Damage Analysis Of Structures Research Articles

Probabilistic seismic performance evaluation of composite frames with concrete-filled steel tube columns and buckling-restrained braces

The concrete-filled steel tube (CFT) composite frames using blind bolts and buckling-restrained braces (BRBs) have been studied with the development of building industrialization and energy dissipation technology. However, there has been no research so far on the probabilistic seismic fragility analysis for the blind-bolted end-plate CFT composite frames with BRBs (BRB-BECFT). Therefore, a total of 6-, 9-, 12- and 20-story BRB-BECFT prototype structures were designed based on the performance-based plastic design method. The results obtained from nonlinear static and dynamic analyses indicated that the four structures achieved predefined performance objectives in terms of story drift, joint rotation, and BRB ductility demand. Subsequently, fragility curves including non-collapse and collapse states were established to evaluate the behavior of the structure for a given intensity measure using the incremental dynamic analysis approach. Meanwhile, the geometric mean of spectral acceleration over a period range (Sa,avg) was selected as the intensity measure to assess the structural collapse capacity. Results showed that the adoption of Sa,avg can result in 32–42% lower data dispersion for the determination of collapse point, and simplification of the process of calculation of the collapse margin ratio of a structure. Furthermore, based on the combination of Sa,avg, residual story drift and BRB core plate strain, a framework of probabilistic seismic damage analysis of structures for combined damage evaluation at three levels of the system, subsystem, and component was summarized and conducted by the 6- and 12-story case study. This is practically useful to assess structural damage state after an earthquake because it could present more information on the probability distribution of various damage scenarios.

Damage analysis of Ti6Al4V lattice structures manufactured by electron beam melting process subjected to bending load

High levels of stiffness, strength, and lightweight can be achieved through lattice structures. Many different technologies can be adopted for their construction; among them, additive manufacturing presents high flexibility and the capacity to produce complex shape parts. In this paper, a detailed analysis of the fracture surface was carried out on titanium sandwich panels, having a lattice core and produced through electron beam melting (EBM) process. The specimens were subjected to the three-point bending test; then, the fracture surfaces were observed by means of a scanning electron microscope (SEM). The occurrence of dimples was found on the fracture surface, demonstrating the ductile behavior of the material; moreover, the micrographies showed a different morphology between the core of the struts and the surface.

Influence of Maxwell Stiffness in Damage Control and Analysis of Structures with Added Viscous Dampers

Viscous damping systems are often implemented in structures to reduce seismic damage. The stiffness of these elements is dominated by the most flexible part of the set including brace extender, auxiliary mounting elements and damping unit. Existing experimental data are used in this study to show that the actual stiffness of the set is about 25% to 50% of the value generally adopted in current engineering practice, which is based solely on the brace extender. A numerical study shows that this reduction has large implications for several variables related to damage control: residual drift ratio, storey acceleration and plastic strain energy dissipated by the frame members. Other variables, such as member forces and rotations, can experience large variations, particularly for non-linear dampers and high damping levels, especially in the top part of the building and more conspicuously for moderate earthquake intensities. In the absence of accurate data, Maxwell stiffness for analysis based on brace extender properties should be substantially reduced, with recommended factors between 0.25 and 0.50. Given the scarcity of experimental data, these results should be considered preliminary.

Seismic behavior & risk assessment of an existing bridge considering soil-structure interaction using artificial neural networks

The Peak Ground Acceleration (PGA) is extensively used in earthquake engineering practice to describe the ground motion characteristics for establishing the seismic vulnerability curves. However, a single parameter is not enough to describe the seismic excitation and does not allow expressing the complex relationship between the structural damage and the ground movement. Motivated to overcome these shortcomings, several ANN-based models were proposed to predict the seismic structural damage using other parameters. Unfortunately, not all include soil structure interaction. This paper aims to explore the predictive power of an ANN-based approach to reproduce the nonlinear dynamic behavior taking into account the various ground motion intensities, the variability of soil, and SSI. The basic strategy is to train a neural network by a numerical database obtained from a FEM model. This numerical model is further validated by experimental results. An optimum prediction for a nonlinear dynamic response is achieved using Artificial Neural Networks. Finally, fragility curves were established considering SSI for three different soil classes. Results revealed the importance of considering SSI effects on the evaluation of seismic structural damage and risk assessment analysis.

Numerical simulation of structural damage subjected to the near-field underwater explosion based on SPH and RKPM

In the present work, numerical simulation of structural damage subjected to the near-field underwater explosion is carried out by coupling the SPH and RKPM. The fluid solver is established based on the compressible SPH method, while the dynamic response of the structure is calculated based on the RKPM shell formulation. Since large deformation with contact will occur in the underwater explosion problem, a contact detection algorithm for the RKPM shell formulation is proposed. The contact force is calculated based on the volume strain. The fluid-structure interaction solver is established by adopting the normal-flux method, in which the structure is treated as a moving solid boundary for the fluid domain, while the fluid pressure is considered as the load act on the structure surface. Thus, the numerical model for the simulation of structural damage analysis in the underwater explosion is obtained, which is a part of the FSLAB software developed by the FSI laboratory of Harbin Engineering University. Finally, several numerical examples are studied to verify the robustness and accuracy of the present numerical model.

CEDLES: a framework for plugin-based applications for earthquake risk prediction and loss assessment

To evaluate the seismic risk and loss caused by an earthquake, many earthquake disaster loss assessment softwares have been developed. However, it is difficult to apply one earthquake disaster loss assessment software for all countries due to the different characteristics of seismic, architectural and economic of various countries. China is one of the high-seismicity regions in the world. Thus, it is imperative to develop an earthquake disaster loss assessment software suitable for China. In this paper, a novel framework for plugin-based applications named CEDLES is designed considering the scalability of the software. The features provided by CEDLES to ease the development of extensible applications are described. This framework includes a startup project, a common plugin framework base, a geographic information system plugin framework base, and a plugin manager project. These utilities allow rapid development and integration in which robustness and quality play a fundamental role. A first prototype, Earthquake Risk Prediction and Loss Assessment System (ERPLAS) is designed and implemented. It integrates the plugins of seismic hazard analysis, structural damage analysis, loss assessment, earthquake insurance rate estimation, and benefit–cost analysis of building retrofit, especially for China. ERPLAS is applied to Baqiao District in Xi’an and the estimation results are displayed and debated, which verify the practicality of ERPLAS and the feasibility and facility of CEDLES framework.

An efficient multiscale surrogate modelling framework for composite materials considering progressive damage based on artificial neural networks

Modelling of the progressive damage behaviour of large-scale composite structures presents a significant challenge in terms of computational cost. This is due to the detailed description in finite element (FE) models for the materials, i.e., with each unidirectional layer defined as required by the applicability of laminate failure criteria, and numerous iterations required to capture the highly nonlinear behaviour after damage initiation. In this work, we propose a method to accelerate the nonlinear FE analysis by using a pre-computed surrogate model which acts as a general material database representing the nonlinear effective stress-strain relationship and the possible failure information. Developed using artificial neural network algorithms, the framework is separated into an offline training phase and an online application phase. The surrogate model is first trained with a vast number of sampling data obtained from mesoscale unit cell models offline, and then used for online predictions on a macroscale FE model. The prediction accuracy of the surrogate model was examined by comparing the results with conventional FE modelling and good agreement was observed. The presented method enables progressive damage analysis of composite structures with significant savings of the online computational cost. Lastly, the surrogate model is only based on material designs and is reusable for other structures with the same material.

Damage analysis of RC tall building structures under earthquake loading

A Practical 1D cyclic model for concrete is established. The model is a combination between the skeleton curves in Chinese Concrete Code (GB50010-2010) and the modified hysteretic rule in Yassin model. The cyclic model has the tensile and compress damage variables which are able to depict the damage of concrete. The present model is developed as a user material subroutine VUMAT in ABAQUS. Then, the damage evolution analysis of a RC tall building structure was performed by the proposed damage model and the built-in damage model for concrete in ABAQUS. The results show that the cyclic model is suitable for the damage evolution and pattern analysis of RC tall building structures under earthquake loading.

Progressive damage analysis of composite structures using higher-order layer-wise elements

The objective of the current work is the development of a numerical framework for the simulation of damage in composite structures using explicit time integration. The progressive damage is described using a Continuum Damage Mechanics (CDM) based material model, CODAM2, in which the damage initiation and progression are modelled using Hashin's failure criteria and crack-band theory, respectively. The structural modelling uses higher-order theories based on the Carrera Unified Formulation (CUF). The current work considers 2D-CUF models where Lagrange polynomials are used to represent the displacement field through the thickness of each ply, resulting in a layer-wise element model. Numerical assessments are performed on coupon-level specimens, and the results are shown to be in good agreement with reference numerical predictions and experimental data, thus verifying the current implementation for progressive tensile damage. The capability of the proposed framework in increasing the polynomial expansion order through the ply thickness, and its influence on the global behaviour of the structure in the damaged state, is demonstrated. The advantages of using higher-order structural models in achieving significant improvements in computational efficiency are highlighted.

Damage Probability Matrices and Empirical Fragility Curves From Damage Data on Masonry Buildings After Sarpol-e-zahab and Bam Earthquakes of Iran

The weakness of tensile strength and high weight in masonry structures under the dynamic loads of earthquakes have always led to structural damage, financial losses, injuries and deaths. In spite of the cheap and affordable masonry materials, it has been very limited their use in constructions over the past three decades. However, common masonry materials are still found in monumental and historical structures, deteriorated texture and rural buildings. Identifying the seismic behaviour and the probability of the structural damage is vital for pre-earthquake seismic risk reduction of urban areas and the rapid post-earthquake assessment. The earthquake event occurred in Ezgeleh on 2017 November 12th with Mw=7.3 triggered the greatest damage in the Sarpol-e-zahab city at a distance of about 37 kilometres from the epicentre. Post-earthquake reconnaissance, microtremor analysis and rapid visual inventory of structural damages in different zones were performed by the research teams. In the present study, the strong ground motion, the peak ground acceleration and its corresponding intensity distribution, which are based on the site response analysis in different parts of the city, are introduced. Afterward, damage probability matrices of different types of masonry buildings, namely unreinforced masonry and confined masonry buildings, are determined for both bins of peak ground accelerations and intensities. Finally, the fragility curves of two types of masonry structures are extracted based on RISK-UE level 1 (LM1) method by assuming beta distribution to estimate the probability distribution function of the damage. These curves are useful in assessing pre-earthquake possible damages in masonry structures with similar construction methods and similar materials to reduce seismic risks.

Numerička analiza uticaja eksplozije na oklopno vozilo za različite geometrije V-trupa

The main objective of this research is to develop a numerical model of vehicle damage caused by an explosion of a mine, as well as to find the most favorable case of V-hull geometry and to point out a possible solution for mitigating the effects of mine explosion on an armored vehicle. Seven different V-hull geometries were considered and structure damage analysis was performed for all seven options. Also, the mass change for different geometries was analyzed. The effect of the mine explosion on the target structure was analyzed using the overpressure function according to the empirical CONWEP model, using Abaqus / Explicit software. An example of an explosion of 8 kg of Composition B acting on a vehicle with a total mass of 8000 kg was analyzed. The vehicle has two main parts - the cabin with mass of 6 t and a V-hull of mass of 2 t. The V-shaped hull in all the examples shown is made of 10 mm thick plates of Hardox 400 steel. The position of the explosive charge is the same for all geometry examples and is 0.6 m below the center of the vehicle. After analysis of the obtained results the most favorable V-hull geometry is determined. The guidelines for the further work and model improvement are suggested.

A novel approach to distinguish the uniform and non-uniform distribution of blast loads in process industry

The blast load distribution is an important factor affecting the accuracy of structural damage and domino effect analysis caused by explosions in petroleum and chemical industries. The distribution is usually treated as the uniform or non-uniform and the latter is more suitable for the real scenarios. However, the applicability of the uniform distribution has not been studied in details. In the present study, both the blast load intensity model (BLIM) and blast damage intensity model (BDIM) are developed to represent uniform or non-uniform blast loads quantitatively. Three explosion types (free air burst, air burst and surface burst) and three target structural surfaces (rectangular plates, cylindrical shells and spherical shells) are considered in BLIM and BDIM. The element superposition method based on finite element model (FEM) is proposed, which can solve BLIM and BDIM accurately. Furthermore, the relative difference between the uniform and non-uniform distribution can be obtained on basis of BLIM and BDIM. Finally, the application condition for the rectangular plates - critical stand-off distances with the relative difference of 5%, is defined and verified to distinguish the uniform and non-uniform distribution. The study can provide an insight into the proper application of blast load distribution.

Microstructure and fatigue performance of high strength concrete under compression after exposure to elevated temperatures

The fatigue tests of high-strength concrete after exposure to elevated temperatures of 200 °C, 500 °C, and 800 °C under low cyclic compression at different stress levels were carried out by an electro-hydraulic servo fatigue tester. The microstructure of high-strength concrete specimens during fatigue was studied with the aid of five comprehensive microscopic research methods—scanning electron microscopy, X-ray diffraction, ultrasonic, microhardness testing, and mercury intrusion porosimetry. By measuring the microscopic parameters such as ultrasonic velocity, microhardness, and the most probable aperture, the variation of microstructure during the fatigue process was analysed. It was found that with the increase of fatigue cycles, the variation speed of microscopic parameters follows a three-phase trend. The relationship between microscopic parameters and residual strain or elastic modulus ratio was established, and the fatigue damage models based on the microscopic parameters were obtained. A simplified mean damage variable was proposed and the residual life of concrete was predicted. The research results can provide reference for non-destructive testing, fatigue damage analysis and structural evaluation of high-strength concrete structures subjected to elevated temperature processes.

Formation Factors of Cytogenetic Violation of Rutilus rutilus (Cypriniformes, Cyprinidae) in Transformed River Ecosystems

Abstract For the first time, an analysis of structural damage of the peripheral blood erythrocyte nucleus in Rutilus rutilus (Linnaeus, 1758) was carried out for the rivers of the north-western region of Ukraine. The effect of the hydrochemical regime on the formation of cytogenetic disturbances of the representatives of this species was also clarified. It was observed that during 2013–2017, the content of phosphates, suspended solids, fluorides, iron, copper, zinc, manganese, nitrite nitrogen and nitrate nitrogen in the surface waters of rivers most significantly exceeded the current quality standards. The average frequency of nuclear disorders of peripheral blood erythrocytes R. rutilus from the studied hydrosystems is 5.25 ± 0.29 ‰ (p < 0.01), with a noticeable excess of the level of spontaneous mutations in the older age groups of fish. In all analyzed samples of R. rutilus, among the total number of identified structural disorders of the nucleus, the largest share is made up of red blood cells from the micronucleus (from 40.0 to 62.0 %), which is evidence of cytogenetic disturbances in the body of fish. At the same time, disturbances of erythrocyte blood of roach from small rivers are on average 1.3 times (or 21.9 %) higher compared with individuals from medium-sized rivers. The formation of cytogenetic disturbances in R. rutilus under the conditions of the hydrochemical regime of rivers is described by a close (r = 0.99 at p < 0.003) multifactorial regression dependence. More important regressive coefficients of the dependency are acquired by such biogenes (NH4+, NO3−, PO4−) and toxicants (Cu2+, Zu2+, Mn2+, F2) in the background of oxygen regime peculiarities (COD, BOD5, O2).

Damage Analysis and Experimental Study of Composite Structures with Initial Delamination

Composite laminates are prone to delamination during hot pressing and cooling, this delamination is one of the most important defects that affect the properties of composite structures, the formation and propagation of delamination in composite materials can significantly reduce the structural strength of composite materials and even lead to catastrophic failure. In this paper, the two parameters of the initial stratified position and the initial stratified diameter are selected to research the effects of these two parameters on the mechanical properties of composite laminates through numerical simulation and experiment, and concludes that the influence of initial delamination along the thickness direction on the average compression modulus and strain of the linear segment is small; the influence of delamination on the ultimate bearing capacity increases with the decrease of the distance between the delamination and the center plane. When the diameter of the delamination is in the range of 8%~20% of the effective area(18~44 mm), the influence on the average compression modulus, ultimate bearing capacity and strain of the linear segment is not obvious. When the diameter is increased to 27% of the effective length(60 mm), the above properties have changed greatly. And then, this paper introduces the bilinear controlled cohesive elements into the progressive failure method to calculate the ultimate load capacity of composite laminates, and demonstrate the accuracy of the simulation method by experiments.

Effect of different loading systems on acousto-ultrasonic characteristics of concrete under axial compression

Abstract In order to study the effects of different loading systems and stress history on the damage evolution of concrete, the acoustic emission characteristic parameters, the acoustic emission release rate, acousto-ultrasonic pulse wave velocity and the Rv value were compared and analyzed in the process of axial compression damage of concrete with different water cement ratios under step and intermittent loading. In this paper, the intermittent period led to a certain degree of “closure” in the internal microcracks of concrete, thus in the same HB to HD holding period, the acoustic emission release rate, mean value of acoustic emission characteristic parameters and mean acousto-ultrasonic pulse wave velocity under intermittent loading were all higher than that of step loading. The acousto-ultrasonic pulse wave velocity decreased with the increasing of the stress level and increased during the IA to ID intermittent period. Among them, with the decreasing of water cement ratio (from 0.6 to 0.4), the acoustic emission cumulative hits and the acoustic emission release rate increased, while the acousto-ultrasonic pulse wave velocity increased, and there were some differences in the acoustic emission release rate of the two loading systems at different water cement ratios. Furthermore, the Rv value decreased with the decreasing of water cement ratio in the IA to IC intermittent period and in the ID intermittent period, the Rv value increased with the decreasing of water cement ratio, thus the Rv value could reflect the evolution law of concrete with different water cement ratios during the intermittent period. The obtained results show that the acoustic emission and acousto-ultrasonic characteristic parameters are not consistent under two different loading systems, so research in this paper can provide a theoretical basis for the damage identification and analysis of concrete structures under cyclic loading based on the acousto-ultrasonic technology in practical engineering.

An approach integrating BIM, octree and FEM-SBFEM for highly efficient modeling and seismic damage analysis of building structures

This paper presents a novel BIM-Octree-FEM-SBFEM method (BOFSM) for rapid modeling and seismic damage analysis of structures. The BOFSM enables rapid and accurate modeling of structures by incorporating three innovative improvements. Firstly, integrating the digital building information method (BIM) with the Octree algorithm for discretization, a complex geometric model can be directly transformed into an analysis model. The automated transformation process eliminates considerable manual efforts typically expended in the traditional method. Secondly, the solver is improved using finite element method (FEM) to solve the hexahedrons elements while using scaled boundary FEM (SBFEM) to solve the polyhedrons. Thirdly, a nonlinear similar element (NSE) technique is proposed for cubes that occupy about 80% of the meshes. The matrices of one unit cubic element are pre-computed and stored in memory. Subsequently, the parameters of each element can be directly computed by scaling the dimensional coefficient and damage factor, thus offering an economical computational approach for massive matrices in damage analyses. The above methods are implemented in an in-house program GEODYNA, with CPU+GPU parallelization and multitasking capacity. Two refined seismic destruction analyses for frame buildings were conducted and some potential advantages are discussed. The results demonstrate the efficiency, universality and robustness of the BOFSM.

Peridynamics formulation for beam structures to predict damage in offshore structures

Progressive damage analysis of structures is still a major challenge. Peridynamics is a non-local theory using the integral equations rather than differential equations which makes it suitable for damage prediction. In this study, a novel bond based peridynamic model is developed for three-dimensional complex beam structures with 6 degrees of freedom based on Timoshenko beam theory. The numerical algorithm for dealing with complex beam structures is provided for the first time in the peridynamic literature. A damage criterion for beam structures with 6 degrees of freedom is also presented. The validity of peridynamic predictions is established by considering various examples. Initially, the proposed peridynamic model is used to predict the structural behavior of straight and curved beams. Next, the proposed peridynamic model is used to investigate a jacket platform. The jacket platform is subjected to both static and dynamic sea load induced by waves, winds, and currents. The peridynamic predictions are verified by comparing with finite element solutions. Peridynamic damage prediction for a pre-notched beam is verified by comparing with the previous literature. After verifying the peridynamic model, the proposed model is used to predict damages for a jacket platform due to sea loads and due to ship-jacket platform collisions.

Structural damage analysis of explosive testing experimental bay using HEXDAM Modelling software

Modelling of structural damages is a tool for making blast damage assessments resulting from an explosion on a localized area. This can be used as a damage/ injury assessment tool to determine the amount of blast damage/injury done to individual structures/ persons in a certain geographical area due to the detonation of explosives at ground level or at a specified height above the ground. This paper deals with prediction the structural damages of an experimental bay building when subjected to explosive testing, using HEXDAM (High Explosive Damage Assessment Modelling) software. The modelling software helps to predict the blast parameters at various points and the structural damages caused to the structures with in a facility. The basic outputs of HEXDAM are designed to provide data such as before/after blast display; damage/injury table; damage vs distance; pressure contours; damage/injury contours and the data tables for overpressure, dynamic pressure and damage/injury at each grid point. The experimental bay building along with the facility building was scientifically modelled with the trial set up using this software. The structural damages to the experimental bay and the nearby facilities are analysed when the building set up is subjected to the explosive loading at the height of 1m. The over pressure data at various points from the ground level to the height of 9m have been generated in this modelling. The Outputs are in the form of Damage vs injury tables, before and after blast displays, pressure and damage vs injury contour plots and Damage, injury-versus-distance graphs.

Study on Fatigue Damage of Small-scale Isolated Piers Based on Rain-flow Counting Method

The pier structure is a common infrastructure in marine engineering. The pier structure has been subjected to complex wave force for a long time, and fatigue failure is likely to occur over time, which may lead to the overall failure of the offshore infrastructure. Therefore, it is very important to analyze the fatigue damage of the pier structure. In this paper, a small-scale isolated pier is taken as an example. First of all, the wave force is simulated based on the Morison equation simulation. Then, the loop counting, which is based on the rain-flow counting method, is introduced. After obtaining the load cycles, the S-N curve theory and the Miner linearity cumulative damage theory are used to estimate fatigue damage. In this paper, a feasible method is proposed for the fatigue damage analysis of the pier structure, which is used as a reference for the design of the pier structure, and provides a means of verification for the subsequent structural fatigue damage analysis theory.