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CEE 221 Theory of Structures 1 (ch.1 (Structure Classifications (Trusses…

- - - - must be analyzed to ensure stiffness, strength, and stability following codes and local specifications
      - Tie rods are used for cross bracing to stiffen the roof of a building to resist wind loads
      - beams wirh varied cross sections are refered to as tapered or haunched beams, and they also can be built up by adding plates to their top and bottom.
        
        metal(i.e steel, aluminum, etc.) wide flange beams are good for short span beams intending to carry large loads that cause large internal shear forces
        Plate Girders cross sections are fabricated by using a large plate for the web and welding or bolting plates to its ends for flanges; is often transported to the field in segments, and the segments are designed to be spliced or joined together at points where the girder carries a small internal moment
        
        Splice Plate Joints used to connect plate girders; typical in highway design
        
        Wide flange members are often used for columns
        
        Concrete Beams usually rectangular in cross section for ease of construction; weak in tension so usually reinforced with steel rods cast into the beam in cross sections where tension is expereinced
        Precast Concrete Beams have varied cross sections and are fabricated at a shop or yard and transported to the site
        
        Prestressed concrete girders can be simply supported on piers and
        
        Wood Beams can be made from solif timber ot laminated. Laminated Beams often called Glulam beams are constructed from strips of wood, which are fastened toether using high-strength glues
      - When a column is subjected to both axial loads and bending moments it can be a beam column
  - - - Planar trusses are composed of members that lie in the same plane(i.e. bridge and roof support)
      - Space trusses have members extending in three dimensions(derricks and towers)
    - - Can be made of rigid materials (aluminum, reinforced concrete, etc.) and can be shaped in to folded plates, cylinders, or hyperbolic paraboloids, all of which refered to as thin plates or thin shell
        
        Their three-dimensional surface geometires make them difficult to analyze
  - - - Design Codes detailed technical standards that are used to establish the requirements for the actual structural design.
        
        Building Code Requirements for Reinforced Concrete, Am. Conc. Inst. (ACI)
        
        Manual of Steel Construction, American Institute of Steel Construction (AISC)
        
        Standard Specifications for Highway Bridges, American Association of State Highway and
        Transportation Officials (AASHTO)
        
        National Design Specification for Wood Construction, American Forest and Paper Association
        (AFPA)
        
        Manual for Railway Engineering, American Railway Engineering and Maintenance-of-Way
        Association (AREMA)
      - General Building Codes specify the requirements of governmental bodies or organizations for minimum design loads
        
        International Building Code
        
        Minimum Design Loads for Buildings and Other Structures, ASCE/SEI 7-16, American Society of
        Civil Engineers
    - - Users
        
        People, Furniture, Machinery/Equipment, etc
      - Highway Bridge Loads
      - Impact Loads
      - Wind Loads
        
        Wind Pressure
      - Hydrostatic and Soil Pressure
      - Other(Blast, earthquake temp. changes, differential settlement, etc)
    - - Gravity
        
        Dead, live, snow, rain
      - Lateral
        
        Soil, Hydrostatic, Wind, Earthquake, Blast
      - Some loads are actually omnidirectional
  - - - Some typical load combinations as specified by the ASCE 7-16 Standard include: dead load, dead load+live load, 0.6(dead load)+0.6(wind load)
      - Single safety factor on capacity side
        ex. using 60 ksi yield strength steel, allowable stress is 24 ksi
        This is the old fashioned method and is not used for used structures anymore. This method leads to overdesign structure
    - - According to the ASCE 7-16 Standard, some of the load factors and combinations that are not to be exceeded include: 1.4(dead load), 1.2 (dead load)+1.6 (live load)+0.5 (roof live load or snow load or rain load), 1.2 (dead load) + 1.0 (wind load) + 1.0 (live load) + 0.5 (roof live load or
        snow load or rain load), 0.9 (dead load)+1.0 (wind load)
        
        The combinations are thought to provide a maximum yet realistic loading on the structure
      - Safety factors for both demand and capacity
        αD < фC
        Where, generally speaking,
        α > 1 as a load factor
        ф < 1 as a resistance factor
        Where the advantage lies in the fact that you can tailor safety to each limit state, making a more efficient structure.
- - - - structural engineers need to be able to make idealized models to accommodate this
        
        Line drawings
    - - Pin
      - Roller
      - Fixed
  - - - Free Body Diagram
        A dimensioned sketch of an objected highlighting geometry as well as showing all the forces.
        note:utilize the sign convention defined in your FBD and do not deviate
        Equilibrium Equations
        Derived from Newton's Second Law but adapted to static (i.e. Acceleration = 0)
        For an object in equilibrium, any part of that object also is equilibrium with its internal forces
        ∑Fx=0
        ∑Fy=0
        ∑M(anypoint)=0
        (∑Mx=∑My=∑Mz=0)
        Internal Forces
        Forces which reside inside elements.
        ex:Axial(P), Shear(V), Bending Moment(M), Torsion9=(T)
  - - - Special Conditions for Instability
        a) All reactions are parallel
        b) All reactions pass through a single point(will not be able to satisfy moment equilibrium)
        c) Violations of he small deformation assumption(i.e. geometries change)