The limit state design of spun concrete columns using load combinations recommended by EN 1990 and ASCE/SEI 7–05

The expediency of using precast spun concrete columns of annular cross‐sections reinforced by high‐strength steel bars is discussed. Test material properties, efficiency factors and resisting compressive stresses of plain and reinforced spun concretes are presented. Modelling a bearing capacity of eccentrically loaded members of annular cross‐sections is based on the concepts of compression with a bending moment and bending with a concentrical force. The comparison of test and modelling data of concentrically and eccentrically loaded members is analysed. The expediency to use in design practice the approaches of current methods of partial safety factors design (PSFD) legitimated in Europe and load and resistance factors design (LRFD) suggested in the USA and other countries is considered and illustrated by a numerical example. Santrauka Aptariamas didžiastiprio plieno strypais armuotų žiedinio skerspjūvio centrifuguotojo betono kolonų naudotinumas. Pateiktos armuotojo ir nearmuotojo centrifuguotojo betono medžiagų savybės, efektyvumo veiksniai ir laikomieji gniuždymo įtempiai. Ekscentriškai gniuždomų žiedinio skerspjūvio elementų laikomajai galiai modeliuoti taikomos lenkiamojo gniuždymo ir gniuždomojo lenkimo sampratos. Analizuojamas centriškai ir ekscentriškai apkrautų elementų eksperimentinių ir modeliavimo duomenų sugretinimas, nagrinėjamas Europos, JAV ir kitų šalių projektavimo praktikoje įteisintų ir paplitusių dalinių veiksnių ir apkrovų bei atsparių veiksnių metodų taikymo tikslingumas, kurį rodo skaitmeninis pavyzdys. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: centrifuguotasis betonas, didžiastipris plienas, gniuždymo bandymas, ekscentrinis apkrovimas, ribinių būvių metoda

Probability‐based design of spun concrete beam‐columns

The attention of engineers is turned to the application of precast spun concrete columns reinforced by high‐strength steel bars for office and administrative buildings. The paper discusses a possibility of using the reliability index approach to designing beam‐columns of building frames and analyses resistance criteria for beam‐columns of annular cross sections as compression members with bending moments and bending members with compressive forces. First and second order effects of beam‐columns are considered. The article also presents time‐dependent resistance safety margin and its stationary equivalent and investigates the unsophisticated applied models for probability‐based design of frame beam‐columns. The design of a beam‐column of the braced frames is illustrated providing a numerical example. Santrauka Atkreiptas inžinieriu demesys i didžiastiprio plieno strypais armuotu sijiniu kolonu iš centrifuguotojo betono naudojima istaigu ir administraciniuose pastatuose. Aptarta galimybe projektuojant pastato remo sijines kolonas taikyti patikimumo indekso būda. Analizuojamas sijiniu kolonu kaip lenkiamai gniuždomu ir gniuždomai lenkiamu žiedinio skerspjūvio ele‐mentu atspario kriterijus. Nagrinejamos sijiniu kolonu pirmosios ir antrosios eiles iražos. Pateiktas laike kintantis ribines saugos atsparis ir jo stacionarusis ekvivalentas. Tyrinejamas nesudetingas taikomasis modelis remo sijiniu kolonu ti‐kimybiniam projektavimui. Skaitiniu pavyzdžiu iliustruojamas stabilizuojamu remu sijines kolonos projektavimas. First Published Online: 10 Feb 2011 Reikšminiai žodžiai: centrifuguotasis betonas, remai, antrosios eiles iražos, ribine atspario sauga, patikimumo indekso skaičiavima

The quasi‐ductile resistance of compressed spun concrete beam‐columns

The expediency of reinforcing precast spun concrete members of annular cross sections reinforced by high‐strength steel bars is discussed. Test materials, mechanical properties, production and testing procedures of plain and rein‐forced spun concrete specimens are presented. The quasi‐ductile strength and strain features of concentrically and eccentrically loaded specimens are considered. The modelling of a bearing capacity of beam‐columns of annular cross sections is based on the concepts of bending with a concentrical force and compression with a bending moment. The comparison of modelling and test data of spun concrete beam‐columns is analysed. Santrauka Aptariamas didžiastipriais plieniniais strypais armuotu gamykliniu žiedinio skerspjūvio elementu iš centrifuguotojo betono tinkamumas. Pateiktos grynojo ir armuotojo centrifuguotojo betono bandiniu medžiagos, mechanines savybes, gamybos ir bandymo tvarka. Nagrinejamos centriškai ir ekscentriškai apkrautu bandiniu tartum stamantraus stiprumo ir deformaciju ypatybes. Žiedinio skerspjūvio sijiniu kolonu laikomajai galiai modeliuoti taikomos gniuždomojo lenkimo ir lenkiamojo gniuždymo sampratos. Analizuojami sijiniu kolonu iš centrifuguotojo betono modeliavimo ir bandymo duomenys. First Published Online: 24 Jun 2011 Reikšminiai žodžiai: centrifuguotasis betonas, didžiastipris plienas, žiedinio skerspjūvio elementai, ekscentrinis apkrovimas, gniuždymo bandyma

Structural safety of rolled and welded beams subjected to lateral‐torsional buckling

The expediency of using probability‐based approaches in the analysis of beams subjected to lateral‐torsional buckling is discussed. The values of buckling resistance moments and their uncertainties for rolled and equivalent welded I sections as particular members of the designed structures are analyzed. The safety margins of buckling steel sections exposed to permanent and variable vertical loads are modeled. The survival probability and reliability index of sections exposed to lateral‐torsional buckling are considered. The prediction of probability‐based safety of rolled and welded beams in buildings and civil engineering works are provided and illustrated by numerical examples. Santrauka Aptariamas tikslingumas naudoti tikimybinius metodus skaičiuojant šoniniu sukimu klupdomas sijas. Analizuojamos val‐cuotuju ir suvirintuju I profiliuočiu, kaip ypačiuju elementu, klupdomuju atspariu momentu vertes ir ju neapibrežtys. Mo‐deliuojama nuolatine ir laikinaja vertikalia apkrova klupdomu plieniniu profiliuočiu ribine sauga. Nagrinejama šoniniu sukimu klupdomu profiliuočiu išlikties tikimybe ir patikimumo indeksas. Pateiktas ir skaitiniu pavyzdžiu iliustruotas pas‐tatu ir inžineriniu statiniu valcuotuju ir suvirintuju siju tikimybines saugos prognozavimas. First Published Online: 24 Jun 2011 Reikšminiai žodžiai: plieniniai profiliuočiai, klupdymas šoniniu sukimu, ribine sauga, išlikties tikimybe, suvirintosios sijo

The Structural Safety Assessment of the Overloaded Members of Highway Bridges

A residual reliability index of load-carrying structures of existing highway bridges overloaded by unforeseen vehicular live loads is discussed. The primary and inspection structural safety margins of particular members of bridges are considered. The primary and revised survival probabilities of intact particular members are analysed. Target reliability indices of the structural members of road bridges are presented. A transformed Bayes theorem in the analysis of revised failure probabilities of overloaded members of highway bridges is recommended. The Bayesian approach is combined with the method of transformed conditional probabilities for series systems. The simple calculation of revised reliability indices of particular members is demonstrated by a numerical example

On design features of propped and unpropped hyperstatic structures

An effect of structural and technological features on the design methodology of hyperstatic precast reinforced concrete and composite steel‐concrete structures is discussed. Permanent and variable service, snow and wind loads of buildings and their extreme values are analysed. Two loading cases of precast reinforced concrete and composite steel‐concrete continuous and sway frame beams as propped and unpropped members are considered. A redistribution of bending moments for the ultimate limit state of beams is investigated. A limit state verification of hyperstatic beams by the partial factor and probability‐based methods is presented. It is recommended to calculate a long‐term survival probability of beams by the analytical method of transformed conditional probabilities. Apie ramstytinių ir neramstytinių statiškai neišsprendžiamų konstrukcijų projektavimo ypatybes Santrauka Aptariama konstrukcinių ir technologinių ypatybių įtaka statiškai neišsprendžiamų gelžbetoninių ir kompozitinių (plieninių-betoninių) konstrukcijų projektavimo metodologijai. Analizuojamos nuolatinės, kintamosios eksploatacinės, sniego ir vėjo apkrovos bei jų ekstremalios vertės. Du gamyklinių gelžbetoninių ir kompozitinių nekarpytųjų sijų bei rėmsijų kaip ramstytinų ir neramstytinų elementų apkrovimo atvejai yra nagrinėjami atsižvelgiant į įrąžų persiskirstymą jų ribiniame būvyje. Sijų ribiniam būviui patikrinti taikomi dalinių faktorių ir tikimybiniai metodai. Rekomenduojama sijų ilgalaikės išlikties tikimybę apskaičiuoti analitiniu transformuotų sąlyginių tikimybių metodu. First Published Online: 14 Oct 2010 Reikšminiai žodžiai: nekarpytosios sijos, rėmsijos, ramstytinės konstrukcijos, poveikiai, dalinių faktorių metodas, tikimybinis patikimumas

Precast Spun Concrete Piers in Road Bridges and Footbridges

The usability of precast spun concrete members of annular cross-sections as pier shafts for road bridges and footbridges is discussed. The probability distribution of traffic loads is considered, their coefficient of variation is specified. First and second-order load effects for shafts of braced and bracing piers are analysed. The modeling of resisting compressive forces and bending moments of eccentrically loaded spun concrete shafts is considered. The features of mechanical properties of compressed spun concrete specimens reinforced by cold worked high-strength steel bars are presented. A simplified but fairly exact analysis of pier shafts under persistent situations by limit state and probabilitybased approaches is provided. A design of tubular shafts of braced piers using semi-probabilistic and probabilistic reliability verifications is illustrated by a numerical example

Probabilistic durability prediction of existing building elements

An effect of service and proof actions on probabilistic reliability (serviceability, safety and durability) of building elements (components and members) of existing enclosure and bearing structures is under consideration. Timeâ€dependent models for reliability assessment of elements under sustained variable and multicycle actions are presented. Revised reliability indices of existing elements exposed to service permanent and variable actions are discussed. It is recommended to assess the longâ€term reliability index of elements taking into account the effect of latent defects. Truncated probability distributions of physicalâ€mechanical resistances of elements and an effect of their latent defects on reliability index assessment are taken into account. Methodological peculiarities of durability prediction of elements and avoiding unfounded premature repairs or replacements are analysed. The applied illustration of the presented method on the probabilistic reliability prediction of deteriorating concrete covers is demonstrated. First Published Online: 14 Oct 201

Analysis of the Time-Dependent Reliability Index for Deteriorating Load-Carrying Members

AbstractThe probability-based prediction and analysis of time-dependent survival probabilities and reliability indexes of non-deteriorating and deteriorating structural members exposed to extreme gravity and climate action effects are presented. A degradation function of reinforced concrete members under corrosion actions and sulphate attacks is discussed. The time-dependent safety margin of particular members as a random finite sequence of auto structural members is analyzed. Their time-dependent survival probability and reliability index values are expressed in simplified analytical manner. The merit of the method of transformed conditional probabilities based on more accurate conventional correlation factors is demonstrated by numerical examples