This paper describes the most important results of a theoretical, experimental and in situ investigation developed in connection with a water supply pumping pipeline failure. This incident occurred after power failure of the pumping system that caused the burst of a prestressed concrete cylinder pipe (PCCP). Subsequently, numerous hydraulic transient simulations for different scenarios and various air pockets combinations were carried out in order to fully validate the diagnostic. As a result, it was determined that small air pocket volumes located along the pipeline profile were recognized as the direct cause of the PCCP rupture. Further, a detail survey of the pipeline was performed using a combination of non-destructive technologies in order to determine if immediate intervention was required to replace PCC pipes. In addition, a hydraulic model was employed to analyze the behavior of air pockets located at high points of the pipeline.
2015): Failure of a drainage tunnel caused by an entrapped air pocket, Urban Water Journal,A severe storm event occurred over the western area of Mexico City causing the rupture of a drainage tunnel, resulting in surface flooding, severe infrastructure damage and three deaths. This paper describes the methodology followed in order to validate the diagnostic of the event. The detailed investigation comprised in situ observation of the system, as well as hydraulic and structural analyses. In this case, severe pressure oscillations inside the tunnel caused by rapid filling and sudden air leakage through a large orifice (manhole) were recognized as the direct cause of the conduit burst. Further, the low strength of the concrete pipes of the tunnel, constructed without reinforced steel, and the low confinement by the dead load due to the soil above the tunnel also contributed to the rupture. The numerical results show a very unfavorable stress distribution along the tunnel stretch where the accident occurred, sufficient to cause the rupture.
Passive damping systems have been widely studied to improve the response of wind turbine structures under operational conditions. However, there is insufficient information on how these systems enhance reliability for extreme loads. Wind farm construction has been growing rapidly in recent decades, thereby moving wind turbine structures to sites with higher seismic and hurricane hazards. This research presents a numerical study performed on three land‐based wind turbines, similar to typical turbines installed in Mexican wind farms, under cyclone‐induced wind and earthquake action. The fictional location of the turbines is justified by the wind capacity distribution of Mexico, which is a country with high seismic and tropical cyclone risk. The wind field is simulated from semiempirical mean velocity models, and the ground motion records are obtained from real events recorded near the assumed site. All the time history analyses assume that the turbines are in parked condition. The results indicate that a fragility reduction of approximately 80% can be achieved under cyclone‐induced winds when passive damping systems are added to the structure, and that the fragility reduction is significantly less under seismic action.
This paper presents a case study of an existing wastewater rising main (WWRM) in which an extreme transient event produced by simultaneous power failure of the pumps caused the rupture of a 1.2 m (48 in) prestressed concrete cylinder pipe (PCCP), causing an important leakage of sewage. The event and the methodology followed in order to validate the diagnostics of the failure are described. The detail study included in situ observation of the system, experimental investigation in a setup, hydraulic analysis, as well as details of the structural strength of the WWRM. After the extensive investigation and several simulations of fluid transients for different scenarios and flow conditions, it was found that stationary small gas pockets accumulated at high points of the WWRM were identified as the principal contributory factor of the failure. This case study serves as clear warning of the consequences of operating a WWRM with gas pockets at its high points.
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