Institution of Structural Engineers Headquarters

This project repurposed a tired office block to become a new home for the Institution of Structural Engineers, demonstrating how selective engineering interventions can unlock the potential of an existing building, eliminating the wasteful process of full-scale demolition and reconstruction and reducing programme time and cost.

The four-storey concrete-encased steel frame building was structurally sound, and it suited both the budget and sustainability aspirations of the client to retain it. Member areas including an auditorium and a library  were proposed for the lower floors, with the upper floors accommodating office and administration space.

A large opening was cut through the first floor, taking up half the width of the floor plate to create an atrium and allow a feature staircase to be introduced for circulation between the member areas. In order to do this we had to first strengthen the precast floor planks with carbon fibre strips, both to maintain diaphragm action around the opening, and to increase the floor strength under the first-floor library for book storage.

The horizontal cantilever staircase is a modern interpretation of traditional stone stairs, using custom-designed steel stringers and precast concrete treads. As the design was novel, we wanted to test the dynamic behaviour of the structure to see how it aligned with our predictions; however the cost of commissioning professional testing services would have been disproportionate to the scale of the project.

Our solution was to use the built-in accelerometer function on a smartphone to gather data from a series of tests, using a freely-available accelerometer app. While the data gathering was straightforward, we believed the time-consuming post-processing would be a barrier to wider adoption of our idea.

Hence we developed a free Android-based app – Vibrate It – that measures acceleration, performs the post-processing, and provides fundamental frequencies and a response factor for the accelerations recorded during a given test; all in near-real time. The app allows engineers to quickly identify whether dynamic performance is an issue that may need further investigation, as well as giving them a deeper insight into the as-built dynamics of their designs.