Reliability evaluation of 2D semi-rigid steel frames accounting for corrosion effects

Nowadays, steel frames are widely used in civil and industrial engineering structures. The design process for steel frames with semi-rigid beam-column connections is an interesting topic for designers and researchers. However, the current design codes purely deal with the structural reliability at the pristine and the degradation of steel due to corrosion is not specified. This study proposes a procedure for evaluating the reliability of two-dimensional semi-rigid steel frames considering corrosion effects. A series of Monte Carlo simulations are performed to evaluate the reliability of the corroded steel structures. The random variables including corrosion phenomenon, semi-rigid connection, and applied load, are considered in the proposed method. The safety deterioration of the steel structures due to the corrosion phenomenon until 50 years is obtained. Additionally, the effects of input parameters, which are safety factors and coefficients of variation, on the reliability of structures are examined in the present study. Finally, a verification of this study and previous results is performed, highlighting the capability of the proposed method.

Reliability evaluation of 2D semi-rigid steel frames accounting for corrosion effects

Nowadays, steel frames are widely used in civil and industrial engineering structures. The design process for steel frames with semi-rigid beam-column connections is an interesting topic for designers and researchers. However, the current design codes purely deal with the structural reliability at the pristine and the degradation of steel due to corrosion is not specified. This study proposes a procedure for evaluating the reliability of two-dimensional semi-rigid steel frames considering corrosion effects. A series of Monte Carlo simulations are performed to evaluate the reliability of the corroded steel structures. The random variables including corrosion phenomenon, semi-rigid connection, and applied load, are considered in the proposed method. The safety deterioration of the steel structures due to the corrosion phenomenon until 50 years is obtained. Additionally, the effects of input parameters, which are safety factors and coefficients of variation, on the reliability of structures are examined in the present study. Finally, a verification of this study and previous results is performed, highlighting the capability of the proposed method.

Evaluation of loading capacity of corroded reinforced concrete beams using experiment and finite element method

The purpose of this paper is to evaluate the performance of corroded reinforced concrete (RC) beams using experiments and a proposed finite element (FE) model, which is able to consider the reduction of the reinforcement diameter and adhesion force. The developed FE model comprised of three main components including concrete elements, reinforcing bar elements, and adhesion elements, in which the plane cross-section hypothesis was adopted. Thus, the necessary number of elements in the model of corroded RC beam was greatly reduced, while the accuracy of the model was still ensured. An experimental test was employed to verify the developed FE model. The results show that the proposed FE model in this study is capable of modeling RC beams under corrosion effects. Additionally, the rebar diameter and adhesion force have a significant influence on the load-carrying capacity of corroded RC beams. Moreover, a series of experimental tests of corrosive RC beams including 1-month, 2-month, and 3-month corrosion levels was conducted for various exposed times to investigate the influences of the corrosion time on the strength of RC beams. It reveals that the effect of the corrosion time on the strength of RC beams show to be pronounced

Influence of ground motion duration on seismic fragility of base isolated NPP structures

This study investigates the influence of earthquake duration on seismic fragility of base isolated nuclear power plant (NPP) structures. Two groups of ground motions are employed in performing time history analyses, in which short duration (SD) and long duration (LD) characteristics are considered. The advanced power reactor 1400 (APR1400) NPP structures are used for developing finite element model, which is constructed using lumped-mass stick elements. A series of 486 lead rubber bearings (LRBs) are installed under the base mat of the NPP structures to reduce the seismic damage. Seismic responses of the base isolated NPP are quantified in terms of lateral displacements and hysteretic energy distributions of LRBs. Seismic fragility curves for damage states, which are defined based on the deformation of LRB, are developed. The results reveal that the average lateral displacements of LRBs under SD and LD motions are very similar. For PGA larger than 0.4g, the mean deformation of LRB for LD motions is higher than that for SD motions. The probability of damage of base isolated NPP structures under LD motions is reduced approximately 15% compared to that asubjected to SD earthquakes. This finding emphasizes that it is crucial to use both SD and LD ground motions in seismic evaluations of base isolated NPP structure

Influence of ground motion duration on seismic fragility of base isolated NPP structures

This study investigates the influence of earthquake duration on seismic fragility of base isolated nuclear power plant (NPP) structures. Two groups of ground motions are employed in performing time history analyses, in which short duration (SD) and long duration (LD) characteristics are considered. The advanced power reactor 1400 (APR1400) NPP structures are used for developing finite element model, which is constructed using lumped-mass stick elements. A series of 486 lead rubber bearings (LRBs) are installed under the base mat of the NPP structures to reduce the seismic damage. Seismic responses of the base isolated NPP are quantified in terms of lateral displacements and hysteretic energy distributions of LRBs. Seismic fragility curves for damage states, which are defined based on the deformation of LRB, are developed. The results reveal that the average lateral displacements of LRBs under SD and LD motions are very similar. For PGA larger than 0.4g, the mean deformation of LRB for LD motions is higher than that for SD motions. The probability of damage of base isolated NPP structures under LD motions is reduced approximately 15% compared to that asubjected to SD earthquakes. This finding emphasizes that it is crucial to use both SD and LD ground motions in seismic evaluations of base isolated NPP structure

A New High Performance Decoder for LDPC Codes

The article introduces a new decoder for LDPC codes based on the general check matrix and soft syndrome. Simulation result shows that the new decoder can improve the performance of LDPC codes. Compared with some other improvements, the new decoding algorithm is simpler, and it can detect errors and be applied to great length LDPC codes

Using penalty function method in identification of elastic fixed stiffness of frame - pile structure

This paper studies a method to identify the elastic fixed stiffness of the frame structure. The model of the problem is three dimensionals structure, linear elastic deformation, pile - soil link is replaced by elastic fixed with stiffness. The problem will be solved by the penalty function method - the minimum of the objective function (which is the total squared error between the measured value and the calculated values particular) - combined with the finite element method. The numerical calculations show that the model, algorithm and calculation program are reliable. The program can be used to identify the elastic fixed stiffness of the frame structure in three dimensions, serving to determine the actual working state of the structure, to propose solutions for reinforcement, repairing, improving bearing capacity, prolonging the life of the structure

Possibility of reservoir-triggered earthquake occurrence in the Huoi Quang and Ban Chat hydropower dam area

The possibility of reservoir-triggered earthquake occurrence in the Huoi Quang and Ban Chat hydropower dam area has been assessed based on studying and analyzing the relationships between the reservoir-triggered earthquake occurrence and the following factors: (1) the types of rocks underlying the reservoir; (2) the oscillating reservoir loads on faults in the reservoir area; (3) the incremental stress caused by reservoir loads; (4) the slip tendency of faults in the reservoir area; and (5) the Coulomb stress change of faults in the reservoir area. The results show that these factors have interactive effects and simultaneously contribute to the favorable conditions for reservoir-triggered earthquake occurrence. The Huoi Quang and Ban Chat hydropower reservoirs are located in the area of moderate seismicity; however, with the favorable conditions due to these five factors, reservoir-triggered earthquakes can possibly occur. If reservoir-triggered earthquakes occur, they will be concentrated around the Ban Chat hydropower dam area within a radius of 11 - 12 km and at a depth of about 6 ± 1 km