ANALYSIS AND DESIGN OF MEMBERS FOR AXIAL TENSION

Tension members are structural elements that are subjected to axial tensile forces. They are used in various types of structures which include truss members, bracing for buildings and bridges, cables in suspended roof systems, and cables in suspension and cable-stayed bridges. Tension members typically consist of round bars, wire cables, plates, and rolled sections. In addition, end connections may consist of threaded ends, eyebars, pinned, bolted, and welded connections.

tension members

The stress in an axially loaded tension member is given by f=P/A, where P is the magnitude of the load and A is the cross-sectional area (the area normal to the load).
Based from the module given, there are two limit states which govern the design of tension members. These are the limit state of yielding and the limit state of rupture. The limit state of yielding applies to failure on the gross cross-sectional area of the member.The limit state of rupture applies to failure on the net cross-sectional area of the member.
Shown in the left figure are the design and allowable strength in tensile yielding and tensile rupture

effective net area

The detail of plates as shown in the right indicates a bolted connection and welded connection. When only part of the cross-section of a member is connected, the resulting shear lag effect produces a concentration of stress at the connection. To allow for this, a reduction factor is applied to the net area at a connection. Thus, the effective net area is given by AISC 360 Eq. (D3-1) as

Ae=AnU

where An = net area (gross area with area of holes deducted)

U = shear lag factor

plates with bolted connection

The effective net area of the plate for bolted connections is expressed as shown

For a staggered fracture, the effective net width is obtained by deducting from the gross width the sum of the bolt holes in the failure path and adding, for each gage space traversed by a diagonal portion of the failure path, the quantity s2/4g where g is the transverse center-to-center spacing between faste
For flat plates with bolted connections, AISC 360 Table D3-1 specifies a value for the shear lag factor of U = 1.0 by which,

Ae=An

The nominal diameter of a standard hole is detailed as 1/16 in larger than the bolt diameter.the effective hole diameter is expressed as

dh=db + 1/8 in

plates with welded connection

For the transverse welded connection shown in the left, all of the net area participates in transmitting the load and the shear lag factor is U = 1.0. Therefore,

Ae=An=Ag

For the longitudinal fillet welded connection, the shear lag factor is expressed based on the l to w ratio.

supplementary materials and recorded meetings

20221005 - CENG131 Module 2.pdf

20221012- CENG131 Module 2b.pdf

njq-jeys-gbr (2022-10-06 19:10 GMT+8)

rft-ybah-idd (2022-10-20 19:05 GMT+8)

fri-uodf-ihn (2022-10-19 18:02 GMT+8)

reflection

The second module entailed the analysis and design of members subjected to axial tension. After reading the module and attending the synchronous meetings, I have grasped lots of takeaways and learnings in this module. Also, I have seen the differences between two approaches between ASD and LRFD. Regardless of the method, I can still use both approaches. But unlike ASD, LRFD for me requires considerable effort for the loads should be factored before adding them all. In ASD, most of the loads are simply added. Also, I have learned that one of the factors which influences the performance of a tension member is on how it is connected. That is why shear lag factors are used because there are factors affecting the effectiveness of the member, including ductility of the material, fastener spacing, stress concentrations at holes, and the fabrication procedure. Lastly solving example problems helped me master the design concept for axial tension members. Whether if it is bolted or welded connection, I was able to answer them correctly by reading and understanding the uploaded modules thoroughly.

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