Chung-Che Chou

Establishing absorbed energy spectra—an attenuation approach

For energy-based seismic design, energy demand in the form of absorbed energy spectra was established by an attenuation relationship. The absorbed energy is proposed for evaluating the energy demand in an inelastic system because the absorbed energy is directly related to the pseudo-velocity in the elastic case. Based on a total of 273 ground motion records from 15 significant earthquakes in California, an attenuation relationship of the absorbed energy was established from a two-stage non-linear regression analysis. This relationship was established for a given earthquake magnitude, source-to-site distance, site class, and ductility factor. A similar expression for the normalized absorbed energy was also developed. This study showed that the absorbed energy for near-field ground motions can be significantly larger than that predicted by the attenuation relationship for normal ground motions. Copyright

Cyclic performance of a type of steel beam to steel-encased reinforced concrete column moment connection

Abstract Two full-scale subassemblies with steel-encased reinforced concrete (SRC) columns and steel beams were tested to evaluate the seismic performance of the connection details. For ease of construction, continuity plates were eliminated and less transverse reinforcement than that specified in the NEHRP seismic provisions was used in the connection region. The reduced beam section was introduced to reduce the shear demand on the connection. In addition, two doubler plates were placed away from the column web to enhance the connection shear resistance. This study showed that: (1) the stringent requirement for the transverse reinforcement could be relaxed; (2) the offset doubler plates were able to resist a significant amount of connection shear; and (3) the inner concrete strut could be mobilized in the two-sided moment connection, but not in the one-sided moment connection.

Development of Steel Dual-Core Self-Centering Braces: Quasi-Static Cyclic Tests and Finite Element Analyses

This work presents mechanics, tests, and finite element analyses of a novel steel dual-core self-centering brace (SCB) with flag-shaped re-centering responses. The axial deformation capacity of the brace is doubled with respect to the SCED brace by serial deformations of two sets of parallel tensioning elements when both braces use the same tensioning elements. The mechanics of the brace is first explained; six tensioning elements and four dual-core SCBs are tested to evaluate their cyclic performance. The braces exhibit excellent performance up to a drift of 2% with a maximum axial force around 1,400 kN. The braces also survive 15 low-cycle fatigue tests at a drift of 1.5%. Tensioning elements fail when the braces are overloaded to 2.5–3% drift. Finite element analysis is conducted to further verify hysteretic responses of the dual-core SCB in cyclic tests. A design procedure for the proposed dual-core SCB is also included in the paper.

Numerical and experimental investigation of steel structural component of the new San Francisco-Oakland Bay Bridge

Publisher Summary The cyclic testing of large-size steel shear links for the new San Francisco–Oakland Bay Bridge (SFOBB) revealed brittle fracture. A parametric study, aimed to reduce the local strain demand in highly restrained area, was performed with the use of a general-purpose nonlinear finite element analysis program. The analysis results lead to improved welding details, which were shown by subsequent testing to be effective for preventing brittle fracture. A same program was used to perform correlation study for the compression test of orthotropic steel deck. By introducing the initial geometric imperfection to the model, the analysis tool was able to predict the maximum strength and the buckling mode well.