martinwinlow
New Member
- Joined
- Feb 6, 2021
- Messages
- 12
Hi All,
I have a 10 module (each pretty much 1m wide x 2m high in portrait orientation) dual tracking array to install - making the array 5m wide x 4m high. I'm after some help with the foundation design. I am planning to use a reinforced concrete base attached to the bedrock which is only 500mm below soil surface using cement grout-fixed steel rebar (tho stainless rebar is an option as it's pretty wet here and I'm only 3km from the sea).
I had in mind a flat-topped pyramid shaped base 120mm square at the bottom, stopping about 600mm above soil level and the portion below ground having vertical sides (ie a flat-topped pyramid sitting on a box).
I'd like to come up with a suitable design of the reinforcing and concrete to bedrock interface ie how much rebar I'd need and of what diameter and what size/depth of rebar penetration into the bedrock. I'd rather not use resin for the rock fixing to reduce the cost. I have access to a portable/dismantle-able 20T hydraulic press (with pressure/force gauge) and thought I could do a couple of trial pins and then test their pull strength (up to 20T anyway).
From an online calculator I gather the deployed array at approximately 45 degree inclination in a 40mph wind (the most I'd be likely to use the array in before it automatically levels itself to reduce wind load) is 2800N. The main support column is 2m high at the point where the array pivots on the column giving a 'lever' length of 2.6m at bed rock level. Am I on the right track thinking that if the concrete to bedrock pins are 600mm out from the centre of the support column's axis that the loading at the pins would be 2800N x 2.6m/0.6m = 12000N?
If I then shared that load by, say, 4 x 12mm diameter steel pins along each side of the base (12 in all) would I be right in thinking that the shear strength of the pins (at 30KN for 12mm diamiter) will be way more than adequate? So, it's then just a case of ensuring the pins are deep enough and that the cement/sand grout is strong enough to withstand the pull-out forces... As I say, I'll do a couple and test them to 20T and see how it goes... I guess could test them all...
Does this all sound reasonable or am I way off? Does anyone have any professionally designed examples they would be willing to share here (or by PM)?
Regards, MW
I have a 10 module (each pretty much 1m wide x 2m high in portrait orientation) dual tracking array to install - making the array 5m wide x 4m high. I'm after some help with the foundation design. I am planning to use a reinforced concrete base attached to the bedrock which is only 500mm below soil surface using cement grout-fixed steel rebar (tho stainless rebar is an option as it's pretty wet here and I'm only 3km from the sea).
I had in mind a flat-topped pyramid shaped base 120mm square at the bottom, stopping about 600mm above soil level and the portion below ground having vertical sides (ie a flat-topped pyramid sitting on a box).
I'd like to come up with a suitable design of the reinforcing and concrete to bedrock interface ie how much rebar I'd need and of what diameter and what size/depth of rebar penetration into the bedrock. I'd rather not use resin for the rock fixing to reduce the cost. I have access to a portable/dismantle-able 20T hydraulic press (with pressure/force gauge) and thought I could do a couple of trial pins and then test their pull strength (up to 20T anyway).
From an online calculator I gather the deployed array at approximately 45 degree inclination in a 40mph wind (the most I'd be likely to use the array in before it automatically levels itself to reduce wind load) is 2800N. The main support column is 2m high at the point where the array pivots on the column giving a 'lever' length of 2.6m at bed rock level. Am I on the right track thinking that if the concrete to bedrock pins are 600mm out from the centre of the support column's axis that the loading at the pins would be 2800N x 2.6m/0.6m = 12000N?
If I then shared that load by, say, 4 x 12mm diameter steel pins along each side of the base (12 in all) would I be right in thinking that the shear strength of the pins (at 30KN for 12mm diamiter) will be way more than adequate? So, it's then just a case of ensuring the pins are deep enough and that the cement/sand grout is strong enough to withstand the pull-out forces... As I say, I'll do a couple and test them to 20T and see how it goes... I guess could test them all...
Does this all sound reasonable or am I way off? Does anyone have any professionally designed examples they would be willing to share here (or by PM)?
Regards, MW