Local Bond Stress-Slip Model of High-Strength Stainless Steel Wire Ropes in ECC

Ke Li,Dapeng Zhao,Jiajun Fan,Juntao Zhu 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.5

Engineered cementitious composites (ECC) reinforced with high-strength stainless steel wire ropes (HSSSWR) is a new composite that has attracted much attention. Comprehensive understanding of the local bond stress-slip relationship of HSSSWR in ECC is a significant aspect to popularize the application of this new composite. In this research, the local bond stress-slip relationship between HSSSWR and ECC was investigated experimentally and theoretically, considering the influences of bond lengths, nominal diameters of HSSSWR and compressive strength of ECC. In order to accurately predict the bond stress and slip at different positions along the embedded length, a local bond stress-slip model was proposed for HSSSWR-ECC interface, and the model parameters were determined based on the pull-out test results and microsegment analysis of HSSSWR in ECC by using a nested iteration procedure. Furthermore, the three-dimension (3D) nonlinear finite element (FE) modeling method by using the proposed model was used to predict the bond-slip performance of HSSSWR in ECC. Finally, the global load-slip relationships calculated by using the iterative procedure and the 3D FE modeling method were compared with test results, which validated the acceptability of the developed local bond stress-slip model and the FE modeling method.

Investigation of bond-slip modeling methods used in FE analysis of RC members

Serhat Demir,Metin Husem 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.2

Adherence between reinforcement and the surrounding concrete is usually ignored in finite element analysis (FEA) of reinforced concrete (RC) members. However, load transition between the reinforcement and surrounding concrete effects RC members’ behavior a great deal. In this study, the effects of bond-slip on the FEA of RC members are examined. In the analyses, three types of bond-slip modeling methods (perfect bond, contact elements and spring elements) and three types of reinforcement modeling methods (smeared, one dimensional line and three dimensional solid elements) were used. Bond-slip behavior between the reinforcement and surrounding concrete was simulated with cohesive zone materials (CZM) for the first time. The bond-slip relationship was identified experimentally using a beam bending test as suggested by RILEM. The results obtained from FEA were compared with the results of four RC beams that were tested experimentally. Results showed that, in FE analyses, because of the perfect bond occurrence between the reinforcement and surrounding concrete, unrealistic strains occurred in the longitudinal reinforcement. This situation greatly affected the load deflection relationship because the longitudinal reinforcements dominated the failure mode. In addition to the spring elements, the combination of a bonded contact option with CZM also gave closer results to the experimental models. However, modeling of the bond-slip relationship with a contact element was quite difficult and time consuming. Therefore bond-slip modeling is more suitable with spring elements.

Bond-slip Constitutive Relation between BFRP Bar and Basalt Fiber Recycled-aggregate Concrete

Wen-jing Meng,Hua-xin Liu,Gen-jin Liu,Xiang-qing Kong,Xue-zhi Wang 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.5

In order to investigate the bond stress-slip constitutive relation between BFRP bar and basalt fiber recycled-aggregate concrete, 81 central pullout specimens were tested. Basalt fiber volume percent, fiber length and concrete strength grade were considered to be experimental variables to obtain the bond stress-slip curves. The results showed that adding basalt fiber into recycled-aggregate concrete will reduce the bond stress between BFRP bar and recycled-aggregate concrete but enhance the ductility of bond property; the bond stress increases with the increasing of fiber length and concrete strength grade. The bond stress-slip constitutive model was proposed and the results showed that the model is good in effect of fitting. The constitutive model can reflect the bonding mechanism between BFRP bar and basalt fiber concrete well, it also can provide reference for theoretical analysis and engineering applications of the bond and anchor property between BFRP bars strengthened recycled concrete.

Effect of high temperatures on local bond-slip behavior between rebars and UHPC

Chao-Wei Tang 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.2

This paper aimed to study the local bond-slip behavior between ultra-high-performance concrete (UHPC) and a reinforcing bar after exposure to high temperatures. A series of pull-out tests were carried out on cubic specimens of size 150×150×150 mm with deformed steel bar embedded for a fixed length of three times the diameter of the tested deformed bar. The experimental results of the bond stress-slip relationship were compared with the Euro-International Concrete Committee (CEB-Comité Euro-International du Béton)-International Federation for Prestressing (FIP-Fédération Internationale de la Précontrainte) Model Code and with prediction models found in the literature. In addition, based on the test results, an empirical model of the bond stress-slip relationship was proposed. The evaluation and comparison results showed that the modified CEBFIP Model code 2010 proposed by Aslani and Samali for the local bond stress-slip relationship for UHPC after exposure to high temperatures was more conservative. In contrast, for both room temperature and after exposure to high temperatures, the modified CEB-FIP Model Code 2010 local bond stress-slip model for UHPC proposed in this study was able to predict the test results with reasonable accuracy.

부착슬립을 고려한 철근콘크리트 구조체의 비선형 거동해석

곽효경(Kwak Hyo-Gyoung),나채국(Na Chaekuk) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.3A

This study introduces a numerical model that can simulate the nonlinear behavior of reinforced concrete (RC) structures subject to monotonic loading. Based on the force equilibrium and strain compatibility conditions, a criterion to consider the ten?sion-stiffening effect is proposed using the concept of average stresses and strains. To avoid defining the relation between shear stress and shear strain, a distributed steel model based on the rotating crack model is used to describe the crack angle according to crack propagation. In particular, the bond-slip behavior of embedded reinforcing bars, dominantly developed with the occurrence of cracking at the end face in a beam or column, is taken into account by defining the relation between the steel stress and bond-slip. The consideration of the bond-slip effect makes it possible to precisely simulate the cracking behavior of shear dominant and/or axial loaded RC structures, as these structures accompany a large amount of slip behavior with an increase in nonlinear deformation. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed boundary spring element model. 이 논문에서는 단조증가 하중에 대하여 철근콘크리트 구조체의 비선형 거통 해석 모델을 소개하고 있다. 힘의 평형과 변형률 접합조건에 따라 평균응력과 평균변형률 개념을 사용하여 인장강화효과(tension-stiffening effect)를 고려한 규준을 제안하였다. 회전균열모델을 사용함으로써 불필요한 전단응력과 전단변형률 관계의 정의를 피하였고, 균열의 진전에 따른 균열각을 모사하기 위해 분포철근모델을 사용하였다. 특히, 보나 기둥의 끝 단에서 주로 발생하게 되는 균열에 의한 배근된 철근의 부칙슬립 효과는 철근응력과 부칙슬립과의 관계를 정의함으로써 고려하였다. 철근콘크리트 구조체가 비선형 변형이 증가하여 많은 슬립이 발생하기 때문에, 전단이 주로 발생하거나 축력을 받는 철근콘크리트 구조체의 균열 거동은 부착슬립 효과를 고려함으로써 정확하게 모사할 수 있다. 이 논문에서는 제안된 경계 스프링 요소(boundary spring element) 모델의 정확성을 검증하기 위하여 해석적 결과와 실험적 결과를 비교하여 평가하였다.

Bond Behavior of Spiral Ribbed Ultra-high Strength Steel Rebar Embedded in Plain and Steel Fiber Reinforced High-Strength Concrete

Xiangyu Li,Jianwei Zhang,Juan Liu,Wanlin Cao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.10

The bond behavior of spiral ribbed ultra-high strength (SRUHS) steel rebar embedded in plain high strength concrete (HSC) and steel fiber reinforced high strength concrete (SFRHSC) is experimentally studied using pull-out tests. The influencing factors of concrete type, embedded length, cover thickness and stirrup ratio are considered and the bond failure characteristics as well as the whole process of stress-slip behavior are analyzed. The research shows good anchorage ductility between SRUHS steel rebar and HSC. Since SRUHS steel rebars have continuous spiral bite teeth with concrete, the concrete in the rib dales is not easily sheared off, thereby leading to a reliable bond strength. Compared to specimens without steel fibers, steel fiber reinforcement can increase the ultimate bond strength, bond stiffness and residual strength. Meanwhile, it will also reduce the influence of cover thickness, stirrup ratio on the specimens with steel fibers. Finally, a prediction calculation for ultimate bond stress and an analytical model for bond stress-slip relation are proposed, which match well with test results.

Bond-Slip Behaviors Between BFRP Bar and Ecological High Ductility Concrete Using the Beam Test

Li-Juan Chai,Li-Ping Guo,Bo Chen,Zhu Li,Rui Ma,Kai Li 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

To better understand the design parameters of bridge deck link slab made by basalt fiber reinforced polymer (BFRP) bar and ecological high ductility concrete (Eco-HDC), the bond behaviors of BFRP bar embedded in Eco-HDC using beam test based on RILEM standard were studied. The beam specimens had variable factors namely diameter of BFRP bar, embedment length and cover thickness. The results indicate that most beam specimens display a failure mode of BFRP bar pulled out with specimen splitting. Besides, with the increase of diameter and embedment length, the bond strength decreases. While as the cover thickness increases, the bond strength and first bond stress show an increasing trend. The free end slip increases as the embedment length or cover thickness increases. In addition, the strain at loaded end is larger than that at free end as the load increases. Moreover, the formulas of bond strength and peak slip are proposed based on the test data of specimens. At last, embedment length and cover thickness of BFRP bar in the bridge deck link slab are recommended.

Bond Behaviors between Ribbed BFRP Bars and Ecological High Ductility Cementitious Composites

Lijuan Chai,Liping Guo,Bo Chen,Jiandong Wu 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.11

Direct pull-out method was conducted to explore the bond stress-slip response of ribbed basalt fiber reinforced polymer (BFRP) bars embedded in ecological high ductility cementitious composites (Eco-HDCCs). The effects of the embedment length and cover thickness on the bond properties between Eco-HDCCs and the bars were described. Results indicate that the failure characteristics of the specimens depend on the embedment length and cover thickness of the BFRP bars. As the embedment lengths of the bars increase, the ultimate bond stress decreases while the ultimate slip increases. Besides, both the ultimate bond stress and ultimate slip show an increasing trend if the specimen has a cover thickness of less than 45 mm, while the increasing trend is slower if the specimen has a cover thickness of more than 45 mm. In addition, the strain of the specimen surface depends on the cover thickness, and the strain increases when the cover thickness is in a range of 15 mm − 35 mm. Moreover, certain embedment lengths and cover thicknesses of the BFRP bars are recommended in the structural design of bridge deck link slabs. The bond stress-slip relationship models of the BFRP bars in Eco-HDCCs are proposed based on the test results.

Uniaxial bond stress-slip behavior of reinforcing bars embedded in lightweight aggregate concrete

Chao-Wei Tang 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.5

This paper presents an experimental study of bond-slip behavior of reinforced lightweight aggregate concrete (LC) and normal weight concrete (NC) with embedded steel bar. Tests were conducted on tension-pull specimens that had cross-sectional dimension with a reinforcing bar embedded in the center section. The experimental variables include concrete strength (20, 40, and 60 MPa) and coarse aggregate type (normal-weight aggregate and reservoir sludge lightweight aggregate). The test results show that as concrete compressive strength increased, the magnitudes of the slip of the LC specimens were greater than those of the NC specimens. Moreover, the bond strength and stiffness approaches zero at the loaded end, or close to the central anchored point of the specimen. In addition, the proposed bond stress-slip equation can effectively estimate the behavior of bond stress and steel bar slipping.

Predicting the bond between concrete and reinforcing steel at elevated temperatures

Aslani, Farhad,Samali, Bijan Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.5

Reinforced concrete structures are vulnerable to high temperature conditions such as those during a fire. At elevated temperatures, the mechanical properties of concrete and reinforcing steel as well as the bond between steel rebar and concrete may significantly deteriorate. The changes in the bonding behavior may influence the flexibility or the moment capacity of the reinforced concrete structures. The bond strength degradation is required for structural design of fire safety and structural repair after fire. However, the investigation of bonding between rebar and concrete at elevated temperatures is quite difficult in practice. In this study, bond constitutive relationships are developed for normal and high-strength concrete (NSC and HSC) subjected to fire, with the intention of providing efficient modeling and to specify the fire-performance criteria for concrete structures exposed to fire. They are developed for the following purposes at high temperatures: normal and high compressive strength with different type of aggregates, bond strength with different types of embedment length and cooling regimes, bond strength versus to compressive strength with different types of embedment length, and bond stress-slip curve. The proposed relationships at elevated temperature are compared with experimental results.