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.

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.

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.

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.

Flat plate system with circular steel column

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).

Figure 2.0 : Base plate details for column

In the concrete column with flat plate design, the connection is more simplified without the need for base plate connection. In this case, reinforcement bars should be properly detailed between the columns and slabs. Punching shear checks are critical and vertical shear reinforcement should be detailed accordingly.

Figure 3.0 : Examples of shear reinforcement

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.

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.

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.

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. 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.]

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.