唔少去過BIM相關嘅 seminar / CPD 甚至 MasterClass 嘅朋友都反映,去完有種好空虛嘅感覺,一係就商家們攞彩嘅宣傳,再唔係就講啲劃大餅摸不著邊際願景,好難得係上完堂有實質嘢學到。筆者今次試下用一啲具體啲嘅例子,分析BIM嘅合約相關問題。
睇返今日嘅主題,究竟conceal conduit需唔需要BIM modelling?
先講結論,要睇下單project合約嘅BIM Specification。多數情況下,Conceal Conduit都係需要畫BIM;當然,Client肯主動豁免,就另一回事。
好多人有以下嘅誤解﹕
1. 50mm以下嘅嘢就唔需要BIM;
2. 去到LOD 500都唔需要畫conduit;
先講1., 呢個講法係邊度嚟?睇返CIC BIM Standards Phase 1 (2015 version), 的確係有句嘢咁講﹕
"2D lines and symbols may be used to complement the model when smaller elements are not modelled in 3D. For example, some elements smaller than 50mm may not need to be modelled.”
不過呢本Standards早就過時,我地係應該睇最新嗰本CIC BIM Standard General (2020 version or latest)。業界有聲音認為呢句嘢冇存在嘅必要性,所以於新版本嘅Standards搣咗。更何況,即使係舊嘅 2015 Standards,都只係話"may not need to be modelled”
再講2., LOD 500有冇話過唔需要畫conduit?好多人以為,LOD只係描述緊個BIM入面啲elements要畫到幾細緻。
但實際上,早於CIC MEP BIM Standards (2019 version),已經將LOD分拆成 LOD-Graphic (LOD-G) 及 LOD-Information (LOD-I) [1]。LOD-G係先係描述緊個elements要model到有幾細緻,如圖﹕
而LOD-I,係描述緊個element嘅資料有幾詳盡,如圖﹕
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即使係去到As-Built Stage,CIC MEP BIM Standards (2019 version) 只建議 LOD-G 去到300。最主要係考慮到modelling太多細節位的話,個BIM file size會好大,好多電腦硬件行唔到;當然,LOD-I 就建議去到500。不過,上述都唔係conceal conduit 需唔需要入BIM嘅原因。因為LOD只係用嚟描述一個物件/系統嘅graphic or information有幾detail,但唔係描述緊需唔需要畫呢個物件/系統。 咁應該睇合約嘅邊度決定邊樣嘢需唔需要畫? 係應該睇BIM Uses入面嘅"Drawing Generation”一段。如果跟CIC BIM Exchange Information Requirements (EIR) (version 2019 or latest) 寫合約,就會有以下一段﹕
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[1]: 於 CIC BIM Standard General (2020/2021 version) 再細分成 LOD-G, LOD-I, DOC。以後到講DOC係乜嚟
[2]: 茶餘飯後嘅談天說地資料
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