Apparatus, systems and methods for repairable precast moment-resisting buildings

Abstract

The disclosed apparatus, systems and methods relate to reinforced concrete moment-resisting buildings with precast beams, precast columns, and replaceable buckling restrained reinforcements. Modular channels and pins or boxes are provided that allow for the replacement and repair of the precast moment-resisting beams and columns. Replaceable buckling restrained reinforcements are used to attach the beams and columns via embedded reinforcements and couplers.

Claims

1. A repairable and replaceable moment-resisting precast beam-column joint comprising: a. at least one precast beam having top and bottom sides and comprising: i. at least one neck; ii. at least one beam top longitudinal reinforcing bar disposed therein at the top side and having a beam top exposed portion; and iii. at least one beam bottom longitudinal reinforcing bar disposed therein at the bottom side and having a beam bottom exposed portion; b. at least one precast column having top and bottom ends and comprising: i. at least one column top longitudinal reinforcing bar embedded in the column having a column top exposed portion constructed and arranged to couple to the beam top exposed portion; and ii. at least one column bottom longitudinal reinforcing bar embedded in the column having a column bottom exposed portion constructed and arranged to couple to the at least one beam bottom exposed portion; c. at least one modular pin; d. at least one modular channel; e. a plurality of replaceable buckling restrained reinforcements; and f. a plurality of detachable couplers, wherein: i. the at least one modular pin is configured to couple to the at least one channel so as to join the at least one beam to the at least one column, ii. the at least one column top longitudinal bar is disposed axially and to the top end above the pin, iii. the at least one column bottom longitudinal bar is disposed axially and to the bottom end below the pin, and iv. the exposed portions of the at least one beam top and at least one beam bottom longitudinal reinforcing bar and at least one column top and at least one column bottom bar are constructed and arranged to be correspondingly joined via the plurality of replaceable buckling restrained reinforcements and couplers.

2. The repairable and replaceable moment-resisting precast beam-column joint of claim 1, wherein at least one opening is defined in the at least one beam and the at least one pin is inserted into the at least one column.

3. The repairable and replaceable moment-resisting precast beam-column joint of claim 1, wherein at least one opening is defined in the at least one column to support the at least one modular beam in which the at least one pin is embedded.

4. The repairable and replaceable moment-resisting precast beam-column joint of claim 1, further comprising at least one neck longitudinal reinforcement.

5. The repairable and replaceable moment-resisting precast beam-column joint of claim 1, further comprising at least one steel plate at the end of the precast beam and/or the face of the precast column.

6. The repairable and replaceable moment-resisting precast beam-column joint of claim 1, wherein the at least one neck has a length (L.sub.neck) and each of the plurality of replaceable buckling restrained reinforcements have a BRR fuse length (L.sub.fuse), and L.sub.neck is not less than L.sub.fuse plus four times the length of the couplers (L.sub.sp).

7. The repairable and replaceable moment-resisting precast beam-column joint of claim 6, wherein the neck depth (d.sub.neck) is not be less than the depth of the beam (d.sub.beam) less three times the coupler diameter (D.sub.sp).

8. The repairable and replaceable moment-resisting precast beam-column joint of claim 6, wherein the beam has a body having a depth (d.sub.beam) and L.sub.fuse is not less than about 0.25 d.sub.beam.

9. The repairable and replaceable moment-resisting precast beam-column joint of claim 8, wherein L.sub.fuse does not exceed about 0.75 d.sub.beam.

10. A repairable and replaceable moment-resisting precast beam-column joint comprising: a. a precast beam having top and bottom sides and comprising: i. a body comprising: A. at least one beam top longitudinal reinforcing bar disposed therein at the top side and having a beam top exposed portion; and B. at least one bean bottom longitudinal reinforcing bar disposed therein at the bottom side and having a beam bottom exposed portion; ii. an elongate opening disposed therethrough; iii. first and second necks disposed at either end of the body; and iv. first and second modular channels disposed in the elongate opening within the first and second necks, respectively; b. a precast column having top and bottom ends and comprising: i. at least one column top longitudinal reinforcing bar embedded in the column having a column top exposed portion constructed and arranged to couple to the bean top exposed portion; ii. at least one column bottom longitudinal reinforcing bar embedded in the column having a column bottom exposed portion constructed and arranged to couple to the at least one beam bottom exposed portion; and iii. a modular pin; c. a plurality of replaceable buckling restrained reinforcements; and d. a plurality of detachable couplers, wherein: i. the modular pin is configured to couple to the modular channel, ii. the at least one column top longitudinal bar is disposed axially and to the top end above the pin, iii. the at least one column bottom longitudinal bar is disposed axially and to the bottom end below the pin, and iv. the exposed portions of the at least one beam top and at least one beam bottom longitudinal reinforcing bar and at least one column top and at least one column bottom bar are constructed and arranged to be correspondingly joined via the plurality of buckling restrained reinforcements and couplers.

11. The repairable and replaceable moment-resisting precast beam-column joint of claim 10, wherein the modular pin and first and second modular channels are constructed and arranged so as to be replaceable.

12. The repairable and replaceable moment-resisting precast beam-column joint of claim 10, wherein the plurality of buckling restrained reinforcements are dog bone buckling restrained reinforcements.

13. The repairable and replaceable moment-resisting precast beam-column joint of claim 10, wherein the plurality of buckling restrained reinforcements comprise: a. a confining steel tube; b. filling materials; and c. a steel bar.

14. The repairable and replaceable moment-resisting precast beam-column joint of claim 13, wherein the steel bar is a deformed steel bar.

15. The repairable replaceable moment-resisting precast beam-column joint of claim 10, wherein the at least one neck has a length (L.sub.neck) and each of the plurality of replaceable buckling restrained reinforcements have a BRR fuse length (L.sub.fuse), and L.sub.neck is not less than L.sub.fuse plus four times the length of the couplers (L.sub.sp).

16. The repairable replaceable moment-resisting precast beam-column joint of claim 15, wherein the neck depth (d.sub.neck) is not be less than the depth of the beam (d.sub.beam) less three times the coupler diameter (D.sub.sp).

17. The repairable replaceable moment-resisting precast beam-column joint of claim 15, wherein the beam has a body having a depth (d.sub.beam) and L.sub.fuse is not less than about 0.25 d.sub.beam.

18. The repairable replaceable moment-resisting precast beam-column joint of claim 17, wherein L.sub.fuse does not exceed about 0.75 d.sub.beam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a schematic representation of a structure built using a repairable precast moment-resisting beam-column joint, according to certain implementations.

(2) FIG. 1B is a detailed exploded schematic representation of a structure built using a repairable precast moment-resisting beam-column joint, according to one implementation.

(3) FIG. 1C is a detailed exploded schematic representation of a structure built using a repairable precast moment-resisting beam-column joint, according to another implementation.

(4) FIG. 2 is a close-up cross-sectional detailed view of an exemplary embodiment of a repairable precast moment-resisting beam-column joint.

(5) FIG. 3A is a cross-sectional of a detachable buckling restrained reinforcement, according to one embodiment.

(6) FIG. 3B is a cross-sectional of a detachable buckling restrained reinforcement, according to another embodiment.

(7) FIG. 4 depicts an exemplary embodiment of a precast beam-column specimen.

(8) FIG. 5 shows a graph of force-displacement relationships for beam-column specimens, according to exemplary embodiments.

(9) FIG. 6 shows a graph of cyclic force-displacement relationships for beam-column specimens, according to exemplary embodiments.

(10) FIG. 7A depicts an exemplary embodiment of damage to a OP specimen at 2% drift ratio.

(11) FIG. 7B depicts an exemplary embodiment of damage to a precast specimen at 2% drift ratio.

(12) FIG. 8A depicts an exemplary embodiment of damage to a CIP specimen at 3.65% drift ratio.

(13) FIG. 8B depicts an exemplary embodiment of damage to a precast specimen at 3.65% drift ratio.

(14) FIG. 9 depicts the damage to the precast specimen of FIG. 8B at 8% drift ratio.

DETAILED DESCRIPTION

(15) The various embodiments disclosed or contemplated herein relate to precast beams and columns, detachable buckling restrained reinforcement, and mechanical bar splices to accelerate construction of reinforced concrete moment-resisting buildings and to reduce post-event damage and repair need.

(16) Turning to the drawings in greater detail, FIG. 1A illustrates a precast frame 1 including precast columns 2, precast beams 4. In various implementations, these precast beams 4 are connected to precast columns 4 using precast beam-column (PBC) joints 10. Other configurations and element orientations would be understood by those of skill in the art.

(17) FIG. 1B illustrates a PCB joint 10 shown in FIG. 1A, where a precast beam 4 is connected to a precast column 2, according to certain detailing. It is understood that fully precast columns 2 and beams 4 are typically fabricated offsite in a controlled environment for improved quality, for assembly into the structure on-site.

(18) As shown in FIG. 1B, the precast beam 4 consists of a reduced, or neck section 8 at each precast beam end, and a full depth section elsewhere.

(19) In various implementations, the exterior precast beam longitudinal bars 6A can be debonded from the concrete for a length of approximately six times the diameter of the bar from the intersection of the body 6 and the neck 8. It is understood that debonding of the beam longitudinal bars 6A can be done by wrapping the bars with two layers of duct tape. Other approaches include encasing the bar with a PVC pipe.

(20) In various implementations, the neck 8 is longitudinally reinforced with bars 8A extended to the beam 4. In various implementations, these neck longitudinal reinforcement 8A shall be sufficient to resist approximately 1.25 times the plastic moment of the original beam section 6. In these and other implementations, the neck longitudinal reinforcement 8A is placed or otherwise oriented inside the beam 4 compliant with current code development length requirements. That is, the neck 8 should remain capacity protected with minimal damage.

(21) In various implementations, one or more plates 12 such as steel plates 12 can be placed at the either end of the beam 4. These plates are constructed and arranged to surround boxes or pins 14. In one non-limiting, illustrative implementation, steel plates 12 with a minimum thickness of approximately 0.5 inches are placed at any joint 10 to prevent concrete damage during lateral deformations. It is understood that steel plates 12 provide more uniform stress distribution at the beam-column interface joint 10 and will minimize the concrete damage. It is further understood that a wide array of sizes and shapes of plates 12 are contemplated.

(22) In various implementations, the plastic shear loads are transferred between the precast beams 4 and the precast columns 2 via the PCB joint 10 as shown in FIG. 1B. In some implementations, one or more modular shear boxes or pins 14 mate with modular channels 16 (as shown in FIG. 1B) or the openings 17 defined in the beam (sometimes also called a channel that is an opening running from end-to-end within the beam) or sockets 17 (as shown FIG. 1C). It is therefore understood that as described herein, the sockets 17 relate to openings 17 defined in either the column 2 or beam 4 used to support or enclose the modular channels 16. Likewise, the pins 14 are housed within lumens defined in openings in the co-joining piece so as to mate with the modular channel 16 or socket.

(23) That is, in various implementations, modular steel channels 16 can be embedded in the channel opening 17 in the distal end of the beam 2 in the neck 8 or within the side of the column 2 in a socket 17, so as to be coupled with a corresponding pin 14 disposed in the adjoining member in a male/female, tongue-and-groove configuration, as would be understood by those of skill in the art.

(24) It is further appreciated that in various implementations, the modular channel 16 is optional, and the pin 14 can be disposed directly into a channel opening 17 or socket 17, though this implementation is structurally viable.

(25) Further, it is readily appreciated that these componentsthe pin 14 and/or channel 16are modular, meaning that they can allow removal and replacement of beam and column in the event of damage.

(26) Accordingly, in alternative implementations, like that of FIG. 1C, male steel pins 14 are embedded in the beams 4 to be inserted into columns 2 having female modular channels 16/sockets 17. In certain implementations, the pins 14 can be moveable (that is, move in the axial direction of the beam) for the ease of construction, for example via handles 19 on one or more sides of the pin. Those of skill in the art would readily appreciate the advantages of either configuration.

(27) Importantly, in each of these implementations, the connection between the modular pin 14 and the modular channel 16 (or the pin 14 and the socket 17) provides shear resistance at the PCB joint 10. While steel is discussed in the implementation of FIG. 1B and FIG. 1C, it is understood that both the modular channel 16, the socket 17, and/or the modular box or pin 14 can be comprised of other materials such as high-strength alloys and the like, as would be appreciated by those of skill in the art.

(28) Importantly, these pins 14 and channels 16 are modularthat, is PCB joints 10 formed via these implementations allow the beams 4 to be easily removed for architectural reconfiguration of the structure or replaced individually, as would be understood by one of skill in the art.

(29) As shown in FIG. 2 as well as in FIG. 3A and FIG. 3B, the neck 8 of the precast beam is reduced, or otherwise tapered, with a length of L.sub.neck.

(30) In various implementations, the beam longitudinal reinforcement bars 6A-1, 6A-2 extend into the neck region, where they are joined to column bars 7A-1, 7A-2 disposed within the column 2 above 7A-1 and below 7A-2 the pin 14 and/or channel 16 or socket 17. In these implementations the beam longitudinal reinforcing bars 6A-1, 6A-2 are coupled with the column bars 7A-1, 7A-2 through mechanical bar splices or couplers 22 and buckling restrained reinforcement (BRR) 24 disposed between the couplers 22 to provide flexural capacity for the joint 10. Further implementations comprise bars beyond the couplers 22. These implementations allow for quick and easy replacement of exposed bar after a severe event such as an earthquake, hurricane, explosion or the like.

(31) The assembled top and bottom longitudinal bars, as shown in FIG. 2, include the beam longitudinal reinforcement bars 6A-1, 6A-2, column bars 7A-1, 7A-2, couplers 22 and BRR 24 at the neck region of the precast beams 2, should at least match the OP reinforcement to provide sufficient flexural strength. In these implementations, the box 14 and channel 16 or socket 17 are constructed and arranged to provide sufficient strength to remain linear elastic. Only yielding and damage of BRR is allowed in this implementation to minimize the building overall damage and to quickly repair buildings by replacing damaged BRR.

(32) FIG. 2 depicts an additional detailing of the shear-pin 14/channel 16 connection, according to certain implementations. In implementations like that of FIG. 2, for optimal structural performance according to these implementations, the neck 8 length (L.sub.neck) shall not be less than the BRR fuse length (L.sub.fuse) plus four times the length of the coupler (L.sub.sp). The neck depth (d.sub.neck) shall be at least approximately the depth of the original beam (d.sub.beam) less three times the coupler 22 diameter (D.sub.sp). It is understood that many other configurations are possible. One may use larger beam sections to accommodate all components of 10.

(33) In various implementations, the BRR fuse areas (0.25d.sub.fuse, where d.sub.fuse is the diameter of the bar 34 inside BRR 22, as shown in FIG. 3A and FIG. 3B) shall not be less than the top and bottom longitudinal reinforcement areas of a corresponding conventional cast-in-place beams at the same location. In addition, it is understood that the reinforcement adjacent to the BRR 24 reinforcement assembly should have an area larger than the BRR fuse reinforcement areas to ensure the yielding within BRR fuse areas.

(34) As shown in the implementations of FIG. 3A and FIG. 3B, in certain implementations each BRR 24 has a confining steel tube 30 filled with a cementitious material 32 such as grout 32, both of which are encasing a deformed steel bar 34. As would be understood, many other implementations are possible.

(35) In certain implementations, the BRR fuse 24 length, which is defined as the length of the yielding portion of the BRR, shall not be less than approximately 0.25 times the original (unreduced) depth of the precast beam (0.25d.sub.beam) and does not exceed approximately 0.75 times the depth of the precast beam (0.75d.sub.beam). That is, a BRR fuse with a length of approximately 0.25 times the depth of the precast beam (0.25d.sub.beam) is preferential, as it is understood that such a BRR fuse length can provide sufficient displacement capacity exceeding that in corresponding cast-in-place buildings.

(36) Accordingly, in use according to exemplary implementations, onsite construction begins with erecting the precast columns 2, which can be three- or four-stories or more tall depending on transportation and lifting limitations, wherein the embedded boxes 14 are disposed at each floor level.

(37) Subsequently, the precast beams 4 with embedded steel channels 16or a channel 16 made of two anglesare laterally placed between the columns 2, for example using the implementation presented in FIG. 2B. Alternatively, the precast beams 4 with movable boxes 14 can be secured in place then the boxes 14 are moved into the socket 17 using the handles 19 as shown in FIG. 2C.

(38) Next, the beam 4 longitudinal bars 6A and the column longitudinal reinforcement 7A are connected to BRR 24 incorporating couplers 22. BRR 24 can be assembled/disassembled through attachable/detachable mechanical bar splices 22. To align the beam 4 and column 2 reinforcement with BRR 24, the beam depth should be reduced at either end 8, as would be appreciated by those of skill in the art.

(39) Additionally, in certain implementations, precast slabs, such as hollow core slabs, are installed to complete a floor in the structure. It is expected that the detailing imposes tighter construction tolerance compared to cast-in-place methods. Nevertheless, the tolerance would be comparable to that in current practice for steel structures. Further implementations are of course possible and would be appreciated by those of skill in the art.

(40) Ranges can be expressed herein as from about or approximately one particular value, and/or to about or approximately another particular value. When such a range is expressed, a further aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedents about or approximately, it will be understood that the particular value forms a further aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as approximately that particular value in addition to the value itself. For example, if the value 10 is disclosed, then approximately 10 is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

EXPERIMENTAL EXAMPLES

(41) The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

(42) FIG. 4 shows an example precast beam-column (PBC) joint 10 erected for testing. The PCB joint 10 of the implementation of FIG. 4 is made with the same geometry and reinforcement as those found in a beam-column joint specimen constructed using conventional cast-in-place (CIP) method, which was used as the benchmark model. In this implementation, the shear pin or box was a steel pipe embedded in the precast beam to be inserted into a steel channel/socket installed in the precast column, much like the implementation shown above at FIG. 1C.

(43) To simulate the lateral displacements of the test beam-column specimen within a portal frame, the column was pinned at the base while the beam was supported by a roller at the end. The pinned support (the rocker) was fabricated using a heavy-duty steel shaft passing through vertically slotted steel chair and through steel pipe installed at the column base. The roller support was constructed using the same configuration for the rocker but with the steel chair had a long horizontal slotted-hole to allow the beam to displace in its axial direction or the lateral direction of the frame. The vertical gap between the steel shaft and the chair was closed using a hand-tight bolt to prevent any uplift in the beam. An axial load of 68 kips (302.5 kN) was applied to the top of the column using two post tensioning bars and two 100 kips (445 kN) hollow-core jacks. A 22-kip (98-kN) actuator with a 5-in. (127-mm) stroke was used at the column tip to apply lateral displacements using a cyclic loading protocol. Furthermore, two 50-kip (222-kN) compressive load cells were installed at the ends of the beam to measure the beam reactions, each with be activated during push or pull.

(44) Eighteen strain gauges were utilized in the precast specimens to measure the strains at different locations. Four strain gauges were installed on the top and the bottom longitudinal reinforcing steel bars of each precast beam (two per bar), four strain gauges were placed on one of the top and the bottom BRR (two per bar), four were installed on the longitudinal bars of the precast column, and six were installed on the transverse reinforcement of beam or column.

(45) To measure the rotations and curvatures of the beam in the plastic hinge region, six linear variable displacement transformers (LVDT) were placed at the top and bottom of the beam. Four string potentiometers (string POT) were used to measure lateral displacements of the specimen.

(46) A displacement-based loading protocol was utilized for testing of all beam column specimens. Each target displacement was repeated twice per displacement amplitude. Two loading rates was used: a slow displacement rate of 0.03 in./sec (0.76 mm/sec) up to two times the expected yield displacement to capture the yield point, and a faster rate of 0.15 in./sec (3.8 mm/sec) at higher displacements.

(47) FIG. 5 depicts the drift ratio and column tip displacement (in inches) compared with the lateral force at the column tip (kips and kN) of an initial PBC and a repaired PBC (PBC-R) after testing and performing the repair, which was done by simply replacing the damaged buckling restrained reinforcement 24 (BRR), with new BRR 24. Drift ratio is defined as the ratio of the column tip displacement to the column height. The repaired PBC 10 (PBC-R) was retested with the same loading protocol as that for CIP and PBC 10.

(48) FIG. 6 shows the cyclic measured force-displacement relationships for CIP, PBC, and PBC-R. It can be seen that the PBCs have higher displacement capacities than that for the CIP. Furthermore, the performance of the precast specimens was essentially the same before and after the repair (which consisted of replacing the buckling restrained reinforcement) indicating that the PBC is a viable precast option with quick and low-cost repair approach.

(49) FIG. 7A and FIG. 7B depict exemplary photographs of the damage of the control specimen CIP and a PBC at a 2% drift ratio, which is the maximum allowable displacement demand for a special moment-resisting RC frame. The damage of the precast specimen was observably significantly less than that for CIP, indicating superior structural performance.

(50) As shown in FIG. 8A, at a drift ratio of 3.65%, CIP failed since the longitudinal bars of the CIP beam fractured at the column-to-beam interface. However, as shown in FIG. 8B, the damage of PBC at this displacement was limited to some cosmetic cracking, thereby indicating superior structural performance for buildings that are constructed with the herein disclosed PBC 10. It is worth noting that the effect of the apparent cracks was structurally insignificant since the force-displacement relationship of the repaired PBC was the same as that for the original PBC, as was shown in FIG. 6.

(51) The PBC of FIG. 8B was pushed to 8% drift ratio where its longitudinal bars fractured. As shown in FIG. 9, the damage was the same as that observed in FIG. 8B. Therefore, PBCs according to the disclosed implementations have significantly higher displacement capacities and lower damaged compared to most-ductile RC buildings practiced by current codes.

(52) Further testing information and detail can be found in Boudaqa, Abdullah, Repairable Precast Buildings and Bridges (2018). Electronic Theses and Dissertations. 2467 (https://openprairie.sdstate.edu/etd/2467) which is hereby incorporated by reference in its entirety.

(53) As will be appreciated by those of skill in the art, various aspects of these joints provide substantial advantages over the prior art.

(54) One aspect is to reduce the impact of natural hazards by improving the resiliency of structures and infrastructures. Another aspect is to design and construct repairable precast MR RC buildings for high seismic regions. Another aspect is that an RC building can be constructed using detachable modular structural components to be replaced after a strong event or at the end of its service life. According to certain implementations, a building or other structure is therefore formed which is a system with replaceable modular structural components, rather than being a single unit.

(55) In various aspects, the disclosed systems, methods and devices simultaneously accelerate construction and provide disassembly features for MR RC frames. The rationale underlying these implementations is that an MR RC building can be constructed as quickly as a steel building, total building replacement after an earthquake is avoided since damage is controlled and limited to the replaceable components, and building downtime and repair costs are minimal since the repair can be done in a few hours using simple tools such as pipe wrenches.

(56) According to certain embodiments, the disclosed implementations offer unique advantages over current practice for reinforced concrete moment-resisting buildings. In certain aspects, the RC MRBs can be constructed as fast as steel MRBs. In additional aspects, the structural components of RC MRBs can be repaired in a few hours after a severe event such as earthquake and hurricane with minimal cost and unskilled labor. It is understood that the latter advantage is unique for any steel or concrete MRB. Even though current practices are sometimes able to prevent the collapse of MRBs, structural damage after a strong event may require demolition of the building and replacing with a new one, which imposes substantial material, labor, and downtime costs.

(57) Various implementations achieve several various aspects. One aspect of the present system is to accelerate construction for MR RC buildings. One of the advantages of steel structures to RC is the speed of construction. Fully prefabricated RC members to be assembled onsite, thereby significantly reducing the construction time and will make RC buildings competitive to steel ones.

(58) Another aspect is to eliminate MR RC building total replacement. Avoiding total building replacement will save millions of dollars. The repair technique through replacement of damaged components is simple and fast, which reduces the building downtime after severe earthquakes.

(59) The system for MR RC buildings provides several improvements over the prior art because, by incorporating only conventional concrete and steel, RC buildings can be constructed relatively fast, are expected to exhibit better seismic performance, and will need minimal repair after strong earthquakes. The repair is done by replacing the damaged components.

(60) Although the disclosure has been described with reference to certain embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the disclosed apparatus, systems and methods.