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Article Citation - WoS: 30Citation - Scopus: 29Acoustic Control of Flow Over Naca 2415 Airfoil at Low Reynolds Numbers(Asce-amer Soc Civil Engineers, 2016) Genc, M. Serdar; Acikel, H. Hakan; Akpolat, M. Tugrul; Ozkan, Gokhan; Karasu, IlyasIn this study, the effects of acoustic excitation frequency on flow over an NACA 2415 airfoil were determined, and all of the experiments were done both with and without the presence of the acoustic excitation. The acoustic excitation was applied for a range of angles of attack (0 degrees-25 degrees) and Reynolds numbers of 50,000, 75,000, 100,000, 150,000, and 200,000. To examine the effects of acoustic excitation on the flow, force measurements, pressure measurements, hot-wire anemometry, smoke-wire flow-visualization, and particle image velocimetry techniques were employed. The results indicated that for stall and some limited poststall angles of attack of the acoustic excitation having a frequency in a certain range forced the separated shear layer to reattach to the surface of the airfoil. As the Reynolds number increased, the effective excitation frequency increased, but the range of Zaman number [St/(R-1/2)] was the same. With the acoustic excitation, the stall angle was delayed from 12 degrees to 16 degrees at R = 50,000, and there was a 30% and 50% increase on the maximum value of the lift coefficient and the ratio of the lift and drag forces, respectively. Moreover, the stall angle was delayed from 13 degrees to 17 degrees at R = 75,000, from 15 degrees to 18 degrees at R = 100,000, from 15 degrees to 17 degrees at R = 150,000. Furthermore, it was concluded that acoustic excitation shrunk laminar separation bubble, and an effect of the acoustic control on the separation bubble decreased as the Reynolds number increased. (C) 2016 American Society of Civil Engineers.Article Citation - WoS: 106Citation - Scopus: 141Flexibility Based Approach for Damage Characterization: Benchmark Application(Asce-amer Soc Civil Engineers, 2004) Bernal, D; Gunes, BA flexibility based damage characterization technique is described and its performance is examined in the context of Phase 1 of the benchmark study developed by the IASC-ASCE SHM Task Group. Noteworthy features of the analytical development are: (1) the methodology used to extract a matrix that is proportional to the flexibility when the excitation is stochastic; (2) the technique used to interrogate the changes in flexibility (or flexibility proportional matrices) with regards to the location of the damage; and (3) the method used to quantify the damage without the use of a model. The strategy proved successful in all the cases considered.Article Citation - WoS: 8Estimation of Polypropylene Concentration of Modified Bitumen Images by Using K-Nn and Svm Classifiers(Asce-amer Soc Civil Engineers, 2015) Tapkin, Serkan; Sengoz, Burak; Sengul, Gokhan; Topal, Ali; Ozcelik, ErolThe goal of this study is to design an expert system that automatically classifies the microscopic images of polypropylene fiber (PPF) modified bitumen including seven different contents of fibers. Optical microscopy was used to capture the images from thin films of polypropylene fiber modified bitumen samples at a magnification scale of 100 x. A total of 313 images were pre-processed, and features were extracted and selected by the exhaustive search method. The k-nearest neighbor (k-NN) and multiclass support vector machine (SVM) classifiers were applied to quantify the representation capacity. The k-NN and multiclass SVM classifiers reached an accuracy rate of 87% and 86%, respectively. The results suggest that the proposed expert system can successfully estimate the concentration of PPF in bitumen images with good generalization characteristics. (C) 2014 American Society of Civil Engineers.Article Citation - WoS: 1Citation - Scopus: 1Experimental Determination of Resistance Characteristics of Support Details Used in Prestressed Concrete Bridge Girders(Asce-amer Soc Civil Engineers, 2009) Baran, Eray; Rohne, Ryan; French, Catherine E.; Schultz, Arturo E.Static load tests were performed on support details used at the ends of prestressed concrete pedestrian bridge girders to determine the resistance characteristics of girder supports in the direction perpendicular to the longitudinal axis of the girders. The specimens tested represent support details that have also been widely used in prestressed concrete highway bridges in Minnesota and in other states. Two specimens, one representing the free-end detail and one representing the restrained-end detail were subjected to a combination of vertical and lateral loads. The applied loading was intended to simulate the loading conditions to which the girder ends would be subjected in the event of an over-height vehicle collision with the bridge. The tests revealed two types of lateral load resisting mechanisms depending on the type of support detail. The specimen with the free-end detail resisted the lateral loading through sliding friction between the components of the support assembly. Deformation of this specimen was a combination of shear deformation of the bearing pad and sliding of various support components. The restrained-end detail exhibited larger lateral load capacity than the free-end detail due to the resistance provided by the anchor rods that were intended to prevent the lateral movement of the girder ends. Failure of the specimen with restrained-end detail was due to the concrete breakout and bending of the anchor rods.Article Citation - WoS: 24Activity Uncrashing Heuristic With Noncritical Activity Rescheduling Method for the Discrete Time-Cost Trade-Off Problem(Asce-amer Soc Civil Engineers, 2020) Sonmez, Rifat; Aminbakhsh, Saman; Atan, TankutDespite intensive research efforts that have been devoted to discrete time-cost optimization of construction projects, the current methods have very limited capabilities for solving the problem for real-life-sized projects. This study presents a new activity uncrashing heuristic with noncritical activity rescheduling method to narrow the gap between the research and practice for time-cost optimization. The uncrashing heuristic searches for new solutions by uncrashing the critical activities with the highest cost-slope. This novel feature of the proposed heuristic enables identification and elimination of the dominated solutions during the search procedure. Hence, the heuristic can determine new high-quality solutions based on the nondominated solutions. Furthermore, the proposed noncritical activity rescheduling method of the heuristic decreases the amount of scheduling calculations, and high-quality solutions are achieved within a short CPU time. Results of the computational experiments reveal that the new heuristic outperforms state-of-the-art methods significantly for large-scale single-objective cost minimization and Pareto front optimization problems. Hence, the primary contribution of the paper is a new heuristic method that can successfully achieve high-quality solutions for large-scale discrete time-cost optimization problems.Article Citation - WoS: 21Citation - Scopus: 28Damage in Reinforced-Concrete Buildings During the 2011 Van, Turkey, Earthquakes(Asce-amer Soc Civil Engineers, 2014) Baran, Eray; Mertol, Halit Cenan; Gunes, BurcuTwo major earthquakes with magnitudes Mw=7.2 (ML=6.7) and ML=5.6 occurred in eastern Turkey on October 23 and November 19, 2011. The maximum measured peak ground accelerations for the two ground motions were 0.18g and 0.25g, respectively. The earthquakes resulted in various levels of damage to RC moment-resisting frame buildings ranging from minor cracking in brick partition walls to total collapse. This paper summarizes the field observations of the Atilim University Reconnaissance Team carried out in the region a few days after the two main shocks with an emphasis on the performance of RC buildings. A summary of the evolution of the Turkish seismic design code during the last 35 years is given, followed by an explanation of the behavior of RC buildings during the October 23 and November 9 earthquakes. The deformation types that were commonly observed in the heavily damaged or collapsed RC buildings include plastic hinging in columns attributable to stiffer beams, localization of damage in ground-story columns attributable to changes in the stiffness of the lateral load-resisting system caused by brick partition walls, and shear failure of columns caused by discontinuities in the partition walls adjacent to the columns. Poor concrete quality, inadequate development and lap splice length for reinforcement, and inadequate confinement in columns also contributed to the poor seismic behavior.Article Citation - WoS: 13Citation - Scopus: 18Reconstruction of Historical Inflows Into and Water Supply From Shasta Dam by Coupling Physically Based Hydroclimate Model With Reservoir Operation Model(Asce-amer Soc Civil Engineers, 2016) Trinh, T.; Jang, S.; Ishida, K.; Ohara, N.; Chen, Z. Q.; Anderson, M. L.; Kavvas, M. L.Long-term water supply data are important for the current practice of water resources management at a target region. However, long-term water outflow data from reservoirs are typically limited at fine time resolution (hourly). In this study, the historical data on water supply from the Shasta Dam were reconstructed by a reservoir operation model with reconstructed reservoir inflow data. Before embarking on this exercise, first the inflow data were reconstructed by means of a watershed environmental hydrology hydroclimate model, with its input provided from historical atmospheric reanalysis data. The reanalysis data used in this study are from the National Center for Atmospheric Research and the National Center for Environmental Prediction (NCAR-NCEP) at spatial resolution of 2.5 degrees (210km at the modeled region). The NCAR-NCEP reanalysis data were dynamically downscaled to 3-km spatial grid resolution at hourly intervals by means of the regional atmospheric component of the hydroclimate model. The downscaled atmospheric data were then used as input to the hydroclimate model hydrologic module for the simulation of snowmelt and runoff conditions over Shasta Dam watershed. Then the reconstructed runoff from the watershed was used as input to a reservoir operation model for regulating outflow from Shasta Dam. The coupled hydroclimate model and reservoir model were successfully validated at Shasta Dam watershed by means of comparisons of the model simulations against the observations. Hence, the combination of proposed models were able to reconstruct the historical water supply data during a 60-year historical period (1950-2010) from Shasta Dam watershed.Article Citation - WoS: 13Citation - Scopus: 23Numerical Analysis of a Tunnel Support Design in Conjunction With Empirical Methods(Asce-amer Soc Civil Engineers, 2008) Sari, Yasin Dursun; Pasamehmetoglu, A. Gunhan; Cetiner, Erkan; Donmez, SenayiIn this paper, preliminary support design of a tunnel was analyzed by numerical and empirical approaches. The case study for this analysis is a tunnel to be constructed on the Bilecik-Istanbul roadway in Turkey. The rock mass properties of the tunnel route and design support recommendations were obtained by using an empirical approach. The rock mass properties obtained from the empirical method were used as input parameters for the numerical analysis. The empirical and numerical results, in terms of support design, were evaluated. It was seen that the numerical analysis results supported by empirical values were logical and reliable.Article Citation - WoS: 25New Methodology To Develop Future Flood Frequency Under Changing Climate by Means of Physically Based Numerical Atmospheric-Hydrologic Modeling(Asce-amer Soc Civil Engineers, 2016) Trinh, T.; Ishida, K.; Fischer, I.; Jang, S.; Darama, Y.; Nosacka, J.; Kavvas, M. L.Effect of climate change on hydrologic flow regimes, particularly extreme events, necessitates modeling of future flows in order to best inform water resources management. This study simulated future flows in the Cache Creek watershed in California over the 21st century using a hydro-climate model (Watershed Environmental Hydrology Hydro-Climate Model; WEHY-HCM) forced by future climate projections. The future climate projections, based on four emission scenarios simulated by two global climate models (GCMs), the fifth-generation atmospheric global climate model and third-generation community climate model (ECHAM5 and CCSM3), under several initial conditions, were dynamically-downscaled using the fifth-generation mesoscale atmospheric model (MM5), a regional climate model. The downscaled future precipitation data were bias-corrected before being input into the WEHY model to simulate the detailed flow at hourly intervals along the main Cache Creek branch and its tributaries during 2010-2099. The results suggest an increasing trend in flood magnitudes and their intensities at the outlet of the study region throughout the 21st century. Similarly, estimates of the 100-year and 200-year floods increased throughout the study period. The observed differences in the estimated future flood frequencies between the first half and the second half of 21st century may be an evidence of the nonstationarity in the 21st century hydrological regime over the study region.Article Citation - WoS: 3Citation - Scopus: 2Performance of a Prestressed Concrete Pedestrian Bridge System Under Equivalent Static Lateral Impact Loads(Asce-amer Soc Civil Engineers, 2013) Baran, Eray; Schultz, Arturo E.; French, Catherine E.The resistance of prestressed concrete through-girder (PCTG) pedestrian bridges to lateral loads was studied in response to the increasing number of vehicular impacts in the United States. This research was motivated by the lack of reported studies analyzing the behavior of such bridges to lateral impact loads, as well as their potential vulnerability in comparison with bridges that are better able to redistribute and transfer locally applied impact loads through alternate load paths. Pedestrian bridges are of lighter construction than highway bridges and they do not have the high degree of redundancy, making them more vulnerable to collapse in the event of vehicular impact. Results from static lateral load analyses using three-dimensional, geometrically nonlinear, full-scale finite element (FE) models of a typical bridge system and bridge subassemblages were used to evaluate the characteristics of the system. The FE models were calibrated with experimental test data on typical subassemblages and connection details for PCTG bridges. Results of the experimental part of the program have already been published elsewhere. This paper summarizes the observations obtained from nonlinear static FE analyses of a PCTG pedestrian bridge system subjected to lateral impact loads. The analyses indicated that the location of impact, the type of connector, and the flexibility of the end support details affected bridge performance. Improved connection details are suggested for enhanced PCTG pedestrian bridge performance.
