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Workability and Quality Control of Concrete

The word workability is a term that refers to properties of fresh concrete, that is, of the concrete before it has set and hardened, and it is legitimate to ask why any attention should be given to these properties at all.

The performance of concrete will in practice be assessed in terms of whether the hardened material performs in the way intended and continues to do so: it will be judged in terms of shape and finish, strength, deflection, dimensional changes, permeability and durability.

So why should the properties of the fresh concrete be considered to be important, and why should they be the concern of the practising engineer?

The answer to the first of these questions lies in the fact that the properties of any finished material are affected by the properties at an earlier stage and by the processes applied to it, while the answer to the second one is that all, or a major part of, the processing of concrete is actually carried out on site.

The first stage is, of course, the making of a homogeneous mix and then, assuming this has been done properly, the material is subjected to other processes as follows.

The concrete must be capable of giving a good finish direct from the formwork, withouth oneycombing or an excessive number of blowholes or other surface defects.

If there is a free surface, it must also be capable of giving a good finish in response to an operation such as floating or trowelling.

A workable concrete is one that satisfies these requirements without difficulty and, ingeneral, the more workable it is, that is, the higher its workability, the more easily it can be placed, compacted and finished.

Workability can be increased by simply increasing the water content of the mix but, if that method is used, a point will be reached at which segregation and/or bleeding become unacceptable so that the concrete is no longer homogeneous and, before that, the water/cement ratio may have reached a level such that the hardened concrete will not attain the required strength.

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BIM and Construction Management

This book shares a rounded perspective of how BIM and enabling technologies are changing the way we collaborate and distribute information.

As an industry, we are constantly facing new challenges in the field of construction.

This book will show how many of these challenges are being addressed with cutting-edge tools, leveraged with experience, and a practical application of the “right tools for the right job.

” There is a shift happening in the construction management market in the context of technology, and this book serves as a catalyst for more fundamental changes that create positive outcomes.

This book was written for those who wish to learn more about better ways to holistically
leverage BIM and technology in the construction process. Those who will find this book
useful may be:

⦁ Designers wanting to better understand construction managers’ tools and processes
⦁ Construction managers looking to better understand the ways BIM and technology
can be used to create better outcomes
⦁ Subcontractors and project stakeholders looking to find ways to become a more
valued player
⦁ Owners and construction consumers who want to be more informed and who wish
to create a more successful project and project team
⦁ Students who want to grow their knowledge of BIM and technology in
construction and learn how they should challenge the constructs of the industry
where there are better ways of working

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Failures in Concrete Structures

Many failures, when investigated, have been found to arise from a combination of causes.

The traditional design sequence starts with the sizing of members.

These are determined from the loading (permanent and variable actions) with reference to bending moments and, for beams, shear forces.

The reinforcement is then calculated to cater for these forces.

Much of the reinforcement is detailed only after completion of the contract documents.

Later, if problems are found in fitting the required reinforcement into an element or joint, it is difficult to change the size of section on which the architect and services engineers agreed.

Many such problems could have been avoided by producing sketches early on to show how the joint details could work before sizes were finalised.

This book is a personal selection of incidents that have occurred related to reinforced and prestressed concrete structures.

Not all have led to failures and some of the mistakes were discovered at the design stage.

Each incident required some form of remedial action to ensure safety of the structure.

Some of the incidents were caused by mistakes in design or construction or both.

Some involved collapse of part of the structure, but in such cases the cause was from mor than one unrelated mistake or problem.

A few of the errors and incidents were caused by deliberate intent.

Chapters 1 to 11 describe specific incidents such as structural misunder standing, extrapolation of codes of practice, detailing, poor construction, and other factors.

When a particular incident involved more than one of these causes, it is described in the most relevant section.

Chapters 12 and 13 discuss issues related to procurement and research and development.

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Why buildings fall down how structures fail

Why buildings fall down: how structures fail

Once upon a time there were Seven Wonders of the World.

Now only one survives: the mountainlike Pyramid of Khufu in the Egyptian desert near Cairo.

The other six have fallen down.
It is the destiny of the man-made environment to vanish, but we, short lived men and women, look at our buildings so convinced they will stand forever that when some do collapse,

we are surprised and concerned.

Our surprise may be partly due to the fact that most of us judge buildings by their facades:

They look beautiful when very old and ugly when very young, the opposite of human faces.

But this kind of judgment is superficial and misleading; a much better metaphor
for a building is the human body.

A building is conceived when designed, born when built, alive while standing, dead from old age or an unexpected accident.

It breathes through the mouth of its windows and the lungs of its airconditioning system.

It circulates fluids through the veins and arteries of its pipes and sends messages to all parts of its body through the nervous system of its electric wires.

A building reacts to changes in its outer or inner conditions through its brain of feedback systems, is protected by the skin of its facade, supported by the skeleton of its columns, beams, and slabs, and rests on the feet of its foundations.

Like most human bodies, most buildings have full lives, and then they die.

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Structural Vibration Analysis and Damping

The analysis of structural vibration is necessary in order to calculate the natural frequencies
of a structure, and the response to the expected excitation.

In this way it can be determined whether a particular structure will fulfil its intended function and, in addition,

the results of the dynamic loadings acting on a structure can be predicted, such as the dynamic stresses, fatigue life and noise levels.

Hence the integrity and usefulness of a structure can be maximized and maintained.

From the analysis it can be seen which structural parameters most affect the dynamic response so that if an improvement or change in the response is required,

the structure can be modified in the most economic and appropriate way.

Very often the dynamic response can only be effectively controlled by changing the damping in the structure.

Structural Vibration: Analysis and Damping benefits from my earlier book Structural Vibration Analysis: Modelling,

Analysis and Damping of Vibrating Structures which was published in 1983 but is now out of print.

This enhanced successor is far more comprehensive with more analytical discussion, further consideration of damping sources and a greater range of examples and problems.

The mathematical modelling and vibration analysis of structures are discussed in some detail, together with the relevant theory.

It also provides an introduction to some of the excellent advanced specialized texts that are available on the vibration of dynamic systems. In addition,

it describes how structural parameters can be changed to achieve the desired dynamic performance and, most importantly,

the mechanisms and methods for controlling structural damping.

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Construction Project Management

Many books have been written on project management and there are two
approaches to it. One deals mainly with the tools and techniques of project
management and provides instruction on what they are and how to use
them. The other approach takes a managerial viewpoint and is concerned
more with the context and the way in which decisions are made and the
tools which are most appropriate in that situation. This book is more allied
to the managerial approach, analysing how techniques have been applied
in traditional and best practice and synthesising additional guidance on
evaluating contextual factors, which make the projects unique.

In construction in particular, there is a long history of project management
and standard systems have been set up which have become comfortable, but
have not always produced the best value for the client. Every project is
different and has at least a unique location, and due to the time and budget
constraints the final product is an untested prototype, which has been subject
to continuing design variations. Therefore, at first, it is a particular challenge
to an industry that has not standardised its products.

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Analysis and Design of Shallow and Deep Foundations

Advances in foundation engineering have been rapid in recent years. Of note
are the maturity of the concepts of soil–structure interaction, the development
of computer codes to deal with advanced topics, the advent of new methods
for the support of structures, and the proliferation of technical publications
and conferences that present a variety of useful information on the design and
performance of foundations.

This book takes advantage of these advances by presenting methods of analysis while being careful to emphasize standard methods such as site visits and the role of engineering geology.

The goals of the engineer in the design of foundations are to achieve a
system that will perform according to stipulated criteria, can be constructed
by established methods, is capable of being inspected, and can be built at a
reasonable cost.

Builders have realized the need for stable foundations since structures began
rising above the ground. Builders in the time of the Greeks and the Romans
certainly understood the need for an adequate foundation because many of
their structures have remained unyielding for centuries.

Portions of Roman aqueducts that carried water by gravity over large distances remain today. The Romans used stone blocks to create arched structures many meters in height
that continue to stand without obvious settlement.

The beautiful Pantheon, with a dome that rises 142 ft above the floor, remains steady as a tribute to builders in the time of Agrippa and Hadrian. The Colosseum in Rome, the
massive buildings at Baalbek, and the Parthenon in Athens are ancient structures
that would be unchanged today except for vandalism or possibly
earthquakes.

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Design and Control of Concrete Mixtures

Design and Control of Concrete Mixtures has been the cement and concrete industry’s primary reference on concrete technology for over 85 years. Since the first edition was published in the early 1920s, the U.S. version has been updated 15 times to reflect advances in concrete technology and to meet the growing needs of architects, engineers, builders, concrete producers, concrete technologists, instructors, and students.

This fully revised 15th edition was written to provide a concise, current reference on concrete, including the many advances that occurred since the last edition was published in 2002. The text is backed by over 95 years of research by the Portland Cement Association. It reflects the latest information on standards, specifications, and test methods of ASTM International (ASTM), the American Association of State Highway and Transportation Officials (AASHTO), and the American Concrete Institute (ACI).

Concrete’s versatility, durability, sustainability, and economy have made it the world’s most widely used construction material. The term concrete refers to a mixture of aggregates, usually sand, and either gravel or crushed stone, held together by a binder of cementitious paste. The paste is typically made up of portland cement and water and may also contain supplementary
cementing materials (SCMs), such as fly ash or slag cement, and chemical admixtures Understanding the basic fundamentals of concrete is necessary to produce quality concrete. This publication covers the materials used in concrete and the essentials required to design and control concrete mixtures for a wide variety of structures.

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Quality Management in Construction Projects

Quality is a universal phenomenon that has been a matter of great concern throughout recorded history. It was always the determination of builders and makers of products to ensure that their products meet the customer’s desire.

With the advent of globalization and the competitive market, the emphasison quality management has increased. Quality has become the most important single factor for the survival and success of today’s companies.

Customer demands for better products and services at the lowest possible costs have put tremendous pressure on firms to improve the quality of products, services, and processes to compete in the market and improve business results.

It became important that construction projects be more qualitative, competitive,and economical to meet owner’s expectations.

Construction projects have the involvement of many participants including the owner, designer, contractor, and many other professionals from construction-related industries.

Each of these participants is involved in implementing quality in construction projects. These participants are both influenced by and depend on each other in addition to “other players”

involved in the construction process. Therefore, the construction projects have become more complex and technical, and extensive efforts are required to reduce rework and costs associated with time, materials, and engineering.

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Code of Practice for Project Management for Construction and Development

Project management has come a long way since its modern introduction to construction
projects in the late 1950s. Now, it is an established discipline which executively
manages the full development process, from the client’s idea to funding coordination
and acquirement of planning and statutory controls approval, sustainability, design
delivery, through to the selection and procurement of the project team, construction,
commissioning, handover, review, to facilities management coordination.

This Code of Practice positions the project manager as the client’s representative,
although the responsibilities may vary from project to project; consequently,
project management may be defined as ‘the overall planning, co-ordination and
control of a project from inception to completion aimed at meeting a client’s
requirements in order to produce a functionally and financially viable project that
will be completed safely, on time, within authorised cost and to the required
quality standards’.

The fifth edition of this Code of Practice is the authoritative guide and reference to the
principles and practice of project management in construction and development. It
will be of value to clients, project management practices and educational establishments
and students, and to the construction and development industries. Much of
the information contained in the Code of Practice will also be relevant to project
management practitioners operating in other commercial spheres.

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