THE USE OF FUSE CONNECTORS IN COLD-FORMED STEEL DRIVE-IN

RACKSChris Wodzinski

WHAT ARE WE LOOKING AT?

Drive-In RackHR Largertechnik (2010).

Fuse Connector Ingal Pty Ltd. (2008).

MY AIM

Investigate the feasibility of incorporating fuse connectors into the design to prevent

the progressive collapse of a DIR in the event of an upright failure.

THESIS OBJECTIVES

1. Conduct a literature review regarding the design and behaviour of cold-formed steel drive-in

storage racks under both static (operational) and dynamic (impact) conditions.

2. Re-analyse maximum portal beam tensile forces and verify previous finite element model

results Yadwad (2011).

3. Investigate the response of pallet influence on portal beam forces.

4. Refine residual capacity model to be applied in conjunction with a newly developed model.

5. Develop finite element model for various arrangements of drive-in racks.

6. Apply both linear and nonlinear inelastic techniques to determine the maximum and

minimum portal beam tensile forces experienced during operation and after local failure.

7. Provide recommendations regarding the feasibility of using fuse connectors to prevent

progressive collapse of cold-formed steel drive-in racks of various arrangements.

THESIS OBJECTIVES

1. Conduct a literature review.

2. Re-analyse FEA undertaken by Yadwad (2011) .

3. Investigate the response of pallet influence on portal beam forces.

4. Refine residual capacity mechanism.

5. Develop finite element model for each DIR topology.

6. Determine maximum portal beam tensile forces following impact and local upright failure.

7. Provide recommendations on the feasibility of fuse connectors.

WHY

• More crazy when seen in concrete buildings, usually induced by explosions

• In DIRs can occur after sufficient impact loading onto uprights

• Can easily occur

• Video

• Due to high density of storage expenses can be high

• Saftey

GAP IN LITERATURE

• Current specifications do not propose procedures to mitigate progressive collapse

failure

• Only recently have included accidental impact loading for DIRs

• Yadwad (2011)

• Problems with residual capacity

• Validation of models/theory

METHODOLOGY – FINITE ELEMENT ANALYSIS

Modelling

• Topology and Connections

• Effect of Pallets

• Residual Capacity

Analysis

Operational Conditions

(Impacts)

Analysis

Following Local Failure

(Removals)

FROM ‘PEN’ TO ‘PAPER’

FROM ‘PEN’ TO ‘PAPER’

FINITE MODELS, DIR1 – DIR4

FINITE MODEL, DIR5

EFFECT OF PALLETS

Pallet Masses in FEA. Modelling the Effect of Pallets in FEA.

• Investigated as oscillation of the independent masses, in cases, caused large portal beam

forces when adjacent uprights translated in opposite directions.

• Gathering results from both modelled gives a range in which the true behaviour must lie.

RESIDUAL CAPACITY

(Bristol Storage Equipment Limited, 2014)

RESIDUAL CAPACITY

• Yadwad (2011) utilised supporting force,

does not account for upward translation

and therefore will not counteract

movement.

• Springs are not suitable due to

development of high reaction forces as the

gap is closed.

• Viscous Damper was utilised.

• Theoretical dynamic impact load of 6.28kN

• Applied in FEA through Factor Time Table

• Structural damping greatly affects

oscillation and therefore maximum tensile

forces.

IMPACT LOADING

Process:

1. Determine Supporting Reactions

2. Assign them to Factor-Time table

3. Determine Failed Members

4. Removal of Members

5. Apply supporting reactions and assign

them to new Factor-Time Tables

6. Repeat until progressive collapse has

developed.

REMOVAL PROCESS

Process:

1. Determine Supporting Reactions

2. Assign them to Factor-Time table

3. Determine Failed Members

4. Removal of Members

5. Apply supporting reactions and assign

them to new Factor-Time Tables

6. Repeat until progressive collapse has

developed.

REMOVAL PROCESS

Zero Collapse Mechanism, Structure resists

loading

Local Collapse Mechanism only.

• No development of progressive collapse

REMOVALS

Majority of analyses resulted in either of the following collapse mechanisms:

THE PROGRESSIVE RACK, DIR3

Of all DIR topologies, DIR3 following upright failure resulted in local collapse which developed into

progressive collapse.

The location of failures were directly under plan bracing therefore compromising it leading to the

development of collapse.

FUSE CONNECTOR DEFINITION

DIR TopologyLower Limit

(kN)Type of Collapse

Upper Limit

(kN)Type of Collapse

DIR1 6.232 Zero 13.605 Local

DIR2 6.694 Zero 8.240 Local

DIR3 7.676 Zero 5.562 Local

DIR4 7.800 Zero 6.441 Zero

DIR5 7.022 Zero 12.511 Local

Type of

Collapse

Removed

Upright/s

Maximum Tensile force at failure Propagation (kN)

First

FailureMember

Second

FailureMember

Third

FailureMember

Prog 2A, 2C, 2B 2.684 B34 1.883 A34 3.945 A34

Prog 3A, 3C -0.886 B12 3.095 A34 - -

EFFECT OF PALLETS

Front View of DIR4 following impact showing

portal beam tensile force magnitudes.

Front View of DIR4 following impact showing

portal beam tensile force magnitudes including

pallet effects.

Axial Force Magnitudes

Max = 10kN, Pink

Min = -20kN, Blue

EFFECT OF RAYLEIGH DAMPING

Oscillation occurring in DIR3 following impact

on upright 2A (0% Rayleigh Damping).

Oscillation occurring in DIR3 following impact

on upright 2A (5% Rayleigh Damping).

No change to the nature of collapse following upright removal

DIR3 AND DIR4 REMOVALS

Displacements scaled by 0x Displacements scaled by 5x

Wodzinski (2014)

No cases where fuse connectors are

defined as feasible.

Residual capacity prevented the

development in a number of cases.

Bracing to be provided to reduce

the development of progressive

collapse.

Yadwad (2011)

Cases where fuse connectors are

defined as feasible.

Residual capacity delayed but not

prevented the development.

Bracing to be provided to reduce

the development of progressive

collapse.

CONCLUSIONS

ADDITIONAL PREVENTION MEASURE

Yadwad (2011)

RECOMMENDATIONS

• Tests to be conducted on Residual Capacity

• Additional information on structural damping

• Modelling the effect of pallets

IN CLOSING

Aim:

Investigate the feasibility of incorporating fuse connectors into the design to prevent

the progressive collapse of a DIR in the event of an upright failure.

Importance:

• Increases site safety

• Reduces costings associated with collapse

• Provides information for progressive collapse mechanism modelling

THANK YOU