static and dynamic cyclic performance of a low-yield-strength

7/26/2019 Static and Dynamic Cyclic Performance of a Low-yield-strength

1/9

Static and dynamic cyclic performance of a low-yield-strength steel shear

panel damper

Zhang Chaofeng a,, Zhang Zhisheng b, Zhang Qiujua

a School of Mechanical Engineering, Jiangnan University, Chinab School of Mechanical Engineering, Southeast University, China

a b s t r a c ta r t i c l e i n f o

Article history:

Received 20 April 2012Accepted 30 July 2012

Available online 31 August 2012

Keywords:

Low-yield-strength steel

Shear panel damper

Static and dynamic tests

Strain rate

Temperature

Lowcycle fatigue

Low-yield-strength steel 100 (LYS100) is widely applied to design a metallic shear panel damper for its high

ductility. A low-yield-strength steel shear panel damper (LYSPD) with the maximum shear strain of 70% is

developed and veried by static incremental cyclic loading in previous research. In this paper, further re-

search on the performances of the developed LYSPD including the fatigue characteristic is carried out by static

and dynamic constant cyclic tests. Four different shear strain amplitudes (20%, 30%, 40% and 50%) are selected

in both static and dynamic tests. Two frequencies, 0.5 Hz and 1 Hz, are adopted for each of the four ampli-

tudes in dynamic tests. Large differences such as stress softening, fatigue cycle deterioration, and tempera-

ture increase caused by high strain rate and internal friction are observed in dynamic tests. The test results

suggest that the seismic performance of the LYSPD may be overestimated by static tests and the dynamic

tests are essential to guarantee the reliability of the LYSPD.

2012 Elsevier Ltd. All rights reserved.

1. Introduction

Shear panel dampers (SPD) are widely developed to dissipate theenergy and to reduce or avoid the damage of the primary structures

such as bridge and building, as demonstrated in Fig. 1[1,2]. Generally

speaking, the passive metallic damper for seismic applications in struc-

ture must exhibit: a) adequate elastic stiffnessto withstand small earth-

quake and wind; b) yield strength not exceeding that of the structure;

c) high energy absorbability; d) stable hysteretic force-displacement

response which can be modeled easily; e) good low-cycle fatigue per-

formance. As the low-yield-strength steel 100 (LYS100, yield strength

100 N/mm2) possesses such merits as low yield strength, large defor-

mation capacity and good low-cycle fatigue performance, it is undoubt-

edly a proper metallic material for SPD[35].

Failure in the LYSPD caused by repeated loadsis typically attributedto

the accumulation of a small number of cycles of large amplitude strains,

which are normally considered within the plastic range for the gross

section. Tensioncompression cyclic tests are conducted on LYS100 for

investigating the stressstrain behavior within the plastic range and the

potential low-cycle fatigue characteristics in most researches[6,7]. How-

ever, the performance of the LYSPD would be affected by the stress con-

centration resulting from the emergence of the out-of-plane buckling,

the formation of tension eld and the material deterioration caused by

welding and so on. That means the fatigue performance of material

LYS100 can't reect the real fatigue performance of the LYSPD. Therefore,

the LYSPD mechanical properties and low-cycle fatigue characteristics

should be veried by tests directly. On the other hand, for the limitation

of test equipments, the full-scale LYSPD cyclic tests are concentrated on

static tests currently [8,9]. However, the temperature of the steelLYS100 will increase for the high speed loading and internal friction.

And the stressstrain relation would also be affected by high temperature

[10,11]. To understand the performance of the LYSPD under dynamic

loading and improve the credibility of application, the dynamic cyclic

tests are put forward in this paper.

Recently, extensive experimental research has been undertaken at

the Seismic Research Center of Aichi Institute of Technology in Japan

in order to investigate the energy dissipation capacity (deformation

capacity) of shear panels made from LYS100. A compact LYSPD serv-

ing as the bridge damper, with 70% shear strain (horizontal displace-

ment/height) which is the largest deformation capacity at present in

the world[12], is developed and veried by 5% shear strain static

incremental hysteretic loading. Here, further investigation on the

static and dynamic hysteretic performance of the developed LYSPD

is attached importance on. Useful information taken as the prelimi-

nary design references such as mechanical properties and low-cycle

fatigue are provided, compared and discussed based on constant stat-

ic and dynamic tests.

2. Specimen details and test setup

2.1. Specimen

Tensile coupon tests for LYS100 are conducted and the obtained

stressstrain curves are shown inFig. 2. The yield strength y dened

by the 0.2% offset value of LYS100 0.2is 100 N/mm2 and the elongation

Journal of Constructional Steel Research 79 (2012) 195203

Corresponding author. Tel.: +86 183 5150 0918.

E-mail address:[email protected](C. Zhang).

0143-974X/$ see front matter 2012 Elsevier Ltd. All rights reserved.

http://dx.doi.org/10.1016/j.jcsr.2012.07.030

Contents lists available at SciVerse ScienceDirect

Journal of Constructional Steel Research
http://dx.doi.org/10.1016/j.jcsr.2012.07.030http://dx.doi.org/10.1016/j.jcsr.2012.07.030http://dx.doi.org/10.1016/j.jcsr.2012.07.030mailto:[email protected]://dx.doi.org/10.1016/j.jcsr.2012.07.030http://www.sciencedirect.com/science/journal/0143974Xhttp://www.sciencedirect.com/science/journal/0143974Xhttp://dx.doi.org/10.1016/j.jcsr.2012.07.030mailto:[email protected]://dx.doi.org/10.1016/j.jcsr.2012.07.030


2/9

reaches 60%, which is about 3 times larger than that of SS400 ordinary

steel. The correspondingyield shear strengthy 0:2=ffiffiffi

3p

is 57.7 N/mm2.

The shape and size of specimen are shown inFig. 3(a). Except the

welding seam (width 10 mm) located at left and right sides of the

panel, the pure size of the shear panel that cuts from 24 mm to

12 mm at the center of the original panel is characterized with height

d=120 mm and width w=160 mm respectively. The yield shear

force Fy y w t is 110 kN. The width/thickness ratio Rw is de-ned as follows

Rww

t

ffiffiffiffiffiffiffiffiffiffiffi ffiffiffiffiffiffiffiffiffiffiffiffi ffiffiffiffiffi12 12

y

k2E

s 1

an expression widely known where Eis the modulus of elasticity (=

206103 N/mm2), is Poisson's ratio (=0.3), t (=12 mm) and

w are the thickness and the width of the shear panel respectively.

The coefcient k, known as shear buckling coefcient, depends on

k 5:35 4:0 w=d 2 w=d1 2

k 5:35 w=d 2 4:0 w=d1 3

as w=d 1:29 is larger than 1 in this study, the width/thickness ratioR of the shear panel is only 0.065 according to Eqs. (1) and (3). 0.065

is a fairly small value compared with that of in the previous re-

searches. Under this circumstance, the out-of-plane buckling is not

prone to producing. At the same time, the cracks at four panel corners

resulting from the stress concentration under the hysteretic loading

are observed.

Ribs are widely applied to the design of the shear panels or other

structures for the purpose of improvingthe stressconcentration located

at the corners. Although the stress concentration could be improved

when the shear angle is small, the rib ends are easy to crack under the

hysteretic loading with large shear angle for the material deterioration

resulting from welding. Moreover, the stress concentration at panelfour corners would be more serious for the existence of welding inter-

sections. Taking these two points into consideration, two stiffeners

(thickness t=24 mm, height h=50 mm) at the up and down sides of

the panel are shapedfrom original panel insteadof welding. Local plas-

tic hingesat the corners of effective panel area are separated from the

rib ends by this optimization. In addition, in order to prevent the stress

concentration caused by sharp variable cross-section, the arcs with

47 mm radius are introduced to connect two different panel thick-

nesses. The ribs are the thin panels that are also made from LYS100

with length 266 mm, width 72 mm and thickness 12 mm. The defor-

mation capacity of the shear panel can reach 70% shear strain by theop-

timization[12].

As shown in Fig. 3(b, c), a link mechanism (test xture) is also

designed to simulate the separation function and suppress the bending

moment when the horizontal force acts on the LYSPD. The shear panel

is welded to the top and bottom beams. Except that the material of the

link is SM490, the other material of link mechanism is made from

SS400.The LYSPD isxed on the bottomx plate by 12M24 high strength

bolts and the seismic function could be recovered after the earthquake as

soon as possible because it is very easy to be replaced or re-centered.

2.2. Test setup

As shown inFig. 4, one head of the 100 t MTS dynamic actuator is

xed on the back strength wall and another head is connected with the

beam that can move horizontally. Two counterforce devices are installed

on the beam to provide the force acting on the topside of the LYSPD.

2.3. Measurement equipment

In this experiment, force is measured through the actuator load cell

(precision 0.5 kN) and displacement is measured through laser exten-

someters (laser extensometer precision 0. 05 mm). In order to eliminate

the errors causedby test equipmentto secure the accurate dataof damper

horizontal displacement, two laser extensometers (LEX1 and LEX2) are

used to measure the horizontal displacement at the LYSPD's top and bot-

tom beams. The difference of the LEX1 and LEX2 values is taken as thepure horizontal displacement of the LYSPD. Furthermore, the tempera-

ture of the LYSPD is measured by non-contact temperature sensor

TH6300R on real-time.

2.4. Test plan

The horizontal displacement/panel effective height is dened as shear

strain . The waveforms are applied with constant amplitudes of 20%,

30%, 40% and 50% shear strain respectively in both static and dynamic

tests. One example of the loading pattern when the shear strain is 50%

(displacement 60 mm) is illustrated in Fig. 5. The cycles arefully reversed

with strain ratio R= min/max =1 and only varies in shear strain

amplitude and shear strain rate v. The shear strain rate v of

quasi-static loading is 0.4%/s (0.5 mm/s). Two kinds of frequencies0.5 Hz and 1 Hz that represent the typical vibrationfrequencies of bridge

systems are selected as the dynamic loading frequencies[13].

The notation of the static specimen is composed of the abbreviation

of static (ST) and shear strain amplitude (20% simplied as 20) such as

ST20. The notation of the dynamic specimen is characterized by the ab-

breviation of dynamic (D), frequency (0.5 Hz simplied as 05) and

shear strain amplitude (20%simplied as 20) suchas D05-20. The detail

loading information of the twelve specimens is listed inTable 1.

(a) Bridge (b) Building

Pier

Superstructure

Fig. 1.Application of the SPD.

0 20 40 600

100

200

300

400

500

Stress(

kN/mm)

Strain (%)

SS400

LYS100

Fig. 2.Tensile coupon experiment results.

196 C. Zhang et al. / Journal of Constructional Steel Research 79 (2012) 195203


3/9

3. Results and discussion

3.1. Hysteretic characteristic

The static and dynamic force-shear strain hysteretic curves are

shown inFig. 6. X axis represents shear strain amplitude while Y

axis represents shear force. The rst row ofFig. 6is the static hys-

teretic curves and the shear strain amplitude is in ascending order.

The dynamic results of frequency 0.5 Hz and 1 Hz follow as the

second row and the third row respectively. The shape of static hys-

teretic curves is demonstrated as spindle while the appearance of

dynamic hysteretic curves is showed as rectangular approximate-

ly. Since the maximum damper force (MDF) at the maximum

damper displacement (MDD) in each cycle is slightly larger than

the damper force when the displacement is 0 in static test, this dif-

ference is negligible. The maximum damper force can be taken as

the effective damper force of the plastic range and both static anddynamic hysteretic curves could be nearly modeled as perfect

elasticplastic.

Except the rst cycle, the MDFs at two loading directions are nearly

the same from the second cycle in all of the specimens which exhibit

good symmetry without the occurrence of Bauschinger effect. Therefore,

the MDF histories at the positive loading direction, within each cycle

recorded during the 12 individual tests of three types of loading frequen-

cies, are plotted in Fig. 7 for comparison. The damper forces all increase in

the MDFs of both static and dynamic tests during the rst cycle. And the

MDFs also increase with the increase of the shear strain. Subsequently,

the distinct difference of MDF histories between static and dynamic

tests is observed from the second cycle. The MDFs show as a constant

in static tests with the increase of cycles before cracking (Fig. 7(a))

while they decrease linearly with the increase of cycles in dynamic tests(Fig. 7(b) and (c)).

3.1.1. Damper force history of the rst cycle

3.1.1.1. Strain hardening under virgin loading. In general, responding to the

rst reversal of the loading pattern (Fig. 5), the cyclic response of the

shear panels follows hysteretic stressstrain behavior starting witha pos-

itive shear excursion that includes the transition from elastic to plastic.

Strain hardening, when stress increases with the increase of shear strain,

is ordinarily observed in most researches in this stage under virgin load-

ing. Therefore, the forces at the rst reversal of the loading pattern are

usually the rst quarter cycle maximum damper forces (MDFq, the rst

MDF at the positive direction) in the hystereticcurves. The MDFq of static

tests is illustrated as inFig. 8and it increases by 33% averagely when the

shear strain amplitude increases from 20% to 50%. Allof the useful test re-

sults are also listed inTable 2.

3.1.1.2. Strain rate hardening. Besides strain hardening observed in the

virgin loading stage, the strain rate hardening also emerges. The MDFqsof dynamic tests are generally higher than those of static tests ( Fig. 8

dash line). The strain rate hardening is distinct when the shear strain is

30% and 40% while it is small when the shear strains are 20% and 50%.

Compared with the MDFqof ST20, the strain rate hardening does not ap-

pear in D05-20 while it is observed in D10-20. It can be inferred that the

strain rate hardening is not signicant when the strain rate is low. In ad-

dition, there are no MDFqdifferences between static and dynamic tests

when the shear strain is 50%. It can be considered that there is small

room for the strain rate hardening when the shear strain amplitude is

too large. This phenomenon where the damper force remains as a con-

stant when the shear strain is larger than 50% is also observed in static

incremental hysteretic loading tests of previous study [12]. The MDFs

of D10-30 and D10-40 resulting from strain rate hardenings increase

nearly 20% in the dynamic loading tests on the basis of the results ofthe static tests.

(a)Dimension of shear panel (b) Panel with link mechanism (c)Side view

Fig. 3.Specimen details (units: mm).

Specimen

100t MTS ActuatorLoading beam

Fig. 4.Test setup.

197C. Zhang et al. / Journal of Constructional Steel Research 79 (2012) 195203


4/9

3.1.1.3. Cyclic hardening.The unloading from therst reversal to the sec-

ond reversal of the loading pattern (Fig. 5) follows the elastic slope and

initiates plastic behavior in negative shear at a cyclic negative shear

force that is larger than the MDFq. At the second reversal (Fig. 5), the

unloading again follows the elastic slope and initiates plastic behavior at

a cyclic positive MDF that is almost the same with the cyclic negative

MDF completing the rst cycle. That means the cyclic hardening mainly

occurs during therst reversal and the second reversal. The MDFs at the

end of the rst cycle (Fig. 8solid line) are about 3050% larger than that

of the MDFqs (Fig. 8dash line).

The strain hardening and cyclic hardening based on static test re-

sults have been already incorporated into the hysteretic model analysis

for predicting the damper strength accurately in most cases while the

strain rate hardening is seldom paid attention to. It is because the dy-

namic test devices are not popularized and the static test devices are

dominated in the test systems at present. However, seen from Fig. 8,

the strain rate hardening is still obviously at the end of the rst cycle.

Thus, it is essential to be taken into the consideration of MDF in the dy-

namic loading unless the loading speed is fairly small or the stress is

fully exerted under the large shear strain in the static tests.

3.1.2. MDF history from the second cycle

Typical structural components can dissipate the heat more efcient-

ly under low strain rate or proximity to elastic range. After reaching a

MDF in the rst cycle, the remaining cycles follow the trends of no

damper force increase caused by cyclic hardening and no damper

force deterioration caused by the slight developed warm temperatures

until failure in static tests. However, rapid working of the material

through plastic strainscan result in temperature increase that can inu-

ence the mechanical properties of the LYSPD. The temperature increase

caused by strain rate under the constant strain tests is shown inFig. 9.

Temperature increase rate is linear with the shear strain rate while it

has weak or no correlation with the shear strain amplitude. It could be

veried by two specimens D05-40 and D10-20. In these two experi-

ments, two different shear strain amplitudes 20% and 40% are chosen

respectively while the shear strain rates are the same. However, the

same temperature increase rate of these two specimens is observed.

Subsequentcycles of the same shear strain amplitude could result in

the MDFs less than the previous cycles from the second cycle, corre-

sponding to the stress softening caused by temperature in dynamic

tests. As the damper force deterioration is affected by high temperature

based on different shear strain rates, it is more convenient to establishthe relation between shear strain rate and damper force deterioration

directly. The relation between damper force decrease rate and shear

strain rate from the second cycle is shown inFig. 10. The linear relation

between damper force decrease rate and shear strain rate can be repre-

sented as follows:

Fv 0:17v4:8 40%=secbvb200%=sec; 20%bb50% : 4

3.1.3. Discussion on the damper hysteretic characteristic

After the displacement-base development obtained by improving

the deformation capacity of theLYSPD,the major challengeis thedesign

of rational and effective model for analyzing the hysteretic performance

that is capable of predicting the structural response. Two simplied

modes such as bi-linear force-displacement relation model and equiva-lent linearization model have been widelyincorporated in several codes

like Japan Road Association[13], AASHTO[14]and Eurocode 8[15].

3.1.3.1. Force-displacement bi-linear model.In both static and dynamic

tests, the majority of stress hardenings include strain hardening, cyclic

hardening, and strain rate hardening occurring within the rst cycle

and reaching the MDFs of each test. These hardenings can be simplied

and the force-displacement hysteretic curve could be modeled as per-

fect elasticplastic briey,as shown in Fig. 11. The elastic slope is decid-

ed according to the unloading part of hysteretic curve.

As mentioned above, theMDF in static incremental hysteretic curves

is a constant around 610 kN (5.5 times of Fy) when the shear strain is

larger than 50%. In addition, the MDFs are narrowed to a small range

around 610 kN when shear strain amplitude is larger than 30% in dy-namic tests with different loading frequencies (Fig. 8solid line). There-

fore, the effective damper force of the plastic range of the supposed

bi-linear model could be set as 610 kN approximately. On the other

hand, it is observed that the MDFs decrease dramatically after the sec-

ond cycle in constant dynamic tests when the shear strain amplitude

is 50%. Therefore, the damper hysteretic curves could be supposed as

perfect elastic-plastic without force deterioration if the cycle number

is no more than 3 cycles when the shear strain is larger than 50% in

the random wave. Furthermore, heat will be more easily be dissipated

in the random wave, and heat is absolutely overestimated in the con-

stant dynamic tests. Thus, whether the force deterioration should be

taken into consideration or not needs to be further veried by random

wave dynamic tests of the LYSPD which will be conducted in the next

research.

3.1.3.2. Equivalent linearization model.It is generally accepted that the

KelvinVoigt model is able to model the damping characteristics of hys-

teretic type dampers and to describe the energy dissipation of the spec-

imen vibrator system. For practical use it is sometimes more preferable

to express the device properties in an equivalent linearization system

[16,17]. This is basically a single degree of freedom oscillator with an ef-

fective stiffness Kefand an equivalent damping ratioeq.

A typical force-displacement hysteretic curve is shown inFig. 12,

the Kefand eqcould be obtained by static and dynamic constant ex-

perimental hysteretic curves. Kefand eqare dened as follows,

Kef MDFMDF

MDDMDD 5

0 10 20 30

-80

-60

-40

-20

0

20

40

60

80

Time(t)Displacement(mm)

first reversal

second reversal

Fig. 5.Loading pattern (=50%).

Table 1

Test plan.

Specimen f (Hz) T (Sec) (%) v(%/s)

Static (ST) ST20 20 0.4

ST30 30

ST40 40

ST50 50

Dynamic

(D05)

D05-20 0.5 2 20 40

D05-30 30 60

D05-40 40 80

D05-50 50 100

Dynamic

(D10)

D10-20 1.0 1 20 80

D10-30 30 120

D10-40 40 160

D10-50 50 200



5/9

eq 1

4W

W 6

where MDF+and MDFare the maximum damper force at positive

and negative directions, MDD+and MDD are the maximum damper

displacement at two opposite directions. W is the energy loose per

cycle represented by the area enclosed inside the hysteresis loop. W

is the energy stored in an elastic spring with a stiffness K efand MDD.

The equivalent stiffness Kef decreases when LYSPD undergoes

larger displacement in both static and dynamic tests. Furthermore,

the equivalent stiffness Kef is also likely to decrease if the damper

force declines in the dynamic loading. On the other hand, whether

or not in the quasi-static tests with the strain rate closes to 0 or in

the dynamic tests with the strain rate changes from 40%/s to 200%/

s, the equivalent damping ratio eqkeeps as a constant value around

0.53. It conrms that the equivalent damping ratio eq of the LYSPD

is strain rate-independent. Compared with other developed metallic

shear panel dampers, the developed LYSPD in this research can pro-

vide higher damping ratio which means better seismic performance.

3.2. Low-cycle fatigue'

3.2.1. Shear strain-fatigue cycle curve

The fatiguefailure criterion should establish correlationbetween the

criterion parameter and the number of cycles to fracture or to macro-

crack initiation. In previous static constant hysteretic experimental

studies, the number of fatigue cycles to fracture is set as the MDF

-60 -30 0 30 60-800

-400

-800

-400

0

400

800

Shear Strain (%) Shear Strain (%) Shear Strain (%)




-60 -30 0 30 60

0

400

800

-60 -30 0 30 60-800

-400

0

400

800

(a)ST20 (b)D05-20 (c)D10-20

-60 -30 0 30 60

-800

-400

0

400

800

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

Force(kN)

-60 -30 0 30 60

-800

-400

0

400

800

-60 -30 0 30 60

-800

-400

0

400

800

(d)ST30 (e)D05-30 (f) D10-30

-60 -30 0 30 60-800

-400

0

400

800

-60 -30 0 30 60-800

-400

0

400

800

-60 -30 0 30 60-800

-400

0

400

800

(g)ST40 (h)D05-40 (i)D10-40

-60 -30 0 30 60-800

-400

0

400

800

-60 -30 0 30 60-800

-400

0

400

800

-60 -30 0 30 60-800

-400

0

400

800

(j)ST50 (k)D05-50 (l)D10-50

Fig. 6.Static and dynamic force-shear strain hysteretic curves.



6/9

dropped to 90% in ordinary. It is observed that the damper still has

enough energy dissipation ability when this fatigue failure criterion is

applied to dynamic constant hysteretic tests. Seen fromFig. 7,the dra-

matic damper force decrease begins at 90% MDF in static tests while it

beginsat 70% MDFin dynamic tests. Although the dynamictests are sel-

dom conducted at present due to the limitation of test equipment and

the lack of similar researches that could be taken as reference, it is be-

lieved that the slow droppingof theMDF should not be taken as fatigue

failure criterion in dynamic tests. At the same time, there is no fatigue

cycle difference when the fatigue failure criterion depends on the

force dropping to 90% MDF or 70% MDF. Therefore, the fatigue failure

criterion can be unied as the MDF drops to 70% in both static and dy-

namic constant tests.

The fatigue cycles (N70%) are calculated according to the fatigue cri-

terion mentioned above and plottedin Fig. 13. The symbol represents

the static test results while and represent the dynamic results of

D05 and D10 respectively. The fatigue cycles all decrease with the in-

crease of the shear strain amplitude in all the tests. The corresponding

shear strainfatigue cycle function relations under three different load-

ing frequencies based on test results can be expressed as:

239N0:6670% ST 5

294N0:7870% DO5 6

275N0:8170% D10 : 7

Besides the shear strain amplitude, the fatigue cycles also decrease

with the increase of the shear strain rate in dynamic tests. The relationbetween shear strain rate and fatigue cycles is illustrated inFig. 14. The

nonlinear relation between shear strain rate and fatigue cycles is ob-

served when the shear strain amplitude is 20% while thelinearrelations

are observed in other three shear strain amplitudes (30%, 40% and 50%).

At the same time, theinuence of the strain rate getssmaller and small-

er with the increase of the shear strain amplitude. Although the strain

rates are the smallest ones when the shear strain amplitude is 20%,

the fatigue cycle deteriorations in dynamic tests are the most dramatic

ones. Compared with the static tests, the fatigue cycles of D05-20 and

D10-20 decrease by 33% and 40% respectively which decrease more

than that of other dynamic specimens.

0 10 20 30 40 500

200

400

600

Cycles (N)

Damperforce(kN)

ST20ST30ST40ST50

0 10 20 30 40 500

200

400

600

800

Cycles (N)

Cycles (N)

Damperforcee(kN)

D05-20D05-30D05-40D05-50

(a)Static MDF history

(b)D05 dynamic MDF history

0 10 20 30 40 500

200

400

600

800

Damperforce(kN)

D10-20D10-30D10-40D10-50

(c) D10 dynamic MDF history

Fig. 7.MDF history.

0 10 20 30 40 50 600

200

400

600

800

Shear strain (%)

MDF(kN)

MDFq (ST)

MDFq (D05)MDFq (D10)

MDF (ST)

MDF (D05)MDF (D10)

Fig. 8.Strain hardening in the rst cycle.

Table 2Test results.

Test type Specimen First cycle N70%(N) CPS

(%)

CEA

(kNm)MDFq(kN) MDF (kN)

Static

(ST)

ST20 357 507 42 3110 1550

ST30 342 533 23 2677 1400

ST40 424 564 15 2371 1344

ST50 476 615 10.5 2136 1270

Dynamic

(D05)

D05-20 352 521 28 2396 1023

D05-30 435 573 20 2368 1075

D05-40 395 595 13 1816 935

D05-50 488 616 9 1795 968

Dynamic

(D10)

D10-20 397 513 25 1931 829

D10-30 423 598 15 1813 881

D10-40 477 623 11 1744 910

D10-50 502 636 8 1612 890



7/9

Crack and stress softening resulting from high temperature for the

internal friction are the main two factors that lead to the MDF dete-

rioration and the LYSPD failure. Crack is the dominant factor that

leads to sharp MDF deterioration and the LYSPD failure in static

tests as the temperature increase is negligible. Meanwhile, the stress

softening is another factor that leads to the gradual MDF deteriora-

tion and accelerates the LYSPD failure in dynamic tests. The LYSPD

may still fail as crack similar with static failure in dynamic tests before

the stress softening is dominated, because the fatigue cycle is small

when the shear strain amplitude is large. Under this circumstance,

only small fatigue cycle difference will be observed between static

and dynamic tests. It is accordance with the test results when the

shear strain is 50%, only 12 cycles' difference between static test

and dynamic test results is observed. On the opposite, the fatigue

cycles will be affected by stress softening greatly when the shear

strain is small. This is the main reason for the sharp fatigue cycle de-

crease in dynamic tests when the shear strain amplitude is 20%.

3.2.2. Cumulative plastic shear strain

Many damage accumulation models, proposed in professional liter-

ature, can be evaluated by stress, cumulative plastic shear strain (CPS),

cumulative energy absorption (CAE) and local accumulate damage [18]

besides the shear strainfatigue cycle mentioned above. They are for-

mulated on the grounds of experiments or theoretical analysis. As the

stress and local accumulate damage are not easy to be gained in engi-

neer practical use, the CPS and the CAE are attached importance on in

this research. Furthermore, the calculation of the CPS and CAE is based

on the aforementioned fatigue failure criterion N70%.

The CPSs of theLYSPD, corresponding to each shear strain under static

and dynamic loading, are plotted in Fig. 15. From top to bottom ofFig. 14,

they are the approximate curves of static, D05 and D10 successively. The

approximate curve of static test is shownas index while the approximate

curves of dynamic tests are demonstrated as linear. It is obvious that CPS

decreases with the increase of dynamic loading frequency. Similar with

the downward trend of fatigue cycles between static and dynamic tests,

CPS has droppeddramatically as the shear strainis 20%while it is relative-

ly small as the shear strain is 50%. Furthermore, CPS also decreases with

the increase of shear strain in both static and dynamic tests. However,

the CPS difference betweendifferent shear strains is large (974%) in static

tests while it is narrowed to a small value gap (319%) in dynamic tests

(D10). In accordance with the trend from static tests to D10 dynamic

tests, the correlationbetween the CPS and shear strain amplitude is grad-

ually becoming smaller and smaller with the increase of dynamic loading

frequency.

In simple terms, regardless of shear strain,only the CPS is focused on

the discussion of the LYSPD's fatigue performance in most studies. Fromthe perspective of security application, the minimum CPS, when the

shear strain is 50% and loading frequency is 1 Hz (D10-50), is taken as

the lower limit value of the LYSPD which equals 1612%.

3.2.3. Cumulative energy absorption

Similar toFig. 12, the energy of every cycle can be calculated by the

area enclosed inside the hysteresis loop. The accumulation of the total

energy is the energy dissipation capability of the LYSPD. The CAE of all

the tests is plotted inFig. 16. The overall distribution and trend of the

CAE in static and dynamic tests are almost the same with that of the

CPS. The difference is that CPS is greatly inuenced by shear strain

0 50 100 150 200 2500

20

40

60

80

temperatureincreaserate(C/sec)

Shear strain rate (%/sec)

D05

D10

Fig. 9.Temperature increase rate and shear strain rate.

0 50 100 150 200 2500

10

20

30

40

Shear strain rate (%/sec)

Forcedecreaserate(kN/s

ec)

D05

D10

Fig. 10.Damper force decrease rate and shear strain rate.

-100 -50 0 50 100-800

-400

0

400

800

Displacement (mm)

Force(kN)

Fig. 11.Perfect elasticplastic model.

MDF+

MDF-

Kef

MDD+MDD-

W

W

Fig. 12.Hysteretic damping denition.



8/9

amplitude and the approximate curve shows as an index curve, while

the CAE is slightly inuenced by shear strain and the approximate

curve shows as a linear in static tests. Seen fromFig. 15, both in static

and dynamic tests, the CAE of the LYSPD could also be nearly regarded

as a constant in the same loading frequency regardless of different

shear strains. The minimum CAE (830 kNm) in D10 tests (D10-20) is

taken as the lower limit value of the LYSPD.

3.3. Failure mode

Specimen nalfailuremodes of staticand dynamic tests are shownin

Fig. 17. In spite of the rarely low width/thickness ratio of panel, the

out-of-plane shear buckling is still observed under the static cyclical

loading (Fig. 17(a)(d)). The failure modes of static specimens are al-

most the same. With the increase of shear buckling, the cracks appear

at the panel corners or the welding seams between panel and ribs. Sub-

sequently, the LYSPD collapses with the expanding of the crack.

Instead of shear buckling in static tests, the in-plane shear defor-

mation is dominant in the dynamic tests. Signicant heat developingduring the dynamic tests on the LYSPD, prior to failure, is also ob-

served within the effective panel deformation area. The maximum

temperatures in dynamic tests are all about 550 C. The horizontal

high temperature red band is mainly caused by internal friction

resulting from in-plane shear while the vertical cracks between the

panel and ribs are inuenced by material deterioration resulting from

welding greatly. Based on these 12 specimens, the failure mode distinc-

tion is observed between static and dynamic test results.

4. Conclusion

Four static and eight dynamic specimens have been conducted to

verify the cyclical hysteretic behavior, the damper force history and

the fatigue life of the developed LYSPD. These test results suggest that

the LYSPD subjected to dynamic loading would be greatly affected by

strain rate and the main conclusion could be concluded as follow:

(1) The majority of stress hardening occurs within therst cycle and

reaches the maximum damper force of each test in both static

and dynamic tests. The strain rate hardening occurs within the

rst quarter cycle of virgin dynamic loading and keeps to the

end of the rst cycle.

(2) After reaching a maximum force, stable damper force is kept

unchanged until failure in static tests and the cyclic damper force

deteriorationtowards failurewith theincreasing cyclesin dynamic

tests.

(3) A linear relation is setup between damper force deterioration and

strain rate which provides the reference on modeling and design-ing the LYSPD according to the constant dynamic tests.

(4) The LYSPD can provide the stable, high damping ratio around 0.53

regardless of the strain rate which benets for structure seismic

performance.

(5) The fatigue cycles decrease with the increase of frequency and

shear strain amplitude at the same time. The fatigue cycle is

inuenced by strain rate greatly in dynamic tests when the shear

strain amplitude is small while it can be ignored when the shear

strain amplitude is larger than 50%.

(6) The CPS decreases with the increase of shear strain amplitude in

0 10 20 30 40 500

20

40

60

80

She

arstrain(%)

Fatigue Cycles N70% (N)

ST

D05

D10

Fig. 13.Strain and fatigue cycle relation.

0 10 20 30 40 500

50

100

150

200

250

Strainrate(%/sec)

20%

30%

40%

50%

Fatigue Cycles N70% (N)

Fig. 14.Strain rate and fatigue cycle relation.

0 20 40 600

1000

2000

3000

4000

5000

CPS(%)

Shear strain (%)

STD05

D10

Fig. 15.CPS and shear strain.

0 20 40 600

500

1000

1500

2000

CAE(kNm)

Shear strain (%)

D05

D10

ST

Fig. 16.CAE and shear strain.



9/9

static tests while it shows weak correlation with shear strainam-

plitude in dynamic tests. The lower limit value can be conserva-

tively estimated as 1612%.(7) The CAE shows weak or no correlation with shear strain ampli-

tude in both static and dynamic tests and thelower limit value is

around 830 kNm.

(8) The response of the static specimens is dominated by out-of-plane

deformation while in-plane shear deformation dominates the re-

sponse in the dynamic specimens.

(9) Whether the damper performance deterioration of dynamic ran-

dom wave should be taken into consideration or not is depending

on the cycle numbers and shear strain amplitudeat the same time.

Attention should be paid to the damper force deterioration when

the shear strain amplitude is small and the cycle number is large

or when the shear strain amplitude is large and even if the cycle

number is only around 3 cycles.

Acknowledgment

The authors acknowledge the supports given by the assistance

coming from the staff of Seismic Research Center at Aichi Institute

of Technology in Japan.

References

[1] Tanaka Kiyoshi, Sasaki Yasuhito, Yoneyama Shin-ichiro. An experimental study on hys-teretic performance of shear panel dampers using different strength type of steel understatic loading. J Struct Constr Eng AIJ 1999;520(6):117-24 (In Japanese).

[2] Chan Ricky WK, Albermani Faris, Williams Martin S. Evaluation of yieldingshear paneldevice for passive energy dissipation. J Constr Steel Res 2009(65):260-8.

[3] De Matteis G, Landolfo R, Mazzolani FM. Seismic response of MR steel frames withlow-yield steel shear panels. Eng Struct 2003;25:155-68.

[4] Hitomi Yasuyoshi, Konomi Hatsunobu Wada Shinzo, Satito Kiichirou, NakataYasuhiro, Iwata Mamoru. Development of the high ductile shear panel. J AIJ1996;12:118-23.

[5] Shih Ming-hsiang, Sung Wen-pei, GO Cheer-germ. Investigation of newly devel-oped added damping and stiffness device with low yield strength steel. J ZhejiangUniv Sci 2004;5(3):326-34.

[6] Dusicka Peter, Itani Ahmad M, Buckle Ian G. Cyclic response of plate steels underlarge inelastic strains. J Constr Steel Res 2007;63:156-64.

[7] Saeki Eiichiro, Sugisawa Misturu, Yamaguchi Tanemi, Mochizuki Haruo, WadaAkira. A study on low cycle fatigue characteristics of low yield strength steel. JStruct Constr Eng AIJ 1995;472:139-47.

[8] ChenSheng-Jin, Jhang Chyuan. Cyclic behavior of low yield point steel shear walls.Thin-Walled Struct 2006(44):730-8.

[9] Tanaka Kiyoshi, Sasaki Yasuhito. Hysteretic performance of shear panel dampersof ultra low yield-strength steel for seismic response control of buildings.12WCEE 2000; 2000. p. 1-8.1248.

[10] Aoki T, Dang J, Zhang C, Takaku T, Fukumoto Y. Dynamic shear test of low-yieldsteel panel dampers for bridge bearing. STESSA 2009; 2009. p. 647-52.

[11] Aoki Tetsuhiko, Zhang Chaofeng, Yuan Huihui. Dynamic loading test of shear

panel damper. EUROSTEEL 2011; 2011. p. 975-80.[12] Zhang Chaofeng,ZhangZhisheng,Shi Jinfei.Developmentof high deformation capacity

low yield strength steel shear panel damper. J Constr Steel Res 2012;75:116-30.[13] Japan Road Association. Seismic design specications of highway bridges; 1996.[14] AASHTO. Guide specications for seismic isolation design. Washington (D.C.):

American Association of State Highway and Transportation Ofcials; 1999.[15] Eurocode 8. Design provisions for earthquake resistance of structures, Part2: brid-

ges. ENV 1998-2. Brussels; 1994.[16] Hwang JS, Sheng LH. Equivalent elastic seismic analysis of base isolated bridges

with lead-rubber bearings. Eng Struct 1994;16:201-9.[17] Jangid RS. Equivalent linear stochastic seismic response of isolated bridges. J

Sound Vib 2008;309:805-22.[18] Borodii MV, Adamchuk MP. Life assessment for metallic materials with the use of

the strain criterion for low cycle fatigue. Int J Fatigue 2009;31:1579-87.

(a)ST20 (b)ST30 (c)ST40 (d)ST50

(e)D05-20 (f)D05-30 (g)D05-40 (h)D05-50

(i)D10-20 (j)D10-30 (k)D10-40 (l)D10-50

Fig. 17.Failure mode.


static and dynamic cyclic performance of a low-yield-strength

Documents