e-mosty December 2017 MSS and Formwork Travellers | Page 24

1.3 Further Development of the System
The OPS solution leads to minimal compression values
but it is necessary to pay attention to fatigue damage
in organic cables, fretting fatigue, deformations and
vibrations.
The prestressing losses are greatly reduced because in
OPS the permanent prestressing forces are of a small
value. Other losses can be partially compensated by
increasing the stressing values on the OPS cables.
Deformation in the central part of the MSS is
measured with sensors installed in strategic points of
the structure. The information from them is
transmitted and processed according to the control
algorithm to maintain or change the intensity of
prestressing.
The system also comprises safety measures such as
monitoring and alarm warnings. Structures with OPS
are designed for accidental limit states which
comprise system breakdown so, in case of
malfunction of the OPS, the structure remains safe.
Due to the improved waste management and
adaptive strength of the intelligent OPS system,
critical savings are generated by allowing for faster
construction cycles, the creation of significantly
lighter and safer structures, and a reduction in the
consumption of steel, energy, fuel, and consequently,
CO2 emissions.
In its early days, BERD anticipated that, in the near
future, lighter structures enabled by the intelligent
OPS system would make it possible to work with spans
of up to 100 metres, thereby expanding construction
with Movable Scaffolding Systems to a dimension
never seen before.
This is what is currently happening in Turkey where
MSS M1-90-S is used for construction of high-speed
railway viaducts. It allows to extend the maximum
span of 70 metres of its predecessors to 90 metres in
multi-span bridges.
1.4 MSS General Description
1.4.1 Main Truss
The most important structural element of the MSS is
the main truss. It holds the beams that support the
transverse structures where the formwork is placed. It
is constituted by the front nose, the main body with
the arch, and the rear nose.
During the concrete-pouring stage, when the load
achieves its maximum value, the main girder is
supported by two elevation hydraulic cylinders per
supporting section: on the deck concreting frame (the
girder rear support) and on the pier frame (the girder
front support).
During the launching stage, the main girder is fully
supported by the rollers on the bogies (Figure 8) that
are assembled over the pier frames. They transmit
both vertical and horizontal loads to pier segments
which are properly connected to the pier.
Figure 6: MSS M45-S Elevation
4/2017