Railway Geotechnics is written by four colleagues who studied at the University of Massachusetts, Amherst, in an academic program advised by Professor Ernest T. Selig.
Our collective time at the university spanned over a decade, during which we were individually inspired by Professor Selig to work on and further advance the subject of railway geotechnology, whichhe pioneered and developed into a rigorous field of study.
Since graduation, the aggregate of our professional experience includes railway operations,
consulting, research, and education.
The field of railway geotechnology was in its infancy when we were in our early careers.
Because the engineering behavior of track substructure was not well understood up to that point, perspectives on the causes and cures of substructure instability were often informed by anecdote rather than by verifiable fact. Mystique surrounded the subject in the absence of critical thinking,
often resulting in costly applications of remedial methods that did not address the root causes of track substructure problems.
Advancing the field of railway geotechnology by the writing of this book is a natural step for each of us in our careers.
The book continues the work Track Geotechnology and Substructure Management by Selig and Waters (1994) and provides an update to this field of study so that current railway
engineers and managers have easier access to new and emerging best practices.
During years of writing and discussions, we each had moments that challenged some of our beliefs while we debated the merits of emerging technology and practices.The goal of this book is to provide a better understanding track substructure in order to enable more effective design, construction, maintenance, and management of railway track so as to ensure the vitality of rail transportation.
We hope that this work will prove useful to current railway engineers and managers as well as college students pursuing careers in the field of railway engineering.
Earthquake engineering is an independent scientific discipline that has come into being
along with engineering seismology over the past 100 years and is therefore still evolving,as happens in every new scientific field.
It started as a framework of codified rules for the seismic design of buildings at the begin-
ning of the twentieth century, after the catastrophic San Francisco earthquake of 1906.
This design procedure was based, on one hand,
on a framework of empirical rules for avoiding seismic damage observed in previous earthquakes, and on the other,
on the simulation of the seismic action on a set of lateral forces equal to a percentage of the gravity loads of the building.
This loading pattern constituted one additional load case, the ‘seismic loading’.
The above simulation was based on the fact that the acceleration of the masses of a building
due to earthquake causes inertial lateral forces proportional to the masses of the building,
and in this respect proportional to the gravity loads.
The considerations of earthquake engineering briefly presented above will be adapted and applied in the forthcoming chapters to buildings with a structural system made of reinforced concrete,
which constitute the major part of the building stock of the built environment in developed countries.
The material of this book has been formulated into three main parts:
In the first part, seismic demand issues are examined (Chapters 2 through 6).
More par-ticularly, this part includes at the outset a short overview of basic issues of structural dynamics,
which have been considered of special importance for the comprehension of the material of subsequent chapters.
It also includes the procedure for the determination of the seismic actions and the ductility coefficients.
The description of the acceptable methods for seismic analysis, and the application of the capacity design rules to the seismic effects (internal forces) are included in this part as well.
Finally, the conceptual design of building structural systems is also examined in detail, and guidelines are given for the proper structural system for various types of buildings.
Principles of Structural Design Wood Steel and Concrete
Buildings and other structures are classified based on the risk associated with unacceptable performance of the structure, according to Table 1.1.
The risk categories range from I to IV, where category I represents buildings and other structures that pose no danger to human life in the event of failure and category IV represents all essential facilities.
Each structure is assigned the highest applicable risk category.
Assignment of more than one risk category to the same structure based on use and loading conditions is permitted.
To safeguard public safety and welfare, towns and cities across the United States follow certain
codes for design and construction of buildings and other structures.
Until recently, towns and cities modeled their codes based on the following three regional codes, which are normally revised at 3-year intervals:
1. The Building Officials and Code Administrators National Building Code
2. The Uniform Building Code
3. The Standard Building Code
The book is appropriate for an academic program in architecture, construction management,
general engineering, and civil engineering, where the curriculum provides for a joint coursework in wood, steel, and concrete design.
The book has four sections, expanded into 17 chapters. Section I, comprising Chapters 1
through 5, enables students to determine the various types and magnitude of loads that will be acting on any structural element and the combination(s) of those loads that will control the design.
ASCE 7-10 has made major revisions to the provisions for wind loads. In Section I, the philosophy of the load and resistance factor design and the unified approach to design are explained.
Wood design in Section II from Chapters 6 through 8 covers sawn lumber, glued laminated
timber, and structural composite or veneer lumber, which are finding increased application in wood structures.
The NDS 2012 has modified the format conversion factors and has also introduced some
new modification factors.
First, the strength capacities in accordance with the NDS 2012 for tensile, compression, and bending members are discussed and the basic designs of these members are performed.
Steel Design, Fifth Edition covers the fundamentals of structural steel design for buildings.
This book is intended for junior-and senior-level engineering students, although some of the later chapters can be used in a combination undergraduate/graduate course.
Practicing civil engineers who need a review of current practice and the
current AISC Specification and Manual will find the book useful as a reference.
Students should have a background in mechanics of materials and analysis of statically determinate structures.
Knowledge of statically indeterminate structural analysis is not a prerequisite for the use of this book.
Structural design is a complex endeavor, involving the synthesis of many processes.
This book does not cover the integrated design of buildings, but presents some of the “building blocks” for structural steel design.
We focus on the analysis and design of individual members and connections, rather than complete structures.
Depuis sa commercialisation en 1993, Graitec OMD s’est imposé comme le logiciel de référence pour la conception et le dessin de bâtiments en béton armé. A partir d’un module 3D de bâtiment composé de dalles, poutres, poteaux, voiles et fondations, Arche analyse la stabilité globale de l’ouvrage et produit automatiquement tous les plans de ferraillage. Le logiciel Arche se distingue avant tout par les innovations techniques qu’il met en œuvre : pré-dimensionnement de la structure, calculs de descente de charges et de contreventement mixant méthode traditionnelle et modélisations numériques sophistiquées, production automatique des plans de ferraillage des éléments de structures suivant différentes normes, notamment les EC0, EC1, EC2 et EC8.
Melody automatise le dimensionnement et la vérification des profilés et des attaches pour les portiques, les planchers ou les chemins de roulement. Melody produit également des métrés, des estimatifs et des notes de calcul complètes en quelques minutes.
Geotechnical Engineering Principles and Practices of Soil Mechanics and Foundation Engineering
This book has the following objectives:
1. T o explain the fundamentals of the subject from theory to practice in a logical way
2. T o be comprehensive an d mee t th e requirements o f undergraduate students
3. T o serve as a foundation course for graduate students pursuing advanced knowledge in the subject
There are 21 chapters i n this book. The first chapter trace s the historical background o f the
subject and the second deals with the formation and mineralogical composition o f soils.
Chapter 3 covers th e inde x properties an d classification of soil. Chapters 4 and 5 explain soi l permeability , seepage, an d th e effec t o f water on stress conditions in soil .
Stresses developed in soil due to imposed surface loads , compressibility and consolidation characteristics , and shear strength characteristics o f soil are dealt with in Chapters 6,7 , and 8 respectively. The first eight chapters develop the necessary tools for computing compressibility an d strength characteristics o f soils.
Chapter 9 deals with methods for obtainig soil samples in the field for laboratory tests and for constructed on an outcrop of sound rock, no foundation is required. Hence, in contrast to the
building itself which satisfies specific needs, appeals to the aesthetic sense, and fills its
matters with pride, the foundations merely serve as a remedy for the deficiencies of whatever
whimsical nature has provided for the support of the structure at the site which has been
selected. On account of the fact that there is no glory attached to the foundations, and that
the sources of success or failures are hidden deep in the ground, building foundations have
always been treated as step children; and their acts of revenge for the lack of attention can be
very embarrassing.
The comments made by Terzaghi are very significan t an d shoul d b e take n not e o f by all
practicing Architects an d Engineers. Architects or Engineers who do not wish to make use of the growing knowledge of foundation design are not rendering true service t o their profession. Since substructures are as important as superstructures, persons wh o are well qualified in
the design ofsubstructures should always be consulted an d the old proverb tha t a ‘stitc h i n time save s nine ‘ should always be kept in mind.
The aim of this book is to serve as an introduction to and an overview of the latest structural earthquake engineering. The book deals with aspects of geology, engineering seismology and geotechnical engineering that are of service to the earthquake structural engineering educator, practitioner and researcher. It frames earthquake structural engineering within a framework of balance between ‘ Demand ’ and ‘ Supply ’ (requirements imposed on the system versus its available capacity for action and deformation
resistance).
In a system – integrated framework, referred to as ‘ From Source – to – Society ’ , where ‘ Source ’ describes the focal mechanisms of earthquakes, and ‘ Society ’ describes the compendium of effects on complex societal systems, this book presents information pertinent to the evaluation of actions and deformations imposed by earthquakes on structural systems. It is therefore a ‘ Source – to – Structure ’ text.
Practising engineers with long and relatively modern experience in earthquake – resistant design in high – seismicity regions will fi nd the book on the whole easy to read and rather basic. They may however appreciate the presentation of fundamental response parameters and may fi nd their connection to the structural and societal limit states refreshing and insightful. They may also benefi t from the modelling notes of Chapter 4 , since use is made of concepts of fi nite element representation in a specifi cally earthquake engineering context. Many experienced structural earthquake engineering practitioners will fi nd Chapter 3 on input motion useful and practical. The chapter will aid them in selection of appropriate aracterization of ground shaking. The book as a whole, especially Chapters 3 and 4 is highly recommended for practising engineers with limited or no experience in earthquake engineering.
The principle behind LiDAR is really quite simple. Shine a small light at a surface and measure the time it takes to return to its source. When you shine a torch on a surface what you are actually seeing is the light being reflected and returning to your retina. Light travels very fast – about 300,000 kilometres per second, 186,000 miles per second or 0.3 metres per nanosecond so turning a light on appears to be instantaneous. Of course, it’s not! The equipment required to measure this needs to operate extremely fast. Only with the advancements in modern computing technology has this become possible.
The actual calculation for measuring how far a returning light photon has travelled to and from an object is quite simple:
Distance = (Speed of Light x Time of Flight) / 2
The LiDAR instrument fires rapid pulses of laser light at a surface, some at up to 150,000 pulses per second. A sensor on the instrument measures the amount of time it takes for each pulse to bounce back. Light moves at a constant and known speed so the LiDAR instrument can calculate the distance between itself and the target with high accuracy. By repeating this in quick succession the insturment builds up a complex ‘map’ of the surface it is measuring. With airborne LiDAR other data must be collected to ensure accuracy. As the sensor is moving height, location and orientation of the instrument must be included to determine the position of the laser pulse at the time of sending and the time of return. This extra information is crucial to the data’s integrity. With ground based LiDAR a single GPS location can be added for each location where the instrument is set up.
Generally there are two types of LiDAR detection methods. Direct energy detection, also known as incoherent, and Coherent detection. Coherent systems are best for Doppler or phase sensitive measurements and generally use Optical heterodyne detection. This allows them to operate at much lower power but has the expense of more complex transceiver requirements. In both types of LiDAR there are two main pulse models: micropulse and high-energy systems. Micropulse systems have developed as a result of more powerful computers with greater computational capabilities. These lasers are lower powered and are classed as ‘eye-safe’ allowing them to be used with little safety precautions. High energy systems are more commonly used for atmospheric research where they are often used for measuring a variety of atmospheric parameters such as the height, layering and density of clouds, cloud particles properties, temperature, pressure, wind, humidity and trace gas concentration.
Most LiDAR systems use four main components:
Lasers :
Lasers are categorised by their wavelength. 600-1000nm lasers are more commonly used for non-scientific purposes but, as they can be focused and easily absorbed by the eye, the maximum power has to be limited to make them ‘eye-safe’. Lasers with a wavelength of 1550nm are a common alternative as they are not focused by the eye and are ‘eye-safe’ at much higher power levels. These wavelengths are used for longer range and lower accuracy purposes. Another advantage of 1550nm wavelengths is that they do not show under night-vision goggles and are therefore well suited to military applications.
Airborne LiDAR systems use 1064nm diode pumped YAG lasers whilst Bathymetric systems use 532nm double diode pumped YAG lasers which penetrate water with much less attenuation than the airborne 1064nm version. Better resolution can be achieved with shorter pulses provided the receiver detector and electronics have sufficient bandwidth to cope with the increased data flow.
Scanners and Optics :
The speed at which images can be developed is affected by the speed at which it can be scanned into the system. A variety of scanning methods are available for different purposes such as azimuth and elevation, dual oscillating plane mirrors, dual axis scanner and polygonal mirrors. They type of optic determines the resolution and range that can be detected by a system.
Photodetector and receiver electronics :
The photodetector is the device that reads and records the signal being returned to the system. There are two main types of photodetector technologies, solid state detectors, such as silicon avalanche photodiodes and photomultipliers.
Navigation and positioning systems :
When a LiDAR sensor is mounted on a mobile platform such as satellites, airplanes or automobiles, it is necessary to determine the absolute position and the orientation of the sensor to retain useable data. Global Positioning Systems provide accurate geographical information regarding the position of the sensor and an Inertia Measurement Unit (IMU) records the precise orientation of the sensor at that location. These two devices provide the method for translating sensor data into static points for use in a variety of systems.
