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8

Your idea could be ok, but depending on the situation it has a major flaw. The PE pipe would basically be there to contain the wet concrete, while we wait for the concrete to cure (i.e. to set and strengthen). This is the situation where we need to worry about pressure from the concrete on the pipe. Once the concrete is cured, however, the concrete on its ...


8

If you are looking at the column as being supported at the ends, you are correct that the n=1 mode gives the lowest buckling load. The other modes (n=2,3,...) aren't useless though. Long columns are often braced at regular intervals to reduce the unbraced length of the column. For a given length of column, these braces force the column to buckle under a ...


7

Whether or not buckling modes with $n>1$ exists depends on how you look at the structure. As @hazzey notes in his answer, columns with bracing may display buckling modes with $n>1$. These buckling modes, however, are simply equivalent to the $n=1$ modes of the individual segments that compose the column. To be clear, this doesn't mean that the ...


6

The column top holds some narrow thunk and that thunk holds the driveway floor. I think we have some nomenclature that needs to be cleared up here. What I believe you're calling a "thunk" is actually a bearing plate. This is a little steel platform that transfers the load from the bridge to the column. (source) The expanded portion at the top of the ...


5

Compared to steel, polyethylene (PE) is a weak material. Steel is an order of magnitude stronger than PE. This site from the US gives a tensile yield strength for PE of 3800-4800 psi, which is 26-33 MPa and this other site from South Africa gives a tensile yield strength of 26 MPa ($N/{mm}^2$ is the same as $MPa$). Whereas this site lists the tensile ...


2

AISC's magazine, Modern Steel Construction periodically publishes a guide to specifying grades of steel to help engineers stay aware of developments in the market. Their latest edition, from this February mentions A1085, but still suggests A500 Grade C as the standard. They recommend checking that A1085 is available and affordable in your area - it sounds ...


2

Set maximum yield stress of 70 ksi (useful for seismic applications, though I am not well versed in this area) If I have no need to restrict the maximum yield strength of the material and I have no fatigue concerns, is there any benefit to specifying the newer A1085 tube steel material over the existing A500 specification? For practicing engineers in non- or ...


2

So there's a permutation of rotation and translation each being either fixed or free for a column. What do each mean? To say that a specific degree of freedom of a support is "fixed" is to say that the support cannot translate along, or rotate about, that axis. For example, if it is stated that the translation of a beam is fixed in the X axis at one end, ...


2

That triangle marquee is called a gable. And the house is built in Colonial style. And of course it can be removed, provided you get the required permit. One alternative that may be less costly and is in line with this style, and may be even a bit more classical, is to keep the columns and gable roof but add a balcony on the first level to do the job of ...


2

I find such a column hard to justify. As mentioned by @grfrazee and @ChrisJohns, what you are calling a "thunk" is usually called a bearing plate, and these are responsible for transmitting the force from the superstructure (beams) to the mesostructure (columns). As mentioned by @ChrisJohns, these bearing plates may well be bolted, in which case a minimal ...


1

Columns like this are often connected to the horizontal elements of the structure they support by bearings which are designed to support the vertical load from the weight of the structure but not transfer horizontal loads to the columns. This ensures that the columns are loaded only in compression and allows movement of the structure they support (in this ...


1

You should use $ K=2 $ and the allowable stress $$\sigma_{allowable}= \frac{\pi^2*E}{n_u(\frac{kl}{r}^2)} \quad (Eq. 3.4.7-3) $$ $n_u= buildings safety factor =1.9 $ $r= radius of \ gyration=\sqrt {I/A}$ Source: Aluminum Design Manual 2005.


1

You should remove the rocks by explosion or rolling them away from the foundation. A site with large boulders is usually a young geology. deferential settlement and high underground water table are likely. You should get a geologist check it.


1

You've calculated the Euler buckling force, not the compressive strength. The part of the code you want is EN 1993-1-1 section 6.3.1, which specifies how to account for imperfections and safety factor in order to calculate the allowable load. The size of the imperfections depend on whether the profile is cold formed or hot finished and the relevant safety ...


1

You should take $\psi=0$, typically for fixed braced concrete column, design aids set the bottom as zero flexibility. Common sense then tells us that if we have a column with top and bottom fixed; it has 2 inflection points at 1/4 length of the column from the bottom and top. Hence we get K= 1/2, which is as shown on this chart.


1

The root problem of your question is that you're asking us to make some engineering judgement calls and calculations for a building where we don't know all the relevant details. You could however calculate the slenderness of the existing column and then propose a section that has this slenderness or less. The slenderness parameter that is commonly used here ...


1

No, you make the tubular strong enough to take the loads.


1

Structural metal tubing is normally used to take bending, axial and shear loads, i.e. to globally transfer load from one place to another. It also has to resist local loads, i.e. if there is a concentrated force or impact force in a particular location, the member has to not buckle locally. In other words: bending shear and axial and taken by (more or less) ...


1

As I understand your question, you are asking how to determine how the loads from the upper floors are divided between the lower columns. For instance, column C14 is going to transmit its loads to C12, C17, C18 and the unnamed wall near the core (assuming its load-bearing). How much of the load will go to each of the columns? Curiously enough, the answer to ...


1

Using a purely energy-based approach, while theoretically possible, is not recommended. Not because it wouldn't work, but simply because most codes don't use such methods. The reason is that railings, as well as any structural elements, are ruled by codes. In Brazil, the relevant code is the NBR 14718, which defines the static and dynamic horizontal and ...


1

To start off, I thought I'd just throw up a conceptual sketch of an interaction diagram as a point of reference. Re: Question #1 --- My best guess is that you're referring to a location in the compression controlled region where the strain profile is as in Case A, below. As you state in your question: By definition, $c$ is the distance from the extreme ...


1

Your integration limits should be y to 1 to get force at height y. For example at y=1m force due to self weight is zero, and deformation is again zero; Again when y=0, self weight is maximum. I will leave the further work outs to you.


1

This approach has been used in many, many scientific studies, and is an active area of research in the materials engineering community, but with a different material. FRP (Fiber Reinforced Plastic) is used to wrap around an existing concrete column (or using an FRP pipe filled with concrete), with very good results. Sources: 1 2 3 4


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