Flexural Noncontact Lap Splices in Ultra-HighPerformance Concrete

Ultra -high-performance concrete (UHPC) has the potential to create more -durable structures that can be economized based on performance criteria. An experimental program consisting of 47 small-scale, noncontact lap splice specimen tests under fourpoint loading was conducted to investigate the bond strength and slip mechanisms within UHPC. Parameters studied in the testing matrix included aspect ratio, clear cover, lap length, and bar size. An inverse analysis on a numerical model of the flexural tests was employed to compute the bond stress -slip parameters representative of each specimen group. Results showed an enhanced bond stress -slip behavior inducing reinforcing bar yielding for clear cover greater than 1.5db and lap splice lengths of 9db. The postpeak response of all specimens exhibited ductile behavior, including those that experienced slip. By controlling the lap parameters and using this ductile mechanism, the maximum bar stress can be limited to a target value in the design process.