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Pull Out Testing Methodology Ultimate Load Tests for Rebar Dowels

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  This procedure is intended to provide additional guidance for the testing of fixings away fromlaboratory conditions such that the users of the results can be confident that the fixing’sperformance has been properly assessed.This procedure coversthe requirements for applyingUltimate Loads.This procedure coversUltimate load Tests and maybeappliedto chemical anchors and rebar dowelsusing chemical mortars.The purpose of site tests may be either:a.To establish thesuitability of a fixing and/or admissible loads in a particular base material.To establish the suitability of a fixing in a particular base material then ULTIMATE LOAD testsshould be carried out and the results compared with the required Design Load, and theManufacturer’s Recommended (Safe Working) Load.b.To validate installationThe position of fixings for Ultimate Tests should be chosen carefully. The base material and any edgedistances should be representative of the application concerned but tests should be positionedwhere damaged to the structure will not be detrimental to its strength and can be made good.Tester set-up would berepresentative of the loads actingon theanchor.  Set-up of the test apparatus is listed below: 1. Placethesteel spacers and hydraulic jack basein position (see diagram). 2. Mount the hydraulicjack on the steel base followed by the grip. 3. Tighten the bolts on the grip until maximum torque is achieved. 4. Position the hand pump so that the gauge can be easily read. 5. Apply the necessary load.Increase the load until the required test load is attained. Hold thisload and observe any falling back of the gauge pointer which would indicate movement andpossible failure of theconnection. Record the satisfactory result. 6. Release theload on thedowelby turning therelease knob on the hydraulicjack. 7. Remove thegrip and piston andmove to the next location for testing.SAFETY. It is the responsibility of all parties involved to take particular care to ensure the safety of allbystanders during the application of loads especially when testing to failure. When using pulling rodsin tension ensure no one stands in line with the rod.WITNESSES. It is strongly recommended that all tests are tests are witnessed by a representative of the client or engineer requesting the tests.Ultimate Load Tests recording first movement orserviceability limit–Applythe load slowly andprogressively until the Design Load or Manufacturer’s Recommended Load is reached; note whetheror not any movement has occurred. Continue loading until first movement is visible, note appliedload. Continueloading progressively until maximum load is achieved. Once no further load increaseis possible the test may be discontinued to avoid damaging the structure. Note the maximum loadachieved, mode of failure and any damage to the structure or the fixing.The number of tests required should be decided by the engineer requesting thetests;however, thefollowing guide-lines may be used.For Ultimate Tests to establish the suitability of the fixing in a particular base material at least 3 testsshould be carried out.If Safe Loads are to be determined from the tests at least 5 should be carried out.Testing of the anchor should meet the proof load that will be applied for it to pass the proof load testing. Anchors should be free of defects before using it for testing; also the substrate should  be checked for cracks or other defects. There are modes of failure that anchor will be subjected towhen the applied load had reached the maximum capacity of the anchor. It includes: a. pull-out andpull-through failure; b. concrete cone failure; c. edge failure; d. splitting failure; e. steel materialfailure. In proof loading, it is required to limit the load to be applied to the design load or permanentdamage to the fixing assembly will occur. If the anchor does not experienced any of the abovementioned modes of failure, it is safe to conclude that the anchor passed the test criteria.On-site condition is different in design condition whereas we are having some toleranceswith regardsin installation of anchor on site. Below is the following tolerances we recommend onsome site problems… Hitting of Reinforcement  –From the previous drilled hole that encounters a rebar, move two drilldiameters from the center of the drilled hole. Fillthe previous hole with mortar or grout. Inclinationof Anchor–Recommended inclination of anchor is 5 degrees from the axis that is perpendicular tothe substrate. Effective Embedment depth not achieved  –Based on approval minimum anchorage depth of anchoris 4d or minimum of 40 mm whichever is higher.
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