Author: Chris Hackney
Chris founded Revolutio in 2012 as a part-time endeavour while working as a consulting structural engineer, but the underlying work can be traced back to his time as an undergraduate at the University of Sydney in 2007. He has worked for Taylor Thomson Whitting, SCP Consulting and Opus International Consultants and was involved in a number of high-profile engineering projects across Oceania, such as retrofitting walkways to the Sydney Harbour Bridge, earthquake assessments in Christchurch, and developing a tablet-based structural inspection application for the Northwest Rail Link.
CHECKPOLE v8.4.0 released
LOADING: Enable/disable/delete entire load categories by hovering on the “ID”label.
CHECKPOLE v8.4.0 is now live and can be downloaded here. New features and enhancements include:
- STRUCTURE: Improved shaft reinforcement module based on linear-elastic design assumption as per TIA-222-H Annex V. Supports complex, overlapping, multi-generational reinforcement differentiated by colour.
- SITE: Automatic Regional Wind Speed (VR) interpolation for Regions C and D to AS/NZS 1170.2-2021.
- LOADING: Enable/disable/delete entire load categories by hovering on the “ID” label.
- LOADING: Specify SHROUD headframes.
- LOADING: Linear Loads can be specified externally or internally.
- Access proxy settings from Help ribbon.
CHECKSTEEL v3.4.0 released
CHECKSTEEL v3.4.0 is now live and can be downloaded here. New features and enhancements include:
- Introduction of flat bar sections.
- Access proxy settings from Help ribbon.
CHECKWIND v6.3.0 released
CHECKWIND v6.3.0 is now live and can be downloaded here. New features and enhancements include:
- SITE: Introduction of AS 4055-2021.
- SITE: Automatic Regional Wind Speed (VR) interpolation for Regions C and D to AS/NZS 1170.2-2021.
- Access proxy settings from Help ribbon.
CHECKWIND v6.2.0 released
CHECKWIND v6.2.0 is now live and can be downloaded here. New features and enhancements include:
- SITE: Detailed Site Reports with higher resolution imagery and topography profiles for all 16 directions.
- SITE: Warning when switching off Directional Multiplier (Md) override for AS/NZS 1170.2-2021 when analysing monopoles.
CHECKPOLE v8.3.0 released
CHECKPOLE v8.3.0 is now live and can be downloaded here. New features and enhancements include:
- STRUCTURE: Introduction of fibre-reinforced plastic (FRP) monopoles.
- STRUCTURE: Improved tnxTower model import capability.
- LOADING: Specify default directory for tnxTower Appurtenance Library (*.arc) files.
Explained: Key changes introduced in AS/NZS 1170.2-2021
AS/NZS 1170.2-2021 introduces significant changes to load calculations which will have a profound impact on structural design in Australia and New Zealand for the next decade. This is not an exhaustive list of all changes and is intended to highlight the key differences from the 2011 version. You can download a copy here.
Key Changes to AS NZS 1170.2-2021
- New wind region maps: Melbourne no longer has it’s own region, and central Australia is covered by the new A0 region. Linear interpolation is now allowed for Regions C and D based on the relative distance from the “smooth coastline”. New Zealand regions have been revised and have a new naming scheme.
- Directional Multiplier (Md): Standalone poles and chimneys with circular or polygonal cross-sections to be designed using Md = 1.0. This is not applicable to structures with significant directional loading such as transmission lines.
- Climate Change Multiplier (Mc): Effectively replaces FC and FD factors from AS/NZS 1170.2-2011, but now relevant to the new Region B2.
- Terrain/Height Multiplier (Mz,cat): Terrain Category 1.5 for “open water surfaces subjected to shoaling waves” has been removed. The averaging distance is now MAX(500, 40z) instead of MAX(500, 40h) from AS/NZS 1170.2-2011. For buildings ≤ 25m, use z = h. For all other structures and buildings > 25 m, use z.
- Shielding Multiplier (Ms): This section has been expanded to remove the ambiguity present in the previous versions regarding maximum slope requirements. Structures exceeding 25 m in height must now adopt a value of 1.0 for all values of z unless wind tunnel testing is carried out to prove otherwise. The number of upwind shielding buildings (ns) is now defined as the number of buildings with an average structure height (hs) exceeding the height of the structure (h) under consideration.
- Topographic Multiplier (Mt): Sites in Region A0 now have their own equation, Mt = 0.5 + 0.5 x Mh. Topographic features less than 10 m in height can now be ignored. Further clarification is given that a topographic feature may be ignored “provided the crest is distant from the site of the structure by more than 10 times its crest elevation above sea level, and any intervening valley is more than 10 times the distance of the valley floor below the crest”.
- New lee zone maps: Entirely new lee zone maps for New Zealand, including “lateral transition zones” to prevent the previous situation where Mlee could equal 1.35 in one location but 1.0 just 100 m away.
- Internal Pressure Coefficients (Cp,i): Values now adjusted by Ka and Kl factors for situations with “dominant” openings. Cases where Kl > 1.0 must be considered in the calculation of Cp,i for all structural elements (both cladding and non-cladding).
- Volume Factor (Kv): A new factor designed to adjust internal pressure coefficients (Cp,i) for buildings with dominant wall openings based on the internal volume exposed to that opening.
- Area Reduction Factor (Ka): Can now be applied to windward and leeward walls for buildings with h < 25 m.
- Dynamic Response Factor (Cdyn): A different equation is used for towers, poles and masts where the total projected area of attachments exceeds the total projected area of the structure.
The good news is that our CHECKPOLE, CHECKWIND and CHECKWIND.API software have all of these changes integrated to make your life as simple as possible.
CHECKWIND v6.1.0 released
CHECKWIND v6.1.0 is now live and can be downloaded here. New features and enhancements include:
- STRUCTURE: Building openings listed with edit/copy/delete function buttons.
- SITE: Introduction of AS/NZS 1170.2-2021.
- SITE: Removed limitations for automated terrain/exposure detection for very tall structures and replaced them with a warning.
New CHECKWIND.API endpoints: AS/NZS 1170.2-2021 and CSA S37-18
Two new CHECKWIND.API endpoints are now live:
- AS/NZS 1170.2-2021: Structural design actions – Part 2: Wind actions. This does not replace the existing AS/NZS 1170.2-2011 endpoint. Both endpoints will run side-by-side for at least 1-2 years while the industry transitions to the new version and we will continue to keep both updated as necessary. The only change to the response for AS/NZS 1170.2-2021 is the introduction of the climate change multiplier Mc. A sample response is given below.
- CSA S37-18: Antennas, towers, and antenna-supporting structures.
{
"results": {
"siteElevation": 11.5,
"windRegion": "B1",
"critical": "SOUTH WEST",
"regionalWindSpeed": {
"vr10": 33,
"vr25": 39,
"vr50": 44,
"vr100": 48,
"vr200": 52,
"vr500": 57,
"vr1000": 60,
"vr2500": 64
},
"north": {
"md": 0.75,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 3.6,
"mzcat": 0.782,
"zones": [
{
"extent": 400.0,
"category": 4.0
},
{
"extent": 600.0,
"category": 3.0
}
]
},
"shielding": {
"ns": 1.0,
"hs": 30.0,
"bs": 76.24,
"ms": 0.7045
},
"topography": {
"critical": "NORTH NORTH EAST",
"type": "FLAT",
"h": 9.5,
"lu": 173.04,
"x": -80.04,
"upwindSlope": 0.0275,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": null
}
}
],
"structures": [
{
"height": 30.0,
"elevation": 7.5,
"footprint": [
{
"lat": -27.468529,
"lng": 153.025103
},
{
"lat": -27.468864,
"lng": 153.024655
},
{
"lat": -27.468886,
"lng": 153.024647
},
{
"lat": -27.469183,
"lng": 153.024936
},
{
"lat": -27.469183,
"lng": 153.024952
},
{
"lat": -27.46915,
"lng": 153.025011
},
{
"lat": -27.469031,
"lng": 153.02517
},
{
"lat": -27.469033,
"lng": 153.025175
},
{
"lat": -27.469057,
"lng": 153.025178
},
{
"lat": -27.4692,
"lng": 153.024982
},
{
"lat": -27.469219,
"lng": 153.024974
},
{
"lat": -27.469433,
"lng": 153.025175
},
{
"lat": -27.469445,
"lng": 153.025178
},
{
"lat": -27.469502,
"lng": 153.025234
},
{
"lat": -27.469507,
"lng": 153.025253
},
{
"lat": -27.469393,
"lng": 153.02539
},
{
"lat": -27.469267,
"lng": 153.025558
},
{
"lat": -27.469155,
"lng": 153.025693
},
{
"lat": -27.469143,
"lng": 153.025693
},
{
"lat": -27.468529,
"lng": 153.025113
},
{
"lat": -27.468529,
"lng": 153.025103
}
]
}
]
},
"northEast": {
"md": 0.75,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 4.0,
"mzcat": 0.75,
"zones": [
{
"extent": 600.0,
"category": 4.0
}
]
},
"shielding": {
"ns": 1.0,
"hs": 30.0,
"bs": 29.22,
"ms": 0.7689
},
"topography": {
"critical": "NORTH NORTH EAST",
"type": "FLAT",
"h": 9.5,
"lu": 173.04,
"x": -80.04,
"upwindSlope": 0.0275,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": null
}
}
],
"structures": [
{
"height": 3.0,
"elevation": 9.5,
"footprint": [
{
"lat": -27.469302,
"lng": 153.025577
},
{
"lat": -27.469314,
"lng": 153.02555
},
{
"lat": -27.469538,
"lng": 153.025274
},
{
"lat": -27.4696,
"lng": 153.025309
},
{
"lat": -27.469595,
"lng": 153.025328
},
{
"lat": -27.469495,
"lng": 153.025459
},
{
"lat": -27.469504,
"lng": 153.025478
},
{
"lat": -27.469388,
"lng": 153.025634
},
{
"lat": -27.46935,
"lng": 153.025617
},
{
"lat": -27.469302,
"lng": 153.025577
}
]
}
]
},
"east": {
"md": 0.85,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 3.8,
"mzcat": 0.766,
"zones": [
{
"extent": 500.0,
"category": 4.0
},
{
"extent": 600.0,
"category": 3.0
}
]
},
"shielding": {
"ns": 2.0,
"hs": 12.0,
"bs": 21.65,
"ms": 0.8034
},
"topography": {
"critical": "EAST SOUTH EAST",
"type": "FLAT",
"h": 15.5,
"lu": 405.15,
"x": -260.92,
"upwindSlope": 0.0191,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": null
}
}
],
"structures": [
{
"height": 15.0,
"elevation": 6.0,
"footprint": [
{
"lat": -27.469788,
"lng": 153.026181
},
{
"lat": -27.469788,
"lng": 153.026167
},
{
"lat": -27.469838,
"lng": 153.026106
},
{
"lat": -27.46979,
"lng": 153.026055
},
{
"lat": -27.46979,
"lng": 153.026044
},
{
"lat": -27.470009,
"lng": 153.02576
},
{
"lat": -27.470021,
"lng": 153.02576
},
{
"lat": -27.470268,
"lng": 153.026001
},
{
"lat": -27.470256,
"lng": 153.026028
},
{
"lat": -27.469992,
"lng": 153.026368
},
{
"lat": -27.469976,
"lng": 153.026366
},
{
"lat": -27.469788,
"lng": 153.026181
}
]
}
]
},
"southEast": {
"md": 0.9,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 3.6,
"mzcat": 0.782,
"zones": [
{
"extent": 400.0,
"category": 4.0
},
{
"extent": 600.0,
"category": 3.0
}
]
},
"shielding": {
"ns": 3.0,
"hs": 13.0,
"bs": 20.24,
"ms": 0.7712
},
"topography": {
"critical": "SOUTH EAST",
"type": "ESCARPMENT",
"h": 10.0,
"lu": 70.3,
"x": -400.83,
"upwindSlope": 0.0711,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": "Distance between site and feature crest (x) is greater than 10 × Crest Elevation (160.00 m)."
}
}
],
"structures": [
{
"height": 3.0,
"elevation": 7.5,
"footprint": [
{
"lat": -27.470444,
"lng": 153.02573
},
{
"lat": -27.470442,
"lng": 153.025682
},
{
"lat": -27.470449,
"lng": 153.025674
},
{
"lat": -27.470466,
"lng": 153.025674
},
{
"lat": -27.470528,
"lng": 153.025591
},
{
"lat": -27.47053,
"lng": 153.025561
},
{
"lat": -27.470578,
"lng": 153.025499
},
{
"lat": -27.470575,
"lng": 153.025481
},
{
"lat": -27.470606,
"lng": 153.025451
},
{
"lat": -27.470618,
"lng": 153.025451
},
{
"lat": -27.470628,
"lng": 153.025459
},
{
"lat": -27.470628,
"lng": 153.025473
},
{
"lat": -27.470594,
"lng": 153.025518
},
{
"lat": -27.47064,
"lng": 153.025564
},
{
"lat": -27.470649,
"lng": 153.025564
},
{
"lat": -27.470649,
"lng": 153.025577
},
{
"lat": -27.470516,
"lng": 153.025752
},
{
"lat": -27.470504,
"lng": 153.025752
},
{
"lat": -27.47048,
"lng": 153.025727
},
{
"lat": -27.470444,
"lng": 153.02573
}
]
},
{
"height": 3.0,
"elevation": 7.0,
"footprint": [
{
"lat": -27.470221,
"lng": 153.025674
},
{
"lat": -27.470247,
"lng": 153.025642
},
{
"lat": -27.470256,
"lng": 153.025642
},
{
"lat": -27.470311,
"lng": 153.025695
},
{
"lat": -27.470344,
"lng": 153.025655
},
{
"lat": -27.470354,
"lng": 153.025655
},
{
"lat": -27.470373,
"lng": 153.025674
},
{
"lat": -27.470375,
"lng": 153.025741
},
{
"lat": -27.47034,
"lng": 153.025744
},
{
"lat": -27.470323,
"lng": 153.025768
},
{
"lat": -27.470309,
"lng": 153.02577
},
{
"lat": -27.470221,
"lng": 153.025685
},
{
"lat": -27.470221,
"lng": 153.025674
}
]
},
{
"height": 3.0,
"elevation": 11.0,
"footprint": [
{
"lat": -27.469747,
"lng": 153.025188
},
{
"lat": -27.469747,
"lng": 153.025175
},
{
"lat": -27.469792,
"lng": 153.025111
},
{
"lat": -27.469807,
"lng": 153.025111
},
{
"lat": -27.46984,
"lng": 153.025143
},
{
"lat": -27.469838,
"lng": 153.025159
},
{
"lat": -27.469795,
"lng": 153.025221
},
{
"lat": -27.469785,
"lng": 153.025221
},
{
"lat": -27.469747,
"lng": 153.025188
}
]
},
{
"height": 3.0,
"elevation": 8.5,
"footprint": [
{
"lat": -27.470459,
"lng": 153.025508
},
{
"lat": -27.470459,
"lng": 153.025497
},
{
"lat": -27.470497,
"lng": 153.025446
},
{
"lat": -27.470511,
"lng": 153.025446
},
{
"lat": -27.470528,
"lng": 153.025465
},
{
"lat": -27.470528,
"lng": 153.025475
},
{
"lat": -27.470487,
"lng": 153.025526
},
{
"lat": -27.470478,
"lng": 153.025526
},
{
"lat": -27.470459,
"lng": 153.025508
}
]
}
]
},
"south": {
"md": 0.95,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 3.6,
"mzcat": 0.782,
"zones": [
{
"extent": 400.0,
"category": 4.0
},
{
"extent": 600.0,
"category": 3.0
}
]
},
"shielding": {
"ns": 2.0,
"hs": 12.0,
"bs": 30.35,
"ms": 0.7747
},
"topography": {
"critical": "SOUTH SOUTH EAST",
"type": "RIDGE",
"h": 17.0,
"lu": 60.12,
"x": -301.21,
"upwindSlope": 0.1414,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": "Distance between site and feature crest (x) is greater than 10 × Crest Elevation (225.00 m)."
}
}
],
"structures": [
{
"height": 15.0,
"elevation": 9.0,
"footprint": [
{
"lat": -27.470178,
"lng": 153.025644
},
{
"lat": -27.470121,
"lng": 153.025588
},
{
"lat": -27.470121,
"lng": 153.025575
},
{
"lat": -27.470354,
"lng": 153.025269
},
{
"lat": -27.470368,
"lng": 153.025263
},
{
"lat": -27.470378,
"lng": 153.025272
},
{
"lat": -27.470392,
"lng": 153.025253
},
{
"lat": -27.470321,
"lng": 153.025183
},
{
"lat": -27.470321,
"lng": 153.025164
},
{
"lat": -27.47029,
"lng": 153.025137
},
{
"lat": -27.47029,
"lng": 153.025127
},
{
"lat": -27.470325,
"lng": 153.025084
},
{
"lat": -27.470414,
"lng": 153.025076
},
{
"lat": -27.470435,
"lng": 153.025111
},
{
"lat": -27.470466,
"lng": 153.025129
},
{
"lat": -27.470471,
"lng": 153.025145
},
{
"lat": -27.470494,
"lng": 153.025162
},
{
"lat": -27.470494,
"lng": 153.025202
},
{
"lat": -27.470521,
"lng": 153.025215
},
{
"lat": -27.470513,
"lng": 153.025239
},
{
"lat": -27.470528,
"lng": 153.025333
},
{
"lat": -27.470468,
"lng": 153.025411
},
{
"lat": -27.470404,
"lng": 153.025419
},
{
"lat": -27.470333,
"lng": 153.025513
},
{
"lat": -27.470335,
"lng": 153.025626
},
{
"lat": -27.470333,
"lng": 153.025644
},
{
"lat": -27.470316,
"lng": 153.025666
},
{
"lat": -27.470304,
"lng": 153.025666
},
{
"lat": -27.470247,
"lng": 153.025609
},
{
"lat": -27.470228,
"lng": 153.025609
},
{
"lat": -27.470209,
"lng": 153.025636
},
{
"lat": -27.470195,
"lng": 153.025634
},
{
"lat": -27.470178,
"lng": 153.025644
}
]
},
{
"height": 9.0,
"elevation": 10.5,
"footprint": [
{
"lat": -27.46979,
"lng": 153.025288
},
{
"lat": -27.46979,
"lng": 153.025274
},
{
"lat": -27.469854,
"lng": 153.025186
},
{
"lat": -27.469885,
"lng": 153.025156
},
{
"lat": -27.469923,
"lng": 153.025078
},
{
"lat": -27.469969,
"lng": 153.025027
},
{
"lat": -27.469978,
"lng": 153.025027
},
{
"lat": -27.470026,
"lng": 153.024966
},
{
"lat": -27.470035,
"lng": 153.024966
},
{
"lat": -27.47008,
"lng": 153.025014
},
{
"lat": -27.470102,
"lng": 153.025003
},
{
"lat": -27.470092,
"lng": 153.025025
},
{
"lat": -27.470171,
"lng": 153.025105
},
{
"lat": -27.470171,
"lng": 153.025119
},
{
"lat": -27.469945,
"lng": 153.025424
},
{
"lat": -27.469928,
"lng": 153.025419
},
{
"lat": -27.46983,
"lng": 153.025328
},
{
"lat": -27.46983,
"lng": 153.025312
},
{
"lat": -27.469819,
"lng": 153.025298
},
{
"lat": -27.46979,
"lng": 153.025288
}
]
},
{
"height": 3.0,
"elevation": 11.0,
"footprint": [
{
"lat": -27.470107,
"lng": 153.024987
},
{
"lat": -27.470285,
"lng": 153.024968
},
{
"lat": -27.470302,
"lng": 153.024987
},
{
"lat": -27.470311,
"lng": 153.025057
},
{
"lat": -27.470273,
"lng": 153.025108
},
{
"lat": -27.470264,
"lng": 153.025108
},
{
"lat": -27.470221,
"lng": 153.025068
},
{
"lat": -27.470192,
"lng": 153.025076
},
{
"lat": -27.470123,
"lng": 153.025006
},
{
"lat": -27.470107,
"lng": 153.024998
},
{
"lat": -27.470107,
"lng": 153.024987
}
]
},
{
"height": 3.0,
"elevation": 11.5,
"footprint": [
{
"lat": -27.470468,
"lng": 153.025044
},
{
"lat": -27.470468,
"lng": 153.025033
},
{
"lat": -27.470502,
"lng": 153.024993
},
{
"lat": -27.470513,
"lng": 153.024993
},
{
"lat": -27.47053,
"lng": 153.025009
},
{
"lat": -27.470525,
"lng": 153.025027
},
{
"lat": -27.470497,
"lng": 153.025062
},
{
"lat": -27.470485,
"lng": 153.025062
},
{
"lat": -27.470468,
"lng": 153.025044
}
]
}
]
},
"southWest": {
"md": 0.95,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 2.4,
"mzcat": 0.878,
"zones": [
{
"extent": 300.0,
"category": 4.0
},
{
"extent": 400.0,
"category": 2.5
},
{
"extent": 600.0,
"category": 1.0
}
]
},
"shielding": {
"ns": 1.0,
"hs": 9.0,
"bs": 4.18,
"ms": 1.0
},
"topography": {
"critical": "SOUTH SOUTH WEST",
"type": "ESCARPMENT",
"h": 15.5,
"lu": 34.29,
"x": 339.97,
"upwindSlope": 0.226,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": "Distance between site and feature crest (x) is greater than 10 × Crest Elevation (155.00 m)."
}
}
],
"structures": [
{
"height": 3.0,
"elevation": 12.5,
"footprint": [
{
"lat": -27.470128,
"lng": 153.024883
},
{
"lat": -27.47013,
"lng": 153.024867
},
{
"lat": -27.470323,
"lng": 153.024612
},
{
"lat": -27.470342,
"lng": 153.024612
},
{
"lat": -27.470387,
"lng": 153.024657
},
{
"lat": -27.470385,
"lng": 153.024711
},
{
"lat": -27.470394,
"lng": 153.024722
},
{
"lat": -27.47039,
"lng": 153.024749
},
{
"lat": -27.470397,
"lng": 153.024762
},
{
"lat": -27.470397,
"lng": 153.024802
},
{
"lat": -27.470364,
"lng": 153.02485
},
{
"lat": -27.470344,
"lng": 153.02485
},
{
"lat": -27.470278,
"lng": 153.024877
},
{
"lat": -27.470166,
"lng": 153.024885
},
{
"lat": -27.470157,
"lng": 153.024896
},
{
"lat": -27.47014,
"lng": 153.024896
},
{
"lat": -27.470128,
"lng": 153.024883
}
]
},
{
"height": 3.0,
"elevation": 13.0,
"footprint": [
{
"lat": -27.470442,
"lng": 153.024582
},
{
"lat": -27.470454,
"lng": 153.024582
},
{
"lat": -27.470492,
"lng": 153.02462
},
{
"lat": -27.470494,
"lng": 153.024687
},
{
"lat": -27.47054,
"lng": 153.024732
},
{
"lat": -27.470535,
"lng": 153.024751
},
{
"lat": -27.470466,
"lng": 153.024837
},
{
"lat": -27.470444,
"lng": 153.024837
},
{
"lat": -27.470433,
"lng": 153.024641
},
{
"lat": -27.470421,
"lng": 153.024622
},
{
"lat": -27.470421,
"lng": 153.024609
},
{
"lat": -27.470442,
"lng": 153.024582
}
]
},
{
"height": 3.0,
"elevation": 13.0,
"footprint": [
{
"lat": -27.470147,
"lng": 153.024687
},
{
"lat": -27.470147,
"lng": 153.024676
},
{
"lat": -27.470216,
"lng": 153.024585
},
{
"lat": -27.47024,
"lng": 153.024598
},
{
"lat": -27.470247,
"lng": 153.02462
},
{
"lat": -27.47018,
"lng": 153.024708
},
{
"lat": -27.470147,
"lng": 153.024687
}
]
}
]
},
"west": {
"md": 0.95,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 3.6,
"mzcat": 0.782,
"zones": [
{
"extent": 400.0,
"category": 4.0
},
{
"extent": 600.0,
"category": 3.0
}
]
},
"shielding": {
"ns": 0.0,
"hs": 0.0,
"bs": 0.0,
"ms": 1.0
},
"topography": {
"critical": "WEST NORTH WEST",
"type": "ESCARPMENT",
"h": 20.0,
"lu": 49.02,
"x": -1039.1,
"upwindSlope": 0.204,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": "Distance between site and feature crest (x) is greater than 10 × Crest Elevation (195.00 m)."
}
}
],
"structures": []
},
"northWest": {
"md": 0.9,
"mc": 1.0,
"points": [
{
"z": 5.0,
"terrain": {
"category": 3.2,
"mzcat": 0.814,
"zones": [
{
"extent": 200.0,
"category": 4.0
},
{
"extent": 600.0,
"category": 3.0
}
]
},
"shielding": {
"ns": 1.0,
"hs": 30.0,
"bs": 3.28,
"ms": 0.926
},
"topography": {
"critical": "WEST NORTH WEST",
"type": "ESCARPMENT",
"h": 20.0,
"lu": 49.02,
"x": -1039.1,
"upwindSlope": 0.204,
"mh": 1.0,
"mlee": 1.0,
"mel": 1.0,
"mt": 1.0,
"comment": "Distance between site and feature crest (x) is greater than 10 × Crest Elevation (195.00 m)."
}
}
],
"structures": []
},
"snow": {
"region": "NA",
"alpine": "False"
}
},
"elevationData": null,
"version": "2.3.0.0"
}
Explained: TIA-222-H Shielding Factors (Ka) for appurtenances attached to headframes/platforms
Welcome to the first of a series of posts intended to help engineers understand specific aspects related to tower analysis and design.
Today, we’re looking at the Shielding Factor (Ka) from TIA-222-H as it relates to groups of appurtenances mounted to towers and monopoles via to headframes/platforms. The values below are for appurtenances only, and not the headframes/platforms themselves, which have separate requirements.
1. Multiple Mounting Frames: For lattice towers, these are individual mounting frames fixed directly to the outside of the tower. For monopoles, they would likely be a Mercedes-style headframe. Appurtenances attached to these headframes can be assumed to have Ka = 0.75 or Ka = 0.8, depending on the mounting arrangement as per Figure 2-8 (extract below). However, a minimum of 3 mounting frames at the same elevation are required to assume Ka < 1.0.
2. Symmetrical Truss Platforms: Triangular and square headframes with a trussed construction when viewed in elevation. These headframes are designed to accommodate people for maintenance and antenna replacement activities. Appurtenances attached to these headframes can be assumed to have Ka = 0.75.
3. Low-Profile Platforms: Any platform constructed from a single members when viewed in elevation. These headframes are usually not designed to accommodate people for maintenance and antenna replacement activities as they have neither a grill-mesh for standing nor safety handrails to prevent falls. Appurtenances attached to these headframes can be assumed to have Ka = 0.8.
4. Circular Ring Platforms: Circular headframes with a trussed construction when viewed in elevation. These headframes are designed to accommodate people for maintenance and antenna replacement activities. Appurtenances attached to these headframes can be assumed to have Ka = 0.8.
5. All Other Cases: Appurtenances attached to all other types of headframes, such a tip-mounted turrets, must be assumed to have Ka = 1.0.
You’ll be pleased to know that our CHECKPOLE software handles all of these cases automatically when you select your headframes and linked appurtenances (which you can of course override), and can lead to significant load reductions for monopoles supporting large numbers of antennas.
