Comparison of different fracture modelling approaches to gravity dam failure

2014 ◽  
Vol 31 (1) ◽  
pp. 18-32 ◽  
Author(s):  
Jianwen Pan ◽  
Yuntian Feng ◽  
Feng Jin ◽  
Chuhan Zhang ◽  
David Roger Jones Owen
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Safety Evaluation ◽  
Dam Safety ◽  
Loading Capacity ◽  
Concrete Dams ◽  
Gravity Dams ◽  
Content Type ◽  
Modelling Approach ◽  
Modelling Approaches

Purpose – There is not a unified modelling approach to finite element failure analysis of concrete dams. Different behaviours of a dam predicted by different fracture methods with various material constitutive models may significantly influence on the dam safety evaluation. The purpose of this paper is to present a general comparative investigation to examine whether the nonlinear responses of concrete dams obtained from different fracture modelling approaches are comparable in terms of crack propagation and failure modes. Design/methodology/approach – Three fracture modelling approaches, including the extended finite element method with a cohesive law (XFEM-COH), the crack band finite element method with a plastic-damage relation (FEPD), and the Drucker-Prager (DP) elasto-plastic model, are chosen to analyse damage and cracking behaviour of concrete gravity dams under overloading conditions. The failure process and loading capacity of a dam are compared. Findings – The numerical results indicate that the three approaches are all applicable to predict loading capacity and safety factors of gravity dams. However, both XFEM-COH and FEPD give more reasonable crack propagation and failure modes in comparison with DP. Therefore, when cracking patterns are the major concern for safety evaluation of concrete dams, it is recommended that XFEM-COH and FEPD rather than DP be used. Originality/value – The comparison of cracking behaviours of concrete dams obtained from different fracture modelling approaches is conducted. The applicability of the modelling approaches for failure analysis of concrete dams is discussed, and from the results presented in this work, it is significant to consider the suitability of the selected fracture modelling approach for dam safety evaluation.

scholarly journals Modeling of Hydraulic Fracture of Concrete Gravity Dams by Stress-Seepage-Damage Coupling Model

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Sha Sha ◽  
Guoxin Zhang
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Hydraulic Fracture ◽  
Carrying Capacity ◽  
Damage Model ◽  
Coupling Model ◽  
Propagation Path ◽  
Concrete Dams ◽  
Gravity Dams ◽  
Concrete Gravity Dams

High-pressure hydraulic fracture (HF) is an important part of the safety assessment of high concrete dams. A stress-seepage-damage coupling model based on the finite element method is presented and first applied in HF in concrete dams. The coupling model has the following characteristics: (1) the strain softening behavior of fracture process zone in concrete is considered; (2) the mesh-dependent hardening technique is adopted so that the fracture energy dissipation is not affected by the finite element mesh size; (3) four coupling processes during hydraulic fracture are considered. By the damage model, the crack propagation processes of a 1 : 40 scaled model dam and Koyna dam are simulated. The results are in agreement with experimental and other numerical results, indicating that the damage model can effectively predict the carrying capacity and the crack trajectory of concrete gravity dams. Subsequently, the crack propagation processes of Koyna dam using three notches of different initial lengths are simulated by the damage model and the coupling model. And the influence of HF on the crack propagation path and carrying capacity is studied. The results reveal that HF has a significant influence on the global response of the dam.

A Discussion about FBG Sensors Application of Crane SHM System

2013 ◽  
Vol 336-338 ◽  
pp. 185-191
Author(s):  
Xiao Peng Xie ◽  
Dong Hui Wang ◽  
Guo Jian Huang ◽  
Xin Hua Wang
Keyword(s):  
Finite Element ◽  
Real Time ◽  
Failure Modes ◽  
Safety Evaluation ◽  
Structural Condition ◽  
Sensor Data ◽  
Gantry Crane ◽  
The Real ◽  
Time Stress ◽  
Fbg Sensors

The arrangement positions and the quantities are different for different types of cranes. In order to make suitable decision, much investigate and survey was done at preliminary stage, and we know that the flange connected gate legs and turntables, the connections between load-bearing beam and rotary column under the engine room and the connections between jib and turntable are easy to lose efficient, and their mainly failure modes are cracks. By the method of finite element, 32 sensors (including 21 welding strain FBG sensors and 11 temperature FBG sensors) were used after doing much investigate and survey and finite element modeling analysis, which are arranged in different places of a gantry crane of MQ2533, for real-time structure health monitoring. This method makes the sensor data obtained more realistically reflects the crane structural condition, which provides reliable data support for crane safety monitoring and safety evaluation. Then a software platform is developed to monitor the real-time stress. If the real-time stress exceeds the allowable stress, it issues an alarm signal to the operator.

Concrete constitutive models for nonlinear seismic analysis of gravity dams — state-of-the-art

1992 ◽  
Vol 19 (3) ◽  
pp. 492-509 ◽  
Author(s):  
Sudip S. Bhattacharjee ◽  
Pierre Léger
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Crack Propagation ◽  
Seismic Analysis ◽  
Numerical Models ◽  
Ground Motions ◽  
Constitutive Models ◽  
Concrete Dams ◽  
Gravity Dams ◽  
Seismic Safety

The seismic safety of concrete dams is a matter of serious concern around the world. During severe ground motions, the dams are likely to experience cracking due to low tensile resistance of concrete. Several analytical methods have been proposed in the literature for finite element crack propagation analysis of concrete structures. Due to lack of consistent results, and virtually impossible verification because of limited field experience in seismic cracking of concrete dams, the choice of a reliable constitutive model has become a complex task. A review of concrete constitutive models for nonlinear seismic analysis of gravity dams is presented herein. The relative merits of the proposed models have been critically examined. Comparing the theoretical soundness, and the advantages and inconveniences of the different analytical procedures, the nonlinear fracture mechanics model applied with a smeared crack analysis technique appears to be very promising. The present state of knowledge on material fracture parameters under transient conditions has been found to be limited. Review of the past finite element seismic fracture analyses of concrete gravity dams reveals that reliable numerical models for safety evaluation of the structures during severe ground motions have not yet been satisfactorily developed. Key words: gravity dams, constitutive models, fracture mechanics, seismic response, nonlinear analysis, finite element, crack propagation.

Research on High Arch Dam Failure Probability Based on Failure Mode

2007 ◽  
Vol 348-349 ◽  
pp. 597-600 ◽  
Author(s):  
Zai Tie Chen ◽  
Qing Wen Ren
Keyword(s):  
Failure Mode ◽  
Failure Probability ◽  
Failure Modes ◽  
Safety Evaluation ◽  
Economic Loss ◽  
Arch Dam ◽  
Computational Method ◽  
Dam Failure ◽  
Dam Safety ◽  
High Arch Dam

In order to overcome the weakness in traditional high arch dam safety evaluation without considering the randomness, failure mode and risk analysis, it is proposed to apply three indexes namely failure probability, economic loss and life loss to high arch dam safety evaluation. On the basis of the analysis of accidents and on-site measured data, expert discussion as well as analytical analogy and by means of Fault Tree Analysis, a probe is made into the four major failure modes and the causes of high arch dam failure, namely destabilization collapse, shear-slipping collapse, excess cracking and man-caused destruction. Based on the calculating of the probability of high arch dam shearing-slipping failure, the computational method and procedures are established by means of Second Moment Method for the calculation of the occurrence probability of the major failure modes of high arch dam. A study is made of the degree of correlation between the major failure modes and of the method for calculating the high arch dam failure probability under multi-failure-modes.

Numerical study on racking behavior of light steel frames with K-shaped bracing

2019 ◽  
Vol 16 (2) ◽  
pp. 238-247
Author(s):  
Mohammad Javad Kazemi ◽  
Shahabeddin Hatami ◽  
Abdolreza Zare ◽  
Ali Parvaneh
Keyword(s):  
Finite Element ◽  
Parametric Study ◽  
Failure Modes ◽  
Numerical Study ◽  
Shear Walls ◽  
Element Analysis ◽  
Content Type ◽  
Lateral Strength ◽  
Cold Formed Steel ◽  
Lateral Behavior

Purpose This paper aims to study the lateral behavior of cold-formed steel walls with K-shaped bracing by finite element modeling. Design/methodology/approach The braces which have the same section as those for studs and tracks are connected to the frame by screw connections. By pushover analysis, lateral performance of two frame categories, with different dimensions and bracing arrangements, is examined, and the force-displacement diagram and the ultimate strength of walls are extracted. Probable failure modes during lateral loading including distortional buckling of studs, buckling in braces and failure of connections are simulated in the numerical model, and some strengthening suggestions would be offered to prevent brittle failures and, therefore, to increase the lateral strength of the walls. Findings The strengthened walls are examined, and their seismic behavior is compared with the original walls. Finally, a parametric study is carried out to evaluate the effect of factors such as thickness of frame members, frame height and yield tension of members on lateral behavior of the shear walls. Originality/value In the present research, lateral strength and failure modes of nine types of cold-formed steel shear walls with different arrangements of K-shaped bracing are examined by non-linear finite element analysis, and a parametric study is carried out to extract the effect of the wall frame characteristics on the lateral behavior. Shear walls are classified into two series.

Decision Support System in Thailand's Dam Safety with a Mobile Application for Public Relations

2022 ◽  
Vol 14 (1) ◽  
pp. 0-0
Keyword(s):  
Public Relations ◽  
Remote Monitoring ◽  
Mobile Application ◽  
Failure Modes ◽  
Safety Evaluation ◽  
Dam Safety ◽  
The Public ◽  
Remote Monitoring System ◽  
Further Development ◽  
Full Operation

This paper describes the decision-making based on civil engineering expertise of the Dam Safety Remote Monitoring System: DS-RMS, which decides on action-based advice depending on every-day scenarios and special occurrences such as earthquakes and floods. The system has been in full operation since 2016 and automatically evaluates 35 failure modes for 3 major dam types 24 hours a day. Key benefits include quick and reliable access to current information about the dams and being a reliever to dam executives in critical situations. In further development, parts of the real-time dam information were selected and made available to the public together with dam safety evaluation results automatically and continuously via a mobile application.

scholarly journals Fire performance of LSF walls made of hollow flange channel studs

2017 ◽  
Vol 8 (2) ◽  
pp. 149-180 ◽  
Author(s):  
Sivakumar Kesawan ◽  
Mahen Mahendran
Keyword(s):  
Mechanical Property ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Elevated Temperature ◽  
Failure Modes ◽  
Fire Performance ◽  
Element Analysis ◽  
Content Type ◽  
Elevated Temperature Mechanical Property ◽  
Reduction Factors

Purpose This paper aims to present an investigation conducted to evaluate the effects of important parameters affecting the structural fire performance of light gauge steel frame (LSF) walls. It also evaluates the applicability of commonly used critical hot flange temperature method to determine the fire resistance ratings (FRR) of different LSF walls. Design/methodology/approach The effects of important parameters such as stud section profiles and their dimensions, elevated temperature mechanical property reduction factors of the steel used, types of wall configurations and fire curves on the FRR of LSF walls were investigated. An extensive finite element analysis-based parametric study was conducted to evaluate their effects (finite element analysis – FEA). For this purpose, finite element models which were validated using the full-scale fire test results were used. Using the structural capacities obtained from FEAs, the load ratio versus FRR curves were produced for all the different LSF walls considered. Findings Stud depth and thickness significantly affected the fire performance of LSF walls because of the differences in temperature development pattern, thermal bowing deflections and the failure modes of stud. The FRR of LSF walls increased significantly when steel studs with higher elevated temperature mechanical property reduction factors were used. FRR significantly changed when realistic design fire curves were used instead of the standard fire curve. Furthermore, both the critical hot and average flange temperature methods were found to be unsuitable to predict the FRR of LSF walls. Originality/value The developed comprehensive fire performance data would facilitate the development of LSF walls with enhanced fire performance, and, importantly, it would facilitate and advance the successful applications of hollow flange channel section studs in LSF walls.

Homogenization of selective laser melting cellular material for impact performance simulation

2015 ◽  
Vol 6 (4) ◽  
pp. 439-450 ◽  
Author(s):  
G. Labeas ◽  
Evangelos Ptochos
Keyword(s):  
Selective Laser Melting ◽  
Failure Modes ◽  
Sandwich Structures ◽  
Sandwich Panels ◽  
Core Material ◽  
Laser Melting ◽  
Stress Strain ◽  
Content Type ◽  
The Core ◽  
Modelling Approaches

Purpose – The purpose of this paper is to present, the global behaviour of sandwich structures comprising cellular cores is predicted by finite element (FE) analysis. Two modelling approaches are investigated, providing different levels of accuracy; in both approaches, the sandwich structure is idealised as a layered stack with the skin modelled using shell elements; while the core is either modelled with fine detail using beam micro-elements representing the cell struts, or is modelled by three-dimensional solid elements after an appropriate core homogenisation. Design/methodology/approach – The applied homogenisation methodology, as well as the all important modelling issues are presented in detail. Experimental tests performed using a mass-drop testing machine are used for the successful validation of the simulation models. Findings – It was concluded that the core microscale models having detailed FE modelling of the core unit cells geometry with fine scale beam elements are suitable for the analysis of the core failure modes and the prediction of the basic core stiffness and strength properties. It was demonstrated that the homogenised core model provides significant advantages with respect to computing time and cost, although they require additional calculations in order to define the homogenised stress-strain curves. Research limitations/implications – Special microscale material tests are required for the determination of appropriate materials parameters of the core models, as steel selective laser melting (SLM) microstrut properties differ from the constitutive steel material ones, due to the core manufacturing SLM technique. Stress interactions were not taken into account in the homogenisation, as the applied core material model supports the introduction of independent stress-strain curves; however, the predicted load deflection results appeared to be very close to those obtained from the detailed core micromodels. Originality/value – The paper is original. The dynamic behaviour of conventional sandwich structures comprising conventional honeycomb type cores has been extensively studied, using simple mass-spring models, energy based models, as well as FE models. However, the response of sandwich panels with innovative SLM cellular cores has been limited. In the present paper, novel modelling approaches for the simulation of the structural response of sandwich panels having innovative open lattice cellular cores produced by SLM are investigated.

Load Testing to Collapse Limit State of Barr Creek Bridge

2000 ◽  
Vol 1696 (1) ◽  
pp. 92-102 ◽  
Author(s):  
Nicholas Haritos ◽  
Anil Hira ◽  
Priyan Mendis ◽  
Rob Heywood ◽  
Armando Giufre
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Flexural Rigidity ◽  
Load Capacity ◽  
Limit State ◽  
Dynamic Test ◽  
Service Condition ◽  
Flat Slab ◽  
Testing Program ◽  
Static Testing

VicRoads, the road authority for the state of Victoria, Australia, has been undertaking extensive research into the load capacity and performance of cast-in-place reinforced concrete flat slab bridges. One of the key objectives of this research is the development of analytical tools that can be used to better determine the performance of these bridges under loadings to the elastic limit and subsequently to failure. The 59-year-old Barr Creek Bridge, a flat slab bridge of four short continuous spans over column piers, was made available to VicRoads in aid of this research. The static testing program executed on this bridge was therefore aimed at providing a comprehensive set of measurements of its response to serviceability level loadings and beyond. This test program was preceded by the performance of a dynamic test (a simplified experimental modal analysis using vehicular excitation) to establish basic structural properties of the bridge (effective flexural rigidity, EI) and the influence of the abutment supports from identification of its dynamic modal characteristics. The dynamic test results enabled a reliably tuned finite element model of the bridge in its in-service condition to be produced for use in conjunction with the static testing program. The results of the static testing program compared well with finite element modeling predictions in both the elastic range (serviceability loadings) and the nonlinear range (load levels taken to incipient collapse). Observed collapse failure modes and corresponding collapse load levels were also found to be predicted well using yield line theory.

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