Foundation, Concrete and Earthquake Engineering
Reinforcement Requirement of Two Way Concrete Slab
In case of flexural reinforcement extending in one direction only, reinforcement for shrinkage and temperature stresses shall be provided perpendicular to flexural reinforcement in structural slabs. But, in case of, two-way slab where reinforcement requirements are determined by flexure in critical section, the minimum reinforcement is set to the limit of those of temperature and shrinkage.
Spacing of reinforcement at critical sections shall not exceed two times the slab thickness, except for portions of slab area that may be of cellular or ribbed construction. In the slab over cellular spaces, reinforcement shall be provided as required by shrinkage and temperature, stated above.
Positive moment reinforcement perpendicular to a discontinuous edge shall extend to the edge of slab and have embedment, straight or hooked, at least 150 mm in spandrel beams, columns or walls.
Negative moment reinforcement perpendicular to a discontinuous edge shall be bent, hooked, or otherwise anchored, in spandrel beams, or wall, and shall be developed at face of support according to provisions for standard development and splices reinforcement.
Corner Reinforcement
1.Special reinforcement shall be provided at exterior corners in both bottom and top of the slab, for a distance in each direction from the corner equal to one-fifth the larger span of the corner panel.
2.Corner reinforcement at the top of the slab shall be parallel to a line bisecting the angle at the relevant corner.
3.The corner reinforcement at the bottom of the slab shall be perpendicular to a line bisecting the angle at the relevant corner.
4.The top and bottom corner reinforcement shall be of size and spacing equivalent to that required for the maximum positive moment in the panel
Spacing of reinforcement at critical sections shall not exceed two times the slab thickness, except for portions of slab area that may be of cellular or ribbed construction. In the slab over cellular spaces, reinforcement shall be provided as required by shrinkage and temperature, stated above.
Positive moment reinforcement perpendicular to a discontinuous edge shall extend to the edge of slab and have embedment, straight or hooked, at least 150 mm in spandrel beams, columns or walls.
Negative moment reinforcement perpendicular to a discontinuous edge shall be bent, hooked, or otherwise anchored, in spandrel beams, or wall, and shall be developed at face of support according to provisions for standard development and splices reinforcement.
Corner Reinforcement
1.Special reinforcement shall be provided at exterior corners in both bottom and top of the slab, for a distance in each direction from the corner equal to one-fifth the larger span of the corner panel.
2.Corner reinforcement at the top of the slab shall be parallel to a line bisecting the angle at the relevant corner.
3.The corner reinforcement at the bottom of the slab shall be perpendicular to a line bisecting the angle at the relevant corner.
4.The top and bottom corner reinforcement shall be of size and spacing equivalent to that required for the maximum positive moment in the panel
Guidance for Removal of Forms and Shores
No construction loads shall be supported on, nor any shoring removed from, any part of the structure under construction except when that portion of the structure in combination with remaining forming and shoring system has sufficient strength to support safely its weight and loads placed thereon.
Sufficient strength shall be demonstrated by structural analysis considering proposed loads, strength of forming and shoring system, and concrete strength data. Structural analysis and concrete strength test data shall be furnished to the engineer when so required.
No construction loads exceeding the combinations of superimposed dead load plus specified live load shall be supported on any unshored portion of the structure under construction, unless analysis indicates adequate strength to support such additional loads.
Forms shall be removed in such a manner as not to impair safety and serviceability of the structure. All concrete to be exposed by form removal shall have sufficient strength not to be damaged thereby.
Forms supporting prestressed concrete members shall not be removed until sufficient prestrtessing has been applied to enable prestressed members to carry their dead load and anticipated construction loads.
Sufficient strength shall be demonstrated by structural analysis considering proposed loads, strength of forming and shoring system, and concrete strength data. Structural analysis and concrete strength test data shall be furnished to the engineer when so required.
No construction loads exceeding the combinations of superimposed dead load plus specified live load shall be supported on any unshored portion of the structure under construction, unless analysis indicates adequate strength to support such additional loads.
Forms shall be removed in such a manner as not to impair safety and serviceability of the structure. All concrete to be exposed by form removal shall have sufficient strength not to be damaged thereby.
Forms supporting prestressed concrete members shall not be removed until sufficient prestrtessing has been applied to enable prestressed members to carry their dead load and anticipated construction loads.
Destruction of Bhuj Earthquake, Gujarat
The Mw7.6 Bhuj earthquake that shook the Indian Province of Gujarat on the morning of January 26, 2001 (Republic Day) is one of the two most deadly earthquakes to strike India in its recorded history.
One month after the earthquake official Government of India figures place the death toll at 19,727 and the number of injured at 166,000.
Indications are that 600,000 people were left homeless, with 348,000 houses destroyed and an additional 844,000 damaged. The Indian State Department estimates that the earthquake affected, directly or indirectly, 15.9 million people out of a total population of 37.8 million.
Indications are that 600,000 people were left homeless, with 348,000 houses destroyed and an additional 844,000 damaged. The Indian State Department estimates that the earthquake affected, directly or indirectly, 15.9 million people out of a total population of 37.8 million.
More than 20,000 cattle are
reported killed. Government estimates place direct economic losses at
$1.3 billion. Other estimates indicate losses may be as high as $5
billion.
Slope Stability & Protection against Excavation
The possibility of overturning and sliding of the surrounding building shall be considered during excavation. The minimum factor safety against overturning of the structure as a whole shall be 1.5. Stability against overturning shall be provided by the dead load of the building, the allowable uplift capacity of piling, anchors, weight of the soil directly overlying footing provided that such soil can't be excavated without recourse to major modification of the building, or by any combination of these factors.
The minimum factor of safety against sliding of the structure under lateral load shall be 1.5. Resistance to lateral loads shall be provided by friction between the foundation and the underlying soil, passive earth pressure, batter piles or by plumb piles, subject to the following:
- The resistance to lateral loads due to passive earth pressure shall not be taken into consideration where the abutting soil could be removed inadvertently by excavation.
- In case of pile supported structures, frictional resistance between the foundation and the underlying soil shall be discounted.
- The available resistance to friction between the foundation and the underlying soil shall be predicted on an assumed friction factor of 0.5. A greater value of the co-efficient of friction may be used subject to verification by analysis and test.
The faces of cut and fill slopes shall be prepared and maintained to control erosion. The control may consist of effective planting. The protection for slopes shall be installed as soon as practicable. Where cut slopes are not subjected to erosion due to erosion resistant character of the materials, such protection may be omitted.
Where necessary, check dams, cribbing, riprap or other devices or methods shall be employed to control erosion.
Splice in Steel Piles
Steel piles are usually rotted H shapes or pipe piles. Wide-flange beams or I beams may also be used; However, the H-shape is especially proportioned to withstand the hard driving stress which the pile may be subjected.
Splices in steel plate are made in the same manner as in steel columns, i.e., by welding (most commonly) or by bolting. Except for small projects involving only a few piles, currently most splices are made with prefabricated (and patented) splices connectors. For H piles, web plates are prefabricated in the form of two channels back-to-back, of adequate length which fit snugly against the web and inside flange.
The splice is then welded to the web across the ends and the flanges are butt welded to complete the splice pipe pile splicers consists in a ledge ring with an inner dia slightly larger than the pipe outer dia. The two sections of pipe to joined rest against the inside ledge and an end weld is made around the pipe at both ends of the splice. Generally these splices will develop the strength of the pile in compression, tension, bending, and shear to satisfy most building code requirements.
When a pile must be spliced to develop adequate embedment length, all the necessary equipment should be standing by so that when the hammer is shut off the splice can be quickly made. If this is not done – and sometimes if it is done-the soil tends to set or "freeze" about the pile, and resumption of driving is difficult and sometimes requires changing hammers. These large driving stresses may cause considerable damage to the upper part of the pile. This is a phenomenon which is independent of pile materials.
Formation of Andes (Tectonic Cause)
The Andes mountain range is the highest mountain range outside Asia. The highest peak, Aconcagua, rises to 6,962 m (22,840 ft) above sea level. The summit of Mount Chimborazo in the Ecuadorean Andes is the point on the Earth's surface most distant from its center, because of the equatorial bulge.
But the Andes are the world's longest exposed mountain range. They lie as a continuous chain of highland along the western coast of South America. The range is over 7,000 km (4,300 mi) long, 200 km (120 mi) to 700 km (430 mi) wide (widest between 18° to 20°S latitude), and of an average height of about 4,000 m (13,000 ft).
The Andes are the result of plate tectonics processes, caused by the subduction of oceanic crust beneath the South American plate. The main cause of the rise of the Andes is the compression of western rim of the South American Plate due to the subduction of Nazca Plate and the Antarctic Plate.
The formation of the modern Andes began in the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting, faulting and folding of sedimentary and metamorphic rocks of the ancient cratons to the east. Tectonic forces along the subduction zone along the entire west coast of South America where the Nazca Plate and a part of the Antarctic Plate are sliding beneath the South American Plate continue to produce an ongoing orogenic event resulting in minor to major earthquakes and volcanic eruptions to this day. In the extreme south a major transform fault separates Tierra del Fuego from the small Scotia Plate. Across the 1,000 km (620 mi) wide Drake Passage lie the mountains of the Antarctic Peninsula south of the Scotia Plate which appear to be a continuation of the Andes chain.
Corrosion Problem of Steel Piles
According to National Bureau of Standards ( NBS), pile driven in disturbed, or fill, soils will tend to undergo relatively more corrosion. This study is applicable for both sheet-pile and bearing pile. Undistured soils were found to be Oxygen-deficient from a few feet below the ground surface while the disturbed soil contain a high concentration.
The soil considered as corrosion susceptible, according to NBS, is:
PH = 2.3 - 8.6
b) Electrical resistivity of 300 to 50200 ohm. cm.
The soil considered as corrosion susceptible, according to NBS, is:
Soil exposed to sea water or effluents with a PH much above 9.5 or below 4.0 will required painting or encasement in concrete to resist corrosion. This is also true for zones where the piles are subjected to water fluctuations foe several feet. A splice, increasing section slightly in the corrosive zone, may suitable alternative to the treatment stated above.
Some of the newer grades of high-strength and copper-alloy steels claim substantial corrosion resistance. The A690 high-strength low-alloy steel has approximately two to three times more corrosion resistance to sea water them ordinary carbon steel of A36 grade.
Formation of Mount Everest disappearing Tethys Sea
About 50 million years ago, the collision of the Indian subcontinent and Asia, gave a great height to Mount Everest. Although the northward drift of India slowed dramatically with initial collision, the two continents have continued to converge as India slides under Asia.
Prior to the initial collision between India and Asia, the vast Tethys Sea existed between the two. The sea disappeared, a victim of plate tectonics, but its presence before 50 million years ago is recorded by scraps of oceanic crust preserved in the southern Tibetan plateau. It is not surprising that scientists consider the Himalayan range to be one of the planet’s best natural laboratories for studying the mountain building process and associated seismic activity. Dr. Bilham, a geophysicist on the EVEREST team, is conducting research to better understand the processes that drive seismic activity in Nepal and to help assess the danger of destructive earthquakes in Nepal and northern India. In this century, four earthquakes of Richter Magnitude 8 or greater have occurred in the Himalayas. Scientists expect another of similar magnitude to occur yet this century, putting millions of lives at risk.
At 29,028 feet, Mount Everest is five miles up — about the cruising altitude of a jet airliner. Data collected by Dr. Bilham indicates the world’s highest mountain is creeping skyward 3 to 5 millimeters with every passing year. Every time a team reaches the summit, the climbers are essentially setting a new altitude record.
Prior to the initial collision between India and Asia, the vast Tethys Sea existed between the two. The sea disappeared, a victim of plate tectonics, but its presence before 50 million years ago is recorded by scraps of oceanic crust preserved in the southern Tibetan plateau. It is not surprising that scientists consider the Himalayan range to be one of the planet’s best natural laboratories for studying the mountain building process and associated seismic activity. Dr. Bilham, a geophysicist on the EVEREST team, is conducting research to better understand the processes that drive seismic activity in Nepal and to help assess the danger of destructive earthquakes in Nepal and northern India. In this century, four earthquakes of Richter Magnitude 8 or greater have occurred in the Himalayas. Scientists expect another of similar magnitude to occur yet this century, putting millions of lives at risk.
At 29,028 feet, Mount Everest is five miles up — about the cruising altitude of a jet airliner. Data collected by Dr. Bilham indicates the world’s highest mountain is creeping skyward 3 to 5 millimeters with every passing year. Every time a team reaches the summit, the climbers are essentially setting a new altitude record.
Loads on Helicopter Landing Area
In addition to the all loads (Rain loads, loads due to flood and surge, temperature effects, snow load, soil and hydrostatic pressure, loads due to explosions, and vertical forces on air raid shelter) that may occur in this(Helicopter Landing Area) area including dead loads, the minimum live load on helicopter Landing or touchdown Area shall be one of the loads L1, L2, L3 as given below producing the most unfavorable effect:
1. L1 = W1
2. L2 =KW2
3. L3 = w
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| World Highest Helipad in Burj Al Arab |
Where, W1 = Actual weight of the helicopter in KN,
W2= Fully loaded weight of the helicopter in KN,
w = A distributed load of 5.0 KN/m2,
K=0.75 for helicopters equipped with hydraulic type shock absorbers and
= 1.5 for helicopters with rigid or skid type land
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| Helicopter Landed on World Highest Helipad in Burj Al Arab |
The live load, L1 shall be applied over the actual of contact of landing. The load, L2 shall be a single concentrated load including impact applied over a 300 mm X 300 mm area. The loads, L1 and L2 may be applied anywhere within the landing area to produce the most unfavorable effects of loading.
Volcano-Earthquake Relationship of Philippines
The 1991 eruption of Mount Pinatubo is the world's second largest terrestrial eruption of the 20th century. Successful predictions of the onset of the climactic eruption led to the evacuation of tens of thousands of people from the surrounding areas, saving many lives, but as the surrounding areas were severely damaged by pyroclastic flows, ash deposits, and later, lahars caused by rainwater remobilising earlier volcanic deposits, thousands of houses were destroyed.
Fig: Map showing major volcanoes of the Philippines.
Fig: Map showing major volcanoes of the Philippines.
Mayon Volcano is the Philippines' most active volcano. The volcano has steep upper slopes that average 35–40 degrees and is capped by a small summit crater. The historical eruptions of this basaltic-andesitic volcano dates back to 1616 and ranges from Strombolian to basaltic Plinian eruptions.
Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas.
Fig: Mayon Volcano overlooks a pastoral scene approximately five months before the volcano's violent eruption in September 1984.
Taal Volcano has had 33 recorded eruptions since 1572. A devastating eruption occurred in 1911, which claimed more than a thousand lives. The deposits of that eruption consisted of a yellowish, fairly decomposed (non-juvenile) tephra with a high sulfur content. The most recent period of activity lasted from 1965 to 1977, and was characterized by the interaction of magma with the lake water, which produced violent phreatic explosions. Although the volcano has been dormant since 1977, it has shown signs of unrest since 1991, with strong seismic activity and ground fracturing events, as well as the formation of small mud geysers on parts of the island.
Kanlaon is the most active volcano in central Philippines and has erupted 25 times since 1866. Eruptions are typically phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano. On August 10, 1996, Kanlaon erupted without warning, killing British student Julian Green and Filipinos Noel Tragico and Neil Perez, who were among 24 mountainclimbers who were trapped near the summit.
Need for Structural Safety
A structural failure, in some cases, would merely be an inconvenience. In other cases, loss of life and significant loss of property may be involved. This occurrence is considered in proportioning and designing structural member seriously. The methods of designing has been developed to have sufficient warning before failure before failure. Safety is provided to the structures to develop adequate strength against all loads that may foreseeable act on it.
If the strength of a structure, built as designed, could be predicted accurately, and if the loads and their internal effects (moments, shear, and axial forces) were known accurately, safety could be ensured by providing a carrying capacity just barely in excess of the known loads. However, there are a number of sources of uncertainty in the analysis, design and construction of reinforced concrete structures. These sources of uncertainty, which require a definite margin of safety, may be listed as follows:
1. The assumed intensity of load may not be same as that of actual intensity.
2. Actual loads may be distributed in a manner different from that assumed.
3. The assumptions and simplifications inherent in any analysis may result in calculated load effects-moments, shears etc. different from those that, in fact, act in the structures.
4. The actual structural behavior may differ from that assumed , owing to imperfect knowledge.
5. Actual member dimensions may differ from those specified.
6. Reinforcement may not be in its proper position.
7. Actual material strength may be different from that specified.
It is evident that the selection of an appropriate margin of safety is not a simple matter. But, considering the consequence of failure, the design codes are developing rational safety provisions.
If the strength of a structure, built as designed, could be predicted accurately, and if the loads and their internal effects (moments, shear, and axial forces) were known accurately, safety could be ensured by providing a carrying capacity just barely in excess of the known loads. However, there are a number of sources of uncertainty in the analysis, design and construction of reinforced concrete structures. These sources of uncertainty, which require a definite margin of safety, may be listed as follows:
1. The assumed intensity of load may not be same as that of actual intensity.
2. Actual loads may be distributed in a manner different from that assumed.
3. The assumptions and simplifications inherent in any analysis may result in calculated load effects-moments, shears etc. different from those that, in fact, act in the structures.
4. The actual structural behavior may differ from that assumed , owing to imperfect knowledge.
5. Actual member dimensions may differ from those specified.
6. Reinforcement may not be in its proper position.
7. Actual material strength may be different from that specified.
It is evident that the selection of an appropriate margin of safety is not a simple matter. But, considering the consequence of failure, the design codes are developing rational safety provisions.
Most Destructive Known Earthquake (Life loss)
The earthquake occurred near Huaxian, Shaanxi (formerly Shensi), China, about 50 miles (80 km) east-northeast of Xi'an, the capital of Shaanxi. More than 830,000 people were killed. Damage extended as far away as Taiyuan, the capital of Shanxi (formerly Shansi) and about 270 miles (430 km) northeast of the epicenter. There are felt reports as far away as Liuyang in Hunan, more than 500 miles (800 km) away. Geological effects reported with this earthquake included ground fissures, uplift, subsidence, sandblows, liquefaction and landslides. Most towns in the damage area reported city walls collapsed, most to all houses collapsed and many of the towns reported ground fissures with water gushing out (ie. liquefaction and sandblows). Gu, et.al. says that "the identified death toll of soldiers and civilians was 830,000, and the unidentified was uncountable." The earthquake was felt in all or parts of 9 provinces: Anhui, Gansu, Hebei, Hubei, Henan, Hunan, Shaanxi, Shandong and Shanxi. The maximum intensity is XI in the Huaxian-Weinan area and the estimated magnitude is 8. Additional details from Gu, et.al.:
In Huaxian, "city walls, temples, offices and civilian houses were demolished, without a single wall left standing.... The ground fissured and sunk. Water gushed out and formed canals. Sixty percent of the people (several tens of thousands were killed or injured."
In Weinan [15 miles (24 km) west of Huaxian], "city walls, temples, storehouses, offices and civilian houses collapsed totally.... In the city, the ground sunk for more than 3 meters. Fifty percent of the people were killed."
In Xi'an [one of China's major cities then as it is now], "city walls, storeyed buildings and terraces collapsed. Most temples were destroyed. More than half of the houses toppled down. Only 10-20 percent of the walls were left standing. The ground fissured crisscross. Thirty percent of the people were killed."
Even as far away as Taiyuan, "houses were destroyed in great numbers."
In many references, this earthquake is referred to as the "Shensi Province earthquake of 1556" using the old spelling for the province.
In Huaxian, "city walls, temples, offices and civilian houses were demolished, without a single wall left standing.... The ground fissured and sunk. Water gushed out and formed canals. Sixty percent of the people (several tens of thousands were killed or injured."
In Weinan [15 miles (24 km) west of Huaxian], "city walls, temples, storehouses, offices and civilian houses collapsed totally.... In the city, the ground sunk for more than 3 meters. Fifty percent of the people were killed."
In Xi'an [one of China's major cities then as it is now], "city walls, storeyed buildings and terraces collapsed. Most temples were destroyed. More than half of the houses toppled down. Only 10-20 percent of the walls were left standing. The ground fissured crisscross. Thirty percent of the people were killed."
Even as far away as Taiyuan, "houses were destroyed in great numbers."
In many references, this earthquake is referred to as the "Shensi Province earthquake of 1556" using the old spelling for the province.
Destruction of 2004 Great Sumatra Earthquake
This is the third largest earthquake in the world since 1900 and is the largest since the 1964 Prince William Sound, Alaska earthquake. In total, 227,898 people were killed or were missing and presumed dead and about 1.7 million people were displaced by the earthquake and subsequent tsunami in 14 countries in South Asia and East Africa. (In January 2005, the death toll was 286,000. In April 2005, Indonesia reduced its estimate for the number missing by over 50,000.) The earthquake was felt (IX) at Banda Aceh, (VIII) at Meulaboh and (IV) at Medan, Sumatra and (III-V) in parts of Bangladesh, India, Malaysia, Maldives, Myanmar, Singapore, Sri Lanka and Thailand. The tsunami caused more casualties than any other in recorded history and was recorded nearly world-wide on tide gauges in the Indian, Pacific and Atlantic Oceans. Seiches were observed in India and the United States. Subsidence and landslides were observed in Sumatra. A mud volcano near Baratang, Andaman Islands became active on December 28 and gas emissions were reported in Arakan, Myanmar.
FLAT PLATE SYSTEM HAVING STEEL/ CONCRETE COLUMN
Popularity of Flate Plate
The use of flatplate appeals to designers particularly because design flexibility is possible through shifting of walls without the need for columns to be properly aligned. With increasing demand for flexibility in interior layout, the use of flat plate for landed houses is gaining much popularity amongst architects. The main and unique feature of this system is that it provides a way for the architect to achieve the concept of high and completely flat ceiling with no beam protrusion. The services can be installed within or below the slab and there are flexibilities in relocating vertical small penetrations. The soffit is often flat and high ceiling height can be achieved.
Columns Used
The columns used in this system are either cast in-situ concrete columns or circular steel hollow sections. When the columns used are steel hollow sections with concrete in-fill, the desired finish with exposed steel can be easily achieved.
Connection & Detailing
The main consideration for steel column connection to flat plate is to ensure that the base plate for the steel columns are cast into the concrete flat plate. Hence the positioning and alignment of the base plates are of utmost importance.
If concrete in-fill and column bars are required within the steel hollow section, the starter bars for the columns have to be placed and fixed in position prior to casting of concrete flat plate (see figure 2.0 for base plate connection).
Columns Used
The columns used in this system are either cast in-situ concrete columns or circular steel hollow sections. When the columns used are steel hollow sections with concrete in-fill, the desired finish with exposed steel can be easily achieved.
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| Flat plate system with circular steel column |
The main consideration for steel column connection to flat plate is to ensure that the base plate for the steel columns are cast into the concrete flat plate. Hence the positioning and alignment of the base plates are of utmost importance.
If concrete in-fill and column bars are required within the steel hollow section, the starter bars for the columns have to be placed and fixed in position prior to casting of concrete flat plate (see figure 2.0 for base plate connection).
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| Figure 2.0 : Base plate details for column |
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| Figure 3.0 : Examples of shear reinforcement |
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| Figure 4.0 : Hidden beam within column strip |
Limitation of CFRP
CFRP is used in civil engineering, automobile and other fields. But it have some drawbacks which limits its use in some fields. The first one is cost. Though CFRP is generally regarded as having superior properties, it is more costly material that its counterparts in the construction industry, glass fibre reinforced polymer (GFRP) and aramid fibre reinforced polymer (AFRP). In case of prestressing construction it cannot be used due to difficulties in anchorage of strands.
Much research continues to be done on using CFRP both for retrofitting and as an alternative to steel as a reinforcing or prestressing material. Cost remains an issue and long term durability questions still remain. Some are concerned about the brittle nature of CFRP, in contrast to the ductility of steel. Though design codes have been drawn up by institutions such as the American Concrete Institute, there remains some hesitation among the engineering community about implementing these alternative materials. In part this is due to a lack of standardisation and the proprietary nature of the fiber and resin combinations on the market, though this in itself is advantageous in that the material properties can be tailored to the desired application requirements.
It have no endurance limit when exposed to cyclic loading. In case of recycling to reclaim the carbon fibre, the milling or shredding at low temperature shortens the fibres dramatically. The shortened fibres cause the recycled material to be weaker than the original material. Other processing of reclaiming carbon fibre are costly.
Much research continues to be done on using CFRP both for retrofitting and as an alternative to steel as a reinforcing or prestressing material. Cost remains an issue and long term durability questions still remain. Some are concerned about the brittle nature of CFRP, in contrast to the ductility of steel. Though design codes have been drawn up by institutions such as the American Concrete Institute, there remains some hesitation among the engineering community about implementing these alternative materials. In part this is due to a lack of standardisation and the proprietary nature of the fiber and resin combinations on the market, though this in itself is advantageous in that the material properties can be tailored to the desired application requirements.
It have no endurance limit when exposed to cyclic loading. In case of recycling to reclaim the carbon fibre, the milling or shredding at low temperature shortens the fibres dramatically. The shortened fibres cause the recycled material to be weaker than the original material. Other processing of reclaiming carbon fibre are costly.
In case of automative application, its use is limited for creating body-panel for some of high-end cars, hood, spoiler. However, these parts are rarely made of full carbon fibre. They are often just a single layer of carbon fiber laminated onto fiberglass for the "look" of carbon fiber. It is common for these parts to remain unpainted to accentuate the look of the carbon fiber weave.
Application of CFRP in Sports Equipments
In high-end sports equipments carbon fibre reinforced polymer has found perfect due to its light weighing property in compare to aluminium or steel. Racing bicycle is the thing where it is used widely. It produce bicycle tubing of less weight.
Fig: IVW Develops World Record Racing Bike(1).
[1. German bicycle manufacturer Canyon Bicycles GmbH, has developed a racing bike chassis of carbon fibre reinforced polymer with the Institut fuer Verbundwerkstoffe (IVW).
The lightweight Carbon Ultimate F10 bike boasts a total weight of only 1260 grams (for the frame and fork) and its high stiffness for the first time exceeded the cyclists magical limit of 100 of the stiffness to weight ratio, the so-called STW-coefficient.
The Carbon Ultimate F10 chassis received the coveted red dot award, the international trademark for quality of design, in the red dot design award 2005, one of the largest design competitions worldwide with more than 4000 applications from 40 countries.]
The choice of weave can be carefully selected to maximize stiffness. The variety of shapes it can be built into has further increased stiffness and also allowed aerodynamic considerations into tube profiles. Carbon fiber reinforced polymer frames, forks, handlebars, seatposts and crank arms are becoming more common on medium- and higher-priced bicycles. Carbon fiber reinforced polymer forks are used on most new racing bicycles.
Other sporting goods applications include rackets, fishing rods, longboards and rowing shells. Sports shoe manufacturers may use carbon fiber as a shank plate in their basketball sneakers to keep the foot stable. It usually runs the length of the sneaker just above the sole and is left exposed in some areas, usually in the arch of the foot.
Carbon fiber reinforced polymer is used extensively in high end automobile racing. The high cost of carbon fiber is mitigated by the material's unsurpassed strength-to-weight ratio, and low weight is essential for high-performance automobile racing.
The choice of weave can be carefully selected to maximize stiffness. The variety of shapes it can be built into has further increased stiffness and also allowed aerodynamic considerations into tube profiles. Carbon fiber reinforced polymer frames, forks, handlebars, seatposts and crank arms are becoming more common on medium- and higher-priced bicycles. Carbon fiber reinforced polymer forks are used on most new racing bicycles.
Other sporting goods applications include rackets, fishing rods, longboards and rowing shells. Sports shoe manufacturers may use carbon fiber as a shank plate in their basketball sneakers to keep the foot stable. It usually runs the length of the sneaker just above the sole and is left exposed in some areas, usually in the arch of the foot.
Carbon fiber reinforced polymer is used extensively in high end automobile racing. The high cost of carbon fiber is mitigated by the material's unsurpassed strength-to-weight ratio, and low weight is essential for high-performance automobile racing.
Tectonic Summary of Sumatra earthquake, 2009-09-30
The magnitude 7.6 southern Sumatra earthquake of September 30, 2009 widely felt throughout Sumatra and Java, Indonesia, Malaysia, Singapore and Thailand. A small local tsunami with wave heights of 27 centimeters (amplitude measured relative to normal sea level) was generated. This occurred as a result of oblique-thrust faulting near the subduction interface plate boundary between the Australian and Sunda plates. At the location of this earthquake, the Australian Plate moves northeast with respect to the Sunda plate at a velocity of approximately 65 mm/yr.
On the basis of the currently available fault mechanism information and earthquake depth of 80 km, it is likely that this earthquake occurred within the subducting Australian Plate rather than on the plate interface itself. The recent earthquake was deeper than typical subduction thrust earthquakes that generally occur at depths less than 50 km.
The subduction zone surrounding the immediate region of this event has not witnessed a megathrust earthquake in the recent past, rupturing last in an earthquake of M 8.5 or larger in 1797. Approximately 350 km to the south, a 250 km section of the plate boundary slipped during an Mw 8.4 earthquake in September 2007, while approximately 300 km to the north, a 350 km section slipped during the Mw 8.7 earthquake of March 2005. In early 2008, the plate boundary updip of today’s earthquake was active in a sequence of Mw 5-6 earthquakes. It is not clear how today’s earthquake is related to the sequence of megathrust subduction zone events on the shallower section of the plate boundary.
On the basis of the currently available fault mechanism information and earthquake depth of 80 km, it is likely that this earthquake occurred within the subducting Australian Plate rather than on the plate interface itself. The recent earthquake was deeper than typical subduction thrust earthquakes that generally occur at depths less than 50 km.
The subduction zone surrounding the immediate region of this event has not witnessed a megathrust earthquake in the recent past, rupturing last in an earthquake of M 8.5 or larger in 1797. Approximately 350 km to the south, a 250 km section of the plate boundary slipped during an Mw 8.4 earthquake in September 2007, while approximately 300 km to the north, a 350 km section slipped during the Mw 8.7 earthquake of March 2005. In early 2008, the plate boundary updip of today’s earthquake was active in a sequence of Mw 5-6 earthquakes. It is not clear how today’s earthquake is related to the sequence of megathrust subduction zone events on the shallower section of the plate boundary.
Application of CFRP in Aerodynamics
Carbon Fibre Reinforced Polymer has found a lot of use in aerodynamics. For the same strength, a carbon-fiber frame weighs less than a aircraft of any alloy. The New arrived Boeing (fuselage) 787 Dreamliner and Airbus A350 XWB will be composed of CFRP, making the aircraft lighter than a comparable aluminum fuselage, with the added benefit of less maintenance thanks to CFRP's superior fatigue resistance.
[1. Thick large-sized panel of a high-aspect swept-forward wing of the highly maneuverable aircraft made from high-modulus CFRP by automated lay-up technique with the use of special non-metallic moulding equipment.
A kit of 4 panels (two upper panels and two lower panels):
A kit of 4 panels (two upper panels and two lower panels):
A. Mass of one panel - no more than 250 kg
B. Plan size - more than 6500x2500 mm2
C. Thickness - more than 18 mmLarge panel thickness and overall dimensions, as well as stringent requirements placed upon the accuracy of the aerodynamic surface, render this development unique. High accuracy of the aerodynamic surface has been obtained.]
B. Plan size - more than 6500x2500 mm2
C. Thickness - more than 18 mmLarge panel thickness and overall dimensions, as well as stringent requirements placed upon the accuracy of the aerodynamic surface, render this development unique. High accuracy of the aerodynamic surface has been obtained.]
Due to its high ratio of strength to weight, CFRP is widely used in micro air vehicles (MAVs). In MAVSTAR Project, the CFRP structures reduce the weight of the MAV significantly. In addition, the high stiffness of the CFRP blades overcome the problem of collision between blades under strong wind.
CFRP is used, either as standard equipment or aftermarket parts, in high performance radio controlled vehicles and aircraft, i.a. for the main rotor blades of radio controlled helicopters -- which should be light and stiff to perform 3D manoeuvres.
Fire resistance of polymers or thermoset composites is significantly improved if a thin layer of carbon fibers is molded near the surface -- dense, compact layer of carbon fibers efficiently reflects heat. This property is also make it important in this field.
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