اتصالات سنجاقی لوله ای پایه
Abstract
1. Introduction
2. Base pipe pin connection concept
3. Experimental studies
4. Analytical studies
5. Parametric studies
6. Conclusions
Acknowledgement
References
Abstract
Base pipe pin connections were developed to simulate a hinge behavior at the base of cast-in-place or precast bridge columns. Base pipe pins are composed of two steel pipes: one pipe is embedded in the column and the other in the adjoining member. Shear force is transferred through contact of the pipes and friction. The uplift force is resisted by a tension member and welded studs on the surface of the column pipe. To investigate the behavior and failure mode of base pipe pins under direct tension and to determine the ultimate tensile capacity of the pins, two scaled pipe pin connections were tested under direct tension. Elaborate nonlinear finite element (FE) studies of the pipe pins were also conducted to explore the effects of different parameters on the response of the pins. There are many possible failure modes that could occur under tension. Test results depicted that rupture of the pin tension member with no damage to the connection was the dominant failure mode in pure tension. The FE models accurately estimated the response of the test models and the observed failure mode. The analytical results showed that decreasing the pipe height alters the failure mode but does not affect the ultimate capacity of the connection significantly. Furthermore, reducing the pipe height or increasing the number of stud layers has a small effect on the ultimate capacity and stiffness of the connections.
Introduction
Top pipe pin hinges were first developed by the California Department of Transportation (Caltrans) engineers to eliminate moment transfer between column and cap beam in cast-in-place (CIP) construction. Pipe pins consist of a steel pipe that is anchored in the column and extended into a steel can inside the cap beam. This type of connection is designed to transfer (1) axial load through bearing of the cap beam on the column while no tension is transferred, (2) shear between the column and the cap beam through contact of the part of the pipe that is protruded and the can in the cap beam and friction at the column-cap beam interface, and (3) no moment from the column to the cap beam [1]. To investigate the seismic performance of the pipe pins and to develop a reliable design method, extensive analytical and experimental studies have been conducted. Five groups of experiments were conducted at the Large Scale Structural Laboratory at UNR: (1) and (2) quasi-static test of two 0.3 scale hinged cantilever columns under pure shear and combined flexure, shear, and axial loads to investigate overall response of the pipe pins [2], (3) static test of six 1:3.5 scale push-off specimens to formulate the bearing strength of concrete against steel pipes [3], (4) static pure shear test of six infill steel tubes to determine the shear capacity and develop an empirical design equation for shear strength of the tubes [3], and (5) shake table test of a 1:5 scale twocolumn bridge bent model incorporating top pipe pins to validate the design method developed for the pins [1].