Seismic Retrofit of Ductile Concrete Moment Frames with Innovative Pin-Supported Walls

Hiroyasu SakataZhe QuSaburoh MidorikawaAkira Wada

Tokyo Institute of Technology

14th U.S.-Japan Workshop on the Improvement of Structural Design and Construction Practices

Kobe city hall after 1995 Kobe EQ

RC frame after 2008 Wenchuan EQShearwall damage in 2010 Chili EQ

（EERI, 2010）

Moment Frame Shearwall

Pin-Supported Wall-Frame System

Background

Pin-Supported Walls

Weak story(Soft story) Strengthening Coordinator

Hinge

FEQ,i

V

V

FEQ,j

Vj

Vi

EQ,j j

EQ,i i

Mw

Pin-Supported Walls

Post-tensioned wall (1~11F)

Bottom hinge

Steel damper (2~9F)

Connector (1~11F)

SRC frame

Transverse shearwall (1~9F)xz

y

After– 2010.3

During – 2009.12

Before– 2008.10

G3 Building in Tokyo Tech

Existing columnRocking wall

Existing beams

Horizontal truss

Shear key

2004501180

4300

Post-tensioned tendon 30- 12.7 (SWPR7B)

Steel rib-22

Steel web-12CL

Lateral rebar 13@200

Longi. rebar D29

Pcon= 0.68Py

cp ≈ 7 MPa

Post-Tensioned Wall and Connector

Steel Damper

xz

1170 kN

585 kN

779 kN

Weight: 2500 kN

∑ dy

wall7.5

∑ dy

wall4.6

Window

SRC

Col

umn

PT W

all

Damper

Stiffener

Rocking wallExisting column

Anchor bolt

Stud

Web

Rib

H

L

Web: PL-6, SLY225Flange: PL-19, SN400BRib: PL-6, SS400 at 250mm spacing

Web height H = 312mmTotal length L = 750~1500mm

Steel Damper

SRC Column PT Wall

Steel Damper

Plan ViewTwo sets of fasteners to make dampers replaceable

Bottom Hinge

0

2

4

6

8

10

12

0 0.005 0.01 0.015 0.02

IDR

Stor

y

Median84th percentile

0

2

4

6

8

10

12

0 0.005 0.01 0.015 0.02IDR

Stor

y

Median84th percentile

(a) (b)

Before After

Story drift ratio Story drift ratio

Numerical Evaluation

• Nonlinear Time History Analysis• Fiber-sectioned beam elements in ABAQUS• 22 Ground Motions (scaled to PGV = 50 cm/s)

Numerical Evaluation

Pre-TensionedCracking

OrdinaryCracking

Nominal shearstrength of

bottom hinge

Moment (kNm) Shear force (kN)

Longi (x) Trans (y)

X PGA: 67.3 cm/s2 and PGV: 14.4 cm/sY PGA: 52.8 cm/s2 and PGV: 12.7 cm/s

Diagonal cracks on transverse shear walls during 2011 Tohoku EQ

Diagonal ruston steel damper

Protective coating peeled off at bottom hinge

Thanks for your attentions!

14th U.S.-Japan Workshop on the Improvement of Structural Design and Construction Practices