scholarly journals Fragility analysis of concrete elevated water tanks under seismic loads

2021 ◽  
Vol 15 (57) ◽  
pp. 93-113
Author(s):  
Hocine Hammoum ◽  
Amar Aliche ◽  
Karima Bouzelha ◽  
Younes Aoues ◽  
Ouali Amiri ◽  
...  
Keyword(s):  
Failure Modes ◽  
Fragility Curves ◽  
Probabilistic Approach ◽  
Seismic Loading ◽  
Soil Types ◽  
Structural Failure ◽  
Safety Factors ◽  
Partial Safety Factors ◽  
Elevated Water ◽  
Water Tanks

The design of concrete elevated water tanks involves several kinds of uncertainties. Traditionally, the design of these structures is based on a deterministic analysis. Partial safety factors prescribed in design codes are applied to take into account these uncertainties and to ensure sufficiently safe design. However, this approach does not allow rational evaluation of the risk related to the structural failure and consequently its reliability. In fact, the partial safety factors can lead to over-designed structures; or to under designed structural components leading to a lack of structural robustness. In this study, a probabilistic approach based on Monte Carlo simulations is used to analyze the reliability of elevated water tanks submitted to hazard seismic loading. This reliability approach, takes into account mainly two parameters. Firstly, the hydraulic charge in the tank container which is a function of time, and secondly, the hazard seismic loading through the Peak Ground Acceleration is considered as a random variable. Fragility curves depending on seismic zones and soil types are obtained by using the probabilistic approach, where they demonstrate the dominant failure modes that can cause the structural failure with respect to different seismic levels, soil types and water height level in the tank container.

scholarly journals Dynamic Behavior of Elevated Water Tanks under Seismic Excitation

2020 ◽  
Vol 9 (9) ◽  
pp. 123-127
Keyword(s):  
Dynamic Behavior ◽  
Transient Analysis ◽  
Seismic Loading ◽  
Water Tank ◽  
Seismic Excitations ◽  
System Effect ◽  
Elevated Tanks ◽  
Elevated Water ◽  
Element Technique ◽  
Water Tanks

Elevated tanks are considered very sensitive to seismic excitations. That is why several researchers have studied the performance of these structures under seismic loading. The elevated tanks support‘s design are the most responsible reason of the damages and failures of this kind of structure . In this present paper, we are used the finite element technique to study the seismic response of them with taking into account the interaction between fluid and structure in the presence of sloshing. Modal and transient analysis are carried out on two types of the elevated tanks support, while keeping the same quantity of concrete and the same fluid volume. The displacements at the top of the tank and The fundamental period of the impulsive mode of the elevated water tank with shaft support decreased compared to the elevated water tank with frame support .The obtained results confirm the supporting system effect on dynamic behavior of elevated water tanks .

Corrosion Effects on Reliability of Flat Plates in Tension

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Weiwei Yu ◽  
Dale G. Karr ◽  
Pedro M. Vargas
Keyword(s):  
Stress Concentration ◽  
Limit State ◽  
Analytical Formula ◽  
Safety Index ◽  
Structural Failure ◽  
Safety Factors ◽  
Flat Plates ◽  
Partial Safety Factors ◽  
Concentration Factors ◽  
Stress Concentration Factors

Neuber’s theory of elastic and inelastic stress concentration factors are applied to the pit corrosion of plates. The finite element method is then employed to model the problem numerically and to calculate the stress concentration factors for semioblate spheroidal pits. Furthermore, corrosion development is a process with many random factors such as the geometry and the growth rate. A realistic reflection of corrosion effects on structural failure is to consider it within the framework of reliability analysis. By knowing the analytical formula of stress concentration factor, reliability analyses are conducted to calculate the reliability safety index of the panel based on a strain-based limit state. The structural failure can then be directly related to the reliability safety index. The reliability procedure is demonstrated in an example of a highly deformed bottom shell panel during ship grounding. Partial safety factors of two random variables which describe pit corrosion geometry and the effective nominal strain level are also calculated. Recommendations for using partial safety factors are provided.

Vulnerability-Based Design of Sliding Concave Bearings for the Seismic Isolation of Steel Storage Tanks

2016 ◽  
Author(s):  
Hoang Nam Phan ◽  
Fabrizio Paolacci ◽  
Silvia Alessandri ◽  
Phuong Hoa Hoang
Keyword(s):  
Liquid Steel ◽  
Seismic Isolation ◽  
Failure Modes ◽  
Fragility Curves ◽  
Time History ◽  
Probability Of Failure ◽  
Design Parameters ◽  
Economic Losses ◽  
Storage Tanks ◽  
Isolation System

Liquid steel storage tanks are strategic structures for industrial facilities and have been widely used both in nuclear and non-nuclear power plants. Typical damage to tanks occurred during past earthquakes such as cracking at the bottom plate, elastic or elastoplastic buckling of the tank wall, failure of the ground anchorage system, and sloshing damage around the roof, etc. Due to their potential and substantial economic losses as well as environmental hazards, implementations of seismic isolation and energy dissipation systems have been recently extended to liquid storage tanks. Although the benefits of seismic isolation systems have been well known in reducing seismic demands of tanks; however, these benefits have been rarely investigated in literature in terms of reduction in the probability of failure. In this paper, A vulnerability-based design approach of a sliding concave bearing system for an existing elevated liquid steel storage tank is presented by evaluating the probability of exceeding specific limit states. Firstly, nonlinear time history analyses of a three-dimensional stick model for the examined case study are performed using a set of ground motion records. Fragility curves of different failure modes of the tank are then obtained by the well-known cloud method. In the following, a seismic isolation system based on concave sliding bearings is proposed. The effectiveness of the isolation system in mitigating the seismic response of the tank is investigated by means of fragility curves. Finally, an optimization of design parameters for sliding concave bearings is determined based on the reduction of the tank vulnerability or the probability of failure.

Development of Ultimate Strength Evaluation Method for Piping Subjected to Seismic Loads

2013 ◽  
Author(s):  
Hideo Machida ◽  
Hiromasa Chitose ◽  
Tatsuhiro Yamazaki
Keyword(s):  
Power Plants ◽  
Evaluation Method ◽  
Failure Modes ◽  
Limit State ◽  
Seismic Loading ◽  
Earthquake Resistance ◽  
State Function ◽  
Limit State Function ◽  
Input Acceleration ◽  
Resistance Tests

This paper reports the results of the study on the failure modes and limit loads of piping in nuclear power plants subjected to cyclic seismic loading. By investigating the past fracture tests and earthquake resistance tests, it became clear that dominant failure mode of piping was fatigue, and the effect of ratchet strain was negligible. Until now, the stress generated with the acceleration of an earthquake was classified into the primary stress. However, the relationship between the input acceleration and the seismic response displacement of the pipe observed from earthquake resistance tests is non-linear, and increasing rate of displacement is lower than that of input acceleration in elastic-plastic stress condition. Therefore, the seismic loading can be treated as displacement controlled loading. To evaluate the reliability-based critical acceleration, a limit state function was defined taking the variations in the fatigue strength or some parameters into consideration. By using the limit state function, the reliability was evaluated for the typical piping of boiling water reactor (BWR) plants subjected to cyclic seismic loading, and a partial safety factors were calculated. Based on these results, a fatigue curve corresponding to the target reliability was proposed.

scholarly journals Elevated Water Tank

2019 ◽  
Vol 8 (12S2) ◽  
pp. 271-276
Keyword(s):  
Water Treatment ◽  
Treatment Plant ◽  
Water Treatment Plant ◽  
Water Tank ◽  
Elevated Water ◽  
Water Tanks ◽  
The Way

Water tanks are the capacity booths for putting away water. Raised water tanks are built to be able to deliver required head with the purpose that the water will movement affected by gravity the development exercise of water tanks is as antique as enlightened guy. The water tanks project has an firstrate want as it serves ingesting water for amazing populace from exceptional metropolitan urban groups to the little population dwelling in cities and towns. The smaller than ordinary project is led for a time of 15 days to have total all the way right down to earth information on unique tactics and issues appeared within the field. An change issue like construction factors, layout Parameters, information of Formwork, information of aid, process of Water treatment Plant and Execution had been controlled over the span of our smaller than regular undertaking."improved water tanks" via raising water tank, the enlargement upward push makes a conveyance strain at the tank outlet. The profile of water tanks begins offevolved with the utility parameters, consequently the type of materials applied and the form of water tank become directed by way of approach of those factors: 1. Vicinity of the water tank (inner, out of doors, over the floor or underground). 2. Volume of water tank need to preserve. 3. What the water may be utilized for? Four. Temperature of territory wherein might be located away, fear for solidifying. Five. Weight required conveying water. 6. How the water to be conveys to the water tank. 7. Wind and quake plan contemplations allow water tanks to endure seismic and excessive wind occasions

Failure Analysis of Thinned Wall Elbows Under Excessive Seismic Loading

2002 ◽  
Author(s):  
Masaki Shiratori ◽  
Yoji Ochi ◽  
Izumi Nakamura ◽  
Akihito Otani
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Local Buckling ◽  
Seismic Loading ◽  
Cycle Fatigue ◽  
Finite Element Analyses ◽  
Residual Thickness ◽  
Limited Period

A series of finite element analyses has been carried out in order to investigate the failure behaviors of degraded bent pipes with local thinning against seismic loading. The sensitivity of such parameters as the residual thickness, locations and width of the local thinning to the failure modes such as ovaling and local buckling and to the low cycle fatigue damage has been studied. It has been found that this approach is useful to make a reasonable experimental plan, which has to be carried out under the condition of limited cost and limited period.

Corrosion Margins for Redundant Ship Structures

2018 ◽  
Author(s):  
Yordan Garbatov ◽  
C. Guedes Soares
Keyword(s):  
Differential Equation ◽  
Degradation Process ◽  
Step Function ◽  
Order System ◽  
Safety Factors ◽  
Ship Structures ◽  
Degradation Model ◽  
Corrosion Depth ◽  
First Order ◽  
Partial Safety Factors

The work presented here analyses the structural corrosion degradation of two sets of corrosion depth measurements collected with a one-decade difference. The corrosion degradation process is associated to a first order system, subjected to a sudden disturbance, where a step function is used as an input to define the solution of the differential equation of this system leads to the exponential corrosion degradation model as developed earlier. Corrosion margins of redundant ship structures with serious consequences of failure are derived and several conclusions related to the new trend in the ageing structures are presented and discussed. Partial safety factors with respect to the corrosion environment and corrosion margins are developed that can be used in the design, avoiding a complex probabilistic analysis.

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