# Static and Seismic Responses of Eco-Friendly Buried Concrete Pipes with Various Dosages of Fly Ash
## 3 Static and Seismic Loading  
### Static Loading  
The determination of static loads for analysis and design of underground concrete pipelines are commonly carried out for the entire load comprising the efficacies of dead loads applied by soil and live loads affected by traffic. Therefore, the optimal vertical displacement as structure response is the resultant of both dead and live loads which will be applied as total static loading on the GPC pipe. The deformability of underground pipes is mainly determined through the structure response of the GPC pipe to the static loads which are affected by soil weight, traffic loads, and other accidental loads. In addition, the wall thickness of GPC pipes can be considered as the criterion for evaluating the flexibility of GPC pipes which are treated as flexible rings resulting in a deformation pattern in the form of horizontally oriented ovals [28; 36].  
As regards the static loading in this study, the soil weight is calculated as the gravity load through the FE software (ANSYS) considering the gravitational acceleration of 9.81 m/s\({}^{2}\) in Y-direction. In addition, internal fluid pressure (swage) will be considered in this investigation given that, the water flow has had an effective role in the deformability of underground pipes based on the previous studies carried out in this field [36]. The most important reason which can be assumed in this phenomenon is the fact that the pipe stiffness may be enhanced due to the long-term effect caused by the steady flow of water in underground pipes. The value of water pressure in pipelines is typically in the range of 276-414 KPa in which the maximum amounts will be considered to distinguish the critical condition of the underground pipeline.  
Moreover, for detecting the most critical state of static loading in this study, an active fault in the middle part of the concrete pipe is applied. Generally, in seismology, faults are divided into three main categories: active, semi-active, and inactive faults. The criterion for defining ground faults is the movement of their surface relative to each other. For instance, the fault slip ratio is approximately 1 cm each year which means that the fault slip is 20 cm over a 20-year activity. For this purpose, the slip with the movement of 20 cm is assumed in the middle of GPC pipes to evaluate fault behavior in this field. Therefore, for applying this displacement, the nodes on the right side of the fault are moved 0.1 m downwards and the nodes on the left side are moved 0.1 m upwards in Y-direction (Figure 9).  
It is essential to point out that the dead loads on the underground pipeline are typically more efficient than the live loads. Because the efficacies of live load, which can be applied as traffic, are to diminish rapidly with the increment of soil depth. However, the live load may be more critical compared to dead loads for underground pipes at shallow depth [36; 37]. In this study, the efficacy of live load on a GPC underground pipeline has been presented by using the details derived from the AASHTO standard which was used in previous studies. According to AASHTO, the spread area affected by the truckload has a length of 2 m and the width of 1.5 m considered in the middle part of the GPC pipe to the bearing performance of solid under static loading at failure moment [38]. Thus, the live load used for validating the numerical results will also be used which is calculated as follows:  
P = 50,000 lbs = 222,411 N;  
A = 2 \(\times\) 1.5 = 3 m;  
Pressure (Live load) = 74,137 Pa (N/m\({}^{2}\)).