Determining the tensile pull-out resistance of new-type anchoring fasteners is a critical qualification and acceptance test that verifies whether post-installed anchors can safely transfer loads into concrete and masonry substrates. This article explains the testing standards, sample categories, test items, laboratory procedures, and data evaluation methods used by accredited third-party laboratories for anchor tensile testing. It provides engineers, QA managers, and procurement specialists with a practical reference covering ASTM E488, EAD, ACI 355, EN 1992-4, and GB series requirements.
Technical Overview
New-type anchoring fasteners—including post-installed mechanical expansion anchors, undercut anchors, screw anchors, and bonded (chemical) anchor systems—are widely used to connect structural and non-structural components to hardened concrete and masonry. Because the load capacity of these fasteners cannot be reliably predicted by calculation alone, direct tensile testing is the primary method used to determine their actual pull-out resistance and to establish characteristic design values.
Tensile testing of anchors measures the maximum axial tension that a fastener can carry before failure, together with the load–displacement behavior that governs serviceability. The test results are evaluated against recognized standards such as ASTM E488/E488M, ACI 355.2, ACI 355.4, EAD 330232 and EAD 330499 (formerly ETAG 001), EN 1992-4, JGJ 145, and GB 50367. Testing is typically performed by accredited third-party laboratories using calibrated load frames, reaction rigs, and displacement transducers, and the reported characteristic values are directly usable for design verification and product certification.
Testing Samples
Mechanical Expansion Anchors
Torque-controlled expansion anchors and deformation-controlled drop-in anchors are tested in both uncracked and cracked concrete test members. Samples cover the full declared diameter range and embedment depths, including the minimum and maximum values stated in the manufacturer's installation instructions.
Undercut Anchors
Undercut systems, which achieve interlock by cutting a conical cavity in the concrete, are tested to verify the geometric undercut requirements and the resulting steel and concrete capacity, since their behavior differs fundamentally from friction-based expansion anchors.
Bonded and Chemical Anchors
Capsule systems and injection mortar systems based on epoxy, vinylester, polyester, or hybrid formulations are tested after full curing under controlled temperature and humidity. These systems additionally require sustained-load (creep) tensile testing because long-term behavior governs their design resistance.
Plastic and Insulation Anchors
Polymer anchors used for facade insulation systems are tested in both concrete and masonry base materials, including hollow brick and autoclaved aerated concrete (AAC), to determine pull-out capacity and plate stiffness.
Base Material Test Members
Tensile tests are performed on concrete members with strength classes typically ranging from C20/25 to C50/60, at an age of at least 28 days or after achieving the specified compressive strength. Masonry tests use representative brick, block, and AAC units. Test member dimensions must be large enough to avoid unrepresentative splitting failures unless splitting is the parameter under investigation.
Testing Items
The tensile determination program for new-type anchors generally includes the following measured and derived quantities:
- Ultimate tensile (pull-out) load for each anchor size and embedment depth
- Characteristic tension resistance calculated as the 5% fractile at 90% confidence level
- Displacement at reference service loads and residual displacement after unloading
- Failure mode classification: steel fracture, pull-out, pull-through, concrete cone failure, splitting, or edge blow-out
- Tension capacity in cracked concrete, including crack movement cycling where applicable
- Minimum edge distance and spacing to avoid splitting during installation and loading
- Sustained tensile load (creep) displacement for adhesive anchor systems
- Sensitivity to installation parameters such as hole cleaning, drilling method, and installation torque
- Jobsite proof-load verification values for construction acceptance testing
Testing Methods
Sample Installation
Anchors are installed in accordance with the manufacturer's printed installation instructions (MPII), including specified drilling tools, hole cleaning procedures for bonded systems, torque application, and curing time. Installation tolerances are recorded, because installation quality is one of the dominant variables affecting tensile resistance.
Test Setup and Instrumentation
Tensile load is applied through a hydraulic or servo-electric actuator with a reaction frame positioned to avoid influencing the failure cone. The clear distance between the support ring and the anchor satisfies the standard requirements—typically at least twice the effective embedment depth. Applied load is measured with a calibrated load cell, and displacement is recorded with LVDTs or digital displacement transducers mounted on an independent magnetic reference base.
Loading Procedure
Laboratory qualification tests follow a controlled loading regime in which failure occurs within the time window prescribed by ASTM E488 or the EAD reference methods, generally achieved by applying load at a constant rate or under displacement control. Load–displacement curves are recorded continuously until failure. For jobsite acceptance tests, load is applied in increments with holding periods—commonly five equal steps with a one-minute hold at each step—up to the specified proof load.
Data Evaluation
For each configuration, at least five valid tests are usually required. Results are checked for validity, outliers, and unrepresentative failure modes. Characteristic resistance is calculated by statistical analysis of the test population using the 5% fractile at 90% confidence with the appropriate k-factor for the sample size. Where required, results are converted to a reference concrete strength before comparison with design values in EN 1992-4, ACI 318, or GB 50367.
Test Report
A complete report documents the anchor type and batch, base material properties, installation records, calibration certificates for load and displacement instrumentation, individual load–displacement curves, ultimate loads, failure modes, statistical evaluation, and the resulting characteristic tensile resistance. This documentation supports product certification, technical approval, and construction quality records.
Applications
Tensile resistance determination for new-type anchors supports a broad range of engineering and construction scenarios:
- Curtain wall and facade bracket anchorage on concrete and masonry structures
- Post-installed rebar connections for structural strengthening and retrofit works
- Steel column base plates, machinery foundations, and equipment anchorage
- Pipeline, cable tray, and MEP support systems in industrial plants
- Seismic and cracked-concrete qualifications for infrastructure and energy projects
- Facade insulation systems anchored to AAC, hollow block, and brick substrates
- Factory production control and batch release testing for anchor manufacturers
- Third-party product certification and technical approval submissions
FAQ
How many anchor samples are required for a valid tensile test series?
Most qualification standards require a minimum of five valid tests per configuration—defined by anchor size, embedment depth, base material, and concrete crack condition. Additional samples may be needed when results show high scatter or unrepresentative failure modes.
What is the difference between ultimate load and characteristic resistance?
The ultimate load is the measured maximum tensile force for an individual test. The characteristic resistance is a statistically derived value representing the 5% fractile at 90% confidence, which is then used as the basis for design after applying appropriate partial safety factors.
Why is cracked concrete testing important for new anchors?
Structural concrete frequently contains cracks that open and close under service loads, significantly reducing the capacity of expansion and bonded anchors. Testing in cracks of defined width, often 0.3 mm or 0.5 mm, verifies performance under realistic conditions and is mandatory for many seismic and structural applications.
How long does bonded anchor testing take?
Basic pull-out tests can be completed within days after the mortar cures. However, sustained-load creep tests for adhesive anchors typically run for 42 days or longer at elevated temperature to establish long-term displacement behavior, so full qualification programs require careful scheduling.
Can laboratory results be applied directly to jobsite conditions?
Laboratory characteristic values are established under reference conditions such as concrete strength, crack state, and temperature. On site, verification tests using the same pull-out apparatus with incremental proof loads are recommended, particularly when base materials, drilling equipment, or installation crews differ from the qualified configuration.