Pomiary charakterystyk dynamicznych jako element projektowania wspomaganego badaniami przy wyznaczaniu obciążenia wiatrem stalowych wież kratowych wg Eurokodu

Previous authors’ publications, related to the analysis of steel lattice towers, describe some problems connected with it, especially ones referring to the calculations made according to the past Polish Standards. This paper presents the possibilities of measuring the dynamic characteristics of towers, as one of experimental methods allowed in Eurocode, practicable in verification of load capacity of existing structures.Dotychczasowe publikacje autorów, związane z obliczaniem stalowych wież kratowych wg norm Eurokod, wskazywały między innymi na specyfikę i złożoność tego procesu, w porównaniu do prac wykonywanych na podstawie poprzednich norm krajowych. Niniejsza praca opisuje już przeprowadzone oraz planowane przez autorów prace badawcze, związane z pomiarami charakterystyk dynamicznych przedmiotowych konstrukcji, wraz z ogólnym podaniem uzyskanych do tej pory wyników. Pomiary takie rozpatrywane są tu jako jedna z metod doświadczalnych, dopuszczanych normami PN-EN, możliwa do wykorzystania, szczególnie w ocenie nośności istniejących obiektów

Determination of bond model for 7-wire strands in pretensioned concrete beam

A correct choice of a bond model for prestressing tendons is crucial for the right modelling of a structural behaviour of a pretensioned concrete structure. The aim of this paper is the determination of an optimal bond model for 7-wire strands in a prestressed concrete beam produced in a precast concrete plant of Consolis Poland. ATENA 3D is used to develop finite element models of the beam that differ only in a bond stress-slip relationship of tendons. The bond stress-slip relationships for modelling are taken from the results of bond tests carried out by different researchers in previous years. Moreover, for comparison purposes, a simplified 2D model of the beam is created in Autodesk Robot. The strain distribution at the time of the strand release is found for each of the finite element models. The determined strain distributions are compared with the strain distribution in the beam established by an experimental test using a measuring system based on a digital image correlation. On the basis of the comparison results, the most appropriate bond models for 7-wire strands used in the beam are identified

Structural Analysis of Slender Glass Panel Subjected to Static and Impact Loading

Slender glass panels are widely used as storefronts and indoor separating walls in shopping malls and public buildings. To ensure that the design and construction is technically safe for general use and that it meets current and accepted technical standards, in-situ testing is required by the building administrator or authorities. A case study was performed of an indoor glass lantern in a public building made from slender two-side supported glass panels with a complex geometry. It provides structural assessments and results of in-situ experiments including static loading and soft body impact test. Results from numerical simulations of impact loading on the glass panels complementing the experimental results are also presented. The in-situ testing proved that the structural design meets current standards regarding the static loading. The soft body impact test proved the safety of the intact panel and the panel with one ply deliberately broken. The numerical study showed that, for a more complicated geometry, the stress distribution can dramatically change over time and that stress concentrations can develop at certain locations at a late stage in the impact history

Application of fibre composite grids as reinforcement of foamed PC and GP concrete

Cellular concretes cannot be reinforced as easily as traditional ones. Generally porous materials do not ensure sufficient bond of reinforcement; additionally, due to limited amount of aggregate, interlock between aggregate particles and reinforcement ribs is not satisfactory. The idea of reinforcement presented in the paper incorporates bi-directional composite reinforcing grids placed in tensile zone of the cellular concrete slab where transverse fibres are ensuring anchorage for fibres located in the main direction of stresses. The concept is based on geotechnical applications where grids are commonly used as soil stabilization, but the grids adopted in this solution are much stronger thanks to introduction of high strength fibres as composite reinforcement

Anchors in KBO, KBOS and KBS post-tensioned girders

Historia stosowania w Polsce dachowych dźwigarów kablobetonowych trwała od roku 1953 do 1976. Do dzisiaj użytkowane są setki obiektów z dachami na takich dźwigarach. Jednymi z podstawowych elementów zapewniających bezpieczeństwo tych konstrukcji są zakotwienia kabli sprężających systemu Freyssineta (bloki i stożki kotwiące), a te ewoluowały w okresie projektowania i wykonawstwa kolejnych typów dźwigarów. W artykule przedstawiono przegląd stosowanych rozwiązań wraz z przykładami praktycznymi, a także pokrótce ustosunkowano się do zasad oceny stanu zakotwień oraz sposobu postępowania w przypadku ich wad lub uszkodzeń.The history of the use of post-tensioned concrete roof girders in Poland lasted from 1953 to 1976. Until today, hundreds of structures with roofs on such post-tensioned girders are in use. One of the basic elements ensuring the safety of these structures are the anchors of the Freyssinet cables (anchoring blocks and conical plugs). They evolved during the design and construction of subsequent types of girders. The article presents an overview of the applied anchor solutions together with practical examples. In addition, the principles of assessing the condition of anchorages and the procedure in case of their defects or damage is also discussed

On untypical roof solutions in the form of post-tensioned concrete girders used in Poland

Pomimo upływu ponad 40 lat od ostatnich realizacji w Polsce wciąż użytkowanych jest kilkaset hal z dachami na dźwigarach kablobetonowych. Większość z nich tworzą elementy typowe, mieszczące się w licznej grupie rozwiązań ujętych w katalogach pod symbolami KBO, KBOS, KBS lub KBU. Jednak istnieją też dźwigary nieskatalogowane, a czasem powstałe nawet poza tak zwanymi projektami typowymi. W artykule pokrótce scharakteryzowano wybrane rozwiązania nietypowe oraz te, które pozostały na etapie koncepcji lub prototypów. Opisy poprzedzono garścią wiadomości o genezie powstania tych interesujących i śmiałych rozwiązań oraz krótką charakterystyką rozwiązań typowych.Although more than 40 years have passed since the last realizations, still several hundreds of halls with roofs on post-tensioned concrete girders are used in Poland. Most of these roofs are constructed with typical elements, included within the large group of solutions mentioned in catalogues under the symbols KBO, KBOS, KBS or KBU. However, one can also find girders which are uncatalogued, and sometimes even created outside the so-called typical projects. The article briefly characterized the selected untypical solutions as well as solutions which remained at the stage of concepts or prototypes. The descriptions have been preceded by a handful of facts about the origins of these interesting and daring solutions together with some short characteristics of typical solutions

Historical buildings in an emergency technical condition

Ideą artykułu jest pytanie - czy zabytkowy obiekt budowlany pozostaje nim niezależnie od stanu technicznego, czy też pewien stopień zrujnowania uprawnia do starania się o wykreślenie go z rejestru zabytków? Pokrótce odniesiono się do stanu prawnego uznania obiektów budowlanych za zabytki, a następnie przedstawiono wybrane przykłady budynków zabytkowych, które z czasem uległy daleko posuniętej destrukcji. Przedstawiono tu, ilustrując fotografiami, podstawowe uszkodzenia elementów konstrukcyjnych i wykończeniowych, a następnie opisano dalsze losy przedmiotowych obiektów. Zwrócono też uwagę na problem odpowiedzialności za obiekt zagrożony katastrofą budowlaną, a niemożliwy do likwidacji.The main idea of the article is whether a historical building remains a monument regardless of the technical condition or is there a certain degree of destruction that entitles its removal from the register of monuments? The legal status of recognizing buildings as monuments has been briefly referred, then selected examples of historical buildings that have been badly damaged over time were presented. The basic damages to construction and finishing elements are presented and illustrated on photographs, then the further fate of the objects in question is described. The problem of the responsibility for the facility at risk of a construction disaster that cannot be demolished has also been highlighted

Basic Chemical Tests of Concrete during the Assessment of Structure Suitability—Discussion on Selected Industrial Structures

Making a decision to perform an overhaul of a damaged reinforced concrete structure should be preceded by an analysis of the real durability of that structure after the repair in connection with the anticipated service life. One of the basic problems is the avoidance of further corrosion of concrete and steel after the repair, which depends on the degree of concrete contamination with harmful chemical factors. It is particularly important to determine the content of chloride and sulfate ions which cause corrosion. Concrete pH is equally significant because it conditions effective passivation of the reinforcement. The paper presents the basic issues related to the main chemical threats, including the main sources of their origin as well as their limit values. It emphasizes the importance of conducting the chemical tests of concrete, which should be treated as one of the methods of determining structure suitability for an overhaul, especially in the context of subsequent durability. This seems obvious to an experienced specialist, but in practice, such studies are often ignored. Those considerations are backed up with selected examples of reinforced concrete industrial structures exposed to aggressive chemicals during their operation. The text shows the correlation between their technical condition and chemical test results as well as the influence of those results on making decisions concerning effective overhauls

Aerodynamiczne tłumienie drgań w obliczeniach stalowych wież kratowych

Structural analysis of lightweight freestanding structures, such as steel lattice towers, mainly consists of determining the along-wind dynamic response of the vibrating structure. These vibrations are damped not only structurally but also by the aerodynamic forces. In the Polish design practice, aerodynamic damping concept was introduced together with the rules of Eurocode standards. With respect to the lattice towers, in many cases, these rules are inaccurate, therefore the paper contains some suggestions of authors.Obliczanie stalowych wież kratowych sprowadza się przede wszystkim do wyznaczenia odpowiedzi dynamicznej konstrukcji, drgającej w kierunku średniej prędkości wiatru. Te drgania, smukłej i stosunkowo lekkiej konstrukcji, podlegają tłumieniu, nie tylko konstrukcyjnemu, ale także spowodowanemu oporem ośrodka w jakim się odbywają. W odniesieniu do przedmiotowych konstrukcji, fakt występowania drugiego z wymienionych tu czynników tłumiących ujawnił się w praktyce inżynierskiej dopiero poprzez procedury norm Eurokod. Formuły te w wielu przypadkach pozostają jednak mało precyzyjne – stąd zawarte w niniejszym referacie propozycje autorów. Rozbieżności podanych metod ilustruje przykład obliczeniowy