Research on Early Cracking of the CRCP in the Tunnel under Low Temperature Difference

2013 ◽  
Vol 857 ◽  
pp. 133-140
Author(s):  
Jian Wei Liu ◽  
Dui Jia Zhao ◽  
Shao Wen Liu ◽  
Jun Min Shen
Keyword(s):  
Temperature Field ◽  
Temperature Difference ◽  
Crack Width ◽  
Cement Hydration ◽  
Concrete Strength ◽  
Concrete Pavement ◽  
Crack Spacing ◽  
Internal Temperature ◽  
Temperature Changes ◽  
Maximum Crack

Calculate and analysis influence of the temperature field for Continuously Reinforced Concrete Pavement design. The temperature and crack of pavement are tested, so that the temperature changing and early cracks development inside the tunnel have been got. Studies have shown that: the tunnel temperature changes slowly, the temperature difference is small. In the first two days after concrete paving, the internal temperature of the slab was significantly higher than the ambient temperature, 79% of early cracking appears in this stages; Panel temperature rise because of the cement hydration. Strain increases in process of the growth of the concrete strength and shrinkage, the cracks appears. The number of cracks in the first two days accounted for 50% of the total number in 7 days, only the number of the second day accounted for 37.59%. Crack width accounted for 60.5% of the total, which is mainly concentrated in 0.1 mm and 0.2 mm. The crack spacing is mainly concentrated in 2m to 8m, accounted for 76.8% of all. The maximum crack spacing is 84 m, the minimum is only 0.5m.

scholarly journals Transverse Crack Behavior in Continuously Reinforced Concrete Pavement with Basalt Fiber Reinforcement

2020 ◽  
Vol 10 (21) ◽  
pp. 7458
Author(s):  
Yating Zhang ◽  
Zhiyi Huang
Keyword(s):  
Elastic Modulus ◽  
Reinforced Concrete ◽  
Crack Width ◽  
Basalt Fiber ◽  
Concrete Pavement ◽  
Crack Spacing ◽  
Design Parameters ◽  
Mean Values ◽  
Crack Behavior ◽  
Reinforcement Content

Continuously reinforced concrete pavement (CRCP) is a pavement structure with a high performance and long service life. However, the corrosion of the longitudinal steel can result in a poor bond relationship between the steel and the concrete, affecting the load transfer efficiency between the adjacent panels and being responsible for the development of CRCP distresses. Basalt fiber-reinforced polymer (BFRP) is corrosion-resistant and has the potential to be used in CRCP. In this paper, the layout of a CRCP test section with BFRP bars constructed on G330 National Road in Zhejiang Province, China, is presented. An analytical model is proposed to predict the crack behavior of CRCP with BFRP reinforcement, with the predicted results are compared to field-measured ones. A sensitivity analysis of the BFRP design parameters on the crack spacing and crack width is conducted as well. The results show that the mean values for field-measured crack spacing and crack width are 4.85 m and 1.30 mm, respectively, which are higher than the results for traditional CRCP with steel due to the lower elastic modulus of BFRP. The analytical predictions agree reasonably well with the crack survey results. The higher the elastic modulus of BFRP, the reinforcement content (with both BFRP spacing and diameter related), and the bond stiffness coefficient between the BFRP and concrete, the less the crack spacing and crack width will be. Given the same or similar reinforcement content, a lower diameter with a smaller spacing is recommended because of its contribution to a smaller crack spacing and width.

scholarly journals CRACK ANALYSIS OF CFRP REINFORCED CONCRETE BEAMS UNDER SECONDARY LOADING

2021 ◽  
Vol 30 (4) ◽  
Author(s):  
Jinliang Liu ◽  
Jiawei Wang ◽  
Yanmin Jia
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Concrete Beam ◽  
Reinforced Concrete Beam ◽  
Crack Spacing ◽  
Reinforced Concrete Beams ◽  
Calculation Formula ◽  
Plate Area ◽  
Average Crack ◽  
Maximum Crack

The paper established the calculation formulas on the average crack spacing and the maximum crack width of CFRP（Carbon Fiber Reinforced Polymer）reinforced concrete beam under the secondary loading. Conversion of CFRP plate area into the reinforcement ratio of the reinforced beam, the calculation formula on the average crack spacing of CFRP reinforced concrete beam under the secondary loading was established. On basis of the calculation formula on the maximum crack width of concrete beam, the calculation formula on the maximum crack width of CFRP reinforced concrete beam under the secondary loading was established. The average crack spacing and the maximum crack width calculated by the formulas in the paper were compared with the test data, it was verified that the formula is correct.

Experimental Investigation on Flexural Behavior of 500MPa Reinforced Concrete Beams with and without Skin Reinforcement

2013 ◽  
Vol 368-370 ◽  
pp. 1668-1673
Author(s):  
Zhi Hua Li ◽  
Xiao Zu Su
Keyword(s):  
Crack Width ◽  
Concrete Beams ◽  
Limit State ◽  
Crack Spacing ◽  
Reinforced Concrete Beams ◽  
Flexural Behavior ◽  
Test Results ◽  
Average Crack ◽  
Maximum Crack ◽  
Short Time

Fourteen concrete beams reinforced with 500MPa longitudinal steel bars, of which 6 with skin reinforcement and 8 without skin reinforcement, were tested under two-point symmetrical concentrated static loading to investigate their flexural behavior. The results indicate that the flexural behavior and deflection mode of test beams with skin reinforcement are basically consistent with those of test beams without skin reinforcement. The use of skin reinforcement can significantly reduce average crack spacing and short-time maximum crack width. And the use of skin reinforcement can also slightly increase the short-time stiffness. Under the serviceability limit state, mid-span deflections are in good agreement with the calculated values according to formula in GB50010-2010. However most of calculated average crack spacing and short-time maximum crack width are larger than measured values. According to the test results, the normal formula of crack width should be revised.

Continuously Reinforced Concrete Pavement Cracking Patterns and Properties with Internal Curing and Active Cracking

2021 ◽  
pp. 036119812110416
Author(s):  
Sachindra Dahal ◽  
Jeffery Raphael Roesler
Keyword(s):  
Reinforced Concrete ◽  
Crack Width ◽  
Concrete Pavement ◽  
Crack Spacing ◽  
Internal Curing ◽  
Temperature Management ◽  
Crack Control ◽  
Crack Patterns ◽  
Transverse Cracking ◽  
Control Section

Transverse cracking in continuously reinforced concrete pavement (CRCP) develops over time and may exhibit irregular patterns such as cluster cracks, Y-shaped cracks, and divided cracks. These undesirable cracking patterns can increase the probability of premature spalling and punchouts. Ideally, a uniform transverse cracking pattern with small crack widths leads to favorable long-term performance in CRCP. An experimental field project was constructed with internally cured concrete and active cracking to control crack initiation timing, patterns, and properties. Prewetted fine lightweight aggregate was used for internal curing, and edge notches of 2 in. depth and 2 ft length every 4 ft along the test section were sawcut for active crack control. The three experimental CRCP sections in Illinois were monitored for crack spacing, crack width, and formation of undesirable cracks over a 4-year period. Internally cured concrete significantly reduced the undesirable crack patterns relative to the control section. Internally cured concrete coupled with active crack concrete produced superior crack patterns and properties, that is, uniform crack spacing of 3.6 ft without cluster cracks, 0.2 mm surface crack width, and only a small number of undesirable cracks. Active crack control produced a higher number of transverse cracks near the terminal joint (last 150 ft) compared with the control section. Moisture and temperature management with active crack control during construction of the CRCP provided a desirable crack pattern and properties that should increase the overall service life of a pavement.

scholarly journals Three-Dimensional Electro-Thermal Analysis of a New Type Current Transformer Design for Power Distribution Networks

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1792
Author(s):  
Bingbing Dong ◽  
Yu Gu ◽  
Changsheng Gao ◽  
Zhu Zhang ◽  
Tao Wen ◽  
...  
Keyword(s):  
Boundary Condition ◽  
Temperature Field ◽  
Temperature Gradient ◽  
Field Distribution ◽  
Distribution Network ◽  
Current Transformer ◽  
Internal Temperature ◽  
Temperature Field Distribution ◽  
Type Design ◽  
New Type

In recent years, the new type design of current transformer with bushing structure has been widely used in the distribution network system due to its advantages of miniaturization, high mechanical strength, maintenance-free, safety and environmental protection. The internal temperature field distribution is an important characteristic parameter to characterize the thermal insulation and aging performance of the transformer, and the internal temperature field distribution is mainly derived from the joule heat generated by the primary side guide rod after flowing through the current. Since the electric environment is a transient field and the thermal environment changes slowly with time as a steady field under the actual conditions, it is more complex and necessary to study the electrothermal coupling field of current transformer (CT). In this paper, a 3D simulation model of a new type design of current transformer for distribution network based on electric-thermal coupling is established by using finite element method (FEM) software. Considering that the actual thermal conduction process of CT is mainly by conduction, convection and radiation, three different kinds of boundary conditions such as solid heat transfer boundary condition, heat convection boundary condition and surface radiation boundary condition are applied to the CT. Through the model created above, the temperature rise process and the distribution characteristics of temperature gradient of the inner conductor under different current, different ambient temperatures and different core diameters conditions are studied. Meanwhile, the hottest temperature and the maximum temperature gradient difference are calculated. According to this, the position of weak insulation of the transformer is determined. The research results can provide a reference for the factory production of new type design of current transformer.

Early Age Performance of Continuously Reinforced Concrete Pavement with Different Types of Aggregate

1997 ◽  
Vol 1568 (1) ◽  
pp. 35-43
Author(s):  
Yoon-Ho Cho ◽  
Terry Dossey ◽  
B. Frank Mccullough
Keyword(s):  
Reinforced Concrete ◽  
Field Test ◽  
Field Tests ◽  
Concrete Pavement ◽  
Crack Spacing ◽  
Winter Period ◽  
Thermal Coefficient ◽  
Curing Methods ◽  
Pavement Construction ◽  
New Variables

The effect of coarse aggregate on pavement performance has been attributed to the volume of aggregate used in pavement construction. The different patterns of crack development for limestone (LS) and siliceous river gravel (SRG) are a typical example of aggregate-induced variable performance in continuously reinforced concrete pavement (CRCP). An attempt was made to find a reasonable solution for pavements with SRG. As a way to solve the performance problem observed from the SRG pavement, a blended aggregates mixture was suggested. Laboratory and field tests were performed to check the feasibility of their application in pavements. From the laboratory test, a 50:50 blending ratio was suggested after considering the effect on tensile strength and thermal coefficient of expansion. Field test sections were also constructed to verify previous performance observations for the two aggregates and to provide performance data for new variables such as blended aggregates and special curing methods. Unexpectedly, the blended mixture did not improve the performance of SRG pavement; rather it experienced worse cracking than SRG alone. A controlled experiment with additional field test sections is needed to verify or disprove this finding. The only definitive finding was that selection of aggregate in the concrete pavement is a vital consideration for the design of the pavement. The CRCP8 analytical program reasonably predicted crack spacing for both SRG and LS pavements, predicting mean crack spacing of 0.99 m (3.25 ft) for SRG and 1.98 m (6.41 ft) for the limestone. These values are somewhat below the actual spacing observed at 100 days. Data collected after the first winter period will be required to calibrate the program.

scholarly journals Procedure for determining the thermoelastic state of a reinforced concrete bridge beam strengthened with methyl methacrylate

2021 ◽  
Vol 4 (7(112)) ◽  
pp. 26-33
Author(s):  
Vitalii Kovalchuk ◽  
Yuliya Sobolevska ◽  
Artur Onyshchenko ◽  
Olexandr Fedorenko ◽  
Oleksndr Tokin ◽  
...  
Keyword(s):  
Temperature Field ◽  
Reinforced Concrete ◽  
Methyl Methacrylate ◽  
Concrete Beam ◽  
Vertical Direction ◽  
Reinforced Concrete Beam ◽  
Temperature Stresses ◽  
Temperature Changes ◽  
Structural Reinforcement ◽  
Elasticity Module

This paper reports the analysis of methods for determining temperature stresses and deformations in bridge structures under the influence of climatic temperature changes in the environment. A one-dimensional model has been applied to determine the temperature field and thermoelastic state in order to practically estimate the temperature fields and stresses of strengthened beams taking into consideration temperature changes in the environment. The temperature field distribution has been determined in the vertical direction of a reinforced concrete beam depending on the thickness of the structural reinforcement with methyl methacrylate. It was established that there is a change in the temperature gradient in a contact between the reinforced concrete beam and reinforcement. The distribution of temperature stresses in the vertical direction of a strengthened reinforced concrete beam has been defined, taking into consideration the thickness of the reinforcement with methyl methacrylate and the value of its elasticity module. It was established that the thickness of the reinforcement does not have a significant impact on increasing stresses while increasing the elasticity module of the structural reinforcement leads to an increase in temperature stresses. The difference in the derived stress values for a beam with methyl methacrylate reinforcement with a thickness of 10 mm and 20 mm, at elasticity module E=15,000 MPa, is up to 3 % at positive and negative temperatures. It has been found that there is a change in the nature of the distribution of temperature stresses across the height of the beam at the contact surface of the reinforced concrete beam and methyl methacrylate reinforcement. The value of temperature stresses in the beam with methyl methacrylate reinforcement and exposed to the positive and negative ambient temperatures increases by three times. It was established that the value of temperature stresses is affected by a difference in the temperature of the reinforced concrete beam and reinforcement, as well as the physical and mechanical parameters of the investigated structural materials of the beam and the structural reinforcement with methyl methacrylate

scholarly journals Experimental Study on Doweled Expansion Joints on Behavior for Plain Concrete Pavement System

2018 ◽  
Vol 14 (3) ◽  
pp. 68-80
Author(s):  
Zainab Ahmed Al-kaissi ◽  
Mohammed Hashim Mohammed ◽  
Nabaa Sattar Kareem
Keyword(s):  
Failure Load ◽  
Concrete Slab ◽  
Concrete Strength ◽  
Plain Concrete ◽  
Concrete Pavement ◽  
Type I ◽  
Expansion Joints ◽  
Subgrade Soil ◽  
Dowel Bar ◽  
Bar Diameter

This paper deals with load-deflection behavior the jointed plain concrete pavement system using steel dowel bars as a mechanism to transmit load across the expansion joints. Experimentally, four models of the jointed plain concrete pavement system were made, each model consists of two slabs of plain concrete that connected together across expansion by two dowel bars and the concrete slab were supported by the subgrade soil. Two variables were dealt with, the first is diameter of dowel bar (12, 16 and 20 mm) and the second is type of the subgrade soil, two types of soil were used which classified according to the (AASHTO): Type I (A-6) and type II (A-7-6). Experimental results showed that increasing dowel bar diameter from 12 mm to 20 mm has a little effect on load-deflection behavior of the tested specimens with only 5% increase in failure load. This may be attributed to that the failure (caused by flexural crack) depends mainly on concrete strength. Results also showed that decreasing CBR value of subgrade soil from 7% to 5% decreases failure load by about 33%.

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