Study On Piping Stresses At Gas District Cooling (GDC) Universiti Teknologi Petronas (UTP) Plant

Stresses in piping system have been a major concern in designing a plant because pipes are the main transportation medium for many processes. Stresses are found in pipes where failure to these pipes can cause severe problem due to their criticality. This study was aimed to investigate the types of piping system in GDC UTP plant, identify and analyze which system having critical stresses and also find ways to rectify them. To date, there was no study conducted to check the stresses on the critical piping system of the plant. The scope of study was to determine the stresses in piping systems and to suggest ways to rectify them. The study was performed by identifying the critical piping system based on the characteristics and specifications of the piping system using the plant design data. Analyses were conducted by modelling the pipe using stress analysis software, CAESAR II 5.0, to check the types and also the value of the stresses exerted. The values were then compared for conformance with the governing codes. From the analyses done, piping systems in GDC UTP plant were categorized into four (4) groups according to the fluid they were carrying; namely natural gas (primary fuel), diesel (secondary fuel), chilled water and instrument air piping systems. The study concluded that only chilled water piping system was considered critical. In the analyses done on the chilled water piping system, it was found that the axial stress, hoop stress and torsion stress on the pipe were well below the allowable stresses as govern by ASME B31.1. However, the bending stress was found to be over the maximum allowable design limit. To rectify the excessive bending stress problem, it was recommended that modification could be done with the number of supports along the pipe. Analyses done on the recommended modification showed that it could reduce the maximum bending stress along the pipe

Reliability-based Assessment of Concrete Dam Stability

Risk management is increasingly used in dam safety and includes risk analysis, risk evaluation and risk reduction. Structural Reliability Analysis (SRA) is a probabilistic methodology that may be used in the risk assessment process. SRA has been frequently used for calibration of partial factors in limit state design codes for structures (not dams). In a reliability analysis a mathematical description of the failure mode, a limit state function, is defined. All parameters describing the limit state function should be random variables and are described by stochastic distributions (or, where appropriate, a deterministic value). The safety index (or probability of failure) may be determined by e.g. First Order Reliability Method and the result is compared to a target safety index to determine if the structure is safe enough. Several difficulties exists in the use of SRA for concrete dams, mainly due to the fact that only a few examples of such analysis for dams exist. One difficulty is how to define the failure modes. In this thesis a complete system of failure modes is identified, where failure is considered as a series system of “failure in the concrete part”, “failure in the concrete-rock interface” and “failure in the rock mass”. Failure in the concrete-rock interface may occur due to sliding or overturning. Sliding is the joint occurrence of sliding with a partially bonded contact (fails at very small displacement) and sliding with broken contact (fails at larger displacement) and both have to occur for sliding to occur, hence they are treated as a parallel system. Adjusted overturning is a combination of overturning and crushing of the concrete or crushing of the rock. A substantial part of the work has been to define the necessary input data. - Cohesion in the interface is very important. Due to the expected brittle failure in a partly intact interface, treatment of the shear resistance as a brittle parallel system is proposed. - Description of the headwater results in a series system; either failure occurs for water levels at retention water level (rwl) or for water levels above rwl, the latter described by an exponential distribution. - Uplift is one of the most important loads. A geostatistical simulation procedure is presented, where the hydraulic conductivity field of the foundation is described by a variogram and uplift is simulated by a FE-analysis. This methodology is demonstrated to be very useful and gives estimates of the statistical distribution of uplift. Three papers on this subject are included; the first is a description of the methodology, the second presents a sensitivity analysis performed for a large number of different combinations of input data and the last is an application to a Brazilian dam, where water pressure tests and monitoring results are available. In two papers SRA is applied to concrete dams and the system reliability is determined. In the first paper a spillway section where information of e.g. cohesion, friction angles etc. were available is analysed. In the last paper an idealized dam and a power intake structure are analysed. The conclusions are that SRA may be used for assessment of concrete dam stability and that it is well fitted for the dam safety risk management process. Every dam is a unique prototype and SRA enables specific behaviour and properties of a certain structure to be taken to consideration. The system reliability analysis is a very valuable tool in understanding the relationship between failure modes and enables the safety for the whole structure to be determined. In a reliability analysis the most important parameters may be identified and thus safety measures can be focused where it gives the best possible output. A general safety consideration is that development of the safety concept for concrete dams, from deterministic to probabilistic or semi-probabilistic, will give a known and more uniform level of safety

A guide to a range of electrical energy storage devices (ESDs), with an assessment of fuel cells.

It is always desirable to de-couple the generation and the use of electrical energy, for example, to power mobile devices, to provide remote energy power support, or to simply spread electricity demand evenly over the daily cycle. This is achieved by using some form of an electrical energy storage system. Nowadays there are many such systems available each with its own cost, efficiency, and suitability for different applications with developments continuing all the time. This survey will aim to summarize the available electrical energy storage devices (ESD), assessing their general advantages and disadvantages, reviewing their main applications available focusing on the storage of energy for electrical purposes. Finally a detailed survey is given for Fuel cells to be used in energy storage as well as in more clean and efficient energy production

Energy Systems - The Broader Context

Energy and energy systems are fashionable subjects, and this has generated a lot of papers, apparently beyond the carrying capacity of the subjacent methodology. In this written version of a presentation at the Third Energy Status Report, various examples serve to show the highly unsatisfactory situation, pointing especially to the internal contradiction of results. Some hints are given about the potential of an analysis based on information theory and the negentropy concept, and about the signifigance of a search for precise methods of forecasting

Thermo- and Hydro-mechanical Processes along Faults during Rapid Slip

Field observations of maturely slipped faults show a generally broad zone of damage by cracking and granulation. Nevertheless, large shear deformation, and therefore heat generation, in individual earthquakes takes place with extreme localization to a zone <1–5 mm wide within a finely granulated fault core. Relevant fault weakening processes during large crustal events are therefore likely to be thermal. Further, given the porosity of the damage zones, it seems reasonable to assume groundwater presence. It is suggested that the two primary dynamic weak- ening mechanisms during seismic slip, both of which are expected to be active in at least the early phases of nearly all crustal events, are then as follows: (1) Flash heating at highly stressed frictional micro-contacts, and (2) Thermal pressurization of fault-zone pore fluid. Both have characteristics which promote extreme localization of shear. Macroscopic fault melting will occur only in cases for which those processes, or others which may sometimes become active at large enough slip (e.g., thermal decomposition, silica gelation), have not sufficiently reduced heat generation and thus limited temperature rise. Spontaneous dynamic rupture modeling, using procedures that embody mechanisms (1) and (2), shows how faults can be statically strong yet dynamically weak, and oper- ate under low overall driving stress, in a manner that generates negligible heat and meets major seismic constraints on slip, stress drop, and self-healing rupture mode.Earth and Planetary SciencesEngineering and Applied Science

Temperature Effects On Integral Abutment Bridges For The Long-Term Bridge Performance Program

The United States Department of Transportation (US-DOT) Federal Highway Administration (FHWA) initiated in 2009 the Long-Term Bridge Performance (LTBP) program to gather high-quality data on a representative sample of bridges over a twenty-year period of time. The goal of this program is to quantify how bridges behave during their service life while being exposed to different types of loadings and deterioration due to corrosion, fatigue and various climate conditions along with their corresponding maintenances. The data gathered will result in the creation of databases of high quality data, acquired through long-term instrumentation, to be used for improved design practices and effective management of infrastructures by employing best practices for maintenance. As part of the LTBP Program two integral abutment bridges, a California Bridge near Sacramento, CA and a Utah Bridge near Perry, UT, were selected to be monitored for temperature changes as well as to undergo periodic live-load testing. Live-load testing included slowly driving a truck over the bridges. The bridges were instrumented to collect test data and use it to calibrate a finite-element model. This finite-element model was used to determine the actual bridge behavior and compare it with the AASHTO LRFD Specifications. This thesis also examined how different parameters such as thermal gradients, mean temperature, and end-rotation affect these two integral abutment bridges

The feasibility of wireless power transmission for an orbiting astronomical station

Microwave or laser energy for wireless transfer of power from manned earth orbiting station to unmanned astronomical substation

Landfill side slope lining system performance: a comparison of field measurements and numerical modelling analyses

Low permeability engineered landfill barriers often consist of a combination of geosynthetics and mineral layers. Even though numerical modelling software is applied during the landfill design process, a lack of data about mechanical performance of landfill barriers is available to validate and calibrate those models. Instrumentation has been installed on a landfill site to monitor multilayer landfill lining system physical performance. The lining system comprises of a compacted clay layer overlaid by high density polyethylene geomembrane, geotextile and sand. Data recorded on the site includes: geosynthetic displacements (extensometers), strains (fibre optics, Demec strain gauges, extensometers) and stresses imposed on the liner (pressure cells). In addition, temperature readings were collected by a logger installed at the surface of the geomembrane, at the clay surface using pressure cell thermistors and air temperature using a thermometer. This paper presents readings collected throughout a period of three years and compares this measured performance with the corresponding numerical modelling of the lining system for stages during construction. Numerical modelling predictions of lining system behaviour during construction are comparable with the measurements when the geosynthetics are covered soon after placement, however, where the geosynthetics are left exposed to the sun for an extended period of time, in situ behaviour of the geosynthetics cannot be replicated by the numerical analysis. This study highlights the significant influence of the effect of temperature on geosynthetics displacements. A simple thermal analysis of the exposed geosynthetics is used to support the explanation for observed behaviour

Numerical simulation of fracture of a nano-paper coated e-glass/polyester composite with thermal damage

Aerospace research for next-generation travel increasingly focuses on the use of advanced composites to reduce weight and cost while retaining strength. One subset of materials with great potential is based on the combination of resin matrix and glass-fiber reinforcement. This research explores the application of a candidate nanopaper coating with a given composite. Prior research applied a set of given heat fluxes to the top surface of the composite for a set of given periods of time, and subsequently performed a 3-point flexural test to determine the elastic modulus for both the coated and uncoated composite for all of the combinations of heat flux and time. A finite element (FE) model is developed using the ANSYS general purpose finite element analysis (FEA) software that models the degradation in strength/stiffness properties based on heating condition and with the goal of predicting cracking using the element death feature in ANSYS. This thesis describes the prior research suggesting both the need for and novelty of this model, and the procedures used to form the model. The loading conditions of the 3-point flexural test are replicated, and four measures of accuracy are developed based on the force versus displacement curve of the test and the FE model. It is envisioned that continuum-level models developed as a part of these research be applied for design of next-generation space components These measurements are used to verify the FE model, and this model is then employed to extrapolate beyond the context of experimental conditions