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About freebutterflyx

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  • Birthday 01/01/74

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    Brugge, Belgium
  1. I (we) have been asked to make a 3D calculation model. I only have to model the geometry, the loads, combinations,.... The actual calculation and the optimalisation will be done by someone else. The project consists of : - 2 buildings with each 4 office levels + 8 levels with 4 appartment on each level - "bridge" between them Each building has a center concrete core, concrete outer/inter load-bearing walls and concrete floor slabs. (footprint of the building is +- 22m x 22m) The model itself isn't very difficult. But I have a question about combining the variabel loads on the floor. Each level has 4 "units" (office or appartement) and there are 12 levels. Should I make 1) 1 loadcase for each unit? So I have 12 x 4 loadcases = 48 loadcases of variabel loads to make combinations of? 2) or 1 loadcase for each level = 12 loadcases to combine? 3) of 1 loadcase for each unit (all levels together) = 4 loadcases I would think in theory, I need to make 48 loadcases. But this will give a lot of combinations. How would you handel this?
  2. There is no "public" road over the basement. It is just a private access road to the rear part of the building. This private road can be used for people moving in or out, for fire turck, maintenance vehicle,... This access road will only be occasionally used (and hopefully never be used by firetrucks). At first, I thought of using the loads of EN1991-2 bridges but these loads are to big (2 axles of 300kN or 1 axle of 400kN). Where as the maximum allowable vehicle weight on the road is 3 axles of 100kN.
  3. "Eurocode 1" only handles vehicles up to 160 kN gros weight: "table 6.7 - Traffic and parking areas in buildings". This is traffic IN a building. Sometimes a larger vehicle or a large fire truck can drive ON TOP OF a basement . Using "EN1991-2 - loads on bridges"? It not a bridge but only an access road with slow traffic. I can't find any other chapters that mention traffic loads. If the maximum legal weight of a vehicle on the road is 3 axles of 100kN, then I could use these exact weights. But I can't find a reference.
  4. Eurocode 1 gives the actions of vehicles in buildings: "table 6.7 - Traffic and parking areas in buildings". Category G is for "medium" vehicles with a weight between 30kN and 160kN. As examples are given: "delivery zones, zones accessible to fire engines (<160kN gross vehicle weight)" But what about larger vehicles? In traffic, the vehicle weight can be more than 160kN. Lets say 3 rear axles of 100kN each. I suppose a firetruck can be more than 160kN? Lets say you have a large building with a basement and the basement is larger than the building area. It is possible a firetruck, a "moving vehicle" (possible with elevator), a delivery truck,... can drive over the basement. What loads should be used in this case? It is still a traffic area and not a bridge. Should the exact loads being used?
  5. CPT results give you the cone resistance and the local or total friction. Somethimes also the internal friction angle or some other parameters are mentioned. I was talking to some other engineers about how the CPT results are used and I got some different methods. 1) using the exact values of the CPT result For the bearing capacity of a pile, we use a xls spreadsheet where we have to input the coneresistance. So we input all the CPT-values of the cone resistance to the end of the CPT test. We also have a similar spreadsheet for the bearing capacity of a fondation slab, retaining wall,.. 2) using a "mean" CPT result A collegue doesn't use the exact values of the CPT results but he divides the results in "blocks with +-equal results". Then he uses these mean block-results in the xls spreadsheets. 3) using "soil-type" based on CPT results A collegue (another company) uses the CPT results to determine the soil type (sand, clay,...) or layers of soil-type (soil behavior charts). Then he uses this soil-type in his GEO software with predetermined soil types. So he doesn't input CPT results directly but only the soil types. 4) using "soil-type" in 3D FEM software Similar to (3) but using the soil-type as the "soil" in an 3D FEM analysis. I was wondering what others are doing with CPT results.
  6. I need to check an existing structure. In this structure is a beam-column connection. According to the reinforcement this node could take a moment of Md = 150kNm. (beam 25x50) I would like to use this moment in my 3D model to limit the max moment in this node so I can check the moment at the middle of the beam (lower reinforcement of the beam). If I make this node full-moment resistand, the moment is bigger compared to the 150kNm. But how can I model this? I thought of a non-linear or plastique hinge or something like that? With a non-linear analysis? Any suggestions?
  7. Calculating the bearing capacity of a spread foundation (according to EC7) is based on some parameters. 2 of the parameters are the width and the length of the foundation (and so the area). But are there any limitations on the width and length of the spread foundation that can be used. Lets says I have a building (lets say 20m x 20m) on a large "spread foundation" of 20m x 20m. Maybe this can be the bottom of a basement. Can I still use the same principals for calculating the bearing resistance of this large spread foundation?
  8. I need to design a basement. It is a basement without a building on it , just some ground on it. The groundwaterlevel can vary between high and almost below the basement. So I have 1) the stabelizing force Gstbd = self weight of the basement and soil on top x 0.9 (safety factor EC7) 2) the destabelizing uplift action Vdstd = Archimedes uplift force x safety factor EC7 My question is: what is the safety factor for the uplift force? Is the waterlevel or upliftforce a permanent of a variabel destabilising action? If destabilising permanent action --> safety factor = 1 If destabilising variabel action --> safety factor = 1.5 This makes a big difference. Some say a permanent action (factor 1) and other say a variabel action (factor 1.5). What do you use of think?
  9. I have some questions about mixed steel/concrete structures. Years ago I had a small (free) program to calculate a steel (square or round) column filled with concrete and some reinforcement. Depending on length and RF ratio the column was calculated. I don'nt remenber the name any more. Would anyone know such programme. A collegea mentioned "Concfill" but it wasn't that program. BTW Concfill seems to do the same but I can't find it to download. A second question: In a project I have 6 heavy beams with large section and large reinforcement. All these beams have different lenghts. Because all these beams were different in lenght, the architect didn't want "standard" prestressed beams. He thinks it would cost to much to make 6 individual (different) beams. The project developper suggested of asked why i didn't use steel beams in the concrete beam. So a steel beams with concrete and reinforcement around it in such a way it is a stronger beams compared to the normal concrete beam. I never designed such a beam. So what are the pro and cons for such a beam? Is this being done? If so, what software can be used for it? Our software can't handle this.
  10. We need to renovate 2 old buildings. De oldest building was build somewhere between world wars I and II. (industrial building of 3 levels) The second building was build somewhere between 1960 and 1975. (industrial and office building of partly 2 and 3 levels) We don't have any drawings for the buildings, so we don't know anything from the contrete or the reinforcement. Before we do further tests, I would like to know when they started to use certain concrete and reinforcement qualitys so I have a starting point for the investigation. For concrete? What could be used for those buildings? C25/30 of C20/25 (of already C30/37)? For the reinforcement? I suppose for the old building it was B220. But from when was B400 or B500 being used? When was prestressed concrete commenly being used?
  11. The basis of this spreadsheet hasn't changed for about 18 years. I don't know the whole history of it but there where added extension (options) to it during the years (besides layout changes). I did some extra testing in the last weeks (togheter with a colleague). The calculation of a simple "short" column with nomal laoding (not extremely high), no fire restistance, ... no second order moment,... always give relatively the same results (no big differences). The big differences come when calcutating longer columns (with a second order moment). The output of the test programs we used isn't always very clear to see what the second order moment is or how the second order moment is calculated. One of the test-programmes gave a second order moment that was a lot bigger then our spreadsheet. So the reinforcement was also a lot bigger. So for the testing: our chief has decided we should use the old test programme which always give results within the 95% tot 105% range of our spreadsheet. (with RF and with a calculated second order moment). I was told this old programma had been used in the past (should be some 15 to 18 years ago) to test/design this spreadsheet.
  12. At the company I work, we use - commercial software (3D FEM) - some small programmes - a lot of XLS sheets These XLS sheets are allready in use for at least 18years I have been told. Only the layout has changed over the years (made them more modern). So far no problem. The older guys use these sheets more than the others because some older guys don't have a lot of the experience with modern software. They like manual and small calculations. For one of our latest projects we needed to list the software we were going to use. And so we also listed out XLS sheets in case we should use them. But our client now asks a proof these sheets work correctly (manual comparison of compared to other software). The answer that we are using them for already 18 years isn't good for them. So I have been given the task to document these XLS sheets. I started with an XLS sheet for calculating the reinforcement of an concrete column. I was told this had been tested in the past. It was tested compared to some sort of trail version (printing not available) of a commercial program (program doesn't exist any more). We have this program still available on an old WIN2000 machine. The results between this and the XLS sheets only differ for maximum 1 or 2%. In some cases there is maybe 5% difference. This sometimes in + and sometimes in -. So I conclude our XLS sheet is good. But I also tested it with other software. I used 4 other programmes (most (30-day)trials but they should be fully usable to test it) and I asked a friend from another company. -our XLS sheet: lets say 100% reinforcement -old test-programme : almost the same (95%-105%) -program 1 : less reinforcement (80%) compared to our XLS. It looks like the 2de order moment is less. -program 2 : a little more reinforcement (110%) needed -program 3 : more reinforcement needed (130%) -program 4 : a lot more reinforcement needed (almost 200%) So ... I have big differences for the some columns. How come? Do some programmes calculate it to heavy? Anyone has experience with such differences? We use our XLS sheet for at least 18 years allready without problems. Below I have 2 examples (no real columns, just test examples). Can anyone calculate the reinforcement needed? (with what software?) Both exemples are fixed at the bottom and free at the top. (lk = 2 x l) and have a normal force (Nsk) at the top and a moment (Msk) at the bottom. With 50% of the forces fixed and 50% variable. 1) column 40x40 C30/37 Rf = 30 min l = 5m --> lk = 10m Nsk = 1020kN, Nsd = 1480kN Msk = 60 kNm, Msd = 85kNm 2) column 60x70 (width x height) C50/60 Rf = 2h l = 13.6m ==> lk = 27.2m Nsk = 990kN, Nsd = 1330kN Msk = 240kNm, Msd = 320kNm
  13. They will try to position the holes where Md is as close as possible to 0. (lets say a position with max 25% of the maximum Md at the position of the hole). Both the basis bottom and top reinforcement are continious over the total beam. Only at the middel of the span and at the supports, there is extra reinforcement. The main reinforcement (top and bottom) will not be cut. The holes will be at +- the middle of the height. Only some stirrups will be cut.
  14. I have a concrete beam with dimensions 20x100 continious over 3 spans of +- 7m. The concrete floorslabs are 22cm. So the beam is 78cm under the floorslabs. This beam was made +- 40 days ago. Now they want to drill some holes in the beam. The holes are diameter 300mm and 250mm and are lets say 80 or 90cm from each other. They can't be both positioned where the Md is close to 0. With a hole of 30cm in the middle of the height , I still have 70cm (35cm above and 35cm under the hole) left of the beam. The main reinforcement will not be cut by this hole. Is it possible to calculate the influence of this hole? I would think the influence of such a local hole is minimal? Any advice?
  15. Following an interesting conversation with a colleague, I'm wondering how do you make your calculations. When do you use 3D software or 2D software of even manual calculations? Or do you always use 3D software? Do you use old-style calcuation tables (like the Czerny tables for plate calculations)? some exemples from my side: 1) concrete or steel column/beam grid with a couple of levels with concrete slabs and no load bearing walls. --> a complete 3D model 2) "simple" structure with masonary load bearing walls with beams above windows/doors/..., some internal beams/columns,.. concrete floor slabs (like an normal/small, simple appartement of office building) --> If it is a simple structure I use 2D software/exell sheets to do the calculations, no 3D model of the structure 3) Underground concrete box (something like a watertank) --> depending on the size. For small ones I sometimes use the "old-style" calculation tables (Czerny plates) and I calculate every side on his own (in combination with an excel sheet). For large structures I use a complete 3D model. (sometimes a mix between old-style and a 2d model of one side) 4)... From a colleague (older guy with less experience in computer 3D calculations): 1) tries to split it in simple beams of floor slabs so it can be calculated manual of with an excel sheet 2) manual of with excel sheet 3) always the old style methode (manual of with excel sheet) 4)... Another colleague (young guy, just graduated): Allways a computer model (3D or 2D), no manual calculations of excel sheets So, I'm in the middle between the old and the young guy for my calculationmethode. I'm interested in what other use/do. And what software?