Mobile detection of structural damage to girder bridge segments

Abstract

Method for, in particular mobile, detection of structural damage to a girder bridge segment, where the structural length of the girder bridge segment is known or determined and, wherein a deflection of the beam bridge segment is measured during a load on the beam bridge segment, wherein structural damage is assumed to be detected at least if the deflection exceeds a predetermined reference deflection by more than a predefined range, in particular 25% of the reference deflection, and / or wherein at least if the reference deflection is not exceeded, it is assumed that no structural damage is present, where the reference deflection is in the range of 0.001 and 0.005 mm per 1 m of structure length at 1 t load.

Description

[0001] The present invention relates to the detection of structural damage to girder bridge segments.

[0002] Such methods are widely known from the state of the art, such as US 2015 / 0 198 502 A1 or CN 2 07 751 471 U. However, they usually require preparation, great effort and / or long closures of the bridge segment.

[0003] It has also been shown that even under favorable conditions, frequency shifts caused by damage lie in the noise band of temperature-induced frequency changes and are therefore generally unsuitable.

[0004] DE 10 2019 000 013 A1 also discloses a method in which the behavior of a structure under the application of a load is observed, but structural damage to the structure is not detected.

[0005] The task is to provide a simple and fast method for reliable detection.

[0006] In numerous experiments, the inventor surprisingly discovered that the various beam bridge segments can be easily examined, analyzed and classified.

[0007] The problem is solved, among other things, by a method for, in particular mobile, detection of structural damage to a girder bridge segment and / or for, in particular mobile, determination of the load-bearing capacity reduction of a girder bridge segment, wherein the structural length of the girder bridge segment is known or determined, and wherein a deflection of the girder bridge segment is measured during a load on the girder bridge segment. This load is applied to the bridge, in particular by a weight, in particular a truck.

[0008] In particular, an averaged deflection is used to average out vibrations of the bridge segment. The deflection is measured in particular in comparison to the unloaded state, in particular before and / or after, in particular within less than one hour, in particular less than five minutes before application and / or after removal of the load. In particular, after removal of the load, the system waits until the vibration has subsided before determining the rest position, or the measurement data of the rest position are mathematically adjusted / corrected so that the post-oscillation is calculated out, in particular averaged out.

[0009] In particular, the difference between the rest position and the loaded position is determined as a deflection. The measurement is taken in the middle or a central area, in particular of a maximum of 15%, in particular a maximum of 5%, of the supporting structure length, and / or the maximum deflection is determined over the supporting structure length.

[0010] In particular, structural damage is assumed to be detected at least if the deflection exceeds a predetermined reference deflection by more than a predefined range, in particular 25% of the reference deflection, and / or at least if the reference deflection is not exceeded, it is assumed that there is no structural damage, the reference deflection being in the range from 0.001 to 0.005, in particular from 0.0015 and / or up to 0.0027 mm, per 1 m of supporting structure length at 1 t load.

[0011] The object is also achieved by using a predetermined reference deflection in the range of 0.001 to 0.005, in particular from 0.0015 and / or up to 0.0027 mm, per 1 m of supporting structure length at a 1 t load, for detecting structural damage to a girder bridge segment and / or for determining the load-bearing capacity reduction of a girder bridge segment. Wherein the supporting structure length of the girder bridge segment is known or determined.

[0012] In this case, a deflection of the girder bridge segment is measured during a load on the girder bridge segment and compared with the reference deflection. This advantageously detects structural damage if the reference deflection is exceeded by more than a predefined range, in particular 25% of the reference deflection, and / or if the reference deflection is not exceeded, it is assumed that no structural damage is present.

[0013] In this way, reliable detection of structural damage can be achieved in a very simple manner, even without prior reference measurements, at least of damage that has a relevant impact on safety and / or planning.

[0014] Particularly advantageous is the ability to perform detection in a more differentiated manner. For this purpose, the reference value can be set precisely within the specified range and / or adapted to the bridge type, and / or the predefined range can be reduced or subdivided.

[0015] In particular, different degrees of damage severity can be subdivided and / or the loss of load-bearing capacity can be approximately derived from the extent to which the reference deflection is exceeded. In particular, the percentage loss of load-bearing capacity can be derived from the extent to which the reference deflection is exceeded by multiplying it by a factor in the range of 2 to 3.5, in particular 2.5 to 3, particularly preferably 2.6 to 2.7, in particular 2.65.

[0016] Loss of load-bearing capacity means, in particular, a reduction in stiffness and / or greater deformation under the same load.

[0017] This has been shown by tests and measurements on numerous bridges.

[0018] The ranges can be subdivided, for example, by defining damage classes for which different measures are taken. For example, in a first damage class, monitoring can be improved and / or intensified, for example by recording the bending line and / or repeating the recording / measurement at shorter intervals or continuously. In a second damage class, the traffic load can then be reduced, for example. In particular, it has proven effective to define a first damage class with load-bearing capacity losses up to a load-bearing capacity reduction in the range of 20 to 35% and a second with load-bearing capacity losses exceeding that of the first damage class. For this purpose, it is advisable to define the distinction between the first and second damage classes at a predetermined value in the range of 15 to 30%, in particular in the range of 20 to 30%.

[0019] Furthermore, it is advisable to set the lower limit for accepting the first damage class as an exceedance of the reference deflection by a predetermined value below, in particular at least 10 percentage points below, the predetermined value for accepting the second damage class, and / or in the range of 2 to 20%, in particular 5 to 20%. In particular, for lower exceedances, negligible and / or no damage is assumed. The measurement is advantageously carried out using a laser, in particular laser distance measurement, in particular on a target with an inclined mirror surface, and / or using strain gauges.

[0020] This means that fast and accurate measurements can be achieved even with mobile measuring devices. The intervention in the traffic flow can be reduced to a few minutes and only a slight influence. In particular, a truck, which represents the load, can be driven onto or over the bridge in such a way that it, especially on its own, puts a strain on the bridge. By driving over it, the influence of the load can also be recorded at different points. To do this, it is sufficient to slow down the traffic on both sides before the bridge slightly, so that a small time window is created in which there is essentially no load on the bridge and before and / or after the truck represents the only or essentially the only load.

[0021] With particular advantage, the reference deflection is predetermined in the range of 0.002125 mm + / - 20% per 1m of structure length at 1t load.

[0022] This allows for an even more precise and discriminatory statement.

[0023] Preferably, the reference deflection is predetermined for individual beam bridge segment types from the following list and / or groups of beam bridge segment types from the following list, in particular deviating from one another: • Beams made of solid material • Beams as hollow boxes • Truss girders • Prestressed concrete bridges • Prestressed concrete solid slab bridge • Prestressed concrete slab girder bridge • Prestressed concrete slab-girder bridge with subsequently prestressed individual webs • Prestressed concrete slab-girder bridge with factory-prestressed individual webs • Prestressed concrete box girders • Steel composite bridges • Steel composite bridge with box girder superstructure • Two-span steel composite bridge • Multi-span steel composite bridge • Steel girder bridges • Steel girder bridge with orthotropic deck • Steel box girder bridge with orthotropic deck • Steel girder bridge with concrete slab • Steel girder box girder bridge • Steel truss bridge

[0024] This allows subtle differences between the individual types to be taken into account and recognition to be further improved.

[0025] Advantageously, upon detection of structural damage, a predetermined reduction in load-bearing capacity, and / or the identification of a damage class, an alarm is triggered and / or an at least partial closure of the girder bridge segment and / or a reduction in traffic flow over the bridge segment is initiated. This can increase safety while avoiding unnecessary traffic disruption.

[0026] Preferably, the deflection is determined with an accuracy of better than 1 mm, especially better than 0.5 mm per 100 m of structure length. This increases the validity, accuracy, and reliability of the bridge.

[0027] It is particularly advantageous if the load is in the range of 10 to 100 t, and / or is applied over an area of less than 5% of the structure length and / or less than 20 m, in particular less than 15 m. This area is located around the middle of the structure length. This increases the significance, as conventional bridge segments react particularly sensitively to centrally applied loads.

[0028] Further aspects and advantages will be explained schematically and exemplarily below using the figures. They show: Fig. 1 Illustration of the deflections of bridge segments with different ranges after different damages and Fig. 2 Representation of the damage and measured values of a bridge segment

[0029] Fig. Figure 1 shows the deflections of girder bridge segments in an undamaged state and after four different levels of damage. Within a span, the columns are assigned from left to right to damage levels DS#0 (no damage) to DS#4 (maximum damage). The type of damage in damage classes DS#0 to DS#4 is the Fig. 2 can be seen under severed clamping elements.

[0030] To determine the damage, the specified percentage of the cross-sections of the tensioning cables were cut. A 40 t load was then applied to the center and the Fig. 1 shown deflection measured.

[0031] Fig.Figure 2 shows a partial cross-section through a girder bridge segment with 19 identical steel cables for each damage class. Some of these were gradually severed, indicated by hollow circles with crosses, in contrast to the undamaged steel cables represented by solid circles.

[0032] Among the cross-sections, the increase in deflection compared to DS#0 and the reductions in the total effective steel cable cross-section compared to DS#0 resulting from the cutting of the steel cables are listed.

[0033] The deflection is the one at the central load of 40t compared to the unloaded state.

Claims

[1] Method for, in particular mobile, detection of structural damage of a girder bridge segment, where the structural length of the girder bridge segment is known or determined and, wherein a deflection of the beam bridge segment is measured during a load on the beam bridge segment, wherein structural damage is assumed to be detected at least if the deflection exceeds a predetermined reference deflection by more than a predefined range, in particular 25% of the reference deflection, and / or wherein at least if the reference deflection is not exceeded, it is assumed that no structural damage is present, where the reference deflection is in the range of 0.001 and 0.005 mm per 1 m of structure length at 1 t load. [2] Method according to the preceding claim characterized bythat the reference deflection is in the range of 0.002125 mm + / - 20% per 1m of structure length at 1t load. [3] Method according to the preceding claim characterized by that the reference deflection for individual girder bridge segment types from the following list and / or groups of girder bridge segment types from the following list is predetermined, in particular deviating from one another: • Beams made of solid material • Beams as hollow boxes • Truss girders • Prestressed concrete bridges • Prestressed concrete solid slab bridge • Prestressed concrete slab girder bridge • Prestressed concrete slab-girder bridge with subsequently prestressed individual webs • Prestressed concrete slab-girder bridge with factory-prestressed individual webs • Prestressed concrete box girders • Steel composite bridges • Steel composite bridge with box girder superstructure • Two-span steel composite bridge • Multi-span steel composite bridge • Steel girder bridges • Steel girder bridge with orthotropic deck • Steel box girder bridge with orthotropic deck • Steel girder bridge with concrete slab • Steel girder box girder bridge • Steel truss bridge [4] Method according to one of the preceding claims, wherein upon detection of structural damage an alarm is triggered and / or an at least partial closure of the girder bridge segment and / or a reduction of the traffic flow over the bridge segment is initiated. [5] Method according to one of the preceding claims, wherein the deflection is determined with an accuracy of better than 1 mm, in particular better than 0.5 mm per 100 m of supporting structure length. [6] Method according to one of the preceding claims, wherein the load is in the range of 10 to 100 t, and in particular is applied over a region of the supporting structure length of less than 20 m. [7] Use of a predetermined reference deflection in the range of 0.001 and 0.005 mm per 1 m of supporting structure length at 1 t load, for detecting structural damage to a girder bridge segment, wherein the supporting structure length of the girder bridge segment is known or determined and wherein a deflection of the girder bridge segment is measured during a load on the girder bridge segment and compared with the reference deflection, wherein if the reference deflection is exceeded by more than a predefined range, in particular 25% of the reference deflection, structural damage is detected and / or wherein at least if the reference deflection is not exceeded, it is assumed that there is no structural damage. [8] Use according to one of the preceding claims, wherein upon detection of structural damage an alarm is triggered and / or an at least partial closure of the girder bridge segment and / or a reduction of the traffic flow over the girder bridge segment is initiated.

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