We are searching data for your request:
Upon completion, a link will appear to access the found materials.
Bailey Bridge being constructed, Italy
Here we see a Bailey Bridge being pushed into place to bridge a gap in a road bridge somewhere in Italy. The bridge was built on the existing road surface, and pushed over the void, with the weight of the bridge on the near side balancing the overhang.
Ancient Roman Bridges
Connection between cities, ports, mines and neighboring civilizations brought the need of creating stable and permanent roads. For this purposes, many ancient civilizations started to leave their mark on history buy leveling up uneven terrain, forging their way through wilderness and eventually, bridging rivers and extreme land formations with wood logs and stones. These early bridge building efforts finally received massive update in Greece, where builders and mathematicians discovered new ways of molding the weight of bridge material into structures that could remain strong enough to carry incredible weights.
With the arrival of Roman Empire, bridge building techniques were revolutionized with the introduction of arches. Rather than crudely covering entire surface below the deck of the bridge with the stone or wood, architects of that time built their bridges with the arching shapes, enabling downward force from the top of the bridge arch to meet the equal force that was pushed from the ground in the bridge foundations. Result of this design was an incredibly squeezed material and bridge structure that was very rigid and strong. The Roman stone arch bridges were so strong, that they had the potential to carry as much load as its own weight (or even more).
With such powerful knowledge in their hands, roman road builders spread across the Europe, Asia and Africa, building over 900 bridges during the life of Roman Republic and Empire. They did not build bridges to carry pedestrians and cargo traffic, but also incredibly complex aqueducts and viaducts, which carried water and goods from all parts of Europe to Italy. All in all, original Roman bridge architecture reached 26 different modern countries, from Portugal on the west, to Turkey on the east. Testament of the building techniques of Ancient Rome can be witnessed even today, with hundreds and hundreds of their bridges still left standing in all across the world.
Roman stone arch bridges were semicircular, with several being made in segmental form which offered greater protection from forces of flood waters and enabled builders to infuse less material into bridge itself, making it lighter. One of the best examples of the segmented arch bridges can be seen in Limyra Bridge in southwestern Turkey which features 26 segmental arches with average span-to-rise ratio of 5.3:1 and in the Alcántara Bridge in span which is today viewed as one of the most impressive and best preserved masterpieces of ancient Roman architecture. 17 meter long Turkish Karamagara Bridge that was built in 5th or 6th century represents the oldest surviving Roman bridge that features pointed arch.
Construction of stone arch bridges was not an easy task. Builders first had to created wooden arches in exact measurements as a finished bridge, and then use that wooden construction as a contained for stones and another substance that enabled Roman Empire to become such an architectural force – mortar (they were the first civilization on earth which discovered that mortar did not dissolve in the rain). Stones that were used for building bridges were usually found locally, but mortar components had to be imported from far away (ground up volcanic rock).
The first permanent dry crossing of the Grand Canal in Venice was achieved by Nicolò Barattieri who oversaw the construction of the wooden pontoon bridge called “Ponte della Moneta” in 1181. This structure boosted the importance of that part of the city, enabling the formation of larger markets and gathering of trade both near and on the bridge itself. As with many other city bridges in medieval Europe, merchants saw the appeal of the permanent water crossing as the perfect place for establishing their stores. On some larger bridges, the shops were placed directly on the decking (or immediately on the side of them, supported by wooden beams above the water), or near bridge entrances.
As the Rialto market became larger and more developed, foot traffic on the east side of the city increased so much that the pontoon bridge became congested with travel not only during peak hours of trading but often during the entire day. Additionally, water traffic across Grand Canal was greatly affected by the pontoon bridge, which prevented ships of all sizes from moving freely across the central waterway of the entire city of Venice.
The first solution for those problems was attempted to be made in 1255 with the construction of the first permanent wooden bridge across the Grand Canal. To enable boats to move across the canal easily, the bridge featured two inclined ramps that met at a movable central section. This section could be raised to allow passage of even tall ships.
The wooden bridge was renamed into Rialto Bridge during the 14th century, but in the 15th century, it becomes part of the market with the installation of shops directly on the bridge structure. Shops were arrayed in two rows along the sides of the bridge, with central decking being left for on-foot passage.
Even though the city officials collected taxes for funding and maintain the bridge, the wooden Rialto Bridge did not manage to survive undamaged between the time it was constructed, and the time it was replaced with a permanent stone bridge. The bridge was partially burned during 1310 revolt led by Bajamonte Tiepolo, it collapsed into the water during the 1444 wedding ceremony of Marchessa di Ferrara (plunging into the water all the spectators), and it fully collapsed in 1524, decades after the start of the movement that demanded complete replacement of the wooden bridge.
Bridge Construction Equipment
Heavy equipment will be used extensively during the bridge construction including bulldozers, excavators, asphalt mixers, formworks, and fabrication equipment. The construction and other equipment needs to be identified thoroughly, according to their capability and other desired functions. The foundation and the superstructure design will need to be considered. This expensive equipment should
not remain idle, and must be used cautiously to obtain optimum advantage.
10 Famous Bridge Collapses
On August 1, 2007, the Interstate -35 westbound bridge over the Mississippi River in Minneapolis came tumbling down during the evening rush hour, killing 13 and injuring 145. The incident brought the crumbling infrastructure of the US to the front of the news, but as usual, little if anything was done about it. Bridges have been falling as long as men have built them. The sorry state of repair and maintenance of American bridges means more deadly failures are likely to occur, sooner rather than later. Here we list 10 notable bridge failures, not necessarily the deadliest or most famous, but ones we hope you find interesting due to the varied reasons for collapse.
10. Ulyanovsk Bridge, 1983.
The Russian ship, Aleksandr Suvorov , a river cruise ship 445 feet long and almost 4000 tons, plowed into a bridge support at Ulynaovsk on the Volga River because of going through the wrong part of the bridge. The ship had been going its maximum speed, about 16 mph. A freight train passing at the time was taken down as the bridge collapsed, and the ship was heavily damaged (but later repaired). Fatalities numbered 177, but the number injured are unknown.
9. Rafiganj Railway Bridge, 2002.
Maoist terrorists had sabotaged the bridge by removing structural plates from the metal structure, weakening its ability to carry trains. The ensuing wreck killed a minimum of 130 (to 200) people and injured an unknown number (150+) more, the worst terror related bridge disaster in history and the worst bridge disaster of the 21st Century so far.
8. Rialto Bridge, 1444.
Spanning the Grand Canal in Venice, Italy, this bridge was built of wood in 1255. Jammed with spectators watching a boat parade celebrating the wedding of the Marquess of Ferrara, the bridge collapsed, sending all those hundreds of people into the canal. Casualties are unknown. The current bridge at that location is made of stone.
7. Angers Bridge, 1850.
Spanning the Maine River in Angers, France, this suspension bridge was built in 1839. As a battalion of French soldiers marched across the bridge, the harmonic nature of marching in step caused the bridge to collapse. With 226 dead, this tragedy is possibly the worst bridge disaster in human history. Soldiers no longer march “in step” when crossing bridges, and are given the order to “route step.”
6. Hyatt Regency Walkway, 1981.
Located inside the Kansas City, Missouri hotel, this double deck suspended footbridge apparently had too many people on it, causing poorly designed and overloaded joints to fail, spilling hundreds of luckless pedestrians from the 2nd and 4th floor level walkways. The hotel atrium was crowded with 1600 people due to a dance contest going on. Fatalities numbered 114 and injuries over 200.
5. Harrow & Wealdstone Footbridge, 1952.
Located at a train station in England, the footbridge had hundreds of people on it when one train hit another, causing train cars to hit the bridge and collapse the entire structure. Casualties included 112 people killed and 340 injured.
4. Ludendorff Bridge, 1945.
Constructed for the purpose of moving German troops west in time of war, the bridge at Remagen, Germany over the Rhine River was captured by the US Army after failed attempts by the German Army to blow up the bridge. US men and equipment poured across the bridge into Germany for 10 days until it finally collapsed, killing 28 Americans. By that time, other river crossing arrangements had been made and the flood of Allied forces continued. The bridge is the star of the aptly named 1969 movie, The Bridge at Remagen .
3. Silver Bridge, 1967.
Chronicled in the 1975 book and 2002 movie, The Mothman Prophecies, the collapse of this bridge over the Ohio River at Point Pleasant, West Virginia is said to have been foretold by a mysterious being, resulting in fewer casualties than if the normal amount of people had been on the bridge when it collapsed. As it was, 37 vehicles went into the drink and 46 people died. The reason for failure was corrosion of an eyebar in the suspension chain.
2. Stirling Bridge, 1297.
At the famous battle by this name between the English and the Scots, the charging English army was attacking across the bridge when it collapsed under their weight. Rumor has it the Scots may have cheated a bit, and pre-weakened the bridge. This battle is depicted in the 1995 movie, Braveheart (starring Mel Gibson as William Wallace), but without the bridge!
1. Tacoma Narrows Bridge, 1940.
“Galloping Gertie” was known for its swaying and gyrations, but one day the harmonics of the wind and the structure were such that the waving bridge surface could not take it anymore and down she went. Luckily for posterity, the spectacular collapse was caught on film. The cause of failure is known as aeroelastic flutter. After this failure bridges were built with the wind and the bridge’s harmonic frequency in mind. Unfortunately, 1 dog died in the collapse, but people had plenty of time to get to safety.
Question for students (and subscribers): What other bridge failures would you include in this list? Please let us know in the comments section below this article.
If you liked this article and would like to receive notification of new articles, please feel welcome to subscribe to History and Headlines by liking us on Facebook and becoming one of our patrons!
• Adaptable – pre-engineered to match each application
• Fast – modular stocked components, open to traffic in days
• Lower Cost – an alternative to custom designed bridges
• Easy – to handle, transport, assemble, install and reuse
MATERIALS & FINISHES
Domestic steel is used throughout. Most load-bearing components use low-alloy, high-tensile ASTM A242 steel with a yield point of 50,000 psi. Excellent corrosion resistance is achieved with an inorganic zinc silicate coating. Final color is lusterless light gray. Hot dipped galvanized is also available.
The key to the Bailey system is the ingenious set of precision-made, interchangeable steel
components from which all Bailey structures are assembled
MADE IN THE U.S.A
The U.S. M2 Bailey components supplied by Bailey Bridges, Inc., are either original U.S. Army equipment, or newly manufactured in the U.S.A. to those exacting specifications, utilizing domestic steel. It remains the current standard panel bridge of the U.S. Army.
ASSEMBLY AND INSTALLATION
Most Bailey bridges are assembled and installed in a matter of days by a small crew. Common hand tools are utilized. All connections are pinned, bolted or clamped. No welding is necessary. Disassembly is similarly easy, and components can be stored in minimal space until reused. Bailey bridges are often installed by the cantilever launching method, in which the assembled bridge together with a “launching nose” is rolled out across the gap, without falsework or heavy equipment. The cantilever method allows bridges to be quickly erected over rivers or deep gorges. Additionally, some Bailey bridges may be hoisted into place by crane.
Bailey bridge components can be assembled in seven different configurations to efficiently accommodate a wide range of span and capacity requirements. Panels, the primary Bailey components, are pinned together at the job site to make girders of any length. Various girder strengths are achieved by assembling either a single row of panels, or two or three rows side-by-side. Panels may also be stacked in double-story height for further increase strength. For greatest strength, longer spans may be chord-reinforced.
For highway use, typical Bailey bridge clear spans range from 20 ft to 200 ft. Multiple-span bridges of any length are possible by incorporating intermediate supporting piers.
By the end of the 11th century, motte-and-bailey castles (especially those made entirely out of earth and timber) began to fall from favor. There were several reasons behind this fact.
One thing that made the motte-and-bailey design so popular was the use of wood as the primary building material, however, this also became the design's Achilles heel. Because timber burns easily, firing flaming arrows at the castle could have devastating consequences.
Sophisticated fire-launching techniques designed to burn down the castle were developed and used with great success.
Moreover, the broad base of the mottes meant that attacks could come from any direction, and raiders were quick to use this to their advantage, often surprising the defenders inside the keep.
Timber also tends to rot easily, and many of these early castles quickly ran into disrepair and were often abandoned or required significant (and often expensive) repairs and ongoing maintenance.
Small and medium mottes could not sustain a large keep, and this meant that living quarters were usually small and cramped. There was little space to house soldiers and peasants, let alone provide the stature yearned for by many nobles.
To build a large tower that could properly accommodate the lord and his servants, castles needed a large motte. However, a large motte was extremely difficult to build as it took disproportionately more effort to pile up the earth than in the case of smaller hills. As an example, a large motte is estimated to have required up to 24,000 man-days of work while smaller ones required perhaps as little as 1,000.
The cost of this design was not easily scalable and the reality of the times forced local nobles to forego the simple motte and bailey design and turn to more complex design principles to build the large castles that their status and people needed for economics, politics, and defense. To avoid the perils of fire, improve durability and increase the castle defense capability, the obvious solution was to replace (wherever possible) timber with stone.
Chateau de Gisors in Normandy, a perefect example of a motte-and-bailey castle, where the wooden tower was replced with a stone keep
The History of Concrete
The time period during which concrete was first invented depends on how one interprets the term &ldquoconcrete.&rdquo Ancient materials were crude cements made by crushing and burning gypsum or limestone. Lime also refers to crushed, burned limestone. When sand and water were added to these cements, they became mortar, which was a plaster-like material used to adhere stones to each other. Over thousands of years, these materials were improved upon, combined with other materials and, ultimately, morphed into modern concrete.
Today&rsquos concrete is made using Portland cement, coarse and fine aggregates of stone and sand, and water. Admixtures are chemicals added to the concrete mix to control its setting properties and are used primarily when placing concrete during environmental extremes, such as high or low temperatures, windy conditions, etc.
The precursor to concrete was invented in about 1300 BC when Middle Eastern builders found that when they coated the outsides of their pounded-clay fortresses and home walls with a thin, damp coating of burned limestone, it reacted chemically with gases in the air to form a hard, protective surface. This wasn&rsquot concrete, but it was the beginning of the development of cement.
Early cementicious composite materials typically included mortar-crushed, burned limestone, sand and water, which was used for building with stone, as opposed to casting the material in a mold, which is essentially how modern concrete is used, with the mold being the concrete forms.
As one of the key constituents of modern concrete, cement has been around for a long time. About 12 million years ago in what is now Israel, natural deposits were formed by reactions between limestone and oil shale that were produced by spontaneous combustion. However, cement is not concrete. Concrete is a composite building material and the ingredients, of which cement is just one, have changed over time and are changing even now. The performance characteristics can change according to the different forces that the concrete will need to resist. These forces may be gradual or intense, they may come from above (gravity), below (soil heaving), the sides (lateral loads), or they might take the form of erosion, abrasion or chemical attack. The ingredients of concrete and their proportions are called the design mix.
Early Use of Concrete
The first concrete-like structures were built by the Nabataea traders or Bedouins who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan in around 6500 BC. They later discovered the advantages of hydraulic lime -- that is, cement that hardens underwater -- and by 700 BC, they were building kilns to supply mortar for the construction of rubble-wall houses, concrete floors, and underground waterproof cisterns. The cisterns were kept secret and were one of the reasons the Nabataea were able to thrive in the desert.
In making concrete, the Nabataea understood the need to keep the mix as dry or low-slump as possible, as excess water introduces voids and weaknesses into the concrete. Their building practices included tamping the freshly placed concrete with special tools. The tamping process produced more gel, which is the bonding material produced by the chemical reactions that take place during hydration which bond the particulates and aggregate together.
An ancient Nabataea building
Like the Romans had 500 years later, the Nabataea had a locally available material that could be used to make their cement waterproof. Within their territory were major surface deposits of fine silica sand. Groundwater seeping through silica can transform it into a pozzolan material, which is a sandy volcanic ash. To make cement, the Nabataea located the deposits and scooped up this material and combined it with lime, then heated it in the same kilns they used to make their pottery, since the target temperatures lay within the same range.
By about 5600 BC along the Danube River in the area of the former country of Yugoslavia, homes were built using a type of concrete for floors.
Around 3000 BC, the ancient Egyptians used mud mixed with straw to form bricks. Mud with straw is more similar to adobe than concrete. However, they also used gypsum and lime mortars in building the pyramids, although most of us think of mortar and concrete as two different materials. The Great Pyramid at Giza required about 500,000 tons of mortar, which was used as a bedding material for the casing stones that formed the visible surface of the finished pyramid. This allowed stone masons to carve and set casing stones with joints open no wider than 1/50-inch.
About this same time, the northern Chinese used a form of cement in boat-building and in building the Great Wall. Spectrometer testing has confirmed that a key ingredient in the mortar used in the Great Wall and other ancient Chinese structures was glutenous, sticky rice. Some of these structures have withstood the test of time and have resisted even modern efforts at demolition.
By 600 BC, the Greeks had discovered a natural pozzolan material that developed hydraulic properties when mixed with lime, but the Greeks were nowhere near as prolific in building with concrete as the Romans. By 200 BC, the Romans were building very successfully using concrete, but it wasn&rsquot like the concrete we use today. It was not a plastic, flowing material poured into forms, but more like cemented rubble. The Romans built most of their structures by stacking stones of different sizes and hand-filling the spaces between the stones with mortar. Above ground, walls were clad both inside and out with clay bricks that also served as forms for the concrete. The brick had little or no structural value and their use was mainly cosmetic. Before this time, and in most places at that time (including 95% of Rome), the mortars commonly used were a simple limestone cement that hardened slowly from reacting with airborne carbon dioxide. True chemical hydration did not take place. These mortars were weak.
For the Romans&rsquo grander and more artful structures, as well as their land-based infrastructure requiring more durability, they made cement from a naturally reactive volcanic sand called harena fossicia. For marine structures and those exposed to fresh water, such as bridges, docks, storm drains and aqueducts, they used a volcanic sand called pozzuolana. These two materials probably represent the first large-scale use of a truly cementicious binding agent. Pozzuolana and harena fossicia react chemically with lime and water to hydrate and solidify into a rock-like mass that can be used underwater. The Romans also used these materials to build large structures, such as the Roman Baths, the Pantheon, and the Colosseum, and these structures still stand today. As admixtures, they used animal fat, milk and blood -- materials that reflect very rudimentary methods. On the other hand, in addition to using natural pozzolans, the Romans learned to manufacture two types of artificial pozzolans -- calcined kaolinitic clay and calcined volcanic stones -- which, along with the Romans' spectacular building accomplishments, are evidence of a high level of technical sophistication for that time.
Built by Rome's Emperor Hadrian and completed in 125 AD, the Pantheon has the largest un-reinforced concrete dome ever built. The dome is 142 feet in diameter and has a 27-foot hole, called an oculus, at its peak, which is 142 feet above the floor. It was built in place, probably by starting above the outside walls and building up increasingly thin layers while working toward the center.
The Pantheon has exterior foundation walls that are 26 feet wide and 15 feet deep and made of pozzolana cement (lime, reactive volcanic sand and water) tamped down over a layer of dense stone aggregate. That the dome still exists is something of a fluke. Settling and movement over almost 2,000 years, along with occasional earthquakes, have created cracks that would normally have weakened the structure enough that, by now, it should have fallen. The exterior walls that support the dome contain seven evenly spaced niches with chambers between them that extend to the outside. These niches and chambers, originally designed only to minimize the weight of the structure, are thinner than the main portions of the walls and act as control joints that control crack locations. Stresses caused by movement are relieved by cracking in the niches and chambers. This means that the dome is essentially supported by 16 thick, structurally sound concrete pillars formed by the portions of the exterior walls between the niches and chambers. Another method to save weight was the use of very heavy aggregates low in the structure, and the use of lighter, less dense aggregates, such as pumice, high in the walls and in the dome. The walls also taper in thickness to reduce the weight higher up.
Another secret to the success of the Romans was their use of trade guilds. Each trade had a guild whose members were responsible for passing their knowledge of materials, techniques and tools to apprentices and to the Roman Legions. In addition to fighting, the legions were trained to be self-sufficient, so they were also trained in construction methods and engineering.
During the Middle Ages, concrete technology crept backward. After the fall of the Roman Empire in 476 AD, the techniques for making pozzolan cement were lost until the discovery in 1414 of manuscripts describing those techniques rekindled interest in building with concrete.
It wasn&rsquot until 1793 that the technology took a big leap forward when John Smeaton discovered a more modern method for producing hydraulic lime for cement. He used limestone containing clay that was fired until it turned into clinker, which was then ground it into powder. He used this material in the historic rebuilding of the Eddystone Lighthouse in Cornwall, England.
Finally, in 1824, an Englishman named Joseph Aspdin invented Portland cement by burning finely ground chalk and clay in a kiln until the carbon dioxide was removed. It was named &ldquoPortland&rdquo cement because it resembled the high-quality building stones found in Portland, England. It&rsquos widely believed that Aspdin was the first to heat alumina and silica materials to the point of vitrification, resulting in fusion. During vitrification, materials become glass-like. Aspdin refined his method by carefully proportioning limestone and clay, pulverizing them, and then burning the mixture into clinker, which was then ground into finished cement.
Composition of Modern Portland Cement
Before Portland cement was discovered, and for some years afterward, large quantities of natural cement were used, which were produced by burning a naturally occurring mixture of lime and clay. Because the ingredients of natural cement are mixed by nature, its properties vary widely. Modern Portland cement is manufactured to detailed standards. Some of the many compounds found in it are important to the hydration process and the chemical characteristics of cement. It&rsquos manufactured by heating a mixture of limestone and clay in a kiln to temperatures between 1,300° F and 1,500° F. Up to 30% of the mix becomes molten but the remainder stays in a solid state, undergoing chemical reactions that can be slow. Eventually, the mix forms a clinker, which is then ground into powder. A small proportion of gypsum is added to slow the rate of hydration and keep the concrete workable longer. Between 1835 and 1850, systematic tests to determine the compressive and tensile strength of cement were first performed, along with the first accurate chemical analyses. It wasn&rsquot until about 1860 that Portland cements of modern composition were first produced.
In the early days of Portland cement production, kilns were vertical and stationary. In 1885, an English engineer developed a more efficient kiln that was horizontal, slightly tilted, and could rotate. The rotary kiln provided better temperature control and did a better job of mixing materials. By 1890, rotary kilns dominated the market. In 1909, Thomas Edison received a patent for the first long kiln. This kiln, installed at the Edison Portland Cement Works in New Village, New Jersey, was 150 feet long. This was about 70 feet longer than the kilns in use at the time. Industrial kilns today may be as long as 500 feet.
Although there were exceptions, during the 19 th century, concrete was used mainly for industrial buildings. It was considered socially unacceptable as a building material for aesthetic reasons. The first widespread use of Portland cement in home construction was in England and France between 1850 and 1880 by Frenchman Francois Coignet, who added steel rods to prevent the exterior walls from spreading, and later used them as flexural elements. The first home built using reinforced concrete was a servant&rsquos cottage constructed in England by William B. Wilkinson in 1854. In 1875, American mechanical engineer William Ward completed the first reinforced concrete home in the U.S. It still stands in Port Chester, New York. Ward was diligent in maintaining construction records, so a great deal is known about this home. It was built out of concrete because of his wife&rsquos fear of fire, and in order to be more socially acceptable, it was designed to resemble masonry. This was the start of what is today a $35 billion industry that employs more than 2 million people in the U.S. alone.
The home built by William Ward is commonly called Ward&rsquos Castle.
In 1891, George Bartholomew poured the first concrete street in the U.S., and it still exists today. The concrete used for this street tested at about 8,000 psi, which is about twice the strength of modern concrete used in residential construction.
Court Street in Bellefontaine, Ohio, which is the oldest concrete street in the U.S.
By 1897, Sears Roebuck was selling 50-gallon drums of imported Portland cement for $3.40 each. Although in 1898 cement manufacturers were using more than 90 different formulas, by 1900, basic testing -- if not manufacturing methods -- had become standardized.
During the late 19 th century, the use of steel-reinforced concrete was being developed more or less simultaneously by a German, G.A. Wayss, a Frenchman, Francois Hennebique, and an American, Ernest L. Ransome. Ransome started building with steel-reinforced concrete in 1877 and patented a system that used twisted square rods to improve the bond between steel and concrete. Most of the structures he built were industrial.
Hennebique started building steel-reinforced homes in France in the late 1870s. He received patents in France and Belgium for his system and was highly successful, eventually building an empire by selling franchises in large cities. He promoted his method by lecturing at conferences and developing his own company standards. As did Ransome, most of the structures Hennebique built were industrial. In 1879, Wayss bought the rights to a system patented by a Frenchman named Monier, who started out using steel to reinforce concrete flower pots and planting containers. Wayss promoted the Wayss-Monier system.
In 1902, August Perret designed and built an apartment building in Paris using steel-reinforced concrete for the columns, beams and floor slabs. The building had no bearing walls, but it did have an elegant façade, which helped make concrete more socially acceptable. The building was widely admired and concrete became more widely used as an architectural material as well as a building material. Its design was influential in the design of reinforced-concrete buildings in the years that followed.
25 Rue Franklin in Paris, France
In 1904, the first concrete high-rise building was constructed in Cincinnati, Ohio. It stands 16 stories or 210 feet tall.
The Ingalls Building in Cincinnati, Ohio
In 1911, the Risorgimento Bridge was built in Rome. It spans 328 feet.
Rome&rsquos Risorgimento Bridge
In 1913, the first load of ready-mix was delivered in Baltimore, Maryland. Four years later, the National Bureau of Standards (now the National Bureau of Standards and Technology) and the American Society for Testing and Materials (now ASTM International) established a standard formula for Portland cement.
In 1915, Matte Trucco built the five-story Fiat-Lingotti Autoworks in Turin using reinforced concrete. The building had an automobile test track on the roof.
The Fiat-Lingotti Autoworks in Turin, Italy
Eugène Freyssinet was a French engineer and pioneer in the use of reinforced- concrete construction. In 1921, he built two gigantic parabolic-arched airship hangars at Orly Airport in Paris. In 1928, he was granted a patent for pre-stressed concrete.
The parabolic-arched airship hangar at Orly Airport in Paris, France
Airship hangar construction
In 1930, air-entraining agents were developed that greatly increased concrete&rsquos resistance to freezing and improved its workability. Air entrainment was an important development in improving the durability of modern concrete. Air entrainment is the use of agents that, when added to concrete during mixing, create many air bubbles that are extremely small and closely spaced, and most of them remain in the hardened concrete. Concrete hardens through a chemical process called hydration. For hydration to take place, concrete must have a minimum water-to-cement ratio of 25 parts of water to 100 parts of cement. Water in excess of this ratio is surplus water and helps make the concrete more workable for placing and finishing operations. As concrete dries and hardens, surplus water will evaporate, leaving the concrete surface porous. Water from the surrounding environment, such as rain and snowmelt, can enter these pores. Freezing weather can turn this water to ice. As that happens, the water expands, creating small cracks in the concrete that will grow larger as the process is repeated, eventually resulting in surface flaking and deterioration called spalling. When concrete has been air-entrained, these tiny bubbles can compress slightly, absorbing some of the stress created by expansion as water turns to ice. Entrained air also improves workability because the bubbles act as a lubricant between aggregate and particles in the concrete. Entrapped air is composed of larger bubbles trapped in the concrete and is not considered beneficial.
Expertise in building with reinforced concrete eventually allowed the development of a new way of building with concrete the thin-shell technique involves building structures, such as roofs, with a relatively thin shell of concrete. Domes, arches and compound curves are typically built with this method, since they are naturally strong shapes. In 1930, the Spanish engineer Eduardo Torroja designed a low-rise dome for the market at Algeciras, with a 3½-inch thickness that spanned 150 feet. Steel cables were used to form a tension ring. At about the same time, Italian Pier Luigi Nervi began building hangars for the Italian Air Force, shown in the photo below.
Cast-in-place hangars for the Italian Air Force
The hangars were cast in place, but much of Nervi&rsquos work used pre-cast concrete.
Probably the most accomplished person when it came to building using concrete shell techniques was Felix Candela, a Spanish mathematician-engineer-architect who practiced mostly in Mexico City. The roof of the Cosmic Ray Laboratory at the University of Mexico City was built 5/8-inch thick. His trademark form was the hyperbolic paraboloid. Although the building shown in the photo below was not designed by Candela, it&rsquos a good example of a hyperbolic paraboloid roof.
A hyperbolic paraboloid roof on a church in Boulder, Colorado
The same church under construction
Some of the most striking roofs anywhere have been built using thin-shell technology, as depicted below.
The Sydney Opera House in Sydney, Australia
In 1935, the Hoover Dam was completed after pouring approximately 3,250,000 yards of concrete, with an additional 1,110,000 yards used in the power plant and other dam-related structures. Bear in mind that this was less than 20 years after a standard formula for cement was established.
Columns of blocks being filled with concrete at the Hoover Dam in February 1934
Engineers for the Bureau of Reclamation calculated that if the concrete was placed in a single, monolithic pour, the dam would take 125 years to cool, and stresses from the heat produced and the contraction that takes place as concrete cures would cause the structure to crack and crumble. The solution was to pour the dam in a series of blocks that formed columns, with some blocks as large as 50 feet square and 5 feet high. Each 5-foot-tall section has a series of 1-inch pipes installed through which river water and then mechanically chilled water was pumped to carry away the heat. Once the concrete stopped contracting, the pipes were filled with grout. Concrete core samples tested in 1995 showed that the concrete has continued to gain strength and has higher-than-average compressive strength.
The upstream-side of the Hoover Dam is shown as it fills for the first time
Grand Coulee Dam
The Grand Coulee Dam in Washington, completed in 1942, is the largest concrete structure ever built. It contains 12 million yards of concrete. Excavation required the removal of over 22 million cubic yards of dirt and stone. To reduce the amount of trucking, a conveyor belt 2 miles long was constructed. At foundation locations, grout was pumped into holes drilled 660 to 880 feet deep (in granite) in order to fill any fissures that might weaken the ground beneath the dam. To avoid excavation collapse from the weight of the overburden, 3-inch pipes were inserted into the earth through which chilled liquid from a refrigerating plant was pumped. This froze the earth, stabilizing it enough that construction could continue.
Concrete for the Grand Coulee Dam was placed using the same methods used for the Hoover Dam. After being placed in columns, cold river water was pumped through pipes embedded in the curing concrete, reducing the temperature in the forms from 105° F (41° C) to 45° F (7° C). This caused the dam to contract about 8 inches in length, and the resulting gaps were filled with grout.
The Grand Coulee Dam under construction
In the years following the construction of the Ingalls Building in 1904, most high-rise buildings were made of steel. Construction in 1962 of Bertrand Goldberg's 60-story Twin Towers in Chicago sparked renewed interest in using reinforced concrete for high-rises.
The world's tallest structure (as of 2011) was built using reinforced concrete. The Burj Khalifa in Dubai in the United Arab Emirates (UAE) stands 2,717 feet tall.
Soaring Suspension Spans
The history of the suspension bridge and its use for railroads can almost completely be traced to one span - the Niagara suspension bridge. Like all bridges of the type, two tall towers support a thick steel cable that sags down on either side between them while the far ends of the cable terminate into heavy anchorages that resist the pull or tension exerted on the cables from the weight of the bridge deck. The deck of the bridge hangs from a series of thin, vertical cables called stringers that are connected to the two main cables. The tall towers and swooping lines of a large scale suspension bridge can make them the most breathtaking and spectacular of all bridge types.
Designed by John Augustus Roebling, who became famous for designing the Brooklyn bridge 30years later, the New York to Canada structure at Niagara Falls would become the only major North American suspension bridge ever built to carry full size trains with heavy locomotives. Its success nearly led to the building of a similar bridge across the Kentucky River before it was decided to build a steel cantilever bridge - America’s first - that would be more suited for heavy trains. Ultimately, early suspension bridges, even with the addition of stiffening trusses, were too susceptible to distortions and unwanted movements that could eventually damage the structure. With increased traffic and the demand for a double-track across the gorge, the 821 foot long (250 meter) suspension bridge was finally replaced in 1897 with an arch that was built underneath and around the Roebling span.
Roebling’s two other great 1800s suspension bridge crossings at Cincinnati, Ohio and Brooklyn, New York would also have rail lines but only for lighter transit trains and trolleys. In the early 1900s, transit lines would also be built on New York City’s two other big suspension bridge projects, the Williamsburg and Manhattan bridges. After these, the last two North American suspension bridges to ever have a light rail line would be Philadelphia’s Benjamin Franklin bridge in 1926 and San Francisco’s Oakland Bay Bridge in 1936. The two rail lines on the lower deck of the Bay Bridge were converted to road use in 1963, leaving New York and Philadelphia as the last two cities in North America to have rail line suspension bridges.
In recent years, the most interesting road and rail suspension bridges have been opening overseas. The most prominent of these is the Seto-Ohashi rail line that skips across several islands and bridges on the middle crossing of the massive Honshu-Shikoku bridge project that opened in 1988 in Japan. Of the six major spans, three are suspension including the Kita and Minami bridges which are back to back, sharing a common anchorage in the same way as the suspension bridges of the San Francisco-Oakland Bay bridge.
In 1997 the Tsing Ma suspension bridge opened in Hong Kong, China and is currently the longest span railway bridge in the world with a central span of 4,518 feet (1,377 meters). It carries 2 MTR transit lines on the lower level as well as 6 lanes of roadway on the upper level.
The Construction of Venice, the Floating City
Venice, Italy, is known by several names, one of which is the ‘Floating City’. This is due to the fact that the city of Venice consists of 118 small islands connected by numerous canals and bridges. Yet, the buildings in Venice were not built directly on the islands. Instead, they were built upon wooden platforms that were supported by wooden stakes driven into the ground.
The story of Venice begins in the 5 th century A.D. After the fall of the Western Roman Empire, barbarians from the north were raiding Rome’s former territories. In order to escape these raids, the Venetian population on the mainland escaped to the nearby marshes, and found refuge on the sandy islands of Torcello, Iesolo and Malamocco. Although the settlements were initially temporary in nature, the Venetians gradually inhabited the islands on a permanent basis. In order to have their buildings on a solid foundation, the Venetians first drove wooden stakes into the sandy ground. Then, wooden platforms were constructed on top of these stakes. Finally, the buildings were constructed on these platforms. A 17 th century book which explains in detail the construction procedure in Venice demonstrates the amount of wood required just for the stakes. According to this book, when the Santa Maria Della Salute church was built, 1,106,657 wooden stakes, each measuring 4 metres, were driven underwater. This process took two years and two months to be completed. On top of that, the wood had to be obtained from the forests of Slovenia, Croatia and Montenegro, and transported to Venice via water. Thus, one can imagine the scale of this undertaking.
The city of Venice was built on wooden foundations.
The use of wood as a supporting structure may seem as a surprise, since wood is relatively less durable than stone or metal. The secret to the longevity of Venice’s wooden foundation is the fact that they are submerged underwater. The decay of wood is caused by microorganisms, such as fungi and bacteria. As the wooden support in Venice is submerged underwater, they are not exposed to oxygen, one of the elements needed by microorganisms to survive. In addition, the constant flow of salt water around and through the wood petrifies the wood over time, turning the wood into a hardened stone-like structure.
As a city surrounded by water, Venice had a distinct advantage over her land-based neighbours. For a start, Venice was secure from enemy invasions. For instance, Pepin, the son of Charlemagne, attempted to invade Venice, but failed as he was unable to reach the islands on which the city was built. Venice eventually became a great maritime power in the Mediterranean. For instance, in 1204, Venice allied itself with the Crusaders and succeeded in capturing the Byzantine capital, Constantinople. Nevertheless, Venice started to decline in the 15 th century, and was eventually captured by Napoleon in 1797 when he invaded Italy.