scholarly journals Performance Degradation of Subsea Shield Tunnel Segment Accounting for Concrete Strength Loss and Steel Bar Corrosion

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Jiaqi Guo ◽  
Weiling Yang ◽  
Chong Xu ◽  
Bo Peng ◽  
Jinhai Lin ◽  
...  
Keyword(s):  
Concrete Strength ◽  
Strength Loss ◽  
Performance Degradation ◽  
Concrete Cover ◽  
Chloride Penetration ◽  
Dissipated Energy ◽  
Shield Tunnel ◽  
Steel Bar ◽  
Steel Bars ◽  
Saturated Concrete

Subsea shield tunnels usually serve in a typical corrosive marine environment. Under the action of chloride penetration and carbonization, tunnel lining segments are often damaged because of concrete strength loss and steel bar corrosion induced concrete cracking during their service life, which seriously degrades the service performance of the tunnels. A systematical experimental and numerical investigation into the performance degradation of subsea shield tunnel segments accounting for concrete strength loss and steel bar corrosion is presented in this paper. The study demonstrates that chloride penetration decreases the peak strength and elastic modulus of the segment concrete by 42% and 46.1%, respectively. The average of the ratio of dissipated energy to the total energy of dry concrete is much smaller than that of water saturated concrete and chlorine solution saturated concrete, and chloride penetration reduces the energy storage capacity of concrete, and the ability to resist damage is weakened. When steel bars corrode for 120 days, the outer cracks continue to extend, and the concrete around the inner steel bars just begin to crack initiation; when corrode for 20 years, the length of the inner cracks gradually exceeds that of the outer cracks, and the inner cracks initiating from different steel bars coalesce with each other and form a continuous failure surface, causing great serious damage to the segment. Due to the difference in concrete strength, for the outer layer, the evolution processes of steel bar corrosion-induced cracks show the characteristics of early initiation, slow propagation, and late coalescence, and those for the inner layer have the characteristics of late initiation, rapid propagation, and early coalescence. During the whole process the propagation speed of the inner and outer cracks appears to be fast first and then slow. Moreover, the study also illustrates that the final state of segment performance degradation after crack coalescence presents the characteristics of whole lamellar exfoliation of the concrete cover.

The Analysis of the Reliability and Design for Mechanical Anchorage of HRB500 Steel Bars

2011 ◽  
Vol 94-96 ◽  
pp. 970-974
Author(s):  
Xian Rong ◽  
Peng Cheng Liu ◽  
Xue Li
Keyword(s):  
Concrete Strength ◽  
Concrete Cover ◽  
Statistical Regression ◽  
Analysis Method ◽  
Anchorage Length ◽  
Pull Out ◽  
Steel Bar ◽  
Steel Bars ◽  
Mechanical Anchoring ◽  
Cover Thickness

The factors on mechanical anchoring performance of HRB500 steel bars, such as concrete strength, concrete cover thickness, diameter of steel bar, anchorage length of steel bar and transverse reinforcement ratio, were studied based on pull-out tests of 45 specimens. And the formula of mechanical anchoring bond strength for HRB500 steel bars was concluded by statistical regression analysis method. Through the reliability analysis, the mechanical anchoring length of design value and the table of conversion ratio between mechanical and direct anchoring length of HRB500 steel bars have been proposed. So it could be used as a basis for practical projects. The results indicate that the mechanical anchorage length of HRB500 steel bars can be still designed with the formula proposed in GB 50010-2002 “Code for design of concrete structures”.

scholarly journals Basic Mechanical Properties of Duplex Stainless Steel Bars and Experimental Study of Bonding between Duplex Stainless Steel Bars and Concrete

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2995
Author(s):  
Qingfu Li ◽  
Yunqi Cui ◽  
Jinwei Wang
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Concrete Strength ◽  
Concrete Cover ◽  
Bond Stress ◽  
Reinforcing Steel ◽  
Anchorage Length ◽  
Steel Bar ◽  
Steel Bars

In recent years, as a result of the large-scale use of stainless steel bars in production and life, people’s demand for stainless steel bars has increased. However, existing research information on stainless steel bars is scant, especially the lack of research on the mechanical properties of duplex stainless steel bars and the bonding properties of duplex stainless steel bars to concrete. Therefore, this paper selects 177 duplex stainless steel bars with different diameters for room temperature tensile test, and then uses mathematical methods to provide suggestions for the values of their mechanical properties. The test results show that the duplex stainless steel bar has a relatively high tensile strength of 739 MPa, no significant yield phase, and a relatively low modulus of elasticity of 1.43 × 105 MPa. In addition, 33 specimens were designed to study the bonding properties of duplex stainless steel bars to concrete. In this paper, the effects of concrete strength, duplex stainless steel reinforcement diameter, the ratio of concrete cover to reinforcing steel diameter, and relative anchorage length on the bond stress were investigated, and a regression model was established based on the experimental results. The results show that, with the concrete strength concrete strength from C25 to C40, the compressive strength of concrete increased by 56.1%, the bond stress increased by 27%; the relative anchorage length has been increased from 3 to 6, the relative anchorage length has doubled, and the bond stress has increased by 13%; and, the ratio of concrete cover to reinforcing steel diameter increased to a certain range on the bond stress has no significant effect and duplex stainless steel reinforcement diameter has little effect on the bond stress. The ratio of concrete cover to reinforcing steel diameter from 3.3 to 4.5 and the bond stress increased by 24.7%. A ratio of concrete cover to reinforcing steel diameter greater than 4.5 has no significant effect on the bond stress, with the average bond stress value of 20.1 MPa. The duplex stainless steel bar diameter has little effect on the bond stress for the diameters of 12 mm, 16 mm, 25 mm duplex stainless steel bar, and their average bond stress is 19.9 MPa.

Experimental Study on Bond-Slip between Steel Bar and Recycled Aggregate Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 1651-1656 ◽  
Author(s):  
Qing Feng Huang ◽  
Da Fu Wang
Keyword(s):  
Concrete Strength ◽  
Concrete Cover ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Bond Slip ◽  
Pull Out ◽  
Steel Bar ◽  
Cover Thickness

By a static and repeated pull-out experiment between steel bar and recycled aggregate concrete, and bond-slip curves between recycled concrete with different recycled coarse aggregate(RCA) replacement percentages were recorded. Based on the analysis of the experimental results, replacement percentages of recycled concrete, cover thickness, anchorage length, concrete strength and loading method was investigated. At last, the bond-slip constitutive relation was also discussed.

Numerical Simulation of Bond Properties of Steel Bars in Concrete with Machine-Made Sand

2012 ◽  
Vol 238 ◽  
pp. 176-180
Author(s):  
Shun Bo Zhao ◽  
Xin Xin Ding ◽  
Shi Ming Liu
Keyword(s):  
Concrete Strength ◽  
Experimental Studies ◽  
Theoretical Method ◽  
Finite Element Models ◽  
Bond Properties ◽  
Ansys Software ◽  
Bond Slip ◽  
Bond Behavior ◽  
Steel Bar ◽  
Steel Bars

Based on the experimental studies, finite element models were built using ANSYS software to simulate the bond properties of steel bars in machine-made-sand concrete (MSC), which considered the nonlinear bond behavior of interface between steel bar and MSC. The concrete strength and the bond length of steel bar are considered as the main parameters for calculation. The complete bond-slip curves of plain and deformed steel bars are well simulated comparing those obtained from the experimental studies. The study gives an theoretical method to analyze the bond properties of steel bar in MSC.

The Experimental Study on Concrete-Filled Thin-Walled Square Steel Box Short Columns Fixed with Composite Steel Bar

2011 ◽  
Vol 94-96 ◽  
pp. 1590-1595
Author(s):  
Hai Chao Wang ◽  
Xi Quan Xu ◽  
Li Jun Zhou
Keyword(s):  
Bearing Capacity ◽  
Concrete Strength ◽  
Testing Machine ◽  
Short Columns ◽  
Steel Bar ◽  
Bonding Effect ◽  
Steel Bars ◽  
Thin Walled ◽  
Transverse Steel ◽  
Composite Steel

The method of construction about the concrete-filled thin-walled square steel box short columns is studied in this paper. Composite steel is designed inside of the concrete-filled thin-walled square steel box short columns. The use of the transverse steel bars’ constraining effect on the concrete and bonding effect on the walls enhances the local stability and bearing capacity of the wall. According to the concrete strength C30/C35/C40 and the thickness of the steel 1.25mm/1.75mm/2.5mm,42 short column specimens are made and the size of all specimens is 200mm×200mm×690mm.The static bearing capacity test is done by the 500-ton electro-hydraulic serve testing machine. The whole curve is made .The composite steel and the thin-walled steel’s strain is tested. The results show that this method of construction has a certain effect on constrainting concrete and bonding effect on the walls, significantly improving their mechanical properties, increasing the carrying capacity and ductility, and it is easy to be accomplished.

Experimental Study of Reinforced Concrete Eccentric Compression Columns with HRBF400 Steel Bars

2010 ◽  
Vol 168-170 ◽  
pp. 1725-1729
Author(s):  
Wen Jie Ge ◽  
Ji Wen Zhang ◽  
Hang Dai ◽  
Yong Ming Tu
Keyword(s):  
Experimental Study ◽  
Strain Distribution ◽  
Concrete Strength ◽  
Concrete Columns ◽  
Lateral Deformation ◽  
Fine Grain ◽  
Steel Bar ◽  
Steel Bars ◽  
Experimental Parameters ◽  
Design Value

Nine concrete columns reinforced with fine grain high steel bars under eccentric loading were tested to study the effects of experimental parameters, such as eccentricity distance, reinforcement ratio and concrete strength, on the failure pattern, the strain distribution and the lateral deformation. The experimental results indicate that the columns reinforced by fine grain high steel bars work harmonically with concrete, and the strength of fine grain steel bars could be utilized fully. Finally, the design value of 400MPa fine grain steel bar is 360MPa in column was proposed based on the experiment and the comprehensive theoretical analysis.

Laboratory Fast Corrosion Test of Plain Steel Bars in Concrete Beams

2012 ◽  
Vol 535-537 ◽  
pp. 1803-1806
Author(s):  
Shun Bo Zhao ◽  
Peng Bing Hou ◽  
Fu Lai Qu
Keyword(s):  
Reinforced Concrete ◽  
Concrete Beams ◽  
Numerical Models ◽  
Concrete Strength ◽  
Reinforced Concrete Beams ◽  
Uniform Corrosion ◽  
Pure Bending ◽  
Accelerated Corrosion ◽  
Steel Bars ◽  
Bending Length

An experimental study was carried out to examine the non-uniform corrosion of plain steel bars in reinforced concrete beams partially placed in 5% sodium chloride solution under conditions of accelerated corrosion. 4 reinforced concrete beams with different concrete strength were made. The crack distributions of the beams due to pre-loads and expansion of corrosion product, and the sectional corrosion characteristics of plain steel bars are described in detail. The sectional area loss relating to mass loss and change along pure bending length of the beams are discussed. These can be used as the basis of test for further studies to build the numerical models of serviceability of corroded reinforced concrete beams.

scholarly journals Inclusion of CFRP-Epoxy Composite for End Anchorage in NSM-Epoxy Strengthened Beams

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Md. Akter Hosen ◽  
Mohd Zamin Jumaat ◽  
A. B. M. Saiful Islam
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Concrete Cover ◽  
Structural Members ◽  
Premature Failure ◽  
Near Surface ◽  
Steel Bars ◽  
Near Surface Mounted ◽  
Separation Failure ◽  
Concrete Cover Separation

Nowadays, the use of near surface mounted (NSM) technique strengthening reinforced concrete (RC) structural members is going very popular. The failure modes of NSM strengthened reinforced concrete (RC) beams have been shown to be largely due to premature failure such as concrete cover separation. In this study, CFRP U-wrap end anchorage with CFRP fabrics was used to eliminate the concrete cover separation failure. A total of eight RC rectangular beam specimens of 125 mm width, 250 mm depth, and 2300 mm length were tested. One specimen was kept unstrengthened as a reference; three specimens were strengthened with NSM steel bars and the remaining four specimens were strengthened with NSM steel bars together with the U-wrap end anchorage. The experimental results showed that wrapped strengthened beams had higher flexural strength and superior ductility performance. The results also show that these beams had less deflection, strain, crack width, and spacing.

An Investigation on Bending Capacity of Support Stiffness Wall-Slab Structural System by Using Single Layer and Double Layer of Rebar for Residential Project

2012 ◽  
Vol 446-449 ◽  
pp. 3670-3673
Author(s):  
Hooi Min Yee ◽  
Siti Isma Hani Ismail
Keyword(s):  
Double Layer ◽  
Concrete Strength ◽  
Single Layer ◽  
Concrete Cover ◽  
Structural System ◽  
Average Percentage ◽  
High Rise ◽  
Percentage Difference ◽  
Average Percentage Difference ◽  
Bending Capacity

Wall-slab structural system is a system suitable for use in the field of high-rise building where the main load resisting system is in the form rigidly connected wall slab member. Concrete vertical walls may serve both architecturally partitions and structurally to carry gravity and lateral loading. Moment transfer of joint is an important aspect for proper structurally functioning of wall-slab system. Hence, the main aim of this study is to investigate experimentally the effect of reinforcement details in the wall on bending capacity for support stiffness in wall-slab system for residential project in Malaysia. A total of six wall specimens were tested based on the specification given by the project contractor. Three of this specimens consisted single layer of rebar while another three specimen consisted of double layer of rebar. The size of the wall-slab’s specimens is 1000mm in length (L), 1080mm in width (W), 1000mm in height (H) and 80mm in thickness (T). The average concrete strength was 23.49MPa with Grade 30N/mm2 and the average yield strength of R5 bar was 817MPa. The predicted bending capacity at failure is in the range from 5.36kNm to 7.12kNm, depending on actual concrete cover. The bending capacity at failure for single layered of rebar in wall for specimen 1, 2 and 3 were found to be 3.59kNm, 3.81kNm and 3.15kNm, respectively. The bending capacity at failure for double layered of rebar in wall for specimen 1, 2 and 3 were 5.50kNm, 6.31kNm and 7.00kNm, respectively. The average percentage difference in stiffness of double layered of rebar in wall based on load-deflection curve obtained is in the range from 116.17% to 289.88% higher than single layered of rebar in wall. Based on the experimental results, specimens consisted of double layered of rebar in wall is found to provide higher bending capacity to the joint of wall-slab structural system in the range from 56.25% to 98.86% compared with single layered of rebar in wall.

scholarly journals Leaching, carbonation and chloride ingress in reinforced alkali-activated fly ash mortars

2018 ◽  
Vol 199 ◽  
pp. 02025 ◽  
Author(s):  
Gregor J. G. Gluth ◽  
Petr Hlaváček ◽  
Steffi Reinemann ◽  
Gino Ebell ◽  
Jürgen Mietz
Keyword(s):  
Fly Ash ◽  
Visual Inspection ◽  
Electrochemical Behaviour ◽  
Transport Coefficients ◽  
Chloride Penetration ◽  
Chloride Ingress ◽  
Reaction Products ◽  
Steel Bars ◽  
Alkali Activated Binders ◽  
Alkali Activated

Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in highand low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation.

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