Flexural Fracture and Fatigue Behavior of RC Beams Strengthened with CFRP Laminates under Constant Amplitude Loading

2006 ◽  
Vol 306-308 ◽  
pp. 1343-1348 ◽  
Author(s):  
Guowen Yao ◽  
Pei Yan Huang ◽  
Chen Zhao
Keyword(s):  
Fatigue Damage ◽  
Failure Modes ◽  
Fatigue Behavior ◽  
Bending Stiffness ◽  
Rc Beam ◽  
Rc Beams ◽  
Constant Amplitude ◽  
Damage State ◽  
Engineering Structures ◽  
Damage And Fracture

Externally bonded carbon fiber reinforced polymer (CFRP) materials are well suited to the rehabilitation and reinforcement of civil engineering structures due to their high specific strength, specific stiffness and corrosion resistance. To probe the fatigue behavior of CFRP strengthened concrete structures, three point bending experiments of reinforced concrete (RC) beams strengthened with carbon fibre laminate (CFL) under constant amplitude loading were performed. The histories of midspan flexibility and bending stiffness of strengthened beams were recorded automatically. And the linear curve between fatigue strength and the logarithm of fatigue life was obtained. The failure modes go through concrete cracking, CFL debonding from concrete and steel bars yielding and fracture with increasing cycles of fatigue loading. Bonded CFL increases the ductility of strengthened RC beam and results in dense distribution of cracks compared with normal RC beam, and it’s bending stiffness at damage state as well. The fatigue damage evolvement shows three stages of nucleation, steady expansion and failure. Then the failure mechanism was studied and a cumulative damage model was proposed to describe the fatigue damage and fracture process of CFL strengthened RC beams under constant amplitude loading.

Defects and Failure Modes in PZT Films for a MEMS Microengine

2000 ◽  
Vol 657 ◽  
Author(s):  
D.F. Bahr ◽  
B.T. Crozier ◽  
C.D. Richards ◽  
R.F. Richards
Keyword(s):  
Fatigue Damage ◽  
Thermal Stresses ◽  
Failure Modes ◽  
Fatigue Testing ◽  
Failure Strain ◽  
Fatigue Behavior ◽  
Mechanical Strain ◽  
Solution Deposition ◽  
Mechanical Fatigue ◽  
Pzt Films

ABSTRACTPiezoelectric films for a MEMS microengine have been deposited using solution deposition routines onto platinized silicon wafers. These films are used as membranes above a bulk micromachined cavity. A dynamic bulge tester and interferometer were used to characterize the deformation of the films when pressurized. The mechanical strain at failure, as well as the fatigue behavior, have been characterized. Membranes between 300 and 500 nm thick have been shown to sustain mechanical fatigue damage over approximately 10 million cycles at strains of 30% of the monotonic failure strain. Defects in the films due to growth and thermal stresses during processing, and their role in membrane failure, are identified. Crack growth is demonstrated in these films by compliance measurements during fatigue testing, and interfacial failure is identified between the PZT and Pt layers.

A New Approach to Fatigue Damage Modeling of Composite Laminates

2011 ◽  
Vol 338 ◽  
pp. 315-318 ◽  
Author(s):  
Peng Gang Mu ◽  
Xiao Peng Wan ◽  
Mei Ying Zhao
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Composite Laminates ◽  
Fatigue Behavior ◽  
Failure Criteria ◽  
Damage State ◽  
Damage Indices ◽  
Model Combining ◽  
Proposed Model ◽  
Fatigue Damage Accumulation

Fatigue damage of composites can be described by the residual stiffness and residual strength, and the same damage state can be described by the two mechanical parameters equivalently. Based on this assumption, a new pair of fatigue damage accumulation models are established to simulate fatigue behavior and predict the fatigue life of composites. Each of two equations contains three parameters and has the similar form, and the power function relationships between the two damage indices are constructed. The proposed model, combining with constant life diagrams and failure criteria are used to estimate the fatigue life of composites, and good agreement is observed between the present model and experimental results.

Study on the Evaluation of Fatigue Life of RC Beams Strengthened with FRP Laminates

2011 ◽  
Vol 250-253 ◽  
pp. 2079-2084
Author(s):  
Li Hua Huang ◽  
Tian Qing Li ◽  
Yue Fang Wang
Keyword(s):  
Fatigue Life ◽  
Life Span ◽  
Elastic Stress ◽  
Fatigue Behavior ◽  
Fatigue Tests ◽  
Rc Beam ◽  
Rc Beams ◽  
Stress Strain ◽  
Externally Bonded ◽  
Stress Concentration Factors

Extensive tests have shown that externally bonded fiber reinforced polymer (FRP) laminates are particularly suited for improving the short-term and long-term behavior of deficient reinforced concrete (RC) beam. Fatigue tests conducted to date indicate that fatigue life of RC beam bonded with FRP laminates lies in the response of steel rebar. Study on the method of nominal elastic stress (strain) for evaluating life-span of FRP strengthened beam is carried out in this paper. By analyzing fatigue tests, the acceptable stress concentration factors and S-N curves are suggested to be used to account for the fatigue behavior of RC beams strengthened with FRP laminates. Analytical results are compared with experimental data from two sets of fatigue tests on stresses and life-span, which shows agreeable trend. Based on the findings, the approach of nominal elastic stress (strain) can be extended to evaluate the fatigue life of RC beam bonded with FRP laminates.

scholarly journals Effects of pre-fatigue damage on high-cycle fatigue behavior and chloride permeability of RC beams

2019 ◽  
Vol 122 ◽  
pp. 9-18 ◽  
Author(s):  
Jieqiong Wu ◽  
Runxiao Zhang ◽  
Bo Diao ◽  
Wuman Zhang ◽  
Jianchao Xu
Keyword(s):  
Fatigue Damage ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Rc Beams ◽  
Cycle Fatigue ◽  
Chloride Permeability

scholarly journals FLEXURAL CAPACITY ASSESSMENT OF BRICK AGGREGATED PRE-CRACKED RC BEAM STRENGTHENED WITH CARBON FIBER POLYMER

2019 ◽  
Vol 31 (1) ◽  
Author(s):  
Niaz Md Mamun ◽  
G. M. Sadiqul Islam ◽  
Md Jahangir Alam
Keyword(s):  
Carbon Fiber ◽  
Failure Modes ◽  
Fiber Reinforced Polymers ◽  
Capacity Assessment ◽  
Rc Beam ◽  
Rc Beams ◽  
Flexural Capacity ◽  
Carbon Fiber Reinforced Polymers ◽  
Rc Structures ◽  
Fiber Sheet

Ageing and improvements to design code has led to many existing RC structures made of locally available brick aggregates are now found structurally deficient and are in need of rehabilitation. This research emphases on flexural capacity assessment and investigation of failure modes of Carbon Fiber Reinforced Polymers (CFRP) strengthened brick aggregated RC beams. Flexural performance of the RC beam specimens are evaluated using four point bending method. Six RC beams (initially cracked) with CFRP strengthening were tested by varying (i) type of CFRP, (ii) reinforcing area, (iii) anchorage type; and (iv) number of CFRP layers. Two beams were tested as control specimens. Unidirectional carbon fiber sheet (Tow Sheet) and individually hardened continuous fiber strands woven into sheet form (Strand Sheet) were used. Simple flexure failure was obtained for unstrengthened RC beams while end plate and interfacial debonding were observed for the initially cracked CFRP strengthened RC beams. Strengthening of pre-cracked beams using Strand Sheet gave better performance compared to Tow sheet. Overall flexural strength improvement of CFRP strengthened beams varied from 12% to 34% with respect to unstrengthened beams depending on strengthening methods.

scholarly journals Fatigue Damage Evolution and Monitoring of Carbon Fiber Reinforced Polymer Bridge Cable by Acoustic Emission Technique

2012 ◽  
Vol 8 (10) ◽  
pp. 282139 ◽  
Author(s):  
Dongsheng Li ◽  
Qian Hu ◽  
Jinping Ou
Keyword(s):  
Acoustic Emission ◽  
Carbon Fiber ◽  
Fatigue Damage ◽  
Failure Modes ◽  
Fatigue Testing ◽  
Bridge Engineering ◽  
Fiber Reinforced ◽  
Engineering Structures ◽  
Cfrp Composites ◽  
Carbon Fiber Reinforced

Desirable properties of carbon fiber-reinforced plastic (CFRP) composites include their high strength, high rigidity, light weight, corrosion free, and fatigue resistance. CFRP composites are popularly applied in bridge engineering structures, but the causes of fatigue damage in CFRP bridges have not been thoroughly investigated. We adopt acoustic emission (AE) technology to monitor fatigue damage and failure of CFRP bridge cables. The relationship between AE signal characteristics and CFRP cable fatigue damage, as well as the pattern of AE signals during a fatigue test, is investigated. Results show that the failure models exhibit matrix and fiber-matrix interface failures at the initial stage of fatigue testing, followed by delamination and fiber rupture. The b value, Kurtosis index, and RA value based on AE characteristic parameters are proposed to describe the different damage stage failure modes. Finally, the failure types of AE waveform are extracted and analyzed using wavelet transformation. The AE technique proved to be a potential means for evaluating the fatigue damage characteristics of CFRP cables.

RC Beam Bridge’s Fatigue Cumulative Damage Rule Research

2013 ◽  
Vol 787 ◽  
pp. 829-832
Author(s):  
Hong Bing Zhu ◽  
Bo Xia ◽  
Yao Zhao
Keyword(s):  
Fatigue Damage ◽  
Fatigue Tests ◽  
Cumulative Damage ◽  
Rc Beam ◽  
Constant Amplitude ◽  
Advantages And Disadvantages ◽  
Damage Theory ◽  
Theory Research ◽  
Beam Bridge ◽  
Damage Rule

Fatigue damage is the RC beam bridge is facing a big problem, for the RC beam bridge fatigue tests and fatigue cumulative damage theory research is very meaningful. Summarizes the research achievements of the RC beam bridge fatigue test, from constant amplitude fatigue, luffing fatigue and stochastic fatigue, etc, are discussed in this paper. Analyses the existing linear, nonlinear and probability fatigue cumulative damage theory and its applicable conditions, advantages and disadvantages. RC fatigue tests were discussed and the problems that exist in the fatigue cumulative damage theory research.

Fatigue Performance of Partially Prestressed RC Beams with HRBF500 Bars

2012 ◽  
Vol 174-177 ◽  
pp. 1463-1470
Author(s):  
Ke Li ◽  
Xin Ling Wang ◽  
Shuang Yin Cao
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beams ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Repeated Loading ◽  
Rc Beams ◽  
Constant Amplitude ◽  
Hot Rolled

500 MPa level hot-rolled ribbed bars of fine grains (HRBF500) is a successfully developed new-type steel in Chain. The fatigue behavior of partially prestressed reinforced concrete (RC) beams with HRBF500 bars was investigated in fatigue tests of pre-tensioned T-beams. The beams are simply supported with the same overall dimensions, and the main parameter in the study is prestress degree and longitudinal steel ratio. Four beams were constructed and tested under constant-amplitude fatigue loading. All beams are initially cracked before the application of repeated loading. The stress evolution of HRBF500 bars and prestressed strands, the information about crack growth and the deflection developments of test beams were presented. The main factors that affect the fatigue properties of prestressed concrete test beams were fully discussed. Test results indicate that, the prestressed concrete beams reinforced with appropriate amount of HRBF500 bars and reasonable prestressing configurations can survive 2.5 millions cycles of constant-amplitude fatigue loading using an upper-bound fatigue load producing tensile stress of less than 150 MPa in HRBF500 bars. The results provide important guidance for the fatigue design of prestressed concrete beams with HRBF500 bars.

scholarly journals Fatigue Stress-Life Model of RC Beams Based on an Accelerated Fatigue Method

2019 ◽  
Vol 4 (2) ◽  
pp. 16
Author(s):  
Eljufout ◽  
Toutanji ◽  
Al-Qaralleh
Keyword(s):  
Cyclic Loading ◽  
Fatigue Testing ◽  
Three Dimensional ◽  
Rc Beam ◽  
Rc Beams ◽  
Testing Methods ◽  
Load Range ◽  
Fatigue Stress ◽  
Life Model ◽  
Prediction Band

Several standard fatigue testing methods are used to determine the fatigue stress-life prediction model (S-N curve) and the endurance limit of Reinforced Concrete (RC) beams, including the application of constant cyclic tension-tension loads at different stress or strain ranges. The standard fatigue testing methods are time-consuming and expensive to perform, as a large number of specimens is needed to obtain valid results. The purpose of this paper is to examine a fatigue stress-life predication model of RC beams that are developed with an accelerated fatigue approach. This approach is based on the hypothesis of linear accumulative damage of the Palmgren–Miner rule, whereby the applied cyclic load range is linearly increased with respect to the number of cycles until the specimen fails. A three-dimensional RC beam was modeled and validated using ANSYS software. Numerical simulations were performed for the RC beam under linearly increased cyclic loading with different initial loading conditions. A fatigue stress-life model was developed that was based on the analyzed data of three specimens. The accelerated fatigue approach has a higher rate of damage accumulations than the standard testing approach. All of the analyzed specimens failed due to an unstable cracking of concrete. The developed fatigue stress-life model fits the upper 95% prediction band of RC beams that were tested under constant amplitude cyclic loading.

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