Reinforced Concrete Components Research Articles

Experimental study on rehabilitation of corrosion-damaged reinforced concrete beams with carbon fiber reinforced polymer

The repair and rehabilitation of reinforced concrete (RC) structures in coastal areas is a challenging engineering problem. In order to retrofit the degraded RC structures, numerous studies have been devoted to the method of non-corroded RC components retrofitted with carbon fiber reinforced polymer (CFRP). There is, however, less research available on corroded, patched and CFRP-repaired RC specimens. The purpose of this paper is to investigate rehabilitation of corrosion-damaged RC beams with CFRP, which focus on the effectiveness of CFRP-repaired methods and the effects of CFRP amount on flexural behavior of the beams. In this study, a modified retrofit method based on substrate repairs was developed, which is bonding CFRP after replacing V-notch of substrate concrete with polymer mortar. To compare the modified method with two common retrofit methods, which are respectively bonding directly CFRP and bonding CFRP after replacing damaged concrete, four-point bending experiments were conducted on a series of corrosion-damaged RC beams with CFRP. Important factors were considered in the experimental study, including the number of CFRP layers and corrosion level denoted by the mass loss rate of tensile steel. There were totally 32 RC beams (250mm×150mm×1400mm) constructed in these experiments, 27 of which were corroded by an accelerated aging approach. The results show that the modified retrofit method could provide better load carrying capacity for the beams having more than 15% mass loss of tensile steel. In addition, to improve the short-term performance, the simple method of directly bonding CFRP was suitable for the beams having less than 15% mass loss of tensile steel. It is noted that bonded CFRP could not work for the damaged beams which undertaken more than 50% mass loss of tensile steel. In particular, it is indicated that by optimizing the amount of CFRP, it is possible to balance strength recovery with control of failure mode.

Seismic Performance of Degraded Shear Walls for Long-Term Compliance Periods

Seismic performance evaluations of nuclear facilities are usually based on seismic probabilistic risk analyses that do not include the effects of concrete aging, which may decrease the capacity of reinforced concrete (RC) components with time. This study relates the physical mechanisms that take place during aging of concrete (e.g., cracking, and rebar corrosion) and the deterioration of mechanical properties that affect the system capacity under seismic events. The seismic performance evaluation uses available experimental data of steel reinforcement corrosion and variability of concrete parameters as a function of time. To obtain the variation in the system capacity caused by concrete aging, detailed numerical models of RC components and models of the selected structural systems are developed. The probability of unacceptable performance, or seismic failure, is computed by convolving the fragility data and selected hazard curves. The calculation includes the gain of concrete compressive strength with time. However, this gain in strength does not overcome the degradation of seismic performance caused by concrete cracking and corrosion of steel rebars. The results indicate that aging effects on RC components are largely influenced by seismic hazard at the site.

Research on Accelerated Corrosion of Steel Bar in Reinforced Concrete Components

The most effective method to quickly produce large quantities of corroded reinforced concrete component is electrochemical corrosion. In this study, what effects corrosion rate as well as the process of accelerated corrosion was experimentally investigated.

Fatigue lives of RC beams strengthened with CFRP at different temperatures under cyclic bending loads

ABSTRACTFatigue performance of reinforced concrete (RC) components strengthened with fibre reinforced polymer (FRP) is largely improved. However, temperature changes of service environment have a great effect on the fatigue behaviour of RC components strengthened with FRP. Concerning about temperature variations in subtropical areas such as South China, this paper analyses the fatigue behaviour of RC beams strengthened with carbon fibre laminate (CFL) from experimental studies and theoretical analysis under four different temperatures (5 °C, 20 °C, 50 °C, 80 °C) and five different stress levels (0.60, 0.66, 0.72, 0.78, 0.84). The paper discusses temperature fatigue behaviour of RC beams strengthened with CFL under cyclic bending loads in different service environments, and proposes a calculation formula of fatigue lives of RC beams strengthened with CFL under environmental temperatures and external forces coupling. Experimental results show that the formula not only effectively predicts the fatigue lives of the RC beams strengthened with CFL under environmental temperatures and bending loads coupling but also estimates the fatigue limits.

Complex analysis and evaluation of the condition of reinforced-concrete components in power-generating structures

Complex analysis and evaluation of the condition of reinforced-concrete components in power-generating structures

Sensitivity to Constitutive Modeling in Fiber-Based Discretization of Reinforced Concrete Members for Performance-Based Seismic Evaluation

Accurate constitutive models of the constituent materials in a reinforced concrete (RC) section, namely, unconfined concrete, confined concrete and reinforcing steel are necessary in fiber-based discretization of RC components for use in nonlinear analysis of RC structures. This paper examines the sensitivity to different constitutive models in predicting the inelastic seismic behavior of RC frame structures. In particular, the importance of incorporating confinement effects in modeling concrete behavior and including degrading effects in modeling the behavior of reinforcing steel bars so as to predict the monotonic, cyclic and seismic response of RC columns and frames is investigated. At the component level, it is shown that the inelastic response is controlled predominantly by the behavior of reinforcing steel. At the system level, the response of non-ductile structures is less sensitive to confined concrete models while the modeling of reinforcing steel is shown to influence the inelastic response of both non-ductile and ductile structures.

Hysteretic models that incorporate strength and stiffness deterioration

This paper presents the description, calibration and application of relatively simple hysteretic models that include strength and stiffness deterioration properties, features that are critical for demand predictions as a structural system approaches collapse. Three of the basic hysteretic models used in seismic demand evaluation are modified to include deterioration properties: bilinear, peak-oriented, and pinching. The modified models include most of the sources of deterioration: i.e. various modes of cyclic deterioration and softening of the post-yielding stiffness, and also account for a residual strength after deterioration. The models incorporate an energy-based deterioration parameter that controls four cyclic deterioration modes: basic strength, post-capping strength, unloading stiffness, and accelerated reloading stiffness deterioration. Calibration of the hysteretic models on steel, plywood, and reinforced-concrete components demonstrates that the proposed models are capable of simulating the main characteristics that influence deterioration. An application of a peak-oriented deterioration model in the seismic evaluation of single-degree-of-freedom (SDOF) systems is illustrated. The advantages of using deteriorating hysteretic models for obtaining the response of highly inelastic systems are discussed. Copyright © 2005 John Wiley & Sons, Ltd.

ÉMAKO-Series Materials for the Repair of Concrete and Reinforced-Concrete Components of Power-Generating Structures

ÉMAKO-Series Materials for the Repair of Concrete and Reinforced-Concrete Components of Power-Generating Structures

Insurance against construction risks and foundation engineering to prevent structure emergencies

Problems of the insurance of structural, design, and survey work for the installation of foundation beds and substructures are examined for the first time. It is demonstrated that additional examination of the quality of survey, design, and construction-assembly operations by insurance organizations, as well as continuous monitoring of work production based on a section of the trenches, and the installation of artificial beds and reinforced-concrete components of the substructures of buildings make it possible to prevent emergency situations with the foundation of structures.

Consideration of the effect of construction joints on the strength of massive reinforced-concrete components

1. When designing massive reinforced-concrete components and their elements it is necessary to take into account the presence of construction Joints between the blocks. 2. The developed design requirements imposed on elements of massive reinforced-concrete components having construction joints and the method of calculating the strength of inclined sections permit a rational arrangement of the construction joints, ensuring reliability and durability of the structures. 3. A differentiated approach to carrying out measures on the surface of blocks in conformity with the graph in Fig. 1 and indications in Table 1 is necessary. 4. The cost effectiveness of using the proposed solutions is expressed in a reduction of the cost of works: for components of the first group (Table 1), due to the elimination of technological and design measures on the surface of the blocks in the case of the arrangement of the joints within zone 1 (Fig. 1); for components of the second group (Table 1), due to the elimination of technological or design measurements on the surface of the blocks and also due to a savings of transverse reinforcement in the case of a rational arrangement of the construction joints and use of shortened reinforcement cages. 5. The proposed solutions permit an experimental and theoretical evaluation of the state of operating reinforced-concrete components on the basis of the strength of inclined sections in the zone of construction joints, which in certain cases effects a savings due to elimination of costly investigations and repair works. 6. It is expedient to introduce the given suggestions into the standards during their revision with respect to the calculation and design of massive reinforced-concrete components and their construction.