**Author details**

In terms of the performance of the building codes with regard to expressing the site specifics, all of them are on the safer side (EC8 is the most conservative one and the IBC is the least) following the similar flow of spectral acceleration of the observed data from the nonlinear analyses. IBC's spectra would be considered as the most economical one compared to the others with missing some longer period content, and it would possibly be a better representation if the flat part of the spectra shifted on the right (by using larger corner periods). About the TEC2018, the spectra at higher period were estimated better, but the content from small to medium periods would not be cost-effective in the seismic design. As seen in the figure, EC8 envelope is not practical at all, and such design would be the most

*Geotechnical Engineering - Advances in Soil Mechanics and Foundation Engineering*

Equivalent linear analyses are easy to perform with less parameter needed to constitute a site and widely used in the practice and literature. However, one should be cautious to use this approach in such cases. Since this frequency-based analytical approach is not suited for liquefaction analyses, the results may canalize the engineer to an inappropriate design. Although the details of the results obtained from the equivalent linear analyses will not be covered here, it is important to call attention to the differences. The spectral acceleration of 15 analyses is presented in

As seen in the figure, the soil amplified the base motion and lengthened it to the

Pore pressure generation under cyclic loading is an important phenomenon for liquefaction triggering, and the number of cycles and/or duration to liquefy soil is affected a lot by the frequency content of the loading. Three different stress levels were tested at varying loading patterns, and it can be concluded that harmonic loading to estimate the liquefaction initiation is not that reliable in order to evaluate the dynamic behavior of sands. Regarding the number of cycles, it took almost 1848 cycles to liquefy the sand samples which is at least two times later than Type 5 loading, and this value goes up to 5.5 times at most for Type 6 at CSR = 0.15. The same comparison at CSR level of 0.20 shows that the shortest time to trigger liquefaction is 130 seconds, whereas it lasted 1110 seconds for harmonic loading being almost nine times later. Even among the irregular loading types, the difference was calculated as 2.5–3 times in terms of the number of cycles for soil to lose its stability at different stress levels. Therefore, frequency content and its link with the CSR level are of great importance on excess pore pressure buildup. With reference to the stress-based models in the literature to estimate the recorded data in the laboratory, the mentioned models were not that distinct to predict the data, and it

was noted that the best prediction was noticed at the medium stress level (CSR = 0.2). Moreover, the model proposed by Baziar [16] had a better job

Though nonlinear site response is a bit complicated to gather enough information to simulate the ground response, it is the most appropriate way to model the

**Figure 15** with their corresponding envelopes suggested by building codes.

higher periods for these earthquake scenarios. None of the building codes were capable of expressing the data very well, neither the peak spectral acceleration nor the corner frequencies. However, it should be underlined here that it is not the performance of the building codes, but instead it is the analytical approach of the equivalent linear analysis lacking to model the excess pore pressure generation and the damping behavior of the soil. Thus, nonlinear site-specific response in liquefied areas is crucial in the design, and the concept of liquefaction susceptibility should be

expensive one among three building codes.

explained more clearly in the building codes.

presenting the test data than the other two.

**4. Conclusions**

**138**

Kamil Bekir Afacan Eskisehir Osmangazi University, Eskisehir, Turkey

\*Address all correspondence to: kafacan@ogu.edu.tr

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
