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Dutch inaugurate the 3D Printed Reinforced Concrete Bridge Designed by Technical University of Eindhoven

3D printing has emerged in the recent past as a smart and quick alternative to many fields of production. Its applications in the field of construction are no exception. It is however relatively easier to handle 3D printing of small or medium sized products, ensuring stability, strength and durability in case of a structure for the built environment pose serious challenges.

The cycle bridge is part of the Noord-Om project which is a new section on the ring road around the village of Gemert in Netherlands. Although the team claims it to be World's 1st 3D printed bridge, there was already a 3D printed pedestrian bridge built this year in Madrid, Spain which in our opinion is the rightful deserver of the title '1st 3D printed bridge'. Another project was to be initiated by a company named MX3D to print a steel bridge with huge robotic arms but the project appears to be still.

Dutch inaugurate the 3D Printed Reinforced Concrete Bridge Designed by Technical University of Eindhoven

Inauguration of the 3D printed bridge in Netherlands (Image courtesy: BAM Infra)

This Dutch bridge is a practical bridge for cyclists which was printed using a custom built cement printer at the Technical Universty of Eindhoven. Individual layers each having a thickness of 1cm are printed by injecting liquid mortar into the printhead through the storage. Steel reinforcing wire is fed down before a layer dries and the process goes on. The printer builds up sections layer by layer which are approximately 1m high.

(Images courtesy: BAM Infra)

3D-printed concrete bridge from Royal BAM Group nv

Six of the printed sections were transported to the site to be glued together to form a bridge that is 8 m long, 3.5 m wide and is 0.9 m thick. During the testing phase, the bridge was found to support an imposed load of 5 Tons which is far greater than that of the cyclists. The expected life of the bridge is 30 years. The bridge was built by the company BAM Infra and the team claims to have gained valuable experience from this versatile project which will allow the members to print much larger sections for much bigger structures.

3D printing in construction has endless possibilities and benefits. A very important aspect is the economical use of cement and other materials. Another aspect is not requiring a formwork or minimum if at all needed which also saves costs and material wastage.

Hangzhou Bay Bridge, Jiaxing, China

1:04 PM Bridges , Civil Engineering , structures

The longest ocean-crossing bridge in the world, the Hangzhou Bay Bridge is an S-shaped stayed-cable bridge with six lanes in both directions that shortens the distance between Shanghai and Ningbo by 120 kilometers. The 36 kilometer long bridge required a great number of new techniques, new materials, new equipment and new theories due to the large scale and design of the project. It took close to 600 experts and a total of nine years to design the bridge. The Hangzhou Bay Bridge is expected to boost the economic development of the Yangtze River Delta, also called the Golden Industrial Triangle. Work on the bridge began in June 2003 and was completed in June 2007. The bridge was opened to the public in May 2008 and carried about 50,000 vehicles per day in its first year of operation. The total project cost was approximately $1.5 billion.

Construction

Hangzhou Bay is located in an area that has complicated geological conditions, is prone to typhoons and the Qiantang River Tide creates fast water and large waves. The tides frequently change direction making it difficult for construction vessels to maintain a position. Operations are only possible for half of the year and the seawater and strong currents have a corrosive effect on the steel infrastructure. Additionally, beneath the seabed lies large pockets of natural gas which would make any construction work in the area hazardous. Construction feasibility was a major concern and over 120 technical studies were carried out before any actual work started.

Hangzhou Bay Bridge (Image: Stuffpoint)

Engineers finally agreed on a cable-stayed bridge design because it could withstand the adverse conditions, multi-directional currents, high waves, and geologic conditions at the site. To ensure the bridge looks exquisite and grand, designers ensured that the aesthetics were prominent in every aspect from the shaping and color of each component, transitions between structures, choice of bridge deck systems, and structural lighting. From a bird’s eye view, the bridge is meant to look like a dragon nestled in the Hangzhou Bay.

To ward off the difficulty of onshore construction, engineers built some parts on land such as bridge foundations, piers and box girders. The steel piles were 71 – 88 meters in height and 1.5 – 1.6 meters in diameter. Numerous studies and tests were conducted by scientists before they finally settled on a spiral welding method as a suitable construction method for the steel piles. When they were completed, they were transported to the desired location and fitted in. Giant floating cranes with accurate anchoring devices and launching gantries were used to ship and erect these prefabricated components. Severe marine conditions also made it difficult for engineers to anchor barges and construction vessels. The floating cranes made it possible to transport the girder from the shore to the site and then anchor it stably to erect and install the precast concrete box girder.

In order to resist the corrosive effects of the seawater, engineers mixed a large quantity of coal ash and slag to the concrete to produce a special high-density variety. Silicone water repellents were also applied over the concrete and steel to protect the structure from salt water corrosion. The silicone water repellents are able to penetrate the pores of concrete and make the surface more resistant to water penetration. Engineers decided to tackle the natural gas issue by carrying out an exploration to investigate the distribution of the gas and the property of the soil during and after releasing the gas. The gas was then released before pile driving to avoid any disturbance to the soil, collapsing of ground or eruption and flaming of gas.

The entire structure of the Hangzhou Bay Bridge comprises of nine sections:

The first section is the bank lead road to the north approach.
The second section is the north approach that leads to the north navigable bridge; a cable-stayed bridge with twin diamond-shaped towers, double cable and steel box-girders.
The third section has north piers with continuous 70 meter, post-tensioned, concrete box-girder spans with a total length of 1,470 meters.
The fourth section is the middle bridge approach, laid on low piers with 70 meter, post-tension, concrete box-girder spans with a total length of 9,380 meters.
The fifth section is the south navigable bridge – a cable-stayed bridge with an A-shaped single tower, double-cable and steel box-girders.
The sixth section is the main span which is 318 meters.
The seventh section features the south high piers that has continuous 70 meter, post-tension, concrete box-girder spans with a total length of 1,400 meters.
The eighth section measures to a total of 19,373 meters, and is composed of three parts: an in-water section with girders and steel piles, a mud-flat section with girders and drill-shafts; and a land section with drill shaft foundations
The final section is the Bank Lead Road at the south approach.

A Global Positioning System (GPS) was used to monitor the progress of the construction which required precise positioning and accurate placing of piles and pre-fabricated sections of the bridge.

The middle of the bridge has a service island targeted towards drivers who can enjoy a full range of services, including hotels, restaurants, petrol stations and a viewing tower. It also acts as a tourist site for the Qiantang River Tide. During the construction, this offshore platform acted as a living and working base for the offshore constructors. It also served as a relay station for offshore survey and communication as well as an offshore location for emergency rescue and maritime administration.

The Hangzhou Bay Bridge was built to serve for 100 years and can stand up to earthquakes that measure seven on the Richter scale. The bridge has a height of 62 meters, which allows fourth and fifth generation container ships to pass through in all conditions. The Hangzhou Bay Bridge is a stellar example of the possibilities allowed by new innovations and technology in the world today.

Basics of a Bridge

11:28 AM Bridges , Civil Engineering

Because of the wide range of structural possibilities, this article shows only the most common fixed (non-movable) bridge types. The drawings are not to scale. Additional related info is found on the other Terminology pages which are linked to the left.

The four main factors are used in describing a bridge. By combining these terms one may give a general description of most bridge types.

Span (simple, continuous, cantilever), material (stone, concrete, metal, etc.)
Placement of the travel surface in relation to the structure (deck, pony, through)
Form (beam, arch, truss, etc.).

1. Span

The three basic types of spans are shown below. Any of these spans may be constructed using beams, girders or trusses. Arch bridges are either simple or continuous (hinged). A cantilever bridge may also include a suspended span.

2. Travel Surface

Examples of the three common travel surface configurations are shown in the Truss type drawings below. In a Deck configuration, traffic travels on top of the main structure; in a Pony configuration, traffic travels between parallel superstructures which are not cross-braced at the top; in a Through configuration, traffic travels through the superstructure (usually a truss) which is cross-braced above and below the traffic.

3. Form

Beam & Girder Types

Simple deck beam bridges are usually metal or reinforced concrete. Other beam and girder types are constructed of metal. The end section of the two deck configuration shows the cross-bracing commonly used between beams. The pony end section shows knee braces which prevent deflection where the girders and deck meet.

One method of increasing a girder's load capacity while minimizing its web depth is to add haunches at the supported ends. Usually the center section is a standard shape with parallel flanges; curved or angled flanged ends are riveted or bolted using splice plates. Because of the restrictions incurred in transporting large beams to the construction site, shorter, more manageable lengths are often joined on-site using splice plates.

Many modern bridges use new designs developed using computer stress analysis. The rigid frame type has superstructure and substructure which are integrated. Commonly, the legs or the intersection of the leg and deck are a single piece which is riveted to other sections.

Orthotropic beams are modular shapes which resist stress in multiple directions at once. They vary in cross-section and may be open or closed shapes.

Arch Types

There are several ways to classify arch bridges. The placement of the deck in relation to the superstructure provides the descriptive terms used in all bridges: deck, pony, and through.

Also the type of connections used at the supports and the midpoint of the arch may be used - - counting the number of hinges which allow the structure to respond to varying stresses and loads. A through arch is shown, but this applies to all type of arch bridges.

Another method of classification is found in the configuration of the arch. Examples of solid-ribbed, brace-ribbed (trussed arch) and spandrel-braced arches are shown. A solid-ribbed arch is commonly constructed using curved girder sections. A brace-ribbed arch has a curved through truss rising above the deck. A spandrel-braced arch or open spandrel deck arch carries the deck on top of the arch.

Some metal bridges which appear to be open spandrel deck arch are, in fact, cantilever; these rely on diagonal bracing. A true arch bridge relies on vertical members to transmit the load which is carried by the arch.

The tied arch (bowstring) type is commonly used for suspension bridges; the arch may be trussed or solid. The trusses which comprise the arch will vary in configuration, but commonly use Pratt or Warren webbing. While a typical arch bridge passes its load to bearings at its abutment; a tied arch resists spreading (drift) at its bearings by using the deck as a tie piece.

Masonry bridges, constructed in stone and concrete, may have open or closed spandrels A closed spandrel is usually filled with rubble and faced with dressed stone or concrete. Occasionally, reinforced concrete is used in building pony arch types

Truss - Simple Types

A truss is a structure made of many smaller parts. Once constructed of wooden timbers, and later including iron tension members, most truss bridges are built of metal. Types of truss bridges are also identified by the terms deck, pony and through which describe the placement of the travel surface in relation to the superstructure (see drawings above). The king post truss is the simplest type; the queen post truss adds a horizontal top chord to achieve a longer span, but the center panel tends to be less rigid due to its lack of diagonal bracing.

You may also like to learn to analyze trusses.

Geotechnical Studies in Planning of Bridges

12:43 PM Bridges , Civil Engineering , Transportation Engineering

Geotechnical studies in the planning of bridges should provide the following Information:

The types of Rocks, Dips, Faults and Fissures
Subsoil Ground Water Level, Quality, Artesian Conditions if any
Location and extent of soft layers
Identification of hard bearing strata
Physical properties of soil layers

Figure 1. X-sec of crossing over the Seine via the Bir Hakeim bridge and the limestone quarries under Trocadéro(Paris)

Traffic Studies in Planning of Bridges

12:21 PM Bridges , Civil Engineering , Transportation Engineering

Traffic studies need to be carried out to ascertain the amount of traffic that will utilize the New or Widened Bridge
This is needed to determine Economic Feasibility of the Bridge
For this Services of a Transportation Planner and or Traffic Engineer are required
Such Studies are done with help of Traffic Software such as Trans CAD, EMME2 etc.
Traffic Studies should provide following information
- Traffic on Bridge immediately after opening
- Amount of traffic at various times during life of the Bridge
- Traffic Mix i.e. number of motorcars, buses, heavy trucks and other vehicles
- Effect of the new link on existing road network
- Predominant Origin and Destination of traffic that will use the Bridge
- Strategic importance of the new/improved Bridge

Introduction to Under Water Concreting

4:29 PM Bridges , Civil Engineering , Construction Materials , Special Concrete

Placing concrete under water is a specialized subject and should be avoided whenever practical to do so . Where concrete works have to be constructed below water level as in the case of marine works, deep foundations of bridges etc; one of the two courses may be adopted. Either water may be excluded temporarily from the site by using cofferdams, caissons, pumps, dewatering equipment OR Concrete may be placed in water using special methods.Whilst concrete will set and harden under water its placing presents several problems. The most difficult is the prevention of segregation and loss of cement. Formwork except for simpler forms of construction, is difficult to place accurately and in all cases must be anchored firmly. In view of these difficulties, underwater concreting in generally confined to mass un-reinforced work and consideration should always be given to use of pre-cast block for the whole work or as permanent formwork.

General Requirements

Concrete should not be placed underwater when the temperature of water is below 4°C.
It requires a very workable concrete with slump as high as 7" and cement content upto 650 Ibs/cuyd.
Placing is done in caissons, confer dam or forms.
Foundation clean up is required using hydraulic jets or pumps.
Concrete must not be placed in running water.
Concrete must not be allowed to fall in water.
Concrete should not flow horizontally by more than 10 ft.

Suspension Bridges

7:33 PM Bridges , Civil Engineering

A suspension bridge is a type of bridge in which the deck (the load-bearing portion) is hung below suspension cables on vertical suspenders.

1.Components

Anchorage (blocks or tunnel type), towers, main cables, hangers, stiffened (box) girder and deck, substructure and foundation.

2.Form

An arch upside down or the shape of a catenary.

3.Anchorage

3.1 The anchorage, constructed as a concrete block or by tunneling the ground, forms a giant weight to anchor the bridge and transmit the tension generated through the cables firmly to ground.

General Type Anchorage

3.2 The anchorage type is determined by the terrain where the anchorage points are constructed.

3.3 A general type anchorage that supports unidirectional forces transmitting through cables. (One block for one bridge).

3.4 An anchorage of a type that supports bi-directional forces transmitting through cables. (One block for two bridges)

__located between two bridges and serving as two anchorage points.

__cable strands crossing each other in the air before entering the anchorage.

Bi-directional forces transmitting type

__The Kurushima Kaikyo Bridge use four anchorages for which three types of forms are employed.

3.5 .1 A tunnel type anchorage which allows minimum alterations to be made to the existing landform.

3.5.2 Cable anchor frames securing the cables to the tunnels.

4.Tower

Tower of a Suspension Bridge

4.1 The main tower functions to transmit forces through the cables and into the main tower foundation.The towers can be prefabricated in the plants or cast in situ.The blocks for the main tower were fabricated at the shop in blocks 6 m in length. The blocks are erected in the field using a climbing type of tower crane in building-block fashion to form the main tower.Towers of Kurushima Kaikyo Bridge: The blocks for the main tower were fabricated at the shop in blocks 6 m in length. The blocks are erected in the field using a climbing type of tower crane in building-block fashion to form the main tower.

5.Cables

5.1 Cables usu. of high tensile steel wires support bridge girders and other loads, including vehicle loads, and transmit these dead and live loads into the anchorage points.

5.2 Wires, strands, and ropes

5.2.1Galvanized bridge wire for parallel wire bridge cables. Recommended diameter .196 inch.

5.2.2 Galvanized bridge strand--consists of several bridge wires, of various diameters
twisted together.

5.2.3Galvanized bridge rope--consists of six strands twisted around a strand core.

5.3 Types of Cables

5.3.1 Parallel wire cables: This type of cable is made up of a large number of individual wires parallel to one another. Neither the cables nor the wires are twisted in any manner. The wire is shipped to the site of the bridge on reels and the individual wires are installed or' "spun" on the bridge and later compacted together to form a round crosssection. Cables of this type are used on monumental structures, such as the Golden Gate Bridge and the George Washington Bridge.

5.3.2 Parallel Strand Cables, Closed Construction--These consist of several prefabricated Galvanized Bridge Strands, all laid parallel and in contact with one another. Wood or aluminum fillers are used to bring the cable to a circular cross-section, after which the whole cable is wrapped with wire for protection. The cable may contain 7, 19 37, 61, 91 or 127 strands.

5.3.3 Parallel Strand Cables, Open Construction--This type of cable consists of several prefabricated galvanized bridge Strands which are all laid parallel to one another and not in contact. The strands are usually arranged in the form of a rectangle and the cable may contain 2, 4, 6, 9, 12, 16, 20, 24 or 30 strands.

5.3.4 Parallel Rope Cables, Open Construction--These are the same as Parallel Strand Cables except that Galvanized Bridge Rope is used in place of Bridge Strand.

5.3.5 Single Rope or Single Strand Cables--These are used for small structures.

5.4 A single-stranded cable with a hexagonal in cross section is formed by tying together 127 high-tension galvanized steel wires each about 5 mm in diameter. (as used for Kurushima Kaikyo Bridge)

5.5 Erecting cables

5.6 Squeezing the cables

__After all the strands are laid, they are squeezed to form one single cable with a circular cross section.

__The strands are first tapped manually using a wooden maul to form a cable roughly circular and then squeezed using a hydraulic squeezing machine to form a circular cross section.

Multi Stranded Cable

5.7 Cable strength

5.7.1 Strength of cables
One single steel wire (about 5 mm in diameter) is strong enough to hoist three passenger cars (1.2 tons each), and one stranded cable (consisting of 127 steel strands) is strong enough to hoist six space shuttles (74 tons each).

5.7.2 Length of cables

The main cables for the Kurushima Kaikyo Bridges weigh 16,000 tons, and the strands are long enough to run round the earth two and one half times.

6.Stiffening Girder

6.1 The stiffening girder functions as a driveway for vehicles. The girder was designed with a cross section in the shape of a slim box to reduce vibrations in strong winds to a minimum.

6.2 Erecting box girder with barge.

Stiffening Box Girder

Stiffening girder sections, each 36m in length, are prefabricated in the plant and loaded on a self-propelled barge for transport to a site directly below each erection points. There they are lifted into position by a lifting beam and secured to hanger ropes.

7.Features of Suspension Bridges

7.1. Aesthetic, light, and strong

7.2 Span range: 2,000 to 7,000 feet -- far longer than any other kind of bridge

7.3 Most expensive to build

7.4 Complicated in force bearing and distribution.

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