Ispitivanje ponašanja ovješenih mostova pod probnim opterećenjem

A field load testing is an effective method for understanding the behavior and fundamental characteristics of cable-stayed bridges. This paper presents results of the behavior of the reconstructed cable-stayed bridge over river Danube in Novi Sad under test load. The bridge was built between 1976 and 1981 and in 1999 was heavily damaged by two Tomahawk missiles. In 2003 process of the reconstruction began and at the end of 2005 Faculty of Civil Engineering, University of Belgrade was invited to test reconstructed bridge structure. The results of static load testing presented herein include displacements, rotations and strains of the 351 m long main span. Vibrations of the bridge were obtained by impact load produced by heavy truck passing the bridge and the time history response of vertical accelerations was recorded. The frequency content of the signals was determined using Fourier transformation and five flexural natural periods were extracted. The geological structure and engineering properties of the soil are also given. A finite element model of the bridge was made and a good agreement is achieved between the experimental and analytical results. These results have shown that the bridge is in the elastic state under the code-specified serviceability load, which indicates that the bridge has adequate load-carrying capacity and can be put safely into service.Ispitivanje ovješenih mostova opterećenih probnim opterećenjem je efikasan način za sagledavanje ponašanja i određivanje glavnih karakteristika takvih mostova. Ovaj rad prikazuje ponašanje rekonstruiranog ovješenog mosta preko Dunava u Novom Sadu. Most je izgrađen između 1976. i 1981. godine, a 1999. godine bio je teško oštećen kada su ga pogodile dvije Tomahawk rakete. Godine 2003. počela je rekonstrukcija mosta, a krajem 2005. godine Građevinski fakultet Sveučilišta u Beogradu bio je pozvan ispitati rekonstruiranu konstrukciju mosta. U ovom radu prikazani su rezultati koji se odnose na pomake, rotacije i deformacije glavnog nosača konstrukcije duljine 351 m. Vibracije mosta izazvane su udarnim opterećenjem uslijed prolaska teškog kamiona preko mosta, pri čemu su određena vertikalna ubrzanja glavnog nosača. Potrebne funkcije u frekventnoj domeni određene su primjenom Fourier-ove transformacije i na taj način je izdvojeno prvih pet perioda osciliranja. U radu su prikazane geološke karakteristike terena. Formiran je numerički model mosta na bazi metode konačnih elemenata i dobiveno je dobro slaganje eksperimentalnih i numeričkih rezultata. Ovi rezultati pokazuju da se most ponaša elastično pod utjecajem probnog opterećenja, što ukazuje da konstrukcija ima odgovarajuću nosivost i da se sigurno može pustiti u promet

Assessment of Liquefaction Potential Relevant to Choice of Type and Depth of Foundations in Seismically Active Areas

There is evidence of great increase of pore pressures in saturated sand soils during cyclic loading caused by earthquakes. These increased pore pressures can often increase to effective stresses in soil. Dependant on sand density, this can lead to a total loss of shear strength, liquefaction or greater deformability of soil. Emergence of liquefaction or great deformations within soil can cause significant damage or total destruction of constructions on the ground, even when they have been correctly designed. For this reason, it is very important to perform detailed geotechnical and seismic investigations of ground conditions and evaluate liquefaction potential for saturated sand soil in seismically active terrain. It is not possible to design stable constructions in certain types of terrain without the analyses of liquefaction potential. This paper refers to the comparative cost-analyses of two possible ways of the foundations of the business complex: shallow foundations with stabilization of potentially liquefiable sand deposit using vertical gravel drains versus deep pile foundation on unliquefiable soil

Effect of initial conditions on strength of unsaturated compacted loess soil

U radu je prikazan utjecaj granulometrijskog sastava, početne vlažnosti, suhe zapreminske težine i veličine kapilarnog usisa na uvećanu čvrstoću smicanja nezasićenog zbijenog prašinastog lesnog tla. Čvrstoća nezasićenog tla je određena na osnovi eksperimentalno ispitanih ovisnosti vlažnost-kapilarni usis i efektivnih parametara čvrstoće smicanja zasićenog tla, c’, ’. Pokazano je da s povećanjem veličine zrna u tlu, opada utjecaj kapilarnog usisa, vlažnosti i suhe zapreminske težine na čvrstoću nezasićenog zbijenog tla.The influence of grain size distribution, initial moisture, dry bulk density, and capillary suction on an increase in shear strength of unsaturated compacted silty loess soil is presented in the paper. The unsaturated soil strength is determined via the experimentally determined dependencies between the moisture-capillary suction and the effective shear strength parameters for saturated soil, c’, ’. It is demonstrated that the influence of capillary suction, moisture and dry bulk density on the strength of unsaturated compacted soil reduces with an increase of grain size in soil

Geotehnički uzroci oštećenja Doma Narodne skupštine u Beogradu

The Parliament building of the Republic of Serbia is one of the biggest and most beautiful cultural monuments in Serbia from the first half of 20th century. Right now, there are numerous structural damages over the building. In order to define remedial measures for rehabilitation of the Parliament building, it was necessary to carry out detailed geotechnical investigations. These investigations were performed by the Faculty of Mining and Geology, University in Belgrade. Thus, geotechnical properties of the terrain in a zone of its interaction with the building were defined according to the obtained results. The bearing capacity of foundation soil and settlements of footings were calculated, too. These analyses showed that the existing footings loads values are less than allowable values, but the settlements of footings are much larger than it is allowable, and it is a main reason of the structural damages over the building. The settlements were determined by two methods: conventional and finite element. The obtained values are very close. In addition, by the finite element analysis it was concluded that the building has no resistance to the effects of earthquakes. Remedial measures were proposed on the basis of these results, and in cooperation with engineers responsible for rehabilitation of the structure. These measures permanently solve the problems related to the static and dynamic stability of the Parliament building from the geotechnical point of view.Dom Narodne skupštine je jedan od najznačajnijih spomenika kulture u Srbiji iz prve polovine dvadesetog veka. Na njemu su uočena brojna oštećenja i u cilju njegove sanacije bilo je neophodno izvođenje detaljnih geotehničkih istraživanja koja je izvršio Rudarsko-geološki fakultet Univerziteta u Beogradu. Ovim istraživanjima definisana su geotehnička svojstva terena u zoni njegove interakcije sa objektom, a određena su i sleganja temelja i nosivost temeljnog tla. Utvrđeno je da su stvarna opterećenja temelja manja od dozvoljenih, ali da su sleganja temelja višestruko veća od dopuštenih i da je to glavni uzrok oštećenja objekta. Ova sleganja su određena konvencionalnom metodom i metodom konačnih elemenata i dobijeni su slični rezultati. Osim toga, analizom sa konačnim elementima, utvrđeno je i da objekat ne zadovoljava uslove stabilnosti u slučaju dejstva zemljotresa. Stoga su, u saradnji sa projektantom sanacije objekta, predložene sanacione mere koje sa geotehničkog aspekta trajno rešavaju probleme kako statičke tako i dinamičke stabilnosti Doma Narodne skupštine u Beogradu

Geotehnički uzroci oštećenja Doma Narodne skupštine u Beogradu

The Parliament building of the Republic of Serbia is one of the biggest and most beautiful cultural monuments in Serbia from the first half of 20th century. Right now, there are numerous structural damages over the building. In order to define remedial measures for rehabilitation of the Parliament building, it was necessary to carry out detailed geotechnical investigations. These investigations were performed by the Faculty of Mining and Geology, University in Belgrade. Thus, geotechnical properties of the terrain in a zone of its interaction with the building were defined according to the obtained results. The bearing capacity of foundation soil and settlements of footings were calculated, too. These analyses showed that the existing footings loads values are less than allowable values, but the settlements of footings are much larger than it is allowable, and it is a main reason of the structural damages over the building. The settlements were determined by two methods: conventional and finite element. The obtained values are very close. In addition, by the finite element analysis it was concluded that the building has no resistance to the effects of earthquakes. Remedial measures were proposed on the basis of these results, and in cooperation with engineers responsible for rehabilitation of the structure. These measures permanently solve the problems related to the static and dynamic stability of the Parliament building from the geotechnical point of view.Dom Narodne skupštine je jedan od najznačajnijih spomenika kulture u Srbiji iz prve polovine dvadesetog veka. Na njemu su uočena brojna oštećenja i u cilju njegove sanacije bilo je neophodno izvođenje detaljnih geotehničkih istraživanja koja je izvršio Rudarsko-geološki fakultet Univerziteta u Beogradu. Ovim istraživanjima definisana su geotehnička svojstva terena u zoni njegove interakcije sa objektom, a određena su i sleganja temelja i nosivost temeljnog tla. Utvrđeno je da su stvarna opterećenja temelja manja od dozvoljenih, ali da su sleganja temelja višestruko veća od dopuštenih i da je to glavni uzrok oštećenja objekta. Ova sleganja su određena konvencionalnom metodom i metodom konačnih elemenata i dobijeni su slični rezultati. Osim toga, analizom sa konačnim elementima, utvrđeno je i da objekat ne zadovoljava uslove stabilnosti u slučaju dejstva zemljotresa. Stoga su, u saradnji sa projektantom sanacije objekta, predložene sanacione mere koje sa geotehničkog aspekta trajno rešavaju probleme kako statičke tako i dinamičke stabilnosti Doma Narodne skupštine u Beogradu

Application of 3D slope stability analysis in defining the excavation conditions of coal at the open pits

Three-dimensional slope stability analysis has many advantages over the two-dimensional (2D), primarily due to more realistic view of slope geometry and slip surface, and involving side force resistance in the slope. Because of that in the paper, based on numerous 2D stability analyses applying the Morgenstern-Price method, critical slip surfaces were determined and 3D safety factors for them, involving the lateral resistance on the sides of linear lamellas excavation, were defined. Based on 3D stability analyses the zone excavation was proposed and width of slice excavation and safe distance from the front part of the slope were defined for each zone. The size of safety factor, obtained from comparative 2D and 3D stability analysis, clearly show that if 3D conditions were realized during excavation, as is the case with linear lamellas excavation, then much greater quantity of coal can be mined than when excavation is done in 2D stability conditions

3D terrestrial laser scanning and GPS technology for slope stability investigations - case studies

As the rapid adoption of new technologies for landslide and rock slope engineering continues - the natural evolution of equipement for landslide mapping and monitoring has started. The technological evolution of LIDAR (Light Detection And Ranging) system creates the potential for automated remote collection of accurate, high resolution data and represents step foreward that will increase speed, precision, cost effectivenes and overall quality of geotechnical investigations. This paper presents features and benefits of introducing relatively new approach in order to provide quality plans as a base for detailed geotechnical investigations

Water retention parameters and sediment dispersivity of the Zemun loess plateau (Belgrade, Serbia)

The paper presents the results of recent investigations of the Zemun Loess Plateau, which focused on unsaturated and dispersive loess soil. Soil water retention curves, SWRCs, were determined experimentally, using a pressure plate apparatus for suction values of up to 1500 kPa, according to ASTM(1). Soil dispersivity was determined by means of the double hydrometer test, crumb test and pinhole test according to BS2 and ASTM1. The tests were carried out on samples of loess soil with different grain-size distributions, as well as natural and artificially prepared samples with different degree of compaction. The results of the study confirm that an indirect correlation can be established between SWRC parameters and soil dispersivity. Soil dispersivity increased with increasing soil entry values (u(a) - u(w))(b) and the residual degree of saturation S-res, and decreased with decreasing coefficient lambda. The air entry value and residual degree of saturation increased and the desaturation rate decreased with increasing proportions of the clay-size fraction. Soil compaction appears to have a greater effect on SWRC parameters than on soil dispersivity. The air entry value increased, but coefficient lambda. decreased with increasing density. Loess soil dispersivity tends to depend more on the chemical and mineral composition. Soils with more sodium and clay minerals are more dispersive

Investigation of Vibration Caused by Traffic and Railway Load

Two examples related to the investigation of vibrations in civil engineering structures are presented. In the first example, it is shown how it is possible to decrease vibration in underground structures. These vibrations are caused by train load. It is shown by the results of the presented dynamic analysis that the use of special elastomer is very important in engineering practice in order to decrease structural vibrations. The second example presents the foundation for special equipment - eletronic balances, which are very sensetive, even to small displacement. Presented dynamic analysis is related to the vibrations caused by heavy traffic load in order to obtain optimum foundation solution

Investigation of Vibration Caused by Traffic and Railway Load

Two examples related to the investigation of vibrations in civil engineering structures are presented. In the first example, it is shown how it is possible to decrease vibration in underground structures. These vibrations are caused by train load. It is shown by the results of the presented dynamic analysis that the use of special elastomer is very important in engineering practice in order to decrease structural vibrations. The second example presents the foundation for special equipment - eletronic balances, which are very sensetive, even to small displacement. Presented dynamic analysis is related to the vibrations caused by heavy traffic load in order to obtain optimum foundation solution