
==== Front
Heliyon
Heliyon
Heliyon
2405-8440
Elsevier

S2405-8440(24)11917-2
10.1016/j.heliyon.2024.e35886
e35886
Review Article
Development and systematic review of connection techniques for RC Precast structural elements: Beam and Column Connection
Xiao Shuoting Shuotingxiao@gmail.com
⁎
Fomin Nikita Igorevich ni.fomin@urfu.ru

Institute of Civil Engineering and Architecture, Ural Federal University, 620002, Ekaterinburg, St. Mira19, Russia
⁎ Corresponding author. Shuotingxiao@gmail.com
09 8 2024
30 8 2024
09 8 2024
10 16 e3588629 2 2024
18 6 2024
6 8 2024
© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Precast reinforcement concrete (RC) structures have attracted increasing attention in the global construction industry. They offer advantages such as reduced construction time, improved quality, and sustainability. However, their seismic performance and construction pose unique challenges. This study comprehensively reviewed and systematically analyzed the nodal connection techniques of RC precast structures. Using a data-driven approach combining quantitative and qualitative analyses, relevant literature was collected from the Web of Science database based on specific search criteria. Historical and recent trends in the scientific landscape were visualized, and citation networks were analyzed. In addition, the study reviewed different types of beam-column connections, which is a significant research focus. The results indicate that although various types of nodal connections demonstrate good seismic performance in experiments, they still face challenges of complexity and long-term maintenance in actual construction.

Keywords

Precast reinforcement concrete structures
Bibliometric analysis
Prefabricated concrete buildings
Connection joint design
Seismic performance
Building standardization
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pmc1 Introduction

With the resurgence of prefabricated construction, the global prefabricated building market has experienced significant growth in recent years. From 2020 to 2022, the total global export trade of prefabricated buildings increased by $3.46 billion, a growth rate of 39.5 %. Fig. 1 illustrates the global export trade volume of prefabricated buildings and for major exporting countries, including China, the United States, Canada, the Czech Republic, and the Netherlands. The export volume of China has grown particularly rapidly, increasing by approximately $1.5 billion from 2015 to 2022, representing a growth rate of 38.1 %. This growth reflects the increasing adoption and recognition of prefabricated buildings as viable and efficient construction methods worldwide, making them a significant development direction in the construction industry.Fig. 1 Global export trade value of prefabricated buildings (1995–2022): Key exporting countries and overall market trends (Data source: CEPII [1]).

Fig. 1

Compared with traditional monolithic concrete building construction, precast reinforcement concrete (RC) construction applying Building Information Modeling (BIM) is esteemed for its shorter duration, higher quality, more environmentally friendly nature, and lower cost [[2], [3], [4], [5], [6], [7]]. Based on the construction feature where the components are fabricated in the factory and then assembled into the building at the construction site, RC precast construction has been widely used in civil building construction and emergency response projects [3]. However, the construction method of precast RC structures differs from traditional construction methods, leading to unique formations, mechanical properties, and methods of load transfer between the joints of the components in the structure. Joints in prefabricated structures are usually located at corners, which often have the largest bending moments, making it challenging to form joints [8]. Several studies have shown that if the joints between members in precast RC structures are not well designed or constructed, joints failure and the continuous collapse of building structures can occur [[9], [10], [11]]. In addition, a recent analysis of the effects of earthquakes on precast RC structures showed that damage was mainly caused by the connection system [[12], [13], [14]]. For example, the 2009 earthquake in L'Aquila showed that the lack of design performance of the joints in prefabricated structures resulted in the extrusion of neighboring buildings, confirming that the connections should be emphasized for the seismic performance of prefabricated buildings as a whole [14].

There are many types of connections between different components in a precast RC structure, and the standard connections are beam-column connections, wall-plate connections, and beam-beam connections. The member connection behavior significantly affects the design of prefabricated structures [15]. In Chapter 2, a literature review is presented to explore research focusing on different types of component connections in precast RC structures. To address the broader challenges in structural engineering, scholars have conducted extensive research on structural component connections in recent years (Fig. 2). Chapter 2 includes a bibliometric analysis of the literature search results to classify, organize, and summarize the vast body of literature. Chapter 3 primarily focuses on the different types and specific designs of beam-column connections in precast RC structures, providing a comparative analysis of the performance differences between the various designs.Fig. 2 Statistics on the number of relevant studies.

Fig. 2

By reviewing the progress, research, and analysis concerning the design of various existing connection joints for precast RC structures, an effort was made to shift through extensive literature and systematically summarize and assess the current advantages and issues, identifying potential directions for future research.

2 Literature survey and analysis

To ensure the objectivity and accuracy of the review of the corresponding studies, this work adopts a systematic mixed-method approach of quantitative and qualitative analysis, that is, first of all, a systematic search and screening of literature, and then bibliometric analysis of the literature base, and finally analyzing the content of each literature study; the overall research framework within the framework of the study is shown in Fig. 3.Fig. 3 Structure of the systematic review methodology.

Fig. 3

During the literature search phase, the initial step was to ensure that the selected literature covered key topics in the research area by defining the search criteria. The Web of Science, an authoritative and well-established scientific citation indexing database, is widely used by researchers to access scientific literature and track the impact of research [16]. Publications were collected from the Web of Science Core Collection literature database [17]:((TS=(PREFABRICATED) OR TS=(ASSEMBLY) OR TS=(PRE-FABRICATED)) AND (TS=(RC) OR TS=(CONCRETE) OR TS=(REINFORCED CONCRETE) OR TS=(COLUMN) OR TS=(BEAM) OR TS=(FOUNDATION) OR TS=(WALL))) AND (TS=(JOINT) OR TS=(NODAL) OR TS=(CONNECTION))

After obtaining key literature covering essential aspects related to the research topic from the search results, the content of the search results was preliminarily screened to ensure the high relevance and quality of the final literature base. The preliminary screening process included removing duplicates from the search results and excluding documents that were not relevant to the research topic. After eliminating duplicates, documents that were not highly relevant to the research topic were excluded by scrutinizing the abstracts and keywords.

The screened literature was manually reviewed to gain an in-depth understanding of the research methodology, data collection, and presentation of the results of each piece of literature to ensure that the literature ultimately included in the study was of high quality and scientific value. By exhaustively reading and paying particular attention to the methodology, experimental design, and interpretation of the results, prerequisites for further assessment and selection of literature were established. The quality assessment and selection process will be based on predefined criteria covering methodological quality, rigor of the study design, contribution to the research field, credibility and significance of the results, existing problems, and future research directions. Upon completion of this in-depth quality assessment and selection process, a rigorously screened literature base was constructed to provide a reliable foundation for subsequent bibliometric and content analyses. This process helped ensure that the conclusions drawn from the study were credible and practical.

2.1 Bibliometric analysis

The VOSviewer software was used to analyze and process a large volume of literature data. This involved downloading publication information from the search results and exporting it as a plain text file, enabling the import of publication data into VOSviewer for further analysis and processing [18]. This software primarily analyzes keywords and citation information.

In keyword analysis, VOSviewer examines keywords within the imported literature data. After filtering out the high-frequency keywords, it calculates the frequency of each keyword and generates a “heat map” of keywords. High-frequency keywords are then clustered to identify related research subfields or trends. This clustering analysis helps to pinpoint the hot keywords or topics within the current research field, aiding in understanding the focus or trend of the research and providing guidance for subsequent research directions.

Citation analysis involves calculating the citation frequency of each document using VOSviewer software, followed by the generation of a citation network graph. This helps identify key or foundational documents in the field and discern mainstream and fringe research areas through the cross-referencing of citations. This process highlights the core literature, which typically contains key techniques, methods, or discoveries and traces the origin and evolution of research topics or methodologies. Core citations offer a starting point and frame of reference for researchers aiming to delve into specific subfields.

2.2 Previous review studies

Most previous literature reviews have concentrated on specific structural systems and member connections, discussing the structural performance and reliability of their connection joints in depth. Ravikumar et al., 2022, conducted a comprehensive review of the parameters affecting the shear strength of external reinforced concrete RC column joints, including the covering behavior, influencing parameters, and constraints at the joints [19]. Similarly, Ghayeb et al. evaluated the design and performance of beam-column connections in prefabricated structures against seismic challenges by reviewing experimental studies that compared three hybrid prefabricated connection types with monolithic connections [20].

Comprehensive reviews of the literature on various connection types for the mechanical performance in precast RC structures are limited. In 2023, Chang et al. discussed several types of beam-column connections, wall panel connections, and column/wall-foundation connections in precast RC structures by comparing their mechanical and structural properties [21]. A consolidated analysis of previous reviews indicates that this remains an area ripe for research, with many connection joint types requiring comprehensive evaluation and analysis.

2.3 Overview of publications

According to the literature search results, 87.83 % of the research advances were journal articles, 9.37 % were conference proceedings, and 1.17 % were reviews (Fig. 4). There has been a general increase in publications, particularly since 2015, with publications from 2015 to 2023 accounting for 80.24 % of all the publications. This surge can be attributed to the revival of prefabricated buildings, which are prized in contemporary academic research for their significant advantages in enhancing building efficiency, reducing environmental impacts, and promoting sustainable development [[22], [23], [24]].Fig. 4 Statistics on the distribution of literature types.

Fig. 4

Fig. 5 shows the top 25 publications based on the number of articles related to the research topics published from 1988 to 2022. From the data for all years, it can be seen that Engineering Structures, as the leading journal in the field, ranked first, with 217 articles, far surpassing other journals, indicating its leading position and broad influence in the field. Following closely is Journal of Constructional Steel Research, which contains 147 articles. Structures, Journal of Building Engineering ranked third and fourth with 75 and 70 articles, respectively, which also play relatively essential roles in the publication of results in related research fields.Fig. 5 Map of development of publication sources.

Fig. 5

From the perspective of historical publication trends, the number of articles related to research topics published in various journals has shown a significant upward trend since 2015. This increase may be attributed to the rapid development of prefabricated construction technology and the growing demand for high-performance and more efficient structural connection technologies. Additionally, emerging journals such as Buildings have quickly gained attention and published a substantial number of articles in a short period. Recently, a considerable number of articles related to this research topic have chosen new publishing platforms to promote research dissemination and exchange.

2.4 Cluster analysis results

Fig. 6 illustrates the co-occurrence analysis of research locations in the publications. In the figure, larger circles indicate a higher number of related research publications from a country, darker circles represent stronger international collaboration, and thicker lines denote stronger collaboration between specific countries. Overall, China, the United States, Italy, Australia, and the United Kingdom had the highest number of publications in that order. China has the most prominent and darkest circles, indicating a significant increase in the number of research publications, reflecting its substantial research volume and experience in the field. China collaborates closely with the United States and Australia. The United States ranks second in terms of research volume and collaboration strength, demonstrating considerable research experience and ongoing contributions. Italy ranks third in terms of publication count, more than Australia, but Australia exhibits greater collaborative strength than Italy.Fig. 6 Study location co-occurrence map for publications.

Fig. 6

Fig. 7 shows the collaborative strength, cooperation network, and temporal evolution of these collaborations at the research locations. Consistent with the analysis in Fig. 6, China, as one of the most active nodes in the collaboration network, frequently collaborates with multiple countries (e.g., the United States, Australia, the United Kingdom, and Italy), making it a crucial research hub that has accumulated a substantial body of research experience through extensive international cooperation. The United States is also a significant node, maintaining close cooperative relationships with many countries in Europe and the Asia-Pacific region. In addition, European countries cooperate closely with each other. The dense lines between countries such as Germany, Italy, the United Kingdom, and France reflect their alignment and standardization efforts in the design of RC prefabricated component connection joints.Fig. 7 Chronological retrospective of the number of publications in the study locations.

Fig. 7

In Fig. 7, the colors of the lines indicate the temporal evolution of collaborations. Older collaborations (2014) are shown in blue, whereas more recent collaborations (2020) are shown in yellow. The research outputs of China, Australia, and Italy were primarily concentrated around 2018–2020, indicating more recent research experiences and findings. By contrast, the research outputs of the United States, the United Kingdom, and South Korea were mainly from 2015 to 2016 (Fig. 8), reflecting an earlier accumulation of research experience.Fig. 8 Keyword co-occurrence map for publications.

Fig. 8

Keyword analysis was conducted using VOSviewer to screen keywords that have at least 10 occurrences of consistent or synonymous terms, generating a publication keyword correlation analysis graph (Fig. 8). The figure shows that the initial focus of the research was the performance and reliability analysis of the joints. These studies primarily examined the behavior of joints under different conditions to ensure structural stability and safety. However, over time, the research focus has gradually expanded to include the finite element analysis of joint performance and various experimental tests.

The keywords “performance” and “behavior” occupy central positions in the figure, indicating their core importance in the research on RC prefabricated component connections. The dense connections between these two keywords and others demonstrate their broad associations. For example, “finite-element-analysis” and “experimental test” are closely linked to “performance,” reflecting the recent trend toward more in-depth analysis of joint performance.

“Seismic performance” is a widely studied topic, and researchers are increasingly concerned with the behavior of joints under seismic conditions. In the figure, keywords such as “seismic behavior,” “seismic response,” “ductility,” and “stiffness” are closely related to seismic performance research, highlighting the importance of this field.

Further analysis of the temporal changes in the figure reveals that after 2015, the keywords “prefabrication” and “modular construction” indicate newer research trends. This aligns with the recent surge in research attention towards improving construction efficiency and quality through innovative construction techniques while ensuring the performance requirements of structural and connection designs.

The connections between keywords not only illustrate the associations between different research topics but also reveal the multilevel and multifaceted nature of the research. For example, the link between “numerical simulation” and “experimental test” indicates the complementary nature of experimental and simulation methods in research, showing that most studies use a combination of experimental and simulation approaches to achieve precise results.

Among material-related keywords, the co-occurrence of “steel” and “concrete” is significant, indicating a large body of research focusing on structures using these materials. Notably, the keyword “composite beam” is positioned very close to the center, underscoring the critical research role of composite structures in the design of prefabricated beams and joints. Another prominent keyword is “bolted joint,” which has a large circle in the figure, indicating a substantial amount of research on this type of connection.

By analyzing the frequency and connection strength of keywords, this research focused on different types of connection joints, as shown in Fig. 9. Research on beam-column joints had the highest publication proportion among all types of connection joints. This is also reflected in Fig. 8, where keywords such as “Beam,” “Column,” “beam-column joint,” “column-column joint,” and “column joint” are prominently visible and positioned near the center, indicating extensive research and attention on these structures and joints.Fig. 9 Occurrence and total link strength of different joint types.

Fig. 9

Owing to the different components, structural design requirements, structural operating characteristics, and their influence on the stress-strain state of the building structure, various types of precast RC structural connection joints were determined. As shown in Fig. 10, the statistical results of keywords can be used as a basis for classifying and reviewing the literature content with keywords like “Dry connection,” “Wet connection,” and “Hybrid connection.”Fig. 10 Occurrence and total link strength of different connection types.

Fig. 10

3 Beam-column connection

Beam-column connections play a vital structural role in precast RC structures, serving to transfer loads between beams and columns. Their design must consider the effect of the load transfer to ensure the stability and safety of the structure. Consequently, they are often viewed as potential weak points in a structure and require careful design and construction to fulfill the tasks of bearing and dispersing loads efficiently.

In recent years, numerous studies have proposed new solutions for the design of beam-column connections. These design methods aim to enhance the seismic performance of the beam-column connections, delay joints damage, and improve the load-carrying capacity of the joints. Based on the connection method, three common types of connection joints are identified within the selected ranges: dry, wet, and hybrid.

3.1 Beam - column dry connection node

A beam–column dry connection is a type of connection between prefabricated concrete members that does not use wet materials such as mortar or cement paste. Instead, they rely on mechanical connections to transfer the loads between beams and columns [25,26]. The purpose of using Dry joints are used between beams and columns to provide ductile moment-resistant connections that can develop plastic hinges and offer improved seismic performance [27].

Traditionally, beam-column dry connection joints have been connected using welded plates, bolts, or pins [28,29]. However, traditional connections, such as pinned connections, may not satisfy large load requirements, and heat transfer from the welded plates during welding operations may damage the structure [30]. In 2015, Brunesi et al. conducted an experimental study on the cyclic response of beam-column structures using common pinned connection joints, as shown in Fig. 11. The results indicated a significantly poor seismic performance and low ability of the structure to withstand cyclic loading [31]. In 1993, Ersoy tested precast concrete beams using welded joints under reversed cyclic loading and found that owing to the absence of significant plastic hinge regions in the structure, its performance in dissipating energy was poor due to the susceptibility of its welds to brittle damage under loading [32].Fig. 11 Schematic of pin connection system.

Fig. 11

As a result, recent years have seen the development of a new type of beam-column dry connection, that is, a rigid beam-column dry connection joint. This joint uses rigid steel connectors instead of traditional connections that can achieve plastic hinge development under significant loads, thus improving the toughness and vibration-damping performance of the structure [33]. Rigid steel connectors typically consist of bolts and steel plates fastened with bolts to connect beams and columns. For example, Nzabonimpa et al. in their 2017 study proposed a new connection system, as shown in Fig. 12, for joining beams and columns using steel end plates and bolts and experimentally demonstrated its structural behavior [34]. Similarly, Ye et al. proposed a connection system comprising RC, I-beam connectors, bolts, and cladding plates in 2021 [35]. To further enhance the energy-dissipation ability of connectors, Yang et al., 2022 proposed a rotational friction energy-dissipating joint that provides reliable seismic resistance to the structure [36].Fig. 12 Сonnection system using steel end plates and bolts.

Fig. 12

Alternatively, connections using bolts as semirigid joints have also been explored. For instance, in 2013, Vidmelopriya et al. designed a nodal scheme in which bolts were inserted into concrete columns and beams, and the beams and columns were connected by fixing the ribbed angles, as illustrated in Fig. 13 [37]. In 2019, Ma et al. proposed a similar design using bolts and steel reinforcement to fix the connection between columns and beams. Load tests performed on this design showed that the bolted connection joint design had high strength, an entire hysteresis curve, and high seismic capacity [38]. In 2022, Zhang et al. proposed a new dry-connected prefabricated beam-column joint similar to the connection mentioned above and conducted experimental studies. Studies have demonstrated that the load-carrying capacity of a prefabricated joint is comparable to that of a cast-in-place joint [39]. A similar design was implemented by Liu et al., in 2023, in which two new types of connections were designed to connect columns to beams using connectors, transfer rods, and high-strength reinforcement bars. The results of this study indicated that the new types of joints have good seismic and energy-dissipation properties [40] (see Fig. 15).Fig. 13 Schematic of the connection system using bolts and ribbed angles.

Fig. 13

Fig. 14 Schematic of the connection system using bolts and ribbed angles.

Fig. 14

Fig. 15 Ring-lap beam-column nodes.

Fig. 15

A novel approach to beam-column connections involves the use of connectors. For instance, Ye et al. introduced a connector connection utilizing a connector and cladding plate in 2021. This design allows effective control of the stress distribution at the joint by varying the connector position, cladding plate length, and axial compression ratio, thereby improving the seismic capacity of the structure [41]. The advantage of connector connections lies in their potential to enhance specific structural properties by incorporating additional structures within the connector itself. For example, incorporating energy-absorbing structures within connectors can significantly improve the overall seismic performance. In 2020, Zhang et al. developed a connector that utilized energy-absorbing connector plates and I-beams, effectively transferring plastic hinges to the connection area [42]. Similarly, in 2021, Li et al. proposed a prefabricated beam-column connector using metal dampers designed for easy assembly and disassembly. Tests revealed that plastic damage is predominantly concentrated in metal dampers [43] (See Fig. 14)

3.2 Beam - column wet connection node

Wet connections, also known as precast postcast beam-column connections, offer enhanced building integrity and strength compared to dry connection joints. Their seismic performance may surpass that of conventional dry-connection joints [44]. A prevalent type of beam-column wet connection is the ring-lap joint, in which the lower reinforcement of precast beams extends into the precast columns for lapping, with concrete subsequently poured to finalize the connection. In 2015, Yuksel et al. conducted cyclic loading tests on ring-lap beam-column joints and analyzed the strength, seismic performance, and damage distribution between the two joint types [45].

One strategy involves augmenting the strength of the concrete to enhance the shear performance of such joints. In 2020, Deng et al. applied highly ductile fiber-reinforced concrete to critical joint areas and demonstrated that this approach could convert brittle shear damage into beam-end damage [46]. A 2021 study by Weichen Xue et al. showed that using ultra-high-performance concrete with its superior bond characteristics enables precast beam-column joints to match the load-carrying capacity, ductility, and stiffness degradation patterns of monolithic joints while reducing the lap length of the reinforcing bars [47].

Research indicates that modifying the structural reinforcement design or the connection design can improve structural performance or fulfill specific engineering objectives. For instance, in 2014, Hossein Parastesh introduced a new ductile flexural beam-column connection that achieves superior seismic performance by altering the reinforcement layout [48] (Fig. 16). In 2018, Yan Q et al. proposed a beam-column connection suitable for installing beams in both directions, with joint seismic performance comparable to that of cast-in-place joints [49].Fig. 16 Ductile flexural beam-column connection.

Fig. 16

D Guan et al. in 2016, introduced a connection structure using ball anchors (bulb anchors) [50], as depicted in Fig. 17. Experimental results indicated that this structure possesses commendable seismic capacity, exhibiting higher forward bending strength and less stiffness degradation compared to monolithic specimens [51].Fig. 17 Precast concrete beam-column connection using ball anchors.

Fig. 17

In addition to pouring concrete after lapping the reinforcement bars, the utilization of grouted sleeve connections is another prevalent solution for wet connections. Typically, there are two variations of grouted sleeves: full- and half-grouted sleeve connections. In Yan Q's research, fully-grouted sleeve connections were employed for beam reinforcement, while half-grouted sleeve connections were utilized for column reinforcement to implement a novel design [49]. In 2021, Lu et al. introduced an innovative approach to connecting a prefabricated beam-column connection joint using double-grouting sleeves, as illustrated in Fig. 18 [52]. The control test results indicated that the designed prefabricated beams exhibited a lower initial stiffness but performed well in terms of yield and ultimate bearing capacity. As the diameter of the lower-transition reinforcement increases, the yield and ultimate bearing capacities of the prefabricated beams under three-point bending improve. Additionally, these beams exhibited better ductility than monolithic beams. However, one drawback is the stress concentration in the filler region owing to the discontinuous stiffness, which can be mitigated by increasing the diameter of the lower transition reinforcement.Fig. 18 Prefabricated beam-column connection with double grouting sleeve connection.

Fig. 18

3.3 Beam - column hybrid connection node

Beam-column hybrid connection blend the attributes of both dry and wet connections, typically by incorporating a mix of field-cast concrete and preinstalled connectors. This combination aims to enhance the construction efficiency while preserving robust structural mechanics, although their construction may present increased complexity and difficulty.

One high-performance approach involves the integration of couplers with lap joints. In 2013, Choi et al. designed a novel precast concrete beam-column hybrid connection by merging steel couplers with lapped reinforcing bars that were subsequently encased in concrete [53]. The strength of this connection joints was tested and found to be 1.15 times greater than that of traditional monolithic RC connections. Similarly, Ghayeb et al. in 2020, advocated the use of steel couplers in conjunction with reinforced lap-postcast joints [54]. An innovative hybrid prefabricated RC connection design, as shown in Fig. 19, was tested on three specimens. All the specimens exhibited plastic hinges at the beam ends. By relocating the plastic hinge position outside the connection area, the hybrid connection enhanced the safety of the prefabricated structure. The test results showed that the average ductility of the designed hybrid connection was slightly higher than that of the monolithic connection, and the energy dissipation significantly increased. Both the strength and stiffness were markedly higher than those of the other connections, indicating a significant advantage in terms of seismic performance.Fig. 19 Hybrid connection reinforced with steel couplers.

Fig. 19

In 2020, Esmaeili et al. introduced a hybrid connection reinforced with a steel box and a peripheral slab, as depicted in Fig. 20 [55]. This study conducted reversed cyclic loading tests and compared the results with those of traditional cast-in-place beam-column connections. The test results indicated that the specimens using the designed hybrid joints had cracks primarily concentrated outside the beam-column joint, extending into the plastic hinge region of the beam, demonstrating good crack resistance and ductility. In contrast, the traditional cast-in-place specimens exhibited more cracks concentrated in the beam-column joint area. Similar to the findings of Ghayeb et al. the specimens with connections designed by Esmaeili et al. exhibited a slightly higher energy-dissipation capacity than the traditional cast-in-place specimens. Throughout the entire test, they also displayed higher initial stiffness and post-yield stiffness with superior strength and ductility compared to traditional cast-in-place beam-column specimens, demonstrating an advantage in seismic performance.Fig. 20 Hybrid connection reinforced with steel boxes and perimeter panels.

Fig. 20

Another innovative approach to hybrid connections employs corbel support. Lacerda et al. introduced a semi-rigid connection utilizing corbel supports to join beams and columns by employing steel pins and rebar laps (Fig. 21) [56]. A comparative test was conducted using four cruciform specimens to determine their corresponding mechanical properties. The tests revealed that the cracks were mainly concentrated in the cast-in-place slab and distributed symmetrically and parallel to the minor faces of the columns. Grouting filled the horizontal and vertical interfaces between the column and beam, increasing the compressed area of the connection and enhancing the lever arm of the precast beam section. This resulted in an improved bending strength and stiffness of the connection. Similarly, Fan devised a connection structure that combined grouting sleeves and rebar laps. This design facilitates the direct installation of precast beams with U-shaped shells onto the corbel supports of multistory precast columns [57]. In the experiments conducted in this study, all the precast specimens exhibited similar crack distributions and failure patterns, primarily observed between the surfaces of the PC beams and columns. The use of stirrups in the overlapping region of the flexural reinforcement and longitudinal rebars of the beam effectively enhanced the bond-slip performance of the reinforcement, increasing the energy dissipation capacity by 16.5 %. However, for onsite assembly construction, the side thickness of the PC U-shell must be sufficient, indicating that there is room for optimization in the design of the U-shell length, thickness, internal surface, and stirrups.Fig. 21 Hybrid connection using flanges to support beams.

Fig. 21

4 Discussion and conclusions

This paper provides a comprehensive review of connection techniques for precast RC structural elements, with a particular focus on beam-column connections. Precast RC structural systems, as non-traditional, sustainable, and efficient construction methods, have experienced rapid growth in the global industrial market in recent years and are increasingly used worldwide. However, the unique characteristics of precast RC structures, particularly their joint formation and load transfer methods, present distinct challenges. The failure of these joints, particularly under seismic conditions, underscores the need for robust designs and construction techniques for precast RC structures.

A literature review and bibliometric analysis were conducted to explore the various types of component connections in precast RC structures. The analysis revealed a significant increase in the number of publications since 2015, reflecting a growing interest in prefabricated construction because of its advantages in enhancing building efficiency, reducing environmental impacts, and promoting sustainable development. Notably, from 2015 to 2023, publications related to precast RC structures will surge, comprising 80.24 % of all publications in this field.

Journals such as Engineering Structures, Journal of Constructional Steel Research, Structures, and Journal of Building Engineering are prominent platforms for disseminating research findings in RC precast structures. This concentration in specific journals highlights their central role and influence in this field. China, the United States, Italy, Australia, and the United Kingdom are the leading countries in terms of publications. China had the highest number of research publications, reflecting its extensive research activities and advancements in prefabricated construction. Recent research outputs have been concentrated around 2018–2020 in countries such as China, Australia, and Italy. By contrast, the United States and the United Kingdom showed earlier research peaks between 2015 and 2016.

Most research has focused on understanding and improving the performance and reliability of precast RC structures, particularly under seismic conditions. The analysis shows a shift towards the application of advanced methods, such as finite element analysis and experimental tests, to evaluate joint performance. Significant research attention has been directed towards steel and concrete materials, with composite beams and bolted joints being frequently studied. This reflects the ongoing efforts to optimize material use and joint designs for better structural performance.

Research has predominantly focused on different types of joints in precast RC structures, with beam-column joints receiving the most attention. Through the co-occurrence analysis of keywords, beam-column connections can be categorized and reviewed as “beam-column joint,” “column-column joint,” and “dry connection,” thereby facilitating a more structured discussion. These connection designs offer clear advantages over conventional monolithic concrete structures by enhancing the overall performance, seismic capacity, and construction efficiency of the buildings.

Dry connection joints, utilizing mechanical means such as bolts and welded plates, offer the advantages of ease of assembly and the potential for rapid construction. However, traditional dry connections such as pinned and welded joints often exhibit limitations in their load-carrying capacity and seismic performance owing to brittle failures and poor energy dissipation. Recent innovations in dry connections have focused on improving seismic performance and energy dissipation. The development of rigid beam-column dry connections using steel connectors and rotational friction energy-dissipating joints significantly enhanced the ductility and seismic resistance of these connections. Studies have shown that these advanced designs can achieve better load distribution and structural integrity than traditional methods.

Wet connection joints, also known as precast–postcast connections, offer improved integrity and strength through the incorporation of cast-in-place concrete. These connections often demonstrate superior seismic performance compared to dry connections owing to better continuity and bonding between the precast elements. Key advancements in wet connection design include the use of highly ductile fiber-reinforced concrete and ultra-high-performance concrete, which improve the shear performance and reduce the lap length of the reinforcing bars. Innovative designs, such as ring-lap joints and grouted sleeve connections, have been shown to enhance the load-carrying capacity, ductility, and stiffness of beam-column joints, making them comparable to monolithic joints.

Hybrid connections combine the advantages of both dry and wet connections by combining field-cast concrete with preinstalled connectors. These joints aim to optimize the construction efficiency and maintain robust structural mechanics. However, the complexity of hybrid connections is evident in their Figure, which often shows numerous installation components and elaborate construction steps. This complexity can lead to increased construction time and labor requirements, potentially offsetting some of the efficiency gains achieved through prefabrication. Innovative hybrid designs, such as the integration of steel couplers with lap joints and the use of steel boxes and peripheral slabs, have demonstrated enhanced seismic performance, strength, and ductility. These designs effectively transfer plastic hinges to the connection area, improving energy dissipation and overall structural safety. Additionally, the use of corbel supports and grouting sleeves in hybrid connections has shown promising results in enhancing the bond-slip performance and energy dissipation capacity. Therefore, hybrid connections often exhibit superior seismic performance compared to both monolithic and prefabricated connection joints.

Despite these advances, several challenges remain in the design and implementation of precast RC structural connections.- There is still a relative lack of research on dry connections, particularly regarding their maintenance and durability during long-term operations. Although dry connections offer significant advantages in certain aspects, such as faster construction speeds and less wet work on site, there is a lack of in-depth understanding and research on their performance and maintenance requirements for long-term use. This is essential to ensure the long-term safety and functionality of building structures.

- The complexity of efficient connection joint designs significantly increases the difficulty and cost of construction. For example, the complexity of hybrid connections, along with their numerous components and intricate construction steps, can lead to increased construction times and labor costs. Simplifying these designs without compromising their performance is essential.

Currently, most studies in this field focus on the use of steel and concrete structures. As new high-performance materials, composite materials have received relatively little research attention for connection design applications.

Future research could address these challenges by exploring new material applications and refining connection designs. The application of composites and high-performance fibers, with their potential advantages in terms of strength, durability, and seismic resistance, could lead to significant advancements in connection technology. The development of standardized, easy-to-install connection systems can reduce construction time and labor costs while maintaining or enhancing structural performance. Additionally, the long-term performance and maintenance requirements of dry connections are important research topics. This included investigating the effects of environmental factors, load cycles, and aging on the durability and functionality of these connections. By addressing these challenges and focusing on future research directions, the construction industry can develop more resilient, efficient, and sustainable precast RC structures.

CRediT authorship contribution statement

Shuoting Xiao: Writing – original draft, Conceptualization. Nikita Igorevich Fomin: Writing – review & editing, Methodology.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The financial support provided by 10.13039/501100004543 China Scholarship Council (CSC) to the first author is also gratefully acknowledged.
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