Perspectives on European Earthquake Engineering and Seismology: Volume 1

Civil Engineering; Natural Hazards; Geotechnical Engineering & Applied Earth Sciences Industry Sec; 2ECEES; Earthquake Engineering; Performance Based Design and Earthquake Engineering; Irregular Buildings and Earthquakes; Historical Structures and Earthquakes; Precast Buildings and Earthquakes; Bridge Design and Earthquake

Perspectives on European Earthquake Engineering and Seismology: Volume 2

Geotechnical Engineering & Applied Earth Science

Probabilistic seismic microzonation for ground shaking intensity, a case study in Türkiye

The purpose of seismic microzonation is to estimate earthquake characteristics on the ground surface based on a probabilistic approach to mitigate earthquake damage in the foreseeable future for the new buildings, as well as for the existing building stock. The probabilistic analysis and related results are very important from an engineering perspective since the nature of the problem can only be dealt with in a probabilistic manner. The uncertainties associated with these analyses may be large due to the uncertainties in source characteristics, soil profile, soil properties, and building inventory. At this stage, the probability distribution of the related earthquake parameters on the ground surface may be determined based on hazard-compatible input acceleration-time histories, site profiles, and dynamic soil properties. One option, the variability in earthquake source and path effects may be considered using a large number of acceleration records compatible with the site-dependent earthquake hazard. Likewise, large numbers of soil profiles may be used to account for the site-condition variability. The seismic microzonation methodology is proposed based on the probabilistic assessment of these factors involved in site response analysis. The second important issue in seismic microzonation procedure is the selection of microzonation parameters. The purpose being mitigation of structural damage, it is possible to adopt earthquake parameters like cumulative average velocity (CAV) or Housner intensity (HI) that was observed to have better correlation with building damage after earthquakes. A seismic microzonation procedure will be developed with respect to ground shaking intensity considering probabilistic values of the cumulative average velocity (CAV) or Housner intensity (HI).WOS:001087844900003ArticleUluslararası işbirliği ile yapılmayan - HAYIRNovember2023YÖK - 2022-23Kası

Evaluation of Liquefaction Susceptibility for Microzonation and Urban Planning

Various procedures were developed to evaluate liquefaction susceptibility of soil layers for implementing engineering remediation measures. The approach that has gained wide acceptance within the framework of urban planning is to establish microzonation maps with respect to liquefaction susceptibility to mitigate possible earthquake damage related to liquefaction. In this context, microzonation maps were produced recently for six municipalities in Turkey as a part of a major Pilot Project. Two variables are required for the assessment of liquefaction resistance of sandy soil layers; the seismic demand expressed in terms of cyclic stress ratio, CSR; and the capacity of the soil layers to resist liquefaction, expressed in terms of cyclic resistance ratio, CRR. The approach adopted to perform microzonation maps for liquefaction susceptibility was based on the procedure proposed by Youd et al., 2001 and Iwasaki et al., 1982. The variation of the safety factors with depth were determined for each representative borehole where CSR is calculated using stress reduction factor and CRR based on SPT blow counts. In addition CSR was calculated based on site response analyses. The results are compared and the source of uncertainties and the effects of the two approaches are discussed in terms of the final microzonation maps

Factors affecting site-specific response analysis

The engineering purpose of a site-specific response analysis is to estimate the uniform hazard acceleration spectrum on the ground surface for a selected hazard level. One of the mandatory components for site response analyses is one or more representative acceleration time histories that need to be scaled with respect to the calculated seismic hazard level for the selected site. The selection and scaling procedures of earthquake acceleration records play an important role in this approach. The effects and differences in using two different scaling approaches are studied: scaling with respect to ground motion parameters and response spectrum scaling. A set of homogeneous ground motion prediction relationships are developed for peak ground acceleration, peak ground velocity, root-mean-square acceleration, Arias intensity, cumulative absolute velocity, maximum spectral acceleration, response spectrum intensity, and acceleration spectrum intensity based on a uniform set of acceleration records for ground motion parameter scaling. The uncertainties associated with site response analysis are considered as epistemic and aleatory uncertainties in source characteristics, soil profile, and soil properties. Aleatory variability is due to the intrinsic randomness of natural systems; it cannot be reduced with additional data (Passeri et al. 2020), however; its variability may be modeled by probability distribution functions. Thus, one possibility is to determine the probability distribution of the acceleration spectrum calculated on the ground surface for all possible input acceleration records, site profiles, and dynamic soil properties. The variability in the earthquake source and path effects are considered using a large number of acceleration records compatible with the site-dependent earthquake hazard in terms of fault mechanism, magnitude, and distance range recorded on stiff site conditions. Likewise, a large number of soil profiles may be considered to account for the site condition variability. The uncertainties related to dynamic soil properties may be considered as possible variability of maximum dynamic shear modulus in site response analyses. A methodology is proposed to estimate a uniform hazard acceleration spectrum on the ground surface based on the probabilistic assessment of the factors involved in site response analysis. The uniform hazard acceleration spectra obtained from a case study are compared with the spectra calculated by probabilistic models proposed in the literature.WOS:000743801200001Scopus - Affiliation ID: 60105072Science Citation Index ExpandedQ1-Q2Article; Early AccessUluslararası işbirliği ile yapılmayan - HAYIROcak2022YÖK - 2021-22Oca

The Consolidation Behavior of the Clay-Core in a Rock Fill Dam — Atatürk Dam Case Study

Unexpectedly large settlements occurred in the 165 meter high clay core of Atatürk Dam during the reservoir filling stage. An investigation was conducted based on laboratory experiments and numerical analysis. Consolidation tests were performed on compacted samples under stress levels expected to take place in the field by considering the possible factors affecting the consolidation behavior. The experimental findings were used to model the observed settlements based on a parametric study and by back-calculation. The total expected settlements were determined to be in the order of 16.0 m. While a good fit was captured between the observed and modeled settlements prior to the reservoir filling, it was not possible to model the significantly large settlements observed within the clay core located approximately 120 meter below the crest following the reservoir filling. Evaluating other observations and findings, it was concluded that this phenomenon could be attributed to the lateral displacement of the core material into the filter and shell zones that were prone to instabilities due to disintegration under water

Damage to Water and Sewage Pipelines in Adapazari During 1999 Kocaeli, Turkey Earthquake

Vulnerability of pipeline systems were studied for the city of Adapazari based on available information on the performance of the water and sewage pipeline systems during 1999 Kocaeli, Turkey Earthquake. The water supply pipeline system in Adapazari experienced extensive damage. The main damage was observed in transmission and distribution systems primarily due to brittle asbestos cement (AC) pipes used in the system combined with the fracturing effect of ground deformations associated with liquefaction and softening of alluvial sediments. Recently, pipeline damage inventory was compiled based on repair reports and interviews with water works technicians. Since the entire system was replaced after the earthquake only limited number of repair reports was available. The geotechnical and geological site conditions were evaluated based on available borings, and in-situ tests. Vulnerability of water pipelines due to ground shaking and liquefaction was evaluated separately. Variation of earthquake characteristics on the ground surface was estimated based on 1D site response analyses using the outcrop motion recorded in Adapazari during the 1999 Earthquake as input motion. Liquefaction susceptibility was estimated based on a simplified liquefaction analysis and SPT blow counts obtained during the site investigations. Distribution of damage predicted by means of empirical vulnerability functions proposed in literature was compared to the pipeline damages observed during the 1999 Earthquake

The cyclic undrained stress?strain behaviour of saturated sand

Depremin neden olduğu tekrarlı kayma gerilmelerinin zeminin fiziksel ve mühendislik özelliklerine bağlı olarak zeminlerde oldukça farklı boyutlarda deformasyonlara yol açtığı ve bundan dolayı zeminin kayma mukavemetinin azaldığı; gerilme–deformasyon özelliklerinin değiştiği bilinmektedir. Özellikle suya doygun gevşek kumların tekrarlı yükler altında ortaya koydukları deformasyon yumuşaması ile beraber mukavemetlerini hızla kaybetme özellikleri bu tür zeminleri diğerlerinden oldukça farklı kılmaktadır. Bu çalışmada burulmalı kesme deney aleti ile suya doygun kumların değişik fiziksel özellikler ve deneysel koşullar altında gerilme–şekil değiştirme özelliklerindeki değişimler incelenmiştir. Drenajsız koşullarda ve gerilme kontrollü olarak gerçekleştirilen deneylerde kumların tekrarlı yükler altında dinamik gerilme–şekil değiştirme özelliklerine bazı faktörlerin etkisi araştırılmıştır.Anahtar Kelimeler: Burulmalı kesme, laboratuar deneyi, kum zemin, gerilme–şekil değiştirme özellikleri.It is known that cyclic shear stresses induced by earthquake, cause a range of shear strain due to granular and index properties of soil and thus losing shear strength of soil and changing stress?strain behavior. In particular, saturated loose sands differ from the other type of soils because of losing quickly their shear strength due to strain softening under cyclic loading. In this study, changing in stress?strain properties of saturated sand having different physical characteristics under different test conditions was investigated with a series of hollow cylindrical torsional shear test in laboratory. In the tests, which are performed on sand using torsional shear apparatus, the changes of the shear stress amplitude, the excess pore water pressure and the shear strain due to the number of cycles shall be determined. The effect of some factors on stress?strain relationships in sand was evaluated with stress?controlled, consolidated?undrained tests. The changes of the shear modulus and the damping ratios depends on the shear strain amplitude were tried to determine in different confining stresses, relative densities and initial consolidation conditions with performed tests. In results of the tests, it was seen that the stress?strain behavior of sand was significantly influenced by these factors. Keywords: Torsional shear, laboratory test, sandy soil, stress?strain behavior

Use of simulated and real acceleration records for microzonation

Mikrobölgelemenin bir tanımı; olası deprem özellikleri ile mevcut zemin özellikleri arasındaki karşılıklı etkileşimi göz önüne alarak, zemin yüzeyinde seçilen deprem özelliklerini ve bunlarla ilişkili yapı tasarım parametrelerinin değişimini belirlemek olarak verilebilir. Bu çalışmada, mikrobölgeleme amaçlı zemin davranış analizlerinde yapay ve ölçeklenmiş gerçek kayıtlar kullanılarak farklı deprem ve yapı tasarımı parametrelerinin zemin yüzeyindeki değişimi incelenmiştir. Çalışmanın ilk aşamasında, gerçek deprem kayıtları kullanılarak en büyük ivme ölçekleme yöntemi ve RASCAL yapay kayıt programı yardımıyla iki farklı şekilde ivme zaman kayıtları üretilmiştir.  Balıkesir tasarım depremi için üretilen bu kayıtlar, 105 zemin profilinin davranış analizlerinde kullanılmış ve yüzeydeki yer hareketi parametrelerinin frekans dağılımları hesaplanmıştır.  En büyük yatay ivme, Arias şiddeti ve spektral ivme olarak seçilen parametrelere ait frekans dağılımlarında, kullanılan gerçek kayıtların önemli bir faktör olduğu görülmüştür. Sonuçlar özellikle en büyük ivme ölçekleme yöntemi için kullanılan gerçek kayıtlara dayalı olarak frekans dağılımlarının önemli oranda değişebileceğini göstermiştir. Diğer taraftan bu etki tasarım parametresine göre de farklılık gösterebilmektedir. Çalışmanın ikinci aşamasında RASCAL programı ile üretilen kayıtların kullanıldığı davranış analizleri için, NEHRP kriterlerinin sağlandığı bir optimizasyon yaklaşımına dayalı olarak spektral ivmeler belirlenmiş ve bu ivmeler aynı tehlike seviyesi için NEHRP yaklaşık yöntemine göre bulunan spektral ivmelerle karşılaştırılmıştır.  Sonuçlar tasarım depremi ve zemin özellikleri arasındaki karşılıklı etkileşime dayalı farklılıkların D grubu zeminler için daha yüksek olduğunu ve bu etkileşimde yüzeydeki yer hareketi özelliklerinin zemin davranış analizleri ile bulunmasının önemli olduğunu göstermektedir. Anahtar Kelimeler: Mikrobölgeleme, yapay deprem kayıtları, ölçekleme, en büyük ivme, Arias şiddeti, spektral ivme.Soil layers under earthquake excitations can strongly influence earthquake characteristics on the ground surface. These effects may be evaluated with respect to structural design parameters based on microzonation studies. In a microzonation study, the variation of selected ground motion parameters on the ground surface are determined by taking into account the interaction between ground motion and local soil conditions. In this study, the interaction between earthquake and soil characteristics were evaluated based on simulated and real acceleration records used for site response analyses with respect to different parameters. In the first stage, simulated acceleration records were generated by RASCAL frequency domain procedure (Silva and Lee, 1987) and real acceleration records were scaled with respect to the estimated peak ground acceleration. RASCAL (Response Spectra and Acceleration Scaling) is a semi-empirical procedure, which evolved from random vibration theory-based techniques, with the additional utilization of the observed Fourier phase spectrum of a real ground motion recording. Input target spectra used in this simulation procedure are uniform hazard spectra developed using two attenuation relationships based on different data sets for predetermined probabilistic earthquake hazard (M=7.5 with epicenter of R=40km corresponding to exceedance probability of 10% in 50 years) (Ansal, 2001). Input acceleration time histories were selected from the earthquake records in Turkey with magnitude range, M≥5 and distance, 27km<R<71km. Taking into account regional source characteristics for Balıkesir, stress drop was taken as Δσ=100 bar. For the whole-path attenuation, frequency-dependent Q model of Q(f)=300 f 0.5 was adopted. As for the near surface attenuation, the kappa values was taken as κ=0.035. With RASCAL program, six simulated time histories were generated based on six different real earthquake records. In the scaling option, previously recorded real acceleration records were scaled with respect to the peak ground acceleration estimated based on the earthquake design parameters (M=7.5, R=40 km). The peak ground acceleration on the rock outcrop was calculated as 0.26g, corresponding to the exceedance probability of 10% in 50 years. Previously recorded real acceleration records were selected with respect to ratio factor determined for scaling procedure. With scaling option, six acceleration time histories were calculated based on different earthquake records. Characteristics of both sets of acceleration records were calculated and compared. It was observed that the range of some parameters such as maximum velocity and velocity spectrum intensity were smaller for the records calculated by RASCAL procedure. Using two groups of acceleration records, site response analyses were conducted by SHAKE91 (Idriss and Sun, 1992) based on 1D equivalent linear method for 105 soil profiles selected previously. Response variability on the ground surface was evaluated in terms of histograms of peak acceleration, Arias intensity and spectral acceleration at 0.2s. In the case of peak and spectral accelerations at 0.2s, the analyses using real scaled records yielded very different statistical distributions for each record. However, the results of the analyses using input records generated by RASCAL gave very similar statistical distributions for all the records in this set. In the case of Arias intensity, both sets of records were found to be more effective yielding different statistical distributions on the ground surface for each input record. In the second stage of this study, the average acceleration response spectra for each soil profile were calculated according to the analyses conducted with records simulated by RASCAL. Utilizing an optimization approach that provide all the requirements of the NEHRP design spectrum, spectral accelerations for short and long periods were determined for average response spectra. These spectral accelerations were compared with spectral accelerations obtained from the NEHRP formulation corresponding to the same earthquake hazard level. The results indicate that the variability based on the interaction between earthquake and soil characteristics was relatively large for D group soils and that the frequency content of ground motions have significant effect on site response.  Keywords: Microzonation, simulated acceleration records, scaling, peak ground acceleration, Arias intensity, spectral accelerations.&nbsp