Scott M. Tarr, FACI, is President of North
S.Tarr Concrete Consulting, Dover, NH.
He is a licensed engineer with nearly
30 years of experience in concrete floor
slab design and floor covering issues.
He has authored numerous articles and
documents, including the book Concrete
Floors on Ground. He is Chair of ACI
Committee 360, Design of Slabs on
Ground, and a member of several ACI committees, including 301,
Specifications for Structural Concrete, and 302, Construction of
Concrete Floors. He is also a member of ACPA, ASCC, ASCE,
ASTM International, and ICRI.
ACI member Matthew J. Sheehan is
President of Concrete & Construction
Consultants, LLC (3CON), Palatine,
IL. He is a licensed engineer with
nearly 25 years of field and laboratory
experience performing design, research,
investigations, and forensic evaluations
related to the construction and
serviceability of infrastructure, including
cement-based materials, slab-on-ground floors, pavements,
and reinforced concrete structures. He is a member of ACI
Committees 301, Specifications for Structural Concrete; 302,
Construction of Concrete Floors; 325, Concrete Pavements; and
360, Design of Slabs on Ground. He is also a member of ASCC,
ASCE, ASTM International, and TRB.
ACI member Eric J. Van Duyne is a
Principal at Building Infrastructure
Consultants, LLC. He is a licensed
structural engineer with 19 years
of experience in forensic analysis,
evaluation, repair, and design of
concrete structures. He is a member of
ACI Committee 437, Strength Evaluation
of Existing Concrete Structures, and
Joint ACI-ASCE Committee 550, Precast Concrete Structures. He
is also a member of the Precast/Prestressed Concrete Institute
(PCI) and the 9th Edition PCI Handbook Committee. He received
his BS and MS in civil engineering from the University of Illinois
at Urbana-Champaign, Urbana, IL.
www.concreteinternational.com | Ci | JANUARY 2020 35
Connection of wall panels to a slab-on-ground, whether for
seismic requirements or to prevent panel bowing, increases
the risk of random cracking in the slab. This risk should be
discussed in predesign and preconstruction meetings, and
alternative details should be considered. Other topics that
should be discussed include the amount of slab that must be
mobilized and the long-term implications of requiring slab
reinforcing to remain in place.
Even when the wall-panel connection is made only to
restrain out-of-plane movement of the wall panel, the area
of the slab requiring reinforcing bars may become excessive.
As previously noted, the area of slab that must be mobilized
to transfer the force will be a function of the coefficient of
friction between the slab and underlying base. This may
become a significant cost consideration if a subslab vaporretarder
sheet is required to avoid damage to moisture-sensitive
flooring, to avoid moisture damage to goods stored directly
on the floor, or to lower the risk of slab sweating. Because a
vapor-retarder or slip sheet reduces the coefficient of friction
between the slab and base, some engineers have required the
reinforcement to extend several bays into the slab interior,
impacting cost as well as increasing the risk of cracking.
It also must be communicated that the tie reinforcement
and the reinforcement in the slab-on-ground cannot be cut or
removed during the life of the structure. As discussed by PCI,6
this is a significant consideration as it is very common to
remove and replace deteriorated portions of slabs-on-ground,
especially in high-traffic areas. Further, slab-on-ground
repairs are generally doweled into the existing slab with
smooth dowels that minimize restraint of the replacement
concrete shrinkage after setting. If the tie-back reinforcement
is required to be maintained, this can substantially change the
repair detail and associated risk of cracking in the replacement
concrete. For this reason, ACI 318-14 and ACI 318-19,
Provision 188.8.131.52(d), requires:
“Saw cutting in slabs-on-ground identified in the construction
documents as structural diaphragms or part of the seismicforce
resisting system shall not be permitted unless specifically
indicated or approved by the licensed design professional.”
Early discussion of these issues may allow the introduction
of alternative details that will provide more economical means
of ensuring the long-term performance of the wall panels, the
floor slab-on-ground, and the complete structural system.
1. ACI Committee 360, “Guide to Design of Slabs-on-Ground
(ACI 360R-10),” American Concrete Institute, Farmington Hills, MI,
2010, 72 pp.
2. ACI Committee 318, “Building Code Requirements for Structural
Concrete (ACI 318-14) and Commentary (ACI 318R-14),” American
Concrete Institute, Farmington Hills, MI, 2014, 519 pp.
3. ACI Committee 318, “Building Code Requirements for Structural
Concrete (ACI 318-19) and Commentary (ACI 318R-19),” American
Concrete Institute, Farmington Hills, MI, 2019, 629 pp.
4. ACI Committee 302, “Guide to Concrete Floor and Slab
Construction (ACI 302.1R-15),” American Concrete Institute,
Farmington Hills, MI, 2015, 76 pp.
5. “Concrete Floors on Ground,” EB075, third edition, Portland
Cement Association (PCA), Skokie, IL, 2001, 136 pp.
6. PCI Committee on Precast Sandwich Panels, “State of the Art of
Precast/Prestressed Concrete Sandwich Wall Panels,” second edition,
PCI Journal, V. 56, No. 2, Mar. 2011, pp. 131-176.
Selected for reader interest by the editors.