Description

(a) Since its opening in 2012, the Structural and Material Demonstration Laboratory has been used for multiple activities by the College of Civil and Architectural Engineering at a local university. The conducted labs allow students to practice construction techniques at full scale. The size of these projects is problematic when assemblies need to be moved or when the finished structure needs to be removed from the building. Installing a crane overhead would allow projects to be conducted safely. The existing lab structure consists of a series of portal frames spaced at 5 m along the length, i.e., normal to the plane of the frame. A typical representation of these pitched roof frames is as shown in Figure Q2(a). You, among a group of students, were assigned to propose solutions for installation of the crane to the existing structure. You are asked, furthermore, to provide arguments and design calculations in support of your proposals taking into account structural, geotechnical, architectural and environmental considerations. Your tasks include verifying existing conditions, evaluating carrying capacity of existing structure, etc. Assume that you ended up with three proposals as follow: Proposal I: Attaching the crane runways to the columns, Proposal II: Attaching the runways to the existing frame, and Proposal III: Installing separate frames that would support the crane completely apart from the existing structure.

Now consider Proposal III, a 2-D schematic representation is shown in Figure Q2(a). According to the manufacturer, the crane carrying capacity is 20 kN. The dynamic effects may be neglected as the crane has a limiter on its speed to lessen those effects. However, it was decided to include 4 kN lateral force acting on the beam BE. The load P is transmitted to the girder beam C’D’. The girder beam can move along the structure length. Detailed sections CC’ and DD’ are not shown for simplicity. You may, furthermore, assume that the load P is transferred to the frame ABEF and consider 2 extreme cases where P acts at C’ and in the middle of the beam C’D’. Take a factor of safety of 1.5 and calculate the required plastic moment of resistance for the frame Mp. Comment on the merits/demerits of adopting Proposal III and provide arguments in support of your answer.