Behaviour of bolted link-column joints in eccentrically braced frames

Current seismic provisions require that shear links in eccentrically braced frames be fully welded to the column flanges at the link-column joint. Since field welding may have its disadvantages, the use of bolted extended end-plate connection is examined. An experimental program is conducted to assess the response of extended end-plate connections of link-column joints in eccentrically braced frames. Six link-column joint specimens are tested using a cyclic load that represents the severe load reversals that the frame may be subjected to during strong earthquakes. The specimens are selected on the basis of different connection designs. Measurements of forces, strains, and displacements are made. Interaction curves relating the shear force and moment acting on links with semirigid connections are developed. The slip tendency and energy dissipation capacity of the different specimens are compared. On the basis of the test results, a design procedure is developed for the bolted extended end-plate link-column connection. It is concluded that bolted extended end-plate connections can be used for link-column joints of eccentrically braced frames. In properly designed connections bolt slippage was not measured even at high shear forces that are characteristic of link-column joint. Existing guidelines for the design of extended end-plate link-column joints are modified to account for the variable shear force and moment associated with links of different lengths. Key words: steel, frame, eccentric, braced, bolted, end plate, link, connection.