Chapter 5 - Welded Connections
© 2006, 2007, 2008, 2009, 2011 T. Bartlett Quimby
As presented in Chapter 1, the homework problems involve the design of elements of three different structures plus some unrelated details. Please see the relevant links below for each structure. When completing the problems, consider both ASD and LRFD design philosophies unless otherwise specified by the instructor. Consider all limit states presented in this and prior chapters. Consider developing a generic spreadsheet that you can apply to similar problems.
Problems M5.1: MISCDET_STL_STL 1/S2.2 shows a braced pile system for a dock structure located in Whittier, Alaska. The drawing is not an accurate as-built drawing. Assume an E70XX electrode has been used. Express your results in terms of service load levels assuming that the applied load is 0.5 part dead load, 0.5 parts live load, and 1.75 part seismic load.
Problem M5.2: MISCDET_STL 2/S2.1 shows two MC sections attached to a gusset plate. Using a 1/2" thick gusset plate, a pair of C10x30 channels, E70XX electrodes and A588 steel design a fillet welded connection that is 50% stronger than the channels in tensile yielding. Neatly draw a scaled detail of the connection. Note: There are a number of situations where parts of a structure are designed to be stronger than other parts, regardless of structural analysis results. This is typically done to ensure that a particular failure mode will not control the design. In this case, failure would be tensile yielding of the brace instead of fracture of the connection!
Problem M5.3: For this problem refer to drawing MISCDET_STL 4/S2.1. A pair of L3x3x5/16 are welded to a 7/16" thick gusset plate with fillet welds as shown. Use E70XX electrodes. Design the connection to have a balanced weld group and to have a capacity 25% greater than the tensile yielding capacity of the angles.
Problems M5.4: For this problem refer to drawing MISCDET_STL 4/S5.1. Create a general purpose spreadsheet (in MS Excel unless otherwise approved by your instructor) to compute the capacity, Pn for the fillet welded connection shown. Consider only weld strength. The design variables are the weld leg size "a", electrode type and grade, the distances A and B, the location of the force (X), and the angle of loading (Angle) from the vertical. Group the design variables and the resulting value at the beginning of the spreadsheet.
Problems M5.5: For this problem refer to drawing MISCDET_STL 5/S5.1. Create a general purpose spreadsheet (in MS Excel unless otherwise approved by your instructor) to compute the capacity, Pn for the fillet welded connection shown. Consider only weld strength. The design variables are the weld leg size "a", electrode type and grade, the distances A and B, and the location of the force (X). Group the design variables and the resulting value at the beginning of the spreadsheet.
Problem M5.6: Using the connection in MISCDET_STL 1/S1.3, assume that the W section is a W14x30 and the plates are all 3/8" thick. F7XX electrodes are used. Determine the minimum practical length "L" for which the weld connection is at least as strong as the bolted connection. Note that all welds are equally stressed since they deform equally.
Problem M5.7: Using the connection in MISCDET_STL 1/S1.3, assume that the W section is a W16x31, the plates are all 1/2" thick, and L = 16". Determine the maximum moment nominal moment, Mn, that the welded connection can transfer. Consider that only the flange plates are effective in transferring moment. Recall that moment equals the couple formed by the weld forces on each flange times the distance between the center of the connection plates.
The braces in this building may be connected to the frames by welds, depending on the detail used. In these problems, the connections will be designed based on weld strength and shear rupture of the base metal.
The tower diagonal braces are connected to the tower legs via gusset plates welded to the tower legs. In the alternate connection details, end plates are welded to the brace members so that the braces can be bolted to the legs.
The bridge has all bolted connections, however, for this chapter, we will investigate the use of partially welded connections.