scholarly journals Strengthening of steel member using unbonded CFRP laminates

2020 ◽  
Vol 156 ◽  
pp. 05025
Author(s):  
Fengky Satria Yoresta ◽  
Ryotaro Maruta ◽  
Genki Mieda ◽  
Yukihiro Matsumoto
Keyword(s):  
Steel Structures ◽  
Small Scale ◽  
Great Success ◽  
Adhesively Bonded ◽  
Engineering Structures ◽  
Rc Structures ◽  
Cfrp Laminates ◽  
Cfrp Composites ◽  
Steel Members ◽  
Load Carrying

Excellent mechanical and physical properties make carbon fiber reinforced polymer (CFRP) the best options for repair, retrofit, and rehabilitation of civil engineering structures. A great success on application of this material in reinforced concrete (RC) structures has attracted much attention from many researchers to develop it in combination with steel. The number of studies on the use of CFRP composites for strengthening steel structures has still been limited and needs to be more explored. To date, the research in this field has mainly focused on CFRP strengthening with adhesively-bonded technique. This paper reports an experimental study to investigate the performance of slender axial compression steel members partially strengthened with unbonded CFRP composites. The requirements for stiffener to prevent buckling occurred in stiffening region are derived from structural equilibrium conditions. Vacuum-assisted Resin Transfer Molding (VaRTM) method is adopted to form CFRP laminates in the strengthened specimens. Totally eight small scale specimens are tested, and it is clear from the test that improvement in load-carrying capacity can be achieved by using CFRP.

Flexural strengthening of pre-cracked RC slabs with prestressed NSM CFRP laminates and evaluation of strain loss

2021 ◽  
pp. 136943322110105
Author(s):  
M.R. Mostakhdemin Hosseini ◽  
Salvador J.E. Dias ◽  
Joaquim A.O. Barros
Keyword(s):  
Carrying Capacity ◽  
Load Carrying Capacity ◽  
Limit States ◽  
Transfer Length ◽  
Rc Structures ◽  
Cracked Concrete ◽  
Flexural Strengthening ◽  
Cfrp Laminates ◽  
Load Carrying ◽  
Rc Slabs

The strengthening intervention of RC structures often involves already cracked concrete. To evaluate the effect of the level of damage prior to the strengthening (pre-cracks) on the behavior of the flexurally strengthened RC slabs with prestressed NSM CFRP laminates, an experimental research was carried out. Two pre-cracking levels of damage were analyzed and, for each one, three levels of prestress were tested (0%, 20% and 40%). The obtained results showed that the strengthening of damaged RC slabs with prestressed NSM CFRP laminates results in a significant increase on the load carrying capacity at serviceability limit states. Pre-cracked RC slabs strengthened with prestressed NSM CFRP laminates presented a load carrying capacity almost similar to the corresponding uncracked strengthened slabs. To determine the effective prestress level in CFRP laminates, the variation of strain over the length of the CFRP and over time was experimentally recorded. The prestress transfer length was also evaluated. The experimental results revealed that the transfer length of CFRP laminates was less than 150 mm, and the maximum value of strain loss out of transfer length (around 14%) was measured close to the cracked section of the damaged RC slabs. Significant part of strain loss in CFRP laminates occurred during 24 h after releasing the prestress load.

scholarly journals Strengthening of steel structures with fatigue cracks using adhesively bonded non-prestressed and prestressed CFRP lamellas

2019 ◽  
Author(s):  
Yvonne Ciupack ◽  
Lukas Ledecky ◽  
Yann Kasper ◽  
Achim Geßler ◽  
Matthias Albiez ◽  
...  
Keyword(s):  
Fatigue Cracks ◽  
Crack Tip ◽  
Steel Structures ◽  
Positive Influence ◽  
Fatigue Tests ◽  
Small Scale ◽  
Adhesively Bonded ◽  
Repair Welding ◽  
Reinforcement Measures ◽  
Adhesive Materials

In comparison to classic strengthening methods of fatigue-damaged steel structures, adhesively bonded CFRP lamellas show several advantages. Compared to bolted reinforcement measures and the drilling of the crack tip, crosssectional weakening is avoided. Heat-induced, negatively acting residual stresses and distortions, usually occurring during repair welding, can also be excluded. Therefore, the effectiveness of adhesively bonded CFRP lamellas to enhance the remaining lifetime of fatigue damaged steel structures is examined in a German research project. Selected results are presented in this paper. To characterize the steel, CFRP and adhesive materials, different tests on small scale specimens are carried out. With the help of fatigue tests on CT-samples the remaining fatigue lifetimes of specimens strengthened with adhesively bonded CFRP lamellas is compared to the remaining lifetimes of specimens strengthened by established methods such as drilling the crack tip and repair welding. Based on the evaluation of the crack propagation after the rehabilitation measures, the great potential of adhesively bonded CFRP reinforcements can be deduced. By prestressing the lamellas, the remaining lifetime can generally be increased further. The combination of adhesively bonded CFRP lamellas together with established rehabilitation methods shows a particularly high positive influence on the remaining lifetime of the CT-specimens.

scholarly journals Small Scale Experiments to Assess the Bearing Capacity of Footings on the Sloped Surface

Eng ◽  
2020 ◽  
Vol 1 (2) ◽  
pp. 240-248
Author(s):  
Mohammad Nurul Islam
Keyword(s):  
Bearing Capacity ◽  
Carrying Capacity ◽  
Maximum Load ◽  
Scale Model ◽  
Small Scale ◽  
Load Carrying Capacity ◽  
Engineering Structures ◽  
Load Carrying ◽  
Limiting Condition ◽  
The Impact

Construction of civil engineering structures on or next to a slope requires special attention to meet the bearing capacity requirements of soils. In this paper, to address such a challenge, we present laboratory-scale model tests to investigate the effect of footing shape on the sloped surface. The model comprised of a well stiffened mild steel box with three sides fixed and one side open. We considered both with and without reinforcement to assess the effectiveness of reinforcement on the sloped surface. Also, we used three types of footing (i.e., square, rectangular, and circular) to measure the footing shape effects. We considered three different slope angles to evaluate the impact of the sloped face corresponding to the applied load and the reinforcement application. We obtained that the maximum load carrying capacity in the square footing was higher than the rectangular and the circular footing for both the reinforced and the unreinforced soil. With the increase of geo-reinforcement in all three footing shapes and three sloped angles, the load carrying capacity increased. We also noticed a limiting condition in geo-reinforcement placement effectiveness. And we found that with the increase of slope, the load bearing capacity decreased. For a steep slope, the geo-reinforcement placement and the footing shape selection is crucial in achieving the external load sustainability, which we addressed herein.

scholarly journals Experimental Investigation on the Buckling Capacity of Angle Steel Strengthened at Both Legs Using VaRTM-Processed Unbonded CFRP Laminates

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2216
Author(s):  
Fengky Satria Yoresta ◽  
Phan Viet Nhut ◽  
Daiki Nakamoto ◽  
Yukihiro Matsumoto
Keyword(s):  
Failure Modes ◽  
Slenderness Ratio ◽  
Plastic Hinge ◽  
Steel Structures ◽  
Strengthening Effect ◽  
Growth Trend ◽  
Promising Alternative ◽  
Cfrp Laminates ◽  
Steel Members ◽  
Angle Steel

Strengthening steel structures by using carbon fiber reinforced polymer (CFRP) laminates showed a growth trend in the last several years. A similar strengthening technique, known as adhesive bonding, has also been adopted. This paper presented a promising alternative for strengthening steel members against buckling by using vacuum-assisted resin transfer molding (VaRTM)-processed unbonded CFRP laminates. A total of thirteen slender angle steel members (L65x6), including two control specimens, were prepared and experimentally tested. The specimens were strengthened only at both legs and were allowed to buckle on their weak axes. The test showed that the unbonded CFRP strengthening successfully increased the buckling capacity of the angle steel. The strengthening effect ranged from 7.12% to 69.13%, depending on various parameters (i.e., number of CFRP layers, CFRP length, and angle steel’s slenderness ratio). Flexural stiffness of the CFRP governed the failure modes in terms of location of plastic hinge and direction of buckling curvature.

scholarly journals Failure Analysis of Locally Damaged Slender Steel Bars Strengthened with CFRP Composites: Experiments, Theory, and Computational Simulations

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Bin Li ◽  
Hua Luo ◽  
Xianqiao Wang
Keyword(s):  
Steel Structures ◽  
Critical Force ◽  
Damage Degree ◽  
Reinforced Polymer ◽  
Cfrp Composites ◽  
Load Carrying ◽  
Steel Bars ◽  
Reinforced Steel ◽  
Buckling Failure ◽  
The Stability

Carbon fiber-reinforced polymer/plastic (CFRP) composites bear attractive performance in resistance to tension, fatigue, and corrosion and, thus, have been recognized as a promising candidate for repairing and strengthening steel structures in engineering. Here, we combine experiments, theory, and numerical simulations to elucidate how the location and degree of local damages, as well as the reinforcement mode, affect the stability of slender steel bars repaired by CFRP. The deformation, failure mode, and the critical buckling load of the reinforced steel flat bars subjected to axial compressive forces are experimentally evaluated. We show that all tested specimens exhibit buckling failure, before which the damaged steel bars have entered an elastic-plastic stage. Our theoretical analysis provides an upper bound for the critical force, which is sensitive not only to the damage degree but also to the damage location. Damage locating at the middle regime of the specimens will remarkably reduce stability of the steel bars, but an optimized combination of wrapping method and number of CFRP layers can restore and even enhance the stability of the damaged structures beyond the undamaged counterparts. Finite element simulations are implemented in the same scenario as experiments, showing good agreement with our measurements. Our findings suggest that, to improve the stability of the damaged steel bars reinforced by CFRP, the load carrying capacity of the the bars, the number of CFRP layers, and the construction convenience should be taken into account.

Effectiveness of CFRP composites on compression flange of structural I-beam

2019 ◽  
Vol 17 (4) ◽  
pp. 782-792
Author(s):  
Prashant Rangrao Jagtap ◽  
Sachin M. Pore
Keyword(s):  
Carrying Capacity ◽  
Steel Structures ◽  
Local Failure ◽  
Elastic Behavior ◽  
Steel Beams ◽  
Load Carrying Capacity ◽  
Content Type ◽  
Cfrp Laminates ◽  
Load Carrying ◽  
Strengthened Beam

Purpose This study aims to use carbon fiber-reinforced polymer (CFRP) laminates to strengthen the compression flange of structural I-beam so as to avoid local failure of compression flange and to take a load to its full capacity. Light weight beam (LB) 100 at 5.1 kg/m and LB 115 at 8.1 kg/m are used for this purpose. The compression flange of a beam is well prepared to ensure a rust-free surface so as to achieve proper bonding between the flange and fiber sheet to avoid de-bonding at the time of testing. A flange of the beam is strengthened using CFRP sheets applied to it with the help of adhesive. The beam with CFRP is cured in air for 48 h before testing. Experiments are performed in a loading frame of 100 T capacity. Results show that the load carrying capacity of the strengthened beam increased by 25-30 per cent compared to the control beam (non-strengthened), and the local failure of the compression flange due to the applied load is totally avoided. The elastic behavior of the strengthened beam is also increased compared to the non-strengthened beam, which gives a higher yield point. Design/methodology/approach Different methods exist for strengthening various structures. Use of CFRP appears to be an excellent solution. Vast research has been conducted on the use of CFRP for strengthening and retrofitting of steel structures. The load carrying capacities of steel beams can be increased by strengthening their compression flange by using CFRP and avoiding the local failure of beams at early stages. Findings The load carrying capacity of a beam strengthened with CFRP increased by 25-30 per cent compared to the non-strengthened beam. In addition, the elastic behavior of the strengthened beam is also improved. Originality/value The compression flange of the steel beam is strengthened using different layers of CFRP strips to avoid the local failure, and its deflection is observed using linear variable deformation transducer.

Model studies of the elastic buckling of a stiffened plate

1976 ◽  
Vol 11 (3) ◽  
pp. 137-143 ◽  
Author(s):  
J D Tulk ◽  
A C Walker
Keyword(s):  
Strain Range ◽  
Scale Model ◽  
Small Scale ◽  
Elastic Buckling ◽  
Engineering Structures ◽  
Model Studies ◽  
Plate Elements ◽  
Scale Models ◽  
Load Carrying ◽  
Post Buckling

The paper reports on an experimental investigation of the elastic buckling behaviour of a small-scale model of a stiffened plane. The model was made from epoxy resin to allow large buckle deflections within the elastic strain range. These tests are part of a programme aimed at proving the feasibility of using small-scale models to elucidate the behaviour of large stiffened plates such as are used in marine or civil engineering structures. It is shown for the geometry examined here that, although the component stringer and plate elements of the panel would individually exhibit stable post-buckling, together they interact to give unstable behaviour. The effects of imperfections are systematically studied and it is shown that the load-carrying capacity of such a structural configuration is sensitive to initial geometric deformations. A simple mathematical analysis is developed which indicates the parameters governing the physical problem and which could form the basis for future rational studies of the level of imperfections at which sensitivity may be considered slight.

scholarly journals Elastic-plastic load-carrying capacity of steel members

2018 ◽  
Vol 146 ◽  
pp. 02001
Author(s):  
Pavol Juhas
Keyword(s):  
Carrying Capacity ◽  
Local Stability ◽  
Steel Structures ◽  
Plastic Behavior ◽  
Load Carrying Capacity ◽  
Analysis And Design ◽  
Elastic Plastic ◽  
Steel Members ◽  
Load Carrying ◽  
Plastic Analysis

The load-carrying capacity of steel structures and members subjected mostly to bending depends in large measure on local stability of their compressed flanges and bending webs in decided cross-sections and areas. Depending on local stability, the elastic or plastic, eventually the elastic-plastic analysis and design can be applied. The actual standards for design of steel structures contain relatively detailed rules for elastic analysis by the elastic theory and for plastic analysis by the plastic theory. The elastic-plastic analysis and design of steel members are meanwhile still problematic from theory, standard and application point of view. The real elastic-plastic behavior of the steel members is complicated strength and stability problem. Therefore, the representative experimental knowledge and results about the real elastic-plastic behavior and mechanisms of failure of the steel members have been very important from the scientific and applied aspects. The author of paper realized in previous time the wide experimental research within the range of this intention. The paper contains selected knowledge and results of the previous experimental-theoretical investigation of the elastic-plastic local stability of the steel members subjected mostly to bending. The adequate slenderness – strain relation and methodology for practical calculation of the elastic-plastic bending load-carrying capacity of the steel cross-sections and members are presented in the paper.

scholarly journals Flexural Performance of RC Beams Strengthened with Externally-Side Bonded Reinforcement (E-SBR) Technique Using CFRP Composites

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2809
Author(s):  
Md. Akter Hosen ◽  
Fadi Althoey ◽  
Mohd Zamin Jumaat ◽  
U. Johnson Alengaram ◽  
N. H. Ramli Sulong
Keyword(s):  
Absorption Capacity ◽  
Experimental Program ◽  
Rc Beams ◽  
Rc Structures ◽  
Functional Changes ◽  
Flexural Strengthening ◽  
Cfrp Laminates ◽  
Flexural Performance ◽  
Design Loads ◽  
Predicted Values

Reinforced concrete (RC) structures necessitate strengthening for various reasons. These include ageing, deterioration of materials due to environmental effects, trivial initial design and construction, deficiency of maintenance, the advancement of design loads, and functional changes. RC structures strengthening with the carbon fiber reinforced polymer (CFRP) has been used extensively during the last few decades due to their advantages over steel reinforcement. This paper introduces an experimental approach for flexural strengthening of RC beams with Externally-Side Bonded Reinforcement (E-SBR) using CFRP fabrics. The experimental program comprises eight full-scale RC beams tested under a four-point flexural test up to failure. The parameters investigated include the main tensile steel reinforcing ratio and the width of CFRP fabrics. The experimental outcomes show that an increase in the tensile reinforcement ratio and width of the CFRP laminates enhanced the first cracking and ultimate load-bearing capacities of the strengthened beams up to 141 and 174%, respectively, compared to the control beam. The strengthened RC beams exhibited superior energy absorption capacity, stiffness, and ductile response. The comparison of the experimental and predicted values shows that these two are in good agreement.

Causes of Structural Failures with Steel Structures

2017 ◽  
Author(s):  
Goran Alpsten
Keyword(s):  
Structural Damage ◽  
Human Error ◽  
Structural Reliability ◽  
Steel Structures ◽  
Fatigue Loading ◽  
Structural Instability ◽  
Human Errors ◽  
Collapse Mode ◽  
Load Carrying ◽  
Structural Failures

This paper is based on the experience from investigating over 400 structural collapses, incidents and serious structural damage cases with steel structures which have occurred over the past four centuries. The cause of the failures is most often a gross human error rather than a combination of “normal” variations in parameters affecting the load-carrying capacity, as considered in normal design procedures and structural reliability analyses. Human errors in execution are more prevalent as cause for the failures than errors in the design process, and the construction phase appears particularly prone to human errors. For normal steel structures with quasi-static (non-fatigue) loading, various structural instability phenomena have been observed to be the main collapse mode. An important observation is that welds are not as critical a cause of structural steel failures for statically loaded steel structures as implicitly understood in current regulations and rules for design and execution criteria.

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