# Automated constructability rating framework for concrete formwork systems using building information modeling

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## Abstract

The main objective of this research is to develop an automated constructability rating framework for different concrete formwork systems that are commonly used for the construction of reinforced concrete residential buildings. Initially, various constructability criteria (cost, time, quality, safety and environmental sustainability) that are analogous to the concrete formwork construction are rationally characterized through an intriguing data acquisition mechanism (a complete process involving the collection, recording and processing of data) known as constructability survey. Withal, an unified 3D Building Information Modeling (BIM) Model (i.e., 3D Structural BIM Model and 3D BIM Formwork Family or Module) is developed to providence CONSTaFORM, an automated constructability assessment framework for concrete formwork systems. The CONSTaFORM is a supplementary Add-in for Autodesk Revit developed by a process called API-fication, i.e., customizing Revit API to provide additional functionalities and hence enhancing the capabilities of existing framework invariably. The optimal constructability scores of various concrete formwork systems obtained from the constructability survey are initially fed into their respective 3D BIM formwork families as shared parameters, which are later used for the computation of the overall constructability rating of the formwork systems involved in the entire project, using BIM via CONSTaFORM Add-in. To reinforce the profundity and advocacy of CONSTaFORM Add-in, a suitable case study is reported.

## Keywords

CONSTaFORM Constructability Concrete formwork systems Building information modeling Parametric model Shared parameters API-fication## Introduction

Concrete formwork systems are temporary framework systems which are used for the cast-in-situ or precast construction (providing structural shape and texture of the plastic concrete on hardening) of Reinforced Cement Concrete (RCC) structures. It plays a paramount role in the construction of RCC structures, precisely, the cost of formwork construction (forming cost) and construction time pertaining to erection and assembly of formwork systems (forming time) contributes to 10 and 50% of the overall cost and overall time of the entire construction project, respectively (Hanna 1999; Peurifoy and Oberlender 2010; Jha 2012; Hurd 2005). Besides both forming cost and forming time, other associated attributes like forming quality, forming safety and environmental sustainability, significantly influences the concrete formwork systems (Kannan and Santhi 2013a).

These intrinsic and interdependent characteristics which influence the profitability of formwork construction can be fragmented into five major criteria as cost, time, quality, safety and environmental sustainability. These five criteria are instantiated using a phenomenal construction project management technique known as ‘Constructability’.

## Constructability

Construction Industry Institute (CII) (1986) defined constructability as “a system for achieving optimum integration of construction knowledge and experience in planning, engineering, procurement and field operations in the building process and balancing the various project and environmental constraints to achieve overall project objectives”. ASCE, Construction Management Committee (1991) defines constructability program as “the application of a disciplined, systematic optimization of the construction-related aspects of a project during the planning, design, procurement, construction, test and start-up phases by knowledgeable, experienced construction personnel who are part of a project”. Constructability is the only project management technique designed and developed solely by the construction industry for the construction industry (McGeorge et al. 2012). The concept and scope of constructability and buildability are synonymous similar and are used interchangeably by many researchers, however, for the sake of clarity, the term ‘constructability’ is monologously considered and used throughout this research. To integrate constructability efficiently and efficiently into overall phases of the project, a specialized classification system incorporating all the attributes or factors that influences constructability are to be identified and listed in a logical sequence (Hanlon and Sanvido 1995).

### Constructability information model

Nomenclature of concrete formwork systems

Alternative | Sub-alternative | Formwork | Notation |
---|---|---|---|

Conventional | Horizontal | Site-fabricated timber joist formwork | \({A_1}\) |

Vertical | Site-fabricated timber joist formwork | \({A_2}\) | |

Inclined | Site-fabricated timber joist formwork | \({A_3}\) | |

Combined | Site-fabricated timber joist formwork | \({A_4}\) | |

Horizontal | Site-fabricated timber board formwork | \({A_5}\) | |

Vertical | Site-fabricated timber board formwork | \({A_6}\) | |

Inclined | Site-fabricated timber board formwork | \({A_7}\) | |

Combined | Site-fabricated timber board formwork | \({A_8}\) | |

System | Horizontal | Prefabricated H-beam formwork | \({A_9}\) |

Horizontal | Prefabricated box-beam formwork | \({A_{10}}\) | |

Horizontal | Prefabricated girder formwork | \({A_{11}}\) | |

Vertical | Prefabricated H-beam formwork | \({A_{12}}\) | |

Vertical | Prefabricated box-beam formwork | \({A_{13}}\) | |

Vertical | Prefabricated girder formwork | \({A_{14}}\) | |

Inclined | Prefabricated H-beam formwork | \({A_{15}}\) | |

Inclined | Prefabricated box-beam formwork | \({A_{16}}\) | |

Inclined | Prefabricated girder formwork | \({A_{17}}\) | |

Combined | Prefabricated H-beam formwork | \({A_{18}}\) | |

Combined | Prefabricated box-beam formwork | \({A_{19}}\) | |

Combined | Prefabricated girder formwork | \({A_{20}}\) | |

Horizontal | Prefabricated board formwork | \({A_{21}}\) | |

Vertical | Prefabricated board formwork | \({A_{22}}\) | |

Inclined | Prefabricated board formwork | \({A_{23}}\) | |

Combined | Prefabricated board formwork | \({A_{24}}\) | |

Horizontal | Prefabricated transverse telescopic formwork | \({A_{25}}\) | |

Vertical | Prefabricated vertical telescopic formwork | \({A_{26}}\) | |

Inclined | Prefabricated telescopic transverse and vertical formwork | \({A_{27}}\) | |

Combined | Prefabricated telescopic transverse and vertical formwork | \({A_{28}}\) | |

Modular | Combined | Panellized/Boxed formwork | \({A_{29}}\) |

Combined | Apartment or Half-Tunnel formwork | \({A_{30}}\) | |

Combined | Gang formwork | \({A_{31}}\) | |

Special | Horizontal | Permanent formwork | \({A_{32}}\) |

Vertical | Permanent formwork | \({A_{33}}\) | |

Inclined | Permanent formwork | \({A_{34}}\) | |

Combined | Permanent formwork | \({A_{35}}\) | |

Horizontal | Formwork for precast concrete | \({A_{36}}\) | |

Vertical | Formwork for precast concrete | \({A_{37}}\) | |

Inclined | Formwork for precast concrete | \({A_{38}}\) | |

Combined | Formwork for precast concrete | \({A_{39}}\) | |

Horizontal | Horizontally transported and manually mounted table formwork without hoist | \({A_{40}}\) | |

Horizontal | Horizontally transported and manually mounted table formwork with hoist | \({A_{41}}\) | |

Horizontal | Horizontally transported and automatically mounted table formwork with hoist | \({A_{42}}\) | |

Horizontal | Horizontally transported and automatically mounted table formwork without hoist | \({A_{43}}\) | |

Horizontal | Slipform | \({A_{44}}\) | |

Vertical | Slipform | \({A_{45}}\) | |

Inclined | Slipform | \({A_{46}}\) | |

Combined | Slipform | \({A_{47}}\) | |

Vertical | Crane dependent climbing formwork | \({A_{48}}\) | |

Inclined | Crane dependent climbing formwork | \({A_{49}}\) | |

Vertical | Semi-crane dependent climbing formwork | \({A_{50}}\) | |

Inclined | Semi-crane dependent climbing formwork | \({A_{51}}\) | |

Vertical | Automatic climbing formwork | \({A_{52}}\) | |

Inclined | Automatic climbing formwork | \({A_{53}}\) |

### Constructability Assessment of Concrete Formwork Systems

The appreciable work on implementing the concept of constructability in concrete formwork design was initially carried out by Touran (1988). O‘Connor and Davis (1988) and CRSI Report No. 32 (1989) depicted the importance of interaction between formwork contractor and Engineers for attaining rapid construction cycle by virtue of performance-oriented specifications of formwork construction such as selection of suitable formwork systems (Gang formwork system and flying truss formwork system) for rapid cycle, strength and serviceability consideration of formwork systems and choice of shore-replacement methods: backshoring, reshoring and preshoring. Meanwhile, Fischer (1991) realized the importance of incorporating constructability even in the formwork planning phase for reinforced concrete construction projects. He also emphasized the importance of selection of appropriate construction crew for specialized formwork systems like self-climbing formwork, etc., as they are generally complex in nature requires highly skilled and qualified personnel and mostly custom-made systems demands a higher degree of planning garnering space adequacy, access for materials transport and crew during construction (Hanlon and Sanvido 1995) etc. Generally, to achieve these details, a well-documented framework or guide comprising set of rules/criteria developed by expert members are employed. For this research, a comprehensive overview of all the constructability criteria pertaining to concrete formwork construction for performing constructability analysis, the promulgated ideas and information pertaining to the global concrete formwork construction by various experts are recorded through an intriguing mechanism known as ‘Constructability Survey’.

### Constructability survey

ASCE, Construction Management Committee (1991) emphasized that to enhance constructability into construction projects ‘experienced construction personnel need to be involved with the project from the earliest stages to ensure that the construction focus and experience can properly influence the owner, planners, and designers, as well as material suppliers’. Experienced personnel mean persons having a full understanding of the nature of the project from start-to-finish and acquired knowledge from the previous and similar projects (Kartam and Flood 1997) which was done earlier rather than sticking with the project for a long period of time. More importantly, the experienced personnel should have deeper knowledge on modern or innovative construction process or methods (O’Connor and Miller 1994). These skills are generally acquired through a process called ‘Constructability Survey’.

*N*is the total number of responses recorded. For instance, RII for Forming cost, \(C_i\) is calculated as shown in the Eq. 2.

*N*is the total number responses (173). Similarly, the RII value of other constructability criteria are determined, the sum of all the RII values is 4.0. The weight of each constructability criteria is calculated using Eq. 3

RII value and weight for each constructability criteria

Constructability criteria | RII | Weight | Rank |
---|---|---|---|

Forming cost (\({C_i}\)) | 0.95 | 0.24 | 1 |

Forming Time (\({C_j}\)) | 0.92 | 0.23 | 2 |

Forming Quality (\({C_k}\)) | 0.79 | 0.20 | 3 |

Forming Safety (\({C_l}\)) | 0.69 | 0.17 | 4 |

Environmental sustainability (\({C_m}\)) | 0.65 | 0.16 | 5 |

Total | 4.00 | 1.00 | – |

Constructability survey report

Pro. no. | AreaConstr. | No. storey | HghtConstr. | ConstTime | CycleTime | \({C_1}\) | \(\cdots \) | \({C_{20}}\) | \(\cdots \) | \({C_{30}}\) | \(\cdots \) | \({C_{40}}\) | ConstScr. |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|

(in sq.m) | (in m.) | (in years) | (in days/floor) | (Out of 10) | |||||||||

P1 | 9301–18600 | 07–15 | 25.1–65.0 | 2.1–4.0 | 04–07 | 8.10 | \(\cdots \) | 8.50 | \(\cdots \) | 8.20 | \(\cdots \) | 7.80 | 8.38 |

P2 | \(\ge 25001\) | 46–85 | 185.1–345.0 | 4.1–6.0 | 01–03 | 6.84 | \(\cdots \) | 6.52 | \(\cdots \) | 5.88 | \(\cdots \) | 6.42 | 6.96 |

P3 | \(\ge 25001\) | 46–85 | 185.1–345.0 | 4.1–6.0 | 01–03 | 6.84 | \(\cdots \) | 6.52 | \(\cdots \) | 5.88 | \(\cdots \) | 6.42 | 6.96 |

P4 | 9301–18600 | 07–15 | 25.1–65.0 | 2.1–4.0 | 08–14 | 5.26 | \(\cdots \) | 5.56 | \(\cdots \) | 4.04 | \(\cdots \) | 5.48 | 6.06 |

P5 | \(\ge 25001\) | 16–25 | 65.1–105.0 | 2.1–4.0 | 08–14 | 6.00 | \(\cdots \) | 6.20 | \(\cdots \) | 5.00 | \(\cdots \) | 5.60 | 6.49 |

\(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) |

P50 | 5001–9300 | 07–15 | 25.1–65.0 | 2.1–4.0 | 08–14 | 6.28 | \(\cdots \) | NA | \(\cdots \) | 5.00 | \(\cdots \) | 5.60 | 5.79 |

P51 | 2001–5000 | \(\le 06\) | \(\le 25\) | 2.1–4.0 | 08–14 | 5.26 | \(\cdots \) | 5.56 | \(\cdots \) | 4.04 | \(\cdots \) | 5.48 | 6.06 |

P52 | 2001–5000 | \(\le 06\) | \(\le 25\) | \(\le 2\) | 08–14 | 5.00 | \(\cdots \) | 5.04 | \(\cdots \) | NA | \(\cdots \) | 5.44 | 4.90 |

P53 | 9301–18600 | \(\le 06\) | \(\le 25\) | 2.1–4.0 | 08–14 | 5.26 | \(\cdots \) | NA | \(\cdots \) | NA | \(\cdots \) | NA | 3.97 |

P54 | 9301–18600 | 26–45 | 105.1–185.0 | 4.1–6.0 | 08–14 | 5.68 | \(\cdots \) | 6.16 | \(\cdots \) | 5.62 | \(\cdots \) | 6.30 | 6.76 |

P55 | 9301–18600 | 26–45 | 105.1–185.0 | 4.1–6.0 | 08–14 | 5.68 | \(\cdots \) | 6.16 | \(\cdots \) | 5.62 | \(\cdots \) | 6.30 | 6.76 |

\(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) |

P100 | 2001–5000 | 07–15 | 25.1–65.0 | 2.1–4.0 | 08–14 | NA | \(\cdots \) | 5.04 | \(\cdots \) | 3.92 | \(\cdots \) | 5.44 | 5.76 |

P101 | 2001–5000 | \(\le 06\) | \(\le 25\) | \(\le 2\) | 08–14 | 5.00 | \(\cdots \) | 5.04 | \(\cdots \) | 3.92 | \(\cdots \) | 5.44 | 5.99 |

P102 | 5001–9300 | \(\le 06\) | \(\le 25\) | 2.1–4.0 | 08–14 | 6.28 | \(\cdots \) | 5.90 | \(\cdots \) | 5.00 | \(\cdots \) | 5.60 | 6.39 |

P103 | 5001–9300 | 07–15 | 25.1–65.0 | 2.1–4.0 | 08–14 | 6.28 | \(\cdots \) | 6.84 | \(\cdots \) | 5.70 | \(\cdots \) | 7.14 | 2.75 |

P104 | 9301–18600 | 07–15 | 25.1–65.0 | 2.1–4.0 | 08–14 | 5.26 | \(\cdots \) | 5.56 | \(\cdots \) | 4.04 | \(\cdots \) | 5.48 | 6.06 |

P105 | 5001–9300 | \(\le 06\) | \(\le 25\) | \(\le 2\) | 08–14 | 6.00 | \(\cdots \) | 6.20 | \(\cdots \) | 5.00 | \(\cdots \) | 5.60 | 6.49 |

\(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) |

P170 | 5001–9300 | 16–25 | 65.1–105.0 | 2.1–4.0 | 08–14 | 5.00 | \(\cdots \) | 5.04 | \(\cdots \) | 3.92 | \(\cdots \) | 5.44 | 5.99 |

P171 | 2001–5000 | \(\le 06\) | \(\le 25\) | \(\le 2\) | 08–14 | 5.00 | \(\cdots \) | 5.04 | \(\cdots \) | 3.92 | \(\cdots \) | 5.44 | 5.99 |

P172 | 5001–9300 | 16–25 | 65.1–105.0 | 2.1–4.0 | 08–14 | 6.00 | \(\cdots \) | 6.20 | \(\cdots \) | 5.00 | \(\cdots \) | 5.60 | 6.49 |

P173 | 9301–18600 | \(\le 06\) | \(\le 25\) | 2.1–4.0 | 08–14 | 5.26 | \(\cdots \) | 5.56 | \(\cdots \) | 4.04 | \(\cdots \) | 5.48 | 6.06 |

Constructability score for different formwork systems from the constructability survey

S. no. | Notation | Type | Category | Forming cost | Forming time | Forming quality | Forming safety | Sustainability | CS | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

\({C_{1}}\) | \(\cdots \) | Avg | \({C_{9}}\) | \(\cdots \) | Avg | \({C_{17}}\) | \(\cdots \) | Avg | \({C_{25}}\) | \(\cdots \) | Avg | \({C_{33}}\) | \(\cdots \) | Avg | |||||

1 | A1 | Con_Form | Horizontal | 9.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 2.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 | \(\cdots \) | 6.00 | 4.00 |

2 | A2 | Con_Form | Vertical | 6.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 2.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 | \(\cdots \) | 6.00 | 4.00 |

3 | A3 | Con_Form | Inclined | 7.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 1.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 | \(\cdots \) | 6.00 | 4.00 |

4 | A4 | Con_Form | Combined | 8.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 1.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 | \(\cdots \) | 6.00 | 4.00 |

5 | A5 | Con_Form | Horizontal | 7.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 2.00 | 7.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 |

6 | A6 | Con_Form | Vertical | 7.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 2.00 | 7.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 |

7 | A7 | Con_Form | Inclined | 8.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 2.00 | 7.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 |

8 | A8 | Con_Form | Combined | 8.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 2.00 | 7.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 6.00 | 6.00 | \(\cdots \) | 6.00 | 5.00 |

9 | A9 | Sys_Form | Horizontal | 8.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 2.00 | 8.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 7.00 | 5.00 |

10 | A10 | Sys_Form | Horizontal | 6.00 | \(\cdots \) | 4.00 | 9.00 | \(\cdots \) | 2.00 | 8.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 7.00 | 5.00 |

\(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) |

20 | A20 | Sys_Form | Combined | 7.00 | \(\cdots \) | 4.00 | 9.00 | \(\cdots \) | 2.00 | 9.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 7.00 | 6.00 | \(\cdots \) | 7.00 | 5.00 |

21 | A21 | Sys_Form | Horizontal | 6.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 9.00 | \(\cdots \) | 9.00 | 9.00 | \(\cdots \) | 9.00 | 8.00 | \(\cdots \) | 8.00 | 6.00 |

22 | A22 | Sys_Form | Vertical | 6.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 9.00 | \(\cdots \) | 9.00 | 9.00 | \(\cdots \) | 9.00 | 8.00 | \(\cdots \) | 8.00 | 6.00 |

23 | A23 | Sys_Form | Inclined | 7.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 9.00 | \(\cdots \) | 9.00 | 9.00 | \(\cdots \) | 9.00 | 8.00 | \(\cdots \) | 8.00 | 6.00 |

24 | A24 | Sys_Form | Combined | 7.00 | \(\cdots \) | 3.00 | 9.00 | \(\cdots \) | 1.00 | 9.00 | \(\cdots \) | 9.00 | 9.00 | \(\cdots \) | 9.00 | 8.00 | \(\cdots \) | 8.00 | 6.00 |

25 | A25 | Sys_Form | Horizontal | 5.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 9.00 | 9.00 | \(\cdots \) | 9.00 | 8.00 | \(\cdots \) | 8.00 | 6.00 |

\(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) |

30 | A30 | Mod_Form | Combined | 7.00 | \(\cdots \) | 4.00 | 7.00 | \(\cdots \) | 4.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 8.00 |

31 | A31 | Mod_Form | Combined | 7.00 | \(\cdots \) | 4.00 | 7.00 | \(\cdots \) | 4.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 8.00 |

32 | A32 | Spl_Form | Horizontal | 9.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 9.00 | 7.00 |

33 | A33 | Spl_Form | Vertical | 9.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 9.00 | 7.00 |

34 | A34 | Spl_Form | Inclined | 9.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 9.00 | 7.00 |

35 | A35 | Spl_Form | Combined | 9.00 | \(\cdots \) | 3.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 10.00 | 9.00 | \(\cdots \) | 9.00 | 7.00 |

\(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) | \(\vdots \) |

50 | A50 | Spl_Form | Vertical | 9.00 | \(\cdots \) | 2.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 7.00 |

51 | A51 | Spl_Form | Inclined | 9.00 | \(\cdots \) | 2.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 7.00 |

52 | A52 | Spl_Form | Vertical | 9.00 | \(\cdots \) | 2.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 7.00 |

53 | A53 | Spl_Form | Inclined | 9.00 | \(\cdots \) | 2.00 | 10.00 | \(\cdots \) | 1.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 10.00 | \(\cdots \) | 10.00 | 7.00 |

#### Constructability rating

Constructability scoring or rating of concrete formwork systems for determining optimal constructability score for simpler constructions can be performed manually and more accurately without any difficulties, but for the heavy construction projects due to its inherent difficulties and complexities associated with the projects, performing constructability rating is quite perplexing rather challenging and hence additional guides and tools are required. Many researchers developed computerized solution for constructability implementation for concrete formwork construction starting from integrated microcomputer packages (Christian and Mir 1987; Tah and Price 1997), 2D CAD and 3D CAD models to sophisticated ‘Enterprise Design/Data Management’ (EDM) and Building Information Modeling (BIM) for developing nD models (Kannan and Santhi 2013b; Kannan and Knight 2012; Lee et al. 2009; Kannan and Santhi 2013a, 2015; Jun and Yun 2011; Meadati et al. 2011; Neto and Ruschel 2015) and collaborative construction process using customized software tools (Multimedia constructability tool 1998; Ganah et al. 2005; Hijaji et al. 2009).

### Building information modeling

BIM is a digital representation of physical and functional characteristics of the buildings developed in the pre-construction stage or even during the conceptual stage (pre-design stage) of the project which provides provision for the participation of client, stakeholders, engineers and contractors in a single platform so as to eliminate all the possible errors that could probable occur in a project even at the beginning of the project so as to produce flawless diagrams and could be readily updated at any point of time, generally this features is called as ‘parametric-change characteristics’.

The parametric change characteristics of 3D BIM formwork module was visualized and portrayed in detail by Kannan and Knight (2012). The parametric change capabilities of 3D BIM formwork module were further extended to account for the automatic layout and simulation of concrete formwork systems and to perform 4D and 5D constructability analysis by Kannan and Santhi (2013a). A detailed retrospective assessment of constructability analysis of three major types of climbing formwork systems, namely, crane-independent climbing formwork system, semi-dependent climbing formwork system and automatic climbing formwork system traversing the cost, time, attributes using 3D BIM was carried out by Kannan and Santhi (2013b). The 3D BIM formwork module proves to be an essential tool in checking for clashes with the associated 3D BIM architectural, structural and MEP models in the pre-construction stage of the construction project, which is commonly termed as ‘clash detection’ (Kannan and Santhi 2015) to identify and eliminate obstacles or prevent error, delays and cost over-run that could probably occur during construction. Thus, the interoperability characteristics of BIM plays a vital role in incorporating the constructability criteria of formwork construction (Kannan and Santhi 2013b, 2015; Hijaji et al. 2009; Kim and Cho 2015). In this research, the implementation of BIM for constructability assessment of concrete formwork systems is portrayed for the pre-construction visualization and decision-making phase of a project

This is achieved by developing an unique add-in functionality for Autodesk Revit known as ‘CONSTaFORM’.

## CONSTaFORM

This unified 3D BIM Model plays a key role in the development of ‘CONSTaFORM’, an Add-in for Autodesk Revit to perform constructability assessment of concrete formwork systems using BIM. This can be achieved through a cutting edge methodology known as ‘API-fication’.

### API-fication

API is a short form of ‘Application Programming Interface’ is an all-embracing term related to computer programming, which is a set of protocols and tools used by developers for building application software and also in many cases, it used to enhance the functionality of the existing application software. Thus, the process of revamping the application software architecture by modification or alteration to enhance additional functionality is termed as API-fication. In this research, the CONSTaFORM Add-in is developed by customizing Revit API through both Revit Macro Manager (MM) as shown in Fig. 11 and Visual Studio software using C# language in .Net Framework (Rudder 2013). The detailed description of the development environment of the CONSTaFORM Add-in is given in the Algorithm 1.

## Results and discussion

The parametric change characteristics of the BIM not only accommodates the effective modification of the 3D BIM formwork families but also provides a semi-intelligent markup, i.e, when changing the 3D BIM system wall formwork family to 3D BIM conventional wall formwork family as in Fig. 14, the associated formwork accessories of the 3D BIM system wall formwork family are deleted instantaneously. This brings down some of the major complexities associated with the formwork planning. Moreover, for a greater understanding of the clashes between different 3D BIM Formwork families and 3D BIM structural model, a sophisticated process known as ‘clash detection’ is carried out using the same integrated 3D BIM model in a separate software, say, Autodesk Navisworks. Then, after resolution of the clashes in the integrated 3D BIM Model, it is then transferred to Autodesk Revit for performing the constructability rating.

One of the advantages of the CONSTaFORM Add-in is that the outputs, i.e., the overall constructability scores as well as the constructability scores of each concrete formwork system can be exported to Microsoft Excel, MySQL and other database management systems for further data analysis.

In addition to the capabilities of incorporating parametric change characteristics, it should be incorporated in a real-time construction projects for actual advocacy and validation.

### Validation

## Conclusion

The CONSTaFORM Add-in developed in this research is an innovative automated constructability rating framework system for assessing constructability of different concrete formwork system. The developmental procedure adapted for CONSTaFORM Add-in, in this research, is based on various possible techniques and tools by trial and errors. From Figs. 13, 15 and 18, we infer that, the CONSTaFORM Add-in is capable of adapting in all the situations traversing from the 3D BIM models to a real-time project.

### Further research

This research promulgates the interoperability of BIM for constructibility assessment of concrete formwork systems, withal this concept can be extended to incorporate in other modern reality technologies such as virtual reality, augmented reality and mixed reality so as to enhance and explore further functionalities of BIM (Boga et al. 2018). Additionally, the capabilities of BIM can be further enhanced by coupling with the open source graphical software like Dynamo (Griendling 2016), blender and so on. Additionally, the clash detection process of the 3D Integrated BIM Model (3D BIM structural + 3D BIM formwork module) is carried out externally using Autodesk Navisworks, thus, the API-fication process (customizing Navisworks API) can be incorporated in Autodesk Navisworks to synchronize with Revit API to perform the clash detection process of the integrated 3D BIM Model intermediately or simultaneously.

## Notes

### Acknowledgements

The authors would like to thank the following individuals and organizations for their valuable support and guidance in accomplishing this research. Autodesk Education Community, Autodesk, Inc., California, USA for providing free access to the Autodesk Revit 2018 software for our teaching and research. Mr. Amitendra Nath Sarkar (Engineering Manager), Mr. Devendra Dalal (Former Design Engineer), Mrs. Shobana Gajhbiye (Design Engineer), Mr. Sashikanth Deshmukh (Draughtsman), Mr. Suryakanth Kolekar (Draughtsman), Mr. R. Kumar (Senior Formwork Instructor) and Mr. Muthuvinayaga Krishnan (Formwork Instructor) of Doka India Pvt. Ltd, Navi Mumbai, India for their valuable information and technical guidance on system formwork and special formwork (climbing formwork systems) Engineering. Mr. Eldo Vargehese (General Director), PASCHAL Formwork (India) Pvt. Ltd., Hyderabad, India; Mr. Ketan Shah (Managing Director), MFE Formwork Technology India Pvt. Ltd., Mumbai, India and Mr. Arul Raja (Vice President), RMD Kwikform, Chennai, India for their support during the constructability survey. The contribution of various other technical experts and discussants, directly and indirectly during the constructability survey and API-fication process are also highly regarded. The authors would like to thank the anonymous reviewers for their insightful comments and constructive suggestions that greatly contributed to enhance the quality of final version of this manuscript.

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