Use of Frequency Change for Damage Identification in Reinforced Concrete Beams

2003 ◽  
Vol 9 (3-4) ◽  
pp. 475-491 ◽  
Author(s):  
Maria Nilde Cerri ◽  
Fabrizio Vestroni
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Damage Identification ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Frequency Change ◽  
A Value ◽  
Damaged Zone ◽  
Minimization Procedure ◽  
Identification Techniques

The detection of damage will become one of the most frequent applications of identification techniques. In this paper we deal with a particular use of these techniques to identify damage in reinforced concrete beams due to cracking, based on frequencies only as measured quantities. Damage is obtained by comparing the identified model in the undamaged and damaged conditions. A simple interpretative model is adopted: the damaged zone is represented by a beam element with a lower value of bending stiffness. Three parameters are necessary to define damage: the position and the extension of the damaged element and the reduction of its flexural stiffness. The optimal values of damage parameters are determined by means of a minimization procedure based on an output error equation. The characteristics of the inverse problem are first investigated using pseudo-experimental data. Static and dynamic tests are performed on reinforced concrete beams; the static load is increased in different steps up to a value close to failure. Frequencies are measured at each load step. These experimental data and others taken from the literature are used to examine the efficiency of the illustrated procedure to identify the damage pattern.

scholarly journals Assessing the Instantaneous Stiffness of Cracked Reinforced Concrete Beams Based on a Gradual Change in Strain Distributions

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Chunyu Fu ◽  
Dawei Tong ◽  
Yuyang Wang
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Cross Section ◽  
Concrete Beams ◽  
Internal Force ◽  
Experimental Results ◽  
Reinforced Concrete Beams ◽  
Gradual Change ◽  
Concrete Cracking ◽  
Good Agreement

Concrete cracking causes a gradual change in strain distributions along the cross section height of reinforced concrete beams, which will finally affect their instantaneous stiffness. A method for assessing the stiffness is proposed based on the gradual change, which is considered through modeling different strain distributions for key sections in cracked regions. Internal force equilibria are adopted to find a solution to top strains and neutral axes in the models, and then the inertias of the key sections are calculated to assess the beam stiffness. The proposed method has been validated using experimental results obtained from tests on five reinforced concrete beams. The predicted stiffness and displacements are shown to provide a good agreement with experimental data. The instantaneous stiffness is proven to greatly depend on the crack number and depth. This dependence can be exactly reflected by the proposed method through simulating the gradual change in concrete strain distributions.

Crack Analysis on Reinforced Concrete Beams Strengthened by Externally Prestressing Vertical Tensioning Method

2012 ◽  
Vol 204-208 ◽  
pp. 3104-3113
Author(s):  
Bo Wen Shi ◽  
Tian Wen Wang
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Reinforced Concrete Beams ◽  
Tension Zone ◽  
Stress Mode ◽  
Reinforced Beams ◽  
Internal Forces ◽  
Externally Prestressing ◽  
Resistance Equation

In this paper, seven reinforced concrete beams (two contrast beams and five externally reinforced beams) were tested. The crack regularity under different tension stresses was analyzed through experimental data. Taking the stress mode under pressure for the triangle area, in the tension zone in the shape of a trapezoid , the crack resistance equation of externally prestressing reinforced rectangle beam is derived from balance method of the internal forces and moment, and the results coincide with the experiment results well.

scholarly journals Limiting Reinforcement Ratios for Hybrid GFRP/Steel Reinforced Concrete Beams

2021 ◽  
Vol 11 (1) ◽  
pp. 01-11
Author(s):  
Duy Phan Nguyen ◽  
Viet Quoc Dang
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Concrete Beams ◽  
Steel Reinforcement ◽  
Reinforcement Ratio ◽  
Reinforced Concrete Beams ◽  
Equilibrium Equations ◽  
Steel Reinforced Concrete ◽  
Glass Fiber Reinforced ◽  
Load Carrying

In this work, a theoretical approach is proposed for estimating the minimum and maximum reinforcement ratios for hybrid glass fiber reinforced polymer (GFRP)/steel-reinforced concrete beams to prevent sudden and brittle failure as well as the compression failure of concrete before the tension failure of reinforcements. Equilibrium equations were used to develop a method for determining the minimum hybrid GFRP/steel reinforcement ratio. A method for determining the maximum hybrid GFRP/steel reinforcement ratio was also developed based on the equilibrium of forces of the balanced failure mode. For estimating the load-carrying capacity of concrete beams reinforced with hybrid GFRP/steel, less than the minimum and more than the maximum reinforcement ratio is recommended. Comparisons between the proposed expressions, experimental data, and available test results in the literature shows good agreement between the theoretical and experimental data, with a maximum discrepancy of 7%.

scholarly journals Experimental Study on the Relationship between the Natural Frequency and the Corrosion in Reinforced Concrete Beams

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Liye Zhang ◽  
Limin Sun ◽  
Lijuan Dong
Keyword(s):  
Reinforced Concrete ◽  
Natural Frequency ◽  
Structural Damage ◽  
Concrete Beams ◽  
Polynomial Model ◽  
Reinforced Concrete Beams ◽  
Frequency Change ◽  
Corrosion Depth ◽  
The Relationship ◽  
Corrosion Time

Due to many nondamage factors such as temperature, humidity, carbonation, and corrosion effects on natural frequency, the key problem of the application frequency-based method to detect damage is to reveal the rules of these factors affect natural frequency and further to eliminate their effects. The long-term characteristics of reinforced concrete structures require a lot of attention, especially in corrosive environment. In this paper, an experimental investigation was conducted to study the deflection and natural frequency of reinforced concrete beam in a marine environmental chamber for six corrosion stages (accelerated corrosion for 0, 20, 40, 70, 100, and 140 days). The experimental results demonstrated that deflection increases with corrosion time, while natural frequency decreases with corrosion time. Based on the accelerate corrosion test data of reinforced concrete beams, the general expression of the relationship between corrosion depth and natural frequency has been established through the fitting curve method. The polynomial model has been selected for establishing the relationship between steel corrosion depth (including the main reinforcement and stirrup) and natural frequency. The reason for selecting the polynomial model is that the sum of squares due to error (SSE) is closer to 0 and the coefficient of multiple determination (R-square) is closer to 1. This investigations help to discriminate the cause of reinforced concrete beams natural frequency change, to eliminate nondamage factors affects, and to apply many structural damage identification methods effectively.

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