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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28 views

How to build instant mountain? [closed]

Create an instant mountain that is up to 2 km high, 5 km length, and 3 km width using expanding foam concrete. Would it be possible? Can we build houses on top?
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1answer
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Building lightweight 1 km high fence [closed]

I would like to build a fence that is 5 km2 and height of 1 km. This wouldn't be feasible as the material needed and cost implications plus environmental factors. Therefore I thought of finding the ...
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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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2answers
76 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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1answer
47 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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2answers
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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
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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
39 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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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
46 views

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
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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3answers
63 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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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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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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4answers
97 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
37 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
74 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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5answers
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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
74 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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0answers
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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1answer
42 views

Why isn't there yet such a thing as a “Minimum Life Module” standard and concept deployed? [closed]

Why are large companies not producing, selling and maintaining the concept of "Minimum Life Modules"? What I mean is a standardized "module" hosting exactly one human being, with ...
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2answers
586 views

Why do air entrainment admixtures improve the freeze-thaw resistance of concrete?

It is stated on here that: Air-entraining admixtures cause small stable bubbles of air to form uniformly through a concrete mix. The bubbles are mostly below 1 mm diameter with a high proportion ...
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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
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The difference between two load combinations in LRFD

In ASCE 7-16 there is a load combination as: 1.2D + 1.0E + L + 0.2S but then there is also another combination as: 0.9D + 1.0E In both of them earthquake load is the same so why would we use the ...
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3answers
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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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double integration of continues beam to find the deflection at mid span [duplicate]

does any one know how to derive the deflection equation of a continues beam of three span of equal length and equal UDL load some of the steps of this explanation I didn't understand it Here's a link ...
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41 views

Continues beam deflection

does any one know how to derive the deflection equation of a continues beam of three span of equal length and equal UDL load Here's a link these two pictures shows my tries to solve the question
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1answer
41 views

What is “hyperstatic moment”?

Above is a picture I found online, showing a prestressed concrete beam. It mentions a "hyperstatic moment". When a beam is prestressed, it deflects upwards. According to the picture, this ...
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1answer
62 views

What exactly is Hooke's law defined for?

I used to think that Hooke's law was a relationship between how much a bar under uniaxial loading deformed and the internal force (per unit area) that developed within that bar. But this clearly isn't ...
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1answer
134 views

What's the difference between Creep and Dynamic Viscous Damping?

What's the mechanism behind each phenomenon and what's the difference between them? Why is Creep considered in the Constitutive Equation (taken as an inelastic strain) while damping is considered in ...
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Design of T-Beam

Please design a T-beam section size such that hf ≥ 125 mm, bw ≥ 200 mm, be ≥ 500 mm, d ≥ 300 mm, the concrete f'c strength is 25 MPa; the calculated concrete shear strength Vc that can be provided is ...
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1answer
29 views

How do hooks/bends cause bearing stresses in reinforced concrete?

Can someone please explain the exact mechanics of development of bearing stresses in concrete on account of bending of steel reinforcement and/or providing of hooks at the beam-column junction for ...
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2answers
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Can anyone help me with the concept of bearing stresses in steel reinforcement in Reinforced Concrete?

When there is tension reinforcement(steel) embedded in concrete, does it not also undergo bearing stresses on account of the weight of the concrete and other forces which are acting above the steel? ...
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1answer
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What is this circular metal object embedded in spalled concrete?

Consider the piece of spalled concrete shown in the attached image. It has spalled due to the corrosion of the reinforcement bar. There is a small circular piece of metal embedded within the spalled ...
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5answers
590 views

How does the parabolic curve help in the integrity of a suspension bridge?

Why do suspension bridges need to be parabolic? Why can't they connect the towers directly? Would it not use less material and cost less?
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1answer
37 views

What fluid is generally used for laboratory testing of hydraulics?

Which liquid is generally used or is it better to carry out hydraulic laboratory tests?
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1answer
28 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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1answer
62 views

How to calculate the square footage of a duplex building

In a college project, I was instructed to design the floor plans and the conduit layout of a duplex building. It was instructed that the duplex is 2500 square feet. No other instruction was provided. ...
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1answer
51 views

Why is there a side walk in the ditch in between two highways?

I noticed what looked like a side walk in the ditch in between the freeway. It repeated for a few miles. At the ends of the sidewalk were small gray slated boxes about 6” or so. The length of the ...
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1answer
24 views

Does bulk specific gravity (Gmb) of asphalt specimen change with sample size?

If a 6"x4" asphalt sample is cut down to smaller dimensions (let's say to prepare a DCT testing specimen), does the Gmb value change from the original bigger sample? If it does change during ...
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1answer
35 views

Tunnel lining vs structural support

Is tunnel lining the same thing as tunnel structural support? And then also there is always the initial and final lining? Are three all different things? And how do they relate to waterproofing? It ...
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60 views

Choice for HEAVY blacksmith table

I have an old 7,000 lb. blacksmith table (I had it weighed at truck stop). Similar to the one this man has: Sorry for the size of the pic. I need to lift one end the way he is doing and I have a farm ...
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1answer
36 views

Can changing the colour of roofs change the average temperature in a suburb?

I want to be able to determine if changing the colour of the roofs in a suburb will change the average temperature of the suburbs. E.g. if the roofs in a suburb were changed from black to white would ...
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2answers
56 views

Concrete rebar cover requirements - Hook lift anchors

ACI 318 7.7 covers requirements for cover when designing rebar placement within concrete. However, they are for general components and makes no exceptions for small irregularities such as lifting hook ...
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27 views

Modern equivalent concrete strength to 'Class Ws 3/4" '

Consider the following extract from a UK reinforced concrete detail drawing dated 1970: What is the modern equivalent to this concrete class?
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23 views

Help sizing of lug attachment flange/plate?

Apologies for the crude drawing attached, but here goes. Given Fx, Fy, and Fz loads applied at the lug hole, I've distributed the loading into each of the 6 fasteners to size them. I've also sized the ...
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0answers
36 views

What does “Percent Trucks in Design Lane” input represent?

In the AASHTO Pavement ME program version 2.6, for the traffic input "Percent Trucks in Design Lane" is the default value of 95% based on the maximum percent of trucks that can occur in the ...
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2answers
49 views

Standard vs code

As an example ASCE 7 is a code that every civil / structural engineer must follow in USA. But if you look at ASCE 7 itself, search the word "standard", it calls itself a standard in many ...
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1answer
48 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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