With the growing demand for sustainable, cost-effective and overall-efficient building solutions, the need for dependable modular construction systems is steadily on the rise. In the present paper a novel hybrid modular construction system named INNO3DJOINTS is introduced, employing cold-formed welded steel tubular columns, fabricated according to EN 10219, and cold-formed steel thin-wall section based truss-girders, joined by the innovative plug-and-play (P&P) connector, designed to provide ease-of-assembly and -disassembly. The experimental investigation conducted on isolated sub-frame configurations of the novel system is presented, where 6 full-scale specimens were subjected to horizontal and vertical loading. The test configurations differed in the P&P joint socket thickness and the absence/presence of the light steel framing (LSF) wall, encased with oriented strand board (OSB). In addition, a numerical model for predicting the system's global behaviour is proposed, developed in SAP2000. Initially, the behaviour of the employed P&P joint configurations, categorized as partial-strength, is characterized using experimental and validated ABAQUS finite element model (FEM) data, resulting in a spring model implemented into the global FEM. Finally, the numerical and experimental results are compared and discussed, leading to conclusions regarding the system's 2D structural performance, identified behaviour governing phenomena, P&P joint influence, LSF wall and OSB contribution, as well as the capabilities of the developed FEM.

This paper presents the development, implementation, and validation of a macro-element suitable for the linear analysis of innovative 3D plug-and-play joints between tubular columns and lightweight steel truss-girders. The macro-element is based on the component method, accounts for the three-dimensional interaction between the tube faces, and its components have a clear physical meaning. Simplified procedures are developed for the closed-form computation of the stiffness matrix of the macro-element based on the geometric and mechanical properties of the nodal zone. This facilitates practical application in everyday design scenarios. Furthermore, the macro-element's architecture is implemented in the framework of OpenSees as a standalone beam-to-column joint finite element. Validation of the conceptual design is accomplished through parametric studies, comparing its performance with models generated in higher-order finite element commercial software, Abaqus. This research offers a valuable resource for the linear analysis and design of innovative 3D plug-and-play joint connections in structural engineering, enhancing efficiency and reliability in construction practices.

Tubular structures are rather efficient systems due to the ease of fabrication, erection, and the high strength-to-weight ratio of their elements. However, they have seen limited use due to difficulties associated with the design and execution of joints. This scenario has changed over the years as more research focused on the behavior of these structural elements, leading to the appearance of design recommendations for some tubular joint configurations. Recently, a new plug-and-play joint configuration suitable for hybrid modular construction systems, comprising tubular columns, lightweight cold-formed steel truss-girders and cross-laminated timber slabs, has been developed in the scope of the INNO3DJOINTS project (RFCS No. 749959). The mechanical behavior of the structural system was experimentally analyzed, and macro-element models suitable for global structural analysis, explicitly including the joint behavior, were developed. In tubular structures, the out-of-plane behavior of the column’s faces is influenced by the condition of each individual face and the three-dimensional interaction between them. Currently, there is no universally accepted modelling approach for this interaction under various loading conditions. This study addresses this issue and presents a general three-dimensional macro-model for the beam-to-column joints based on the component method and accounting for the interaction between the faces of the tubular column. The architecture of the macro-element of the joint is implemented in a finite element object-oriented software framework, OpenSees, as a standalone joint finite element, and its robustness is verified by using high-order finite element commercial software.

Steel tubular members are efficient and aesthetic structural solution, yet the bolted connections between then are challenging due to the restricted access to the inside of the tube. There are several solutions, which try to overcome this difficulty, by adoption of special fasteners and/or additional connecting elements. This paper presents the experimental and numerical characterization of a novel plug-and-play joint that was developed as a demountable solution to connect tubular steel columns to cold-formed steel trusses. The research program comprised a large number of experimental tests on components and the full-scale joints, complemented by numerical models calibrated with the experimental tests. These calibrated numerical models were subsequently used to perform a large parametric study on the components and joint that allowed to propose guidelines on the geometries that maximise the performance of these joints.

In recent years, modular construction has been used in low-to medium rise multi-story and even high-rise buildings. Pre-fabrication by off-site manufacture leads to faster and safer construction, improved quality, reduced resources and waste. The research activity summarized in this paper is carried out within the European project INNO3DJOINTS and it aims at developing innovative plug-and-play joints which enable modularity, faster construction and deconstruction. The developed modular construction system is hybrid, whereby tubular columns are combined with cold-formed lightweight steel profiles using plug-and-play connections to provide an efficient structural system. The influence of the type of floor system, the horizontal and vertical load-bearing systems and the type of truss on the structural performance are investigated. The results obtained from numerical analyses allowed optimizing the geometry of the examined hybrid modular system. To highlight its effectiveness and versatility, a case study building was used to compare the proposed hybrid system with other conventional structural solutions.

In recent years, modular construction has been used in low-to medium rise multi-story and even high-rise buildings. Pre-fabrication by off-site manufacture leads to faster and safer construction, improved quality, reduced resources and waste. The research activity summarized in this paper is carried out within the European project INNO3DJOINTS and it aims at developing innovative plug-and-play joints which enable modularity, faster construction and deconstruction. The developed modular construction system is hybrid, whereby tubular columns are combined with cold-formed lightweight steel profiles using plug-and-play connections to provide an efficient structural system. The influence of the type of floor system, the horizontal and vertical load-bearing systems and the type of truss on the structural performance are investigated. The results obtained from numerical analyses allowed optimizing the geometry of the examined hybrid modular system. To highlight its effectiveness and versatility, a case study building was used to compare the proposed hybrid system with other conventional structural solutions.