During earthquakes, large man made structures such as houses are frequently damaged and collapse as a result of the structural damage caused by the earthquake ground movement. People trapped in the fallen structures are often severely injured or killed. While many newer structures are built to withstand earthquakes up to a certain predicted magnitude, many other existing structures must be retrofitted with additional support to prevent failure in the event of a large earthquake.
An area of particular weakness is the garage door, which is typically a large rectangular opening in the wall of the garage structure. The door normally includes a frame that has two side posts and a horizontal member that spans the two posts. The space between the posts must provide enough space to drive one or more cars through. The door area is weak because of this large unsupported opening. In contrast, the walls of the garage may comprise closely spaced posts and beams or may even be solid materials such as poured concrete.
The garage door itself typically is positioned behind the door frame and is attached to an opening mechanism such as a track or beam actuator. During a large earthquake, the top of the door frame sways from side to side while the base is typically bound to the foundation and does not move. Because the door is behind the door frame, both will move independently during the earthquake and the door will not provide any structural support for the door frame.
The door frame is particularly vulnerable to the earthquake movement that is in line with the plane of the frame. As the ground moves below the garage, the posts of the door frame sway which causes stress at the upper corners of the door frame. If the corners of the frame are broken, the frame can easily collapse. Because of this inherent weakness, garage door frame need to be heavily reinforced to prevent failure during a strong earthquake. Unfortunately, many garage doors are not reinforced and are susceptible to failure during an earthquake. What is needed is a system that improves the strength of the garage door frame that can be retrofitted onto existing garage doors.
The inventive system improves the structural strength of a garage door frame in the event of an earthquake. During an earthquake, the garage door frame sways in response to the ground movement. The garage door is typically mounted behind the door frame and does not provide strength to the frame or garage structure. The inventive system uses coupling mechanisms to attach the garage door to the garage door frame during the earthquake. This allows the strength of the door to be transferred to the frame which significantly enhances the strength of the garage door frame and may prevent the collapse of the garage structure.
In an embodiment, the inventive system uses “L” brackets mounted to the corners of the garage door with a planar portion extending forward into the plane of the door frame. The planar portions are parallel to the frame posts closely spaced to the inner edges. While the garage is stationary, there is no contact between the brackets and the door frame and the garage door can be opened and closed normally by sliding along tracks that extend into the ceiling. During an earthquake, the door frame will sway from side to side with the upper posts of the frame alternately moving towards the door and away from the door and the lower posts remaining stationary in the foundation. When a post moves towards the door it contacts the upper bracket which transfers the shear force to the door and helps to stop the swaying movement of the post. In a larger earthquake, the upper post movement may cause the door to slide horizontally and the lower brackets may contact the lower frame posts to further resist the movement of the posts.
When the brackets at opposite corners of the frame the door simultaneously contacts the frame posts, the door is compressed and provides shear strength to the door frame. A solid door transfers the shear force through the door structure which may be reinforced with structural diagonal members. A panel or sectional door will transfer the shear forces from the upper panel to the lower panels through the hinges that connect the panels. The panel or sectional door and other door types may be reinforced with flexible members such as wires or cables that are coupled to opposite corners of the door. When a shear force is applied to the door, one of the flexible members mounted will be pulled tight and will provide tension resistance to shear deformation of the door.
In other embodiments, the coupling mechanisms may reduce or prevent vertical movement between the door and frame. The coupling mechanism may use brackets that have holes that engage protrusions extending inward from the door frame. When an upper post sways towards the door in an earthquake, one or more protrusions engage corresponding holes in the brackets mounted to the door. The right beam of the frame moves towards the door to engage the holes in the upper right brackets while the protrusions in the left beam move away from the door and are free from the holes in the upper left bracket. As the garage sways back in the opposite direction, the protrusions in the left beam engage the holes in the upper left bracket while the protrusions in the right beam are freed. The coupling mechanism prevents vertical movement between the door and frame and transfers vertical forces from the post to the door. This vertical coupling further improves the strength of the door frame.
In another embodiment, the door to frame coupling mechanism includes plates having a series of ramped surfaces. These ramped plates are mounted to the corners of the door and the corresponding inner surfaces of the door frame. The ramped surfaces are configured to face each other and become coupled to each other in the same way as the protrusion/hole mechanism described above. While the protrusion and hole embodiment resists all vertical and inward horizontal forces, the ramped surfaces may only transfer downward vertical forces and inward horizontal forces from the frame to the door. The ramped surfaces may require less alignment of the door within the frame and also release or decouple more easily that the protrusion/hole embodiment.
Alternatively, the inventive system may actuate a coupling mechanism to lock the door to the door frame when it is in its closed position. In an embodiment, the inventive system uses the brackets with holes that are mounted at the upper corners of the garage door. When the door is closed or when an earthquake is detected, the system actuates rods that extend inward from the frame through the holes in the brackets. The coupling mechanisms remain engaged to the garage door throughout the earthquake. The coupling mechanisms remain engaged until the system is reset. This engagement of both corners further improves the transfer of strength from the door to the frame and enhances the earthquake resistance of the garage.
The present invention is a device and system for improving the structural strength of a garage door. In the event of an earthquake, the ground will move which causes the garage to sway. This swaying force is increased in proportion to the height of the structure. The movement is typically horizontal and absorbed by the vertical beams in the structure. If the beams fail, the structure can collapse. The garage door frame is an area of weakness because the large opening requires the vertical posts to be spaced far apart and must support much higher loads than a normal wall posts. Similarly, the beam that spans the garage posts must also support higher loads than a cross beam in a normal wall.
There are many types of garage doors. With reference to
A stronger door 111 will result in more support for the door frame 115 and the garage 107 in an earthquake. Because these cross beams 117 are aligned with the shear forces they are able to enhance the shear strength of the door 111. This strengthening will also cause the door 111 to be much heavier making it more difficult to open and close. The perimeter members 109 and cross beams 117 of the door also resist the horizontal shear forces in compression as the upper edge of the frame 115 sways from side to side. Thus, the solid door 101 is strong in shear and can provide resistance against horizontal forces directed in opposite directions.
Another type of garage door are panel or sectional doors. With reference to
There are also many ways for reinforcing the panel or sectional garage door 121 to improve its resistance to shear forces. Because the perimeter 115 and cross beam 117 members are not be flexible discussed with reference to
A problem with panel or sectional garage doors 121 as shown in
The inventive system improves the strength of the garage 107 by coupling the panel or sectional door 121 to the door frame 115 during an earthquake. This coupling is particularly useful with panel or sectional doors 121 but may also be used to keep the solid door 111 within the door frame 115 and to reduce horizontal motion during the earthquake. The door frame 115 by itself is normally fairly weak in shear strength because the frame 115 spans a large open area and has weak connections at the post-to-beam location. However, when the door 121 is closed and physically coupled to the frame 115, the shear strength is dramatically enhanced. In an embodiment, the door 121 supports the door frame 115 with coupling mechanisms mounted at each of four corners. These coupling mechanisms strengthen the frame 115 by attaching the door 121 to the structure in order to resist shear forces that are applied to the door frame 115 during an earthquake.
The inventive reinforcement system is particularly useful with panel or sectional garage doors 121 that slide through tracks 124 that are loosely mounted behind the plane of the door frame 115. The tracks 124 guide the door 121 but do not provide any significant strength to the garage door frame 115. In an earthquake, the tracks are easily bent away from the door frame 115. Door 121 will move independently of the garage door frame 115 and does not provide any structural support to the garage 107.
There are various ways to modify the door 121 to support the door frame 115. These support devices should provide a temporary support mechanism that can be released so that the door 121 can easily be opened when access to the garage 107 is needed. In some embodiments, the support device may only be engaged when there is ground movement from an earthquake. In other embodiments, the support device may also include a coupling mechanism that has a coupled setting that locks the door to the frame and an uncoupled setting that releases the door 121 from the frame 115. This mechanism may be manually actuated or automatically triggered in the event of an earthquake.
For example, with reference to
When the frame 115 sways towards the left, the right side of the frame 115 moves inward and contacts the bracket 141 at the upper right side of the door 121. The bracket 141 and door 121 resist the inward movement of the right side of frame 115 and are therefore able to strengthen the door frame 115. In a strong earthquake, the force of the frame 115 against the bracket 141 may cause the door 121 to slide to the left side of the frame 115. When the door 121 moves to the left, the bracket 141 at the bottom left corner of the door 121 contacts the lower side of frame 115. Although the upper portions of frame 115 sway, the lower portions remain stationary within the foundation. Thus, the lower frame 115 provides a strong structure to resist any further horizontal movement of the door 121.
Once the frame 115 simultaneously contacts the brackets 141 at opposite (upper right and lower left) corners of the door 121, the door frame 115 is structurally supported by the compression and shear strength of the door 121. The door 121 transfers the force diagonally in shear across to the lower left corner which stops against the lower left side of frame 115 to help further resist the inward movement of the right side of frame 115. Thus, the upper left and lower right brackets 141 strengthen the door frame 115 as it sways right. As discussed, the shear forces are transferred through the hinges 125 in
The movement of earthquakes is cyclical and after the left movement the earthquake will cause the garage door frame 115 to move in the opposite direction towards the right and a similar sequence of events will occur. The frame 115 will sway inward and contact the bracket 141 mounted on the upper left side of the door 121. The door 121 may then slide to the right and the bracket 141 mounted to the lower right side of the door 121 may contact the lower right side of frame 115. The upper right and lower left brackets 141 strengthen the door frame 115 as it sways left. By resisting shear forces, the inventive bracket system improves the strength of the garage structure during an earthquake.
In another embodiment, the brackets have a different design that includes a coupling mechanism that helps to keep the garage door 121 from lifting up as forces are applied horizontally within the plane of the door frame 115 during an earthquake. This feature is important because the garage door 121 can only strengthen the door frame 115 if the door 121 remains in its fully closed position within the plane of the door frame 115 during the earthquake. If the door 121 lifts or becomes misaligned with the frame 115 during an earthquake, the garage structure will be weakened at the door area.
There are various coupling mechanisms that can be used to reduce uplift of the door 121 with the frame 115.
The coupling mechanisms may be passive or active devices. A passive device will couple the door 121 to the frame 115 in response to the earthquake movement and then disengage the door 121 after the earthquake has ended. An active device senses or responds to early earthquake forces and actuates a coupling mechanism to lock the door 121 to the frame 115. When the earthquake has ended, the active device may automatically disengage the coupling mechanisms or may require the mechanisms to be manually reset.
With reference to
The protrusion 153 may be tapered so that it will engage the hole 155 more easily. As the frame 115 moves closer towards the door 121, the hole 155 will slide down to a wider and stronger portion of the protrusion 153. The hole 155 and protrusion 153 may have corresponding shapes, such as circular or rectangular cross sections. In other embodiments, the protrusions 153 are uniform in cross section rather than tapered. The corresponding shapes provide a larger contact area than mismatched shapes, i.e. a round protrusion engaging a square hole. However, it is contemplated that mismatched protrusions and holes will also provide the described functionality.
There are various options for the lower corners of the door 121 when used with the upper protrusion 153 and hole 155 in L bracket 159 configuration. In one embodiment, there are no protrusions extending from the lower corners of the frame 115, the door 121 slides horizontally and the simple planar bracket 141 shown in
In yet another embodiment, there are no brackets at the lower corner of the door.
There are many ways in which to attach the protrusions 153 to the door frame 115. With reference to
Alternatively, as illustrated in
There are other passive coupling mechanisms in addition to protrusions and holes. For example with reference to
As an alternative to passive coupling devices the inventive system may also be used with an active system. The active coupling mechanism requires the activation of a coupling mechanism. With reference to
The extended rods 191 remain engaged with the holes of the bracket throughout the earthquake as the frame side to side swaying movement of the frame 115. Because both sides of the door 121 are coupled to the frame 115, the active coupling embodiment provides the better structural support than the passive devices. Only after the earthquake has stopped may the rods 191 be retracted so that the door 121 can be opened. The retraction of the rods 191 may be through a manual reset. Although the active coupling mechanism has only been described with reference to movable rods 191, it is contemplated that various other coupling mechanisms may be used including: clamps, wedges, calipers, blocking or restraints at the top of the door or any other type of friction mechanism to prevent uplift of the door 121 with respect to the frame 115.
While the present invention has been described in terms of a preferred embodiment above, those skilled in the art will readily appreciate that numerous modifications, substitutions and additions may be made to the disclosed embodiment without departing from the spirit and scope of the present invention. It is intended that all such modifications, substitutions and additions fall within the scope of the present invention that is best defined by the claims below.
The present application claims priority to U.S. Provisional Patent Application No. 60/797,147, “System And Method For Transferring Shear Forces In Garage Door Openings” filed May 2, 2006.
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