Artificial Intelligence in Civil Engineering

Artificial intelligence is a branch of computer science, involved in the research, design, and application of intelligent computer. Traditional methods for modeling and optimizing complex structure systems require huge amounts of computing resources, and artificial-intelligence-based solutions can often provide valuable alternatives for efficiently solving problems in the civil engineering. This paper summarizes recently developed methods and theories in the developing direction for applications of artificial intelligence in civil engineering, including evolutionary computation, neural networks, fuzzy systems, expert system, reasoning, classification, and learning, as well as others like chaos theory, cuckoo search, firefly algorithm, knowledge-based engineering, and simulated annealing. The main research trends are also pointed out in the end. The paper provides an overview of the advances of artificial intelligence applied in civil engineering

Invited Review: Recent developments in vibration control of building and bridge structures

This paper presents a state-of-the-art review of recent articles published on active, passive, semi-active and hybrid vibration control systems for structures under dynamic loadings primarily since 2013. Active control systems include active mass dampers, active tuned mass dampers, distributed mass dampers, and active tendon control. Passive systems include tuned mass dampers (TMD), particle TMD, tuned liquid particle damper, tuned liquid column damper (TLCD), eddy-current TMD, tuned mass generator, tuned-inerter dampers, magnetic negative stiffness device, resetting passive stiffness damper, re-entering shape memory alloy damper, viscous wall dampers, viscoelastic dampers, and friction dampers. Semi-active systems include tuned liquid damper with floating roof, resettable variable stiffness TMD, variable friction dampers, semi-active TMD, magnetorheological dampers, leverage-type stiffness controllable mass damper, semi-active friction tendon. Hybrid systems include shape memory alloys-liquid column damper, shape memory alloy-based damper, and TMD-high damping rubber

Fuzzy semi-active control for seismic response reduction with magnetorheological dampers

Based on the dynamic characteristics obtained with a three-dimension finite element method, a reduced mechanical model and parameters for the ship lift can be modified and obtained. Simulated analysis shows that the reduced mechanical model can adequately represent the dynamic characteristics and earthquake responses. The reduced mechanical model can be used to control the seismic whiplash effect of the top workshop of the ship lift with intelligent control methods. A modified Bingham model was proposed to simulate the machinery property of a magnetorheological smart damper. A roof intelligent isolation system was also proposed. Seismic simulation analysis of the ship lift was conducted using a fuzzy control strategy. Simulation analysis results show that the fuzzy semi-active control with a magnetorheological smart damper is beneficial in suppressing the seismic whiplash effect on the top workshop and confirm that the fuzzy semi-active control strategy is valid in this scenario

Adaptive Tracking Controller for Real-Time Hybrid Simulation

Real-time hybrid simulation (RTHS) is a versatile and cost-effective testing method for studying the performance of structures subjected to dynamic loading. RTHS decomposes a structure into partitioned physical and numerical sub-structures that are coupled together through actuation systems. The sub-structuring approach is particularly attractive for studying large-scale problems since it allows for setting up large-scale structures with thousands of degrees of freedom in numerical simulations while specific components can be studied experimentally.The actuator dynamics generate an inevitable time delay in the overall system that affects the accuracy and stability of the simulation. Therefore, developing robust tracking control methodologies are necessary to mitigate these adverse effects. This research presents a state of the art review of tracking controllers for RTHS, and proposes a Conditional Adaptive Time Series (CATS) compensator based on the principles of the Adaptive Time Series compensator (ATS). The accuracy of the proposed controller is evaluated with a benchmark problem of a three-story building with a single degree of freedom (SDOF) in a realistic virtual RTHS (vRTHS). In addition, the accuracy of the proposed method is evaluated for seven numerical integration algorithms suitable for RTHS

Development of Dynamic Models for a Reactive PackedDistillation Column

This work has been carried out to develop dynamic models for a reactive packed distillation column using the production of ethyl acetate as the case study. The experimental setup for the production of ethyl acetate was a pilot scale packed column divided into condenser, rectification, acetic acid feed, reaction, ethanol feed, stripping and reboiler sections. The reaction section was filled with Amberlyst 15 catalyst while the rectification and the stripping sections were both filled raschig rings. The theoretical models for each of the sections of the column were developed from first principles and solved with the aid of MATLAB R2011a. Comparisons were made between the experimental and theoretical results by calculating the percentage residuals for the top and bottom segment temperatures of the column. The results obtained showed that there were good agreements between the experimental and theoretical top and bottom segment temperatures because the calculated percentage residuals were small. Therefore, the developed dynamic models can be used to represent the reactive packed distillation column

Designing optimal controllers for nonlinear frames by considering the effect of response feedback

AbstractThe effect of response feedback on designing optimal controllers for nonlinear frames has been studied. Different combinations of response feedback have been used in the performance index. The Newmark based nonlinear instantaneous optimal control algorithm has been used as the control algorithm in controlling the response of an eight-story bilinear hysteretic frame subjected to white noise excitation and real earthquakes, and controlled by either eight actuators or a single actuator. While the objective has been to minimize the maximum control force for reducing the maximum drift to below the yielding level, the distributed genetic algorithm (DGA) has been used to determine the proper set of weighting matrices in the performance index. Results show that the performance of the active control system depends on the combination of response feedback, where the velocity feedback has been more effective than acceleration and displacement. Also, although using the full feedback of response in the performance index leads to the design of optimal controllers that require the smallest control force, it is costlier, because it requires more online measurements. Finally, it has been concluded that amongst all possibilities, using only velocity feedback can provide the best results regarding the maximum required control force and online measurement, simultaneously

Application of Tuned Mass Dampers for Structural Vibration Control: A State-of-the-art Review

Given the burgeoning demand for construction of structures and high-rise buildings, controlling the structural vibrations under earthquake and other external dynamic forces seems more important than ever. Vibration control devices can be classified into passive, active and hybrid control systems. The technologies commonly adopted to control vibration, reduce damage, and generally improve the structural performance, include, but not limited to, damping, vibration isolation, control of excitation forces, vibration absorber. Tuned Mass Dampers (TMDs) have become a popular tool for protecting structures from unpredictable vibrations because of their relatively simple principles, their relatively easy performance optimization as shown in numerous recent successful applications. This paper presents a critical review of active, passive, semi-active and hybrid control systems of TMD used for preserving structures against forces induced by earthquake or wind, and provides a comparison of their efficiency, and comparative advantages and disadvantages. Despite the importance and recent advancement in this field, previous review studies have only focused on either passive or active TMDs. Hence this review covers the theoretical background of all types of TMDs and discusses the structural, analytical, practical differences and the economic aspects of their application in structural control. Moreover, this study identifies and highlights a range of knowledge gaps in the existing studies within this area of research. Among these research gaps, we identified that the current practices in determining the principle natural frequency of TMDs needs improvement. Furthermore, there is an increasing need for more complex methods of analysis for both TMD and structures that consider their nonlinear behavior as this can significantly improve the prediction of structural response and in turn, the optimization of TMDs

Optimal Structural Control Using Wavelet-based Lqr Algorithm

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2014Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2014Dünyada yapı alanında yürütülen faaliyetler incelendiğinde, yapıların daha yüksek ve daha hafif yapılması yönünde ilerleme olduğu görülmektedir. Bu özelliklerinden dolayı söz konusu yapılar daha esnek ve sönüm oranları da daha azdır. Bunun sonucunda yapıların yaşam konforunda azalma olmaktadır. Günümüzde yapıların titreşimini minimuma indirmek için çeşitli teknikler mevcuttur. Bu araştırmada yapıların titreşim kontrolü için kullanılan LQR (doğrusal kuadratik düzenleyici) algoritmalarında wavelet tekniği ile yapılacak iyileştirme incelenmiştir. Deprem gibi rastgele yükler karakter itibariyle dinamik ve değişken frekans özelliğine sahiptir. Bundan dolayı sistemin doğal frekansı ve depremin baskın frekanslarının birbirlerine çok yakın olduğu durumlarda rezonans benzeri durumlara oluşur. Klasik LQR kontrolunda ağırlık matrisleri önceden belirlenir ve yapı dış kuvvetlerin etkisinde kontrol edilirken sabit kalırlar. Bu sebepten dolayı rezonansın yapıya etkisini göz önüne almak için LQR kontrol yönteminde iyileştirme amaçlı değişiklik yapmak gerekmektedir. Eğer R ağırlık matrisinin elemanları depremin tüm kontrol aralığında Q ağırlık matrisinin elemanlarından çok daha fazla olursa yapının tepkisi azalır. Fakat buna karşılık kontrol kuvvetleri ve dolayısıyla da maliyet artar. Bu sorunu çözmek için, ağırlık matrisini yapının her andaki ihtiyacına göre değiştirmek uygun bir çözüm olabilir. Rezonansın olduğu frekanslarda yapının tepkisini azaltmak için ağırlık matrislerini belirtilen frekans bantlarında revize etmek gerekir. Eğer R ağırlık matrisi rezonansın ortaya çıktığı alt aralıklarda azaltılırsa kontrol enerjisinin gereksiz artışı önlenebilir. Bunun için deprem sinyalini ayrıştırmak gerekir ki; deprem frekansları her zaman aralığında belirlensin. Sinyalleri ayrıştırmak için çeşitli yollar mevcuttur. Fourier analizi sinyalleri zaman alanından frekans alanına dönüştüren klasik bir yöntemdir. Fourier analizi tekniğinin en önemli kusurlarından biri frekans alanına dönüştürmede zaman alanındaki bilgiler silinmektedir. Sonuç olarak, Fourier dönüşümündeki bir sinyale bakınca belirli bir olayın ne zaman olduğunu belirtmek zordur. Eğer sinyal özellikleri dönüşüm süresince fazla değişmedi ise, başka bir değişle sinyal sabit (stationary) kalırsa hiçbir sorun yaşanmaz. Ama deprem sabit olmayan özelliklere sahiptir ve bundan dolayı Fourier dönüşümüyle belirtilen özellikleri gözlemek mümkün değildir. Belirtilen sorunu çözmek için bu çalışmada daha önce geliştirilen Wavelet yöntemi kullanılmıştır. Wevelet yönteminin her andaki zaman-frekans dönüşüm özelliğinden yararlanarak LQR algoritmasını iyileştirmek mümkündür. İlk andan itibaren son kontrol anına kadar, her frekans bandında deprem nedeniyle oluşan enerji sonucunda Wavelet in her andaki ayrık kontrol değeri güncellenir. Bu bilgiler her frekans bandındaki ağrılık matrislerini güncellemek için kullanılır. Bu nedenle kazanç matrisleri zamanla değiştiği için karşı gelen Riccati matris denklemleri de değişmektedir. Klasik LQR kontrol yönteminde Q ve R ağırlık matrisleri sabit iken, bu çalışmada incelenen yöntemde kazanç matrislerinin önceden belirlenen ağırlık matrislerinden elde edilmesi yerine her andaki tepkiye bağlı olarak wavelet yaklaşımı ile güncellenen ağırlık matrislerinden elde edilen kazanç matrisleri kullanılmaktadır. Önerilen yöntemin etkinliğini gösterebilmek için, deprem etkisinde ve en üst katında aktif sönümleyici olan ve fay hattına yakın 10 katlı bir binanın dinamik davranışı araştırılmış ve önerilen yöntemin LQR yaklaşımını iyileştirmek için kullanılabileceği gösterilmiştir.Current trends in construction industry demands taller and lighter structures, which are also more flexible and having quite low damping value. This increases failure possibilities and also problems from serviceability point of view. Now-a-days several techniques are available to minimize the vibration of the structure. In this study to control the response of buildings, a modified linear quadratic regulator (LQR) algorithm based on wavelet analysis has been proposed. The formulation of the proposed wavelet-LQR algorithm uses the information derived from the discrete wavelet transform (DWT) analysis of the motivation in real time. The real time DWT controller is applied to obtain the local energy distribution over frequency bands for each time interval. This information is used to adaptively design the controller by updating the weighting matrices. The optimal LQR control problem is solved for each time interval with updated weighting matrices, through the Riccati equation, leading to time-varying gain matrices. The positive aspect of current work is that, the gain matrices are achieved adaptively in real time. The method is tested on a 10-story structure subject to several historical pulse-like near-fault ground motions.The results indicate that the proposed method is more effective at reducing the displacement response of the structure in real time than conventional LQR controllers.Yüksek LisansM.Sc

Optimal seismic retrofitting of existing RC frames through soft-computing approaches

2016 - 2017Ph.D. Thesis proposes a Soft-Computing approach capable of supporting the engineer judgement in the selection and design of the cheapest solution for seismic retrofitting of existing RC framed structure. Chapter 1 points out the need for strengthening the existing buildings as one of the main way of decreasing economic and life losses as direct consequences of earthquake disasters. Moreover, it proposes a wide, but not-exhaustive, list of the most frequently observed deficiencies contributing to the vulnerability of concrete buildings. Chapter 2 collects the state of practice on seismic analysis methods for the assessment the safety of the existing buildings within the framework of a performancebased design. The most common approaches for modeling the material plasticity in the frame non-linear analysis are also reviewed. Chapter 3 presents a wide state of practice on the retrofitting strategies, intended as preventive measures aimed at mitigating the effect of a future earthquake by a) decreasing the seismic hazard demands; b) improving the dynamic characteristics supplied to the existing building. The chapter presents also a list of retrofitting systems, intended as technical interventions commonly classified into local intervention (also known “member-level” techniques) and global intervention (also called “structure-level” techniques) that might be used in synergistic combination to achieve the adopted strategy. In particular, the available approaches and the common criteria, respectively for selecting an optimum retrofit strategy and an optimal system are discussed. Chapter 4 highlights the usefulness of the Soft-Computing methods as efficient tools for providing “objective” answer in reasonable time for complex situation governed by approximation and imprecision. In particular, Chapter 4 collects the applications found in the scientific literature for Fuzzy Logic, Artificial Neural Network and Evolutionary Computing in the fields of structural and earthquake engineering with a taxonomic classification of the problems in modeling, simulation and optimization. Chapter 5 “translates” the search for the cheapest retrofitting system into a constrained optimization problem. To this end, the chapter includes a formulation of a novel procedure that assembles a numerical model for seismic assessment of framed structures within a Soft-Computing-driven optimization algorithm capable to minimize the objective function defined as the total initial cost of intervention. The main components required to assemble the procedure are described in the chapter: the optimization algorithm (Genetic Algorithm); the simulation framework (OpenSees); and the software environment (Matlab). Chapter 6 describes step-by-step the flow-chart of the proposed procedure and it focuses on the main implementation aspects and working details, ranging from a clever initialization of the population of candidate solutions up to a proposal of tuning procedure for the genetic parameters. Chapter 7 discusses numerical examples, where the Soft-Computing procedure is applied to the model of multi-storey RC frames obtained through simulated design. A total of fifteen “scenarios” are studied in order to assess its “robustness” to changes in input data. Finally, Chapter 8, on the base of the outcomes observed, summarizes the capabilities of the proposed procedure, yet highlighting its “limitations” at the current state of development. Some possible modifications are discussed to enhance its efficiency and completeness. [edited by author]XVI n.s

Control of a benchmark structure using GA-optimized fuzzy logic control

Mitigation of displacement and acceleration responses of a three story benchmark structure excited by seismic motions is pursued in this study. Multiple 20-kN magnetorheological (MR) dampers are installed in the three-story benchmark structure and managed by a global fuzzy logic controller to provide smart damping forces to the benchmark structure. Two configurations of MR damper locations are considered to display multiple-input, single-output and multiple-input, multiple-output control capabilities. Characterization tests of each MR damper are performed in a laboratory to enable the formulation of fuzzy inference models. Prediction of MR damper forces by the fuzzy models shows sufficient agreement with experimental results. A controlled-elitist multi-objective genetic algorithm is utilized to optimize a set of fuzzy logic controllers with concurrent consideration to four structural response metrics. The genetic algorithm is able to identify optimal passive cases for MR damper operation, and then further improve their performance by intelligently modulating the command voltage for concurrent reductions of displacement and acceleration responses. An optimal controller is identified and validated through numerical simulation and fullscale experimentation. Numerical and experimental results show that performance of the controller algorithm is superior to optimal passive cases in 43% of investigated studies. Furthermore, the state-space model of the benchmark structure that is used in numerical simulations has been improved by a modified version of the same genetic algorithm used in development of fuzzy logic controllers. Experimental validation shows that the state-space model optimized by the genetic algorithm provides accurate prediction of response of the benchmark structure to base excitation