# Recent content by pongo38

1. ### Engineering Plastic Analysis: Upper Bound Theorem

In your initial sketch, allegedly without sway, you have included some sway of the left hand column, but not of the right hand column. The line AF produced meets the line DC produced at a point 4 m above C. This is the instantaneous centre of rotation of the beam segment FC, say call it point...
2. ### Simple Question - Preloading of a Cantilever Beam

Could this be an axial load in the direction -ve x in order to prevent tension developing at top left corner?
3. ### Frame Deflection homework

You seem to be ignoring the deflection of E in the y direction. That will increase the deflection at C.
4. ### Force members

In order for there to be a vertical component of reaction at C, member CD would have to be inclined rather than horizontal..
5. ### Shear force in influence line of beam

There are at least two ways of learning about influence lines. The first way is algebraic, as given in the solution quoted. If you have learned about shear force diagrams before coming to influence lines, it is easy to get the two things confused. It is necessary to keep returning to the...
6. ### Evenly distributed beam with overhang and multiple supports

I think you seem intent on using elastic analysis, which is fine at working loads, if can do it. However, plastic analysis is easier, and arguably safer, whilst admittedly not giving you deflections.
7. ### Statics problem. Cable with distributed load

You know the forces at the ends of the cable. You know those forces are tangential to the cable ends. You know the drag. That makes 3 forces. If they are in equilibrium they must all meet at one point. You don't have enough information about the cable self-weight to take account of that. Can you...
8. ### Stress in steel and concrete

Still looks funny. I am struggling to visualise 3.174 mm2. You haven't declared your units. Can you explain the 10^6 and the 10^3 in your corrected equation?
9. ### Stress in steel and concrete

Your answer of 0.52 mm2 seems improbable, if not impractical, and so, without looking at your working, I am inclined to try a different approach. The usual problem here is often the units; so stick to, say N and mm. Try a concrete area of say 50 mm x 50 mm. At 14 MPa (ie N/mm2) , its resistance...
10. ### Force Couple on Frame

The assumption that a point of zero moment occurs half-way up the columns is unconvincing, because the conditions at the top and the bottom of the columns are not the same; at the bottom it is encastre and no rotation is assumed to occur, but at the top of the columns, the fixity is provided by...
11. ### Moments in beam

The diagram is quite a good representation of what I mean, although I am struggling to understand your language: "800Nm is the diffrence in length of the triangle"
12. ### Moments in beam

You are right to recognise that the 2400 has a different orientation to the -2000. But, just as you can add a positive number (say, +6) to a negative number (say, -2) to give a result of +4, so you can add areas on a graph. At a point just to the right of C, the result is +2400 -2000= +400 (the...
13. ### Beam deflection

Because the expression for M is the summation of moments to the LEFT of section X, but the 12 kN load is to the right. If you were to write down an expression for the moment to the RIGHT of x, you would get an expression that may at first sight look different, but, if correctly drawn up, will be...
14. ### Moments in beam

Unfortunately the M diagram you gave us is not drawn to scale. I suggest you redraw it to scale on graph paper. Let's call C the point of application of the 400 Nm moment, and point D the point of application of the 1000 N load. If you redraw the 2000 Nm triangle above the horizontal axis, as if...
15. ### Moments in beam

The so-called 'missing' 400 Nm is the difference between 2400 and -2000. This is a graph preparing for gaphical summation. If you like, you can imagine folding the lower triangle about the horizontal axis, to cancel a good bit of the right hand upper triangle. The zero line would then, in that...