Analytical Investigation of Steel Slit Panels for Lateral Resistance of Steel Frame Buildings

1
Analytical Investigation of Steel Slit Panels for
Lateral Resistance of Steel Frame
Buildings Gustavo Cortés1, Judy Liu2
1Graduate Student, School of Civil
Engineering, Purdue University, West Lafayette,
IN 47907-2051 Email gcortes_at_purdue.edu
2 Associate Professor, School of
Civil Engineering, Purdue University, West
Lafayette, IN 47907-2051 PH [phone] Fax
[phone] Email jliu_at_purdue.edu
Abstract
Benefits of the Steel Slit Panels

• High energy dissipation capabilities
• Relatively easy fabrication and installation
• Architectural versatility
• Seismic retrofitting possibility

The Steel Slit Panel (SSP) is studied for its
viability as a Lateral Force Resisting System
(LFRS) for regions of high seismicity.
Anticipated benefits for the SSP are
architectural flexibility, as well as repair and
retrofit possibilities. This paper is focused on
the stiffness of the SSP frames, since it depends
not only on the SSP but also on the beams
bounding the panels, the position in the bay, the
thickness of the panel, and other factors. The
stiffness has been studied by means of finite
element models (FEM). A methodology for the
calculation of the stiffness is in development.

• The stiffness also depends on the story where it
  is located
• The reduction becomes greater at stories above
  the first story (see Figure 4)
• The first level total rotation is ? 1 the
  second level total rotation is ?1 ? 2

Stiffness of the Panels

• SSP frames must have (1) enough strength to
  resist the lateral loads, and (2) sufficient
  stiffness to avoid excessive sway of the building
• Stiffness requirements controlled the number of
  panels needed for a three-story case-study
  building
• The beams bounding the panels are not perfectly
  rigid, they rotate, and this rotation reduces the
  stiffness of the panels
• The stiffness of the SSP frames increases as the
  flexural stiffness (EI) of the beams increase
  (see Figure 3)

Figure 4. Two story frame deformed shape

• Figure 5 reflects the reduction of stiffness at
  higher levels
• The location of the panels in a bay, the numbers
  of panels, and the thickness of the panels are
  other factors that affect the SSP frame stiffness

Introduction

• SSPs are steel shear walls with vertical slits
  equally spaced, forming columns of links (see
  Figure 1)
• The links behave as beams in double curvature,
  dissipating energy in flexure
• SSPs are an adapted version of the shear walls
  with slits studied in Japan by researchers Hitaka
  and Matsui 1

B Panel Width H Panel Height n numbers of
links per row (9) m number of rows (3) w edge
stiffener width
Section A-A
Front View
Figure 1. SSP schematic drawing

• An SSP frame is a frame which uses SSPs as the
  LFRS (see Figure 2)
• Beam-column connections are made using simple
  connections
• Panel-frame connections are fixed

Figure 5. Panel stiffness vs. beam moment of
inertia
Summary
Figure 3. Frame stiffness vs. beam moment of
inertia
SSP frames are a new LFRS being investigated by a
combined analytical and experimental study. In
this paper, results of analytical studies are
presented, the focus is given to the stiffness of
the panels and how it is affected when
interacting with the rest of the frame. It has
been shown that the stiffness of an SSP frame
depends on the flexural stiffness of the beams,
and on the location of the panels. Future work
includes experimental testing of SSP frames to
validate the analytical findings.

• In Figure 3, the horizontal line represents the
  optimum stiffness of the panel
• The optimum stiffness is the theoretical
  stiffness of a panel, calculated using Equation
  (1)

Equation (1)
Figure 2. Three story SSP frame
Acknowledgements
Design
The authors would like to thank the American
Institute of Steel Construction (AISC) and the
AISC project oversight committee for their
support and contribution to this research.

• E Youngs Modulus G shear modulus k
  shear deformation shape factor (1.2 for
  rectangular sections) B panel width
  h panel height t panel thickness m
  number of rows of links n number of links
  in a row l link length and b link width

• The number of panels required is obtained by
  dividing the strength and stiffness demand at
  each level by the corresponding strength and
  stiffness of the panel being used
• The stiffness of the panels needs to be reduced
  to account for the flexibility of the panel-frame
  interaction this is explained in the section
  Stiffness of the Panels

References
Hitaka, T., and Matsui, C. (2003). Experimental
Study on Steel Shear Wall with Slits, Journal of
Structural Engineering, ASCE, 129(5), 586-595.