoons and floor of the Winston arrangement suggests that in some circumstances the housing unit
300
may not float.
Another technique proposed for constructing floatable buildings at grade level on dry land is disclosed in U.S. Pat. Nos. 5,647,693 & 5,775,847, by Herman Carlinsky et al (hereinafter referred to as “Carlinsky”). As shown in
FIG. 4
, Carlinsky discloses a prefabricated building
400
including a watertight basement
405
, the floor and walls
410
of which are of unitary concrete constriction. Rollers
415
are attached to outer surfac

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