scholarly journals Time-Varying Reliability Evaluation of Concrete Based on Carbonation Depth

2019 ◽  
Vol 9 (23) ◽  
pp. 5116
Author(s):  
Jiao Wang ◽  
Weiji Zheng ◽  
Yangang Zhao ◽  
Xiaogang Zhang
Keyword(s):  
Safety Assessment ◽  
Concrete Surface ◽  
Reliability Evaluation ◽  
Structural Safety ◽  
Time Varying ◽  
Carbonation Depth ◽  
The Third ◽  
Mc Simulation ◽  
Traditional Approaches ◽  
Third Moment

When studying concrete impairment, the carbonation depth of concrete is regarded to be variable. Therefore, a time-varying reliability evaluation is important to perform a structural safety assessment. By analyzing 13,198 data on the carbonation depth of concrete, we propose a time-varying reliability evaluation based on the third-moment (TM) method to predict the service life of concrete. Validated by Monte Carlo (MC) simulation, the errors of the calculated results using time-varying reliability evaluation were within 4%. It is shown that the TM method proposed in this paper is more practical than traditional approaches such as MC simulation and second-moment (SM) methods in probability analysis. In this paper, exponential distribution was used to characterize the distribution of carbonation depths. Since paint was present on the concrete surface, numerous uncarbonized concrete components were found in the experiments; to develop a time-varying model considering the uncarbonized components, a function for evaluating the ratio of carbonized concretes is proposed. Overall, the time-varying TM method provided in this paper can act as a foundation for other investigations on probabilistic analysis, e.g., of compressive strength, deflection, and crack of concrete, which can be used to evaluate the reliability of concrete.

scholarly journals Prediction of Concrete Failure Time Based on Statistical Properties of Compressive Strength

2020 ◽  
Vol 10 (3) ◽  
pp. 815
Author(s):  
Jiao Wang ◽  
Weiji Zheng ◽  
Yangang Zhao ◽  
Xiaogang Zhang
Keyword(s):  
Compressive Strength ◽  
Failure Time ◽  
Reliability Evaluation ◽  
Structural Safety ◽  
Time Varying ◽  
Concrete Failure ◽  
Proposed Model ◽  
Compressive Strength Of Concrete ◽  
Mc Simulation ◽  
Good Agreement

Since the heterogeneity of the cement-based material contributes to a random spatial distribution of compressive strength, a reliability analysis based on the compressive strength of concrete is fundamental to carry out structural safety assessment. By analyzing 10,317 datapoints on compressive strength of concrete, a time-varying reliability evaluation based on the third-moment (TM) method was proposed to predict the service life of concrete. Unlike the second-moment (SM) method, skewness is taken into account in the TM; thus, the calculated result of concrete failure time based on the TM is more accurate. In this paper, the errors of the calculated results using time-varying reliability evaluation are within 3%, as shown by Monte Carlo (MC) simulation. In addition, the proposed model (aiming to calculate the equivalent design compressive strength) verifies the concrete failure time calculated by time-varying reliability. According to the results, concrete failure times calculated by these two models are in good agreement. Overall, based on the simple and effective methodology adopted in this paper, it is feasible to develop time-varying reliability based on other factors that might also lead to concrete failure, such as carbonation-induced corrosion, cracking, or deflection of the concrete.

Monte Carlo Algorithms for Moments of Transition Arrays

1988 ◽  
Vol 102 ◽  
pp. 79-81
Author(s):  
A. Goldberg ◽  
S.D. Bloom
Keyword(s):  
Monte Carlo ◽  
State Vector ◽  
Basis Vector ◽  
Collective State ◽  
Dispersion Characteristics ◽  
Dipole Strength ◽  
The Third ◽  
Monte Carlo Algorithms ◽  
Third Moment ◽  
Very High

AbstractClosed expressions for the first, second, and (in some cases) the third moment of atomic transition arrays now exist. Recently a method has been developed for getting to very high moments (up to the 12th and beyond) in cases where a “collective” state-vector (i.e. a state-vector containing the entire electric dipole strength) can be created from each eigenstate in the parent configuration. Both of these approaches give exact results. Herein we describe astatistical(or Monte Carlo) approach which requires onlyonerepresentative state-vector |RV> for the entire parent manifold to get estimates of transition moments of high order. The representation is achieved through the random amplitudes associated with each basis vector making up |RV>. This also gives rise to the dispersion characterizing the method, which has been applied to a system (in the M shell) with≈250,000 lines where we have calculated up to the 5th moment. It turns out that the dispersion in the moments decreases with the size of the manifold, making its application to very big systems statistically advantageous. A discussion of the method and these dispersion characteristics will be presented.

scholarly journals Development and Validation of a Post-Earthquake Safety Assessment System for High-Rise Buildings Using Acceleration Measurements

Mathematics ◽  
2021 ◽  
Vol 9 (15) ◽  
pp. 1758
Author(s):  
Koji Tsuchimoto ◽  
Yasutaka Narazaki ◽  
Billie F. Spencer
Keyword(s):  
Safety Assessment ◽  
Large Scale ◽  
Model Updating ◽  
Safety Evaluation ◽  
Assessment System ◽  
Shaking Table ◽  
Structural Safety ◽  
High Rise ◽  
Steel Building ◽  
Earthquake Safety

After a major seismic event, structural safety inspections by qualified experts are required prior to reoccupying a building and resuming operation. Such manual inspections are generally performed by teams of two or more experts and are time consuming, labor intensive, subjective in nature, and potentially put the lives of the inspectors in danger. The authors reported previously on the system for a rapid post-earthquake safety assessment of buildings using sparse acceleration data. The proposed framework was demonstrated using simulation of a five-story steel building modeled with three-dimensional nonlinear analysis subjected to historical earthquakes. The results confirmed the potential of the proposed approach for rapid safety evaluation of buildings after seismic events. However, experimental validation on large-scale structures is required prior to field implementation. Moreover, an extension to the assessment of high-rise buildings, such as those commonly used for residences and offices in modern cities, is needed. To this end, a 1/3-scale 18-story experimental steel building tested on the shaking table at E-Defense in Japan is considered. The importance of online model updating of the linear building model used to calculate the Damage Sensitive Features (DSFs) during the operation is also discussed. Experimental results confirm the efficacy of the proposed approach for rapid post-earthquake safety evaluation for high-rise buildings. Finally, a cost-benefit analysis with respect to the number of sensors used is presented.

Structural Safety Assessment of a 1100 TEU Container Ship, Based on a Enhanced Long Term Fatigue Analysis

2014 ◽  
Vol 1036 ◽  
pp. 935-940
Author(s):  
Leonard Domnisoru ◽  
Ionica Rubanenco ◽  
Mihaela Amoraritei
Keyword(s):  
Safety Assessment ◽  
Safety Evaluation ◽  
Irregular Waves ◽  
Structural Safety ◽  
Random Wave ◽  
Wave Loads ◽  
Strength Assessment ◽  
Integrated Method ◽  
Hydroelastic Response

This paper is focused on an enhanced integrated method for structural safety assessment of maritime ships under extreme random wave loads. In this study is considered an 1100 TEU container test ship, with speed range 0 to 18 knots. The most comprehensive criteria for ships structural safety evaluation over the whole exploitation life is based on the long term ship structures analysis, that includes: stress hot-spots evaluation by 3D/1D-FEM hull models, computation of short term ship dynamic response induced by irregular waves, long term fatigue structure assessment. The analysis is enhanced by taking into account the ships speed influence on hydroelastic response. The study includes a comparative analysis on two scenarios for the correlation between the ships speed and waves intensity. The standard constant ship speed scenario and CENTEC scenario, with total speed loss at extreme waves condition, are considered. Instead of 20 years ship exploitation life estimated by classification societies rules from the long term structural safety criteria, the enhanced method has predicted more restrictive values of 14.4-15.7 years. The numerical analyses are based on own software and user subroutines. The study made possible to have a more realistic approach of ships structural strength assessment, for elastic and faster ships as container carriers, in compare to the standard one based only on naval rules, delivering a method with higher confidence in the designed structural safety.

scholarly journals Structural safety assessment for FLNG-LNGC system during offloading operation scenario

2017 ◽  
Vol 31 (2) ◽  
pp. 192-201 ◽  
Author(s):  
Zhi-qiang Hu ◽  
Dong-wei Zhang ◽  
Dong-ya Zhao ◽  
Gang Chen
Keyword(s):  
Safety Assessment ◽  
Structural Safety

scholarly journals Sunspot Number Series Envelope and Phase

1985 ◽  
Vol 38 (6) ◽  
pp. 1009 ◽  
Author(s):  
RN Bracewell
Keyword(s):  
Analytic Function ◽  
Sunspot Number ◽  
Hilbert Transform ◽  
Cycle Length ◽  
Time Varying ◽  
Number Series ◽  
Third Harmonic ◽  
The Third ◽  
Envelope Amplitude ◽  
Time Varying Medium

The sunspot number series R( t) from 1700 to date is found to be representable by R( t) = I Jf' {Re( E( t) exp[i {wo t + ( t) I]) + U( t) 1 I, where Wo is the angular frequency corresponding to a period of 22 years, E(t) is the instantaneous envelope amplitude, (t) is the instantaneous phase of a complex time-varying analytic function, U(t) is an undulation of low amplitude and period about 30 (22-year) cycles and jy is a nonlinear operator whose main effect is to introduce a small amount of third harmonic (period about 7 years). The justification for the 22-year period is the known fact that the observable sunspot magnetic fields reverse polarity every 11 years or so at the time of sunspot minimum; the undulation has been demonstrated, and its period determined, in fossil records discovered by Williams; and the third harmonic is an expected consequence of minor nonlinearity in the dependence of the arbitrarily defined R( t) on the physical cause of sunspots. The algebraic representation is established by the Hilbert transform method of forming a complex analytic function as proposed by Gabor. The method reveals three obscuring features that may be alleviated as follows: use the alternating series R� (t) in which alternate II-year cycles take opposite signs, remove the third harmonic, and subtract the undulation. These justifiable steps remove artificial components, such as sum and difference frequencies, that are gratuitously and nonlinearly introduced by conventional Fourier analysis as applied to the rectified, or absolute, value of the 22-year oscillation. Then a complex envelope E( t) exp {i ( t)j can be discerned whose intrinsic behaviour can be studied to reveal statistics that bear on the physical origin of the solar cycle. The results favour a deep monochromatic oscillator whose influence is propagated to the observable surface via a time-varying medium. The r.m.s. value of the component of E(t) is 0�4 of the mean and the characteristic time is a century. Frequency analysis of the envelope does not support a 78-year period in the modulation noticed by Wolf. Both the statistical frequency distribution of the amplitude E( t) and its spectrum are subject to refinement by analysis of fossil solar records. The results do not favour the theory that the 22-year period is set by the natural frequency of a resonator with characteristic damping subject to random turbulent excitation. Also disfavoured is the theory of energy release at intervals determined by a relaxation process. Correlation has been found between the phase departure ~(t) from linear and envelope amplitude and attributed to propagation of the magnetic .cycles through a time-varying, such as a convecting, medium. A correlation not depending on Hilbert transform analysis is predicted between the reciprocal cycle length and envelope amplitude and found to� exist. Variability of the sunspot cycle length can be viewed as a Doppler shift due to propagation in a time-varying medium and the Wolf modulation then represents the concomitant intensity change. Agreement has been found between E(t) and '(t) but not explained. If the explanation is dispersion in the propagation of the assumed magnetic flux waves then there is a mode of oscillation. that has the characteristics required for the undulation U( t). Extra buoyancy possessed by the magnetic field of strong cycles accounts for the fast rise time of strong cycles.

scholarly journals Multi-source data fusion method for structural safety assessment of water diversion structures

2021 ◽  
Author(s):  
Sherong Zhang ◽  
Ting Liu ◽  
Chao Wang
Keyword(s):  
Data Fusion ◽  
Safety Assessment ◽  
Evidence Theory ◽  
Weighted Average ◽  
Water Diversion ◽  
Sensor Data ◽  
Structural Safety ◽  
Fusion Method ◽  
Bhattacharyya Distance ◽  
Source Data

Abstract Building safety assessment based on single sensor data has the problems of low reliability and high uncertainty. Therefore, this paper proposes a novel multi-source sensor data fusion method based on Improved Dempster–Shafer (D-S) evidence theory and Back Propagation Neural Network (BPNN). Before data fusion, the improved self-support function is adopted to preprocess the original data. The process of data fusion is divided into three steps: Firstly, the feature of the same kind of sensor data is extracted by the adaptive weighted average method as the input source of BPNN. Then, BPNN is trained and its output is used as the basic probability assignment (BPA) of D-S evidence theory. Finally, Bhattacharyya Distance (BD) is introduced to improve D-S evidence theory from two aspects of evidence distance and conflict factors, and multi-source data fusion is realized by D-S synthesis rules. In practical application, a three-level information fusion framework of the data level, the feature level, and the decision level is proposed, and the safety status of buildings is evaluated by using multi-source sensor data. The results show that compared with the fusion result of the traditional D-S evidence theory, the algorithm improves the accuracy of the overall safety state assessment of the building and reduces the MSE from 0.18 to 0.01%.

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