Experimental Investigation Into The Static And Cyclic Performance Of Bar-splice Assemblies Used In Prefabricated Frame Structures

This study presents results from the static and cyclic performance of a bar-spliceassembly. Construction errors and geometric imperfections in the materials used for thecivil engineering works are a continuing challenge that Engineers face on a daily basis.Due to economic aspects and deadlines, they are forced to make ad-hoc decisions torepair the imperfection and/or error. An investigation is made into the performance oftwo connectors meant to join two-16-mm and two-18-mm rebar to transfer forces acrossthe splice in the safest way possible. A number of imperfections/errors are envisagednamely: bent bar in the grouted end (MT16B/MT18B); and an eccentricity introduced inthe grouted end of the connector (MT16E/MT18E). In addition, a headed rebar in thegrouted end is proposed because it not only averts eccentricity but it presumablydistributes forces to the grout in a more effective manner. Hence, an assessment is madefor this kind of set-up (MT16HR/18HR). Furthermore, a typical bar-splice assembly isused as a control for this study. The acronym MT stands for monotonic tension for thestatic aspects; CE stands for cyclic elastic and CP stands for cyclic plastic whichmeasure the cyclic performance. For a period of50-years, precast systems have been inuse, to-date, no empirical or analytical approach exists for assessing strength ofbar-splice assemblies in codes of practice. The need for research in this direction is longoverdue.A total of85specimens were tested in an experiment with an MTS equipment ofcapacity2500kN. The loading rates were consistent with existing codes of Practice. TheMTS was chosen for the experiment because of the ease with which the cyclic loadingwould be applied. A test matrix was designed with four tests including: monotonictension test; two-cyclic elastic tests; and cyclic plastic test. Each category of testcomprised of four differently connected specimens (MT16/MT18; MT16B/MT18B;MT16E/MT18E; and MT16HR/MT18HR). The loading sequence was obtained fromthe existing codes.The prominent failure mechanism was bar-rupture at the threaded end with minimalgrout spalling observed at the grouted end. The reduction of area at the threaded endwas responsible for the rupture of the bar but it was interesting to note that the yieldstrength values were consistent with specified yield strength values on a generalperspective. In addition, the intended construction errors and geometrical imperfections had minimal effect on the expected peak loads, however, the same could not be deducedfor ductility. There was observable reduction in ductility for the different bar-spliceassemblies. From a practical engineering perspective, the connector will perform wellwith or without errors in areas of low seismicity but would not be effective in areas ofhigh seismicity.