Structural Efficiency of Non-Prismatic Hollow Reinforced Concrete Beams Retrofitted with CFRP Sheets

Abstract

Non-prismatic reinforced concrete (RC) beams are widely used for various practical purposes, including enhancing architectural aesthetics and increasing the overall thickness in the support area above the column, which gives high assurance to services that this will not result in the distortion of construction features and can reduce heights. The hollow sections (recess) can also be used for the maintenance of large structural sections and the safe passage of utility lines of water, gas, telecommunications, electricity, etc. They are generally used in large and complex civil engineering works like bridges. This study conducted a numerical study using the commercial finite element software ANSYS version 15 for analysing RC beams, hollow longitudinally sectioned and retrofitted with carbon fibre reinforced polymers (CFRPs), which were subjected to concentrated vertical loads. The numerical analysis results on the simulated beam models were in excellent agreements with the previous experimental test results. This convergence was confirmed by a statistical analysis, which considered the correlation coefficients, individual arithmetic means and standard deviations for all the calculated deflections of the simulated beam models. A proposed numerical simulation model with the hypotheses can be considered suitable for modelling the behaviours of simple supported non-prismatic RC beams under vertical concentrated loads. The numerical results showed that altering the cross-section from solid to hollow could reduce the load carrying capacities of the beams by up to 53% and increase the corresponding deflections by up to 40%, respectively. Using steel pipes for making recesses could enhance the loading capacity by up to 56%, increase the ductility, and reduce the corresponding deflections by up to 30%, respectively. Finally, it was found that bonding the CFRP sheets in the lower middle tensile areas of the hollow beams could improve the resistance and reduce the deformations by up to 27%. The failure patterns for all the numerical models were shear failure. The cylinder compressive strength could be used as a mechanical parameter for modelling and assessing the structural behaviours of the beam models, as its increase could improve the load carrying capacities and reduce the deflections by 30–50%.

Numerical Simulations on the Flexural Behaviours of Reinforced Concrete Girders Strengthened with Bolts

“…Also, several influencing factors have been explored, e.g., sizes and locations of openings, flexural and shear reinforcement ratios, and strengthening of hollow beams with various ways. Many studies have assessed the performances of RC beams with various positions of cavities, e.g., longitudinal openings [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Meanwhile, other studies have investigated the performances of RC beams with openings in webs [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37].…”

“…The reinforcing steel bars of various diameters, as well as the strengthening bolt rods, were represented by the connecting element link 180, which contained two nodes with three degrees of freedom at each node. For the steel plates placed at the supports and loading points, the element solid 185 was used, which had eight nodes with three degrees of freedom at each node [19,21,22].…”

“…The coefficients of open and closed concrete cracks were defined as 0.2 and 0.7, respectively. The stress-strain relationships for all materials were assumed to be completely elasticperfectly plastic [21,22]. The components of the stress-strain curves of concrete were formulated and defined during the simulation by the ANSYS program [38].…”

“…The basic hypothesis considered that the relationship was linear up to 0.85f c , and then became plastic to the concrete strain of 0.003. Also, the self-weights of the models were neglected and considered as homogeneous with a complete full bond between all parts [21,22]. Figures 9 and 10 show the basic steps of numerical modelling by the software ANSYS [38], which included the dimensions of the RC girder models, three-dimensional models, reinforcing rebars, openings (transverse holes), strengthening bolts, steel plates under the loading, and supports.…”

Experimental study of reinforced concrete piles wrapped with fibre reinforced polymer under vertical load

“…The strength of FRP depends on a variety of elements [1][2][3], including fiber composition, orientation, and matrix. FRP has lately acquired favor around the world in civil engineering [4,5], and engineers are confident in its application [2,[6][7][8][9][10][11] due to its many advantages. FRP is commonly utilised to reinforce internal structural parts like beams and slabs.…”