# Tag Info

Accepted

### Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

If I model this as a simply supported beam having load at mid span [...] I suspect that this is where your analysis went awry. First off, you should always model bridges with distributed loads, not a ...
• 13.1k

### Is it structurally sound to cut an I beam to a T on one end?

While not an ideal situation, it is common enough that this type of cut/reduction of the beam as it comes to its support actually has a name. This is more often referred to as a coped or dapped steel ...
• 1,221

### Is it structurally sound to cut an I beam to a T on one end?

This is a textbook example of what not to do. We don't get into stress concentration at the cut off of the corner of the beam, or the fact that the two very different stiffnesses of the beams are a ...
• 22.5k
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### Why does a continuous beam have less deflection than a pair of simply supported beams?

For a simple visual demonstration, take one of the spans in your example. If it is fully hinged, then each span can be represented as a simply-supported beam. If the beam is continuous, then each ...
• 13.1k
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### Stiffness of a cantilever beam

Stiffness is a murky term frequently used ambiguously in engineering. However, the most common definition of stiffness is the product of a beam's Young's Modulus $E$ (which is a function of its ...
• 13.1k

### Is it structurally sound to cut an I beam to a T on one end?

If the white beam on the left is adequate, the one on the right is much bigger than it needs to be, so hacking a piece out of it might not matter. In general this idea is a horrible example of ...
• 12.5k
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### Given the tensile strength of a rod, how do you calculate the max weight that can be hung from it?

You're hanging it from a rod supported by both ends - and need to use the bending equations. For this case (case 7 in the link), the max weight is: $$W_{max} = \frac{\pi d^3 \sigma}{8L}$$ $\sigma$ ...
• 5,333

### Is it structurally sound to cut an I beam to a T on one end?

TL;DR: Since we can't see how the beam is supported on the other end, its not clear whether its structurally safe. Still, I don't believe this configuration can transfer safely any substantial ...
• 24.4k

### Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Since this bridge is crossing over a waterway, besides aesthetics, the arch-shaped bridge provides several advantages: Less restrictive over the height of marine traffic due to more headroom in the ...
• 8,202
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### How much weight can an aluminum tube beam support?

We use this equation for a simply supported beam loaded at its center with 200lbs. M= P x L/4 =200 x 3 /4 = 150 lbs.ft for calculating the tube stress we convert this to 150 x 12 = 1800 lbs.inch ...
• 22.5k

### Determining stiffness of a beam w/varying moment of inertia

You could insert the variable $I(x)$ into the integral equation for the rotation and the deflection. First determine your model. Then determine the equation of the moment $M(x)$. Then enter this in ...
• 393

### What does it mean when actual member reaction is 100% of allowed?

This means that the member is considered to be fully loaded for a failure mode which is being analyzed by that stress calculation. Some things to (probably) keep in mind include: Some conservatism ...
Accepted

### Deflection of a cantilever beam composed of separate (not bonded) planks

in a cantilever beam the deflection is $$\delta_{max} = \frac {PL^3}{3EI}$$ In this case assuming free sliding between the planks the load P is going to be supported equally between the 3 planks. ...
• 22.5k
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• 13.1k
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### Reinforcing beam and slab with correct steel bar structure

Model 1 is always better, but may need some modifications Whenever you have two reinforced concrete elements, you always need to facilitate the transfer of internal stresses between them. This is ...
• 13.1k

### How does stiffness/rigidity affect the bending moment of a beam

There are two basic types of structure. Statically determinate structures are those where you can calculate the forces at the restraints without knowing anything about the flexibility of the ...
• 12.5k