Complex challenges of designing concrete to concrete connections can be easily addressed

Discussions around whether challenges faced by designers for concrete-to-concrete connections are different to those faced on concrete-to-steel connections was the starting point for a free NCE webinar last week.

The event, which was chaired by NCE editor Claire Smith and sponsored by Hilti, is now available to view on demand.

Panellists for the discussion were Arup associate director and Global Structural Skills Manager Andy Gardner, Concrete Centre technical director Tony Jones and Hilti marketing manager Laura Martinez-Melida.

In explaining the difference when it comes to concrete to concrete connections, Jones said: “When you’re designing concrete-to-concrete connections, you’re generally trying to achieve continuity between the existing and the bit you’re fixing to the concrete. So that’s very different to if you’re casting in say holding down bolts for a steel column or something where you’re just trying to anchor the element into the body of the concrete.

“It’s all about the global behaviour rather than the local behaviour when you’re looking at concrete-to-concrete fixings.”

Martinez-Melida also said that steel to concrete connections are “really commonly done in our day-to-day lives as civil engineers or structural engineers”, before stating that “when we face concrete-to-concrete, it’s a more specific requirement and not everybody is that familiar with it”.

The conversation progressed onto the need for better optioneering when designing concrete to concrete connections for rehabilitation projects, as well as the need for designers to understand how the connection will be built on site.

Gardner said that when designing such connections there’s a need for “quite adaptable solutions, perhaps developed in a design office in advance of getting to site and really knowing the individual scenarios – that hopefully allow for construction to proceed without too many scenarios cropping up that don’t work with the design”.

Panellists agreed on there being a need for flexibility in design to deal with unknowns and Gardner and Jones both gave real world examples of typical issues which crop up during design and installation of concrete to concrete connections during the event.

Martinez-Melida also made a case for fast-paced solutions to solve problems when it comes to new build construction before the panel looked at how Hilti’s new PROFIS software, which was launched in the UK on 31 January, could help designers with concrete connections.

According to Martinez-Melida, the software contains “all the options to calculate” with transparency for the formulas used. “It’s a structural software, it’s not a company software – and it can be used as so,” she said.

“Another good thing is that right now we have three official methods to calculate post-installed rebar by law. Eurocode has two parts and we have TR069, so engineers need to ask which code is the right one for my connection? And this is something that the software solves straight away – because in the right hand side you will have the full list of full solutions and full codes that were able to calculate your connection.”



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