scholarly journals Mathematical Modeling of the Resistance of Pulling out Steel Bars from High Strength Concrete

2018 ◽  
Vol 7 (3.2) ◽  
pp. 516 ◽  
Author(s):  
Yevgenij Babych ◽  
Sergij Filipchuk ◽  
Oleksiy Fenko
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
High Strength Concrete ◽  
High Strength ◽  
Strength Concrete ◽  
Steel Bars ◽  
Specific Factors ◽  
The Impact ◽  
Experimental Researches ◽  
The Mathematical Model

The article gives the results of the experimental researches of the bond between steel and high strength concrete. According to these results the mathematical model was built to define the boundary stresses of the bond between steel and concrete on their contact surface. The analysis of the impact of the specific factors on the boundary stresses of the bond between steel and concrete was carried out. 

scholarly journals Reduce the Influence of Horizontal and Vertical Cold Joints on the Behavior of High Strength Concrete Beam Casting in Hot Weather by Using Sugar Molasses

2018 ◽  
Vol 7 (4.19) ◽  
pp. 794
Author(s):  
Fatimah Hameed Naser Al-Mamoori ◽  
Ali Hameed Naser Al-Mamoori
Keyword(s):  
High Strength Concrete ◽  
Concrete Beam ◽  
Setting Time ◽  
Weather Condition ◽  
High Strength ◽  
Point Load ◽  
Concrete Element ◽  
Strength Concrete ◽  
Hot Weather ◽  
The Impact

The current research studies the effect of cold joints on the behavior shear and flexure of High Strength Concrete (HSC) beams caused by delayed casting sequence during the hot weather in summer of Iraq.Fresh concrete should be kept alive during the various casting batches for concrete element by re-vibration. However, the over vibration caused loss in homogeneity and it is difficult to keep the workability of concrete during hot weather due to the effect of setting time.To deal with this problem of improper casting sequence, which eventually leads to the formation of cold joints, it will be used sugar waste (named as Sugar Molasses (SM)) is a by-product resulted from refining process of sugar as a delayed agent to increase the setting time in order to prevent early set of concrete due to adverse effects in construction joint of hot weather.In the current study, the first objective aims to investigate some of fresh and hardened mechanical properties of HSC (with high cement content) using SM at percentages of (0, 0.05, 0.1, 0.2, 0.3) % from the weight of cement under the concept of sustainable development. The second objective aims to investigate the location and surface texture effect of horizontal and vertical cold joints on the flexural and shear behavior of beam with/without SM. This objective includes testing of twenty four plain concrete beam of (110×110×650 mm) under two point load; half of them casting without roughing (smooth) the old layer and the other casted after roughed it.SM content of 0.2% of cement weight can improve compressive strength by about 11.2% at 28 days and delay initial setting time by about 4.617 hours (277 minutes). No adverse effect on concrete have been observed at this dosage of SM concentration for the ages of concrete cylinders studied. Delays in the setting of concrete at this dosage of SM content help in reducing the early setting of concrete and therefore reduced the impact of the cold joints formation in concrete beams under Iraqi hot weather condition. The failure load for the beams with SM of smooth and rough vertical joints is in the range between (1.95 - 2.12) and (1.46-1.37); respectively times that of the case of beam without SM. 

scholarly journals Fire Performance of Columns Made of Normal and High Strength Concrete: A Comparative Analysis

2016 ◽  
Vol 711 ◽  
pp. 564-571 ◽  
Author(s):  
Thomas Gernay
Keyword(s):  
Bearing Capacity ◽  
High Strength Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Strength Loss ◽  
Fire Performance ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Strength Concrete ◽  
The Impact

The use of high strength concrete (HSC) in multi-story buildings has become increasingly popular. Selection of HSC over normal strength concrete (NSC) allows for reducing the dimensions of the columns sections. However, this reduction has consequences on the structural performance in case of fire, as smaller cross sections lead to faster temperature increase in the section core. Besides, HSC experiences higher rates of strength loss with temperature and a higher susceptibility to spalling than NSC. The fire performance of a column can thus be affected by selecting HSC over NSC. This research performs a comparison of the fire performance of HSC and NSC columns, based on numerical simulations by finite element method. The thermal and structural analyses of the columns are conducted with the software SAFIR®. The variation of concrete strength with temperature for the different concrete classes is adopted from Eurocode. Different configurations are compared, including columns with the same load bearing capacity and columns with the same cross section. The relative loss of load bearing capacity during the fire is found to be more pronounced for HSC columns than for NSC columns. The impact on fire resistance rating is discussed. These results suggest that consideration of fire loading limits the opportunities for use of HSC, especially when the objective is to reduce the dimensions of the columns sections.

scholarly journals EFFECT OF USING METALLIC AND NON METALLIC - FIBER AND RIB GEOMETRY OF STEEL BARS ON BOND STRENGTH FOR HIGH STRENGTH CONCRETE (H. S. C.)

2011 ◽  
Vol 39 (4) ◽  
pp. 681-696
Author(s):  
Aly Abdel-Zaher ELsayed ◽  
Hosny M. Soghair ◽  
Mohamed M. Rashwan ◽  
Ali Mohamed Abdallah Abou-Zied
Keyword(s):  
Bond Strength ◽  
High Strength Concrete ◽  
High Strength ◽  
Strength Concrete ◽  
Steel Bars ◽  
Metallic Fiber

Flexural performances of prestressed high strength concrete piles reinforced with hybrid GFRP and steel bars

2019 ◽  
Vol 38 (5) ◽  
pp. 518-526 ◽  
Author(s):  
Ping Wu ◽  
Yang Guo ◽  
Dayong Zhu ◽  
Weiliang Jin ◽  
Zhenhua Zhang ◽  
...  
Keyword(s):  
High Strength Concrete ◽  
High Strength ◽  
Strength Concrete ◽  
Concrete Piles ◽  
Steel Bars

scholarly journals Rebound Hammer Tests of High-Strength Concrete: Effects of Internal Stress and the Shape of the Impact Area of the Test Specimens on the Measurement Results

2019 ◽  
Author(s):  
Jiri Brozovsky ◽  
Lenka Bodnarova ◽  
Jiri Brozovsky jr
Keyword(s):  
Compressive Strength ◽  
Internal Stress ◽  
High Strength Concrete ◽  
High Strength ◽  
Test Area ◽  
Destructive Testing ◽  
Strength Concrete ◽  
Impact Area ◽  
The Impact ◽  
Calibration Relations

This study examines the factors affecting the results of non-destructive testing of high-strength concrete performed on cubes and on cylinders and examines the processing of calibration relations. Tests were performed with both a type N and a type L Schmidt impact hammer (with a standard impact energy of 2.205 Nm and 0.735 Nm respectively). The assessed factors were internal stress in a specimen and the shape of the impact area. Test specimens were loaded by a force corresponding to the stress in specimen 0%, 10%, 20%, 30%, and 50% from the expected compressive strength. Rebound numbers of the unloaded test specimens were significantly lower than those of the loaded specimens. Therefore, calibration relations and/or correction coefficients processed by measurements of unloaded specimens can be assessed as unsuitable. To process calibration relations, we recommend exerting internal stress in amounts of 15% to 20% of the expected compressive strength of the tested HSC samples. During the determination of the effect of the shape of the test area on the cylindrical test specimen, it was assumed that the rebound numbers on the plane and the round test area would be the same. However, the test results revealed that the rebound numbers in the differently shaped test areas were different. For Schmidt impact hammer type N, the rebound numbers in the round test area were lower by 0.7 units on average, and for Schmidt impact hammer type L, the rebound numbers in the round test area were lower by 1.7 units on average compared to the plane test area rebound numbers.

scholarly journals Chloride Ion Corrosion Pattern and Mathematical Model for C60 High-Strength Concrete after Freeze-Thawing Cycles

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yan Li ◽  
Bing Li ◽  
Lian-ying Zhang ◽  
Chao Ma ◽  
Jiong Zhu ◽  
...  
Keyword(s):  
Mathematical Model ◽  
High Strength Concrete ◽  
Chloride Ion ◽  
High Strength ◽  
Chloride Ions ◽  
Diffusion Method ◽  
Freeze Thaw ◽  
Strength Concrete ◽  
Artificial Environment ◽  
Transport Control

In this study, the porosities of C60 high-strength concrete after 0, 30, 60, and 90 freeze-thaw cycles determined via the water retention method are 1.30%, 3.65%, 5.14%, and 7.34%, respectively. Furthermore, a mathematical model of porosity varying with the number of freeze-thaw cycles is established. Using an artificial environment simulation experimental system and the natural diffusion method, the chloride diffusion law of C60 high-strength concrete after 0, 30, 60, and 90 freeze-thaw cycles is obtained. The corresponding diffusion coefficients are calculated based on the experimental results and Fick’s law, where 0.3431 × 10−12, 0.5288 × 10−12, and 0.6712 × 10−12, and 0.8930 × 10−12 m2/s are obtained, respectively, and a mathematical model of diffusion coefficient with freeze-thawing is established. Transport control equations comprising solution flow and solute migration control equations are established for chloride ions in concrete after freeze-thawing cycles. The equations consider the effects of freeze-thawing, solution pressure, solution concentration, solution density, convection, mechanical dispersion, and chemisorption on chloride ion transport in concrete. Using COMSOL numerical software, the transport control equations for chloride ions are solved using a real concrete numerical model, and the chloride ion corrosion process in concrete after freeze-thaw cycles is simulated. The simulation results are consistent with the experimental values.

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