This paper describes axial compression test results of 27 concrete cylinders confined by carbon fiber reinforced polymer composite jackets. The experimental parameters include plain concrete compressive strength and the thickness of the composite jacket. It is found that the carbon fiber composite jacketing can significantly increase the compressive strength and ductility of concrete. The test results indicate that concrete strength and confinement modulus, defined as the ratio of transverse confinement stress and transverse strain, are the most influential factors affecting the stress-strain behavior of confined concrete. The failure of the confined concrete was dominated by the rupture of the jacket at an average strain much smaller than the ultimate strain obtained from tension tests of flat coupons. In order to describe the main mechanical features of the confined concrete, a simple bilinear stress-strain model is suggested based on the theory of elasticity and minimum number of empirical equations determined from the tests. The simple model is shown to compare well with test results from previous studies by other researchers.

This paper describees theoretical and experimental studies related to seismic assessment and retrofit of bridge columst footings. One "as built" model columm footing and three retrofit model colunzn footings have been tested under sinmulated seiatnic actions. Test results of the "'as built" footing indicated that columu/footing joint shear failure is a potential danger to existitng bridge, structures. Test results also indicated that if there is no dependable tensile capacity in the pile/footing connectiosz, a rocking behaveior may dominare pier resporzse, minimizing damage to footing and column. Model column footitzgs retrofit using current retrofit standards depeloped relatively stable hysteretic responses up to moderate ductility levels. However. experinzental obserations and theoretical analyses based on a strut-and-tie model and yield-line theory indicated that with current footing retrofit design, which lacks the consideration for joint shear design, the reiinforced concrete overlay may not develop a fully effective postcracking tnechanism. Improved retrofit details including long dowels to insure developnent of an effective joint shear-resistitlg nlechatlism are proposed and verified hy experimental results.

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.

This paper introduces an innovative concrete filled steel tubular (CFT) column structure for improved seismic design of steel and concrete composite structures. Based on fundamental mechanics, the design concept is aimed at controlling the local buckling of the steel tube and confining the concrete in the potential plastic hinge zones of a CFT column. To achieve this, several efficient details of transverse confinement have been examined through experimental testing. The new type of CFT column, named as CCFT, is expected to overcome many disadvantages of the conventional CFT column and to provide the ideal choice for structural design of tall buildings in seismic regions. Experimental tests validated the concept of the CCFT.