Theory and Practice in Earthquake Engineering and Technology

Earthquake engineering and technology has been dealt with by introducing different sub-disciplines thereof, contemporary practices, and the latest developments. Upon giving background to open-up various topics, the expertise required and professionals involved in various disciplines have been systematically presented by giving information exchanges between the domains and sub-disciplines. Genesis of earthquakes from seismology viewpoint is given by explaining plate tectonics and its numerical modelling along with applications. Causes of earthquake in Himalayan subduction zone are described, upon describing seismic waves and their propagation from a medium. Gradually changing over the discussion from geology and seismology to geotechnical and structural earthquake engineering, seismic (dynamic) soil-structure interaction (SSI) has been introduced. The discussion on infrastructure resilience pave way for earthquake disaster management. Therefore, ongoing efforts being made in developing seismic design philosophy based on performance-based seismic analysis has then been elaborated. To this effect, static pushover analysis procedure has been explained. Subsequently, some of the advanced dynamic response modification devices have been presented in greater details, including different types of damping devices, tuned mass dampers, seismic base isolation systems, new seismic protection means, and their practical applications have then been shown. In case of the semi-active control devices, this chapter also has presented structural control algorithms and latest techniques thereof. Finally, the need for future research in earthquake engineering has been highlighted for benefit to students and researchers.

Site response study is one of the most powerful tools in engineering seismology as it models the influence of the near surface layers of soil on earthquake ground motions and is an important component of Seismic Hazard Microzonation. Site response parameters, viz. peak frequency (f_o), amplification (A_m) and nature of response curve defining the transfer function at site, are one of the most important inputs in hazard evaluation and ground characterization for seismic hazard and risk microzonation. There are several methods each having merits and demerits are available in literature for the estimation of site response and used world over. In the present chapter, therefore, the national and international scenarios of ground response studies are briefly reviewed, and choice of the methodologies is discussed in the Indian context.

The purpose of a foundation/substructure is to transfer the loads from the superstructure safely to the underlying soil. Safe and economical design of foundations to withstand various probable loading conditions is the prime role of a geotechnical engineer. The design of an earthquake-resistant foundation is highly challenging, as seismic loads are quite complex in nature. Design of a foundation against seismic loading requires not only a thorough understanding of the behaviour of the founding soil, response of the structure and interaction of the founding soil and the structure under earthquake loading but also a proper understanding of the basis for the recommendations of the relevant design standards of the country. An attempt is made here to discuss the basis for the recommendations of the Indian geotechnical design standards for shallow foundation design which deal with fixing the plan area and the founding depth (location from the ground surface), the prime focus being demystifying the design philosophy of IS 1893 for the seismic design of shallow foundations. In summary, a clear step-by-step design procedure that is to be adopted while designing a shallow foundation as per Indian Standards is presented.

Limited availability of land resources and increasing population have led to closely spaced buildings in cities, in which the stipulated separation distance is most often not available between the buildings. When subjected to an external excitation, such as from wind or earthquake, the differences in the dynamic characteristics of these adjacent buildings cause phase differences in their responses, leading to chances of structural collision or pounding. Pounding between closely spaced buildings under earthquake excitation has been identified as a serious hazard, due to falling of building material, as well as a major cause of structural damage, that may range from minor, affecting non-structural components only, to heavy. There have been reports of significant pounding damage during several past earthquakes in not only buildings but between decks and abutments and at expansion joints of bridges as well. There is, thus, a necessity of mitigating the effects of pounding at the design stage, or in existing structures, through construction details or by the installation of vibration control devices. In this chapter, first, the various situations in which structural pounding can arise under seismic excitation are presented, followed by the types of pounding, such as one-sided pounding and two-sided pounding. A summary of the pounding damage that has been reported in past earthquakes is provided. The different pounding models developed by researchers are examined, and the effects of varying dynamic properties and separation distance on pounding are studied. Codal specifications on the minimum separation distance are highlighted and a discussion is made on the various mitigation strategies for seismic pounding.

The safety and serviceability of an engineering structure rely on the prediction of response and failure mechanism of the structure. The accurate prediction of the response of the structures subjected to earthquake loading is a difficult and great concern of the researchers. The prediction of response of pile foundations which are surrounded by different soil types throughout their length becomes difficult due to the complex soil-structure interaction mechanism during earthquake. This has led to the failure of many structures due to earthquake. This further emphasizes the importance of the non-linear soil-structure interaction for designing pile foundations. The pushover analysis is a static non-linear seismic analysis which can be used to predict the seismic response of the pile foundation with the incorporation of soil-structure interaction. In this research work the modeling of the pile-soil system is done in OpenSees PL, a user-friendly interface of OpenSees. The piles embedded in layers of cohesionless and cohesive soil having different relative densities and layer thickness are pushed to a pile head displacement of 2% of pile length. From the response of pile obtained from pushover analysis, the yield moments are determined. The yielding moment generated in pile is influenced by the stratification of soil. The density of the soil and soil type influences the yield moment generated in pile.

Historic earthquakes followed by liquefaction failures are familiar and are being studied since the past years [1, 2, 3]. Development of liquefaction susceptibility maps is considered to be prominent as most of the damages during past earthquakes are confirmed to be due to liquefaction phenomenon. In the present study, Liquefaction Severity Index (LSI) and Liquefaction Potential Index (LPI) are used for developing susceptibility maps. LSI and LPI are used to examine the performance of the soil under seismic excitation. In this paper, an attempt has been made to construct response spectrum for the site from the results of earthquake hazard assessment provided by Putti and Satyam (in response analysis and liquefaction hazard assessment for Vishakhapatnamcity. Innov Infrastruct Solut 3:12, [4]). Based on the maximum credible earthquake intensity from the site-specific response spectra Bhuj earthquake strong motion data has been scaled to 0.1 g and is used as an input ground motion for response analysis and liquefaction assessment. The outcomes of the present study suggest that some of the sites in the study area are prone to medium liquefaction probability where silty sands and marine clays with high silt content are found to be predominant. The peak ground accelerations (PGA) are observed to be varying from as low as 0.6–0.14 g. As the study area Vishakhapatnam (India) is the financial capital of Andhra Pradesh state as well as the rapidly growing industrial area, the PGA, LPI and LSI hazard maps are further helpful for infrastructure development and solving future engineering problems in the study area.

Domes are constructed historically over the last many centuries. They are doubly curved structures, without angles and corners. The most important advantage of dome structures is that they enclose an enormous amount of column-free interior space, in addition to providing decent aesthetic sight. Historically, domes were built of masonry material. Masonry structures have very low ductility, and hence they are weak in resisting the lateral loads. Most of the domes are designed for gravity loads using simple geometrical rules, considering the dome as an arch of identical section. Due to the absence of reinforcement in the masonry domes, their thickness must be kept high to resist the tensile stresses. Because of their large thickness, masonry domes attract a large magnitude of seismic forces due to higher mass thus, making them vulnerable to earthquake excitations. Due to earthquake forces, the masonry domes are subjected to tensile forces at the bottom rings and as a result, cracks are developed in the bottom parts of domes. The conventionally designed and constructed masonry domes are vulnerable to severe damage or total collapse under strong seismic excitations. To preserve these ancient structures of historic importance from being damaged due to seismic excitations, base isolation can prove to be a very effective technique. In the present research, seismic response of the case study masonry dome of span 25 m, located in Maharashtra, India, is investigated analytically. The specific objectives of the study are (i) to analyse the seismic performance of the fixed base masonry dome structure under real earthquake ground motions, (ii) to analyse the seismic performance of the masonry dome installed with base isolation systems, viz. lead rubber bearings (LRB) and friction pendulum systems (FPS) and (iii) to compare the seismic performance of the fixed base masonry dome with that, installed with LRB and FPS. The response of the base-isolated dome is obtained using SAP2000 by performing nonlinear time history analysis and is compared with the corresponding response of the conventional dome without base isolators. The nonlinear time history analysis is performed considering real earthquake ground motions of PGA ranging between 0.1 g and 0.35 g. The effectiveness of base isolation technique in improving the response of the dome is explored. The major evaluation criteria considered are tensile stresses, base shear and displacement at the apex point of the dome. It is observed that the seismic response of the base-isolated dome diminishes significantly in comparison with the conventionally constructed dome, depicting the effectiveness of the base isolation strategy. Both, the elastomeric and sliding systems, are found to be very effective in decreasing the response quantities, substantially. The force–displacement loops for both the isolators show considerable energy dissipation. The original uniqueness and aesthetic value of the historical monumental dome are maintained unaltered, even after employing base isolators at the foundation level of the dome.

Collapse of many buildings and bridges in past earthquakes can be primarily attributed to damage in RC columns due to insufficient ductility. Studies have shown that addition of lateral confinement to concrete increases its strength and ductility significantly. Prestrained strips/wires (2–8%) made of shape memory alloy (SMA), a smart material, have recently gained popularity for their ability to provide in-situ active confinement of RC columns without the use of mechanical anchorages and in much lesser time. Prestrained SMAs can regain their original (undeformed) shape when heated above their transformation temperature. Thermal activation of prestrained SMA while restrained leads to the development of a large recovery stress, which is utilized to exert active confinement pressure externally on RC column. A low-cost iron-based SMA (Fe-SMA) is adopted for rapid retrofitting of RC column. A parametric study on behavior of Fe-SMA-confined concrete was carried out. It was found that the residual stress of Fe-SMA confined concrete is independent of concrete strength and only function of active confinement pressure on concrete. This material-level study was further expanded to the component-level for retrofitting of RC columns using Fe-SMA strips. Design of rapid retrofitting strategies of RC column using Fe-SMA strips in its plastic hinge region is discussed in this chapter.

Earthquake early-warning system (EEWS) uses modern communication infrastructure and real-time seismology to estimate the size of the earthquake and gives warning to target cities well before arrival of damaging waves. For earthquakes originating from the central Himalayas, such a system can provide tens of seconds of warning to the adjoining plains and Delhi can get as much as 70 s of warning time. A successful EEWS, in the event of 7+ magnitude earthquake from the central Himalayas, can save millions of lives. This paper provides concept, methodology, algorithms, and other details of EEWS and its importance for India. The paper also presents details and performance of a pilot project of EEWS operational in Uttarakhand, India.

The city of Guwahati is one of the most rapidly growing cities in India, at the same time being the most important hub of Northeast (NE) India. According to the reported seismic activity in India, the entire Northeastern region, where Guwahati City falls into, is among the most seismically active parts of the Indian subcontinent and even of entire South Asia. The seismicity of NE India has been proven by many damaging earthquakes in the past and is also reflected by the seismic zoning map of India’s current seismic building code which classifies the entire region into Zone V, i.e. the country’s highest seismic zone. The present chapter describes the different technical aspects that were implemented for the development of an earthquake loss information system for the city of Guwahati. The development of the system has involved both extensive fieldwork and computational efforts including ground shaking modelling considering soil amplification effects, defining ground shaking scenarios for earthquakes on local active faults and significant historical earthquakes, demarcation of the Guwahati City area and its subdivision into geographical units, the definition of building typology classes and generating their vulnerability functions, collection of building inventory data and socio-economic information throughout the city and finally the computation of damage and loss scenarios. The developed earthquake loss information model for Guwahati City can be used as guidance to local authorities on future city planning and earthquake mitigation and response actions.

River valley projects have a lot of promise in the seismically active Himalayan orogenic region. Some hydroelectric projects are now operational, some are in the planning stages, and a few more will be built shortly. Knowing the nature of ground motion at these locations is critical. The present study uses a probabilistic seismic hazard analysis (PSHA) technique to estimate Peak Ground Acceleration (PGA) for the three hydropower projects in Uttarakhand, Himachal Pradesh, and Jammu and Kashmir (India). Given all potential earthquakes, the aim of probabilistic seismic hazard analysis (PSHA) is to quantify the rate of surpassing certain ground motion levels at the project site. Hazard curves may be used to determine the seismic design input for a location, and they can also be used to analyze the tunnel seismic reaction. The fundamental methods of PSHA are presented in this article in an attempt to offer a clear and brief introduction to the theoretical basis and implementation of PSHA in today’s engineering practice.

Generally, seismic risk is discussed with respect to the structures that include lifelines. Less discussed with regard to the equipment and piping that also contribute to the total seismic risk in terms of life and economy. In view of this, in the present paper, the detailed procedure to estimate the design seismic forces in equipment and piping systems is discussed. Focus is given on structure-equipment interaction and equipment-piping interaction. Detailed explanation is made on generation inputs for the design of floor-mounted equipment and piping systems. Also, procedure for evaluating the response of piping system supported at multi locations of structure is explained.

The concept of performance-based design (PBD) is to achieve the design of structures with a reliable understanding of the risk to life and accompanied losses that may occur due to future earthquakes. The design methodology is based on the assessment of a building’s performance to determine its probability of experiencing different types of damage levels, considering a range of potential earthquakes that may affect the building structure. The performance objectives (or damage levels) such as immediate occupancy, life safety, or collapse prevention are used to define the damage state of the building. Thus, the methodology enables the owner with a means to select the desired performance goal of the building. The Indian seismic design code (IS 1893 Part 1 [6]), like most other national codes worldwide, provides simplified guidelines for the design of buildings intended to provide life safety performance level of the building against a design level earthquake. However, the prescriptive nature of these guidelines does not provide any framework to estimate the actual intended/expected seismic performance of such buildings. This article describes the technical basis of PBD and its application to building archetypes of moment frame and frame-shear wall buildings. The buildings are designed using the hazard and member design procedures of the relevant Indian codes.

The Northeast part of India falls under seismic Zone V (IS:1893–2002), the highest seismic activity zone. However, there is a lack of sufficient dense seismic arrays in the region to record the seismic activity. Irrespective of the availability of the seismic records this study attempts to decsribing the two site response analysis methods: Standard Spectral Ratio (SSR) and Horizontal to Vertical Spectral Ratio (HVSR). Three locations in the west Guwahati Region of the state of Assam in Northeast India, namely, Boko-Palashbari, Goalpara and Guwahati Central Region, have been considered for this study in order to analyze available strong motion data and quantify the site response. The quantification is attempted in terms of site amplification. This chapter also provides a comparison between the two methods under study. 5(five) and 15(fifteen) strong-motion recordings of earthquake events have been considered in this study for the SSR and HVSR methods respectively. The strong motion as recorded in Nongstoin has been considered as a reference site station record for the SSR study. This finding of this study compliments the findings of Field and Jacob (Field and Jacob in Bull Seismol Soc Am 85:1127–1143, 1995) that, if the SSR estimates are taken as the most reliable, the HVSR method under-predicts the site response. The results provided by HVSR are less than that of the SSR results by a factor of 2–4.