Framing System  

The framing system used in Macalister Hall is made of structural steel.  He engineers who designed it chose steel rather than concrete beams because of the height of the building.  Concrete frame structures are typically between one and five stories.  The steel was selected based on ASTM standards.  Steels with 50 ksi yield stress are typically used in construction.  Steels with higher yield stresses can be achieved with a higher grade of steel.  Since this building doesn’t have to carry any excessive loads, we have assumed that the 50 ksi steel was used. 

Grade 50 steel (50 ksi) is appropriate for the Philadelphia climate.  When temperature decreases, there is an increase in tensile strength, modulus of elasticity, and fatigue strength.  Ductility and toughness decrease with a reduction in temperature. 

The steel frame also aids in fire resistance.  Fire resistance of the member is dependant on its mass, geometry, loading, and supports.  In many parts of the country, the steel members alone would be up to fire resistance codes.  However, in Philadelphia, the National Building Code, published by Building Officials and Code Administrators International (BOCA) is enforced.  This code requires fire protection as a function of area, height and building occupancy.  Since this is a medium sized building in Philadelphia, the BOCA codes apply.   This code requires another source of fire protection, whether it is steel accompanied by sprinklers, or spray fire proofing over the steel members. 

The steel used in this building consists basically of W shaped members.  This means that they have essentially parallel flange surfaces.  The three basic sizes used are W14’s, W16’s, and W18’s.  Each one has different dimensions; area, depth, web thickness, flange width and thickness, and heights.  They also have different properties such as weight per foot, elasticity, and plastic modulus.  The W14’s are the smallest, in this case, and the W18’s are biggest and heaviest.  The W18’s are used around the exterior walls.   

There are shear walls in this structure surrounding the elevators and stair towers.  Shear walls are designed to resist lateral loads.  The most common lateral load in Philadelphia is wind.  Earthquakes are not a concern.

A typical floor was designed with four 26’ bays by six 26’ bays.  Then in a typical bay, there are four beams running perpendicular to the cells in the metal deck.  There are one beam at each end and two splitting the space evenly into three sections.  There are three elevators in the building and two stair towers. 

The building frame is attached to the curtain wall, which is then attached to the spandrel beams.  The beams then support the precast panels.