# Design a tension member w/ cross section

• General_Sax
In summary, the task is to design a tension member (square rod) with a cross section to hold a mass of 575,000 kg with a safety factor of 2 against yield and a safety factor of 3 against static fracture. The design stress chosen will be the lowest allowable stress, which is 426 MPa for static fracture and 431 MPa for yield strength. The appropriate bar dimensions for use would be a length and width of 6574 mm and a cross-sectional area of 13148.6014 mm^2.
General_Sax
design a tension member w/ cross section...

## Homework Statement

You are to design a tension member (square rod) with a cross section to carry a mass of 575 000 kg with a safety factor of 2 against yield and a safety factor of 3 against static fracture (overload).

a) What is the design stree that you will use for the application? Why?

b) What are the appropriate bar dimensions for use?

FS = UTS / R

[sigma] = F / Ao

Ao = L * w

## The Attempt at a Solution

FS = 1279MPa / 3 = 426.33333... MPa ~ 426 MPa
that's the design stress considering static fracture

FS = 862 / 2 = 431 MPa
that's the design stress consider yield stress/strength

So, I'm considering using a design stress that is the average of these two values, which would be: 429 MPa

I'm just confused, because we haven't done anything like this in class.

Now for part b)

[sigma] = F / l*w

F = 575 * 103(kg) * 9.81(m/s2)
F = 5.641 MN (mega Newtons)

429 = 5.641 MN / Ao[/SUP]

Ao = 13148.6014 MM (mega meters? I'm not sure about the units on this one)

l = w = 6574 MM

General_Sax: First, where did 1279 MPa, and 862 MPa, come from? I do not see that in the problem statement. Secondly, MN/MPa = MN/(MN/m^2) = m^2. Or N/MPa = mm^2. Third, use the lowest allowable stress, not the average.

Thanks for the help!

## What is a tension member and why is it important in structural design?

A tension member is a structural element used to resist tensile forces, or forces that pull the member apart. It is important in structural design because it helps distribute the load and prevent the structure from collapsing.

## What factors should be considered when designing a tension member?

When designing a tension member, factors such as the magnitude and direction of the applied load, the material properties, and the cross-sectional shape and dimensions of the member must be taken into account. Other considerations may include the environment in which the member will be used and any potential for corrosion.

## How is the cross-sectional area of a tension member determined?

The cross-sectional area of a tension member is typically determined by calculating the maximum stress that the member can withstand without failing, and then dividing the applied load by this stress. The resulting value is the minimum required cross-sectional area of the member.

## What are some common types of cross-sectional shapes used for tension members?

Some common types of cross-sectional shapes used for tension members include circular, square, rectangular, and I-shaped sections. Each shape has its own advantages and disadvantages, and the appropriate shape is often chosen based on the specific requirements of the structure.

## How can the strength of a tension member be increased?

The strength of a tension member can be increased by using a stronger material, increasing the cross-sectional area of the member, or using a more efficient cross-sectional shape. Additionally, proper connections and detailing can also contribute to the overall strength of the member.

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