Lateral loads near the top of a masonry wall
 

Yeah - I have a bit of a paranoia about lateral forces on tops of walls.
Just wondered if anyone could see any problems with this:


View of wall (plan, from top)

D
|
|
C_____|A
xxx|
xxx|
|__________E
B

xxx is a 390mm deep wall mount network cabinet (6U or 9U) weighing
12-15kg and carrying another 30-ishkg of load from switches etc.


All walls are single thickness brick and the cabinet will mount near the
top of the wall which stops at the ceiling.


BD is a main load bearing wall so does have the weight of the dormer
floor above on it. AC and BE do not have any top load.

BD is topped with a conventional wooden wall plate.

Point B near enough also has a pillar supporting part of the dormer roof
on top

Planning on screwing into the 2nd or 3rd course of brick from the top.

So if xxx is screwed to AB, it benefits from both the kicks in the
adjoining walls and some load on top.


Lateral force at the top of the cabinet pulling out the screws will be
180-240N depending.


Another way of phrasing the question: would you hang a boiler up there?
Because this is a less heavy but it's not trivially light either.


Cheers - Tim




Working:

I reckon the top bolts on the cabinet will have a lateral pull out force
of around 243N or 24kg-f

(450N acting in the center of the cabinet 0.2m from the wall and
assuming a 6U cabinet which is 0.37m high)

450*0.2/0.37=243

reducing to 180N or 18kg-f for a 9U cabinet.

Lateral loads near the top of a masonry wall
 

On 12/02/2020 18:40, Tim Watts wrote:
Yeah - I have a bit of a paranoia about lateral forces on tops of walls.
Just wondered if anyone could see any problems with this:


View of wall (plan, from top)

Â*Â*Â*Â*Â* D
Â*Â*Â*Â*Â* |
Â*Â*Â*Â*Â* |
C_____|A
Â*Â* xxx|
Â*Â* xxx|
Â*Â*Â*Â*Â* |__________E
Â*Â*Â*Â*Â* B

xxx is a 390mm deep wall mount network cabinet (6U or 9U) weighing
12-15kg and carrying another 30-ishkg of load from switches etc.


All walls are single thickness brick and the cabinet will mount near the
top of the wall which stops at the ceiling.


BD is a main load bearing wall so does have the weight of the dormer
floor above on it. AC and BE do not have any top load.

BD is topped with a conventional wooden wall plate.

Point B near enough also has a pillar supporting part of the dormer roof
on top

Planning on screwing into the 2nd or 3rd course of brick from the top.

So if xxx is screwed to AB, it benefits from both the kicks in the
adjoining walls and some load on top.


Lateral force at the top of the cabinet pulling out the screws will be
180-240N depending.


Another way of phrasing the question: would you hang a boiler up there?
Because this is a less heavy but it's not trivially light either.

Short answer, I can't see it being a problem - especially with the top
load and the lateral support from the adjacent wall.

For extra peace of mind, stick in a 12U cabinet - it will convert more
of the load to shear, and you know you will always run out of cabinet
sooner or later :-)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Lateral loads near the top of a masonry wall
 

On 13/02/2020 13:01, John Rumm wrote:
On 12/02/2020 18:40, Tim Watts wrote:


Short answer, I can't see it being a problem - especially with the top
load and the lateral support from the adjacent wall.

For extra peace of mind, stick in a 12U cabinet - it will convert more
of the load to shear, and you know you will always run out of cabinet
sooner or later :-)
Hi John,

I like the cut of your jib :)

Can't go wrong with 12U...


It's a really good location too - hall (easy access, bothers no one),
great throughway above bewteen the joists), power socket below it (might
stick a small Eaton MEM UPS on the floor as we get a *lot* of power
cuts, like about 15 in one day last weekened.


Cheers,

Tim

Lateral loads near the top of a masonry wall
 

On 13/02/2020 20:47, Tim Watts wrote:
On 13/02/2020 13:01, John Rumm wrote:
On 12/02/2020 18:40, Tim Watts wrote:


Short answer, I can't see it being a problem - especially with the top
load and the lateral support from the adjacent wall.

For extra peace of mind, stick in a 12U cabinet - it will convert more
of the load to shear, and you know you will always run out of cabinet
sooner or later :-)
Hi John,

I like the cut of your jib :)

Can't go wrong with 12U...

Well with hindsight I could have got a 16 in :-)

It's a really good location too - hall (easy access, bothers no one),
great throughway above bewteen the joists), power socket below it (might
stick a small Eaton MEM UPS on the floor as we get a *lot* of power
cuts, like about 15 in one day last weekened.

Yup I did similar:

http://wiki.diyfaq.org.uk/index.php/...ntCommsCab.png

(right down to the MEM UPS on the floor).

I modified a 1U cable tidy by snapping off the rings, and mounting it on
the rear rack struts to support the back of that shelf - since a 1U
shelf was not really upto 2 NAS units!




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Lateral loads near the top of a masonry wall
 

On 13/02/2020 20:47, Tim Watts wrote:
On 13/02/2020 13:01, John Rumm wrote:
On 12/02/2020 18:40, Tim Watts wrote:


Short answer, I can't see it being a problem - especially with the top
load and the lateral support from the adjacent wall.

For extra peace of mind, stick in a 12U cabinet - it will convert more
of the load to shear, and you know you will always run out of cabinet
sooner or later :-)
Hi John,

I like the cut of your jib :)

Can't go wrong with 12U...


It's a really good location too - hall (easy access, bothers no one),
great throughway above bewteen the joists), power socket below it (might
stick a small Eaton MEM UPS on the floor as we get a *lot* of power
cuts, like about 15 in one day last weekened.

A little engineering theory may help you here.

Lateral loads on masonry have long been understood - mediaeval
buttresses are there for that reason.

The problem is that masonry is way better at compressive loads than
tensile ones, and has very low elasticity, and that means its liable to
failure by buckling with asymmetric loads.

The approach that fundamentally solves this is by ensuring that the
thrust vector of the load falls inside the walls. Buttresses achieve
this by effectively widening the base of the wall but another approach
for a given lateral thrust is to increase the total vertical load on the
wall.

That 'bends' the resultant combined vector inside the base.

A wall piled with lead weights on top is harder to push over than the
same wall without..





Cheers,

Tim


--
The biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

Lateral loads near the top of a masonry wall
 

On 13/02/2020 21:37, John Rumm wrote:
On 13/02/2020 20:47, Tim Watts wrote:
On 13/02/2020 13:01, John Rumm wrote:
Â* On 12/02/2020 18:40, Tim Watts wrote:

Â*
Â* Short answer, I can't see it being a problem - especially with the top
Â* load and the lateral support from the adjacent wall.
Â*
Â* For extra peace of mind, stick in a 12U cabinet - it will convert more
Â* of the load to shear, and you know you will always run out of cabinet
Â* sooner or later :-)
Hi John,

I like the cut of your jib :)

Can't go wrong with 12U...

Well with hindsight I could have got a 16 in :-)

It's a really good location too - hall (easy access, bothers no one),
great throughway above bewteen the joists), power socket below it
(might stick a small Eaton MEM UPS on the floor as we get a *lot* of
power cuts, like about 15 in one day last weekened.

Yup I did similar:

http://wiki.diyfaq.org.uk/index.php/...ntCommsCab.png

I have a Nas, a miniITX pfSense router and a couple of other widgets - I
like the idea of shoving these inside.


(right down to the MEM UPS on the floor).

How do you find MEM?


I modified a 1U cable tidy by snapping off the rings, and mounting it on
the rear rack struts to support the back of that shelf - since a 1U
shelf was not really upto 2 NAS units!

Good idea :)


I'm going for tool-less keystone jacks for my wall outlets and panel.

Cat5e, 6 or 6a I am undecided. Under 55m runs, but the sheilding in 6a
might be beneficial with all the mains stuff and dimmers nearby. Depends
how much of a mare the cable is to route. If it's too horrible, Cat5e
will be sufficient for my needs.


Already have a Ubiquiti PoE switch and Wifi AP which have far
outperformed anything I've had before - well pleased with those.

Lateral loads near the top of a masonry wall
 

On 14/02/2020 08:19, The Natural Philosopher wrote:
On 13/02/2020 20:47, Tim Watts wrote:

A little engineering theory may help you here.

Lateral loads on masonry have long been understood - mediaeval
buttresses are there for that reason.

The problem is that masonry is way better at compressive loads than
tensile ones, and has very low elasticity, and that means its liable to
failure by buckling with asymmetric loads.

The approach that fundamentally solves this is by ensuring that the
thrust vector of the load falls inside the walls. Buttresses achieve
this by effectively widening the base of the wall but another approach
for a given lateral thrust is to increase the total vertical load on the
wall.

That 'bends' the resultant combined vector inside the base.

A wall piled with lead weights on top is harder to push over than the
same wall without..

In theory I have at least 1-2kN load from the pillar that supports the
dormer flat roof, bearing down on the corner and through the wallplate.

And probably quite a lot from the floor above which sits on that wall.

Lateral loads near the top of a masonry wall
 

On 14/02/2020 11:04, Tim Watts wrote:
On 14/02/2020 08:19, The Natural Philosopher wrote:
On 13/02/2020 20:47, Tim Watts wrote:

A little engineering theory may help you here.

Lateral loads on masonry have long been understood - mediaeval
buttresses are there for that reason.

The problem is that masonry is way better at compressive loads than
tensile ones, and has very low elasticity, and that means its liable
to failure by buckling with asymmetric loads.

The approach that fundamentally solves this is by ensuring that the
thrust vector of the load falls inside the walls. Buttresses achieve
this by effectively widening the base of the wall but another approach
for a given lateral thrust is to increase the total vertical load on
the wall.

That 'bends' the resultant combined vector inside the base.

A wall piled with lead weights on top is harder to push over than the
same wall without..

In theory I have at least 1-2kN load from the pillar that supports the
dormer flat roof, bearing down on the corner and through the wallplate.

And probably quite a lot from the floor above which sits on that wall.

there you go then. I think it will be FINE.

I mounted a CRT telly on a swinging arm brcket affixed to a true single
(4") brick outside wall. Apart from the brick falling in half when
drilling leaving a gaping hole to the outside, a bit of mortar stuck it
all back together and the wall and the telly stayed up..


--
No Apple devices were knowingly used in the preparation of this post.

Lateral loads near the top of a masonry wall
 

On 14/02/2020 11:00, Tim Watts wrote:
On 13/02/2020 21:37, John Rumm wrote:
On 13/02/2020 20:47, Tim Watts wrote:

Well with hindsight I could have got a 16 in :-)

It's a really good location too - hall (easy access, bothers no one),
great throughway above bewteen the joists), power socket below it
(might stick a small Eaton MEM UPS on the floor as we get a *lot* of
power cuts, like about 15 in one day last weekened.

Yup I did similar:

http://wiki.diyfaq.org.uk/index.php/...ntCommsCab.png

I have a Nas, a miniITX pfSense router and a couple of other widgets - I
like the idea of shoving these inside.

(right down to the MEM UPS on the floor).

How do you find MEM?

Ordered online - on the doorstep next day :-)

In use? Well it seems to do what it says on the tin. Its a fairly slim
unit so not much battery space in it, and that is reflected in the run
time. I have a relatively light load on it (I have not counted but
certainly less than 100W), and so could probably get 20mins of run time
or more. I have it wired to the main NAS via USB so that can do an
orderly shutdown after 10 mins (i deliberately leave some spare capacity
should I find the need to manually power up later during an extended
power cut).

Not had that one there long enough to comment on battery longevity.
Hopefully its kinder to its batts than the APC unit it replaced (that
was physically too big for this application)

I modified a 1U cable tidy by snapping off the rings, and mounting it
on the rear rack struts to support the back of that shelf - since a 1U
shelf was not really upto 2 NAS units!

Good idea :)

With hindsight, buying a more sturdy shelf in the first place might have
been a good move.

I'm going for tool-less keystone jacks for my wall outlets and panel.

Cat5e, 6 or 6a I am undecided. Under 55m runs, but the sheilding in 6a
might be beneficial with all the mains stuff and dimmers nearby. Depends
how much of a mare the cable is to route. If it's too horrible, Cat5e
will be sufficient for my needs.

I ran CAT5e everywhere - but then again that was over ten years ago now.
So for gig ethernet everywhere seems to cope with any needs I have at
the moment. Screening wise I have not had any issues, and analogue audio
on the various phone extensions seems clean.

I used decent enough patch panels and mid priced sockets at the wall
ports. With hindsight, its not worth economising on the wall jacks -
since while in low churn applications like mine they hold up just fine,
they are much less pleasant to install than the Excel stuff I use these
days:

https://www.comms-express.com/produc...ttered-module/

(only marked in 568B colours so less metal effort required when wiring,
and they grip the wires nicely prior to punchdown. The domed faceplates
allow a little more cable space when wiring)

Already have a Ubiquiti PoE switch and Wifi AP which have far
outperformed anything I've had before - well pleased with those.

Yup they make some nice kit.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/