Dynamic Seismic Analysis Research Articles

Representation of Concrete-Filled Steel Tube Cross-Section Strength

This paper presents the development of a polynomial equation to represent the three-dimensional (3D) cross-section strength of square or rectangular concrete-filled steel tube (CFT) beam-columns. The equation provides an accurate representation of the cross-section strength of a CFT subjected to a combination of axial force, strong axis flexure, and weak axis flexure. This expression is verified against the results of a detailed fiber analysis formulation, and against experimental tests of short, square CFTs available in the literature. This CFT cross-section strength equation forms a compact expression of the failure surface of square or rectangular CFTs having a wide range of cross-section dimensions and material strengths. The cross-section strength surface also provides the basis for a bounding-surface concentrated plasticity model in 3D force space for CFT beam-columns, presented in related work by the writers. This beam-column model, in turn, is suitable for conducting monotonic static, cyclic static, or transient dynamic seismic analysis of complete composite unbraced frame structures composed of steel I-girders framing biaxially into CFT beam-columns.

Seismic dynamic response by approximate methods

AbstractCurrent seismic safety evaluation for earth dams relies on approximate methods of analysis for prediction of non‐linear, transient, dynamic response. One of these approximate methods uses a Strain Reduction Factor (SRF), and has been widely applied in a variety of one‐dimensional and two‐dimensional soil structural analyses. A second method considered, Equivalent Temporal Damping (ETD), has been previously applied to several seismic dynamic analyses of earth dams. The relative accuracy of the two methods is assessed by comparing them with incremental plasticity, nearly exact numerical solutions. For a simple shear element subjected to deterministic and non‐stationary random input accelerations, a serious overprediction of the maximum peak shear response occurs by the SRF method, whereas the ETD results agree very closely with the incremental plasticity solutions. The SRF and ETD methods are also applied to seismic dynamic response analysis of a Vertical Soil Column system, and the same trends as established in the previous case are observed. It is concluded that, in lieu of combined incremental plasticity and finite difference or finite element numerical solutions, the ETD approach is the more accurate of the methods tested for seismic dynamic response analysis of earth dams.