What is Underwater Antiwash Concrete?

PDF version here
Although underwater concreting has been in use for a long time, development of the technique has mainly proceeded in the areas of concrete placing method and improvements to the construction machinery. The prepacked concrete method, tremie method, concrete pump method, and others are now the representative underwater concreting methods. With all these concreting methods, the essential aim of technological development has been to improve how the concrete is placed and to minimize contact between the water and mortar so as to prevent the concrete from segregating under water.

On the other hand, antiwashout underwater concrete is quite different in concept from the methods mentioned above; the developmenta1aim in this case was improved performance of the fresh concrete. That is, the viscosity of the concrete was increased and its resistance to segregation under the washing action of water was enhanced by mixing an antiwashout admixture with the concrete. The effect of this is not only to greatly improve the reliability of Concrete placed underwater, but it also has remarkable effects on environmental preservation in the construction area. In addition, the earlier tremie and concrete pump placing methods can be adopted for construction.

The specific advantages of antiwashout underwater concrete include the following:

• Compared with ordinary concrete, antiwashout underwater concrete is highly resistant to the washing action of water, and rarely separates even when dropped under water

• Its yield value is small and viscosity high, so the concrete components never segregate and it displays high fluidity.

• As a result of the high fluidity, filling property and self-leveling ability are improved.

• Almost no bleeding occurs.

These qualities are taken full advantage of in work which would be difficult to handle using conventional underwater concrete. This includes work where high reliability is required, work in flowing water, work where water turbidity is restricted due to environmental considerations, and work where construction stretches over a considerable area and good flatness is necessary. On the other hand, however, handling is more difficult than with ordinary concrete, and in order to produce concrete of the required quality and a structure of the required performance, careful consideration of mix proportion, mixing, transport, and placing, etc. is necessary when antiwashout underwater concrete is used.

In particular, when producing the underwater antiwash concrete it is necessary to mix it for longer than ordinary concrete in a mixer large enough to uniformly disperse the antiwashout admixture. Also, when using concrete pumps for placement, it is necessary to design a pumping plan with care as regards pumping equipment, pumping distance, etc., because the pumping resistance is increased by the higher viscosity.

What is Porous Pavements?

What is Porous Pavements?

Porous pavements, both asphalt and concrete have been around for years.  In most areas they haven’t really caught on.  Now, with the large focus on environmental issues and green building, are they worth looking at again?
Pavement design
Traditional pavement design
Typically when pavement mixes are designed, they include different sizes of aggregate.  They use a wide range from fine sand to coarse stone.  The largest size depends on the expected use of the material.  Then it is all bound together with binder or cement.  With asphalt pavement that top layer will go on a water proof layer then a base.  Concrete pavement may go on a base or directly on the ground.
This results in an impenetrable surface that blocks rain water from getting into ground water systems and increases runoff.
Porous pavement design
Porous pavement or pervious pavement is designed using medium and large sized aggregate without any smaller fines such as sand.  It is then held together using with cement or binder.  The lack of fines in the mix creates relatively large pore space in the pavement.  This large pore space allows water to pass through.
The top layer is placed either directly on the ground or on other porous base layers to allow water to drain completely through the system into the ground.
Pros and Cons
Here are some pros and cons as well as a few notes on them.
Pros
Increased water quality – Oils, heavy metals and other contaminates on the pavements are not carried downstream and into stormwater drainage systems.  Also, water is filtered as it passes through the pavement.
Lower initial construction costs – Construction costs may be lower because porous pavements lower the amount of stormwater drainage facilities that a site will need.  Fewer and smaller inlets, detention ponds and storm drain pipes means lower construction costs.
Lower long term costs – less maintenance needed for storm drain and filtration systems.
Fewer fees – Storm water impact fees may be lower since porous pavements are proven to reduce runoff.
Less runoff – Less runoff means less potential flooding and lower peak flows.
Increased safety – Since water drains through the pavement there is a lower chance of hydroplaning and an increase in traction.
LEED Points – It can indirectly help gain LEED Points.  It can contribute in the areas of Stormwater Design, Heat Island Effect, Water Efficient Landscaping, Recycled Content, and Regional Materials.  There may be other ways that using it can help LEED certification.
Cons
Higher initial construction cost – Yes, I know I listed construction cost as a pro also.  The cost of constructing the pavement itself tends to be higher than regular pavement.
Soil restrictions – The soil below the pavement must drain at least as well as the pavement.
Clogging – The pores in the pavement may clog.  Suppliers and other proponents say that regular cleaning and maintenance will nearly eliminate clogging.
Pavement strength – Porous pavements are structurally weaker than standard pavements.   That generally results in them being used only for low traffic roads and parking lots.  Extra care must be taken when designing a pavement for high traffic or heavy traffic.
New/Untested technology – That’s not entirely accurate.  The technology has been tested since at least 1971.  However, most contractors don’t have experience with it.  Proper training, clear instructions, material testing, and site investigations should be done to ensure that the pavement meets all applicable standards during construction.
Contamination – Pavement surfaces usually have a lot of contaminates on them.  Porous pavements can filter contaminants, but no system is 100%.  Since water drains directly into ground soil it is possible that it will take the contaminants with it.
Conclusions
There is a lot of potential for porous pavements in future projects.  Each project would have to be investigated independently to determine any cost or environmental savings that might be gained by using porous pavements.  However, the potential positives do seem to outweigh the potential negatives.  It would certainly be worth your time to investigate it and present your findings to your client.
What are your thoughts on Porous and Pervious Pavements?

What is Right of Way (ROW)?

What is Right of Way (ROW)?


Right of Way (ROW)is something that civil engineers work with a lot. It’s on virtually all of the surveys that we use. It’s a key point that must be known if you’re working on a project where private property meets public property. This is especially important when working on transportation projects for local governments. There are a lot of aspects to Right of Way and Right of Way Acquisition. I’m going to talk about it mainly from the transportation side.

What is Right of Way

Here’s an example of what Right of Way (ROW) is. A city owns a public street that goes through a residential neighborhood. They also own a few feet past the pavement on both sides of the street. If a residential street is 30-36 feet wide the city may own a total of 46-50+ feet wide area. So, yes they own part of your front yard. Virtually all public streets are like this, from local residential streets on up to interstate highways which may have ROWs that are hundreds of feet wide.

Why Right of Way

The government holds a right of way wider than the actual street for several reasons. They use the extra land for things like public sidewalks, utilities, or to widen the road in the future. Also, street lights, traffic signals and street parking are all in the ROW.

Right of Way is something that we have to know where is, but civil engineers don’t typically worry about why it’s where it is or how to get more. That sort of thing is typically handled by the government agency itself. Or was figured out when the property was first developed. Civil engineers don’t generally get more once an area is already developed.

However, I’ve had the privilege recently to work on a ROW acquisition project recently. That’s a service that our company offers, and my background in roadway design helped get me involved in a roadway ROW project.

The project

Here are the basics of the project. A two lane county road needed to be widened because of all of the development nearby. Plans were drawn up and the road was designed, but the county didn’t actually own enough land to make the road wider. That’s where we came in on the project. The county hired us to acquire the land for them.

What you have to do

There are several steps involved in ROW acquisition. I’m going to go over the broad steps. Perhaps at a later date I’ll write a more detailed article, or ask our resident expert to put one together for me.

Survey

It seems that everything in civil engineering begins with a survey. The same applies here. With the survey and the plans we can see exactly how much land is needed from each land owner. The surveyor provides documents showing exactly how much land is needed. They generally will also mark the area with flags or other markers.

Initial Letter

An initial letter is sent to the current land owner to let them know about the surveyors and appraisers coming onto their property. The letter also lets the owner know what’s going on with the project; the whys, the whos, etc.

Appraisals

Next the appraisers go to work. They appraise each plot of land that the government needs to buy. The appraisers generally will take into account mailboxes, fences, trees and anything else that may be in the proposed right of way area that current land owner would have to move or lose value if it’s removed.

Title Search

Just like when you buy any piece of property, you do a title search to find out who actually owns the land. This will also tell you about any liens on the property such as a mortgage, tax lien or unpaid debt. Any lien will affect the sale.

Offer Letters

Send the initial offer letter. Basically the offer is for what the appraiser valued the land at.

Negotiation

This can be real long or real short depending on what the land owner wants. I’ve seen some just sign the paperwork and send it back. Some think their land is worth more, some will want fences or custom mailboxes replaced, trees paid for, or many other things. Some just flat out refuse to sell. In most cases something can be worked out to the benefit of both the land owner and the municipality.

Partial Release of Lien

We do have to deal with any liens that are on the property. If there is a mortgage, for example, we have to get a partial release of lien. Basically the bank has to give up that part of the land on their deed. Lien holders may have the right to the money first. That varies some by location. Banks sometimes require a percentage of the money based on a percentage of the property sold.

Acceptance or Condemnation

Eventually, after the negotiations, the land owner accepts or they don’t. If they accept, then the paperwork is signed, they get their money and the government gets the land. If they are unwilling to sign, then it goes to condemnation. That means that it goes before a third party to decide the case. Generally when this happens the government gets the land and the land owner gets fair market value for their property. Because of the expense it really doesn’t do anybody any good to go to condemnation. As long as we follow the laws and our engineering ethics guidelines we are fine.

There is a lot more to it, but that covers the basic process. It is certainly a good thing to know, even if you never do ROW acquisition yourself. Having the knowledge gives you a better understanding of the process and what the municipality has to do on some projects. However, having the expertise can give your company another product to offer municipal clients.

What is GIS?

Definition: A map is a graphic form, normally to scale, of spatial abstraction of features on, or in relation to, the surface of the Earth.

Types of maps

1. Topographic maps
2. Thematic maps

Topographic map:

A reference tool, showing the outlines of selected natural and man-made features of the Earth. „ "Topography" refers to the shape of the surface, represented by contours and/or shading, but topographic maps also show roads and other prominent features.

Thematic map:

A tool to communicate geographical concepts such as

• The distribution of population densities, climate, movement of goods, land use etc.
• Line maps versus photo (image) maps

„* 2D vs 3D maps

Characteristics of maps

• Scale
• Projection

Scale

The scale of a map is the ratio between distances on the map and corresponding distances in the real world, e.g., if a map has a scale of 1:50,000, then 1 cm on the map equals 50,000 cm or 0.5 km on the Earth's surface.
"Small scale" and "large scale" is often confused, e.g, 1:50,000 vs. 1:500,000
The scale controls not only how features are shown, but what features are shown, e.g., Engineering building: 0.2mm*50,000=10 m„ Map projections. The Earth's surface is curved but as it must be shown on a flat sheet, some distortion is inevitable.

Projection

A projection is a method by which the curved surface of the earth is represented on a flat surface.
Numerous projections have been invented for various applications

• „ Cartographic abstraction „- Selection of the few features in the real world to include classification of selected features into groups (e.g., bridges, churches, railways)

• Simplification of jagged lines (e.g., coastlines)

• Exaggeration of features to be included that are to small to show at the scale of the map Symbolization to represent the different classes of features chosen

Geographic (Geo-spatial) information

1. Information about places on the earth’s surface
2. „ Knowledge about where something is
3. Knowledge about what is at a given location
4. Can be very detailed or very coarse
5. Often relatively static
6. „ Can be very voluminous

Basic Concept of a GIS

GIS can be considered as a map information system for management, analysis, presentation and distribution.the applicaion of GIS can be found "here".

The Academic Definition
"A system of hardware, software, data, people, organizations and institutional arrangements for collecting, storing, analyzing, and disseminating information about areas of the earth." (Dueker & Kjerne, 1989)

Tao’s Definition
A GIS is a computer-based information system for collection, management, manipulation, analysis, presentation, and dissemination of geospatially referenced data.

A Mathematical Definition

• Measure aspects of geographic phenomena and processes;
• Represent these measurements in the form of a computer database;
• Operate these representations to produce more measurements and
• To discover new relationships;
• Transform these representations to conform to other frameworks of entities and relationships.

GIS Workflow

GIS is a location based information system:
A GIS stores information about the world as a collection of layers that can be linked together by geography.
Why themes (layers)?

Modeling of actual features in GIS

• Logical breakdown of data - related objects in each theme
• Assemble maps for different purposes by combining themes
• Examine interaction between themes
• Create new themes

Paper maps use symbolism to distinguish between layers, to compensate for the limitations of the technology

Alternative Names

• Geospatial (Spatial) Information System
• Geographic(al) Information System
• Land Information System
• Environmental Information System
• Automated Mapping/Facilities Management
• Geographical Information Sciences (GIScience)
• Geographical Information Services (GIServices)
• Desktop Mapping

Components of a GIS

Components required for full functionality of geographic Information System

1. Hardware
2. Software
3. Data
4. People
5. Methods

Hardware

• Computers (PC, workstations, servers)
• CPU, Pentium 4 2.5GHz ? Memory, 8GB
• Storage devices (Mass storage)
• Hard disks, Tape (4mm, 8mm 8GBs), Optical disks (>1GB, $100 per Disk), CD –ROM (640MB, $1-2 per CD)/DVD
• Zip drivers (100-200MB, $20 per disk), Jazz-drivers (1G, $50 per disk), Flash cards, USB HD

Input devices

• Keyboard, Scanner, Digitizer, Camera, Voice recognition
• GPS, stereo plotter, remote sensing sensors
• Output devices
• Graphics monitors (graphics cards)
• Printers (dot matrix/Laser/Inkjet)
• Plotter (Drum/Flatbed)
• Communication/networking devices
• WAN/LAN/High-Speed Network
• Modem/Phone Lines/Cable

As the Internet evolves, its data transfer rate is increasing very quickly. From the first level(CA-1, 10MB/s), to the second(CA-2, 150MB/s), to the third(CA-3, 10GB/s), and beyond.

Software

• Operating systems
• Windows/UNIX/LINUX
• Basic GIS software
• ESRI: ArcGIS, ArcInfo, ArcView
• Intergraph: Geomedia, MGE
• Auto Desk: AutoCAD Map, MapGuide
• MapInfo: MapInfo
• Bently: Microstation
• PCI Geomatica (PANMAP, SPANS)
• Caris Data Base Management Systems (DBMS)
• Oracle, DB2, Informix, Sybase, Microsoft SQL, Access

Development languages

• Common programming languages: VC, VB, Java, Fortran
• Micro Language: Does not exist anymore( e.g., Avenue: Arcview, MapBasics: Mapinfo, AML, MDL: Microstation)

Data

1. Spatial data e.g., Coordinates, location of a well, boundaries, road networks
2. Non-spatial data (attributes, aspatial data) …e.g., Land ownership, address, population densities, soil PH values
3. Data relationships (spatial relationship-topology, attribute relations)
   
   
   
   1. Temporal data
   2. Metadata (data about data)

Spatial data„ Objects or entities that are referenced by their location

• Latitude / longitude coordinates …x / y coordinates
• Street address
• Administrative unit

Attribute data

• Data that are linked to the spatial objects
• Census data by administrative unit
• Land parcel ownership records
• Soil or vegetation characteristics
• Health records by medical center
• Road quality information

Data Relations Traditionally information is organized in lists, maps add information about the “where” of the data

Exploring Relationships

• Based on geographic location and proximity, GIS makes connections between activities
• Looking at data geographically can often suggest new insights,

explanations

• These connections are often unrecognized without GIS, but can be vital to understanding and managing activities and resources e.g., we can link pollution sources with disease patterns

Methodology

…GIS expertise and knowledge

People

• Problem solving skills
• Team skills
• Communication skills
• Management skills

Which is the most costly component in a GIS?
Functional Requirements for GIS

• Data input
• Existing maps, field observations, aerial photographs, sensors (airborne and satellites)
• Data storage and management
• Data processing and analysis
• Data output and presentation: Maps/tables/figures/video/audio/3D models
• Various interaction techniques: mouse, keyboard, Voice, 3D mouse, VR (view, voice, motion, tasting, smelling)

Capabilities of GIS

• Data capture/input: …Input data by digitizing, scanning, or direct coordinate entry…
• Edit data in the GIS to correct errors or add features
• …Label the spatial features so they can be identified (names or codes)

Management

• Link attribute data to spatial objects
• Link to external databases
• Make changes in existing databases
• Update database features
• Import and export from/to other GIS or DBMS
• Combine map sheets to create large databases
• Match the edges of neighboring map sheets

Manipulation

• …Make maps from different sources compatible so that they can be drawn on top of each other
• Transformation of coordinates
• …Projection change

Analysis

…Query

• Select features by their attributes: “find all districts with literacy rates < 60%”
• Select features by geographic relationships: “find all family planning clinics within this district”
• Combined attributes/geographic queries: “find all villages within 10km of a health facility that * have high child mortality”

Buffer

• Find all settlements that are more than 10km from a health clinic
• Point-in-polygon operations: identify for all villages into which vegetation zone they fall
• Polygon overlay: combine administrative records with health district data
• Geocoding/address matching: match an address list with a street map
• Network operations: find the shortest route from village to hospital

Modeling

• Identify or predict a process that has created or will create a certain spatial pattern
• Diffusion: how is the epidemic spreading in the province?
• Interaction: where do people migrate to?
• …What-if scenarios: if the dam is built, how many people will be displaced?

Display/output

…Exploratory

• Visualize pattern and identify anomalies
• Compare information in map space and data space

…Cartography

• Produce high quality map output for publication
• Create a digital or paper census atlas
• Export map output to other packages

what is Reinforced Concrete ?

Concrete is a stone like substance obtained by permitting a carefully proportioned mixture of cement, sand and gravel or other aggregate and water to harden in forms of the shape and of dimensions of the desired structure.

Reinforced cement concrete:

Since concrete is a brittle material and is strong in compression. It is weak in tension, so steel is used inside concrete for strengthening and reinforcing the tensile strength of concrete. The steel must have appropriate deformations to provide strong bonds and interlocking of both materials. When completely surrounded by the hardened concrete mass it forms an integral part of the two materials, known as "Reinforced Concrete".

Advantages and disadvantages of reinforced concrete

Reinforced Concrete is a structural material, is widely used in many types of structures. It is competitive with steel if economically designed and executed.

Advantages of reinforced concrete It has relatively high compressive strength It has better resistance to fire than steel It has long service life with low maintenance cost In some types of structures, such as dams, piers and footings, it is most economical structural material. It can be cast to take the shape required , making it widely used in pre-cast structural components. It yields rigid members with minimum apparent deflection. Yield strength of steel is about 15 times the compressive strength of structural concrete and well over 100 times its tensile strength By using steel, cross sectional dimesions of structural members can b ereduced e.g in lower floor columns.

Disadvantages of reinforced concrete

• It needs mixing, casting and curing, all of which affect the final strength of concrete.
  
• The cost of the forms used to cast concrete is relatively high.
  
• It has low compressive strength as compared to steel (the ratio is about 1:10 depending on material) which leads to large sections in columns/beams of multistory buildings Cracks develop in concrete due to shrinkage and the application of live loads
  

What is Burj Khalifa (formerly Burj Dubai)?

 General Information

Burj Khalifa (formerly Burj Dubai)

Dubai, United Arab Emirates

Burj Khalifa, formerly Burj Dubai, at the center of a large-scale development, is the tallest building in the world. The design combines cultural influences with cutting-edge technology to achieve a high-performance building. Its massing is manipulated in the vertical dimension to minimize the impact of wind on the tower's movement.

Project Facts

Completion Year: 2010
Site Area: 104,210 m²
Project Area: 454,249 m²
Building Height: 828 m

Project Awards

2010 • Arab Investment Summit • Arab Achievement Award 2010: Best Architecture Project
2010 • Chicago Athenaeum • International Architecture Award
2010 • Cityscape Awards for Real Estate in the Middle East and North Africa • Best Mixed Use Built Development
2010 • CTBUH • Best Tall Building Middle East & Asia
2010 • LEAF Awards • Best Structural Design of the Year: Shortlisted
2010 • Structural Engineers Association of Illinois • Excellence in Structural Engineering: Most Innovative Structure
2010 • World Architecture Festival • Award: Shortlisted
2010 • World Architecture Festival • Award: Shortlisted / Structural System 
see more about the design concept of the building

What is ECC?

   The new trend of Civil Engineering is to utilize the most effective and sustainable solution to the built environment. Since most of the Civil Engineering application are unavoidable to deal with the infrastructures encountering with the impact of the surrounding environment, the engineers thus seek to use the most durable and cost-effective materials in their built infrastructure.

    ECC is one of the most outstanding material developed by using Nanotechnology. Several researchers are currently working to drive the high performance ingredients of ECC to use in various Civil application; for example, Prof. Victor Li. His research is very famous and highly impacted like On Engineered Cementitious Composites (ECC) A Review of the Material and Its Applications (Invited paper)
Victor C. Li, published in Journal of Advanced Concrete Technology, 1(3) 215-230, 2003

     This article surveys the research and development of Engineered Cementitious Composites (ECC) over the last decade since its invention in the early 1990's. The importance of micromechanics in the materials design strategy is emphasized. Observations of unique characteristics of ECC based on a broad range of theoretical and experimental research are reviewed. The advantageous use of ECC in certain categories of structural, repair and retrofit applications is reviewed. While reflecting on past advances, future challenges for continued development and deployment of ECC are noted. This article is based on a keynote address given at the International Workshop on Ductile Fiber Reinforced Cementitious Composites (DFRCC)- Applications and Evaluations, sponsored by the Japan Concrete Institute, and held in October 2002 at Takayama, Japan.

    ECC, unlike common fiber reinforced concrete, is a micromechanically designed material[2]. This means that the mechanical interactions between ECC's fiber and matrix are described by a micromechanical model, which takes into account material properties and helps predict properties and guide ECC development.

    ECC looks similar to ordinary portland cement-based concrete, except that it does not include coarse aggregate and can deform (or bend) under strain[1] . A number of research groups are developing ECC science, including those at the University of Michigan, Delft University of Technology, the University of Tokyo, the Czech Technical University, and Stanford University. Traditional concrete’s lack of durability and failure under strain, both stemming from brittle behavior, have been a pushing factor in the development of ECC.

   ECC has a variety of unique properties, including tensile properties superior to other fiber-reinforced composites, ease of processing on par with conventional cement, the use of only a small volume fraction of fibers (~ 2 %), tight crack width, and a lack of anisotropically weak planes [3]. These properties are due largely to the interaction between the fibers and cementing matrix, which can be custom-tailored through micromechanics design. Essentially, the fibers create many microcracks with a very specific width, rather than a few very large cracks (as in conventional concrete.) This allows ECC to deform without catastrophic failure.

   This microcracking behavior leads to superior corrosion resistance (the cracks are so small and numerous that it is difficult for aggressive media to penetrate and attack the reinforcing steel) as well as to self-healing[4]. In the presence of water (during a rainstorm, for instance) unreacted cement particles recently exposed due to cracking hydrate and form a number of products (Calcium Silicate Hydrate, calcite, etc.) that expand and fill in the crack. These products appear as a white ‘scar’ material filling in the crack. This self-healing behavior not only seals the crack to prevent transport of fluids, but mechanical properties are regained. This self-healing has been observed in a variety of conventional cement and concretes; however, above a certain crack width self healing becomes less effective. It is the tightly controlled crack widths seen in ECC that ensure all cracks thoroughly heal when exposed to the natural environment.

    When combined with a more conductive material (metal wires, carbon nanotubes, etc.) all cement materials can increase and be used for damage-sensing. This is essentially based on the fact that conductivity will change as damage occurs; the addition of conductive material is meant to raise the conductivity to a level where such changes will be easily identified. Though not a material property of ECC itself, conductive ECC for damage-sensing applications are being developed by a number of research groups.

Field Applications

    ECC have found use in a number of large-scale applications in Japan, Korea, Switzerland, Australia and the U.S.[3]. These include:

    * The Mitaka Dam near Hiroshima was repaired using ECC in 2003[5]. The surface of the then 60-year old dam was severely damaged, showing evidence of cracks, spalling, and some water leakage. A 20 mm-thick layer of ECC was applied by spraying over the 600 m2 surface.

    * Also in 2003, an earth retaining wall in Gifu, Japan, was repaired using ECC[6]. Ordinary portland cement could not be used due to the severity of the cracking in the original structure, which would have caused reflective cracking. ECC was intended to minimize this danger; after one year only microcracks of tolerable width were observed.

    * The 95 m (312 ft.) Glorio Roppongi high-rise apartment building in Tokyo contains a total of 54 ECC coupling beams (2 per story) intended to mitigate earthquake damage [7]. The properties of ECC (high damage tolerance, high energy absorption, and ability to deform under shear) give it superior properties in seismic resistance applications when compared to ordinary portland cement. Similar structures include the 41-story Nabeaure Yokohama Tower (4 coupling beams per floor.)

    * The 1-km (0.6 mile) long Mihara Bridge in Hokkaido, Japan was opened to traffic in 2005 [8]. The steel-reinforced road bed contains nearly 800 m3 of ECC material. The tensile ductility and tight crack control behavior of ECC led to a 40 % reduction in material used during construction.

   * Similarly, a 225-mm thick ECC bridge deck on interstate 94 in Michigan was completed in 2005[9] . 30 m3 of material was used, delivered on-site in standard mixing trucks. Due to the unique mechanical properties of ECC, this deck also used less material than a proposed deck made of ordinary portland cement. Both the University of Michigan and the Michigan Department of Transportation are monitoring the bridge in an attempt to verify the theoretical superior durability of ECC; after 4 years of monitoring, performance remained undiminished.

    In conclusion,  ECC is one of the most outstanding material developed by using Nanotechnology.  The material is to meet the requirement for the new trend of Civil Engineering that utilizes the most effective and sustainable solution to the built environment.

what are B and D regions?

      B-Regions are parts of a structure in which Bernoulli's hypothesis of straight-line strain profiles applies. D-Regions, on the other hand, are parts of a structure with a complex variation in strain. D-Regions include portions near abrupt changes in geometry (geometrical discontinuities) or concentrated forces (statical discontinuities). Based on St. Venant's principle, the extent of a D-Region spans about one section depth of the region on either side of the discontinuity.

Figure 1 and Figure 2 show examples of the division between B-Regions and D-Regions in building and bridge structures, respectively. In the figures, the unshaded area with a notation B indicates B-Region, and the shaded area with a notation D is used to indicate D-Region. The notations h₁, h₂, h₃, ... are used to denote the depth of structural members. The notations b₁ and b₂ denote the flange width of structural members.

Figure 1   Example of D-Regions in a Common Building Structure
(Click here to view a larger image)

Figure 2   Example of D-Regions in a Common Bridge Structure
(Click here to view a larger image)

    Most design practices for B-Regions are based on a model for behavior. As examples, design for flexure is based on conventional beam theory while the design for shear is based on the well-known parallel chord truss analogy. By contrast, the most familiar types of D-Regions, such as deep beams, corbels, beam-column joints, and pile caps, are currently still designed by empirical approaches or by using common detailing practices. For most other types of D-Regions, code provisions provide little guidance to designers. The Strut-and-Tie Method (STM)  is emerging as a code-worthy methodology for the design of all types of D-Regions in structural concrete.

     It is worth noting that although the STM is equally applicable to both B- and D-Region problems, it is not practical to apply the method to B-Region problems. The conventional beam theory for flexure and parallel chord truss analogy for shear are recommended for those designs.

What is LRFD?

Limit state design (LSD) refers to a design method used in structural engineering. The method is in fact a modernization and rationalization of engineering knowledge which was well established prior to the adoption of LSD.[citation needed] Beyond the concept of a limit state, LSD simply entails the application of statistics to determine the level of safety required by or during the design process for LRFD from Bridge Design, please read this book about Design of Highway Bridges: An LRFD Approach

Criteria

Limit state design requires the structure to satisfy two principal criteria: the ultimate limit state (ULS) and the serviceability limit state (SLS).[1] A limit state is a set of performance criteria (e.g. vibration levels, deflection, strength, stability, buckling, twisting, collapse) that must be met when the structure is subject to loads.

Example Treatment of LSD in Codes

The following is the treatment of LSD found in the National Building Code of Canada:

NBCC 1995 Format
φR > αDD + ψ γ {αLL + αQQ + αTT}

where φ = Resistance Factor
ψ = Load Combination Factor
γ = Importance Factor
αD = Dead Load Factor
αL = Live Load Factor
αQ = Earthquake Load Factor
αT = Thermal Effect (Temperature) Load Factor


Any design process involves a number of assumptions. The loads to which a structure will be subjected must be estimated, sizes of members to check must be chosen and design criteria must be selected. All engineering design criteria have a common goal: that of ensuring a safe structure and ensuring the functionality of the structure.
The State of the Art

Limit state design has replaced the older concept of permissible stress design in most forms of civil engineering. Notable exceptions are geotechnical engineering and transportation engineering. Even so, new codes are currently being developed for both geotechnical and transportation engineering which are LSD based. As a result, most modern buildings are designed in accordance with a code which is based on limit state theory. For example, in the UK, Steel structures are designed in accordance with BS 5950, and reinforced concrete structures to BS 8110, both of which are codes based on limit state theory. Australia, Canada, China, France, Indonesia, and New Zealand (among many others) utilise limit state theory in the development of their design codes. In the purest sense, it is now considered inappropriate to discuss safety factors when working with LSD, as there are concerns that this may lead to confusion.
Limit State Design in the United States

The United States has been particularly slow to adopt Limit State(s) design (known as Load and Resistance Factor Design in the US), and as a result it is more thoroughly adopted outside the United States. Inside the U.S. there has been significant resistance to this technique, so much so that the American Institute of Steel Construction (AISC) is now issuing a combined manual of steel construction (the 2005 manual) that contains two methods of design side by side (newly named ASD - Allowable Strength Design, not to be confused with ASD - Allowable Stress Design last updated in 1989), and LRFD - load and resistance factor design).[citation needed] In terms of the US steel code, research and progress has been reserved to LRFD code, with the exception of addenda regarding safety concerns. Even so, many American engineers continue to prefer the former ASD code. The difficulty may lie in the high regionalization of US Engineering practice, coupled with the high number of governing bodies, codes and states which each regulate the engineering profession individually.

what is PE Exam?

Principles and Practice of Engineering Exam

The Principles and Practice of Engineering exam is the examination that is required to be passed before one can become a Professional Engineer (PE) in the United States. It is the second exam required after the Fundamentals of Engineering exam. The recommended guides for PE exams is Civil Engineering Reference Manual for the PE Exam; for example.


Upon passing the PE exam and meeting other eligibility requirements such as education and experience that vary by State, an engineer is then eligible to be registered in their State to stamp and sign engineering drawings and calculations as a PE.

While the PE itself is sufficient for most engineering fields, some states require a further certification for structural engineers. These require the passing of the Structural I exam and/or the Structural II exam.


The PE Exam is created and scored by the National Council of Examiners for Engineering and Surveying (NCEES). NCEES is a national non-profit organization composed of engineering and surveying licensing boards representing all states and U.S. territories.[1]
Contents


Disciplines

PE exams are offered in the following engineering disciplines:

* Agricultural
* Architectural
* Chemical
* Civil
* Control Systems
* Electrical
* Computer
* Environmental
* Fire Protection
* Industrial
* Mechanical
* Metallurgical and Materials
* Mining and Mineral
* Naval Architecture and Marine Engineering
* Nuclear
* Petroleum
* Structural I
* Structural II[2]

Exams are offered twice a year, once in April and once in October.[3] Three disciplines offer a choice of concentration as of 2010, chiefly Civil(5), Mechanical(3), and Electrical and Computer (3).
[edit] Exam format

Each of the discipline specific PE Exams is eight hours long and consists of two 4-hour sessions administered in a single day with a lunch break. The exam consists of 80 or 100 multiple choice questions, the only exception being the essay style responses of the PE Structural II Exam. Several disciplines require a common morning breadth exam which broadly covers the discipline and then a more detailed afternoon depth exam where the test taker selects a more detailed area of the discipline. Other disciplines essentially have morning and afternoon breadth exams.[2]

Unlike the Fundamentals of Engineering Exam, outside reference sources are allowed for the PE Exam. The general rule is that any such materials must be in some sort of permanent binding (book, three-ring, spiral, etc.); loose papers and notes are prohibited. No writing tools or scratch paper may be brought in, and only calculators specifically approved by NCEES may be used. Examinees are provided with mechanical pencils, while the test booklet may be used for working problems.
[edit] Pass rates

The PE exam is a professional exam much like the examinations required for public accounting, law, and other professions for which protection of the public is of the utmost concern. Consequently exam candidates typically spend large amounts of time preparing for the exam[4]. Exam pass rates vary by discipline module and test date, for the April 2010 exam, the pass rates for first time test takers ranged from 85% (Naval Architecture) to 46% (Structural I). The pass rates for repeat test takers is considerably lower.[5]

What is Biocement?

It’s safe to say that without microbes, biotechnology would be an extremely limited science. Microbes are microscopic organisms such as fungi (which include yeasts), bacteria and viruses. They not only provide the foundation for much of the basic research involved in biotechnology, they help to create durable building materials and structures. The early scientific study of microbes concentrated on their effects, such as causing disease. Eventually, scientists discovered microbes could be used for the study of processes which are common to all living organisms. An innovative alternative approach lies in the combined use of microorganisms, nutrients and biological processes naturally present in the subsurface soils to effectively improve their engineering properties. Considerable research on carbonate precipitation by bacteria has been performed using ureolytic bacteria. These bacteria are able to influence the precipitation of calcium carbonate by the production of an enzyme, urease (urea amidohydrolase, EC 3.5.1.5). Calcium carbonate precipitation occurs as a consequence of bacterial metabolic activity that raises the pH of the proximal environment.
Recently I discovered and improved few bacterial species which were able to precipitate calcite at higher rate and eventually this process lead to improved compressive strength, reduced permeability and low corrosion rate of reinforcement.

Biocement, a self-healing material to enhance durability of building structures and conservation of cultural heritages
Although hundreds of thousands of successful concrete and buildings are annually constructed worldwide, there are large numbers of concrete structures (including historical monuments) that deteriorate or become unsafe due to changes in loading, changes in use or changes in configuration. The constant developments in the field of civil engineering and the growth of industrial activity have created a growing demand for materials for the construction industry that do more and more to comply with structural requirements and meet stricter demands for working conditions and environment. Traditionally, mechanical strength has been the main criterion used when choosing building materials such as cement, concrete or bricks. Compressive strength, permeability and corrosion analysis are the most common used measures in designing of buildings structures. Considerable effort has been devoted to develop high-strength materials. However, with increasing volumes of constricted facilities that need to be maintained the focus is shifting towards durability.
Besides building materials preservation of the cultural heritage, socioeconomic growth and sustainable development is finding considerable resonance amongst specialists in the field. It calls for an innovative strategy for the maintenance of our cultural heritage. This strategy implies that the protection of historical buildings represents an important prerequisite for peace and stability and provides social and economic opportunities at the same time. The preservation of culture contributes to the identity of the citizens, creates jobs, supports the economy and promotes the responsible handling of societal resources. Although there is a great deal of knowledge and information on world heritage monuments, this is lacking in respect of standard monuments both at national level and international level. There is a need for research at this level into the number and quality of monuments and historical sites. Large sums of money are being spent worldwide on measures for the preservation of monuments and historical buildings. The economic and ecological commitment to the preservation of monuments and historical buildings requires, however, a prudent handling of the appropriate funds. This demands an optimization of damage analysis procedures and damage process controls as well as the development of monitoring and early warning systems for damage prevention. Therefore, the goal needs to be the implementation of permanent preservation measures, which requires long-term maintenance.
All building materials are porous. This porosity of building material along with ingress of moisture and other harmful chemicals such as acids, chlorides and sulfates affect the material and seriously reduce their strength and life. An additive that seals the pores and cracks and thus reduces the permeability of the structure would immensely improve its life. Conventionally, a variety of sealing agents such as latex emulsions and epoxies etc.; and surface treatments with water repellents such as silanes or siloxanes are used to enhance the durability of the concrete structures. However, they suffer from serious limitations of incompatible interfaces, susceptibility to ultraviolet radiations, unstable molecular structure and high cost. They also emanate toxic gases.
In order to overcome the shortcomings of conventional sealing agents, materials with self-healing capability can be used effectively. Use of urease producing microbes addresses these problems effectively, as these continue to survive and grow within the concrete structure after the initial use. Urease helps in mineralization of calcium carbonate, by hydrolyzing urea present in the environment. It releases carbon dioxide from urea that combines with calcium ions resulting in deposition of calcium carbonate in the form of calcite. Due to urease activity, bacteria are able to use urea as a sole nitrogen source and produce ammonia, which increases the pH in the proximal environment, causing Ca2+ and CO32- to precipitate as CaCO3. These unique properties make it particularly suitable for many applications in civil engineering (concrete structures, plasters, mortars, prefabricated elements, refractory elements, bricks, natural stones, etc.)
A microbial additive that helps in calcite precipitation with urease would enhance durability of building materials as well preserve the cultural heritage.
I am pleased to present herewith my preliminary findings of the effects of microbial additives (where I used Sporosarcina pasteurii, previously known as Bacillus pasteurii, a facultative anaerobic Gram-positive soil bacterium) to enhance the durability of building materials. The significant amount of data, some of which are attached hereto, accumulated to date leads us to the preliminary findings:
1. Microbial additive resulted in improvement in compressive strength of mortar by up to 38%.
2. Microbial additive can remediate cracks in building materials and monumental stones and regain strength within 28 days.
3. To make the process economic, microbial additive can be prepared by growing cells using industrial by products such as lactose mother liquor, corn steep liquor as nutrient sources.
4. Microbial additive can enhance the durability of bricks by reducing their permeability and increasing compressive strength.
5. The reduced permeability rates resulting from the microbial additive will increase the concrete structures’ useful life.
The data accumulated to date are, in my opinion, sufficient in quantity and trend to allow me to draw some preliminary conclusions with a reasonable confidence that in future it will further support the preliminary findings. As previously stated though the study period has not yet run the full course, the data and trends indicate the microbial additive is having the beneficial effect of enhancing the durability of building materials and preservation of cultural heritage.