Gear-based buckling resisting bracing system

Abstract

A brace for absorbing lateral loads imposed on a structure includes a first frame part operable to connect to the structure at a first location and is moveably coupled to the brace. The brace further includes a second frame part operable to connect to the structure at a second location. The second frame part is moveably coupled to the brace so that the first and second frame parts can move with respect to one another. The brace further includes at least one rotational element mounted to the second frame part and coupled with the first frame part and at least one cable connected to the first frame part and connected to the at least one rotational element. The lateral loads imposed on the structure are transferred through the first and second frame parts and the at least one rotational element to the at least one cable.

Description

GEAR-BASED BUCKLING RESISTING BRACING SYSTEMCROSS-REFERENCE TO RELATED PATENT APPLICATION

[0001] This application claims the benefit of United States Provisional Patent Application No. 63 / 675,537 filed July 25, 2024; the entire contents of United States Provisional Patent Application No. 63 / 675,537 is hereby incorporated herein in its entirety.FIELD

[0002] The various embodiments described herein generally relate to retrofitting of deficient structures. More specifically, the various embodiments relate to braces for retrofitting.INTRODUCTION

[0003] Existing structures can become structurally deficient in several ways. For example, the building may undergo changes (e.g., importance, use or occupancy changes), the building may have errors in design or construction, or design codes may be updated. Such deficient structures must remain safe and code compliant through their remaining life.

[0004] To do so, the building may undergo retrofitting. Retrofitting involves adding components to a structure that were not there during manufacturing, so as to reinforce weak or deficient sections of the building.

[0005] One type of retrofitting is bracing, which involves adding braces to a structure. Braces aid in resisting lateral loads (e.g., loads from an earthquake). Braces are strong in tension, but may buckle prematurely in compression (i.e. , the brace may fail under compressive forces that are lower than the material’s strength).

[0006] Buckling Resisting Braces (BRBs) are designed to prohibit buckling within the system. BRBs typically have a core unit that takes the load. Other components within the BRB prevent the core from buckling. However, an issue with BRBs is that the elements of the brace under a load need to yield to dissipate energy. Once yielded, the elements must be replaced in conventional BRBs. For example, a brace will yield during an earthquake and will need to be replaced before the next earthquake.

[0007] Accordingly, a need exists for a BRB with elements that do not need replacement after being subjected to a load.SUMMARY OF VARIOUS EMBODIMENTS

[0008] According to one broad aspect of the teachings herein, in at least one embodiment described herein there is provided a brace for absorbing lateral loads imposed on a structure. The brace includes: a first frame part operable to connect to the structure at a first location on the structure, the first frame part being moveably coupled to the brace; a second frame part operable to connect to the structure at a second location on the structure, the second frame part being moveably coupled to the brace so that the first and second frame parts can move with respect to one another; at least one rotational element mounted to the second frame part and coupled with the first frame part; and at least one cable connected to the first frame part and connected to the at least one rotational element. The lateral loads imposed on the structure are transferred through the first and second frame parts and the at least one rotational element to the at least one cable.

[0009] In at least one embodiment, the first frame part includes at least one rack, and the at least one rotational element is a gear coupled with the at least one rack, and the loads are transferred through the at least one rack and at least one gear to the at least one cable.

[0010] In at least one embodiment, the at least one rack includes a pair of racks on opposite sides of the first frame part, and the at least one gear includes two gears arranged symmetrically on opposite sides of the first frame part.

[0011] In at least one embodiment, the second frame part includes two beams, and the at least one rotational element includes a rotational element mounted to each of the two beams, and the brace further includes a shaft extending between the rotational elements.

[0012] In at least one embodiment, the first frame part includes a beam extending from a first end to a second end.

[0013] In at least one embodiment, the at least one cable is connected to the first frame part towards the first end and towards the second end.

[0014] In at least one embodiment, the first frame part further includes at least two brackets, a first bracket of the at least two brackets positioned at the first end of the first frame part and a second bracket of the at least two brackets positioned at the second end of the first frame part.

[0015] In at least one embodiment, a first cable of the at least one cable is connected to the first bracket and a second cable of the at least one cable is connected to the second bracket.

[0016] In at least one embodiment, in operation, the first frame part is connected to the structure at the first end.

[0017] In at least one embodiment, the at least one cable is connected to the at least one rotational element via a cable mount.

[0018] In at least one embodiment, the at least one rotational element includes a cable mount, and the at least one cable includes two cables each connected to the cable mount.

[0019] In at least one embodiment, the at least one rotational element includes one rotational element with two cable mounts on either side of the rotational element.

[0020] In at least one embodiment, the at least one rotational element has two cable mounts, and the at least one cable includes four cables, a first end of each of the four cables connected to one of the cable mounts.

[0021] In at least one embodiment, a second end of each of the four cables is connected to the first frame part.

[0022] In at least one embodiment, each cable is configured to absorb tension, and when one cable of a pair of the cables is in tension, the other cable of the pair is inactive.

[0023] In at least one embodiment, the at least one cable is configured to absorb tension.

[0024] In at least one embodiment, the at least one cable is configured to return to its original shape upon unloading of the structure.

[0025] In at least one embodiment, the at least one cable is made of a shape memory alloy.

[0026] In at least one embodiment, the brace includes at least two cables, and movement of the first frame part or second frame part puts one of the at least two cables under tension.

[0027] According to one broad aspect of the teachings herein, in at least one embodiment described herein there is provided a use of a brace for seismic retrofit of a structure and the structure includes a bridge or a building.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] For a better understanding of the various embodiments described herein, and to show more clearly how these various embodiments may be carried into effect, reference will be made, by way of example, to the accompanying drawings which show at least one example embodiment, and which are now described. The drawings are not intended to limit the scope of the teachings described herein.

[0029] FIG. 1 is a front view of a brace according to an example embodiment;

[0030] FIG. 2A is a front view of a gear of the brace of FIG. 1 ;

[0031] FIG. 2B is a front view of a gear according to another example embodiment;

[0032] FIG. 3A is a top view of the brace of FIG. 1 ;

[0033] FIG. 3B is a cross-sectional side view of the brace of FIG. 1 along the line A- A of FIG. 3A;

[0034] FIG. 3C is a top view of a brace according to another example embodiment;

[0035] FIG. 4 is a perspective view of a portion of the brace of FIG. 1 attached to a testing apparatus;

[0036] FIG. 5 is a front view of a portion of the brace of FIG. 1 attached to the testing apparatus;

[0037] FIG. 6 is a top view of a portion of the brace of FIG. 1 attached to the testing apparatus;

[0038] FIG. 7 is a graph of the hysteretic response of a prototype of the brace in a moving-pillow block configuration;

[0039] FIG. 8 is a graph of the hysteretic response of the prototype of the brace in a fixed-billow block configuration;

[0040] FIG. 9 is a graph of the simulated drift at midspan of retrofitted and original bridges during an earthquake;

[0041] FIG. 10 is a graph of the simulated concrete column behaviour of retrofitted and original bridges during an earthquake;

[0042] FIG. 11 is a graph of the simulated base shear of retrofitted and original bridges during an earthquake; and

[0043] FIG. 12 is a graph of the energy absorption of the prototype during the simulated earthquake.

[0044] Further aspects and features of the example embodiments described herein will appear from the following description taken together with the accompanying drawings.DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] Various embodiments in accordance with the teachings herein will be described below to provide an example of at least one embodiment of the claimed subject matter. No embodiment described herein limits any claimed subject matter. The claimed subject matter is not limited to devices or methods having all of the features of any one of the devices or methods described below or to features common to multiple or all of the devices and or methods described herein. It is possible that there may be a device or method described herein that is not an embodiment of any claimed subject matter. Any subject matter that is described herein that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such subject matter by its disclosure in this document.

[0046] It will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements or steps. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein.

[0047] It should also be noted that the terms “coupled” or “coupling” as used herein can have several different meanings depending in the context in which these terms are used. For example, the terms coupled or coupling can have a mechanical, fluidic or electrical connotation. For example, as used herein, the terms coupled or coupling can indicate that two elements or devices can be directly connected to one another or connected to one another through one or more intermediate elements or devices via an electric signal, an electrical connection, a mechanical element, a fluid or a fluid transport pathway, for example, depending on the particular context.

[0048] It should also be noted that, as used herein, the wording “and / or” is intended to represent an inclusive-or. That is, “X and / or Y” is intended to mean X or Y or both, for example. As a further example, “X, Y, and / or Z” is intended to mean X or Y or Z or any combination thereof. As another example, the phrases “A, B, C or any operable combination thereof” or “any combination of A, B and C” are meant to cover any combination of elements A, B and C that provides utility which may, for example, include A, B, C, A and B, A and C, B and C, or A, B and C.

[0049] It should be noted that terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree may also be construed as including a deviation of the modified term such as, but not limited to, 1 %, 2%, 5% or 10%, if this deviation would not negate the meaning of the term it modifies.

[0050] Furthermore, the recitation of numerical ranges by endpoints herein includes all numbers and fractions subsumed within that range (e.g., 1 to 5 includes 1 , 1.5, 2, 2.75, 3, 3.90, 4, and 5). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term "about" which means a variation of up to a certain amount of the number to which reference is being made if the end result is not significantly changed, such as, but not limited to, 1 %, 2%, 5% or 10%, for example.

[0051] Some elements herein may be identified by a part number, which is composed of a base numberfollowed by an alphabetical or subscript-numerical suffix (e.g., 112a, or 112i). Multiple elements herein may be identified by part numbers that share a base number in common and that differ by their suffixes (e.g., 112i , 1122, and 1123).All elements with a common base number may be referred to collectively or generically using the base number without a suffix (e.g., 112).

[0052] Reference is now made to FIG. 1 , which shows a brace 100 for absorbing loads imposed on a structure. The brace 100 includes a frame 102. The frame 102 comprises a first frame part 150, which is a longitudinally extending structure (e.g., a beam-like structure), which extends from a first frame part fixed end 150a to a first frame part free end 150b. The frame 102 further comprises second frame parts 152 having second frame part fixed ends 152a and second frame part free ends 152b (described further below). The second frame parts 152 comprise one or more longitudinally extending structures (e.g., beam-like structures) which extend from second frame part fixed ends 152a to second frame part free ends 152b. In operation, the first and second frame parts 150, 152 are installed adjacent to each other and may move laterally with respect to each other via a rack 104 and gear 106 system, described below.

[0053] When the brace 100 is installed in a structure (not shown), the first frame part 150 is connected to the structure at a first connection point 107 at a portion of the first frame part fixed end 150a. The second frame part 152 is connected to the structure at a second connection point 109 at a portion of the second frame part fixed end 152a. If the brace 100 includes multiple second frame parts 152, for example as shown in FIG. 3A, each second frame part 152 may be connected to the structure at second connection point 109 (i.e., there may be multiple connection points 109). As shown in FIG. 1 , the first and second connection points 107, 109 may be provided generally opposite each other with the brace 100 installed in between them. In some embodiments, the first and second frame part fixed ends 150a, 152a may be connected to the structure via intermediary components. For example, as shown in FIG. 3C, the second frame part fixed ends 152a may be mounted at the second connection point 109 via a common plate 154 (e.g., a steel plate). The first and second frame part free ends 150b, 152b are not directly attached to the structure when the brace 100 is installed.

[0054] The first frame part 150 may contain at least one rack 104 (e.g., when the brace 100 includes a gear 106, as described below). The rack 104 may be integrated into the first frame part 150 or may be an external rack 104 that is located on an external surface of the first frame part 150. In the embodiment shown in FIG. 1 , thefirst frame part 150 has two racks 104 on opposite sides of the first frame part 150 vertically offset from one another. For example, a first rack 104 is located towards an upper side 108 of the first frame part 150, and a second rack 104 is located towards a lower side 110 of the brace first frame part 150.

[0055] The brace 100 also includes at least one rotary component 106, such as but not limited to, a gear or rotating plate. For example, FIG. 1 shows the rotary component 106 as a gear 106 coupled with the at least one rack 104. In particular, the teeth of the gear 106 are meshed with the teeth of the rack 104. The embodiment of FIG. 1 includes two gears 106, each coupled with the racks 104. The gears 106 are arranged symmetrically on opposite sides of the first frame part 150. The gear 106 may be, for example, a spur gear. The gear may be made of any suitable material, for example, steel (e.g., 1045 carbon steel).

[0056] The gear 106 may have at least one cable hole 112 and a shaft hole 113. For example, the gear 106 may include one cable hole 112, as shown in FIG. 2A, which is radially offset from the shaft hole 113 and located near a periphery of the gear 106. In other embodiments, the gear 106 may include more than one cable hole 112. For example, as shown in FIG. 2B, the gear 106 may include two cable holes 112 positioned towards opposite ends of the gear 106 in a mirrored fashion radially offset from the shaft hole 113 and located near a periphery of the gear 106. Both the cable and shaft holes 112, 113 may be through holes, extending from one side face of the gear 106 to the other. The shaft hole 113 may be provided at the center of the gear 106. The cable hole 112 may be provided towards an outer edge of the gear 106. A cable mount 114 may be mounted in the cable hole 112 (FIG. 1 and FIG. 4). The cable mount 114 may be any structure that allows for a cable to be mounted or attached to the gear 106 (e.g., a structure that allows a cable to be hooked or wrapped around it). For example, as shown in FIG. 4, the cable mount 114 may be a knob-like structure that extends from both sides of the gear 106. In other embodiments, the cable mount 114 may extend from only one side of the gear 106.

[0057] The brace 100 also includes at least one cable 116. It will be understood by one skilled in the art that the at least one cable 116 may comprise one cable consisting of one strand, one cable consisting of multiple strands woven together, multiple cables (i.e. , a set of cables) each consisting of one strand, and / or multiple cables (i.e. , a set of cables) each consisting of multiple strands woven together. In other words, any typeand number of suitable cable(s) may be used depending on the structure size and strength requirements.

[0058] The at least one cable 116 is connected to the gear 106. The cable 116 may be connected to the gear 106 via the cable mount 114. For example, the cable 116 may wrap around the cable mount 114 in order to secure the cable 116 to the cable mount 114. In some embodiments, the brace 100 may include one cable 116. In other embodiments, the brace 100 may include more than one cable 116. For example, as shown in FIG. 1 , the brace 100 may include eight cables 116 (i.e. , four cables 116 per gear 106, with two cables connected to the left and right sides of each gear 106 via the cable mounts 114). The number of cables 116 may be chosen both based on the expected loads, which may vary according to the application, and to maximize the energy dissipation capacity and efficiency. Too many cables 116 may cause less overall yielding, while too few may cause failure.

[0059] The first frame part 150 may further include end brackets 118. The end brackets 118 may be mounted towards each of the first frame part fixed and free ends 150a, 150b. The end brackets 118 may be mounted above and / or below the first and second connection points 107, 109. The end brackets 118 may include one or more cable anchor points 120. The cable(s) 116 may be connected to the first frame part 150 via the cable anchor points 120. The cable anchor points 120 may have any suitable structure. For example, the cable anchor points 120 may include a shaft onto which the cable 116 may hook or wrap around. Therefore, as shown in FIG. 1 , each cable may extend between a cable mount 114 and a cable anchor point 120.

[0060] The cables 116 may be made of a shape memory alloy (SMA). An SMA is a superelastic material able to withstand severe deformations without sustaining permanent damage upon unloading. Under load, the SMA will stretch and yield. Once the load is removed, the SMA will revert the plastic yielding strain and return to its original shape. The specific SMA may be chosen both based on the expected loads and system dimensions, and to maximize the efficiency of the system.

[0061] As shown in FIG. 3A, for example, the brace 100 also includes a gear support system 122. The gear support system 122 may be any suitable structure for supporting the gear(s) 106 in place. For example, the gear support system 122 may include a shaft 124. The shaft 124 may extend through the shaft hole 113 of the gear 106. Theshaft 124 may be supported at either end (i.e., on either side of the gear 106) by shaft supports 126. Shaft supports 126 may have any structure suitable for supporting and allowing for rotation of the shaft 124. For example, the shaft supports 126 may be pillow blocks.

[0062] The shaft supports 126 may be positioned on second frame parts 152. As shown in FIG. 3A, the frame 102 may include two second frame parts 152, positioned on either side of the first frame part 150. The shaft supports 126 may be fastened (e.g., bolted) to the second frame parts 102b.

[0063] In operation, the brace 100 may be installed in a structure (e.g., a building, a bridge, or anywhere a traditional lateral-load resisting brace may be used) by connecting to the structure at first and second connection points 107, 109. For example, the brace 100 may be connected within a bay (i.e., between columns) of a building. In some cases, depending on the use, the first and second connection points 107, 109 may be connected to a building (e.g., to the columns of the building) via intermediary steel sections. The brace 100 may be installed at any suitable location within the structure (e.g., towards the ground level or at a higher level of a building). The brace 100 may be installed at an angle (i.e., first connection point 107 may be vertically higher than second connection point 109, or vice versa).

[0064] During an earthquake, for example, lateral loads imposed on a structure may cause the structure to move laterally. When installed in a building, brace 100 helps resist the lateral loads. For example, if the brace 100 is connected at the first and second connection points 107, 109 to columns of a building, and the columns tilt towards either side, the loads are transferred through first and second frame parts 150, 152 to the rack(s) 104 and gear(s) 106 and then to the cable(s) 116. This load transfer is accomplished when one or all of the first and second frame parts 150, 152 move laterally relative to each other, causing the rack(s) to move laterally and the gears to rotate, and leading to tension in one or more cables 116.

[0065] Each cable 116 is configured to activate in a specific loading direction. The loading direction may vary depending on the installation direction (e.g., whether first connection point 107 is vertically higher or lower than second connection point 109). The end of the brace 100 that experiences the movement depends on the installation direction and installation location relative to the location of the force that is experiencedby the brace 100. For example, consider the scenario where the brace 100 is installed at an angle, with the first connection point 107 being vertically higher than second connection point 109, and the second connection point 109 being towards the ground level. If the columns tilt to the left, the first frame part 150 is pulled towards the left (e.g., when considered in the orientation of FIG. 1). The movement of the rack(s) 104 to the left will cause the gear(s) 106 to turn clockwise (for the top gear 106 in FIG. 1) or counterclockwise (for the bottom gear 106 in FIG. 1), putting the cable(s) 116 on the left side of the gear(s) 106 into tension, due to both the movement of the first frame part 150 and the rotation of the gear 106. The cable(s) 116 on the right side of the gear(s) 106 remain inactive during this loading. If the columns tilt to the right, the first frame part 150 is moved towards the right. The movement of the rack(s) 104 to the right will cause the gear(s) 106 to turn counterclockwise (for the top gear 106 in FIG. 1 ) or clockwise (for the bottom gear in FIG. 1 ), putting the cable(s) 116 on the right side of the gear(s) 106 into tension, due to both the movement of the frame 102 and the rotation of the gear 106. The cable(s) 116 on the left side of the gear(s) remain inactive during this loading.

[0066] The brace 100 therefore acts as a strain amplification system. Traditional braces strain according to the applied displacement. For example, a 1 mm displacement applied on a cable of 1 mm length would result in an engineering strain of 1 mm / mm. In contrast, the brace 100 is likely to amplify the applied displacement on the cable(s) 116 in this scenario, allowing for the cable(s) 116 to strain by more than 1 mm / mm when the applied displacement on the brace 100 is 1 mm. Instead of using solely the cables 116 to dissipate the energy, the rotation of the gears 106 causes the further strain in the cables 116. This dissipates the energy faster and allows the energy from earthquakes, for example, to be absorbed at a faster rate. The cables 116, being made of an SMA, will also return to their original shape once the load is removed.

[0067] For example, with reference to FIG. 3A, when a displacement of 10 mm to the left is applied to the brace 100, the first frame part 150 displaces by 10 mm to the left. This motion causes strain on the cables 116. During this motion, the racks 104 come into contact with the gears 106, causing the gears 106 to rotate. Cable mount 114 moves in the opposite direction than the applied displacement (i.e. , to the right in this example). The rotation, therefore, causes further strain in the cables 116. In otherwords, the cables 116 are strained from both the movement of the first frame part 150 and the gear 106 rotation. The cables 116 will stretch more than the applied displacement. For example, the cables 116 may strain approximately two times more compared to traditional braces. With an applied displacement of 10 mm, the cables may strain approximately 19.5 mm (i.e., nearly two times greater than a strain of 10 mm which would be achieved with a traditional brace).

[0068] As such, the rotation of the gear adds an additional displacement component, causing the SMA cable to stretch more than the applied displacement. Given the current system setup, the amplification varies between 85-95% as a displacement is applied. This is due to the fact that there is a component of the rotation that is not in the same direction as the applied displacement. Accordingly, when brace 150 displaces by 10 mm due to an applied 10 mm displacement, the gear might rotate around 7.6°, causing point 114 to move approximately 9 mm to the right (and to move by some distance, less than 1 mm, downwards or upwards, depending on which gear is observed, or in other words, towards brace 150). The extent of amplification can be controlled with factors such as gear size and the position of connection points 112. As such the system may be designed so that in its expected working span the efficiency of strain amplification would remain within the expected values.

[0069] The brace 100 as described herein is also a symmetric buckling resisting brace. The system is symmetric since cables 116 have the same length and material properties are located on each of the left and right sides of the gear(s) 106. Having one or more cables 116 which activate when the brace 100 is in tension and others which activate when the brace is in compression allows for the system to be symmetric regardless of the direction of the load.

[0070] Reference is now made to FIGS. 4-6, which show the brace 100 without cables 116 and connected to a testing apparatus 130. The testing apparatus 130 may be used to verify the proper functioning of the brace 100. The testing apparatus 130 may comprise an actuator connected to a hybrid testing setup. The hybrid testing setup may comprise a testing computer and a simulation computer. The testing apparatus 130 allows for displacements to be applied on a prototype of the brace 100.

[0071] Testing was conducted on a prototype of the brace 100 using a testing apparatus similar to testing apparatus 130. The length of the prototype wasapproximately 1 m. The length of the prototype may be upsized for real-world application by increasing the length of first and second frame parts 150, 152, as to allow brace 100 to connect to a structure. The first and second frame parts 150, 152 used as part of the testing apparatus were 2 in by 2 in steel sections, which may be resized for real-world application as needed. The first and second frame parts 150, 152 are selected to be stronger than the SMA cables 116 so as to localize the yielding to the cables only. The gears 106 used as part of the testing apparatus were SSA2.5- 60J40 gears, which were 25 mm wide with a diameter of 155 mm and a pitch diameter of 150 mm. The diameter of the shaft hole 113 for the testing apparatus was 40 mm. The dimensions of the gears 106 may be changed as needed based on size and strength requirements. The cables 116 used as part of the testing apparatus were three SMA wires each of a diameter of 2 mm, woven into a strand. Less SMA was used as part of the testing apparatus since the brace was downsized compared to real-world applications.

[0072] Multiple cyclic tests were performed on the prototype. The prototype displayed stable hysteretic behaviour with self-centering capacity. This is shown in the graphs of FIGS. 7-8, which show the hysteretic response for a moving pillow block and fixed pillow block configuration, respectively.

[0073] The system withstood larger loads than anticipated due to SMA strainhardening post-yield. The system also displayed largely symmetrical behaviour. Slight differences that occurred were likely due to inaccuracies in the initial tightening of the SMA cables. Although the system was downsized (e.g., by reducing the amount of SMA used and shortening the frame, as described above) in the lab due to equipment limits, it may be upsized to withstand larger loads.

[0074] Further testing was conducted which included hybrid testing of the system. The hybrid testing utilizes both experimental and numerical models to simulate the performance of the prototype on a real structure when subjected to an earthquake. In this case, a deficient bridge was considered. The bridge was a two-span, 66 m long bridge with two 1 .2 m diameter reinforced concrete columns supporting it at midspan. The bridge considered is located in Vancouver, Canada on a class C site. The simulated bridge was upgraded with the brace as described herein and displayed significant improvement in seismic behaviour. Several earthquake ground motions were used to simulate various seismic scenarios: (1 ) crustal earthquakes at amagnitude of 6.53 for around 75 seconds, (2) intra-slab earthquakes at a magnitude of 6.5 for around 225 seconds, and (3) Cascadia earthquakes at a magnitude of 7.7 for around 725 seconds. FIGS. 9-12 show the results of the first of these simulations. FIG. 9 is a graph of the drift of the bridge at midspan during an earthquake scenario. As shown in FIG. 9, the drift of the retrofitted bridge is reduced compared to the original bridge. The peak drift was reduced from approximately 49.5 mm to 42.5 mm, resulting in a reduction of approximately 14%. FIG. 10 is a graph of the concrete column behaviour during an earthquake scenario. As shown in FIG. 10, the strain in the columns of the retrofitted bridge is reduced compared to the original bridge, and the concrete column hinging was greatly reduced. FIG. 11 is a graph of the base shear during an earthquake scenario. As shown in FIG. 11 , the base shearwith the retrofitted bridge is reduced compared to the original bridge. Peak base shear was reduced by around 5%. FIG. 12 is a graph showing the energy absorption of the downsized lab prototype for this simulated earthquake. FIG. 12 shows the overall behaviour of the prototype and the rate of energy absorption during an earthquake loading. As seen in FIG. 12, the prototype is capable of absorbing high loads.

[0075] Other seismic simulations were tested. A second test earthquake consisted of a larger magnitude ground motion. For this test, the peak drift was reduced by approximately 26.5%. The peak base shear was reduced more significantly, by approximately 30%. A third test earthquake resulted in peak drift being reduced by around 14% and peak base shear displayed a marginal reduction. For the lab testing of the prototype under the various seismic simulations, the downsized lab prototype absorbed between 5000 kNmm and 10000 kNmm.

[0076] While the applicant's teachings described herein are in conjunction with various embodiments for illustrative purposes, it is not intended that the applicant's teachings be limited to such embodiments. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, without generally departing from the embodiments described herein. For example, while the teachings described and shown herein may comprise certain elements / components and steps, modifications may be made as is known to those skilled in the art. For example, selected features from one or more of the example embodiments described herein in accordance with the teachings herein may be combined to create alternative embodiments that are not explicitly described. Allvalues and sub-ranges within disclosed ranges are also disclosed. The subject matter described herein intends to cover and embrace all suitable changes in technology.

Claims

CLAIMS:

1. A brace for absorbing lateral loads imposed on a structure, the brace comprising: a first frame part operable to connect to the structure at a first location on the structure, the first frame part being moveably coupled to the brace; a second frame part operable to connect to the structure at a second location on the structure, the second frame part being moveably coupled to the brace so that the first and second frame parts can move with respect to one another; at least one rotational element mounted to the second frame part and coupled with the first frame part; and at least one cable connected to the first frame part and connected to the at least one rotational element; wherein the lateral loads imposed on the structure are transferred through the first and second frame parts and the at least one rotational element to the at least one cable.

2. The brace of claim 1 , wherein the first frame part comprises at least one rack, and wherein the at least one rotational element is a gear coupled with the at least one rack, and wherein the loads are transferred through the at least one rack and at least one gear to the at least one cable.

3. The brace of claim 2, wherein the at least one rack includes a pair of racks on opposite sides of the first frame part, and the at least one gear includes two gears arranged symmetrically on opposite sides of the first frame part.

4. The brace of any one of claims 1 to 3, wherein the second frame part comprises two beams, and the at least one rotational element comprises a rotational element mounted to each of the two beams, and wherein the brace further includes a shaft extending between the rotational elements.

5. The brace of any one of claims 1 to 4, wherein the first frame part comprises a beam extending from a first end to a second end.

6. The brace of claim 5, wherein the at least one cable is connected to the first frame part towards the first end and towards the second end.

7. The brace of any one of claims 5 to 6, wherein the first frame part further includes at least two brackets, a first bracket of the at least two brackets positioned at the first end of the first frame part and a second bracket of the at least two brackets positioned at the second end of the first frame part.

8. The brace of claim 7, wherein a first cable of the at least one cable is connected to the first bracket and a second cable of the at least one cable is connected to the second bracket.

9. The brace of any one of claims 5 to 8, wherein, in operation, the first frame part is connected to the structure at the first end.

10. The brace of any one of claims 1 to 9, wherein the at least one cable is connected to the at least one rotational element via a cable mount.

11. The brace of any one of claims 1 to 10, wherein the at least one rotational element includes a cable mount, and the at least one cable includes two cables each connected to the cable mount.

12. The brace of any one of claims 10 to 11 , wherein the at least one rotational element includes one rotational element with two cable mounts on either side of the rotational element.

13. The brace of claim 12, wherein the at least one rotational element has two cable mounts, and the at least one cable includes four cables, a first end of each of the four cables connected to one of the cable mounts.

14. The brace of claim 13, wherein a second end of each of the four cables is connected to the first frame part.

15. The brace of any one of claims 13 to 14, wherein each cable is configured to absorb tension, and when one cable of a pair of the cables is in tension, the other cable of the pair is inactive.

16. The brace of any one of claims 1 to 15, wherein the at least one cable is configured to absorb tension.

17. The brace of any one of claims 1 to 16, wherein the at least one cable is configured to return to its original shape upon unloading of the structure.

18. The brace of any one of claims 1 to 17, wherein the at least one cable is made of a shape memory alloy.

19. The brace of any one of claims 1 to 18, wherein the brace includes at least two cables, and movement of the first frame part or second frame part puts one of the at least two cables under tension.

20. A use of a brace for seismic retrofit of a structure, wherein the brace is defined according to any one of claims 1 to 19 and the structure includes a bridge or a building.

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