24th Concrete Days 2017

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Authors: Radoslav Vida, Jaroslav Halvonik, Lucia Majtánová
Abstract: An ability of reinforced concrete slabs to distribute concentrated load in transverse direction is an important property for their verification. Several methods for the assessment of transverse distribution (effective width) were proposed but they were not incorporated in the current standards. This paper deals with an experimental analysis of the effective width for shear verification of slabs subjected to concentrated load. Shear resistance of the slab specimens subjected to concentrated load obtained from tests has been compared with resistance of the slab strips loaded by uniform shear. Based on this check, the effective width has been evaluated. Experimental results were also compared with results of models introduced in relevant standards.
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Authors: Kamil Laco, Viktor Borzovič
Abstract: The transition zone of the road bridges is located right behind the abutment. Function of this structure is to ease the vehicle transition from the bridge on the rigid support to the embankment with much smaller stiffness. The main function of the approach slab is, as a part of the transition zone, helping the backfill to overcome different stiffness of the bridge foundations and embankment. The paper deals with shear resistance of the slabs for different lengths and widths. Parametrical study was performed according to Eurocode loading model 1 (Uniformed distributed load and Tandem system). Each of the analysed slabs was loaded with sets of different TS positions and location of the loading lanes. Envelopes of the shear forces of the approach slabs were analysed for each type of the slab. After that shear resistance of the slab with or without the shear reinforcement was calculated. The slab was divided into areas with same shear reinforcement distribution. The analysis is the part of the engineering tool for the bridge designers. According to length and width of the slab, the engineer can easily choose the shear reinforcement diameter and its distribution. The tool also provides the construction details of the shear reinforcement. There will be also the option for the reinforcement design of the slab, with hints for the structural scheme and calculation method.
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Authors: Jakub Venclovský, Petr Štěpánek, Ivana Laníková
Abstract: It is possible to see various applications of mathematical optimization in civil engineering (structural design, reconstruction of transportation networks etc.) Initially, deterministic approaches have been introduced to solve these problems. But despite their complexity, these approaches are insufficient to comprehend the probabilistic nature of said problems and thus provide only suboptimal solutions. Hence the effort comes to reconsider these deterministic approaches and deal with uncertainties involved in said problems in less straightforward way. The goal of the paper is to present the algorithm for stochastic optimization of design of steel-reinforced concrete cross-section. This algorithm is based on internal cycle of deterministic optimization using reduced gradient method and external cycle of stochastic optimization using regression analysis. Firstly, the deterministic problem is introduced and described. It is followed by the description of uncertainties, which are involved in the process, and stochastic reformulation of the problem. Then the algorithm itself is introduced and the paper ends with presentation of the results of performed calculations.
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Authors: Břetislav Teplý, Tomáš Vymazal, Pavla Rovnaníková
Abstract: Efficient sustainability management requires the use of tools that enable the quantification, measurement or comparison of material, technological and construction variants. Tools of this kind which have been developed around the world in recent years include various indicators, indexes, etc. Generally, technical, economic, ecological and socio-cultural areas must all be included. Such a tool can be used as a powerful marketing aid and as support for the transition to the “circular economy”. Life Cycle Assessment (LCA) procedures are also used, alongside other approaches. LCA is a method that evaluates the life cycle of a structure from the point of view of its effect on the environment. Processes starting with the mining of mineral resources and including their transport, production and use up to their final processing as waste (recycling) are all taken into account. In addition, consideration is given to energy and raw material costs, and to environmental impact throughout the whole life cycle – e.g. through emissions. The presented contribution focuses on the quantification of sustainability connected with the use of various types of concrete with regard to their resistance against the effect of degrading influences. Sustainability factors are also determined using information regarding service life and “eco-costs”. The aim is to present a suitable methodology which can simplify decision-making concerning the design and choice of concrete mixes from a wider perspective, i.e. not only from the aspects of load-bearing capacity or durability.
273
Authors: Remington G. Reed, Jospeh Daniels III, W. Micah Hale
Abstract: In recent years there has been an increased demand for environmentally conscious and sustainable construction materials. One such material is “geopolymer” or “alkali-activated” binder. Current industry practice uses ordinary portland cement (OPC) in combination with supplementary cementitious materials as binder in concrete and mortar. Cement production is very energy intensive and accounts for approximately 10 percent of the total carbon dioxide emission in the world. In geopolymer materials, OPC is replaced with waste materials such as fly ash or slag cement along with a chemical activator. When supplied with additional chemical constituents, the aluminate and silicate present in fly ash or slag cement arrange into a polymeric structure with similar properties to hydrated cement. Proper application of this material can reduce, or even replace, the use of OPC in concretes and mortars. In addition to the cutback in OPC and the use of waste products, geopolymer materials require less water for curing and are shown to have increased resistance to chemical attack. While this product offers a “green” alternative to OPC, it is a new technological concept. Fly ash variability creates inconsistencies in quality control and chemical content. The chemical activators used to facilitate polymerization are often quite expensive and dangerous to use. Additionally, heat curing can be necessary for a geopolymer material to achieve specified compressive strength. Present limitations warrant extensive research and development to increase practicality of geopolymer materials for field implementation. In order to aid in the design and use of geopolymer materials, it is important that laboratory studies fully address the use of less than ideal materials and conditions in the creation of geopolymer. By using low cost materials and avoiding heat curing, laboratory research on geopolymer mortar can function as a means of developing a material that can be readily adopted into practice.
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Authors: Magdaléna Šefflová
Abstract: This paper is focused on properties of recycled aggregate. Three types of recycled aggregate were used for experiment (designation REC A, REC B and REC C) and for comparison natural aggregate (designation NA). The geometrical and physical properties of recycled aggregate were tested. The test results were comparison with natural aggregate. The results confirmed that the quality of the recycled aggregate depends on kind of demolishing process and subsequent recycling process in the recycling plant.
284
Authors: Tereza Pavlů, Tomáš Vlach, Jakub Řepka
Abstract: This contribution is to verify the utilization of waste glass as partial replacement of fine aggregate for high performance concrete (HPC). Test results of fresh and hardened HPC will be presented. This study has been conducted through basic experimental research in order to analyze the possibilities of recycling waste glasses (grinding glass, milled glass powder from municipal waste) as partial replacement of silica powder for HPC.
290
Authors: Jan Tichý, Pavel Ryjáček, Vit Šmilauer, Bohuslav Slánský, Stanislav Ševčík
Abstract: UHPC (ultra high performance concrete) is used mainly within bridge engineering, due to the demand for subtle but strong material, with high durability against aggressive environment. During the last two years, a series of thin-walled railing panels were made in premises of Skanska a.s. company. They were used for a footbridge in Čeperka village, and this year also for a renovation of a bridge SZ-001 in Sázava municipality. The renovation of a bridge, manufacturing of the railing panels, development of its shape and results of conducted test will be presented.
299
Authors: Libor Mařík, Matěj Bůžek
Abstract: Construction of the Považský Chlmec Tunnel on the D3 Highway in the stretch Žilina (Strážov) – Žilina (Brodno) is being finished and the last structure before installation of the technological equipment has been a concrete pavement and construction works related to design and construction of the pavement. The paper describes not only the issue of road structural layers according to the regulation TP098 Design of Cement Concrete Pavements on Roads, but especially on a specific example of a tunnel already built we demonstrate general particularities of road surfaces in road and highway tunnels. These are, in particular, engineering requirements on the subgrade and possibilities of its drainage, design of joints of the cement concrete pavement in relation to the tunnel lining design, ensuring the necessary long-term roughness of the road surface, design of entries of utility lines (cables, drains) below the road surface, structural details connected with placement of kerbs and channel drains, lay-bys, impacts of use of self-extinguishing road drainage components in the load bearing system of the tunnel lining and other seemingly independent structures, which, however, in the confined tunnel space influence each other substantially. The paper focuses also on construction of the individual road courses with a recommendation for measures to adopt in order to eliminate damage to the tunnel structures completed (in particular, pavements, channel drains and kerbs), coordination of the other works in the tunnel ensuring safety of all workers, logistics (transport of pavers and cement concrete mix) and other apparently tiny details, which result in safe and fast work when placing the road courses in a restricted tunnel space. In the paper, the authors have taken into account requirements of the road engineering segment and also geotechnical requirements and particularities of the tunnel construction and point out the necessity of a multi-professional approach to the design to achieve an optimal solution. Based on their own experience, at the end of the paper, the authors give recommendations on amending the standards and regulations, which in some cases do not allow for construction of road surfaces in tunnels (i.e. deep under the ground).
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Authors: Peter Havlíček, Július Šoltész
Abstract: The construction of bridges with use of seismic isolation is a less-used concept in Slovakia and the Czech Republic. The concept of seismic isolation of bridges is a way of protecting bridge construction without damaging the pillars and substructure unlike the currently used methodology of consideration and development of plastic joints. When using this concept correctly, it is possible to prevent serious damage of construction and greatly reduce economic losses. Creation of a FEM (Fine Element Method) model, that is capable of correct description of the bridge behavior during a seismic event is often problematic. In this paper, the features of designing and modeling of bridge constructions with use of seismic insulation based on elastomeric bearings are presented. Furthermore, the calculations of stiffness constants required for numerical modeling are presented as well. In this paper are described methods of modeling of seismic isolations in a commonly and commercially available FEM based software. The work also contains a comparison of possibilities as well as limits of these programs. We further present recommendations for correct modeling by use of nonlinear material properties or elastic bonds between elements.
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