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Compression Lap Splices and Compression Development of Headed and Hooked Bars in Beam-Column Joints
Valentini, Guido Lequesne, Rémy D. Lepage, Andrés Darwin, David
Valentini, Guido
Lequesne, Rémy D.
Lepage, Andrés
Darwin, David
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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) produce calculated lengths longer than Class B tension lap splice lengths under certain design conditions. The provisions were shown to also be a poor fit to a database of 89 test results (with 72 specimens in the database violating the ACI 318-19 minimum lap splice length). Several equations exist that better fit the dataset, including several tension development length equations. Defining compression lap splice length requirements as a function of the tension development length is a 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.
Provisions for headed and hooked bar development were compared against databases of exterior beam-column connection tests with 35 and 27 specimens, respectively. Analyses show that satisfying the compression development length requirements of §25.4.9, as mandated by §18.8.2.2, is not necessary for preventing anchorage distress in special moment frame joints with either headed or hooked bars. None of the 59 specimens (35 with headed bars and 24 with hooked bars) with drift ratio capacities above 3% satisfied §25.4.9. The analyses also show that joints that did not satisfy the ACI 318-19 provisions for headed or hooked bar tension development length (§18.8.5.2 for headed bars and §25.4.3 for hooked bars) still exhibited satisfactory behavior, suggesting that §18.8.5.2 and §25.4.3 are considerably conservative. Other equations were evaluated and found to better fit the data, including the equation in ACI 318-19 §18.8.5.1, which analyses suggest might be applicable to both headed and hooked bars.
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2024-07
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University of Kansas Center for Research, Inc.
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Valentini, G., Lequesne, R. D., Lepage, A., and Darwin, D., “Compression Lap Splices and Compression Development of Headed and Hooked Bars in Beam-Column Joints,” SM Report No. 159, The University of Kansas Center for Research, Inc., Lawrence, KS, July, 2024, 188 pp.