Structural Design - GENERAL INFORMATION
The attached sheet shows preliminary plans for an addition to an existing materials handling facility. A large steel hopper will be suspended from a system of beams which are supported on one side by new steel columns and on the other by existing columns which are part of an existing building.
The hopper hangs from four support points on two secondary beams, which are themselves supported by two primary beams. Trucks drive underneath the hopper for loading.
Data for this exercise will be sent via e-mail to each student in the class. Students must use their own data set when completing the assignment.
REQUIREMENTS OF THIS EXERCISE & DESIGN DATA
I. Design of the secondary beams
Determine a suitable size for the secondary beams, using UB or Welded Beam (WB) sections and Grade 300 steel.
Note the following:
- Apart from their self weight, each secondary beam carries two concentrated loads from the hopper at a distance of ‘E' from each end. This load is due to the hopper self weight plus its contents. Data necessary for determination of this loading is provided in the tabulation at the end of this document.
- The secondary beams may be regarded as fully restrained (F) at their ends where they sit on the primary beams. However, since it is conceivable that these beams might buckle simultaneously, with their top flanges moving laterally in the same direction and the hopper moving with them, the load points should not be regarded as restraint points. Hence, these beams each comprise just one segment. In addition, a kl value of 1.4 would be appropriate in this case, in accordance with AS4100 Table 5.6.3(2).
- The web bearing capacity of the secondary beams should be checked at the points where they sit on the primary beams. It may be assumed that the web bearing capacity elsewhere along the secondary beams is satisfactory.
- Since the aesthetics of this support system is not a major issue, deflections are not an important design consideration, but it has been decided that, under maximum loading, beam deflection should not exceed Span/200.
II. Design of the Primary beams
Determine a suitable size for the primary beams, using UB or WB sections and Grade 300 steel. Note the following:
- A 120mm-thick reinforced concrete slab will be cast on top of the primary beams as depicted. This slab will be ‘locked' down onto the tops of the beams by the provision of shear connectors which will be welded onto the tops of the beams and cast into the slabs. The shear connectors will restrain any possible lateral buckling of the beam top flange wherever the slabs are located. Allow for a live loading on the slabs of 2 kN/m2.
The slabs will be supported by additional steelwork not shown on the diagram and not relevant to this exercise.
- Assume the cross-section of the primary beams at both ends is fully (F) restrained.
- Use the same deflection limitation as specified for the secondary beams, but only the deflection due to the beam self weight and hopper need be considered (i.e. the additional small deflection due to the slab loading may be neglected).
- The shear capacity of the primary beams should be checked.
- The web bearing capacity of the primary beams should be checked at the points where the secondary beams bear down on them. It may be assumed that the web bearing capacity elsewhere along the primary beams is satisfactory.
III. Design of the columns
Determine a suitable size for the columns, using SHS sections and Grade 350 steel. Note the following:
- The columns may be designed as pin-ended top and bottom.
- Allowance should be made in accordance with AS4100 Cl. 4.3.4 for eccentricity of the applied loading on the columns. Strength under the combined actions of axial compression and bending should be assessed as discussed in week 2 lecture. Be noted that, as discussed, the combination of axial compression with a bending moment can lead to an amplification of the bending moment. This is to be evaluated in accordance with AS4100 Cl. 4.4.2.2. Since the column is being treated as pinned-base, the factor cm will be 0.6 and the effective length factor ke may be taken as 1.0
- A SHS may not be the most appropriate section type to use in this application, but is specified here as we are limiting our attention in this course to the simple case of combined actions in SHS and CHS members only.
IV. Design of the connection at the right-hand end of the primary beams
The connection of the right-hand end of each primary beam to the column of the existing building will utilise a web side plate. For this connection, determine the number and size of bolts required (assume Grade 4.6 unless Grade 8.8 is required) and suitable dimensions for the plate. Produce a neat sketch to summarise your design of this connection.
V. Detailing of the connections at the ends of the primary and secondary beams
It has previously been stated that the cross-sections at both ends of the primary and secondary beams should be assumed to be fully (F) restrained. Provide sketches of suitable details which would achieve this (the connection at the right-hand end of the primary beam has already been designed) and briefly explain why this detail achieves a fully restrained (F) cross-section.
ASSESSMENT CRITERIA
The assessment of this exercise will take into consideration:
- Technical correctness;
- Neatness of the presentation and the extent to which diagrams are used to explain the calculations;
- The standard of drawing and amount of information provided on the final diagrams summarizing the designs;
- The extent to which cross-referencing is used to clarify where numbers have come from.
Attachment:- Sample Solution.rar