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Damage potential of seismic ground motion considering local site effects
Abstract and Figures
The main objective of the present work is to establish a link between the scientific fields of engineering seismology and structural engineering. Substantially it deals with the application and enhancements of methods coming from engineering seismology as well as their junctions to the fields of structural engineering respectively earthquake engineering. Based on real occurred earthquake damage inflicted to multistoried reinforced-concrete frame buildings, the influence of local site effects on the grade of structural damage is worked out. This relying on comprehensive investigations conducted during numerous field missions of German TaskForce after damaging earthquakes in Venezuela and Türkiye. Instrumental investigations on both the structure and its local subsoil in order to identify the damage potential of seismic ground motion take center stage of the thesis. Thereby it is examined whether or not an estimated seismic demand representative in amplitude level and frequency characteristics is able to cause structural damage considering the vulnerability of the structure itself as well as the local site and subsoil conditions. Investigations are concentrated on selected RC frame structures with or without masonry infill walls.
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... On the basis of the experimentally identified natural building periods, Tn,exp, a calibration of the modal analysis results was performed through reduction of Young's modulus, E, for all elements of identical material. The goal was not to achieve a perfect match for the individual building, but to derive a transferable reduction factor or at least tendency, which could then be applied to other buildings of the same type [8] [9]. ...
... In doing so, the application of spectral H/Vratio technique on microtremor data (HVNR) recorded at the ground surface provides a rapid and feasible tool to identify ranges of predominant site periods, Ts. Figure 8 correlates ranges of predominant site periods, T s , with natural building periods, T n,exp . Results indicate that local site effects entailing resonance effects between the site and the structure of damage cases discussed here may not have contributed to the extent of structural damage [9]. ...
... Reconnaissance missions of German TaskForce for Earthquakes are sponsored by Hannover Rück Eisen und Stahl, GeoForschungsZentrum Potsdam, and Earthquake Damage Analysis Center at Bauhaus-University Weimar Figure 8: Correlation between T n, exp and ranges of site periods T s,i for all investigated damage cases [9] ...
During a recent field mission of the engineering group of German TaskForce for Earthquakes into different Turkish earthquake regions experimental testings on reinforced-concrete frame structures were conducted. The buildings selected suffered no or only slight structural damage during the subsequent mainshock and seem to represent the typical type of residential buildings for the respective region. In order to obtain the dynamic vibration characteristics of the buildings, different dynamic excitations were used, such as wind and environmental traffic, as well as horizontally twitching the building by a rope fixed at a primary structural element from the outside by manpower. Based on the application of both, time-history and spectral analysis procedures, fundamental frequencies, corresponding mode shapes as well as structural damping can be determined, allowing a more realistic modeling of the structure.
... However, most studies are either based on the standard spectral ratio (SSR) method (Borcherdt 1970) or the horizontal-to-vertical spectral ratio (HVSR) method (Nogoshi and Igarashi 1971;Nakamura 1989). The first method's main challenge is that finding a suitable reference site meeting a range of necessary conditions often turns out to be very difficult (Steidl et al. 1996) if not impossible (Lang 2004). In this respect, finding a reference site located on outcropping rock while at the same time not being influenced by surface topography and being not too far from the topographical feature under investigation, is the most challenging part. ...
... Pagliaroli et al. 2007). Reasons for this might be that the applicability of the HVSR method postulates that the recording sites under investigation shall not be affected by surface topography or the fact that this method's application to earthquake ground motion data is reported to be problematic as it depends on a number of factors (Lang 2004). ...
Many of the world’s high-seismic hazard regions are characterized by hilly topography. Topographical features pose significant problems when it comes to the seismic safety of buildings and infrastructure facilities, both with respect to the seismic impact, the structure’s vulnerability and potential secondary hazards such as slope stability-related issues. The seismic ground motion characteristics are greatly influenced by the geometry of topographical features such as slopes, hilltops, ridges and canyons and their relationship with the geologic materials partly overlying these features. Both, topography and geology lead in most cases to a significant amplification of the seismic ground motion and hence increased seismic demand to buildings located in these areas. This comes in addition to the fact that buildings located in hilly areas have a significantly lower structural capacity. Due to the limitations posed by the hill topography and the scarcity of flat building plots, many buildings are placed on hill slopes thus have highly irregular configurations, both in plan and elevation, making them highly vulnerable to seismic impact.The manuscript focuses on selected case studies in the Indian Himalayas, which are not only the youngest mountains, but also one of the most seismic areas in the world. Influence of topography on seismic hazard and vulnerability of buildings in the study area is illustrated using extensive numerical studies. The gross effect of these two parameters is demonstrated by comparing the probabilistic earthquake loss estimates with and without considering the topographic effects.KeywordsTopographic amplificationHill buildingsSeismic risk assessment
... Hence, the ratio of the Fourier amplitude spectra of sedimentary site to reference site expresses the local site effects or in other terms amplification at the sedimentary site. Alternatively, it can be said that the technique depends on two basic assumptions (Lang, 2004): ...
This study attempts, through a very limited number of data to explain the requirement of a detailed seismic analysis of the western part of the Guwahati metropolitan region of Assam, India, which falls under seismic zone-V(IS:1893-2002) and consists of mainly alluvial deposits. This study carries out a Site Response study of Western part of Guwahati by employing Standard Spectral Ratio (SSR) method, which is a reference site method, where the ratio of Fourier spectrum of ground motions recorded at a soil site to that of ground motions recorded at a nearby reference site (rock site) is obtained to define the site response. Significant site response in terms of site amplification is observed in the frequency range of 0.1 to 1.00 Hz, which concretes the necessity of a detailed analysis program for the region.
... classify the soil based on fundamental period of soil deposit (T 0 ). It is well known that depth of soil column is having significant effect on soil amplification even though it is still not a criteria of classification in most of the national codes (Lang 2004;Kamatchi et al. 2010a;Adhikary et al. 2014). Pitilakis et al. (2018) proposed the new soil classification scheme for the revision of European seismic code which consider various parameters (viz. ...
This paper aims to improve the site classification scheme and amplification factors for the Indian Seismic Code. The present code IS 1893 (1):2016 ignores the amplification of effective peak ground acceleration due to the existence of soft soil layers. This results in lower design spectral accelerations on soil sites compared to those adopted by codes in other nations. 124 well documented sites from India are considered for ground response analysis using the equivalent linear procedure of DEEPSOIL. Time histories recorded from India and abroad are made spectrum compatible with the Type I spectra of Indian code, corresponding to all the seismic intensities with Effective Peak Ground Acceleration of 0.1 g, 0.16 g, 0.24 g and 0.36 g. Statistical methods are used to construct mean, mean plus standard deviation and mean minus standard deviation response spectra and amplification factors for the sites considered. Before the statistical analysis, each amplification factor curve is normalized with the effective site period (Tg) which exhibits a “characteristic peak at values of T/Tg not far from 1”. Normalized acceleration response spectra as well as period dependent soil amplification factors and equations are proposed for the new classification system. It is observed that the stratigraphy, impedance contrast, sediment thickness and site period play an important role in determining the soil amplification factors and therefore, should be considered in the future site classification schemes of the Indian Seismic Code.
... Microtremor is a constant vibration from the surface of the earth. Microtremor occurs due to vibrations that caused, for instance, by people walking, car vibrations, vibration of factory machinery, wind vibrations, ocean waves or natural vibrations from the ground [6]. Microtremors are dominated by surface waves that can be used in seismic techniques. ...
Research on the potential for seismic vulnerability has been carried out in the Boyolali, Central Java. The purpose of this study was to determine the microzonation of the seismic susceptibility index by using the HVSR method (Horizontal to Vertical Spectral Ratio). The study was conducted by using a set of Portable Digital Seismograph TDS-303S (YGI-I). Data acquisition was carried out at 15 sites with intervals between sites around 1-2 km. The duration of data acquisition for each site is around 60 minutes. The data was processed using the HVSR method to estimate the frequency value and amplification of local geological conditions by comparing the horizontal spectrum with its vertical spectrum. Based on the HVSR curve, the dominant frequency parameter (f0) and amplification value (A0) are obtained. These two parameters are used to calculate the seismic vulnerability index value. The results show that the value of f0 around Boyolali City is in the interval 0,89 Hz to 13,53 Hz, the value of A0 is in intervals of 2,9 to 17,42, and the seismic vulnerability index value is in the interval of 2,00 to 81,13. The highest seismic vulnerability index value is found at site 12, which is in the area of Karanggeneng village, Boyolali. A large seismic vulnerability index value indicates a high level of disaster-prone area when an earthquake happened.
... In order to allow a homogeneous site classification even of those Californian strong-motion sites where detailed information on the geological subsoil conditions is missing, a hybrid procedure based on analytical investigations of model soil profiles and instrumental measurements based on noise recordings was developed. This allowing the classification of a site of interest into site-specific subsoil classes of the German seismic code DIN 4149: 2005(NABau, 2005 simply by the shape of spectral H/V-ratio on microtremor data recorded at the site (Lang, 2004;Lang et al., 2004;Lang and Schwarz, 2006 C: fine-grained soil (fine sands, loesses) 150 < v s,25 1) < 350 C-R C-T C-S ...
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.
Research on soil vulnerability assesment based on Ground Shear Strain (GSS) has been conducted in Liang Village, Central Maluku Regency, Ambon Island. This study aims to determine the potential for soil vulnerability based on the GSS value. Microtremor data is taken at 7 measurement points with a distance between points of 500 m. Data from microtremor processing were used to calculate the seismic susceptibility index value and the maximum value of Peak Ground Acceleration (PGA). The PGA value was determined by the Kanai method with earthquake parameters obtained from earthquake data on September 26, 2019. The PGA value was used to calculate the GSS value. The results showed that the GSS value in Liang Village ranged from (1.50 x10⁻⁴ - 8.78 x10⁻⁵). The area with the lowest GSS value was in Location 1 of 8.78 x10⁻⁵, while the location with the highest GSS value was in Location 2 of 5.93 x10⁻⁴. The magnitude of the classification of the GSS phenomenon, in Liang Village, experienced the phenomenon of building cracks and land subsidence.
Ground Shear Strain (GSS) research was conducted in Waai Village, Ambon Island based on microtremor measurements. The purpose of this research is to see the phenomenon of ground motion arising from the value of ground shear strain due to the earthquake. The large number of buildings that do not have earthquake-resistant construction and quality useless building materials are the main causes of building damage due to the devastating earthquake. The results of microtremor analysis showed that the values of Ag and fg were obtained for each measurement point. The value of the seismic vulnerability index, Kg in Waai Village ranges from 0.26 to 1.24 s²/cm. The lowest seismic vulnerability index value was at location 6 of 0.26 s²/cm, while the highest seismic vulnerability index value was at location 7 of 1.24 s²/cm. The value of the Peak Ground Acceleration (PGA), ag ranges from 245.79 to 659.55 gal. For the highest maximum PGA value is at location 4 of 659.55 gal and the lowest is at location 7 of 245.79 gal. The lowest value of the GSS, γ in Waai Village is at location 6 of 0.000151 and the highest is at location 4 of 0.0007. The phenomenon of the Ground Shear Strain value, γ in Waai Village, Ambon Island is building cracks and land subsidence.
Im Beitrag werden die Grundlagenuntersuchungen vorgestellt, die zur Bereitstellung der seismischen Einwirkungsgrößen für den neuen nationalen Anhang zu DIN EN 1998‐1/NA‐2021 geführt haben. Dargestellt wird, wie für die Ergebnisse moderner probabilistischer seismischer Gefährdungsanalysen (PSGA) die seismischen Einwirkungen normkompatibel bereitgestellt werden können. Einleitend werden Vorgehensweisen zur Ermittlung und Überprüfung der Spektren für unterschiedliche Untergrundklassen vorgestellt. Mit den standortspezifischen Bodenbewegungsmodellen wird gezeigt, wie künftig baupraktische Anwendungen auf Grundlage von Starkbebenregistrierungen erfolgen können. Da die Besonderheiten der deutschen Erdbebengebiete durch das im EC 8 vorgesehene Klassifikationsschema nicht abgedeckt werden, ist weiterhin dem Konzept der geologie‐ und baugrundabhängigen Spektren und der Einführung entsprechender Kombinationen in Form von Untergrundklassen Präferenz einzuräumen. Die Kontrollparameter der elastischen Spektren für die Untergrundverhältnisse gem. DIN EN 1998‐1/NA‐2021 werden auf Grundlage simulativer Standortanalysen an repräsentativen Modellprofilen für den interessierenden Bereich von Einwirkungsintensitäten und somit auch für verschiedene Wiederkehrperioden ermittelt. Damit wird auch der Bezug zu den Verhaltens‐ bzw. Grenzzuständen und den zugehörigen Nachweisaufgaben hergestellt. Abschließend wird ein Ausblick auf die nächste Phase der europäischen Erdbebennormung gegeben.
This paper presents results of numerical modeling of site response for Euroseistest. Ground motion been simulated at the surface of this valley for vertically incident SH waves. The predominance of locally generated surface waves is clear in the synthetic seismograms. These results are then compared with an analysis of two events in the time domain. It is discussed in which sense it is possible to obtain a good fit between observations and 1D models, even though the real behavior involves locally generated Love waves. It is stressed that in order to predict ground motion in alluvial valleys the information contained in the phase cannot be neglected.
Obviously, structural damage caused by strong earthquakes can not only be attributed to defects in design or construction, but rather the widely discussed phenomenon of local site effects has to be considered as well.
In the last decade extensive strong-motion measurements were carried out by the reconnaissance team of the German TaskForce for Earthquakes. Missions to Turkey in 1998 (Adana, Ceyhan) and in 1999 (Izmit/Kocaeli and Duezce) provided a unique database of recorded aftershocks at sites where building damage occurred.
To gain more insight into the effect of local site conditions post-earthquake investigations were initiated in Adana and Kocaeli (October 2000). Microtremors were recorded at sites of the previously installed strong-motion accelerographs and locations of evident concentration or variation of building damage spreaded over the area of main shaking effects. The predominant frequencies and amplification potential at recording sites were identified by H/V spectral ratio method. On the basis of H/V-spectra the sites were classified (into soft soil, stiff soil, rock-type conditions) enabling more detailed studies of recorded strong motion data which were obtained by previous TaskForce missions.
Attenuation laws for spectral and peak ground acceleration were statistically determined similar to the approach by Ambraseys et al. (1996). As it can be concluded, the differences between ground motion on soft and stiff soil are less pronounced and of a similar level of amplitudes. It has to be emphasized that the studies are supported by different data types referring to an unique and consistent data-set. Thus, conclusions concerning the reliability of recently applied site response estimation techniques will be derived in dependence on soil conditions.
Finally, it will be discussed to which extent subsoil conditions are responsible for the enforcement of building damage. For this purpose and in relation to geological features, a macroseismic map of shaking effects (intensity) was prepared taking into consideration the results of a damage survey undertaken immediately after the 1999 Izmit/Kocaeli earthquake as well as meanwhile presented intensity assignments of other research groups. As a result, instrumentally investigated (micro)sites are correlated with macroseismic shaking effects.
The amplitude characteristics as the fundamental natures of microtremors are discussed at present paper. The experimental field is Hakodate City in Hokkaido.
The power spectral density functions of microtremors were compared with amplitude functions of Rayleigh wave (M11) computed from underground structure. Furthermore, theoretical ratio of the horizontal component to the vertical component of Rayleigh wave (M11) was compared with that of the observed microtremors. From these comparisons, it was shown that the amplitude characteristics of microtremor was mostly composed of Rayleigh wave (M11).