Category: Aci anchor bolt design

Aci anchor bolt design

Option D is selected. Option C is selected. Factored Tensile Force Input tensile force here and the value shall be positive value. Key in 0 here if there is no tensile force or there is only compression force. Anchor Bolt Embedment Depth h ef - anchor bolt embedment depth. Pedestal Height h or h a - pedestal height or concrete thickness. Outermost Anchor Bolt Line Spacing S 1 s 1 is the distance between two outermost columns of anchor bolt linealong shear force acting direction.

Outermost Anchor Bolt Line Spacing S 2 s 2 is the distance between two outermost rows of anchor bolt lineperpendicular to shear force acting direction. Rebar Yield Strength Rebar yield strength used in vertical anchor reinforcement calculation to resist concrete tensile breakout. Rebar Yield Strength Rebar yield strength used in horizontal anchor reinforcement calculation to resist concrete shear breakout.

Anchor Rod Corrosion Allowance Anchor rod may have corrosion issue if it is exposed to exterior or extreme environmental conditions. Save My Inputs Please key in your file name below. File Name:. Load My Inputs. About This Spreadsheet This spreadsheet is to design group headed anchor bolt anchorage to concrete using ACI code.

Using ACI code in imperial unit Anchor bolts work as group Anchor bolts are subject to tensile and shear force, no moment Using anchor reinforcement to resist concrete tensile and shear breakout.

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Turn Side Menu Off. Turn Suggestion Off. Check License Status. About This Calc. View Help. Combined Tension and Shear. ACI Yes No. To be considered effective for resisting anchor tension, vertical reinforcing bars shall be located.

No of ver. To be considered effective for resisting anchor shear, hor. Tension Shear Interaction. Seismic Design. For tie reinft, only the top most 2 or 3 layers of ties 2" from TOC and 2x3" after are effective. Strut-and-Tie model is used to anlyze the shear transfer and to design the required tie reinft. Anchor bolt washer shall be tack welded to base plate for all anchor bolts to transfer shear. Anchor Rod Tensile Resistance.Min Rquired Anchor Reinft.

Column Depth. No of ver.

Anchor Bolt Design: Overview of the ACI Seismic Provisions

To be considered effective for resisting anchor shear, hor. Anchor Rod Corrosion Allowance Anchor rod may have corrosion issue if it is exposed to exterior or extreme environmental conditions.

Anchor Bolt Embedment Depth h ef - anchor bolt embedment depth. Pedestal Height h or h a - pedestal height or concrete thickness. Rebar Yield Strength Rebar yield strength used in vertical anchor reinforcement calculation to resist concrete tensile breakout.

Rebar Yield Strength Rebar yield strength used in horizontal anchor reinforcement calculation to resist concrete shear breakout. Save My Inputs Please key in your file name below.

aci anchor bolt design

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

Quick Input method allows users to switch between different anchor bolt patterns and design options quickly and get the design result immediately in one user interface. It also allows user to design anchor forces in 2 directions at the same time. No license Issued for This Spreadsheet You are a registered user but you didn't get a license for this spreadsheet. The reason may be Your license has expired You own license for other module but don't have license for this module Your license has been checked out by other user on other PC You are now using the spreadsheet on demo mode.

Trial Version Limitation This field cannot be edited by trial version user. Internal Bolt Line Spacing s b2 s b2 is the internal bolt line spacing.

Ignore this input if it is 2 Bolt Line or 3 Bolt Line case. Internal Bolt Line Spacing s b1 s b1 is the internal bolt line spacing. Ignore this input if it is 2 Bolt Line case. Column Depth d Column depth d. For an anchor bolt group carrying moment, only part of anchor bolts in the group mobilizes tensile force.

Civil Bay. Save Input. Load Input. Turn Side Menu Off. Turn Suggestion Off. Check License Status.Most building codes currently reference ACI — 11 Appendix D as the required provision for designing a wide variety of anchor types that include expansion, undercut, adhesive and cast-in-place anchors in concrete base materials. This blog post will focus on section D. Ductility is a benefit in seismic design. A ductile anchor system is one that exhibits a meaningful degree of deformation before failure occurs.

However, ductility is distinct from an equally important dimension called strength. Add strength, and a ductile steel element like the one shown in Figure 1 can now exhibit toughness. During a serious earthquake, a structural system with appreciable toughness i. Any visible deformations could help determine if repair is necessary. Section D. We will focus on achieving the ductility option, aof D. To understand anchor ductility we need to first identify the possible failure modes of an anchor.

Figure 2 shows the three types of failure modes we can expect for an adhesive anchor located away from a free edge. These three failure modes generically apply to virtually any type of anchor expansion, screw, cast-in-place or undercut.

Breakout N b and pullout N a are not considered ductile failure modes. Breakout failure N b can occur very suddenly and behaves mostly linear elastic and consequently absorbs a relatively small amount of energy. To achieve ductility, not only does the steel need to be made of a ductile material but the steel must govern out of the three failure modes. Additionally, the anchor system must be designed so that steel failure governs by a comfortable margin.

Breakout and pullout can never control while the steel yields and plastically deforms. This is what is meant by meeting the ductility requirements of Appendix D. For this size anchor, the published characteristic bond strength is psi. Anchor software calculations will produce the following information:.

Pullout clearly governs i. So it might come as a surprise to learn that this adhesive anchor actually is ductile! To understand why, we need to look at the nominal strength not the design strength of the different anchor failure modes. However, manufacturers will list factors specific to their adhesive based on anchor testing. The mandatory 0. The important thing to remember is that the nominal strength provides a better representation of the relative capacity of the different failure modes.

Remove these reduction factors and we get the following:. Now steel governs since it has the lowest strength. This is to account for the fact that F Gr. With this in mind, the next step would be to additionally meet section D. The values to compare finally become:. Now steel governs, but one more thing is required. As shown in Figure 3, Section D. Research has shown that a sufficient stretch length helps ensure that an anchor can experience significant yielding and plastic deformation during tensile loading.

Lastly, section D.By: Javier Encinas October 2, This document covers the required steps in the process of the design of the cast-in anchor rods normally encountered in column base plates. Anchor rods are usually subjected to a combination of tension and shear forces. The Part 1 of this post will discuss the tension anchor bolt design.

For compression columns with no moments, the bearing diagram is uniform, as shown in the left picture below. If now we add a small moment, the bearing diagram varies but the full base plate is still under compression, as shown in the center picture below. As the applied moment increases, only a portion of the plate is under compression and the anchor rods provide the required tension to maintain the static equilibrium.

The calculation of the tension in the anchor rods depends of the strain compatibility assumption for the base plate. For a discussion of the different theories please refer to our blog post Base Plate and Anchor Rod Design. Once the tension force has been calculated, the anchor rods should be checked for the following failure modes:.

The denominator is the breakout area of a single anchor, and the numerator is the group breakout area. The former can be easily calculated, but the latter may be quite difficult, since it depends on the geometric conditions of the support, as shown below. A further complication arises when the plate is located less than 1. ASDIP Steel accurately calculates, for any support conditions, the breakout area Anc and the effective embedment depth hef and provides a graphic view, as shown below.

The calculation of the breakout failure mode is particularly important since a concrete failure would be non-ductile, and therefore it should be avoided.

To prevent this kind of failure, the Code allows the use of reinforcing steel across the failure surface.

This anchor reinforcement, however, must be designed and detailed carefully so that the strength of the rebars can be developed at both sides of the failure surface. Abrg is the net bearing area of the anchor head. If the controlling failure mode is either the steel strength or the anchor reinforcement strength, then the failure will be ductile. Any concrete failure, either breakout, pullout or side blowout, will be a brittle failure.

Unlike the anchor reinforcement, the supplementary reinforcement does not need to be designed and detailed to take the full tension load.

The Part 2 of this post deals with the design of anchor rods for shear, as well as the tension-shear interaction. Please log in again. The login page will open in a new tab. After logging in you can close it and return to this page.

Steel failure — This is a measure of the capacity of the anchor material, regardless of the anchoring conditions. The calculations are based on the properties of the anchor material and the physical dimensions of the anchor. The nominal steel strength is: where Ase is the effective cross sectional area of the anchor. Concrete breakout — It assumes a failure forming a concrete cone based on a prism angle of 35 degrees.

The CCD Method predicts the strength of a group of anchors by using a basic equation for a single anchor Nband multiplied by factors that account for the number of anchors, edge distance, spacing, eccentricity, etc.

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aci anchor bolt design

Leslie Gunatilleka says:. October 3, at pm. Javier Encinas, PE says:. Close dialog. Session expired Please log in again.Anchorages designed to resist seismic load conditions require special consideration. ACI seismic anchoring provisions are given in Part D.

ACI seismic anchoring provisions are given in Section ACI Part D. The ACI and IBC codes assume cracked concrete conditions for the design of cast-in-place and post-installed anchors because the existence of cracks in the anchor vicinity can result in a reduced ultimate load capacity and increased displacement at ultimate load.

ACI requires post-installed anchors to be qualified for seismic load conditions via testing in cracked concrete. Flexural crack widths corresponding to the onset of reinforcing yield under seismic loading are assumed to equal 0. ACI seismic anchoring provisions must be satisfied for both tension and shear. In contrast to these provisions, ACI and ACI seismic anchoring provisions permit design for either tension, or shear, or both tension and shear.

Masonry Anchor Bolt Design Calculator

The provisions in the option selected must be satisfied for both tension and shear load conditions. The commentary RD. This criterion will be covered when discussing Part D.

Part D.

aci anchor bolt design

The design steel strength in tension, defined by the parameter N samust be the controlling tension design strength compared to the non-steel tension design strengths defined by the parameter 0.

Likewise, the design steel strength in shear, defined by the parameter V samust be the controlling shear design strength compared to the non-steel shear design strengths defined by the parameter 0.

Anchor elements that do not satisfy these criteria, or for which these criteria are not determined, are assumed to be brittle steel elements, which precludes them from design with the provisions of D.

The force calculated to yield the attachment must be less than or equal to the calculated anchor design strengths. Tension anchor design strengths are defined as N sa for steel failure and 0. Shear anchor design strengths are defined by V sa for steel failure and 0. The ACI code recognizes, however, that an anchorage design controlled by a ductile failure mode may not be possible.

For example, anchor spacing and edge distance, concrete member thickness, or base plate properties may preclude an anchorage design controlled by a ductile failure mode.

Therefore, Part D. The provisions of Part D. For simplicity, this factor will be referred to in this article as nonductile. The default value for nonductile is 0. The IBC Section ACI and ACI seismic anchor calculations do not have to be performed if the earthquake component of the factored load acting on the anchorage is less than or equal to twenty percent of the total factored load acting on the anchorage.

Unlike ACI Appendix D seismic provisions, ACI and ACI seismic anchor provisions permit design for either tension conditions, or shear conditions, or both tension and shear conditions. Equations consisting of factored load combinations are given in ACI Section 9. The parameter E in these equations corresponds to the earthquake force component of the factored load.

When considering tension loads that include E, if the value calculated for E is less than or equal to twenty percent of the total factored load, no seismic calculations are required for tension.

In this case, the tension design for the anchorage will be per Table D. If E is greater than twenty percent of the total factored tension load, Part D.Section 1. The first formal concrete anchorage design provisions were set forth in Appendix D of the edition of ACI The applications in this first code for anchorage design were limited to cast-in-place anchors and post-installed mechanical expansion anchors. In the edition of ACIprovisions were given for another type of post-installed anchors— adhesive or bonded anchors.

aci anchor bolt design

Appendix D or the chapter Anchoring to Concreteoutlines 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. If analysis indicates cracking at service level loading in the anchor location. Additional factors that have the potential to result in cracked concrete are:. Because concrete anchors are constantly evolving in the structural engineering industry, the ACI design provisions for concrete anchorage will continue to be improved and updated along with modifications in the IBC.

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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 design provisions for concrete anchorage will continue to be improved and updated along with modifications in the IBC. Leave a comment. Cancel reply Your email address will not be published.The function of anchor bolts is to transfer loads to the masonry from attachments such as ledgers, sills, and bearing plates.

Both shear and tension are transferred through anchor bolts to resist design forces such as uplift due to wind at the top of a column or wall or vertical gravity loads on ledgers supporting joists or trusses see Figure 1.

The magnitude of these loads varies significantly with the application. This TEK summarizes the requirements to properly design, detail and install anchor bolts embedded in concrete masonry construction based on the provisions of the edition of Building Code Requirements for Masonry Structures ref.

Anchor bolts can generally be divided into two categories: embedded anchor bolts, which are placed in the grout during the masonry construction; and post-installed anchors, which are placed after the masonry is constructed. Post-installed anchors achieve shear and tension pull out resistance by means of expansion against the masonry or sleeves or by bonding with epoxy or other adhesives. Anchor bolt configurations covered by Building Code Requirements for Masonry Structures fall into one of two categories:.

For other anchor bolt configurations, including post-installed anchors, design loads are determined from testing a minimum of five specimens in accordance with Standard Test Methods for Strength of Anchors in Concrete and Masonry Elements, ASTM E ref. Building Code Requirements for Masonry Structures ref. Note that Chapter 5 of the code also includes prescriptive criteria for floor and roof anchorage that are applicable to empirically designed masonry, but these provisions are not covered here.

While many of the requirements for anchor design vary between the allowable stress and strength design methods, some provisions are commonly shared between the two design approaches. The following discussion and topics apply to anchors designed by either the allowable stress or strength design methods.

Understanding and Meeting the ACI 318 – 11 App. D Ductility Requirements – A Design Example

For both design methods, the anchor bolt net area used to determine the design values presented in this TEK are taken equal to the following, which account for the reduction in area due to the presence of the anchor threading:. The minimum effective embedment length for anchor bolts is four bolt diameters 4 d b or 2 in. For bent-bar anchors, the effective embedment length is measured parallel to the bolt axis from the masonry surface to the bearing surface on the bent end minus one anchor bolt diameter.

This requirement applies to anchor bolts embedded in the top of a masonry element as well as those penetrating through the face shells of masonry as illustrated in Figure 2. While research ref. Although it rarely controls in typical masonry design, Building Code Requirements for Masonry Structures also requires that the distance between parallel anchors be at least equal to the diameter of the anchor, but not less than 1 in.

Existing masonry codes do not address tolerances for anchor bolt placement. In the absence of such criteria, construction tolerances used for placement of structural reinforcement could be modified for application to anchor bolts. In order to keep the anchor bolts properly aligned during grout placement, templates can be used to hold the bolts within the necessary tolerances.

Templates, which are typically made of wood or steel, also prevent grout leakage in cases where anchors protrude from the side of a wall.

The projected tension breakout area, A ptand the projected shear breakout area, A pvfor headed and bent-bar anchors are determined by Equations 1 and 2 as follows:. The anchor bolt edge distance, l beis measured in the direction of the applied load from the center of the anchor bolt to the edge of the masonry. Any portion of the projected area that falls within an open cell, open core, open head joint, or falls outside of the masonry element is deducted from the calculated value of A pt and A pv.

A graphical representation of a tension breakout cone is shown in Figure 4. The allowable axial tensile load, Ba, for headed and bent-bar anchor bolts is taken as the smaller of Equation 3, allowable axial tensile load governed by masonry breakout, and Equation 4, allowable axial tensile load governed by anchor yielding. For bent-bar anchors, the allowable axial tensile load must also be less than that determined by Equation 5 for anchor pullout.

The allowable shear load, B vfor headed and bent-bar anchor bolts is taken as the smallest of Equation 6, allowable shear load governed by masonry breakout, Equation 7, allowable shear load as governed by crushing of the masonry, Equation 8, allowable shear load as governed by masonry pryout, and Equation 9, allowable shear load as governed by anchor yielding.

Anchor bolts subjected to combined axial tension and shear must also satisfy the following unity equation:. The relationship between applied tension and shear loads versus allowable tension and shear loads is illustrated in Figure 5. The design provisions for anchor bolts using the strength design method is nearly identical to that used for allowable stress design, with appropriate revisions to convert the requirements to produce nominal axial tension and shear design strengths. The nominal axial tensile strength, B anfor headed and bent-bar anchor bolts is taken as the smaller of Equation 11, nominal axial tensile strength governed by masonry breakout, and Equation 12, nominal axial tensile strength governed by anchor yielding.

For bent-bar anchors, the nominal axial tensile strength must also be less than that determined by Equation 13 for anchor pullout. The nominal shear strength, Bvn, for headed and bent-bar anchor bolts is taken as the smallest of Equation 14, nominal shear strength governed by masonry breakout, Equation 15, nominal shear strength as governed by crushing of the masonry, Equation 16, nominal shear strength as governed by masonry pryout, and Equation 17, nominal shear strength as governed by anchor yielding.

As with allowable stress design, anchor bolts subjected to combined axial tension and shear must also satisfy the following unity equation:. The bolts have an effective yield stress of 60 ksi With this, the total design shear force for the connection is 1, lb 7. As is typical with bolted connections subjected to shear, the load is imparted at an offset distance, e which is equivalent to the additive thickness of the ledger and connector elements.

This eccentric load generates a force couple with tensile forces in the anchor and bearing of the masonry wall.


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