The impact of the welded wire mesh as internal reinforcement on the flexural behavior of RC beams exposed to elevated temperature

Abstract

This paper investigates the efficiency of using the welded wire mesh (WWM) as internal reinforcement to regain the structural performance of heat-damaged reinforced concrete (RC) beams to achieve a 28-days average compressive cylinder strength of 40 MPa. These (150 × 200 × 1100 mm3) were prepared using ordinary-strength concrete, cured for 28 days in moist burlap, and heat-damaged at temperatures (23–750 Celsius degree (°C)) two hours after internal strengthening. The mechanical response of control and strengthened beams was evaluated under a four-point loading test setup. The reduction percentage is ranged from 7% to 44 %, 2% to 20%,2%–20%, 2 %–31 %, 17 %–65 %, 4 %–36 %, 17 %–40 %, and 17 %–65 % for 250 °C to 750 °C, respectively, in terms of the ultimate load, the ultimate deflection, the elastic stiffness, the energy absorption, the deflection ductility index, the energy ductility index, and the performance factor, respectively. Furthermore, cracking and failure modes were monitored and characterized during the loading process. The results show that exposing reinforced concrete beams (to the above-elevated temperatures) creates intense cracking on their surface and degrades their mechanical performance. The proposed schemes using internal WWM help avert/ reduce the tendency of concrete cover separation. Hence, the overall mechanical performance of heat-damaged beams is noticeably improved. The efficiency of the number of WWM layers is enhanced with further heat damage in which the enhancement percentage is ranged from 15 % to 97 %, 47% to 129%, 12% to 92%, 81 %–415 %, 43 %–123 %, 81 %–415 %, and 69 %–352 % for beams strengthened internally one to five layers of WWM for the ultimate load, the ultimate deflection, the elastic stiffness, the energy absorption, the deflection ductility index, the energy ductility index, and the performance factor, respectively. Finally, this study indicated that using WWM as internal reinforcement represents an acceptable technique for enhancing the loading capacity of flexural-deficient reinforced and thermally damaged RC beams than internal carbon fiber reinforced polymer (CFRP) after considering the profitability index issue. The contribution of one layer of FRP is equivalent to 5.00, 1.31, 1.52, 1.70, 1.10, 1.70, 1.68, and 0.50 times the contribution of one layer of WWM in terms of the ultimate load, the ultimate deflection, the elastic stiffness, the energy absorption, the deflection ductility index, the energy ductility index, the performance factor, and profitability index. Through demonstrating an outstanding structural performance with significant enhancement in the ultimate strength, ultimate deflection, stiffness, and energy absorption, the findings of this paper strongly attest that WWM can be effectively utilized as internal flexural reinforcement in reinforced concrete beams exposed to elevated temperatures. New guidelines are developed for predicting the damage level and flexural strength of heated damaged RC beams internally reinforced with WWM and considering the influence of the number of WWM layers and elevated temperature.