Flood and post flood performance of historic stone arch

Flood And Post Flood Performance Of Historic Stone Arch-Free PDF

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164 ARCH 07 5th International Conference on Arch Bridges. interpreted more or less appropriately Also the data on the height of water during the flood. culmination are usually well documented in situ on different types of high water line records. Table 1 Review of the oldest European medieval stone arch bridges Velfl k 1921. City Years of Number Comments on technical features and flood damages. construction of arches,Toledo 996 2,Albi 1035 1178 7. Palermo 1113 5,Dresden 1119 1206 16, W rzburg 1133 The bridge was heavily destroyed during 1342 flood. Regensburg 1135 1146 15 The 336 m long bridge has never been substantially. destroyed by high water even though a massive ice block. and flood in 1784 destroyed two timber bridges repairing. damaged built in 1633 or missing built in 1499 1502 parts. of the bridge, Prague 1169 1171 23 The bridge had in the river 12 arches of span between 12 3. 19 8 m It was severely damaged during 1342 flood,Avignon 1177 1188. Figure 1 Historic high water line scale in Limburg Germany on the Lahn River Photo T Drd ck. Let us illustrate a typical life of a medieval bridge by several historical examples An ancient. bridge in Prague across Vltava Moldau river was built from timber in 795 and it was. destroyed by flood several times in the 9th Century in 935 929 when the body of St. Wenceslas was transported across it Cristiane chronicle in 1118 due to high water about 3. me above the bridge deck Cosmas chronicle and lastly in 1159 then a stone masonry bridge. was built by the Queen Judith, The Queen Judith s bridge in Prague successfully survived heavy floods in 1180 1257 1259.
1264 1273 1311 1315 1316 and 1322 probably with minor damages only But the high water. on the 12th March 1272 with a lot of ice broke through the bridge in the middle of the river. Moldau Dobner The damage had been so large that the bridge managers the Knights of. the Cross Hospitaliers monastery had to collect a special tax approved by the King P emysl. Otakar II throughout the kingdom Tomek 1855 Eventually an ultimately destroying flood. had happened in night on the 3rd February 1342 when a large mass of ice had caused a collapse. of about two thirds of the bridge that then never had been repaired and replaced later by the. famous Charles Bridge, The second oldest Bohemian bridge in P sek was built about the year 1265 Even though the. bridge had been attacked several times with severe floods his six from seven originally erected. M F Drd ck and Z Sl kov 165, piers and arches never collapsed The 1342 disastrous flood destroyed the spandrel walls the top. of which reached 5 5 meters above the normal water level In February 22nd 1768 ice floes. partly destroyed cutwaters of three piers during a splash flood and one land pier with the. adjacent vault collapsed Few years later 27th February 1784 two central piers were heavily. damaged and undermined Two other significant high water events in 1845 and 1890 when. water entirely filled the profile of arches did not cause major damage. The Charles bridge in Prague in the row of large medieval bridges being the fourth in. Bohemia and the thirty first in Europe was founded on July 9th 1357 Even the partially built. bridge was damaged by large floods in 1359 1367 1370 1373 and 1374 The most serious. damage was caused by a catastrophic flood in 1432 21st July when the huge mass of floating. material blocked all bridge arches with hay timber and even wooden houses The created dam. obstructed free flow of water which substantially elevated the high water line and contributed to. destructive undermining of five piers with a subsequent collapse The damage increased another. flood in January 28th 1496 when further pier with two adjacent arches had failed which was. repairing till 1503 After another heavy damage in 1655 three bridge piers had to be partly. rebuilt as a consequence of a strong flood on 28th February 1784 Figure 2 The last partial. collapse of the Charles Bridge occurred in 1890 when again a huge amount of timber blocked. the water way and after undermining of two other piers the bridge arches fell into water on three. places Thus only one pier and one arch from the original medieval Charles bridge structure. have remained after the above mentioned damages and failures. From these examples it follows that flooding is a natural and quite frequent loading situation. for historic stone arch bridges A detailed evaluation of the Lahn River water gauge shows that. in the years 1255 1984 the bridges suffered 60 floods 22 of them major i e in average a flood. in every 12 years Naturally the major and namely catastrophic floods represent exceptional. loads for such bridges with specific features and a strongly destroying action. The large stone bridges mostly sustained the static as well as dynamic pressure loads of water. provided they were not combined with other loads ice timber or with occurrence of dams and. barriers piled up from floating material which changed the water flow and caused problems to. foundations Small usually timber or improperly maintained bridges inclined to collapse totally. which has been referred to in several cases For example the flood on Curych Lake in 1778. July 8th caused besides 63 fatalities also a total destruction of 15 houses and 8 bridges. Swissworld 2007, However the modern time changed the flood loads compared to the historic ones First there. is practically no timber floating in large amounts in the rivers because of stopping the transport. and water treatment of logs in rafts Also the ice does not represent so high hazard as before due. to increased temperature of water in most rivers and thanks to a better control and tools for. early removal of cumulating barriers On the other hand the floating cottages and garden houses. are usual and during the 2002 flood there occurred also lorries containers and steel boats which. all have a quite high mass and energy at impacting into a historic bridge Fig 2 Further the. water has a higher chemical contamination which creates specific conditions for chemical. degradation and biological attacks, Figure 2 Floating lorry and a container at a foot bridge in Prague Troja during the flood in 2002. 166 ARCH 07 5th International Conference on Arch Bridges. 2 STRUCTURAL DAMAGE AND FAILURES DUE TO FLOODING,2 1 Failure of foundations.
The undermining of foundations of piers inside a river as well as on the banks were the most. recorded failures observed at large historic bridges during disastrous floods They mostly. occurred in situations when the water way under the arches was obstructed by floating barriers. from ice wood or other materials and objects Then the stream along the river bed has a higher. speed and turbulences which wash out the subsoil layers and undermine the piers The bridges. founded on piles or directly on rock usually have less heavy damages that those standing. directly on gravel without piled grids unless they were provided with protective walls which. has been adopted for all recent repairs, Foundations of light small bridges can suffer from uplift forces that was the case of a short. romantic stone arch bridge in the park of the castle at Veltrusy during the 2002 flood Fig 3. Here flooding destroyed a dike around a water channel which partially served also as a. balancing ballast for the stability of a bridge pavilion which partially collapsed. Figure 3 Left bridge pier was uplifted during flooding and damaged by wide cracks. 2 2 Typical damages on piers, The cutwaters were extremely loaded namely by ice friction Even the ashlars mutually jointed. with iron clamps were pulled out from the structure and the cutwaters had to be repaired almost. after all spring floods There are recorded needs for a remedial walling up of a partially failed. cutwater masonry e g in P sek in 1768, Failure of piers is closely connected with foundation subsidence or rotation due to the above. mentioned undermining They usually do not collapse entirely but their tilting might be so. expressive that they have to be rebuilt in order to serve as a support to the arched vaults A. typical case is demonstrated in Fig 4 the Charles Bridge in Prague after the 1890 flood. In some cases water penetrates behind the bridge abatements and can cause failure of land. piers as happened in P sek in 1768 where the left land pier collapsed and caused a partial. collapse of a bridge tower accompanied with fatal injuries. 2 3 Failure of arches, The arches have a quite high load carrying capacity for vertical loads but they are very sensitive. to any support movement The strength of arches is substantially influenced by the height of. M F Drd ck and Z Sl kov 167, spandrel walls which has been proved during full scale experiments on British arch bridges.
Harvey 2007 namely when strengthened with sufficiently thick and integrated parapet walls. Therefore under usual situations the arches sustain very well even high vertical loads. Figure 4 The Charles Bridge in Prague after a catastrophic flood in 1890 photo J Eckert. Unfortunately during severe floods the parapet walls usually do not resist the load and fall on. the bridge deck which simultaneously increases the load and decreases the load carrying. capacity of the arches Altogether with the high water and ice loading a tilting and subsidence. of the undermined piers mostly cause the collapse of vaults The safety of arches is further. decreased by their water uplift which reduces the stabilizing compressive stresses in the vaults. The situation is worsen by many defects and namely cracks in the vaults due to long term. cyclic deformations from moisture and temperature fluctuations J ger Witzany 2005. 2 4 Failure of parapet walls, Historic parapet walls were usually quite high because they were used for defending activities. too For example the Queen Judith s bridge had parapet or breast walls of 2 meters high and. 30 cm thick the original Charles Bridge then of 160 cm high At very heavy floods the water. line reaches levels pretty high above the bridge deck and the parapet walls are too weak to. sustain such a dynamic pressure In Fig 5 we can follow a typical case of collapsed parapet. walls bridge in P sek 2007 Here the wall ashlars were saved after the flood from the river. Figure 5 The medieval bridge in P sek during high water left and the view of destroyed parapet. walls after the flood right Photo Wikipedia, 168 ARCH 07 5th International Conference on Arch Bridges. 3 NON STRUCTURAL DAMAGE AFTER FLOODING, Non structural damage of stone arch bridges after flood situations include mainly the increased. moisture contents problems of drying accompanied with efflorescence of salts and biological. attack of wet surfaces which is further influenced by high contamination of high water. Biological colonization of stone bridges is very rich and divers owing to different nutrition. conditions environmental conditions and their fluctuations The flooding temporarily changes. these conditions and a study of history of biotic colonization of stone bridges after the 2002. flood has shown that real situations can substantially differ from the expected scenarios. Wasserbauer 2003 The predicted danger of a massive distribution of moulds was after the. flood blocked and delayed by different species of bacteria that colonized the flooded materials. within the earliest 24 hours This bacterial microfilm on the surface was even resistant to. majority of disinfection means aimed to extirpate higher organisms As long as after remarkable. decrease of moisture in materials the bacteria were gradually replaced by colonies of moulds. and other organisms typical for wet environments, A detailed analysis of salt efflorescence was carried out on a small sandstone ashlar bridge in. the castle at Veltrusy The efflorescence which appeared more than two years after the flood. was intensive in thin cracks between the stone blocks and mortar joints even though it covered. also other parts of the masonry Fig 6 The salts have been analyzed by the semi quantitative. method XRD and a mixture of the Na3H CO3 2 2H2O and the Na2CO3 H2O in an approximate. ration of 1 1 has been mostly discovered Further the salts K3Na SO4 2 and Na2SO4 have been. identified in lesser concentrations in samples taken from the stone surface During the flood the. bridge building material was leached by the percolation and the salts crystallized from the. mineralized water on the surface thanks to a slow drying of the bridge The salts carbonated. reacting with the aerial CO2 Infill material above the vault Portland cement in repair mortars. and former conservation of masonry with water glass are supposed to be possible sources of the. identified alkali and sulfates High crystallization pressures can damage building materials. therefore the structure should dry slowly in order to accumulate salts on the surface from where. they should be regularly removed It is further recommended to check a subsurface salt content. and if appropriate to carry out desalination procedures on the masonry. Figure 6 Salts effloresced on a bridge arch surface more than two years after the flood. 4 MONITORING OF DAMAGES AFTER FLOOD, The small pavilion bridge shown in Fig 3 exhibited wide cracks after the high water relief The.
natural restitution of foundations as well as changes from remedial works have been monitored. since 2002 Three independent quantitative measurement systems have been installed i a set of. had happened in night on the 3rd February 1342 when a large mass of ice had caused a collapse of about two thirds of the bridge that then never had been repaired and replaced later by the famous Charles Bridge The second oldest Bohemian bridge in P sek was built about the year 1265 Even though the bridge had been attacked several times with severe floods his six from seven originally erecte

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