Strengthening of steel hollow pipe sections subjected to transverse loads using CFRP

Kambiz Narmashiri,Ghadir Mehramiz 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.60 No.1

Nowadays using Carbon Fiber Reinforced Polymer (CFRP) has been expanded in strengthening steel structures. Given that few studies have taken about strengthening of steel hollow pipe sections using CFRP, in present study, the effects of CFRP sheets using two layers as well as in combination with additional reinforcing strips has been assessment. Strengthening of five specimens was carried out in laboratory tests. As well as numerical simulation was performed for all specimens by Finite Element Method (FEM) using ABAQUS software and high correlation between the results of numerical models with experimental data indicate the power of FEM in this field. The results of both laboratory and simulated specimens showed that load-bearing capacity of circular cross-sections can be significantly increased using CFRP retrofitting technique. Also, application of additional CFRP reinforcing strips and layers caused more strength for the strengthened specimens.

Effects of deficiency location on CFRP strengthening of steel CHS short columns

Razieh Shahabi,Kambiz Narmashiri 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.3

Structures may need retrofitting as a result of design and calculation errors, lack of proper implementation, post-construction change in use, damages due to accidental loads, corrosion and changes introduced in new editions of construction codes. Retrofitting helps to compensate weakness and increase the service life. Fiber Reinforced Polymer (FRP) is a modern material for retrofitting steel elements. This study aims to investigate the effect of deficiency location on the axial behavior of compressive elements of Circular Hollow Section (CHS) steel short columns. The deficiencies located vertically or horizontally at the middle or bottom of the element. A total of 43 control column and those with deficiencies were investigated in the ABAQUS software. Only 9 of them tested in the laboratory. The results indicated that the deficiencies had a significant effect on the increase in axial deformation, rupture in deficiency zone (local buckling), and decrease in ductility and bearing capacity. The damages of steel columns were responsible for resistance and stiffness drop at deficiency zone. Horizontal deficiency at the middle and vertical deficiency at the bottom of the steel columns were found to be the most critical. Using Carbon Fiber Reinforced Polymer (CFRP) as the most effective material in retrofitting the damaged columns, significantly helped the increase in resistance and rupture control around the deficiency zone.

Experimental and numerical investigation of strengthened deficient steel SHS columns under axial compressive loads

Shahraki, Mehdi,Sohrabi, Mohammad Reza,Azizyan, Gholam Reza,Narmashiri, Kambiz Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.2

In past years, numerous problems have vexed engineers with regard to buckling, corrosion, bending, and overloading in damaged steel structures. This article sets out to investigate the possible effects of carbon fiber reinforced polymer (CFRP) and steel plates for retrofitting deficient steel square hollow section (SHS) columns. The effects of axial loading, stiffness, axial displacement, the position and shape of deficient region on the length of steel SHS columns, and slenderness ratio are examined through a detailed parametric study. A total of 14 specimens was tested for failure under axial compression in a laboratory and simulated using finite element (FE) analysis based on a numerical approach. The results indicate that the application of CFRP sheets and steel plates also caused a reduction in stress in the damaged region and prevented or retarded local deformation around the deficiency. The findings showed that a deficiency leads to reduced load-carrying capacity of steel SHS columns and the retrofitting method is responsible for the increase in the load-bearing capacity of the steel columns. Finally, this research showed that the CFRP performed better than steel plates in compensating the axial force caused by the cross-section reduction due to the problems associated with the use of steel plates, such as in welding, increased weight, thermal stress around the welding location, and the possibility of creating another deficiency by welding.

Experimental and numerical investigation of strengthened deficient steel SHS columns under axial compressive loads

Mehdi Shahraki,Mohammad Reza Sohrabi,Gholam Reza Azizyan,Kambiz Narmashiri 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.2

In past years, numerous problems have vexed engineers with regard to buckling, corrosion, bending, and over-loading in damaged steel structures. This article sets out to investigate the possible effects of carbon fiber reinforced polymer (CFRP) and steel plates for retrofitting deficient steel square hollow section (SHS) columns. The effects of axial loading, stiffness, axial displacement, the position and shape of deficient region on the length of steel SHS columns, and slenderness ratio are examined through a detailed parametric study. A total of 14 specimens was tested for failure under axial compression in a laboratory and simulated using finite element (FE) analysis based on a numerical approach. The results indicate that the application of CFRP sheets and steel plates also caused a reduction in stress in the damaged region and prevented or retarded local deformation around the deficiency. The findings showed that a deficiency leads to reduced load-carrying capacity of steel SHS columns and the retrofitting method is responsible for the increase in the load-bearing capacity of the steel columns. Finally, this research showed that the CFRP performed better than steel plates in compensating the axial force caused by the cross-section reduction due to the problems associated with the use of steel plates, such as in welding, increased weight, thermal stress around the welding location, and the possibility of creating another deficiency by welding.

Experimental Investigation on Fatigue Behavior of Wide-Flange Steel I-Beams Strengthened Using Diff erent CFRP End Cutting Shapes

Mohamed Kamruzzaman,MohdZamin Jumaat,N.H. Ramli Sulong,Kambiz Narmashiri,Khaled Ghaedi,Md. Akter Hosen 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3

In recent decades, the application of carbon fi bre-reinforced polymer (CFRP) composites for strengthening structural elements has become an effi cient option to meet the increased cyclic loads, or repair due to fatigue cracking. The premature failure due to end-debonding is a key limitation to achieve high fatigue performance of strengthened steel beams with externally bonded CFRP plates. The objective of this study is to explore the reinforcing techniques using the CFRP in-plane end cutting shapes and the triangular spew fi llet of adhesive at the tips of the plate to care for fatigue damaged of wide-fl ange steel I-beams due to end-debonding. Four in-plane CFRP end cutting shapes were chosen, namely: rectangular, semi-elliptical, semi-circular and trapezoidal. The application of the trapezoidal end shape was found to be the best confi guration for delaying the end-debonding failure mode and high fatigue life compared to the other CFRP in-plane end cutting shapes. Applying the triangular spew fi llets of adhesive signifi cantly increased the end-debonding and steel beam fracture initiation life of the strengthened beams.

Strengthening of deficient steel SHS columns under axial compressive loads using CFRP

Mehdi Shahraki,Mohammad Reza Sohrabi,Gholamreza Azizyan,Kambiz Narmashiri 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.1

Numerous problems have always vexed engineers with buckling, corrosion, bending, and over-loading in damaged steel structures. The present study aims to study the possible effects of Carbon Fiber Reinforced Polymer (CFRP) for strengthening deficient Steel Square Hollow Section (SHS) columns. To this end, the effects of axial loading, stiffness values, axial displacement, the shape of deficient on the length of steel SHS columns were evaluated based on a detailed parametric study. Ten specimens were tested to failure under axial compression in laboratory and simulated by using Finite Element (FE) analysis based on numerical approach. The results indicated that the application of CFRP sheets resulted in reducing stress in the damage location and preventing or retarding local deformation around the deficiency location appropriately. In addition, the retrofitting method could increase loading the carrying capacity of specimens.