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Hybrid fiber-reinforced polymer (FRP) concrete-steel double-skin tubular columns are a new form of hybrid columns recently proposed by the second writer. The new column consists of an inner steel tube and an outer FRP tube, with the space between them filled with concrete. The new column possesses several advantages over existing columns including excellent ductility and corrosion resistance. This paper first examines the behavior of the confined concrete between the two tubes using a finite-element model to understand the effects of the key parameters including the stiffness of the FRP tube, the stiffness of the steel tube, and the size of the inner void. Based on the available experimental observations and the results from the finite-element model, a simple stress-strain model for the confined concrete is proposed for use in practical design. Comparisons with test results show that the proposed model provides reasonably accurate and conservative predictions. DOI: 10.1061/(ASCE)ST.1943-541X.0000121 CE Database subject headings: Stress strain relations; Concrete; Fiber reinforced polymer; Composite columns. Author keywords: Stress-strain relations; Concrete; Fiber-reinforced polymer; Composite columns.

In regions without seismic provisions, it is common to use transfer plates as part of the structural system. In this paper, pseudodynamic tests with substructure techniques were conducted on an 1:4 scale test specimen representing the first 2 stories of a 18-story high-rise building with a transfer plate under earthquake actions. Columns of the test specimen were strengthened to prevent failure under the pseudodynamic tests. Three types of time-history records were applied, including triangular waves and a series of El-Centro Earthquakes. Based on the experimental results, it is predicted that the bottom of the transfer plate will be severely damaged when subjected to an El-Centro Earthquake with maximum acceleration at 64% g. CE Database subject headings: Dynamic tests; Seismic effects; Plates; Reinforced concrete; Substructures; Prestressed concrete; Precast concrete.

The reinforced concrete building considered in this study has 34 typical floors above a 2.7 m thick transfer plate and a three-level podium. The transfer plate is a reinforced concrete thick plate that transfers the loads from the walls at the typical floors to widely spaced columns in the three-level podium. A microconcrete model representing the high-rise building was constructed in 1:20 scale. Shaking table tests were conducted and the model was subjected to earthquake actions representing minor, moderate, major, and supermajor earthquakes for a region of moderate seismicity, with basic seismic intensity at the VIIth degree pursuant to GB50011-2001. Seismic performance was qualitatively assessed, and it is predicted that the prototype building will not collapse when subjected to major earthquakes. The majority of the damage and failure occurred at the story above the transfer plate. To minimize the damage, it is desirable to strengthen the walls between the 4th and 15th floors as well as reducing any change in stiffness within the transfer plate zone. Data obtained from the shaking table tests were analyzed. Spectral frequencies of the acceleration spectra estimated by the fast Fourier transform method and deformation measurements are good indicators on structural damage. Plots of acceleration against displacement would be useful in assessing the locations of structural damage. The use of the ratio of lateral stiffness to check the existence of a soft story may not be appropriate for high-rise buildings. However, story drift relates well with the degree of structural damage. CE Database subject headings: Buildings. high-rise: Seismic effects: Plates: Concrete, reinforced: Earthquakes: Shake table tests.

This paper presents the experimental results obtained from the testing of nine 1:3 scale square-shaped column specimens. Characteristics of the specimens are low-lateral confinement, low-to-moderate shear span, and high-axial load. Detailing of the transverse reinforcement includes both 90[degrees] and 135[degrees] hooks. Specimens with low-shear span failed under shear in a brittle manner. Flexural failures were observed in specimens with moderate shear span and having a lateral confinement ratio of 0.003. Lateral confinement has significant influence on the ultimate drift, of which an increase from 0.001 to 0.003 could increase the ultimate drift capacity by up to 100%. Seismic performance of columns with low-to-moderate shear span may not be accurately reflected by the ductility factor. Better representation is provided by the ultimate drift ratio, and can be estimated by an empirical equation. The use of 90[degrees] hooks in detailing the transverse reinforcement leads to a 40% reduction on the ultimate drift capacity. Guidelines are also given to estimate the corresponding reduction on the ductility factor. DOI: 10.1061/(ASCE)0733-9445(2003)129:6(733) CE Database subject headings: Concrete, reinforced; Drift; Axial loads; Confinement; Tests.

An analytical procedure is proposed to establish the nonlinear moment-rotation (M-[Phi]) characteristics for the bolted end-plate connections in flexibly jointed steel frames. The connection characteristics are assumed to depend on the component behavior of the tension zone, the compression zone, and the shear zone. The column flange and end plate with each bolt row in the tension zone are considered as a series of T-stub assembly with the effective length recommended by the Eurocode 3. Based on the beam and yield-line theory, the elastoplastic force-deformation relationship for each T-stub assembly is derived. With the consideration of the deformation of column web in compression and shear zone, the connection rotation [Phi] under bending moment M is evaluated accordingly. The proposed analytical model is compared with some experimental results of extended and flush end-plate connections, and the feasibility and validation of the proposed model are demonstrated.