Torsional Behaviour of RC Flanged Beam and Hollow Beam Strengthened with SSWM

Abstract

When a concrete structure is loaded from the outside, it undergoes a complicated set of internal stresses and strains. Axial force, shear force, bending moment, and torsion are the four primary internal actions. Axial force, shear force, and bending moment are all designed into Reinforced Concrete (RC) members. Significant torsional loading, in addition to flexure and shear forces, is applied in many cases, such as a helical stair, a beam supporting a cantilever slab, floor joists on one side, a curved bridge deck subjected to eccentric load, an electric pole subjected to loads from wires on one side, and beams supporting lateral overhanging projections. To strengthen such structural sections under torsion, various types of mending materials, such as Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP), are used. Brittleness or FRP de-bonding characteristic the failure of such FRP-enhanced structural parts. As a result, a need of new material that is more ductile and has superior bonding properties. The application of locally available Stainless Steel Wire Mesh (SSWM) for structural element reinforcing is being investigated in present study. The application of SSWM to reinforce RC hollow & flanged beams subjected to pure torsion have not received much attention. The main purpose of this study is to use various SSWM configurations to improve the torsional resistance of RC hollow beams and flanged beams. In the present study total of 12 beams are prepared, including 6 RC Hollow beam specimens and 6 flanged beam specimens of M25 grade of concrete. 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 flanged beam specimens is 225 mm wide and 50 mm deep flange and 150 mm deep and 100 mm wide web with 4-10 mm diameter longitudinal bars at top and 2-10 mm diameter longitudinal bar at bottom with 2 leg 8 mm diameter stirrups at 150 mm c/c are considered for the present study. Out of 6 RC Hollow beams two RC hollow beams are designated as control specimens and 4 beams are strengthened using two different wrapping configuration. SSWM wrapping configurations considered for RC Hollow Beam With Diagonal of SSWM Strip At 45° Wrapping (HD45W) and Hollow Beam With Corner and Diagonal SSWM Strip Wrapping (HCO&DS). SSWM wrapping configurations considered for flanged beam under pure torsion are T-Beam with 100mm Strip Wrapping In-between Stirrups (T100SIS) and T-Beam With Corner & 100mm strip wrapping In-between Stirrups (TCO&100SIS). These specimens are tested under pure torsional loading in torsional loading frame. The torsional moment and corresponding twist at first crack and at an ultimate stages as well as torque-twist behavior of SSWM strengthened beam specimens are compared with control beam specimens. Based on investigations and failure patterns it is observed that RC beam wrapped with different configuration by SSWM wrapping exhibited significant increase in cracking and ultimate torsional strength as well as corresponding twist compared to control specimens. Hollow Beam With Corner and Diagonal SSWM Strip Wrapping (HCO&DS) is most efficient in enhancement of the torsional resistance of RC Hollow beams compare to other SSWM wrapping configuration when beams are tested under pure torsion. T-Beam With Corner & 100mm strip wrapping In-between Stirrups (TCO&100SIS) is most efficient in enhancement of the torsional resistance of flanged beams compared to other SSWM wrapping configuration when beams are tested under pure torsion.