Questions tagged [civil-engineering]

Questions that fall into the problem domain of civil engineering or one of its sub-disciplines. Questions about buildings or other structures could usually use the "structural-engineering" tag also.

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30 views

Response time and time constant of Mercury thermometer

I searched to find differences between response time and time constant of a thermometer. So I found that those two are not same and we have to get 99.3% of the total step change to find response time ...
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1answer
19 views

Force required to vertically pull a post out of ground with various soil types

I am trying to determine the force required to vertically lift a typical traffic sign post (round, square and/or channel) out of the ground based on typical soil types at standard installation below ...
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Do PVC concrete joint water stops degrade over time? Or were they never installed correctly?

A UK subterranean reinforced concrete structure built in the late 1960s has experienced sustained water ingress over time as shown by the deposition of minerals of the walls: According to the ...
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1answer
98 views

PE exam: situations in which two question choices are close to my final answer: how to pick one?

Consider this question: I solve this eventual question and my answer is 7.29667: Among the question choices are 7 x 7 ft and <...
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2answers
42 views

Elasticity values in stiffness matrix?

Stiffness, k, is defined by $$k=\frac{Force}{deformation}$$ if you insert this into formula $deformation = \frac{\text{Force}\times\text{ Length}}{AE}$ you get $$k=\frac{A.E}{L}$$ where E is ...
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Maximum Compressive stress [closed]

My peers and I have been stuck on this problem for days and our final is in 38 hours. Our professor won't provide practice exam solutions so any advice for solving this would be much appreciated.
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How do I start determining the forces in the 3 bars?

For part A I have $\Delta$A + $\Delta$B = $\delta$. For part B I've tried summing forces at the joints but keep getting lost. Any help is appreciated my final is on Friday.
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1answer
79 views

Designing PVC structure

I am an electrical engineering student that wishes I could have taken some civil engineering courses. Anyways I'm trying to design a pvc structure that I will use as a somewhat complicated room ...
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0answers
39 views

How would you build a road system that respected nature? [closed]

How would build a road system or transportation system that respected nature with the following constraints: No paved roads or less than 10% paved roads can’t use gasoline (oil) allow nature to ...
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How can steno's law of superposition be relevant in construction? [duplicate]

Steno's law of stratigraphic superposition states that younger layers of rock sit atop older layers. Meaning that the youngest stratum in a sedimentary sequence will be at the top and the oldest at ...
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1answer
48 views

How do engineers reduce vibration of system with multiple known natural frequencies? How do they design the isolation system for specific frequencies?

I have a system that is pretty much a chamber that needs to sit on the ground. I measured the transmissibility of the chamber vs the ground (output/chamber acceleration over input/ground acceleration) ...
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Stiffness factor of beam member

If I have a beam with the left end being "A" and it is fixed at that end and the right end being "B" with a roller support, would KAB=3EI/L??
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Fixed end moments

If B is a roller or pinned, should the fixed end moment for AB be (wl2)/8?
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what means Probablity of event excedence of so many years

I like to know about occurrence of earthquake events when we say that earthquake of 0.5 g will occur in 50 years in excedence of.
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1answer
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Is it possible to use Plain Cement Concrete post for fencing?

I am in need of around 700-800 posts to fence my farm in a semi-arid area in TN state, India. In my place granite posts mined from quarries are normally used. It costs around Rs 300-400 per post(6-7ft)...
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1answer
84 views

What approaches are there for demolishing a structure and how is an approach chosen?

From my office on the 21st floor of a building in Vancouver, BC two parking garages in the process of being demolished are visible. A third is just out of view a few more blocks away. One of these ...
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How is any kind of structural reliability achieved if the probability of annual wind speed exceedance is 0.02?

Above is the definition of fundamental basic wind velocity from Eurocode 1. According to its instructions, wind loads on building are supposed to be calculated based on this velocity. It says that ...
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1answer
428 views

Is there a method to determine the runoff for arid areas in developing countries?

Note: this question was totally rephrased and expanded on, addressing the comments and questions posed to the first version. The de-facto standard source for runoff calculations in South Africa is ...
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1answer
89 views

Difference in flow measurements in an open channel

I'm undertaking a civil hydraulics question. It involves the flow of water in an open channel down a river at $5m^3/s$ until the flow is split in two by a weir acting as a sluice gate allowing flow ...
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3answers
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How are tunnels dug from two endpoints joined?

Let's assume I want to build a subway system. I dig two subway stations and now I start digging a tunnel from both of these endpoints simultaneously. How can I ensure that the two tunnels dug from ...
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3answers
73 views

Statically determinate system

The exercise is taken from linear algebra and its applications, prof. G. Strang Exercise 2.4.8 Truss I have already found that: m=n=8 → system is statically determinate, therefore solvable by ...
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2answers
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How is high static water pressure avoided in municipal water systems?

Most cities get their water supply from local sources (springs, rivers, lakes) so the pressure in the system is never more than what is produced by the pumps. But some cities get their water from ...
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1answer
67 views

Questions about a controlled demolition video

I came across the following Youtube video which shows the controlled demolition of a chimney. https://www.youtube.com/watch?v=Sb62_QesDTw The construction of the chimney appears to be reinforced ...
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1answer
397 views

Finding the velocity of water flowing through a gravel filled pipe

I have a scenario where I have water flowing through a gravel filled pipe, and I need to find the velocity. The pipe is gravity fed (no pumps). My approach is to find the seepage velocity ($V_s$) ...
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1answer
50 views

Linear Motion Stage with Offset Loading Problem

I'm currently developing a linear motion system which will have to withstand a large offset load (see image below). There will be two rails, each with a carriage on, which will be connected by a beam/...
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2answers
83 views

How to simplify a truss bridge diagram?

Hello I have this truss structure question. I understand that we need to determine the zero-force members first so that we can simplify the diagram. But I am not sure which one that I need to ...
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3answers
404 views

Maximum hole size in brickwork before a lintel is required

Holes are made in brickwork walls for all kinds of reasons including gas flues, to route cabling and to fit windows. At some point that hole gets large enough that a lintel is required to support the ...
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3answers
69 views

how much force is required to drive a fence post 2ft into soil or sand using a hydraulic press?

I'm building a post driver for the farm and it got me thinking: what force is required to drive a 6ft(1.8 m) 4 inch (100 mm) post 2 ft into the ground? I'm wondering how different soils affect driving ...
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1answer
360 views

Industry standard factor of safety for ballast design

What design standards exist for the design of ballast against uplift forces, and what factor of safety against uplift do these design standards promulgate? I am familiar with a typical FS of roughly 1....
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1answer
48 views

FE Exam practice: “How many years until you're a millionaire?” [closed]

One of the early questions in the NCEES FE Industrial/Systems Exam studyguide has a solution that I can't decipher. The question is as follows: ...
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1answer
854 views

What is the purpose of digging up trench and then filling with something similar to asphalt crack filler?

Recently there has been road construction around on the main road leading into my office building. I observed the construction crew removing asphalt in the form of a trench as showed in pictures below....
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Civil Engineering - Detailing of free draining backfill and modelling of hydrostatic pressure in retaining walls

It is considered best practise to specify free draining backfill material (eg gravel) to be placed immediately behind a retaining wall. Supposedly, this alleviates hydrostatic pressure on the wall, ...
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4answers
155 views

Why does a beam in shear crack at 45 degrees?

Why does a beam in shear like in this picture crack at 45 degrees instead of vertically? This is called "Punching shear", and requires concrete reinforcement at an angle: Assuming that the ...
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1answer
40 views

Lintel construction technique in UK in 80s using blockwork

An issue has been raised when replacing windows that the blockwork inner leaf is missing a lintel. The hollow blocks have been in-filled with concrete which makes me believe that this is a ‘cast-it-...
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109 views

Could pre-stressed graphene be used to reinforce granite block construction?

I am curious whether this will become an option, especially for longer lasting structures. Could pre-stressed graphene or another high tensile strength material by used to reinforce granite block ...
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26 views

Conversion of orthographic projection to isometric projection [duplicate]

I'm new to engineering drawing, and I am having trouble drawing isometric projection from orthographic projections. Can someone give the steps/thought process behind this conversion? I can upload the ...
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1answer
399 views

Is possible for a silt soil to be compacted hard as a rock?

I had been told that a silt soil, when professionally compacted (from all the laboratory essays to the compaction with a vibratory roller), ends hard as a rock, and when hit with a metal bar it makes ...
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1answer
31 views

What should be the relation between flange length and web thickness for an optimum I - beam?

While learning about I-beams I became curious to know if there is any relation between the flange length and web thickness of I-beams or if its arbitrary.
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66 views

A mechanical system with coupled oscillators and dampers

I found here Coupled oscillators, the last one on this page, a system named by the author "Vehicle Suspension System". But I am not sure this modelizes a suspension for a vehicle. I am ...
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3answers
81 views

Axially loaded member with a spring / Mechanic of Materials

i've been struggling with this problem i made up. It is about a cylindrical copper member (diameter $d=20$ mm and length $L=250$ mm) with a spring (stiffness $k=166,5$ kN/mm) fixed on a wall, as the ...
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63 views
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4answers
98 views

Deflection of a fixed-fixed pvc pipe under self weight

I would like to start by saying I am not an engineer, so I apologize if this question seems simpleminded. I am making a manual tarp reel from pvc pipe, and I am trying to decided whether to use ...
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1answer
42 views

How do you determine flow distribution at a dividing T-Junction?

So I've been trying to find out how to determine what proportion of fluid will flow down a given path when a main line branches into two lines at a 90 degree T-Junction and I can't find anything ...
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1answer
92 views

What is a 'rocker slab'?

See below for an extract from a general arrangement drawing from the 1980s. It makes reference to a '9" rocker slab' which appears to be a slab supported by steel beams. Does anyone have any ...
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2answers
117 views

Cooling tower for nuclear power plants

Cooling towers for nuclear power plants often have the shape of a hyperboloid. At first glance, I thought that an obvious reason for this would be the smaller sectional area, meaning the tower would ...
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5answers
5k views

Why are some public benches made with arm rests that waste so much space?

While watching a YouTube video today, I noticed this public/park bench somewhere in the USA: It looks strange to me the way the arm rests on each side are so far into the bench, wasting a rather ...
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2answers
75 views

What's the name of the calculus used to make smooth transitions in roads?

So I'm not actually an engineer, I'm a novice computer programmer but I think in order to solve a problem I have I'm going to need some help from the world of engineering. I remember in high school ...
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1answer
86 views

How to professionally mount an air duct through a core hole in limestone brickwork

We need to add ventilation holes to an existing building. The holes will be core-hole drilled through a limestone brick wall. The bricks have crevices. The contractor is acting stupid and obstructive ...
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2answers
89 views

Eulerian description of fluid flow

In Eulerian description of fluid flow, we observe how the properties of the fluid are changing at a point. Since a point has zero dimension hence a zero area, how can we make sense of the 'finite ...
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27 views

Inspection chamber in sewage drain

For civil engineers, There is a high drain connection work is under progress in my location. Few days ago, a contractor visited my house and asked me to construct 2ftX2ft inspection chamber inside the ...

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