Structures Detailing Manual | Jan 2008
14 - Structural Steel |

# 14 - Structural Steel

## 14.1 General Detailing (01/05) Jan 2005 Added reference to AASHTO/NSBA Documents G 1.1-2000 & G 1.2-2003; renumbered sections.

### 14.1.1 Design Drawings

A. See Structures Preferred Details for suggested details. Refer to these details and use them as a guide in the preparation of specific details. The designer may select structural members other than those shown.

B. Refer to the AASHTO/NSBA Steel Collaboration Document G 1.2-2003 Design Drawing Presentation Guidelines. http://www.steelbridge.org/

### 14.1.2 Shop Drawings

Refer to AASHTO/NSBA Steel Bridge Collaboration Document G 1.1-2000, Shop Drawing Review/Approval Guidelines and G 1.3-2002, Shop Detail Drawing Presentation Guidelines. http://www.steelbridge.org/

## 14.2 Connections

For welded steel girders, designers and detailers must account for fatigue problems caused by secondary members and displacement induced stresses in connections to the main girders. These problems exist because most bridges are essentially linear and are designed for in-plane loading and deflection of the main girders and diaphragms. Although interaction between longitudinal girders and diaphragms does not alter in-plane behavior enough to economically justify space frame analysis for these effects, it is of paramount importance that the designer and detailer consider the distortions resulting from such interaction. See Structures Preferred Details for additional information.

## 14.3 Welds (07/04) July 2004 - Required Field Weld Symbol for shear connectors.

A. Even the best welds may have imperfections such as porosity, slag inclusions, cold laps and other comparable conditions that cannot be eliminated. These imperfections are assumed to be unavoidable and have been considered in the allowable stress range for the weld.

B. Avoid using details that cause stress concentrations in the weld and a decrease in the basic allowable stress range.

C. It is the designer's responsibility to design the connections; however the detailer should be familiar with Table 6.6.1.2.3-1 and Figure 6.6.1.2.3-1 in the AASHTO-LRFD Specifications. This table indicates that welds cause reductions in allowable fatigue strength and the reductions are governed by the magnitude of discontinuities in the welds.

D. Avoid the following Category E weld types:

1.) Intersecting welds: Do not use this type detail.

2.) Longitudinal weld terminations: Plates on cover-plated beams should terminate at the ends of beams. Welds should be continuous. When attachments require longitudinal welds on beams or girders, refer to the AASHTO-LRFD Specifications.

E. Any detail can be used provided it is properly accounted for in the design and details. The simplest detail consistent with the stress requirements will generally be the most desirable from the standpoint of design, fabrication and economics.

F. Show a field weld symbol where the stud shear connectors are applied.

## 14.4 Stay-in-Place Metal Forms

Incorporate stay-in-place metal forms in the design and details except when prohibited by the S tructures Design Guidelines. Form details must be generic because the actual form material (depth, pitch, thickness, etc.) cannot be predetermined. See Structures Preferred Details for suggested details. To avoid conflicts with the top flange lateral bracing system, take special care for forms inside box girders.