# Static and Seismic Responses of Eco-Friendly Buried Concrete Pipes with Various Dosages of Fly Ash
## 6 Static and Seismic Analysis
### Dynamic Analysis of GPC Underground Pipe  
After weighing up all methods of the transient dynamic analysis (time-history), it seems that the full-time method can certainly offer more benefits than the other methods. Indeed, the unlimited application of all nonlinear behaviors and the utilization of various loads such as non-zero displacements are two superior features that distinguish the full-time method from the other methods numerically utilized in the previous studies. Thus, the decision is made to employ the full-time method in the time-history analysis of the GPC pipe through the ANSYS platform. Further explanations in the case of the full-time method will be illuminated in the following points [51; 52; 53; 54; 55]:  
* All linear and nonlinear properties of geometric material and linear and nonlinear elements are applicable. Young's modulus and density are the minimum properties of the material to be determined.
* The first loading in the transient dynamic analysis (time history) is typically performed to provide the initial conditions governing the model in a very short time. Subsequently, the settings subjected to the main loading are to be conducted in continuation of the first solution.
* The effects of temporal integration must be active in transient dynamic analyses with damping effects or inertial loads. Otherwise, the problem is solved in static mode. This option is commonly active by default in the ANSYS software.
* The effect of stress stiffening is typically active by default, except that the following two cases can be inactive:  
* Dynamic analysis is performed in a linear state;
* It should be ensured that the structure is not in the range of its buckling load and does not suffer from buckling due to the applied load.  
The 7.6-m model comprising soil and the GPC pipe is employed for executing the transient (time history) analysis under the seismic loading described by the Tabas earth  
Figure 24: Comparison of vertical and horizontal displacements at node 20, element 1126 among all GPC mixtures with 0%, 10%, 20%, 30%, 50%, 70% FA.  
quake. The peak values corresponding to the displacement time series and acceleration data, released from Peer Nga Storing Motion Database Record (PNSMDR), are around 0.092 m and 0.64 g, respectively. In this section, the displacements related to seismic loading and other relevant forces such as acceleration in X-direction and reaction force at node 1 are analyzed through the ANSYS software to distinguish the most critical state in the nonlinear performance of the GPC underground pipe throughout the occurrence of an earthquake. Since the number of maximum time steps in the ANSYS platform is 1000. Beyond that, the specific command and the powerful finite element software for commercial purposes are required without the limitations of the FE software available in the academic community due to the high computational time. Thus, this FE model is analyzed under the effect of the Tabas earthquake with 3-s duration as the number of rows in the text file is 300 given that 3 s from the record of the Tabas earthquake with the time step of 0.01 equals 300.  
The only route for recognizing the critical region of GPC pipe interacting with two types of soils for both static and seismic analysis is node 20 located in the crown on the upper half of the GPC pipe in the middle span of the buried pipe. Indeed, the significant aim in this section is to compare the response of the GPC underground pipe under the applied seismic loading for both GPC mix designs with the inclusion of 20% FA as a PC replacement and 0% FA as the benchmark in this study. It is essential to note that there is a limitation about the depth of the GPC pipe as the width and depth of sidefill and backfill, two soil types used in this study, are arranged under ACPA and AASHTO standards. In addition, it is assumed that the boundary condition of the fixed-support is similar to static analysis.