Mid-America Earthquake Center Hybrid Simulation for the Assessment of Semi-Rigid Partial-Strength Steel Frames in Seismic Regions Quake Summit 2012 July

Mid-America Earthquake Center

Hybrid Simulation for the Assessment of Semi-Rigid Partial-Strength Steel Frames in

Seismic RegionsQuake Summit 2012

July 11, 2012

Boston, Massachusetts

Hussam N. Mahmoud, Ph.D.

Colorado State University

• Introduction• Structure Design• Hybrid Simulation Approach

- Experimental module

- Analytical module

• Experimental Results and Observations • Conclusion• Questions

Overview

• Numerous examples of brittle fracture of welded moment connections, Northridge (1994), Kobe (1995)

• Fracture initiation at the connection (backing bar detail)- Poor design practice- Poor toughness

Damage to Welded Connections

Structure DesignStructure DesignIntroductionIntroduction Exp. ModuleExp. Module Ana. ModuleAna. Module ResultsResults ConclusionsConclusions

Moment

Rotationkq1

kq2

Rotational spring

Subassembly FEM Analysis

Frame with rotational springs

Idealized M-q

Experimental Testing

Realistic M-q

Current Limitations


• The structure is 2-story, 4-bay longitudinal and 2-bay transverse

• The lateral load resisting system is SMRF designed using IBC 2006

• Load combination of 1.0 DL + 10 psf (partitions) + 0.25 LL + EQ

Specimen Design

SMRF, Typ.

30 ft 30 ft 30 ft 30 ft

W 18 x 40

Experimental Component


Connection Capacity d

(in) T

(in) k

(in) La (in)

ts (in)

ta (in)

l (in)

ga (in)

p (in)

G (in)

W (in)

70% Mpbeam 17.9 1-3/16 3 8 1 5/8 16 2-3/4 5-1/2 3 1-1/4

50% Mpbeam 17.9 1-3/16 3 8 3/4 1/2 14 2-3/4 5-1/2 3 1

30% Mpbeam 17.9 1-3/16 3 8 1/2 3/8 14 2-3/4 5-1/2 3 1

Specimen Design

• Connection is designed as top-and seat-angles with double web-angles

• According to EC 3 with capacity of 70%, 50%, and 30% of the beam plastic moment

Ks

Kt

la

Web Angle

Flange Angle

tt = t

f(Fastener Dia.) = W

ls

lt = l

ga

p Seat Angle

Top Angle

ts (thickness of seat angle) and ta (thickness of web angle)


Hybrid Simulation Approach

{F}

Computational: FEA

Measure forces

SimulationCoordinator

Experimental: LBCB

Target Disp.

Measured forces

{u}

Calc. forces


Small-Scale Setup

Steel

Small-Scale Setup

Rubber

Small-Scale Validation


Small-Scale Validation


SIMCOR Space

(3 control points)

LBCBs Space

(2 control points)

x1,y1,dq1

x2,y2,dq2

x3,y3,dq3

(x1+dx1, y1+dy1, dq1)

(x2+dx2, y2+dy2, dq2)(x3+dx3, y3+dy3, dq3)

Fixed B.C.

LBCB1

LB

CB

2

Control Development

[T]

[T]-1

Y

X

Y

q

qX


• Elastic deformation- Problem Definition

- LBCB platform movement controlled internally- LBCB frame, reaction wall/floor have finite stiffness- Internal actuator displacements include both specimen and external

deformations

Inelastic specimen

Rigid actuator

Elastic box

x

u1

u2

F

F = f1(u1)

F = f2(u2)

F

K2

K1

- Solution- An external measurement and feedback system was developed- 3 DOF (x,y, rz) for each LBCB for a total of 6 DOFs- System of 6 high tension string pots with low friction connections- Precisely monitors and accounts for the movement of the LBCB platform in

space

Control Development


Full-Scale Setup


Control Instrumentation

Control Development


• Global- Still images and videos - Global drift - Global strain- M-q

• Local- Still images and videos- Bolt slip- Localized strain- Angle deformation relative

to the beam and column

Instrumentation


Cyclic Loading of the Model


• The Loma Prieta, PGA = 0.26 g

• USGS 1662 Emeryville, 77 km from the epicenter

• Soft soil (Vs = 199 m/s)

Record Selection


Hybrid Results


65.2% Mpbeam

82% Mpbeam

43.6% Mpbeam

ki

(kips.in/rad) ku

(kips.in/rad) kdeg (%)

| M |Max (kips.in)

%Mpbeam qMax (rad)

Energy Dissipated (kips.in.rad)

70% Mpbeam 510,683 390,827 23.47 3,222 82.0 0.0196 195.18

50% Mpbeam 494,314 266,718 46.04 2,556 65.2 0.0271 177.45

30% Mpbeam 306,521 203,565 33.59 1,708 43.6 0.034 109.56

Hybrid 30% Mpbeam

Hybrid Simulation Results (local)


| 2nd |Max (in)

| 1st |Max (in)

| Base Shear |Max (kips)

70% Mpbeam 6.48 2.89 281.6

50% Mpbeam 7.17 3.35 253.6

30% Mpbeam 7.13 2.84 202.8

Hybrid Simulation Results (global)


IDR limit of 5%

IDR limit of 2.5%

1

(%)

stMaxIDR 1

41

stMax

DBEASCE

IDRIDR

1

41

stMax

MCEASCE

IDRIDR

2

(%)

ndMaxIDR 2

41

ndMax

DBEASCE

IDRIDR

2

41

ndMax

MCEASCE

IDRIDR

70% Mpbeam 1.61 0.322 0.644 2.32 0.464 0.928

50% Mpbeam 1.86 0.372 0.744 2.42 0.484 0.968

30% Mpbeam 1.58 0.316 0.632 2.70 0.540 1.080

Hybrid Simulation Results (global)


A new Hybrid simulation approach for the seismic evaluation of semi-rigid steel frames is executed

Conclusions

• Three simulations were conducted• Large hysteretic loops characterize the connection

behavior• No failure in any of the connection components• The maximum moment sustained by the 70%

Mpbeam, 50% Mpbeam, and 30% Mpbeam connections is 3,222 kips.in (82% Mpbeam), 2,556 kips.in (65% Mpbeam), and 1,708 kips.in (43% Mpbeam), respectively


• The corresponding rotations are 0.0196 rad, 0.0271 rad, and 0.3400 rad, respectively

• The procedure used to scale the records does not allow for direct comparison with the interstory drift limits in ASCE 41-10

• The 50%Mpbeam and 70% Mpbeam frame are deemed acceptable for LS limit state (DBE) while the 30%Mpbeam violates the requirements as its roof drift ratio is calculated to be 2.70%, which is slightly higher than the limit of 2.5% for DBE

• For the expected maximum period elongation, the demand is always higher than the DBE and in some cases even higher than the MCE

Conclusions (cont.)


Acknowledgements

Mid-America Earthquake Center

• Dr. Elnashai, Dr. Spencer, and Dr. Kuchma• Fellow former graduate students at UIUC • NEES staff at UIUC (MUST-SIM)• The analytical and experimental investigations

on the steel frames were supported by the MAE Center

• The experimental investigation was supported by NEES (shared-use)

Questions

Documents

Mid-America Earthquake Center Hybrid Simulation for the Assessment of Semi-Rigid Partial-Strength Steel Frames in Seismic Regions Quake Summit 2012 July