331 Introduction

The stub girder system was developed in response to a need for new and innovative construction techniques that could be applied to certain parts of multistory steel-framed buildings. Originated in the early 1970s, the system aimed at providing construction economies through the integration of the electrical and mechanical service ducts into the part of the building volume that is occupied by the floor framing system of the building [1,2]. Since the overall height of the floor system at times could become large, increases in the overall height of the structure and hence the steel tonnage for the project could be significant. At other times the height could be reduced, but only at the expense of having sizeable web penetrations for the ductwork to pass through. This solution often entailed reinforced web openings, further increasing the construction cost.

The composite stub girder floor system was developed subsequently. Making extensive use of relatively simple shop fabrication techniques, basic elements with limited fabrication needs, simple connections between the main floor system elements and the structural columns, and composite action between the concrete floor slab and the steel load-carrying members, a floor system of significant strength, stiffness, and ductility was devised. This led to a reduction in the amount of structural steel that traditionally had been needed for the floor framing. When coupled with the use of continuous, composite transverse floor beams and the shorter erection time that was needed for the stub girder system, this yielded attractive cost savings.

Since its introduction, the stub girder floor system has been used for a variety of steel-framed buildings in the United States, Canada, Mexico, and Europe, ranging in height from 2 to 72 stories. Despite this relatively widespread usage, the analysis techniques and the design criteria remain unknown to many designers. This chapter will offer examples of practical uses of the system, together with recommendations for suitable design and performance criteria.

0 0

Post a comment