Title:
Seismic Behavior of External Socket Connections for Reinforced Concrete Columns
Author(s):
Julio A. Samayoa, Giorgio T. Proestos, and Mervyn J. Kowalsky
Publication:
Structural Journal
Volume:
123
Issue:
3
Appears on pages(s):
239-252
Keywords:
accelerated bridge construction; external socket connection; large-scale tests; reinforced concrete column, seismic design; seismic performance
DOI:
10.14359/51749376
Date:
5/1/2026
Abstract:
This study uses six large-scale experimental tests to investigate the seismic behavior of external socket connections for reinforced concrete columns. The tests evaluated the effects of key design parameters, including socket height and grout strength, on the performance of these connections under reverse cyclic lateral loads. The results indicate that socket height significantly affects whether the plastic hinge forms in the column above the connection or inside the socket and influences the required strength of the structural components. Shorter socket heights required higher grout strengths and increased shear capacity to avoid undesirable failure modes. Three primary failure modes were observed: grout crushing, shear failure, and flexural failure above the socket. Regardless of socket height, all tests showed that external socket connections effectively protect adjoining structural members by limiting plastic strain demands. These findings provide valuable insights into optimizing the design and performance of external socket connections in seismic regions.
Related References:
1. Culmo, M. P., “Accelerated Bridge Construction: Experience in Design, Fabrication and Erection of Prefabricated Bridge Elements and Systems,” Federal Highway Administration, Washington, DC, 2011.
2. Saiidi, M. S.; Mehraein, M.; Shrestha, G.; Jordan, E.; Itani, A.; Tazarv, M.; Sanders, D.; Murphy, T. P.; Reno, M. L.; and Pohll, M. N., “Proposed AASHTO Seismic Specifications for ABC Column Connections,” Transportation Research Board, Washington, DC, 2020. doi: 10.17226/2580310.17226/25803
3. Restrepo, J. I.; Matsumoto, E. E.; and Tobolski, M. J., Development of a Precast Bent Cap System for Seismic Regions, National Academies Press, Washington, DC, 2011. doi: 10.17226/1448410.17226/14484
4. Fulmer, S. J.; Kowalsky, M. J.; and Nau, J. M., “Grouted Shear Stud Connection for Steel Bridge Substructures,” Journal of Constructional Steel Research, V. 109, 2015, pp. 72-86. doi: 10.1016/j.jcsr.2015.02.009
5. Marsh, M. L.; Stanton, J. F.; Wernli, M.; Eberhard, M. O.; Garrett, B. E.; and Weinert, M. D., Application of Accelerated Bridge Construction Connections in Moderate-to-High Seismic Regions, National Academies Press, Washington, DC, 2011. doi: 10.17226/1457110.17226/14571
6. Culmo, M. P., “Connection Details for Prefabricated Bridge Elements and Systems,” Report No. FHWA-IF-09-010, Federal Highway Administration, Washington, DC, 2009.
7. Tazarv, M., and Saiidi, M. S., “Design and Construction of Precast Bent Caps with Pocket Connections for High Seismic Regions,” University of Nevada, Reno, Reno, NV, 2015.
8. Wang, Z.; Li, T.; Qu, H.; Wei, H.; and Li, Y., “Seismic Performance of Precast Bridge Columns with Socket and Pocket Connections Based on Quasi-Static Cyclic Tests: Experimental and Numerical Study,” Journal of Bridge Engineering, ASCE, V. 24, No. 11, 2019, p. 04019105. doi: 10.1061/(ASCE)BE.1943-5592.0001463
9. Canha, R. M. F.; Ebeling, E. B.; De Cresce El Debs, A. L. H.; and El Debs, M. K., “Analysing the Base of Precast Column in Socket Foundations with Smooth Interfaces,” Materials and Structures, V. 42, No. 6, 2009, pp. 725-737. doi: 10.1617/s11527-008-9416-4
10. Mehrsoroush, A., and Saiidi, M. S., “Cyclic Response of Precast Bridge Piers with Novel Column-Base Pipe Pins and Pocket Cap Beam Connections,” Journal of Bridge Engineering, ASCE, V. 21, No. 4, 2016, p. 04015080. doi: 10.1061/(ASCE)BE.1943-5592.0000833
11. Motaref, S.; Saiidi, M. S.; and Sanders, D. H., “Seismic Response of Precast Bridge Columns with Energy Dissipating Joints,” University of Nevada, Reno, NV, 2011.
12. Mohebbi, A.; Saiidi, M. S.; and Itani, A. M., “Shake Table Studies and Analysis of a Precast Two-Column Bent with Advanced Materials and Pocket Connections,” Journal of Bridge Engineering, ASCE, V. 23, No. 7, 2018, p. 04018046. doi: 10.1061/(ASCE)BE.1943-5592.0001247
13. Haraldsson, O. S.; Janes, T. M.; Eberhard, M. O.; and Stanton, J. F., “Seismic Resistance of Socket Connection between Footing and Precast Column,” Journal of Bridge Engineering, ASCE, V. 18, No. 9, 2013, pp. 910-919. doi: 10.1061/(ASCE)BE.1943-5592.0000413
14. Haraldsson, O. S.; Janes, T. M.; Eberhard, M. O.; and Stanton, J. F., “Precast Bent System for High Seismic Regions – Laboratory Tests of Column-to-Footing Socket Connections,” University of Washington, Seattle, WA, 2013.
15. Wu, R.-Y., and Pantelides, C. P., “Rapid Repair and Replacement of Earthquake-Damaged Concrete Columns Using Plastic Hinge Relocation,” Composite Structures, V. 180, 2017, pp. 467-483. doi: 10.1016/j.compstruct.2017.08.051
16. Rutledge, S. T.; Kowalsky, M. J.; Seracino, R.; and Nau, J. M., “Repair of Reinforced Concrete Bridge Columns Containing Buckled and Fractured Reinforcement by Plastic Hinge Relocation,” Journal of Bridge Engineering, ASCE, V. 19, No. 8, 2014, p. A4013001. doi: 10.1061/(ASCE)BE.1943-5592.0000492
17. Samayoa, J. A.; Proestos, G. T.; and Kowalsky, M. J., “External Pocket and Socket Connections for the Seismic Design of Alaska Bridges,” Alaska Department of Transportation and Public Facilities, Juneau, AK, 2024.
18. ASTM C39/C39M-24, “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens,” ASTM International, West Conshohocken, PA, 2024. doi: 10.1520/C0039_C0039M-24
19. Goodnight, J. C.; Feng, Y.; Kowalsky, M. J.; and Nau, J. M., “The Effects of Load History and Design Variables on Performance Limit States of Circular Bridge Columns - Volume 1,” North Carolina State University, Raleigh, NC, 2015.
20. Jacobsen, L. S., “Damping in Composite Structures,” Proceedings of the 2nd World Conference on Earthquake Engineering, 1960.
21. Goodnight, J. C.; Feng, Y.; Kowalsky, M. J.; and Nau, J. M., “The Effects of Load History and Design Variables on Performance Limit States of Circular Bridge Columns - Volume 2: Experimental Observations,” North Carolina State University, Raleigh, NC, 2015.
22. Priestley, M. J. N.; Calvi, G. M.; and Kowalsky, M. J., Displacement-Based Seismic Design of Structures, second edition, IUSS Press, Pavia, Italy, 2007.