When animals are exposed to softwood shavings the aromatic hydrocarbons are absorbed through the respiratory tract and enter the blood. The acids given off by pine and cedar shavings are very damaging to the respiratory tract. These acids can actually destroy cells that line the lungs and trachea (2).For a complete summary of the respiratory toxicity of pine shavings, go to. .hen animals are exposed to softwood shavings the aromatic hydrocarbons are absorbed through the respiratory tract and enter the blood. The acids given off by pine and cedar shavings are very damaging to the respiratory tract. These acids can actually destroy cells that line the lungs and trachea (2).
Bowstring trusses are made with a curved top chord and a straight bottom chord. The top chords were originally made with multiple leaf chords where the curvature was cut into the solid sawn chord members.A second style of bowstring truss used glued-laminated chords. The top chord in these trusses was curved in the laminating process.While these trusses have carried the roof load for decades, it is not uncommon to receive calls regarding broken trusses following a heavy snow event.he top chords were originally made with multiple leaf chords where the curvature was cut into the solid sawn chord members. A second style of bowstring truss used glued-laminated chords. The top chord in these trusses was curved in the laminating process.
All bridges have 4 main characteristics: form, span, material, and travel surface in relation to the structure. A truss bridge is one form that a bridge can take and there are at least 30 different kinds of truss bridges, including the Warren, Pratt, and Howe designs among others. Truss bridges can have any of the 3 span types including simple, continuous, or cantilever. They are often made of metal, specifically steel or iron, but can also be made of wood (such as covered bridges). The travel surface of a truss bridge may be called deck, pony, or through truss. A deck truss allows traffic to travel on top of the structure whereas a pony truss allows traffic to travel between two superstructures that do not connect at the top. Finally, a through truss is similar to pony truss, except the superstructures connect overhead. What makes a truss bridge historic?