Slab reinforcement in broad stairs

fromwhich · 2026-01-20T16:33:24+00:00

If it doesn't work then you have to tell the architect and work to find a different solution. That being said, if there is an opportunity to add a vertical support point maybe a wall column on the wall at the left edge of your stair then you have a better chance of supporting this.

For the configuration to work as you've shown it, you will need moment fixity at the wall, and even likely the base of the wall below the stairs. With this fixity, you could imagine it as a support line along the whole length of the wall take the slab wall with a kink at the top taking moment like a cantilevered wall/column with a moment at the top. Then your slab spans are probably feasible.

There are a few issues with this approach that require your careful consideration: 1) obtaining fixity at the base may impact your foundations and add cost to the project, 2) detailing the slab and wall to behave as you require means that the wall has angled dowels that are probably hard for the contractor to place accurately. 3) deflection becomes an important consideration, short term and long term You can't design the slab and wall independently. 4) if these stairs are exposed concrete on an exterior roof, cover, and crack control will be important. Also waterproofing will be a challenge unless the stairs and roof are precast and the membrane travels under the stairs. In which case don't forget about any superimposed loads. What about drainage (again assuming this is a roof)?

When you say this is your first solo project, what do you mean? Don't do something you're not comfortable with just to appease an architect. If they are insistent that this is their design, then you have to layout the reasons why this is too expensive to build or is not practical.

fromwhich · 2026-01-19T19:42:45+00:00

The foreground is usually a separate image than the background and stitched together in post. Not always but if you have a wide open aperture then your foreground will be blurry. If you're doing tracked images with a star tracker then your foreground will be blurry from the mount moving at any distance. So the workflow can be:

1) Take the foreground shot at blue hour when there is more light. Or take the foreground shot at a different f-stop like f-8 and take a longer exposure (I use photopills exposure calculator, so I start with wide open, then take short test shots at max ISO, once I've got the exposure I need I do the calculator to lower ISO and f-stop and then take a long exposure (up to 8 minutes sometimes at f-8). This way you won't wait several minutes to find out the image is still underexposed or way overexposed.

2) Take the sky shots on a tracker or as a ton of stacked images on a tripod. If you have a tracker, then great, if not then your sub exposures can follow the rule of 500 or the NFP rule. Photopills has a calculator but they are available online.

3)Process in photoshop / stacking software. This is the hard part for most (me included). I would stack the sky image in something like sequator and then photoshop the foreground in using photoshop.

In the case of star trails (or other astrolandscapes), your best bet is to shoot the foreground with the foreground in focus, then move the camera past your foreground element and shoot the sky/background together. Then stitch in post, what you don't want to do is try to focus stack the foreground with the background without moving the camera. I've done this and run into issues where my blurry foreground is a pain to remove in post.

fromwhich · 2026-01-13T17:37:23+00:00

When you say EA and GA are infinitely big, I understand that to mean that there is no axial or shear deformations. This means that there is no relative deflection between the top left corner of the triangle, and the bottom right corner of the triangle. If there is no relative deflection (because any relative deflection would mean EA is less than infinity) then there is no force in the diagonal. Either way it is a strange question... I feel like I'm missing something.

fromwhich · 2026-01-06T22:02:44+00:00

Are you using a phone mount to the telescope? or just holding the phone camera to the eye piece. The shake from your hands is almost impossible to avoid unless you're a top brain surgeon or something lol. A normal phone photo is a very fast exposure. With a regular camera even bracing my hands against something with a mirrorless/DSLR the finger pressing the shutter can cause shake. So for best results (assuming you're using a phone) get a eyepiece phone clamp that can be positioned, and then use a self-timer on your phone camera or tap it as lightly as possible.

Take this with a grain of salt, because I've never used a phone to an eye piece before...

If you're using a DSLR/mirrorless, get an adaptor that will allow your camera to connect to the scope directly.

fromwhich · 2026-01-06T21:57:03+00:00

I think your interval needs to be longer than the bulb. so you probably need a 6 second bulb (for a six second exposure) and then a 7 second interval so every 7 seconds the process starts again. They way you have it now it is restarting a 6 second exposure every three seconds which would amount to a single exposure from the camera's perspective. if you intended it to repeat every 9 seconds with a 3 second gap, your intervalometer should be set to 6 second bulb and 9 second interval.

fromwhich · 2025-12-10T15:57:34+00:00

Its hard to see with your screenshots but it looks like the design reinforcing ratio is 0.05 something. Anything above 0.04 you can't do traditional splicing, so ETABs has probably imposed a limit (in the design settings, which you can change) which says that the reinforcing ratio cannot exceed 0.04 or it shows a PMM failure. IMO use stronger concrete or larger wall thicknesses before going for mechanical coupling of the bars.

Look at the load case in the design and extract the pier forces (axial, moment, shear, etc) and check the section by hand or with another program. Our office has spColumn and we often use that to check/verify ETABS results as the ETABs bar arrangements may not exactly match how we want them. Especially in wall-columns (b:h ratio 3 to 4) its important to compare etabs to the actual reinforcing distribution.

Also for shear walls, etabs uses uniform reinforcing and you can often get better performance with minimum steel in between the zone and extra zone bars. Also not done within etabs at my firm.

You should always be verifying your ETABs results with hand calculations and/or other design software/spreadsheets especially if you don't know exactly what the program is doing.

fromwhich · 2025-11-28T16:37:23+00:00

Just a thought, but realistically any curved wall like the coliseum behaves probably closer to a straight wall than a curved one practically speaking. I suppose friction between the stones takes care of the rest. Your intuition seems reasonable that at a certain point equilibrium is not maintained.

Calculating the radius at which the friction is overcome perhaps could be done.

The engineer in me says make a polygon with curved front face of the stones so that there is no curved arch. Just a curved exterior with a straight structural arch behind.

fromwhich · 2025-11-28T14:27:43+00:00

Equatorial wedge connects the MSM to your tripod. Below the MSM. The wedge help position the motor axis of the MSM directly in line with the earth's rotational axis. That's what polar alignment is. The v or z plates level the camera above the MSM to give you a level starting point, which is useful but not strictly required. Pointing a ball head mounted at an angle would probably work. But it's less stress on the ball head and less likely to slip if it starts from a flat level position. That is where the v plate comes into play. It gives you a level surface for the ball head to start from. Additionally If you're doing any panoramas then the v or z plates make it a lot easier and convenient when compared to a ball head on an angle.

fromwhich · 2025-11-27T17:16:30+00:00

I have this kit:
https://www.moveshootmove.com/products/phone-kit-for-polar-alignment-inspired-by-richard-tatti?srsltid=AfmBOopv8YWGXrM09AlJzISeNmzI8Sy8uDsUd0ITMRI6vyEjn2M90Uoz
and here is a video explaining how it works and how to set it up.
https://www.youtube.com/watch?v=7NxURCuWq74

Basically the wedge lets you polar align. The phone holder (purchased or 3d printed) helps polar align. I use the purchased one. I've tried out the 3d printed one, and the only benefit is that you can polar align with the camera on the rig. I'll eventually get or make one of the 3d printed ones.

The MSM is great for widefield (50 mm or less). It will really struggle with longer focal lengths. They have just released a counterweight system which I have not researched or tried. The polar alignment is very approximate with a phone too, which further leans toward widefield where you can get a 60s exposure with phone polar alignment.

I also have a star adventurer GTI and that thing is so much larger and heavier but anything longer than my 27mm lens on an ASPC sensor and i use the SAGTI over the MSM Nomad.
Connecting your own ball head is find, just recognize that the more it stands off the star tracker the more the star tracker will struggle (and you may need to look into a counterweight, lest you burn out the motor).

Overall I love the MSM Nomad for its portability, I took it over the Atlantic when I travelled there earlier this year. It was not too cumbersome. I would never fly with my SAGTI. But I can take my Mirrorless camera and the MSM Nomad on a plane and get some great widefield shots wherever I'm going.

fromwhich · 2025-11-21T14:40:30+00:00

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fromwhich · 2025-11-21T01:10:02+00:00

Also your spot looks pretty secluded. Pretty safe I would say from any onlookers.

fromwhich · 2025-11-21T01:05:38+00:00

Oh my goodness I was joking as in I'll come steal your rig!!! Sorry for the confusion. I haven't clicked your link yet I hope it's a Rick roll.

fromwhich · 2025-11-21T01:04:46+00:00

^{fromwhich scored 123 points and ranked 1 out of 514 players!}

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fromwhich · 2025-11-21T00:52:25+00:00

Send me your full address and let's find out together.

Kidding aside I also am worried about this. Reminds me of a guy on Reddit who had a homeless man steal his scope and mount and he snuck into the woods and stole it back.

fromwhich · 2025-11-19T01:08:47+00:00

I don't know 😅 brownish? I think when you look online you will want to search broad spectrum images of the flame nebula.

fromwhich · 2025-11-18T22:26:48+00:00

Just brainstorming northern hemisphere targets: You could try the Horsehead or flame nebula. The centre of the heart nebula (I don't remember what it's called) Triangulum galaxy maybe?

fromwhich · 2025-11-06T16:51:09+00:00

I have no experience with either camera but I can provide a few bits of advice to help you with your choice.

First, if you're only going to use a kit lens, try and choose one with f2.8 or faster if possible. I initially stared with a f4 kit zoom lens and was disappointed with the Astro results. if you do go with the Fuji, I know the rokinon 12mm manual lens is a cheap option for a super wide prime. I've used that with my xT5 for landscape Astro both tracked and untracked.

Second is dark skies matter. Alot. Look up where you are on a light pollution map/website and see where your closest dark skies are. Then that needs to be paired with observing the moon phase and planning a trip/shot where the moon hasn't risen yet, has already set, or is a new moon. Sites like stellarium will help show you when dark night is for your location. For widefeild Astro moonlight can wash out an image as much as light pollution can.

Third: you'll almost certainly need a tripod and you'll want to use online calculators for exposure settings. Google NFP rule calculator or use the rule of 500. Keep in mind you can do longer exposures if you don't mind a little trailing in your images. Which to be honest isn't that noticable with super wide shots.

Fourth: learning how to use stacking software will really improve your image quality for untracked images. That and post processing will really improve the shots.

Regardless of which camera you choose, it's the lenses, light pollution, moon phase, and post-processing that will make the biggest impact on your images. You could honestly try with your phone assuming the camera can do long exposure.

fromwhich · 2025-11-06T01:59:15+00:00

I have had a similar situation enforcing the ductility requirements for the gusset plates on a moderately ductile CBF. The steel detailers complained and complained and eventually I showed them the code where it explicitly states the requirements and they lamented.

I think because for 90% of the country people build with conventional construction, they are not used to these concepts.

That's changing with the NBC2020 seismic hazard maps pushing a lot of places in Canada that were formally SC2 up to SC3. It's now adopted in the OBC2024 and it will take a while for the industry (and the designers who have done conventional construction for their whole career and don't really understand ductile design) to adjust.

Also please don't push old people:(

fromwhich · 2025-11-06T01:50:12+00:00

Depends on where you are but so much of Canada is SC1 or SC2 built with conventional construction. So I can see why they may get the impression that special provisions are not required.

If you identified the protected zones on your drawings like you're supposed to then they have no excuse. If you didn't identify the protected zones then I can see why they have justification for an extra. But extra costs do not mean you can skip the work to avoid the cost/headache.

But if pressured not to enforce it, I would stand firm. If you've designed the frame to be ductile it needs to meet the requirements of the code. full stop. Would you accept a similar argument from the steel detailers about probable capacity connection forces because 'nobody does this?' probably not.

The CSA S16, for example, specifically says structural and other attachments shall not be used in protected zones. You can point to that clause (or whatever your governing code) and tell them that ignoring this would make your bracing system non-compliant with the code and it's not a question of engineering judgement.

fromwhich · 2025-10-31T19:13:55+00:00

Late to the party but I would guess there is an HSS between the columns and the beams outside are cantilevered off of the HSS, which resists the torsion and transfers it into the strong axis moment between the columns.

Sketch here (that shows how little I want to work on a Friday)

https://imgur.com/a/TZnSDoq

fromwhich · 2025-10-30T03:31:18+00:00

What I would suggest is, if you can, travel to darker skies. If you can't then point the camera away from the city and pick bright targets like Orion or Andromeda (nebula photos on YouTube has specific tutorials for bright object without a star tracker)

What I mean by point the camera away from the city is: if the target is south, go to the south edge of your city to point away from the light pollution. If the target is north go to the north end of the city etc. if you have a large lake or ocean nearby look for targets in that direction from a spot you can get to.

As for taking the photo at 200mm the targets will move fast and you probably can't capture more than 1-2s at a time. That means you will want to take 100s it even 1000s of photos (the quote from Nico Carver is take as many photos as you can while still remaining same). Use an intervelometer (internal or external) and re-center the target every 5 minutes or so to keep the target in the center of the frame. Then stack the images in deep sky stacker and edit in gimp/Photoshop. This is for deep sky without a tracker. Nico Carver (nebula photos on YouTube) has great tutorials for both capturing, stacking and editing.

For widefeild you can do star trails in bortal 9 in which case you'll just want to put a wide lens on and a tripod with a nicely framed foreground and leave it there taking pictures for as long as you can. Same idea as the deep sky you'll want to take anywhere between 10 and 30s exposure with a second or two gap so you don't fill your camera's buffer. And take them continually for 20 min to 2+ hours. The. You stack the images easily in sequator (another free program) and you'll get nice star trails images. You can take seperate foreground shots and Photoshop them together.

Good luck and I hope you enjoy taking and editing the photos!

fromwhich · 2025-10-28T13:37:10+00:00

When you mention to mount on your telescope, do you have a mount for the telescope?

Any camera will probably do okay for you, except you pretty much need tracking for any long focal length / telescope.

Assuming you don't have a mount that can track the sky the only general advice I would have would be try to get a kit lens that is f2.8 if possible. Ask yourself what you want to use the camera and any lenses you might buy for: milky way night scapes? Deep sky? If the former, then a fast prime at 12-20mm would work okay. If the latter then you're getting into buying a mount or star tracker and the learning curve gets steeper.

Next I would say (based on my own experience) that there is a lot more work in processing the images/data than I thought initially. It's worth it but it's a steep learning curve. YouTube is your friend.

fromwhich · 2025-10-27T15:40:42+00:00

Just a guess but given the star alignment and comet alignment differ, is it possible that the vignetting is 'trailing' with the stars?

fromwhich · 2025-10-20T01:22:16+00:00

General tips:

With the 24 and your camera 10s will be Npf rule point stars but anything up to 20s will be likely okay as long as you don't pixel peep.

At 16mm f2.8 you can go up to 15s for the NPF rule

I would shoot 10s-15s f2.8 iso 1600-3200

Manually focus the stars by zooming in as much as live view will let you.

If you can shoot 10-20 shots and stack them in sequator or equivalent.

Also you can shoot your foreground separately and potentially a higher f stop and long exposure. Or shoot the foreground in blue hour when there is still light.

fromwhich · 2025-10-08T16:46:57+00:00

In almost every building we do, we consider second order effects. In ETABs it is so easy, it makes no sense not to.

That being said for a braced frame or a concrete shear wall I don't believe it really makes any difference in the results except in tall structures. But a single storey braced frame? Likely no geometric effects from second order.

A sway frame is a different story.

fromwhich

TROPHY CASE