Stiffness analysis of glued connection of the timber-concrete structure

This paper presents results of experimental and mathematical analysis of stiffness characteristics of a composite timber-concrete structure. The composite timberconcrete structure presented herein is non-typical compared to similar types of building structures. The interaction between the timber and concrete part of the composite cross-section is not based on metal connecting elements, but it is ensured by a glued-in perforated mesh made of plywood. The paper presents results of experimental and mathematical analysis for material alternatives of the solution of the glued joint. The slip modulus values were determined experimentally. Data obtained from the experiment evaluated by means of regression analysis. Test results were also used as input data for the compilation of a 3D model of a composite structure by means of the 3D finite element model. On the basis of result evaluation, it can be stated that the stress-deformation behaviour at shear loading of this specific timber-concrete composite structure can be affected by the type of glue used. Parameters of the 3D model of both alternative of the structure represent well the behaviour of the composite structure and the model can be used for predicting design parameters of a building structure.Web of Science6124924

Finite element modelling of porous buildingmaterials

Import 15/01/2013V současné době jsou ve stavebnictví ve velké míře využívány vysoce pórovité materiály. Díky jejich malé objemové hmotnosti dosahují velmi dobrých tepelně izolačních parametrů. Tyto materiály mají také své nevýhody. Vysoká pórovitost způsobuje výrazné snížení mechanických a odolnostních parametrů. Velmi nepříznivě působí na vlastnosti pórovitých materiálů také vlhkost, která může do pórového systému pronikat. Při navrhování a posuzování stavebních konstrukcí je potřeba tyto okolnosti zohlednit. Normy pro navrhování stavebních konstrukcí se všakt této problematice věnují velmi omezeně. Předložená diplomová práce se zabývá modelování mechanického chování pórovitých materiálů. V numerických modelech je s pomocí experimetnálních měření zohledněn vliv vlhkosti na mechanické parametry. S využitím komerčního, volně dostupného, ale i vlastního programového vybavení je využito několik podmínek plasticity zohledňujících pórovitost materiálů.Porous materials are widely used in building industry at present. Due to their low bulk density they have very good thermal insulation properties. These materials has also some disadvantages. High porosity causes significant reduction of mechanical and durability parameters. Very adverse effect causes moisture which can penetrate to pore system. In the design and assesment of building structures it is neccesary to take account these circumstances. Standards for designing of building structures are very limited in this problematic. This diploma thesis is focused on modeling of mechanical behavior of porous materials. Numerical models with using of experimental data take into account effect of moisture on mechanical parameters. Some yield criterions for porous material from commercial, opens source and also custom software are used.Prezenční221 - Katedra konstrukcívýborn

Portable optical fiber Bragg grating sensor for monitoring traffic density

The paper examines the development of a portable sensor strip with fiber optic Bragg grating for monitoring urban traffic density up to 80 kph. It contains a 2.5-m-long and a 2-cm-high sensor created from a combination of silicone addition rubber (bicomponent addition silicone rubber) and Bragg grating placed inside a carbon tube. The design of the portable sensor permits traffic density and cars crossings to be monitored and detected in a single lane. The functionality of the sensor was verified in real traffic; the results of this study are based on the detection of 1518 vehicles of different types and sizes. According to the measurements, the sensor is characterized by a high detection rate of 98.946%.Web of Science922art. no. 479

Fiber-optic Bragg system for the dynamic weighing of municipal waste: A pilot study

The publication focus on a pilot study (design, implementation and verification) of a dynamic weighing system designed for weighing of municipal waste during the dumping of garbage containers. The presented solution is based on fiber Bragg gratings (FBG) and can be additionally implemented into the lifting equipment of commonly employed garbage trucks. The weighing principle is based on the measurement of deformation effect and vibration response of the lifting equipment during the dumping of garbage bins. The measuring system leverages the advantages of power measurement, which use the conversion of the spectral shift of modulated light signal during the measurement to the change in optical power of a pair of spectral overlapping Bragg gratings. Two different methods are presented and discussed: the amplitude method, which analyze the maximum amplitude change of the signal and/or the method, which analyze the time period of the dampened oscillation of the lifting device. Due to the small dimensions, the complete system can be installed together with FBG sensors directly onto the lifting device. The pilot tests of the presented system were carried out for over 4 months, showing an accuracy of up to +/- 4.04 kg in the range of 10-100 kg for standardized containers used for municipal waste. The system worked in completely standalone mode and the garbage trucks were not modified in any inconvenient way.Web of Science9990599905

Study of properties of lime mortars and plasters with admixture of light-weight metakaolin

Import 07/02/2011Cement a vápno představují hlavní pojiva, používaná v současném stavebnictví. Světová produkce cementu přesahuje 1,5 miliardy tun, produkce vápna a vápenného hydrátu se pohybuje okolo 150 mil. tun. Výroba těchto pojiv je vysoce energeticky náročná a odhaduje se, že přispívá 5 – 7% k celosvětové produkci oxidu uhličitého. Výzkum v materiálovém inženýrství stavebních hmot se proto začíná zaměřovat na hmoty, které by byly schopny v maltovinách částečně nahradit zejména cement, jejichž výroba by byla více šetrná k životnímu prostředí a které by zároveň přispívaly ke zlepšení užitných vlastností betonu a malt. Jedním z materiálů, který splňuje uvedené nároky je metakaolín, produkt tepelné aktivace kaolínu a kaolinitem bohatých jílů. V tuzemském stavebnictví dosud našel metakaolín uplatnění především jako aktivní příměs do vápenných malt, používaných při opravách historických budov. Předložená diplomová práce se zabývá přípravou a hodnocením vlastností vápenných malt s obsahem lehčeného metakaolínu, který se vyznačuje nízkou objemovou hmotností a zvýšenou pórovitostí. Lehčený metakaolín představuje zcela nový typ metakaolínu, který dosud není průmyslově vyráběn a komerčně nabízen na trhu. Kromě pozitivního vlivu na mechanické a trvanlivostní vlastnosti by ve formě plniva měl připívat k podstatnému zlepšení tepelných vlastností malt a omítek. Tato diplomová práce je jedním z prvních příspěvků v problematice lehčeného metakaolínu.Cement and lime represent the main binder used in the present building. World production of cement exceeds 1.5 billion tonnes, the production of lime and hydrated lime moves around 150 million tonnes. Production of these binders is highly energetically intensive and it is estimated to contribute 5-7% of global production of carbon dioxide. Therefore the research in building materials begins to focus on (matters) materials, which would be able to replace the cement in mortats partially; their production would be more environmentally friendly and it would also contribute to improvement of the concrete and mortar use properties. One material that meets these requirements is metakaoline, the product of thermal activation of kaolin and kaolinite-rich clays. In the domestic construction industry the metakaolin is used mainly as an active ingredient to lime mortar which is used for the historic buildings repairs. This thesis deals with the preparation and evaluation of properties of lime mortars containing lightgweight metakaoline, which is characterized by low density and increased porosity. Lightweight metakaoline is a completely new type of metakaoline, which has not yet been industrially manufactured and commercially offered on the market. Apart from the positive influence on the mechanical and durability properties, in the form of aggregates it should contribute to a substantial improvement of thermal properties of mortars and plasters. This thesis is one of the first contributions in the (issue) field of lightweight metakaoline problem.Prezenční223 - Katedra stavebních hmot a hornického stavitelstvívýborn

Study of Properties of Cement Mortars with Addtion of Metakaolin made from Alternative Raw Materials

Import 01/09/2009Prezenční223 - Katedra stavebních hmot a hornického stavitelstvívýborn

Interfacial Transition Zone Between Aggregate And Alkali-Activated Blast Furnace Slag – A Scanning Electron Microscopy

Alkali-activated binders are currently a widely-researched material. Thanks to the use of secondary raw materials such as slag from metallurgical production and ash from combustion, it appears to be a more promising and more environmentally friendly material than conventional cement concrete. Considerable attention is paid to the bonding phase itself, but only a few works deal with the binder-aggregate interaction. With cement concrete, much more attention is paid to this issue. This paper deals with the possibility of observation using electron microscopy and the information that can be obtained by this method. The problems of sample preparation and difficulties in the course of our own observation are observed

Interactions of Various types between Rock and Alkali-Activated Blast Furnace Slag

Alkali-activated binders (AAB) are very intensively studied materials nowadays. Because of possible usage as secondary raw materials, they can be environmentally efficient. Intensive research is focused especially on binder matrix, composition and its structure. For industrial usage, it is necessary to work with some aggregate for the preparation of mortars and concretes. Due to different structures of alkali-activated binders, the interaction with the aggregate will be different in comparison to an ordinary Portland cement binder. This paper deals with the study of interactions between several types of rocks used as aggregate and alkali-activated blast furnace slag. The research was focused especially on mechanical properties of prepared mortars

Interaction of various types of rock and alkali-activated blast furnace slag

Alkali-activated binders (AAB) are very intensively studied materials nowadays. Because of possible usage as secondary raw materials, they can be environmentally efficient. Intensive research is focused especially on binder matrix, composition and its structure. For industrial usage, it is necessary to work with some aggregate for the preparation of mortars and concretes. Due to different structures of alkali-activated binders, the interaction with the aggregate will be different in comparison to an ordinary Portland cement binder. This paper deals with the study of interactions between several types of rocks used as aggregate and alkali-activated blast furnace slag. The research was focused especially on mechanical properties of prepared mortars