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Pacheco Vivero J.R.,La Salle University at Cuauhtemoc | Gomez Ramirez E.,La Salle University at Cuauhtemoc | Rivero Angeles F.J.,SEISMIC Ingenieria y Construccion | Rodriguez Rocha R.,Escuela Superior de Ingenieria y Arquitectura IPN | Martinez Garcia M.A.,La Salle University at Cuauhtemoc
SHMII-5 2011 - 5th International Conference on Structural Health Monitoring of Intelligent Infrastructure | Year: 2011

In the area of damage detection in civil structures there are several techniques that give information about whether the structure is healthy or damaged by detecting variations or extract modes from a signal of an instrumented structure. The traditional applied method is the Fast Fourier Transform (FFT) with the consequent problem that many times it is not possible to extract all the modal parameters. The present work shows a comparison of the ICA (Independent Component Analysis) and WT (Wavelet transform) as a processing tool, along with the FFT for modal parameter extraction. Results show that processing signals of a four-story building model in distinct scenarios with WT requires fewer motion records than ICA; but ICA is able to compute all the modal parameters when the records at every story are available. In real life it could be costs of instrumentation, so if only a few accelerometers are to be installed on the building WT should be preferred or to ensure correct modal parameter extraction in expert systems with ICA. Source


Hernandez Abraham V.F.,Escuela Superior de Ingenieria y Arquitectura IPN | Rodriguez Rocha R.,Escuela Superior de Ingenieria y Arquitectura IPN | Rivero Angeles F.J.,S.A. de C.V. | Vazquez Hernandez A.O.,Mexican Institute of Petroleum
SHMII-5 2011 - 5th International Conference on Structural Health Monitoring of Intelligent Infrastructure | Year: 2011

Steel Catenary Risers (SCR) are subject to vessel movements, wave, wind, current and tidal forces, also the SCR are subject to the movement of water particles of wave and current. Current can provoke vortex-induced vibrations during their lifetime that could provoke fatigue damage in the riser. The fatigue damage on welds may depend on the dynamic behavior of the riser. In oil industry is important to evaluate the probability of damage since failure of a single crack could cause serious environmental, safety and cost problems. The reason is because risers have no high structural redundancy, and failure of one weld could result in failure of the whole system. In order to apply Structural Health Monitoring (SHM) of these structures the identification of modal parameters are needed. Also, accuracy in damage detection depends on the number of sensors and their position along the riser. For this reason, a numerical study on the optimal location of sensors in welded SCR is presented for the purpose of modal parameter identification. Modeling of the riser is based on Finite Element Method involving nonlinear behavior of the system and structure-fluid interaction. Acceleration records from several locations along the riser are processed utilizing the Frequency Domain Decomposition Method to obtain frequencies and mode shapes. These identified parameters are compared to the theoretical values for intact and damage condition of the risers in several sea states cases. Conclusions about the number of sensors and their location are stated. Results demonstrate the feasibility of the proposed methodology that will be useful for future SHM studies. Source


Garcia Solano J.,Escuela Superior de Ingenieria y Arquitectura IPN | Rodriguez Rocha R.,Escuela Superior de Ingenieria y Arquitectura IPN | Zernandez Sola L.R.,Metropolitan Autonomous University
SHMII-5 2011 - 5th International Conference on Structural Health Monitoring of Intelligent Infrastructure | Year: 2011

In this work, the influence of Soil-Structure Interaction (SSI) on the estimation of damage (loss of stiffness) for multi-storey buildings is determined utilizing the Baseline Stiffness Method (BSM). This method locates damage and determines its magnitude in buildings without baseline modal information (undamaged state) using, solely, the approximated lateral stiffness of the first storey and some acceleration records of the damaged system. Controlled damage cases were simulated in a 10-storey shear-beam model, reducing the stiffness of certain storeys. Two cases were studied, one considering a fixed base and another considering the flexibility of the soil. Results demonstrate the efficiency of the proposed method to identify damage considering SSI. Source

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