Ertugrul Taciroglu | University of California, Los Angeles (original) (raw)

Papers by Ertugrul Taciroglu

Frontiers of Structural and Civil Engineering, 2020

Some of the current concrete damage plasticity models in the literature employ a single damage va... more Some of the current concrete damage plasticity models in the literature employ a single damage variable for both the tension and compression regimes, while a few more advanced models employ two damage variables. Models with a single variable have an inherent difficulty in accounting for the damage accrued due to tensile and compressive actions in appropriately different manners, and their mutual dependencies. In the current models that adopt two damage variables, the independence of these damage variables during cyclic loading results in the failure to capture the effects of tensile damage on the compressive behavior of concrete and vice-versa. This study presents a cyclic model established by extending an existing monotonic constitutive model. The model describes the cyclic behavior of concrete under multiaxial loading conditions and considers the influence of tensile/compressive damage on the compressive/tensile response. The proposed model, dubbed the enhanced concrete damage pla...

Procedures and computer programs are developed for determining the response of soil-foundation-st... more Procedures and computer programs are developed for determining the response of soil-foundation-structure interaction systems during earthquakes and to investigate the nature of soil and interaction effects. Assuming the linear elastic stress-strain behavior of the soil, the author develops a two-dimensional analytical model of soil-foundation-structure interaction. The model consists of one-dimensional structural members, a two-dimensional rigid foundation block, and quadrilateral finite elements which idealize soil deposits. The ...

Vehicle System Dynamics

The near fault (NF) line waves send out signal envelopes that oscillate over lengthy periods of t... more The near fault (NF) line waves send out signal envelopes that oscillate over lengthy periods of time with periodic impulses. Like train bridges, train tracks demonstrate comparable track-bridge (TB...

Title: Field Testing of a Non-ductile Reinforced Concrete B... more Title: Field Testing of a Non-ductile Reinforced Concrete Building in Turkey (NEES-2010-0929) Year Of Curation: 2013 Description: This project brings together the technical expertise and advanced testing capabilities of a group of researchers from the US and Turkey to provide unique data on behavior and performance of older reinforced concrete buildings. This type of construction comprises the majority of residential, public service (i.e., schools, hospitals), and commercial buildings in the industrial heartland of Turkey; and there are a significant number of similarly vulnerable buildings within more active seismic regions in the USA (e.g., California, Washington, Utah, South Carolina, etc). In California, the vulnerable buildings are typically pre-1973 vintage. Award: http://www.nsf.gov/awardsearch/showAward?AWD_ID=0755333 PIs & CoPIs: Ertugrul Taciroglu, John Wallace Dates: July 01, 2010 - December 15, 2010 Organizations: University of California, Los Angeles, CA, United States Facilities: University of California, Los Angeles, CA, United States Sponsor: NSF - 0755333 Keywords: health monitoring, system identification, vibration testing Publications: Kutay Orakcal, Hilmi Lus, Erdal Safak, "Ambient and Forced Vibration Testing of a Reinforced Concrete Building Before and After its Seismic Retrofitting" <nb:citations></nb:citations>

Website: https://github.com/NHERI-SimCenter/BRAILS What is BRAILS BRAILS is the acronym for Build... more Website: https://github.com/NHERI-SimCenter/BRAILS What is BRAILS BRAILS is the acronym for Building Recognition using AI at Large-Scale, which is an AI-Based pipeline for city-scale building information modeling (BIM). What can BRAILS do BRAILS helps users create regional-scale database of building inventory, where buildings properties are extracted from satellite or street view images using deep learning. Why it's important BIM, as an efficient way for describing buildings, gives architecture, engineering, and construction (AEC) professionals the insight and tools to more efficiently plan, design, construct, and manage buildings and infrastructure. Natural disasters cause losses to human society by damaging or destroying buildings, which consequently endangers lives and goods. Buildings are the major components of a human built environment, hence are of the major considerations in planning for, responding to and recovering from disasters. BIM contains information showing build...

This work delineates the stable implementation of an innovative method of accounting for the effe... more This work delineates the stable implementation of an innovative method of accounting for the effects of inertial soil-structure interaction in time domain time-history analyses through the use of recursive discrete-time digital filters as approximations of frequency dependent foundation impedance functions. To this end, an algorithm inserting the recursive filter into a numerical integration scheme of the dynamic equations of motion is derived. Its implementation is then demonstrated by subjecting various elastic structure-foundation-soil systems to ground motion records. The resultant time histories are subsequently verified through comparison with those obtained both in the frequency domain and using various state-of-practice time domain solution methods. Finally, the stability of the combined integration-recursion algorithm is investigated both analytically and numerically.

Acta Geotechnica, 2018

The Rankine earth pressure theory is extended herein to an inclined c-/ backfill. An analytical a... more The Rankine earth pressure theory is extended herein to an inclined c-/ backfill. An analytical approach is then proposed to compute the static passive and active lateral earth pressures for a sloping cohesive backfill retained by a vertical wall, with the presence of wall-soil interface adhesion. The proposed method is based on a limit equilibrium analysis coupled with the method of slices wherein the assumed profile of the backfill failure surface is a composite of log-spiral and linear segments. The geometry of the failure surface is determined using the stress states of the soil at the two boundaries of the mobilized soil mass. The resultant lateral earth thrust, the point of application, and the induced moment on the wall are computed considering global and local equilibrium of forces and moments. Results of the proposed approach are compared with those predicted by a number of analytical models currently adopted in the design practice for various combinations of soil's frictional angles, wall-soil interface frictional angles, inclined angles of backfill and soil cohesions. The predicted results are also verified against those obtained from finite element analyses for several scenarios under the passive condition. It is found that the magnitude of earth thrust increases with the backfill inclination angle under both the passive and active conditions.

Structural Control and Health Monitoring, 2017

A probabilistic method is presented for identifying the dynamic soil-foundation stiffnesses of bu... more A probabilistic method is presented for identifying the dynamic soil-foundation stiffnesses of building structures. It is based on model updating of a Timoshenko beam resting on sway and rocking springs, which respectively represent the superstructure and the soil-foundation system. Unlike those previously employed for this particular problem, the proposed method is a Bayesian one, which accounts for the prevailing uncertainties due to modeling and measurement errors. As such, it yields the probability distribution of the system parameters as opposed to average/deterministic values. In this approach, the joint probability density function of the parameters that control the flexible-base Timoshenko beam model, together with the fundamental natural frequency and mode shape of the system, forms the prior distribution. Using Bayes' theorem, a posterior distribution is obtained by updating the prior distribution with a sparsely measured mode shape and frequency. The most probable realizations of the system parameters are then determined by maximizing the posterior distribution. For this purpose, first-and second-order derivatives of the objective function are analytically computed via direct differentiation. The proposed method is verified using a synthetic example. Additionally, sensitivity analyses are carried out on both the system parameters and standard deviations of the sources of error. Subsequently, the proposed method is applied to real-life data recorded at the Millikan Library building, which is located at the California Institute of Technology campus in Pasadena, California, and the results are compared with a previous deterministic study.

Advances in Structural Engineering, 2015

Transformer substations are among the most significant components of an electric power distributi... more Transformer substations are among the most significant components of an electric power distribution system. These critical elements must remain operational during and after any extreme event, especially a severe earthquake. In past studies, the interaction between the main plant and the electrical equipment (EE) in a transformer substation was usually ignored. While a few considered this interaction through numerical simulations, there were no experimental studies to validate the findings. The aim of the present paper is to analyze the seismic reaction of a substation with explicit consideration of the dynamic interaction between the main plant and the EE mounted inside—achieved through a shaking table test and numerical simulations. A 1:8 scale model of a transformer substation plant with EE on its second floor is built and tested on a shaking table. Dynamic response data are gathered during seismic excitations of the substation, with and without the EE. These measurements and the ...

tdmd.org.tr

... Boğaziçi Üniversitesi Kuzey Kampüsü'nde bulunan Eğitim Teknolojileri B Blok (ET-B) binas... more ... Boğaziçi Üniversitesi Kuzey Kampüsü'nde bulunan Eğitim Teknolojileri B Blok (ET-B) binası depreme karşı güçlendirilmesi ... Depreme karşı güçlendirme çalışmaları, binanın taşıyıcı sistemineperde duvalar eklenmesi ve mevcut kolonların mantolanması olarak gerçekleştirilmiştir. ...

International Journal of Impact Engineering, 2012

International Journal for Numerical and Analytical Methods in Geomechanics, 2021

Numerous experiments and prior analyses have confirmed that soil inelasticity, which is known to ... more Numerous experiments and prior analyses have confirmed that soil inelasticity, which is known to come into effect even at very low strain levels, can significantly affect site response and dynamic soil‐structure interaction (SSI) behavior. To date, only a few studies were able to consider multi‐axial wave propagation problems with appropriate models of soil nonlinearity. Most existing works are limited to either homogeneous soil configurations or equivalent linear soil models. The instances wherein soil nonlinearity is accurately considered have been confined to single element tests and one‐dimensional problems. In this study, an improved pressure‐dependent bounding surface plasticity soil model—with appropriate plastic strain rate direction definition and overshooting correction scheme—is implemented in Abaqus, and validated using recordings from both the Lotung borehole array and centrifuge test data on embedded flexible structures. The implemented model is capable of comprehensively reproducing complex soil behaviors, such as stiffness degradation, damping, dilatancy, and compaction while under a wide strain range, and under general loading conditions using only a few material parameters to be calibrated. Consequently, numerically predicted results are observed to be in better agreement with experimentally measured data, in comparison with linear and another plasticity model, which include accelerations, and bending and hoop strains along the walls of the specimen structures, for low‐ as well as high‐amplitude input motions.

33rd Conference on Neural Information Processing Systems (NeurIPS 2019), Vancouver, Canada. Corre... more 33rd Conference on Neural Information Processing Systems (NeurIPS 2019), Vancouver, Canada. Corresponding author: Chaofeng Wang, c_w@berkeley.edu In this paper, we provide two case studies to demonstrate how artificial intelligence can empower civil engineering. In the first case, a machine learning-assisted framework, BRAILS, is proposed for city-scale building information modeling. Building information modeling (BIM) is an efficient way of describing buildings, which is essential to architecture, engineering, and construction. Our proposed framework employs deep learning technique to extract visual information of buildings from satellite/street view images. Further, a novel machine learning (ML)-based statistical tool, SURF, is proposed to discover the spatial patterns in building metadata. The second case focuses on the task of soft-story building classification. Soft-story buildings are a type of buildings prone to collapse during a moderate or severe earthquake. Henc...

Long-span bridges provide vital transportation links to metropolitan regions, and their damage du... more Long-span bridges provide vital transportation links to metropolitan regions, and their damage during earthquakes will cause significant hardship. Recognizing their importance, the California Department of Transportation (Caltrans) and California Geological Survey have been deploying strong motion instrumentation on these structures for 25 years. In the present study, existing gaps between responses predicted using numerical models and real-life data are investigated through system identification and finite element model updating techniques for the Samoa Channel Bridge, located in Humboldt County. Seismic response of this bridge is different from its operational response, and the discrepancy increases with the shaking intensity. Also, while existing reduced-order numerical models of soil-pile interaction are observed to work well, they should be calibrated for specific vibration amplitudes.

The seismic response of underground structures is a complex soil-structure interaction (SSI) prob... more The seismic response of underground structures is a complex soil-structure interaction (SSI) problem in which two fundamental mechanisms are at play. Kinematic SSI is concerned with the motion of the structure in the presence of spatially variable ground motions and the interface pressures that develop as a result of different structural and free-field motions. Inertial SSI captures the soil reactions that develop to resist inertial forces associated with the acceleration of the structure. The kinematic component is generally considered to be most significant for embedded structures, due to their modest mass. Existing methods of analysis for the seismic response of embedded structures are not based on a rational conceptual framework that recognizes the essential role of SSI in the response prediction. These methods of analysis therefore have an unknown degree of reliability for the problem. We propose a two-year project that will significantly advance our understanding of SSI for em...

This paper is aimed at quantifying the variability in predicted seismic response of bridges due t... more This paper is aimed at quantifying the variability in predicted seismic response of bridges due to uncertainty in exterior shear key behavior. Shear keys are usually modeled as sacrificial elements; however, experiments show that the behavior of shear keys depend on their reinforcement detailing, and the construction joint between the shear key and the bridge abutment's stem wall. This paper focuses on modeling approaches for shear keys in bridges with box-girder deck and seat-type abutments. Construction of this type of bridge is common in California since 2000. An enhanced ductile shear key model, generated based on experimental results is used in this study. As for sacrificial (brittle) shear keys, a simplified analytical model is developed based on experimental evidence. The model matrix is comprehensive and comprises bridges with various abutment skew angles and a suite of forty near-fault ground motions. Three parameter lognormal distribution is employed for probabilistic ...

In this study, we formulate an improved finite element model updating method to address the numer... more In this study, we formulate an improved finite element model updating method to address the numerical difficulties associated with ill conditioning and rank-deficiency. These complications are frequently encountered model updating problems, and occur when the identification of a larger number of physical parameters is attempted than that warranted by the information content of the experimental data. Based on the standard Bounded Variables Least-squares (BVLS) method, which incorporates the usual upper/lower-bound constraints, the proposed method (henceforth referred to as BVLSrc) is equipped with novel sensitivity-based relative constraints. The relative constraints are automatically constructed using the correlation coefficients between the sensitivity vectors of updating parameters. The veracity and effectiveness of BVLSrc is investigated through the simulated, yet realistic, forced vibration testing of a simple framed structure using its frequency response function as input data....

By harvesting data from publicly available sources, locations of bridges in a region as well as t... more By harvesting data from publicly available sources, locations of bridges in a region as well as their essential structural and geotechnical properties, and hazard exposure can be extracted. This data is crucial in image-based modeling procedures, given images are best utilized for geometry and material-type extraction, hence they provide only a part of the data necessary for constructing detailed structure-specific models. ShakeReady database, currently under development, contains a collection of bridge data obtained from web-based resources (Figure 1).

Structural Control and Health Monitoring, 2021