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Non-destructive inspection of corroded steel bars in concrete structures
Published in Hiroshi Yokota, Dan M. Frangopol, Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations, 2021
Reinforcing bars (rebar) placed in concrete structures have an extremely important role in load-carrying capacity. If the corrosion of the rebars progresses due to the neutralization or salt damage of concrete, cracks are induced, and the progress of the corrosion is accelerated, furthermore, the surface concrete may be peeled off (Kajikawa et al. (1990)). The corrosion damage of rebars can be found after rust juice has been revealed on the surface. In order to grasp the signs of rebar corrosion at an early stage and reflect it in the maintenance management plan, it is necessary to develop a non-destructive evaluation method to visualize the rebars in concrete to check the presence of corrosive damage.
Stochastic analysis of reinforcement corrosion and its induced cover cracking in chloride contaminated RC structures
Published in Airong Chen, Xin Ruan, Dan M. Frangopol, Life-Cycle Civil Engineering: Innovation, Theory and Practice, 2021
Recently, some stochastic models have been developed to predict the time-dependent probability of chloride-induced deterioration in RC structures (Zhang et al. 2015). Most of these studies are based on the simple assumption of uniform corrosion, while non-uniform corrosion of reinforcing steel usually occurs in chloride contaminated RC structures. Obviously, compared with uniform corrosion, non-uniform corrosion of rebar can lead to earlier surface cracking and faster crack evolution, causing premature failure of the structure and seriously shortening the service life. Thus, circumferential non-uniform corrosion of rebar should be considered to accurately simulate the corrosion-induced deterioration process in marine environments.
Steels
Published in M. Rashad Islam, Civil Engineering Materials, 2020
Rebar (short for reinforcing bar) is a steel bar or mesh of steel wires used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and hold the concrete in tension. It is a common hot-rolled steel bar that is widely used in the construction industry, especially for concrete reinforcement. Concrete is very strong in compression and weak in tension. To compensate for this weakness, reinforcement bars are cast into the concrete to carry the tensile loads. Common steel or concrete reinforcement bars are supplied with heavy ridges (ribbed) to assist in binding the reinforcement to the concrete mechanically, which is referred to as the deformed bar. Coating is used on the bars if they are to be used in close proximity to water, so as to avoid corrosion, as shown in Figure 9.6.
Experimental study, numerical simulation and GRNN model for predicting the flexural loading capacity of corroded reinforced concrete beams
Published in European Journal of Environmental and Civil Engineering, 2023
Tan Nguyen Ngoc, Anh Tran Hoai, Hiep Dang Vu, Giang Nguyen Hoang
Table 10 typically shows the experimental results of control and corroded beams. Generally, the under-reinforced corroded beams have experienced failure mode by rebar yielding before the concrete fails. In particular, experimental observations displayed that for beam D2-H, a longitudinal reinforcement in the tension zone was broken, followed by the crushing of concrete (Figure 19). The high amount of steel bar corrosion could result in the change of failure mode from rebar yielding to rupture of rebars. This is also observed in the research of Dang and François (2013) and in the recent report of Hansapinyo et al. (2021). The scatter of the load values that produce the first bending crack and the corresponding deflection is observed. The reason can be explained as follows. For the corroded beams, since the stiffness is reduced compared to the control beam, the deflection enhances when the first crack appears. The deformability of a corroded beam depends not only on the mechanical properties of the material but also on the type of corrosion. Localised corrosion could lead to a decrease in the elongation of the steel bar, resulting in a reduction in beam deflection. The deformation of RC beams strongly depends on the amount of rebar. Theoretically, the higher the amount of rebar, the lower the deformation capacity of the RC beams. At a certain corrosion level, the deformation capacity of the beam may improve due to the loss of rebar area.
Analysis of tensile mechanical characteristics of fibre reinforced backfill through splitting tensile and three-point bending tests
Published in International Journal of Mining, Reclamation and Environment, 2022
Gaili Xue, Erol Yilmaz, Guorui Feng, Shuai Cao
Laying bottom and hanging reinforcements is one of the main links in the construction of artificial CTB roof. A rebar having 12 mm diameter is selected as the bottom reinforcement (including the main reinforcement and the secondary reinforcement) with 0.5 m spacing between the primary reinforcements and between the secondary reinforcements. The main reinforcement is arranged along the direction in the stope with the drift section of 3 m ×3 m. A groove-shaped secondary reinforcement with 3 m length and 0.5 m height at both ends is vertically arranged on the main reinforcement, and the cross position of the main and secondary reinforcements is bound by an auto-strapping machine. The field investigations reveal that the original artificial CTB roof in this mine has been destroyed due to the bending deformation and collapse of the ‘bulging belly’. Hence, vertical pipe joint anchors are incorporated to artificial CTB roof for enhancing its overall stability. The anchor rods are arranged at the intersection of the main and auxiliary reinforcements in the middle and are fixed by welding with a spacing of 1.5 m. The 42 mm pipe joint anchor rod with1.8 m length is selected.
Crowdsourcing Exposure Data for Seismic Vulnerability Assessment in Developing Countries
Published in Journal of Earthquake Engineering, 2021
Iason Grigoratos, Ricardo Monteiro, Paola Ceresa, Antonella Di Meo, Marta Faravelli, Barbara Borzi
The exterior infill walls (cladding) of the buildings in Nablus usually consist of hollow concrete blocks (100 mm), weak unreinforced concrete layer (130 mm, 12 MPa estimated mean compressive strength) and stone layer of about 70 mm. Despite their mid-low construction quality, their influence on the seismic response can be crucial, especially if their configuration leads to soft-story plastic mechanism or stiffness/strength irregularities in plan (torsional response). The mean concrete compressive strength (cylinder) can vary between 15 (pre-1980) and 32 MPa (post-2000). The transverse reinforcement for post-1980 buildings is usually around 6 mm diameter rebars, with 250 mm spacing. The steel has a yield stress of 420 MPa and is ribbed. All the aforementioned values are indicative, drawn from estimations of local constructors, given that official sources are unavailable in the case-study region. More information about the structural elements of the RC residential buildings in Palestine can be found in Grigoratos et al. [2016a].