Ground Motion Simulation Validation for building design and response assessment
Earthquake ground motion records are used as inputs for seismic hazard analysis, development of ground motion prediction equations and nonlinear response history analysis of structures. Real records from past earthquake events have traditionally been recognized as the best representation of seismic input to these analysis. However, our current way of implementing recorded ground motions is poorly constrained and suffers from the paucity of certain condition ground motions, such as the one with short distance and large magnitude. Meanwhile, even though the scaled ground motion is capable of matching the target spectrum, the content of frequency domain and ground motion parameters become unrealistic. With the rapid growth of computational ability and efficiency of computers, simulated ground motion can be an alternative to provide detailed and accurate prediction of earthquake effect. At the same time, simulated ground motions can provide a better representation of the whole ground motion generation process, such as fault rupture, wave propagation phenomena, and site response characterization. Hence, the aforementioned disadvantage of recorded ground motion can be overcame.
Despite ground motion simulations have existed for decades, and the design code, such as ASCE/SEI 7-10 (ASCE, 2010), allow use of simulated ground motions for engineering practice, engineers still worried about the stability in ground motion simulation process and similarity between response of engineered structures to similar simulated and recorded ground motions. In order to draw simulated ground motions into engineering applications and make them practical, this dissertation is making contribution to address this issue. Simulated ground motions have to be validated and compared with recorded ground motions to prove their equivalence in engineering applications.
This dissertation proposes a simulation validation framework. First step: Identify ground motion waveform parameters that well correlate with response of Multi-Degree of Freedom (MDOF) buildings and bridges. Second step: Develop goodness-of-fit measures and error functions that can describe the difference between simulated and recorded ground motion waveform characteristics and their effect on MDOF systems. Third step: Device the required update to ground motion simulation methods through which better simulations are possible. Forth step: Assess the current state of simulated ground motions for engineering applications.
In general, simulated ground motions are found to be an effective surrogate and replenishment of natural records in engineering applications. However, certain drawbacks are detected, 1) Simulated ground motions are likelihood to mismatch certain ground motion parameters, for example, Arias intensity, duration and so on; 2) Structural behavior resulting from recorded ground motions and simulated ground motions are different. The difference stems from the fact that simulated motions are mostly pulse like motions. Because the simulation methods are still developing, our intent is not ranking or classifying them, but rather to provide feedback to update ground motion simulation techniques such that future simulations are more representative of recorded motions.