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Recent content by sven

  1. sven

    advice for horizontal reactions on trusses

    You must be very careful if you tell your software that you have 2 pinned ends. The analysis will distribute forces in the truss quite differently from the pin-and-roller support case. This exact design case caused collapse of a large steel school roof truss in Singapore, 2 years ago. The...
  2. sven

    Train Rail

    Andy, I believe that your method is basically correct, but for a "construction" design to work you will have to modify the usual conservative structural assumptions. Also, I don't agree that the subgrade will provide any significant support unless it is extremely stiff and then you...
  3. sven

    Why is that in proving the theorem

    xter, It's just a sign convention. You can use any mathematically consistant system. Many structural engineers prefer to call downwards deflection "+ve" and the corresponding bending moment positive also. Mathematically however, a downwards load causing a downwards deflection is...
  4. sven

    Slab edge supporting steel balcony

    Rcslab, I assume that you have checked the existing concrete slab for the new balcony load. My preference for fixing in such cases is to extend the new steel beams as far under the existing balcony as possible so as to maximise the favourable lever-arm. Also, at the slab edge fix into the...
  5. sven

    Beam with kink

    Aimmee, If your beam is carrying relatively small loads, as a stair does and has a relatively short span say less than 8-10m and is a relatively unimportant part of the structure, then I would say that you could design as if it were straight. You must allow for the additional wself weight due...
  6. sven

    Is a col tie or beam stirrup smaller than a #3 bar possible

    SamDamon, Here we use "hard drawn wire" ties, grade 500MPa steel. Spiral ties are a good solution, if you can get them in a suitably rectangular shape. To restrain your steel during concreting, I would recommend maximum spacing 300mm for 6mm dia ties.
  7. sven

    Design by rule of thumb

    Timber floor joist design: Take the span in feet, divide by 2 and add 1 for hardwood, or add 2 for softwood. The result is the joist depth in inches. eg 10' joist needs to be 6" hardwood or 7" softwood. This appears to be based on joists @ 18" centres, domestic loads only.
  8. sven

    Is a col tie or beam stirrup smaller than a #3 bar possible

    In Australia our codes allow the use of ligatures down to 6mm dia in columns, to restrain small bars (max 20mm I think). For beams, I have used 6mm ligs in small, narrow and lightly loaded beams without problems. The main problem with small dia bars is the lack of section area to resist shear...
  9. sven

    Steel Fibers in Concrete Slab

    Ludvik, Steel fibre slabs are used in Australia for heavy machinery slabs both in buildings and in the open. Usually, this is done because of the significantly improved tensile strength of the mix, with resistance to wear a bonus. Steel fibres are expensive, here they increase cost by 50% to...
  10. sven

    wood beams with partial steel flitch plate

    Jeff, Fitch plates are reasonably common in domestic construction where a beam span is to be increased without significantly changing the profile eg when an intermediate support is removed. Timber is often strong enough but not stiff enough. Steel being 10-20x stiffer that timber, a 5mm steel...
  11. sven

    Temporary roof supports

    Either method is OK, provided it is properly designed and detailed. The conventional solution would be to provide temporary support from below eg scaffolding etc and then remove and replace the structure. In m experience, this is also the cheapest option and hence most usually adopted. If the...
  12. sven

    4" by 4 " angle 1/4 "

    The angle has different strengths depending on its orientation and load direction. In general, it is strongest with a flat top and one leg vertically down, when loaded vertically downwards. Deflection will be the same whether the orientation is leg up or leg down. Hope this helps.
  13. sven

    Uplift Capacity of Sill Plate Anchor Bolts

    Dave, Timber has a very high short-term strength and therefore under wind load you can generally use a significant "overload" factor. In the Australian code, a factor of 2 is allowed for this. Otherwise, your approach sounds correct. Sven.
  14. sven

    torsion on bridge girder

    Dison, There is no question that the eccentric load will produce a torque on the beam. This torque will twist the beam. For design, we usually consider the interaction of shear and torsion in the beam. Where torsion is significant, this usually results in additional ligatures and additional...
  15. sven

    CONCRETE FOLDED PLATE

    V2, It is important to consider horizontal reactions from your folded plate, and how these will be resisted by the supporting structure. Alternatively, if you do not provide full horizontal restraint, you must accurately calculate and allow for the horizontal movements of the plate. If the...
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