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To answer the original post Concrete is permitted to have an in situ strength lower than the cube or cylinder strength, to account for the fact that it is not possible to replicate the compaction and curing of the cube or cylinder specimens in the actual work. ACI 318 recommends for strength...

If there is no possibility of finding out the rebar information then a good start is to assume the minimum reinforcement corresponding to the age of the beam, bearing in mind at some time in the past people could use exclusively mild steel rebar too. The bending capacity of a RC beam can be...

stanier, The pea gravel has an elastic modulus and is easily deformable. Unless the pipe is concrete surrounded the celerity isn't going to change much. The standard waterhammer analysis uses the method of characteristic at specified intervals. To avoid interpolation between grid points...

Let me advocate the greatest engineering technique "Trial and error" Just tabulate the Manning equation on a spreadsheet List a depth and compute the flow When the flow first exceeds your known target flow refine the depth to any accuracy you fancy. If you know a bit of Visual Basic you can...

All structural elements are springs with axial, shear and torsional stiffness. If the cables are properly modelled they should have very little shear and torsional stiffness and should take up the bulk of the axial loads as expected. For its small cross section a cable can take very little...

From the practical view point the celerity of a fully rigid pipe in a rock tunnel is about 1300m/s and the normal wave speed for a thermal plastic pipe would be between 400 to 700m/s (GRP, PVC etc). The soil would have little impact unless the circumference is fully restrained to the point the...

From my line of work people use fly ash to reduce heat from a large pour or improve the chemical resistance of the concrete. Microsilica is more used for protection of the rebar. As Daveflax said it is 100th the size of a cement grain and so the concrete matrix is less permeable than OPC or...

I have come across threaded bars in the design. The threaded bars were there for other reasons as I cannot imagine an engineer in his/her right mind would want to thread a bar to save in the development length. I would just specify the development length of unthreaded bar even if it is...

I would use just a plane frame program to find out the forces in the system as the first stab and look for refinement if needed. The large deflection theory isn't as complicated as it looks because in order to be serviceable the bridge has to be pretty stiff and its variation with...

Normally the first nat freq would lie somewhere in between simpply supported and fully fixed conditions, both are well defined by the textbooks. Should use them for sanity check after FEA work.

BBC news report 1 July 2005 http://news.bbc.co.uk/1/hi/england/beds/bucks/herts/4639671.stm I am sur there will be a thorough investigation despite no injury to people. However to any structural engineer an arch has been used by our predeceesors to take compression only, usually for uniformly...

If the source point of the sewerage has a sufficient head above the discharge point there is nothing technically against the power recovery by dropping in a Kaplan unit. The erosion of the runner is obviously an issue but at 250kW the associated equipment and maintenance work may not be as...

Been away for a month and come back to this thread again. I think notnats has got it. The system acts like a series of U-tubes. Each summit will have an air lock which must be compressed in order to push the oil column along. After flushing with water the first downhill section will be full...

pumpdesigner, Thanks for the reference. However it is for thermoplastic underground irrigation pipeline for maximum pressure upto 315 psi or about 21 bar. The failed pipe is ductile iron and is rated at 26 bar. I would appreciate any feed back on if such practice is widespread. There is...

Sorry Got mixed up with 1 N/mm2=145 psi

I must be missing something here. The terrain has 200ft rises or 60.96m. Water rising to the top of a 200ft peak must require a pressure of at least 6 bar (1 bar = 10m of water pressure and 1 bar = 145 psi). Thus pumping water at 150 psi gives us a pressure of no more higher than 11m water...

I am in an fortunate situation of having to investigate the collapse of a rebar cage that killed two working crew members while I heard another rebar wall panel collapsed and killed 5 in another site. We don't rely on ties for strength but it is prudent to evaluate the full consequence of the...

I have come across a bell & spigot joint pulling out in front of a thrust block. Except for a small concrete plinth supporting the dead weight of the pipe body the joint has not been restrained and is part of an above-ground installation to a 62" welded pipe system. The below ground portion is...

Not an electronic engineer myself but your idea is just automating the hot swap of the USB 2 hard disks. Thus in theory it should be OK but I don't see the real benefit. By the time you hook up the 25 disks together and use them sequentially you will lose touch of which disk is holding what...

I can't recall any rule on the minimum diameter of tensile reinforcement and have seen both 10mm and 8mm used in very thin slab (insitu layer pour over precast concrete slabs). Frequently used mesh reinforcement are around 10mm to 8mm. Many codes do specify minimum diameter for compression...