Connections made of jumbo and super jumbo steel shapes: a practical guide

ArcelorMittal, a leading global producer of steel shapes used in construction, created this handbook that brings together advice and information on connecting jumbo and super jumbo steel shapes in building structures not subject to seismic loading. It is aimed at designers, offering them insights into international best practices and additional resources beyond those of typical European and American building standards.

The handbook draws heavily from the ECCS (European Convention for Constructional Steelwork) book ‘Joints in steel and composite structures,’ which focusses on structural connections and covers topics such as how to design, fabricate, and assemble these connections.

 

Published: 28 May 2024

Optimising design and cost

This handbook provides guidelines for effectively designing, building, and assembling projects that involve large and exceptionally thick steel sections, known as ‘jumbo shapes’ and ‘super jumbo shapes.’ These shapes have flange thicknesses equal to or greater than 50 mm as defined by standards such as EN 10365 and AISC 360 (2016). Due to their size and thickness, special attention is needed when connecting these steel shapes to ensure safety and structural integrity.

Steel is an anisotropic material, which means it has different properties depending on the direction in which it rolled. For hot rolled structural shapes, the best properties are found in the direction of rolling, and it is crucial to consider properties across the thickness of the material (through-thickness properties). This is especially important for welded connections, where improper planning can lead to weld strains surpassing the material's strength. Therefore, careful planning and coordination among project stakeholders – including design engineers, architects, fabrication shops, assemblers/erectors, quality control offices, and suppliers – are essential to create efficient connections.

Throughout the stages of design, detailing, fabrication, and erection of a steel structure, there is room for optimising cost-effectiveness. Designers and detailers can work together to find the most efficient solutions, taking into consideration the capabilities of the fabricator. Prefabricating components in the workshop not only streamlines transport and installation on site but also influences the design of connection types, which can positively impact the project's costs. The more prefabrication done in the workshop, the higher the quality and cost-efficiency of the steel structures.

Contents of this handbook

Chapter 1 discusses how choosing the right type of steel is crucial for ensuring the longevity of a structure. It provides guidance from ArcelorMittal on how to select the appropriate steel grade throughout the design process, from the initial stages to when the steel is used as a structural element. The chapter covers concepts like ductility, through-thickness properties, and material characteristics in detail. It also introduces the concept of fracture toughness and explains its importance. The chapter further delves into the methodology for selecting materials based on fracture toughness according to a specific standard, EN 1993-110:2005, particularly for components subjected to quasi-static compression loading.

In Chapter 2, welded connections are detailed, starting from design code principles to the metallurgical perspective. It emphasises the importance of preparing jumbo beams before welding to ensure quality and minimise fabrication costs. The chapter discusses how steel's ductile nature doesn't necessarily translate into a ductile structure and explains the strategic placement of weld access holes. Additionally, it covers lamellar tearing, a type of cracking related to welding in the base material, and provides guidance on avoiding and detecting it. Various welding parameters such as welding processes, electrodes, heat input, and post-weld heat treatment are highlighted as crucial for executing proper welds and ensuring reliable connections.

Chapter 3 classifies connections based on their structural role and the external loads they endure. It includes categories like connections subjected to tension and compression loads, beam and column splices, trusses, and beam-column connections. The chapter also showcases examples of actual structures utilising connections of jumbo shapes.

Chapter 4 addresses the key factors influencing the connection of jumbo profiles, including architectural considerations, specifying the correct steel shape and grade, manufacturing processes, safety measures, and transportation requirements.

The handbook is supplemented with several Annexes: Annex A presents an example of butt welding with H5 of HD 400 x 1299 (tf = 140mm) in HISTAR® 460, Annexes B and C detail proper steel specification for a column under axial and eccentric compression respectively to avoid brittle fracture, and Annex D provides a design example for a column splice of the bearing type with no net tension (HD 400 x 744 and HD 400 x 990).

Design requirements and material specifications

Connections must be strong enough to support applied forces without compromising the structure's stability. They should be designed to:

  • be robust enough to guarantee structural integrity
  • minimise any additional effects on the structure
  • allow for sufficient rotation
  • be able to sustain cyclic loads where needed

Welded connections of jumbo and super jumbo profiles, especially those made from high strength steel, require specific expertise. This involves understanding the welding process and choosing appropriate steel materials, including filler metals. Welded connections, especially those experiencing tension and bending forces, need careful consideration.

We recommend that designers consult ArcelorMittal's technical advisory department (steligence.engineering@arcelormittal.com) for guidance, especially when dealing with flange thicknesses exceeding 50 mm for ML sub-grade and 80 mm for M sub-grade steel.

Text:
Constructalia
ArcelorMittal Global R&D

Images:
ArcelorMittal