A Beginner's Guide to the Steel Construction Manual, 14th ed.

Chapter 10 - Composite Beams

2006, 2007, 2008, 2011  T. Bartlett Quimby

Introduction

Mechanics of Composite Behavior

Shear Strength

Flexural Strength

Design of Shear Connectors

Deflection Calculations

Design Process

Example
Problems

Homework Problems

References


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Section 10.9

Homework Problems

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.


Miscellaneous Steel Problems


Problem M10.1:  The floor framing plan depicted in MISCDET_STL 1/S6.2 consists of a flat concrete slab supporting office floor live load and partition loadings.  The slab acts compositely with steel joist beams to span the bay shown.  The joist beams are supported by girder beams.  Note that the shown number of joists per bay is only representative.  You may change this to find the best solution.

The objective of this problem is to accomplish the following tasks:

  1. Select slab thickness.
  2. Select the size and spacing of the joist beams (using W sections) that results in the least cost per square foot of floor area.
  3. Select the size and spacing of the shear studs for the joists.

The following criteria are applicable:

  1. The slab thickness is to equal the C-C spacing of the supporting beams divided by 20 and rounded up to the nearest half inch.  The slab minimum thickness shall be 4".
  2. The beams are to be unshored during construction.
  3. Deflection due to floor live load is to be limited to L/360.
  4. Total deflection during construction is to be limited to L/240.
  5. The floor supports the following loads:
    1. Self weight of structure (reinforced concrete weighs 150 lbs per cubic foot)
    2. Additional floor dead load = 25 psf (includes partition loading, carpet, etc.)
    3. Floor live load = 50 psf
    4. Construction Live Load = 20 psf
  6. The building dimensions and materials for the cases given in Table 10.8.1.
  7. Concrete is assumed to cost $160 per cubic yard (installed) and the steel is assumed to cost $1.20 per pound (installed).

Table 10.8.1
Problem Cases

Case Bay Span Shored? Bay Width Concrete Strength, f'c
1 40 ft No 30 ft 3,000 psi
2 40 ft Yes 30 ft 3,000 psi
3 40 ft No 30 ft 4,000 psi
4 40 ft Yes 30 ft 4,000 psi
5 60 ft No 40 ft 3,000 psi
6 60 ft Yes 40 ft 3,000 psi
7 60 ft No 40 ft 4,000 psi
8 60 ft Yes 40 ft 4,000 psi

 


Dormitory Building Design Problems


All the floor beams in the dormitory building are candidates for composite construction.

Problem D10.1:  Repeat Problem D8.1 using 1/2" diameter headed studs with the joists.  Assume that the slab is 4" thick and the maximum joist spacing is 6'-0".  If you completed problem D8.1, compare the results from this problem with the results from problem D8.1 and comment as appropriate. Assume unshored construction, however assume that the form work will provide lateral support for the beams during construction.  Use a construction live load of 20 psf. Complete the following table:

Joist Type of Live Load Joist Size Joist Spacing Number & Spacing of Studs
J201 Dorm Room      
J202 Corridor      
J203 Dorm Room      
J204 Corridor      

Problem D10.2:  Repeat Problem D8.2 using 1/2" diameter headed studs with the beams.  If you completed problem D8.2, compare the results from this problem with the results from problem D8.2 and comment as appropriate. 


Tower Design Problems


Being an axial force truss system, the tower does not provide us with opportunity to use flexural cover plates nor beam bearing plates.  Consequently, there are no assignments for the tower in this chapter.


Truss Bridge Design Problems


The principle flexural members in the bridge are the deck beams, girders and end girders.  All are statically determinate.  They are also relatively short allowing a single wheel to be the defining vehicle load.   Use L/260 as the total load deflection limit and L/360 as the live load only deflection limit.  Assume the concrete deck is 6 inches thick, the 28-day concrete strength, f'c, is 4,000 psi, and that the beams are shored during construction.

Problem B10.1:  Repeat Problem B8.1 using 1/2" diameter headed studs with the beams.  If you completed problem B8.1, compare the results from this problem with the results from problem B9.1 and comment as appropriate. 

Problem B10.2:  Repeat Problem B8.2a using 1/2" diameter headed studs with the beams.  If you completed problem B8.2a, compare the results from this problem with the results from problem B8.2a and comment as appropriate.