Evaluation of contact and non-contact lap splices in concrete block masonry specimens

Abstract

An experimental program was performed for qualitative and quantitative comparison of the maximum tensile resistance of contact and non-contact lap spliced bars in reinforced concrete block masonry using double pullout and wall splice specimens. A total of 32 specimens were tested, consisting of an equal number of double pullout specimens and full-scale wall splice specimens. Both specimen types had the identical cross-section. Eight replicate specimens for each specimen type were constructed with both contact and non-contact lap splice arrangements. Grade 400 deformed reinforcing bars with a 300 mm lap splice length were provided in all specimens.

The double pullout specimens were tested applying direct tension to the lapped reinforcing bars. The splice resistance and displacement were recorded during testing. All double pullout specimens with contact lap splices developed, as a minimum, the yield strength of the reinforcing bars and generally displayed evidence of a yield plateau. In contrast, the double pullout specimens with non-contact lap splices failed when only 46.1% of the theoretical yield strength of the reinforcing bars was recorded as the maximum splice resistance. The difference between the average value of the tensile resistance in the contact and non-contact spliced bars was identified as being statistically significant at the 95% confidence level.

Wall splice specimens were tested under a four-point loading arrangement with the lapped bars located in the constant moment region. The applied load and specimen deflection were recorded until failure occurred. A numerical analysis was then performed to calculate the maximum resistance of the spliced bars. The specimens with contact lap splices developed the theoretical yield capacity of the reinforcing bars. In contrast, the wall splice specimens with non-contact lap splices developed an average tensile resistance of 78% of the theoretical yield capacity. The difference between the average tensile resistances of the lapped bars in the two splice arrangements was identified as being statistically significant at the 95% confidence level.

On average, the contact and non-contact lap spliced bars in the double pullout specimens developed 8.47% and 41.2% less tensile resistance, respectively, as compared to the wall splice specimens with the identical splice arrangement. Both differences were identified as being statistically significant at the 95% confidence level.

Bond loss between the reinforcing bars and the surrounding grout was identified as the failure mode for both the double pullout and wall splice specimens with contact lap splices. In contrast, bond loss at the masonry block/grout interface was observed along the non-contact lapped bars in both specimen types, as identified by visual observations upon removal of the face shell and the surrounding grout. Based on the test results of the wall splice specimens with non-contact lap splices, a correction factor of 1.5 is suggested when calculating the effective splice length for the non-contact splice arrangement as tested.