Roof Structure Research Articles

Determination of working resistance of support parameter variation of large mining height support: the case of Caojiatan coal mine

Aiming at the problem that it is difficult to determine the reasonable working resistance of support in fully-mechanized top coal caving face with large mining height, this paper discusses it from the perspective of preventing rib spalling of coal wall, and holds that the support resistance of working face should not only maintain the stability of roof structure of working face, but also prevent rib spalling of coal wall. Taking Caojiatan 122,107 working face as the engineering background. Using theoretical analysis, numerical simulation, orthogonal test, and similar simulation, it is concluded that reducing the end distance b, reducing the distance l between the action point of the support force and the coal wall, increasing the vertical force Pv and the horizontal force Ph of the support are beneficial to the integrity and stability of the coal wall. The proportion index η of the plastic zone of coal wall is established, and the fitting relationship between η and support parameters is: η=-0.21gPv+0.04gPh+0.551gb-0.039gl+0.665\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\eta { = } - 0.21{\ ext{g}}P_{v} + 0.04{\ ext{g}}P_{h} + 0.551{\ ext{g}}b - 0.039{\ ext{g}}l + 0.665$$\\end{document}. Taking η as the index, the calculation formula of the lower limit value of support strength is constructed, and the lower limit value of support strength required to prevent coal wall spalling in 122,107 working face is 12,369 kN. On-site monitoring and adjustment have achieved good results.

Structural analysis and damage assessment of a fortified church – A case study: The Evangelical Church of Apos, Sibiu County

Globally, there is a wide range of monuments that require conservation and restoration work in order to maintain their values as a whole, both from the aesthetic and historical perspective and to ensure their preservation for future generations. The aim of this paper is to showcase the historical development of the fortified church structure in Apoș, in addition to examining the reasons for its structural damage and exploring possible ways to strengthen the entire church – tower complex. The Evangelical Church is located in the village of Apoș, in the central region of Transylvania, along the Hârtibaciu Valley. This region is of national importance, being part of the Hârtibaciu Plateau and also within the Natura 2000 sites. The church complex consists of the church itself, which is also listed in the Historical Monuments List with the code SB-II-a-B-12313, the bell tower and the clergy house. However, this paper concerns only the church and the tower. The evolution of the church spans over several centuries, during which its structure underwent reconfigurations, consolidation works, but also invasive interventions with incompatible materials that further altered the entire structure and its behaviour. Thus, from the point of view of interventions, they were carried out progressively, the most extensive works being the replacement of the nave ceiling with cylindrical vaults and the replacement of the choir ceiling with a semispherical vault, as well as the consolidation works of the building in the 20th century. The investigation of the Evangelical Church was carried out, first of all, by conducting an on-site investigation, followed by using traditional survey methods in order to identify the structure failures. Additionally, contemporary visualization methods, such as three-dimensional laser scanning, were utilized to gather information on dimensions, heights and ornament details. Through these steps, a survey was obtained that includes accurate data on the church complex. Following these stages, the main degradations identified were a series of cracks caused by differential settlements and the lack of cooperation between structural elements, mechanical damage caused by the detachment of the buttresses from the walls and due to the sliding of the land towards the south, after the demolition of the fortifications. Additionally, two types of brickwork damage were identified: pronounced crack indicating its displacement, contributed by seismic activity and smaller but numerous cracks indicating the disintegration of the brickwork caused by differential settlements combined with prolonged moisture. Besides these, human factors and execution defects were identified, as well as physicochemical degradations with internal causes, such as composition defects or crystal cohesion defects. The repair and consolidation works, including seismic safety measures, have proposed technologies based on the principles of reversibility and preservation of the church’s authenticity. Thus, the main interventions aim to strengthen the structural walls, arches and vaults, eliminate the source of humidity causing the erosion of the masonry through capillary water infiltration, strengthen the floors, roof structure and openings, as well as the interior elements, such as balconies and stairs.

Thermography of the extensive green roof of multifunctional building Brno

The article describes the state of the extensive green roof in winter. It deals with heat transmission on a vegetated roof with a vegetation layer thickness of up to 10 cm. The case study describes the condition of the green roof, which was implemented a year ago on a multi-functional building on Bratislavská Street in Brno. A pre-grown vegetation carpet on a coir mat was installed on the roof. A control segment of the vegetation roof is installed in the roof structure, the influence of which was also monitored as part of the preparation of the article. The article follows the control measurement of humidity in a green roof and the investigation of the influence of the vegetation composition on the thermal-technical properties of the roof.

Life cycle analysis of timber roof structures

Construction industry is rapidly prospering. With numbers as high as they are in the construction industry, it is imperative to find alternative building materials and reduce waste. Proper combination and selection of materials helps to reduce the environmental burden on the surroundings. It is therefore appropriate to use local, natural, renewable, recyclable and low-emission materials in their production, which also helps to promote biodiversity and to restore and replace green spaces. In the fight against climate change, the construction industry is trying to reduce the emissions of buildings by means of life cycle assessment. The study assessed the life cycle of 55 wooden timber roofs in terms of their environmental impact. Based on the assessment of the timber roof compositions, it can be concluded that the best rating was achieved by the composition with structural construction timber, cellulose insulation, vented gap and aggregate backfill. When using wood fibre and cellulose insulation, a 65% reduction in global warming emissions is achieved.

The process for designing and constructing the Sunpu Kaikan

AbstractThis study aims to reveal the difficulty of realizing large hyperbolic paraboloid (HP) shell structures comprising reinforced concrete in earthquake‐prone Japan in the 1950s. The analysis focused on the design and construction of Sunpu Kaikan, focusing on the roles of Kenzo Tange and Yoshikatsu Tsuboi, alongside their architectural laboratory staff. It revealed how the experience gained in the Sunpu Kaikan project contributed to two architectural projects in the 1960s: the Niigata City Gymnasium, with its steel‐frame concrete HP shell, and the Yoyogi National Stadium, with its suspension roof structure.

Natural lighting of interiors and sun protection of premises with roof lighting system

The article describes the contemporary issues of natural lighting of interiors of civil and industrial buildings. The major attention is given to the roof lighting system of the buildings in question, as far as this system provides not only increased levels of natural lighting, but sometimes an undesirable heat gains, due to prolonged insolation period and hence, extra solar radiation. It is noted, that this reason leads to design and construct the means of natural lighting in such a way, that to provide interiors with sufficient natural illumination and efficient sun protection at the same time. Some principal conclusions and recommendations were made as a result of analytic studies, presented in the article. For example, it was competently proved that the best solar standing solution for roof lighting installations are sheds, or sawtooth roof structure. The worst solution, to protect interiors from solar overheating are roof skylights. These skylights require extra sun protection in form of jalousies, blinds, etc. The same additional solar shading, though to less extend, is needed to provide additional sun protection for roof monitors.

Projektovanje i realizacija fotonaponske elektrane izlazne snage 1500 kW na krovu fabrike „Flash“-Apatin

The paper presents the realization of a photovoltaic power plant with an output power of 1500 kW on the roof of the "Flash" factory hall in Apatin, Serbia. The solar power plant is connected to the LV bus-bars in the 20/0.4 kV 1600 kVA transformer station and supplies the factory's consumers through them. In periods when there is not enough solar insolation, the power of consumers in the factory is realized from the power grid. The solar power plant contains 3780 mono-crystalline photovoltaic panels, each with a power of 455 W. The roof surface of the building faces southwest - northeast. Photovoltaic panels are installed on the roof surface of the production hall with the administrative part. The specificity of the roof structure composed of two units (a roof with roof slopes and a flat roof) caused a series of design solutions that will be presented in more detail in the paper. The paper also shows the disposition of DC/AC power converters-inverters and their mutual communication, as well as the system for monitoring output parameters (voltage, current, power) and the quality of electricity delivery to consumers in the factory.

Structure and Functions of Green Roof and Its Development in Urban Areas, China

The green roof is an environmentally friendly design, which is important for sustainable development and improvement of resilience in urban areas. This paper offers a systematically review of the classification, material selection, functionality, limiting factors of green roofs, and provides suggestions. The green roof is classified into intensive, extensive and semi-intensive ones according to the substrate depth and vegetation type. Its basic structure includes vegetation, substrate, filter, drainage, protection, anti-root, insulation and waterproofing layers from top to base. Among which, vegetation, waterproofing and drainage are vital layers to decide the roof efficient. The factors such as light, temperature and humidity conditions of the site are vital for determination of vegetations for a green roof. Green roofs provide benefits for urban areas via saving energy, reducing stormwater runoff and improving aesthetic. Roof load-bearing, seepage, survival of vegetations and support from all sectors are the main issues for the development of green roofs at current stage.

Determination of Multiple-target Equivalent Static Wind Load of Large-span Roof Structures based on Clustering Analysis Techniques

Spatial structures in modern society exhibit a city’s distinguishing features and show its strength in building technology. Large-span roof structures are mostly seen among spatial structures for various activities. Large-span roof structures are usually sensitive to wind loads due to their lightness in materials and curved geometric appearance. However, spatial structures are generally designed with many structural members, making it challenging to determine adequate load distributions for structural safety analysis. This paper intends to introduce the concept of the multiple-target equivalent static wind loads and to demonstrate how to reduce the heavy computational burden when the structural designer needs to consider multiple loading effects of the target structure. The wind tunnel test of an elliptical-shaped stadium structure with a flat roof is first conducted to show the fundamental aerodynamic characteristics. The methodologies of the background-component wind force based on the load-response-correlation (LRC) method and the resonant-component wind force based on the inertial force method are then introduced for the specification of single-target equivalent static wind loads. Finally, the clustering analysis technique is adopted to explain the concept of the multiple-target equal static wind loads. A decay index is proposed to indicate how the clustering technique improves the specification of equivalent static wind loads.

Finite element analysis of a light-frame wood panelized gable roof

This paper presents a three-dimensional (3D) finite-element analysis of a light-frame wood panelized gable roof. The study developed equivalent macro elements representing the major roof components, such as the roof panel and support wall, in the finite-element model (FEM) by utilizing analytical models of the diaphragm and shear wall of CSA 086–19. The most critical load response of the panelized roof structure was obtained by considering the governing load cases, including the partial load case for snow load. The load path analysis revealed that the panelized roof had a two-way load distribution due to the deep beam action of the support wall. The gable ends of the roof carry approximately one-third of the load. In the gravity load case, the in-plane shear governed the connection design at the eave and support wall lines. Self-tapping screws were very effective in resisting wind uplift forces due to their high withdrawal capacity. Furthermore, the deflection pattern of the ceiling joist revealed the effect of panelized construction on the load path.

Technology of Forming Roof Top Flowers: Basic Principles

This scientific article rigorously investigates the formation of rooftop flowers, addressing key factors such as climate characteristics, construction requirements, rules, and drainage considerations. Employing a scientific and theoretical approach, the study delves into the technological aspects, including the filter layer and other relevant techniques. The goals encompass understanding the intricate relationship between rooftop vegetation and environmental factors. The research employs systematic methods to explore the theoretical underpinnings and practical implications of rooftop flower construction. Results highlight the significance of meticulous design, robust roof structures, efficient irrigation, suitable plant selection, and sustainable practices. The concluding remarks underscore the importance of these findings in enhancing both the aesthetic appeal and functionality of green rooftops, providing valuable insights for global researchers and practitioners in related fields. Highlights: Innovative Design: Meticulous design principles play a pivotal role in achieving visually appealing and environmentally beneficial rooftop flower formations. Climate-Responsive Construction: The study emphasizes the significance of constructing rooftop gardens resilient to diverse climatic conditions, ensuring long-term viability and adaptability. Effective Drainage Management: Successful implementation relies on optimized drainage systems, preventing water stagnation and safeguarding both the rooftop structure and the underlying environment. Keywords: Irrigation, Drainage, Rooftop Flowers, Green Roof Technology, Sustainable Urban Design

Enhancing Thermal Efficiency through the Use of Graphite-Infused Phase Change Materials in Roof Structures to Reduce Building Cooling Demand

This research focuses on the thermal properties of three distinctive paraffin waxes—PCMA, PCMB, and PCMC—each characterized by a specific melting point. The crucial phase transition temperature intervals and latent heat values were examined using differential scanning calorimetry (DSC) in the temperature range of 0 °C to 80 °C. These parameters are pivotal for the effective application of these phase change materials (PCMs) in building envelopes, influencing the overall heat storage performance. The study delved into the development and encapsulation of blends containing both the phase change material (PCM) and graphite. This involves combining the chosen PCM with graphite powder and examining the weight ratios of 10% and 20%. The thermal characteristics of these blends revealed that a 10% ratio of graphite powder proved effective in improving the PCM with graphite. This resulted in a reduced range of melting and solidification temperatures while maintaining the essential chemical structure of the PCM without additives. Furthermore, the practical application of PCM–graphite composites within a building’s envelope was explored, revealing a substantial reduction in heat transfer from the exterior to the interior of the building. This underscores the potential for energy-efficient building designs.

The effect of an explosive shock wave on the plate of a protective structure of a critical infrastructure

The article presents the outcomes of an analysis on the stress-strain conditions of reinforced concrete structures subjected to an explosive shock wave resulting from the detonation of a combat unit from a kamikaze drone against a protective screen. When designing protective structures for critical infrastructure, employing computer simulation enables an assessment of the genuine impact of explosive loading on the structural elements' strength. The active phase of explosive loading is exceptionally brief, lasting only a fraction of a second. Under such circumstances, modeling is best performed using explicit methods of direct integration in time.
 The structure considered in this work is a reinforced concrete slab supported by a metal beam cage with I-beam cross-sections, topped with a sand backfill. The study was executed within the SIMULIA Abaqus software suite, incorporating models depicting nonlinear material behavior in a three-dimensional context. Discretely positioned reinforcement was considered for reinforced concrete structures, and the "Concrete Damage Plasticity" model was applied for concrete, accounting for damage accumulation. The devised computational scheme for the shelter represents a section of the protective structure's roof under conditions of cyclic symmetry.
 The article elucidates the core principles of incorporating explosive loading according to algorithm CONWEP.The results demonstrate that during the detonation of a kamikaze drone, an explosive wave created a crater in the sand backfill, exposing the slab. The study illustrates the development of damage in the reinforced concrete slab at various time intervals. Despite the identified damage to the slab, the protective structure overall withstood the explosive load. The intensity of the explosive shock wave diminishes significantly as it propagates away from the explosion site.

A pitched roof-like hybrid piezo/triboelectric nanogenerator with reliable supply capability for building a self-powered industrial monitoring system

As a result of increasingly stringent power supply requirements and diverse application scenarios, the development of hybrid nanogenerators that can combine multiple power generation modes has gradually become a hot research topic. In this work, the PR-HNG, a piezo/triboelectric hybrid nanogenerator based on a pitched roof structure, is proposed and is used efficiently to perform discrete mechanical energy harvesting. Using the flexible connection of its separated roof-like trigger mechanism, the PR-HNG operates through inertia under vibration conditions and achieves a satisfactory working state with very low mechanical loss. At 10 Hz, the instantaneous open-circuit voltage VOC and short-circuit current ISC of the PR-HNG can reach 800 V and 9.6 mA (1.60 A/m2), respectively, and no obvious attenuation occurs during high-intensity and long-term operation. After connection to a load via a rectifier bridge, the PR-HNG has a maximum power output of 575 μW/cm2 and can charge a 2 mF capacitor up to more than 2.5 V in only 30 s; these two performance parameters are better than the reported values for other similar types of HNG. In practical applications, this PR-HNG can easily drive more than 1440 commercial light-emitting diodes and can drive small electronic devices in real time. Therefore, the PR-HNG has been demonstrated to provide a credible and promising solution for fabrication of self-powered monitoring systems for use in industrial environments.

Vectorizing planar roof structure from very high resolution remote sensing images using transformers

ABSTRACT Accurately predicting the geometric structure of a building's roof as a vectorized representation from a raster image is a challenging task in building reconstruction. In this paper, we propose an efficient and precise parsing method called Roof-Former, based on a vision Transformer. Our method involves three steps: (1) Image encoder and edge node initialization, (2) Image feature fusion with an enhanced segmentation refinement branch, and (3) Edge filtering and structural reasoning. Our method outperforms previous works on the vectorizing world building dataset and the Enschede dataset, with vertex and edge heat map F1-scores increasing from 87.1 % , 76.2 % to 89.1 % , 78.1 % , and from 69.7 % , 68.8 % to 71.2 % , 69.5 % , respectively. Furthermore, our method demonstrates superior performance compared to the current state-of-the-art based on qualitative evaluations, indicating its effectiveness in extracting global image information while maintaining the consistency and topological validity of the roof structure.

Roof structure above the Presbytery of the Church of Our Lady's Nativity in Miličín - the Power of Tradition and Uneasy Adoption of Construction Innovations

Roof structure above the Presbytery of the Church of Our Lady's Nativity in Miličín - the Power of Tradition and Uneasy Adoption of Construction Innovations

Role of applying PCMs on thermal behavior of innovative unit roof enclosure

As a technical approach, using Phase Change Materials (PCM) can be an effective method to prevent energy losses through building enclosures. In the present paper, different roof structures containing PCM have been examined to analyze their thermal behavior. The governing equations were developed and solved for a sample unit extracted from a typical roof. The control volume based finite element method has been applied for solving coupled equations governing heat transfer through the roof and flow of melted PCM. The effect of key parameters including thermal diffusivity of the PCM and the wall, Prandtl number (Pr), Rayleigh number (Ra) and solid wall thickness to total thickness has been examined. The main results indicate an enhancement of heat transfer through the increase of the thermal diffusivity of the PCM with respect to the building material. Increasing the thermal diffusivity ratio from 1 to 25 doubles the heat transfer rate and decreases the full melting time by 80% for high Rayleigh. Pr affects the mode of heat transfer but has little impact on PCM melting rate. Raising Ra improves heat transfer under the condition of high thermal diffusivity in the PCM. Increasing Rayleigh number from 104 to 106 doubles the heat transfer rate and reduces the melting by 67% for high thermal diffusivity ratio. Finally, increasing the size of the wall thickness does not affect the fraction of melted PCM but reduces the heat transfer rate. The heat transfer rate can be increased by up to 75% when the non-dimensional thickness of the solid layer is reduced from 0.5 to 0.005.

Parameter determination and effect evaluation of gob-side entry retaining by directional roof cutting and pressure releasing

Cutting the roof and releasing pressure to form a roadway is a crucial technical measure to guarantee the stability of the gob-side entry, and the parameters for cutting the roof are the core issue that requires consideration in the technique. This paper studies the engineering case of the gob-side entry on the 3405 working face of the Danyang coal mine. Theoretical calculation and analysis were conducted to obtain the range of roof cutting heights and roof cutting angles, numerical simulation method was used to simulate different roof cutting parameters. It is found that the roof cutting and pressure releasing technique can sever the cantilever beam structure of the main roof, segregate stress transmission between rock bodies, diminish deformation of the roadway, alleviate stress on the flexible formwork concrete wall, and enhance the stability of the gob-side entry. Furthermore, the appropriate height and angle of the roof cutting were verified to be 15 m and 15° in the case and the effect of cutting was checked by using borehole viewer. On the basis, flexible formwork concrete wall stress and roadway deformation in uncut and cut roof were measured and analyzed in field test. The results show that the maximum stress on the flexible formwork concrete wall is reduced from 160 kN to 20 kN after the roof cutting, total roadway deformation reduced by around 40 %, the stability of the gob-side entry is effectively ensured. Meanwhile, the transformation laws of stress on the flexible formwork concrete wall were changed by cutting roof. It is transitioning from a three-stage pattern of rapid rise, slow rise, and stabilization before the roof cutting to a three-stage pattern of rapid rise, gradual decrease, and stabilization after the roof cutting.

Fluid-structure interaction behaviors of tension membrane roofs by fully-coupled numerical simulation

This study aims to investigate fluid-structure interaction (FSI) behaviors of an enclosed-type tension membrane flat roof. The roof with rectangular shape is chosen as the object because of its relatively idealized geometry for FSI analysis, which is a simplified shape compared to typical membrane roofs. Fully-coupled numerical simulations are performed to obtain the wind induced vibration, aerodynamic forces and surrounding flow field of the tension membrane roof structure, where large-eddy simulation (LES) is used for solving of the flow field, non-linear membrane elements are adopted for the structure field and partitioned algorithm is applied for the coupling between the flow and membrane vibration. The numerical simulations are validated by the aero-elastic experimental results. The characteristics of the wind-induced displacements and aerodynamic forces of the tension membrane roof are investigated in both time and frequency domains. The energy transfer characteristics between wind and the vibrating roof are investigated based on the phase analysis between the generalized forces and displacements of the membrane roof. The underlying mechanism of the modal-jump phenomena that the vibration mode of the membrane jumps from the first mode to the second mode with increasing wind velocity, as well as the instability mechanism of the tension membrane roof, are revealed by flow visualizations and unsteady aerodynamic forces identifications. It is found that the aero-elastic instability of the flat membrane roof is a kind of vortex-induced vibration (VIV), where the modal-jump phenomena and unstable vibration of the membrane roof occur with the occurrence of negative aerodynamic damping, induced by the interaction between the vortex transporting and the roof motion.

Hygrothermal Performance of simple intensive Green Roofs with Different Irrigation Schemes

Urban mesoclimate is formed by a multitude of factors enhancing climate change characteristics like increasing temperature levels, reduced air moisture content, atmospheric pollution or extreme rain events. All of these factors could be attenuated by green roof structures. Unfortunately, this potential is not being tapped in current building practice. The majority of erected green roofs are built as extensive, i.e. non-irrigated, types. This results in a poor mesoclimatic impact as the water contents of these roof substrate layers are meagre, and vegetation layers are more or less inactive during the dry, hot summer months. Intensive green roofs, on the other hand, require higher load-bearing capacities and costs, both often not eligible for refurbishments. A promising approach is a combination of simple intensive green roof structures featuring a thin substrate layer with reduced irrigation techniques, especially under the usage of grey water. The hygrothermal performance of these structures in comparison between different irrigation schemes and solar radiation levels is shown in this article. Measurements were performed over a period of about two years. Hygrothermal performance shows the importance of an optimised relationship between irrigation scheme, substrate type and thickness in order to achieve a sufficient evapotranspiration and temperature balancing effect.