Punching of column footings - comparison of experimental and calculation results

Proboj stupa kroz ploču najčešće se vezuje za međukatne konstrukcije, rjeđe i za ploče temelja samaca ispod stupova. Proračunski modeli za ova dva problema često nisu razdvojeni. Zbog nedostatka eksperimentalnih rezultata na temeljima, primjenjuju se modeli za međukatne ploče. U radu je prikazan pregled literature o teorijskim i eksperimentalnim istraživanjima i propisi za proračun proboja stupa kroz ploču. Opisan je program eksperimentalnih istraživanja i njegova realizacija. Dobiveni rezultati uspoređeni su s rezultatima proračuna prema različitim propisima. Dane su preporuke i naznačene smjernice budućih istraživanja.The column punching through the slab is most often related to floor structures, and less often to foundation slabs under columns. Calculation models for these two problems are often not separated. The deficit of experimental results for column footings results in the use of floor slab models. A review of the theoretical and experimental research references, including Codes/Regulations for punching calculation of column footings, is presented in the paper. The experimental research program and its implementation is described. The results obtained are compared with calculation results based on various regulations. Recommendations and directions for future research are outlined

Dynamic Analysis of a Deeply Buried Tunnel Influenced by a Newly-built Adjacent Cavity with a Special Emphasis on the Minimum Seismically Safe Tunnel Distance

Contemporary life streams, more often than ever, impose the necessity for construction of new underground structures in the vicinity of existing tunnels, with an aim to accommodate transportation systems and utility networks. A previously uninvestigated case, in which a newly-constructed tunnel opening is closely positioned behind an existing tunnel, referred to as the tunnel–cavity configuration, has been considered in this study. An exact analytical solution is derived considering a pair of parallel circular cylindrical structures of infinite length, with the horizontal alignment, embedded in a boundless homogeneous, isotropic, elastic medium and excited by time-harmonic plane SV-waves under the plane-strain conditions. The Helmholtz decomposition theorem, the wave functions expansion method, the translational addition theorem for bi-cylindrical coordinates, and the pertinent boundary conditions are jointly employed in order to develop a closed-form solution of the corresponding boundary value problem. The primary goal of the present study is to examine the increase in dynamic stresses at an existing tunnel structure due to the presence of a closely driven unlined cavity, as well as in a localized region around the tunnel (at the position of the cavity in close proximity), under incident SV-waves. A new quantity called dynamic stress alteration factor is introduced and the aspect of the minimum seismically safe distance between the two structures is particularly considered

COMPARATIVE ANALYSIS OF ATTERBERG’S LIMITS OF FINE-GRAINED SOIL DETERMINED BY VARIOUS METHODS

Determination of the Atterberg’s limits is necessary for the classification of fine-grained soil. That limits can be determined according to the valid standard SRPS EN ISO 17892-12. Two methods are prescribed by the standard for determining the liquid limit: the Casagrande cup and the Fall Cone test, and one method for determining the plasticity limit: the thread-rolling method. In this paper the Fall Cone method was also used as an alternative method to determine the plastic limit. Ten samples of various fine-grained materials, originating from the wider area of the city of Niš, were tested. The classification of all samples was performed based on the results obtained by the methods prescribed by the standard and alternative methods. Comparative analysis shows that the results obtained by applying standard and alternative methods are close, but also that the scattering of results obtained by the Fall Cone method is significantly less, whereas the reproducibility is higher

Technical conditions concerning the quality of shallow foundations material according to en and BAB87

Građevinske konstrukcije su tokom svog životnog veka izložene različitim agresivnim uticajima koji izazivaju njihovu degradaciju i smanjuju trajnost. Kada su u pitanju konstrukcije od armiranog betona, istraživanja su pokazala da se problem njihove trajnosti može svesti na probleme degradacije betona i armature u betonu. U radu je najpre ukratko data analiza agresivnih uticaja, a zatim predstavljene mere za sprečavanje degradacije betona i armature kod plitkih temelja. Posebna pažnja je poklonjena određivanju zaštitnog sloja betona temelja i proračunu temelja na osnovu graničnih stanja upotrebljivosti. Dat je paralelan prikaz ovih mera prema našem Pravilniku (BAB 87) i Evropskim normama (EN - Evrokod 2). .Engineering structures during their service life are exposed to a variety of aggressive actions causing their degradation and reducing durability. In reinforced concrete structures, the problem of their durability can be reduced to concrete and reinforcement degradation problem. In the paper, an analysis of aggressive influences was given, and then measures for prevention of concrete and reinforcement degradation in shallow foundations. Special attention was paid to the determination of the protective layer of foundation concrete and the calculation of the foundation on the basis of limit states of serviceability. A parallel presentation of these measures was provided, according to the national code (BAB 87) and European norms (EN - Eurocode 2)

Punching of column footings -comparison of experimental and calculation results

The column punching through the slab is most often related to floor structures, and less often to foundation slabs under columns. Calculation models for these two problems are often not separated. The deficit of experimental results for column footings results in the use of floor slab models. A review of the theoretical and experimental research references, including Codes/Regulations for punching calculation of column footings, is presented in the paper. The experimental research program and its implementation is described. The results obtained are compared with calculation results based on various regulations. Recommendations and directions for future research are outlined. Proboj temelja samaca -usporedba proračuna i eksperimenta Proboj stupa kroz ploču najčešće se vezuje za međukatne konstrukcije, rjeđe i za ploče temelja samaca ispod stupova. Proračunski modeli za ova dva problema često nisu razdvojeni. Zbog nedostatka eksperimentalnih rezultata na temeljima, primjenjuju se modeli za međukatne ploče. U radu je prikazan pregled literature o teorijskim i eksperimentalnim istraživanjima i propisi za proračun proboja stupa kroz ploču. Opisan je program eksperimentalnih istraživanja i njegova realizacija. Dobiveni rezultati uspoređeni su s rezultatima proračuna prema različitim propisima. Dane su preporuke i naznačene smjernice budućih istraživanja

FINITE DIFFERENCE METHOD APPLICATION IN DESIGN OF FOUNDATION GIRDER OF VARIABLE CROSS-SECTION LOADED ON ENDS

Abstract. Deflection of foundation girder supported by the deformable base has been defined by the system of differential equations, where the differential equation of the elastic line of the girder is of the fourth order. The most convenient solution of the problem is application of numerical procedures, in this case it is the finite difference method. In the paper, the mentioned method is applied in the special case of foundation girder of variable cross section loaded by arbitrary load on its ends. Key words: foundation girder, finite differences method, matrix equation, load 1

DEPENDENCE OF THE BASIC DYNAMIC PARAMETERS ON THE DISTURBING FORCE OF THE IMPACT IMPULSE TYPE WITH DIFFERENT FORMS

Abstract. In the modern civil engineering design, especially in the field of machine foundations, the dynamic actions in the form of the impulse load that is short-term, high intensity loads are very frequent. When an acting force, during a short time interval remains constant, the impulse is of a rectangular form, as opposed to the trapezoid, triangular, parabolic and sinusoid form, with defined time of increase and decrease of the load. This paper considers the influence of the form of the impact impulse load on the dynamic response of the foundation structure, without changing the remaining parameters. Key words: impulse load, form of the impulse, foundation, dynamic response. 1

SAVREMENE METODE ZAŠTITE TLA I VODE OD UTICAJA ŽELEZNIČKOG SAOBRAĆAJA

One of the basic assignments of modern society is preserving the quality of freshwater resources, especially drinking water. Line facilities potentially pose a higher risk to the environment due to the large length of the extension and the diversity of the environment they may affect. Storm water drained from railway could pollute the surrounding land besides railway track.  Based on the data from available research, it has been determined that heavy metals (iron, copper, zinc, manganese and chromium), polycyclic aromatic hydrocarbons (PAHs) and herbicides stand out in significant quantities from substances hazardous to the environment. This paper proposes the solutions using some self-sustainable techniques, based on the analysis railway drainage needs. The proposals that have been made refer to the open-air railway and railway station.Jedan od osnovnih zadataka savremenog društva je očuvanje kvaliteta slatkovodnih resursa, posebno vode za piće. Linijski objekti potencijalno predstavljaju veći rizik po životnu sredinu zbog velike dužine prostiranja i raznovrsnosti okoline na koju mogu uticati. Atmosferske vode koje se odvode sa trupa železničke pruge mogu zagaditi i površine u neposrednoj blizini. Prema dostupnim istraživanjima, od materija opasnih po životnu sredinu u značajnim količinama izdvajaju se teški metali (gvožđe, bakar, cink, mangan i hrom), policiklični aromatični ugljovodonici (PAHs) i herbicidi. U radu su predložena neka od rešenja samoodrživih tehnologija, a na osnovu analize potreba pri odvodnjavanju trupa železničkih pruga. Predlozi koji su dati, odnose se na prugu na otvorenom i železničku stanicu

MATEMATIČKA INTERPRETACIJA RASIPANJA I REFRAKCIJE SEIZMIČKIH TALASA U PRISUSTVU TUNELSKIH OBJEKATA KRUŽNOG POPREČNOG PRESEKA

Mathematical interpretation of the elastic wave diffraction in circular cylinder coordinates is in the focus of this paper. Firstly, some of the most important properties of Bessel functions, pertinent to the elastic wave scattering problem, have been introduced. Afterwards, basic equations, upon which the method of wave function expansions is established, are given for cylindrical coordinates and for plane-wave representation. In addition, steady-state solutions for the cases of a single cavity and a single tunnel are presented, with respect to the wave scattering and refraction phenomena, considering both incident plane harmonic compressional and shear waves. The last part of the work is dealing with the translational addition theorems having an important role in the problems of diffraction of waves on a pair of circular cylinders.U fokusu ovog rada je interpretacija difrakcije i rasipanja seizmičkih talasa u polarno-cilindričnim koordinatama primenom odgovarajućeg matematičkog aparata. U radu je najpre dat pregled nekih od najznačajnijih svojstava cilindričnih Bessel-ovih funkcija, koje su podesne za matematičko opisivanje problema difrakcije i rasipanja seizmičkih talasa. Takođe, dat je prikaz jednačina koje predstavljaju osnovu tzv. metode ekspanzije talasnih funkcija (wave function expansion), u polarno-cilindričnim koordinatama i za slučaj seizmičkih talasa sa ravnim frontom. Prikazana su i rešenja primenom metode ekspanzije talasnih funkcija za slučaj nepodgrađenog tunelskog otvora i slučaj podgrađenog tunelskog objekta, sa aspekta fenomena rasipanja i refrakcije seizmičkih talasa, pod uticajem incidentnih harmonijskih P-talasa i S-talasa sa ravnim frontom. Na kraju rada prezentovane su i teoreme translatornog sabiranja (translational addition theorems), koje imaju važnu ulogu u matematičkom rešavanju problema difrakcije i rasipanja seizmičkih talasa u prisustvu dva blisko položena tunelska objekta

PREDLOG MODIFIKACIJE EVROKODA 2 U POGLEDU PRORAČUNA NOSIVOSTI AB TEMELJA SAMACA NA PROBIJANJE

The paper first presents the calculation of the punching shear capacity of concentrically loaded reinforced concrete column footings according to the current Eurocode 2, which can be carried out in two ways: by conducting an iterative procedure and by a simplified procedure applying the diagrams. By using these procedures, the punching shear capacity calculation was performed for the footings examined within the experimental research of the authors of this study, as well as for the footings that were considered by experiments conducted by other authors. Based on the conducted analysis of the calculation results and experimentally recorded results, a modification of the expression of the current Eurocode 2 with regard to the calculation of the punching shear capacity of concentrically loaded RC column footings is proposed. The proposed modification more realistically takes into account the influence of compressive strength of concrete and the reinforcement ratio  in the footing, so that its application provides the results of punching failure forces that are closer to the results recorded by experimental tests.U radu je najpre predstavljen proračun nosivosti centrično opterećenih armiranobetonskih temelja samaca na probijanje prema aktuelnom Evrokodu 2, koji se može sprovesti dvojako: sprovođenjem iterativnog postupka i primenom zamenjujućih dijagrama. Primenom ovih postupaka, urađen je proračun nosivosti pri probijanju za temelje ispitivane u okviru sopstvenih eksperimentalnih istraživanja, kao i za temelje koji su bili sagledani  eksperimentima sprovedenim od strane drugih autora. Na osnovu sprovedene analize rezultata proračuna i eksperimentalno registrovanih rezultata, predložena je modifikacija izraza aktuelnog Evrokoda 2 u pogledu proračuna nosivosti centrično opterećenih AB temelja samaca na probijanje. Predložena modifikacija realnije uzima u obzir uticaj čvrstoće na pritisak betona i procenta armiranja temelja, tako da se njenom primenom dobijaju rezultati sila probijanja koji su bliži rezultatima registrovanim tokom eksperimentalnih ispitivanja