Structural collapse

EarthquakesEvery earthquake provides us with new knowledge and new found knowledge gained from past earthquakes. Fazlzal Mexico City September 1985 can be seen as a huge amount of energy and losses. Has lasted four minutes and led to the destruction of more than 250 buildings and killed more than 10,000 people (Figure 2.4). And the positive effect only for such an event is knowledge that can we achieve to mitigate the effects of future disaster.There is nothing better than to show a strong earthquake is directly related to the limited human engineering energy destructive potential of the natural environment. Despite the great amount of progress achieved in the assessment of the impact of earthquakes on the facilities we still have much to learn.James Omrhin and is the Structural Engineer and Executive Director of the Association of American builders gave the following description of the Structural Engineering:"Structural Engineering is the art and science that in the modeling of materials that do not fully understand,To the forms we can not analyze accurately, to resist the loads can not be expected to fully,All this in a society that the vast majority do not realize the limited knowledge that we take it "The science of geology has developed our capabilities to predict the places where potential earthquakes occur significantly, and the theory of evolution has given us a better understanding of platelet origin of geological earthquakes. Despite this we know that there is no area where an earthquake is impossible to obtain. And actually has got many severe earthquakes in areas far from the seismic packages "plate boundaries", and Examples include earthquake Charleston in South Carolina in 1886 and three successive earthquakes in New Madrid in Missouri between 1811-1812. Missouri and frequency tremors years 1811-1812 (estimated intensity on the Richter scale 8.5) may cause damage estimated at $ 50 billion to increase the area of ​​500,000 km ^ 2.The impact of earthquakes can be divided according to the following four items: (1) cracking of the earth's surface, (2) the collapse of the soil, (3) tsunami, and (4) vibration of the earth. Among these four species and the impact of vibration of the ground can be significantly lower during the implementation of high-quality engineering. While the land survey is an effective tool used more for the remaining three varieties.Cracking of the surface occurs in regions of the cracks. Where the cracks and the relative standing Alandziahat potential significantly, if possible, determine the expected locations of the surface cracks, you should simply avoid these places for installations and facilities. Has led the San Francisco earthquake 1906 to shifts relative horizontal along the San Andreas fault more than six meters, it is clear that it is impossible to design system construction to comply with such shifts, and thus regardless of the knowledge engineering impossible for us to secure the safety of installations in places that have cracked the earth potential .The collapse of the soil can be expected in the soils of others fixed at the time of vibration of the earth. And the phenomenon of collapse These include landslides, huge Alhbutat few in the soil compaction, and liquefaction. These effects may occur in places far from the epicenter of the earthquake. Impossible to determine where the breakdown may occur in the soil (Figure 2.5). And the best strategy to counter this problem is to avoid the expansion of sensitive sites, and again through the enactment of regulations on land survey and characterization. Taatmaa when the soil is losing the ability to bear shear, and thus lose the foundation surface - no matter how good construction - stability.Seismic sea waves, or tsunami, is a real threat to the residential communities near the beaches everywhere, and in some cases be very devastating tsunami, and their effects can not Structural Engineering and quality of implementation cope with, but the best defense is simply a warning and evacuation. The damage to the built environment as a result of seismic sea waves will continue to obtain, but the tragic loss of life decreased significantly with the development of prediction and warning capabilities. The most destructive tsunami recorded associated with the volcanic eruption of Krakatoa in 1883. Where the wave height was more than 40 m and has cleared the island of Java lethal over 36.000 people and removing all the villages, and killed in 1896 tsunami 27.000 10.000 Japanese and destroyed a house. The seismic sea waves can cause damage far from the epicenter of the earthquake, Fazlzal Onchoraj, born 1964 Alaska tsunami flooded the 30 buildings in the Crescent City, California, which lies more than 2500 km from the Onchoraj.Most of the structural engineering solutions focused on mitigating the effects of vibration of the earth. And fortunately there is much we can do to improve the performance of our facilities when subjected to seismic tremors. Since the forces concentrated on the mass of the entity established, thus light weight materials will decrease the harmful effects of the earthquake. And have learned that the architectural composition plays an important role in withstanding earthquakes. Valmsagt Tabaka regular solid with elements distributed symmetrically help reduce the possibility of a torsion stresses. It also provides the system construction pliant ability to store energy in the form of temporary distortions and prevent the total collapse in strong earthquakes. On the other hand must be limited to avoid the distortions suffered non-structural elements.It is known that the lack of structural continuity, such as declines in projected cuts and a change in hardness at the floor level and lead to dangerous concentrations of a stress. The safety of construction joints and abundance plays a critical role in the resilience of the facility. And must be aware that the fall of the unknown elements construction (panels concrete pre-casting, barriers balconies, and the walls of incisors stone) are likely to be a threat to human safety like the collapse of structural elements important, and these elements must be designed and tailored carefully (to Lagorio 1990).We have concluded that these principles through experience - and learn from the collapse of success. And is included in modern building codes, these codes and the updated responsible for the noticeable decrease in the losses, deaths, and injuries, where it had been implemented.One of the major disadvantages is the problem of seismic tremors for high seismic intensity in the regions of the world is not qualified enough to deal with them both in terms of social, economic or technical. And although we now know the value of the force, and Almtoaih, and light weight, and reliability of the materials, and the importance of the quality of the study and implementation, the appropriate material and economic resources and engineering expertise is not available in most areas, the massive loss of life caused by earthquakes in many areas are, for example, is clearly related with the limited construction materials, where the heavy stones of others and pliant unarmed is the only material available for residential buildings.The following table shows the number of earthquakes causing more loss of life:Intensity earthquake on the Richter scale(Almost) the number of deathsItaly 1908 7.5 75.000Italy 1915 7.0 30.000China 1920 8.6 180.000Japan 1923 8.3 143.000China 1927 8.3 200.000China 1932 7.6 70.000India in 1935 7.5 30.000Chile 1939 8.3 30.000Peru 1970 7.8 67.000China 1976 7.8 250.000Iran 1990 7.7 50.000
In most of these earthquakes because of the crush of people or large stone buildings, concrete reinforcing bad. The amount of loss of life is Tgber about the quality of construction materials and quality of implementation and how to prepare for seismic intensities such as those obtained. In 1960 Morocco claimed the earthquake (5.6 Richter) killed 12,000 people. 1980 in Italy earthquake (6.8 Richter) has led to the deaths of 3,000 people and damage estimated at $ 24 billion, and has strongly 6.0 Richter earthquake killed 2,000 Yemeni. And has lost more than 1000 people lost their lives in the 1986 El Salvador earthquake (5.4 Richter), while the 1988 Armenia earthquake (6.9 Richter) has reached 25,000 people human losses and material and $ 16 billion due to the collapse of the buildings pre-cast stone buildings and non-armed and implemented poorly, and in 1990 Iran earthquake (7.7 Richter) to the deaths of nearly 50,000 people due to the collapse of the stone buildings and unarmed residential buildings carried a brick-covered roofs and thick mud.Maxhexo city has suffered many earthquakes and some of the lessons learned from this earthquake, earthquakes, especially in 1985 (19 September 1985, 8.1 Richter, 10,000 victims, $ 5 billion damage) produced by successive recommendations that:• given the paramount importance of symmetry in architectural design and as a result of a number of landslides due to twisting.• Achieving and reinforcing the implementation of a detailed and careful to ensure the reduction of damage to the concrete, and be sure to match the design details of the reality of implementation.• ensuring the safety of links in the facility.• lay the foundations for an officer to implement the facilities contiguous, and as a result of obtaining many of the tragic landslides, especially in the neighboring buildings with floor area of ​​various elevations, which led to a collision between the tiles with solid multi-story building adjacent columns, and for collapse.Characterized by earthquakes in the United States, up losses of material and the low loss of life compared with other countries and may be one reason for this is the adoption of timber as building material.The earthquakes last two in Northridge, California (1994) and Kobe, Japan (1995) show that the developed countries technically and economically not in Manat for severe damage and casualties resulting from earthquakes, perished more than 5,400 people in Kobe and is the area were not prepared For a good earthquake.It is noted that the BB construction was developed from the sorts of experiences of trial and error, and there may be no link clearer between the landslides and the development of codes and specifications best of tags seismic, the Building Code Standard UBC and one of the best BB seismic design in the world, and reserves resulting from the study of many of the sites for earthquakes around the world. And the efforts made by the insured and does not doubt the safety of many engineering structures and maintained on the lives of many.And we can easily trace the development of reserves Quad seismic construction and its relationship with major earthquakes in the United States and other parts of the world, where every earthquake followed a significant improvement in the accession codes and specifications result of knowledge gained through experiences of trial and error (Ross, 1984).The seismic San Francisco, Tokyo, 1906 and 1923 led to increased awareness of the potential damage from earthquakes, and trade unions have begun to document the engineers took observations and seek to legislate what is art, and in 1925 Santa Barbara earthquake led California to adopt the first building codes seismic, precautions, which aimed to improve the performance of specific types of installations and facilities mainly built of stone blocks and concrete structures.And in 1933 was tested a number of new ideas in the Long Beach earthquake in California and led to improvements in the specifications of facilities may reduce earthquake losses.