Civil Engineering / İnşaat Mühendisliği

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    Cpt-Based Liquefaction Resistance of Clean and Silty Sands: a Drainage Conditions Based Approach Nurhan Ecemis (aug, 10.1007/S10518-022-01501-0, 2022)
    (Springer, 2022) Arık, Mustafa Sezer; Ecemiş, Nurhan; Monkul, Mehmet Murat; Tütüncü, Yunus Emre
  • Conference Object
    Citation - WoS: 2
    Evaluation of Streamflow Drought Index in Aegean Region, Turkey
    (Springer, 2022) Vaheddoost, Babak; Safari, Mir Jafar Sadegh; Gülmez, Ayşe; Mersin, Denizhan
    Water is an invaluable substance of which ensures the life cycle and hydrological events across the world. In this respect, water deficit also known as drought is a natural disaster related to water scarcity in time and space. Although there is no solid definition for the phenomenon, the outcome of repeated wet and dry spells cause in economic, social, and political problems at regional, country-wide, and world-wide scale. In this study, drought associated with the streamflow in the Aegean region, which has an important economic, historical and wsocio-cultural role in the western Turkey, is investigated through the well-known streamflow drought index (SDI). Therefore, average discharge in the Cicekli-Nif, Besdegirmenler-Dandalas, Bebekler-Rahmanlar and Kocarli-Koprubasi station respectively related to on Gediz, Buyuk Menderes and Kucuk Menderes basins were used. Then SDI with 1, 3, 6,12 months moving average are acquired to express the drought severity associated with the streamflow in the basins. Results showed that the SDI values in all of stations together with the 1, 3, 6, and 12-month moving averages depicts similar results and no abnormal situation exist during the study period.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 8
    Cpt-Based Liquefaction Resistance of Clean and Silty Sands: a Drainage Conditions Based Approach
    (Springer, 2022) Ecemis, Nurhan; Monkul, Mehmet Murat; Tütüncü, Yunus Emre; Arik, Mustafa Sezer
    The cone penetration test-based simplified liquefaction triggering evaluations are largely based on linking liquefaction manifestations in the field to cone penetration resistance. These relationships are interpreted in such a way that for given penetration resistance, the liquefaction resistance increases as non-plastic fines content (FC) increases. However, several studies have indicated discrepancies in this relationship. Hence, there is a lag in rational scientific understanding of this observation. In this study, an experimental research program was undertaken to investigate the CPT-based liquefaction assessment by considering the effects of drainage conditions on the relationship between CPT resistance and liquefaction resistance. First, clean sand and silty sands having 5, 15, and 35% FC were tested at different relative densities by stress-controlled cyclic direct simple shear (CDSS) tests to investigate cyclic resistance of silty sand with varying amounts of non-plastic fines. Then, a set of tests involving piezocone penetration (CPTu), seismic CPTu (SCPTu), and direct push permeability (DPPT) were undertaken in a large-scale box filled with the same soils used in the CDSS tests. The large-scale test results quantified the effect of drainage conditions (coefficient of consolidation) on cone penetration resistance. Finally, by combining the CDSS and CPTu test results, an alternative CPT-based liquefaction resistance relationship was proposed by considering the effects of drainage conditions.
  • Article
    Citation - WoS: 13
    Citation - Scopus: 12
    Geotechnical Reconnaissance Findings of the October 30 2020, Mw7.0 Samos Island (aegean Sea) Earthquake
    (Springer, 2022) Ziotopoulou, Katerinaa; Pelekis, Panagiotis; Klimis, Nikolaos; Çetin, Kemal Önder; Altun, Selim; Sezer, Alper; Ecemiş, Nurhan
    On October 30, 2020 14:51 (UTC), a moment magnitude (Mw) of 7.0 (USGS, EMSC) earthquake occurred in the Aegean Sea north of the island of Samos, Greece. Turkish and Hellenic geotechnical reconnaissance teams were deployed immediately after the event and their findings are documented herein. The predominantly observed failure mechanism was that of earthquake-induced liquefaction and its associated impacts. Such failures are presented and discussed together with a preliminary assessment of the performance of building foundations, slopes and deep excavations, retaining structures and quay walls. On the Anatolian side (Turkey), and with the exception of the Izmir-Bayrakli region where significant site effects were observed, no major geotechnical effects were observed in the form of foundation failures, surface manifestation of liquefaction and lateral soil spreading, rock falls/landslides, failures of deep excavations, retaining structures, quay walls, and subway tunnels. In Samos (Greece), evidence of liquefaction, lateral spreading and damage to quay walls in ports were observed on the northern side of the island. Despite the proximity to the fault (about 10 km), the amplitude and the duration of shaking, the associated liquefaction phenomena were not pervasive. It is further unclear whether the damage to quay walls was due to liquefaction of the underlying soil, or merely due to the inertia of those structures, in conjunction with the presence of soft (yet not necessarily liquefied) foundation soil. A number of rockfalls/landslides were observed but the relevant phenomena were not particularly severe. Similar to the Anatolian side, no failures of engineered retaining structures and major infrastructure such as dams, bridges, viaducts, tunnels were observed in the island of Samos which can be mostly attributed to the lack of such infrastructure.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 6
    Kinematic Reverse Flood Routing in Natural Rivers Using Stage Data
    (Springer, 2022) Tayfur, Gökmen; Moramarco, Tommaso
    In many developing countries, due to economic constraints, a single station on a river reach is often equipped to record flow variables. On the other hand, hydrographs at the upstream sections may also be needed for especially assessing flooded areas. The upstream flow hydrograph prediction is called the reverse flood routing. There are some reverse flood routing pocedures requiring sophisticated methods together with substantial data requirements. This study proposes a new reverse flood routing procedure, based upon the simple kinematic wave (KW) equation, requiring only easily measurable downstream stage data. The KW equation is first averaged along a channel length at a fixed time, t, assuming that channel width is spatially constant, and then the spatially averaged equation is averaged in time, Δt. The temporally averaged terms are approximated as the arithmetical mean of the corresponding terms evaluated at time t and t + Δt. The Chezy roughness equation is employed for flow velocity, and the upstream flow stage hydrograph is assumed be described by a two parameter gamma distribution (Pearson Type III). The spatially averaged mean flow depth and lateral flow are related to the downstream flow stage. The resulting routing equation is thus obtained as a function of only downstream flow stage, meaning that the method mainly requires measurements of downstream flow stage data besides the mean values of channel length, channel width, roughness coefficient and bed slope. The optimal values of the parameters of reverse flood routing are obtained using the genetic algorithm. The calibration of the model is accomplished by using the measured downstream hydrographs. The validation is performed by comparing the model-generated upstream hydrographs against the measured upstream hydrographs. The proposed model is applied to generate upstream hydrographs at four different river reaches of Tiber River, located in central Italy. The length of river reaches varied from 20 to 65 km. Several upstream hydrographs at different stations on this river are generated using the developed method and compared with the observed hydrographs. The method predicts the time to peak with less than 5% error and peak rates with less than 10% error in the short river reaches of 20 km and 31 km. It also predicts the time to peak and peak rate in other two brances of 45 km and 65 km with less than 15% error. The method satisfactorily generates upstream hydrographs, with an overall mean absolute error (MAE) of 42 m3/s.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 10
    Usage of Tyre Derived Aggregates as Backfill Around Buried Pipelines Crossing Strike-Slip Faults; Model Tests
    (Springer, 2022) Karaman, Mustafa; Demirci, Hasan Emre; Ecemiş, Nurhan; Bhattacharya, Subhamoy
    Buried pipelines crossing active faults are exposed to excessive soil forces under fault movements due to large relative movement between pipes and the soil surrounding them. As a result, extreme longitudinal strains develop within pipelines under large fault movements and this leads to pipeline failures. Several seismic mitigation techniques were proposed to improve the performance of buried pipelines crossing active faults. In this study, the potential of using Tyre Derived Aggregates (TDA) as a backfill material for mitigating the effects of strike-slip faulting are investigated through physical model tests. First, the details of the physical model test setup and model configuration are presented. Then a comparative study is carried out to study the effect of TDA content in the backfill and trench configurations on TDA mitigation. Model tests revealed that using a sloped trench with 100% TDA content in the backfill can decrease peak axial pipe strains up to 62% and peak bending strains up to 19%. It is observed that enlarging the trench and using an inclined trench improve the performance of the TDA mitigation technique.
  • Conference Object
    Citation - Scopus: 3
    Seismic Performance of Cfrp Jacketed Sub-Standard Rc Columns Under High Axial Stress and Shear Demand
    (Springer, 2022) Demir, Merve Nur; Demir, Uğur; Demir, Cem; İlki, Alper
    In the last decades, lessons learnt from the major earthquakes, that occurred in many countries, brought revisions in prevailing seismic design codes. As a consequence of this phenomenon, the current building stock in Turkey is mainly comprised of reinforced concrete (RC) buildings which were designed according to different seismic design codes. The presented paper is a component of a comprehensive investigation which containing three variables i) high axial load ratio defined as axial load divided by the axial capacity, ii) high shear demand defined as the ratio of shear demand at flexural yielding to shear resistance and iii) low transverse reinforcement ratio owing to large spacing among steel reinforcements. Thus, a total of four full-scale square RC columns comprised of i) one column designed to comply with the former Turkish Seismic Design Code (TSDC, 1975) and ii) three columns which are not compliant to any design codes (referred as sub-standard), were tested under high axial load ratio, 0.4 for code-conforming and 0.75 for sub-standard columns, combined with reversed cyclic lateral loading. The columns were also designed to have high shear demand in the order of 0.62 and 0.80 for bare sub-standard according to ACI 318 (2019) and TBEC (2018) design codes as sometimes observed in existing sub-standard structures. In addition to that, the ratio of shear demand for the code-conforming column is calculated 0.43 and 0.50 as per design codes, respectively. Besides, the ratio of transverse reinforcement area to the minimum required transverse reinforcement area was 0.19 and 0.77 for sub-standard columns according to ACI 318 (2019) and TBEC (2018), respectively. For the code-conforming column, the aforementioned ratio was 0.57 and 1.32 for both design codes, in the same manner. One of the sub-standard columns was kept as a reference column while the other two of them have been externally jacketed with one layer or two layers of carbon fiber-reinforced polymer (CFRP) sheets. Test results pointed out that the confinement provided by CFRP jacketing has remarkably improved the performance of seismically-deficient RC columns subjected to high axial compression under high shear demand in terms of lateral load capacity and ductility. The experimental results were also supplemented with theoretical work to evaluate the effects of CFRP jacketing on the seismic behavior of sub-standard RC columns.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 2
    Seismic Performance of Substandard Rc Columns Retrofitted With Sprayed Gfrm
    (Springer, 2022) Kian, Nima; Demir, Uğur; Demir, Cem; Maraşlı, Muhammed; İlki, Alper
    There is a myriad amount of substandard reinforced concrete (RC) buildings in developing countries that do not comply with the requirements and instructions of the current building design codes. In particular, columns in these substandard buildings demonstrate unsatisfactory and undesired behavior against lateral loads, mainly due to low concrete compressive strength and poor reinforcement detailing. The problem is exacerbated when the axial load ratio (ratio of applied axial load to the axial load capacity) and/or the shear ratio (ratio of shear force corresponding to moment capacity (Ve) to the shear capacity (Vr)) is/are high, leading to brittle failure modes. In this study, three full-scale substandard RC columns subjected to high axial load ratio of 0.75 were tested under constant axial load combined with reversed cyclic lateral displacements. Shear ratio (Ve/Vr) of the substandard columns were 0.75 and 0.82 according to ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and (Turkish Building Earthquake Code (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), respectively. According to the TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey), columns had a high Ve/(fctmbd) ratio of 1.12, where, fctm, b, and d are the direct tensile strength of concrete, width of the cross-section, and effective depth of the section. The ratio of transverse reinforcement to minimum required transverse reinforcement according to the ACI 318-19 (ACI 318 (2019) Building Code Requirements for Structural Concrete. American Concrete Institute, Farmington Hills, MI, USA) and TBEC (Turkish Building Earthquake Code (TBEC) (2018) Disaster & Emergency Management Authority, Ankara, Turkey) was 0.19 and 0.77, respectively. Two of the columns were retrofitted with an innovative, cost-effective, and easily-applicable strengthening method, through external jacketing with sprayed glass fiber reinforced mortar (GFRM) of different characteristics. The remaining column was tested as the reference specimen to evaluate the efficiency of the strengthening method. The test results demonstrated the extremely poor performance of the reference substandard column as well as the remarkable lateral load capacity and ductility improvement provided by the adopted novel strengthening approach.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 12
    Carbon Dioxide Emissions Mitigation Strategy Through Enhanced Geothermal Systems: Western Anatolia, Turkey
    (Springer, 2022) Chandrasekharam, Dornadula; Baba, Alper
    Although Turkey is not the biggest GHG polluter, its emissions have increased by 110.4% since 1990. Currently, its CO2 emissions alone have crossed 400 Mt. Within the scope of 2 °C targets (2D scenario), the country can easily surpass this target test by increasing its renewable energy sources as a primary energy source mix, by developing its Enhanced Geothermal Sources (EGS) locked up in the radiogenic granites of western Anatolia. The radiogenic heat generated by these granites, spread over an area of 4221 sq. km, varies from 5.3 to 16.34 µW/m3. Based on the electricity generation capacity of granites from Soultz-sous-Forets and Cooper Basin EGS sites, the combined electricity generation capacity of Kestanbol and Kozak granite plutons is about 830 billion kWh. For the period extending from 2019 to 2023, Turkey is aiming at reducing the usage of gas for electricity generation from 29.9 to 20.7%, increasing the share of renewable energy sources from 32.5 to 38.8%, increasing the electricity production from local energy sources from 150 to 219 TWh and increasing the electricity usage per-capita from 3.7 to 4.3 MWh. These energy targets can be achieved by major contributions from hydrothermal and EGS energy sources. This review demonstrates that besides electricity and heat, EGS energy can be utilized, together with other renewable energy sources, such as hydrothermal, wind, and concentrated solar for providing fresh water through the desalination process. These energy sources would provide food, energy, and water security to the country for several decades.