Compression Lap Splices of Straight Bars and Compression Development of Headed and Hooked Bars in Beam-Column Joints

Abstract

ACI 318-19 Building Code provisions for compression lap splices and for headed and hooked bar development in special moment frame (SMF) joints were evaluated against databases of test results. Recommendations are made for simplifying and improving code requirements.Compression lap splice length provisions (ACI 318-19 §25.5.5) were shown to produce calculated lengths longer than Class B tension lap splice lengths under certain design conditions and also to be a poor fit to a database of 89 test results (it must be emphasized that 72 specimens in the database violated the ACI 318-19 minimum lap splice length). It was shown that several equations exist that better fit the dataset, and that it may be possible to define the compression lap splice length as a function of the tension development length. Use of tension development length equations for compression lap splice design is a practical, more accurate alternative to §25.5.5 that eliminates the need to calculate both tension and compression development lengths and prevents design cases where calculated lengths are longer in compression than in tension. Analyses show that ACI 318-19 §18.8.2.2 should not require that headed and hooked bars satisfy §25.4.9. Comparisons with results from exterior beam-column connections with headed or hooked beam reinforcement terminating in the joint show that satisfying §25.4.9 is not a necessary condition for preventing anchorage distress in SMF joints. None of the 55 specimens (36 with headed bars and 19 with hooked bars) with drift capacities above 3% and no evidence of anchorage distress satisfied §25.4.9. The analyses also show that complying with §18.8.5.2 is not a necessary condition for joints with headed bars to exhibit satisfactory behavior, suggesting that §25.4.4, which §18.8.5.2 refers to, may be overly conservative. Other equations were considered and found to better fit the data.