In existing bridge structures, reinforced concrete dapped-end beams/girders (RCDEB) are frequently subjected to service loadings that exceed their design capacity, due to increasing economic and population growth. Dapped-end beams are prone to the accumulation of water due to improper drainage and sealing of the joint, providing favorable conditions for corrosion due to the stagnation of chloride rich water from de-icing salts used on roads. The situation can get even worse when freezing and thawing due to extreme weather conditions is present. Due to difficulties in maintenance of the dapped-end regions, this often leads to the deterioration of the concrete around the recess and bond deterioration, which ultimately results in durability issues. Unfortunately, the performance of RCDEB exhibiting corrosion induced bond deterioration is still not well understood. Hence, experimental, and numerical investigations were conducted to understand better the response of RCDEB subjected to static and cyclic loading, with the presence of bond deterioration. Furthermore, the static capacity of the beam was adopted to consider the variable amplitude cyclic loading at an increment of 15% static capacity for every 20 cycles. The reliability of the numerical examination under the direct-path constitutive models of concrete was extended to the moving load scenario by applying a lower load amplitude than the static capacity. It is shown that the prominent failure mechanisms observed in both static and cyclic tests were diagonal tension and shear. Through numerical investigations, it is also shown that from the damage level developed in the RCDEB under the moving load at a relatively low magnitude, high stresses were found within a relatively short number of cycles, which raises a serious cause for concern.

The current study focuses on the mechanical behavior of fly ash (FA) and wood ash (WA) as cement replacements at increased temperatures. Mortars containing 5, 10, 15, and 20% FA and WA as cement replacement were made and then exposed to temperatures of 200 ℃, 400 ℃, 600 ℃, and 800 ℃, with chosen samples being air-cooled or water-cooled. Curing times for the specimens were 28, 56, 150, and 365 days, respectively. For each age, compressive and tensile strength tests, weight loss at increased temperatures, and scanning electron microscopic examinations were performed. The control sample and FA at 10% replacement without temperature exposure showed a maximum compressive strength of 18 MPa and 1.4 MPa tensile strength at 28 days. Significant moisture was lost at high temperatures, decreasing strength performance. The control sample had a compressive strength of 23.3 MPa after 28 days of exposure to high temperatures under 600 ℃ air-cooled conditions. FA had the maximum value of 18.30 MPa at 15% replacement for 365 days air-cooled at 200 ℃, while WA had the highest strength of 16.40 MPa observed at 200 ℃ for 365 days. The cooling method had a considerable effect on the strength performance, with air-cooled being the better alternative. The study’s findings demonstrate the potential of FA and WA as environmentally friendly cement substitutes that can improve mortars’ durability and heat resistance at elevated temperature. This has significant implications for the building sector, particularly in regions prone to high thermal stress. It encourages the use of environmentally friendly materials without sacrificing structural integrity.