Next Level Looks at ACI 318, "Building Code Requirements for Structural Concrete

Anchor Bolt Design: Appendix D of the Building Code Requirements for Structural Concrete

In follow up to our last post, Next Level Looks at ACI 318, “Building Code Requirements for Structural Concrete , we ‘re now going to dig a little deeper into this code and look at what used to be called Appendix D, the section that specifically addresses concrete anchorage and anchor bolt design. The Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks (ANSI/RMI MH16.1) references ACI 318 Appendix D for anchor bolt design regarding securing pallet racks to the concrete floor. Section 1.4.7 of the specification states that all rack columns be anchored to the floor with anchor bolts, which are to be designed in accordance with Section 7.3, which in turn states that anchor bolt design shall be in accordance with the provisions of ACI 318 Appendix D. The International Building Code (IBC) also references ACI 318 Appendix D regarding its requirements for concrete anchorage.

A Brief History of Appendix D

The first formal concrete anchorage design provisions were set forth in Appendix D of the 2002 edition of ACI 318. Prior to this, designers relied on the manufacturers ‘ design tables which did not always represent all the characteristics associated with a particular anchor ‘s design capacity. The applications in this first code for anchorage design were limited to cast-in-place anchors and post-installed mechanical expansion anchors. In the 2011 edition of ACI 318, provisions were given for another type of post-installed anchors- adhesive (or bonded) anchors. Currently, screw anchors fall outside the scope of ACI 318 Anchoring to Concrete, but will be studied for inclusion during the next code cycle.

While “Appendix D technically no longer exists in the most recent incarnation of the American Concrete Institute ‘s code (ACI 318-14), the design provisions, Anchoring to Concrete, are still in the code, residing in Chapter 17 rather than an appendix.

“Appendix D in a Nutshell

Appendix D (or the chapter Anchoring to Concrete), outlines the general requirements for concrete anchors including the theory of design, seismic design requirements, and strength reduction factors. It also introduces the different anchor failure modes and includes both steel and concrete failure modes. In a nutshell, Appendix D is an all-encompassing document for every anchor situation.

A Note on Cracked Concrete

The state of the concrete can significantly influence the anchor ‘s capacity, and design professionals must determine whether to consider the state of the concrete “cracked or “uncracked. Appendix D explicitly does not define which concrete applications should be categorized as cracked or uncracked, which leaves the designer to determine by analysis the likelihood of the concrete cracking in the area where the anchors are installed. In the absence of such analysis, many designers choose to assume “cracked concrete. There are however, two situations that require designing for cracked concrete:

1. If a structure is in Seismic Design Categories C, D, E, or F.

2. If analysis indicates cracking at service level loading in the anchor location.

Additional factors that have the potential to result in cracked concrete are:

Temperature changes
Soil pressure
Differential settlement
Restrained shrinkage

Because concrete anchors are constantly evolving in the structural engineering industry, the ACI 318 design provisions for concrete anchorage will continue to be improved and updated along with modifications in the IBC. As new provisions and changes are made, manufacturers will develop new anchor types to answer engineering requirements.

Photo Credit: By Dmitry G (Own work) [CC BY-SA 3 or GFDL], via Wikimedia Commons

We take every part of your pallet rack system seriously. From starting with high yield strength carbon steel(we can produce mill certificates for every piece of coil that we purchase) to superior engineering & product design for every inch and element of your rack system (including the anchor bolts!), to expert systems design & equipment integration, Next Level is committed to on-going quality assurance in the design, manufacture, sale and service of quality storage products. For more information on how we can help you increase efficiency and profitability, contact us here or call 800-230-8846 now to speak to a design expert.

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We ‘ve mentioned ACI 318 Appendix D a few times lately. First, in our article, Concrete Anchor Bolts: Why These Little Components Are A Big Deal, and then again in Engineering and Design of Concrete Anchor Bolts. The upshot is that ANSI/RMI MH16.1 – Specification for the Design, Testing and Utilization of Industrial Steel Storage Racks references ACI 318 Appendix D for anchor bolt design regarding securing pallet racks to the concrete floor.The International Building Code (IBC) also gets into the act with its requirements for concrete anchorage which references ACI 318 Appendix D, which establishes the design rules for anchoring to concrete.

But all of that really doesn ‘t explain what ACI 318 and its Appendix D are all about. Let ‘s take a a closer look.

A Brief History of the ACI

Before we get into ACI 318, let ‘s look at the ACI (American Concrete Institute), it ‘s history, and it ‘s purpose. Formerly known as he National Association of Cement Users (NACU), this non-profit technical society was formed in 1904 when Charles C. Brown discussed in an editorial the idea of forming an organization to bring order and standard practices to the concrete building industry. The first committees were appointed at a 1905 convention in Indianapolis and offered preliminary reports on several subject areas. In 1909 a committee (later called the ACI Committee 318) was established to develop a concrete code. The “Standard Building Regulations for the Use of Reinforced Concrete” was adopted at the 1910 convention and became the association’s first reinforced concrete building code.

What is the ACI 318?

By the end of the 1930s, the code known as ACI 318 became the single document in the US dealing with concrete design. In 1989 the name of ACI 318 was changed from “Building Regulations for the Use of Reinforced Concrete to “Building Code Requirements for Structural Concrete.

The “Building Code Requirements for Structural Concrete” covers the materials, design, and construction of structural concrete used in buildings and where applicable in non-building structures. ACI 318 also covers the strength evaluation of existing concrete structures.

The ACI states:

The “Building Code Requirements for Structural Concrete (“Code ) provides minimum requirements for the materials, design, and detailing of structural concrete buildings and, where applicable, nonbuilding structures. This Code addresses structural systems, members, and connections, including cast-in-place, precast, plain, nonprestressed, prestressed, and composite construction. Among the subjects covered are: design and construction for strength, serviceability, and durability; load combinations, load factors, and strength reduction factors; structural analysis methods; deflection limits; mechanical and adhesive anchoring to concrete; development and splicing of reinforcement; construction document information; field inspection and testing; and methods to evaluate the strength of existing structures.

There have been many changes and additions to the code over the years. For example, the 1971 code had 750 provisions; there are now more than 2,500 provisions. Here ‘s a synopsis of the significant changes since 1971.

• Development lengths

• Torsional strength

• Seismic design and detailing

• Integrity reinforcement

• Concrete exposure classes

• Strain-based strength reduction factors

• Anchoring to concrete

Though there have been nine editions of the concrete code since 1971. T latest edition, ACI 318-14, has undergone a complete restructuring and represents the first reorganization of the concrete code in 45 years. Not only has the size of the manual grown dramatically since 1971, but the location of key elements has changed significantly.

According to the ACI, the major goals of the reorganization were for users to quickly find information, to increase certainty that a design fully meets the code, and for the ability to add new topics easily. Now organized from a designer’s perspective, the new ACI 318-14 assembles contractor provisions into one chapter instead of sprinkled throughout the manual to reduce the possibility of mistakes. The intention is that contractors should no longer need to learn the entire ACI 318-14 Code; rather, the new Chapter 26 Construction Chapter outlines what licensed design professional needs to provide to the contractor via the construction documents.

In addition to the many organizational changes in ACCI 318-14, there are a number of technical changes. The chapters that encompass most of the technical changes from the old code to the new are chapters 18, “Earthquake Resistant Structures and chapter 19, “Concrete: Design and Durability Requirements .

What is Appendix D?

In the old code, ACI 318-11, the installation, testing, and inspection of concrete anchors were addressed in Appendix D, “Anchoring to Concrete . In the new code, ACI 318-14, Appendix D is gone (as well as all other Appendices). The former Appendix D on concrete anchors is now contained in Chapter 17 of ACI 318-14 and is still called “Anchoring to Concrete . Our next post will delve into this 50 page chapter, so stay tuned! ( (Be the first to know -subscribe to our blog now to get the next post delivered directly to your email!)

Photo Credit: macrolepis [CC BY 3.0], via Wikimedia Commons

We take every part of your pallet rack system seriously. From starting with high yield strength carbon steel (we can produce mill certificates for every piece of coil that we purchase), to superior engineering & product design for every inch and element of your rack system (including the anchor bolts!), to expert systems design & equipment integration, Next Level is committed to on-going quality assurance in the design, manufacture, sale and service of quality storage products. For more information on how we can help you increase efficiency and profitability, contact us here or call 800-230-8846 now to speak to a design expert.