مقاله انگلیسی رایگان در مورد روش التیام غیرخطی تیرهای بتن مسلح – تیلور و فرانسیس 2022

Abstract

     This paper has proposed a new formula relating the damage state and effective state of the flexural member, this formula enables studying different concrete healing variables. A new relation between the effective reinforced concrete healing/damage variable and the effective healing/ damage variables of concrete and steel has been introduced to relate concrete and steel healing/ damage and the reinforced concrete healing/ damage. The proposed formula has been verified with experimental results of full-healed flexural members, it has achieved good agreement. The flexural member stiffness has been studied considering different parameters like concrete healing variables, concrete cover and percentage of steel reinforcement. The flexural member stiffness has increased as the concrete healing variable has increased, it has increased as the concrete cover has increased and the steel reinforcement percentage of 1% has given the higher flexural member stiffness.

Introduction

     Self-healing is one of the most attractive research topics in the last decades, reinforced concrete is a heterogeneous material that needs the self-healing to protect the reinforcement during serviceability life. Robins et al. (2001) studied cracks progression of reinforced concrete beam with steel fibers to obtain response in the form of a load deflection. The nonlocal formulation through concepts of continuum damage mechanics was proposed by Jirásek (2004), the standard continuum theory with a stress-strain law were shown and he increased efficiency of the non-local simulation. The analytical results of the concrete behaviour under plane strain conditions were introduced by Bobinski and Tejchman (2005) by using a simple damage continuum isotropic model which was enriched by non-local terms to avoid a pathological mesh sensitivity and to get a well-posed rate boundary value problem. Voyiadjis and Kattan (2009) investigated the damage tensor that was used to link the damage state of the material with effective undamaged configuration using different paths including fabric tensors to connect the two configurations.

     Harries et al. (2012) developed the current ACI and AASHTO crack control provisions using high-strength reinforcing steel to anticipate the higher service level stresses. Allam et al. (2012) investigated and verified codes of practice provisions beside some equations calculating the crack width of reinforced concrete beams, five reinforced concrete models were studied theoretically. Voyiadjis and Kattan (2012) introduced and verified new damage variables, by using higherorder strain energy to lay the theoretical results for the design of undamageable materials. Darabi et al. (2012) proposed a novel continuum damage mechanics approach to model the micro-damage/ healing state in the materials that perform self-heal. Several presented examples were used to show the powerful of the proposed model to treat microdamage healing.

Conclusion

     A new nonlinear healing/ damage formula was introduced to interrelate the damage state and effective state that enables determining the effective state geometric properties to help in finding the response of the flexural member in healing / damage state. In addition, a new relation between the effective reinforced concrete healing/damage variable and the effective healing/ damage variable for concrete and steel was introduced. These new formulas enable controlling the damage of flexural members and design the healing of these members where the reinforcement, concrete dimensions, healing variables, damage variables are correlated in these formulas. Good agreement between the new proposed formula and experimental results was achieved. The proposed model’s efficiency increases as the spacing of healing points decreases, the proposed model becomes very close to experimental results when the healing becomes continuous. The beam’s stiffness increased by increasing the concrete healing variables (hc) and the concrete healing variable hc ¼ 2 3 was the reasonable healing variable that achieved the majority of the beam stiffness. Effective healing can be obtained by increasing concrete cover to increase the beam stiffness. Also, the proposed model shows that the percentage of steel reinforcement affects the behavior of reinforced concrete in healing, where the percentage of steel reinforcement affected the efficiency of the healing, where 1% gave high beam stiffness, but 2% of steel reinforcement reduced beam stiffness and 3% increased beam stiffness again.