Organizational Unit: Civil Engineering
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ArticlePublication Metadata only Numerical analysis of segmental tunnel linings - Use of the beam-spring and solid-interface methods(Techno-Press (테크노프레스), 2022-04-16) Rashiddel, A.; Hajihassani, M.; Kharghani, M.; Valizadeh, Hadi; Rahmannejad, R.; Dias, D.; Civil Engineering; VALIZADEH, HadıThe effect of segmental joints is one of main importance for the segmental lining design when tunnels are excavated by a mechanized process. In this paper, segmental tunnel linings are analyzed by two numerical methods, namely the Beam-Spring Method (BSM) and the Solid-Interface Method (SIM). For this purpose, the Tehran Subway Line 6 Tunnel is considered to be the reference case. Comprehensive 2D numerical simulations are performed considering the soil's calibrated plastic hardening model (PH). Also, an advanced 3D numerical model was used to obtain the stress relaxation value. The SIM numerical model is conducted to calculate the average rotational stiffness of the longitudinal joints considering the joints bending moment distribution and joints openings. Then, based on the BSM, a sensitivity analysis was performed to investigate the influence of the ground rigidity, depth to diameter ratios, slippage between the segment and ground, segment thickness, number of segments and pattern of joints. The findings indicate that when the longitudinal joints are flexible, the soil-segment interaction effect is significant. The joint rotational stiffness effect becomes remarkable with increasing the segment thickness, segment number, and tunnel depth. The pattern of longitudinal joints, in addition to the joint stiffness ratio and number of segments, also depends on the placement of longitudinal joints of the key segment in the tunnel crown (similar to patterns B and B').ArticlePublication Metadata only Site response analysis in performance based approach(Elsevier, 2024-03) Ansal, Mustafa Atilla; Tönük, G.; Sadegzadeh, Shima; Civil Engineering; ANSAL, Mustafa AtillaA performance based approach for site response analysis requires a probabilistic approach accounting for the observed variability in soil stratification and engineering properties of the soil layers. The major variability in site-specific response analysis arises from the uncertainties induced by the (a) local seismic hazard assessment, (b) selection and scaling of the hazard compatible input earthquake time histories, (c) soil stratification and engineering properties of encountered soil and rock layers, and (d) method of site response analysis. Even though the uncertainties related to first item, local seismic hazard assessment, has primary importance on the outcome of the site-specific response analyses, the discussion in this article focuses on the possible uncertainties in selection and scaling of the hazard compatible input earthquake time histories, soil stratification, thickness, type and their engineering properties, depth of ground water table and bedrock and properties of the engineering bedrock. One alternative may be to conduct site response analyses for large number of soil profiles generated by Monte Carlo simulations using relatively large number of hazard compatible acceleration time histories to assess probabilistic performance based design acceleration spectra and acceleration time histories calculated on the ground surface with respect to different performance levels. A remaining issue may be considered as the variability induced by 1D, 2D, and 3D site response analysis.ArticlePublication Metadata only Formalization of occupant feedback and integration with BIM in office buildings(ASCE, 2021-01-01) Ergen, E.; Kula, B.; Işın, Gürşans Güven; Artan, D.; Civil Engineering; IŞIN, Gürşans GüvenOccupant feedback is not effectively used in the facility management (FM) phase for operations and maintenance activities as well as retrofit and refurbishment investment decisions. One of the reasons is related to incomplete or mostly unstructured occupant feedback data. The goal of this paper is (1) to formalize occupant feedback in office buildings by developing a semantic data model, and (2) to implement the semantic data model in a prototype to demonstrate that capturing and storing occupant feedback and integrating it with building information modeling (BIM) improves the experience of both occupants and FM personnel. Interviews were conducted with office occupants and facility managers, and use cases were created to develop the semantic data model. This data model was implemented in the Industry Foundation Classes (IFC) schema and a case study was conducted, in which a prototype for collecting occupant feedback integrated with BIM was developed to test the proposed approach. The applicability, practicability, and usability of the system were measured via usability tests that were applied to the occupants and FM team members. The findings showed that the proposed semantic data model can be utilized to store occupant feedback in a structured manner and to integrate this information with BIM-enabled FM systems. This approach facilitates (1) continuous collection of occupant feedback along with the vital contextual information including geometric data, and (2) effective utilization of this information in FM operations by providing visualization and analysis capabilities.ArticlePublication Metadata only Use of natural minerals to immobilize bacterial cells for remediating cracks in cement-based materials(ASCE, 2022-03-01) Tezer, M. M.; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep BaşaranCracks in cement-based materials are one of the main factors affecting the durability of structure. Recent research in the field of concrete materials showed that self-healing in cement-based systems can be achieved by triggering biogenic calcium carbonate (CaCO3) precipitation. The goal of this study is to establish a comparative evaluation of the use of sepiolite, bentonite, and diatomaceous earth (DE) as an immobilization barrier of Sporosarcina pasteurii (S. pasteurii) cells to trigger self-healing in cement-based systems. For the first time in the literature, this study will provide insight into the use of natural minerals, such as bentonite and sepiolite, as protective carriers for vegetative S. pasteurii cells in cement-based materials and present a comparative evaluation of factors influencing crack healing, such as the microstructure and composition of immobilization barriers. A two-phase self-healing bioadditive was obtained by immobilizing vegetative S. pasteurii cell samples on natural porous minerals with or without the use of required nutrients. Then the samples were cracked by a three-point bending test, and the healing process was screened via stereomicroscope imaging and ultrasonic pulse velocity (UPV) testing after subjecting the cracked samples to 28 days of moist curing. Flexural cracks induced in mortar samples were filled with biogenic precipitate. Relatedly, the water absorption capacity of the samples was decreased in mortar samples containing bacterial cells, the nutrients were added in the curing solution. Fourier transform infrared spectroscopy and scanning electron microscopy analyses showed that calcite was the predominant polymorph of CaCO3 sealant in cracks.ArticlePublication Metadata only Design method for quantifying embankment safety against lateral spreading and determining contribution of basal reinforcements(Elsevier, 2020-06) Oser, C.; Çinicioğlu, Safiye Feyza; Çinicioğlu, Ö.; Civil Engineering; ÇİNİCİOĞLU, Safiye FeyzaThis study proposes an analytical method for the calculation of the safety factor against lateral spreading in embankments, both for cases with and without basal reinforcement. Hence, a new limit equilibrium approach is presented based on the lower bound plasticity theorem, which allows the computation of the required distribution of stresses along presumed slip surfaces at the limit state. Comparing the required distribution of stresses with the available resistances, the safety factor in the absence of basal reinforcement is calculated. If the safety factor is unsatisfactory, basal reinforcement can be introduced and its contribution to stability quantified. The lower bound approach allows the computation of mobilized resistance along the reinforcement. Accordingly, the proposed method allows the calculation of the safety factor against lateral spreading for problems involving basal reinforcements. Finally, the proposed method is compared with well-established methods in literature. Results suggest that the proposed method is reliable, practical, and applicable to safe and economical designs.ArticlePublication Metadata only Impact spectrum of flood hazard on seismic vulnerability of bridges(Techno-Press, 2018-05-25) Yılmaz, Taner; Banerjee, S.; Civil Engineering; YILMAZ, TanerMultiple hazards (multihazard) conditions may cause significant risk to structures that are originally designed for individual hazard scenarios. Such a multihazard condition arises when an earthquake strikes to a bridge pre-exposed to scour at foundations due to flood events. This study estimates the impact spectrum of flood-induced scour on seismic vulnerability of bridges. Characteristic river-crossing highway bridges are formed based on the information obtained from bridge inventories. These bridges are analyzed under earthquake-only and the abovementioned multihazard conditions, and bridge fragility curves are developed at component and system levels. Research outcome shows that bridges having pile shafts as foundation elements are protected from any additional seismic vulnerability due to the presence of scour. However, occurrence of floods can increase seismic fragility of bridges at lower damage states due to the adverse impact of scour on bridge components at superstructure level. These findings facilitate bridge design under the stated multihazard condition.ArticlePublication Metadata only Performance of two real-life California bridges under regional natural hazards(2016-03) Yılmaz, Taner; Banerjee, S.; Johnson, P. A.; Civil Engineering; YILMAZ, TanerThe performance of two real-life California bridges is assessed under a possible regional multihazard condition involving floods and earthquakes. For flood events with varied frequency, expected scour depths at bridge piers are calculated and incorporated in finite-element analyses (FEAs) of the bridges under earthquakes that represent regional seismic hazards. Based on FEA results, fragility curves of bridges are developed at component and system levels. Fragility surfaces are generated to acquire comprehensive knowledge on bridge failure probability for the combined effect of earthquake and flood events of varying frequency. Quantified bridge vulnerability is applied to a risk evaluation framework that combines hazard probability with bridge failure consequences. Obtained results depict that the occurrence of flood events can increase the seismic vulnerability and risk of bridges, although the amount of increase depends on bridge attributes. Bigger (large-diameter) foundations tend to reduce the impact of flood hazard on bridge seismic performance. Moreover, the multihazard response of the bridges indicates that the seismic design philosophy used for bridges can play a role in attaining the seismic safety of bridges with flood-induced scour at the foundations.ReviewPublication Restricted End-of-life materials used as supplementary cementitious materials in the concrete industry(MDPI, 2020-04) Nicoara, A. I.; Stoica, A. E.; Vrabec, M.; Rogan, N. S.; Sturm, S.; Ow-Yang, C.; Gulgun, M. A.; Bundur, Zeynep Başaran; Ciuca, I.; Vasile, B. S.; Civil Engineering; BUNDUR, Zeynep BaşaranA sustainable solution for the global construction industry can be partial substitution of Ordinary Portland Cement (OPC) by use of supplementary cementitious materials (SCMs) sourced from industrial end-of-life (EOL) products that contain calcareous, siliceous and aluminous materials. Candidate EOL materials include fly ash (FA), silica fume (SF), natural pozzolanic materials like sugarcane bagasse ash (SBA), palm oil fuel ash (POFA), rice husk ash (RHA), mine tailings, marble dust, construction and demolition debris (CDD). Studies have revealed these materials to be cementitious and/or pozzolanic in nature. Their use as SCMs would decrease the amount of cement used in the production of concrete, decreasing carbon emissions associated with cement production. In addition to cement substitution, EOL products as SCMs have also served as coarse and also fine aggregates in the production of eco-friendly concretes.ArticlePublication Metadata only Impact of air entraining admixtures on biogenic calcium carbonate precipitation and bacterial viability(Elsevier, 2017) Bundur, Zeynep Başaran; Amiri, Ali; Ersan, Y. C.; Boon, N.; Belie, N. de; Civil Engineering; BUNDUR, Zeynep Başaran; Amiri, AliThe applications of self-healing in cement-based materials via biomineralization processes are developing quickly. The main challenge is to find a microorganism that can tolerate the restricted environment of cement paste matrix (i.e. very high pH, lack of oxygen and nutrients, small pore size etc.). The focus of this work was to determine the possible use of an ammonium salt-based air-entraining admixture (AEA) as a protection method to improve the survival of incorporated Sporosarcina pasteurii cells in cement-based mortar. Bacterial cells were directly added to the mortar mix with and without nutrients. Nutrients should be provided to keep the microorganisms viable even at early ages (i.e. 7 days). Surface charge of the bacterial cells and in vitro biogenic calcium carbonate (CaCO3) precipitation were not affected by the incorporation of AEA. However, introducing AEA did not influence the viability in mortar samples, which might be attributed to the type and chemistry of AEA used.ArticlePublication Metadata only Multi-criteria decision-making model for risk management in modular construction projects(Taylor & Francis, 2024) Khodabocus, Sabah Fatima; Seyis, Senem; Civil Engineering; KAZAZOĞLU, Senem Seyis; Khodabocus, Sabah FatimaThe modular sector needs a precise guide to determine the most efficient risk management approaches. The main research objective of this study is to develop a multi-criteria decision-making model to find the most efficient risk management approach according to the relevant risk criteria. The risk criteria and risk management approaches for modular construction projects were also identified and classified within this scope. A systematic literature review, semi-structured interviews, and open-ended questionnaires were performed for identification and classification purposes. For ranking and quantifying the identified risks and risk approaches, as well as developing the decision-making model, the Delphi method and the Analytical Hierarchy Process (AHP) were conducted. A two-round Delphi method, with eleven experts, was conducted to achieve efficient performance scores of the identified risk management approaches. The percentage standard deviation decreased, Relative Importance Index (RII), Cronbach’s alpha, and Kendall’s coefficient of concordance (Kendall’s W) were calculated to ensure the outputs’ reliability, validity, and agreement level. The AHP method opted to quantify the Delphi method outputs, solve the multi-criteria decision-making process, and develop the multi-criteria decision-making model for risk management of modular construction projects. Triangulation results show that the critical risk categories are supply chain, health and safety, stakeholders, and governmental support. Lean principles such as the Last Planner System, Value Stream Mapping, Just in Time, and Kaizen are top-rated risk management approaches. This research’s novelty is identifying and analyzing crucial risk categories, providing the relevant risk management approaches ranked according to efficiency performance, and presenting a decision-making model as a guideline for risk management of modular construction projects.