Earthquake Loads & Earthquake Resistant Design of Buildings
1. 1
2. Summary 2
3. Earthquake Design - A Conceptual Review 2
4. Earthquake Resisting Performance Expectations 3
5. Key Material Parameters for Effective Earthquake Resistant Design 3
6. Earthquake Design Level Ground Motion 4
6.1. Elastic Response Spectra 4
6.2. Relative Seismicity 5
6.3. Soil amplification 6
7. Derivation of Ductile Design Response Spectra 7
8. Analysis and Earthquake Resistant Design Principles 8
8.1. The Basic Principles of Earthquake Resistant Design 8
8.2. Controls of the Analysis Procedure 8
8.3. The ‘Conventional’ Earthquake Design Procedure 11
9. The Capacity Design Philosophy for Earthquake Resistance 11
9.1. General Approach 11
9.2. The Implications of Capacity Design 12
10. Earthquake Resistant Structural Systems 12
10.1. Moment Resisting Frames: 12
10.2. Shear Walls 13
10.3. Braced Frames 13
11. The Importance & Implications of Structural Regularity 13
11.1. General 13
11.2. Vertical Regularity 14
11.3. Horizontal Regularity. 14
11.4. Floor Diaphragms 14
12. Methods of Analysis 15
12.1. Integrated Time History Analysis 15
12.2. Multi-modal Analysis 15
12.3. Equivalent Static Analysis 15
13. Trends and Future Directions 16
14. Conclusions 16
15. References 17
1.
Summary
The primary objective of earthquake resistant design is to prevent building collapse during earthquakes thus minimising the risk of death or injury to people in or around those buildings. Because damaging earthquakes are rare, economics dictate that damage to buildings is expected and acceptable provided collapse is avoided.
Earthquake forces are generated by the inertia of buildings as they dynamically respond to ground motion. The dynamic nature of the response makes earthquake loadings markedly different from other building loads. Designer temptation to consider earthquakes as ‘a very strong wind’ is a trap that must be avoided since the dynamic characteristics of the building are fundamental to the structural response and thus the earthquake induced actions are able to be mitigated by design.
The concept of dynamic considerations of buildings is one which sometimes generates unease and uncertainty within the designer. Although this is understandable, and a common characteristic of any new challenge, it is usually misplaced. Effective earthquake design methodologies can be, and usually are, easily simplified without detracting from the effectiveness of the design. Indeed the high level of uncertainty relating to the ground motion generated by earthquakes seldom justifies the often used complex analysis techniques nor the high level of design sophistication often employed. A good earthquake engineering design is one where the designer takes control of the building by dictating how the building is to respond. This can be achieved by selection of the preferred response mode, selecting zones where inelastic deformations are acceptable and suppressing the development of undesirable response modes which could lead to building collapse.
2. Earthquake Design - A Conceptual Review
Modern earthquake design has its genesis in the 1920’s and 1930’s. At that time earthquake design typically involved the application of 10% of the building weight as a lateral force on the structure, applied uniformly up the height of the building.
In 1910 a series of fifty-two earthquakes struck Arizona between September 10th-23rd and it caused much of the Flagstaff residents to flee the area as even strong households cracked and chimneys crumbled. The fifty-two earthquakes were all light-shock earthquakes with magnitudes between 4.0-4.2 that came right after another. If only one earthquake occurred in that timespan then it is likely that only objects would be knocked from shelves but no damage would be done to infrastructure, but the earthquakes happened right after another causing significant slight
The enormous responsibility that an engineer has when designing a project is often overlooked. His or her job is not only to create a design that will work under ideal conditions, but that will meet the regulations of environmental and building codes and will also survive the unpredictable forces of nature that structures are sometimes subjected to. An article in the Seattle Daily Journal of Commerce, "Structures are Held up by Both Skill and Luck,"1 describes many risks involved in the designing process and the failures that can occur when small details are overlooked. In light of a recent surge of failures in the Northwest, the article says:
While I was looking for an article for the review one of my classmates asked me a question. Can a whole house be built out of metal studs? The technical answer is yes, but in practice no. Don’t get me wrong it could be done and I like working with metal studs. The first obstacle would be availability of materials. Second most custom homebuilder haven’t had a lot of experience with metal studs on a large scale. In addition, this type of framing would have a huge impact on the other systems in the house.
Skyscrapers are amazing! Architectural defeats. Wonders of the world. How are they able to withstand even the strongest of winds and earthquakes?
Heller, Arnie. "The 1906 San Francisco Earthquake." Science & Technology (2006): 4-12. Web. 8 May 2014.
The science of the natural disaster has baffled many, but from studying the San Francisco earthquake, scientists have made a number of important discoveries and they have a better understanding of earthquakes. At 5:12 on a fateful April morning in 1906, the mammoth Pacific and North American plates sheared at an incredible twenty-one feet along the San Andreas fault, surpassing the annual average of two inches (“San Francisco Earthquake of 1906”)(“The Great 1906 Earthquake and Fires”). The shearing caused a loud rumble in the Californian city of San Francisco. A few seconds later, the destructive earthquake occurred. The ground shifted at almost five feet per second, and the shaking could be felt all the way from southern Oregon to southern Los Angeles to central Nevada (“Quick”)(“The Great 1906 San Francisco Earthquake”). Moreover, the earthquake could be recorded on a seismograph in Capetown, South Africa, an astounding 10,236 miles away from San Francisco (“San Francisco ea...
From studying the science behind the San Francisco earthquake, scientists have made a number of important discoveries involving how earthquakes function. At 5:12 on a fateful April morning in 1906, the mammoth Pacific and North American plates sheared each other at an incredible twenty-one feet along the San Andreas fault, surpassing the annual average of two inches (“San Francisco Earthquake of 1906”) (“The Great 1906 Earthquake and Fires”). A few seconds later, the destructive earthquake occurred. The ground shifted at almost five feet per second, and the shaking could be felt all the way from southern Oregon to southern Los Angeles to central Nevada (“Quick”) (“The Great 1906 San Francisco Earthquake”). In fact, the earthquake could be registered in a seismograph on Capetown, South Africa, an astounding 10,236 miles away...
producing a earthquake safe environment. In a nuclear facility that in itself is a danger, an honest
Concrete is a composite material used widely in the construction industry. Concrete is basically a mixture of cement, water, aggregates and admixture (sometimes). Cement is a fine gray powder that consists of oxidizes calcium, silicon and aluminum. The aggregate used is normally gravel, crushed stone or sand. Admixture is a solid or liquid substance that gives a certain characteristics of the concrete. The cement reacts with water chemically and binds the aggregates together through a process called hydration during hardening or curing of concrete. It means that water helps in the hardening of the concrete while the cement bind the aggregate and also react with water to form a solid mass.
With the interaction between the development of computational approaches in architecture and the contemporary forms of spatial design intelligence, some new architectural design theories emerged to make differences between architects and control designing processes. These theories are almost employed in all designing realms, from architecture to urban design to provide fields of ideas and solutions that privilege by complexity. Most of these theories are oriented to relay on understanding and using computational methods to generate exotic and complex geometries. In this respect, three of these theories will discussed and tested against three buildings. The theories are: parametric design, genetic architecture and emergence, which characterize some of the contemporary architectural design approaches.
There are 25 major specialties in engineering that are recognized by professional societies. In any one of those 25 specialties, the goal of the engineer is the same. The goal is to be able to come up with a cost effective design that aids people in the tasks they face each day. Whether it be the coffee machine in the morning or the roads and highways we travel, or even the cars we travel in, it was all an idea that started with an engineer. Someone engineered each idea to make it the best solution to a problem. Even though engineer’s goals are similar, there are many different things that engineers do within their selected field of engineering. This paper will focus on the architectural field of engineering.
Earthquakes are vibrations felt at the surface of the earth which are caused by disturbances of the energy in the earth's interior. These vibrations are known as seismic waves. (Skinner Robinson McVerry 1) There are different type sof seisimc waves such as Primary (P) waves, whcih travel the fastest, Secondary (S) waves which cause the earth to vibrate vertically, Surface (L) waves. P and S waves are "affected by changes in the density and the rigidity of the materials through which they pass." (Columbia Encyclopedia) Earthquakes vary in their intensity and duration. Often times they are strong enough to cause massive destriction. Tall buildings often suffer as a result of these natural disasters. In recent years this has become a larger and larger threat with both the number of large buildings, and their number of occupants increasing. In an effort to try to minimize the damage caused by earthquakes many some engineers focus primarily on designing and constructing earthquake resistant buildings. Earthquake engineers have gathered much of their information from analyzing past earthquakes, and learning which buildings can and can't withstand the tremors. The goals of these engineers is to design buildings that can withstand moderate earthquakes and obtain minimal damage, and that the buildings will not collapse lowering the probability of human deaths.
Taher, R. (2011). General recommendations for improved building practices in earthquake and hurricane prone areas. San Francisco, CA: Architecture for Humanity Retrieved from
As new demands for comfort emerged in buildings during the 1970's, adaptation concepts became more prevalent. The term adaptation is mentioned in architecture to describe the process performed by systems in which specific properties of a building are changed within a specific time frame in order to manage changing environmental conditions or occupant's demands. The environment is in a constant flux over time and space, thus there is a need to accommodate and manage the environmental changes for the occupant's satisfaction. For example, "an ideal cladding system would have quite different thermal and optical properties at different times of the day and night, at different outdoor temperature conditions, and in summer and winter" [Gregory 1986].
Since the 10-story steel-frame Home Insurance Building, the world’s first skyscraper, which was opened in Chicago in 1885, architects have had to think about wind pressure, or “wind loading,” as they’ve built higher and higher. Today, wind engineering is an integral aspect in the design of any high rise building. As Garber explains, a building is like “a giant sail” with a great deal of area that the wind can push against. “The wind is blowing on the building causing it to sway and twist,” he says. “For certain shapes, the wind can form a wake similar to what you’d see behind a boat with vortices shedding off, alternating on both side and pushing the building from side to