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The geotechnical seismic isolation of historical buildings through polyurethane injections: A numerical study
Published in Renato Lancellotta, Carlo Viggiani, Alessandro Flora, Filomena de Silva, Lucia Mele, Geotechnical Engineering for the Preservation of Monuments and Historic Sites III, 2022
Vulnerable structures that are not dilapidated could be sufficiently protected by reducing the seismic acceleration, i.e. the so-called peak ground acceleration (PGA) which acts directly on them. Since PGA strongly depends on the soil type through the site effects, on this issue the scientific literature includes both structural and geotechnical solutions: the first mainly regard the base isolation techniques (Barone et al. 2019; De Domenico et al. 2020; Eröz & DesRoches 2018), while the second are referred to as “Geotechnical Seismic Isolation” (GSI) and consist of interventions aimed at improving the dynamic properties of the foundation soil (Tsang et al. 2012; Tsiavos et al. 2020; Tsang et al. 2021). Despite the scientific evidence of the efficiency of GSI techniques in the seismic risk mitigation, there are often doubts concerning their feasibility, almost exclusively possible underneath new buildings, and secondary effects, e.g. on mechanical aspects, such as settlements because of the materials’ deformability. However, intervening in the soil for the seismic protection of existing buildings appears to be the best solution for aesthetic conservation.
Earthquake Loads
Published in Ram S. Gupta, Principles of Structural Design, 2020
Two terms are applied to consider the most severe earthquake effects: Maximum Considered Earthquake Geometric Mean (MCEG)Peak Ground AccelerationThe earthquake effects for this standard are determined for geometric mean peak ground acceleration without adjustment for targeted risk. MCEG, adjusted for site class effects, is used for soil-related issues—liquefaction, lateral spreading, and settlement.Risk-Targeted Maximum Considered Earthquake (MCER)Ground Motion Response AccelerationEarthquake effects for this standard are determined for the orientation that results in the largest maximum response to horizontal ground motions with adjustment for targeted risk. MCER, adjusted for site class effects, is used to evaluate seismic induced forces.
Probabilistic multi-hazard assessment of seismic and scour effects on bridge structures
Published in Nigel Powers, Dan M. Frangopol, Riadh Al-Mahaidi, Colin Caprani, Maintenance, Safety, Risk, Management and Life-Cycle Performance of Bridges, 2018
The seismic fragility or the probability of structural damage given a seismic IM can be modeled as a conditional probability, P(Z>z* | IM), where z* is a specifically defined value of the demand variable. The expression Z > z* defines a limit state that indicates occurrence of a certain level of damage or even collapse. For measuring the seismic intensity, a sufficient IM should be chosen. Peak ground acceleration (PGA) is often used as an objective scalar measure of seismic intensity. When a structure is considered, the spectral displacement (Sd) and spectral acceleration (Sa) defined at the structure’s modal period (Tn) are two commonly used measures. In this paper, Sa is adopted; particularly, Sa measured at the fixed-base first-mode period of the bridge model is used
The Effect of Earthquake Frequency Content on the Internal Forces in the Tunnels Permanent Lining
Published in Journal of Earthquake Engineering, 2022
Mohammad Oliaei, Rouhollah Basirat
Considering that the earthquake records did not have the same duration of earthquakes selected, the duration of all accelerograms is first set to 30 s and then the peak point in this duration is located in a way that earthquake intensity does not exceed 2–5% of the initial intensity. Using this method, in addition to a remarkable reduction in the computation time, the effect of earthquake duration is removed. Figure 3 illustrates 15 accelerograms after equalization. Then, earthquake frequency content including the peak particle velocity (PPV), the peak particle displacement (PPD), and specific energy density (SED) was calculated. Peak ground acceleration (PGA) denotes the maximum ground acceleration recorded during the seismic shaking. PPV denotes the maximum ground velocity recorded during the seismic shaking. This parameter is obtained by integrating the acceleration time history and taking the maximum value of the corresponding velocity-time history. PPD denotes the maximum ground displacement recorded during the seismic shaking by the three components of the seismic station. This parameter is obtained by double integrating the acceleration time history and taking the maximum value of the corresponding displacement time history. The SED is defined by the following equation (Sarma and Yang 1987):
Development of a Numerical Tool for the Seismic Vulnerability Assessment of Vernacular Architecture
Published in Journal of Earthquake Engineering, 2021
Javier Ortega, Graça Vasconcelos, Hugo Rodrigues, Mariana Correia, Tiago Filipe Da Silva Miranda
The application of DM algorithms to extract models or patterns that explain relationships between variables from databases is one of the main steps of KDD [Fayyad, Piatetsky-Shapiro, and Smyth 1996]. The employment of these tools allows analyzing the complex database obtained from the numerical analyses performed, which presents a large number of variables and complex and unclear relationships among them. The SAVVAS method arises precisely from the intention of delving more deeply into the research question of whether the simple key parameters variables selected can be used to predict the seismic load capacity of vernacular buildings. The final objective of the method is to derive regression models able to quantitatively estimate a value of a load factor that causes the structure to reach the different LS, which can later be correlated with different degrees of structural damage suffered by the building. Moreover, since the load factors that define each LS are expressed in terms of g, they can be compared in a straightforward way with an expected seismic event. The seismic input used for comparison is expressed in terms of Peak Ground Acceleration (PGA) or, when a more refined assessment is required, the site response spectra and the building fundamental period can be used to take into account specific accelerations adapted to each building and site.
Development of correlation between SPT-N value and shear wave velocity and estimation of non-linear seismic site effects for soft deposits in Kolkata city
Published in Geomechanics and Geoengineering, 2021
Srijit Bandyopadhyay, Aniruddha Sengupta, G.R. Reddy
For seismic analysis of structures, the peak ground acceleration (PGA) is one of the important parameters. The global seismic assessment programme (Zhang et al. 1999) estimates PGA of Kolkata between 0.08 g and 0.13 g with 10% probability of exceedance in 50 years. The variation of PGA obtained in this present study for different GMPEs are given in Table 3. From Table 3, it is noticed that the Eocene Hinge Zone (EHZ) shows the highest hazard. Among the 10 GMPEs, Youngs et al. (1997) show the highest value for PGA. The values of PGA and their corresponding response spectra are presented in Figure 8. The response spectra obtained from GMPE, Youngs et al. (1997), envelopes all the other response spectra and it is selected for the generation of spectrum compatible time histories for the study area. The PGA to peak spectral value ratio is found to be 2.18 for this response spectrum. However, Indian standard code (BIS 2002) proposes this ratio be 2.5.