Sp 17(11) The Reinforced Concrete Design Manual Volume 2: Benefits, Challenges, and Applications
Sp 17(11) The Reinforced Concrete Design Manual Volume 2: A Comprehensive Guide for Anchorage to Concrete
Reinforced concrete is one of the most widely used construction materials in the world. It has many advantages such as high strength, durability, fire resistance, and versatility. However, reinforced concrete also requires careful design and detailing to ensure its safety and performance. One of the key aspects of reinforced concrete design is anchorage to concrete, which refers to the connection of steel reinforcement or other embedded items to concrete members.
Sp 17(11) The Reinforced Concrete Design Manual Volume 2
Sp 17(11) The Reinforced Concrete Design Manual Volume 2 is a publication by the American Concrete Institute (ACI) that provides guidance and information on anchorage to concrete in accordance with ACI 318-11, the building code for structural concrete. This manual is part of a two-volume set that covers various topics related to reinforced concrete design. Volume 1 includes design and analysis for columns, flexure, footings, seismic, shear, deflection, and strut-and-tie.
In this article, we will focus on Volume 2 of the manual, which includes design and analysis for anchorage to concrete. We will explain what anchorage to concrete is, why it is important, what are the types of anchors and their applications, how to design anchors according to ACI 318-11, and what are the design examples and aids provided in the manual. By the end of this article, you will have a better understanding of Sp 17(11) The Reinforced Concrete Design Manual Volume 2 and how it can help you with your reinforced concrete projects.
Anchorage to concrete
Anchorage to concrete is the process of transferring forces from steel reinforcement or other embedded items to concrete members. Anchors are devices that provide this connection and resist tension, shear, or combined tension and shear forces. Anchors can be classified into two main categories: mechanical anchors and adhesive anchors.
Mechanical anchors
Mechanical anchors are anchors that rely on mechanical interlock or friction between the anchor and the concrete for load transfer. They can be further divided into two types: headed anchors and hooked anchors.
Headed anchors are anchors that have an enlarged head at one end that prevents pullout from the concrete. They can be either straight bars or deformed bars. Examples of headed anchors are headed studs, bolts, and deformed bars with welded plates.
Hooked anchors are anchors that have a bend or a hook at one end that engages the concrete and provides resistance against pullout. They can be either straight bars or deformed bars. Examples of hooked anchors are hooked bars, J-bolts, L-bolts, and U-bolts.
Mechanical anchors are typically used for applications where high loads are expected, where installation is easy and fast, where post-installed anchors are not feasible, or where fire resistance is not a concern.
Adhesive anchors
Adhesive anchors are anchors that rely on a bonding agent or an adhesive between the anchor and the concrete for load transfer. They can be either bonded anchors or grouted anchors.
Bonded anchors are anchors that are inserted into pre-drilled holes in the concrete and bonded with an adhesive such as epoxy, polyester, or vinylester. They can be either threaded rods, deformed bars, or smooth bars. Examples of bonded anchors are threaded rods with nuts and washers, deformed bars with couplers, and smooth bars with sleeves.
Grouted anchors are anchors that are placed into pre-formed pockets or sleeves in the concrete and grouted with a non-shrink cementitious or resinous material. They can be either threaded rods, deformed bars, or smooth bars. Examples of grouted anchors are threaded rods with grout caps, deformed bars with grout sleeves, and smooth bars with grout tubes.
Adhesive anchors are typically used for applications where low to moderate loads are expected, where installation is difficult or requires precision, where post-installed anchors are required, or where fire resistance is a concern.
Design of anchors according to ACI 318-11
The design of anchors according to ACI 318-11 is based on the strength design method, which requires the determination of the nominal strength of the anchor and the reduction factor for the strength. The nominal strength of the anchor is the lowest of the following three components: steel strength, concrete breakout strength, and concrete pullout or side-face blowout strength. The reduction factor for the strength is based on the reliability of the anchor system and the consequences of failure. The design strength of the anchor is then obtained by multiplying the nominal strength by the reduction factor.
The design of anchors also requires the consideration of various limit states and failure modes, such as ductility, bond, splitting, pryout, group effects, edge effects, interaction effects, and seismic effects. The design of anchors must satisfy the requirements for both serviceability and ultimate limit states. The serviceability limit state refers to the condition where the anchor does not exhibit excessive deformation or damage under normal service loads. The ultimate limit state refers to the condition where the anchor does not fail under factored loads.
The design of anchors must also comply with the provisions for installation, inspection, and testing of anchors. The installation of anchors must follow the manufacturer's instructions and specifications, as well as the applicable codes and standards. The inspection and testing of anchors must ensure that the anchors are installed properly and have adequate capacity and performance.
Design examples and aids in Sp 17(11) The Reinforced Concrete Design Manual Volume 2
Sp 17(11) The Reinforced Concrete Design Manual Volume 2 provides several design examples and aids for anchorage to concrete in accordance with ACI 318-11. The design examples illustrate the application of the design provisions and procedures for various types of anchors and loading conditions. The design aids are tables and graphs that facilitate the calculation of the nominal strength and the reduction factor for different types of anchors.
The following table shows a summary of the design examples and aids in Sp 17(11) The Reinforced Concrete Design Manual Volume 2.
Chapter
Topic
Design Examples
Design Aids
1
Anchorage to concrete: General
1.1: Design example for headed stud anchor subjected to tension load1.2: Design example for hooked bar anchor subjected to tension load1.3: Design example for bonded anchor subjected to tension load1.4: Design example for headed stud anchor subjected to shear load1.5: Design example for hooked bar anchor subjected to shear load1.6: Design example for bonded anchor subjected to shear load1.7: Design example for headed stud anchor subjected to combined tension and shear load1.8: Design example for hooked bar anchor subjected to combined tension and shear load1.9: Design example for bonded anchor subjected to combined tension and shear load
A-1: Nominal steel strength in tensionA-2: Nominal steel strength in shearA-3: Nominal concrete breakout strength in tensionA-4: Nominal concrete breakout strength in shearA-5: Nominal concrete pullout strength in tensionA-6: Nominal concrete side-face blowout strength in tensionA-7: Reduction factor for steel strength in tensionA-8: Reduction factor for steel strength in shearA-9: Reduction factor for concrete breakout strength in tensionA-10: Reduction factor for concrete breakout strength in shearA-11: Reduction factor for concrete pullout or side-face blowout strength in tension
<tr Continuing the article: Ductility of anchors
Ductility is the ability of a material or a system to undergo large deformations without losing its load-carrying capacity. Ductility is always an advantage in seismic design, as it allows the structure to absorb and dissipate energy during an earthquake and avoid brittle failure. A ductile anchor system shows a considerable degree of deformation before failure occurs, as shown in the graph below.
ACI 318-11 requires that anchors used in structures assigned to Seismic Design Categories C, D, E, or F must be designed to be ductile unless the anchor forces are amplified to account for the lack of ductility. The ductility of an anchor depends on several factors, such as the type of anchor, the type of loading, the type of concrete, the installation method, and the reinforcement details.
ACI 318-11 defines a ductile steel element as an element with a tensile elongation of at least 14 percent and a reduction in area of at least 30 percent. The ductility of an anchor can be verified by checking the properties of the steel element (such as the minimum specified yield strength and the minimum specified ultimate strength) and the load-displacement behavior of the anchor (such as the ratio of ultimate load to yield load and the displacement at ultimate load) as provided by the manufacturer or the qualification report.
Sp 17(11) The Reinforced Concrete Design Manual Volume 2 provides guidance on how to verify the ductility of anchors for different types of loading conditions. For example, for anchors subjected to tension load only, the manual recommends that the following criteria be satisfied:
The nominal steel strength in tension (N sa) must not exceed 90 percent of the nominal concrete breakout strength in tension (N cbg).
The ratio of ultimate load to yield load (N u/N y) must not be less than 1.25.
The displacement at ultimate load (u u) must not be less than 0.03 in.
The following table shows an example of verifying the ductility of a bonded anchor subjected to tension load only using the design aids from Sp 17(11) The Reinforced Concrete Design Manual Volume 2.
Parameter
Value
Criteria
Check
N sa
15.9 kips
<= 0.9 N cbg
OK (15.9 <= 0.9 x 20.8)
N u/N y
1.38
>= 1.25
OK (1.38 >= 1.25)
</tr Continuing the article: Seismic effects on anchors
Seismic events can have a significant impact on the loading and behavior of anchors in concrete. During an earthquake, anchors can be subjected to high cyclic loads in multiple directions, resulting in large deformations and damage in the concrete and the steel elements. Therefore, anchors used in structures assigned to Seismic Design Categories C, D, E, or F must be designed to resist seismic forces and ensure adequate safety and performance.
Seismic effects on anchors can be influenced by several factors, such as the type and magnitude of the earthquake, the location and orientation of the anchor, the type and condition of the concrete, the type and arrangement of the reinforcement, the type and installation of the anchor, and the type and stiffness of the attached element. Some of the main seismic effects on anchors are:
Cracking: Seismic loading can cause cracking in the concrete around the anchor, which reduces the concrete strength and stiffness and affects the anchor capacity and stiffness. Cracks can also open and close during an earthquake, causing cyclic tension and compression in the anchor. The crack width can be up to 0.8 mm during seismic according to ETAG 001.
Slip: Seismic loading can cause slip or displacement of the anchor relative to the concrete, which reduces the load transfer and increases the deformation. Slip can also cause fatigue damage in the anchor or the adhesive material. The slip behavior depends on the type of anchor, the type of loading, and the type of concrete.
Bending: Seismic loading can cause bending moments in the anchor due to eccentricity or prying effects. Bending moments can reduce the axial capacity and increase the stress concentration in the anchor. Bending moments can also cause buckling or fracture of slender or brittle anchors.
Group effects: Seismic loading can cause interaction effects among multiple anchors in a group due to load redistribution or crack propagation. Group effects can reduce the individual anchor capacity and increase the variability of anchor behavior.
Edge effects: Seismic loading can cause edge effects for anchors close to a free edge or a corner due to reduced concrete confinement or spalling. Edge effects can reduce the concrete breakout strength and increase the sensitivity to cracking.
Sp 17(11) The Reinforced Concrete Design Manual Volume 2 provides guidance on how to account for seismic effects on anchors for different types of loading conditions. For example, for anchors subjected to tension load only, the manual recommends that the following criteria be satisfied:
The nominal concrete breakout strength in tension (N cbg) must be multiplied by a seismic reduction factor (ψ c,T) that depends on the edge distance, the crack width, and the seismic design category.
The nominal concrete pullout or side-face blowout strength in tension (N pn or N sbn) must be multiplied by a seismic reduction factor (ψ cp,T) that depends on the crack width and the seismic design category.
The nominal steel strength in tension (N sa) must be multiplied by a seismic reduction factor (ψ s,T) that depends on whether steel failure is ductile or brittle.
The following table shows an example of accounting for seismic effects on a bonded anchor subjected to tension load only using the design aids from Sp 17(11) The Reinforced Concrete Design Manual Volume 2.
Parameter
Value
Criteria
Check
</tr Continuing the article: Benefits and challenges of using Sp 17(11) The Reinforced Concrete Design Manual Volume 2
Sp 17(11) The Reinforced Concrete Design Manual Volume 2 is a valuable resource for engineers and designers who are involved in the design of reinforced concrete structures and connections. The manual provides the following benefits:
It covers various topics related to anchorage to concrete in accordance with ACI 318-11, such as general requirements, design methods, failure modes, limit states, seismic effects, installation, inspection, and testing.
It provides concise theoretical background and explanations for the design provisions and procedures based on the latest research and practice.
It provides numerous solved examples that illustrate the application of the design provisions and procedures for different types of anchors and loading conditions.
It provides design aids such as tables and graphs that facilitate the calculation of the nominal strength and the reduction factor for different types of anchors.
However, the manual also poses some challenges for users, such as:
It requires familiarity with ACI 318-11 and its terminology and notation.
It does not cover all possible types of anchors and applications that may be encountered in practice.
It does not provide guidance on how to select the most appropriate type of anchor for a given situation or how to optimize the anchor layout and spacing.
It does not address some specific issues or limitations related to certain types of anchors or concrete conditions.
Therefore, users of the manual should exercise professional judgment and discretion when applying the information and recommendations provided in the manual. Users should also consult other sources of information and guidance, such as manufacturer's instructions, qualification reports, codes and standards, technical literature, and engineering experience.
Conclusion
In this article, we have introduced Sp 17(11) The Reinforced Concrete Design Manual Volume 2, a publication by ACI that provides guidance and information on anchorage to concrete in accordance with ACI 318-11. We have explained what anchorage to concrete is, why it is important, what are the types of anchors and their applications, how to design anchors according to ACI 318-11, what are the design examples and aids provided in the manual, what are the ductility and seismic effects on anchors, and what are the benefits and challenges of using the manual. We hope that this article has helped you to gain a better understanding of Sp 17(11) The Reinforced Concrete Design Manual Volume 2 and how it can help you with your reinforced concrete projects.
FAQs
Here are some common questions and answers related to Sp 17(11) The Reinforced Concrete Design Manual Volume 2 and anchorage to concrete:
What is Sp 17(11) The Reinforced Concrete Design Manual Volume 2?Sp 17(11) The Reinforced Concrete Design Manual Volume 2 is a publication by ACI that provides guidance and information on anchorage to concrete in accordance with ACI 318-11. It is part of a two-volume set that covers various topics related to reinforced concrete design.
What is anchorage to concrete?Anchorage to concrete is the process of transferring forces from steel reinforcement or other embedded items to concrete members. Anchors are devices that provide this connection and resist tension, shear, or combined tension and shear forces. Anchors can be classified into two main categories: mechanical anchors and adhesive anchors.
How to design anchors according to ACI 318-11?The design of anchors according to ACI 318-11 is based on the strength design method, which requires the determination of the nominal strength of the anchor and the reduction factor for the strength. The design of anchors also requires the consideration of various limit states and failure modes, such as ductility, bond, splitting, pryout, group effects, edge effects, interaction effects, and seismic effects. The design of anchors must satisfy the requirements for both serviceability and ultimate limit states. The design of anchors must also comply with the provisions for installation, inspection, and testing of anchors.
What are the design examples and aids provided in Sp 17(11) The Reinforced Concrete Design Manual Volume 2?Sp 17(11) The Reinforced Concrete Design Manual Volume 2 provides several design examples and aids for anchorage to concrete in accordance with ACI 318-11. The design examples illustrate the application of the design provisions and procedures for various types of anchors and loading conditions. The design aids are tables and graphs that facilitate the calculation of the nominal strength and the reduction factor for different types of anchors.
What are the benefits and challenges of using Sp 17(11) The Reinforced Concrete Design Manual Volume 2?Sp 17(11) The Reinforced Concrete Design Manual Volume 2 provides the following benefits: it covers various topics related to anchorage to concrete in accordance with ACI 318-11; it provides concise theoretical background and explanations for the design provisions and procedures; it provides numerous solved examples that illustrate the application of the design provisions and procedures; and it provides design aids such as tables and graphs that facilitate the calculation of the nominal strength and the