Der Beitrag von Profilblechdecken zur passiven Kühlung

The potential of profiled steel sheet deck systems in reference to passive cooling strategies. The use of the thermal inertia of building components to improve the indoor temperature and to reduce the energy consumption was covered in various research projects in the past. Generally, thermal building simulation tools (TRNSYS, TAS, e.g.) are used for the assessment of the effect of thermal inertia, and also the current version of the standard DIN V 18599 takes the effect of the heat capacity of the affected surfaces. Both, DIN V 18599 and thermal building simulation tools, assume a one‐dimensional characterization of walls and flooring systems, that means they are assembled based on plane layers. This approach is not valid for inhomogeneous components like profiled steel sheet deck systems. In this report thermal equivalent values for such elements are developed, based on the analysis of transient Finite Element Calculations (FEM), thus the one‐dimensional are suitable using these equivalent properties. For a selection of available profiles the effect of such deck systems referring heat‐intake and heat‐disposal was investigated.     

ComfSim – Interaktive Simulation des thermischen Komforts in Innenräumen auf Höchstleistungsrechnern

ComfSim – Interactive indoor thermal comfort simulation on high performance computers. The paper outlines the current state of the development of a ‘computational steering’ environment for interactive indoor thermal comfort simulation and assessment. The system consists of a parallel CFD kernel, a fast 3D mesh generator and an integrated virtual reality‐based visualization component. The numerical method is based on a hybrid thermal lattice Boltzmann method with extensions for simulations of turbulent convective flows. Utilizing high‐performance supercomputing facilities allows for modifying both the geometric model and the boundary conditions during runtime with immediate visualization of changes in the results. We currently enhance our model by a radiation model with fast visibility check and integrate a local thermal comfort model developed in cooperation with our partners. The application is demonstrated by turbulent convection in a train's passenger carriage.     

Aero‐hygrothermisches Verhalten von Umfassungskonstruktionen mit Hohlräumen

Aero‐hygro‐thermal behaviour of building enslosure components with opened and enclosed air cavities. Air cavities with different functions can be found in historical as well as in modern structural design. In the past, air cavities mainly have been made for practical reasons to improve the thermal insulation properties of wall and roof constructions. In modern architecture, hollow spaces frequently arise due to constructional or due to aesthetic reasons such as in glass curtain walls or in cladding of inside walls. On environmental grounds the obligations towards the energy efficient construction and operating of buildings are tightened increasingly. This leads, under compliance with today's room climatic requirements, to the focusing of activities on appropriate use of building materials and the expenses and energy optimized design of building envelopes. On the rehabilitation of historical structures often questions regarding the hygro‐thermal evaluation of such air cavities and the therein occurring convection processes arise. So, a long term cross flow in open cavities with moisture‐loaded air can cause damages on the service ability and bearing capacity of components. The consideration of cross flows in enclosed cavities of single components or in open constructions, such as wall or roof constructions, can be calculated at present only by use of special assumptions. For the solution of this complex problem the coupling of a CFD‐solver with a hygro‐thermal building simulation software has been carried out. Within the scope of a research project a CaFD (cavity fluid dynamics) simulation code has been developed which especially is adjusted to the requirements and boundary conditions of hygro‐thermal component simulations. Therefore, the functional range concentrates on building physical problems definitions of structural designs. With the implementation of the CaFD‐tool as an additional application for the software package DELPHIN 4.x, an independent operational CFD software module has been developed. By means of the SIMPLE‐Algorithm it solves the Navier‐Stokes‐Equations additionally under consideration of the heat and mass transport in the cavity. A data interface controls the interactive data interchange between DELPHIN and the CaFD‐tool. The presentation of simulations of the aero‐hygro‐thermal behaviour of components with opened and enclosed air cavities completes the contribution. With selected test cases the coupled simulation is analysed and discussed more closely from the building physical point of view.     

Verification for transient heat conduction calculation of multilayer building constructions

Validation and verification of building simulation programs and load calculation programs is of continuing interest. Dynamic thermal behavior data, including conduction transfer function (CTF) coefficients, thermal response factors and periodic response factors, are used to calculate transient heat conduction through building constructions. Computational inaccuracy sometimes occurs in calculating CTF coefficients and response factors. In this paper, a method for verification of the CTF coefficients and response factors over the whole frequency range is introduced. This method is based on the equivalence of dynamic models for a linear system and the frequency characteristics of building transient heat transfer models. Bode diagrams and error criteria are proposed to verify the CTF coefficients and response factors. Some examples are given to demonstrate the methodology.     

Simulation dynamisch‐thermischen Langzeitverhaltens in Gebäuden mittels CFD

Dynamic CFD simulation of thermal long‐term behaviour of buildings. The design of complex buildings increasingly demands the usage of simulation programmes. Actual dynamic thermal simulation programmes in use are incapable to determine the air flow and the temperature distribution in a room. One solution is to displace building simulations to a CFD platform which involves extremely long calculation times and large amounts of data. To reduce the calculation time a new freeze‐flow method was developed for ANSYS CFX‐5. It is based on the periodic freezing of the hydrodynamic equations enabling long term simulations. The CFD simulations were validated for free convection which is the dominating driving force of flow in rooms. Freeze‐flow simulations of simple test models confirmed a dramatic reduction in calculation time without any loss in accuracy compared to full dynamic CFD simulations.     

Toolbox for development and validation of grey-box building models for forecasting and control

As automatic sensing and information and communication technology get cheaper, building monitoring data becomes easier to obtain. The availability of data leads to new opportunities in the context of energy efficiency in buildings. This paper describes the development and validation of a data-driven grey-box modelling toolbox for buildings. The Python toolbox is based on a Modelica library with thermal building and Heating, Ventilation and Air-Conditioning models and the optimization framework in JModelica.org. The toolchain facilitates and automates the different steps in the system identification procedure, like data handling, model selection, parameter estimation and validation. To validate the methodology, different grey-box models are identified for a single-family dwelling with detailed monitoring data from two experiments. Validated models for forecasting and control can be identified. However, in one experiment the model performance is reduced, likely due to a poor information content in the identification data set.     

Mapping actual thermal properties to building elements in gbXML-based BIM for reliable building energy performance modeling

The ability to import building geometric and construction thermal data from building information models (BIM) has significant potential to reduce the time and uncertainty in building energy modeling process. In today's BIM-based energy modeling practice, thermal properties are mainly derived from generic building construction types in BIM. However, for energy modeling of existing buildings, such assumptions are often inaccurate as they do not account for diminishing thermal resistances of building materials instigated by their deteriorations. To improve the reliability of BIM-based energy modeling, we present a system, together with new methods for automated association and updating of actual thermal property measurements with BIM elements in gbXML schema. By leveraging collections of digital and thermal images and based on environmental measurements, our system first produces a 3D thermal model for the building under inspection and then derives the actual thermal resistances of the building assemblies at the level of 3D vertexes. By associating these measurements with their corresponding elements in gbXML, thermal properties of the BIM elements are automatically updated. Our experiments in real-world residential and instructional buildings show how actual thermal properties can be automatically associated with BIM elements and updated in gbXML. The proposed method shortens the gap between architectural information in BIM and the actual data needed for energy performance simulation, and enables reliable BIM-based energy analysis for retro-commissioning, continuous commissioning, and retrofit.     

Energieausweis nach DIN V 18599 und mittels Gebäudesimulation – ein Projektbericht

Energy performance assessment based on DIN V 18599 vs. building simulation – a project report. The new German Energy Conservation Ordinance (EnEV 2007), which came into force on 1^st October 2007, stipulates a new approach to energy performance assessment for non‐domestic buildings. In the past the calculations based on DIN 4701‐10 for office buildings and heated halls, for example, were relatively simple. DIN V 18599, in contrast, now specifies a rather time‐consuming procedure. In parallel, since the 1970s the approach to energy performance assessment increasingly developed from “passive” calculations to an “active” and key component of the design and formation process for a project, and this is indeed how it should be if the aim is to create an energy‐optimised building design. Based on a specific project the suitability for practical application and the benefit for the client of the calculation procedure according to DIN V 18599 were compared with a thermal building simulation. The resulting implementation issues are discussed in this paper. The Energy Conservation Ordinance 2007 no doubt represents a further milestone with far‐reaching consequences for the planning process and for building design and raises new issues that will have to be addressed in future.     

Structural investigation of the collapse of the 16‐story Plasco building due to fire

On January 19, 2017, the 16‐story Plasco tower located in Tehran, the capital city of Iran, collapsed in several stages, due to a fire lasting 3.5 h. This paper presents the results of numerical investigations on how the structure behaved during that incident. In this regard, initially, a part of floor system including main truss girders, secondary truss beams, tie beams, and reinforced concrete slab is simulated to study its deformed shape and collapse modes. Then 2D and 3D models of the building are developed to evaluate the global behavior of the structure under fire. The results show that at elevated temperatures, deflection of the floor system, main trusses, and out‐of‐plane bending of the beam‐to‐column gusset plates become excessive, leading to partial collapse of floor, in the location of fire initiation. Also, 2D models show that thermal expansion and catenary action of heated truss induce large lateral displacement and bending moment in perimeter column that cause failure of this column at about 650°C. Finally, 3D models indicate that general collapse of the building is initiated by buckling of the external columns located in the southern perimeter of the building. This result is in good agreement with videos and photos showing actual collapse of the structure.     

3D‐Tragwerkssimulationen zur Erfassung der aerodynamischen Beanspruchungen bei der Planung von Brückenstrukturen

On the Modeling of Aerodynamic Effects in the Design Phase of Bridges via 3D Structural Simulations. The use of innovative building materials has led to a trend towards increasingly light and slender structures. Especially for cable‐stayed and suspension bridges, but also for girder bridges, there has been observed a growing dynamic vulnerability. The vibrations are caused, besides pedestrian and traffic‐induced vibrations, mainly by wind action. Apart from local vibrations of cables, the global dynamic behaviour of the bridge deck is of special interest. This paper gives an overview of the analysis methods currently used in practice. Load models which are based on a two‐dimensional treatment of the flow around the cross‐sections and their numerical treatment within the framework of a 3D structural simulation are presented. The experimental measurement of stationary and instationary cross section parameters is briefly recapitulated. Application in engineering practice in both preliminary and final design phases is demonstrated by four examples.     

Co-simulation of a HVAC system-integrated phase change material thermal storage unit

A co-simulation environment, consisting of a detailed mathematical model of a thermal energy storage unit which is incorporated with an EnergyPlus simulation model of a full building HVAC system, is described. The two models are integrated using the user-defined plant component feature in EnergyPlus and the Building Controls Virtual Test Bed (BCVTB) environment. The thermal energy storage unit, which consists of encapsulated phase change material in a series of flat plates and a heat transfer working fluid (water), is modelled using a transient one-dimensional forward finite difference method. The thermal storage model is executed within MATLAB and is verified against experimental data, showing a discharging heat transfer accuracy to within 2.5%. The building model, which incorporates a retrofitted ground source heat pump system within a thermally massive building, is simulated in the EnergyPlus environment. The co-simulation arrangement allows for in-depth analysis of the integrated system under dynamic operating conditions, which is currently not possible within the EnergyPlus environment. Moreover, the overall adopted approach, based on generic integration of a detailed mathematical model, using a third party generalised programming environment, into an established building simulation environment, serves as a successful exemplar for other researchers and practitioners working in the field.     

Instationäres 3D Thermo‐mechanisches Modell für Beton

Transient 3D thermo‐mechanical Model for Concrete In the present paper a transient three‐dimensional thermo‐mechanical model for concrete is presented. For a given boundary conditions, temperature distribution is calculated by employing a three‐dimensional transient thermal finite element analysis. The thermal properties of concrete are assumed to be constant and independent of the stress‐strain distribution. In the thermo‐mechanical model for concrete the total strain tensor is decomposed into pure mechanical strain, free thermal strain and load induced thermal strain. The mechanical strain is calculated by using temperature dependent microplane model for concrete [1]. The model is implemented into a three‐dimensional FE code. The performance of headed stud anchors exposed to fire was studied. For a given geometry of a concrete member and for a constant concrete properties a three‐dimensional transient thermal FE analysis was carried out for three embedment depths and for four thermal load histories. The analysis shows that the resistance of anchors can be significantly reduced if they are exposed to fire. The largest reduction of the load capacity was obtained for anchors with relatively small embedment depth. The numerical results agree well with the available experiments.     

Vorhersage und Analyse natürlicher Lüftungsvorgänge

Prediction and analysis of natural ventilation. The computational prediction of natural ventilation is often raising difficulties because of problematic boundary conditions and the unsteady nature of the flow. In addition, the pure ventilation process only delivers a part of information, for instance in case of night ventilation for cooling purposes. Using the possibilities of a special stabilized FEM‐code one is able to find formulations for boundary conditions, which are very useful for the simulation of natural ventilation problems. Furthermore we present some criteria and possibilities for the analysis of transient ventilation tasks from the energetic and the hygienic point of view. By combining indoor air flow computation and thermal building simulation the energetic consideration can be especially performed.     

Untersuchungen zu Einsatzmöglichkeiten von Holzleichtbeton mit Latentwärmespeichermaterialien in Gebäuden

Investigation of the application of PCM in wood‐lightweight‐concrete in buildings. Wood‐lightweight‐concrete (WLC) is a compound material, consisting of cement, shavings from sawmill, water and additives. The material is characterised by good properties of heat and noise insulation as well as strength. Within the framework of R&D‐projects the combination of wood‐lightweight‐concrete with organic phase change materials (PCM) was examined. A lot of experimental tests have been done, models in different scales have been built. Finally, parallel preliminary practise‐tests have been conducted. Mixtures with different density (between 1000 and 1450 kg/m³) have been investigated (strength up to 20 N/mm² and thermal insulation l between 0.28 and 0.50 W/mK). Furthermore in a thermal building simulation three different partition walls (in addition to a reference case, one with WLC and the other with WLC+PCM) of a south‐orientated office‐room have been studied. An increase in heat capacity of wood‐lightweight‐concrete with PCM leads to a reduction of overheating in summer, considering external shading and adequate change of air in the night. The obtained results showed, that composite materials from wood, inorganic binders have interesting options for the use in building constructions. WLC with phase change materials may provide additional functional and constructive advantages, i. e. lighter and thinner outer wall elements with concurrent better thermo‐dynamic material properties.     

Analyse des Gefüge‐ und Feuchtezustandes in mineralischen Baustoffen mit der Mikro‐Röntgen‐3D‐Computertomografie

Condition Assessment of Microstructure and Moisture Distribution in Mineral Building Materials by Micro X‐Ray Computed Tomography. The knowledge of microstructure and moisture condition in capillary porous building materials is essential for building climate control and building durability. The 3D X‐ray computed tomography (3D‐CT) opens up new vistas for the visualization of both parameters. In this article the performance of this innovative non‐destructive testing method is demonstrated by means of two studies showing its feasibility. The first feasibility study was carried out with a drilling core taken from a fair‐faced concrete cladding which was strongly damaged by freeze‐thaw cycling. The 3D‐CT investigations have shown that it is possible to visualize the crack and moisture distribution especially interesting besides the spatial distribution of aggregates and hardened cement paste. So the method opens up new vistas for the tracing of interactions between cracks due to frost and moisture distribution without any destructive interventions. This can help to clarify the damage mechanisms in concrete due to frost which are partly not sufficient known up to now. Objective of the second feasibility study was to demonstrate not only the spatial but also the temporal distribution of the moisture in tuff during the capillary water absorption test. The 3D‐CT investigations have shown that the spatial motion of the capillary moisture front with delayed water absorption of pumice, a magmatic tuff component, can be visualized. Based on these studies this article finally shows the next steps which are necessary to improve the performance of the test method.     

Structure‐aware 3D reconstruction for cable‐stayed bridges: A learning‐based method

A powerful deep learning‐based three‐dimensional (3D) reconstruction method for reconstructing structure‐aware semantic 3D models of cable‐stayed bridges is proposed herein. Typically, conventional bridge semantic 3D model reconstruction methods are not robust when low‐quality point clouds are used. Furthermore, they are suited particularly for their respective fields and less generalized for cable‐stayed bridges. Hence, a structure‐aware learning‐based cable‐stayed bridge 3D reconstruction framework is proposed. The encoder part of the network uses both multiview images and a photogrammetric point cloud as input, whereas the decoder part uses a recursive binary tree network to model a high‐level structural relation graph and low‐level 3D geometric shapes. Two actual cable‐stayed bridges are employed as examples to evaluate the proposed method. Test results demonstrate that the proposed method successfully reconstructs the bridge model with structural components and their relations. Quantitative results indicate that the predicted models achieved an average F₁ score of 99.01%, a Chamfer distance of 0.0259, and a mesh‐to‐cloud distance of 1.78 m. The achieved result is similar to that obtained using the manual reconstruction approach in terms of component‐wise accuracy, and it is considerably better than that obtained using the manual approach in terms of spatial accuracy. In addition, the proposed recursive binary tree network is robust to noise and partial scans. The potential applications of the obtained 3D bridge models are discussed.     

Effective thermal conductivity of porous building materials – analysis and verification

Effective thermal conductivity of porous building materials is a very important parameter particularly in the thermal performance analysis of building envelopes. In this part of the paper the selected models of effective thermal conductivity of 2‐phase porous building materials fully filled with air or water are analyzed and verified. The calculated values from models are compared with measured data from literature and recommendations for selecting models are provided.     

Optimierung eines Raumes mithilfe von DIN 18599‐4 (Tageslicht), DIN 4108‐2 (sommerlicher Wärmeschutz) und weiterführenden Simulationen

Room optimisation based on DIN 18599‐4 (Daylight), DIN 4108‐2 (Thermal comfort during summer) and simulations. DIN 18599‐4 is successfully used as a tool for optimising daylight quality in office spaces with respect to dimensions and window size and positioning. Further room optimisation with respect to thermal comfort during summer based on DIN 4108‐2 can lead to uncomfortable conditions, as shown in comparative simulations. Comfortable conditions can be achieved with further optimisation measures based on simulation programs and thermal comfort evaluation based on DIN EN 15251. Recommendations for relevant room parameters including shading, natural ventilation and artificial light switching are provided.