PSI - Issue 64

Eric Williams et al. / Procedia Structural Integrity 64 (2024) 1573–1580 Williams, Annooz, and Myers / Structural Integrity Procedia 00 (2024) 000 – 000

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Notes: Figure shown for 19 mm bar test. 5d b =95 mm for 19 mm dia bar. 5d b =65 mm for 13 mm dia. bar.

a

b

Fig. 1. Cross-section of a 19 mm specimen (a) without repair material and (b) with repair material.

2.3 Pull-out tests and results For the test setup, a rubber mat and steel plate with holes in the center are placed atop a UTM, and the longer end of the rebar protruding from the specimen is fed through the hole such that the UTM can grip it below, and the concrete is resting on the rubber mat. An LVDT sensor was placed on the smaller end of the rebar to measure the slip behavior of the rebar. The specimen was preloaded to 1.33 kN, then loaded at a rate of 2.5 mm/min to failure. The load, P , was recorded, then the average bond stress, τ , was calculated using the equation below:

P d l



=

(1)



b b

where d b is the rebar diameter and l b is the embedment length. The relationship between the average bond stress and the slip measurements from the LVDT would be used to analyze the bond behavior in accordance with Baena et al. (2009); however, due to an error in the test setup, LVDT readings were invalidated. Two failure modes were observed during testing (shown in Figure 2): concrete splitting and pull-out. Almost all tests failed via concrete splitting, and the bond-slip behavior would not have been meaningful for these tests as the rebar would pull-out with little force. Failure types and peak average bond stresses are show in Table 5 and Figure 3. It should be noted that the epoxy coated bars were provided by a different vendor than the uncoated and MKPC coated rebars, such that the lug configurations of all bars were not identical providing for an inherent variable that was not accounted for within the evaluation.