53 Highstrength Bolts Nuts And Washers

For general purposes, A325 and A490 high-strength bolts may be specified. Each type of bolt can be identified by the ASTM designation and the manufacturer's mark on the bolt head and nut (Fig. 5.1). The cost of A490 bolts is 15 to 20% greater than that of A325 bolts.

Job specifications often require that "main connections shall be made with bolts conforming to the Specification for Structural Joints Using ASTM A325 and A490 Bolts.'' This

Steel Robot Made Nuts Bolts

FIGURE 5.1 A325 high-strength structural steel bolt with heavy hex nut; heads are also marked to identify the manufacturer or distributor. Type 1 A325 bolts may additionally be marked with three radial lines 120° apart. Type 3 (weathering steel) bolts are marked as A325 and may also have other distinguishing marks to indicate a weathering grade.

specification, approved by the Research Council on Structural Connections (RCSC) of the Engineering Foundation, establishes bolt, nut, and washer dimensions, minimum fastener tension, and requirements for design and installation.

As indicated in Table 5.1, many sizes of high-strength bolts are available. Most standard connection tables, however, apply primarily to 3/4-and 7/8-in bolts. Shop and erection equipment is generally set up for these sizes, and workers are familiar with them.

Bearing versus Slip-Critical Joints. Connections made with high-strength bolts may be slip-critical (material joined being clamped together by the tension induced in the bolts by tightening them) or bearing-type (material joined being restricted from moving primarily by the bolt shank). In bearing-type connections, bolt threads may be included in or excluded from the shear plane. Different stresses are allowed for each condition. The slip-critical connection is the most expensive, because it requires that the faying surfaces be free of paint (some exceptions are permitted), grease, and oil. Hence this type of connection should be used only where required by the governing design specification, e.g., where it is undesirable to have the bolts slip into bearing or where stress reversal could cause slippage (Art. 5.1). Slip-critical connections, however, have the advantage in building construction that when used in combination with welds, the fasteners and welds may be considered to share the stress (Art. 5.2). Another advantage that sometimes may be useful is that the strength of slip-critical connections is not affected by bearing limitations, as are other types of fasteners.

TABLE 5.1 Thread Lengths for High-Strength Bolts

Bolt diamter, in

Nominal thread, in

Vanish thread, in

Total thread, in

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