Tab. 1:
The three levels of the collected data.
| Main categories | Sub-category | Factors | Description | Reference |
|---|---|---|---|---|
| Design attributes | Standardisation and repetition | Prefabrication | Precast concrete, prefabricated utility products, prefabricated MEP, etc. | Boton (2018), Hijazi et al. (2009), Zhang et al. (2016), and Khan (2019) |
| Grid layout | (Horizontal/vertical/radial) grid dimensions, a repeated grid layout will lead to faster construction sequences | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Standard dimensions | Dimensions for door, windows, partitions, tiles, etc. | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Economic | Component flexibility | Flexibility of movement of internal partitions (fixed/mobile) | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | |
| Resources availability | Various resources such as building material, labour, and equipment can be approached, hired, and put to work for the execution of the project | Boton (2018), Hijazi et al. (2009), Zhang et al. (2016), and Shash and Almufadhi (2021) | ||
| Labour skills | Availability of special labour skills | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Team expertise | The project team must be selected based on their experience knowledge and skills requirement for the project | Shash and Almufadhi (2021) | ||
| Application of advance information technology | Adoption of latest and modern computerised means of technology for the project | Khan (2019) | ||
| Coordination or communication | Coordination and communication among team members (builder and designer, site staff) | Khan (2019) and Yoon et al. (2018) | ||
| Simplification of Design | Designs considered efficient construction | Khan (2019), Shash and Almufadhi (2021) | ||
| Construction methodology | Major construction method options, in the project’s design phase | Shash and Almufadhi (2021) | ||
| Structure system | Structural frame types | Steel frame, concrete frame, wood frame | Yoon et al. (2018) | |
| Roof types | Gable, hip, Dutch, etc. | Yoon et al. (2018) | ||
| Slab types | Conventional, flat, waffle slabs | Yoon et al. (2018) | ||
| Structural reinforcement scope | The design and type of reinforcement | Yoon et al. (2018) | ||
| High-strength concrete application | The usage of high-strength concrete | Yoon et al. (2018) | ||
| Construction attributes | Space | Material access | Space for material storage and transportation on site | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) |
| Personnel access | Accessibility of personnel for different site locations | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Equipment access | Accessibility of equipment and tools for and from different site locations | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Installation | Construction sequence | Sequence of installation of components | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | |
| Time under ground | Construction time under ground level | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Building envelope | Construction of the whole building envelope | Boton (2018), Hijazi et al. (2009), Zhang et al. (2016), and Yoon et al. (2018) | ||
| Weather effect | Effect of climate conditions on construction work | Boton (2018), Hijazi et al. (2009), Zhang et al. (2016), Khan (2019), and Yoon et al. (2018) | ||
| Safety | Effect of construction sequence of workers’ safety | Boton (2018), Hijazi et al. (2009), Zhang et al. (2016), and Yoon et al. (2018) | ||
| Waste management and appraisal recycling | Organise and regulate the waste and convert waste into reusable products | Khan (2019) | ||
| Encouragement to innovations | Promotion of new ideas, the projects constructability can be enhanced using innovation ideas during the construction stage | Khan (2019) | ||
| Document control | Specifications | The projects constructability can be enhanced by developing transparent specifications | Khan (2019) | |
| Simplification of technical specifications | Detailed description of technical requirement in terms of suitability for design development of an item | Khan (2019) | ||
| Qualifications, feedback and improvement in construction | The projects constructability can be enhanced by utilising the lesson-learned databases and best-practices for other projects | Shash and Almufadhi (2021) | ||
| Inspections and site meetings | Quality of inspections and site meetings, level of knowledge sharing and capturing project objectives in accordance with client objectives | Kotze and Wium (2019) | ||
| External impacts | Utility availability | Government facilities | Availability of governmental facilities like electrical and infrastructure services | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) |
| Road-use ability | Applicability of public roads for transportation | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Site impact | Adjacent site | Effect of current construction on adjacent constructions | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | |
| Infrastructures | Effect of current construction on adjacent or nearby infrastructure constructions | Boton (2018), Hijazi et al. (2009), and Zhang et al. (2016) | ||
| Other | Corporate objectives | Understand the project objectives as well as the client’s objectives | Shash and Almufadhi (2021) | |
| Bidding process | The type of bid (design–build/ design–bid–build) | Khan (2019) and Yoon et al. (2018) | ||
| Construction-driven schedule | The schedules are prepared in the construction projects to keep a check on the various design and construction activities | Khan (2019) and Shash and Almufadhi (2021) |
Tab. 2:
Summary of the open questionnaire (expert samples).
| Institutes | No. of interviews | Job tittle |
|---|---|---|
| Mayoralty of Baghdad | 5 | 2 Senior chief engineer, senior associate engineers, chief engineer, senior engineer |
| Ministry of Higher Education and Scientific Research | 1 | Senior university lecturer |
| Ministry of Construction, Housing, Municipalities, and Public Works | 4 | Senior chief engineer, chief engineer, senior chief engineer, senior associate engineers |
| The new Central Bank of Iraq project | 4 | Project manager, consultant, chief engineer, site engineer |
Fig. 1:
The chosen factors and their classification.
Fig. 2:
The academic qualification of responses.
Fig. 3:
The practical experience.
Tab. 3:
The values of mean, standard deviation and Cronbach’s alpha.
| Categories, sub-categories and factors | Mean | Standard deviation | Cronbach’s alpha |
|---|---|---|---|
| Design attributes | 4.0556 | 0.71492 | 0.963 |
| Construction attributes | 3.6389 | 0.76168 | 0.962 |
| External impacts | 3.2778 | 0.88192 | 0.963 |
| Standardisation and repetition | 3.5556 | 0.84327 | 0.963 |
| Economic | 4 | 0.86189 | 0.963 |
| Structure system | 3.6667 | 0.79282 | 0.962 |
| Space | 3.5556 | 0.93944 | 0.962 |
| Installation | 3.6389 | 0.86694 | 0.962 |
| Document control | 3.4722 | 0.90982 | 0.963 |
| Utility availability | 3.5 | 0.87831 | 0.962 |
| Site impact | 3.7222 | 1.00317 | 0.962 |
| Other factors | 3 | 0.92582 | 0.962 |
| Prefabrication | 3.5556 | 0.84327 | 0.963 |
| Grid layout | 3.6111 | 0.72812 | 0.963 |
| Standard dimensions | 3.3611 | 0.83333 | 0.963 |
| Component flexibility | 3.4167 | 0.60356 | 0.963 |
| Resources availability | 3.9444 | 0.75383 | 0.963 |
| Labour skills | 4.0556 | 0.75383 | 0.962 |
| Team expertise | 4.1111 | 0.85449 | 0.962 |
| Application of advance information technology | 3.6111 | 0.80277 | 0.963 |
| Coordination or communication | 3.9167 | 0.90633 | 0.962 |
| Simplification of design | 3.9444 | 0.82616 | 0.962 |
| construction methodology | 3.8333 | 0.87831 | 0.963 |
| High strength concrete application | 3.3333 | 0.79282 | 0.962 |
| Structural frames types | 3.6944 | 0.85589 | 0.962 |
| Material access | 3.5833 | 0.76997 | 0.961 |
| Personnel access | 3.6389 | 0.99003 | 0.961 |
| Equipment access | 3.7222 | 0.88192 | 0.962 |
| Construction sequence | 3.6667 | 1.01419 | 0.962 |
| Time under ground | 3.5556 | 0.90851 | 0.962 |
| Building envelope | 3.25 | 0.87423 | 0.962 |
| Weather effect | 3.3611 | 1.07312 | 0.962 |
| Safety | 3.75 | 0.99642 | 0.962 |
| Waste management and appraisal recycling | 3.25 | 1.10518 | 0.962 |
| Encouragement to innovations | 3.2222 | 1.09834 | 0.962 |
| Specifications | 3.8889 | 0.78478 | 0.961 |
| Simplification of technical specifications | 3.8056 | 0.85589 | 0.961 |
| Qualifications, feedback and improvement in construction | 3.5556 | 0.77254 | 0.962 |
| Inspections and site meetings | 3.5278 | 0.90982 | 0.962 |
| Government facilities | 3.8611 | 0.86694 | 0.962 |
| Road-use ability | 3.7222 | 0.88192 | 0.962 |
| Adjacent site | 3.4444 | 0.73463 | 0.962 |
| Infrastructures | 3.5556 | 0.77254 | 0.962 |
| Corporate objectives | 3.6111 | 0.83761 | 0.962 |
| Bidding process | 3.6389 | 0.89929 | 0.962 |
| Construction-driven schedule | 3.7222 | 0.8489 | 0.962 |
Tab. 4:
The relative weights and developed weights.
| Main categories | Relative weight | Sub-category | Relative weight | Factors | Relative weight | Decomposed weight |
|---|---|---|---|---|---|---|
| Design attributes | 0.370 | Standardisation and repetition | 0.317 | Prefabrication | 0.338 | 0.040 |
| Grid layout | 0.343 | 0.040 | ||||
| Standard dimensions | 0.319 | 0.037 | ||||
| Economic | 0.356 | Component flexibility | 0.111 | 0.015 | ||
| Resources availability | 0.128 | 0.017 | ||||
| Labour skills | 0.132 | 0.017 | ||||
| Team expertise | 0.133 | 0.018 | ||||
| Application of advance Information Technology | 0.117 | 0.015 | ||||
| Coordination or communication | 0.127 | 0.017 | ||||
| Simplification of Design | 0.128 | 0.017 | ||||
| Construction methodology | 0.124 | 0.0 16 | ||||
| Structure system | 0.327 | Structural frames types | 0.526 | 0.063 | ||
| High-strength concrete application | 0.474 | 0.057 | ||||
| Construction attributes | 0.332 | Space | 0.333 | Material access | 0.327 | 0.036 |
| Personnel access | 0.332 | 0.037 | ||||
| Equipment access | 0.340 | 0.038 | ||||
| Installation | 0.341 | Construction sequence | 0.152 | 0.017 | ||
| Time under ground | 0.148 | 0.017 | ||||
| Building envelope | 0.135 | 0.015 | ||||
| Weather effect | 0.140 | 0.016 | ||||
| Safety | 0.156 | 0.018 | ||||
| Waste management and appraisal recycling | 0.135 | 0.015 | ||||
| Encouragement to innovations | 0.134 | 0.015 | ||||
| Document control | 0.326 | Specifications | 0.263 | 0.028 | ||
| Simplification of technical specifications | 0.258 | 0.028 | ||||
| Qualifications, feedback and improvement in construction | 0.241 | 0.026 | ||||
| Inspections and site meetings | 0.239 | 0.026 | ||||
| External impacts | 0.299 | Utility availability | 0.342 | Government facilities | 0.509 | 0.052 |
| Road-use ability | 0.491 | 0.050 | ||||
| Site impact | 0.364 | Adjacent site | 0.492 | 0.054 | ||
| Infrastructures | 0.508 | 0.055 | ||||
| Other factors | 0.293 | Corporate objectives | 0.329 | 0.029 | ||
| Bidding process | 0.332 | 0.029 | ||||
| Construction-driven schedule | 0.339 | 0.030 |
Fig. 4:
The factors and their affection percentage on constructability.