Review Paper on Defects in Rigid Pavement

In this project Pavement failure is defined in terms of decreasing serviceability caused by the development of cracks and ruts. Before going into the maintenance strategies, we must look into the causes of failure of rigid pavements. Failures of rigid pavements are caused due to many reasons or combination of reasons. Application of correction in the existing surface will enhance the life of maintenance works as well as that of strengthening layers. It has been seen that only three parameters i.e., unevenness index, pavement cracking and rutting are considered while other distresses have been omitted while going for maintenance operations. Along with the maintenance techniques there are various methods for pavement preservation which will help in enhancing the life of pavement and delaying its failure. The purpose of this study was to evaluate the possible causes of pavement distresses, and to recommend remedies to minimize distress of the pavement. The project describes lessons learnt from pavement failures and problems experienced during the last few years on a number of projects in India. Based on the past experiences’ various pavement preservation techniques and measures are also discussed which will be helpful in increasing the serviceable life of pavement

Effect of Retrofitting on Beam-Column Joints

During the serviceable life of R.C.C structures they are found to show evidence of distress due to various reasons. To bring such structures back to their functional/serviceable condition these structures need urgent attention and enquiry for finding out reasons of distress along with appropriate remedial treatments so as to increase serviceable life of such structures and bring them back to their functional use. So the process of retrofitting involves upgrading and enhancing the strength of deficient structures and their components. Safety of life is a priority issue to be addressed in process of retrofitting. For preventing injury and death of occupants and for preventing damage to structural components and collapse of structure as a whole, some retrofitting techniques try to deal with the issue to avoid damage. As a retrofitting technique, ferrocement technique is one of commonly used procedure of improving strength which is due to their good durability, less cost, easy availability and ease in application with requirement of intricate formwork. Application of ferrocement can be quickly done on the damaged structural elements without any requirements of chemical bonding agents. Also the ferrocement application requires less skill labour in comparison to other retrofit solutions available these days. Ferrocement is light in weight, easy to construct & have low self weight which is why it is preferred to other techniques of retrofitting. It has higher tensile strength then R.C.C. Also the thickness of ferrocement is a fraction of thickness of R.C.C. structural elements which makes it a complementary material for prefabricated structures. In the present study six R.C.C. Beam column joint specimens were casted. Two controlled specimens were initially stressed to ultimate load (100% damage) and other four specimens are stressed to prefixed percentages of ultimate load. All six specimens were then retrofitted using ferrocement for upgrading the strength of Beam column joints in flexure and shear. Chicken wire mesh is wrapped all around the specimen. From the study it is observed that retrofitted specimens has shown considerable decrease in deflection if we compare them to controlled specimens. Also the percentage decrease in deflection for specimens subjected to 75% and 50% of ultimate loads is considerably higher to those specimens which are subjected to 100% damage i.e. ultimate load.

Development of a Correlation between the Resilient Modulus and CBR Value for Granular Blends Containing Natural Aggregates and RAP/RCA Materials

Limited supplies of natural aggregates for highway construction, in addition to increasing processing costs, time, and environmental concerns, have led to the use of various reclaimed/recycled materials. Reclaimed asphalt pavement (RAP) and recycled concrete aggregate (RCA) have prospective uses in substantial amounts in base and subbase layers of flexible pavement in order to overcome the increasing issue of a shortage of natural aggregates. This research presents the development of an empirical model for the estimation of resilient modulus value (MR) on the basis of CBR values using experimental results obtained for 52 remoulded granular samples containing natural aggregates, RCA, and RAP samples. Statistical analysis of the suggested model shows promising results in terms of its strength and significance when t-test was applied. Additionally, experimental results also show that MR value increases in conjunction with an increase in RAP contents, while the trend for the CBR value is the opposite. Statistical analysis of simulation results using PerRoad and KenPave demonstrates that addition of RAP contents in the subbase layer of flexible pavements significantly improves its performance when considering resistance against rutting and fatigue. However, results of repeated load triaxial tests show that residual accumulative strain under a certain range of loading conditions increases substantially due to the addition of RAP materials, which may be disadvantageous to the serviceable life of the whole pavement structure.

Risk Assessment of Gas Turbines Rotors That Have Exceeded Their Design End of Life

The paper will describe the main outcomes of a risk assessment performed by General Electric O&G (GE O&G) in 2013 on a large number of gas turbine rotors that had exceeded their design end of life (EOL). The assessment involves a large number of medium frames (e.g. MS3002J, MS5002C) plus small industrial gas turbines (e.g. MS1002, PGT10). The design end of life is the lifespan inside which the risk of uncontained failure is expected to be improbable and this means the failure has a probability of occurrence of 0.12 total events or less during the life of five hundred gas turbines operating 8000 hours per year for 30 years [1]. GE gas turbine rotors are designed to operate with no need of inspection and maintenance till their design EOL (alias serviceable life). The gas turbines end users may exceed EOL, provided the rotors have been subjected to a specific investigation that includes teardown and a full inspection. The disregard of this recommendation may have catastrophic consequences on the gas turbines and on surrounding equipment and personnel. Such recommendation was provided to customers the first time in 2005 through GETIL 1576 [2], the recommendation was renewed in 2013 with a new communication NIC 13.16 [3]. The risk assessment has essentially focused on rotating parts, because rotors (i.e. shaft, wheel, spacer) are the highest gas turbine energy components, that even if designed with high safety margins, they are not immune from time (e.g. creep) and/or cyclic dependent damage (e.g. fatigue). The assessment has been carried out by following MIL-STD-882C [1] guidelines and in accordance to the principles defined by ISO 12100-2010 [4]. The failure risks have been estimated with the help of specific tools by using field data and life calculations performed with physics-based models. The paper describes the methodology used to support the risk assessment and this means the “rotor life management methodology” that was developed by GE more than ten years ago, and was subsequently improved by including statistical assessments.

Research on Oil and Water Well Casing Damage in the Process of Oil-Field Development

The well casing damage is common during the oilfield exploitation .Analysis on casing damage in a wide range , especially in the late term of exploitation ,indicates that the major influence factors which lead to wide-range casing damage are water injection pressure , block pressure differential and water soaked area .We conclude several types of abnormal strata pressure distribution which are common existing after water injection .These analysis are good preparation for monitoring and take precaution against casing damage .It has significant benefits for prolonging oil and water well casings serviceable life , as well as sustainable and stable production.

Properties Comparison of Two Water Lubricated Rubber Bearings Based on Experimental Test

Water lubricated rubber bearings are used from many years in ship building and other industry because of their advantages such as: long serviceable life, low coefficient of friction, long life of shaft sleeve, good vibration damping, good abrasion resistance, low maintenance required, grit particles and other abrasives are expelled through the grooves [1,2,3,4].

Study on Stay-in-Place Cement Formwork and the Application

Three contents are included in this paper: 1) Through orthogonal experiment, some principal materials and their use levels which will influence performances of cement formwork are optimized and researched. A matched group could bring best comprehensive performance plate suitable to be used as construction formwork is obtained. 2) Through study the strength retention rate of specimens after immersing in various solutions for different ages, the alkali resistance property and lasting quality of the formwork are investigated, and it indicates that during general serviceable life specified by China Structure Design Code, the failure probability due to durability is very low. 3) Through mechanical experiments of combined slabs with different conjoint methods, cooperation performance between formwork and concrete is studied, which prove composite slabs work well.