075

* Based on plates 3/4 X 96 X 240 in. Price factors for shapes tend to be lower. A852 and A514 steels are not available in shapes.

* Based on plates 3/4 X 96 X 240 in. Price factors for shapes tend to be lower. A852 and A514 steels are not available in shapes.

section modulus. Their relative weight W2/W1 and relative cost C2/C1 are influenced by the web depth-to-thickness ratio d/1. For example, if the two members have the same d/1 values, such as a maximum value imposed by the manufacturing process for rolled beams, the relationships are

If each of the two members has the maximum d/t value that precludes elastic web buckling, a condition of interest in designing fabricated plate girders, the relationships are

Table 1.5 shows relative weights and relative material costs for several structural steels. These values were calculated from Eqs. (1.3) to (1.6) and the relative price factors given in Table 1.4, with A36 steel as the base. The table shows the decrease in relative weight with increase in yield stress. The relative material costs show that when bending members are thus compared for girders, the cost of A572 grade 50 steel is lower than that of A36 steel, and the cost of other steels is higher. For rolled beams, all the HSLA steels have marginally lower relative costs, and A572 grade 50 has the lowest cost.

Because the comparison is valid only for members subjected to the same bending moment, it does not indicate the relative costs for girders over long spans where the weight of the member may be a significant part of the loading. Under such conditions, the relative material costs of the stronger steels decrease from those shown in the table because of the reduction in girder weights. Also, significant economies can sometimes be realized by the use of hybrid girders, that is, girders having a lower-yield-stress material for the web than for the flange. HSLA steels, such as A572 grade 50, are often more economical for composite beams in

TABLE 1.5 Relative Material Cost for Beams

Plate girders Rolled beams

Relative Relative Relative Relative Steel weight material cost weight material cost
Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

Get My Free Ebook


Post a comment