The Durability of a Concrete Sewer Pipeline under Deterioration by Sulphate and Chloride Corrosion

AbstractIn the article an issue of corrosion impact both sulphate and chloride on the reliability index was solved by analytical methods. The pipeline was located in a homogenic soil backfill under communication load. The depth of corrosion penetration was estimated by selection of the maximum length of cracks. As a result of deterioration zone appeared to be a function of time in exploitation according to average environmental concentration which can initialise a percent of chemical and mechanical degradation of concrete. The work shows also the complete analytical way which help to assess the safety level of sewer pipelines what can be introduced to geographic information systems

Influence of varying soil properties on evaluation of pile reliability under lateral loads

A three dimensional probabilistic approach to analyzing laterally loaded piles is presented. Two typical subsurface models are used in the analyses: the first one consists of layered linear elastic soil where each layer has a random modulus of elasticity; while the second model takes the form of linear elastic soil with a random modulus of elasticity that increases with depth. Efficient step by step procedures for the reliability computation involving pile displacements are proposed. The solution is based on three-dimensional modeling by the finite element method. A series of results has been obtained for various values of elastic parameters of the soil. Next by a non-linear regression procedure a response surface is obtained. To get the final response surface allowing for a reliability analysis, an iterative algorithm based on the so-called design point concept is applied. The failure criterion is defined as the pile head displacement exceeding displacement threshold. The two cases of piles subjected to lateral load are computed. The paper illustrates the influence of the two distinct types of subsurface variability on the probabilistic analysis. A pronounced effect of the random variability of both the lateral force and the elastic modulus of the upper layer on reliability indices has been shown in results of numerical examples

Zapis warunku plastyczności w języku skryptowym FLEXPDE oraz FLAC 2D

Tyt. z nagłówka.Bibliografia s. 236.Dostępny również w formie drukowanej.ABSTRACT: In the paper the describing of linear-plastic material behaviour in Finite Elements codes: FlexPDE and MRS FLAC is presented. The discussion is restricted to linear elastic-perfectly plastic material, two-dimensional plane strain and associated flow rule. For describing linear-elastic material behaviour (for general stress states): stress-strain behaviour in elastic range, yield function or failure function, flow rule, definition of strain hardening (softening) are needed. In the solution the tension stresses are limited and showed like convex multi segment line. KEYWORDS: procedure-oriented language, yield condition, associated flow rule. STRESZCZENIE: Praca powstała jako rozwiązanie problemu zapisu zagadnień plastyczności w programie MES FlexPDE v5.0 oraz programie MRS FLAC 2D. Zastosowano model ciała sprężysto-idealnie plastycznego w zadaniach płaskiego stanu odkształcenia, założono stowarzyszone prawo płynięcia. Opracowana ścieżka postępowania w dogodny sposób umożliwia zapisanie warunków z dodatkowymi ograniczeniami, tj. zamknięcie od strony naprężeń ściskających w przestrzeni naprężeń głównych oraz ograniczenie rozciągania zapisanych jako wypukłe linie wielosegmentowe. SŁOWA KLUCZOWE : język skryptowy, warunki plastyczności, stowarzyszone prawo płynięcia

The Historical Earthworks of the Warsaw Citadel

In this study, we analyzed the methods and technologies used for constructing earthworks and military engineering in the latter period before the industrial revolution in Poland. The research object, the Warsaw Citadel, is a source of knowledge about military heritage from the aspect of conservation and protection of specific engineering achievements, which were dictated by early Russian geopolitical doctrine. Within the framework of the ongoing project of material heritage protection and popularization of history, the fortress has been transformed into a modern museum building. The new symbolic message of architecture was redefined, leaving behind the gloomy dominance elements in the scenery of the nearby city. In this study, reception tests of ground anchors were used for analysis. They were treated as a tool to determine the heterogeneity of fortification of historical earthworks. In the presented calculation procedure, limitations in the availability of geotechnical tests were overcome. Geological terrain layout and embankment excavation technology significantly impacted their quality and reliability. Currently, the embankments are slashed with anchored retaining walls. Ground anchors were used at short distances and were tested according to the national standard procedures. The results of the load tests are based on the physical properties of the subsoil, the conditions of contact with the supporting elements of the anchors, and the material properties. The soil interaction with the anchors is described using a rheological model, the constants of which were obtained using a fractional derivative model. The spatial variability of the rheological model parameters is presented using theoretical semivariograms matching the empirical data. The semivariograms explain the spatial correlation of the tested constants of the rheological model of the substrate with the anchors. The results of non-destructive testing were influenced by factors such as time and consolidation processes. The obtained results allowed us to directly draw conclusions about the repetitiveness of embankment features and indirectly about the quality of their construction

Probabilistic analysis of a concrete column in an aggressive soil environment.

Sulphate attack is one of the most important factors that limit the lifetime of pure concrete constructions. Harsh environmental conditions have a large impact on the operational costs of concrete columns or piles dipped into soil. The results are non-deterministic; therefore, reliability analysis is often used. The strength characteristics of the substrate around the construction were modelled as one-dimensional prismatic beams related with random p-y curves. Sulphate deterioration is defined as a set of random variables jointed with two dimensional mechanical systems at acceptable levels. Fick's second law describes the penetration of sulphate ingress into pure concrete with explicit numerical solutions for boundary conditions and an increase in the transition factor under the progress of sulphate ingress. This process was partially solved via analytical methods for sulphate ion transport and numerically for a random field. This solves the mechanical task and determines the system reliability. A numerical example is provided to illustrate the proposed method to prevent unexpected structural failures during column service life. The proposed methodology can assist designers and can help to make decisions on existing foundations to ensure the safety of geotechnical construction

Reliability Assessment Approach for the Quality of Railroad Subgrade

The static load plate test is the standard subgrade acceptance test for new or modernised railway lines. Examinations are performed at regular spacings on the track section and a lack of acceptance for even a single test disqualifies a section, forcing remedial treatments on the whole section. In this paper, a nondeterministic description of stiffness related to the spatial characteristics of acceptance measurement results is proposed for a more rational assessment of substructure quality. The concept is based on geostatistical analysis and one-dimensional distributions of stiffness values. The paper also proposes a new concept of rail infrastructure acceptance based on a reliability index already codified in European standards. The functioning of the postulated criterion is presented on the example of an existing railway line and the actual test results

Non-Deterministic Assessment of Surface Roughness as Bond Strength Parameters between Concrete Layers Cast at Different Ages

The importance of surface roughness and its non-destructive examination has often been emphasised in structural rehabilitation. The presented innovative procedure enables the estimation of concrete-to-concrete strength based on a combination of low-cost, area-limited tests and geostatistical methods. The new method removes the shortcomings of the existing one, i.e., it is neither qualitative nor subjective. The interface strength factors, cohesion and friction, can be estimated accurately based on the collected data on a surface texture. The data acquisition needed to create digital models of the concrete surface can be performed by terrestrial close-range photogrammetry or other methods. In the presented procedure, limitations to the availability of concrete surfaces are overcome by the generation of subsequential Gaussian random fields (via height profiles) based on the semivariograms fitted to the digital surface models. In this way, the randomness of the surface texture is reproduced. The selected roughness parameters, such as mean valley depth and, most importantly, the geostatistical semivariogram parameter sill, were transformed into contact bond strength parameters based on the available strength tests. The proposed procedure estimates the interface bond strength based on the geostatistical methods applied to the numerical surface model and can be used in practical and theoretical applications

Assessing the Scale Effect on Bearing Capacity of Undrained Subsoil: Implications for Seismic Resilience of Shallow Foundations

This research investigates the influence of the scale effect on the bearing capacity of fine-grained subsoil under undrained conditions. The analyses were conducted based on laboratory tests of silty clay. Uniformly compacted samples were subjected to an unconfined compression test. The research was performed on cylindrical specimens. Three different variants of the diameter D (38 mm, 70 mm, 100 mm) and the corresponding height H = 2D were analyzed. Based on the tests results, the unconfined compression strength qu was determined, and from this, the undrained shear strength cu was calculated. The obtained results showed a clear decrease in cu with increasing sample size. However, in the existing reference documents, there are no specific guidelines for calculations of bearing capacity with consideration of sample size effect on the soil shear strength. Therefore, this study utilized the laboratory soil test data to calculate the bearing capacity of undrained subsoil, taking into account the seismic impacts, with a particular focus on spread foundations

ПРИМЕНЕНИЕ КОМПЛЕКСНОЙ ТЕХНОЛОГИИ УСТРОЙСТВА ФУНДАМЕНТОВ НА ПРОСАДОЧНЫХ ГРУНТАХ ПРИ СТРОИТЕЛЬСТВЕ МНОГОЭТАЖНОГО ЖИЛОГО ДОМА В РОСТОВЕ-НА-ДОНУ

Предмет исследования: технологические параметры и расчетные схемы устройства комбинированного свайно-плитного фундамента (КСПФ). Произведена оценка влияния уплотнения грунтов основания грунтовыми сваями в формировании напряженно-деформированного состояния системы «плита - свая - грунтовое основание». Цель: с целью снижения стоимости и сроков возведения фундаментов, разработки эффективных методик проектирования проведена оценка внедрения комплексной технологии устройства КСПФ при строительстве здания повышенной этажности в условиях распространения просадочных грунтов. Материалы и методы: данные полевых и лабораторных исследований для определения физико-механических свойств грунтов в основании (влажность, удельный и объемный вес, влажность на границах раскатывания и текучести), зернового (гранулометрического) и микроагрегатного состава, характеристик набухания и усадки, характеристик прочности и деформируемости (одноплоскостной срез, консолидированно-дренированные испытания), характеристик просадочности, коэффициента фильтрации; испытания грунтов статическими вдавливающими и выдергивающими нагрузками; компьютерное моделирование напряженно-деформированного состояния основания программным комплексом Plaxis 2D. Результаты: результатом полевых и лабораторных экспериментов стало внедрение комплексной технологии устройства свайно-плитного фундамента на просадочных грунтах в условиях плотной городской застройки. Выводы: предложенная методика проектирования комбинированного свайно-плитного фундамента позволила улучшить строительные свойства грунтов, значительно повысить несущую способность свайной части, уменьшить глубину заложения свай и эффективно вовлечь в работу грунты основания пролетной части фундамента. Данная методика дает значительный экономический эффект и сокращает сроки строительства