WO2016118430A1

WO2016118430A1 - Seismic-proof connectors to protect buildings and bridges from earthquake hazards and enable fast construction

Info

Publication number: WO2016118430A1
Application number: PCT/US2016/013741
Authority: WO
Inventors: Su Hao; Alexander J. Y. HAO
Original assignee: Su Hao
Priority date: 2015-01-24
Filing date: 2016-01-16
Publication date: 2016-07-28
Also published as: CN110637125B; WO2019139580A1; CN110637125A

Abstract

A class of connecting-apparatuses that can be used as a connecter to connect two units in a structural system, such as a bridge or a building, and as a supporter to carry the loads transferred from one unit to another, for examples, gravity load. Said apparatus provides solidified connection as cast-in-place concrete structure under regular service condition while works as isolation device when the structural system is struck by strong earthquakes. Said apparatus is an assembly that comprises a designed stabilization-pin, partially matched with a pair of cavities in connected units with designed V-shape configuration and, optionally, a pair of built-in V- shaped guiding tubes, a shear-reinforce ring, a damping cone, and a washer. By applying said apparatus it is able to construct the structural system by assembling prefabricated units on site while assures high standard in integrity and robustness for the constructed structure.

Description

Title: Seismic-Proof Connectors to Protect Buildings and Bridges from Earthquake Hazards and Enable Fast Construction

Inventors: Su Hao, Alexander J. Hao

43 Bower Tree, Irvine, CA 92603 U. S. A.

Field of Invention

This application claims the benefit of U.S. Provisional Application No. 62/107388, filled at the 19^th6 of Jan. 2015, disclosing a class of apparatuses that can be used as connectors between two major structural units in large-scaled civil engineering structures such as bridges and buildings, wherein said each unit has its own functions to the structure's integrity; for example, a bridge has a superstructure that includes the beams that span over piers, and a substructure that contains piers and footing or other kinds of foundations. Similarly, a building's superstructure can be an assembly of several stories, wherein said apparatuses, termed "V-Connector", connecting adjacent two units within a said structure for the following functions: (i) providing a robust tie between the connected two units in a structure; (ii) reduce vibrations and associated transient force flows, for example, inertia, from one unit to another when the structure is struck by dynamic loads, e.g. an earthquake; (iii) to shift a structure's natural frequency, so as to avoid resonated vibration when the structure is excited by external vibration; (iv) enabling to assemble prefabricated units into a structure on construction site while preserve desired integrity and robustness; (v) assembled unit can be easily replaced or retrofitted when it is necessary. Therefore, said V-connector can be used as seismic isolation bearing or connector in bridges and buildings for seismic-protection, or as connectors for fast construction of such a structure, or for the both.

Background of the invention

The devastations earthquakes, such as Sendai of Japan in 2011 and Haiti of 2009, remind us of the continuing threat from nature to human-being's life, particularly, for the regions with high seismic risk in United States and those in the world. A mission to engineering community forever is to build our habitations and facilities that will sustain these kinds of disasters.

In the perspective of seismic protection, a primary requirement for a civil engineering structure, such as a building or a bridge, is integrity, which means that major structural units of a construction system are supposed to be integrated as one solid frame that can sustain future earthquakes. The design philosophy from this perspective can be termed "robust design". Needless to say, such a frame's solidness relies on the strength of the joints between its major structural units. For concrete bridges and buildings, "cast-in-place"(CIP) is a common method to achieve this goal. Nevertheless, as compared with other construction methods, for example, prefabricate concrete beams in factories or other convenient places and then assemble the units on site by seismic bearings, CIP is generally time-consuming and less cost-effective. The formwork for on-site casting generally takes about 20-70% share of total construction cost. Also, resonated vibrations are easily triggered for CIP-constructed tall buildings or bridges with high piers if the structure does not have sufficient stiffness. On the other hand, from the viewpoints of economy and construction capability, it is not always feasible to build a building or a bridge as strong as a banker. Hence, another philosophy in modern engineering community, termed "isolation design", emerges. It's concept is to allow a structure temporally losing its integrity when struck by an earthquake through intentionally designed mechanism, for example, temporally weakening some structural units or the connections in-between, so as to reduce or isolate inertia forces within the unit directly exposure to earthquake and to minimize the damage to entire structure. This is because such temporally wakening is able to shift a structure's natural frequency, which may avoid the resonant vibrations associated with the frequencies window caused by an earthquake. Applying isolation bearing as the joint between super and substructure in a bridge or a building is a common method for isolation design, for which the remaining challenges are: (i) for higher capacity to protect a structure against stronger earthquake, it will request not only bigger bearing's dimension but also larger seat for the structural unit that carries the bearing, which often introduces significantly high additional cost; (ii) in those areas that are close to earthquake's epicenters, vertical acceleration is generally with the same amplitudes as that of horizontal or higher. Particularly, recent earthquakes, for examples, that in Big Island at 2005, Chili at 2009, and Sendai of Japan at 2011, remarkably-high vertical ground accelerations were presented in the area far away from epicenter. A striking fact revealed by the Sendai' s earthquake is that, for many bridges survived from the first waves of ground motions, their superstructures were washed away by the following tsunami because the seismic-isolation bearings in those bridges only have the capacity to protect horizontal vibrations. Obviously, for structural designs in the region with high seismic risks, it is crucial to find the balance between structural robustness desired in general and temporal flexibility required when an earthquake occurs. Beside integrated design and isolation bearing, another methodology is termed "vibration mitigation" that has been applied in some buildings and bridges. Its concept is to add additional mass to a structural system through elastic connection, which shifts the original system's natural frequency into a spectrum of frequencies for the new system depending upon the relative motion between the original and added mass when excited by external vibration; this keeps the new system off resonance. However, though resonant vibration is mitigated, the external excitation's acceleration transferred to the system remains. Therefore, this method is more successful for the cases with long duration but weak external vibration resource, for example, wind-induced vertices.

While engineers are exploring better design philosophies and methods of seismic- resistant design in the regions with high seismic risks in US, accelerated construct and rapid retrofit are the general needs of bridge engineering for the country. It has been reported [10, 11] that, 2012 in United States, the average congestion time per day is 4.14 hours; the resulted economic loss is about $121-billion at the year, as compared with $24-billion at 1982. Historical experiences also tell that after each major earthquake in past, timing for fast retrofit and replacement of damaged buildings and life-line bridges means saving lives, for which economic consideration becomes the secondary. For all of these an outstanding challenge is: how to design a bridge or a building that is sufficiently strong and that can be built economically within minimized construction-duration, with the least efforts for maintenance, and easily to be retrofitted or replaced timely.

To this end, innovative apparatuses for large-scaled civil engineering constructions, which has the capability to protect a structure from strong earthquakes and tsunamis while be able to provide both the solidness required under regular service condition and the convenience for fast construction and retrofit, will bring broad impact to construction industries and for public safety. Based on the requirements in the design specifications [4-7], the experiences of the catastrophic earthquakes [2], as well as the research reported in past, for examples, these listed in [1,3,7-9, 12-18], the inventor of this application suggests the following basic criteria for a seismic-proof connector that be able to protect a bridge or a building from earthquakes or other kinds of dynamic impacts along all directions:

(A) Robustness: a stable connection under regular operating condition.

(B) Fuser: capable to accommodate a temporal separation between connected structural units when one of them is dragged by a sudden accelerated motion that may be caused by earthquake, barge or vessel's collision, or explosion; such a separation is able to reduce inertia-induced forces in both units substantially.

(C) Self-healing: capable to self-restore the structure back to original state after an accelerated motion or back to a state that is with engineering acceptable deviation from original state.

(D) Integrity: during a temporal separation the connector should always keep the connected units as an integrated system, in other word, the separation (B) should not result in permanent detachment, which is uniticularly important for the case when a superstructure of a bridge or a building is struck by impacts, for example, tsunami.

(E) Environment-friendly: does not introduce noise or extra material hazards, nor consumes extra energy.

(F) Sustainable for long-term performance, convenience for maintenance.

(G) Convenience for fast construction, retrofit, and replacement.

(H) Cost-effectiveness. The apparatuses disclosed by this article are to be used as connector between major structural units in bridges and buildings to satisfy these criteria.

Brief Review of Prior Arts and Products Available in Market

Design of seismic-resistant buildings and bridges is one of the most active and innovative areas in the field of civil and structural engineering. Using a three-storage building, Figure 2 illustrates various arts and technologies currently proposed or have already been applied in practice. The arts disclosed in this article can be used as vertical connector with the combined functions of the seismic bearing in the left-low corner as well as the shear-key and the cast-in- place support on the right-low corner for the building in this figure.

Figure 3 illustrates the trace of the development for the disclosed embodiments, whereby the key idea by this article, denoted as (3) in the drawing, adopts the V-concept in (2) and the vertical reinforcement pins in (2) by the prior art by the same inventor (PCT/US2012/063127). The V-concept originally was designed to utilize the horizontal component of gravity on sliding- surface as vibration resistance while the stored potential energy, when a superstructure is shaken up along the V-surface, is used as the driving force to restore the system back to original state. By contrast, in (3) the V-concept has been transformed into the crater in V-Shaped Guiding

Tubes(VGT) to accommodate the deformation of the stabilization pin(SBP); the deformation energy stored in the pin is the driving force for restoration, which is exactly the function of the vertical reinforcement pins in (2). Additionally, the V-Shaped crater in (3) is also utilized as the container for damping core.

Fig. 4 shows a prior art "bridge assembly" (US 4977636), by which an array of precast pilings is set out; with temporary support channels placed on the pilings, cap members are placed onto the supports filling with concrete 58; slab members are then used to span the cap members with road surface thereover.

Fig. 5 is the prior art (US4187573) that uses elastomer to damp lateral and vertical vibration while carry the weight of the superstructure. The high friction-coefficient between elastomer and top/bottom pads ensures no sliding. Fig. 6 is such a variation, WO2008/004475, by which the key component is the composite block that is made of the laminar structure by elastomer 2b and reinforce plate 2c. The block contains a center core 3 made of high plasticity material, to reinforce lateral deformation resistance while improve the capacity of damping. When the core material is Lead, this kind of bearings is also termed "Lead-Rubber Bearing (LRB)". However, when a structure is suffering strong ground motion, the friction resistance between elastomer and bearing pads may not be enough to resist inertia-induced sliding force. Once sliding occurs after the core deformed, there is no internal driving force to restore such a bearing back to its original shape.

Fig. 7 is the prior art (US6021992), termed friction pendulum sliding bearing (FPS). It belongs to a group that includes dozen of US patents and tens in other countries which are based on the principal of the pendulum depicted on the right-hand side of the figure, utilizing carried superstructure's weight as a natural force to resist horizontal inertia caused by ground motion. Once the spectrum of ground motion passed, the gravity restores the bearing back to its original position.

Theoretically speaking, a pendulum is a conservative system that does not dissipate energy. Therefore, if there is no friction, an actual pendulum can swing around its static position forever once the motion is triggered. Therefore, in a FPS bearing certain friction between the contact surface-pair is necessary. On the other hand, certain height of curved surface at least for the bottom seat of the bearing in Fig. 7 is needed to gain enough lateral resistance while considerable contact area is required for carrying heavy superstructure; these two factors result in large bottom seat and associated high cost. Also, a FPS bearing, which is the same as elastomeric bearings (EB and LRB) in Figs 5 and 6, does not have the mechanism to preserve the connected sub and superstructure as an integrated system when the superstructure is struck by an external force, for example, hurricane or tsunami.

To preserve sub and superstructure's integrity is particular important for buildings. This is because, even there is no strong external force directly imposed to superstructure, a horizontal ground motion-induced vibration causes turnover moment to a building's superstructure. The magnitude of this turnover moment is approximately proportional to the ratio between the building's height and the largest dimension on earth surface, for example, its width.

To deal with this issue, Fig. 8 is another prior art (US5669189), termed anti-seismic connector (ANSC). It is actually an assembly of a laminated elastomeric bearing 3 plus the cables (tendons) 6 fastened to the connected super and substructure by the rotation-free fastener 21. Whereby the drawback is that the tendons and rotation-free fasteners basically do not have the mechanism against carried superstructure's horizontal sliding, which leads to less resistance against turnover moment when the superstructure starts to decline. A tiny of such declination will trigger higher turnover moment, which may lead to the superstructure into an unstable state.

The prior art (US 8196368 B2) discloses a class of "ductile shear key", see Fig. 9, by which rebar or rod are precast simultaneously into a shear-key block 100 and concrete block 110 while a chuck of opening space, which is termed "sleeve" or "isolation key", is left surrounding the bar or rod adjacent to the overlay interface. Instead of connecting major structural units to transfer loading, the ductile shear key is an enhanced part to pier cap, utilizing the irreversible ductile deformation of the cast-in-rebar or cast-in-rod to absorb impact energy and to protect a bridge's superstructure out of bearing seat when struck by earthquake.

Fig. 10 is the prior art for a method of constructing precast units of bridge (US8341788 B2), which discloses the procedure to assemble a main precast segment with pin grove (129) with another segment with match-cast pin (119) or the same way by a pair of pin (110a) and cylinder hole(llOb), whereas socket (111) has been added surrounding tendon or vertical rebar at the interface between vertically-overlaid concrete segments.

Summary of the invention

This invention discloses a class of apparatuses, termed V-Connectors. Featured by its simplicity and practical for engineering applications, said V-Connector can be used to connecting the units within a civil engineering structure such as a bridge or a building, or the units of a machine, to satisfy the criteria (A) to (H) addressed in the previous section. The basic embodiment of said V-Connector is explained by Fig. 1, which is an assembly of the five basic elements: two V-shape guiding tubes (VGT) that are respectively mounted into the two connected structural units, a bridge's deck and pier in this figure; a vertical stabilization-pin, abbreviation "SBP", as plotted in Fig. 11; the two ends of said SBP are inserted into two said VGTs in two connected units; a damping cone around the pin within the lower VGT, and a washer that have the functions to lubricate the sliding between connected surface-pair while to seal the surfaces and protect them not to be damaged during the relative motion between connected units; whereby the damping core and washer are optional.

Utilizing a pin to connect two structural units, while restricting lateral relative motion in- between, is a common method by engineering designs. For a structure with seismic resistant requirement, pins are often adopted to reinforce structural integrity, for example, the conventional shear-key in bridges. By the author's best knowledge, for the all pin-like connectors applied for bridges and buildings so far, the two end units of a pin are respectively embedded into the connected two structural units without proximity. Though providing robust connection, this kind of pin-connectors lacks of the ductility needed for seismic isolation; it also introduces localized high bending moment and shear stress concentration on both the pin and the edges of connected structural units. When this kind of pins are used to connect a long span and two piers, extra requirement for construction tolerance will be needed; this can be extremely expensive and time-consuming.

Hence, the primary innovation of the V-connector is the design of the V-shaped cavity in said V-shape guiding tubes (VGT) that are respectively mounted into two connected units. Each VGT has a unit of V-shape crater-like geometry with the length Lc and a unit of cylinder geometry with the length L_t, see Fig. 1. This specially-designed geometry of the cavity enables self-centering when said stabilization pin (SBP) is inserted whereas the unit with cylinder geometry holds said SBP tight to assure the connection with the similar robustness as CIP in the respect of structural integrity, when L_t is long enough while the materials to make of SBP and VGT have sufficient strength. The unit of VGT with the length Lc has the specially-designed curvature, like a crater, allowing the pin (SBP) to deform that provides the desired flexibility to a structure as an isolation bearing does but is with gradually-elevated lateral resistance through smoothly-increased contact, so as to avoid concentrated bending moment on the pin, or with gradually-decreasing resistance to achieve interested force-deflection relationship, as illustrated in Fig. 12(a). Therefore, the friction between the contact surface-pair between two connected units, with or without the washer in Fig. 1, results in energy dissipation when a relative motion between the two units occurs, introducing desired ductility as characterized by the hysterical curve illustrated in Fig. 12. The design of the combination of VGT and SBP, which allows confined relative sliding between connected units while utilizing weight-induced natural friction as dissipation mechanism, is the center of the disclosed invention.

Though multiple pins may be used to connect two structural units, sufficient strength and toughness are the obvious crucial requirement for each said SBP, for which high-strength steel alloys can be a candidates-pool to make it. However, steel's strength and Young's module are generally one to two orders higher than concrete. Simply insert such a pin into the V-shaped cavity within a concrete matrix may cause localized damage, for example, the concrete around the end of pin. These highlight the second innovative feature of the V-shape guiding tube (VGT) in Fig. 1. It smears out possible stress concentration caused by the pin without compromise of the functions associated with the cavity's geometry. The guiding tube can be made of regular steel, or composite, e.g. Teflon, pre-casted into connected concrete unit with an attached reinforcement ring to assure robustness with the matrix. Obviously, under the following circumstances: (i) the concrete has sufficient strength or the matrix is other kind of high-strength material; (ii) the pin's diameter is large enough so the result stress concentration is ignorable, VGT is also optional when a cavity with the same geometries can be made within the matrix of a connected unit.

Additional dissipation can be achieved by inserting a damping cone between the pin and VGT, see Fig. 1. Made of the material with visco-liquidity, e.g. lead or filled by silicon powders or sands; a unit of the damping cone will be squeezed away when the pin deforms towards tube's wall; some of these elements will be squeezed back again once the pin is vibrated to opposite direction. This process dissipates involved vibration energy while shifts the structure's natural frequency away from resonation frequency, adding additional damping to that explained in Fig. 12.

Description of Embodiments

The embodiment described in Fig. 1 is listed as Type-I V-connectors for the family of invented apparatuses, which is actually an innovative combination of the previous art "PCT/US2012/0613127 [16]" by the inventor, see Fig. 2.

The benefit of the V-connector is not only to reduce the risk of resonated vibration without the need of additional mass, it actually also improves the stress state in connected structural units if they are made of concrete. It is well-known that many non-metal materials, such as concrete, have strong compression strength but with very limited capacity against tension stress. This is the reason that significant amount of steel rebar have to be embedded into body of concrete. When a concrete column is under bending, the steel rebars on tension side takes almost 100% of tension load while the concrete surrounding rebars just plays the role to assure stability. It has been often observed that persistent shocks during an earthquake eventually caused concrete spalling that results in embedded steel bars' bowing. By contract, an advantage by the V-connector is that this system transfers the tension zone in CIP structure into the compression zone around VGT.

However, as illustrated by the plot on the left most in Fig. 13, on the plane between the two connected units contact surface-pair, shear stress reaches maximum. This is the reason for the design options (b) and (c) in Fig. 11, i.e. the SBP with fins or with enlarged diameters at middle. Instead of those, Fig.5 introduces another solution to reinforce the SBP: to add shear reinforce V-ring (SRV), for which the design options are given on the right of the figure. The obvious advantage by SRV is easy to manufacture. The embodiment described by Fig. 13, i.e. straight said SBP with additional said SRV, is termed "Type-II V-Connector".

In practices another concern of the applicability of V-connectors can be seen from the plot on the right of Fig. 14. This figure hints that, when a bridge's deck's live-loads distribution is un-symmetric to central line of the road over a bridge, the friction between the stabilization pin (SBZ) and the tube (VGT) may not be sufficient to balance the side-turnover moment. This may lift the deck over and out of the pier seat. By detailed quantitative analysis one can find that the lift-out force is limited. This is because such a turnover movement has to be compatible with the pin's gradually bending that results increased lateral force accordingly. Consequently, the moment caused by this increasing lateral force will eventually balance the turnover moment. There is generally no permissible displacement field to allow the pin's suddenly bending and loss of stability if no simultaneous large lateral deformation occurs.

On the other hand, the concern of turnover moment does highlight the need of vertical control for some bridges and high-rising buildings. To solve this problem, another embodiment, termed Type-Ill V-connector, has been invented and is depicted on the left of Fig. 14. As compared with the Type-I V-connector in Fig. 1, by this prototype the upper VGT penetrates through the bottom concrete slab's thickness; its upper end is welded to a washer where the top unit of the stabilization pin (SBP) goes through. The washer prevents the upper VGT falls down. The top of the SBP is fastened by the fastener onto the washer or all of them are welded together. This layout limits the turn-over or lift-up motion for the deck concrete box if the pin is fixed onto somewhere of the pier. For this reason, the lower VGT is designed with two opposite straight cuts with a width b_E. The cuts start at the transition unit where the tube's diameter almost shrinks into a constant value and stretch down to the tube's bottom end. At the location with the distance L_E to the end, the uncut unit's thickness of the tube is machined to gradually decrease until less than the half of the original thickness at its end and then bend the unit of the tube slightly outwards. Similarly, two opposite strip-like mounds with the width b_E are prefabricated at the bottom end of the pin. With the same width as the two opposite cuts on the guiding tube, the mounds also start at the location with the distance L_E to the pin's end and gradually increase their heights until about half of the tube's thickness. So the pin can be inserted into the lower VGT when the two mounds match the positions of the two cuts on the tube. Once the pin reaches the end of the VGT, by rotating 90 degrees it will stay within the tube and can not be pull out if not rotated 90 degrees back. A reinforce ring is welded to the lower VGT at the location just above the distance L_E before it is casted into concrete pier. By this design the pin's up-lift motion has been restricted and the function of vertical constraint has been achieved for the Type-Ill V- connector.

Besides as the connector between bridge's beam and pier, the apparatuses family disclosed by this article can also be used as the connectors between pier and spreading footing, Fig. 15, and that of between factory-manufactured floor units in buildings for fast construction, Fig. 16. Plotted in Fig. 17 are various designs of the washer between two connected structural units, whereby the options (5) and (6) are the designs that consolidate VGT and washer as one component, with or without reinforce-ring surrounding VGT.

The V-Connector can also be applied to the joints between steel superstructure and concrete pier as well as between steel super and substructure; for the former a corresponding embodiment is given in Fig. 17, termed "Type IV V-Connector". For the connected steel unit, which is an I-beam in the figure, obviously there is no need of the cavity and upper VGT that are presented in the Type-I to Type-Ill V-connectors; instead, the stabilization-pin, with enlarged diameters, is attached to a seat that is bolted to the I-beam, this assembly is termed "seat-pin". Two design options for the seat-pin are given in the figure.

The function of the washer in Fig. l is to improve the friction between connected contact interface while protect concrete part when localized pressure occurs. Fig. 18 illustrates three design examples of the washer, whereby options are to design the washer as an individual component that may include multiple parts and to manufacture the washer and the VGT as one piece. A trivial protection cover is maybe needed to prevent the connector from dusts and moistures.

To apply the embodiments disclosed into practical applications, a crucial issue is to select appropriated materials for the elements of each V-connector and to determine optimized geometric parameters to gain better performance. To fulfill these tasks, though need certain theoretic background in structural engineering and materials science, are straight forwards by professional design and analytic methods by means of modern computation tools; whereby a key is to determine applied loads under regular operation conditions and possibly induced by future earthquakes that a structure is supposed to sustain. Method and an analytical model are to be introduced briefly as follows regarding determination of earthquake loads; the analysis of model has actually, in certain degrees, triggered these inventions.

Earthquake belongs to the events that are with great uncertainty. However, based on advanced research and historical records of past seismic events within certain return periods USGS has developed earthquake hazard maps, Fig.19(a). The function of these hazard maps are giving predicted highest values of the following three parameters at any location of US with 0.075 probability of exceedance in the next 75 years: SO.2, the nominal PGA at initiation (0.2 second), SI, the nominal maximum PGA at (1.0 second), and, TL, the transition of earthquake duration to long period. These parameters determine the earthquake spectrum curve that is plotted in the coordinate system with the perpendicular coordinate to represent PGA and the horizontal to represent the duration T, the inverse of vibration frequency, in Fig. 19(b). The underlying idea is that, as actual earthquake is always with a distributed spectrum of vibration frequencies, so the spectrum curve in the chart gives the PGA for any structure at its first-order natural frequency caused by the predicted highest future earthquakes with the 7.5% probability of exceedance in the next 75 years ¹ . By the method termed "seismic spectrum design" recommend by code [5-7], a bridge, for example, the CIP construction on the upper left corner of Fig. 20(a), can be simplified as the one-degree model in the figure, for which the first-order of natural frequency, when expressed as its inverse, i.e. the corresponding period, is given by the following equation:

Substituting T obtained by this equation as the horizontal coordinate in the chart in Fig. 19(b), by the spectrum curve the corresponding SPG on the vertical coordinate can be read. Then applying the second Newton's law, one obtains the design earthquake load, for example, at the neck between deck and pier.

The two-degree model in Fig. 20(b), which represents a structure with V-connectors, is termed V-system. It is a two-freedom nonlinear dynamic model where the V-connector is presented by the Kelvin- Voigt model with the Hooker's constant K_v to represent the stiffness of the pin (SBP) and the visco-plastic coefficient η_ν ίο the dissipation cone; whereas u_p is the

¹ It is 50 years in some building codes. displacement at pier's top and u is the average deck' s displacement above the pier. It is well- known that earthquake radiates stress waves with distributed frequencies spectrum, e.g. that in Fig. 20(b). For simplification, the dynamic behaviors of the model can be quantified by the solutions of the following group of two ordinary differential equations, presuming the system is struck by an external excitation in the form of single sinusoid wave with frequency ω and amplitude F:

M_deck ^T + v ^ - KpU_p + K_vu_d = 0

Mpier ¾T + (^KP + ^Kv)^up - ^KvU_d = F^■ sin(a⁾t) where t is time. To avoid tedious derivation, this proposal only presents the following displacement solutions that were derived after leaving out the visco-plastic term related to ην . The solution, not loss generality, will provide basic information of the system' s behaviors:

_ [l-S_d ²]Mp₀

^{Up ~ U} (3) u

where

U = [1 + η_Μ ² - ω_ρ ²] [ΐ - _α ²] - η_Μ ² (4)

and u_p0 = F/M_pier , ω = ω_α/ω_ν, _ρ = ω/ω_ρ, ω_α = ω/ω_α, η_Μ = M_deck/M_pier, and ω_ρ = j K_pi_er / M_pier . the first order natural frequency of the pier; ωά ⁼ Ky/Mdeck - the first order natural frequency of the deck with V-connector. The physical meaning of (3) and (4) is fairly simple, for which the denominator U in (4) rewritten in the form as: U = 1 - ω_ρ ² - η_Μω²ω_ά ² - ω_ά ² + ω_ρ ²ω_ά ² (5) Considering the case with very large stiffness K_v for the V-connector so it is similar to a rigid connection, which, as explained previously, is essentially the case of CIP. Because very larger K_v leads to very smaller _ά, therefore, under this situation, the denominator U in (2) can be approximated by

U « 1 - ω ² (6)

Accordingly, when ω→ ω_ρ, i.e. the earthquake frequency is approaching the system's natural frequency, _ρ→ 1, U→ 0, which is the condition that resonated vibration occurs for the CIP model in Fig. 20(a). Hence, by design of the flexibility embedded within the V-connector, represented as a finite value of the stiffness K_v in the V-system in figure 19(b), the first-order resonated vibration frequency can be shifted to a desired value. The corresponding relationships between vibration amplitude and the frequency ratio is given in Fig. 20(c), by which a good news is that the first-order resonate frequency has been bifurcated into two branches, providing broad possibilities to choose appropriated parameters of V-connector to obtain the frequencies desired by designs.

Claims

Claims:

1) A class of apparatuses and a method to utilize said apparatus to join a pair of units together in a structural system, which provides robust connection while allows confined relative sliding between said unit-pair when said structural system is under strong external dynamic loads such as earthquakes, wherein said structural system is a machinery system or a civil engineering construction such as a building or a bridge, said unit is one among the group of major structural components that includes beam- span, bent, coping, floor unit, pier, footing, foundation, and all other therein, wherein said major structural component is connected to at least another one of another structural component and transfers load-induced forces in-between, wherein said load includes said major structural components' gravity and the loads they are carrying and imposed.

Said apparatus comprises at least one stabilization pin, referred by the abbreviation "pin" thereof, wherein the geometry and sizes of said pin's cross-sections perpendicular to its axis along length direction are variable, which are designed to avoid localized high shear stress concentration when said apparatus transfers forces between said unit-pair,

Said method is first to pre-cut or precast at least a pair of cavities respectively on each contacted surface of said unit-pair connected by said apparatus; wherein the two axes of said cavity-pair are parallel to each other and neither of them is parallel to said contact surface-pair, wherein said cavity's axis is a central-symmetric line to the

1 cavity's inner perimeter on every cross-section perpendicular to the line. Each said cavity is divided into two parts characterized by different cross-section's geometry and sizes along its axis, wherein the first part starts from said cavity's bottom and is with a length L_t along said axis. In this part said cavity's inner perimeters match the outer perimeters for an end part of said pin with the same length L_t or shorter, so said pin can be inserted into said cavity without proximity in-between along the direction perpendicular to said axis, wherein another end part of said pin is inserted into another said cavity in another unit of said unit-pair by the same way. The second part of said cavity has gradually enlarged cross-section towards to the surface of said unit's matrix, which is able to guide end of a pin towards to the first part when the pin is inserted while allows confined flexural deformation of said pin when the two axes of said cavities on the two connected units are not coincide, or when a relative sliding between said contact surface-pair occurs, wherein said gradually enlarged cross- section of the second part is designed to assure gradually-increased contact between said pin and said cavity 's side-wall within this part when flexural deflection of said in occurs, wherein the length of the second part of said cavity is greater than a half of the maximum size of the cross-section in the first part of said cavity.

2 The apparatus and connection method in claim 1 wherein said apparatus further comprising at least one V-shape guiding tube that is corresponding to one of said cavities, refereed by the abbreviation "tube" thereof, wherein said tube is made of the material with higher strength and hardness as compared with the matrix of said connected unit, wherein said tube's outer geometry and size matches said cavity so it is fitted into said cavity or is precast into the matrix of said unit.

3 3) The apparatus in claim 1 wherein said stabilization pin comprises a part along its axis with enlarged cross-sections.

4 The apparatus in claim 1 wherein said stabilization pin comprises a part along its axis with at least two fin-shaped mounds, wherein said mound is either a part of said pin's material and machined with the shape or a piece of plate attached onto said pin through welding.

5 The apparatus in claim 1 wherein said stabilization pin is made of a tube that is filled with visco-plastic material selected from the group of soft metals that include lead and tin or the group of granular particles for which the average grain diameter is less than half inch.

6 The apparatus in claim 1 further comprising at least one shear-reinforce V-ring (SRV) surrounding the part of said stabilization pin, wherein the size and geometry of outer perimeter of said shear-reinforce V-ring are designed to reinforce the shear strength of said pin.

7 7) The apparatus in claim 1 , wherein one end of said stabilization pin is anchored into the first part of said cavity in one of said connected unit.

8 The apparatus in claim 1 with the V-shape guiding tube in claim 2 wherein the length and the cross-section's outer geometry of said tube only matches the length and inner cross-section's geometry of the second part of said cavity when said stabilization pin is anchored into the first part of said cavity as defined by claim 7.

9 A method to anchor said stabilization pin in claim 7 onto said V-shape guiding tube in claim 2, wherein said pin is attached with at least one mound that starts at an end of said pin with the width bs and height TE, which stretches up with gradually decreased height and merges to said pin's out perimeter at the location with the distance LE to the end of said pin, wherein said tube further comprises the same number of machined cuts as said mounds of said pin, wherein said cut has the width slightly greater than bs, started at the middle of the second part of said tube and stretched down to its end. Starting at the location with the distance LE to said tube's end, the uncut part of said tube is slightly outward-bended and is machined with gradually decreased thickness that is less than half of original thickness at the end, so said pin can be inserted into said tube when said mound matches the position of said cut. Once said pin reaches the end of said tube, it can be rotated freely if the mound's height TE is slightly greater than the half thickness of said tube; hence, said pin is anchored by said tube after a rotation that makes said mound to match the uncut part of said tube.

10 The apparatus in claim 1 wherein one end of said stabilization pin is anchored into the first unit of said unit-pair through the method defined in claim 7 or that in claim 9, wherein another end of said pin is anchored to the second unit by the method selected from one of the group that includes (a) cast-in-place; (b) cast-in-place with said V- guiding tube in claim 2; (c) penetrated through a part of the second unit and bolted at the end; (d) penetrated through a part of the second unit with said V-guiding tube in claim 2 and bolted at the end.

11 The apparatus in claim 1 further comprising a damping cone that is filled within the space left between said pin and the second part of said cavity, wherein said damping cone is made of the material selected from the group that include lead and tin or is filled with granular particles for which the average grain diameter is less than a quarter of inch.

12 The apparatuses and a method to connect a pair of units in a structural system in claim 1 , wherein the first unit of said connected unit-pair is made of metal, wherein said stabilization pin has gradually increased cross-section toward to one end of said pin that is attached to a metal seat through fastening or welding, wherein said seat is fastened onto the first unit; whereas another end of said pin is inserted into said cavity in the second unit that is not made of metal, with or without said V-shape guiding tube.

13 The apparatuses and method to connect a pair of units in a structural system in claim 1, wherein said apparatuses further comprises at least one piece of washer between the contact surfaces of said connected unit-pair, wherein said washer is designed to with at least one of the following functions: (a) lubricate the contact when relative sliding occurs between the pair of connected units; (b) protect the connected units' matrix surfaces and edges when rotation occurs in one of said unit; (c) seal said apparatuses from environmental hazards.

14 The washer for said apparatuses and method to connect a pair of units in a structural system in claim 14, wherein said washer is manufactured as a part of said V-shape guiding tube in claim 2.

15 The apparatuses and method to connect a pair of units in a structural system in claim 1, wherein the contact surface of at least one unit of said unit-pair is covered with a layer of material bonded on the surface.

16 The apparatuses and method to connect a pair of units in a structural system in claim 1 and the V-shape guiding tube (VGT) in claim 2 wherein said tube is precast within concrete matrix of said unit and is pre-manufactured with at least one reinforce ring surrounding its out perimeter, wherein said reinforce ring is either a part of said tube's material or is attached through welding or screw-in.

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