土木工程中英文翻译

青岛理工大学毕业设计（论文）

外文翻译及原文

from

：

journal of Constructional Steel Research.V

olume 59,Number 1,January 2003

Cyclic behavior of steel moment frame

connections under varying axial load and lateral displacements

Abstract

: This paper discusses the cyclic behavior of four steel moment connections

tested

under

variable

axial

load

and

lateral

displacements.

The

beam

specim-

ens

consisted of a reduced beam section, wing plates and longitudinal stiffeners. The test

specimens

were

subjected

to

varying

axial

forces

and

lateral

displace-

ments

to

simulate the effects on beams in a Coupled-Girder Moment- Resisting Framing system

under

lateral

loading.

The

test

results

showed

that

the

specim-

ens

responded

in

a

ductile manner since the plastic rotations exceeded 0.03 rad without significant drop

in

the

lateral

capacity.

The

presence

of

the

longitudin-

al

stiffener

assisted

in

transferring the axial forces and delayed the formation of web local buckling.

1. Introduction

Aimed at evaluating the structural performance of reduced-beam section(RBS)

connections

under

alternated

axial

loading

and

lateral

displacement,

four

full-scale

specimens

were

tested.

These

tests

were

intended

to

assess

the

performance

of

the

moment connection design for the Moscone Center Exp- ansion

under

the

Design

Basis Earthquake (DBE) and the Maximum Considered Earthquake (MCE). Previous

research

conducted

on

RBS

moment

connections

[1,2]

showed

that

connections

with

RBS profiles can achieve rotations in excess of 0.03 rad. However, doubts have

been

cast

on

the

quality

of

the

seismic

performance

of

these

connections

under

combined

axial and lateral loading.

The

Moscone

Center

Expansion

is

a

three-story,

71,814

m2

(773,000

ft2)

structure

with steel moment frames as its primary lateral

force- resisting

system.

A

three

dimensional

perspective illustration is

shown in

Fig. 1. The

overall

height

of

the

building,

at

the

highest

point of the exhibition roof, is approxima- tely 35.36 m (116ft) above ground level.

The

ceiling

height

at

the

exhibition

hall

is

8.23

m

(27

ft)

,

and

the

typical

floor-to-floor height in the building is 11.43 m (37.5 ft). The building was designed as

type I according to the requi- rements of the 1997 Uniform Building Code.

The

framing

system

consists

of

four

moment

frames

in

the

East

–

West

direct-

第

1

页

青岛理工大学毕业设计（论文）

ion,

one

on

either

side

of

the

stair

towers,

and

four

frames

in

the

North

–

South

direction, one on either side of the stair and elevator cores in the east end and two at

the

west

end

of

the

structure

[4].

Because

of

the

story

height,

the

con-

cept

of

the

Coupled- Girder Moment-Resisting Framing System (CGMRFS) was utilized.

By

coupling

the

girders,

the

lateral

load-resisting

behavior

of

the

moment

framing

system

changes

to

one

where

structural

overturning

moments

are

resisted

partially by an axial compression

–

tension couple across the girder system, rather than

only by the individual flexural action of the girders. As a result, a stiffer lateral load

resisting system is achieved. The vertical element that connects the girders is referred

to as a coupling link. Coupling links are analogous to and serve the same structural

role as link beams in eccentrically braced frames. Coupling links are generally quite

short, having a large shear- to-moment ratio.

Under earthquake-type loading, the CGMRFS subjects its girders to wariab- ble axial

forces in addition to their end moments.

The axial forces in

the

Fig. 1. Moscone Center Expansion Project in San Francisco, CA

girders result from the accumulated shear in the link.

2. Analytical model of CGMRF

Nonlinear

static

pushover

analysis

was

conducted on a typical one-bay model of the

CGMRF.

Fig.

2

shows

the

dimensions

and

the

various

sections

of

the

model.

The

link

flange plates were 28.5 mm

??

254 mm (1 1/8

??

10 in) and the web plate was 9.5 mm

??

476

mm

(3

/8

in

??

18

3/4

in).

The

SAP

2000

computer

program

was

utilized

in

the

pushover

analysis

[5].

The

frame

was

characterized

as

fully

restrained(FR).

FR

moment

frames

are

those

frames

for

1170which

no

more

than

5%

of

the

lateral

deflections

arise

from

connection

deformation

[6].

The

5%

value

refers

only

to

deflection due to beam

–

column deformation and not to frame deflections that result

from column panel zone deformation [6, 9].

in

第

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青岛理工大学毕业设计（论文）

The analysis was performed using an

expected value

of the yield stress and ultimate strength. These values

were equal to 372 MPa (54 ksi) and 518 MPa (75 ksi),

respectively.

The

plastic

hinges’

load–

deformation

behavior was

approximated by the

generalized curve

suggested

by

NEHRP

Guidelines

for

the

Seismic

Rehabilitation of Buildings [6] as shown . 3.

△

y

was calcu-

lated based on Eqs. (5.1) and (5.2) from

[6], as follows:

P

–

M

hinge

load

–

deformation

model

points

C,

D

and

E

are

based

on

Table

5.4

from [6] for

△

y was taken as 0.01 rad per Note 3 in [6], Table 5.8. Shear hinge load-

load

–

deformation model points C, D and E are based on Table 5.8 [6], Link Beam,

Item a. A strain hardening slope between points B and C of 3% of the elastic slope

was assumed for both models.

The

following

relationship

was

used

to

account

for

moment

–

axial

load

interaction [6]:

where

MCE

is

the

expected

moment

strength,

ZRBS

is

the

RBS

plastic

section

modulus

(in3),

is

the

expected

yield

strength

of

the

material

(ksi),

P

is

the

axial

force

in

the

girder

(kips)

and

is

the

expected

axial

yield

force

of

the

RBS,

equal

to

(kips). The ultimate flexural capacities of the beam and the link of the model are

shown in Table 1.

Fig. 4 shows qualitatively the distribution of the bending moment, shear force,

and

axial

force

in

the

CGMRF

under

lateral

load.

The

shear

and

axial

force

in

the

beams are less significant to the response of the beams as compared with the bending

moment, although they must be considered in design. The qualita- tive distribution of

internal

forces

illustrated

in

Fig.

5

is

fundamentally

the

same

for

both

elastic

and

inelastic ranges of behavior. The specific values of the internal forces will change as

elements of the frame yield and internal for-

ces are redistributed. The basic patterns

illustrated in Fig. 5, however, remain the same.

Inelastic static pushover analysis was carried out by applying monotonically

increasing lateral displacements, at the top of both columns, as shown in Fig. 6. After

the four RBS have yielded simultaneously, a uniform yielding in the web and at the

ends of the flanges of the vertical link will form. This is the yield mechanism for the

frame , with plastic hinges also forming at the base of the columns if they

are fixed.

The base shear versus drift angle of the model is shown in Fig. 7 . The sequence of

第

3

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青岛理工大学毕业设计（论文）

inelastic activity in

the frame is

shown on the figure. An elastic component, a long

transition (consequence of the beam plastic hinges being formed simultaneously) and

a narrow yield plateau characterize the pushover curve.

The

plastic

rotation

capacity,

qp,

is

defined

as

the

total

plastic

rotation

beyond

which

the

connection

strength

starts

to

degrade

below

80%

[7].

This

definition

is

different from that outlined in Section 9 (Appendix S) of the AISC Seismic Provisions

[8, 10]. Using Eq. (2) derived by Uang and Fan [7], an estimate of the RBS plastic

rotation capacity was found to be 0.037 rad:

Fyf

was

substituted

for

Ry?Fy

[8],

where

Ry

is

used

to

account

for

the

differ

-

ence

between the nominal and the expected yield strengths (Grade 50 steel, Fy=345

MPa and Ry =1.1 are used).

mental program

The experimental set-up for studying the behavior of a connection was based on Fig.

6(a).

Using

the

plastic

displacement

dp,

plastic

rotation

gp,

and

plastic

story

drift

angle qp shown in the figure, from geometry, it follows that:And: in which d and g

include the elastic components. Approximations as above are used

for large inelastic

beam

deformations.

The

diagram

in

Fig.

6(a)

suggest

that

a

sub

assemblage

with

displacements controlled in the manner shown in Fig. 6(b) can

represent the inelastic

behavior of a typical beam in a CGMRF.

The

test

set-up

shown

in

Fig.

8

was

constructed to develop the mechanism shown

in

Fig.

6(a)

and

(b).

The

axial

actuators

were

attached to three

2438 mm ×

1219 mm ×

1219

mm (8 ft ×

4 ft ×

4 ft) RC blocks. These blocks

were

tensioned to the laboratory floor by means

of

twenty-four

32

mm

diameter

dywidag

rods.

This arrangement permitted replacement of the specimen after each test.

第

4

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青岛理工大学毕业设计（论文）

Therefore, the force applied by the axial actuator, P, can be resolved into two or

thogonal

components,

Paxial

and

Plateral.

Since

the

inclination

angle

of

the

axial

actuator

does

not

exceed

3.0

?

,

therefore

Paxial

is

approximately

equal

to

P

[4].

However, the lateral component, Plateral, causes an additional moment at the beam-to

column

joint.

If

the

axial

actuators

compress

the

specimen,

then

the

lateral

components will be adding to the lateral actuator forces, while if the axial actuators

pull the specimen, the Plateral will be an opposing force to the lateral actuators. When

the axial actuators undergo

axial actuators undergo a lateral displacement _, they cause an additional moment at

the beam-to-column joint (P-

△

effect). Therefore, the moment at the beam-to column

joint is equal to:

where

H

is

the

lateral

forces,

L

is

the

arm,

P

is

the

axial

force

and

_

is

the

lateral

displacement.

Four full- scale experiments of beam column connections were conducted.

The member sizes and the results of tensile coupon tests are listed in Table 2

All of the columns and beams were of A572 Grade 50 steel (Fy

344.5 MPa). The

actual measured beam flange yield stress value was equal to 372 MPa (54 ksi), while

the

ultimate strength ranged from 502 MPa (72.8 ksi) to 543 MPa (78.7 ksi).

Table

3

shows

the

values

of

the

plastic

moment

for

each

specimen

(based

on

measured tensile coupon data) at the full cross-section and at the reduced section

at

mid-length of the RBS cutout.

The specimens were designated as

specimen 1 through specimen 4. Test specimens

details are shown in Fig. 9 through Fig. 12. The following features were utilized in the

design of the beam

–

column connection:

The use of RBS in beam flanges. A circular cutout was provided, as illustr- ated in

Figs. 11 and 12. For all specimens, 30% of the beam flange width was removed.

The

cuts

were

made

carefully,

and

then

ground

smooth

in

a

direct-

tion

parallel

to

the

beam flange to minimize notches.

Use of a fully welded web connection. The connection between the beam web and the

column flange was made with a complete joint penetration groove weld

(CJP). All

第

5

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青岛理工大学毕业设计（论文）

CJP welds were performed according to AWS D1.1 Structural Welding Code

Use of two side plates welded with CJP to exterior sides of top and bottom beam flan-

ges, from

the face of the column flange to

the beginning of the RBS, as

shown

in

Figs. 11 and 12. The end of the side plate was smoothed to meet the beginning of the

RBS. The side plates were welded with CJP with the column flanges. The

side plate

was

added

to

increase

the

flexural

capacity

at

the

joint

location,

while

the

smooth

transition was to reduce the stress raisers, which may initiate fracture.

Two

longitudinal

stiffeners,

95

mm

×

35

mm

(3

3/4

in

×

1

3/8

in),

were

welded

with

12.7

mm

(1/2 in) fillet weld at the middle height of the web

as

shown

in

Figs.

9

and

10.

The

stiffeners

were

welded with CJP to column flanges.

Removal

of

weld

tabs

at

both

the

top

and

bottom

beam

flange

groove

welds.

The

weld

tabs

were

removed

to

eliminate

any

potential

notches

introduced

by

the

tabs

or

by

weld

discontinuities

in the groove weld run out regions.

Use

of

continuity

plates

with

a

thickness

approximately

equal

to

the

beam

flange

thickness. One-inch thick continuity plates were used for all specimens.

While

the

RBS

is

the

most

distinguishing

feature

of

these

test

specimens,

the

longitudinal stiffener played an important role in delaying the formation of web local

buckling and developing reliable connection performance4. Loading history

Specimens were tested by applying cycles of alternated load with tip displacement

increments of _y as shown in Table 4. The tip displacement of the beam was imposed

by

servo- controlled

actuators

3

and

4.

When

the

axial

force

was

to

be

applied,

actuators 1 and 2 were activated such that its force simulates the shear force in

the

link to be transferred to the beam. The variable axial force was increased up to 2800

kN (630 kip)

at

?

0.5_y.

After that, this

lo-

ad was maintained

constant

through the

maximum lateral displacement.

maximum

lateral

displacement.

As

the

specimen

was

pushed

back

the

axial

force

remained

constant

until

0.5

y

and

then

started

to

decrease

to

zero

as

the

specimen

passed through the neutral position [4]. According to the upper bound for

beam

axial

force

as

discussed

in

Section

2

of

this

paper,

it

was

concluded

that

P

第

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