Behavior of RC Hollow Beam and T-Flange Beam Strengthened with Stainless Steel Wire Mesh (SSWM) Under Pure Torsion

Abstract

Concrete structure experience a convoluted variety of internal stress and strain, when it is subjected to external loading. Axial Force, Shear Force, Bending Moment and Torsion are four key internal action. Generally Reinforced Concrete (RC) elements are designed for axial force, shear force and bending moment. In many cases, such as helical stair, beam supporting cantilever slab, floor joists on one side, curved bridge deck subjected to eccentric load, electric pole subjected to loads from wires on one side, beams supporting lateral over hanging projections are subjected to significant torsional loading in addition to flexure and shear forces. To strengthen such structural elements in torsion, various type of repairing material like Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) are used. The failure of such FRP strengthened structural element are observed either brittle or debonding of FRP. Thus it is necessary to find an alternative material to FRP, which is more ductile and have better bond characteristic. Locally available Stainless Steel Wire Mesh (SSWM) is considered for strengthening of structural element. Research in area of strengthening of RC members using SSWM subjected to pure torsion is not attempted in greater detail. The major objective of the present study is to improve the torsional resistance of RC hollow beams and T beams with different configuration of SSWM. For this study experimental investigation is conducted on the RC Hollow beams and T beams strengthened using different SSWM wrapping pattern. A total of fourteen beams with eight RC Hollow beam specimen and six T beam specimen with M25 grade of concrete are prepared. The cross sectional dimensions of hollow beam specimens are 150 mm × 150 mm with 50 mm × 50 mm square hollow at the center and reinforced with 4-10 mm diameter longitudinal bars and 2 leg 8 mm diameter stirrups at 150 mm c/c and the length of all the specimens is kept 1.3 m. The cross section dimension of T beam specimens is 225 mm wide and 50 mm depth flange and 150 depth and 100 wide web with 4-10 diameter longitudinal bars at top and 2-10 diameter longitudinal bar at bottom and 2 leg 8 mm diameter stirrups at 150 mm c/c consider for the study. Out of eight RC Hollow beams two RC hollow beams are designated as control specimens and six beams are strengthened using three different wrapping configuration. Out of six T beam specimen two beams are designated as control specimens and four beams are strengthened using two different wrapping configuration of SSWM. SSWM wrapping configurations considered for RC Hollow beams under pure torsion are corner and strip wrapping at the location of stirrups (HCO&100SAS), corner and strip wrapping in between stirrups (HCO&100SIS), and full wrapping (HFW). SSWM wrapping configurations considered for RC T beams under pure torsion are corner and strip wrapping at the location of stirrups (TCO&100SAS) and strip wrapping above stirrups (T&100SAS). These specimen are tested for pure torsional loading in torsional loading frame. The torsional moment and twist at first crack and at an ultimate stages as well as torque-twist behavior of SSWM strengthened specimens are compared with controlled specimens. Failure pattern and strain at different location on beams are observed. The specimen with Hollow Full Wrapping (HFW) exhibited 127.2% increase in cracking torque and 136% increase in ultimate torque compared to control beam. For T beam with corner and strip wrapping at the location of stirrups (TCO&100SAS) exhibited 86.1% increase in cracking torque and 68.1% increase in ultimate torque compared to control beam. The numerical study of SSWM strengthened RC beam under pure torsion is carried out using finite element based software ABAQUS. Results of nonlinear finite element analysis are found in good agreement with experimental results.