DESIGN METHODOLOGY
When Shearing Engineering was handed this project it was only in the initial stages of design. Detailed drawings and plans for the facility were provided however no work had been done yet to put these plans on the ground. Shearing Engineering was able to pick the project up and seamlessly begin working to make this plan come to fruition. The purpose of this structure is mainly for a recreation activity center for the students, staff and faculty of the University. Provided with the details of what they wanted the structure to be used for, the schematics of the building, and the appropriate resources - such as the Steel Construction Manual (15th edition) - the proper codes and regulations were able to be found and designed with the aid of previously mentioned material. The structural drawings, seen in Appendix B, have various LFRS (lateral force-resisting systems). These systems include the bracing's found along column lines 1, 4, A, and C, as well as column strong axis orientation aligned with E-W to provide more stability in the N-S direction. Together, these systems provide an adequate lateral load resisting.
The service loads are calculated using the ASCE 7-16 textbook to find various coefficients. The risk category was determined using Table 1.5-1 and the exposure level was found using section 26.7.2. Other coefficients, such as the Exposure Factor, Thermal Factor, and the Snow Importance Factor, are found using Table 7.3-1, Table 7.3-2, and Table 1.5-2. All of these coeeficents, along with others, are used to calculate the different types of service loads, like dead (C3.1-1a), live (Figure 4.3-1), wind (Table 26.5-1c and 28.5-1), and snow (7.3-7.4) (See in Appendix C). Once these loads were calculated, the appropriate roof and floor decking were able to be determined in Appendix D.
As shown in the Figures for Appendix D, the deck type for both the floor and roof were chosen. For the floor deck the number of spans and the length of each needed to be determined. For this building there will be 3 spans with each being 8 ft. These values are shown used in figure D-2. Using the max allowable stress, the max yield load that the deck has to support also allows for the selection to be made. Along this these distinctions the weight is also needed which can be found in figure D-1. The combination of these two figures determines that the deck type is “1.5 – B24.” The ground floor decking was next in the designing process. Due to the necessity of a concrete slab to help support the building weight a thickness of 3.5 in was chosen. Aside from this the process is the same for determining which deck type to use. The determination of the deck type is shown in figures D-3 and D-4. From the figures the deck type “1.5VL20” was determined to be used in the rest of the design.
Using Appendix C, the service point loads were determined in Appendix E using the tributary area supported by the roof joists which transfer the loads to point loads on the truss in column line 2. The point loads only act on nodes 2-8 since nodes 1 and 9 are resting on the columns. The truss, with a depth of 4 feet, is modeled in Visual Analysis with both the service point loads (dead and snow) acting on it. The analysis was run which resulted in the internal forces of the truss. The maximum force for each chord (top, bottom, vertical, and diagonal) are used to design the truss members.
After the truss design and its loads were put into Visual Analysis the beams were designed in Appendix F. For this process the type of beam being used for all members were double angle with A36 properties. With these assumptions the specific dimensions can be determined. The first type of members that were designed were those in compression, as shown in Appendix F. Using the Max Pu from VA for the beam and its Lc different shapes that met these criteria were chosen. From these the overall lightest shape was picked due to the assumption that lower weight leads to a more inexpensive beam. The Pu values was rechecked to ensure the self-weight of the member would not cause the beam to fail along with the spacing for the connectors and slenderness. This process was repeated for the top chords, vertical chords, and the diagonal chords in compression.
Next in the design process was to determine the shape of tension members (also in Appendix F). For this the minimum gross area had to be determine using the Pu max. Having the minimum area allows for the selection of a beam shape to be used. This now selected shape and its corresponding area allows for the calculation of tension member yielding and rupture. For the rupture calculation an assumption of Ae = .75Ag was used. Once the new φPn for yielding and rupture were determined they were compared to the Pu max to ensure they passed. The slenderness of the beams was also determined. This process was repeated for the bottom chords and the diagonal chords in tension. For the diagonal members the shapes must be the same. This means that the member with the Pu max that can hold the other’s φPn. Thus, the diagonal compression member shape will be chosen for both instances. The max deflection for the truss was calculated and compared to the results from VA in Appendix F.
For Appendix G, the truss member types and their governing shapes are summed, in Table 3, in order to determine the total weight of steel for one truss in pounds and tons. Using the information gained from Enclosure 1, cost estimates, the total cost is determined for each unit required for the materials, erection, and member fabrication.
To start of designing the roof joints in Appendix H the loads acting on the joints need to be calculated. Using this value, a specific designation can be picked from the Vulcraft Steel Joist and Joist catalog that can hold withstand the applied load. Following this the maximum deflection and the actual deflection need to be determined using the provided equations in the Vulcraft catalog along. With these requirements fulfilled the lightest shape is chosen for the building.
Appendix I requires that two roof beams and two roof girders be designed. The beams are designed first with their roof loading being the first step. Using the max moment and max shear equations from the AISC manual, their values are determined and compared to shapes within the manual to find a suitable selection. Once a shape is selected it is then tested against certain limit states such as shear, deflection, and adding the weight of the member into the loading. Once a selected member or members have passed the minimum requirements the lightest option is chosen. For the girder design once the loading is determined it is then put into Visual Analysis so the max moment and max shear can be retrieved. They are then compared to the max values that a certain selected beam can withstand. After this self-weight is checked along with shear and deflection. Once a selected member or members have passed the minimum requirements the lightest option is chosen. The results for this appendix will be displayed in Table 4.
Similar to Appendix I, Appendix J requires that one floor beam and one floor girder be designed. The same process of determining loads and member shape used in Appendix I is applied here. The results of these calculations are cataloged on table 4.
Appendix K begins with the designing the columns of the building. Using RB1 and RG1 as the loads acting on the columns A1/A4/C1/C4 their Pu can be determined. Using the AISC manual, the shapes that can carry the load are chosen and the lightest one is used for the design. Assuming that the column is pin-pin connection the effective length can be found and compared to the actual length of the column. After this the self-weight is checked and the shape is selected. This process is redone for columns B1/B4 and columns A2/A3/C2/C3 and columns B2/B3. The second requirement for Appendix K is to design the base plates for their corresponding columns. The first step was to calculate the area of the base plate using ϕPn and Pu from the column design. Next is to optimize the base plate dimensions using the equations from section J8 of the AISC manual. The third requirement for Appendix K is to design the bracing in A3-A3, C2-C3, B1-C1, B4-C4. Using the end reactions for RB1, RG1, RJ1, RG1, FB1, FG1, and the roof truss we are able to determine the load acting on each column (Pu). The W shapes were selected using ϕPnW tab and checked for self weight.
Appendix L contains the double angle connections (FB1->FG1) and two unstiffened seat connections (FB1->Column B2/B3 and FG1->Column B2/B3). The double angle checks the following limit states: shear strength of web, shear rupture, block shear rupture of beam, connection design, bolted connection of beam, and bolted connection of girder. The unstiffened seat checks the following limit states: bolt bearing on column web, and bolt bearing on angle web.
Appendix M contains the Member Summary Sheet and, Connection Summary Sheet, and the Structural System Cost Calculation Sheet.