Decision-Making Problems in Construction Projects Executed under the Principles of Sustainable Development—Bridge Construction Case

Abstract

The high environmental impact of bridge construction causes numerous dilemmas in decision making related to the choice of the best material and technological solutions and their consequences in subsequent phases. These decisions adopt from the management condition the successful investment in this type of project. A bridge construction project includes consecutive stages: design, construction, operation/maintenance, and decommissioning. The latter usually involves the demolition of the infrastructure, generating elements that cannot be reused. This waste-generating linear production process must be urgently replaced by closed-loop production, framed within the Circular Economy (CE) philosophy that provides a practical response to the challenges related to sustainable development goals (SDGs). This document performs an analysis of case studies in an attempt to sort out the management challenges related to the construction, operation and decommissioning of bridges. The research is based on a questionnaire carried out among civil engineering project managers and explores the possibility of adapting the principles of the Circular Economy in bridge construction projects, especially in the context of the traceability of construction materials used for the construction.

1. Introduction

Construction is a unique sector characterized by the intensity of capital employed and the variability of turnover over time. In particular, global economic crises (including the consequences of the current COVID-19 pandemic or the aftermath of the Russian invasion of Ukraine) have highlighted its importance and impact on other spheres of life [1,2]. Regardless of the specific field (residential construction, industrial construction, transportation, agricultural construction, or water projects), certain circumstances arise that alter the pace of projects, generating deviations between plans and reality. This affects basic parameters such as execution time, cost, scope, or quality. On the other hand, the construction sector has been characterized as an intensive generator of waste and emissions [3,4] that permanently affect the natural environment [5].

Another distinguishing factor of construction projects is their duration, generally long, which increases the risks. These risks must be controlled during the different phases that the projects follow (programming, design, construction) in order to achieve the final success: an assembly of the structure according to the design, complying with the technical requirements in the execution of the construction works.

The specific characteristics of construction projects refer both to the products—built and unbuilt structures—and to the development of the investment process throughout the entire life cycle of the project. The task of stakeholders in construction projects is to prepare and implement responses to environmental risk, leading to the neutralization of their effects, especially to support the management of construction and demolition waste [6,7].

An effective risk management strategy is the priority for the construction sector [8,9]. Multiple threats exist in the design as well as the subsequent phases of construction projects [10,11]. Usually, reliable construction processes that create resilient and safe facilities are expected. Moreover, for facility managers, the management of digital risks turns out to be essential too. For instance, protection against unauthorized intentional access does not have to mean just anti-theft issues. In the era of digitization, it is also necessary to ensure cybersecurity [12,13,14]. Data leakage can even contribute to drastic sabotage attempts [15]. This, in turn, may translate into a reduction in users’ trust in the infrastructure. Thus, civil engineering appears as a discipline where both safety and security become key success factors [13,14,15].

A bridge, as a special case of civil infrastructures, is an object that requires serious insight into its security, resilience, and sustainability [16,17]. Attempts of sabotage can lead to severe consequences, including accidents, environmental pollution, and an influence on socioeconomic and political stability. However, incorrect operation can be a source of danger as well. The bridge administrator must ensure the safe use of the facility in the event of external factors affecting the bridge (excessive loads, storms, seismic shocks, etc.) that may endanger human life or health, property, or the environment.

In addition, poor maintenance of bridges reduces their durability and increases the probability of breakdowns, hence causing unscheduled renovations and repairs. Such a situation may contribute to increased traffic jams, emissions, as well as the frustration of drivers or residents, which may lead to a reduction in their well-being. All in all, bridges need special treatment because of their vulnerability to malfunctions, damages, or collapses that can affect sustainability [16].

In the common conception of the sector, sustainable development in construction is mainly identified with energy efficiency [18], alternative energy sources [19], or expensive and unprofitable operations. Bridge construction projects are quite specific due to their social and engineering nature. They must meet basic technical requirements and, at the same time, serve users. However, nothing prevents the design, construction, and maintenance process from being consistent with sustainable development. Sustainable development can be perceived as socioeconomic development harmonized with respect for the environment. Therefore, its objective is to reduce negative externalities, including environmental impacts, caused by economic growth, hence protecting future generations and enabling their further development. In practice, there are some actions to minimize the negative impact of civil infrastructures (e.g., bridges) on the environment in all phases of their life cycle [17].

The responsible management of bridge construction projects must be supported by a dual economic and environmental analysis. A life cycle cost analysis (LCCA) and life cycle assessment (LCA) should provide decision makers with insights into the benefits of alternative technologies and design solutions [20,21]. It is not without importance what building material a given bridge is made of.

The available statistics show that the scale of the challenges is significant. According to some public reports, in 2021, there were 619,588 bridges in the United States. At the same time, more than 7% of the country’s bridges were in poor technical condition, that is, they were structurally deficient. More than 40% of them were at least 50 years old [22]. At the current rate, it would take about 30 years to repair or replace all of them [23]. In contrast, in Poland, the average age of the country’s bridges, managed by the General Directorate of National Roads and Highways (Polish: Generalna Dyrekcja Dróg Krajowych i Autostrad), is slightly different from that in the United States. Bridges less than 12 years old predominate, with 47.9% [24]. Despite this, 14.8% of all structures are in a state of concern—they have at least some damages, which may lead to a shorter period of safe operation and maintenance. This shows the magnitude of the repairs and the need to build new bridges in the future throughout the world.

However, a limited number of studies in this area creates a problematic gap in knowledge, especially when it comes to management challenges in terms of sustainability. To eliminate some euphemisms, a research question was asked whether bridge construction projects fit in the context of sustainable development. In addition, the construction sector’s propensity to take for granted that construction projects must meet sustainability requirements was considered a secondary motivation for research.

This study contributes to the theoretical description of bridge construction project management strategies. At this point, it must be underlined that in works representing technical disciplines, not only are innovative solutions important. The applicability of the results of scientific research is also crucial from the point of view of contributing to the development of science. Since learning from mistakes is a basic prerequisite for successful project management, the content of the article may be of interest to selected stakeholders, especially those involved in bridge construction projects.

This article discusses decision-making problems in the execution of bridge construction projects within the context of sustainability. To do this, a case study related to a real bridge construction project is analysed. The emblematic example of the cable-stayed bridge over the Brda River in Bydgoszcz was chosen. It is a unique bridge, not only because of its architectural form, but also because it had to be closed within a few years of its opening, and the dispute between the bridge’s contracting company and the designer became a national public debate.

The city of Bydgoszcz is one of the main Polish cities in terms of the number of bridges. Some of them were built in the 19th century (or even earlier). This means that past generations have left their heritage to the present, and it is still in use today. These assets, of course, require appropriate investment outlays. They are even higher as the renovation of historic infrastructure is subject to strict legal regulations. Therefore, it is necessary to build 21st century bridges based on innovative solutions that support the sustainability of projects [20,25,26,27,28] with low maintenance and repair costs in relatively long periods of operation. The simplicity of the repairs or replacement of the bridge parts is a relevant factor for the success of this type of project [29].

This study is complemented by quantitative research on the managerial risks in these projects. For this, a questionnaire distributed to professionals, mainly construction managers and construction managers from Poland, has been used. This qualitative–quantitative study tries to find the conditions for the execution of bridge construction projects and the management of their risks under the principles of sustainable development. With this, we want to achieve our objective, which is to learn about risk management in bridge construction projects within a context of sustainable development.

The article has been divided into six main chapters. The first one is a theoretical introduction to the subject of the paper. Then, the main dimensions of the challenges faced by decision makers in construction projects implemented in accordance with sustainable development are presented. Afterwards, a meaning of sustainability in construction is specified. After a description of the methodology, the results of the analysis (the case study and the survey results) are shown. The end includes a discussion and a concluding paragraph that draws the introduction and the middle together.

2. Main Challenges

2.1. Technology

The specificity of bridge construction is based on some of its characteristics, related to building and non-building structures, as well as the nature of the technological and organizational processes for its production [30]. This process consists mainly of:

• Structures are permanently attached to the ground and have a large mass and size; they have a longer life cycle than other construction projects;
• The individual nature of technical solutions for buildings and non-building structures;
• The differentiated quality standards for this type of construction;
• Differentiated quality standards for construction;
• Need for individual technological and organizational solutions for the execution of construction;
• Complex nature of the execution processes;
• Long production cycles and high costs;
• A large number of specialised processes;
• A significant impact of construction on the natural environment;
• Many different stakeholders are involved in the process;
• The probabilistic nature of construction processes, implying the risk [31].

Bridges, due to their symbolic function (the connection between two banks of a river, valley, etc.), occupy a significant position among construction products, leaving a permanent mark that reflects the time in which they were built. Bridge construction technology has recently been recognized for its long service life, up to 1000 times longer than other technology products, in addition to the requirement of absolute safety throughout the useful life of the bridge. The literature shows the keys to the development of new values of such infrastructures, including the breaking of technological limits in response to new environmental changes and social requirements. Bridge construction technology must take into account all related design requirements, first with the statics and dynamics of the structure. This means that specific construction conditions may apply to individual types of bridges. At this point, bridges serving high-speed rail appear to be relatively interesting and technologically demanding [32].

Bridge-related technology is not just construction technology in the strict sense. Due to the long-term durability of structures (or, more broadly, their life cycle), it must also include monitoring of the functioning of the structure during the maintenance phase. Thanks to modern technologies and the achievements of the 21st century, there are computer-assisted monitoring solutions, sometimes automated monitoring or monitoring supported by artificial intelligence. They can function both in the short and long term and can be responsible for measuring deflections [33], displacements [34], strains [35], etc. In turn, a completely new area of possibilities opens up with 5G technology, which is heralded as a means of creating smart city solutions.

For all these reasons, bridge construction projects today must go beyond their mere technical value, adopting the concept of a combination of national/regional economic, cultural or political values. Therefore, it is necessary to look at the construction of bridges through the prism of sustainable development. This concept also includes the Circular Economy philosophy, which is based on promoting the closed circulation of matter characterized by significant production potential. However, the reuse of recovered materials both in construction, in general, and in the construction of bridges in particular, is limited, and more and more examples of this approach can be found. In the literature, for example, wind blades can be found that were used as load-bearing components in various conceptual bridge designs [36]. Other ideas for the applications of materials used in construction are also being tested, often requiring the development of new technologies in manufacturing.

2.2. Project Management

“Construction project” is understood as the set of all activities related to decision making, the work that precedes the start of the construction work, execution, start-up of the facility (construction, non-building structures), and the achievement of the productive, commercial or service capacity of a specific investment project. This process also includes the technical maintenance of the building structure until its dismantling (for example, deconstruction, demolition, etc.). On the other hand, “investment projects under construction” consist of investments made to create new or additional assets that investors intend to turn into profits in the future.

Decision making during project management is associated with three main constraints: cost, quality, and time [37,38]. Efficient project management requires the simultaneous awareness of these factors, including efforts to make the project cheaper, better, and faster [39]. These challenges, despite the apparent contradiction, mark contemporary trends in the search for optimal solutions in the management of construction projects. They become the object of commitment and constitute key performance indicators (KPI) of construction projects to lead them to final success.

Construction investment projects are executed through various organizational formulas that pose a risk to individual stakeholders. The investor, relying on his capabilities, decides the method of execution of the project: conventional (Design–bid–build) or non-conventional: Design–build, Design–build–finance, Design–build–finance–operate–maintain, etc. [9,40] The latter is sometimes associated with build–own–operate–transfer partnerships since the owner (a private partner), according to the signed agreement, transfers ownership to the public partners at the end of the project.

Construction project management has a mix of tasks resulting from reconciling the aspirations of the stakeholders. Considering the financial aspect of projects, an investor generally wants to spend as little as possible. On the other hand, the contractor wants to earn as much as possible.

The foregoing shows the complexity of the forecasts for the course of investment projects under construction, which is reflected in the risk assessment of said undertakings. The risk understood as a probability of changes in the basic parameters of the project is often shared by all the participants of investment projects in construction, but their results are usually different for them.

It is worth emphasizing here that complex construction projects usually require computer-aided management methods. However, digitization has one significant drawback. It makes the architecture, engineering, and construction (AEC) industry more vulnerable to cyberattacks [14], what is often equated with digital risks. Fortunately, there are specific rules for senior management to understand security problems and organize security processes [12,13].

2.2.1. Risk Management

In a construction project, risk management is a key factor to achieve the objectives [8]. It will be effective when carried out systematically throughout the life cycle of the construction project [21,41]. A wide range of risks are associated with and affect the project [8,11]. The mapping of the risks associated with the project must be based on a study of its internal structure as well as the conditions that emerge from the stakeholders.

The success of the project is a consequence of the effort of all those who are involved in its delivery [10]. As a result, project risk management information should not be restricted to just the project manager but should be disseminated wherever threats exist. Therefore, in addition to the basic tasks of project management staff, their role in raising awareness among all stakeholders of the possibility of discrepancies between plans and reality is also very important.

Managing risk is expecting the unexpected. In the construction sector, where there are formalized construction plans, which become models of future construction facilities (including building and non-building structures), the possibility of risk arising is extremely high. Due to the need to simplify reality, engineers work on construction designs; however, these simplifications complicate reality even more because they create an area of underestimation and, therefore, an environment of uncertainty. Thus, risk management in a construction project must be dynamic, monitoring the sources of risk, verifying the interference of risk factors, and seeking ways to respond to emerging threats (risk response). Designing the construction under the Building Information Modelling (BIM) model, which has become very popular in recent times, reduces the area of uncertainty and can make risk management easier and processes more predictable [42,43]. However, it should be noted that BIM is just a tool whose potential can be used appropriately or inappropriately. The skills of those responsible for executing the construction project primarily determine whether the strengths of this solution will contribute to taking advantage of the opportunities [44].

2.2.2. Resource Management

A construction project is a complex and organized multi-entity activity carried out by people with the appropriate resources and following the established plan. Resources include personnel, materials, equipment, as well as information and financial resources used in the execution of the project. The use of purchased direct materials for a construction project relates to the sphere of technological readiness of the entire construction process.

The availability of work (“work-limited progress”) or the availability of resources (“resource-limited progress”) are perceived as constraints on construction progress [45]. While the job availability determines the potential build rate based on the amount of work available, the resource-based build rate is primarily determined by the availability and productivity of resources. Due to the progressive scarcity of resources, both in terms of work and the availability of resources, there is a growing concern among construction companies about the effective management of resources, including traceability of construction materials [46].

Resource management relates not only to the matter consumed during construction projects. Civil infrastructure can be used to manage resources that serve people generally. For example, drinking water resources that require appropriate rainwater harvesting (RWH) systems are crucial for human existence. Larger and larger areas of the Earth are extremely sensitive to water shortages. Buildings, but also structures such as bridges and tunnels, can support water or energy management [47,48,49].

3. Sustainability in Construction

Each investment, regardless of its location, interferes with the natural environment to some extent. This interference may manifest itself at the stage of construction works, at the stage of operation and maintenance of the facilities, as well as at the moment of locating the structure near protected areas, where the investment affects the immediate and further surroundings, emitting gases, noise, and discharge of sewage, contributing to the lowering the groundwater level [50].

The long life cycles of the investment and construction projects of the erected structures (from the cradle to the grave) make it necessary to take into account the philosophy of sustainable development (ecological–socio-economic), harmonized with respect for the environment. Respect for the principles of sustainable development in construction requires building and structure design solutions, as well as new methods for their erection in a way that respects people and the natural environment, including also economic calculation [31].

When analysing construction projects from an environmental perspective, the following factors should be considered:

• The consumption of non-renewable resources and the energy required for their processing, especially in the construction phase of buildings and non-building structures;
• Emissions level of harmful substances, especially in the operation phase of the facilities;
• Possibility of recycling in the dismantling phase of the facilities.

As a result, it is necessary to eliminate the negative impact of building structures on the natural environment. The construction sector has a significant environmental impact. With the growing demand for sustainable development, it is essential to make efforts to limit the amount of waste generated by the construction industry (mainly on construction sites). Construction and engineering companies can no longer resist the urge to join the “sustainable mainstream” for fear of being ignored and called irresponsible [51]. Sustainable development is currently considered a balance between the natural environment, society, and the economy. However, complying with the principles of sustainable development in construction implies the design and implementation of solutions for structures that are respectful of humans and the environment, as well as being economically justified.

The main challenges of sustainable development in the construction sector include the proper management of waste, as well as the controlled transition from the linear economy model to the Circular Economy model.

3.1. Construction and Demolition Waste (CDW)

The construction industry is very important for policymakers, due to its emission of dangerous gases, generation of waste, and consumption of resources [52]. Currently, one of the key strategies for the European Union is to minimize waste in construction projects [53]. The European Commission adopted the Waste Framework Directive 2008/98/EC (WFD), which provides a comprehensive framework of waste management standards and establishes waste definitions for all members of the European Union. The WFD includes a comprehensive description of the “Waste Hierarchy”, which prioritises the prevention of waste generation over preparation for reuse, recycling, and recovery. A 70% recovery target has been set for construction and demolition waste (C&D) [54]. Unfortunately, public institutions (e.g., Eurostat) usually do not collect direct data on the amount of CDW. Mineral waste is the most significant waste source of CDW by weight, accounting for more than 80% of the total CDW generated in the EU [55]. As a result, the CDW generated in each EU member state is estimated using the mineral waste reference.

Waste from the construction, renovation, and dismantling of buildings and infrastructure is generated in the residential sector and industrial construction, as well as in railways, road construction, and bridge engineering. This type of waste is generated during construction, rehabilitation, and demolition works that are found throughout the life cycle of the construction project. Since this waste can be generated at various stages of the projects, the possibility of prevention is closely related to the technology used. Before renovation and construction work, optimization of the consumption of building materials should be carried out. To minimize CDW, it is suggested to use modern and mostly welcome technologies without waste. However, effective resource management consisting of checking material consumption standards is very helpful in reducing the amount of waste.

3.2. Linear Economy vs. Circular Economy

In the 20th century, the relationship of economic and social systems with the environment was called into question [56] because both Western countries and a sphere of influence of the USSR, participating in the conflict of civilizations, wanted to demonstrate their superiority in the effectiveness of the reconstruction of the world after the Second World War. Nothing mattered except productivity. There was no thought in terms of the entire life cycle. This approach must have resulted in economic problems, overproduction, and environmental problems. The latter was mainly because the “take–make–dispose” approach was the guiding principle in economies, especially in developing countries. The fashion had come to have new and better goods and abandon the old ones. Not everyone succumbed to it because poverty or scarcity forced other alternative actions such as the repairs, improvement, and reuse of old products.

Construction and engineering, especially on a large scale, required the supply of freshly mined raw materials, newly manufactured materials, or semi-finished products. It was faster, more efficient, and the first thing that mattered was the final effect. Providing houses for people, building bridges, or other infrastructure all required large investments in a short time. A model based on a simple “take–make–dispose” relationship has been called “linear economy”.

It maintains the basic idea of abandoning all use of non-renewable resources [57] at the end of the product’s life cycle. Today’s production systems imply a serious challenge based on the change from a traditional linear economic model that creates products and releases waste to a new business production model followed by the transformation of the Circular Economy (CE).

CE can be treated as a concept of reducing the ecological footprint by creating new flows of matter in manufacturing processes. It is necessary to abandon the traditional understanding of the product transformation process based on the “take–make–dispose” principle and replace it with a completely different understanding of the production system.

In the construction sector, this shift is primarily about carrying out only these production processes that are featured by minimal waste and pollution. Thus, modern low-waste design solutions, energy-saving technologies, or environmentally friendly facility management become necessary for the effective implementation of CE. Moreover, a long-lasting circulation of products and construction materials in the whole production system is vital for its resilience. Therefore, decisions made during the design phase about the materials used for construction, the construction strategy (monolithic vs. prefabricated), and the types of joints (between different elements and parts of bridges) affect the efficiency of this flow in the subsequent project phases. The last pillar of the CE-based approach concentrates on care for nature. In the context of the construction sector, this must mean giving preference to biodegradable materials, materials of natural origin, as well as technologies imitating natural processes and solutions emulating natural systems [58].

Unlike the linear economy, the Circular Economy (CE) has more advantages and manifests fewer negative externalities of business activity. The contemporary aspirations of European Union politicians aim to convert the paradigm of the so-called linear economy. Incorporating CE ideas into sustainable supply chain management provides several environmental benefits over a standard linear model [59].

Decision making in bridge construction projects executed under the principles of sustainable development and the Circular Economy requires a lot of simulations, analysis, and certainly basic competencies (knowledge, skills, experience) to manage sustainable construction projects.

3.3. Human Well-Being and Needs of Future Generations

Sustainable development is a broad and frequently misunderstood concept. Originally, it meant ensuring the satisfaction of the current demands without jeopardizing future generations’ ability to develop [60]. The report underlines that civilization can achieve a certain level of prosperity unless poor management occurs. This wrong “path” involves the mutual contradiction of economic growth, respect for the environment and quality of life. Only by integrating these three areas, it is possible to achieve the goals of sustainable development.

However, theoretical considerations sometimes have to receive political support, which usually takes the form of guidelines, recommendations, or resolutions of various international institutions (e.g., European Commission, United Nations, etc.). For this reason, the document called Transforming our world: the 2030 Agenda for Sustainable Development was accepted by all 193 UN member states in 2015 in New York. It defines 17 sustainable development goals (SDGs) and 169 related targets that are to be achieved by the world by 2030 [61]. This document replaces the former UN Millennium Development Goals, which were to be achieved by 2015. It underlines that new investments in infrastructure are crucial to achieving sustainable development and empowering communities in the world.

The protection of human health and well-being plays a significant role in these political instructions. Noises or vibrations caused by transport systems can significantly affect people’s health as well as environmental ecosystems [62]. For instance, railway-induced vibrations in urban zones can cause disturbances and damage to buildings or infrastructures and harm the health of local residents [63,64,65]. Vehicle traffic has a similar negative impact on the environment [66,67]. Fortunately, potentially damaging effects can be evaluated according to international standards [68].

4. Methods

The paper uses a hybrid qualitative–quantitative study of the conditions for the execution of bridge construction projects under the principles of sustainable development.

4.1. Case Studies

The manuscript uses the case study method, which contains the description of a given phenomenon, aimed at its in-depth analysis and evaluation. This approach can be used to allow others to follow the evolution of some processes. It is also used to develop knowledge about a case that is not fully defined. Detailed guidelines for the case study procedure have been discussed in the literature [69]. Since social and behavioral concerns, as well as the unique environment of the project, have a substantial impact on project management, case studies are a powerful research design option in this discipline [70]. It should be noted here that the main problem described in the article concerns the decision-making process and, therefore, the scope of project management.

4.2. Survey

To find out the opinion of professionals on the main topic of the research, an online survey was used. The questionnaire research method allows both a quantitative and qualitative examination of the defined problem. Findings can be presented descriptively or graphically, as a percentage or number. After completing and collecting the data, a questionnaire must be constructed and conclusions formed.

Before the main research phase, the questionnaire template was tested by an expert in the field of construction management. It was a representative of the scientific staff with more than forty years of experience. All recommendations had been implemented before the survey started.

The questionnaire was distributed to more than 1000 randomly selected construction professionals, mainly construction managers (engineering employees) and construction managers (management staff) on construction sites in Poland. They represented both general contractors and entities that carried out construction works as subcontractors. These were construction companies of various sizes, from micro-enterprises to large companies. Filtering criteria were deliberately selected to have uniform coverage of participants geographically and to mimic a model gender distribution in the construction management market. According to the “Women in Business 2020” report by Grant Thornton, the proportion of women in senior management in the European Union is 30%, while globally it is almost similar (29%) [71]. In the construction sector, participation is comparatively similar. However, the age parameter is the most difficult to assess, which is why the duration of the respondent’s professional experience was used as a filter. At least a quarter of all surveyed experts were expected to have worked in the selected position for at least five years. This gives a more objective view of the phenomena studied.

The survey was sent via email in the first half of 2021, and responses were collected between June and July 2021. There was limited access to other techniques, particularly self-administered, due to the COVID-19 pandemic; 112 surveys were returned (response rate ~11%) and formed the database for further analysis.

In the literature, there are many algorithms to calculate the minimum sample size and its representativeness, but they are mainly applied to measurable phenomena expressed numerically [10,72,73]. It can be noted that a representative sample is a subset of the population that allows describing characteristics of the entire population. A sample that does not meet this condition is called unrepresentative or biased [74]. The representativeness postulate can be implemented in various ways, but random sampling [75,76] and quota [77,78] sampling are the most popular methods. In the latter, the most widely used set of characteristics at the national level is education, age, gender, and city size. However, the study on the construction sector is slightly different. In this article, the conditions of the studies on construction management personnel included the Polish specificity.

To become a site manager, construction qualifications and a membership of the Polish Chamber of Civil Engineers are required. Project managers do not have to meet such requirements, but in that case, they do not have independent technical roles in the construction process. Due to the complexity of the matter, another approach was adopted. It should be noted that if the sample size is too small, it will not give valid results, while an appropriate sample size produces accurate results. Therefore, such a practical determination of the number of observations can be evaluated based on the following rule: the number of cases studied will be sufficient when further increasing the observed cases does not change the results of the study. In short, if the 113 surveys seriously change something in a global perspective of the results, we could assume that the 112 surveys are not enough. Fortunately, this does not apply in this case, so finally the total number of questionnaires answered was a sufficient size for the sample. Regarding the profile of the interviewees, the study covered upper and middle management as well as site managers from Poland.

5. Results

5.1. Case Study

An attempt to answer the main research question. “how can bridge building projects fit into the context of sustainable development?” was based on a case study of bridge construction in the city of Bydgoszcz (west-central Poland). The bridge was put into operation in 2013. It is a structure with a characteristic and unusual shape (according to some suggestions, its pylon resembles interpenetrating letters of the Greek alphabet alpha and omega), arousing various emotions ranging from delight to strong criticism. There is no doubt that, due to the complexity of the structure, its construction was not an easy project, imposing the highest professional requirements on a designer and a contractor, Most Uniwersytecki (original name), to carry out a cable-stayed bridge over the river Brda as part of Trasa Uniwersytecka avenue. The view of the main bridge is presented in Figure 1.

The entire Trasa Uniwersytecka construction project lasted three years, and the estimated cost was 211 million Polish zloties (PLN).

The gap between the lowest and the highest part of the route is 30 m. In total, there are eight bridges on the road: two left bank overpasses, each 270 m long (intersection with Jagiellońska Street), two right bank overpasses, each 250 m long (intersection with Toruńska Street and a tram line), a 200 m-long suspension bridge (the main one), and two ramps of 93 m each. Over the route, there is a 32 m-long walkway [79]. This pedestrian overpass allows the passage of traffic without affecting the safety of pedestrians. The most interesting element of the route is the pylon of the bridge (68.7 m high). Its construction was carried out on-site from prefabricated voussoirs, joined together by welding. Each straight leg consists of 25 to 28 segments, 1.5 to 2.5 m tall. The cycle of fusing a segment on each leg of the pylon lasted about four days. A Terex Demag CC2800 crane was used to assemble the last elements at the top of the structure. The heaviest element, which was raised in Bydgoszcz, weighed almost 140 tons. The deck plate was suspended from the pylon with eight pairs of cables.

Every engineering structure (including bridges) in the city is subject to mandatory technical inspections. Depending on the type of structure, some inspections take the form of detailed analyses and require the use of specialized equipment. According to the investor [80], this was also the case here. As the facility manager explains, at the end of 2020, the detailed expertise of the nodes, that is, the elements that anchor the cords (ropes) of the Most Uniwersytecki, was commissioned. The tests showed that the elements that attached the steel wire strand cables to the bridge were deformed. In this situation, the investor introduced traffic restrictions (Figure 2) and immediately commissioned a detailed survey of the entire structure, in particular, the element for fixing the cables to the bridge slab. As a consequence, the bridge was completely closed to traffic, and repair work began (Figure 3), which lasted several months.

The technical condition and failure of the bridge after 7 years of maintenance have been, first of all, a big problem for drivers driving through Bydgoszcz. The traffic jams caused by the closure of the structure cause the impatience and frustration of thousands of people. Second, it has been a challenge for the facility manager to restore the bridge to working order safely in the shortest amount of time. Third, it has been an image problem for the designer and the general contractor (waging a public battle over arguments, and the case could go to court). In addition, it should be noted that the durability of solutions is key to guaranteeing sustainable development. What if in this case, as in other similar ones, it turns out that the bridge must be deconstructed? Such a decision might be made, for example, if the total repair costs exceed the costs of demolishing and rebuilding a new, safe structure.

5.2. Survey

The quantitative part of the exploration of the problem involves the analysis of the online survey carried out [81]. In total, 112 responses were collected between June and July 2021. Initially, all responses were filtered by the professional area represented by the respondent, so additional responses were limited to two groups: management staff and engineering and technical personnel related to construction projects. Other areas were excluded from the database. Subsequently, 97 opinions were analysed (

Table 1. Filtering profiles of interviewed experts.

Group of Experts	Quantity	Comments
Engineering and technical staff related to construction projects	80	Accepted to next round
Management staff related to construction project	17	Accepted to next round
Other areas	15	Not qualified to further studies

).

Taking into account the education level of the respondents, 49% of people answered “bachelor’s degree, engineer” and the vast majority of them (92%) said, “I represent engineering and technical staff related to construction projects”. A comparable subgroup included master’s level graduates (48%). Detailed statistics about the professional experience of the respondents are shown in Figure 4.

There are four sectors represented by the respondents: municipal facilities (66%), transportation networks, including bridge construction (19%), industrial facilities (14%), and hydroengineering (1%).

Next, it was revealed that most of the experts (57%) agree that both the design and construction phase (functional perspective, process-oriented perspective) and the structure itself (subjective perspective, product-oriented) together and inseparably make up the sustainability of the construction projects. Respondents were asked to mark one of four responses, specifically:

• R1: “design and construction phase leads to the creation of a building/non-building structure, and both of these spheres (functional and subjective) must meet the principles of sustainable development”;
• R2: “building/non-building structure is created as a result of design and construction phase that meet the principles of sustainable development”;
• R3: “at the final stage, a building/non-building structure is created and meets the principles of sustainable construction”;
• R4: “I do not know”.

All answers related to this area (Q1) can be seen in Figure 5. Such considerations can be called project-oriented sustainable construction.

Moreover, it was interesting to receive feedback from the experts on how they treat sustainable structures. The most popular concept was that the building structure should result in low cost during the operation and maintenance phases. This suggests the need to calculate the costs of the different phases of the life cycle. This observation can also be applied to bridge construction projects. Detailed statistics, related to this area (Q2), were presented in Figure 6. In this case, such considerations can be called product-oriented sustainable construction.

Another fact that deserves to be highlighted is that 11–12% of all those surveyed do not have a specific opinion on sustainable construction, which can be a barrier to the implementation of projects of these characteristics. This dilettantism among the representatives of the construction industry is manifested in the generation of negative externalities for the natural environment, derived from the execution of construction projects. However, comparing this problem with the experience of the respondents (Figure 7) may explain why younger experts are not sufficiently informed about the issues related to sustainable construction and therefore answer “I don’t know” more often than their more experienced peers.

On the other hand, it can be a stimulus for various educational activities, including expanding the knowledge of professionals within some postgraduate studies, training, or workshops.

6. Discussion

Researchers have been interested in the issues of sustainable construction projects for decades [82,83,84,85,86,87]. In the meantime, new technological and organisational challenges are emerging, including Building Information Modelling [44,46,88], 3D printed structures [20,27], UAVO VLOS-based systems [28], Internet of Things [26], or blockchain [25,26]. However, the main topic is still being studied from the same angle. It is crucial for decision makers to know how to reliably plan and execute construction projects to avoid future risks and losses [11,89]. Particular attention should be paid to the decision-making process [90] and, more generally, to the management of such projects [88,91]. This article has underlined these ideas about the importance of decision-making processes in the implementation of bridge construction projects, especially when the company seeks to meet the requirements of sustainable development. The analysed case study, the bridge over the Brda River in Bydgoszcz shows us how sensitive the project parts are for the design-build phase [21,92] of such a construction project. The results of the survey on managerial challenges revealed the existence of a knowledge gap that remains a major challenge for the sector [93].

On the other hand, two different areas can be distinguished within the analysis of the sustainability of construction projects, on the one hand the “process-oriented” approach and on the other the “product-oriented” approach. Both can be tested separately but must be given simultaneously [17]. Criteria such as durability (no major repairs after several years of operation) and harmony with the environment (including public transport passengers and drivers) must be built in early in the project to ensure that the result satisfies all concerned parties. Therefore, sustainability requirements should not only be limited to the execution phase but should also be captured in whole life cycle project specifications [20,21]. A graphical summary of this idea can be seen in Figure 8.

A specific relationship between the process-oriented and the product-oriented area of the construction project has been shown. The three consecutive states of the bridge, (1) virtual “twin” (model) of bridge, (2) bridge under construction, and (3) real bridge in-use, aggregate milestones for sustainable bridge construction project delivery. All these challenges were imported from the literature review.

It is worth noting that before the virtual infrastructure is designed, the investor should implement the LCA supplemented with the LCCA, as well as select the design office and contractor based on green procurement practices as a part of the sustainable project planning. Hence, when thinking about sustainable development in construction, we must take into account both the process and the product spheres.

7. Conclusions

The qualitative–quantitative hybrid study tracked the conditions for the execution of construction projects under the principles of sustainable development. Bridge construction was treated here as a special case. The most important findings of the research should be addressed to both stakeholders and policymakers.

7.1. Point of View of Stakeholders

Construction projects (including infrastructures such as bridges) must take into account the full life cycle perspective. The multitude of participants in construction projects requires considering the interests of each party. The correctly implemented design phase should contribute to both the error-free construction and risk-free operation and maintenance phases. Therefore, individual stakeholders should see the benefit they receive when a project is implemented correctly, as it signifies the success of the project and therefore their individual success. In addition, the functional (the process) and subjective (the structure) spheres must comply with the principles of sustainable development.

A bridge construction can be a very interesting, but on the other hand demanding, project. Its outcome (bridge) has usually strategic importance. It is a critical element of the whole infrastructure. Its closure, due to a failure, means various problems for stakeholders. The investor may have a grudge against the general contractor, who in turn may transfer the responsibility to the designer. Repair works can take months. In the meanwhile, local residents, drivers, and other users suffer the most. Whereas the bridge improves traffic, its closure leads to traffic congestion, which in turn contributes to an increase in emissions, waste of time, frustration, etc. Hence, a well-designed bridge must be properly constructed, without any need for repairs; otherwise, a reduction of the project sustainability will be the fact.

7.2. Point of View of Policymakers

At the regional, national, and international levels, policymakers must focus on creating legal norms that favor sustainable construction. It is necessary to create incentives for the use of modern technologies, especially based on the concept of sustainable development and in line with the idea of a Circular Economy. The construction of bridges, as durable structures, must also take into account the need to use local materials, respect nature and minimize the impact on the natural environment. Therefore, market mechanisms must be supported by prudent and wise legislation.

Adapting the conditions for the construction of specific facilities, such as bridges, to the requirements of sustainable construction is a challenging process. Bridge construction is mainly carried out as a public contract. The European Union supports decision makers in the public procurement process. For this reason, the collections of good practices and the criteria for selecting the best offer were published by the European Commission. Fourteen groups detailing these principles have been developed. One of them—“Road Design, Construction and Maintenance”—describes challenges related to roads, but unfortunately, it does not cover specific requirements for structures such as bridges. Perhaps this is the right time to prepare a new package with recommendations for the construction of bridges, viaducts, tunnels, and similar types of infrastructure?

7.3. Final Remarks

The long life cycles of construction projects, from the idea through its materialization, operation, and maintenance to dismantling, make it necessary to take into account the philosophy of sustainable socioeconomic development, harmonized with respect for the environment. Compliance with the principles of sustainable development in relation to construction projects means the implementation of cost-effective design solutions for buildings and non-building structures and the methods of their execution in a manner that is friendly to people and their natural environment.

The poor condition of many bridges built several decades ago implies the need to prepare production capacity for large-scale repair projects. In addition, the construction of new structures to replace the old ones must be carried out methodically. In the first place, a plan for the reuse of used materials must be presented under the principle that the products at the end of their useful life become nutrition for the following production cycles. Secondly, it is necessary to prepare designs for new facilities that consider the idea of a Circular Economy. It is essential to list the types of materials that can be reused, reconditioned, and ultimately recycled.

Also important from an environmental point of view is the carbon footprint, understood as the sum of greenhouse gas (GHG) emissions into the atmosphere caused by the construction of the bridge throughout its entire life cycle. It covers the emissions produced during the construction phase, as well as those related to the manufacture of construction materials (embodied carbon), operation and maintenance of the facility, and finally the demolition process at the end of the bridge’s life. Of course, the share of each phase in the carbon footprint depends on the materials used in it and the design solutions adopted. Perhaps in the future, since cement production is responsible for significant CO₂ emissions into the atmosphere, the most popular concrete bridges will be replaced by facilities built with other materials, even those that are not yet widely known. However, to improve the efficiency of the material management, traceability is required. This will make it easier to identify what a particular material is and whether it can be reused or not. Certainly, life cycle assessment (LCA) is an important tool to achieve sustainable development goals, and in any case such analysis should precede the decision on the selection of specific variants of bridge design solutions.

Finally, it is worth mentioning that costs must be calculated for all phases of the project life cycle. Respondents tend to say that sustainable construction means the low-cost servicing of facilities during their operation and maintenance phase. It is also related to the need to build bridges without failure. This will be possible thanks to the use of proven design solutions and the involvement of experienced actors in this type of project.

7.4. Research Limitations and Future Research Lines

Although the goals set in the study were achieved, some simplifications resulting from research limitations were not avoided. Firstly, the case study was based on publicly available sources. In the future, the authors will plan a more in-depth analysis of the classified documentation to refine their observations on the management of bridge construction projects. The analysis was based on the emblematic example of the bridge in Bydgoszcz, Poland. However, further studies may include extended observations of other cases, especially from different countries. A specific definition of managerial dilemmas faced by individual decision makers throughout the life cycle of bridges can become another motivation for further research projects.

Moreover, there are many types of bridges (road, railway, etc.). The article focuses on the road bridge only. It is also worth exploring the differences between them.