• Title/Summary/Keyword: damage plastic

Search Result 821, Processing Time 0.021 seconds

Energy equivalent lumped damage model for reinforced concrete structures

  • Neto, Renerio Pereira;Teles, Daniel V.C.;Vieira, Camila S.;Amorim, David L.N.F.
    • Structural Engineering and Mechanics
    • /
    • v.84 no.2
    • /
    • pp.285-293
    • /
    • 2022
  • Lumped damage mechanics (LDM) is a recent nonlinear theory with several applications to civil engineering structures, such as reinforced concrete and steel buildings. LDM apply key concepts of classic fracture and damage mechanics on plastic hinges. Therefore, the lumped damage models are quite successful in reproduce actual structural behaviour using concepts well-known by engineers in practice, such as ultimate moment and first cracking moment of reinforced concrete elements. So far, lumped damage models are based in the strain energy equivalence hypothesis, which is one of the fictitious states where the intact material behaviour depends on a damage variable. However, there are other possibilities, such as the energy equivalence hypothesis. Such possibilities should be explored, in order to pursue unique advantages as well as extend the LDM framework. Therewith, a lumped damage model based on the energy equivalence hypothesis is proposed in this paper. The proposed model was idealised for reinforced concrete structures, where a damage variable accounts for concrete cracking and the plastic rotation represents reinforcement yielding. The obtained results show that the proposed model is quite accurate compared to experimental responses.

A plastic strain based statistical damage model for brittle to ductile behaviour of rocks

  • Zhou, Changtai;Zhang, Kai;Wang, Haibo;Xu, Yongxiang
    • Geomechanics and Engineering
    • /
    • v.21 no.4
    • /
    • pp.349-356
    • /
    • 2020
  • Rock brittleness, which is closely related to the failure modes, plays a significant role in the design and construction of many rock engineering applications. However, the brittle-ductile failure transition is mostly ignored by the current statistical damage constitutive model, which may misestimate the failure strength and failure behaviours of intact rock. In this study, a new statistical damage model considering rock brittleness is proposed for brittle to ductile behaviour of rocks using brittleness index (BI). Firstly, the statistical constitutive damage model is reviewed and a new statistical damage model considering failure mode transition is developed by introducing rock brittleness parameter-BI. Then the corresponding damage distribution parameters, shape parameter m and scale parameter F0, are expressed in terms of BI. The shape parameter m has a positive relationship with BI while the scale parameter F0 depends on both BI and εe. Finally, the robustness and correctness of the proposed damage model is validated using a set of experimental data with various confining pressure.

Distribution of Optimum Yield-Strength and Plastic Strain Energy Prediction of Hysteretic Dampers in Coupled Shear Wall Buildings

  • Bagheri, Bahador;Oh, Sang-Hoon;Shin, Seung-Hoon
    • International journal of steel structures
    • /
    • v.18 no.4
    • /
    • pp.1107-1124
    • /
    • 2018
  • The structural behavior of reinforced concrete coupled shear wall structures is greatly influenced by the behavior of their coupling beams. This paper presents a process of the seismic analysis of reinforced concrete coupled shear wall-frame system linked by hysteretic dampers at each floor. The hysteretic dampers are located at the middle portion of the linked beams which most of the inelastic damage would be concentrated. This study concerned particularly with wall-frame structures that do not twist. The proposed method, which is based on the energy equilibrium method, offers an important design method by the result of increasing energy dissipation capacity and reducing damage to the wall's base. The optimum distribution of yield shear force coefficients is to evenly distribute the damage at dampers over the structural height based on the cumulative plastic deformation ratio of the dissipation device. Nonlinear dynamic analysis indicates that, with a proper set of damping parameters, the wall's dynamic responses can be well controlled. Finally, based on the total plastic strain energy and its trend through the height of the buildings, a prediction equation is suggested.

New optimum distribution of lateral strength of shear-type buildings for uniform damage

  • Donaire-Avila, Jesus;Lucchini, Andrea;Benavent-Climent, Amadeo;Mollaioli, Fabrizio
    • Structural Engineering and Mechanics
    • /
    • v.76 no.3
    • /
    • pp.279-291
    • /
    • 2020
  • The seismic design of conventional frame structures is meant to enhance plastic deformations at beam ends and prevent yielding in columns. To this end, columns are made stronger than beams. Yet yielding in columns cannot be avoided with the column-to-beam strength ratios (about 1.3) prescribed by seismic codes. Preventing plastic deformations in columns calls for ratios close to 4, which is not feasible for economic reasons. Furthermore, material properties and the rearrangement of geometric shapes inevitably make the distribution of damage among stories uneven. Damage in the i-th story can be characterized as the accumulated plastic strain energy (Wpi) normalized by the product of the story shear force (Qyi) and drift (δyi) at yielding. Past studies showed that the distribution of the plastic strain energy dissipation demand, Wpi/ΣWpj, can be evaluated from the deviation of Qyi with respect to an "optimum value" that would make the ratio Wpi/(Qyiδyi) -i.e. the damage- equal in all stories. This paper investigates how the soil type and ductility demand affect the optimum lateral strength distribution. New optimum lateral strength distributions are put forth and compared with others proposed in the literature.

Site specific fragility modification factor for mid-rise RC buildings based on plastic energy dissipation

  • Merin Mathews;B.R. Jayalekshmi;Katta Venkataramana
    • Earthquakes and Structures
    • /
    • v.27 no.4
    • /
    • pp.331-344
    • /
    • 2024
  • The performance of reinforced concrete buildings subjected to earthquake excitations depends on the structural behaviour of the superstructure as well as the type of foundation and the properties of soil on which the structure is founded. The consideration of the effects due to the interaction between the structure and soil- foundation alters the seismic response of reinforced concrete buildings subjected to earthquake motion. Evaluation of the structural response of buildings for quantitative assessment of the seismic fragility has been a demanding problem for the engineers. Present research deals with development of fragility curve for building specific vulnerability assessment based on different damage parameters considering the effect of soil-structure interaction. Incremental Dynamic Analysis of fixed base and flexible base RC building models founded on different soil conditions was conducted using finite element software. Three sets of fragility curves were developed with maximum roof displacement, inter storey drift and plastic energy dissipated as engineering demand parameters. The results indicated an increase in the likelihood of exceeding various damage limits by 10-40% for flexible base condition with soft soil profiles. Fragility curve based on energy dissipated showed a higher probability of exceedance for collapse prevention damage limit whereas for lower damage states, conventional methods showed higher probability of exceedance. With plastic energy dissipated as engineering demand parameter, it is possible to track down the intensity of earthquake at which the plastic deformation starts, thereby providing an accurate vulnerability assessment of the structure. Fragility modification factors that enable the transformation of existing fragility curves to account for Soil-Structure Interaction effects based on different damage measures are proposed for different soil conditions to facilitate a congenial vulnerability assessment for buildings with flexible base conditions.

Acoustic Emission Monitoring of Lightning-Damaged CFRP Laminates during Compression-after-Impact Test

  • Shin, Jae-Ha;Kwon, Oh-Yang
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.32 no.3
    • /
    • pp.269-275
    • /
    • 2012
  • Carbon-fiber reinforced plastic(CFRP) laminates made of nano-particle-coated carbon fibers and damaged by a simulated lightning strike were tested under compression-after-impact(CAI) mode, during which the damage progress due to compressive loading has been monitored by acoustic emission(AE). The impact damage was induced not by mechanical loading but by a simulated lightning strike. Conductive nano-particles were coated directly on the fibers, from which CFRP coupons were made. The coupon were subjected to the strikes with a high voltage/current impulse of 10~40 kA within a few ${\mu}s$. The effects of nano-particle coating and the degree of damage induced by the simulated lightning strikes on AE activities were examined, and the relationship between the compressive residual strength and AE behavior has been evaluated in terms of AE event counts and the onset of AE activity with the compressive loading. The degree of impact damage was also measured in terms of damage area by using ultrasonic C-scan images. The assessment during the CAI tests of damaged CFRP showed that AE monitoring appeared to be useful to differentiate the degree of damage hence the mechanical integrity of composite structures damaged by lightning strikes.

Finite Element Analysis of Strip Drawing Including the Evolution of Material Damage (재료결함의 성장을 포함하는 스트립 드로잉 공정의 유한요소해석)

  • Hahm, Seung-Yeun;Lee, Yong-Shin
    • Transactions of Materials Processing
    • /
    • v.3 no.1
    • /
    • pp.120-132
    • /
    • 1994
  • Strip drawing of strain-hardening, viscoplastic materials with damage is analyzed by a rigid plastic finite element method. A process model is formulated using two state variables, one for strain hardening from slip dominated plastic distortion and the other for damage from growth of microvoids. Application of the model to aluminum strip drawing is given via implementation in a consistent penalty finite element formulation. The predicted density changes as a result of void growth are compared to those from experiments reported in the literature. The effects of drawing conditions such as drawing speed and die angle on the mechanical property chages are studied.

  • PDF

Damage Analysis of Reinforced Concrete Columns under Cyclic Loading

  • Lee, Jee-Ho
    • KCI Concrete Journal
    • /
    • v.13 no.2
    • /
    • pp.67-74
    • /
    • 2001
  • In this study, a numerical model for the simulation of reinforced concrete columns subject to cyclic loading is presented. The model consists of three separate models representing concrete, reinforcing steel bars and bond-slip between a reinforcing bar and ambient concrete. The concrete model is represented by the plane stress plastic-damage model and quadrilateral finite elements. The nonlinear steel bar model embedded in truss elements is used for longitudinal and transverse reinforcing bars. Bond-slip mechanism between a reinforcing bar and ambient concrete is discretized using connection elements in which the hysteretic bond-slip link model defines the bond stress and slip displacement relation. The three models are connected in finite element mesh to represent a reinforced concrete structure. From the numerical simulation, it is shown that the proposed model effectively and realistically represents the overall cyclic behavior of a reinforced concrete column. The present plastic-damage concrete model is observed to work appropriately with the steel bar and bond-slip link models in representing the complicated localization behavior.

  • PDF

A Study on the Extents of Damage of a Bow Structure According to Collision Scenario (선수 충돌 상황별 손상거동에 관한 연구)

  • Kim, Kui-Me;Kim, Geun-Won;Shin, Ki-Su
    • Journal of the Korea Institute of Military Science and Technology
    • /
    • v.15 no.3
    • /
    • pp.266-271
    • /
    • 2012
  • The rescue methods for the marine casualties are limited due to the characteristics of operation environment of the vessel. Especially the most of marine accidents have been occurred at the bow structure of ship. Moreover the failure of bow structure may lead to catastrophic mishaps. In this paper, the extents of damage of a bow structure fracture subject to collision accident was investigated by using numerical method. The computer simulation approach by using Finite Element Method was employed to accomplish this goal. A finite element model, a 3D model of ship, has been utilized to evaluate damage of bow structure according to collision scenario. In conclusion, we have demonstrated that the plastic deformation occurred at the bow structure. Also it was shown that the collision angle clearly plays a role in determining amount of damage of ship structures.

Plasticity Model for Directional Nonlocal Crack Damage of Concrete (콘크리트의 방향적 비국소 균열 손상을 위한 소성모델)

  • Kim Jae-Yo;Park Hong-Gun
    • Proceedings of the Computational Structural Engineering Institute Conference
    • /
    • 2006.04a
    • /
    • pp.914-921
    • /
    • 2006
  • To describe the effect of the numerous and various oriented microcracks on the compressive and tensile concrete behaviors, the directional nonlocality is defined. The plasticity model using multiple failure criteria is developed for RC planar members in tension-compression. The crack damages are defined in the pre-determined reference orientations, and then the total crack damage is calculated by integrating multi-oriented crack damages. To describe the effect of directional nonlocality on the anisotropic tensile damage, based on the existing test results, the nonlocal damage factor is defined in each reference orientation. The reduced compressive strength in the cracked concrete is defined by the multi-oriented crack damages defined as excluding the tensile normal plastic strain from the compressive equivalent plastic strain. The proposed model is implemented to finite element analysis, and it is verified by comparisons with various existing panel test results.

  • PDF