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Engineering Stack Exchange

Questions tagged [structural-engineering]

Questions related to the integrity, design requirements, or analysis of structures.

Structures can be both large and small. Structures are not necessarily buildings or bridges.

Typical Structural Engineering concerns include, for a given loading on a structure or structural element, ensuring that:

  1. The stresses do not exceed a specified value
  2. The structure does not deflect beyond a specified value
  3. The structure does not buckle
  4. The natural frequencies of the structure are not excited

Sometimes, the given loading is unusual - such as wind or seismic loading. In these cases is it often appropriate to use additional tags to categorize the question.

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How fast does solid waste fall in vertical drain pipes?

Some building are really tall, if you flush the toilet and the contents go into a pipe and straight down, there could be a lot of energy, potentially enough to cause harm to the sewer pipe at the end of the fall. I know that in my home, the pipe…
James Jenkins
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Why are two wires used in railway overhead equipment?

While watching the train videos, I came across these overhead wires. After searching on the internet, I found that both catenary and contact wires carry the same voltage and are connected by vertical wires called "droppers" at intermediate points…
mech_duck
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Why dig out and then fill in before building a large structure?

I work in the middle of London, in an area full of large office blocks. Across the road from my office they have started construction of a large building (10 stories plus). Over the last few weeks, diggers have dug a large (and vertical walled)…
AndrewD
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Why are engine blocks so robust apart from containing high pressure?

Lately, I've been pondering why some engine blocks are so bulky, I always thought intuitively it was because they had to last a long time whilst containing thousands of combustion cycles but the more, I look into the reality of engine design that…
David Nolan
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Why would you launch a large ship by dropping it sideways?

I'm referring to the process shown in this video: https://youtu.be/Quyr5R1Rbfw?t=20 Or this image from Wikipedia: In it, a large warship is launched into the water by essentially dropping it sideways down some ramps and off of a pier. The ship…
aroth
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Why do wooden gate designs recommend a brace under compression instead of tension?

Looking at guides for building wooden frame gates I almost always find the following design recommendation: The idea is that the cross brace will distribute load from the top outside corner into the bottom of the hinge bracket. I understand this…
jesse_b
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Is it structurally sound to cut an I beam to a T on one end?

I'd like to confirm whether the replaced beam in the attached picture is structurally sound given the end was cut to a T instead of an I. I had a qualified structural engineer approve the work but I'm curious about the engineering properties of the…
markroth8
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Does a roadway bridge experience more load when vehicles are parked or when they are moving?

Bridges are designed for the loads that come from the vehicles that are expected to cross them. This includes the weight the vehicle and any dynamic loads that may be introduced from movement of the vehicle. Dynamic loads may be from "bouncing" or…
hazzey
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What is the purpose of building foundations?

According to many sources, one of the purposes of building's foundations is "To distribute the weight of the structure over large area so as to avoid over-loading of the soil beneath." (Wikipedia) On the Wikipedia page on foundations, there is the…
S. Rotos
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Why are truss bridges the way they are?

Just by taking a train ride across my home city I can see truss bridges like the one in above picture everywhere. There are numerous variations, but the most common design seems to be this. But why are they built specifically this way? I can…
S. Rotos
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Why is this bridge thickest above the support pillars instead of the mid-span where the bending stress is highest?

Why is a bridge designed like this? The depth of the section at pillars is more than the depth at middle. If I model this as a simply supported beam having load at mid span then the bending moment will be maximized at the middle and the area is…
MechaTrex
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Why do we even use engineering stress?

Surprisingly this hasn't been asked before, so I must be missing something simple. We use engineering stress and engineering strain in this eq. Stress = (Young's modulus) × (strain). This eq. is used in analysis of bending beams, twisting shafts…
Jessica
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Why does column buckling occur when the load is parallel to the column?

I'm studying Euler's work on structural engineering from a book out of curiosity and it is mentioned that he developed a mathematical theory describing the buckling of columns under a parallel load (the weight-force of the load is directed down…
S. Rotos
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What is the difference between the Polar Moment of Inertia, $ I_P $ and the torsional constant, $ J_T $ of a cross section?

This question is so fundamentally basic that I am almost embarrassed to ask but it came up at work the other day and and nearly no one in the office could give me a good answer. I was calculating the shear stress in a member using the equation,…
William S. Godfrey- S.E.
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How does pressure treatment affect the mechanical properties of lumber?

Pressure treated lumber is specified for many exterior applications because of its resistance to insect damage and fungal rot. But how does it compare to untreated wood, mechanically? For example, consider a rim joist supporting the ground floor of…
Air
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