Hi,
I was thinking of making the first five steps floating. Does anyone know if there are guidelines for what load a step should handle? I found this on boverket page 24, 5:3 in the table. 1500N for point load and 2000N/m². Lastly, it also states: "5 Forces caused by individuals in rapid, vigorous motion are not included in the specified loads. (BFS 2010:2)". If a 100kg person jumps at the far end of a step, what would the load be then?
I
I___________________\/ Load in N?
I __________________ I
I
I
I was thinking of welding an appropriate number of rod steel (U-beam?) to steel columns (KKR square tube? extending from floor to ceiling) that are bolted to the wall. The steps would then be fully covered with oak and the columns hidden in the wall.
So what do you think, is this the right way to go?
/Pär
Some other cool floating stairs.
I was thinking of making the first five steps floating. Does anyone know if there are guidelines for what load a step should handle? I found this on boverket page 24, 5:3 in the table. 1500N for point load and 2000N/m². Lastly, it also states: "5 Forces caused by individuals in rapid, vigorous motion are not included in the specified loads. (BFS 2010:2)". If a 100kg person jumps at the far end of a step, what would the load be then?
I
I___________________\/ Load in N?
I __________________ I
I
I
I was thinking of welding an appropriate number of rod steel (U-beam?) to steel columns (KKR square tube? extending from floor to ceiling) that are bolted to the wall. The steps would then be fully covered with oak and the columns hidden in the wall.
So what do you think, is this the right way to go?
/Pär
Some other cool floating stairs.
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The load is not important, the deflection is what should be minimized. Unfortunately, I cannot fully calculate steel, but my experience with steel stairs is that deflection can be felt and it spreads through the structure as small vibrations.
How do you calculate deflection without load? Calculate 1kN as a point load at the far end, multiply that load by 1.3 and check that the beam holds. After that, take the same load without multiplying it up and check the deflection. If it is less than or equal to the length of the cantilever divided by 450, then you have a stiff and good staircase. Dimensioned according to bkr.
Would you choose to use kkr and set them as anchors in the wall and hide them within the wall, or would you use a U-beam that you weld the steps into, made out of two or three kkr profiles?
Remember that the flex you feel is not just from the profile bending but also from the movement at the anchor point, and keep in mind that static weight is not the same as dynamic movement, so 1kN is nowhere near the strain it will be subject to (imagine someone running up the stairs and pushing off to jump two steps, it's far more than 1kN).
So, I would probably do a control calculation with 3kN at the outermost point, but first check the flex not only in the console but also the movement at the anchor point, and calculate as disadvantageously as possible.
However, if you want help with the calculations, let me know what dimensions and measurements you have in mind, and remember it will place quite high demands on your welding if you want to make it stable.
In theory, you could manage with a 40x40x3mm kkr as a step, but without margins and only at the breaking point (didn't have the energy to do mental arithmetic on the bending). But this brings up my point that it places demands on the weld (with a 1m wide step and 1.5kN at the outermost point, the 4cm long weld would need to handle a tensile force of 75kN, plus vibrations and live energy when weight lands on it). Ignoring that, each cm of weld needs to handle a tensile force of 2 tons with safety, and I wouldn't count on getting such a strong weld if I were doing it myself without it cracking in the weld.
So what were you planning for it to look like?
Remember that the flex you feel is not just from the profile bending but also from the movement at the anchor point, and keep in mind that static weight is not the same as dynamic movement, so 1kN is nowhere near the strain it will be subject to (imagine someone running up the stairs and pushing off to jump two steps, it's far more than 1kN).
So, I would probably do a control calculation with 3kN at the outermost point, but first check the flex not only in the console but also the movement at the anchor point, and calculate as disadvantageously as possible.
However, if you want help with the calculations, let me know what dimensions and measurements you have in mind, and remember it will place quite high demands on your welding if you want to make it stable.
In theory, you could manage with a 40x40x3mm kkr as a step, but without margins and only at the breaking point (didn't have the energy to do mental arithmetic on the bending). But this brings up my point that it places demands on the weld (with a 1m wide step and 1.5kN at the outermost point, the 4cm long weld would need to handle a tensile force of 75kN, plus vibrations and live energy when weight lands on it). Ignoring that, each cm of weld needs to handle a tensile force of 2 tons with safety, and I wouldn't count on getting such a strong weld if I were doing it myself without it cracking in the weld.
So what were you planning for it to look like?
Thanks for the answers so far...
I was thinking U-beams for the ladder where two pieces are welded on each side of a KKR. But already now I have become wiser. VKR is stiffer than KKR which is stiffer than U-beam so the ladder should perhaps be made of VKR. Sankt? is it to weld the profile directly on so you get tensile stress at the top (not on the side as I thought where you get a moment and shear stresses). What is the best way? I will draw up some different options (trying to keep a maximum thickness of the steps at 50mm like the other steps will have) and get back...
The stairs are the ones down to the basement (which is fully furnished) and the wall is 350mm solid lightweight clinker. The intermediate floor is cast so I have concrete slabs in the floor and ceiling. The vertical profiles (which should also be made of the stiff VKR) can be bolted to the lightweight clinker wall, floor, and ceiling which are then covered with suitable material.
Deflection should not be more than a 450th of the length, thanks for that!
I'll get back to you...
/Pär
I was thinking U-beams for the ladder where two pieces are welded on each side of a KKR. But already now I have become wiser. VKR is stiffer than KKR which is stiffer than U-beam so the ladder should perhaps be made of VKR. Sankt? is it to weld the profile directly on so you get tensile stress at the top (not on the side as I thought where you get a moment and shear stresses). What is the best way? I will draw up some different options (trying to keep a maximum thickness of the steps at 50mm like the other steps will have) and get back...
The stairs are the ones down to the basement (which is fully furnished) and the wall is 350mm solid lightweight clinker. The intermediate floor is cast so I have concrete slabs in the floor and ceiling. The vertical profiles (which should also be made of the stiff VKR) can be bolted to the lightweight clinker wall, floor, and ceiling which are then covered with suitable material.
Deflection should not be more than a 450th of the length, thanks for that!
I'll get back to you...
/Pär
Here is a suggestion, have I calculated correctly?
VKR 80×40×5
Iy: 257000mm4
L: 950mm
F: 1000N
E: 210000
Deflection=F×L^3/(3×E×Iy)=5.3mm
If two VKR 80×40×5 are used, the deflection becomes 2.65mm
950/2.65=360 which is not quite 1/450 but if the last drawn 40×40×4 is included, it should be pretty close.
If the staircase should handle 1/450 at 3000N, I only get the equation with double 100×60×6.3 (not including the self-weight). The steps then become a bit too thick...
How the columns are affected, I have not yet calculated.
/Pär
VKR 80×40×5
Iy: 257000mm4
L: 950mm
F: 1000N
E: 210000
Deflection=F×L^3/(3×E×Iy)=5.3mm
If two VKR 80×40×5 are used, the deflection becomes 2.65mm
950/2.65=360 which is not quite 1/450 but if the last drawn 40×40×4 is included, it should be pretty close.
If the staircase should handle 1/450 at 3000N, I only get the equation with double 100×60×6.3 (not including the self-weight). The steps then become a bit too thick...
How the columns are affected, I have not yet calculated.
/Pär
have not double-checked what you have done and if you can bolt it to the wall and floor/ceiling, it should work to not introduce flex in the standing attachments, then I have a few comments I want to make
you should think about how they will be welded together and how the joint is stressed, and as it looks like that, it seems a bit strange to me as you have a 40mm wide hollow section and then above an 80mm wide one, so you can only weld it on one side as it does not contact the other standing profile, and then if you step on the outer step, it will only move, so you should calculate the flex for that alone, but you can weld an edge or brace between the profiles at the edge of the step so they cooperate because if you are putting wood on it, it might feel strange if the outer one bends significantly more than the inner profile
then when I wrote that you should check with 3kN, it was not for flex but for load distribution, so you know it holds at the weld and know what load there is, and then calculate the profiles separately, but as you have drawn now, it becomes a bit uneven with the rear one, so it might be a thought to calculate with 100x50x4 and possibly reduce the standing to 30x60x4 so that there's only 3cm between profiles in the step, and then you get 26cm from the front edge of the step to the front edge of the next step, but it is not much difference from 28cm which you would get by swapping the profile to 100x50, and you also get less load on the weld
(realized it depends a bit on how you're going to weld if it's stick or something else, it would be tight to come in with it between if you have only 3cm there if you are using a MIG nozzle and want to get a good angle on the joint)
then I can add that previously, flex calculations on floors were not to exceed 1cm at point load of 1kN or 1/300, so if you meet 1/300 on the step, it probably won't feel strange as it becomes just 3mm on the step
you should think about how they will be welded together and how the joint is stressed, and as it looks like that, it seems a bit strange to me as you have a 40mm wide hollow section and then above an 80mm wide one, so you can only weld it on one side as it does not contact the other standing profile, and then if you step on the outer step, it will only move, so you should calculate the flex for that alone, but you can weld an edge or brace between the profiles at the edge of the step so they cooperate because if you are putting wood on it, it might feel strange if the outer one bends significantly more than the inner profile
then when I wrote that you should check with 3kN, it was not for flex but for load distribution, so you know it holds at the weld and know what load there is, and then calculate the profiles separately, but as you have drawn now, it becomes a bit uneven with the rear one, so it might be a thought to calculate with 100x50x4 and possibly reduce the standing to 30x60x4 so that there's only 3cm between profiles in the step, and then you get 26cm from the front edge of the step to the front edge of the next step, but it is not much difference from 28cm which you would get by swapping the profile to 100x50, and you also get less load on the weld
(realized it depends a bit on how you're going to weld if it's stick or something else, it would be tight to come in with it between if you have only 3cm there if you are using a MIG nozzle and want to get a good angle on the joint)
then I can add that previously, flex calculations on floors were not to exceed 1cm at point load of 1kN or 1/300, so if you meet 1/300 on the step, it probably won't feel strange as it becomes just 3mm on the step
The idea with the last 40mm is just to get the step under the other step, thinking that it doesn't take much load at the far end which is why it's enough to weld it on one side. But you're right, maybe I should reconsider.
I was a bit sloppy when drawing, but I had that in mind, as well as a sheet over all three to prevent breaking the wooden step if someone steps with a heel right in the 40mm gap.
Good! I prefer not to go up to a 50mm profile on the steps (makes it at least 60mm thick, which is a bit too much).
Thanks for the good points, I'll try to calculate different ways to weld.
Okay, then I think I understand you and how you want it, and what I can imagine might be worth considering is that you take your 60x40 profile that you will be buying anyway, and since you're going to have a wooden board on top, it won't be too noticeable and you can make some solutions.
The first is to stabilize what you’ve already drawn so that it aligns with your calculations. Cut the profile into 40mm long pieces and "stand" it so you have one side facing outwards, and this way you get strong torsional rigidity that fuses the steps.
Then, to get a more stable and stronger attachment, take that profile and make a brace out between the steps, so you first weld 4 welds/profile (top/bottom + front/back) and then insert 60x40 profiles in pieces of about 10-15cm. Due to having a weld that gets slightly in the way, it will come about 5mm away from the standing piece, but you can fill it with a proper weld seam and then weld on the top and bottom of that too. You then get 20-30cm more weld length and then an 8cm longer seam in the standing profile in the wall, or 12cm if you weld around the whole thing.
Or, you make another solution and when you’ve welded everything else beforehand (without those protrusions), lay a 40x40 profile underneath that you weld all over, so you get a longer seam and at the same time, remove the rotation point from the middle of the profile. This way, instead of having a 2-4cm lever, it would be up to 13cm from the rotation point, making a difference in stability so you don’t risk movement in the wall fixture where you have such a large load on such a small fixture.
But this will mean you get a 40x40mm drop down at the very edge near the wall, but maybe that's acceptable?
Then, one suggestion, when I read what you wrote, is perhaps to insert 80x40 or 60x40 standing in some places between the width of the step, or place a long or a few shorter 40x40 pieces between the steps. If you plan to lay a sheet on top, this will give you more points for support under the sheet, or you might even skip the sheet entirely. Alternatively, place a 2mm sheet with those braces underneath, allowing you to replace your solid oak board with an oak veneer, which might be cheaper or at least thinner.
As another suggestion, you might have space for a shorter LED strip or solder one together yourself and attach it in the gap between the first and second profile, illuminating the step in front of it. In this case, it lights up the inner part, or the more you can lower it, the more of the step it can light, and then it's just about placing it so it doesn't shine in the eyes when standing at the bottom.
(There are different length LED strips and spotlights, but they’re usually too large in diameter. Otherwise, standard LEDs have between 2-4V drive voltage, and most strong whites are around 3-3.4V. If you connect 4 in a series, you can drive them with a regular small lamp transformer that gives 12V DC, allowing one, two, or three bundles, or a small cable between to distribute 4 LEDs across the entire width, or 8 depending on preference.)
There are diodes with good distribution down to 6 degrees, but under 20-degree distribution, it's okay to have high-intensity diodes without them being piercing from other directions, like if you walk beside the stairs and can see the diodes. Otherwise, you can hide them with the supports I previously recommended.
If you plan to have a steel profile facing forward, or oak, or the sheet you mentioned before that you bend in front, should you have an oak board, you can mill out or drill holes at the side toward the step and countersink diodes there. There are SMD LEDs from sizes 1x1x2mm to large ones and ordinary ones under 2mm in diameter and upwards, so if you want, you can hide them and illuminate the step from above.
The first is to stabilize what you’ve already drawn so that it aligns with your calculations. Cut the profile into 40mm long pieces and "stand" it so you have one side facing outwards, and this way you get strong torsional rigidity that fuses the steps.
Then, to get a more stable and stronger attachment, take that profile and make a brace out between the steps, so you first weld 4 welds/profile (top/bottom + front/back) and then insert 60x40 profiles in pieces of about 10-15cm. Due to having a weld that gets slightly in the way, it will come about 5mm away from the standing piece, but you can fill it with a proper weld seam and then weld on the top and bottom of that too. You then get 20-30cm more weld length and then an 8cm longer seam in the standing profile in the wall, or 12cm if you weld around the whole thing.
Or, you make another solution and when you’ve welded everything else beforehand (without those protrusions), lay a 40x40 profile underneath that you weld all over, so you get a longer seam and at the same time, remove the rotation point from the middle of the profile. This way, instead of having a 2-4cm lever, it would be up to 13cm from the rotation point, making a difference in stability so you don’t risk movement in the wall fixture where you have such a large load on such a small fixture.
But this will mean you get a 40x40mm drop down at the very edge near the wall, but maybe that's acceptable?
Then, one suggestion, when I read what you wrote, is perhaps to insert 80x40 or 60x40 standing in some places between the width of the step, or place a long or a few shorter 40x40 pieces between the steps. If you plan to lay a sheet on top, this will give you more points for support under the sheet, or you might even skip the sheet entirely. Alternatively, place a 2mm sheet with those braces underneath, allowing you to replace your solid oak board with an oak veneer, which might be cheaper or at least thinner.
As another suggestion, you might have space for a shorter LED strip or solder one together yourself and attach it in the gap between the first and second profile, illuminating the step in front of it. In this case, it lights up the inner part, or the more you can lower it, the more of the step it can light, and then it's just about placing it so it doesn't shine in the eyes when standing at the bottom.
(There are different length LED strips and spotlights, but they’re usually too large in diameter. Otherwise, standard LEDs have between 2-4V drive voltage, and most strong whites are around 3-3.4V. If you connect 4 in a series, you can drive them with a regular small lamp transformer that gives 12V DC, allowing one, two, or three bundles, or a small cable between to distribute 4 LEDs across the entire width, or 8 depending on preference.)
There are diodes with good distribution down to 6 degrees, but under 20-degree distribution, it's okay to have high-intensity diodes without them being piercing from other directions, like if you walk beside the stairs and can see the diodes. Otherwise, you can hide them with the supports I previously recommended.
If you plan to have a steel profile facing forward, or oak, or the sheet you mentioned before that you bend in front, should you have an oak board, you can mill out or drill holes at the side toward the step and countersink diodes there. There are SMD LEDs from sizes 1x1x2mm to large ones and ordinary ones under 2mm in diameter and upwards, so if you want, you can hide them and illuminate the step from above.
It is indeed smart to fill all the cavities in the steps and pillars with profiles.
The steps should be completely covered with oak so you don't see that there is steel underneath, to make them look the same as the other steps sitting in two vang. Veneer is a bit too thin; I want to be able to sand the staircase down at some point. Lighting will probably come from fixtures in the wall. But LED strips are a smart choice.
Thanks for all the suggestions!
/Pär
The steps should be completely covered with oak so you don't see that there is steel underneath, to make them look the same as the other steps sitting in two vang. Veneer is a bit too thin; I want to be able to sand the staircase down at some point. Lighting will probably come from fixtures in the wall. But LED strips are a smart choice.
Thanks for all the suggestions!
/Pär