A Non-stop Method for Building Concrete Structures
Development of the Slipform Technique
Cement, and concrete by its association with it, has an initial setting time of just about thirty minutes, after which the cement and the concrete have gained sufficient strength to remain in the shape into which it has been poured. It is this property that led to the development of slipform building that allows a non-stop method of construction.It is this property of early setting that inspired engineers to develop means of moving the formwork so that the concrete can be poured continuously. The height of the formwork is designed in such a way that while the top of the formwork is being filled by concrete the lowest layer of concrete poured earlier has already gained an initial set. When the formwork is moved upwards the concrete that is then exposed remains firm.Advantages of Slipform Building
A major cost of concrete structure construction comes in the form of the required formwork to retain the concrete while it retains it necessary shape and gains the necessary strength till it can be safely de-shuttered and be able to support itself and other imposed loads. It also requires the formwork to be continually removed to newer locations and then re-erected. All this requires the continuous use of manpower and lifting equipment like cranes. In the case of slipform building, the formwork is erected only once and remains intact until the entire structure is completed.This greatly reduces the cost of the formwork as well as any time that may be required to erect and move it for re-erection, which can result in huge savings in time as well as money.The continuous operations also allow for an evening-out of the manpower requirements and also a huge saving in the labor that may have to be periodically employed during otherwise intermittent concreting operations.The reduction in the movement of formwork and workers also leads to far more safe working conditions that also make it a major advantage.The Components of Vertical Slipform
A slipform assembly can only start after the foundations of the walls have been correctly laid and a starter for the walls laid out in its correct alignment with all the necessary steel for the walls already in position. The slipform shuttering is then firmly aligned to this starter with the means of yokes on each side of the shuttering that help to keep the panels in position. The yokes are all connected by horizontal crossbeams. Hydraulic jacks are then installed rigidly to the crossbeams that can all act simultaneously so that the entire slipform shuttering moves upwards. The heights of such slipform shuttering will normally be between 1. 1 meters to 1. 5 meters in height. The yokes and horizontal crossbeams are also used to support a working platform that can afford space for men and materials. The jacks climb using jacking rods that are installed within the concrete and become a permanent part of the structure, or can be retrieved if so desired.The design of the working deck and the yokes and horizontal crossbeams are a very vital part of efficient slipform construction. It is very important that the entire structure be such that its rigidity and shape is maintained at all times. It is quite normal for the two sides of the shuttering to be inclined towards each other at the top with the correct wall dimension available at the center. This allows the shuttering to move easily and eliminates any drag that concrete can cause on the shutters to prevent its free upward movement. The rigidity of the supporting platform is also essential so that all parts of the structure move simultaneously. If there is any lag from one part to the other, this can cause the shuttering to drag and make it difficult to be pulled up. It is also possible to reduce wall thicknesses as the construction gains height and arrangements have to be made in the slipform structure that will enable such reduction at regular intervals.Non-stop method of Construction
Once the slipform shutters along with the jacks and support deck are in position, concreting operations can then commence. Sufficient working space has to be created on the deck to accommodate reinforcement bar activity. The bars have to be continually lengthened and placed in position as per the structural requirements for the wall. The concrete is poured in layers, and by the time the concrete level has reached the top, the concrete at a level 300 mm above the bottom of the panel should have gained the initial set. The rate of pouring of the concrete has to be adjusted so that this is achieved. The slipform is then moved upwards in steps of 10 mm to 25 mm and both the concreting and placing of the reinforcement bars is done continuously till the final height is reached. All jacks are fitted with brakes that act automatically by mechanical means and do not allow the jacks to slip on the jack rods.Slipform methods of construction can also be adapted to horizontal structures and are used for paving, canals, and tunneling. The technique is more in use for structures that have continuous walls like silos, chimneys, and piers for very tall bridges. It has also been successfully used for construction of buildings, although this requires the manner of leaving inserts for openings like doors and windows to be decided well in advance, as well as also any necessary inserts to support floor slabs after the walls are constructed.
Engineering for Municipal Services
Basics of Municipal Engineering
Municipal engineering deals with many fields concerned with city planning and maintenance. This should not be confused with urban design because urban engineering involves planning the layouts of the streets and placement of buildings and other public places. Engineering for municipal services involves planning, designing, and maintaining the water and drainage systems, the transportation systems, and taking into consideration the various factors like the natural level of the local water table, what dangers the city may be exposed to, and the soil and underlying geological conditions. Urban designing is like designing the body of a car and municipal engineering is like making the entire car, right from the smallest component to the biggest, work the way it was intended to.Waste management, managing water services, hydrology, and providing engineering in vulnerable zones are some of the major responsibilities of municipal engineers.Geology
The condition of soil and the condition of the water table are studies initially done before the first bricks are laid for building the city. This initial phase will prove to be the most important phase in ensuring the safety of people who will reside in the area for years, or perhaps centuries, to come.This series of five articles covers the basics of soil mechanics and should be of interest to those in the geotechnical and civil engineering fields, as well as agriculturists.The study of hydrology includes a variety of topics on management of water resources, including what the term "100 year flood" means, the steps of the water cycle, understanding the water cycle diagram, and how to predict when a flood crest will reach a town. There are three articles in this series.Waste Management
To keep a city clean, waste must be disposed of properly. Waste in the form of garbage, household wastes, and human wastes should be taken far away from city where it can be processed. To carry the wastes to the edges of the city, proper sewage systems have to be implemented. Even the early Romans understood the importance of proper sewage and drainage systems, and records show that their drainage systems were impressive even by today's standards.Other ways of keeping the city clean is by sweeping the streets and making sure that garbage trucks do their duty. Here are a few resources with which you can learn more about waste management and why it is essential to a city’s functioning.Water Services
Water is an important resource for every living being. It is the responsibility of the municipality to provide the people of the city with purified water devoid of any harmful substances. Although this may seem simple, some very complex planning and maintenance goes in making sure that every house in the city is provided with clean water. The engineers who are responsible for this take care of a variety of jobs. They design and maintain the water treatment plants, make sure that the water is not polluted, and make sure water is provided to the residents throughout the year.Municipal Engineering in Vulnerable Zones
Not every city can be built on stable plains. Cities are built on hills, in earthquake prone areas, on or near coastal areas, and in other landscapes of various descriptions. Designing cities in such places requires meticulous planning and taking into account the various dangers posed by nature to the residents living in such areas.The Future of Municipal Engineering
From the Romans to the 21st century, things have changed a lot. With the advancement in technology, certain things have only gotten worse, for instance, the climatic conditions. The drastic changes in the climatic patterns across the world has lea to a growing awareness of global warming and its effects. Modern municipal engineers take this seriously and are slowly moving forward in making every municipal service ecologically friendly and green.Going Green in Communities (in the Green Living Channel)
Highway Construction & Engineering
- Highways connect two or more places and ensure that industries, employment, and development follow. Bridges, traffic lights, pavements, bike paths, and lane dividers make up a safe highway. Modern highways are known for their high capacity, efficiency, and planned construction. Highway networks are very important for the growth of a region. Highways open new trade routes and almost every industrial region in the world is connected to the major highway network system of that particular country.The topics collected in this guide will help you understand much of the terminology and theory of modern day highway engineering and construction. By using the links in the following sections, we will learn about different aspects of highway construction, design, and planning. We begin with the history of highway construction and the major changes highway construction has undergone up to this point.
History of Highways - From Dirt Tracks to Highway Bridges
Animals trails and dirt tracks were the first ever roads that human beings used to travel from one place to another. Icknield Way in England, Harrappan Roads in India, and Apian Way in Rome are examples of ancient roads, and their traces can still be seen. Gradually, human beings started moving out and the condition of roads also improved with time. Today we have highway bridges as high as 245 meters from the ground level.Various Aspects of Designing and Constructing a Highway
Planning remains the most important part of the process of engineering construction, irrespective of the nature and type of construction. Planning works are followed by design works and once designs are completed, execution works are started. Planning is important because global population is increasing at an exponential rate; globalization and technological advancements have made things easier for people, but challenging for engineers. Planning helps in estimation of risks, capacity calculation, and it enables engineers to leave scope for any future modification or expansion of roads or bridges. In this section we find insightful articles about building roads over swamps, geometric design considerations of highways, and design aspects of constructing bridges. Articles related to highway road project management are also discussed in this section.- Geometric Design of Highways and Roadways
- Building Roads Over Swamps - An Engineering Guide
- Highway Road Project Management - Role of Manager
- Design Considerations for Bridge Construction Works
- Cost Effective Pavement Maintenance Methods
- Modern Bridge Construction Methods
- Working With Concrete - Repair of Concrete Cracks
Highway Construction Materials
Highway construction materials are selected on the basis of the type of highway, known and projected traffic density, and the climatic conditions of the region. At some places we manage with bitumen (asphalt) only, however, at some place concrete roads are required. Modern age engineers emphasize the use of eco-friendly methods to construct roads, bridges, and pavements. Maximizing the use of recycled waste products is a smart new trend that has actually helped in making better roads and highways- without doing much damage to our environment. In this group are articles about the importance of constructing green pavements using recycled waste products, using air entrained concrete in construction works, and an interesting comparison of concrete and asphalt roads.- Constructing Green Pavements - Effective Use of Recycled Tires
- Comparison of Asphalt and Concrete Roads
- Benefits of Using Air Entrained Concrete
- Effective Use of Recycled Concrete for Road Construction Works
- Paving Coatings to Fight Air Pollution
- Using Rubberized Asphalt Concrete for Road Construction
- Decomposed Granite for Road Building
Highway Safety Guidelines
Highway safety is an important aspect of highway construction and engineering. Designing a highway means adopting safety measures so that not only vehicular traffic stays safe, but the pedestrians and bikers also feel safe while moving on the highway. Bott's dots, traffic lights, pedestrian marking, zebra crossings, and traffic circles are some of the important aspects of highway design safety. GPS-based road traffic monitoring systems are one of the modern age inventions that make our road travel safe and efficient. Even bike traffic is also considered while safely designing the highway. Articles related to highway safety are discussed in this section.- Bott's Dots and Safe Driving
- Working of Traffic Light Systems Explained
- Roundabouts, Traffic Circles, and Modern Age Traffic
- GPS based Road Traffic Management System
- The Visual Signals of the Kanban System
- Safety Considerations for Safe Bike Paths
- Rumble Strips and Centerline Ruble Strips Create Safer Roads
- Responding to Rockfall Hazards Around Mountain Roads
- Guide to Road Traffic Safety Barriers
Wrapping Up
The articles included in this guide will provide a great information source for those interested in highway design and construction processes. These articles cover the most fundamental aspects of transportation engineering and also let you know about major design and planning considerations related to highway safety and operations.Are there additional topics in road construction, maintenance, and design that you would like to see covered at Bright Hub? If so, please add your suggestions in the comments section below. Please note that comments are moderated and will take some time to appear.
