Report No.: CCEER-08-1

Title: Seismic Response of Telescopic Pipe Pin Connections

Authors: Kelly Doyle and M. "Saiid" Saiidi

Date: February 2008

Sponsoring Agency: California Department of Transportation (Caltrans)

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557


Two-way hinges are often used in reinforced concrete bridge columns to prevent excessive flexural stresses from entering the connection to the superstructure or the footing. A new two-way hinge designed by Caltrans includes a telescopic pipe pin. Since very little research has been conducted on this type of connection, a study was undertaken to understand the behavior of pipe pin connections to help develop a simple and reliable design method. This report presents the result of the first phase of the study that consisted of testing of two specimens and analytical studies. Two 0.3 scale specimens were constructed and tested under cyclic loading to determine if the models behave in pure shear (as assumed in the current design method) and to study the effect of rotation on the connection behavior and strength. The first specimen (PS1) was tested under pure shear and the second (PF1) allowed for flexure and was representative of actual bridge columns. Both specimens exhibited considerable flexural yielding of the pipe. The stiffness and lateral load strength of PF1 were lower than PS1, thus reflecting the effect of rotation and plastic hinging of the column base. The capacity of PF1 was 14% lower than that of PS1.Analytical studies of a simple method gave the foundation for the development of a design method. A sensitivity analysis of the equations revealed that using the ultimate stress of the pipe (rather than the yield stress) in calculations leads to a close estimate of the actual ultimate connection capacity. However, if yielding is to be avoided in the pin, the pipe yield stress should be used in the simple method.