Static structures (e.g. – buildings) – Relatively yieldable preformed separator
Reexamination Certificate
2001-02-12
2002-11-26
Chen, Jose V. (Department: 3637)
Static structures (e.g., buildings)
Relatively yieldable preformed separator
C052S394000, C052S395000, C052S396020, C052S396030, C052S396040, C052S396050, C052S396060, C052S573100, C052S459000, C052S468000, C404S068000
Reexamination Certificate
active
06484462
ABSTRACT:
BACKGROUND OF THE INVENTION
Seismic expansion joint covers for buildings in geographic regions that are prone to earthquakes are of special designs that allow for movements of the building elements on either side of the expansion gap that are very much greater than the movements that occur as a result of thermal expansion and contraction. In that regard, buildings currently being built in earthquake-prone regions are usually supported on isolators that attenuate the intensities of shocks imparted to the building structure but increase the durations and magnitudes of the swaying motions of the structure as it displaces and deforms when forces due to the earthquake are imposed on its foundation supports. When a building is composed of two or more adjacent independent structural units, each structural unit is subject to movements in an earthquake that are different in direction, frequency and magnitude. This is the case, indeed, regardless of whether the units are mounted on isolators or not. Adjacent structural units of a building are, accordingly, subject to large relative movements having components toward and away from each other (perpendicular to the gap)—x-axis movements—and components parallel to the gap—y-axis movements. Because the connections between structural units at expansion joints (which might better be termed “motion-absorbing gaps”) occur at the perimeters of the structural units, the movements include small but meaningful relative displacements vertically and angularly between floor portions on opposite sides of gaps due to the rocking of the floors at the perimeter of the structural unit about a fulcrum in the region of the bottom center of the structural unit.
U.S. Pat. No. 5,644,879 (Shreiner et al. Jul. 8, 1997), which is owned by the assignee of the present invention and is hereby incorporated herein by reference for all purposes, describes and shows a seismic expansion joint cover assembly that is adapted to span a gap between the floors of building sections on opposite sides of a motion-absorbing gap and that permits relative movements of the floors substantially horizontally toward and away from each other along an axis perpendicular to the gap (“x-axis direction”) and substantially horizontally relative to each other along an axis parallel to the gap (“y-axis direction”). The assembly includes a rectangular structural floor bridge panel that spans the gap in all relative positions of the floors. One end of the bridge panel is attached to the floor on one side of the gap (“floor A”) for movement in the y-axis direction and against movement in the x-axis direction relative to floor A. The other end of the bridge panel is supported on the floor of the other building section (“floor B”) for movement in the x-axis direction and against movement in the y-axis direction relative to floor B.
In order for the upper surface of the seismic expansion joint cover to be substantially flush with the upper surfaces of floors A and B, floor B has a rectangular recess having a width in the y-axis direction substantially equal—with some clearance—to the y-axis width of the bridge panel and a length in the x-axis direction sufficient to permit excursions of floor A relative to floor B in the x-axis direction in an earthquake so that floor B supports the bridge panel in all positions of floors A and B relative to each other. In the normal—no earthquake—relative positions of floors A and B, the bridge panel occupies roughly half of the recess in floor B. When floors A and B are farthest apart in an earthquake, the bridge panel must occupy a small part of the recess, inasmuch as its floor B end must remain supported on floor B, but most of the recess is empty. When floors A and B are closest together in an earthquake, the bridge panel occupies most of the recess. Hence, a cover over the recess and the bridge panel provides a flush upper surface of the seismic expansion joint cover for supporting persons and other loads that move over the expansion gap in both a normal (no earthquake) condition and during an earthquake.
In particular, a cover plate frame is installed along the side and end edges of the recess and has side members closely adjacent the sides of the bridge panel and an end member spaced apart from the floor B end of the bridge panel far enough to permit the bridge panel to move toward the end of the recess of floor B relative to the floor bridge panel in the x-axis direction when the gap narrows. A first cover plate (“panel cover plate”) is supported by a portion of the bridge panel proximate to floor A. A second cover plate (“recess cover plate”) is supported by the cover plate frame and by a portion of the bridge panel adjacent the floor B end. The panel cover plate and the recess cover plate have surfaces flush with each other and adjacent end edges slightly spaced apart from each other to permit normal movements of floors A and B due to thermal expansions and contractions of the building structures. The recess cover plate is resiliently attached to the cover plate frame such as to keep it in place horizontally while permitting it to lift from supported relation on the bridge panel and ride up onto and over a portion of the panel cover plate when the motion-absorbing gap narrows in an earthquake.
In its broadest aspects, the seismic expansion joint cover of the '879 patent (referred to above) has a structural floor bridge panel that spans the motion-absorbing gap in all positions of floors A and B, a covered cavity that accepts the floor B end of the bridge panel in all positions of floors A and B, and two flush cover plates that provide a surface over which persons and objects move across the assembly. The recess cover plate is attached resiliently to the cover plate frame of the recess so that the recess cover plate can lift up and slide over the panel cover plate when the gap narrows
In order to avoid having to make the recess cover plate unduly thick and heavy, the '879 patent proposes to provide one or more movable transverse beams to support the recess cover plate between the floor B end of the bridge panel and the end member of the cover plate frame. Each transverse beam extends between and is slidably supported by the side members of the cover plate frame. Control arms move the transverse beam toward and away from the end member of the cover frame upon and in a proportional relationship of one-half to movements of floor B relative to the bridge panel.
Despite having many advantages, some parts and assemblies of the seismic expansion joint cover of the '879 patent are of relatively complicated and costly construction and somewhat time-consuming to install. One of the systems of the '879 patent seismic expansion joint cover that has shortcomings of the foregoing nature is the moving beam assembly for supporting loads on the recess cover plate. The beams, linkages, and slide elements are expensive to make and install and add weight and complexity to the system. The weight produces relatively large inertial forces, which act not only on the components of the moving beam assembly but on the recess frame, the bridge panel, and the y-axis and x-axis supports for the bridge panel. Another undesirably complex arrangement is the resilient mounting of the recess cover plate on the recess frame (see
FIG. 10
of the '879 patent).
SUMMARY OF THE INVENTION
One object of the present invention is to provide a seismic expansion joint cover assembly for floors that is able to sustain a severe earthquake with little likelihood of damage to the components of the assembly or to the floor portions in which it is installed. Another object is to provide an expansion joint cover assembly that can be quickly and easily restored to its normal operating configuration after it has been disturbed by an earthquake. Still another object is to provide an expansion joint cover that has a flush, essentially smooth upper surface. It is also an object to provide a seismic expansion joint cover that can be fabricated in units that are easy to transport to a job s
Barr Roger W.
Shreiner Thomas A.
Chen José V.
Construction Specialties, Inc.
Dorsey Dennis L.
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