The MARS System masonry arch repair and strengthening of bridges and tunnels for roads and railways

MARS system of bridge strengthening by Goldhawk

Masonry Arch Repair and Strengthening – MARS system

Our unique Masonry Arch Repair and Strengthening (MARS) System enables weak bridges, that have had weight restrictions imposed, to be sympathetically strengthened to accept full highway loadings and comply with EU and UK regulations.

The System won the Design Council’s Millennium Award for Innovation and was displayed on the Spiral of Innovation at the Millennium Dome as an example of the very best in British ingenuity.  It has been subject to stringent testing with input from the Transport Research Laboratory and the University of Greenwich to test the theory and the installation in controlled environments.

The MARS System does not add weight to the structure, does not reduce the elevational area, and does not alter the appearance of the structure or require a road/rail closure. It cures/prevents ring separation (the principle mode of failure of brick arches under cyclic loading) and it is significantly cheaper and less disruptive than other practical alternatives. Statutory undertakings such as water, gas, electricity and data cabling remain undisturbed and the integrity of the System can be easily inspected in future years.

As our MARS System fully utilises the inherent strength of the existing masonry arch barrel in which it is installed, only a minimum amount of extra material is required to bring the bridge up to modern loading standards. This means that pollution of the environment from manufacturing and transport is kept at an absolute minimum.

MARSYS software

Goldhawk’s design software, MARSYS, was developed from our ASSARC software. It was described in an Ove Arup report as giving the best fit to the results of tests on redundant bridges of any other program.

Our software enables us to accurately design the amount of reinforcement required for a specified loading on any particular masonry bridge. This enables Goldhawk to potentially increase load carrying capacities of arches from existing low limit status to full vehicle loading cost effectively and with no disruption to traffic over the bridge.

Gallery of illustrations:

Testing a masonry arch to failureMARS – Modified mechanism analysisTRL Test arch at failure point MARS finite element model diagram

Benefits of the MARS system

  • Economical, cost effective and reliable.
  • Huge cost and environmental savings.
  • Preservation of our heritage.
  • Significant loading enhancement.
  • Increased strength with no excessive stiffness.
  • Improved structural behaviour.

  • Allows normal structural movement.
  • Rapid, concealed, sympathetic installation.
  • Zero, or minimal, disruption to traffic.
  • Allows staged, sequential, installation.
  • Minimal disturbance to bridge fabric.

  • No unsightly external plates.
  • Original characteristics retained.
  • Accurate structural computer analysis.
  • Short contract duration.
  • Minimum environmental pollution

Arch reinforcement using radial pins and Helibar

The arch reinforcement system

Helifix HeliBars are installed into the slots

Helibar reinforcement set in Marflex epoxy mortar

Hooked radial pins are installed to anchor the grid

The design and planning process

The existing capacity of an arch is assessed by the ASSARC Programme. Using the proven MARSYS software an appropriate arch repair and strengthening scheme is designed to suit the individual needs of the bridge and the client. For bridges that are being upgraded beyond their original design capacity, the increase in soil pressure under abutments is checked to determine that it is within acceptable limits. For the temporary load condition during strengthening the capacity of the bridge is checked using ASSARC. The required grid pattern is marked out on the bridge soffit and narrow slots are cut at just 12 mm wide and 40 mm deep.

Arch strengthening installation and completion

Services are avoided and all environmental regulations observed. The required number of stainless steel Helifix HeliBars are installed into the slots. At each Helibar intersection between circumferential and longitudinal bars, hooked radial pins are installed anchoring the grid and providing continuity to the rings of the arch. The reinforcement is encapsulated with Marflex structural adhesive, a durable polyureide resin with high bond strength, particularly to damp substrates. The Marflex has perfect characteristics for the installation and can be colour matched or pointed over with a colour matched heritage mortar.