ANTI-SEISMIC CONNECTION JOINT

[0001] This invention relates to an improved anti-seismic connection joint, in particular for prefabricated structures made of reinforced, pre-stressed or normal cement .

[0002] Recent seismic events have focused attention on new anti-seismic connection systems for construction, suitable to allow the structural scheme of the existing building or new construction to which they are applied to adequately withstand the seismic forces and absorb the deformations that arise after ever more frequent seismic events .

[0003] In particular, an anti-seismic joint seismic realises an adequate connection between the major structural elements of the building (such as pillars, beams, tiles, trusses, purlins, etc.) _/ - essential to prevent serious damage and collapses during the earthquake. In fact, precisely due to seismic events, adjacent structural components of the same structure, normally designed in simple support and with a significantly different seismic behaviour, are in danger of colliding with each other and falling, due to loss of support, precisely at the connection points. At the same time, an anti-seismic joint must always allow the free expansion of the building structure due to seasonal temperature changes, preventing damage and cracking.

[0004] In particular, since the scope of application is that of industrial buildings, it is essential that the anti-seismic joint be suitable to support adequately not only the first seismic wave, but also all successive seismic waves.

[0005] The perceived need in the field of anti-seismic construction is to realise, in compliance with current standards and also on existing property, a structural connection between components of the building that is able to adequately withstand the seismic event during its entire duration.

[0006] The purpose of this invention is to resolve the problems of the known art, taking into account the needs of the field.

[0007] This purpose is achieved by a hinged anti-seismic connection joint that combines, in a single anti-seismic device, "fuse" type (thanks to the presence of at least one sacrificial element) and "damping and dissipative" type functioning (thanks to the presence of at least one damping element) .

[0008] This purpose is achieved by an anti-seismic connection joint according to claim 1, below. The dependent claims describe preferred or advantageous embodiments of the connection joint.

[0009] The characteristics and advantages of the connection joint according to this invention will be apparent from the following description, given by way of non-limiting example, in accordance with the accompanying drawings, in which :

[0010] - Figure 1 shows an axonometric view of an anti- seismic connection joint according to this invention, in an embodiment variant;

[0011] - Figure 2 shows a sectional view of the anti- seismic connection joint of Figure 1, obtained along a vertical plane passing through the X axis;

[0012] - Figure 3 shows an axonometric view of the anti- seismic connection joint of Figure 1 in a in a further embodiment variant;

[0013] - Figure 4 shows a sectional view of the anti- seismic connection joint of Figure 3, obtained along a vertical plane passing through the X axis;

[0014] - Figure 5 shows the diagram of the trend of the load-displacement curve of an anti-seismic connection joint according to this invention, in the case of the first seismic wave in which the sacrificial element is activated;

[0015] - Figure 6 shows the diagram of the trend of the load-displacement curve of an anti-seismic connection joint according to this invention, for the successive seismic waves, with exhausted sacrificial element.

[0016] With reference to the accompanying figures, an anti- seismic connection joint is indicated by the reference number 100.

[0017] The anti-seismic connection joint 100 according to this invention is an improvement of the anti-seismic joint of patent IT1415801 in the name of the same applicant as this application.

[0018] The anti-seismic connection joint 100 is a hinge joint comprising a female element 10 and a male element 20, each fixable to a respective structural component 110,120, for example a pillar or bearing wall 110 made of reinforced cement and a beam 120. The female element 10 and male element 20 are fixable to the respective structural components 110,120 by means of mechanical or chemical fixing systems 90, such as screws and bolts, chemical anchors and metal bindings.

[0019] The female element 10 and male element 20 are provided with a plate 11,21 for fastening with the respective structural component 110,120. The plate 11,21 is fixable to the respective structural component 110,120 for example by means of screws 90. The plate 11,21 is provided with holes 91, preferably oval-shaped to allow a plurality of positions of the screw in the hole, so as to avoid the internal reinforcement of the structural component .

[0020] In a variant, shown in Figure 3, the plate 11,21 is provided with lateral shoulders 28 for fixing along the sides around the structural components 110,120, for example, when such structural components do not allow the insertion of screws along the too narrow base.

[0021] The female element 10 and male element 20 are metallic components connected by means of a pin 30, preferably with threaded ends for fixing two nuts that prevent longitudinal displacements.

[0022] The female element 10 and male element 20 are joined by means of the pin 30 to form a connection hinge 40 between the two structural components 110,120 so that the vibratory movement occurs freely for each of the two connected parts.

[0023] In particular, the hinge 40 allows absorbing the axial and transverse stresses of the structure, and particularly of the structural components 110,120, which are caused by seismic events. Moreover, the hinge 40 allows the free expansion of the structural components 110,120 themselves due to seasonal temperature variations .

[0024] The hinge 40 is provided with a damping element 50 positioned between the female element 10 and male element 20. In particular, the damping element 50 positioned inside the hinge 40 realises a damping of the axial stresses that arise as a result of seismic events.

[0025] In particular, having defined longitudinal axis x of the pin 30 and the damping plane P orthogonal to the x axis, the damping element 50 dampens forces having at least one component in the damping plane P.

[0026] The damping element 50 is positioned around the pin 30. In particular, the damping element 50 prevents the pin 30 from being sheared and/or deteriorating due to the brusque and prolonged sudden oscillatory displacements that are caused during seismic events.

[0027] Between the female element 10 and the male element 20 there is a container cylinder 60, preferably metallic, with a cylindrical shape and hollow inside (substantially a tube) , inside of which is housed the damping element 50.

[0028] In the embodiment variant of Figures 1 and 3, the container 60 is rigidly connected with the male element 20.

[0029] The female element 10 is provided with two supports 14, projecting from the plate 11, provided with hole for housing the pin 30.

[0030] The male element 20 is provided with at least two supports 25, projecting from the plate 21, rigidly connectable to the metal container 60, for example by means of bolts 90, to at least two supports 24 projecting from the container 60 itself (Figures 1 and 3) .

[0031] The supports 25 of the male element 20, suitably bolted to the supports 24 of the container 60, inside of which is contained the damping element 50, are placed between the two supports 14 of the female element 10. The assembly is thus joined by the pin 30, which longitudinally crosses the damping element 50, to form the hinge 40.

[0032] In the embodiment variant of Figure 1 and 3, the supports 24 are connected to the corresponding supports 25 (already welded to the plate 21) by means of fixing systems 90, for example bolts or screws. This allows customising the connection joint 100 with different types of plate 21 according to the need, for example with shoulders 28 (Figure 3) or without shoulders 28 (Figure 1) .

[0033] Preferably, therefore, the male element 20 is provided with at least two supports 25 projecting from the plate 21, connectable to the hinge 40 by means of the corresponding supports 24 projecting from the container 60 by means of fixing systems 90, for example screws and bolts. Therefore, the connection plates 11,21 to the pillars 110 and beams 120 can be welded directly on the device 100. Alternatively, the male element 20 is connectable to the beam 21 by means of bolts 90, thus facilitating the connection since the plate 21 can be constructed according to the characteristics of the beam 120 and to be fixed to it in advance.

[0034] The damping element 50 is made of natural and/or synthetic rubber in the different "hard", "medium" or "soft" mixtures. The damping element 50 can then be made of low, medium or high density rubber, based on the damping needs of the anti-seismic joint 100. It is thus possible to change the damping capacity of the anti- seismic connection joint 100 based on the needs of use by simply changing the damping element 50.

[0035] The damping element 50 is a cylindrical element made of rubber, housed in the resulting space between the container 60 of the male element 20 and female element 10 of the hinge joint in which the connection pin 30 is positioned .

[0036] Preferably, the damping element 50 is a cylindrical element made of vulcanised rubber on a central metallic support 52. The central support 52 is cylindrical and the connection pin 30 is positioned inside it.

[0037] For example, the damping element 50 is made of natural rubber (or of elastomeric material in general) having a Shore A hardness (for elastomers or plastomers) between SH 40 and SH 75, preferably SH 65d dissipative, this latter material with particular capacity to dampen vibrations/deformations .

[0038] The anti-seismic connection joint 100 connects the vertical and horizontal structural components 110,120 to each other and, at the same time, being a hinge joint, achieves a decoupling of the masses in such a way that the vibratory movement determined by seismic events occurs freely for each of the two connected parts.

[0039] In addition, the anti-seismic connection joint 100, being a hinge joint with damping element, is designed to allow the structure to collect both the deformations that occur slowly over time, such as thermal deformation or shrinkage, and the forces resulting from seismic type dynamic and impulsive actions. Therefore, an anti-seismic connection joint 100 is particularly suitable for single- storey or multi-storey earthquake-resistant structures, in which the high of the plan of the building necessarily require the presence of thermal expansion systems in correspondence of which the problem of hyperstaticity would intervene if known structural joints were applied. The anti-seismic joint 100, being of the hinge type, does not create any degree of interlocking in correspondence of the support of the beams.

[0040] Moreover, the hinge 40 is provided with at least one lateral damping element 51 positioned between the male element 20 and female element 10, which achieves a damping of the lateral stresses that arise following seismic events.

[0041] In particular, the lateral damping element 51 is positioned between the container 60 and the support 14 of the female element 10. Preferably, the hinge 40 is provided with a lateral damping element 51 on each lateral side of the container 60.

[0042] Preferably, the lateral damping element 51 is outside of the container 60.

[0043] The lateral damping element 51 is a disc provided with a central hole for the insertion of the pin 30. The outer diameter of the lateral damping element 51 is greater than the outer diameter of damping element 50, and preferably the outer diameter of the container 60. Preferably, the thickness of the lateral damping element 51 is comprised between 6 mm and 20 mm.

[0044] The lateral damping element 51 can then be made of low, medium or high density natural and/or synthetic rubber, based on the damping needs of the anti-seismic joint 100.

[0045] Advantageously, the presence of two lateral rubber disks 51 allows also achieving the damping of seismic forces acting in a direction transverse and/or diagonal with respect to the joint 100.

[0046] The connection joint 100 comprises at least one mechanical fuse restraint device, suitable adapted to prevent the relative movements between connected parts up to a force threshold. In fact, the hinge 40 is provided at least one sacrificial element 54. When a certain force threshold is exceeded, thanks to the breaking of the sacrificial element 54, the connection joint 100 allows (albeit limitedly) the relative movements between the connected parts.

[0047] The sacrificial element 54 is positioned between the male element 20 and female element 10, in particular between the damping element 50 and the support 14 of the female element 10. Preferably, the hinge 40 is provided with at least one sacrificial element 54 on each side of the damping element 50.

[0048] Preferably, the sacrificial element 54 is inside the spacer 60.

[0049] The sacrificial element 54 is a rigid disc. Advantageously, the circular shape of the sacrificial element 54 allows a contrast extended to 360° on all the seismic forces in the vertical plane regardless of their direction .

[0050] The sacrificial element 54 is a disc provided with a central hole for the insertion of the pin 30. The outer diameter of the sacrificial element 54 corresponds to the outer diameter of damping element 50, and preferably is less than the outer diameter of the container 60.

[0051] The sacrificial element 54 is made of strong but brittle material, for example metal (for example aluminium), or composite material.

[0052] For example, the composite material is obtained with thermosetting resins and with fabrics based on bidirectional glass fibres applied in several superposed layers .

[0053] In a further example, the sacrificial element 54 is obtained from concentric rings of composite, metal and/or cement materials. For example an inner ring made of metallic material, an intermediate ring made of cementitious , ceramic or composite material and an outer ring made polyvinylchloride (PVC) or composite material.

[0054] The sacrificial element 54, being much more rigid than the damping element 50, acts as a fuse by deforming in a permanent shape with the increase of the relative displacements between the male element 20 and female element 10.

[0055] The sacrificial element 54 can have variable dimensions and shapes and can be made in a single body or with concentric rings, with the main existing composite materials, with cementitious materials or with all metals and their alloys.

[0056] Preferably, the thickness of the sacrificial element 54 is comprised between 6 mm and 20 mm.

[0057] Preferably, the inner diameter of the sacrificial element 54 is greater than the diameter of the pin 30. In this way, in the very early stages of the seismic shock or, in any case, below the minimum initial threshold Si, there is a free deformation of the damping element 50, while due to increasing deformations the sacrificial element 54 begins to be locally compressed.

[0058] Advantageously, the presence of two or more washers made of deformable composite material with function of sacrificial element 54 that, below a certain predetermined force threshold (breaking force) , prevent any movement between the connected parts, makes the joint 100 particularly suitable to best withstand the seismic event for its entire duration, ensuring the operational safety of the building in the case of minor seismic events .

[0059] In addition, the sacrificial elements 54, being fuse restraints, serve to control the transition between the service load condition and the seismic condition.

[0060] Figures 5 and 6 show the diagram of the trend of the load-displacement curve of an anti-seismic connection joint according to this invention, provided with damping element 50 and sacrificial element 54.

[0061] In particular, Figure 5 shows the diagram of the trend of the curve at the first seismic wave, in which the sacrificial element 54 is activated.

[0062] The load values and displacement measured were initially purified by removing the first settling phase of the system that corresponds to the "empty" movement necessary to cover the free play between rubber and metallic elements and thus reach actual contact between the components, displacements that are not accompanied by any increase in the load up to the achievement of an initial displacement Si that corresponds to the attainment of the contact of the pin 30 with the sacrificial element 54. Starting from this point Si, the diagram shows a strong increase in rigidity and proceeds linearly up to the yielding of the sacrificial element 54 due to bearing stress. At this point, having exceeded the bearing stress tension of the sacrificial element 54, there is plasticisation of its contact surface with the pin 30 and ovalisation of the hole of the rigid disc. When the sacrificial element 54 is used up, the trend of the load-displacement curve shows no particular irregularities: the rigidity of the system (of which the slope of the graph is a qualitative index) increases progressively with the increase of the load. [0063] Figure 6 shows the diagram of the trend of the load- displacement curve for the successive seismic waves, when the sacrificial element is by now used up. The trend of the curve shows no particular irregularities, and the rigidity of the system increases progressively with the increase of the load.

[0064] For the successive waves after the "fuse" effect is used up, the anti-seismic connection device 100 behaves like a "dissipative damping" device allowing relative displacements between the connected parts, of a predefined entity compatible with the dimensional characteristics of the various structural components involved .

[0065] The connection joint 100 according to this invention thus combines, in a single anti-seismic device, "fuse" type (thanks to the presence of at least one sacrificial element 54) and "damping and dissipative" type functioning (thanks to the presence of the damping element 50) .

[0066] The rubber damping elements (damping element 50, lateral damping elements 51) can have variable dimensions and shapes and can be made of a single homogeneous body or with concentric rings of rubber, metal or composite materials. The rubber or elastomers used can be of the "low damping" type or the "high damping" and can have varying hardness commonly defined as "soft", "medium" and "hard" .

[0067] The anti-seismic joint 100 of this invention finds application in buildings, for example of the industrial type, for example in sheds (of new construction or already installed and in use) . It is essential that the anti-seismic joint allow a displacement, for example, of the beams on the pillars or on support walls made of reinforced cement with precise limits. Since a pillar generally has indicative dimensions of about 50-60 cm in order to allow the support of two beams having indicative dimensions of about 20-30 cm, when the seismic event is concluded, it is critical that the aforesaid beams, if translated laterally, are still safely resting on the pillar, maintaining their centre of gravity on the pillar. The rubber (damping element 50) contained in the joint 100 has the dual function of ensuring the absorption of the forces during the seismic effect while limiting the relative displacements of the structural elements to displacements of dimensions such as to ensure, at the end of the seismic event , a repositioning of the beam on the pillar such as to maintain the building usable and thus safe.

[0068] In summary then, in the anti-seismic connection joint 100 according to this invention, the damping element 50 has the characteristics of a cylindrical insulator, composed of layers of elastomer alternating with steel sheets, suitably pre-tensioned by means of a suitable mechanical device, with or without central safety pin and with or without sacrificial elements 54.

[0069] Innovatively, an anti-seismic connection joint according to this invention realises a structural connection between the components of the building able to adequately withstand the seismic event for its entire duration.

[0070] Advantageously, the hinge connection joint 100 according to this invention, achieves an adequate and safe structural connection between the components (beam- pillar, beam-beam) both along the main axial direction and in inclined or transverse directions without determining a hyperstatic condition of the structure itself .

[0071] Advantageously, the connection joint 100 ensures a safe and adequate mechanical connection between beams and pillars or between other structural elements present in structures prefabricated in reinforced cement and pre- stressed cement, in full compliance with existing standards and in every way preventing loss of support.

[0072] Advantageously, the presence of the damping element inside the anti-seismic hinge connection joint provides further damping of axial stresses.

[0073] Advantageously, the presence of the lateral damping elements 51 allows also achieving a damping of seismic forces acting in a direction transverse and/or diagonal with respect to the joint 100.

[0074] Advantageously, the anti-seismic joint described above has geometric and dimensional characteristics of universal type and, produced in two or three different sizes, can be used in all major situations present in prefabricated construction.

[0075] Advantageously, the construction characteristics of the anti-seismic joint described above allow the easy inspection of the internal components and their possible replacement as a result of seismic events or the expiration for elastomers in general.

[0076] It is clear that one skilled in the art may make changes to the device described above, all contained within the scope of protection defined by the following claims .