Presentation on theme: "Earthquakes and Architecture. What is an earthquake ? An earthquake is a sudden release of energy due to shifts in the earths plates that has been stored."— Presentation transcript:
Earthquakes and Architecture
What is an earthquake ? An earthquake is a sudden release of energy due to shifts in the earths plates that has been stored in the rocks beneath the earths surface which causes a trembling or shaking of the ground. The energy that is released from the ruptured rock travels in waves which are known as seismic waves. There are two types of seismic waves; body waves which travel through the interior of Earth and surface waves which travel on Earth's surface. The two body waves are primary waves (p-waves) and secondary waves (s-waves).
Kobe Earthquake Japan 1995 Structures in Kobe built since 1981 had been designed to strict seismic codes. Most of these buildings withstood the earthquake. In particular, newly built ductile-frame high rise buildings were generally undamaged.
The compressional (push-pull) wave will vibrate parallel to the direction that the wave is traveling up to speeds of 4 to 8 km per second (2.49 to 4.35 miles per second). The S-wave vibrates perpendicular to the direction of travel and can travel up to speeds of 2 to 5 km per second ( 1.24 to 3.11 miles per second). Love waves and Raleigh waves are known as Surface waves. Surface waves are the slowest of the seismic waves, but because they travel near the surface of Earth and contain a range of oscillating frequencies they often cause the most damage
Northridge Earthquake Southern California 1994
World Earthquake Fault Lines
Plate Tectonics A spreading boundary is where the tectonic plates are separating. These are places where volcanic activity is at a premium because the crust is being torn open (as in splitting and cracking, like an egg breaking open). New crust is forming when molten lava from deep down oozes out of the cracks where the plates are coming apart.
A converging boundary is when one plate (usually the lighter continental crust) rides up over the top of the other it's called a subduction zone - because one plate margin is being subducted under the other.
What is liquefaction? This residential and commerial building sank more than three feet into the partially liquefied soil. Photo credit: Reinsurance Company, Munich Germany
Liquefaction is a type of ground failure in which water saturated sediment turns from a solid to a liquid as a result of shaking, often caused by an earthquake or even a volcanic eruption. In order for the liquefaction to occur the sand grains must be fine grain sand that are not closely packed together nor must it be held but some sort of cohesion. The intense shaking causes the strength of the soil to become weak and the sand and water begin to flow.
A major cause of damage was liquefaction of the recent alluvial deposits that underlaid large portions of the city. The result was excessive settlements and bearing capacity failures for countless buildings, most of which were supported on shallow foundations. This new building was not yet occupied at the time of the earthquake. Again, the bearing failure of its mat foundation was related to its relatively large height- to-width ratio. Adapazari, Turkey, 1999 Kocaeli earthquake
What do Architects do? Architects design buildings and structures. They advise individuals, property owners and developers, community groups, local authorities and commercial organizations on the design and construction of new buildings, the reuse of existing buildings and the spaces which surround them. Architects work closely with other members of the construction industry including engineers, builders, surveyors, local authority planners and building control officers. Much of their time is spent visiting sites assessing the feasibility of a project, inspecting building work or managing the construction process. They will also spend time researching old records and drawings, and testing new ideas and construction techniques. Society looks to architects to define new and better ways of living and working, to develop innovative ways of using existing buildings and creating new ones. Architects can be extremely influential as well as admired for their imagination and creative skills.
What do Structural Engineers do? Structural engineering's combine their knowledge of science and design making as they construct better framework for buildings and other structures to safely resist natural and made-made forces. They are involved in physical testing, mathematical modeling, computer simulation all of which support decisions that Aid in the creation and maintenance of safe and economical structures. /
What is Earthquake Engineering? Earthquake engineers are concerned with creating earthquakes resistant designs and construction techniques to build of all kinds of bridges, roads and buildings. Earthquake engineers are faced with many uncertainties and must be smart in their decisions in developing safe solutions to challenging problems. They rely on state-of-the-art technology, materials science, laboratory testing and field monitoring.
Earthquake-Resistant Structure Building designed to prevent total collapse, preserve life, and minimize damage
Worlds Tallest Bridge Millau, France 2004
San Francisco-Oakland Bay Bridge reconstruction, USA begun 2002
Engineers chose a hybrid girder design that combined the rigidity, noise absorption, and low cost of concrete with the precision manufacturing offered by steel. The systems reinforced-concrete support piers are designed to withstand the seismic forces of earthquakes measuring up to 7.5 on the Richter scale. High-Speed Magnetic Levitation Rail Line Shanghai, China 2004
Nepal Develops Earthquake Resistant Architecture A plan for safer houses in rural areas Nepal has a history of being devastated by major earthquakes every 75 to 100 years, with the first recorded as early as 1255 AD. In 1934 Nepal experienced a deadly earthquake that resulted in the death of 8,500 people and destruction of 20 percent of valley structures, at a time when the population was far less than at present. Seismologists are predicting the occurrence of a large earthquake of this kind in the near future, which is likely to be most intense in the urban core.
Ninety percent of Nepalese houses are made of stone and unfired bricks. The Structural Engineers in Nepal are retrofitting current structures for about $25/home. By creating a one-meter square grid of punched holes in the stone wall covered with a 10 cm mesh of bamboo on the inside and outside the homes become earthquake resistant. This net is Secured to the wall by means of 12-gauge Gabion wire, (a form of riprap contained in a wire cage that is very useful in erosion control.), which is inserted through the holes and fastened strongly. It is covered with a stucco of mud, which is used in rural areas in order to ensure longer life for the bamboo mesh.
The Lefkas (Greece) earthquake resistant technique Two-story houses are built with a ground floor of rough boulder masonry and three lines of wooden posts (one along each long wall, and one in the middle of the room) support the first floor. This one is erected in wood-frame construction (Dajji). Foundations are laid on a three-layer round-poles mat, which could behave as a spring if a gap was left around. The main benefit is outspread of the foundation surface. "Dajji" is traditional in Cashmere (India). It is very efficient and affordable. A wooden frame is built without bracing. The empty rectangular or square "panels" are filled with a mesh of wood and stone cemented with mud. These panels work as bracing, but allow slight movement, and give elasticity to the whole structure. Thus, the house is able to move and to absorb the earthquakes movement. Another advantage of this technique is to be (comparatively) lightweight, and thus being less stressed by earthquakes.
Kobe Earthquake Japan Magnitude Homes and building construction was older built with heavy tile roofs that collapsed
Another anomaly was the large number of about 20-year-old high rise buildings that collapsed at the fifth floor. The older version of the code they were built under allowed a weaker superstructure beginning at the fifth floor.
Behind this completely collapsed wood-frame house is a house of reinforced concrete that suffered no structural damage. The number of wood versus masonry buildings that collapsed in Kobe astonished most observers, as wood-frame structures are usually thought to be much better at resisting shear forces. Possibly the concrete house was better-designed and stronger even for its greater weight. The proportionally heavier tile roofs on wooden houses also might have been a factor.
Mexico City Earthquake, Magnitude Poorly constructed buildings caused thousands of deaths
Damage to the Intercontinental Hotel during Mexico City's 1985 earthquake was severe even though the building was relatively new
The 1985 Mexico City Earthquake Quicklinks Mexico City Main Page -Damage photographs -Modifications to building design -Earthquake Basics -Liquefaction Effects -Cocos Plate Seduction Angle1985 Mexico City Main PageDamage photographsModifications to building designEarthquake BasicsLiquefaction EffectsCocos Plate Seduction Angle Building Design After the earthquake in Mexico City, Mexican officials adopted a new design that can protect the buildings from earthquakes. This design was developed by some engineers at the University of California at Berkeley. Looking at the diagram below you can see that the braces form an X which are anchored in concrete blocks at the base and on the roof of the building. In diagram A we have conventional steel bracing. Under the stress of the earthquake one of the braces collapses under the stress. If all the braces begging to snap then the structural integrity of the building fails. Now in diagram B, the engineers at Berkely used a hydraulic jack to pull or stretch the rods. Once the rods are prestressed they can now be anchored to the base and to the roof of the building. The braces now have some room to contract thereby strengthening the structural integrity of the building.
Northridge Earthquake, 1994 Southern California, USA 6.7 Magnitude most houses were wooden and did not collapse
Problems for Building Structures when Seismic Waves pass For tall buildings the top may sway in the opposite direction as the base Buildings in close proximity with one another may collide do to differing phase motions. Changing types of wave motion cause damage. Buildings with different resonant frequencies will be affected differently by passing seismic waves depending on the wave frequency.
Loma Prieta Earthquake, 1989 San Francisco Bay, California 7.1 magnitude Many homes were damaged because of old construction- unreinforced bricks and mortar Many building and homes were built on were unconsolidated flood plain sedimentary land (In contrast, nearby sections of the city experienced only minor damage. These areas contain sturdy wood frame houses built on relatively stable marine terraces.)
As the second story of this building collapsed, its facade fell into the street, knocking down the tree which in turn damaged the car. This building in downtown was one of the heavily damaged buildings situated on the unconsolidated flood plain sediments of the San Lorenzo River.
An automobile lies crushed under the third story of this apartment building in the Marina District. The ground levels are no longer visible because of structural failure and sinking due to liquefaction
Collapsed brickwork from a corner apartment building, Marina District.
Oakland Support failure pubs.usgs.gov/dds/dds-29 /http:// pubs.usgs.gov/dds/dds-29 /
Oakland Bridge failure
Structural Design Project Part One: In collaboration with Science 7 use KNex to build a 3+ story structure and demonstrate its ability to make it through an earthquake. Keep notes and drawings, make your hypothesis, itemize materials. Group work. Make revisions and demonstrate renewed ability to make it through an earthquake. Part Two: Design an earthquake resistant 3+ story structure constructed using 50% recycled and 50% new materials. As in Part One, demonstrate its ability to make it through an earthquake. Keep notes and drawings, make your hypothesis, itemize materials. Contract project as a group or as individual work. Make revisions and demonstrate renewed ability to make it through an earthquake. Due date Part One: Due date Part Two: All drawings, material critique, hypothesis and conclusions concerning earthquake structural engineering as it relates to architectural design.