How Tower Cranes Build Themselves

When it comes to building skyscrapers, there is no piece of construction equipment more essential than the tower crane. These heavy lifting machines dominate city skylines, hoisting materials and machinery to some of the highest construction sites on Earth.

They have become a part everyday life in almost every major city as contractors race to build high-rise after high-rise, and more than 100 000 can be found in operation around the world at any given time.

Despite how common tower cranes are, they often seem to appear in the sky out of nowhere leaving many of us wondering how they got there in the first place.

The vast majority are erected using mobile cranes that are larger in size, but obviously this cannot always be done when you are building a record-breaking structure and taller cranes simply don’t exist.

Some construction sites in dense urban areas may not have enough space for a large mobile crane either, and many projects also require tower cranes to be erected in stages so that they rise in unison with the constructer portion of the building.

In these scenarios, the cranes must raise themselves to the final working height all on their own using a method known as climbing, and that is what we will be looking at in this post.

In general terms, climbing a tower crane simply refers to the process of adding or removing sections of the mast in order to increase or decrease the overall height.

The concept is fairly straightforward in principle, but it is quite difficult to execute safely in the field with catastrophic consequences if anything should go wrong. It is one of the most dangerous operations that can be performed with a tower crane, and it is only carried out when absolutely necessary to complete a project.

Before climbing can begin, a tower crane must first be erected to an initial height using a suitable mobile crane.

The process begins by constructing a stable foundation, which usually consists of a large concrete slab reinforced with steel rebar, and this takes place about a month before the crane goes vertical so that concrete has enough time to cure.

Once the concrete has reached its full strength, the first steel truss section of the mast is lifted into place, and it is secured with anchor bolts that are embedded in the foundation. Additional sections are then stacked on top of one another to complete the tower portion of the crane, and they are fastened together with high-strength steel bolts.

The mast is topped off with a slewing unit, which is basically a turntable that allows the top of the crane to rotate, and this serves as base for the operator’s cab and lifting components.

The exact arrangement of the top assembly varies depending on the type of tower crane, but the one shown here has a hammerhead configuration with a cathead and a fixed jib that cannot be moved up or down.

The cathead is the first component to be installed on top of the slewing unit, followed by the counter jib and working jib, and these are connected with steel tie rods that help to transfer loads to the mast.

Once the top assembly is complete, a counterweight is then added to the counter jib, which normally consists of several concrete slabs.

The counterweight helps to balance the load when the crane is performing a lift, effectively reducing the bending moment, or torque, that must be carried by the mast.

Since the working jib is fixed on this particular crane, a trolley system must be used to adjust the radius of the hook so that the load can be positioned closer or further from the mast. This is not the case luffing jib tower cranes, however, as they can adjust the radius simply by raising or lowering the working jib.

In either case, the ability to change the position of the load makes it possible to perfectly balance the crane on top of the mast, and this is essential for the climbing process to be carried out safely.

When a tower crane is ready to be climbed, a steel climbing frame is first assembled around the base of the tower, and it is lifted up to the underside of the slewing unit. The frame has a square cross-section with a lattice structure around three sides, but the front is left open so that new mast sections can pass through.

The top is securely fastened to the underside of the slewing unit with high-strength steel bolts, and a hydraulic jack at the bottom is positioned over a push point on the existing mast.

A new mast section is then hoisted up to the frame, where it is either placed on a steel tray or suspended from a guide rail that extends out above the opening. At this point, the top of the crane must be perfectly balanced over the jack before it can be lifted, which is accomplished by placing a weight on the hook to offset the counterweights.

An additional mast section is typically used for this, and it is positioned at a precise radius from the mast so that there is no net moment applied onto the climbing frame.

The crane top essentially behaves like a large balance scale during the climb, and it could topple off the mast if its center of gravity is not in line with the jack. In addition, the climbing frame is not designed to carry significant torsion, and it is extremely important that the crane is not slewed during the climbing process.

The new mast sections are therefore arranged in a straight line on the ground to eliminate any need to rotate the crane, and the operator will usually leave the cabin during the climb so that the crane cannot be slewed accidentally.

Once the crane is confirmed to be in balance and all safety checks have cleared, the hydraulic cylinder is then pressurized to take the weight of the crane top, and the slewing unit is unbolted from the top of the mast.

The cylinder is used to lift the climbing frame along with the top of the crane until there is enough clearance to insert a new mast section, which usually requires several strokes depending on the cylinder’s length.

The mast section can then be maneuvered inside the frame, where it is bolted to the underside of the slewing unit, and the hydraulic cylinder is depressurized so that the bottom of the new section engages with the top of the existing mast.

After the joints are securely fastened, the cylinder is retracted and repositioned on the next push point, and the whole cycle can repeat until the crane reaches the desired height.

One the process is complete, the climbing frame will either be lowered down the mast or removed entirely until it is needed to raise the crane higher or to bring it back down at the end of construction.

11 Common Types of Cranes

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11 Common Types of Cranes

1. Floating Crane :

A floating crane is a ship with a crane specialized in lifting heavy loads. They are useful for loading and unloading heavy items to and from ships. They are also used for transferring equipment from one vessel or platform to another, moving around equipment on the sea deck, and recovering or placing equipment on the seabed.

2. Harbour Cranes:

They are normally used in harbour container lifting operations. Due to their compact design, Harbour Cranes are the world‘s most flexible and powerful cargo handling equipment in ports and container terminals. Today, they can be electrified by means of powerful motorized cable reels, largely keeping their flexibility and agility within the quay infrastructure.

3. Crawler Cranes:

They can move around on site and the crane is stable on its track without outriggers. The main advantage of crawler cranes is that they can move around on site and perform each lift with little set-up, since the crane is stable on its tracks with no outriggers. An additional advantage is that crawler cranes are capable of traveling with a load.

4. Rough terrain Cranes:

They are mounted with four rubber tires and specifically designed to operate on OFF-ROAD and ROUGH surfaces.

All terrain cranes are considered as the luxury version of a mobile hydraulic cranes, used in common construction sites.

5. Truck mounted Crane:

It is a self propelled loading-unloading machine mounted on a truck body.

6. Level Luffing Crane:

A level luffing crane is a crane mechanism where the hook remains at the same level whilst luffing.

7. Railroad Crane:

A railroad crane is a type of crane used on a railroad for, accident recovery work, permanent way maintenance or freight handling in goods yards.

8. Tower Cranes:

Tower cranes are commonly used in construction of tall buildings.

9. Side Boom Cranes:

They are commonly used to lift industrial pipes lines. Side booms are built to meet the unique demands of pipeline customers.

10. Aerial Cranes:

An aerial crane or flying crane is a helicopter used to lift loads.

11. Gantry Crane:

A gantry crane is a crane built at the top of a gantry, which is capable of lifting some of the heaviest loads in the world.

Railway Switch and Crossings – How train change the track?

Railroad track Crossing is the most important steering system in the railroad track. It consists of two parallel steel rails set a fixed distance the standard gauge is 4 feet 8.5 inches.

In the track change process, the inner rim of the wheel called a flange is comparatively greater in diameter than the outer part which prevents the wheel from sliding off the track.

Switchs:

Switch rails or point blades are the movable rails that guide the wheels towards either the straight or the diverging. Track stock rails are the running rails immediately alongside the switch rails against which the switch rails lay when in the closed position points operating rods.

Point blades

Stock Rail

Points operating machine also known as a point switch machine or switch motor is a device for operating railway turnouts especially at a distance.

POE Rods

Points Operating Equipment

Crossing:

Crossing is a pair of switches that connect two parallel rail tracks allowing a train on one track to cross over to the other check rails also known as guard rail laid parallel to a running track to guide the wheels. All these rails are non-movable.

Rail track Crossing

Crossing nose as a device on introduced at the point where gauge faces cross each other to permit the flanges of the railway vehicle to pass from one track to another.

Crossing Nose

The Main Railway Track Components

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The Main Railway Track Components

The distance between the two tracks on any railway route is known as railway gauge. The wooden or concrete supports for the rail tracks are known as a sleeper as British English or cross tie as American English.

Railway Gauge

Sleepers:

A sleeper is a rectangular support for the rail tracks. It is laid perpendicular to the rail sleepers and transfer loads to the track ballast and subgrade.

Sleepers hold the rails upright and keep them spaced to the correct gauge.

Sleeper

Railway Fastening System

Ballast:

Ballast is the name for the stones beneath the track. It forms the track bed upon which railroad sleepers are laid and is used to bear the load from the railroad ties to facilitate drainage of water and also to keep down vegetation that might interfere with the track structure.

Railway Ballast

The ballast also holds the track in place as trains roll over it and absorb the noise. It typically consists of a crushed stone rail fastening system. It is referred to as a group of railway fasteners that are used to fasten steel rail to railway sleeper.

Fish Plate:

Fish plate is used to join two different rail tracks without welding leaving some gaps at the joining of the track so that when they get heated it doesn’t bend. There are foor bolts that hold up the tracks together.

Fish Plate

Rail Track GAP

There is another type of fish plate called juggled fish plate. This is a specially designed fish plate with convexity in the center to accommodate weld collar at newly welded joints to protect defective welded joints and to carry out emergency repair of weld failures.

Joggled Fishplate

How Bridges Are Built Over Water?

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How Bridges Are Built Over Water?

Bridges are marvels of engineering that stand inconspicuously amongst us. We don’t think of them much even when we are passing over them. Nowhere are these structures more impressive then when the are built over water, which brings us to the question how are bridges built over water?

When the water is shallow, construction is easy. A temporary foundation is made on which piers are built to support the upper structure and the bridge is then built! It’s when the water is deep that other techniques are needed.

There are many methods to complete such as task in deep water but here we will explore the main three. These three methods of bridge building are called battered piles, cofferdams and caissons.

Battered Piles:

These are poles that are driven into the soil underneath the water. Piles are hammered into the water until the turn outward or inward at an angle. This makes the piles firm and increases their ability to carry lateral loads.

Piles are inserted in the ground using pile drivers. These are mechanical devices that may be transported to a location on a floating pile driving plant.

Battered Piles at a bridge project in Sweden

Pile drivers may also be cantilevered out over the water from piles that have been installed in advance. With the use of pile frames, pile hammers and winches, pile drivers hammer the piles into the soil until the turn outward or inward at an angle. The pile are now ready to carry lateral loads and can provide the foundation of support for the bridge.

The next step is to construct the pile caps above the piles. Once this is done, the bridge is ready to be built.

Cofferdams:

These are temporary enclosures made be driving sheet piling into the bed of a body of water to form a watertight fence. This is called the cofferdam. There is more to this bridge technique. Once the sheet piles have been inserted in the water to create a cofferdam, the water is pumped out of the enclosure.

Now, the construction workers can built the bridge as if the are working on dry land. The process then becomes relatively easy.

Cofferdam

Caissons:

There are two types of caissons, open and pneumatic.

An open caisson is a structure that is usually shaped like a box. It is open, at the top and bottom. The caisson is usually constructed on land then floated into position and sunk, so that the upper edge is above water level.

The caisson has a cutting bottom edge so that it sinks through soft silt on the bed. Inside is a series of large pipes or dredging wells. These are used to dredge up the bed material. As more material is dredged up, the caisson sinks and more sections are added to the shaft to keep it above water.

Once the caisson reaches the correct depth, concrete is laid to seal the bottom and then more concrete is poured into the caisson to form a solid post.

Steel Open Caisson

A pneumatic caisson is similar to an open caisson but it has an airtight bulkhead above the bottom edge. This is fitted with air locks. The space between the cutting edge and the bulkhead is called the working chamber. In this space, the water is removed using air pressure. Construction workers can then enter the chamber and excavate the soil.

It is important that the air pressure in the chamber be carefully monitored so the workers do not get the bends.

Pneumatic Caisson

But how do engineers pick which technique to use?

This all depends on the condition of the site and the technology available. These are important decisions to make that only exports can fully handle.

Structural Analysis Of Building Offices Spreadsheet

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What You Need To Know About Concrete

Concrete is as much a part of the urban landscape as trees are to a forest. It’s so ubiquitous that we rarely even give it any regard at all. But underneath that drab grey exterior is a hidden world of compexity.

Concerete is one of the most versatile and widely-used construction materials on earth. It’s strong, durable, low maintenance, fire resistant, simple to use, and can be made to fit any size or shape from the unfathomably massive to the humble stepping stone.

However, none of those other advantages would matter without this : it’s cheap. Compared to oter materials, concrete is a bargain and it is easy to see why if we look at what’s made of.

Concrete has four primary ingredients : Water, sand (also called fine agregate), gravel (aka coarse aggregate) and cement.

A recipe that is not quite a paragon of sophistication, one ingredient falls from the sky and the rest essentially straight out of the ground. But, from these humble beginnings are born essentially the basis of the entire world’s infrastructure.

Actually, of the four, cement is the only ingredient in conrete with anay complexity at all. The most common type used in conrete is know as Portland cement. It’s made by quarried materials (mainly limestone) into a kiln, then grinding them into a fine powder with a few extra herbs and spices.

Cement role :

Cement is a key constituent in a whole host of construction materials, insluding grout, mortar, stucco and of course concrete. A lot of people don’t know this, but every time you say cement when you were actually talking about concrete, a civil engineer’s calculator runs out of batteries.

The cement key role es to turn concrete from liquide to a solid. Portland cement cures not through drying or evaporation of the water, but through a chemical reaction called hydration.

The water actually becomes a part of cured concrete, this is why you shouldn’t let concrete dry out while it’s curing. Lack of water can prematurely sop the hydration process, preventing the concrete from reaching its full strenght.

In fact, as long as you avoid washing out the cement, concrete made with Portland cement can be placed and cured completely under water. It will set and harden just as well (and maybe even better) as if it were placed in the dry.

Aggregate role :

But, you may be wondering « If water plus cement equals hard, what’s the need for the aggregate ? ».

To answer that question, let’s take a closer look by cutting this sample through with a diamond blade. Under a macro lense, is tarts to become obvious how the individual constituents contribute to the concrete.

Aggregates for Concrete

Notice how the cement paste filled the gaps between the fine and coarse aggregate. It serves as a blinder, holding the other ingredients together.

You don’t build structures from pure cement the same way you don’t build furniture exclusively out of wood glue.

Instead we use cheaper filler materials – gravel and sand – to make up the bulk of concrete’s volume. This saves cost, but the agregates also improve the structural properties of the concrete by increasing the strenght and reducing the amount of shrinkage as the concrete cures.

The reason that civil engineers and concrete professionales need to be pedantic about the difference between cement and concrete is this : even though the fundamental recipe for concrete is fairly simple with its four ingredients, there is a trmendous amount of complexity involved in selecting the exact quatities and characteristics of those ingredients.

In fact, the process of developing a specific concrete formula is called mix design. One of the most obvious knobs that you can turn on a mix design is how much water is inluded. Obviously, the more water you add to your concrete, the easier if flows into the forms. This can make a big difference to the people who are placing it. But, this added workability comes at a cost to the concret’s strenght.

How to Improve Collaboration and Communication Between Construction Teams

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How to Improve Collaboration and Communication Between Construction Teams

Effective collaboration and communication between different teams are key when it comes to construction projects. As a project manager, it is your task to ensure that all your teams work like a well-oiled machine. Problems with communication and collaboration can lead to a lot of issues for your project, including scheduling issues, poor work performance, sunk costs, and wasted time. Your management style must go beyond delegating tasks and organizing processes. You need to build relationships between your workers and give them the means to collaborate in an optimal way.

However, achieving the aforementioned goals is not as easy as it might look. In order to be successful, you need to combine smart coaching skills, strategic thinking, and technology. In this article, we will provide you with some practical advice on how to improve the collaboration and communication between different construction teams that work on the same project.

Ensure Open Communication

One of the fundamentals of enabling good internal communication, no matter the number and size of your teams, is to form open communication lines. All team members need to feel that their opinion is respected, valued, and sought-after. Each individual needs to feel like an important part of the team — as a result, information will go up and down the chain without any interruptions.

Project managers need to stay on top of all details surrounding a project, which means that you must have up-to-date information at all times. Keeping communication open will ensure no information is kept from you, which will prevent issues during all phases of your construction project.

Think Strategically

When organizing the communication and relationships between your teams, keep in mind that construction projects tend to take several years to complete. The people you work with need to be willing and able to work together efficiently for a prolonged period of time. On top of that, construction teams that really stick tend to go on working together for their entire careers.

Make sure your team is composed of professionals who are not in this particular field of work only temporarily. Find people who want to keep working in the field, as they will be more motivated to form strong work bonds, communicate efficiently, and keep on improving themselves.

Build Relationships

The work surrounding construction projects usually does not encourage lots of interaction between people. In fact, many workers are solely focused on their own tasks and only communicate with others when it is necessary. In order to build a strong team that collaborates and communicates efficiently, you need to take your people out of their comfort zone and make them interact with one another.

A great way to achieve that is to organize team-building events. It is not necessary to spend money on dinners, hotels, and such — a simple game of soccer outside of working hours can achieve the same thing. Socializing outside of the usual work environment works wonders in building relationships between co-workers. Going out to a bar or organizing a party will strengthen the bonds between your people and ensure your project goes smoothly.

Enable Your Leaders

Team managers ought to be your right-hand people when it comes to implementing your communication and collaboration strategies. They need to be aware of the goals you are trying to reach and actively help you to achieve them. Meanwhile, you should motivate them to practice what they preach and keep them included in the decision-making processes.

If you and your managerial staff are on the same page, executing the plans on this list will be quicker. Leaders must set an example and be the driving force behind any change in work culture and organization. Of course, you need to be aware of the so-called “informal leaders” among your teams. Sometimes, such individuals perform even better as agents of change.

Make Effective Use of Data

Modern technologies have allowed managers to access all types of different project data and use it to improve their work. When it comes to communication and collaboration, you need to properly use the available data in order to improve both. Task management systems can be especially helpful for keeping different teams up to speed on specific aspects of the project.

Use data to track progress and manage any inefficiencies in your teams’ work. Having all teams collaborate using the same datasets will help you with scheduling, optimizing resources, and avoiding any duplicate work.

Use BIM Software Solutions

Perhaps the most effective way to improve collaboration and communication between different construction teams is to utilize BIM tools. Building information modeling (BIM) software started out as a means to generate accurate 3D modeling. However, it has evolved into a full-service suite that can help you with all aspects of managing a construction project.

BIM software allows large teams to seamlessly collaborate on a project in real-time since it uses cloud technology. This way all your workers have access to the same plans, data, and schedule at the same time. Modern BIM solutions have a lot of useful collaboration and communication tools, as well as complex 3D visualizations that can be especially effective when it comes to clash detection, on-site safety measures, and overall risk mitigation.

Conclusion

Even the best construction project manager cannot take on a project entirely by themselves. You need your teams to be motivated, energized, and collaborating in the most optimal way. Communication and teamwork are key to the successful completion of a project, no matter its size and scope. Do not limit yourself to just a person who hands out the tasks. Be a leader and build a team that can go through even the toughest challenges together.

About the Author:

Sofia Jaramillo is an Account Executive for the Pacific Northwest area at Microsol Resources. She was born and raised in Colombia, where she got her Business Administration degree. She moved to New York in 2016 and joined Microsol in 2018 where she has found a new passion within the field of design and construction. In her free time, she likes to practice yoga and run in Central Park.

Water Towers Types

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Water Towers Types

Water towers are used as a local source of water at times of peak demand where it would not be economical to increase the size of the supply pipeline and add a booster pump installation.

In undu-lating terrain ground-level storage can provide the pressure needed but in areas of flat topography the storage must be elevated. Many shapes and design features are possible but the designer should aim to produce a structure that meets the requirements of both water supply and planning authorities, bearing in mind that it will become a landmark in the community which it serves.

Ancillary equipment including pipework, valves, ladders, instrumentation and booster pumps, if required, can all be hidden in the cylindrical shaft.

The optimum depth/diameter ratios should be determined taking into account the most efficient shape and the needs of the distribution system. It is usually advisable to avoid large pressure fluctuations in distribution that may be caused by draw down or filling in excessively deep tanks.

The main types of water towers are:

1- Concrete water towers:

Concrete water towers are built with capacities up to about 5000 m3. They are usually circular in plan although rectangular concrete towers have been built. The diameter of circular water towers is not usually sufficient to warrant the use of prestressing since cracks can be controlled by applying normal water retaining concrete criteria.

Concrete water towers allow some scope for architectural statement so that the result can be regarded as a visual asset.

Reinforced concrete water tower

Rectangular water towers are designed as small monolithic service reservoirs with the floor slab supported on some form of open column and beam framework or on a hollow vertical shaft, it self founded on a base slab, piled if necessary.

Wind and seismic loads should be taken into account in the design of tank, supports and foundations. Circular concrete water towers allow more scope for different styling from a simple cylinder with a flat base to a sophisticated form such as the hyperbolic-paraboloid of the 39 m high Sillogue tower near Dublin airport built in 2006.

Sillogue Reservoir

In this case the vase shape resembles an inverted version of the nearby control tower. The Intze type water tower (Rajagopalan, 1990) is designed so that bending moments are as near zero as possible at all sections.

Reinforced concrete water tower (Intze type)

2- Welded Steel Water Towers

Relatively small welded tanks have been used for over 100 years for industry and rail transport.These were usually small radius cylinders supported on a framework of steel columns with braces or ties.

Welded steel water towers of capacities up to 15 000 m3are now available and have been widely used all over the world, particularly in North America, the Middle East and the Far East.

These are now constructed of butt welded steel plate in several configurations: spheroids or ellipsoids on tubular columns belled out at the base; cylindrical or spherical shapes with conical bases and supported on wide steel columns which help resist seismic loads and provide space for plant rooms or offices or on a reinforced concrete frame.

Whilst the forms available for welded steel water towers do not offer much scope for architectural treatment, the coatings provide an opportunity for decoration and can be attractive.

Welded Steel Water Towers

3- Segmental Plate Tanks

The type of steel or GRP panel construction can also be used for elevated storage. However, it is unlikely that segmental plate tanks would be used for anything other than industrial or emergency water storage since their poor visual appearance is exaggerated by height.

Where they are used, the bases are placed on a series of beams which are supported on a framework of braced columns.

GRP Water Storage Tanks

The Benefits Of Machine Control and GPS

What Is GPS and How Does It Work?

GPS is a product of the Cold War. Developed by the US military during the President Reagan years, this system consists of a series of 24 satellites in geosynchronous orbit. That is, these satellites remain in the same fixed location in the sky. Out of 360 degrees of longitude, each satellite covers a 15-degree sweep of the globe. They orbit the earth twice each day, broadcasting a timing signal. These signals can be intercepted by ground antennae mounted on ships, tanks, planes—or the buckets and blades of heavy earthmoving equipment.

Though, like all broadcast signals travelling at the speed of light, there is a small-but-measurable time lag between the signals from adjacent satellites. The difference, measured in milliseconds, allows for the triangulation between the ground antennae and the satellites emitting the signal. This triangulation measurement allows for the measurement of the precise location (measured in latitude, longitude, and elevation above sea level) on the surface of the earth where the receiving antennae is currently located. As is true so often in the history of technology, a technical advancement meant for use in war has been modified and adopted for peaceful civilian applications. A system intended to track the movements of men, weapons, ships, and war planes is now used to follow the movements of commercial shipments, find lost hikers, and guide construction equipment.

GPS guides equipment operations through their Automated Positioning Report System (APRS). Using triangulation between the several of the system’s broadcasting satellites allows for positional measurements with accuracies up to 30 centimeters (1 foot). The use of APRS increases this accuracy to 1 centimeter when used in conjunction with GPS. What APRS does is integrate GPS with the equipment’s controls. An APRS replaces the manually operated hydraulic drive cylinders traditionally used to control the movements of an excavator’s arm or dozer’s blade with electronically controlled servo-type valves. These servos send an electric current that creates magnetic field that rotate suspended armatures, that are further connected to fixed flapper arms. These flapper arms provide the linkage to the rotary spools that increase and decrease hydraulic pressure to the hydraulic systems. These are part of the closed-loop hydraulic system that controls the direction, flow rate, and applied pressure of the hydraulic fluid.

Going from individual pieces to equipment to an entire fleet of equipment or trucks is also easily managed by GPS applications. This allows a fleet owner to coordinate and choreograph the movements and activities of an entire fleet of earthmoving equipment and also track the locations of trucks delivering material to the site or hauling dirt away for disposal. Like pieces on a chessboard (or, more accurately, objects in a video game) these activities are tied to an onsite digital terrain model (DTM) of the project site.

This is a three-dimensional (3D) model created by an AutoCAD program, which utilizes a patchwork of connected triangles. The corners of each triangle is defined mathematically by three special coordinates (northing, easting, and elevation). While not a perfect match (no model ever is) to the actual terrain, this geometric surface comes the closes to matching actual surfaces. This is especially true for post construction or excavation surfaces, which tend to be regular and smooth.

Leica excavator machine control solution

The software interacts with the model and the equipment hardware via sensors attached to the business end of the machine (the edge of the dozer blade, the teeth of an excavator bucket, etc.). These sensors continuously record and update the movements of the equipment using the same 3D location system as the DTM. The sensors relay their current location back through the system to the operating controls, which in turn direct the movement of the equipment in accordance with the programmed DTM for the proposed construction surface or excavation grades.

Coordinating all of the mobile GPS sensors on each piece of equipment is a stationary GPS sensor combined with an antenna with a receiver called the base station that is set up adjacent to the operating area. The base station is permanently located over a pre-surveyed reference point, such as a third order benchmark that has been established by ground survey. If necessary, some relative location (manhole rims, street curbs, and building corners, etc.) whose elevation is not exactly known but can be treated as a local datum for the project area can also be utilized for ground antennae setup.

Grader GPS Control

The hardware for these control signals consists of a control box connected to the servo valves via electrical cable, which, in turn, connects to the hydraulic control system that physically moves the equipment. It is the incoming satellite data from the GPS system that tells the equipment where it is. The DTM design files are stored in a compact-flash memory card, memory stick, or accessed externally from data broadcast by the site’s controlled area network (CAN). The database, CAN, and GPS operate in real time to place a blade or bucket exactly where it needs to go and move it so that it accomplishes its task with the need for rework or wasted effort. All three elements, mobile sensors, base sensors, and equipment operator are in continuous communication with each other. The blades and buckets simultaneously move back and forth, up, and down in combination to achieve the desired movement.

Where and When Is GPS Best Used?

The advantages of using GPS guidance systems are legion. Using advanced systems, an operator can increase productivity by greater than 50% compared to purely manual operations. The increase in productivity comes indirectly by the avoidance of having to perform rework at the site. Guided by GPS, an equipment operator can get his cuts and placements right the first time. Furthermore, material wastage is minimized. GPS doesn’t necessarily increase the number of productive hours per day so much as it makes every hour a machine is active much more productive.

This has all sorts of secondary benefits and cost savings. Getting the most out his earthmoving equipment allows a contractor to get the most out of his workforce as well. This reduces labor costs, another costs savings, while reducing the impact of local labor shortages—always an issue in a booming economy with a considerable amount of construction activity. Furthermore, grades and elevations can be checked in real time as the work is being performed. The operator can check his elevation from within his cab as he is working. There is no more need to stop work at regular intervals and have a manual survey performed of the work zone to check its accuracy. In the past, the accuracy-checking task has traditionally relied on a crewmember inside the trenches to manually check depths and slopes. Now with these systems, the need for that task is greatly reduced—thereby cutting job site costs and improving crew safety. This traditional cause of equipment downtime is mostly avoided with the use of GPS.

Giving operators the tools to perform accuracy checks also gives greater responsibility, initiative, and job satisfaction. The additional training that the operators receive has the effect of empowering them, increasing senses of purpose and self-worth. This alone has a marked, if indirect, impact on productivity. By eliminating rework and improving employee morale, any money spent training operators on GPS is a wise investment that pays for itself very quickly. Human factors also show improvement in the area of site safety. The precision guidance and ability to choreograph equipment movement across a busy site improves safety by maintaining safe work zones, avoiding known utility locations, preserving the foundations of existing structures, and maintaining a safe flow of traffic.

GPS systems are often augmented by laser guidance for precise finish work. Lasers can compensate for some of GPS limitations. GPS works best with an open sky and no significant overhead blockage. (For example, GPS is not used for tunneling operations.) Laser guidance stations and targets mounted on equipment blades can work in any outdoor situation, with or without overhead blockage from trees and tall buildings. GPS, however has a much greater effective operating range, limited only by the availability of open sky. Lasers systems are usually limited to about 1,500 feet. GPS can allow for the construction of complicated surface models as well as flat, sloping surfaces. Lasers, being line of site instruments, are usually limited to operations on long, flat, or sloping surfaces. (Though they, too, can build surfaces as directed by a 3D design model represented by a surface AutoCAD file.)

Grade Control System

Productivity can be measured in many ways: time savings, labor costs, material costs, fuel costs, quality bonuses, and finish bonuses. It begins as early as the job layout.

With Machine Control and GPS, you don’t have to wait for someone to stakeout the project or weather that permits someone to stakeout. This allows you to get started sooner. Any design change will also benefit as productivity increase due to not having to wait for restaking.

As the operator starts moving material you will see great value in being able to move the correct amount of material, to the correct location, the first time. This, along with only using the exact amount of material, will translate into a productivity savings.

You can also use GPS by having job layouts of the site so the machines or supervisors’ tablets can have the precise storage locations of materials, job trailers, or site boundaries. This can help having the right things in the correct location or, better yet, not in the way, therefore reducing excessive handling of material.