WO2017064673A1

WO2017064673A1 - Multiple-friction dissipating device

Info

Publication number: WO2017064673A1
Application number: PCT/IB2016/056183
Authority: WO
Inventors: Raúl O. CURADELLI; Carlos A. Martinez
Original assignee: Consejo Nacional De Investigaciones Cientificas Y Tecnicas (Conicet); Universidad Nacional De Cuyo; Inis Biotech Llc
Priority date: 2015-10-14
Filing date: 2016-10-14
Publication date: 2017-04-20

Abstract

The invention relates to a multiple-friction device for dissipating energy, which can be used to control the dynamic response in terms of displacements and accelerations, and which comprises at least one column surrounded by a set of multiple-friction members which are in contact with same and are secured together by means of securing pins. The device further comprises at least one axial load adjuster mounted on a plurality of compression springs, the adjuster being secured by means of high-strength screws. The device does not have the disadvantages of the implementation of traditional friction dissipators, and can be used in both new and renovated structures.

Description

MULTIPLE FRICTION DISSIPER DEVICE

FIELD OF THE INVENTION

The present invention relates to a friction-based multiple energy dissipation device, which can be used especially to control the dynamic response in terms of displacements and accelerations, both in new and rehabilitated structures.

BACKGROUND OF THE INVENTION

In the last twenty years, great efforts have been made to reduce the vulnerability of structures under dynamic excitations such as earthquakes or wind through the concept of energy dissipation. Instead of increasing the resistance as it was traditional, the present invention provides a novel system called multiple friction heatsink whereby the structural demand is reduced by dissipating the kinetic energy that the structure possesses.

The use of external devices to dissipate energy from dynamic excitation is widely recognized as a structural protection system. Friction heatsinks are widely used in passive vibration control, as they are characterized by offering high power dissipation capacity with relatively low implementation and maintenance costs.

Most of the current friction heatsinks on the market are installed using diagonal braces, which can lead to functional problems since they can obstruct circulation, lighting and / or ventilation openings. The device of the present invention maintains the advantages of a conventional friction heatsink while avoiding the aforementioned disadvantages.

Different types of friction heatsinks have been developed and used to improve the structural performance of both new and existing buildings throughout the world over the past 30 years.

The design commonly used in gantry-type structures is based on abalone joints of limited sliding bracing in an X-shape. Another type of device, which uses friction to dissipate energy, uses a pre-compressed internal spring that exerts a force that converts through an internal wedge and an external wedge in a normal force on the skates that rub against each other.

There is also an energy dissipator called limited energy dissipation (energy dissipating restraint or EDR), which has a friction mechanism where the contact force between the frictional surfaces of the device grows linearly with deformation. Other developments proposed grooved grooved friction connections that are mainly applied to concentric bracing frames.

Another type of friction sink proposed is the CFD (cylindrical friction damper), which consists of a piston and a cylinder, which has an internal diameter slightly smaller than the piston, in order to achieve the contact pressure.

BRIEF DESCRIPTION OF THE INVENTION It is then an object of the present invention to provide an energy dissipation device, based on dry friction, which does not show the disadvantages of implementing traditional friction heatsinks and can be used in both new and rehabilitated structures.

It is therefore an object of the present invention to provide a multiple friction energy dissipating device, which can be used especially to control the dynamic response in terms of displacements and accelerations, both in new and rehabilitated structures, where the device comprises the less a column which is surrounded by multiple friction skates in contact therewith, which are held together by means of fastening bolts, further comprising at least one axial load regulator mounted on a plurality of compression springs, being said regulator secured by high strength screws.

In a preferred embodiment of the invention, the friction skates are dry friction skates.

In another preferred embodiment of the invention, said multiple friction skates form a set of skates stacked together.

In yet another preferred embodiment of the invention, for mounting the device comprises a fastening system by screws between the column and the friction skates.

In a preferred embodiment of the invention, it comprises at least two columns, preferably three or more columns, surrounded by said sets of multiple friction skates.

In another preferred embodiment of the invention, the axial load regulator applies an adjustable axial or normal precompression load. In yet another preferred embodiment of the invention, said friction skates can move horizontally generating frictional forces that dissipate energy and resist horizontal movement.

In another preferred embodiment of the invention, the contact between the column and each skate is made by means of a fixing means comprising a toroidal ring fixed to the column which rests on the internal cylindrical surface of each skate.

BRIEF DESCRIPTION OF THE DRAWINGS

For greater clarity and understanding of the object of the present invention, it has been illustrated in several figures, in which it has been represented in one of the preferred embodiments, all by way of example, where:

Figures la, Ib and show a diagram of the multiple friction heatsink, the exploded view thereof and an axial load regulator detail, respectively;

Figure 2 shows the implementation of the heatsink of Figure 1 in a portico-like structure of a bay.

Figures 3a, 3b, 3c and 3d are graphs showing the Fourier spectrum of the register of displacements in free vibrations for different values of normal heatsink forces (5, 10, 15 and 20% of the structure's weight).

Figure 4 is an image illustrating the arrangement of the instruments for pseudostatic cyclic loading and unloading tests.

Figure 5 shows a graph indicating the hysteresis cycle for each normal force studied.

Figure 6 shows several records of displacements and accelerations for the structure with and without control (Imperial Valley Earthquake) under different normal force values. Figure 7 shows several records of displacements and accelerations for the structure with and without control (Kobe Earthquake) under different normal force values.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described in detail with reference to the drawings that illustrate it, in a preferred embodiment and only by way of example not limiting the scope of the invention.

For the purposes of the present invention, the expression indicating that the column is "surrounded by multiple friction skates" should be understood as that the column is surrounded by a plurality of said skates in the longitudinal direction.

Figures la and Ib show an embodiment of the device of the invention 1 installed in a column 2. Although the friction heatsink 1 is feasible to be installed in columns 2 of any type of section, in said Fig. La and Ib shows how it can be installed in parts through fastening bolts 3 in a column of circular section 2. As can be seen, it consists of multiple stacked friction skates 4, subject to an axial pre-compression load. The contact between the column and each skate 4 is made through a toroidal ring fixed to the column 2 that rests on the internal cylindrical surface of each skate 4. Thus, when the column is deformed, only the horizontal movement of the column in any direction is transmitted to each skate allowing relative rotation between them (Fig. Ib). The normal pre-compression load, which generates the necessary normal force, is applied from the upper end of the skid pack 4 by means of four pre-compressed springs 5 (Fig. Le). Said force can be adjusted by means of high strength screws 6.

Fig. 2 explains the operation of the Multiple Friction Heatsink. As can be seen, when the structure deforms under excitement, the skates 4 are move horizontally generating between the contact interfaces of the skates 4, friction forces that dissipate energy and resist horizontal movement.

Based on experimental dynamic tests on a scale model, the effectiveness of controlling the structural response in terms of displacements and accelerations under different operating conditions and excitation characteristics was evaluated.

To characterize and verify its performance, it was installed in a porch-type structural model of a floor and a span and was tested, under different operating conditions, under different seismic registers (Fig. 4).

The experimental results demonstrate the effectiveness in controlling the dynamic response of the controlled structure.

I. Free vibration tests

Fig. 3a-3d shows the Fourier spectra of the displacement registers measured in the structure lintel, for the tests in free vibrations, for each of the cases of normal force applied. Although in non-linear systems, the concept of frequencies and vibration modes is not applicable, the frequency and effective damping of the system can be estimated through Fourier spectra.

It is observed that the increase in normal force of the dissipation system produces only a small increase in the equivalent fundamental frequency of vibration and consequently in the effective stiffness of the system. The increase in the ratio of effective critical damping in each case can be estimated by measuring the width of the spectrum hood, through the average power method. This way it shows that the control of the response of the system is carried out by energy dissipation and not by an increase in effective stiffness.

II. Pseudostatic loading and unloading test

In addition to the free vibration tests, cyclic loading and unloading tests were performed, in a pseudostatic manner (low loading speed). In Fig. 4 the arrangement of the instruments and the loading system by means of which a cyclic force controlled by a tensioner is applied to the structure is observed.

In Fig. 5, the experimentally obtained force-displacement curves are shown for each of the cases of normal force studied. As expected, the cycles enclose a larger area as the value of the normal force applied is increased, which indicates a greater amount of energy dissipated per cycle.

III. Vibration table forced vibration tests

To evaluate the effectiveness in controlling the structural response of the Heatsink

Friction manifold of the invention, a series of experimental tests on forced vibration were carried out. For this, 10 records of real accelerations with duration and content of different frequencies and with spectral accelerations between 0.23 g and 0.31 g were used, in order to have maximum displacements close to 2.5 cm, corresponding to the elastic limit of the structure. The details of the records used are shown in Table 1. Table 1: Characteristics of the seismic records used (Source:

http://peer.berkeley.edu/ smcat / search.html).

Table 2 shows the structural response in terms of maximum values and mean quadratic values (rms) of displacements and accelerations of the upper beam of the structure for each record of seismic excitation and normal force applied.

Table 2: Structural response

Despl Reduction Reduction Accel Reduction Reduction

Force rms deplo rms acel

Earthquake max deplo max rms deplo max acel max rms acel

Normal (m) (m / s ² )

(m) (%) (%) (m / s ² ) (%) (%)

Without control 0.0172 - 0.0049 - 2.1232 - 0.3512 -

N = 0.05 W 0.0092 -46.51 0.0016 -67.35 1.3345 -37.15 0.1371 -60.96

Coalinga N = 0.10 W 0.0056 -67.44 0.0011 -77.55 0.9361 -55.91 0.1127 -67.91

N = 0.15 W 0.0047 -72.67 7.69E-04 -84.31 0.9209 -56.63 0.1068 -69.59

N = 0.20 W 0.0036 -79.07 6.35E-04 -87.04 0.7535 -64.51 0.1076 -69.36

Without control 0.016 - 0.0038 - 1.9883 - 0.3112 -

N = 0.05 W 0.009 -43.75 0.0013 -65.79 1.2921 -35.01 0.1339 -56.97

Duzce N = 0.10 W 0.0057 -64.38 0.001 -73.68 1.0174 -48.83 0.1237 -60.25

N = 0.15 W 0.0051 -68.13 8.75E-04 -76.97 0.873 -56.09 0.1252 -59.77

N = 0.20 W 0.004 -75.00 7.64E-04 -79.90 0.8264 -58.44 0.1371 -55.94 Without control 0.0172 - 0.0054 - 2.058 - 0.4332 -

N = 0.05 W 0.0069 -59.88 0.0015 -72.22 0.9626 -53.23 0.145 -66.53

Friuli N = 0.10 W 0.0062 -63.95 0.0011 -79.63 1.0231 -50.29 0.1308 -69.81

N = 0.15 W 0.0063 -63.37 8.63E-04 -84.01 1.1056 -46.28 0.1263 -70.84

N = 0.20 W 0.005 -70.93 6.98E-04 -87.08 0.9873 -52.03 0.1237 -71.45

Without control 0,0203 - 0,0043 - 2,3845 - 0,3395 -

N = 0.05 W 0.0066 -67.49 0.0011 -74.42 0.9874 -58.59 0.1084 -68.07

Hollister N = 0.10 W 0.0048 -76.35 6.42E-04 -85.08 0.7878 -66.96 0.0822 -75.79

N = 0.15 W 0.0043 -78.82 5.12E-04 -88.10 0.8287 -65.25 0.0848 -75.02

N = 0.20 W 0.0038 -81.28 4.31E-04 -89.98 0.8016 -66.38 0.0797 -76.52

Without control 0.0164 - 0.0039 - 1.9 - 0.314 -

N = 0.05 W 0.012 -26.83 0.0013 -66.67 1.5529 -18.27 0.1206 -61.59

Imperial

N = 0.10 W 0.0086 -47.56 9.02E-04 -76.86 1.2303 -35.25 0.1036 -67.01 Valley

N = 0.15 W 0.0064 -60.98 7.20E-04 -81.54 1.1427 -39.86 0.105 -66.56

N = 0.20 W 0.0046 -71.95 5.78E-04 -85.18 0.9368 -50.69 0.11 -64.97

Without control 0.0184 - 0.0046 - 2.1883 - 0.5103 -

N = 0.05 W 0.0115 -37.50 0.0015 -67.39 1.5609 -28.67 0.1934 -62.10

Kobe N = 0.10 W 0.0088 -52.17 0.001 -78.26 1.3051 -40.36 0.1568 -69.27

N = 0.15 W 0.0056 -69.57 6.23E-04 -86.46 1.0228 -53.26 0.1214 -76.21

N = 0.20 W 0.0032 -82.61 3.56E-04 -92.26 0.7462 -65.90 0.1017 -80.07

Without control 0.0204 - 0.0039 - 2.4046 - 0.3957 -

N = 0.05 W 0.0121 -40.69 0.0013 -66.67 1.5852 -34.08 0.1576-60.17

Kocaeli N = 0.10 W 0.0095 -53.43 8.75E-04 -77.57 1.3803 -42.60 0.127 -67.90

N = 0.15 W 0.0085 -58.33 6.34E-04 -83.75 1.3896 -42.21 0.1161 -70.66

N = 0.20 W 0.0073 -64.22 5.04E-04 -87.07 1.2802 -46.76 0.1195 -69.80

Without control 0.0204 - 0.0046 - 2.4506 - 0.4486 -

N = 0.05 W 0.0141 -30.88 0.0018 -60.87 1.7755 -27.55 0.202 -54.97

Landers N = 0.10 W 0.0104 -49.02 0.0014 -69.57 1.4591 -40.46 0.1904 -57.56

N = 0.15 W 0.0085 -58.33 0.0011 -76.09 1.4288 -41.70 0.1808 -59.70

N = 0.20 W 0.0064 -68.63 9.12E-04 -80.18 1.1644 -52.49 0.1807 -59.72

Without control 0.0159 - 0.0075 - 1.9248 - 0.4493 -

N = 0.05 W 0.0089 -44.03 0.0026 -65.33 1.1889 -38.23 0.153 -65.95

Mexico N = 0.10 W 0.0068 -57.23 0.0017 -77.33 1.0774 -44.03 0.1213 -73.00

N = 0.15 W 0.0057 -64.15 0.0012 -84.00 1.0266 -46.66 0.1091 -75.72

N = 0.20 W 0.0044 -72.33 9.27E-04 -87.64 0.8768 -54.45 0.1061 -76.39

San No control 0.0154 - 0.0049 - 1.9446 - 0.3327 - Fernando N = 0.05 W 0.0136 -11.69 0.0029 -40.82 1,7492 -10.05 0.2161 -35.05

N = 0.10 W 0.0116 -24.68 0.0021 -57.14 1.6957 -12.80 0.1841 -44.66

N = 0.15 W 0.0113 -26.62 0.0018 -63.27 1.7102 -12.05 0.1735 -47.85

N = 0.20 W 0.0102 -33.77 0.0015 -69.39 1.6432 -15.50 0.163 -51.01

As shown in Table 2, the displacements of the structure are strongly reduced for all cases of normal force applied, even reaching reductions in the maximum displacement of 82%, in the case of the Kobe Earthquake, with a normal force equal to 20% of the weight of the structure. In the maximum acceleration value, reductions of up to 66% are obtained, the minimum reduction being 10%. The reduction in rms value is greater than 40% in all cases. These results demonstrate the effectiveness in reducing the dynamic response of the vibration control system of the present invention.

As representative examples, Figs. 6 and 7 show the records of displacements and absolute accelerations, measured in the lintel of the structure, obtained with and without vibration control for the seismic records of Imperial Valley and Kobe, respectively. It can be seen how the structural response of the main structure is significantly reduced.

Claims

1. A multiple friction energy dissipation device, to control the dynamic response in terms of displacements and accelerations, both in new and rehabilitated structures, where the device comprises at least one column which is surrounded by multiple friction skates, which are held together by means of fastening bolts, further comprising at least one axial load regulator mounted on a plurality of compression springs, said regulator being secured by means of high strength screws.

2. The device according to claim 1, wherein the friction skates are dry defriction skates.

3. The device according to claim 1, wherein said multiple friction skates form a set of skates stacked together.

4. The device according to claim 1, comprising for mounting a fastening system by screws between the column and the friction skates.

5. The device according to claim 1 comprising at least two columns, preferably three or more columns each surrounded by multiple friction skates.

6. The device according to any of the preceding claims, wherein the device is subject to an adjustable axial or normal precompression load exerted by said axial load regulator.

7. The device according to any of the preceding claims, wherein said friction skates can move horizontally generating frictional forces that dissipate energy and resist horizontal movement.

The device according to any of the preceding claims, wherein the contact between the column and each skate is made by means of a fixing means comprising a toroidal ring fixed to the column which rests on the internal cylindrical surface of each skate. .

9. The device according to claim 6, wherein the adjustable axial or normal precompression load is applied from the upper or lower end of the multi-skid assembly by means of at least four pre-compressed springs.

10. The device according to claim 9, wherein said adjustable pre-compressed axial or normal load is adjusted by means of pre-compressed springs and high strength screws.