Embed Size (px)
Citation preview
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design: What They
Didn't Teach You in School
Thomas Mendez, S.E.
WSP USA
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design
• First introduced in
Appendix A of ACI
318-02.
• Moved to Chapter
23 in ACI 318-14,
but remains largely
unchanged.
American Concrete Institute
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design
ACI 318-14
• When must strut-and-tie be used?
o Anywhere plane sections do not remain
plane (D-Regions).
o Any structural component not explicitly
mentioned in the code.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design
• When must
strut-and-
tie be used?
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design
• When must
strut-and-
tie be used?
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design
ACI 318-14
• When may strut-and-tie be used?
o Anywhere.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Procedure
1. Understand how the structural component
is behaving.
2. Develop a truss model.
• Struts (compression)
• Ties (tension)
• Nodes (intersections)
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Procedure
3. Verify truss geometry is appropriate.
• Is equilibrium satisfied?
• Are angles greater than 25 degrees?
• Do struts intersect only at nodes?
4. Analyze the truss and determine truss
member forces.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Procedure
5. Check design capacities of struts, ties and
nodes.
• Verify adequate As is provided in ties.
6. Verify reinforcement can be developed at
critical locations.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #1
ACI SP-208
• Use simple,
statically
determinate strut-
and-tie models.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #1
• Use simple,
statically
determinate strut-
and-tie models.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #1
• Use simple,
statically
determinate strut-
and-tie models.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #1
• Use simple,
statically
determinate strut-
and-tie models.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #1
• Use simple,
statically
determinate strut-
and-tie models.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #2
• Node geometry
does not need
to conform to
the triangular
shapes indicated
in most design
examples.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #2
• Node geometry
does not need
to conform to
the triangular
shapes indicated
in most design
examples.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #3
• Prevent bottle
shaped struts
by confining
concrete with
ties.
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #3
• Prevent bottle
shaped struts
by confining
concrete with
ties.
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #3
• Prevent bottle
shaped struts
by confining
concrete with
ties.
ACI 318-11
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #4
• Use local strut-
and-tie models to
design bottle
shaped struts
when
f’c > 6,000psi.ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #4
• Use local strut-
and-tie models to
design bottle
shaped struts
when
f’c > 6,000psi.
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #4
• Use local strut-
and-tie models to
design bottle
shaped struts
when
f’c > 6,000psi.
ACI Structural Journal/November-December 2006
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #4
• Use local strut-
and-tie models to
design bottle
shaped struts
when
f’c > 6,000psi.
ACI Structural Journal/November-December 2006
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #5
• Be careful with
"incomplete" or
"partial" strut and
tie models.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #5
• Be careful with
"incomplete" or
"partial" strut and
tie models.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #6
ACI 318-14
• Don't consider steel plates with welded reinforcement as act as a compression face of a CCC node.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #6
• Don't consider steel plates with welded reinforcement as act as a compression face of a CCC node.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #7
• Discretize load
transfers at
intersections.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #7
• Discretize load
transfers at
intersections.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #7
• Discretize load
transfers at
intersections.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #7
• Discretize load
transfers at
intersections.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #7
• Discretize load
transfers at
intersections.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #7
• Discretize load
transfers at
intersections.
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #7
• Discretize load
transfers at
intersections.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #8
• Understand
how struts
may form in
tension zones.
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #8
• Understand how struts may form in tension
zones.
Reinforced Concrete,
James Wight
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #8
• Understand how struts may form in tension
zones.
Reinforced Concrete,
James Wight
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #9
• Be mindful of
potential
construction
joints crossing
struts.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #9
• Be mindful of
potential
construction
joints crossing
struts.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #9
• Be mindful of
potential
construction
joints crossing
struts.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #10
• Don’t forget
about self
weight.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #11
• Use
mechanical
terminators
to reduce
congestion.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #11
• Use
mechanical
terminators
to reduce
congestion.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #11
• Use
mechanical
terminators
to reduce
congestion.
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #12
• Don’t allow shear stress to exceed 10 ���.
ACI 318-11
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #12
• Don’t allow shear stress to exceed 10 ���.
ACI 318-14
www.oksea.org OSEA 2017 Fall Seminar
Strut-and-Tie Design Tip #13
• Don’t forget about serviceability and/or
stability.
www.oksea.org OSEA 2017 Fall Seminar
Questions?
ACI Structural Journal/November-December 2006
