• Smart Structures and Systems
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• v.31 no.2
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• pp.101-111
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• 2023

Structural health monitoring (SHM) covers a range of damage detection strategies for buildings. In real-time, SHM provides a basis for rapid decision making to optimise the speed and economic efficiency of post-event response. Previous work introduced an SHM method based on identifying structural nonlinear hysteretic parameters and their evolution from structural force-deformation hysteresis loops in real-time. This research extends and generalises this method to investigate the impact of a wide range of flag-shaped or pinching shape nonlinear hysteretic response and its impact on the SHM accuracy. A particular focus is plastic stiffness (K_p), where accurate identification of this parameter enables accurate identification of net and total plastic deformation and plastic energy dissipated, all of which are directly related to damage and infrequently assessed in SHM. A sensitivity study using a realistic seismic case study with known ground truth values investigates the impact of hysteresis loop shape, as well as added noise, on SHM accuracy using a suite of 20 ground motions from the PEER database. Monte Carlo analysis over 22,000 simulations with different hysteresis loops and added noise resulted in absolute percentage identification error (median, (IQR)) in K_p of 1.88% (0.79, 4.94)%. Errors were larger where five events (Earthquakes #1, 6, 9, 14) have very large errors over 100% for resulted K_p as an almost entirely linear response yielded only negligible plastic response, increasing identification error. The sensitivity analysis shows accuracy is reduces to within 3% when plastic drift is induced. This method shows clear potential to provide accurate, real-time metrics of non-linear stiffness and deformation to assist rapid damage assessment and decision making, utilising algorithms significantly simpler than previous non-linear structural model-based parameter identification SHM methods.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.151-158
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• 2000

Cable dome that consists of three component such as cable, strut and fabric membrane has complex structural characteristics. Main structural system of cable dome is cable-strut tensegric system and fabric membrane element is conceived as cladding roof material. One of the important problem of cable dome is to investigate the structural response from external load effect such as snow and wind. When cable dome is subjected to load each structural component has various special structural characteristics. One is that geometrical nonlinearity should be considered because large deformation is occurred from their flexible characteristic. The other is that wrinkling occurs occasionally because cable and membrane elements can not transmit compressive forces. So this paper researches the physical structural response of cable dome structure and the structural behavior when failure occurred at a part of structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.363-370
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• 2004

This Paper presents the response force distribution factor(RDF) and its application to recalculation of member forces in case of partial changes of structures. Using RDF, the mutuality of response forces between members can be estimated. The reanalysis technique recalculates directly any displacement or member force under consideration in real time without a full reanalysis in spite of local changes in member stiffness or connectivity using RDF. It is expected that RDF and the reanalysis technique can be used to develop efficient analysis techniques for tall buildings.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.95-99
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• 1993

Conventional tuned mass dampers are located on the top floor of tall buildings, which reduce the fundamental mode response of buildings. Higher modes may have a greater contribution toward the acceleration response of tall buildings. To reduce this, additional tuned mass dampers are required and could be substituted as building equipments. This paper shows, with a numerical ezample, how the lecate tuned mass damper in order to reduce the higher mode response effectively

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1996.10a
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• pp.29-36
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• 1996

A procedure for the predictive control for structural vibration control in building subject to wind loads is presented. The building motions are modeled by the first mode of the response. Wind velocities are generated by the simulation using power spectral density function. Predictive control algorithm is the discrete-time formulation and that is developed as a control strategy that computes the control signal which makes the predicted process output equal to a desired process output. Results on the reduction of the dynamic response and control effectiveness of the algorithm are presented and discussed.

• Computational Structural Engineering
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• v.9 no.4
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• pp.229-237
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• 1996

In some current procedures, ground motions from different sources have been scaled by their peak ground accelerations and combined to obtain smoothed response spectra for specific regions. As consideration of the inelastic deformation capacity of structure, inelastic deformations are permitted under seismic ground excitation in all codes. In the ATC(Applied Technology Council) and UBC(Uniform Building Code), the inelastic design spectrum is obtained by reducing the elastic design spectrum by a factor that is independent of structural period. In this study, the average of nonlinear response spectra calculated from a sample of 20 records for each event are constructed to obtain the smoothed response spectra. These response spectra are used to examine the effects of structural strength factors such as the yield strength ratio and damping value. Through the regression analysis of nonlinear response of system for a given damping value and yield strength ratio, the required yield strength for seismic design can be estimated for a certain earthquake event. And a response modification coefficient depending on the natural period for current seismic design specifications are proposed.

• Structural Engineering and Mechanics
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• v.34 no.6
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• pp.779-799
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• 2010

In order to consider high-order effects on the actual limit state function, a new response surface method is proposed for structural reliability analysis by the use of high-order approximation concept in this study. Hermite polynomials are used to determine the highest orders of input random variables, and the sampling points for the determination of highest orders are located on Gaussian points of Gauss-Hermite integration. The cross terms between two random variables, only in case that their corresponding percent contributions to the total variation of limit state function are significant, will be added to the response surface function to improve the approximation accuracy. As a result, significant reduction in computational cost is achieved with this strategy. Due to the addition of cross terms, the additional sampling points, laid on two-dimensional Gaussian points off axis on the plane of two significant variables, are required to determine the coefficients of the approximated limit state function. All available sampling points are employed to construct the final response surface function. Then, Monte Carlo Simulation is carried out on the final approximation response surface function to estimate the failure probability. Due to the use of high order polynomial, the proposed method is more accurate than the traditional second-order or linear response surface method. It also provides much more efficient solutions than the available high-order response surface method with less loss in accuracy. The efficiency and the accuracy of the proposed method compared with those of various response surface methods available are illustrated by five numerical examples.

• Structural Engineering and Mechanics
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• v.32 no.1
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• pp.179-191
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• 2009

A stochastic response spectrum method is proposed for simple evaluation of the structural response of an actively controlled aseismic structure. The response spectrum is constructed assuming a linear structure with an active mass damper (AMD) system, and an earthquake wave model given by the product of a non-stationary envelope function and a stationary Gaussian random process with Kanai-Tajimi power spectral density. The control design is executed using a linear quadratic Gaussian control strategy for an enlarged state space system, and the response amplification factor is given by the combination of the obtained statistical response values and extreme value theory. The response spectrum thus produced can be used for simple dynamical analyses. The response factors obtained by this method for a multi-degree-of-freedom structure are shown to be comparable with those determined by numerical simulations, demonstrating the validity and utility of the proposed technique as a simple design tool. This method is expected to be useful for engineers in the initial design stage for structures with active aseismic control.

• Structural Engineering and Mechanics
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• v.50 no.6
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• pp.797-816
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• 2014

Cooling tower is analyzed as an assembly of layered nonlinear shell elements. Geometric representation of the shell is enabled through layered nonlinear shell elements to define the different layers of reinforcements and concrete by considering the material nonlinearity of each layer for the cooling tower shell. Modal analysis using Ritz vector analysis and nonlinear time history analysis by direct integration method have been carried out to study the effects of the inclination of the supporting columns of the cooling tower shell on its dynamic characteristics. The cooling tower is supported by I-type columns and ${\Lambda}$-type columns supports having the different inclination angles. Relevant comparisons of the dynamic response of the structural system at the base level (at the junction of the column and shell), throat level and at the top of the tower have been made. Dynamic response of the cooling tower is found to be significantly sensitive to the change of the inclination of the supporting columns. It is also found that the stiffness of the structure system increases with increase in inclination angle of the supporting columns, resulting in decrease of the period of the structural system. The participation of the stiffness of the tower in structural response of the cooling tower is fund to be dependent of the change in the inclination angle and even in the types of the supporting columns.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.275-282
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• 2006

System algorithms estimated by deterministic input may occur the error between predicted and actual output. Especially, actual system can't predict the exact outputs due to uncertainty and tolernce of input parameters. A single output to a set of inputs has a limited value without the variation. Hence, we should consider various scatters caused by the load assessment, material characteristics, stress analysis and manufacturing methods in order to perform the robust design or etimate the reliability of structure. The system design with uncertainty should perform the probabilistic structural optimization with the statistical response and the reliability. This method calculated the probability distributions of the characteristics such as stress by combining stress analysis, response surface methodology and Monte Carlo simulation and got the probabilistic sensitivity. The sensitivity of structural response with respect to in constant design variables was estimated by fracture probability. Therefore, this paper proposed the probabilistic reliability design method for fracture of uncorved freight end beam and the design criteria by fracture probability.