A precast segmental concrete bridge pier system is being investigated for use in seismic regions The proposed system uses unbonded posttensioning (UBPT) to join the precast segments and has the option of using a ductile fiber-reinforced cement-based composite (DRFCC) in the precast segments at potential plastic hinging regions The UBPT is expected to cause minimal residual displacements and a low amount of hysteretic energy dissipation The DFRCC material is expected to add hysteretic energy dissipation and damage tolerance to the system Small-scale experiments on cantilever columns using the proposed system were conducted The two main variables were the material used in the plastic hinging region segment and the depth at which that segment was embedded in the column foundation It was found that using DFRCC allowed the system to dissipate more hysteretic energy than traditional concrete up to drift levels of 36% Furthermore, DFRCC maintained its integrity better than reinforced concrete under high cyclic tensile-compressive loads The embedment depth of the bottom segment affected the extent of microcracking and hysteretic energy dissipation in the DFRCC This research suggests that the proposed system may be promising for damage-tolerant structures in seismic regions

Cyclic Response of Unbonded Posttensioned Precast Columns with Ductile Fiber-Reinforced Concrete

Development and testing of precast concrete beam-to-column connections

This paper presents the test results of four types of ductile, moment-resisting precast concrete frame connections and one monolithic concrete connection, all designed for use in high seismic zones. The performance of the precast concrete connections subject to displacement control reversed cyclic loading is compared with that of the monolithic connection. The precast concrete connections tested may be subdivided into three groups, namely cast-in-place, composite with welding, and bolted. The cast-in-place connections were located in either the beam or the column of the precast concrete subassemblies. The composite connection is a common detail used in the Turkish precast concrete industry. Two bolted specimens without corbels were also tested. Through these tests, the responses of different connection types under the same loading pattern and test configuration were compared. Comparisons of performance parameters, such as energy dissipation and ease of fabrication, revealed that the modified bolted connection may be suitable for use in high seismic zones.

Ductile Connections in Precast Concrete Moment Resisting Frames

Performance of a precast concrete beam-to-beam connection subject to reversed cyclic loading

H. 5. Lew Chief, Structural Division United States Department of Commerce National 'Institute of Standards and Technology Gaithersburg, Maryland An experimental study of the behavior of precast concrete beam-to-column connections subjected to cyclic inelastic loading conducted at the National Institute of Standards and Technology is presented. The study was initiated to provide data for the development of a rational design procedure for such connections in seismically active regions. The objective of the study is to develop a moment resistant precast concrete connection that is economical and can be easily constructed. Four one-third scale monolithic concrete beam-to-column connections were tested: two were designed according to the 1985 Uniform Building Code (UBC) Seismic Zone 2 criteria and two to UBC Zone 4 criteria. In addition, two precast, posttensioned concrete beam-to-column connections similar in design to the monolithic Zone 4 specimens were tested. These tests constitute the first phase of a multi-year test program.

Performance of Precast Concrete Beam-to-Column Connections Subject to Cyclic Loading

Four beam-column subassemblages were constructed and tested under cyclic loading to verify the possiblity of obtaining a strong, ductile, and energy-dissipating connection between precast elements in seismic areas. The subassemblages consisted of 2 precast parts joined together by a cast-in-place (CIP) fiber reinforced concrete (FRC) connection. It was observed that the use of fiber reinforced concrete in the CIP connection dramatically improved the cyclic behavior of the specimens. Displacement ductilities up to 6.0 were observed and higher load levels were attained for the FRC specimens when compared to the control specimen. The maximum cumulative energy dissipated by one FRC specimen was more than ten times that for the control specimen.

Cyclic response of fibrous cast-in-place connections in precast beam-column subassemblages

Six beam type specimens, each consisting of 2 precast reinforced concrete parts joined together by a cast-in-place fiber reinforced concrete connector, were tested by under cyclic third-point loading. The tests were part of a comprehensive study aimed at developing a strong, ductile, and energy-dissipating connection for preacast concrete construction in seismic zones. It was observed that the cast-in-place joints, despite experiencing a localized failure due to the presence of a single major crack, exhibited higher levels of ductility and energy dissipation compared to cast-in-place conventional concrete joints.

Khaled S. Soubra

Papers

Cyclic response of fibrous cast-in-place connections in precast beam-column subassemblages

Fiber Reinforced Concrete Joints for Precast Construction in Seismic Areas

Fiber reinforced concrete connections for earthquake resistant design of precast reinforced concrete structures