COMPUTATIONALLY EFFICIENT NONLINEAR STRUCTURAL ANALYSIS

摘要

Seismic displacement demands for design of a bridge frame structure are typically determined from linear-elastic analysis (LEA), which are often incorrect, and compared to displacement capacity from a nonlinear pushover analysis. Nonlinear time-history analysis (NTHA) provides the most realistic assessment of displacement demands because it properly models the physics of the dynamic problem, wherein stiffness of the bridge varies over time. However, using NTHA to determine a bridge response from multiple earthquake motions based on the stiffness method requires excessive time. A unique approach for determining the nonlinear time-history response of a bridge frame is disclosed that is thousands of times faster than the stiffness method while providing the same results. Computational efficiency allows bridge design engineers to use NTHA for the seismic design of bridge structures by producing multiple determinations in less than one second. Displacement demands and capacities are based on nonlinear bridge behavior, resulting in safer bridge structures and reduced construction costs.

主权项

1. A method for seismic analysis of frame structures comprising:
performing an initial dead load analysis of structure moments and stiffness; calculating, from Incremental Closed Form Method (ICFM) Equations, incremental time values of acceleration, velocity, displacement and final structure moments; summing the incremental values to produce a total sum value of all calculated time increment values; adjusting frame stiffness values are for a next incremental time value calculation; scaling the calculated time increment values for the time increment to the time of an event; and repeating the calculating, summing, adjusting and scaling until ICFM calculations of all time increments of ground motion have been completed and summed.