Investigation of the Spatial Variability of Steel Weight Loss and Corrosion Cracking: A Novel X-ray Technique

The performance of corrosion-affected RC members depends strongly on localized damages of reinforcement. Therefore, modeling the spatial variability of steel corrosion is very important for the assessment of the remaining service life of corroded structures or time for maintenance. To study the changes of spatial variability of steel weight loss over time, a continuous monitoring is necessary. In this paper, a novel procedure of X-ray technique application in monitoring the spatial growth of a corroded bar in a RC specimen is demonstrated along with the digital image processing of X-ray images to estimate the steel weight loss. The relationship of steel weight loss and corrosion cracking is studied at different stages of corrosion. The validity of the estimation method of steel weight loss is also presented. In this study, a novel procedure of X-ray technique application in monitoring the spatial growth of corroded bars in RC specimens is demonstrated along with the digital image processing of X-ray images to estimate the steel weight loss. A single RC beam (80 mm × 140 mm × 1460 mm) reinforced with a longitudinal rebar and stirrups were fabricated for the investigation. The steel corrosion was accelerated via an electrochemical test. The relationship of steel weight loss and corrosion cracking was studied at different stages of corrosion. The validity of the method was also discussed. The outcome of spatial variability of steel weight loss might be used to validate analytical models for estimating non-uniform steel corrosion or incorporated with inspected corrosion levels of in-situ structures for the input data in a predicting model to estimate the long-term structural performance of corroded RC structures

Reliability-Based Durability Design of Shield Tunnels in Coastal Regions

In this paper, a reliability-based durability design method for shield tunnels in a marine environment is introduced. In this context, a method for integration of the coupling effects of chlorides and hydrostatic pressure into reliability-based durability design of shield tunnels in a marine environment is proposed. By using the proposed method, material parameters of RC segmental linings can be determined. The target reliability-based durability design level shall be satisfied during structural lifetime

Modeling spatial variability of steel corrosion using Gumbel distribution

Performance of corrosion-affected RC structures depends on the spatial variability of steel corrosion of reinforcing bars. The effect of spatial variability of steel corrosion on the remaining service life of concrete structures is significant. In this paper, an experimental study was conducted to investigate the effect of current density on the spatial variability of steel corrosion. This variability is modeled using Gumbel distribution derived from experiments and incorporated with FE method to estimate the yield loading capacity of RC beams. The results show that using Gumbel distribution parameters derived from the specimens with high current density may lead to an overestimation of load capacity of corroded RC beams.This work was supported by Waseda University Grant for Special Research Projects (project number: 2018B-146)

Time-Dependent Structural Performance Analysis of RC Slab Exposed to Chloride Attack by Incorporating Spatial Variability

It is well recognized that the material properties of a reinforced concrete (RC) structure and its dimensions are random due to the spatial variability associated with workmanship, environment and other factors. This randomness causes spatially corrosion damages such as corrosion crack, cover spalling and steel corrosion. Therefore, it is of great importance to simulate deterioration processes of RC structures in a stochastic field context. In this paper, based on a probabilistic model for steel corrosion in RC structures, steel corrosion distributions over RC slab is estimated using 2D Gaussian stochastic fields. In an illustrative example, a time-dependent structural performance of RC slab represented by the stochastic field was estimated using 2D nonlinear finite element method

Life-Cycle Performance Assessment of Road Network Under Multiple Hazards

A procedure for estimating risk and resilience of road networks associated with bridges and embankments subjected to seismic ground motion and subsequent tsunami caused by the anticipated Nankai Trough earthquake is proposed. Since road networks play a crucial role for the transportation system after a natural disaster, it is important to identify the degradation of functionality and economic loss due to damage to structures in networks. In an illustrative example, risk and resilience of road networks in Mie-Prefecture, where the effects of Nankai Trough earthquake would be very intense, are estimated. The numerical results show that the retrofitting prioritization can be determined by comparing the risk and resilience of road networks.The authors express sincere appreciation to Dr. Masayuki Yoshimi, National Institute of Advanced Industrial Science and Technology of Japan, for his suggestions related to seismic fault parameters

Analytical Study on Seismic Performance of Hollow Spiral Steel Pipes under Cyclic Loading

AbstractThe importance of economical construction of infrastructures has recently increased. The application of spiral steel pipes to bridge piers is considered as one of the effective methods. Spiral steel pipes have been seldom used for bridge piers. Currently, spiral steel pipes have been mainly used as the foundations of buildings or bridges and are relatively economical because they are produced in large quantities in factories. However, roll forming processes of spiral steel pipes are different from those of bending roll pipes which have been generally used as bridge piers, so that seismic performance of spiral steel pipes may be different from that of bending roll pipes. Therefore, it is very important to grasp the ultimate strength and the ductility of spiral steel pipes. In this study, the finite element analysis was conducted for grasping the elasto-plastic behavior of hollow spiral steel pipes. Based on the analysis results, the seismic performance of hollow spiral steel pipes under compressive axial force and bending moment was examined and the influences of the structural parameters on the seismic performances of the spiral steel pipes are discussed

シンライセイ リロン ニモトズク コウゾウケイ アンゼンセイ ヒョウカホウ オヨビ ソノ タイシン セッケイ エノ テキヨウ ニカンスル ケンキュウ

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