• Structural Engineering and Mechanics
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• v.76 no.1
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• pp.101-114
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• 2020

In this paper, an improved experience-based learning algorithm (EBL), termed as IEBL, is proposed to solve the nonlinear hysteretic parameter identification problem with Bouc-Wen model. A quasi-opposition-based learning mechanism and new updating equations are introduced to improve both the exploration and exploitation abilities of the algorithm. Numerical studies on a single-degree-of-freedom system without/with viscous damping are conducted to investigate the efficiency and robustness of the proposed algorithm. A laboratory test of seven lead-filled steel tube dampers is presented and their hysteretic parameters are also successfully identified with normalized mean square error values less than 2.97%. Both numerical and laboratory results confirm that, in comparison with EBL, CMFOA, SSA, and Jaya, the IEBL is superior in nonlinear hysteretic parameter identification in terms of convergence and accuracy even under measurement noise.

• Communications for Statistical Applications and Methods
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• v.5 no.3
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• pp.581-589
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• 1998

An algorithm is proposed for the $L_1$-estimation with linear equality and inequality constraints in linear regression model. The algorithm employs a linear scaling transformation to obtain the optimal solution of linear programming type problem. And a special scheme is used to maintain the feasibility of the updated solution at each iteration. The convergence of the proposed algorithm is proved. In addition, the updating and orthogonal decomposition techniques are employed to improve the computational efficiency and numerical stability.

• Communications for Statistical Applications and Methods
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• v.7 no.3
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• pp.677-686
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• 2000

Outliers may occur with respect to any of the random components in mixed linear models. We develop a use of simple, inexpensive updating formulas to consider the effect of case-deletion for mixed linear models. The method described here requires inversions of an n x n matrix, where n is the number of nonempty cells. A numerical example illustrates the use of computational formulas.

• Structural Engineering and Mechanics
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• v.56 no.5
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• pp.871-897
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• 2015

This paper presents a novel method based on sensitivity of structural response for identifying both the system parameters and input excitation force of a bridge. This method, referred to as "Adjoint Variable Method", is a sensitivity-based finite element model updating method. The computational cost of sensitivity analyses is the main concern associated with damage detection by these methods. The main advantage of proposed method is inclusion of an analytical method to augment the accuracy and speed of the solution. The reliable performance of the method to precisely indentify the location and intensity of all types of predetermined single, multiple and random damages over the whole domain of moving vehicle speed is shown. A comparison study is also carried out to demonstrate the relative effectiveness and upgraded performance of the proposed method in comparison to the similar ordinary sensitivity analysis methods. Moreover, various sources of error including the effects of noise and primary errors on the numerical stability of the proposed method are discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.425-428
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• 2009

This paper presents a sensitivity-based finite element (FE)-model update procedure for prestressed concrete (PSC) girder bridge model using vibration test results. Firstly, the stiffness parameters of the structure such as flexural rigidity of concrete and flexural rigidity of tendon are chosen as updating parameters. Next, the numerical frequencies of first two bending modes are calculated using a three-dimensional FE model which is established for the PSC girder. Then, the corresponding experimental frequencies which are obtained from forced vibration tests are selected. In order to perform the model update, the eigensensitivity-based method is employed. Finally, the effect of prestress-loss on the stiffness parameters is evaluated.

• Structural Engineering and Mechanics
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• v.84 no.4
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• pp.489-502
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• 2022

This paper is aimed at developing an optimization-based Finite Element model updating approach for structural damage identification and quantification. A modal flexibility-based error function is introduced, which uses modal assurance criterion to formulate the updating problem as an optimization problem. Because of the inexplicit input/output relationship between the candidate solutions and the error function's output, a robust and efficient optimization algorithm should be employed to evaluate the solution domain and find the global extremum with high speed and accuracy. This paper proposes a new multi-stage Selective Particle Swarm Optimization (SPSO) algorithm to solve the optimization problem. The proposed multi-stage strategy not only fixes the premature convergence of the original Particle Swarm Optimization (PSO) algorithm, but also increases the speed of the search stage and reduces the corresponding computational costs, without changing or adding extra terms to the algorithm's formulation. Solving the introduced objective function with the proposed multi-stage SPSO leads to a smart feedback-wise and self-adjusting damage detection method, which can effectively assess the health of the structural systems. The performance and precision of the proposed method are verified and benchmarked against the original PSO and some of its most popular variants, including SPSO, DPSO, APSO, and MSPSO. For this purpose, two numerical examples of complex civil engineering structures under different damage patterns are studied. Comparative studies are also carried out to evaluate the performance of the proposed method in the presence of measurement errors. Moreover, the robustness and accuracy of the method are validated by assessing the health of a six-story shear-type building structure tested on a shake table. The obtained results introduced the proposed method as an effective and robust damage detection method even if the first few vibration modes are utilized to form the objective function.

• Earthquakes and Structures
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• v.4 no.5
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• pp.471-487
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• 2013

Performance of a prototype base isolated building located at Indian Institute of Technology, Guwahati (IITG) has been studied here. Two numbers of three storeyed single bay RCC framed prototype buildings were constructed for experimental purpose at IITG, one supported on conventional isolated footings and the other on a seismic isolation system, consisting of lead plug bearings. Force balance accelerometers and a 12 channel strong motion recorder have been used for recording building response during seismic events. Floor responses from these buildings show amplification for the conventional building while 60 to 70% reduction has been observed for the isolated building. Numerical models of both the buildings have been created in SAP2000 Nonlinear. Infill walls have been modeled as compression struts and have been incorporated into the 3D models using Gap elements. System identification of the recorded data has been carried out using Parametric State Space Modeling (N4SID) and the numerical models have been updated accordingly. The study demonstrates the effectiveness of base isolation systems in controlling seismic response of isolated buildings thereby leading to increased levels of seismic protection. The numerical models calibrated by relatively low level of earthquake shaking provides the starting point for modeling the non-linear response of the building when subjected to strong shaking.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.2
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• pp.18-28
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• 2001

Super computers has been utilized to carry out vehicle dynamics in real time. This research propose an implicit integra-tion method for vehicle state variables. Newton chord method is empolyed to solve the equations of motion and con-straints. The equations of motion and constraints are formulated such that the Jacobian matrix for Newton chord method is needed to be computed only once for a dynamic analysis. Numerical experiments showed that the Jacobian matrix generat-ed at the initial time could have been utilized for the Newton chord iterations throughout simulations under various driving conditions. Convergence analysis of Newton chord method with the proposed Jacobian updating method is carried out. The proposed algorithm yielded accurate solutions for a prototype vehicle multibody model in realtime on a 400 MHz PC compatible.

• Journal of The Geomorphological Association of Korea
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• v.24 no.3
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• pp.61-81
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• 2017

Traditional approaches to surface moisture problems in the context of aeolian research have focused on the initiation of sand movement, developing various models for predicting threshold velocity on a wet surface. They have been unsatisfactory, however, in explaining field observations because they have not incorporated spatiotemporal variability of surface moisture, the interactions between transported sand grains and surface, and the role of aeolian transport in controlling surface moisture. As Nield (2011) showed, a simplified numerical model can be used to investigate this issue. This research aims to explore the feedback structures between aeolian transport and surface moisture using a modified sand slab model. Key modifications are the introduction of simultaneous updating scheme for all the slabs and moisture-assigning procedures with and without aeolian transport. The major findings are as follows. Moist surface conditions suppress sand slab movement, leading to the development of smaller-scale topography. Available sands for aeolian transport are determined by the vertical patterns of moisture content with its variations from groundwater to the surface. Sand patches on a wet surface act as a localized source area. Sand movement drives immediate changes in surface moisture rather than time-lag reponses, mostly when moist conditions are dominant.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.737-750
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• 2022

Timber-Concrete Composite construction system consists of combining timber beam or deck and concrete with different connectors. Different fastener types are used in Timber-Concrete Composite systems. In this paper, the effects of two types of fasteners on structural behavior are compared. First, the notches were opened on timber beam, and combined with reinforced concrete slab by fasteners. This system is called as Notched Connection System. Then, timber beam and reinforced concrete slab were combined by new type designed fasteners in another model. This system is called as Notched-Slab Approach. Two laboratory models were constructed and bending tests were performed to examine the fasteners' effectiveness. Bending test results have shown that heavy damage to concrete slab occurs in Notched Connection System applications and the system becomes unusable. However, in Notched-Slab Approach applications, the damage concentrated on the fastener in the metal notch created in the slab, and no damage occurred in the concrete slab. In addition, non-destructive experimental measurements were conducted to determine the dynamic characteristics. To validate the experimental results, initial finite element models of both systems were constituted in ANSYS software using orthotropic material properties, and numerical dynamic characteristics were calculated. Finite element models of Timber-Concrete Composite systems are updated to minimize the differences by manual model updating procedure using some uncertain parameters such as material properties and boundary conditions.