5. Brückenkolloquium - September 2022 419 Prestressed footbridge over Morava River in Kroměříž - strengthening, rehabilitation and measurement using geodetic method in combination with advanced optical methods doc. Ing. Ladislav Klusáček, CSc., Ing. Adam Svoboda, doc. Ing. Jiří Bureš, Ph.D. Brno University of Technology, Brno, the Czech Republic Ing. Petr Gajdoš, Ing. Michal Vajdák X-Sight s.r.o., Brno, the Czech Republic This paper describes the repair works on the footbridge over the Morava River in Kroměříž, which is of the same structural type (stressed ribbon) as the original footbridge in Prague-Troja, which collapsed in 2017 due to the breakage of corrosion-damaged prestressing reinforcement. The paper focuses on the process and results of the diagnostics of the structure, which resulted in the need for static strengthening. It describes the design of the reinforcement using external cables and its structural representation. Further, it focuses on the structure rehabilitation, which was designed to stop or significantly reduce its degradation. It shows the design, installation and evaluation of the monitoring system using sensors that measure strain, temperature and moisture of the concrete. This system was designed to monitor the work of the contractor and it will allow a better prediction of the condition of the footbridge during its future service life. The proposed sensor array was combined with geodetic measurements as well as with advanced monitoring based on image analysis, which allowed logical control of the sensors in relation to the effects of the bridge structure. The monitoring of the verification load test using image analysis is particularly promising because of its relatively low cost, simplicity of application and the measured data processing automation. 1. Introduction The successful repair of the segmental footbridge over the Morava River in Kroměříž consisted of successive stages: diagnosis, strengthening, rehabilitation and monitoring. The footbridge in Kroměříž was closed after a bridge accident in Prague in Troja. After detailed diagnostics were carried out, it became clear that the bridge could not be operated safely without further structural support. At the turn of 2018 and 2019, the structure was statically secured by adding external cables under the segments of the structure. After its reopening in spring 2019, the bridge deck was rehabilitated in the second half of 2020 and a monitoring system was built into it. The work was completed in June 2021 with the prospect of trouble-free operation of the footbridge over the next 30 to 50 years. Fig. 1: View of the footbridge over the Morava River in Kroměříž in 2018 1.1 Description of the footbridge structure The footbridge’s superstructure consists of segments that are suspended in the form of a stressed ribbon and the superstructure is embedded in the outermost monolithic abutments (Fig. 1). The stressed ribbon is made of prefabricated segments type of DS-L and DS-Lv. The outermost segments are supported on unreinforced elastomeric bearings. Since the bearings are not connected to the bridge superstructure, the superstructure could have been unwound from the bearings during prestressing (construction) and rewound during service loading. This arrangement reduces the local stresses on the end segments near the supports. Therefore, the span of the structure is variable from 57.73 m to 63.36 m. The length of the stressed ribbon is 63,36 m. The sag of the superstructure is variable, depending on the temperature and the magnitude of the service load. The design sag at 10°C without variable loads was 1.56 m. At negative temperatures the sag decreases, whereas at high positive temperatures the sag increases. The precast segments are 0.30 m high, 3.80 m wide and 3.00 m long. DS-Lv segments are lightened by the floor compared to DS-L segments cassette recess of the bottom surface. The segments are carried by strand cables “A” 2×5×(3×2) consist of strands ϕ Lp 15,5 mm, prestressed cables “B” 14×(3×2) consist of strands ϕ Lp 15,5 mm and cables “C” 4×2 also consist of strands ϕ Lp 15,5 mm. 2. Diagnostics of the footbridge The diagnostic survey of the footbridge No. L07 over the Morava River in Kroměříž was carried out in predefined stages. [1] The aim of the staged schedule was to minimize the risks of the group of diagnostic survey executors, then of the owner and users of the footbridge. 420 5. Brückenkolloquium - September 2022 Prestressed footbridge over Morava River in Kroměříž During Stage 1, the residual capacity of the supporting cables to carry the weight of the structure was checked, concrete samples were taken for the first laboratory analyses, and probes made from above to the supporting prestressing cables were waterproofed. Upon completion of Stage 1, the following decisive results were found: the load-bearing cables observed from above are surrounded by good quality (compacted, no gaps) concrete, but it is wet with a clear water at the interface between the bridge deck walking layer and concrete of segments; the load-bearing cables observed in the Stage-1 probes were in a state of either no corrosion or at most surface corrosion when observed from above; laboratory analyses of the reaction of the surrounding concrete showed that the pH of the concrete was strongly alkaline (on 35 samples the pH ranged from 10.3 to 12.0; a value of at least 9.0 is sufficient for permanent protection of the reinforcement; only two samples within 30 mm of the bridge deck surface showed a dangerous chloride ratio). Based on the results of Stage 1, it was possible to decide that it was possible to proceed with Stage 2 of the diagnostic survey without the risk of sudden failure of the structure, and it was possible to hold an optimistic estimate that repair of the waterproofing and walking layer would be sufficient to ensure the continued serviceability of the structure and to prevent saturation of the footbridge concrete by rainwater. This optimistic estimate was tentatively communicated to City representatives. Fig. 2: Inspection platform During Stage 2, the footbridge was investigated from the bottom surface using a sliding specially constructed inspection platform (Fig. 2) in accordance with the established methodology. Contrary to the assumption of inspecting and examining six profiles, all parts of the footbridge were inspected, followed by waterproof grouting, chemical analyses to verify the ability of the prestressing cables to carry the weight of the structure. Probing was carried out from the bottom surface of the structure by probing vertically (Fig. 3 and Fig. 4), to the supporting cables (cables “A”) at both edges of the footbridge and to the prestressing cables (cables “B”). After the completion of Stage 2, the following decisive results were found: on the upstream side of the footbridge, an cavern from the construction period was discovered in the first half of the footbridge from the underside of the flat arrangement of supporting strands, approximately 9 m long. The cavern area was empty with signs of water leakage (leachates and calcareous stalactites) (Fig. 5). The supporting cables found in the cavern on the upstream side were some broken, others had been damaged by deep corrosion of the individual wires of these strands; after a refined estimation, 20 of the 30 prestressing strands on the upstream side of the footbridge must be considered to date as either completely non-functional or of unsatisfactory reliability. In other parts of the structure, the strands of this tendon on the upstream side have mostly only surface corrosion and are surrounded by concrete with sufficient pH. Fig. 3: Execution of drilled probes Fig. 4: Probe to prestressing cable Fig. 5: Condition of prestressing strands in the joint between segments 5. Brückenkolloquium - September 2022 421 Prestressed footbridge over Morava River in Kroměříž The prestressing cable on the downstream side have mainly surface corrosion, in some profiles this corrosion is transformed into pitting corrosion (this was confirmed during detailed processing of the image material in Stage 3). As of the date of the diagnostics, the prestressing cable on the downstream side could be considered fully functional. The prestressing strands (cable B) were fully functional and surrounded by protective grouting, except for the section near the abutment 2 (left bank), where 50 % of these strands were ungrouted (from the time of construction) along the length of two segments, and at the same time affected by deep corrosion. Laboratory analyses of the reaction of the surrounding concrete showed that the pH of the concrete is again strongly alkaline (on 39 samples the pH ranged from 9.6 to 11.8). Only 9 samples had higher chloride ratios. Based on the results of Stage 2, it was necessary to decide that the supporting cables of the footbridge were severely weakened on the upstream side and that this weakening, although precluding the collapse of the structure, did not allow it to be further operated and used and that it was necessary to keep the footbridge closed until further decision. The solution seems to be to replace the supporting cable on the upstream side of the footbridge. This was communicated to the city representatives at the end of the implementation of Phase 2. During Stage 3, the evaluation of the data collected in the field and in particular the evaluation of the image material of the probing works was carried out. An evaluation was also made of the geodetic detailed levelling of the structure carried out during the diagnostic stages at two different temperatures. After the completion of Stage 3, it was necessary to further note that the corrosion of the supporting cables on the downstream side was changing from pitting corrosion to deep corrosion. Although the flood-side wire strand bundle could be considered fully functional at the time of diagnosis, it cannot be considered fully functional in the future and it will be appropriate to design a replacement for this wire strands bundle as well. Based on the results of Stage 3, it had to be decided that the supporting cables of the footbridge are also affected by deep corrosion on the flood side to the extent that they cannot be considered reliable in the long term. They will need to be replaced. In terms of conclusions about the state of the structure and recommendations for further action, it was possible to determine: 1. The critical corrosion damage to the main cables on the upstream side is the result of poor construction quality and is of such a magnitude that the footbridge cannot be operated reliably. 2. The corrosion damage to the supporting cables on the downstream side is the result of long-term flooding into the footbridge structure from its upper surface and makes it impossible to predict their service life. 3. The footbridge can be repaired by replacing both bundles of supporting cables with external cables anchored into the existing abutments and at the same time repairing the waterproofing to prevent further continued flooding of the footbridge structure. Fig. 6: Longitudinal section through the footbridge 3. Strengthening of the footbridge 3.1 The strengthening way The proposed strengthening of the footbridge consisted in installing new external cables under the existing footbridge. The external prestressing consists of two cables (one on each side of the footbridge) placed under the cable trays of the original supporting cables (Figure 6). In total, these are 2 × 18 ø 15,7 mm cables (Y1860-S7-15.7 mm) tensioned to 650 MPa (prestressing force per cable Pmax = 97.5 kN). The geometry of the external cables corresponds to a second stage parabola with a span of L = 63.0 m and a deflection of f = 1.38 m. The axis of the external cables in the middle of the span is approximately 70 mm below the bottom surface of the segments, taking into account the size of the retrofitted guard. The distance of the axis of the cables from the bottom surface of the segments increases towards the two abutments due to the position of the mid-span cable and the position of the drilled cable ducts in the abutments. The connection of the cables to the segments is made by means of steel saddles installed in each joint between the segments. The height of the saddles corresponds to the distance of the external cable from the segment (due to the different curvature of the prestressed strip parabola and the external prestressing parabola). The new prestressing strands are secondary protected by a special cover made of 2 mm thick corrosion-resistant sheet metal. The space between the cover and the individual monostrands is filled with self-compacting microcrete. 422 5. Brückenkolloquium - September 2022 Prestressed footbridge over Morava River in Kroměříž 3.2 The static analysis To assess the proposed structural modifications, two computational models were created in ANSYS a computational model of the existing structure without weakening of the prestressing cables and a computational model including the proposed structural modifications including weakening of the prestressing cables (Fig. 7). Fig. 7: Numerical model The computational models were further subjected to static and dynamic analysis [2] The static analysis consisted in the assessment of the serviceability and ultimite limit state. Within the serviceability limit state, the stress limitation in the concrete was also assessed with respect to the allowable stresses in the joints of the segmental structure, the stress limitation in the bearing cables, prestressing cables and new external cables and the crack limitation in the segmental concrete. All the stress limitation and crack limitation assessments met the code requirements. Next, the deflection or uplift of the footbridge was analysed (Fig. 8). The deflection is considered as the height difference between the surface of the abutments and the surface of the segment in the centre of the footbridge. Fig. 8: Deflection changes The predicted deflection of the footbridge at the time of completion of the modifications for a temperature of 10°C is 1.591 m (original condition before repair 1.610-m). Overloading of the footbridge during the repairs caused a deflection of 11 mm to 1.621 m, prestressing the new external cables raised the strip deflection by 30 mm to the final 1.591 m. In short, the level of the footbridge is now 19 mm higher than before the repairs. Temperature effects have the greatest influence on the deflection values. A warming of 29.5°C increases the deflection by 156 mm and a cooling of 34.0°C decreases the deflection by 190 mm. The structural design also includes an analysis of the horizontal and vertical reactions to the foundation. The new structural modification is designed and assessed so as not to cause failure of the understructure. The magnitude of the new prestressing causing an increase in the horizontal force in the foundation utilizes a reserve in the design of the earth anchors (this was verified from the original 1982 structural design of the footbridge). The new static recalculation also reduced the load capacity of the footbridge corresponding to the subjection of the abutments. The last important part of the structural analysis was the assessment of the so-called failure state of the structure within the ultimate limit state. The aim of the proposed structural modification is to prevent the collapse of the footbridge structure as it happened in the Prague Troja footbridge. In our case, it is assumed that the external prestressing under the existing footbridge will form a “safety net” that will catch fragments of the damaged existing footbridge in case of damage to the original strip. This will use the reserve between the tension of the new cables and their ultimate capacity. This will increase the ductility of the structure. 3.3 Execution of construction modifications The implementation of the construction was carried out by the company Mitrenga-stavby from Brno. The construction began with the erection of scaffolding at the supports and the assembly of mobile platforms. After grouting the caverns from the construction period, both supports were dug out and drilled ducts were prepared for routing the external strands. Below the footbridge, the surface in the area above the fairing was rehabilitated and the saddles and the first part of the fairing were installed. The prestressing strands were then stretched along with the reinforcement of the anchorage areas (Fig. 9). Next, the remaining part of the fairing was fitted and its grouting (Fig. 10) and concreting of the anchorage areas was carried out. Fig. 9: Anchoring strands behind the abutment 5. Brückenkolloquium - September 2022 423 Prestressed footbridge over Morava River in Kroměříž Fig. 10: External prestressing cables in the housing The last stage of the modifications was the tensioning of the external cables with simultaneous geodetic and strain gauge monitoring. 3.4 Geodetic monitoring of the bridge Before and during the construction works, the footbridge was geodetically monitored to confirm the behaviour acording the calculation model. The deflection values were monitored with simultaneous temperature measurements, and the horizontal and vertical movement of the footbridge abutments. The geodetic monitoring of the footbridge, especially in the stage of prestressing the external cables, showed almost complete correspondence with the calculation model [1]. 4. Footbridge rehabilitation As part of the rehabilitation of the footbridge, it was necessary to prevent leakage into the footbridge structure, which was caused by cracks in the original cement concrete walking layer, which was 35 to 40 mm high, and which was replaced from the very beginning by the originally designed waterproofing made of asphalt insulation strips and the originally designed walking layer made of cast asphalt. Cracks were formed along the cable-guided gutters and in places in the transverse direction. As a result of the long term water enclosure between the walking layer and the concrete of the footbridge components, there was non-negligible damage to the middle segment in particular and to the adjacent segment towards OP1 by thawing of the surface layer of concrete on approximately 30% of the surface of the components, which was identified by acoustic tracing. Therefore, it was necessary to design and implement a-walking layer system that would eliminate further damage to the concrete of the components. Fig. 11: Installation of a levelling layer of extruded polystyrene, new railing anchor points, cornice grinding and installation of moisture sensors A layer was designed (Fig. 11) that provided the above waterproofing effect while mechanically protecting the waterproofing system and allowing regular maintenance of the footbridge by sanding in winter. Another property is the possibility to carry out minor repairs to the surface by the maintenance forces of the city of Kroměříž. The original cement-concrete roadway was therefore demolished and the resulting space was filled with glued plates of extruded polystyrene. The polystyrene plates and the adjacent elevated parts of the cornices were braced down to create a base for applying a 2 mm thick waterproofing roofing membrane. The edges were fitted with a gutter plate to allow water to drip down if it penetrates through cracks in the new walking layer and on to the waterproofing membrane. For reliable drainage of any rainwater that may have soaked through, a drainage foil was laid on top of the waterproofing foil and then a geotextile with an increased weight of at least 800 g/ m2. On top of the drainage system, a 35 to 40 mm thick layer of SIKA microcrete reinforced with a non-corrosive reinforcement net(basalt reinforcement nets with 50/ 50 mm mesh) was laid. The surface was finally closed with an epoxy coating with silica sand backfill, which can be subsequently repaired locally. The new walking layers are therefore not supposed to insulate the structure against rainwater, this property is only given to the drainage and insulation, which are protected and stabilised by the walking layers. This layer has fully proven itself one year after commissioning and has even survived unplanned car journeys by drivers under the influence of psychtronic substances and the pursuing Police Czech Republic in March 2022. Part of the construction rehabilitation was the removal of the original railing due to its multiple removal and rejoining with welded joints as a result of flooding and due to the increase of the roadway by about 40 mm. The railings were also restored in the foreland of the footbridge, where the cornices were repaired with a remediation layer and the surface was resurfaced with cast asphalt. The whole lower surface of the structure was sprayed with pressure water with local chipping of the disturbed concrete reinforcement cover. This was followed by a connecting bridge, local reprofiling and rehabilitation of the lower surface with a rehabilitation grout. Finally, the bottom surface was coated with a unifying vapour permeable coating (Figure 12). 424 5. Brückenkolloquium - September 2022 Prestressed footbridge over Morava River in Kroměříž Fig. 12: Footbridge after completion from the underside: external cables, surface rehabilitation and monitoring system Such a consistent and certainly generous structural restoration of surfaces and railings rehabilitated the footbridge over the Morava River in Kroměříž to its original elegant form with an expected life extension of another 30 to 50 years (Fig. 13). Fig. 13: Footbridge after completion in view of the right bank towards OP1 5. Geodetic inspection of the structure It is possible to say that the thinner the bridge deck and the larger the span of the bridge, the more geometric changes caused by temperature changes and glare become apparent. Load tests of large bridge structures are therefore often carried out under night conditions. Also, daytime conditions cannot be avoided during load testing or erection during construction, and the influence of external conditions on the structure is a very unfavourable factor. The technology of reinforcement with external prestressing cables consisted in principle of the tensioning cables under the bridge deck and their tensioning and anchoring into the bridge abutments. Certain risks for this technology consisted basically in the strength of the existing bridge abutments, or the impossibility to determine the current state of the strength of the abutments anchored to the substructure. Therefore, convergence geodetic monitoring of the mutual length between the bridge abutments was included in the implementation of the prestressing. The monitoring also included measuring changes in the deflection of the bridge deck at mid-span to document the effectiveness of the prestressing, which was to be reflected in a 29 mm upward change in the deflection of the bridge deck. Experimental continuous geodetic monitoring of the condition of the abutments and the deflection of the bridge deck over a 24-hour period, carried out before the actual static strengthening step of post-tensioning, showed that the changes in the deflection of the bridge deck from the effect of external conditions (temperature, sunshine) alone were up to 48 mm (Fig. 16), which was twice the expected change in deflection from post-tensioning. The main objective of the experimental measurements was to “calibrate” the behaviour of the bridge deck under changing external conditions applicable to the static securing process. It showed that the gradient of the increase in deflection over the day during the heating phase of the bridge deck from solar radiation was up to 6.8 mm with a 1 °C change in temperature. Overnight, in the cooling phase of the structure, the bridge deck returned to its original state with a different gradient of 6.3 mm with a temperature change of 1 °C. An external conditions measuring system was installed on the bridge deck in the middle of the span (Fig. 14, Fig. 15). Fig. 14: Bridge deck with the location of the external conditions measuring system points Fig. 15: Schema of the external conditions measuring system The object of measurement was the contact temperatures of the concrete surface measured at the edge of the bridge deck from above and below. The temperatures were measured at 10-minute intervals with Comet recording thermometers with an accuracy of 0.1 to 0.3 °C. The monitoring of the external conditions included a portable weather station installed on the bridge deck railing, which recorded air temperature, atmospheric pressure, relative humidity, solar radiation intensity and precipitation totals. Using a geodetic polar method 5. Brückenkolloquium - September 2022 425 Prestressed footbridge over Morava River in Kroměříž with a robotic universal measuring station, changes in length between abutments and changes in bridge deck deflection at midspan were measured at 10-minute intervals. The time evolution of the change in the length between abutments (dS), the bridge deck deflection (deflection) and the measured parameters of the external conditions are shown in Fig. 16. Fig. 16: Time evolution of bridge deck deflection and measured parameters external conditions (deflection in red) Figure 17 shows the time evolution of the monitoring of the stability of the abutments (dS) and the deflection of the bridge deck (deflection) during the post-tensioning in the context of the external conditions. The conditions varied quite significantly during the day. The prestressing process started in the morning and ended in the evening, with a difference of only +0.7 °C between the end and the beginning temperature conditions. Fig. 17: Time evolution of monitoring of abutments and bridge deck deflection during post-tensioning in the context of external conditions (deflection in red) Fig. 18: Camera equipment and measurement view from the underside of the bridge structure The change in deflection after post-tensioning was slightly different for the edges of the bridge deck and was 23.8 mm and 24.9 mm. After introducing a deflection correction of 4.6 mm from the temperature change, when the condition was finally considered, the average gradient from the previous calibration measurement was used and the resulting temperature-corrected deflection was 29 mm, which was consistent with the model calculation. 6. Sensor monitoring As part of the structural rehabilitation, to check the correct functioning of the waterproofing and to check the stability of the critical parameters of the structure, a-monitoring system was set up on the lower upper surface of the structure, which collects, stores and remotely transmits data on concrete moisture measured by the resistivity method, on the strain on the lower and upper surface in the middle of the footbridge, on concrete moisture in the middle of the footbridge measured by the Rh method, on possible flooding of the water control pits and on the footbridge temperatures using the Geologer control panel. The system was commissioned during the summer of 2021 and has been sending data regularly since August 2021. The results so far confirm the assumption of increased water saturation of the concrete of the footbridge, where especially the Rh method data are in a state of full saturation, which occurs at an increased gravimetric moisture content of more than 8% despite the fact that visually the footbridge is completely dry. The flooding sensors immediately after installation and closure of the sumps indicated flooding likely from condensed water evaporating from the concrete, as of approximately November 2021 they indicate a dry condition. 7. Advanced Optical Techniques During the measurements, the concept of an optical system for static measurements of bridge structures was tested using the DIC (Digital Image Correlation) method, which allows to measure deformations of large objects based on natural features whose movement can be tracked with high accuracy in the image and thus analyze any deformation in the scanned image. 426 5. Brückenkolloquium - September 2022 Prestressed footbridge over Morava River in Kroměříž This method allows for an arbitrary position of the portable camera device in relation to the structure to be monitored the measuring setup. In this measurement, two measurement setups with different camera device concepts were tested. Measurements were taken from the underside of the bridge structure and also measurements from the side of the structure. Considering the measurement of a real engineering case, this method was tested to identify the advantages, disadvantages and pitfalls of optical measurements using DIC in different designs. Compensation elements are also an essential part of the concepts, recording unwanted movements of the measuring cameras. By knowing the unwanted changes in tilt or movement of the measuring camera, whether due to imperfect tripod stability or the influence of external weather conditions and vibrations, it is possible to compensate for these effects. Measurements from the underside of the bridge structure: The advantage of this measurement setup (Fig. 18) is the minimal distance from the bridge structure in terms of disturbances such as variable sunlight or optical air interference due to thermal changes over the water surface and banks. A complication of the setup is the wide range of the sensed angle and the resulting variable sensitivity of the measured deformations. The site under the bridge may be suitable for making measurements, but its availability lies primarily in the landscaping. Measurements from the bridge structure side: The advantage of this setup (Fig. 19) is the ability to measure the deflection of the bridge along its entire length, including the surrounding reference points on both sides of the bridge. A complication of this setup, however, is the larger measurement distance, which can magnify the surrounding thermodynamic effects and thus reduce the sensitivity of the measurements. This setup allows for a wider range of camera placement options around the bridge structure and is therefore more universal Fig. 19: Camera equipment and measurement view from the side of the bridge structure The graph in Figure 20 shows the record of the measurement run for 90 minutes. Two load cycles occurred during the measurement period and normal walking traffic was present on the footbridge as part of the disturbance. The measurements took place in the morning in full sunlight and throughout the measurement the bridge structure gradually warmed up as shown by the measured curves. Fig. 20: Optical deflection measurement record with two load cycles 8. Conclusion During 2018 to 2021, the footbridge in Kroměříž was diagnosed, strengthened, underwent structural restoration (Fig. 13) and is being rehabilitated to its original elegant form with an expected life extension of another 30 to 50 years. All diagnostic, analytical, calculation and design work was carried out by a team of authors from the Faculty of Civil Engineering, Brno University of Technology, Institute of Concrete and Masonry Structures [1], [2], [3]. They also carried out the author’s supervision during the strengthening of the footbridge and subsequently during its structural reconstruction. He installed the monitoring system himself and handed it over as a subcontract. The optical methods were provided by the company X-Sight s.r.o. Acknowledgements The experiment was funded with state support of the Technology Agency of the Czech Republic and the Ministry of Transport within the DOPRAVA 2020+ Programme, project No. CK01000042 “Upřesnění zbytkové únosnosti předpjatých mostů” (Specification of residual load-bearing capacity of prestressed bridges). References [1] Diagnostic survey of the footbridge over the Morava River in Kroměříž. Research report. FAST BUT Brno, AdMaS Centre, Brno, 2018 [2] KLUSÁČEK, L.; NEČAS, R.; KOLÁČEK, J., STRNAD, J., OLŠÁK, M., SVOBODA, A.; Construction modifications of footbridge ev. no. L07. Project DSP, PDPS, RDS. FAST BUT Brno, Ad- MaS Centre, Brno, 2018 [3] KLUSÁČEK, L.; NEČAS, R.; KOLÁČEK, J., STRNAD, J., OLŠÁK, M., SVOBODA, A.; Construction modifications of the footbridge ev. no. L07 construction renovation. Project DSP, RDS. FAST BUT Brno, AdMaS Centre, Brno, 2019