1. Introduction
Determining a suitable construction scheme is the most critical preparation task in the early stages of an engineering project. How to effectively use existing engineering case data and empirical knowledge to provide decision support for construction schemes for engineers is an important issue. As a key element of the construction organization design, the construction scheme of the primary bridge project directly affects the construction efficiency and economic benefits. However, the determination of the construction schemes of the existing bridge project relies heavily on experienced engineers and managers, which result in the lack of a systematic summary about engineering knowledge in the decision-making process. Additionally, carbon footprint and carbon emissions as hot words frequently appear in the public eye, attracting scholars to carry out research on the assessment and analysis of carbon emissions of buildings. Ref. [
1] focused on possible approaches to reduce carbon emissions about low-carbon materials in construction sector for achieving the goal of control climate change. A study of office buildings showed that steel structures have a certain carbon emission advantage over concrete alternatives [
2]. In the field of infrastructure, there were relevant research results on carbon emission estimation methods [
3]. Concurrently, as a resource and energy-consuming infrastructure facility, bridges are characterized by high energy consumption, high carbon emissions and high resource consumption throughout their life cycle, particularly during construction. Researches on carbon emissions of bridges includes incorporating 3D bridge model information with carbon footprint analysis for lifecycle management [
4], estimating the carbon footprint of bridges to analyze show the trends for different bridge materials and spans [
5], using a life-cycle assessment method to analyze environmental impact [
6]. Ref. [
7] established carbon cost calculation model for the bridge in the construction stage. To complete bridge infrastructure construction in a high-quality, efficient, low-carbon and safe manner, research on methods and technologies that can organize the use of knowledge resources and guide bridge construction in the direction of green, low-carbon, energy-saving and emission reduction is required.
In 2012, Google formally introduced the concept of a knowledge graph, which is a semantic network that describes the relationships between entities and allows for a structured representation of facts such as things generated in the real world and their related relationships, which are typically defined as a collection of entities and relationships. Knowledge graphs can be divided into generic and domain knowledge graphs. Generic knowledge graphs are widely used, but the process of building them is difficult and complex. Generic knowledge graphs are also generally built by large internet enterprises from massive amounts of data [
8]. Conversely, domain knowledge graphs are oriented toward domain-specific knowledge requirements and require only domain-specific knowledge for the construction of knowledge graphs, and are thus less difficult to build [
9]. Although the construction of domain knowledge graphs is currently focused on popular fields such as finance, health care and education, research related to knowledge graphs in the field of engineering construction was also performed. Ref. [
10] constructed a domain knowledge graph for shield construction projects and applied transfer learning algorithms to the adaptive transfer of construction project knowledge. Liu T et al. [
11] proposed a hybrid BERT-BiLSTM model that combined a bidirectional encoder representation from transformers model (BERT) and bidirectional long-short term memory model (BiLSTM) for the textual intelligence analysis of water construction accidents, which provided algorithmic support and a basis for the analysis and decision-making of water construction accidents. Ref. [
12] used entity identification and relationship extraction in power safety hazard records to construct a knowledge graph of power safety hazards that can quickly locate hazard sites based on intelligent reasoning model hazard equipment types and hazard phenomena in power safety hazard scenarios. As shown in existing studies, knowledge graph technology has good application prospects in the engineering field as a new method of knowledge management. However, due to certain variabilities of knowledge contents involved in different fields, specific methods and processes for processing knowledge are different.
In the field of civil engineering, there are also knowledge-based related research and applications, Ref. [
13] developed a knowledge-based risk management tool via case-based reasoning (CBR) to capture, store, retrieve, and disseminate risk-related knowledge. Ref. [
14] compared the relative capabilities of different surrogate modeling techniques to directly estimate seismic losses and explained advantages and disadvantages of knowledge-based surrogate models. In the literature about knowledge graphs in bridge engineering construction, Yang JX et al. [
15] proposed an intelligent ontology model of bridge management and maintenance information based on semantic ontology; used the industry foundation classes (IFC) standard to express bridge structural units and management and maintenance information; analyzed the information conversion mechanism of IFC and ontology wed language (OWL); and established an information conversion framework. Ref. [
16] proposed a knowledge graph construction method in the bridge inspection domain using a joint model based on a transformer encoder, bidirectional long- and short-term memory (BiLSTM) network and conditional random field (CRF) for named entity recognition and relationship extraction. However, no study investigated the application of knowledge graphs to low-carbon construction aspects of bridge engineering. Because a lot of project knowledge experience in the bridge construction field is scattered across various engineering and construction units without systematic collation, the lack of public corpus datasets leads to difficulty in constructing bridge construction scheme knowledge graphs. Thus, the effect of drawing on different domain models for entity recognition and relationship extraction in low-resource conditions is limited by the small amount of training data, which can lead to poor performance problems [
17]. In terms of low carbon-related research in the bridge construction field, there was a green low carbon bridge evaluation system [
18], carbon intensity index for the entire life cycle of bridges [
19], carbon emission model for bridges [
20], green construction technology [
21], etc. However, there is a lack of effective combination with knowledge management tools. Therefore, there is a need to combine methods for effective management of bridge low-carbon construction-related knowledge and establish a knowledge model of bridge construction schemes considering carbon emission constraints to provide knowledge support for decision-making to achieve intelligent construction of bridge projects.
This study, thus, analyzes the methods of extracting bridge construction scheme knowledge and low-carbon construction knowledge in the bridge construction domain, designs and implements entity recognition, relationship extraction and knowledge storage; and proposes an improved model of entity recognition to meet the needs of low-resource conditions. Based on constructing a bridge construction scheme knowledge graph, a bridge construction scheme recommendation process is established based on the similarity calculation. Combining the characteristics of engineering practice, bridge construction scheme recommendations are performed under carbon emission constraints, and carbon emission analysis is performed using low-carbon construction knowledge. Results are then compared with existing construction scheme decision analysis methods, providing a new solution for the intelligent application of low carbon intelligent construction of bridges.
5. Conclusions
This paper proposed a method for recommending bridge construction schemes based on a knowledge graph, which can recommend bridge construction schemes considering carbon emission constraints and assist in decision-making for bridge construction management. The primary findings of this study were as follows:
(1) This study proposed a method that combines knowledge graph technology with scheme recommendation; proposes new knowledge management tools to organize and use construction scheme knowledge and low-carbon knowledge in the bridge engineering field; supplements existing construction unit knowledge management tools; and improves the previous construction units’ inability to fully incorporate carbon emissions when making construction decisions by considering construction scheme recommendations made under carbon emission constraints. This study also provided a new basis for decision-making and analysis by considering carbon constraints.
(2) The CRF model was improved by using a loss function that introduced the Bernoulli distribution to build a BCRF model layer and proposed a BERT-BiLSTM-BCRF model for low-resource entity recognition. Experiments were performed with the bridge construction scheme dataset, and experimental results showed that compared with the generic methods of knowledge graphs in other fields, the proposed bridge construction scheme can be performed effectively with limited datasets. Results also validated the usefulness of the knowledge graph construction method in the low carbon bridge construction field.
(3) The similarity calculation method combined with the knowledge graph can perform the similarity calculation based on the entities and relationships in the knowledge graph, and by setting different combination weights, can recommend bridge construction schemes while considering carbon emission constraints. Recommendations from the proposed method were reasonable compared with traditional decision analysis without considering carbon emission constraints, which can promote the intelligent development of construction decisions in bridge construction. The proposed method can also provide a reference for the design and application of recommendation systems in the engineering field.
The results of this study provide information that can aid the search for and visualization of relevant knowledge, and future research should continue to improve bridge construction scheme knowledge by enriching and complementing the knowledge graph, which can provide more accurate service support for application scenarios such as original graph application, knowledge retrieval, knowledge Q&A and intelligent recommendation of the knowledge graph. This study also provided a comparison and selection for bridge construction scheme decisions and implementation in real engineering project construction.