TEST

The long term test is performed in order to define the actual creep coefficient and long term behaviour of the cable system.
The specimen, manufactured in Redaelli plant, can be fit with laboratory sockets or with sockets equal to permanent ones.
The specimen is installed in the testing machine with proper care, checking alignment and centering of all the elements.

The typical measurement instruments, installed on the specimen, are:
  • extensometer with automatic data reading step by step, used to measure the cable elongation;
  • position transducer installed at the end of the original sockets used to evaluate the cone setting.
Other geometric characteristics (cable diameter, socket geometry, ecc.) can be measured as well.
After the first pre-stretching cycles, performed to remove the initial inelastic deformation, an established load approximately equal to 40% MBF is kept constant throughout the test, for minimum 200 hours.
The test is completed when the partial elongation between the two reading is reasonably stabilized. The gradient has to decrease for minimum 3 subsequent steps.

STRAIN (LINEAR)

The graph above shows an example of results obtained from long term test (200 h). Since the function creep-time is well approximated by a logarithmic function, it is used to evaluate the creep referred to 5 years and 10 years time.

STRAIN (LOGARITHM)

Fire resistance test is performed in order to analyze cables and sockets behaviour and resistance under fire with different socketing (polyester resin and zamak) and to identify the most critical structural details under constant service load.
Tests are carried out on cables and their terminations under a very heavy thermal transient simulating a fire scenario. The fire load could be identified, for instance, by the curve ISO 834 that is normally used for civil applications.
The curve that represents the gradient of the air temperature during the burning process is analytically:

T=To+345*Log10(8xtm+1)
To:environment temperature at the starting point
Tm :time duration in min

The time to failure is determined for different types of sockets materials and compared with the time to failure of the cable.
The axial force is maintained until to have a significant slipping of the cone.
The fatigue test is performed in order to evaluate the effective detail category of the cable system. The fatigue failure usually occurrs at anchorages, saddles or clamps.
The test on the relevant specimen manufactured in Redaelli plant reproduces the actual configuration of the cable, as well as any flexural effect or trasverse stress occurring in practice.
The specimen is installed in the testing machine with proper care, checking alignment and centering of all the elements.
The specimen is properly installed in the pulsatory load machine which is set up according to the relevant test specification.
Typically the fatigue test is performed in accordance whith the requirements of the EN 1993-1-11, summarized in the following table.
After finishing the fatigue test, the following conditions must be verified:
  • Number of the broken wires after 2x106 cycles less than 2% of the total;
  • No failure should occur in the socketing material and in any component of the anchorage;
  • The specimen should develop a minimun tensile force equal to 92% A.B.L. of the cable or 95% M.B.L. of the cable, which ever is greater.
Type of test Fatigue loading before fracture test
1

axial test
(class 3 and 4 according to EN 1993-1-11.)

σsup = 0,45 σuk
Δσ according to Δσc give in Table below
Δα = 0
n=2x106 cycles

2

axial and Flexural test
(class 5 according to EN 1993-1-11)

σsup = 0,45 σuk
Δσ according to Δσc give in Table below
Δα = 0 – 10 milli radians (0 – 0,7 degrees)
N=2x106 cycles

Testing requirements for fatigue according EN 1993-1-11.

Group Tension components Detail category Δσc (N/mm2)
B 2 Fully locked coil rope with metal or resin socketing 150
3 Spiral strands with metal or resin socketing 150
Detail categories for fatigue strength according to EN 1993-1-11.

The E+R test is performed in order to measure cable Modulus of Elasticity and Actual Breaking Force according to EN12385-1.
The specimen, manufactured in Redaelli plant, can be fit with laboratory sockets or with sockets equal to permanent ones.
The specimen is installed in the testing machine with proper care, checking alignment and centering of all the elements.
Typical measurement instruments, installed on the specimen, are:
  • extensometer double bar type with two gauges installed approximately in the middle of the specimen and automatic data reading step by step, used to measure the cable elongation;
  • position transducer installed at the end of the original sockets used to evaluate the cone setting.
Other geometric characteristics (cable diameter, socket geometry, ecc.) can be measured as well.
After the first load cycles in which the specimen is pre stretched, the cable modulus of elasticity is measured and then the load is gradually increased until the breaking force of the sample is reached and the ABL (actual breaking force) is recorded.


Measure of cone setting.

Sample after breaking.
Clamp slippage test is performed in order to determine the value of the slippage force on ring cable connector and on a radial cable clamps.
The specimen is manufactured in Redaelli plant, clamps and bolts equal to the permanent ones are also supplied.
The specimen is installed in the testing machine with proper care, checking alignment and centering of all the elements.
The typical measurement instruments, installed on the specimen, are:
  • Pulling machine;
  • Hydraulic jacks;
  • Hydraulic pump 700 bar;
  • Torque wrench;
  • Digital pressure gauge;
  • Transverse beam;
  • Comparator tool;
  • One bolt for each clamp instrumented with strain gauges.


The slippage test is performed for each clamp installed on the relevant cable specimen. Cables specimen have the same characteristics as cables arriving to delivered job site, the actual process installation of the clamps is accurately simulated on laboratory.