Korrosionsverhalten von Anschweißankern aus nichtrostendem Stahl bei hinterlüfteten Außenwandbekleidungen aus Naturwerkstein

In diesem Beitrag werden Betrachtungen zur Korrosion von Anschweißankern aus nichtrostendem Stahl der Werkstoff‐Nr. 1.4571 bei Naturwerksteinfassaden angestellt. Weiterhin werden Ergebnisse korrosionstechnischer Untersuchungen an derartigen Ankern aus bestehenden, bis zu 23 Jahre alten Bauwerken wiedergegeben. Bei sachgerechter Interpretation der dargestellten Zusammenhänge kann gefolgert werden, dass die im Regelwerk geforderten Maßnahmen zur grundsätzlichen Entfernung von Anlauffarben und zum Verschließen von Spalten bei atmosphärisch beanspruchten geschweißten Verbindungen im Fall der hinterlüfteten Außenwandbekleidungen aus Sicht der Korrosion technisch nicht begründet und unnötig sind. Corrosion behaviour of stainless steel weld‐on anchors of claddings for external walls ventilated at the rear and made of natural stone. In the contribution considerations are made about the corrosion of stainless steel weld‐on anchors of the material No. 1.4571 of claddings for external walls ventilated at the rear. Furthermore, results of corrosiontechnical investigations on such anchors of buildings which are up to 23 years old are reported. With proper interpretation of the shown connections it must necessarily be concluded that the measures in the set of rules concerning the removal of temper colours and the closing of crevices of atmospherically exposed weld‐on anchors are technically not founded and unnecessary from the corrosion point of view if ventilated facades are taken into consideration.     

Thermofluid-dynamic analysis of ventilated facades

Ventilated facades can be used in cases of renovation of existing buildings and new buildings to improve both the thermal performance of building, and external architectural skin. The energy advantage provided by the ventilated facades during the summer is the reduction of the heat load due to the combined effect of the shading of the external wall and the air flow caused by natural convection into the heated duct.The evaluation of ventilated facade performance requires a complete thermofluid-dynamic analysis of a ventilated air duct and an accurate knowledge of heat transfer coefficients, friction factors and thermo-physical properties of the materials.The Authors have used the computer code “Fluent” to investigate the thermal behaviour of three different typologies of ventilated facades.The aim of this research is to show an analytical method for design applications able to provide all the useful criteria for choosing the most suitable ventilated facades both in case of forced convection, due to the action of a fan, and natural convection due to stack effect.     

Behaviour of ventilated double layer external wall briquettes under earthquake loading

Ventilated double layer briquette is used as external walls in the construction of classical as well as modern buildings that are built in regions having climates with high temperatures or rainy and windy seasons. In this construction technique, the external layer which acts as shield against rain, wind and solar rays, and internal layer are laid separately and then interconnected to each other with steel ties.The aim of using such briquettes in the construction of external walls is to obtain ventilated double layer wall by just laying single layer of briquettes. The staggering of vertical joints provides better bond and added structural strength. The hollow cores should be directly above one another so that they can be filled with additional thermal insulation materials as the wall constructed, if required.In this paper, the earthquake response of two walls, one built using the new briquette produced from normal concrete mortar and the other constructed using the proposed briquette made out of lightweight pumice concrete mortar are studied.It was found that the wall produced using lightweight pumice concrete mortar behaves better under earthquake loads and it has higher energy absorption capacity than the other.     

Zertifizierung von Offshore‐Windparks – Erste Erfahrungen

Certification of offshore wind farms – lessons learned. Design and construction of an offshore wind farm is a complex task making it necessary to organize the participation of experts from various fields over several years. Installation costs of such projects may lie in the order of some hundred million Euros. In general, the design process will be accompanied by a project certification by independent third parties like Germanischer Lloyd (GL). Based on their experience from offshore technology as well as onshore wind farms, this procedure guarantees keeping the safety and the so‐called “Principle of Four Eyes”. This article gives an introduction about the basic concept of certification of offshore wind farms. By describing some executed European projects, the focus is put on the complex interaction of external actions, support structure and wind turbine behaviour. The paper is completed by experience from research work in the field of corrosion protection and the operation of the FINO 1 research platform.     

Indoor climate — CIB W77

Dr.‐Ing. Erhard Mayer of the Fraunhofer‐Institüt für Bauphysik, FhG (Director Prof. Dr.‐Ing. habil. Karl A. Gertis) has established that the indoor climate analyzer or artificial skin has proved useful for the objective evaluation of air movement for degrees of turbulence above 20%, and that the convective heat transfer coefficient, instead of mean air velocity, can be used as a basis for thermal comfort.     

Beurteilung von Korrosionsschutzsystemen für Offshore‐Windenergietürme – Teil 1: Problemstellung und Versuchsdurchführung

Assessment of corrosion protection systems for offshore wind energy towers – part 1: Introduction and test scenario. Based on field and on laboratory tests, the corrosion protective performance of different corrosion protection systems for offshore wind energy towers was investigated. The systems under investigation included duplex systems with Zn/Al metallization, multi‐layered organic systems, a single‐layer thick organic system, Zn/Mg metallization and cathodic protection of uncoated sections. Special field specimens and laboratory specimens were utilized in order to investigate the systems. Laboratory tests included immersion tests, ageing tests, test on cathodic compatibility and electro‐chemical impedance spectroscopy. Part 1 of the paper covers the general experimental design and details of the experimental procedures, whereas Part 2 deals with the results of the test programme.     

How passive solar systems perform

Three representative types of passive solar heating arrangements were evaluated by mathematical simulation techniques in a test series in Japan, based on weather data from Sapporo. The results achieved, notably the effect of thermal storage capacity on performance, are discussed here by a research engineer who is now working with Dr Karl Gertis at the University of Essen's Institute of Building Physics, Western Germany.     

Der Einfluss natürlich durchströmter Doppelfassaden auf die Strahlungsbelastung

The influence of naturally ventilated double façades on solar radiation heat load. Air flow and the heat transfer processes in naturally ventilated double façades are known almost exclusively from realized façades. It is usually assumed that the real conditions are quite complicated and therefore only accessible by computational simulations. However, an analytical treatment in analogy to Petzold's procedure of air vented double walls is possible. The computation requires knowledge of the solar transmittance, reflectance and absorption (solar transmission factors) of the façade glasses. With the solar energy transmittance value (g‐value) the radiation load can be determined as an approximation only. Air flow and temperature distribution calculated in this way are in good agreement with the results based on solar transmission factors.     

Empirical validation and modelling of a naturally ventilated rainscreen façade building

In this paper the thermal behaviour of a rainscreen ventilated façade has been investigated both experimentally and numerically. Field measurements were performed during the 2009/10 winter season in a test building located in San Mauro Pascoli (Italy) having a squared base of internal dimension of 2.89 m and a total internal height of 7.75 m. The external walls of this tower are rainscreen ventilated façades with a 24 cm air cavity and an external side composed of stoneware with open joints. Ventilation grills are located at the top and at the bottom of the tower. In this work the modelling of the test building using a dynamic thermal simulation program (ESP-r) is presented and the main results discussed. In order to study the rainscreen ventilated façade three different multi-zone models were defined and the comparison with the experimental results has been used in order to select the best ESP-r air flow network for the modelling of this kind of envelope component. The thermal analysis of this envelope component evidenced that the ventilated façade is able to reverse the direction of the heat flux through the envelope in regions characterized by large solar irradiation during the winter and moderate wind velocity, when the indoor-outdoor air temperature difference is small, thereby reducing the energy consumption required for indoor heating.     

Messtechnische Analyse flachgeneigter hölzerner Dachkonstruktionen mit Sparrenvolldämmung — Teil 3: Hinterlüftete und nicht hinterlüftete Metalldächer

Im dritten und abschließenden Teil dieser Aufsatzreihe werden die Messdaten aus hinterlüfteten und nicht hinterlüfteten flachgeneigten Metalldächern diskutiert. Diese wurden im Freilandversuch über 17 Monate unter besonnten und Vollzeit beschatteten Randbedingungen untersucht. Hierbei zeigt sich, dass bei besonnten Bedingungen in beiden Dachaufbauten die innenseitige Dampfbremsbahn durch eine OSB ersetzt werden kann, ohne dass sich kritische Klimabedingungen oder erhöhte Materialfeuchten im Gefach einstellen. Die verwendete Gleitbügelblecheindeckung beim nicht hinterlüfteten Dach ermöglicht einen diffusionsoffenen Aufbau. Das hinterlüftete Metalldach zeigt trotz geringen Luftvolumenstroms in der Hinterlüftungsebene das günstigste hygrische Verhalten aller untersuchten Dachauf bauten. Measuring investigations of the hygrothermal behaviour of timber flat roofs — Part 3: Ventilated and non‐ventilated metal roofs. In the third and last part of this article serial the measuring values of ventilated and non‐ventilated metal roofs are discussed. The roofs were investigated at a full scale test under sun‐exposed and full‐time shaded conditions. It was shown that at sun‐exposed conditions the vapour retarder membrane in both metal sheeted roofs can be replaced by an OSB without critical climate or increased moisture content in the cavity. The used metal sheeting at the non‐ventilated roofs enables a water vapour permeable construction. The ventilated metal roof showed in spite of the little airflow in the ventilation layer the best hygrical behavior of all investigated roofs.     

Faserbewehrte Putze auf hochdämmenden Untergründen

Fibre reinforced rendering for high insulating external walls. Today's common high insulating “External Thermal Insulation Composite Systems” (ETICS, e.g. brickwork with special porosity‐enhancing material) lead to an increased thermal‐hygric load of the rendering. A reinforcement of the brittle rendering is necessary to enable lasting acceptance of occurring tensile and bending tensile stress. The following article describes material properties as well as usability of fibre‐reinforced light‐weight rendering. By adding a sufficient quantity of high‐strength fibres the brittle rendering matrix with very low ultimate tensile strain turns into a “ductile” material with elastic‐plastic material behaviour. The thermal‐hygric influence on the rendering surface due to natural weathering leads to high stress and strain on the rendering layer. Large‐scale tests with artificial weathering of external wall constructions as well as FEM‐computations show, that only overcritical fibre‐reinforced renderings are able to guarantee a sufficient weather protection of the exterior wall.     

Load carrying capacity enhancement of cold formed steel walls using shotcreted steel sheets

Recently worldwide cold formed steel buildings are recognized as viable alternatives to reinforced concrete buildings especially in seismic areas. This is because they are lightweight (easy to handle), fast constructed, energy efficient (green houses), economical, dimensionally stable and they do not need skilled worker. Under vertical loading the design principles of these buildings are well established and codified, however, under lateral loadings such as wind and earthquake loads efficiently design is needed. In this paper a new sheathing technique uses shotcreted ribbed steel sheets is proposed to improve the stability and increase the lateral load carrying capacities of the CFS walls in order to withstand earthquake and wind loads safely. The idea is to sheath the outer side of CFS structure external walls with thin ribbed steel sheets, then shotcreted the sheets with cement or gypsum mortars. To test the concept full size wall specimens were prepared in the laboratory and tested under monotonic vertical and lateral loads. Some of the specimens were sheathed with the traditional fiber cement boards or gypsum boards with mat reinforcement, while the others were sheathed with the proposed technique. Test results indicates that the lateral load carrying capacities of the walls sheathed with the proposed technique increases by about two times compared with the walls sheathed with traditional boards. And under ultimate loads they fail in local failure modes rather than overall buckling failure modes which commonly occur in the walls sheathed with traditional boards.     

Ohne ihn gäbe es keinen Eiffelturm: Maurice Koechlin (1856–1946)

Without him there would be no Eiffel Tower: Maurice Koechlin (1856–1946). For the “world exhibition of the peace”, 1889 in Paris, beside many competitors also Gustave Eiffel had submitted a plan for a tower later on designated after him. Draft and calculation came however from the Native of Alsace Maurice Koechlin, the leading engineer of its enterprise, who was entrusted after the study of Karl Culman's work in Zurich first with planning and building preparation of the Garabit bridge (Auvergne) and then with the draft for the structure of the liberty statue in New York. Koechlin's main work was afterwards the organization of the tower and its elements with special consideration of the wind effect. Also the organization of the planning office with the treatment of details that was incumbent on him nevertheless approximately 18000 individual parts of the tower. 1893 he took over the line of the enterprise and the presidency of the Eiffel‐Turm society from Eiffel, with which time life a cordial friendship connected him, – up to his retirement in 1926. He spent his old age in Veytaux/Genfer See.     

Zur Tragfähigkeit unbewehrter Betonwände

Load Bearing Capacity of Non‐Reinforced Concrete Walls The simplified approach for the design of compression members made of non‐reinforced concrete according to DIN 1045‐1 leads to large cross sections for slender walls with eccentric loading. Based on the principles of DIN 1045‐1 a design method is deduced in this article. The use of this method allows a simple, standardised and economic design of non‐reinforced compression members. A further increase in load bearing capacity can be achieved by taking into account the concrete tensile strength.     

Beurteilung von Korrosionsschutzsystemen für Offshore‐Windenergietürme – Teil 2: Ergebnisse und Schlussfolgerungen

Im Rahmen von Auslagerungs‐ und Laborprüfungen wurde die Korrosionsschutzwirkung verschiedener, für den Schutz von Offshore‐Windenergietürmen geeigneter Systeme untersucht. Zu den untersuchten Systemen gehörten Duplexsysteme mit Zn/Al‐Metallisierung, mehrschichtige organische Systeme, ein einschichtiges organisches System, eine Zn/Mg‐Metallisierung sowie unbeschichtete Bereiche mit kathodischem Korrosionsschutz. Alle Systeme wurden an speziell gefertigten Auslagerungsprobekörpern sowie an Laborprobekörpern geprüft. Die im Labormaßstab durchgeführten Prüfungen umfassten Tauchversuche, Alterungsversuche, Versuche zur kathodischen Verträglichkeit und Messungen mittels elektrochemischer Impedanzspektroskopie. Im Teil 1 des Beitrages, veröffentlicht im Heft 4/2009, wurden Konzeption und Durchführung der Prüfungen sowie die verwendeten Probekörper und Korrosionsschutzsysteme detailliert beschrieben. Über die Ergebnisse der Prüfungen wird im Teil 2 berichtet. Assessment of corrosion protection systems for offshore wind energy towers – part 2: Results and conclusions. Based on field and on laboratory tests, the corrosion protective performance of different corrosion protection systems for offshore wind energy towers was investigated. The systems under investigation included duplex systems with Zn/Al metallization, multi‐layered organic systems, a single‐layer thick organic system, Zn/Mg metallization and cathodic protection of uncoated sections. Special field specimens and laboratory specimens were utilized in order to investigate the systems. Laboratory tests included immersion tests, ageing tests, test on cathodic compatibility and electro‐chemical impedance spectroscopy. Part 1 of the paper (Stahlbau, No. 4/2009) covererd the general experimental design and details of the experimental procedures, whereas Part 2 deals with the results of the test programme.     

Penetration of snow into roof constructions—Wind tunnel testing of different eave cover designs

Ventilated roof is a common practice of building design in the Scandinavian countries. One problem with this design is the penetration of blowing snow into the ventilated space in the roof. The rate of snow penetration is largely dependent on the design of the eave. In Norway and Greenland, different design solutions have been tried, based on experience and intuition. However, these solutions have, until now, never been verified under controlled laboratory conditions.The ability to prevent snow penetration and still allow ventilation of the ventilated roof or attic is tested for several different eave constructions. The testing has been performed in a wind tunnel in an environment of cold air and with production of artificial snow. The scale of the eave constructions was 1:1.Most of the designs in the experiment are common in Scandinavian building practice. However, new innovative solutions designed for extreme snow drifting environments in Greenland were also tried. Also, the effect of a deflector to deflect snow particles away from the ventilation openings was tested. Over 400 times more snow accumulated in the construction allowing the most snow to enter the roof compared to the construction designed for extreme environments.     

Experimental analysis of natural convection in open joint ventilated façades with 2D PIV

The main particularity of Open Joint Ventilated Facades (OJVF) is that they have an exterior opaque coating separated from the mass wall by a ventilated air cavity. The exterior coating material is arranged in slabs separated by open joints that enable exterior air to enter and leave the cavity all along the wall. Under radiation conditions (and negligible wind velocity) the natural thermal convection produces a chimney effect that forces external air to circulate along the air cavity at an unknown rate. As a consequence of this mass exchange through the openings, the heat transfer problem turns more complex: air motion and thermal field are strongly coupled and therefore highly dependent on geometric characteristics of the wall. This article reports the application of Particle Image Velocimetry technique (PIV) to measure the velocity field inside the air cavity of an OJVF model in laboratory conditions. Measurements were performed for the vertical central plane of the cavity, for three different heating conditions corresponding to Ra = 5.92 × 10⁸, Ra = 9.19 × 10⁸ and Ra = 1.35 × 10⁹, based in the channel height, and with a Re about 10⁴. Detailed information of the flow behaviour inside the air cavity are presented and discussed. Special attention is paid to the ventilation effect through the joints.     

Sensitivity of air change rates in a naturally ventilated atrium space subject to variations in external wind speed and direction

Design guidelines for natural ventilation (NV) in buildings focus on the potential hourly air change (ACH) rates based on the building space parameters. Critically, external airflow data is often assumed on the basis of a single mean wind speed and an associated prevailing wind direction. This can result in significant variation in ventilation rates and comfort conditions when non-design external wind conditions prevail. This paper describes a CFD study aimed at examining the influence of variations in external wind speed and direction on the air change rate for the atrium space of a two-storey naturally ventilated building. The building atrium is ventilated by a series of entry vents on one wall of the building in conjunction with roof vents. External wind speeds from 25 to 250% of the mean site wind speed (5.7 m/s) were examined and found to result in an almost linear increase in the ACH rate. For a single wind speed, the relationship between wind direction and the ACH rate was also found to be approximately linear for wind directions between 0° and 90° (orthogonal and parallel) to the wall vent openings, but non-linear for other wind directions (90–135°). More generally, the significant variation in the atrium ACH rate with changes in external wind conditions, evident in this particular building model, illustrates the importance of considering non-design wind conditions when designing NV buildings.     

Three‐dimensional coupled wind‐induced vibration calculation method for super high‐rise buildings based on high‐frequency force balance technology

High‐frequency force balance test is a major technical means to evaluate the wind effect of super high‐rise buildings. Most super high‐rise buildings have the characteristic that the first two‐order modal frequencies are close, and thus, considerable modal coupling effects (MCEs) may occur under wind load. For a balance model system (BMS), MCEs increase the difficulty of correcting aerodynamic distortion signals. For the wind‐induced vibration analysis of a structural system (PSS), the calculation results of the wind‐induced response and the equivalent static wind load (ESWL) may be significantly affected without considering MCE. Based on the above‐mentioned signal distortion of BMS and the modal coupling problem of PSS, this study proposes a wind‐induced vibration calculation method for the two coupled systems (BMS and PSS). The method uses the second‐order blind identification technique based on complex modal theory and the Bayesian spectral density method considering full aerodynamic characteristics to achieve effective correction of the distortion signal in BMS. In addition, it deduces the calculation method of the wind‐induced response and ESWL considering the three‐dimensional coupled vibration of a super high‐rise building. The wind effect calculation results of a 528‐m super high‐rise building confirm the necessity and effectiveness of the proposed method.     

建筑幕墙风荷载的数值模拟研究

对幕墙结构中风荷载的脉动特性进行了分析，采用沿高度变化的E．Simiu风速谱，用改进的谐波叠加法模拟了不同高度处脉动风速和风压的时程曲线，给出了风荷载的计算公式，结果表明该方法简单有效，且能够反映脉动风的随机特性，解决了玻璃幕墙风荷载的动力计算问题。