Roof Structure Research Articles

Mechanical properties of hoberman radially retractable roof structures

In this paper, a spatial Hoberman radially retractable grid shell is constructed based on its planar version and the mechanical properties of the grid shell are analyzed using ABAQUS commercial software. The analysis shows that given carefully chosen parameters, the spatial grid shell can meet the requirements of the specification. Based on this, the influence of the number of multi-angulated rods, the number of segments of the multi-angulated rod, and the rise-span ratio on the mechanical performance of the structure are analyzed. The results show that the increase of the number of multi-angulated rods is beneficial to the mechanical properties of the structure, but will have a negative effect on the economic performance. To reach an optimized configuration, it is chosen such that the number of multi-angulated rods is 18, the steel consumption and the structural performance response are smaller. The decrease of the number of segments of the multi-angulated is beneficial to the mechanical properties, service performance, and economic performance of the structure, but considering the feasibility of processing, transportation and the driving condition setting, it is recommended to choose 4 segments of the multi-angulated rod. Higher rise-span ratio is beneficial to the mechanical properties of the structure in the closed state, but will adversely affect the mechanical properties and economic performance during the deployment.

Construction Disaster Hazard Caused by a Defective Building Structural Survey

The present paper encompasses an analysis of a production hall reinforced concrete roof structure in terms of its limiting snow load. Errors which were made at the survey and thermal retrofitting design stages for the structure in question have been identified. These contributed to a construction disaster hazard which could occur in the event of intensive snowfall. Reinforced concrete roofing structures are least prone to failures caused by the impact of the weather, however they do occur. This results from both structural wear and also often from the addition of extra loads. These loads may be caused by thermal retrofitting as well as installation of additional equipment on the roof, including the currently popular photovoltaic systems. Using the structure subject to the analysis as an example, the authors have proposed a procedure for diagnosing and analysing reinforced concrete roofing structures in terms of upgrades and installation of additional equipment thereon.

Simplified calculation method of non-Gaussian wind pressure peak factor for large-span spatial roof structures

Based on the wind tunnel test data of a long-span spatial roof structure, the correlation between higher-order statistics and peak factors was obtained according to the time and frequency domain characteristics of wind pressure-time history, as well as the coincidence condition between wind pressure power spectra of measurement points and wind speed power spectra. A simplified peak factor calculation formula was proposed based on the moment-based Hermite polynomial model. The Gaussian part of the peak factor was calculated through the wind speed spectrum based on the zero-crossing theory, and the parameters related to higher-order statistics were considered as the non-Gaussian part of the peak factor. The simplified method was verified through the instantaneous extreme value method based on a coal shed structure with available long-term wind pressure-time history. It revealed that the results of the proposed simplified method correlate well with that of the instantaneous extreme value method, indicating its accuracy and potential value for engineering practice.

Service Life of Pre-Tensioned Concrete Structures in a Chloride Environment on the Example of an Aluminium Foundry Building.

This paper describes a study of the chloride content in the concrete lagging of prestressed concrete elements of the roof structure of an aluminium foundry building. Sources of chloride pollution in industrial facilities are discussed. Methods for collecting dust deposited on the structure and sampling concrete for chloride concentration testing are presented in detail. The test methods used and the apparatus used to assess the chloride content at the thickness of concrete reinforcement lagging are presented. Investigations of the chloride content in the concrete of the reinforcement cover showed a very high concentration of chloride in the near-surface layer, depending on the location of the element in relation to the source of chloride emission into the environment. In contrast, the concrete of the deeper layers of the lagging contained very small amounts of Cl- chlorides. The results of the chloride content of the lagging concrete were plotted against the distance from the surface of the specimen and approximated by the function C(x,t) based on Fick's second law and its solution. A satisfactory fit of the course of this function to the experimental results was obtained. Based on the obtained C(x,t) function, the durability of the main structural components of an aluminium foundry industrial hall operating in a chloride environment was estimated.

Study on prestress distribution and structural performance of heptagonal six-five-strut alternated cable dome with inner hole

The cable dome structure is a highly efficient prestressed space structure with reasonable force, attractive shape, and large spanning capacity. It is increasingly widely used in stadiums, exhibition halls, terminals, and other large-scale public buildings and the roof structure of various transport hub projects. To solve the problem of weak overall structural stability of the traditional cable dome structure, a new type of prestressed space structure is proposed - heptagonal six-five-strut alternated cable dome with an inner hole. The composition of the structural system was given and a theoretical study of the distribution of structural prestress was carried out; based on the symmetry and periodicity conditions, the initial prestress distribution of the structure was accurately calculated using the node balance method, and the formulae for the geometric parameters of the structural cable-strut were derived; the numerical model was established by using the finite element software ANSYS 2022 R1, and the force characteristics of the structure under full-span uniform load, half span uniform live load, wind load, and temperature were studied. The effects of structural prestress, overall shape, and support stiffness, totaling three categories and six parameters, on the structural mechanical performance of the internal force of the member, node displacement, and support reaction force were analysed in detail and the sensitivity of the parameters is assessed quantitatively, accordingly, the values of the main design parameters such as thick-span ratio are given as suggestions. The analysis results show that the new structural system has a high load-carrying capacity and deformation resistance, and its proposal provides a new scheme and new ideas for the selection and design of the cable dome.

Pengaruh Angin Terhadap Tata Letak dan Jumlah Sekrup Konstruksi Baja Ringan Berdasarkan SNI-7971- 2013

Light weight steel material has experienced rapid development in the construction. However, there are still many costruction failures on light weight steel, resulting in cost loss. The failure of light steel structures often occurs at the connections. The connection tool on milld steel is usually using a self-drilling screw. The research location is at Aceh One Stop Integrated Service and Investment Service Building (DPMPTSP) Aceh. The problem in this study is the placement and number of screws on the lightweight steel roof structure in the field which is carried out for each member according to the code, and the effect of wind load on the placement and number of screws on the lightweight steel roof structure. This study aims to determine the effect of the placement and number of screws on the lightweight steel roof structure. The scope of this research of problems including the placement and number of screws on the lightweight steel roof structure. The standars used in the design of light steel structures in this study is SNI 7971 2013 and the loading planning standars using SNI 03 1727 1989. Calculation steps using the LRFD method for steel structure design regulated in SNI 03 1729 2002. Based on the results, it is obtained that the number and placement of the screws in the field are different from those obtained in the calculation. From the calculations, it is obtained from the recapitulation, dead loads with a maximum value of 123.07 kg, live loads with a maximum load of 30.1 6 kg, and for compressed air and suction loads with a maximum load of 180 kg. the maximum design force value is 1241.33 kg and the screws bearing resistance value is 256.752 kg. the number of screws is obtained where the the value of the design force is divided by the value of the bearing resistance, on each member obtained 1screw, 2 screws, 3 screws, 4 screws, and 5 screws. Whilst it is found for each member in the field using 3 screws.

Characteristics performance evaluation of AZ91-fly ash composite developed by vacuum associated stir processing

ABSTRACT The AZ91 class magnesium alloy was familiar with automotive, aviation, and marine applications due to its uniqueness of being lightweight, high strength, good fracture toughness, better dynamic stability, and good castability behaviours. The novel research aims to enhance the AZ91 alloy composite by adapting fly ash (FA) nanoparticles as 0, 2.5, 5, 7.5, and 10 wt%, respectively, and made by using a vacuum liquid stir casting process under constant stir speed. Influences of FA on micro-structural, physical (density/porosity), mechanical (hardness, impact toughness, tensile stress) and corrosion behaviour of AZ91 alloy nanocomposite were investigated. The composite with 10 wt% FA exposed excellent particle dispersion, better Vickers hardness of 95.4HV, good toughness value of 20.6J/mm2, superior tensile stress of 276MPa, and least corrosion rate of 3.81 mm/year. The optimum characteristics of FANC4 (AZ91/10 wt% FA) are suggested for automotive structural (seat and roof frame) applications.

Analysis of Lateral Roof Structure and Stability Control Technology in Island Working Face Mining Roadways

Analysis of Lateral Roof Structure and Stability Control Technology in Island Working Face Mining Roadways

Determination of the Efficiency of Steel Structures of a Warehouse Building Roof

Purpose. The main purpose of this article is to compare the main technical and economic indicators of two proposed structural variants of steel coverings for a class B+ warehouse building in the city of Dnipro. The relevance of the work is related to the constant increase in the volume and pace of freight transportation both globally and in Ukraine, especially in recent years. This requires the creation of new and expansion of existing warehouses of various types. In turn, this leads to the need to create such load-bearing structures for storage areas that would be able to cover significant spans and at the same time ensure minimal costs for their construction and operation. Methodology. To achieve this goal, we analyzed modern classifications of warehouse buildings according to national standards and international approaches, determined the class of the building in question according to these two methods, and developed two structural options for steel roofing - based on a load-bearing beam in the form of a truss truss and based on a beam-frame scheme. Finite element models for both proposed structural options were built using the domestic design complex Lira-CAD. Based on the analysis of their stress-strain state, rational cross-sections were selected for each design option, and the total weight and cost were calculated. Findings. A comparative analysis of the two developed structural solutions for the steel roof of a warehouse building revealed that the variant with the use of a beam-frame system has about 10% less weight and cost. Also, its manufacturability is higher than that of the truss system. Originality. As a result of the numerical analysis, a more rational and efficient design solution for the steel roof of a warehouse building in the city of Dnipro was theoretically substantiated. Practical value. A constructive variant of the steel coating has been developed and proposed for practical implementation, which, in terms of its technical and economic indicators, is the most effective for the conditions of a modern industrial enterprise. Also, the developed constructive variant of the warehouse building is classified in accordance with domestic and international modern approaches.

Water Resistance of Acrylic Adhesive Tapes for Rooftop Fastening

Rooftop solar modules are usually held in place by racks or frames that are mechanically attached to a roof structure and/or by heavyweight, ballasted footing mounts. These mounts ensure that the panel system remains in position against wind load. However, mechanical connectors create penetrations into the water-resistant layer of the roof, whereas ballasted footing mounts cause a significant additional load on the load-bearing structure of roof. For these reasons, adhesive connection seems to be a beneficial solution. Acrylic adhesive tapes, marked as VHBTM, may provide sufficient strength, and they have no need for mechanical fasteners or ballast. Acrylic adhesive tapes also provide a comfortable, fast, and efficient bonding process with no curing compared to liquid adhesives. On the other hand, resistance to water at load-bearing joints has not been sufficiently studied yet and could be critical for connections exposed to the outdoor environment. The present study aims at the determination of water resistance and durability of the VHBTM tapes from the GPH series, which are typically used to bond a variety of substrates including many metals. The mechanical properties and failure modes are compared for the specimens before and after a 21-day immersion in water. A significant reduction in strength was observed, depending on the substrate material. The study of chemical changes in the acrylic tape and in its leachate through infrared spectroscopy (FT-IR), X-ray fluorescence, and X-ray diffraction analyses clarified the reduction in mechanical properties. The selected VHBTM tape demonstrated strong resistance to the effects of water. However, the overall strength of the joint after immersion was significantly impacted by the decrease in adhesion to a specific substrate.

Investigation on seismic performance degradation of hub large‐span roof structures considering corrosion and damage accumulation

AbstractHub transportation facilities are important lifeline projects in cities. Once they are damaged by earthquakes, their functional use will be lost, resulting in significant adverse social impacts. The roof structures of hub transportation facilities are usually made of large‐span steel structures. During service, they bear long‐term vibrations caused by multiple vibration sources such as high‐speed trains and wind loads, resulting in cumulative damage. In addition, the roof structures located in coastal areas may be exposed to a corrosive environment, which can lead to the degradation of structural performance. Currently, the relevant structural design standards do not consider the factor of structural performance variation over time. To address the above problems, this study adopts a time‐dependent constitutive model of steel considering corrosion and damage cumulative to investigate the seismic performance degradation of typical hub transportation facility roof structures. The research results show that the stiffness and seismic performance of 50‐year service hub large‐span roof structure have decreased compared to newly built structures, but the probability of serious damage is lower, indicating that the hub large‐span roof structures have good seismic performance.

History of the Changes in the Roof Structure of a Historical Wooden Church

History of the Changes in the Roof Structure of a Historical Wooden Church

Thinking of Green, Low Carbon, and Energy-Saving Designs Based on the Variable Ventilation of Natatoriums: Taking the Jiading Natatorium of Tongji University as an Example

With the increasing demand for sports activities, sports architecture is flourishing. Creating a comfortable and healthy fitness environment while reducing energy consumption has become a focus for architects. Taking the Jiading Natatorium at Tongji University in Shanghai as an example, this study researched green energy in the variable ventilation of sports venues. The Autodesk Ecotect Analysis 2011 was used to conduct computational fluid dynamics (CFD) simulation analyses on four scenarios of opening and closing the swimming pool’s roof, with ventilation velocity as the primary evaluation indicator to assess the ventilation environment of each scenario. The relationship between the opening ratio of the roof and the ventilation environment of sports buildings was explored. The results showed that when the opening ratio is 37.5%, it achieves good ventilation effectiveness and avoids excessive wind pressure. The study also summarized six common forms of opening and closing roof structures and compared the differences in wind environments of different roof forms. The results indicated that the shape and opening ratio of the roof has a decisive impact on the distribution of indoor wind speed in buildings. Six optimal opening ratios for different roof forms in summer and suitable site conditions were summarized, providing a reference for the design and selection of swimming pool roofs. Furthermore, the wind speed distribution of different roof types showed a trend of gradually becoming uniform with the increase in opening area. However, the position of the wind speed peak is related to the form and size of the roof opening. This research provides valuable references for the low carbon and energy-efficient design of future swimming pool sports buildings.

A Sustainable Approach to Reconstruction: Historical Roof Structure Interventions

The reconstruction of structural subassemblies in historic buildings is a widely debated topic that often arises throughout a building’s lifespan. The most vulnerable structures and, consequently, the most frequently modified are roofs, due to the materials used, which render them susceptible to biological decay or fire. This paper aims to analyse roof reconstructions across various historical periods and under different circumstances depending on the necessity for construction or reconstruction. Several exceptional reconstructions from Europe are examined, where the final solution was determined based on sustainability criteria from the construction period. Wood in roof trusses is often replaced with alternative materials such as metal or reinforced concrete. In the case of the Evangelical Church in Bistrița, destroyed by fire for the second time in 2008, the solution of replication using wood was adopted, and the wooden elements were calculated for fire resistance, according to the Eurocodes. Another important aspect to consider when constructing new roofs is the need for protective or temporary roof structures, where sustainability and reusability are fundamental requirements. The principles used to choose the covering method were different depending on the reconstruction period. Three analysis criteria were defined to compare historical solutions with current sustainability principles in the reconstruction and construction of new roofs for existing buildings.

Experimental investigation of photoelectrical performance and thermal characteristics of ventilated building-integrated photovoltaic system utilizing lightweight and flexible crystalline silicon module

The existing large-scale of industrial buildings with lightweight insulated roofing structures presents a challenge for traditional glass crystalline silicon photovoltaic (PV) systems due to insufficient load-bearing capacity. Meanwhile, traditional PV rooftop applications also face challenges due to limited rooftop resources. To address these issues, this study proposes a ventilated building-integrated lightweight photovoltaic (VL-BIPV) system. The VL-BIPV system incorporates lightweight and flexible crystalline silicon modules, which increase rooftop load by about 6 kg/m2. Additionally, the system features a ventilation channel design to enhance thermal management performance. To evaluate the PV performance and thermal characteristics of the proposed system, an experimental setup was implemented to compare the performances of the VL-BIPV system with a building-attached lightweight photovoltaic (L-BAPV) system that utilizes color steel sheet base plates. The results demonstrate the exceptional performance of VL-BIPV system, with a 100.56% higher ratio of the product of short-circuit current and open-circuit voltage compared to L-BAPV. Moreover, the VL-BIPV system achieved a 1.77% increase in PV efficiency and a 2.35% enhancement in daily electricity generation. In hot weather, the adoption of VL-BIPV reduced the extreme temperature of PV cells by 9.23 °C below 85 °C, surpassing the 6.29 °C reduction achieved by L-BAPV system. Furthermore, the ventilation channel exhibited a gradual temperature increase with slower changes in the flow direction, while the base plate temperature decreased by 13.41 °C, which indicates that VL-BIPV can effectively reduce solar heat gain in the building envelope and improve the indoor thermal environment. The research findings provide important guidance for promoting and applying VL-BIPV technology in large-scale industrial buildings with low rooftop load-bearing capacity, thereby promoting the production and utilization of clean electricity in industrial parks.

ВПЛИВ СУЧАСНИХ ТЕНДЕНЦІЇ ВИКОРИСТАННЯ СОНЯЧНОЇ ЕНЕРГЕТИКИ НА ЕСТЕТИЧНІ ЯКОСТІ МІСТА

Energy independence remains a priority task for most European countries. Along with traditional energy sources, more and more attention is being paid to renewable energy usage. The best solution for city residents is the use of solar energy for the local needs of individual households. However, chaotic installation of solar panels on the roofs has a negative impact on the aesthetic qualities of urban environment. Many problems as well arise during installation of panels itself on the roof structure. After all, solar panels have significant weight, which usually was not taken into account when calculating the roof structure. The wind load, which is higher for planar elements, also was not taken into account, which can provoke negative consequences like destruction of an entire structure during exploitation. Key problem is that in most cases panels are being installed on the already existing roof and were not laid in the project. Conducted research has revealed the negative impact of voluntarily installed solar panels on aesthetic qualities of the city. Argued the importance of coordinating the installation of solar energy accumulating elements with the architecture of the building and the environment by selecting an appropriate shape, texture and color. Proved the need to foresee during the design process the use of solar panels in the construction of the roof and walls to partially supply buildings with energy at the local level. Envisaging solar panels at the design stage will avoid duplicating the roof profile, which will reduce the weight of the roof structure and extend its service life. The analysis of main methods for organizing the "solar roof" showed that the most appropriate, from an aesthetic point of view, is the use of solar roof tiles. Based on analysis of available materials for accumulating solar energy, it was found that today there is no manufacturer that provides a complete solar roof with all its elements (gutters, snow retainers, deaerators, ladders, etc.). However, it is possible to choose elements with the corresponding texture and color and combine roof elements from different manufacturers.

Water Quality and the First-Flush Effect in Roof-Based Rainwater Harvesting, Part II: First Flush

Rainwater runoff samples from a range of roofing materials were temporally collected from 19 small-scale roof structures and two commercial buildings through simulated and actual storm events, and the concentrations of polycyclic aromatic hydrocarbons (PAHs), phosphorus flame retardants (PFLs), and pyrethroid insecticides and other water quality parameters were analyzed. In Part I of this research, the concentrations of these contaminants in roof runoff and soils receiving runoff from a range of roofing materials were evaluated. In Part II, recommendations have been developed for a first-flush exclusion to improve the quality of water harvesting for nonpotable uses. Recommendations focus on a first-flush diversion based on mass removals of total suspended solids (TSS) and PAHs linked to conductivity measurements throughout a storm event. Additionally, an upper-confidence limit (UCL) was constructed to determine the minimum diversion required to obtain 50, 75, 90, and 95% mass removal of TSS and PAH contaminants. The majority of TSS were produced during the initial 1.2 mm of runoff. Likewise, the majority of PAHs were removed during the initial 1.2 mm of runoff, except for the asphalt shingle roofs, where high PAHs were observed after 6 mm of runoff. The Texas Water Development Board (TWDB)-recommended first-flush diversion of one gallon for every 100 square feet of rooftop was not always adequate for removing 50% of TSS and PAHs from the roofs. Rainwater runoff conductivity decreased drastically between 1.2 to 2.4 mm of rainwater runoff. Diverting the first flush based on conductivity has the potential to also divert the majority of TSS and PAHs in roof runoff.

Load Bearing Capacity and Failure Analysis of Fibrous Plaster Wads

ABSTRACT Fibrous plaster is a culturally significant material used in high-status buildings from the late nineteenth century. Fibrous plaster ceilings are typically suspended using load-bearing fibrous plaster wads, which are attached to roof structure components. Understanding the behaviour of wads is highly significant, with important safety implications emphasised by the partial collapse of the Apollo Theatre ceiling in 2013. This study demonstrates an original, innovative test method for fibrous plaster wads that enables quantification of load capacities, with manufactured specimens representative of historic in situ wads. The methodology is rigorously evaluated for traditional and alternative wad designs, reinforced with hessian scrim or continuous fibre glass (CFG) mat, with and without steel wires in looped (untwisted) or looped-twisted configurations. Tensile tests generated load-displacement characteristics and determined failure modes including cracking of plaster, deformation and tearing of fibrous reinforcement, and if present, plastic failure of a wire. Results demonstrate that hessian performs better than CFG in axial tension and inclusion of a wire increases tensile load capacity and ductility. An industry standard repair wad with hessian and looped-twisted wire can typically support 3 kN. Looped wire performed better in isolation than looped-twisted wire, with higher peak loads and greater ductility, while looped-twisted wire carried a greater load as part of a fibrous plaster composite wad. The test methodology and findings have revealed new insights into the mechanical behaviour of wads which will inform commercial practice and conservation of historic buildings, preserving important heritage and promoting safe longevity.

Multi-condition simulation analysis of a sliding hydraulic support system based on elastoplastic mechanics

In response to the challenges of supporting fractured and weak surrounding rock in deep coal mines in the Huainan region of China, a self-moving hydraulic support system for roof support was designed and developed. This innovative solution addresses the difficulties encountered in providing continuous support to roof structures. Based on the theory of elastoplastic mechanics, a numerical analysis model was established to calculate the mechanical parameters such as the displacement, stress, and strain of hydraulic supports during the stepping process under multiple operating conditions. The results of the numerical simulation were compared and verified with those from an actual working site. The results show that the maximum equivalent stress is 245.33 MPa for operating condition 1, 246.82 MPa for operating condition 2, and 245.27 MPa for operating condition 3. The maximum stress values under the three working conditions do not exceed the yield strength of the material, satisfying the requirements for normal bracket support operations. These research findings can establish a theoretical framework for the comprehensive assessment of the reliability and stability of hydraulic supports and the optimization of construction processes.

Application of functionally graded graphene nanoplatelets to improve transient vibrations of the car’s roof under mechanical loading: Introducing machine learning algorithm for transient problems

Doubly curved structures under external force due to their applicable structure can be used in the roofs of various structures. Good knowledge about the transient dynamics of this kind of structure under external shock loading is very important in the engineering field. So, in the current work, steady and transient vibrations of composite doubly curved structures under time-dependent external force for the first time are presented. The current structure is reinforced by graphene nanoplatelets with high efficiency to improve the mechanical properties of the system in the thickness direction due to external shock loading in this direction. The peak pulse pressure, the Laplace transform, and some mathematical work to get time-dependent vibration responses of the composite doubly curved structures under external force. With the aid of different pre-processing of machine learning algorithms (Z-Score, Rrobust, Min-Max, and Quantile transformation), the results are predicted. The optimization algorithm, neural network structure, learning rate, mean of square error, and other training data are obtained for the current machine learning algorithm. The outputs of the machine learning method show that instead of simulating the complex structures in various situations with the aid of mathematical simulation, the researchers can use machine learning algorithms to correctly simulate this kind of system in different situations and material properties to obtain optimum conditions for doubly curved structure structures. The findings in the results section suggest that the time-dependent displacement and stress fields of the system are significantly influenced by the geometrical and physical characteristics of the current composite curved structure.