Comparative nonlinear analysis of a RC 2D frame soil-pile interaction

U radu je sprovedena komparativna nelinearna statička (NSA) i nelinearna dinamička analiza (NDA) seizmičkog ponašanja rama kao dela skeletne konstrukcije AB zgrade fundirane na šipovima. Da bi se dobila realnija slika ponašanja ramovske konstrukcije u analizu je uključena interakcija konstrukcija - temelj - tlo. Pri tome u proračunski model je uključena i linearno-nelinearna dinamička interakcija šip-tlo korišćenjem link elemenata. Konstrukcija temelja sastoji se od bušenih šipove prečnika 60cm. Tlo je modelovano sa više (linijskih) plastičnih veznih elemenata, kao p-y krivama, sa obe strane šipa, za potopljen krut pesak, i uz pretpostavku da p-y krive (eksperimentalno određene nelinearne krive zavisnosti: pomeranje/pritisak, u tlu po dubini šipa) primaju samo pritisak. Analizom je ukazano na probleme, koje prate izdvajanje 2D ramova kao reprezenta regularne prostorne 3D konstrukcije. Proučen je uticaj pojave i lokacije pojedinih plastičnih zglobova na seizmičke performanse analiziranog konstruktivnog sistema, i analizirana relativna spratna pomeranja (driftovi). Zaključeno je da se analizom 2D rama u interakciji sa temeljom i tlom, mogu dobiti dovoljno tačni rezultati ponašanja i ocene seizmičkih performansi skeletne AB višespratne zgrade. To je značajno jer uvođenje prostorne konstrukcije u ovakve analize je veoma kompleksno i zahtevno.Comparative non-linear static (NSA) and non-linear dynamic analyses (NDA) of 2D frames (as parts of skeletal 3D structures) of RC buildings founded on piles are presented in this paper. In order to produce a more realistic presentation of behaviour of a frame structure, the analysis involves a structure-foundation-soil interaction. Also, the model involves a linear-non-linear dynamic pile-soil interaction, using link elements. The foundation consists of drilled piles having 60 cm in diameter. The soil is modelled using Multi-linear plastic link elements, as well as with p-y curves, on both sides of the pile, assuming that p-y curves transfer only compression (p-y curves are experimentally determined non-linear relationships of displacement/pressure in soil, along the depth of a pile). The analysis shows the problems which accompany extraction of a 2D frame, as a representative of a regular 3D space frame. The impact of onset and location of individual plastic hinges on seismic performances of the analyzed structural system are investigated, and relative floor drifts are analyzed. It was concluded that the analysis of 2D frame, in the interaction with the foundation and soil, may provide sufficiently accurate results of behaviour and assessments of seismic performances of skeletal RC multi-storey building. It is important, because introduction of a spatial structure in such analyses is very complex and challenging

Multidisciplinary approach to the assessment of seismic performances and rehabilitation of bridges: nonlinear analyses, probability theory and optimization theory

The paper presents a multidisciplinary approach to the assessment of seismic performances based on the Performance-Based Earthquake Engineering (PBEE), taking into account the multi-criteria optimization theory in analyzing the priority methods for bridge rehabilitation/strengthening. One bridge model was subjected to nonlinear static pushover analyses (NSPA), target displacement analyses using the spectrum capacity method (CSM), vulnerability analyses, and reliability analyses, while for a damaged bridge, in addition to be considered using the above methods, was also analyzed using the VIKOR method of multi criteria optimization. Seismic performances were determined based on monitoring the system's plastification and analyzing the relevant parameters for the level of target displacement, such as target displacement, total shear force, spectral displacement, spectral acceleration, vibration period, damping and ductility. The phases of damage were considered using the probabilistic analysis of vulnerability and reliability: slight, moderate, extensive and complete, as a function of system ductility

Fragility and reliability analyses of soil -pile -bridge pier interaction

U radu je prikazana procedura evaluacije seizmičkih performansi interakcije šip-tlo inkrementalnom nelinearnom dinamičkom analizom (INDA -Incremental Nonlinear Dynamic Analysis). Ulazni signal u sistemu je tretiran preko generisanih veštačkih akcelerograma, a koji su dodatno procesirani po slojevima tla do osnovne stene. Postprocesiranje INDA analiza izvršeno je posebno za stub, a posebno za šip, tako da su konstruisane krive PGA=f(DR) u kapacitativnom domenu. Za ovako konstruisane krive određeni su performansni nivoi, a na osnovu određenih DR i PGA parametara sprovedene su regresione analize. Krive povredljivosti su konstruisane na osnovu rešenja regresione analize i teorije verovatnoće log-normalne raspodele. Takođe, konstruisane su i krive pouzdanosti na osnovu rešenja analize povredljivosti. Metodološki postupak za analizu seizmičkih performansi, prezentovan u ovom istraživanju, omogućava integrisano kvantitativno-kvalitativno razmatranje i evaluaciju kompleksne interakcije konstrukcija-tlo (SFSI -Soil-Foundation-Structure Interaction).The purpose of this paper is to present the methodology for performance-based seismic evaluation of soil-pile-bridge pier interaction using the incremental nonlinear dynamic analysis (INDA). The system's input signal was treated through the generated artificial accelerograms which were subsequently processed by soil layers and for the bedrock. The INDA analysis was post processed separately for the pier and for the pile, so that the constructed PGA=f(DR) curves are in the capacitive domain. For these curves the authors identified the performance levels, while the regression analyses were conducted based on the specific DR and PGA parameters. Fragility curves were constructed based on the solutions of regression analysis and the probability theory of log-normal distribution. Based on the results of fragility analysis, reliability curves were also constructed. The methodological procedure for seismic performance analysis presented in this study provides an integrated quantitative-qualitative consideration and evaluation of the complex soil-foundation-structure interaction (SFSI)

Behavior and analysis of RC bridges during earthquakes

U radu je prikazano ponašanje, i neka karakteristična oštećenja i loma mostova tokom zemljotresa, sa težištem na betonske mostove. Dati su neki uslovi projektovanja mostova prema EC8, primeri i konstruktivni detalji. Mostovi su veoma povredljive konstrukcije podložne oštećenju pri dejstu zemljotresnih opterećenja, pa je neophodno obezbeđenje njihove otpornosti. Seizmička otpornost se postiže: adekvatnim izborom konstrukcije, modela za analizu, samom analizom, ponekad neophodnom dinamičkom interakcijom sa tlom i odgovarajućim izborom detalja. Komentarisana je regulativa za njihovo projektovanje i metode analize mostova na seizmička dejstva. Napomenuti su tehnički propisi i preporuke za projetovanje seizmički otpornih konstrukcija pojedinih zemalja i međunarodnih udruženja uključujući i set Evrokodova 8 (EN1998. Opisane su delimično metode seizmičke analize grednih i kontinualnih mostova. Kod oblikovanja detalja obuhvaćeni su kriterijimi izbora, sa ciljem povećanja otpornosti konstrukcije i veće mogućnosti disipacije energije. Ukazano je na potrebu veće primene kontinualnih i integralnih mostova zbog njihove veće trajnosti u odnosu na klasične mostove. Obuhvaćeni su mostovi uglavnom srednjih i manjih raspona koji su najviše zastupljeni u našoj zemlji, a većih raspona u inostranstvu. Zbog ovako obimno postavljene teme rada, a ograničenog broje stranica, pojedinačna poglavlja nisu mogla biti obrađena dovoljno temeljno. Prikazani su primeri: MRO (most), Painter Street most, Antrion Rion most, Hanshin autoput, Showa most, Zečeve Drage vijadukt, Vijadukt Reber, Kovilj natputnjak.The paper shows the behaviour and some characteristic damages and fracture of the RC bridges during earthquake, with a focus on concrete bridges. The bridges are designed under the conditions defined in EC8, some examples and structural details of bridges are also given. Bridges are very vulnerable and susceptible to damage during earthquake action, therefore, ensuring seismic resistance is essential. Seismic resistance is accomplished by: choice appropriate structure, structural analysis model and analysis itself, choosing dynamic soli interaction model when necessary and by selection adequate details. The paper initially deals with the most common damage of concrete bridges. Designing regulations and analysis methods for common concrete bridges under seismic action are commented upon. The paper gives Technical regulations and recommendations of individual countries and international associations, including the set of Eurocode 8 (EN 1998) for designing seismically resistant structures are considered. Technical regulations and recommendations for designing seismically resistant structures of individual countries and international associations, including the Eurocode set 8 (EN1998) Seismic analysis methods of beam and continual bridges are described to some extent. In addition to EN 1998-2, the analysis includes the norms from the USA and Japan. The methods of analysis of beam and continuous bridges which are appropriate for the type and importance of the bridges are concisely described and commented upon. Appropriate details are selected with an aim of increasing the structural resistance and potential for energy dissipation. It is indicated that there is a need for an increase in usage of continual and integral bridges due to their longer durability in comparison to the classical bridges. The analysis mostly includes the concrete bridges of medium and small spans, which are the most common bridge types in our country and of larger ranges abroad. Extensive subject of the paper and the limitation in the number of pages made it difficult to describe some of the chapters more thoroughly. Shown examples: MRO (bridge), Painter Street bridge, Antrion Rion bridge, Hanshin Expressway, Showa bridge, Zečeve Drage viaduct, Viaduct Reber, Kovilj overpass. Shown examples: MRO (bridge), Painter Street bridge, Antrion Rion bridge, Hanshin Expressway, Showa bridge, Zečeve Drage viaduct, Viaduct Reber, Kovilj overpass

Seismic analysis of concrete structures founded on piles

У овом раду анализирани су утицају интеракције конструкција-темељ- тло током сеизмичких дејстава. Примењене су нелинеарне анализе временске историје (TH) и пушовер метода. Анализирани су модели гредних мостова, на каркатеристичним локацијама и са оптерећењима и материјалима према БАБ'87. Интеракција је третирана преко еластичних опруга и као нелинеарнa преко линк елемената p-y кривама. Криве су моделоване вишелинијским Тaкеда хистерезисним моделом. Проучено је стање конструкција у току и након земљотреса, укључиво и други удар земљотреса. У мањем обиму су анлизиране конструкције зграда према ЕЦ2 и ЕЦ8.U ovom radu analizirani su uticaju interakcije konstrukcija-temelj- tlo tokom seizmičkih dejstava. Primenjene su nelinearne analize vremenske istorije (TH) i pušover metoda. Analizirani su modeli grednih mostova, na karkaterističnim lokacijama i sa opterećenjima i materijalima prema BAB'87. Interakcija je tretirana preko elastičnih opruga i kao nelinearna preko link elemenata p-y krivama. Krive su modelovane višelinijskim Takeda histerezisnim modelom. Proučeno je stanje konstrukcija u toku i nakon zemljotresa, uključivo i drugi udar zemljotresa. U manjem obimu su anlizirane konstrukcije zgrada prema EC2 i EC8.The thesis studies the effects of the structure-foundation- soil interaction during seismic action using non-linear analysis methods Time History and PushOver. Analysis is made of beam bridges, in their typical locations and with loads and construction materials based on BAB’87/-Yu Code. The interaction is treated as linear using elastic spring model, and non-linear as link element on p-y curves which are modeled using the multi-linear Takeda hystheresis model. Studies are made on the performance of the constructions during and after an earthqake including aftershocks. The work, to a lesser extent, also includes similar analyses and studies for buildings, based on EC2 and EC8 codes

Behavior and analysis of RC bridges during earthquakes

U radu je prikazano ponašanje, i neka karakteristična oštećenja i loma mostova tokom zemljotresa, sa težištem na betonske mostove. Dati su neki uslovi projektovanja mostova prema EC8, primeri i konstruktivni detalji. Mostovi su veoma povredljive konstrukcije podložne oštećenju pri dejstu zemljotresnih opterećenja, pa je neophodno obezbeđenje njihove otpornosti. Seizmička otpornost se postiže: adekvatnim izborom konstrukcije, modela za analizu, samom analizom, ponekad neophodnom dinamičkom interakcijom sa tlom i odgovarajućim izborom detalja. Komentarisana je regulativa za njihovo projektovanje i metode analize mostova na seizmička dejstva. Napomenuti su tehnički propisi i preporuke za projetovanje seizmički otpornih konstrukcija pojedinih zemalja i međunarodnih udruženja uključujući i set Evrokodova 8 (EN1998. Opisane su delimično metode seizmičke analize grednih i kontinualnih mostova. Kod oblikovanja detalja obuhvaćeni su kriterijimi izbora, sa ciljem povećanja otpornosti konstrukcije i veće mogućnosti disipacije energije. Ukazano je na potrebu veće primene kontinualnih i integralnih mostova zbog njihove veće trajnosti u odnosu na klasične mostove. Obuhvaćeni su mostovi uglavnom srednjih i manjih raspona koji su najviše zastupljeni u našoj zemlji, a većih raspona u inostranstvu. Zbog ovako obimno postavljene teme rada, a ograničenog broje stranica, pojedinačna poglavlja nisu mogla biti obrađena dovoljno temeljno. Prikazani su primeri: MRO (most), Painter Street most, Antrion Rion most, Hanshin autoput, Showa most, Zečeve Drage vijadukt, Vijadukt Reber, Kovilj natputnjak.The paper shows the behaviour and some characteristic damages and fracture of the RC bridges during earthquake, with a focus on concrete bridges. The bridges are designed under the conditions defined in EC8, some examples and structural details of bridges are also given. Bridges are very vulnerable and susceptible to damage during earthquake action, therefore, ensuring seismic resistance is essential. Seismic resistance is accomplished by: choice appropriate structure, structural analysis model and analysis itself, choosing dynamic soli interaction model when necessary and by selection adequate details. The paper initially deals with the most common damage of concrete bridges. Designing regulations and analysis methods for common concrete bridges under seismic action are commented upon. The paper gives Technical regulations and recommendations of individual countries and international associations, including the set of Eurocode 8 (EN 1998) for designing seismically resistant structures are considered. Technical regulations and recommendations for designing seismically resistant structures of individual countries and international associations, including the Eurocode set 8 (EN1998) Seismic analysis methods of beam and continual bridges are described to some extent. In addition to EN 1998-2, the analysis includes the norms from the USA and Japan. The methods of analysis of beam and continuous bridges which are appropriate for the type and importance of the bridges are concisely described and commented upon. Appropriate details are selected with an aim of increasing the structural resistance and potential for energy dissipation. It is indicated that there is a need for an increase in usage of continual and integral bridges due to their longer durability in comparison to the classical bridges. The analysis mostly includes the concrete bridges of medium and small spans, which are the most common bridge types in our country and of larger ranges abroad. Extensive subject of the paper and the limitation in the number of pages made it difficult to describe some of the chapters more thoroughly. Shown examples: MRO (bridge), Painter Street bridge, Antrion Rion bridge, Hanshin Expressway, Showa bridge, Zečeve Drage viaduct, Viaduct Reber, Kovilj overpass. Shown examples: MRO (bridge), Painter Street bridge, Antrion Rion bridge, Hanshin Expressway, Showa bridge, Zečeve Drage viaduct, Viaduct Reber, Kovilj overpass

Developing a methodology for the integrated numerical evaluation and performance assessment of soil-pile-pier

In the paper is developed a discrete numerical solid pile model with a discontinuity and defects. Model included performance-based seismic evaluation of the soil-pile-bridge pier interaction. The pile discontinuity and defects are modelled by reducing the specific finite elements and elastic modulus of concrete. The wave-propagation response of the pile was analyzed based on a step-by-step numerical integration using the Hilber-Hughes-Taylor (HHT) method in time domain (THA). The response analysis is performed with an integration of individual reflectograms into a reflectogram surface, which is generated in a 3D cylindrical coordinate system. Non-linear response of the system is considered using the incremental-iterative Newton-Raphson`s method, while the stability analysis is performed according to the modified geometrical nonlinearity analysis of stability. Determination of critical load and effective length of the pile are performed based on numerical solution and using regression analysis of the power function. The procedure of the soil-pile-bridge pier performance evaluation is based on the incremental nonlinear dynamic analysis (INDA). The system's input signal is treated through the generated artificial accelerograms, which were subsequently processed by soil layers and for the bedrock. Fragility curves were constructed based on solutions of the regression analysis and the probability theory of log-normal distribution, while the generation of reliability curves is based on a solution of vulnerability

Deciding the order of interventions on the structure of reinforced concrete (RC) bridges for earthquake conditions

A multitude of existing bridges fail to meet the criteria of seismic resistance, as designed according to inadequate regulations, which eventually led to the reduction in their resistance. This practice requires interventions (rehabilitation or strengthening) conducted on their structure, which in turn requires developing methods of assessment of seismic performances of existing reinforced concrete (RC) girder bridges. Due to budget constrains it is impossible to strengthen all the bridges, so that a list of priorities is necessary to be drawn. The rank of a specific bridge in this list is stated by the importance of the road, age of the bridge, technical regulations according to which the bridge was designed and the condition of vital support elements. Ranking requires conducting multi-criteria optimization. This paper is focused on overpass, which is used to demonstrate the developed methodology

Vertiklana krutost šipova i preraspodela tokom interakcije za linernu promenu modula tla po dubini

The paper shows some characteristic problems of determining the axial stiffness of the pile and redistribution in a group. Some advantages and drawbacks of the use of individual design models are indicated. In the redistribution, the zero iteration is considered, which a condition is when the connecting beams or rafts are fully flexible, and the final iteration when the deflections of the piles are equalized. In the zero iteration, all the forces in the piles are of the same intensity, because only the centrically loaded raft is considered, but the deflections of individual piles during interaction are different. Due to the symmetry of the problem, in the zero iteration, only the certain groups have the equalized deflections of piles, but there is no equalized deflection of the groups themselves. In the final iteration, a distribution of forces in which the deflections of the individual piles during interaction are equalized is sought, i.e. a tolerance that is a relative error of 10 -5 in relation to the mean deflection is set. The soil model with the linear distribution with depth is considered. The effect of the distance of piles on the interaction is studied. Key words: Vertical stiffness, Vertical interaction, Redistribution during Pile-Soil- Pile interaction, distance influences of interaction.XXII ЮБИЛЕЙНА МЕЖДУНАРОДНА НАУЧНА КОНФЕРЕНЦИЯ ПО СТРОИТЕЛСТВО И АРХИТЕКТУРА ВСУ’2022 VSU'2022 Plenary lecture, (p. 10); XXII Anniversary International Scientific Conference by Construction and Architecture VSU’2022, 6 - 8 October 2022, Sofia, Bulgari

The strut – and – tie model for analysis of some RC foundation design

Technical beam theory is not applicable for the analysis of non-standard reinforced concrete structural elements (D-region), especially when members are exposed to significant shear stress and/or torsion. In this case strut – and – tie models (STM), which give reliable results, are used. In this paper we present a review of theoretical bases and application of STM for design. The focuse is also on the detailing of pile caps for diferent numbers of piles (2, 3 and 4) in the foundation. Some international recommendations are also commented (ACI, EN 1992, etc.).Tehnička teorija savijanja nije primenljiva kod analize nestandardnih armiranobetonskih (AB) nosača, naročito kada su izloženi znatnim smičućim naponima i/ili torziji. U takvim slučajevima se koriste uprošćene analize, koje daju dovoljno tačne rezultate, za praktične probleme. Rad je usmeren na primenu štapnih modela (pritisnuti kosnici i zatege) kod analize i oblikovanja detalja temeljnih kapa („jastuka“) kod fundiranja na šipovima. Pri tome korišćene su i komentarisane neke međunarodne preporuke (ACI, EN 1992, i dr.).ЗБОРНИК РАДОВА 6. МЕЂУНАРОДНЕ КОНФЕРЕНЦИЈЕ САВРЕМЕНА ДОСТИГНУЋА У ГРАЂЕВИНАРСТВУ 2018 ГРАЂЕВИНСКИ ФАКУЛТЕТ СУБОТИЦА Проф. др Мирослав Т. БЕШЕВИЋ, декан Проф. др Илија М. МИЛИЧИЋ Доц. др Огњен ГАБРИЋ UDK: 624.072.2.012.4