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.Which Drywall Anchor is Best? Let's find out!
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. 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.For full table with more Property Classes - rotate the screen! Proof load is defined as the maximum tensile force that can be applied to a bolt that will not result in plastic deformation.
Ultimate Tensile and Proof loads for metric bolts according ISO "Mechanical properties of fasteners made of carbon steel and alloy steel - Part 1: Bolts, screws and studs with specified property classes — Coarse thread and fine pitch thread". Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro.
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Citation This page can be cited as Engineering ToolBox, Modify access date. Scientific Online Calculator. Make Shortcut to Home Screen?In addition to technical updates, there were four non-technical changes. The second change is that the code has six fewer pages than the edition, being one of the few structural codes that have fewer pages than the previous edition Figure 2. The third change was to incorporate user-friendly tables rather than text throughout the document. The fourth change is not a direct revision to the edition; TMS has approved a six-year code cycle, so the next TMS code will be the edition.
A significant technical change was the addition of shear friction provisions. Masonry shear walls that have a low axial compressive load and a low height-to-length ratio are vulnerable to shear sliding, which normally occurs at the base.
DESIGN OF ANCHOR BOLTS EMBEDDED IN CONCRETE MASONRY
Shear sliding can cause damage to the masonry due to the simultaneous actions of the shear stress, compressive stress, and dowel action. One set of equations is for low height-to-length shear walls, while the provisions for flexurally-dominated walls account for the fact that not all the reinforcement crossing the horizontal shear plane will contribute to the clamping force and provides a reduced coefficient of friction. Although shear friction will govern in a few cases, the reduction in the capacity of the wall is small, in general.
Shear friction can govern with shear-dominated walls. However, these long walls big box structures are generally governed by architectural requirements and not structural requirements; there is usually more than sufficient structural strength. Figure 3 provides Shear Friction Design equations.
There were two major changes to the anchor bolt provisions. This increase was based on examining anchor bolt tests. The average ratio of experimental strength to nominal strength was 2. The change still results in a conservative prediction of nominal strength, with the average ratio of experimental strength to nominal strength being 1.
A similar change was made to Allowable Stress Design. The second change was to the interaction between the tensile and shear strength of anchor bolts. Previously, there was a linear interaction diagram. These two changes, coupled with a change in ASCE that reduces the minimum design strength of anchors not governed by tensile yielding or shear yielding from 2.
Increased energy requirements for building envelopes has resulted in wider cavities in brick veneer walls to accommodate increased insulation thicknesses. Joint reinforcement with cross and longitudinal wires of size W2. Anchor capacities of adjustable anchors are primarily controlled by bending of the pintles at a maximum allowed offset of 1.
This capacity is independent of cavity width and is not affected by the code change. The requirements for anchors for increased cavity widths have compression capacity that equals or exceeds current requirements. TMS has provisions for distributing concentrated loads in walls based on a 2 vertical to 1 horizontal dispersion terminating at half the wall height, or the edge or opening of a wall.
This resulted in very small distribution lengths for concentrated loads near the edge of a wall and no dispersion for loads at the edge of a wall or an opening. This could result in unconservative designs as the axial load generally increases the moment capacity.
A provision was added that a concentrated load could be distributed at 3 vertical to 1 horizontal on one side of an opening. This steeper dispersion will continue away from the opening up to one-half the height of the masonry below the load so that the dispersions can be truncated independently on each side of the bearing Figure 4.
Other technical changes include deleting the prescriptive requirements for masonry piers in strength design, as most of the requirements were redundant with the current prescriptive seismic design.Anchor bolts are used extensively as foundation bolts for rotating equipments like machines and structural members like towers. This series of eight articles will cover all the design guideline of the ACI code with the help of the following concrete anchor foundation bolt design calculation example:.
See the above two figures Fig. Consider the factored tensile load as lb, factored shear load as lb and compressive strength of the concrete as psi. Also assume that the column is mounted at the corner of a large concrete slab.
The aim of this whole exercise is to calculate the design tensile strength and design shear strength of the group of anchor for a selected anchor bolt diameter and check if the design strengths are higher than the applied loads. If they are then we will declare that the selected bolt size is safe or else we will go for next higher size of the anchor bolts. We will start with the anchor diameter of 0. Part Interaction of Tensile and Shear Forces.
The calculation of steel strength of anchor in tension according to the ACI code goes like below:. N sa — Nominal material steel strength of the group of anchor in lb. So, by putting these values, we can get the nominal material strength for the group of anchors in tension from the equation D-3 as. In the next part part-2 we will calculate concrete breakout strength. If you do the calculations based on a perfect installation, it becomes invalid when considering the real time install.
You should vibrate the concrete during construction to ensure that there are no voids. Furthermore, the resistance factor is applied to account for variability in material strength and workmanship. If you have reason to believe that the installation will be poor, then you should reduce the capacity factor accordingly.
Of course vibrating the concrete mix will definitely help get rid of the bubbles surrounding a bolt, but many other factors such as temperature, speed of the setting process, and length of time to vibrate, all are factors that can change the results. The big issue is that many contractors will not vibrate the foundation and that is the question, really. If you assume no vibration and inserting an anchor bolt into the concrete as compared to having an anchor bolt suspension system in place with the bolt in place before the pour, there must be some data on that, all conditions being equal that can be measured and quantified as to the strength variation.
Also, do you have any calculations or data that shows how much pressure in p. This site uses Akismet to reduce spam. Learn how your comment data is processed. Skip to content. Author Recent Posts. Hi, I am Shibashis, a blogger by passion and engineer by profession.
The Titen HD offers low installation torque and outstanding performance. Designed and tested in dry, interior, non-corrosive environments or temporary outdoor applications, the Titen HD demonstrates industry-leading performance even in seismic conditions. The stainless-steel Titen HD is the optimal choice for applications in corrosive or extreme environments such as salt water, or when chemical or corrosive solutions are present.
Intended for some pressure-treated wood sill plate applications. Not for use in other corrosive or outdoor environments. See Supplemental Topics for Anchors. Select One of Our Sites. Product Details The original high-strength screw anchor for use in cracked and uncracked concrete, as well as uncracked masonry.
Finish Zinc plated or mechanically galvanized Not recommended for permanent exterior use or highly corrosive environments. Installation Drill a hole in the base material using a carbide drill bit the same diameter as the nominal diameter of the anchor to be installed. Drill the hole to the specified embedment depth plus minimum hole depth overall see table below to allow the thread tapping dust to settle, and blow it clean using compressed air.
Overhead installations need not be blown clean. Alternatively, drill the hole deep enough to accommodate embedment depth and the dust from drilling and tapping. Insert the anchor through the fixture and into the hole. Tighten the anchor into the base material until the hex-washer head contacts the fixture. Titen HD Diameter in. Wrench Size in. Recommended Fixture Hole Size in. Hole Depth Overdrill in. Suggested fixture hole sizes are for structural steel thicker than 12 gauge only.
Larger holes are not required for wood or cold-formed steel members. Caution Holes in metal fixtures to be mounted should match the diameter specified in the table below. Use a Titen HD screw anchor one time only — installing the anchor multiple times may result in excessive thread wear and reduce load capacity. Do not use impact wrenches to install into hollow CMU.
A comprehensive product and information catalog for Anchoring, Fastening and Restoration Systems products for concrete and masonry.Directions: Enter values for type of fastener bolt, lag screw, or nail ; fastener dimensions; number of shear planes single or double, with double only available for bolted connections ; adjustments duration of load, C Dand wet service factor, C M ; material and section properties for main and side member s ; and fastener spacing, edge and end distances not required for nails.
The unadjusted and adjusted capacity for a single fastener and for the entire connection are calculated, based on "yield limit" theory per NDS Only the capacity based on the fasteners themselves is computed: neither the wood elements themselves, nor any steel side plates specified, are checked for strength or serviceability.
Spacing, edge, and end distances for fasteners are checked for bolts and lag screws in wood members, with the capacity adjusted accordingly. More detailed explanations and examples can be found in the text. Disclaimer: This calculator is not intended to be used for the design of actual structures, but only for schematic preliminary understanding of structural design principles. For the design of an actual structure, a competent professional should be consulted.
First posted Oct. BOX 10d - 3 in. BOX 20d - 4 in. BOX 40d - 5 in. Find the unadjusted capacity for a single fastener, Z lb.
Number of fasteners.Log In. Thank you for helping keep Eng-Tips Forums free from inappropriate posts. The Eng-Tips staff will check this out and take appropriate action. Click Here to join Eng-Tips and talk with other members! Already a Member? Join your peers on the Internet's largest technical engineering professional community. It's easy to join and it's free.
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Students Click Here. Related Projects. Morning Folks, Apologies if this has been covered in another thread but the quick search I ran did not reveal any useful information.
Problem: We are evaluating the existing seismic anchorage of a large silo structure in a poor seismic condition in the US SDC is an "E". The Silo is approximately feet tall with a diameter of approximately 75 feet.
It has been unloaded and out of use for several years but is adjacent to several other large silos that are storing highly volatile material [Boom! The existing anchorage is a series of large diameter j bolts embedded several feet into a concrete pile cap. I am in the process of working through the problem but under Appendix D I think I have slim to no chance of getting the j bolt anchors to work. I am leaning quite heavily toward informing our client to remove the existing silo skirt and retrofit with a large quantity of epoxy bolts.
Has anyone come across any white papers on evaluating the tensile capacities of non-standard hooks on rebar OR large diameter J-bolt anchorage? Trying to make sure we have done our due diligence before ordering a costly repair. Thanks Folks, -Huck.
I think you can find a wealth of literature in recommending that J-bolts not be used for anchorage, in particular seismic anchorage.
The stresses at the corner tend to straighten out the bend and greatly reduce the calculated capacity. So even if you come up with capacities, I would recommend that they be replaced. There's also a reference in ACI on hooked anchors. Personlly, I don't think J bolts are as bad as everyone thinks, but I'm in the minority and the code doesn't help. I agree with JedClampett that the existing J-bolts should be replaced. Following a tornado in our area inI witnessed numerous J-bolts which had pulled out of the foundation, leaving perfectly smooth round holes in the concrete.
They are not a reliable anchor bolt and should not be used where significant tension forces are required.