Scholarly article on topic 'Investigation on Dynamics Nonlinear Analysis of Steel Frames with Steel Dampers'

Investigation on Dynamics Nonlinear Analysis of Steel Frames with Steel Dampers Academic research paper on "Civil engineering"

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Procedia Engineering
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{"Dynamics analysis" / "ADAS damper" / Retrofitting / "Moment resistant frame (MRF)."}

Abstract of research paper on Civil engineering, author of scientific article — M. Khazaei

Abstract Latest experiment shows most of steel structures are damageable against earthquake in IRAN. One way to retrofit the existing structures is the energy dissipater dampers using the Added Damping And Stiffness elements abbreviate ADAS system. This system has significant advantage such as insensitive to heat and environmental agents, reliable and stable behavior and appropriate resistance, made them in the focus of researcher around the world. In this research investigation on the structural behavior of steel frames equipped with ADAS system is conducted in the three different stories 4,8,12. More investigation based on nonlinear dynamics analysis with three earthquake records of Tabas, Northridge, El Centro. Result shows shear force in some floors of frames including ADAS damper reduces in comparison to the frames just only with braces. By increasing number of floors, we observe more uniform displacements, appropriate energy distribution in the frames with ADAS systems.

Academic research paper on topic "Investigation on Dynamics Nonlinear Analysis of Steel Frames with Steel Dampers"

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Procedía Engineering

ELSEVIER

Procedía Engineering 54 (2013) 401 - 412

www.elsevier.com/locate/procedia

The 2nd International Conference on Rehabilitation and Maintenance in Civil Engineering

Investigation on Dynamics Nonlinear Analysis of Steel Frames with Steel

Dampers

M. Khazaeia*

Latest experiment shows most of steel structures are damageable against earthquake in IRAN. One way to retrofit the existing structures is the energy dissipater dampers using the Added Damping And Stiffness elements abbreviate ADAS system. This system has significant advantage such as insensitive to heat and environmental agents, reliable and stable behavior and appropriate resistance, made them in the focus of researcher around the world. In this research investigation on the structural behavior of steel frames equipped with ADAS system is conducted in the three different stories 4,8,12. More investigation based on nonlinear dynamics analysis with three earthquake records of Tabas, Northridge, El Centro. Result shows shear force in some floors of frames including ADAS damper reduces in comparison to the frames just only with braces. By increasing number of floors, we observe more uniform displacements , appropriate energy distribution in the frames with ADAS systems.

© 2013The Authors. Publis hed by Elsevier Ltd.

Selection and peer- review under responsibili ty of Department of Civil Engineeri ng, Sebelas Maret University Keywords: dynamics analysis; ADAS damper; retrofitting; moment resistant frame (MRF).

1. Introduction

Stability and resistance of structures due to earthquake important and essential matter in Iran as it is located on Alp-Himalaya earthquake belt. Steel moment frames, are used normally as its ability to overcome the architectural problems. Although these structures have a suitable ductility, they don't have enough stifiness which results increasing lateral displacements, for controlling "lateral displacements", we have to

* Corresponding author.

E-mail address: mohsen_khazaei@yahoo.com

Civil Engineering Quchan Institute of Engineering and Technology, Iran

Abstract

1877-7058 © 2013 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of Department of Civil Engineering, Sebelas Maret University doi: 10.1016/j.proeng.2013.03.036

increasing the beams and columns sections which is not economic. As important the lateral displacement control retrofitting of structures with steel moment frames are requested by their owners. Concentric Braces are usually used for controlling the lateral displacement of moment frame steel structures, but using of these members decrease the ductility of structures. For removing the fault the frames were retrofitted with two different systems, concentric brace and ADAS.As well as The rate of energy dissipation and the performance of the abovementioned frames have been studied. In the recent years, in some countries such as the U.S.A., Mexico, Italy and New Zealand, energy dissipate systems (dampers) are commonly used as reliable systems in retrofitting buildings against earthquake. ADAS (Added Damping and Stiffness) is a kind of energy dissipation elements which have been formed from several steel plates similar to cross-section of sandglass (Soong and Dargush 1997).

In this article, the behaviour of 6 intermediates steel moment frames which were retrofitted By ADAS; CBF brace are studied and compared with initial structure. The steel frames have different height and bays. The behaviour of structures are studied using nonlinear dynamics analysis of frames under 3 records and compare results of frames with damper, without it.

2. ADAS (Added Damping and Stiffness)

Added Damping and Stiffness (ADAS) elements are designed to dissipate energy thought the flexural yielding deformation of mild-steel plates. ADAS elements consist of multiple X-shaped mild steel plates configured in parallel between top and bottom boundary connections(fig.1,2).The particular advantage of an X-plated is that, when deformed in double curvature, the plate deformation is uniform over its height, and when deformed into its plastic regime, the yielding will be distributed rectangular plate, when deformed plastically in double curvature, will yield only at its ends. This concentration is particularly undesirable both in

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Figure 1. ADAS device

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Figure 2. Hysteretic behaviour of ADAS device

Terms of the amount of energy that can be absorbed by such a deformation pattern and by its inherent lack of stability and repeatability in the plastic range. The X-plate is a development from triangular plate devices, which were developed in New Zealand(Tyler 1978; Boardman,1983) and was first developed as a piping support element(Steimer1980 and 1981).X-plates have been used as the energy dissipating component isolation system in shake table tests(Steimer,1984)(IanD et al. 1993).

Shear stiffness of story (Ks), ADAS shear stiffness (Ke), brace stiffness, and SR and B/D are parameters that play a significant role in frames equipped with such dampers. B/D and SR parameters are defined as the ratio of brace stiffness to damper stiffness and damper stiffness to story stiffness respectively the suggested values of which are commonly 2 and 3 respectively(Xia and Hanson 1992; Xia 1990).

3. The Introduction of under Study Frames

In the present research paper, 12 frames with intermediates steel moment frame system which have been designed but don't satisfy lateral displacement necessities of Iranian 2800 code, i.e. equation No.1[9], in order words, the frames were faced with lateral displacement more than the permitted limit, have been retrofitted by two elements resistant to earthquake, CBF brace and ADAS element. The number of stories of frames has been chosen 4,8 and 12 with 3 and 5 bays. The frames belong to buildings with occupational application and the same bays of 4 meter. and the height of stories of 3 meter . The equal element between these completing systems is "weight". The position of building is relatively high hazard region and has type II soil. The considered roof type is joist and block. Dead and live loads of stories is calculated 600 and 200 ks/ respectively. IPB sections are used for columns and IPE sections for beams and

double channel sections are used for braces. Initial moment frames have the same sections and weights. For brief nomenclature of frames RiXj and RiAj indices have been used. R for moment frame, X and A for frames retrofitted with concentric brace and ADAS are used respectively. i and j indicate the number of stories and bays(Permanent Committee of Revising the code of Designing Buildings Against Earthquake issued by the Building & Housing Research Center 2005; Code national

building, six discussion, Loads imposed on building, office to develop and promote national building regulation1996; Code national building, ten discussion, design of steel structures, office to develop and promote national building regulation2000).

I*! L*i

Figure3. Frames retrofitted by CBF

Figure4. Frames retrofitted by ADAS damper

AM= 0.7^< {J AM: Real relative lateral displacement of project in the story

("0.025// T < 0.7 10.02// T > 0.7

AW : Relative lateral displacement of project in the story

R : Coefficient of structure behaviour T: Main period of the building H: Story height

4. Records

At the nonlinear dynamic analysis with time history method, in attention to type of record change nonlinear response of structures.therefore it's better to use more records as much as possible.According to Iran retrofit ting's Code is necessary to use three records for analysis at least. If it's be used lower than seven records, then our response will be maximum of responses, otherwise will be average of responses.In this research in order to analysis, we use natural earthquake records that for scaling them, was utilized Iran Standard's Code (2800)(Permanent Committee of Revising the code of Designing Buildings Against Earthquake issued by the Building & Housing Research Center 2005; Code national building, six discussion, Loads imposed on building, office to develop and promote national building regulation 1996; Code national building, ten

discussion, design of steel structures, office to develop and promote national building regulation 2000).

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0.4 0.3 0.2 0.1 0 -0.1 -0.2 -0.3 -0.4

Figure 5. Records

Table 1. Characterized of records used in nonlinear dynamics analysis

Record name year PGA(g) time Step(sec)

TABAS 1978 0.313 32.82 0.02

Northridge 1994 0.836 39.98 0.02

El Centro 1940 0.344 39.99 0.01

5. Calibration of Model in the CSI-PERFORM Software

In order to reliability of performance for the CSI-PERFORM software and accuracy of input data for program too, for steel frame with %5 damping that it was impressed to the EL Centro record we compared the DRAIN2DX & the PERFORM 3D software together PERFORM Components And Elements For PERFORM-3D And PERFORM-Collapse, Version 4,CSI(Computers Structures) INC 2006).

6. Description of Selected Model

For accordance of analytic models with tested models, we used a frame with 3 story and 1 bay that exposed to earthquake and El Centro records for time history nonlinear analysis of the frame Three elements was used for energy absorption to reach to its yield point via a connection to the brace. For this selected model, the ADAS element was used for assessment of %5 damping at first mode.

Frame Elevation

Figure 6. Frames retrofitted by ADAS damper

7. Issue and Comparison

This model was analyzed in the DRAIN-2DX nonlinear analysis software. For accordance the selected model with the analytic model, we modelled a frame with the same specification in the PERFORM-3D software ,therefore time history dynamic analysis was accomplished on the model.ADAS's damping element modelled with the Seismic Isolator, Rubber element type in the PERFORM software (Code national building, six discussion, Loads imposed on building, office to develop and promote national building regulation1996), seeing to fig(7 ), we observed damping hysteresis diagram for the ADAS that obtained from two software , was almost similar together

(slop after the same yielding) and the similarity signify accuracy of the analytic results for this research at the PERFORM 3D software.

DBAIN2 DX

"1 .O -O.S O.O O.S 1 -O

Hysteresis ADAS 1 (PERFORM-3D)

-0,5 -0,25 0 0,25 0,5

Displacement (inch)

Figure 7. Compare results of software DRIAN-2DX jPERFORM for 3 story frame

8. Selected Models for Time History Dynamic Analysis

In this section for analysing of the time history comparative among different frames, we considered 4 frames with various bays & stories .Frames consist of bend frames, reinforced frame with X-shape brace reinforced frame with ADAS' damping &reinforced frame with Chevron brace. Numbers of bays are 3 &5 , stories are 4,6 & 12.for summarized in nomination of frames, we use isjb symbol that (S is abbreviation of story , b is bay &i,j present number of stories &bays respectively .)S,b,i,j are abbreviation of story , bay , number of stories &bays respectively say : 4s3b means 4stories & 3 bays frame .

Afterwards for instance time history analyse of frames was accomplished at nonlinear CSI-PE^O^M software. So ADAS's damper element modelized in CSI-PERFORM software with seismic,Isolator type .

9. Investigation Results of Story Base Shear

The values of retrofitting frames base shear with ADAS in short frames are between the value of retrofitting frame with concentric brace & frames with Chevron brace. while with attention to graphs we aimed with increase of stories , value of frame shear with damper is less than of frame with brace .In graphs shear of stories with damping is

lessen of stories with chevron brace .& this decrease is due to factors like capacity of energy absorption .

Figure 8. Story Base Shear 15s5b,12s5b

10. Investigation Results of Story Displacement

For ADAS's damper frames, nonlinear deflection was majority concentrated in ADAS device that cause to increase hysteresis energy absorption of structure without large deflect, also results signify lack of create large deflective in the members of structure & due to the distribution of the displacement at structures height. Diverse frames with brace that observe jumping's(at displacement graph of them).

Figure 9. Story displacement,drift15S5B,12S3B

11. Energy Absorption in Members of Frames

Graphs show excellent performance of yielding dampers at dissipation of input energy. Indeed more percentage of input energy dissipate in dampers. Too, high energy absorption in frame by damper representative was stained in elastic manner or with the slight (little) nonlinear the members of structural.Deflection & minimizing damage of structures,non structures in building and damage concentration in systems retrofitting with metal dampers because of the dampers are replaceable in strong earthquake, without change of workable, can substitute them with another one easily.

Figure 10. Input and dissipated energy by ADAS in frames 4S3B Table 2. Percentage of energy dissipated by chevron brace, damper

Record type Percentage of energy dissipated by damper Percentage of energy dissipated by Chevron brace

TABAS 81% 40%

Northridge 86% 25%

El Centro 85% 70%

12. Dissipated of Energy of Dampers

Hysteresis suitable performance of yielding damper is Favourites specification that indicating process of energy dissipate on it. Whatever integrated of hysteresis of damper to be large, demonstrate large energy dissipate.

Figure 11. Hysteretic diagram damper in 15S3B (a) , 12S5B (b)

13. Conclusion

1. Elements with suitable design dissipate ADAS Large hysteresis energy and limit displacement of story. Also with decrease energy requirement in structural members cause control of nonlinear displacement response frame by suitable design.

2. ADAS elements don't increase need of strength for frame except for members that keep the devise directly increase of yielding force for ADAS devise will cause increase of ADAS shear force, but will low effect on frame shear forces.

3. ADAS element will increase energy absorption capacity clearly, reduce energy need in the structural members. For medium or weak earthquake, concentred hysteresis energy absorption in the ADAS device, keep structure of members in the elastic manner for a strong earthquake. Reserve energy absorption capacity of the structural members that structure can equip for resistant to the earthquake without nonlinear deformation or damage of the nonlinear structure members

References

Code national building, six discussion, Loads imposed on building, office to develop and promote national building regulation,(1996).

Code national building, ten discussion, design of steel structures, office to develop and promote national building regulation,(2000).

IanD.Aikan,DouglasK.Nims,AnddrewS.Whittaker,and JamesM.Kelly(1993). Testing of Passive Energy Dissipation Systems, Earthquake Spectra journal,9(2).

PERFORM Components And Elements For PERFORM-3D And PERFORM-Collapse, Version

4,CSI(Computers Structures) INC ,August (2006).

Permanent Committee of Revising the code of Designing Buildings Against Earthquake issued by the Building & Housing Research Center ,code of Designing Buildings Against Earthquake- Standard 2800, the Third Edition ,2005.

T.T.Soong,G.F.Dargush (1997),Passive Energy Dissipation Systems in Structural Engineering,JOHNWILEY&SONS at Buffalo,USA,.

Xia. Chuan(1990), A study of ADAS element parameters and their influence on earthquake response of building structures, thesis Ph.D., The University of Michigan,.

Xia,C.,& Hanson R(1992)..Influence of ADAS Elements Parameters on Building Seismic Response,ASCE Journal,18(6),pp 1903-1918.