FE modeling of concrete beams and columns reinforced with FRP composites

Compression and flexure members such as columns and beams are critical in a structure as its failure could lead to the collapse of the structure.In the present work,numerical analysis of square and circle short columns,and reinforced concrete(RC)beams reinforced with fiber reinforced polymer composites are carried out.This work is divided into two parts.In the first part,numerical study of axial behavior of square and circular concrete columns reinforced with Glass Fiber Reinforced Polymer(GFRP)and Basalt Fiber Reinforced Polymer(BFRP)bars and spiral,and Carbon Fiber Reinforced Polymer(CFRP)wraps is conducted.The results of the first part showed that the axial capacity of the circular RC columns reinforced with GFRP increases with the increase of the longitudinal reinforcement ratio.In addition,the results of the numerical analysis showed good correlation with the experimental ones.An interaction diagram for BFRP RC columns is also developed with considering various eccentricities.The results of numerical modeling of RC columns strengthened with CFRP wraps revealed that the number and the spacing between the CFRP wraps provide different levels of ductility enhancement to the column.For the cases considered in this study,column with two middle closely spaced CFRP wraps demonstrated the best performance.In the second part of this research,flexural behavior of RC beams reinforced with BFRP,GFRP and CFRP bars is investigated along with validation of the numerical model with the experimental tests.The results resembled the experimental observations that indicate significant effect of the FRP bar diameter and type ont he flexural capacity of the RC beams.It was also shown that Increasing the number of bars while keeping the same reinforcement ratio enhanced the stiffness of the RC beam.

Damage modeling of ballistic penetration and impact behavior of concrete panel under low and high velocities

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete panels.This paper is divided into two parts.The first part consists of numerical modeling of reinforced concrete panel penetrated with a spherical projectile using concrete damage plasticity(CDP)model,while the second part focuses on the comparison of CDP model and Johnson-Holmquist-2(JH-2)damage model and their ability to describe the behavior of concrete panel under impact loads.The first and second concrete panels have dimensions of 1500 mm1500 mm150 mm and 675 mm675 mm200 mm,respectively,and are meshed using 8-node hexahedron solid elements.The impact object used in the first part is a spherical projectile of 150 mm diameter,while in the second part steel projectile of a length of 152 mm is modeled as rigid element.Failure and scabbing characteristics are studied in the first part.In the second part,the comparison results are presented as damage contours,kinetic energy of projectile and internal energy of the concrete.The results revealed a severe fracture of the panel and high kinetic energy of the projectile using CDP model comparing to the JH-2 model.In addition,the internal energy of concrete using CDP model was found to be less comparing to the JH-2 model.

The effects of mismatch fracture properties in encapsulation-based self-healing concrete using cohesive-zone model

Finite element analysis is developed to simulate the breakage of capsule in capsule-based self-healing concrete.A 2D circular capsule with different core-shell thickness ratios embedded in the mortar matrix is analyzed numerically along with their interfacial transition zone.Zero-thickness cohesive elements are pre-inserted into solid elements to represent potential cracks.This study focuses on the effects of mismatch fracture properties,namely fracture strength and energy,between capsule and mortar matrix into the breakage likelihood of the capsule.The extensive simulations of 2D specimens under uniaxial tension were carried out to investigate the key features on the fracture patterns of the capsule and produce the fracture maps as the results.The developed fracture maps of capsules present a simple but valuable tool to assist the experimentalists in designing appropriate capsule materials for self-healing concrete.

The effects of interfacial strength on fractured microcapsule

The effects of interfacial strength on fractured microcapsule are investigated numerically. The interaction between crack and microcapsule embedded in mortar matrix is modeled based on cohesive approach. The microcapsules are modelled with variation of core-shell thickness ratio and potential cracks are represented by pre-inserted cohesive elements along the element boundaries of the mortar matrix, microcapsules core, microcapsule shell, and at the interfaces between these phases. Special attention is given to the effects of cohesive fracture on the microcapsule interface, namely fracture strength, on the load carrying capacity and fracture probability of the microcapsule. The effect of fracture properties on microcapsule is found to be significant factor on the load carrying capacity and crack propagation characteristics. Regardless of core-shell thickness ratio of microcapsule, the load carrying capacity of self-healing material under tension increases as interfacial strength of microcapsule shell increases. In addition, given the fixed fracture strength of the interface of microcapsule shell, the higher the ratio core-shell thickness, the higher the probability of microcapsules being fractured.

Numerical model for prediction of corrosion of steel reinforcements in reinforced concrete structures

Reinforced concrete structures experience alteration and degradation during their lifetime due to the corrosion of the steel reinforcements.Prevention of the steel corrosion is indispensable to avoid structural degradation.In this paper,a preventive numerical approach of corrosion of steel reinforcements is presented.An in-house program which is part of a developed software called REHA is used in the present work.The corrosion initiation time due to carbonatation and penetration of chloride ions is studied.The model is applied on a case study which concerns a reinforced concrete T-beam of a bridge.The results revealed that the penetration of chloride ions represents the unfavorable case,which leads to rapid corrosion of the steel reinforcement,and the environmental conditions do not have high influence on the crack opening width in the service and spalling phases.The objective of the present model is to act as a decision aid for including the problem of corrosion cracking of steel reinforcements when planning strategies for rehabilitation and maintenance of existing structures or when dimensioning elements of new structures.

Ballistic behavior of plain and reinforced concrete slabs under high velocity impact

This work presents a numerical simulation of ballistic penetration and high velocity impact behavior of plain and reinforced concrete slabs.In this paper,we focus on the comparison of the performance of the plain and reinforced concrete slabs of unconfined compressive strength 41 MPa under ballistic impact.The concrete slab has dimensions of 675 mm x 675 mm x 200 mm,and is meshed with 8-node hexahedron solid elements in the impact and outer zones.The ogive-nosed projectile is considered as rigid element that has a mass of 0.386 kg and a length of 152 mm.The applied velocities vary between 540 and 731 m/s.6 mm of steel reinforcement bars were used in the reinforced concrete slabs.The constitutive material modeling of the concrete and steel reinforcement bars was performed using the Johnson-Holmquist-2 damage and the Johnson-Cook plasticity material models,respectively.The analysis was conducted using the commercial finite element package Abaqus/Explicit.Damage diameters and residual velocities obtained by the numerical model were compared with the experimental results and effect of steel reinforcement and projectile diameter were studies.The validation showed good agreement between the numerical and experimental results.The added steel reinforcements to the concrete samples were found efficient in terms of ballistic resistance comparing to the plain concrete sample.

Computational modeling of fracture in concrete: A review

This paper presents a review of fracture modeling of concrete.The complex material,such as concrete,has been widely used in construction industries and become trending issue in the last decades.Based on comprehensive literature review,there are two main approaches considered to-date of concrete fracture modeling,such as macroscopic and micromechanical models.The purpose of this review is to provide insight comparison from different techniques in modeling of fracture in concrete which are available.In the first section,an overview of fracture modeling in general is highlighted.Two different approaches both of macroscopic and micromechanical models will be reviewed.As heterogeneity of concrete material is major concern in micromechanical-based concrete modeling,one section will discuss this approach.Finally,the summary from all of reviewed techniques will be pointed out before the future perspective is given.

Interaction between matrix crack and circular capsule under uniaxial tension in encapsulation-based self-healing concrete

This paper investigates the fracture process of a capsule when subjected to uniaxial tension in encapsulation-based self-healing concrete.A circular capsule embedded in the mortar matrix is considered along with different ratios of core-shell thickness.To represent potential cracks,zero thickness cohesive elements are pre-inserted throughout element boundaries.The effects of fracture strength around the interfacial transition zone of the capsule are analyzed.The crack nucleation,propagation,and fracture mode of capsule are also discussed.The numerical results indicate that increasing the strength of the interfacial transition zone around the capsule can increase the load-carrying capacity of self-healing concrete.Moreover,given a similar fracture strength around the interface of the capsule,the fracture probability of capsule in encapsulation-based self-healing concrete is strongly dependent on the core-shell thickness ratio..

Numerical modeling of high velocity impact applied to reinforced concrete panel

A numerical simulation of a high-velocity impact of reinforced concrete structures is a complex problem for which robust numerical models are required to predict the behavior of the experimental tests.This paper presents the implementation of a numerical model to predict the impact behavior of a reinforced concrete panel penetrated by a rigid ogive-nosed steel projectile.The concrete panel has dimensions of 675 mm675 mm200 mm,and is meshed using 8-node hexahedron solid elements.The behavior of the concrete panel is modeled using a Johnson-Holmquist damage model incorporating both the damage and residual material strength.The steel projectile has a small mass and a length of 152 mm,and is modeled as a rigid element.Damage and pressure contours are applied,and the kinetic and internal energies of the concrete and projectile are evaluated.We also evaluate the velocity at different points of the steel projectile and the concrete panel under an impact velocity of 540 m/s.