Complexity in the AEC industry has been extensively explored. It started with the idea of stating an objective range for complexity reduction of the AEC systems. Currently, the term complexity is mainly applied in the AEC from two perspectives. One is the engineering perspective the other one is the architectural perspective. Both perspectives coincide on warning that current technological advances are allowing for a higher complexity on building design [2,3] and construction projects [1]; which is a tendency that is happening to all the engineering systems [4]. Besides the two main complexity perspectives in the AEC, this research categorizes all the derived complexities from the building design and for specific use as part of the building complexity, which will be discussed under the building complexity title.
Project Complexity
From the engineering perspective, the term complexity is mainly focused on the project complexity because the construction project is considered the most complex compared to others in any industry [8] and its believed that the complexity on a project affects the project’s time, cost, success, and quality [1]. This complexity is something experienced by the project manager [9].
One of the first to categorize a project depending on the complexity was Santana [10]. He proposed a method to classify projects into normal, complex and singular There he considered a project to be ̏ the sum of the planned activities, material or otherwise, of an organization to convert an idea or a design for engineering or construction work to fulfill human or economic needs within limits of quality, cost, and duration. ˝ [11]
Baccarini [8], proposed an even formalized version of project complexity, there he defined project complexity as ̏ consisting of many varied interrelated parts and can be operationalized in terms of differentiation and interdependency ˝ . Which is a definition
that can be applied to any project dimension. Besides the definition, he stated clearly that is very important to recognize the type of complexity that is being dealt with and he declares the two main types of complexities at the moment which were organizational complexity and technological complexity.
Along with the years of exploration and research for the complexity area in projects, many factors, dimensions, and categories were included in the project complexity estimation. Currently, the project complexity has five dimensions, which are:
the socio-political, the pace, the dynamic, the uncertain, the structural [9]. These dimensions are grouped into three categories: the structural category, which includes the pace and the structural complexity; the Socio-political category; and the Emergent complexity, which include dynamic complexity and uncertain complexity [12]. See figure 1.
Design Complexity
From the architectural perspective; the complexity research mainly focuses on the design complexity. The design complexity characterization primary goal is to categorize and open a range for a reduction in the building design [2]. The design complexity is not being as explored as the project complexity and it can be defined from two perspectives
Figure 1 Complexity of projects. [12].
which are the modeling perspective and the shape perspective. This type of complexity is produced by the designer, and it has effects on the project manager and the building users.
The modeling perspective refers to design complexity as for how hard is to create the model. It is measured as the ratio of added design content to added construction content. Where the commands that a computer-aided needed to create an object are the design content and the construction content represent the construction commands that the design object requires [2]
The shape perspective refers to the complexity of the design result or the shape of itself. The shaped result of an architecture model is mainly a 3D model that is made of several elements that together represent the building. A building model shape can be categorized as complex if this one possesses high geometric complexity elements, or it may be considered complex by possessing many low complexity elements [13]. Another way to determine the complexity of the shape in an architectural model is by categorizing it as having a high combinatorial complexity compared with other 3D models in other industries [14].
Building Complexity
The product or the final goal of a building construction project is a building. This one has a structure designed for exclusive use, and it consists of many interacting elements from different disciplines. The shape of that building’s elements represents the geometrical information. All other information represents the nongeometrical information (See figure 2). These two types of information can be used to create new types of complexity measurements, which are independent of the project information but dependent on the geometric information.
The building’s derived complexities may have a direct relationship with the building elements geometry. The geometrical information of the building and the needed
nongeometrical information obtained from the relation between the building elements are the basis to set new complexities depending on what is wanted to be categorized. For different uses, a complexity measurement can categorize the effect of the design on that specific use.
The term complexity in building was first used to categorize the building from energy efficiency and occupant comfort point of view [15]. The building could be categorized as complex if the energy efficiency indicators and the comfort indicator were not showing correct results due to a possible under design building.
The design of the walls, doors position, and hills in a building may affect directly the way people enter and leave the building. This effect can be considered an issue from the fire safety usage perspective. The effect of how hard is to get out of a building is quantified as egress complexity by Donegan, Pollock, and Taylor [16], where the entropy measurement is used to reflect the building 2D plan complexity.
The way a designer creates a 3D model may influence the cost estimation task directly. A measure of how hard is to estimate a building cost from a specific model is
Figure 2 Complexity of buildings, geometric and non-geometric information relation concept.
quantified as the estimation complexity. The number of elements, the shape and geometric features of the building components and the number of trade categories involved in constructing the building components are the factors used to measure the estimating complexity [17].
The shape complexity of the building instances that need to be cast in place is proposed by Jarkas [18] as a factor to calculate the buildability of the formwork labor production. The shape combined with materials and other factors were used as a base to determine the buildable conditions that a design represent from formwork production point of view.
This research proposes a complexity that fits better in the building complexity stream. The complexity referred here is to a way to characterize the effect of the design on the construction directly or indirectly, where the design can make a building increase its construction complexity due to the construction efforts required to create the building.
Also, a design can affect the construction indirectly by increasing the visualization difficulty due to complex design or by increasing the communication due to the number of disciplines involved. See figure 3.
Figure 3 Complexities determining how the design affects directly or indirectly the construction.
The proposed complexity is an analogy of the one defined in the manufacturing industry. The manufacturing industry has three perspectives to define complexity. One of these perspectives is the complexity of a product, which is affected by factors such as number of parts, multidisciplinarity, manufacturability, size, geometry, variety. Another
perspective is the complexity of the manufacturing system; this one is affected by changeability, responsiveness volume, speed, and operational flexibility. The third perspective is the business organization complexity, which is affected by the supply chain dynamics, global competition, market turbulence, and foresight. [5]
Each perspective has factors that affect their complexities established by a specific scope. In the engineering field, the complexities characterization need to have a scope; it could be a part, a product, a system, or system of systems [5]. Due to the similarity of the factors affecting the product complexity and the proposed goal of this research. Its assumed that a building is the product of the construction process, and its complexity may be affected by the factors that characterize the complexity of a product. From this analogy, it is possible to consider using the factors that affect a product from the AEC perspective.
In this case, the factors affecting a building will be the building number of parts, the building size, the multidisciplinarity involved in the building, the buildability, the geometric information of the building and the variety.
The factor affecting the construction complexity and the geometric complexity is obtained from the analogy made to the manufacturing industry and the ones affecting each type of complexity is determined by the author’ try and error process, where the factor and metrics for each factor were tested and changed to obtain the current arrangement. The factors affecting the construction complexity are the buildability, size, and multidisciplinarity. The factors affecting the geometric complexity are the Geometry, variety, and number of elements. See figure 4.
Figure 4 Factors affecting the geometric complexity and the construction complexity.