Inverse reliability analysis of prestressed bridge

Předložená diplomová práce se zabývá aplikací metodiky a prostředků inverzní analýzy při návrhu vybraných parametrů konstrukcí s využitím plně pravděpodobnostní analýzy pro stanovení úrovně její spolehlivosti. K aproximaci inverzní funkce se používá metoda založená na umělých neuronových sítích. Inverzní analýza byla provedena dvěma způsoby, které od sebe odlišuje způsob získání spolehlivostních ukazatelů. Řešenou konstrukcí v této práci byla již existující mostní stavba. Rok výstavby je odhadován přibližně v letech 1955 až 1960. Konstrukce mostu se nachází před obcí Uherský Ostroh. Jedná se o jednopólový betonový deskový most z nosníků MPD3 a MPD4 vzájemně spojenými předpínacími lany. Na základě diagnostického průzkumu v letech 2006 a 2007, laboratorních zkoušek, normativních předpisů či doporučení a v neposlední řadě citlivostní analýzy, byl proveden inverzní návrh vybraných návrhových parametrů pro požadované mezní stavy. Studovány byly různé úrovně zatížitelnosti, různé varianty návrhových parametrů i různé struktury neuronových sítí.The proposed diploma thesis deals with the application of methodology and tools of inverse analysis for design of selected structural parameters using a fully probabilistic analysis to determine the level of its reliability. The method based on artificial neural networks is used to approximate the inverse function. The inverse analysis was carried out in two ways that differs in the method of obtaining reliability indicators. The structure analyzed in this work was an existing bridge. The year of construction is estimated approximately between the years 1955 to 1960. The bridge is located close to the Uherský Ostroh. It is a one-piece concrete slab made of MPD3 and MPD4 girders post-tensioned by tendons. Based on the 2006 and 2007 diagnostic surveys, laboratory tests, normative regulations and recommendations and, last but not least, sensitivity analyses, an inverse design of selected design parameters was performed for required limit states. Various load levels, different alternatives of design parameters and different neural network structures were studied.

Utilization of inverse reliability analysis tools for probability based design of selected structural parameters

Podstatou předložené bakalářské práce je aplikace metodiky a prostředků inverzní analýzy při pravděpodobnostním návrhu vybraných parametrů konstrukcí. Prvním krokem bylo seznámení se s pravděpodobnostním návrhem a posouzením konstrukcí, následně pak s vlastní metodikou inverzní analýzy založené na umělých neuronových sítí. Po nastudování daného tématu bylo možné přejít k samotné problematice. Zprvu pro uvedení teorie do praxe se začalo na lehčích příkladech. Jednalo se o matematické funkce a jeden praktičtější příklad. U těchto příkladů byly předem známé výsledky. Tato skutečnost vedla k snadné kontrole dosažených hodnot. Postupným zdokonalováním v užívání softwarových nástrojů a to zejména programu DLNNET bylo možné přejít na příklady z praxe. Zvoleny byly příklady z předmětů nižších ročníků bakalářského studia na Fakultě stavební VUT Brno. Prvním z nich byl návrh železobetonové desky, u které byly hledanými návrhovými parametry výška desky a plocha vyztužení. Druhým příkladem byl návrh montážního ocelového šroubového spoje u diagonály vazníku. Zde se provedlo dimenzování průměru šroubu a jeho počet.This bachelor thesis deals with the application of methodology and tools of inverse analysis in regards to probabilistic design of selected design parameters of structure. The first step was to get familiar with the probabilistic design and analysis, then understanding of the inverse analysis methodology itself which is based on artificial neural networks. After researching the topic we could get to the actual issue. To put the theory in practice easier examples were used at first. These were mathematical functions and one practical-based example, whereas the results were known in advance. This simplified a process of checking achieved values. Using software tools and especially DLNNET software allowed us to take on practical exercises. Used exercises are chosen from earlier undergraduate studies at the Faculty of Civil Engineering, Brno. The first of these was a design of reinforced concrete slab, where desired parameters were slab’s height and area of reinforcement. The second one was a design of a diagonal truss screw connection, aimed to size the screw diameter and its quantity.

Fracture Tests of Multiple Specimen Sizes: Mechanical Fracture Parameters of C30/37 Concrete by Inverse Analysis

The paper presents a part of the research aimed at developing a comprehensive experimental– computational methodology for determining the values of mechanical fracture parameters of concrete independent of the specimen size and geometry. To this end, laboratory fracture tests in three-point bending and wedge-splitting test configurations were carried out using three different specimen sizes with two well-separated initial notch depths. The test records were used to identify selected mechanical fracture parameters using inverse analysis. Identifications were performed for individual specimens of each test configuration followed by statistical evaluation for individual sizes, notch depths, test configurations and for all specimens tested. The obtained parameters were used in the numerical simulation of the tests and the resulting load vs. displacement diagrams were compared with the experimental ones. The parameters were also analysed in terms of their dependence on the size of the initial uncracked ligament. As expected, a significant dependence of the fracture parameters was confirmed

Experimental and numerical analysis of the fracture response of alkali-activated slag-based materials

The paper deals with the experimental and numerical determination of mechanical fracture parameters of fine-grained composites based on the alkali-activated slag (AAS) at different ages of hardening. Two AAS composites, which differed only in the presence of shrinkage reducing admixture, were studied. The prismatic specimens with the nominal dimensions of 40 × 40 × 160 mm and initial central edge notch were subjected to fracture tests in a three-point bending configuration. The results of the fracture tests in the form load F versus deflection d diagrams were used as input data for the identification of parameters via the inverse analysis based on the artificial neural network whose aim is to transfer the fracture test response data to the desired material parameters. The modulus of elasticity, tensile strength, and fracture energy values were identified and subsequently compared with values obtained based on the direct fracture test evaluation using the effective crack model and work-of-fracture method

Mechanical Fracture and Fatigue Characteristics of Fine-Grained Composite Based on Sodium Hydroxide-Activated Slag Cured under High Relative Humidity

A typical example of an alternative binder to commonly used Portland cement is alkali-activated binders that have high potential as a part of a toolkit for sustainable construction materials. One group of these materials is alkali-activated slag. There is a lack of information about its long-term properties. In addition, its mechanical properties are characterized most often in terms of com-pressive strength; however, it is not sensitive enough to sufficiently cover the changes in micro-structure such as microcracking, and thus, it poses a potential risk for practical utilization. Con-sequently, the present study deals with the determination of long-term mechanical fracture and fatigue parameters of the fine-grained composites based on this interesting binder. The me-chanical fracture parameters are primarily obtained through the direct evaluation of fracture test data via the effective crack model, the work-of-fracture method, the double-K fracture model, and complemented by parameter identification using the inverse analysis. The outcome of cy-clic/fatigue fracture tests is represented by a Wöhler curve. The results presented in this article represent the complex information about material behavior and valuable input parameters for material models used for numerical simulations of crack propagation in this quasi-brittle material

Identification of Mechanical Fracture Parameters of Alkali-Activated Slag Based Composites During Specimens Ageing

The aim of the paper is to present the results of the experiment focused on the development of the mechanical fracture characteristics of alkali-activated slag (AAS) based composites within the time interval from 3 days to 2 years of ageing. Two AAS composites, which differed only in the presence of shrinkage reducing admixture (SRA), were prepared for the purpose of experiments. The composites were prepared using ground granulated blast furnace slag activated by water-glass with silicate modulus of 2.0, standardized quartzite sand with the particle grain size distribution of 0−2 mm, and water. Commercially produced SRA was added into the second mixture in an amount of 2 % by weight of slag. The test specimens were not protected from drying during the whole time interval and were stored in the laboratory at an ambient temperature of 21 ± 2 °C and relative humidity of 60 ± 10 %. The prism specimens made of the abovementioned composites with nominal dimensions of 40 × 40 × 160 mm with the initial central edge notch were subjected to the fracture tests in a three-point bending configuration. The load F and displacement d (deflection in the middle of the span length) were continuously recorded during the fracture tests. The obtained F−d diagrams and specimen dimensions were used as input data for identification of parameters via the inverse analysis based on the artificial neural network, which aim is to transfer the fracture test response data to the desired material parameters. In this paper, the modulus of elasticity, tensile strength, and fracture energy values were identified and subsequently compared with values obtained based on the fracture test evaluation using the effective crack model and work-of-fracture method

Multilevel Determination of Mechanical Fracture Parameters of Concrete from Wedge Splitting Tests

The paper presents the results of a part of the research focused on the development of a complex experimental–computational methodology for determining the values of mechanical fracture parameters of concrete independent of the specimen size and geometry. For this purpose, laboratory wedge splitting tests were carried out on specimens of three different sizes with two different notch depths. Based on the experimentally obtained responses of the test specimens, the fracture mechanical parameters of all specimens were identified by inverse analysis. The obtained parameters were used in the numerical simulation of the tests and analysed in terms of their dependence on the size of the initial uncracked ligament