WO2017141083A1

WO2017141083A1 - Multi-tapered yielding plate energy dissipater

Info

Publication number: WO2017141083A1
Application number: PCT/IB2016/052352
Authority: WO
Inventors: Seyed Sasan ALAVI SHIRKHORSHIDI; Mahmood HOSSEINI
Original assignee: Alavi Shirkhorshidi Seyed Sasan; Hosseini Mahmood
Priority date: 2016-02-15
Filing date: 2016-04-26
Publication date: 2017-08-24

Abstract

Most of current seismic design codes accept heavy damages to the building in case of large earthquakes, provided that the building is prevented against collapse. However, this acceptance leads to some unacceptable consequences in populated cities, like very great number of people who lose their residence or work place for very long time. To overcome these difficulties one approach is design of 'repairable structures' for buildings, by using the idea of 'Directed Damage Design' (DDD), which means guiding the damage to some pre-decided parts or elements of the structural system, so that other parts do not experience any plastic deformation. This invention is based on the DDD idea, making it possible to have repairable steel buildings based on creation of building's rocking motion possibility rather than its shear deformation, by using a central hinge support and circumferential energy dissipating columns at base level. Energy dissipation is done by a Multiple Tapered Yielding Plate Energy Dissipating (MTYPED) device, installed at the bottom of the column, which creates a type of hysteretic behavior in axial deformation of columns. By performing a set of laboratory tests on MTYPED devices their hysteretic behavior were assessed from which their initial stiffness as well as their yielding strength were obtained, and then they were modeled in a real size building by using nonlinear springs, and a series of nonlinear time history analysis were performed on both rocking building and the conventional building with the same geometry. Results show that the proposed rocking system equipped with MTYPED devices not only gives the building a longer natural period, leading to lower seismic demand, but also leads to remarkable energy dissipation capacity in the building structure at base level, and therefore, keeping the seismic drifts in elastic range in all stories of the building above the ground floor, so that the building structure does not need any major repair work after a large earthquake. This is while the conventional building suffers from heavy damage and needs to be demolished after an earthquake.

Description

Invention Description

1- Invention Title

Multi-Tapered Yielding Plate Energy Dissipater (MTYPED)

2- The Usage Field

Earthquake Engineering, Structural Engineering

3- The Aim of the Invention

The Seismic Design Codes mostly accept some level of damage to structures, including buildings systems, subjected to severe earthquakes, so that after the event the building is not repairable and has to be demolished and replaced by a new one. To make the buildings and other similar structures repairable, even after a major earthquake, it is necessary to have some replaceable energy dissipaters to be used in a structure with rocking or seesaw motion under the columns of the lowest story.

4- Background of Energy Dissipating Devices in Structures

Energy dissipaters have been introduced since mid 70s in Earthquake Engineering field, and several types (including ADAS and TADAS) have been proposed by researchers so far. However, these devices are located mostly between the bracing elements and beams, so that energy dissipation can take place by them only if remarkable deformation occurs in the body of the structural systems (Figure 1 ).

Figure 1 - The ADAS device in a simple frame

This means structural damage, which can be so high, in case of severe earthquake, which make it necessary to demolish the whole structure for its replacement. This is while in the invented device introduced here the main elements of the structural system remain elastic and large deformations only occur in the MTYPED devices installed at the bottom of columns at the lowest story, as depicted in the next section.

5- Advantages of the Invented Device

The invented device in its simplest form is consisted of an outer box, and inner box and some tapered plates as shown in Figure 2.

Figure 2- Simplest form of the MTYPED device

As it is seen in Figure 2, the MTYPED device has three main components, and can be easily manufactured and used in structural systems. In case of building structures the outer boxes are connected to the foundation, and the columns' base plates are installed at the top of the inner boxes. Figure 3 shows the usage of the MTYPED device in a building structure with seesaw motion.

Figure 3- a) Using the MTYPED device, modeled as multi-linear links, in a building structure with seesaw motion, and b) Seesaw motion of a building frame

The tapered yielding plates can be easily replaced by new ones, after a major earthquake, if necessary. For this purpose by using some jacks the inclined structure is placed back to its original upright position and then each MTYPED-equipped column is pushed up a few millimeters, by using jacks, and the distorted tapered plates are removed and new one are placed.

As it can be realized from the structural frame shown in Figure 3-b, thanks to the high deformation and energy absorption of the MTYPED devices the main structural elements remains basically elastic. On this basis, the buildings with seesaw structural system equipped with MTYPED devices will act in Immediate Occupancy performance level, even after major earthquakes. The MTYPED device has been tested under vertical cyclic loading as shown in Figure 4, and has shown a very stable and appropriate hysteretic behavior.

Figure 4- a) Testing the MTYPED device under cyclic loading, and b) The resulted force-displacement hysteretic loops of the device

As it is observed in Figure 4-b, the MTYPED device can tolerate several cycles of loading there is no low-cycle fatigue in the MTYPED device has been tested under vertical cyclic loading as shown in Figure 4, and has shown a very stable and appropriate hysteretic behavior.

Claims

Claim

Hereby we, Seyed Sasan Alavi having ID No. 0067402666 born in 16 July 1983 in Tehran, Iran, and Mahmood Hosseini having ID No. 1262231906 born in 22 December 1960 in Kashan, Iran claim that the Energy Dissipater Device for Seismic Protection of Structures with the following components and specifications is our invention.

Components of the Invented Device:

1 - The Outer Box, having a square, round or polygon plan, depending on the usage, and made of steel plates with a specific thickness depending on the amount of load imposing on it. (This load itself is a function of the size of the structure in which the device will be used as an energy dissipater.)

2- The Core or Inner Box, being almost half-size of the Outer Box, and plan shape consistent with it, made of steel plates with a specific thickness depending on the amount of load imposing on it.

3- Tapered Yielding Plates, having trapezoidal form or similar, made of low-carbon steel, and it thickness depends on the imposed load.

Device Specifications:

• It can be made and assembled by using the common tools in steel workshops.

• There is no need to advanced technology for its installation.

• The yielding plates, as the main energy dissipation sources, can be replaced easily by new ones after a major earthquake, if required.

• The stiffness and the strength of the device can be adjusted independently to make it appropriate for various structural systems, including building systems, depending on the design needs.

• The number of yielding plates can be adjusted to create the possibility of various amounts of energy dissipation, depending on structure size and the seismic design requirements.

• The manufacturing cost of the device is very low comparing to other energy dissipaters used in seismic protection of structures

Manufacturing Technique:

The plates required for making the outer and inner boxes are cut and the required slits are created in them, then the plates of outer box are connected together by welding, and the same is done for the plates of the inner box. In the next stage the inner box is held in the proper position by a hand crane or hand winch, and the tapered plates are placed in the corresponding slits and are fixed firmly.