ESQUEMAS UNIONES metalicas

506

CHAPTER 11

263 kips $ 235 kips #Pn " 235 kips $ Puf " 112 kips OK Compression: K " 0.65 (Figure 5-3) L " 3 in. t 0.5 ry " " " 0.144 in. 212 212 (0.65)(3) KL " " 13.5 r 0.144 Since KL!r ! 25, Fcr " Fy (AISC specification, Section J4.4). #Pn " #Fcr Ag " (0.9)(36)(0.5)(8) " 129 kips $ Puf " 112 kips OK The connection is adequate for the applied moment. Note that the column should also be checked for the need of stiffeners to support the concentrated flange force (see Example 11-8).

11.6 MOMENT CONNECTIONS: BEAMS AND BEAM SPLICES In the previous sections, we considered moment connections as they related to connections used in moment frames. In this section, we will consider moment connections for beam elements supporting mainly gravity loads. The simplest type of moment connection is one in which welds are used to connect one beam to another beam or other element. Figure 11-19a shows a small beam cantilevered from the face of a column. The flanges and web have a groove weld to the column. Note that the flanges are welded to develop the flexural strength and the web is welded to develop shear capacity. Figure 11-19b indicates the welds used at a beam splice. In each of these cases, the welds could be partial or full penetration, or fillet welds, depending on the shear and moment loads at the connection.

a. welded moment connection (stub) Figure 11-19 Basic beam moment connections.

b. welded moment connection (splice)

498

CHAPTER 11

a. FR (fully restrained) connections

L

w

w!L

b. PR (partially restrained) connections Figure 11-12 FR and PR connections.

It is also important to note that some moment connections might provide little or no rotation even though an assumption has been made that an FMC has been used when, in fact, a more rigid connection exists. For this reason, the designer should select a known flexible connection when one is required. Figure 11-12 shows common FR and PR connection types. FR connection behavior would resemble curve 3 in Figure 11-11 and PR connection behavior would resemble curve 2 in Figure 11-11.

11.4 MOMENT CONNECTIONS: PARTIALLY RESTRAINED AND FLEXIBLE As discussed in the previous section, the use of PR connections requires knowledge of the moment versus rotation curve, as well as the load sequence. Since very little data is available for PR connections, most designers will use an FMC, which allows conservative and simplifying assumptions to be made. It is important to note that the use of a PR connection

Special Connections and Details

515

M

a. forces on flanges

b. local flange bending

c. local web buckling

Figure 11-25 Concentrated forces on columns.

a. flange stiffener (one side)

d. web doubler plate and flange stiffeners

b. flange stiffener (full-depth)

e. diagonal stiffeners

Figure 11-26 Column stiffeners for concentrated forces.

c. web doubler plate

f. extended shear plate

498

CHAPTER 11

a. FR (fully restrained) connections

L

w

w!L

b. PR (partially restrained) connections Figure 11-12 FR and PR connections.

It is also important to note that some moment connections might provide little or no rotation even though an assumption has been made that an FMC has been used when, in fact, a more rigid connection exists. For this reason, the designer should select a known flexible connection when one is required. Figure 11-12 shows common FR and PR connection types. FR connection behavior would resemble curve 3 in Figure 11-11 and PR connection behavior would resemble curve 2 in Figure 11-11.

11.4 MOMENT CONNECTIONS: PARTIALLY RESTRAINED AND FLEXIBLE As discussed in the previous section, the use of PR connections requires knowledge of the moment versus rotation curve, as well as the load sequence. Since very little data is available for PR connections, most designers will use an FMC, which allows conservative and simplifying assumptions to be made. It is important to note that the use of a PR connection

Structural steelwork and pipework

351

8.2.2 Stanchion splices Splices in stanchions or columns should be arranged at a position above the adjacent floor level so that the joint, including any splice plates, are well clear of any beam (horizontal member) connection. Splices should never be made on a connection, otherwise the bolts or rivets making the joint would be subjected to double loading. Figure 8.3 shows some typical stanchion splices.

Figure 8.3 Stanchion splices

Structural steelwork and pipework

351

8.2.2 Stanchion splices Splices in stanchions or columns should be arranged at a position above the adjacent floor level so that the joint, including any splice plates, are well clear of any beam (horizontal member) connection. Splices should never be made on a connection, otherwise the bolts or rivets making the joint would be subjected to double loading. Figure 8.3 shows some typical stanchion splices.

Figure 8.3 Stanchion splices

Steel

MATERIALS – MODULES Systems

Fig. 33: Erecting a steel column

1

2

3

Base details for pinned-base columns 1 no tension 2 no tension 3 for low tension, with lower base plate installed beforehand 4 no tension, with hinge Base details for fixed-base columns 5 with threaded bars cast in beforehand 6 with base plate installed beforehand, column welded to base plate on site 7 column in pocket to accommodate large bending moments 8 column in pocket to accommodate large bending moments

4

5

6

7

8

Fig. 34 Source: Swiss Central office for Structural Steelwork (SZS) (ed.), C8 – Konstruktive Details in Stahlhochbau, Zurich, 1973

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