This paper presents the experimental results of six scaled high-strength concrete columns with concrete compressive strengths of 76-86 MP& Primary experimental parameters include axial loads ranging from 10 to 20% of column axial load-carrying capacity based on concrete gross section; longitudinal steel ratios of 2.46 to 3.53% of the gross sectional area; and volumetric ratios of transverse reinforcement ranging from 1.63 to 3.67%. Model columns with transverse reinforcement designed following the seismic provisions of current code developed sufficient ductility, with displacement ductility factors equal to or exceeding 6.0. The model columns designed with 50% of the transverse reinforcement required by current code also developed sufficient ductility when the axial load was 10% of its axial load-carrying capacity. Lateral load-carrying capacities of all the columns exceeded the flexural capacities calculated based on the equivalent concrete stress block used in current design code. Seismic shear strength of high-strength concrete columns was also examined, based on the test results and analytical approaches.

This paper presents a network platform developed for remote pseudo dynamic testing of substructures and structural elements, and discusses the results of trial tests. The network platform, NetSLab, was developed based on client/server concept along with a proposed data model and communication protocols. The platform is capable of transferring control and feedback data among remote structural testing laboratories or computers connected by Internet. Several concepts were introduced to realize the platform and to provide relatively easier and friendlier interface for applications and further development by users. Trial tests were successfully carried out at the Hunan University, China and the University of Southern California, USA. In the trial tests, models simulating bridge piers or piles were subjected to recorded earthquake ground motions controlled remotely over the Internet through the platform.

The effectiveness of prefabricated composite jacketing to retrofit existing circular reinforced concrete (RC) bridge columns for enhanced seismic shear strength is described in this paper. The jackets consist of multilayer prefabricated glass fiber reinforced composite shells adhered together. Three half-scale circular columns were tested under cyclic shear in double curvature and constant axial load. One column was tested in the "as built" condition to investigate the shear failure mode of columns designed based on pre-1971 codes. Two other columns were tested after being retrofitted using prefabricated composite jackets. The as built column suffered shear failure at low displacement ductility. The retrofitted columns developed significantly improved hysteretic responses with stable hysteresis loops even at displacement ductility levels as high as 10.0 corresponding to drift ratios exceeding 5.2%. Method for retrofit design using prefabricated composite jacketing is also provided and validated by the test results.

This paper describes experimental and theoretical studies on seismic retrofit of reinforced concrete circular columns with poor lap-splice details using prefabricated composite jacketing. Three 1:2 scale model columns have been tested. One column was tested under the condition of "as built" and two others were tested after being retrofitted using prefabricated composite jacketing. The as-built column suffered brittle failure due to the deterioration of lap-spliced longitudinal reinforcement without developing its flexural capacity or any ductility. The retrofitted columns showed significant improvement in seismic performance. The failed as-built column was retested after being repaired. The repaired column also demonstrated significant improvement in ductility. An analytical model, which takes into consideration the bond-slip deterioration of lap-spliced longitudinal bars, has been developed for seismic assessment and retrofit design.