Steel frame stress reduction connection

• US 20030208985A1
• Filed: 05/02/2001
• Published: 11/13/2003
• Est. Priority Date: 04/11/1995
• Status: Active Grant

• Current Assignee: Seismic Structural Design Associates Incorporated
• Original Assignee: Seismic Structural Design Associates Incorporated
• Inventors: Richard, Ralph M., Allen, Clayton J., Partridge, James E.
• Granted Patent: US 7,047,695 B2
• Time in Patent Office: Days
• US Class Current: 52/653.1
• CPC Class Codes: E04B 1/2403 Connection details of the elongated load-supporting parts
• CPC Class Codes: E04B 2001/2415 Brackets, gussets, joining plates
• CPC Class Codes: E04B 2001/2442 Connections with built-in weakness points
• CPC Class Codes: E04B 2001/2445 Load-supporting elements with reinforcement at the connection point other than the connector
• CPC Class Codes: E04B 2001/2448 Connections between open section profiles

Abstract

The present invention provides for improvement of ductility and strength performance of connections in structural steel buildings made typically with rolled structural shapes, specifically in bolted and/or welded beam-to-column connections with welded flanges, by greatly reducing the very significant uneven stress distribution found in the conventionally designed connection at the column/beam weld, through use of slots in column and/or beam webs with or without continuity plates in the area of the column between the column flanges, as well as, optionally, extended shear plate connections with additional columns of bolts for the purpose of reducing the stress concentration factor in the center of the flange welds. Moreover, the slots in beam web adjacent to the beam flanges allow the beam web and flange to buckle independently thereby eliminating the degrading of the beam strength caused by lateral-torsional bucking.

Claims

1. A steel framework comprising:

a steel column having a first flange, a second flange, and a web therebetween;

a steel beam having a lower flange, an upper flange, and a web therebetween;

the beam being welded orthogonal to the first flange of the column; and

a separation of the beam flange from the beam web equal to or greater than 3.0 times the beam flange thickness in length in the beam positioned adjacent to the lower flange of the beam and adjacent to the first flange of the column.

3. The framework of claims 1 or 2 wherein the beam web and beam flange separation comprises a slot that is tapered from a first relatively wide slot width near the column and beam interface to a second relatively narrow slot width near the opposite end of the slot and narrower than the first slot width.

4. The framework of any claims 1-3 wherein the end of the slot away from the column terminates with a circular radius equal to one half the width of the end of the slot.

2. A steel framework comprising:

a steel column having a first flange, a second flange, and a web therebetween;

a steel beam having a first flange, a second flange, and a web therebetween;

the beam being welded orthogonal to the first flange of the column;

a separation of the beam flange from the beam web equal to or greater than 3.0 times the beam flange thickness in length in the beam positioned adjacent to the first flange of the beam and adjacent to the first flange of the column; and

a separation of the beam flange from the beam web equal to or greater than 3.0 times the beam flange thickness in length in the beam positioned adjacent to the second flange of the beam and adjacent to the first flange of the column.

5. A method for relieving strain concentrations in a load bearing and moment frame connection of a steel frame having a welded beam to column connection with upper and lower beam flange welds, a steel beam due to seismic loads applied to the connection, comprising the steps of:

determining a first strain concentration factor for said connection;

determining a total amount of steel to be removed from the web of the beam to yield a second strain concentration factor having a value less than that of said first strain concentration factor, said first strain concentration factor and second strain concentration factor being determined at the upper and lower beam flange welds and weld access holes at the connection;

removing a first portion of steel from the beam web near the upper beam flange and column flange weld and weld access hole;

removing a second portion of steel from the beam web near the lower beam flange and column flange weld and weld access hole; and

,

whereby the total amount of the first portion and amount of the second portion of steel removed from the beam is equal to said total amount of steel removed.