Abstract: The acids and bases in the water cycle can settle on a bridge through condensation or evaporation. Acidic rain and basic rain are corrosive and have detrimental effects on building materials. Since the water cycle is continuous, acidic or basic rain would have a lasting effect on the strength of a bridge. Four bridges were created and three were suspended over hydrochloric acid, sodium hydroxide, and distilled water. For a week, each bridge was isolated under an aquarium tank. The fourth bridge was not tested with any liquid. The efficiency of each bridge was calculated by dividing the supported mass by the mass of the bridge. It was hypothesized that the bridges suspended above the hydrochloric acid and the sodium hydroxide would result in being less efficient than the bridge suspended over distilled water. The hypothesis was negated; The bridges suspended above the acid and base proved to be more efficient. The experiment is significant because the effects of acidic and basic rain should be considered when designing an effective bridge.
Introduction: A bridge’s structure must meet a set of requirements by the American Association of State Highway and Transportation Officials [1]. There are several variables that affect the design of a bridge, such as the dimensions of the cross section and the positioning of cables. Precautions that are taken when bridges are engineered are the management of stress, properly locating cables, knowledge of capacity and limits of deflection and force eccentricity, and widths of cracks and fatigue [1]. The truss bridge is one of the oldest and most efficient types of bridge, with a geometric structure and can be made from metal, wood, or other materials [2]. The material used to make a truss is positioned further from the center- line of the bridge, strengthening the structure. A truss does not require much structural material, making it lighter than the other components of a bridge [2]. Bridges with trusses have limited bending potential due to the location of the truss and the central axis of the bridge [2]. There is more compression strain, rather than tension strain, found in wires, allowing to support more weight than a simple bridge [3].
Although bridges are built to tolerate rigorous conditions, there are still factors that reduce their strength. High levels of SO2 and NOx can be found in the urban environments with bridges. The acidity of these substances can damage a bridge’s structure [4], such as the corrosion and tarnishing of metals and electrical components, the discoloration of paints and organic coatings, the cracking or weakening of rubber or plastics, and the flaking of bricks [5]. The materials used to build a bridge can be negatively affected by acidic rain, which has a pH less than 5. Steel proves to be the strongest material because it can withstand acidic rain longer than the other two metals [6]. All of these factors weaken the strength of the bridge and deteriorate its structure.
Acids have a pH value less than 7, and bases have a pH value greater than 7. There are some strong bases such as sodium hydroxide, potassium hydroxide, and barium hydroxide [7]. Strong bases behave like strong acids because they can be corrosive, while weaker bases are less reactive. A strong base, like sodium hydroxide, has a pH value of 13 [8]. Rain that is basic can have the same impact on bridges as acidic rain.
However, acidic rain is more likely to be found. The effects of acidic and basic rain are implemented through the water cycle. An experiment was conducted to test the effects of acidic and basic rain on bridge strength. It was hypothesized that the bridges suspended over the hydrochloric acid and sodium hydroxide would result in being less efficient than the bridge suspended over distilled water, because acids and bases have the ability to corrode bridge materials, therefore reducing its strength. The experiment is significant because the effects of acidic and basic rain may now be considered when attempting to design an effective bridge.
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