Civil Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/312

Browse

Now showing 1 - 15 of 15

Metadata only
Assembly-based flood repair cost and time models for industrial buildings in Turkey
(Elsevier, 2023-10) Ölmez, Hasan Numan; Deniz, Derya; Civil Engineering; DENİZ, Derya; Ölmez, Hasan Numan
Flooding is one of the most frequent hazard events significantly affecting the industry in Turkey, leading to severe economic losses and business disruptions. To predict the direct flood losses and business downtimes on the industry, this study proposes probabilistic cost and time models of repairing direct physical flood damage to industrial buildings in Turkey. Using field notes and literature reviews, a typical industrial building was first disassembled into a list of building components vulnerable to flooding. With a focus on façade and interior building components, the flood damage potential of each component was assessed at different flood depths and velocities. Damage state relationships were established for the building components to connect their damage levels under flood actions to their individual repair work. Using the assembly-based approach, costs and times of repairing each flood-damaged component and their associated variabilities were assembled in a probabilistic approach to develop total flood repair cost and time models. The results show that typical repair costs and times for facilities subjected to significant flood depths and velocities might reach substantial levels, up to 28% of building replacement costs and 165 working days on average. The proposed models systematically incorporate existing important uncertainties, therefore, provide reliable estimates.
Metadata only
Automated flow rate control of extrusion for 3D concrete printing incorporating rheological parameters
(Elsevier, 2024-04) Ahi, Oğulcan; Ertunç, Özgür; Bundur, Zeynep Başaran; Bebek, Özkan; Civil Engineering; Mechanical Engineering; ERTUNÇ, Özgür; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Ahi, Oğulcan
The use of inline quality assessment technologies is of great importance in meeting the consistent extrusion requirements of 3D concrete printing (3DCP) applications. This paper presents a system to regulate extrusion speed and maintain the flow rate at a target value during 3DCP processes. The system is based on a new equation that combines printing parameters and the material's rheological properties in the printing process. The proposed control strategy is designed to effectively function with various cement-based mixtures. Validation tests demonstrate that the proposed system can maintain an instantaneous flow rate within a certain range and eventually achieve a constant flow rate. During operation, the flow rate is consistently maintained around the targeted value with an average error rate of 6.7 percent. The flow rate control mechanism shows promise as a reliable and efficient solution for achieving precise and constant flow rates, regardless of the cement mix design used.
Metadata only
A comparative evaluation of sepiolite and nano-montmorillonite on the rheology of cementitious materials for 3D printing
(Elsevier, 2022-10-03) Aydın, Eylül Mina; Kara, Ahmet Burhan; Bundur, Zeynep Başaran; Özyurt, N.; Bebek, Özkan; Gulgun, M. A.; Civil Engineering; Mechanical Engineering; BUNDUR, Zeynep Başaran; BEBEK, Özkan; Aydın, Eylül Mina; Kara, Ahmet Burhan
Through the last decade, methods of digital manufacturing of concrete gained a significant interest compared to conventional concrete. The main challenge in additive manufacturing (3D printing) is to design a highly thixotropic cementitious system. This study aims to investigate the use of sepiolite as a rheology modifier as a novel approach to improve the thixotropic behavior and adapt cementitious systems to 3D printing. To understand the influence of sepiolite on rheological properties, a comparative evaluation with nano-montmorillonite was established. The effectiveness of clay addition was also investigated in fly-ash amended cement-based materials. The rheological analysis was done on cement-paste samples containing both clays in terms of their effects on thixotropy, structural build-up, and recovery. A preliminary printability assessment was done with a lab scale printer having a ram extruder. The results show that the incorporation of clays increased the dynamic yield stress and time-dependent evolution of static yield stress. Moreover, the addition of clays improved the thixotropic behavior of cement-based systems, particularly those containing fly-ash. Herein, the sepiolite was found to be more effective compared to nano-montmorillonite in terms of improving thixotropy, structural build-up and recovery. The results showed that use of fly-ash enhances the printability of the mix for the specified extruder and the samples containing 1% nano-montmorillonite or 0.5% sepiolite can be printed. The positive effects of sepiolite were attributed to opposing surface charges of the clay layers and its micro-fibrous microstructure. The findings in this study enabled an in-depth understanding of the rheology and printability of fly-ash amended clay containing printable cement-based mortars.
Metadata only
A cost-benefit analysis of sensor quality and spatial density for rapid regional post-event seismic damage assessment: Application to Istanbul
(Elsevier, 2022-12) Cheng, Q.; Liao, W.; Fei, Y.; Tian, Y.; Lu, X.; Zhang, W.; Ghahari, F.; Kurtuluş, Aslı; Taciroglu, E.; Civil Engineering; KURTULUŞ, Asli
A quantitative evaluation of the influence of sensor quality and spatial density on the results of rapid regional seismic damage evaluations of buildings can provide an important reference for the deployment of a strong-motion network. However, the influence of sensor quality and spatial density on seismic damage assessment is still unclear. Therefore, a cost-benefit analysis framework of sensor quality and spatial density for rapid regional post-event seismic damage assessment is proposed. In this framework, a simulation method for sensor-recorded ground motions and an interpolation-based ground motion field refinement method are used to consider the influence of the quality and density of the sensor network. The accuracies of seismic damage assessments with different sensor layout schemes were compared using the time-history analysis-based regional seismic damage assessment method, through which the influence of sensor quality and spatial density on the seismic damage assessment can be quantitatively evaluated. Finally, the Zeytinburnu district of Istanbul was selected as an example for illustrating the proposed framework. The main conclusions are as follows: (1) the spatial density of the sensors used is more significant for improving the accuracy of a seismic damage assessment than the quality of the sensors used; (2) the influence of population density can be considered using the proposed framework; and (3) the proposed framework can quantitatively consider the influence of sensor quality and spatial density on the rapid regional seismic damage assessment of buildings, which provides an important reference for the deployment of a strong-motion network for a given budget.
Metadata only
Crack remediation in mortar via biomineralization: effects of chemical admixtures on biogenic calcium carbonate
(Elsevier, 2018-11-30) Amiri, Ali; Azima, Mahzad; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Amiri, Ali; Azima, Mahzad
Limited research on biomineralization in cement-based systems suggested that self-healing of surface cracks could be obtained by triggering biogenic calcium carbonate (CaCO3) precipitation within the cracks. While this is encouraging, there is not enough information regarding the influence of admixtures on crack remediation and durability of the biogenic CaCO3 against weathering conditions. In this study, the microorganisms were introduced to mortar with their growth medium, which included corn steep liquor (CSL) and urea. With this approach, the cracks on mortar surface were sealed with the CaCO3 and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples. The biogenic CaCO3 precipitate was found to be durable against freeze-thaw; however the precipitate was unstable under rain water and light. While the addition of air entraining agents (AEA) did not influence the self-healing ability of cells, use of superplasticizers improved the self-healing ability in terms of crack sealing, water absorption, and durability of the precipitate.
Metadata only
Increasing the stability of nanofluids with cavitating flows in micro orifices
(AIP, 2016) Karimzadehkhouei, M.; Ghorbani, M.; Sezen, M.; Sendur, K.; Mengüç, Mustafa Pınar; Leblebici, Y.; Kosar, A.; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
One of the most critical challenges for nanofluids in practical applications is related to their stability and reusability since a gradual agglomeration of nanoparticles in nanofluids occurs with time and is accelerated by heating. In this study, we propose a technique to maintain the performance and stability of nanofluids with the use of cavitating flows through micro orifices to prevent agglomeration and sedimentation of nanoparticles, which will increase the durability of the nanofluids. γ-Al2O3 (gamma-alumina) nanoparticles with a mean diameter of 20 nm suspended in water were utilized. In the current approach, a flow restrictive element induces sudden pressure, which leads to cavitation bubbles downstream from the orifice. The emerging bubbles interact with the agglomerated structure of nanoparticles and decrease its size through hitting or shock waves generated by their collapse, thereby increasing the stability and reusability of nanofluids. The method does not involve any use of expensive surfactants or surface modifiers, which might alter the thermophysical properties of nanofluids, may adversely influence their performance and biocompatibility, and may limit their effectiveness.
Metadata only
Influence of accelerometer type on uncertainties in recorded ground motions and seismic damage assessment
(Springer, 2022-07) Liao, W.; Fei, Y.; Ghahari, F.; Zhang, W.; Chen, P. Y.; Kurtuluş, Aslı; Yen, C. H.; Cheng, Q.; Lu, X.; Taciroglu, E.; Civil Engineering; KURTULUŞ, Asli
Strong motion data recorded by strong-motion networks are essential for preventing and mitigating earthquake disasters, such as earthquake early warning and earthquake emergency responses, and the type of accelerometer can significantly influence the quality of recorded ground motions (GMs) and the subsequent usage. Different types of accelerometers vary significantly in both the price and the quality of collected data, because cheap accelerometers generate non-negligible self-noise and reduce the quality of the collected GMs. However, the effects of the accelerometer type and spatial density on the accuracy of GM-based seismic damage assessment are still unknown. The present study attempts to quantify these effects comprehensively at a regional scale. First, a method to simulate recorded data from different quality sensors is devised, using characteristics of existing low-, medium-, and high-quality accelerometers. These simulations use input data from either the Pacific Earthquake Engineering GM database or from a high-fidelity fault rupture and regional wave propagation simulation. Subsequently, the simulated sensor data are used to assess the seismic damage to typical buildings at a city scale. The results indicate that low-quality sensors found in most smartphones are currently insufficient for assessing seismic damage. Medium-quality accelerometers (MEMS-based instruments), on the other hand, can provide feasible solutions for cost-effective city-scale deployment and may offer deployment options that are superior to sensor networks with high-quality accelerometers.
Metadata only
Influence of sensor density on seismic damage assessment: A case study for istanbul
(Seismological Society of America, 2022-08) Cheng, Q.; Fei, Y.; Lu, X.; Liao, W.; Zhang, W.; Chen, P. Y.; Kurtuluş, Aslı; Ghahari, F.; Vela, V.; Taciroglu, E.; Civil Engineering; KURTULUŞ, Asli
The strong ground motions (GMs) recorded by strong motion networks are significant to increase the accuracy of seismic damage assessment. However, the influence of sensor density on seismic damage assessment remains unclarified. Therefore, a workflow is proposed in this study to quantitatively analyze the influence of sensor density on seismic damage assessment. The scenario-based earthquake simulation method is first used to provide the time history of GM at each location as the ground truth of the analysis. Subsequently, a GM prediction method, namely the interpolation method, is adopted to predict GMs at locations without sensors using measuring data from the limited sensors. Finally, the building scale and region scale seismic damage under different sensor densities are compared to quantitatively analyze the influence of sensor density on seismic damage assessment. A detailed case study for Zeytinburnu District, Istanbul, Turkey, is performed to demonstrate the proposed methods. The findings of this study can provide an important reference for seismic damage assessment and the deployment of strong motion networks.
Metadata only
Influence of Sporasarcina pasteurii cells on rheological properties of cement paste
(Elsevier, 2019-11-20) Azima, Mahzad; Bundur, Zeynep Başaran; Civil Engineering; BUNDUR, Zeynep Başaran; Azima, Mahzad
Nowadays with the developments in the concrete materials technology, researches started to focus on highly flowable mixes with improved rheological properties. These highly flowable mixes generally require use of viscosity modifying agents (VMAs) to reduce bleeding and segregation. VMAs are water-soluble polymers that can be produced from acrylic polymers and polysaccharide-based biopolymers obtained from cellulose, starch or bacterial fermentation. Through the literature, nopal mucilage, brown algae and bacterial cell walls were proposed as alternatives to these bio-based admixtures. However, these alternatives also require extra processing which results again with a higher unit cost. This paper summarizes the rheological properties of a cement paste including bacterial cells. The main goal of this study was to investigate the influence of Sporasarcina pasteurii (S. pasteurii) cells on viscosity and yield stress of cement-based materials. The bacterial cells were directly incorporated to the mix water and influence of cells on viscosity and yield strength was evaluated by rheological tests. In addition, the influence of bacteria dosage, water to cement ratio (w/c), use of superplasticizers and fly ash on performance of biological VMA were investigated. Our results showed that the apparent viscosity and yield stress of the cement-paste mix were increased with the addition of the microorganisms. Moreover, the provided biological VMA was found to be compatible with the use of fly ash and superplasticizers depending on the w/c of cement paste.
Metadata only
Optimization of spectrally selective Si/SiO2 based filters for thermophotovoltaic devices
(Elsevier, 2017-08) Khosroshahi, F. K.; Ertürk, H.; Mengüç, Mustafa Pınar; Mechanical Engineering; MENGÜÇ, Mustafa Pınar
Design of a spectrally selective filter based on one-dimensional Si/SiO2 layers is considered for improved performance of thermo-photovoltaic devices. Spectrally selective filters transmit only the convertible radiation from the emitter as non-convertible radiation leads to a reduction in cell efficiency due to heating. The presented Si/SiO2 based filter concept reflects the major part of the undesired range back to the emitter to minimize energy required for the process and it is adaptable to different types of cells and emitters with different temperatures since its cut-off wavelength can be tuned. While this study mainly focuses on InGaSb based thermo-photovoltaic cell, Si, GaSb, and Ga0.78In0.22As0.19Sb0.81 based cells are also examined. Transmittance of the structure is predicted by rigorous coupled wave approach. Genetic algorithm, which is a global optimization method, is used to find the best possible filter structure by considering the overall efficiency as an objective function that is maximized. The simulations show that significant enhancement in the overall system and device efficiency is possible by using such filters with TPV devices. The methodology described in this paper allows for an improved filter design procedure for selected applications.
Open Access
Rateworkspace: BIM integrated post-occupancy evaluation system for office buildings
(International Council for Research and Innovation in Building and Construction, 2022-04) Artan, D.; Ergen, E.; Kula, B.; Işın, Gürşans Güven; Civil Engineering; IŞIN, Gürşans Güven
The feedback obtained from occupants regarding their comfort needs and performance of buildings is critical for assessing occupant satisfaction, identifying the operation and maintenance (O&M) issues in time and for improving resource efficiency in buildings. Current facility management (FM) systems and occupant feedback collection practices, however, have limitations in supporting effective decision-making in FM, as they lack the necessary contextual data related to the occupant feedback (e.g., building geometry, systems, elements). Building Information Modeling (BIM)-enabled FM systems are used for combining different types of FM information with building models; however, occupant feedback is still not effectively utilized in FM since it is not integrated with BIM. In this study, a BIM integrated post-occupancy evaluation system prototype is developed for: (1) collecting occupant feedback along with the contextual information related to the feedback items in a structured way, and (2) presenting this information as integrated with BIM to the facility managers. This enables conducting spatio-temporal queries and supports effective decision-making by visualizing the collected feedback. The prototype was designed by using qualitative shadowing with FM teams to identify information needs and use case analysis to determine how contextual data integrated with BIM could be collected from office occupants who are non-technical persons with limited information on building models. This paper identifies the FM query categories that are required to process the occupant feedback and describes the RateWorkSpace prototype developed for office buildings. The deployment of the prototype in a real-world office demonstrates that the proposed system is applicable, practical, usable, and that real-time building performance data can be both collected and analysed with the developed system. This has the potential to increase the effectiveness of the FM and O&M processes, and help to create office spaces with optimized energy use and occupant comfort that also supports occupant well-being and productivity.
Restricted
A rule-based methodology for automated progress monitoring of construction activities: A case for masonry work
(International Council for Research and Innovation in Building and Construction, 2019) Işın, Gürşans Güven; Ergen, E.; Civil Engineering; IŞIN, Gürşans Güven
The conventional approach that is used to monitor construction projects is to collect progress data from the construction site through visual investigation. This results in deficient and sometimes erroneous data, and leads to inefficiencies in project control, delays and cost overruns. To address these problems in building construction projects, an approach was developed to automatically monitor activity progress by tracking major construction equipment and bulk materials using sensor-based technologies that are cost-effective and easy to deploy. In this approach data obtained from sensors (e.g., load sensor) and/or other sensor-based technologies (i.e., Radio Frequency Identification (RFID)), which were deployed on major construction resources, were fused using rule-based algorithms to determine the activity progress. This progress data was compared with human-generated site related data (e.g., schedules, site reports) to determine the activity performance. This paper presents the developed data fusion approach and rule-based data fusion algorithms that incorporate the domain-specific heuristic information for determining the activity's overall progress. To validate the proposed approach, a proof-of-concept prototype was deployed and tested at a construction site for monitoring the progress of masonry work. The results show that the developed approach achieved 95% average accuracy in identifying the progress of the masonry work that was monitored during the field tests. The main contributions of this study are the rule-based data fusion approach and the rules that were developed for processing data from equipment and bulk materials. These rules can be used to determine the progress of other activities that use similar resources.
Metadata only
Scheduling and simulation of maritime traffic in congested waterways: an application to the Strait of Istanbul
(Cambridge University Press, 2021-05) Özlem, Ş.; Or, İ.; Altan, Yiğit Can
The aim of this study is to develop a simulation model which is capable of mimicking actual vessel arrival patterns and vessel entrance decisions (which are made based on expert opinions generally) on congested, narrow waterways. The model is tested on the transit traffic pattern in the Strait of Istanbul. Based on a heuristic scheduling algorithm, this model decides entrance times and vessel types on the strait. The model, with different policies for day and night traffic, is run for a period of seven years with 20 replications for each year. The performance measures of the model are: average interarrival times, number of vessels passed and entrance times for each successive vessel pair in both traffic directions. The model results are congruent with the actual results of performance measures. Therefore, it may be deduced that the proposed algorithm can be a guide for operators regarding scheduling decisions in congested, narrow waterways.
Metadata only
Soil liquefaction-induced uplift of buried pipes in sand-granulated-rubber mixture: Numerical modeling
(Elsevier, 2022-03) Valizadeh, Hadi; Ecemis, N.; Civil Engineering; VALIZADEH, Hadı
The significant uplift of buried pipes observed during recent earthquakes has showed the need for further research in remediation methods for soil liquefaction. Sand-granulated rubber mixture is reported as a new soil improvement method that can be applied as a liquefaction mitigation filling material around buried pipe. In this study, the effects of pipe size, burial depth, and shaking intensity on the pipe uplift and the liquefaction potential of the sand-tire derived granulated rubber mixture placed around the buried pipes were investigated using numerical models. First, the result of 1-g shaking table tests was used for the verification of the numerical analysis. Comparing the numerical results and the experimental measurements showed that the numerical simulation using the UBCSAND constitutive model could accurately estimate the liquefaction-induced uplift of the buried pipes as well as the related failure. Then, a parametric study was conducted to investigate the effects of the pipe diameter, the pipe depth, and the value of the acceleration on pipe uplift and liquefaction potential when the SGR mixture was placed as filling material. Eventually, an analytical formula was proposed to estimate the liquefaction-induced uplift of buried pipes, and the soil failure mode was categorized according to the pipe’s burial depth ratio.
Metadata only
Tracking major resources for automated progress monitoring of construction activities: masonry work case
(Emerald, 2021-10-21) Işın, Gürşans Güven; Ergen, E.; Civil Engineering; IŞIN, Gürşans Güven
Purpose: The purpose of this study is to monitor the progress of construction activities in an automated way by using sensor-based technologies for tracking multiple resources that are used in building construction. Design/methodology/approach: An automated on-site progress monitoring approach was proposed and a proof-of-concept prototype was developed, followed by a field experimentation study at a high-rise building construction site. The developed approach was used to integrate sensor data collected from multiple resources used in different steps of an activity. It incorporated the domain-specific heuristics that were related to the site layout conditions and method of activity. Findings: The prototype estimated the overall progress with 95% accuracy. More accurate and up-to-date progress measurement was achieved compared to the manual approach, and the need for visual inspections and manual data collection from the field was eliminated. Overall, the field experiments demonstrated that low-cost implementation is possible, if readily available or embedded sensors on equipment are used. Originality/value: Previous studies either monitored one particular piece of equipment or the developed approaches were only applicable to limited activity types. This study demonstrated that it is technically feasible to determine progress at the site by fusing sensor data that are collected from multiple resources during the construction of building superstructure. The rule-based reasoning algorithms, which were developed based on a typical work practice of cranes and hoists, can be adapted to other activities that involve transferring bulk materials and use cranes and/or hoists for material handling.

Browse

Browsing by By Publication Category "International Refereed Journal"