Damage detection of jacket type offshore platforms using rate of signal energy using wavelet packet transform

Thanks to its sensitive characteristics to damages, modal strain energy (MSE) has been widely utilized for structural damage identification. Various MSE-related techniques on structural damage iden...

Modal Strain Energy-based Structural Damage Identification: A Review and Comparative Study

To assess the dynamic behavior of monorail–bridge system, an innovative model of train–guideway interaction has been developed based on multibody dynamics and finite element simulation. A finite el...

Dynamic interaction of the monorail–bridge system using a combined finite element multibody-based model

In this study, an approach for the reliability assessment of a fixed offshore jacket platform against earthquake collapse is presented. The platform is modelled using a nonlinear finite-element model taking into account the effect of pile–soil interaction. The platform ultimate base shear resistance is first computed by using a nonlinear progressive collapse analysis and used as a resistance variable for reliability assessment. The seismic-induced dynamic base shear, acting on the platform base, due to seismic loads is then computed. The probability of platform collapse under seismic loading is computed using a finite-element reliability code. The first-order/second-order reliability methods are used for computation of safety indices. These values are then compared with target safety levels as set in offshore platform design codes. A case study for a fixed jacket platform located in the Gulf of Suez offshore of Egypt is analysed using the proposed approach. Results show that computed safety levels are wit...

Reliability of fixed offshore jacket platform against earthquake collapse

In this study, we optimized artificial neural network (ANN) with imperialist competition algorithm (ICA) for the problem of slope stability design charts. To prepare training and testing datasets for the ANN and ICA–ANN predictive models, an extensive number of limit equilibrium analysis modelings (e.g., for the lower bound, LB, limit analysis and upper bound, UB, limit analysis) was conducted. The analyses were conducted using OptumG2 computer software and implemented on two-layered cohesive soil layer sets. For each of the LB and UB limit analysis, the database consisted of 320 training datasets and 80 testing datasets. Variables of the ICA algorithm such as the number of countries, the number of initial imperialists and the number of decades were optimized using a series of trial-and-error process. The input parameters that used thorough the OptumG2 finite element modeling (FEM) analysis include depth factor (i.e., the ratio of first soil layer thickness to the slope height), slope angle, undrained shear strength ratio where the output was taken dimensionless stability number. The estimated results for both of datasets (e.g., training and testing) from ANN and ICA–ANN models were assessed based on three known statistical indices namely value account for (VAF), root means squared error (RMSE), and coefficient of determination (R2). To evaluate the performance of proposed models, color intensity rating (CER) and total ranking method (TRM), i.e., based on the result of statistical indices, was used. After 72 trial-and-error processes (e.g., sensitivity analysis on some neurons) the optimal architecture of 3 × 6 × 1 were found for both of the ANN–UB and ANN–LB models. As a result, both models presented excellent performance, however according to the introduced ranking system the ICA–ANN model could slightly perform a better performance compared to ANN. Based on R2, RMSE and VAF values of (0.9999, 0.0107 and 99.9924) and (0.9991, 0.0102 and 99.9913), respectively, were found for training and testing of the optimized ICA–ANN–LB predictive model. Similarly, for the ICA–ANN–UB predictive model, values of (0.9984, 0.0129 and 99.9659) and (0.9984, 0.01047 and 99.9915) were obtained for the R2, RMSE and VAF of training and testing datasets, respectively. However, in the ANN model, the R2 and RMSE for both of the training and testing datasets were (0.9982 and 0.01815) and (0.9972 and 0.01748), respectively. This proves a better performance of the ICA–ANN model in predicting the behaviors of slope stability of cohesive soils and consequently more reliable design solution charts provided herein.

A predictive model based on an optimized ANN combined with ICA for predicting the stability of slopes

Structural damage detection, damage localization and severity estimation of jacket platforms, based on calculating modal strain energy is presented in this paper. In the structure, damage often causes a loss of stiffness in some elements, so modal parameters; mode shapes and natural frequencies, in the damaged structure are different from the undamaged state. Geometrical location of damage is detected by computing modal strain energy change ratio (MSECR) for each structural element, which elements with higher MSECR are suspected to be damaged. For each suspected damaged element, by computing crossmodal
strain energy (CMSE), damage severity as the stiffness reduction factor -that represented the ratios between the element stiffness changes to the undamaged element stiffness- is estimated. Numerical studies are demonstrated for a three dimensional, single bay, four stories frame of the existing jacket platform, based on the synthetic data that generated from finite element model. It is observed that this method can be used for damage detection of this kind of structures.

Damage detection in Jacket type offshore platforms using modal strain energy

Pile foundations, also known as substructure, are used to carry and transfer the load of the structure to the bearing ground located at some depth below ground surface. The main components of the foundation are the pile cap and the piles. Piles are long and slender members which transfer the load through the shallow soil of lower bearing capacity to deeper soil or rock of high bearing capacity. They are also used in normal soil condition to resist uplift forces or in poor soil condition to resist lateral forces. Most of the piles are made from three main types of material which are wood, steel and concrete. Piles are normally driven, drilled or jacked into the ground and connected to pile caps. Based on a few number of laboratory model results many investigators reported the uplift response of piles in cohesionless soil, a review of related previous works shows that not much research has been done to define the uplift capacity in cohesionless soil, a problem that is often encountered in field. The paper observed that the ultimate uplift capacity is dependent on the relative undrained/drained shear strength of cohesionless soil, the depth ratio of embedment and soil thickness ratio. © 2012 ejge.

Uplift capacity of enlarged base piles in sand

This paper discusses an efficient-cost analysis for the monorail system in developing countries focusing on Middle East cases. Most of the cities in the Middle East are using the metro system and have experience with it. A monorail system is quite new for these countries so the efficiency of the monorail as an important question is always figured out. A function to find payback duration for monorail is generated, using available data for countries which have both systems in the world. Then a correlation between metro and monorail ticket prices is studied to apply it for the countries in the Middle East. The theory has been verified for UAE, USA and China as existing models for both metro and monorail. Then it has been applied for interpreting and predicting the monorail system costs in Egypt and Iran as case studies in the Middle East. The results show that for those countries with a subsidies policy for public transportation, a monorail will not be an economic system for the public transportation, private sectors will not show their interests for long term investment in it and it might be used for the tourism and amusement purposes.

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An efficient cost analysis of monorail in the middle east using statistics of existing monorail and metro models

Slope failures are disasters that happen all around the world. Occurrence of slope failures depends on number of factors. To safeguard the safety of the public from slope failure hazards, proper geotechnical input by the engineers with geotechnical experience is very important. The geotechnical input includes four important stages namely, planning, design, construction and maintenance. Whenever failures occur, engineers are responsible to the problems. The paper observed the assessment of slope failures.

Investigation of slope failures in soil mechanics

Geosynthetics are fibrous materials made of elements such as individuals fibers, filaments, yarns, tapes, etc. that are long, small in cross section and strong in tension. It must be sufficiently durable to last a reasonable length of time in the hostile environment. Use of geotextile in civil engineering structures are rapidly expanding in terms of volume, types of products and range of applications. The largest area of application of these materials in Civil Engineering is Geotechnical Engineering. Based on a few laboratory work and numerical analysis, few investigators reported geosynthetics in slope reinforcement, a review of related last works shows that not much research has been done to define performance of geosynthetics in slopes, a problem that is often encountered in field. The paper observed the performance of geosynthetics in slope reinforcement.

Amin Ghafooripour

Papers

Damage detection in Jacket type offshore platforms using modal strain energy

Uplift capacity of enlarged base piles in sand

An efficient cost analysis of monorail in the middle east using statistics of existing monorail and metro models

Investigation of slope failures in soil mechanics

The role of geosynthetics in slope stability