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Logarithms
Published in John Bird, Bird's Higher Engineering Mathematics, 2021
All types of engineers use natural and common logarithms. Chemical engineers use them to measure radioactive decay and pH solutions, both of which are measured on a logarithmic scale. The Richter scale, which measures earthquake intensity, is a logarithmic scale. Biomedical engineers use logarithms to measure cell decay and growth, and also to measure light intensity for bone mineral density measurements. In electrical engineering, a dB (decibel) scale is very useful for expressing attenuations in radio propagation and circuit gains, and logarithms are used for implementing arithmetic operations in digital circuits. Logarithms are especially useful when dealing with the graphical analysis of non-linear relationships and logarithmic scales are used to linearise data to make data analysis simpler. Understanding and using logarithms is clearly important in all branches of engineering.
Introduction
Published in Hector Estrada, Luke S. Lee, Introduction to Earthquake Engineering, 2017
Although many city building codes have been in existence around the world for decades (even millennia, such as the Hammurabi Code from Babylon, which did not include specifications, rather promoted good construction by prescribing penalties for failures), regional model codes were not developed until the introduction of the Uniform Building Code (UBC) in 1927. The second edition of the UBC published in 1930 incorporated seismic provisions and suggested these be incorporated by cities in areas prone to earthquakes. The UBC seismic provisions were based primarily on two observations of building performance during earthquakes: first, most damage was caused by lateral shaking, and second, structural damage was more extensive for buildings on soft soil deposits (likely the first code to recognize soil effects). The code specified a lateral force equal to 10% of the dead plus design live loads, reducible to 3% for buildings on firm soil. In the ensuing editions of the UBC, maps of the United States depicting zones of different levels of seismic risk were published. These maps recognized the hazard of large magnitude earthquakes for different areas of the country.
Performance-Based Design
Published in Bungale S. Taranath, Tall Building Design, 2016
The following guidelines are suggested as seismic performance objectives for commercial office buildings: Persons within and immediately outside the building must be protected to at least a life-safety performance level during design-level earthquake ground motions.Persons should be able to evacuate the building quickly and safely after the occurrence of design-level earthquake ground motions.Emergency systems in the facility should remain operational after design-level earthquake ground motions.Emergency workers should be able to enter the building immediately after the occurrence of design-level earthquake ground motions, encountering minimum interference and danger.
Seismicity pattern of African regions from 1964–2022: b-value and energy mapping approach
Published in Geomatics, Natural Hazards and Risk, 2023
Alemayehu Letamo, Kavitha B, Tezeswi TP
According to elastic rebound theory (Reid 1911), earthquakes are caused by the release of accumulated energy within fault raptures of rocks during sudden movements of tectonic plates. The distribution and mechanism of active faults, which are the source of significant seismicity, are crucial in seismicity studies. The map of active faults was recently compiled by Styron and Pagani (2020) under the project ‘The GEM Global Active Faults Database’. Figure 1 shows the mechanism of faulting for North Africa. It demonstrates that convergent northern Africa is subject to reverse faulting, and the formation of sizable thrust systems and orogenic belts (the Atlas and Betic/Rif chains) is primarily to responsible for the continent’s seismic activity. Diverging borders, however, show typical faulting (dextral and sinistral). It can be observed from Figure 2, that the East African rift system is now experiencing typical faulting in that it is a developing divergent tectonic plate boundary. Large earthquakes of various sizes have been recorded in historical and current times in the region around the triple intersection (Afar triangle). The area is dominated by normal faulting, according to the region’s surface geology and the focal mechanisms of earthquakes (e.g. Kebede and Kulhánek 1991; Ayele 2002), which is in line with current worldwide analyses of active faults by Styron and Pagani (2020).
Experimental Study on Seismic Response Characteristics of Liquefiable Soil Layers
Published in Journal of Earthquake Engineering, 2021
Mohammad Adampira, Mehdi Derakhshandi, Abbas Ghalandarzadeh
Liquefaction of soil is caused by strong ground motion and causes loss of shear strength, lateral spreading, foundation failure, sand boiling and post-earthquake settlement. These liquefaction mechanisms have been studied intensively since the 1964 Niigata and Alaska earthquakes. Liquefaction-induced ground failure is responsible for considerable damage to structures during major earthquakes, especially in saturated sandy areas. Most building codes and seismic guidelines recommend use of soil improvement methods to prevent its damaging effects. However, limited observational studies and experimental investigations have revealed that a liquefied soil layer can effectively attenuate certain earthquake excitations [Bouckovalas and Tsiapas, 2015; Bouckovalas et al., 2017; Trifunac and Todorovska, 1998]. This has been generally observed where liquefiable soil sub-layers exist at the ground site [Adampira et al., 2015].
On propagation behavior of SH-wave and Rayleigh-type wave in an initially stressed exponentially graded fiber-reinforced viscoelastic layered structure
Published in Waves in Random and Complex Media, 2021
Shalini Saha, Abhishek Kumar Singh, Amares Chattopadhyay
Earthquake occurs due to a sudden violent shaking and vibration of the Earth's surface which generally results from the movements of tectonic plates, volcanic activity or sudden release of stored energy in the Earth's lithosphere i.e. underground explosions leading to the generation of seismic waves. Body waves and surface waves are the two basic seismic waves. P-waves and S-waves together constitute body waves as they travel in the interior of Earth. There are mainly two types of surface wave, viz., Love waves, named after Love [1], and Rayleigh waves which were predicted by Rayleigh [2]. Although the surface waves travel near the surface of Earth with slower velocity than body waves but they possess large amplitude and, therefore, considered to be of most destructive kind. The study of seismic waves imparts a comprehensive idea about the internal structure of the Earth and help seismologists and geophysicists to sketch the model of its interior. The analysis of the surface waves propagation in various layered structure also contributes in predicting and understanding the cause and damages resulted due to the Earthquake. Moreover, such studies help in the detection and understanding of fault plane. Therefore, it is desirable to undertake the study on behavior of surface waves propagating in various layered media.