Prequalified connections in steel structures: concept, types and their design with CYPE Connect and StruBIM Steel 2026
Prequalified connections in steel structures: concept, types and their design with CYPE Connect and StruBIM Steel 2026
DESTACADO:
As of version 2026, CYPE programs can model and analyse prequalified connections following the AISC 358 standard in an Open BIM environment
Prequalified connections, which are essential in seismic zones, can now be designed directly in CYPE Connect and StruBIM Steel with specific tools and codes
In the modern design of earthquake-resistant steel structures, connections play a fundamental role in the overall behaviour of the structural system. As a result, the development and application of prequalified connections has become particularly relevant, especially after significant seismic events such as the 1994 Northridge earthquake.
As of version 2026, CYPE Connect and StruBIM Steel programs can design prequalified connections according to AISC 341 and AISC 358 standards, thus incorporating validated and specific configurations for moment-resisting frames in major earthquake zones:
BEEP type prequalified connection
Origin: the Northridge earthquake
The Northridge earthquake in California in 1994 revealed critical vulnerabilities in steel structures: many of the welded connections in steel moment-resisting frames collapsed from brittle failure. This situation prompted an ambitious research program in the USA to develop and standardise connections that would guarantee ductile and controlled behaviour during an earthquake.
As a result, AISC 358 was developed, which incorporates the seismic-resistant requirements of AISC 341 and defines prequalified connections, joints with specific geometries that ensure that the controlled failure is located in the beam (fusible element) and not in the column or in the joint.
What is a prequalified connection?
A prequalified connection is a structural connection that has had its geometry validated by experimental testing and detailed analysis to ensure that its behaviour under seismic loading is predictable, ductile and strong.
These connections are designed on the principle of "strong column-weak beam", ensuring that the breakage occurs in the beam, outside the connection area, thus preserving the overall structural integrity and ensuring controlled energy dissipation.
Example of stress distribution in an RBS-type prequalified connection (Analysis in CYPE Connect)
AISC 358 standard and prequalified connection types
TThe AISC 358-16 specification establishes the geometric and capacity design requirements for various configurations of prequalified connections. The following are the most relevant connections that can be modelled in CYPE programs as of version 2026:
Reduced Beam Section (RBS)
This connection consists of reducing the flange of the beam in the area close to the column, generating a critical section where the plastic deformation is concentrated. This ensures that the rupture mechanism occurs outside the connection without compromising the column.
Bolted Extended End Plate (BEEP)
This bolted connection consists of an end plate fixed to the beam, connected to the column by high-strength bolts. There are different configurations, depending on the number of bolts and the presence of stiffeners. It is a widely used option due to its simplicity in manufacturing and assembly.
Bolted Flange Plate (BFP)
In this connection, the flanges and web of the beam are connected by plates bolted to the column. This ensures a fully bolted assembly, improving inspection and reducing the need for on-site welding.
Welded Unreinforced Flange-Welded Web (WUF-W)
This is a welded in-situ connection, with full penetration in the flanges and web. Although it is a traditional solution, it requires rigorous quality controls on the welding, especially on-site, to guarantee its expected performance.
Prequalified connection design in CYPE Connect and StruBIM Steel
Connection modelling environment, with a specific option for entering prequalified connections (CYPE Connect / StruBIM Steel)
As of version 2026, CYPE Connect and StruBIM Steel programs incorporate specific prequalified connection operations following AISC 358.
The following are key features that have been implemented in CYPE's software, all under an Open BIM environment:
Parametric modelling of geometry according to AISC 358.
Finite element analysis of local behaviour.
Analysis according to design by capacity.
Automatic generation of reports, quantities and check reports.
Automatic generation of drawings and construction details.
Advantages of using prequalified connections in a BIM environment
Prequalified connection analysed in CYPE Connect and integrated into BIM model via StruBIM Steel
The features listed above are integrated into the Open BIM workflow, which enables interoperability with structural, architectural and manufacturing models.
The incorporation of prequalified connections in a BIM environment offers considerable benefits:
Regulatory compliance from the early stages of the project.
Accurate and automatic documents.
Smooth coordination with other project agents (design, manufacturing, building work).
Reduction of errors and work thanks to standardisation.
Transfer of information between the design and structural fabrication phases.
Prequalified connections represent an advanced and proven technical solution to improve the seismic performance of steel structures.
With CYPE Connect and StruBIM Steel 2026, designers no longer need to perform manual developments or external validations: they can integrate these solutions directly into the structural BIM model, respecting regulatory requirements and taking full advantage of the interoperability offered by the Open BIM environment.
