New chapters cover Risk Management for Infection Control Programs, the participants in the phenomenological experiences as well as for the reader. Genetics and Developmental Psychology by Plomin, Robert, for exampleaffect how those ideas appear, gain influence, and become, like Hegel s thoughts, historical forces in their own right.
A History of News by Stephens, Mitchell, hormone action, and integration and control of metabolism. You will learn how to implement various programs that deal with different topics such as guessing a number game, and people are searching for alternate perspectives on these issues. Tags: ACI The manufacturer should specify proper procedures for permissible installation temperatures as required ensuring correct anchor placement and attainment of maximum bond strength.
Refer to gel time. Short-term elevated concrete temperatures occur over brief intervals, for example, as a result of diurnal cycling. Long-term concrete temperatures are roughly constant over significant periods of time. To establish design bond strengths, two classes of elevated concrete temperature are identified: 1. Where elevated concrete temperatures are transient or part of a regular cycle of heating and cooling, such as day-night temperature rise and fall, they are considered short-term elevated temperatures for the purposes of this standard; and 2.
Where concrete temperatures may remain elevated over weeks or months, they should be considered longterm elevated temperatures. Concrete temperature as an installation parameter is addressed separately in 8. Refer to characteristic value. The residual crack width associated with a hairline crack may be influenced by the presence of anchors installed in the crack path and the crack width cycling history of the test member. Independent Testing and Evaluation Agency ITEA a laboratory accredited in conformance with requirements in Chapter 12 having responsibility for testing and assessment of an anchor product in accordance with the criteria in this standard.
Independent Testing and Evaluation Agency ITEA laboratories engaged in testing and evaluation of adhesive anchor systems must be familiar with the test procedures and reference standards described in this standard as applicable and have demonstrated conformance with the procedures and policies set forth in ISO and ISO Manufacturers Printed Installation Instructions MPII published instructions for correct anchor installation under all covered installation conditions as supplied in product packaging by the manufacturer of the adhesive anchor system.
The MPII shall include information on storage conditions, shelf life, and all restrictions on installation conditions It must be included in packaging for the adhesive anchor system and cannot be supplied in the form of supplementary documentation or verbal instruction. The format, text, pictograms, photos, or other graphic devices used to convey the installation procedures should be legible, self-explanatory, and understandable for persons having a secondary school or higher education level.
The formation of limited-depth conical breakout surfaces shall also be considered as pullout failures. This standard compares the predicted concrete breakout strength with the maximum bond strength, as based on the characteristic limiting bond stress, to determine pullout failure. Shelf life shall. The MPII should clearly state the storage requirements associated with predicted shelf life for the adhesive. The intermediate diameter shall be taken as least 3 mm larger than the smallest diameter and the diameter most closely representing the arithmetic mean of the smallest and largest diameters.
Such statistical equivalence shall be demonstrated using a one-sided Students t-Test at a confidence level of 90 percent. Identification tests to evaluate anchor compliance with manufacturers specifications Chapter 5 2. Reference tests to obtain baseline values for the evaluation of reliability and service-condition test results Chapter 6 3. Reliability tests to assess anchor sensitivity to adverse installation conditions and long-term loading Chapter 7 4. Service-condition tests to establish anchor performance under expected service conditions Chapter 8 R3.
Round-robin tests followed extensive, but inconclusive, investigations to determine the precise nature of concrete composition influence on adhesive anchor performance. Theories regarding this effect include variations in concrete porosity, as reflected in the concrete density, and aggregate hardness. Limited experimental evidence indicates these effects may lessen as the concrete age increases. Round-robin tests are performed in regional concretes to establish and compare a nominal bond strength for generally expected anchor performance against the tested anchor bond strength. Based on round-robin tests establishing a bond strength above or below the ITEA value the reported bond strength is adjusted up or down.
Refer to 9. Omission of optional tests will result in limitations being placed on use of the adhesive anchor system. Presence of water during anchor installation Installation procedures, including hole cleaning procedures, are as specified in the MPII. Hole cleaning procedures typically include vacuuming, evacuation with forced air, and brushing. Quantification of the number, order, and duration of cleaning operations and description of equipment used is required. The default installation condition for verification of the hole cleaning procedure is dry concrete.
Verification in water-saturated concrete is mandatory. Options include installation in water-filled holes and in submerged concrete 7. Drilling methodThe default drilling method uses a rotary hammer drill with carbide bit. Optional drilling methods for assessment includes core drilling and rock drilling 3. Installation directionInstallation direction is the orientation of the axis of the anchor relative to gravity.
Unless otherwise noted, the installation direction is vertically down. Optional installation directions for assessment extenuation are horizontal and vertical 7. Installation temperatureThe default concrete temperature range during anchor installation is 10 to 27C. Options include installation at lower concrete temperatures 8. Embedment depth and anchor diameterThe anchor diameters and associated embedment depth range are specified by the manufacturer within the ranges permitted by this standard refer to Chapter 1.
Anchor element typeAnchor element types used in the anchorage system include different steel material types such as carbon and stainless steels, different tensile strengths of the steel, and different anchor elements such as threaded rods, reinforcing bars, and internally threaded inserts 3. Environmental use conditionsDefault conditions are dry and wet environments with service temperatures ranging from 40C to the maximum long- and shortterm service temperatures corresponding to the temperature categories given in Table 8.
Chemical exposureThe default exposure condition is high alkalinity in a wet environment. The optional exposure condition is sulfur dioxide 8. Concrete conditionOptions include uncracked concrete or uncracked and cracked concrete. LoadingDefault loading conditions are static loading including sustained loads.
Qualification for seismic loading is optional in conjunction with qualification for cracked concrete 8. Refer to 1. Table 3. Note that qualification for seismic loading can only be conducted in the context of qualification for cracked concrete. The reduced test program in Table 3. For optimization of the predicted strength of anchors in cracked. Tables 3. If the additional testing performed using Table 3.
Drilling with diamond core bits, dry or wet, produces a smoother hole wall with a layer of drilling slurry or dust that can impair bond development. Install anchors in accordance with the MPII. If the comparison does not indicate statistical equivalence in test results between carbide rotary-hammer drilling and the alternative drilling method, then the alternative drilling method must be qualified using the test requirements of 3.
There are, however, two exceptions: 1 testing for shear capacity of the anchor element need not be repeated. Additional testing for shear capacity of the anchor element is not required and may be omitted Table 3. Testing using percussive drilling,. Application of torque, confined, single anchor away from edges Service-condition tests. Test small, medium, and large diameters. Optional test. Test all diameters. Test the nominal M12 diameter or the smallest nominal diameter if it is larger than M For overhead and horizontal orientations, test the largest diameter for which recognition is sought.
For tests conducted in accordance with 9. Refer to 4. Refer to 3. Alternatively, tests may be performed as confined tests. Tests are optional if test results of Test 1b can be shown to be statistically equivalent to or greater than the results of Test 1a. If Test 7b is not performed, limit the calculated anchor. Use minimum member thickness h min for these tests. Test in concrete having a measured compressive strength of 21 3.
Sensitivity to hole cleaning, dry substrate Tension, confined, single anchor away from edges. Sensitivity to hole cleaning, installation Tension, confined, single anchor away in water-saturated concrete from edges. Sensitivity to hole cleaning, installation Tension, confined, single anchor away from edges in a water-filled hole. Sensitivity to hole cleaning, installation Tension, confined, single anchor away from edges in submerged concrete. Sensitivity to installation in submerged Tension, confined, single anchor away from edges concrete. Sustained tension, single anchor away from edges, residual capacity, 0.
High installation tension torque or Minimum spacing and edge distance to unconfined tension two anchors near preclude splitting an edge. Tests are optional if test results of Test 1c can be shown to be statistically equivalent to or greater than results of Test 1a. For tests conducted in accordance with Section 9.
Refer to Section 3. Use minimum member thickness hmin for these tests. Test in concrete having a measured compressive strength of 21 MPa 3. Testing Test no. Sensitivity to hole cleaning, Tension, confined, single anchor away from edges installation in a water-filled hole. Sustained tension, single anchor away from edges, residual capacity, confined test. Tension at decreased installation Tension, confined single anchor away from edges temperature.
Tension, unconfined single Edge distance in corner condition anchor in corner with proximate to develop full capacity edges. High installation tension torque or unconfined tension , two anchors near an edge. Round-robin tests for regional Tension, confined and unconfined concrete variation single anchor away from edges. Test nominal M12 diameter or smallest nominal diameter if it is larger than M For overhead and horizontal orientations, test largest diameter for which recognition is sought.
Tests are optional if test results of Test 1b can be shown to be statistically equivalent to or greater than results of Test 1a. Test is required only for anchors having cross-sectional area within five anchor diameters of the shear failure plane that is less than that of threaded bolt having same nominal diameter as anchor. Test in concrete having measured compressive strength of 21 3. Required for anchor elements with reduced cross section; refer to Section 8. In cases where anchor element varies in more than one characteristic for example, material, geometry, or surface coating , test requirements indicated for each variation shall apply.
For stainless steels, conduct tests as required for change in geometry. In cases where results of torque testing can show statistical equivalence to tested anchor element type, repetition of corner and minimum spacing and edge distance tests shall be permitted to be omitted. Where reference test results indicate that anchor element has statistically meaningful influence on bond stress, repeat entire test program for anchor element.
Optional tests required only if conditions of use associated with these tests are to be included for recognition. Results of additional tests performed by the manufacturer can be considered in the evaluation, only if the results are statistically equivalent to those of the ITEA. The primary testing laboratory may have specific tests performed by other qualified laboratories, but retains the overall responsibility for testing and evaluating the anchor system. Tests performed in the manufacturers laboratory shall only be considered for improvement of the statistical accuracy of a test series and must be shown to belong to the same data population by establishing statistical equivalency with test data developed by the primary laboratory or other ITEAs.
Due diligence should be exercised by the ITEA to ensure the samples are representative of production in all cases. Methods for ensuring the integrity of randomly sampled product throughout the custody chain include stamping or signing over the packaging, recording serial and batch numbers, and photographing the sampled product. After production has begun, perform identification and reference tests to verify the constituent materials have not changed and performance of the production anchors is statistically equivalent to the anchors originally evaluated.
The prototypes, however, must be produced using the production methods foreseen for the full-scale production and must be accompanied by a complete MPII. Supplemental testing of the production product to confirm validity of the prototype tests is required. The sample size may be increased at the discretion of the ITEA or manufacturer. To assess the performance of an anchor for use in concrete outside of the scope of ACI The results of these tests are assumed to be generally applicable to a wide range of concrete mixture designs with modification factors applied to the bond strength or concrete breakout strength where applicable.
Where specific qualification is desired for anchors used in lightweight concrete or concrete containing cement replacements, admixtures, or other enhancements such as to support increased design values over those provided for in ACI M, the test program must be repeated using mixture designs that employ the lightweight aggregate, cement replacement, admixture, or enhancement in question. The aggregate description shall include rock and mineral components, shape, hardness, and maximum size and grading specification. Use a maximum coarse aggregate size of either Round-robin tests are required to minimize the potential impact of locally favorable or unfavorable aggregate types on the results of qualification testing.
The concrete mixture shall not include cement replacements such as slag cement, fly ash, and silica fume or limestone powder. If a concrete mixture is used for test members that do not conform to the mixture requirements listed herein, a description of the concrete mixture components and proportions shall be included in the test report. In this case, qualification will be specific to the tested concrete mixture. Use of lightweight aggregates can result in a reduction of bond strength. Where bond values in excess of those specified in ACI M, Appendix D, for adhesive anchors in lightweight concrete are required, these must be based on testing in lightweight concrete.
Tests are conducted in low- and high-strength concrete to assess whether there is a direct or inverse correlation between concrete compressive strength and bond strength for the adhesive anchor system in question. In prior codes, the minimum concrete compressive strength was 14 MPa. Testing in concrete with a compressive strength of 14 MPa may be necessary to validate the use of anchors in existing structures. The results of tests obtained in 14 MPa concrete may not be increased for use of anchors in higher concrete strengths.
Where the requirements of ASTM E conflict with this standard, the provisions of this standard shall take precedence. If the test member is cast vertically, limit the maximum height of a concrete lift to 1. Care should be exercised in vertical casting that the casting process does not result in concrete with significant strength variation due to segregation and bleeding effects, especially in the case of lower-strength concrete.
Cure cylinders to the same environmental conditions as the test member. Remove molds from cylinders concurrent with removal of forms and curing covers from the test member. The results of tests on cylinders and cores shall not be combined for the establishment of the mean compressive strength at a given concrete age. Determine mean strength test values from: a linear interpolation of a test series using the beginning and ending tests as endpoints; or b strength-age relationships developed using compression tests of concrete test members at various test ages.
The potential differences in measured compressive strength resulting from tests on cores or on cylinders should be accounted for. Position such reinforcement so that the capacity of the tested anchor is not affected. For concrete breakout failure, this requirement is satisfied for anchors tested in tension if the reinforcement is located outside of a virtual cone projecting from the embedded end of the anchor to the concrete surface with an internal vertex angle of degrees. Additionally, for splitting failure, reinforcement shall be omitted between the anchor location and the concrete edge.
Where anchors are to be tested in tension, reinforcement should be placed near the surface and toward the outer edges of the member. Where anchors are to be tested in shear, reinforcement should not be placed near the surface or corners of the test member. The cracks should be spaced sufficiently apart to facilitate testing of individual anchors placed in a crack without influence from adjacent cracks. For test members that use internal reinforcement to control the crack width or for specimen handling, place the reinforcement.
Refer to Fig. The ratio of tension reinforcement for top and bottom layers to the area of the crack plane shall be approximately 1 percent. The centerline-tocenterline distance between any crack control reinforcement and the anchor shall not be less than 0. Furthermore, smaller values for center-to-center distance between reinforcement and anchor are allowed in the case of deep embedments where the anchorage mechanism is not influenced by the reinforcement.
It shall be permitted to. Other methods shall be permitted subject to the requirements of ACI Position crack initiators so the capacity of the tested anchor is not affected by their presence. Extend tension reinforcing as required in 4. Apply external loading to both ends of the reinforcement to facilitate development of uniform strain over the length of the reinforcing. External loads for crack opening shall not be reacted against the test member.
Support the test member to permit uniform tension strain distribution over the length of the test member. Individual crack widths shall be within 15 percent of the specified crack width for the test series. Preferably, formed concrete surfaces should be used for shear testing. It is not intended that anchors should be installed with a six-degree tilt as a means of enhancing resistance to tension loads. Bolts, nuts, and washers not supplied with the anchors shall conform to the specifications given by the manufacturer, which shall be included in the test report.
Positioning of the anchor in the crack is likewise a matter of judgment. Ideally, the crack runs vertically down the centerline axis of the anchor over its entire length. For anchors to be tested in tension, deviation of the crack position from the anchor centerline should be limited to the surface of the member. For anchors to be tested in shear, it is more important that the crack transect the anchor position at the concrete surface. These conditions are best confirmed using a boroscope. Bit wear should, nevertheless, be monitored during the test program.
Where differences occur, ACI The recorded displacements should be corrected so that they represent the displacement at the concrete surface. It does not contain specific instructions for many of the tests described in this standard. Where either steel or concrete breakout failures occur, it may be assumed that the maximum potential bond strength associated with the adhesive anchor system is not reflected in the measured peak load. Heat-treatment may also be used to increase the rod strength. In all cases, the thread configuration should be representative of the threaded rod types included in the qualification of the adhesive anchor system.
In cases where the embedment depth must be reduced to avoid failure modes other than bond failure, check the effectiveness of the MPII by other means; with respect to hole cleaning and injection at the unreduced maximum hole depth, also check by other means. The method described in 4. When this step is taken, it is necessary to simulate the hole cleaning and adhesive injection processes for the full-depth hole condition by some other means.
The use of stacked blocks is one such method. Stack concrete blocks A and B, as shown in Fig. Although the core drill is shown, other. Seal the interface between the blocks. Perform adhesive injection in accordance with the procedures described in the MPII. Limit injection depth to the bottom block B Fig.
Remove the upper block A and install the anchor element in accordance with the procedures described in the manufacturers published installation instructions Fig. Perform a confined tension test to failure Fig. Other methods may be used subject to assessment by the primary testing laboratory. If Eq. Alternatively, conduct confined tests with an embedment of approximately 7da in accordance with 4. Many adhesive anchor systems exhibit concrete breakout failure when tested in tension at minimum embedment.
In these cases, it is necessary to increase the embedment to a point where bond failure occurs. The establishment of bond failure solely on the basis of physical observation of the failed specimen, however, is problematic. Development of fracture surfaces that do not project to the concrete surface may preclude the attainment of maximum potential bond strength. Comparison of the mean strength obtained in the tension tests with a predicted value for the concrete breakout.
For cases where the resistance at the embedment required to promote bond failure exceeds the strength of the high-strength rods used for testing, confined tests may be performed and converted to unconfined values via the term setup. Table R4. Figure 4. The hole in the confining plate shall be 1.
In no case shall the results of confined tests be compared with the results of unconfined tests, for example, for the determination of Initiate cracking in the test member. Install the anchor according to 4. Install instrumentation for monitoring crack-opening width. Monitor crack-opening width using dial gauges or electronic transducers located roughly symmetrically on either side of the anchor on an axis. Keep the distance from the crack width measurement point to the anchor centerline as small as possible; not to exceed the greater of 1.
Increase the crack width by the specified crack value prior to applying external loads to the anchor. Verify by suitable means that the system used for crack formation and the associated test procedures produce cracks that remain parallel during the performance of tests. The crack width, as measured at the opposite face of the test member in line with the anchor location, or as estimated based on the crack width measurement on each side of the test member as close to the opposite face as possible, should be approximately equal to the crack width measured on the anchor side.
Verification that the test procedure used for a specific test will produce the appropriate crack geometry shall be performed at the beginning of the test series. It is important that the crack width measurement devices reflect the crack width at the anchor location. It is generally acceptable to check the performance of the specimen at the beginning of the test series. Use a sampling frequency appropriate for the load or strain rate employed for the test.
The ITEA shall determine which tests, if any, shall be performed to determine whether the change in the adhesive anchor system is equivalent to the previously assessed adhesive anchor system. For all changes that might affect the anchor performance, the ITEA shall perform sufficient reference and reliability tests to assess the impact of the change. Test results shall be shown statistically equivalent to those of the originally tested product. If the results of the reference and reliability tests cannot be shown to be statistically equivalent to the results of the original testing, retest and evaluate the modified adhesive anchor system in accordance with ACI Other changes include the adhesive formulation, adhesive confectioning, adhesive mixing and delivery system, and the supplementary tools and devices used to clean the drilled hole.
Anchor element dimensions; constituent materials; and appropriate physical properties including tensile strength, hardness, and coatings. A description of the adhesive components including the adhesive name, packaging system, mixing ratios, gel time, cure time, storage information, and shelf life. If the adhesive material is changed by the manufacturer, that change may or may not significantly affect the published performance of the anchor system.
Selection of appropriate tests for comparison with future batches is a critical function. The use of alternate tests to address other materials is at the discretion of the ITEA. The fingerprinting tests may or may not be part of the manufacturers quality control system. It shall be permitted to test the components separately or their mixture,. Other test methods shall be permitted if approved by the ITEA. As such, it is important that the concrete used for these tests is as closely related as possible to the concrete used for the suitability tests.
Depending on the manner in which the reference tests are conducted, they may also serve as service-condition tests for the system Chapter 8. Confined tests measure the bond strength of the anchorage as opposed to the concrete capacity associated with concrete failure modes such as concrete cone breakout. As such, they are suitable to assess the effects of temperature variation, suboptimal hole cleaning, mixing effort, sustained load, installation direction, temperature variations, and environmental exposure on anchor performance. Confined tests do not generate large spall cones, and as such serve to reduce the volume of concrete required for the test program.
Where unconfined tension tests are used as reference tests, they shall be compared to unconfined reliability or service-condition tests. In all cases, bond failure is required refer to 4. Note the use of unconfined tests for reference tests can lead to an unconservative assessment if the unconfined reference tests result in concrete cone failures. One example is underrepresenting the maximum bond strength of the adhesive anchor system.
Reference tests may be used for comparison with more than one series of reliability or service-condition tests. Reference tests for the assessment of tests conducted in cracked concrete shall be performed in cracked concrete. They are not pass-fail tests, but rather provide the necessary input for determining the characteristic maximum bond stress for the adhesive anchor system.
Reliability tests are performed to establish that the anchor is capable of safe, effective behavior under normal and adverse installation conditions. While it is assumed that the on-site installation personnel will generally conform to the MPII, the potential for inadvertent deviations from the MPII, particularly with respect to hole cleaning procedures, forms the basis for many of the reliability tests. Gross installation errors as denoted in this section are not addressed by this standard and are assumed to be precluded by attention to worker training and job-site inspection and quality control practices.
They are not intended to address gross installation errors. Gross installation errors are characterized by significant deviations from the MPII or design specifications and include, but are not limited to: Deviations from the specified embedment depth Use of a nominal diameter drill bit other than that specified Incorrect assembly or operation of the adhesive mixing and dispensing equipment Use of the product in base materials other than structural concrete Use of the product in concrete exhibiting compressive strength outside of the specified range Use of the product in base materials having a temperature outside of the specified range for the product Violation of specified gel and cure times Violation of storage and shelf life restrictions for the adhesive 7.
This reliability test checks for the sensitivity of anchor bond strength to suboptimal hole cleaning effort 50 percent in dry concrete conditions. The MPII should provide necessary instructions for hole cleaning with the required degree of specificity to permit evaluation of the 50 percent hole cleaning effort. For example, if the MPII calls for blowing out the hole twice with compressed air followed by four insertions of a brush and two additional applications of compressed air, 50 percent effort would be assessed as one application of compressed air followed by two insertions of the brush and one application of compressed air.
Where three repeats of a specific operation are specified, one should be performed; where one is specified, the cleaning step should be omitted. The type of brush, such as steel and nylon, and its diameter should be specified in the MPII together with any other details, such as air pressure, that might affect the effectiveness of the holecleaning process. If the MPII does not contain sufficient information to permit the establishment of a cleaning effort that represents 50 percent of the specified effort, hole cleaning should be omitted.
An effective upper limit on repetitions of any single holecleaning operation of four is intended to prevent the specification of excessive hole cleaning effort in the MPII as a means of satisfying reliability test criteria. Other cleaning methods are permitted; however, the MPII for the product shall contain sufficient specificity to permit the determination of a numeric 50 percent reduction of hole cleaning effort.
For hole cleaning methods involving brushing and blowing operations, such specificity shall include as a minimum: 1. Acceptable methods and minimum number and duration of operations required for removal of drilling debris from hole 3. Acceptable methods and minimum number and duration of operations required for removal of dust or drilling flour from the hole wall 4.
standard-area: ACI Sharing
The required sequence of operations An exception to determine the reduced hole cleaning effort, regardless of the number of hole cleaning operations specified in the MPII, the number of times the operation step is repeated in tests for reduced cleaning effort shall not exceed two.
For the purposes of this section, an operation shall be considered to be an action that is repeated not more than three times in succession. Clean the hole with 50 percent of the specified minimum number of operations in the specified sequence, rounding down to the next whole number of operations. So if a total of four brushing and four blowing operations are specified, install the anchor with only two brushing and two blowing operations. Load the anchor to failure with continuous measurement of load and displacement.
It is anticipated that the MPII will contain specific procedures, such as flushing the hole with water, for cleaning holes drilled into saturated concrete or where the drilled hole has been subjected to water prior to the anchor installation for example, from rain.
Due to the likelihood that products will be installed in concrete exposed to water such as concrete exposed to weather , these tests are mandatory. Fill the pilot hole with potable water and ensure that the hole remains flooded for a minimum of 8 days or hours. Immediately prior to installing the anchor, remove all freestanding water with a vacuum and redrill the existing hole with the specified drill bit diameter.
Clean the hole in accordance with the reduced cleaning effort specified in 7. Install the anchor in accordance with the MPII. Other methods of achieving saturation of the concrete, such as immersing the test member, shall be permitted. If methods other than those described previously are used, it shall be shown by appropriate methods that the concrete in the area of the anchorage is water saturated. If the MPII specifies flushing of the hole with water prior to anchor installation, it shall be permitted to flush the hole with potable water prior to installing the anchors.
Prepare the hole with reduced cleaning effort in accordance with 7. Immediately prior to installing the anchors, remove freestanding water from the hole with a vacuum. These tests are optional; however, failure to assess this condition will result in restrictions on the use of the adhesive anchor system. Drill the hole downward in the submerged concrete, clean the hole in accordance with the reduced cleaning effort specified in 7.
These tests are required only for those anchor systems where the mixing of the adhesive material is substantially controlled by the installer. Such cases include systems that require components to be mixed until a color change is effected throughout the adhesive material, the adhesive materials to be mixed with recommended equipment for a specific duration, and the adhesive materials be mixed with a repetitive mixing operation a specific number of times.
Reduced mixing effort shall be achieved by decreasing the mixing time required for full mixing by 25 percent. It is therefore necessary to perform supplemental checks for the sensitivity of the adhesive anchor system to installation in water-saturated concrete where the full cleaning effort in accordance with the MPII is used. It is therefore necessary to perform supplemental checks for the sensitivity of the adhesive anchor system to installation in water-filled holes where the full cleaning effort in accordance with the MPII is used.
It is therefore necessary to perform supplemental checks for the sensitivity of the adhesive anchor system to installation in submerged concrete where the full cleaning effort in accordance with the MPII is used. Tests on adhesive anchors shall be confined tension tests. Visually confirm the correct location of the crack in the drilled hole prior to installing the anchor in accordance with 4. Open the crack by the specified value w.
Perform a confined tension test to failure with continuous measurement of load, displacement, and crack width. This corresponds to a tolerable crack width for interior exposures. Open the crack to the specified value w. The test consists of three parts: 1. Installation of the anchor in the crack and application of the static sustained load to the anchor. Cycling of the crack width and monitoring of the anchor displacement. Performance of a tension test to failure to measure the residual tension resistance of the tested anchor. Tests for residual capacity following crack cycling are confined tension tests performed in cracked concrete.
Loading shall not exceed the elastic limit of the test member reinforcement. With the test member unloaded, install the anchor in a closed hairline crack that is sufficiently planar to ensure that the crack will approximately bisect the anchor location over the extent of the anchor loadtransfer zone. Visually verify the positioning of the anchor in the crack in accordance with 4. Measure the crack width in accordance with 4. This reliability test checks for the sensitivity of anchor bond strength to suboptimal hole cleaning effort 50 percent in dry concrete conditions. The MPII should provide necessary instructions for hole cleaning with the required degree of specificity to permit evaluation of the 50 percent hole cleaning effort.
For example, if the MPII calls for blowing out the hole twice with compressed air followed by four insertions of a brush and two additional applications of compressed air, 50 percent effort would be assessed as one application of compressed air followed by two insertions of the brush and one application of compressed air. Where three repeats of a specific operation are specified, one should be performed; where one is specified, the cleaning step should be omitted. The type of brush, such as steel and nylon, and its diameter should be specified in the MPII together with any other details, such as air pressure, that might affect the effectiveness of the holecleaning process.
If the MPII does not contain sufficient information to permit the establishment of a cleaning effort that represents 50 percent of the specified effort, hole cleaning should be omitted. An effective upper limit on repetitions of any single holecleaning operation of four is intended to prevent the specification of excessive hole cleaning effort in the MPII as a means of satisfying reliability test criteria. Other cleaning methods are permitted; however, the MPII for the product shall contain sufficient specificity to permit the determination of a numeric 50 percent reduction of hole cleaning effort.
For hole cleaning methods involving brushing and blowing operations, such specificity shall include as a minimum: 1. Acceptable methods and minimum number and duration of operations required for removal of drilling debris from hole 3. Acceptable methods and minimum number and duration of operations required for removal of dust or drilling flour from the hole wall 4. The required sequence of operations An exception to determine the reduced hole cleaning effort, regardless of the number of hole cleaning operations specified in the MPII, the number of times the operation step is repeated in tests for reduced cleaning effort shall not exceed two.
For the purposes of this section, an operation shall be considered to be an action that is repeated not more than three times in succession. Clean the hole with 50 percent of the specified minimum number of operations in the specified sequence, rounding down to the next whole number of operations. So if a total of four brushing and four blowing operations are specified, install the anchor with only two brushing and two blowing operations.
Load the anchor to failure with continuous measurement of load and displacement. It is anticipated that the MPII will contain specific procedures, such as flushing the hole with water, for cleaning holes drilled into saturated concrete or where the drilled hole has been subjected to water prior to the anchor installation for example, from rain. Due to the likelihood that products will be installed in concrete exposed to water such as concrete exposed to weather , these tests are mandatory. Fill the pilot hole with potable water and ensure that the hole remains flooded for a minimum of 8 days or hours.
Immediately prior to installing the anchor, remove all freestanding water with a vacuum and redrill the existing hole with the specified drill bit diameter. Clean the hole in accordance with the reduced cleaning effort specified in 7. Install the anchor in accordance with the MPII. Other methods of achieving saturation of the concrete, such as immersing the test member, shall be permitted. If methods other than those described previously are used, it shall be shown by appropriate methods that the concrete in the area of the anchorage is water saturated.
If the MPII specifies flushing of the hole with water prior to anchor installation, it shall be permitted to flush the hole with potable water prior to installing the anchors. Prepare the hole with reduced cleaning effort in accordance with 7. Immediately prior to installing the anchors, remove freestanding water from the hole with a vacuum.
These tests are optional; however, failure to assess this condition will result in restrictions on the use of the adhesive anchor system. Drill the hole downward in the submerged concrete, clean the hole in accordance with the reduced cleaning effort specified in 7. These tests are required only for those anchor systems where the mixing of the adhesive material is substantially controlled by the installer. Such cases include systems that require components to be mixed until a color change is effected throughout the adhesive material, the adhesive materials to be mixed with recommended equipment for a specific duration, and the adhesive materials be mixed with a repetitive mixing operation a specific number of times.
Reduced mixing effort shall be achieved by decreasing the mixing time required for full mixing by 25 percent. It is therefore necessary to perform supplemental checks for the sensitivity of the adhesive anchor system to installation in water-saturated concrete where the full cleaning effort in accordance with the MPII is used. It is therefore necessary to perform supplemental checks for the sensitivity of the adhesive anchor system to installation in water-filled holes where the full cleaning effort in accordance with the MPII is used.
It is therefore necessary to perform supplemental checks for the sensitivity of the adhesive anchor system to installation in submerged concrete where the full cleaning effort in accordance with the MPII is used. Tests on adhesive anchors shall be confined tension tests. Visually confirm the correct location of the crack in the drilled hole prior to installing the anchor in accordance with 4.
Open the crack by the specified value w. Perform a confined tension test to failure with continuous measurement of load, displacement, and crack width. This corresponds to a tolerable crack width for interior exposures. Open the crack to the specified value w. The test consists of three parts: 1. Installation of the anchor in the crack and application of the static sustained load to the anchor.
Cycling of the crack width and monitoring of the anchor displacement. Performance of a tension test to failure to measure the residual tension resistance of the tested anchor. Tests for residual capacity following crack cycling are confined tension tests performed in cracked concrete.
Loading shall not exceed the elastic limit of the test member reinforcement. With the test member unloaded, install the anchor in a closed hairline crack that is sufficiently planar to ensure that the crack will approximately bisect the anchor location over the extent of the anchor loadtransfer zone. Visually verify the positioning of the anchor in the crack in accordance with 4. Measure the crack width in accordance with 4. Following application of load to the anchor sufficient to remove any slack in the loading mechanism, begin recording the anchor displacement, and increase the tension load on the anchor to Nw as given by Eq.
Apply the load in accordance with 4. While maintaining the static load on the anchor within 5 percent of Nw, cyclically load the test member as required to cause the crack width to alternate continuously between w1 0. Open and close the crack times at a maximum frequency of approximately 0. During crack cycling, adjustment of the force required to maintain the crack opening width w1 constant shall be permitted.
Hold the minimum load applied to the test member constant. The crack opening width w2 shall be permitted to increase Fig. During the test, adjust the amplitude of the load applied to the test member as required to maintain a minimum differential w1 w2 of 0. This may result in an increase in the crack width w1 beyond 0. Running opening and closing cycles serves to stabilize the bond stresses at a constant level and permits control of the crack width via application of a defined external load.
Equation provides a load level Nw on the anchor that is consistent with the load on headed anchors corresponding to the threshold displacements established for this test. Where these threshold displacements are exceeded in the test, the load Nw is reduced to a level that does not generate displacements in excess of the threshold values.
Crack closing is accomplished with the embedded reinforcement and may be influenced by slippage of the anchor in the crack. It is not intended that crack closure should be controlled externally, for example, with a hydraulic cylinder. At load Nw, measure the displacements of the anchor and the crack-opening widths w1 and w2, either continuously or at least after 1, 2, 5, 10, 20, 50, , , , and cycles of crack opening and closing. For anchor diameters greater than 16 mm, the test member shall have a side length 15d lside 25d.
Dimensions of the test member shall be chosen to avoid splitting the test member during the test conduct. Freezing-and-thawing-resistant concrete shall be permitted. Restraint of the test member as required to prevent splitting shall be permitted. Where such restraint is used for example, steel cylinder , dimensions of the specimen may be reduced.
Seal all other exposed surfaces to prevent evaporation of water. Load the anchor with a constant tension load Nsust,ft given by Eq. Maintain load at Nsust,ft throughout the freezing-andthawing test.
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Raise the temperature of the chamber within 1 hour to 20C 2C. Maintain the chamber temperature at 20C 2C for an additional 7 hours. Lower the temperature of the chamber to 20C 2C within 2 hours. Maintain the chamber temperature at 20C 2C for an additional 14 hours. Tests are performed at standard temperature of 23C 4C, and at long-term elevated temperature. The long-term elevated temperature corresponds to the temperature category as per Table 8. If tests at the long-term test temperature are performed with Nsust in accordance with Eq.
Embed thermocouples a maximum of mm from the surface of the concrete into which the anchors are to be installed. Distance from the outer perimeter of the installed anchor and thermocouple shall not exceed 10 mm. The thermocouples shall be either cast in the concrete or positioned in holes drilled in the cured test member. Drilled holes for thermocouples shall have a maximum nominal diameter of 13 mm and shall be sealed in such a manner that the temperature readings reflect the concrete temperature. The exception to this is that thermocouples are not required if it can be experimentally demonstrated that the test procedure will consistently produce test member temperatures in accordance with the target temperatures.
The test procedure will include monitoring of test chamber temperature at maximum 1-hour intervals. The load shall be applied using an unconfined test setup as shown in 4. After the load has been applied, adjust the temperature of the test member until the temperature, as recorded by the embedded thermocouples, is stabilized at the target temperature.
The frequency of monitoring displacements shall be chosen to demonstrate the anchor characteristics. As displacements are greatest in the early stages, monitoring frequency should be high initially, but reduced over time. As an example, the following monitoring schedule would be acceptable: a During the first hourevery 10 minutes b During the next 6 hoursevery hour c During the next 10 daysevery day d Thereafterevery 5 to 10 days 7. Record the concrete test member temperature at maximum 1-hour intervals. If thermocouples are not used in accordance with 7. Raise the temperature of the test chamber to the maximum long-term test temperature either Category A or B according to Table 8.
Apply a tension preload not exceeding 5 percent of. Nsust,lt or N to the anchor prior to zeroing displacement readings. Then increase the load on the anchor to a constant tension load Nsust,lt as given by Eq. For the frequency of displacement monitoring, refer to 7. Where anchors are to be installed in other orientations, such as horizontal and overhead, tests are required to validate the performance of the adhesive anchor system for these orientations. These tests are intended to ensure the MPII is adequate to describe the necessary installation steps, the adhesive anchor system is appropriate for installation in the tested orientation, and the bond strength has been correctly assessed for anchors installed in the tested orientation.
Factors of particular importance in the assessment include completely filling the hole with adhesive, avoiding excessive adhesive run-out during the installation process, and preventing anchor element sag during adhesive cure. Because of the possibility for run-out of adhesive during overhead installations, particular care should be exercised to prevent skin or eye exposure, and all precautions indicated by the MSDS for the product should be exercised. For adhesive anchor systems not designed for other than down-hole installation, these tests may be omitted. To avoid accidental misuse of such products, however, it is necessary to provide a standardized warning label on the product for example, cartridge and foil pack and on the packaging indicating restrictions on use Fig.
Conduct tests on all-thread anchors that have been installed in accordance with the MPII. Perform tension tests to failure with continuous measurement of load and displacement. Install and cure anchors at the minimum and maximum installation temperatures for concrete and adhesive included in the MPII for downhole installation. Perform tension tests at standard temperature. A procedure for verifying the effectiveness of overhead installation procedures using blind injection into a clear tube of equivalent diameter and length is.
The washer shall not turn during the application of torque. The procedure used shall enable the evaluation of the installation procedure as described in For anchor elements that do not require the application of torque, such as deformed reinforcing bar dowels, these tests may be omitted. The fixture shall contain all elements shown. The double-sided abrasive paper shall have sufficient roughness to prevent rotation of the washer relative to the test fixture during the application of torque.
Other methods of preventing rotation of the washer shall be permitted, provided it can be shown they do not affect the anchor performance. Test requirements for adhesive anchors assessed to resist seismic loads are defined in Table 3. This crack width is consistent with the expected response of reinforced concrete structures under sustained load. Depending on the characteristics of the adhesive and the embedment depths for which the system is to be assessed, it may be necessary to take special measures to achieve bond failures in these tests refer to 4. The use of confined tests is permitted under certain conditions and can enable the use of reference tests for establishing characteristic limiting bond stress values.
Temperature Category A provides a standard approach that assumes a potential long-term elevated temperature consistent with hot climate exposures and a short-term temperature reflective of diurnal cycling in such climates for a given sun exposure duration and concrete mass. Typical sources of elevated concrete temperature are anticipated, with the exception of heat of hydration in earlyage concrete, extreme elevated temperature for example, boiler rooms , and exposure to nuclear radiation in containment structure.
Temperature Category B establishes the same long-term temperature as temperature Category A.
355.4-11 Qualification of Post-Installed Adhesive Anchors in Concrete and Commentary
This temperature is relevant for testing to establish response to sustained load. The short-term temperature remains openended, however, and the response of the adhesive anchor to intermediate levels of elevated concrete temperature is established. Products may be tested and assessed for either or both categories under this standard. It shall be permitted to obtain qualification at multiple temperature categories. Alternatively, it shall be permitted to correlate the chamber temperature with the test member. Table 8. Install and test a minimum of five anchors at each temperature data point.
For Temperature Category A, perform tests at the short- and long-term test temperatures. For Temperature Category B, perform tests on anchorsat standard temperature, at the long-term and short-term test temperatures, and at a minimum of two intermediate temperatures between the long-term and shortterm temperatures with a maximum increment of 20C.
If the difference between the standard temperature and the selected short-term test temperature is less than 20C, then testing at intermediate temperatures is not required. Following the recommended cure period, heat and maintain the test members at the desired temperature for a minimum of 24 hours. Remove each test member from the heating chamber and conduct a confined tension test to failure with continuous measurement of load and displacement before the temperature of the test member falls below the temperature listed in Table 8. All adhesive anchor systems qualified for installation in concrete temperatures below 10C are required to be installed and tested at the target concrete temperature.
When the target temperature for the system to be qualified falls below 5C, additional tests are required to assess the effect of rising concrete temperatures on the anchor response. The rate of temperature rise is intended to be consistent with sun exposure. Follow special procedures where the MPII includes them for low-temperature installation conditions.
Where preheating of adhesive cartridges to reduce viscosity and facilitate adhesive flow is specified in the MPII, observations should be made to determine whether this results in retarded cure, lowering of the glass-transition temperature, and impaired resistance to creep. Prior to installation, condition the anchor rod and test member to the lowest installation temperature and maintain it for a minimum of 24 hours. Install anchors in concrete test members and allow them to cure at the stabilized temperature according to the MPII.
Remove the test member from the cooling chamber and tension test the anchors immediately to assure the test members reasonably remains at the conditioned temperature. A thermocouple inserted into the test member may be used to confirm the temperature at the time of testing.
Prior to installation, condition the anchor rod and test member to the target temperature and maintain that temperature for a minimum of 24 hours. Raise the temperature of the test chamber at a constant rate to standard temperature for 72 to 96 hours while monitoring the displacement response for each anchor. A thermocouple inserted into the test member may be used to confirm test member temperatures during the test. Once the test member attains standard temperature, conduct a confined tension test to failure with continuous measurement of load and displacement.
Where cure times are provided for temperature ranges that overlap the standard temperature range, a temperature should be selected that corresponds to the lower end of the range. Tests are conducted on anchors installed in accordance with the MPII at standard temperature. The anchors are allowed to cure for the minimum curing time. Tests are also conducted on anchors installed in the same way and allowed to cure for the time specified in the MPII plus an additional 24 hours. The slice test, where a thin slice of the installed anchor is exposed to a specific environmental condition and then tested for.
Care must be taken in preparation of the slices and punch testing to ensure reliable results. An austenitic stainless steel anchor element of sufficient resistance should be used in the sulfur dioxide tests to avoid steel failure. It does not capture all possible environmental exposures deleterious to anchor performance. The two exposure conditionsalkalinity and sulfurare considered two of the most common and aggressive and, therefore, used as the baseline classification of anchor use.
Verify the durability of the adhesive material with slice tests. With slice tests, the sensitivity of installed anchors to different environmental exposures can be assessed. The test for exposure to high alkalinity 8. The test for exposure to sulfur dioxide 8. Embed anchors in cylindrical concrete test members having a minimum diameter of mm. Cast the concrete test members in lengths of steel or plastic pipe having a wall thickness as required to prevent slice splitting during punch testing.
All test members shall originate from the same concrete batch. Install anchors along the central axis of the concrete test members according to the MPII. For tests in sulfur dioxide, fabricate the anchor element from austenitic stainless steel. After curing the adhesive, concrete cylinders in which the anchors are installed shall be sawn with a diamond saw into 30 mm 3 mm thick slices so the resulting slices are undamaged.
Slices shall be oriented perpendicular to the anchor axis and consist of the concrete, adhesive material, and anchor element. Discard the top and bottom slices. Prepare a minimum of 10 slices for each environmental exposure to be investigated and 10 reference slices subjected to standard climate conditions.
All slices shall be completely covered for hours. Produce the alkaline fluid by mixing water with potassium hydroxide KOH powder or tablets until the pH value of If the measured alkalinity falls below The length of time the pH was less than Monitor the pH value on a daily basis. Perform at least 80 cycles. The loading punch shall act centrally on the metal element. The peak load for each test shall be recorded. Discard results from slices that split during the punch test. Evaluate the bond stress dur,i for each punch test using Eq. This edge distance represents the critical edge distance at which there is no edge influence on the tensile capacity of the anchor as governed by concrete failure.
The tests are performed in concrete members having the smallest thickness hmin for which the manufacturer wishes to qualify the anchor. These tests permit the selection of product-specific values for cac that, in conjunction with some value of hmin, will allow anchor installation without damage in the form of splitting cracks to the concrete. There can be more than one combination of these values. These tests permit the selection of product-specific values for cmin and smin that, in conjunction with some value of hmin , will allow anchor installation without damage in the form of splitting cracks to the concrete.
There can be more than one combination of these three minimum values. While the application of torque is not required to set normal adhesive anchor systems, most MPIIs specify a maximum torque value for the clamp attachment to the concrete. Use of an elevated torque value 1. For conditions in which torque is not applied to the anchor, the minimum edge distance is governed by the drilling process used to install the adhesive anchor. Place the two anchors in a line parallel to the edge of a concrete test element at a distance of at least 3hef from other groups.
Select smin, cmin, and hmin depending on anchor characteristics. The distance to the edge of the bearing plate from the centerline of the corresponding anchor shall be three times the diameter da of the anchor being tested. If the average prestressing force corresponding to 1. Otherwise, perform a load test in accordance with 8. After each increment, inspect the concrete surface for cracks. Stop the test when splitting or steel failure prevents the torque from being increased further.
For each test, simultaneously record the torque at first formation of a hairline crack at one or both anchors and the maximum torque that can be applied to the anchors. Load the anchor group in tension to failure as an unconfined test. Additionally, shallow anchors that exhibit pullout failure in unconfined tension tests may exhibit shear strengths away from edges that are below those predicted by ACI M, Appendix D. Tests shall be performed to establish the appropriate shear capacity in these cases. For anchors assessed for use in cracked concrete and resisting seismic loads, it may be advantageous to establish the reference shear capacity of the anchor system in cracked concrete.
Test anchor elements having a cross-sectional area that is less than a threaded bolt of the same nominal diameter as the anchor within five anchor diameters of the shear failure plane. The crack width is assumed to be roughly percent of the maximum crack width associated with elastic conditions, with the maximum level of cyclic loading approximately twice the service load level under nonseismic conditions. These tests are not intended to simulate all possible loading conditions that may occur in an earthquake or intended to represent the degree of cracking that might occur in plastic hinge regions of reinforced concrete structures.
Qualification for seismic loading shall only be considered in the context of a cracked concrete test program in accordance with Table 3. Install the anchor in a closed crack in accordance with 4. If no torque is specified by the MPII, finger-tighten the anchor prior to testing. Subject the anchors to the sinusoidal tension loads specified in Table 8. Following completion of the simulated seismic-tension cycles, open the crack to a width not less than the crack opening width as measured at the end of the cyclic test and load the anchor in tension to failure.
Record the maximum tension load, that is, residual tension capacity; the corresponding displacement; and plot the load-displacement response. Load cycling may be conducted at a relatively low frequency because the loading rate has not been determined to be a significant factor in anchor performance. The use of a ramped loading function through the zero point of the cyclic load may be advantageous for operation of the testing apparatus.
Qualification for seismic loading shall only be considered in the context of a cracked concrete test program as given in Table 3. Test internally-threaded anchors with the bolt specified by the manufacturer and report the bolt type refer to Table Subject the anchors to the sinusoidal shear loads specified in Table 8. To reduce the potential for uncontrolled slip during load reversal, the alternating shear loading shall be permitted to be approximated by the application of two half-sinusoidal load cycles at the desired frequency connected by a reducedspeed ramped load, as shown in Fig.
Plot the loaddisplacement history in the form of hysteresis loops. Record the maximum shear load or residual shear capacity and the corresponding displacement, and plot the loaddisplacement response. Anecdotal evidence indicates there may be a direct relationship between aggregate types used and bond strength.
ICC-ES Evaluation Reports for post-installed adhesive anchors updated to meet new AC308 criteria
Roundrobin tests are intended to establish the consistency of bond properties of the tested system over a range of concrete mixture designs originating from various geographic regions. Two mixture designsone without and one with fly ash as a cement replacementare intended to provide a representative sample of concrete compositions in North America.
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The three additional independent laboratories shall be selected by the primary testing laboratory and accredited for testing of anchors according to ASTM E If steel failure occurs, the embedment depth shall be reduced for all round-robin tests. Anchor test specimens sampled in accordance with 4. Where the primary laboratory uses data from more than one.
Aggregates used for the concrete shall be representative of typical concrete production in each laboratorys immediate geographic location. It shall be permitted, however, to transport specimens prepared by the regional laboratories in the different geographic regions to the primary testing laboratory for testing.
The aggregates used for the concrete shall be representative of typical production in each laboratorys geographic location. Mixture designs shall be in accordance with 4. Aggregates shall be in accordance with 4. Test member strength shall be confirmed based on field prepared and cured cylinders in accordance with 4. Perform a minimum of five confined and five unconfined tension tests to failure on anchors in concrete produced in accordance with Mixture Design A and a minimum of five confined and five unconfined tension tests to failure in concrete produced in accordance with Mixture Design B.
Perform tests in accordance with 4. Confined round-robin tests may be omitted, however, if Eq. Nu is the mean ultimate tension load in unconfined roundrobin tests, N. Refer also to 8. A test shall consist of drilling the hole, setting the anchor, and inspecting the test member for visible concrete cracking or spalling. For the purpose of these tests, support the test member, that is, slab and beam, with a shear span length, which is the distance from anchor to support, not less than 1.
Qualification of Post-Installed Adhesive Anchors in Concrete and Commentary
Use drilling equipment and setting procedures that are representative of normal anchor installation as specified by the anchor manufacturer. Drilling equipment and setting procedures shall be representative of normal anchor installation as specified by the manufacturer. Subsequent to drilling the holes and setting anchors, the balance of tests in accordance with 8. For steels conforming to a standard, the characteristic tensile strength shall be taken as the minimum specified tensile strength futa.
Table Testing in conformance with round-robin testing requirements may result in significant scatter and adjustment of the characteristic bond stress from round-robin testing should be limited to cases where there is a clear trend. As such, a 5 percent tolerance on the ratio of the round-robin bond stress to the reference bond stress is included in the assessment. Where confined tests have been performed in accordance with Section 9.
If the mean bond stress corresponding to the tests conducted in any one laboratory exceeds the mean of the combined results from the remaining three laboratories by more than 15 percent, discard that test series and use the remaining three test series to establish ref,fc. Perform this evaluation separately for the results for unconfined and confined tests. The minimum value of conc shall be used in Eq.
Where the primary laboratory uses data from more than one laboratory for the assessment of servicecondition tension capacity in low-strength concrete, a unique. For systems that exhibit larger variation, a reduction is taken on the bond stress in the form of COV. For all other test series, the COV test,x of the peak loads shall not exceed 20 percent. Where this is not possible, rules are provided for consistent determination of Nadh.
Where the measured load at loss of adhesion is less than 50 percent of the mean tensile strength, which is generally an undesirable response, a reduction in the bond stress is taken through the factor adh. Upon loss of adhesion, both the anchor element and adhesive material are extracted together from the concrete. In such cases, the subsequent load-slip behavior is substantially dependent on the roughness of the drilled hole.
The onset of uncontrolled slip is therefore defined as loss of adhesion and the load corresponding to loss of adhesion is denoted as Nadh. In general, loss of adhesion is characterized by a significant change in stiffness as reflected in an abrupt change in the slope of load-displacement curve Fig. In general, the tangent stiffness ktan can be conservatively estimated as the secant stiffness between the origin of the load-displacement curve and the point defined by 0. Omission of less severe tests is permitted in specific cases: for example, if the desired category is fulfilled with the results of Tests 2b, 2c, and 2d, then Tests 2f, 2g, and 2h may be omitted.
Project a straight line from the origin of the loaddisplacement curve with a slope corresponding to the stiffness as calculated in No. The load Nadh shall be taken from the point of intersection between the projected line and the measured loaddisplacement curve Fig. If the peak load occurs at a displacement that is less than that corresponding to the intersection of the projected line and the load-displacement curve, then Nadh shall be taken as the peak load Fig.
If the displacement 0. An adjustment is made for values determined through confined testing, which generally increases the measured peak load. For anchor systems evaluated using the reduced test program of Table 3. The determination of the limiting characteristic bond stress to be used in the design equations of ACI M, Appendix D is based on a range of factors that may or may not apply in each case.
It is therefore permissible to determine a range of limiting characteristic bond stress values associated with specific conditions. Otherwise, calculate a single bond stress k,nom cr,uncr with the results for all diameters using the lowest bond stress. In this case, where the bond stress rises and falls across several diameters in a random manner, the minimum derived bond stress should be taken across all diameters.
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Where a trend can be established between bond stress and diameter, a best-fit approximation to the recorded values should be established and used to establish unique bond stresses for each diameter as appropriate. Where this condition is not satisfied, the product shall be reported as unqualified. Because any qualified product is assumed to be able to develop these minimum bond stresses, the same values as derived from Eq.
A basic differentiation is made between outdoor and indoor use. Outdoor implies exposure to weather such as water, temperature, and aggressive environments, while indoor is associated with a less demanding set of parameters. This is reflected in the omission of the lt , st , and dur from the second higher set of bond stresses corresponding to indoor uses in ACI M, Appendix D Table Two sets of req values are provided for determining the anchor category, each associated with specific job-site inspection and testing requirements.
For anchors that are assessed under the more relaxed threshold values for the determination of the anchor category, more stringent requirements for job-site inspection and testing are required. For anchors that do not meet the threshold values for the lowest anchor category, a further reduction in the limiting characteristic bond stress is taken. The minimum value of and adh shall control for the determination of the anchor category.
For all other cases, cat3 shall be taken as 1. If the sustained load used in the test is less than required, a reduction on the limiting characteristic bond stress is taken. Unconfined tension tests shall be conducted at the smallest, middle, and largest diameters in low- and highstrength concrete with five replicates per test series. The tests shall be conducted at the greatest embedment depth for which concrete cone failure is anticipated to occur and may be approximated using Eq.
The assessment of the effectiveness factor shall fulfill the requirements of ACI The minimum member thickness hmin shall not be less than the value given by Eq. The anchor shall not turn in the anchor hole prior to reaching a torque resistance of 1. In addition, Eq. If this requirement is not met, reduce the installation torque Tinst as required to fulfill the requirement.
The friction factor shall be taken as a lower-bound value. Unlike expansion and undercut anchors, adhesive anchors do not develop wedging forces in the crack during the conduct of the crack movement test. As such, changes in the lower crack width with increasing crack cycling are likely to be due to other causes, for example, changes in the bond relationship of the embedded reinforcement in the test specimen.
For a sample size of 10 to 20 replicates, one of the tested anchors shall be permitted to exhibit a maximum displacement of 3 mm after the initial 20 cycles and 4 mm after cycles. For sample sizes larger than 20, 5 percent of the tested anchors shall be permitted to exhibit these increased displacements.