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Site investigation of damages occurred in a steel space truss roof structure due to ponding

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... The spherical joints used to connect the rods to each other and to the supports are made of hot forged steel with the yield stress of 330 MPa and the tensile strength of 590 MPa. The strength values and the chemical decompositions of the materials used in the truss roof system are validated by Piroglu et al [8]. ...
... It is worthy to note that all the analyses are run in a static manner. Since the equivalent static loads are determined using the relevant Turkish standards, it is appropriate to use this simplification [8]. ...
... One of the most important aspects here is that the presented strength and elastic properties of the materials and members used are put through tests and experimental processes and they have found to be consistent in general [8]. So, in the analyses performed for this study, the values which are presented in the reports of the company will be mainly used. ...
Preprint
This study investigates the failure of a roof with steel truss construction of a factory building in Tekirdag in North-western part of Turkey. The failure occurred under hefty weather conditions including thunderbolt, lightning strikes, heavy rain and fierce winds. In order to interpret the reason for the failure, the effects of different combinations of factors on the design and dimensioning of the roof are checked. Therefore, finite element analysis is performed several times under different assumptions and considering different factors aiming to determine the dominant ones that are responsible for the failure. Each loading condition gives out a characteristic form of failure. The scenario with the most similar form of failure to the real collapse is considered as the most likely scenario of failure. Also, the factors included in this scenario are expected to be the responsible factors for the partial collapse of the steel truss structure.
... The standardised loads can be multiple times greater than the structures' own weight. In the case of unexpectedly excessive loads of accumulated snow or rainwater, failure of the designed structure may be unavoidable [8,9]. Geis et al. studied more than 1000 snow-induced building failure incidents all over the world [10]. ...
... The spherical joints used to connect the rods to each other and the supports are made of hot forged steel with a yield stress of 330 MPa and a tensile strength of 590 MPa. The strength values and the chemical decompositions of the materials used in the truss roof system were validated by Piroglu et al. [8]. ...
... One of the most important aspects here is that the presented strength and elastic properties of the materials and members used were put through tests and experimental processes and were found to be consistent in general with the standards [8]. So, in the analyses performed for this study, the values that were presented in the reports of the company were mainly used. ...
Article
Full-text available
This study investigated the failure of the roof, with steel truss construction, of a factory building in Tekirdag in the northwestern part of Turkey. The failure occurred under hefty weather conditions including lightning strikes, heavy rain, and fierce winds. In order to interpret the reason for the failure, the effects of different combinations of factors on the design and dimensioning of the roof were studied. Finite element analysis, using the commercial software Abaqus (Dassault Systèmes, Vélizy-Villacoublay, France), was performed several times under different assumptions and considering different factors with the aim of determining the dominant factors that were responsible for the failure. Each loading condition gives out a characteristic form of failure. The scenario with the most similar form of failure to the real collapse is considered as the most likely scenario of failure. In addition, the factors included in this scenario are expected to be the responsible factors for the partial collapse of the steel truss structure.
... As mentioned earlier, some collapses occur suddenly under excessive impulsive loadings. This study aims to handle a case, which a sudden partial failure of a steel truss roof of a factory built in July 2011, happened under heavy weather conditions on 22.10.2012 in Cerkezkoy Tekirdag in Northwestern part of Turkey [8]. The main focus is on developing a plausible theory for the failure by employing numerical analyses performed using the finite element method, which covers various loading conditions and their combinations. ...
... The spherical joints used to connect the rods to each other and the supports are made of hot forged steel with the yield stress of 330 MPa and the tensile strength of 590 MPa. The strength values and the chemical decompositions of the materials used in the truss roof system are validated by Piroglu et al [8]. ...
... It is worthy to note that all the analyses are run in a static manner. Since the equivalent static loads are determined using the relevant Turkish standards, it is appropriate to use this simplification [8]. ...
Preprint
Full-text available
This study investigates the failure of a roof with steel truss construction of a factory building in Tekirdag in North-western part of Turkey. The failure occurred under hefty weather conditions including thunderbolt, lightning strikes, heavy rain and fierce winds. In order to interpret the reason for the failure, the effects of different combinations of factors on the design and dimensioning of the roof are checked. Therefore, finite element analysis is performed several times under different assumptions and considering different factors aiming to determine the dominant ones that are responsible for the failure using the commercial software Abaqus (Dassault Systèmes, Vélizy-Villacoublay, France). Each loading condition gives out a characteristic form of failure. The scenario with the most similar form of failure to the real collapse is considered as the most likely scenario of failure. Also, the factors included in this scenario are expected to be the responsible factors for the partial collapse of the steel truss structure.
... However, as a result of their frequent lower degree of hyperstaticity, some precast structures have been damaged by certain unforeseen horizontal actions, such as in the case of earthquakes in Turkey [2] or in Italy [3] assembly of these structures, intermediate construction situations are produced in which the structure is made up of a set of isostatic parts that require certain precautions both during the design project and during the construction process. The particular case of roof beams -generally due to the great slenderness of their elements -require special attention in order to avoid pathologies [4][5][6]. ...
... Stabilizing (MS) and overturning (MO) moments of Eqs. (6) and (7) can be derived, see Figs. 11 and 12, as follows: ...
... Improper buckling length evaluation of the upper chord in the roof truss design will influence instability problem (Kozlowski et al., 2004). Piroglu et al., 2014 reported that the roof truss failure in industrial hall building in Marmara Region, Turki was caused by improper fabrication and did not follow the basic design principles for the support assemblies. Guo et al. (2015) reported that editor@iaeme.com ...
... The roof truss can fail due to unpredicted extreme weather events, poor construction and inadequate design subjected to normal load conditions (Piroglu et al., 2014). CFS as a structural element in roof truss is subjected to fail due to buckling, including global buckling, local buckling, distortional buckling and web crippling. ...
Article
The roof truss is an important structure to keep a building safe, protect it from rain and sunshine, and protect home appliances and equipment inside it. The stability of the roof truss system, either by using timber or steel, is necessary to study and investigate. The roof truss material, member section, configuration, connection or fastener, end support and span must be checked. Nowadays, cold-formed steel (CFS) with numerous advantages is selected as chord and web truss. However, the failure of CFS, such as buckling, must be revised to ensure that the CFS roof truss is stable. From the observations of previous research studies, the failure of the CFS roof truss has been broadly discussed and to determine the causes of stability. The effect of CFS truss mainly fails or become unstable due to a slender section of the truss, especially on the compression member. Intentionally, the slender section of the top chord must be replaced with a short section or changed to become a curved section. The idea is to certify the local buckling failure of the top chord and prevent the nearest section from failing. Finally, the guideline for checking the stability of the CFS roof truss was established to give an experience for engineers.
... The vertical eccentricity E2 is proportional to the angle ϕ, being equivalent to the correction distance d. Figure 8 shows that the measurement of d2 is equal to 5t1 of the pipe wall thickness (flange) Several other collapses in 3D trusses have been observed in the world. However, the ranges of space truss structures have been reevaluated and some have been strengthened in recent years [61][62][63][64][65][66][67][68][69][70], thanks to increasingly robust computer systems and commercial Finite Element Method (FEM) programs and complex nonlinear analyses [10,30,56,[71][72][73][74][75][76][77][78][79][80][81][82]. ...
... Several other collapses in 3D trusses have been observed in the world. However, the ranges of space truss structures have been reevaluated and some have been strengthened in recent years [61][62][63][64][65][66][67][68][69][70], thanks to increasingly robust computer systems and commercial Finite Element Method (FEM) programs and complex nonlinear analyses [10,30,56,[71][72][73][74][75][76][77][78][79][80][81][82]. ...
Article
Full-text available
Space trusses are structural systems, generally made of tubes, used worldwide because of their advantages in covering long-span roofs. In addition to having a low cost, the truss weight is relatively reduced. The load capacity of these structures depends also on the strength of their node connection. Connections made with the superposition of flattened tube ends trespassed by one bolt are, generally, known as typical nodes. They are inexpensive but present eccentricities that reduce significantly the strength of such space trusses. To increase the truss load capacity, this research presents the results of an experimental program to reduce the eccentricities of the typical nodes. This reduction is done with a new type of spacer made of encapsulated concrete with steel fiber or sisal fiber. The experimental tests showed that the trusses with typical nodes collapsed under reduced load by local failure due to high distortions at the nodes. The trusses with encapsulated concrete spacer showed good results, with an increase in collapse load of 36% and failure by buckling bars.
... Although timber trusses have been traditionally used for centuries, they fail to meet some necessary requirements such as in small span trusses with raised king-post (Munafò et al. 2015), resistance against deterioration of joi nts (Abramyana and Ishmametova 2016, Foo 1993, Branco 2010, discontinuity of rafter beyond the point of intersection in the tie beam (Barbari et al. 2014), absence of high strength to weight ratio for longer life (Dawe et al. 2010) and need of strengthening by metal bracing (Burdzik and Skorpen 2014). Steel trusses even though stronger than timber trusses might fail if not designed and fabricated properly (Jagadish 1995, Piroglu andOzakgul 2016) or even under unforeseen meteorological events (Piroglu et al. 2014). ...
Article
Full-text available
Structural failures are undesirable events that devastate the construction industry resulting in loss of life, injury, huge property loss, and also affect the economy of the region. Roof truss failures occur mainly due to excessive loading, improper fabrication, deterioration, inadequate repair, etc. Although very rare, a roof truss may even fail due to inappropriate location of supports. One such case was reported from the recent failure of a steel roof truss used in an indoor stadium at Kargil in India. Kargil region, being mountainous in nature, receives heavy snowfall and hence the steel roof trusses are designed for heavy snow loads. Due to inappropriate support location, the indoor stadium‟s steel roof truss had failed under heavy snow load for which it was designed and became an interesting structural engineering problem. The failure observed was primarily in terms of yielding of the bottom chord under the supports, leading to partial collapse of the roof truss. This paper summarizes the results of laboratory tests and analytical studies that focused on the validation of the proposed remedial measure for rehabilitating this distressed steel roof truss. The study presents the evaluation of (i) significant reduction in strength and stiffness of the distressed truss resulting in its failure, (ii) desired recovery in both strength and stiffness of the rectified truss contributed by the proposed remedial measure. Three types of models i.e., ideal truss model, as build truss model and rectified truss model were fabricated and tested under monotonic loading. The structural configuration and support condition varied in all the three models to represent the ideal truss, distressed truss and the rectified truss. To verify the accuracy of the experimental results, an analytical study was carried out and the results of this analytical study are compared with the experimental ones.
... The effect of different types of geometrical imperfections such as member lengths, uneven support settlements, on the safety of space truss systems have been investigated in the past [1,7]. Given the large sensitivity of steel truss covering structures to unavailable geometrical imperfections which can detrimentally affect their load-carrying capacity and their reduced self-weight (often leading to design which is controlled by accidental loads, rather than dead loads), space steel trusses are particularly susceptible to fail, especially due to water-ponding and snow loadings [8][9][10]. In this regard, an emblematic case of an extremely sensitive case of a covering structure sensible to geometric imperfections is represented by the Montreal Stadium roof which failed many times in apparently unexceptional conditions [11]. ...
Article
In 2010, after an ordinary snowfall, the long-span steel trusses roof covering a school building located in a small town in North Italy collapsed. The building construction was completed in 2008, while the school was opened to the public just few months before the collapse. Luckily, at the time of the collapse, the building was empty and no people died or were injured. After the collapse, the Court nominated a first Official Technical Consultant in order to investigate on the causes of failure and related responsibilities. Later on, after that the main responsibilities were identified, a second Official Technical Consultant was nominated to further investigate on few specific technical aspects related to the collapse which were not completely clarified during the first investigations. In the present work, the main attention is paid on the structural behavior of the peculiar joint elements used to connect the members and their influence on the collapse, with emphasis on the role played by geometrical imperfections and structural ductility. The lesson learned from the case study could help professional engineers in being aware on the main peculiarities and structural deficiencies of structural systems made by spatial trusses with brittle connections.
... Although timber trusses have been traditionally used for centuries, they fail to meet some necessary requirements such as in small span trusses with raised king-post (Munafò et al. 2015), resistance against deterioration of joi nts (Abramyana and Ishmametova 2016, Foo 1993, Branco 2010, discontinuity of rafter beyond the point of intersection in the tie beam (Barbari et al. 2014), absence of high strength to weight ratio for longer life (Dawe et al. 2010) and need of strengthening by metal bracing (Burdzik and Skorpen 2014). Steel trusses even though stronger than timber trusses might fail if not designed and fabricated properly (Jagadish 1995, Piroglu andOzakgul 2016) or even under unforeseen meteorological events (Piroglu et al. 2014). ...
... Another research [5] has addressed a long-span steel roof structure collapsed during construction as a result of an out-of-plane buckling phenomenon caused by a gust of wind. The partial collapse of a space truss roof structure that occurred during strong winds and heavy rains was investigated based on the site observation and experimental study on the bolts [6]. An experimental study was performed to investigate the ductility behavior of a space truss roof system that consists of cold-formed hollow square sections attached to a joint through the special welded joint plates and bolted connections [7]. ...
Article
Some bars of space truss roof a major shopping market chain in Adana, Turkey have experienced flexural buckling without any circumstance of overloading induced by snow and rain together with wind that has led to the buckling phenomenon. However, according to the on-site geotechnical surveys that have demonstrated that an increase in consolidation settlement of foundation soil has occurred, it has been realized that differential support settlements may cause the truss bars to buckle. This paper investigates the probable cause of the buckling phenomenon observed in some truss bars based on the soil condition. For this, a photogrammetric survey has initially been performed to determine the existing vertical position of the roof supports located on the top of the cantilever columns. To obtain the amount of settlements of the supports, initial vertical coordinates of the tips of the columns that were determined before assembling of the roof are subtracted from those obtained by the photogrammetric measurement with respect to the reference point. An observation has also been made in site to visually inspect the distribution pattern of the buckled truss bars. A 3D analytical model of the roof has been developed to understand whether or not the buckling failure of the truss bars is resulted from the soil settlement under the individual foundations. When the observed distribution pattern of the buckled truss bars is compared to that obtained by the nonlinear analysis, a reasonably good agreement has been achieved, which shows that the truss bars have buckled because of the effects caused by differential settlements among the individual foundations due to increase in consolidation settlement occurred within the soil that surrounds the structure.
... A numerical investigation on the progressive collapse behavior of double-layer space truss roofs has proved the sensitivity of these structures against the progressive collapse when subjected to increasing applied load [9][10][11]. However, even though some truss bars buckle in flexural mode, the entire roof may not collapse because the system is capable of allowing redistribution of axial forces to a small extent [12]. ...
Article
Full-text available
Spaceframe is a structural roofing system that generally made of steel tubes connected together by ball joints which is called MERO jointed space frame structures and mostly used for covering large space area. In addition, some advantages could be obtained with such a system, for example the lower weight, the high strength-to-weight ratio and the low cost. This study aims to use such a known roof structure for a composite structure in which Ultra-High-Performance Concrete slabs are used to withstand various loads as a structural floor system. Various inclinations of the main elements for space frames were tested, namely 30 °, 45 ° and 60 °. The composite effect is accounted for by testing composite and non-composite samples. The test results were evaluated and compared against several performance indices, such as: Ultimate load, stiffness, hardness, ductility, ductility index and absorbed energy. Test results have shown that spaceframe models with an angle of 60 ° have the highest load-carrying capacity compared to other angles and the highest toughness compared to various techniques. Putting together 40mm UHPC slab panels reflected a slight increase in the models used in this study than traditional spaceframe samples.
... The implementation of parapets around a roof perimeter and clogging of the drainage system are the main reasons that cause the accumulation of rainwater and snow, respectively. To reveal the collapse behavior of space truss roofs due to ponding, substantial investigations were performed by Biegus and Rykaluk [3], Piroglu et al. [4], Piroglu and Ozakgul [5]. Inadequacy of standards and misestimating of Rosen and Schmit [6] investigated the effects of member imperfections and system imperfection on the behavior of structural system. ...
Article
Full-text available
The aim of this paper is to investigate the nonlinear behavior of space truss roofs subject to different load accumulation forms considering the effect of initial imperfection and slenderness ratio of the truss members. For this, a typical space truss roof using MERO-connection type with flat double-layer was selected as a sample. 3D model of the roof was developed and analyzed by using OpenSEES. Nonlinear behavior of each typical bar of the space truss roof, which, was mainly composed of particular sub-elements such as a tubular element, bolts, sleeves and spheres was represented by a single truss bar. Axial load-displacement relationship of each single truss bar was obtained from nonlinear analysis performed under reversal cyclic loading. Besides, three different types of load distribution that simulates accumulation of rainwater or drifted snow were taken into account as an external load acting on upper layer of the roof system. Analyses results showed that load carrying capacity of the space truss roofs was very susceptible to the form of accumulation and reduces abnormally when the accumulation, in particular, occurred locally. Furthermore, failure mode of the system designed with optimal solution was dominated by buckled truss bars and brittle failure occurred. Also initial imperfection had a negative effect on the members in compression.
... Another research [5] has addressed a long-span steel roof structure collapsed during construction as a result of an out-of-plane buckling phenomenon caused by a gust of wind. The partial collapse of a space truss roof structure that occurred during strong winds and heavy rains was investigated based on the site observation and experimental study on the bolts [6]. An experimental study was performed to investigate the ductility behavior of a space truss roof system that consists of cold-formed hollow square sections attached to a joint through the special welded joint plates and bolted connections [7]. ...
Article
Full-text available
Spaceframes steel structures are a common worldwide technique for roofing wide areas. In this study, after validating one of the models experimentally, nonlinear 3d finite element modelling was performed to analyze failure mechanism of space frames models with the help of Abaqus program. Additionally, this study attempts to convert such common roofing structure to a composite structure using ultra high strength concrete slab to withstand various floor loads. Various space frames shaft angles were tested, namely, 30, 45, and 60. Tests results were evaluated and compared in term of ultimate load, load at maximum displacement, toughness, and stiffness. Tests results have shown that spaceframes models with angle 60 have the highest load capacity compared to other angles, and highest toughness compared to various techniques. Also, compositing 40 mm of ultra-high-performance concrete slab method has approved its efficiency to withstand loads and showed comparable results with the conventional spaceframes. the composite systems with sufficient concrete slab thickness and strength have reflected an efficient technique for flooring wide span structures.
... Göçen uzay kafes çatı sistem örneklerine bakıldığında göçmenin genellikle çeşitli imalat kusurları ile birlikte beklenmeyen olayların (kar veya yağmur suyu birikmesi vb.) sonucunda meydana geldiği görülmektedir (Biegus ve Caglayan ve Yuksel, 2008; Piroglu ve Ozakgul, 2016;Piroglu ve diğ., 2014). Üretim ve montaj aşamasındaki hatalar, sistem tasarımında dikkate alınan yük durumlarından farklı yük durumlarının gerçekleşmesi bu durumu tetiklemektedir. ...
Article
The work describes the actions taken as a result of an unforeseen disaster of a shopping facility that had been in operation for several decades. A considerable part of the facility's roof structure unexpectedly collapsed under the impact of a snow layer, whose thickness did not exceed the limit value specified in the current regulations. The roofing was made of steel segmental truss girders (4 × 6 m) with a span of 24 m, joined together by bolts and welds. After securing the facility against a possibility of further collapse, the extent of the damage was investigated. An attempt was made to identify faults in the structural elements and in the connections made several years earlier, as well as possible mistakes made during the modernization works several months before the disaster. The actual strength parameters of the steel structural elements and joints were determined. The effort of basic structural elements was analyzed, with particular emphasis on the state of connections of successive segments of the damaged girders. The causes of the disaster were determined. The work is concluded by presenting a concept and conditions for lifting and reconstructing the damaged roof. It is worth highlighting that the roof was lifted as a whole, without the need to disassemble purlins, steel sheets and insulation. The advantages and disadvantages of different types of butt joints used in the construction were evaluated. Making use of the results of the investigation, the recommendations concerning the design, construction and operation of public facilities were formulated and relayed to participants of the investment process.
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This paper presents investigations on the steel space truss roof of an industrial plant collapsed partially after exceptional snowfalls. This low sloped light weight roof structure supported on steel columns of 16.3 m height and covering totally 26,080 m2 closed area in plan was constructed as Mero type double layer grid steel space truss system having a height of 2 m. Also, parapets of 90 cm height were placed along the perimeter of the building and siphonic system was used for roof drainage. To find out the main reasons of the partial collapse of the roof structure, a site investigation was conducted and findings were collected, then conformity of the structural members were checked with respect to the current Turkish steel building design codes. The material properties of the primary load carrying members of the roof were scrutinized by performing tensile tests. Finally, it was understood that two unexpected catastrophic collapses were experienced as a consequence of ice ponds that occurred on the edge regions of the roof due to discontinuously heated roof parts by the radiant heaters mounted on the roof structure and the freezing of the siphonic system.
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In pin-jointed grid structures, the commonly observed bending deformation of members affects the structural performance. The main aim of this study is to investigate the residual load-bearing capacity of an existing pin-jointed grid structure with crooked members, and a new model updating method using static measurement data is proposed to obtain a practical numerical model of the structure. First, the vertical displacements at multiple positions in the structure and the bending deformations of crooked members are selected as the static measurement parameters and measured. Then, the structure, including the crooked members, is adjusted from the load state at the moment of measurement to the zero-load state through global optimization. Finally, the updated finite element model with crooked members is utilized to assess the residual load-bearing capacity of the overall structure. In this study, a load experiment using a quadrangular pyramid grid structure with artificial crooked members is conducted, and the experimental results validate the proposed method.
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Collapses that do not produce other than economic losses remain often unknown either to the public and to the community of engineers. The technical causes of any collapse deserve attention even if no scientific research is needed since they often show that design and control procedures and code provisions may fail in preventing errors both in the design and in the building phase of standard structural engineering. In this paper the collapse of an industrial steel shed, under a 10cm layer of fresh snow, is discussed showing that its collapse resulted from a chain of errors, in the design phase, during its assemblage and in the final inspection and control phase.
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An experimental program of nine steel deck roof diaphragm specimens was carried out to assess their seismic characteristics. The dynamically loaded diaphragms were able to develop the shear strength but not the shear stiffness values calculated using current diaphragm design methods. Furthermore, the shear stiffness decreased with increasing excitation amplitude. Diaphragm ductility decreased with the use of thicker deck panels and when the deck was oriented parallel to the loading direction. Most of the damaged diaphragms could be repaired to recuperate their original strength. A seismic retrofit scheme was effective in increasing the shear strength and stiffness of an arc-spot weld/ button-punch diaphragm.
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A 1300 m2 flat roof of a three year-old gymnasium collapsed in the early morning of a winter day, fortunately before the opening hours.The snow load was rather high, but still considerably below the design limit. Therefore, the snow could only be the trigger of the collapse. The visual findings, material tests and norm conformity checks pointed towards the buckling of the girder’s stiffener-less web at its supported ends to be the root failure cause. However, relevant contributions of other structural deficiencies still could not be excluded. In order to prove the “buckling-hypothesis”, the optimistic–realistic ultimate resistance of the girders had to be determined and compared with the reconstructed loads acting at the moment of the failure.The present paper focuses on the calculation of the ultimate resistance of the girder’s ends including the non-linear post-buckling process. The procedure consists of a concerted two-stage combination of linear and nonlinear finite element analyses. A sensitivity analysis regarding the girder’s initial geometrical imperfection and the consideration of the real elastic–plastic material behavior were essential to obtain the adequate range of the girder’s ultimate resistance.Based on the quantitative results, the girder’s web buckling under the regular service load due to lack of stiffeners could be proven as the root cause of the accident. The conclusion is supported additionally by the consistency between the retracted collapse and the characteristic visual findings.The presented case study demonstrates the importance of finding the realistic–optimistic load carrying capacity when proving a corresponding failure hypothesis. This required a different approach compared to the stage of design in terms of appropriate assumptions and accuracy.
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Paper describes a bearing structure shaped as a cylindrical shell, designed from cold-formed 1 mm thick steel sheets, according to so called ABM system. The transversal shaping (folding) and longitudinal forming (a circular arch) of ABM profile is executed in situ. The structure is offered for halls with spans reaching even 25 m. The work presents analysis of safety of two such objects whose execution was stopped and two other in Gdansk (Poland) and Tuszyn (Poland) that have collapsed. (C) 2013 Published by Elsevier Ltd.
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Roof sheathing on typical North American timber frame house construction is subjected to high uplift loads during severe windstorms resulting in commonly observed failures. To investigate such failures in detail, ramp and fluctuating wind loads were applied to oriented strand board and plywood panels fixed to rafters with twisted and ring-shank nail varieties, as well as staples. It was observed for panels fixed with twist-shank nails that the panels separate from the rafters in small increments associated with the large peak pressures. In contrast, the failure progression for ring-shank nails is much more sudden. With both types of failure progression, however, it is observed that it is the short duration peak gusts which damage and fail the panels, and always at the nails with the largest tributary areas in the interior of the panel. Tests were also conducted with different missing nail configurations and the capacities assessed. It was observed that fasteners with the incremental failure mechanism were able to more effectively distribute the load such that the effects of missing nails are reduced compared to the panels which fail by the sudden mechanism.
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This paper examines wind loads acting on roof sheathing on typical low-rise, wood-frame houses for a variety of parameters including roof shape, roof slope, building height, upstream terrain and the presence of surrounding structures placed in several patterns. It was found that roof shape and upstream terrain have the most significant effect on wind loads acting on roof sheathing. Considering the variation in wind loads, an effective prescriptive standard for sheathing on gable roofs, would discriminate by terrain and roof zone. Roof height and roof slope could be neglected from such a standard. In contrast, for hip roofs, an effective prescriptive standard would discriminate based on terrain, roof height and roof slope, but without considering roof zones (for the current, nearly square plan dimension houses). Surrounding houses are found to have both shielding and enhancing effects on the loads, depending on the details.
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The adhesion between roofing felt and sheet metal flashings has been measured and analysed and test methods for this have been developed. Both bituminous and polymeric roofing felts have been used. The steel has been PVC-coated galvanised steel sheets and the bituminous roofing felts have been of both SBS and APP modified type. All the joints have been made with heat welding. The tests show that it is possible to obtain joints with sufficient strength using the contractors ordinary welding procedures.
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An explosion of electric furnace caused a local damage of the roof in steel industrial building. This building has a saw-tooth roof covering, constructed from prestressed plates with 12.62m of span. The explosion caused a local damage of plates prestressed ribs, which are the roof main structural elements. The technical condition of the plates has been assessed as an emergency state due to the loss of the plates’ strength and the hazard of their fall down. The damage repair has been presented herein.
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The Katowice Fair Building in Poland collapsed on 28 January 2006. It was a steel building having dimensions 96.360×102.875m in the general plan. The roof was constructed from truss elements, supported on 6 internal and 66 external columns situated along external walls. The results of engineering investigations on the reasons of total collapse of Katowice Fair Building structure has presented herein. Generally the collapse occurred as a consequences of: incorrect arrangement of the structure, unsufficient strength and rigidity of main structural elements, and finally of the overloading action of thick ice – snow layer. The following parameters have been estimated: the reliability model of the structure system, arrangement of bracings, construction of main columns, main girders and supporting, field connections of elements and shaping of the roof surface.
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This paper represents the most thorough examination of siphonic system priming to date. Data is presented which has been obtained from a number of systems. The text details the priming of siphonic roof drainage systems, and outlines how knowledge of the priming process, if considered at the design stage, may be used to improve the operational system performance. The role of different system components in improving “ability to prime”, estimating priming time and reducing ongoing maintenance costs is considered and used as the basis of the “Priming Focused Design” philosophy proposed in this paper.
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A method for the analysis of rainwater ponding on flat or nearly flat one-way and two-way roofs, published in 2007, is modified. The existing method appears accurate for roofs of continuous secondary members and profiled steel sheeting, but is far too pessimistic for roofs in which all composing parts are simply-supported. After summarizing the formerly published method, a modification is proposed in order to fit better with FEM-packages, considered in this context to be exact solutions. In essence, the stored water in the deflected secondary members and steel sheeting elements is estimated more properly. An easy way has been found how to adapt the existing spring-piston model in order to better account for the correct volume of accumulated water in the secondary members and profiled steel sheeting. An application example and discussion of the results complete the article.
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Although siphonic roof drainage systems have been installed in Europe since the 1970s, the design of such infrastructure is still based on steady state theory. Such approaches are only truly applicable at the design condition, under specific rainfall conditions, and cannot be used to assess the response of siphonic systems to alternative rainfall conditions and/or operational scenarios. Previous research at Heriot-Watt University led to the development of a numerical model capable of accurately simulating the performance of single outlet systems under a range of different conditions. The work reported herein details the logical extension to this work; i.e., the development of a numerical model to simulate the performance of multi-outlet siphonic roof drainage systems. The experimental work undertaken to assist in the development of the new model boundary conditions is briefly described, and relevant results are illustrated. The development of the numerical model is then detailed, and model output is presented. Finally, conclusions are drawn regarding the developed model, and plans for future work are outlined.
Article
Ponding on flat or nearly flat roofs keeps drawing attention due to the large number of collapses over the course of years. Though at present computer programs start to offer functionality to check the sensitivity of roofs for water accumulation, true insight appears to be missing on the very nature of the phenomenon. In this paper two models are presented for regular grids, that fill the understanding gap: the piston–spring model for rather stiff roofs and the bar–spring model for extremely flexible ones. The models apply for horizontal roofs, sloped roofs, roofs with initial deflection due to permanent load, camber and composed roofs. Rain showers are considered, so heavy that the water level keeps staying at the specified height of the emergency discharge (full ponding). The case of a specified limited water volume (partial ponding) is not considered. Full ponding is studied for both fully filled roofs and partially filled roofs. The derived theory brings to light that two main roof categories exist; one stress-dominated and one stability-dominated. Four application examples demonstrate that the models are easy-to-use design tools for structural engineers. The derived theory clarifies the effect of the profiled steel roof sheeting on safety and other practical hints are included in the paper.
Article
In this research work, a nonlinear structural analysis by the finite element method (FEM) is carried out to study the structural collapse of a self-weighted metallic roof with and without skylights located in Cabañaquinta’s schoolyard (Principality of Asturias, Northern Spain). The collapse of this cable-arch structure was due to huge snow loads in winters of 2004 and 2006. In order to tackle this structural problem, it is proposed a damage assessment based on the nonlinear post-buckling analysis of the entire self-weighted metallic roof by FEM. Firstly, in order to obtain a diagnosis of the failure causes, several FEM models with six tiles of a 0.83 m wide and 1.25 mm thickness, including methacrylate skylights in one of them, were built and then solved as a three steps procedure: a linear pre-stress analysis, a buckling analysis and a nonlinear analysis. Secondly, a procedure based on the design of experiments (DOEs) applying the FEM technique was used to determine the importance of different parameters on the structural integrity of the roof. Finally, the numerical results of this work are discussed and the structural design recommendations are explained in detail to avoid these structural failures in the future.
Article
The main objective of this research work is to present two case studies of recently constructed public buildings in Portugal which have faced problems in the roof system. Both buildings were constructed in 2004 and are located in the north of Portugal. One is a swimming pool and the other is a multi-use pavilion. They have as main roof structural elements glued laminated timber (glulam) arches and beams, respectively. The adopted roof cover system of both buildings has zinc sheets as the outer face finishing. In this paper the observed defects in these roof systems are presented and analyzed. The associated causes are discussed and the proposed and implemented repairing/retrofitting solutions are also presented. Recommendations for future design and construction of this type of structural solutions are made.
Article
Siphonic roof drainage systems have been in existence for approximately 30 years, and are becoming an increasingly common element of urban drainage infrastructure. In that time, only limited data have been published relating to their performance, and what does exist relates to laboratory test facilities. This text focuses on the analysis of a large data set obtained from installed siphonic roof drainage systems. Particular attention is given to the ability of the studied systems to prime and meet self-cleansing criteria during sub-design criteria events with return periods of less than one year. Conclusions are drawn regarding the performance characteristics of multi-outlet siphonic roof drainage systems, and plans for future work are outlined.
Article
A Mero space truss which is subject of this paper covering the roof of a reinforced concrete building was totally collapsed without any indication on February 25, 2003 at eastern part of Turkey. The plan dimensions of the space truss were 40 m by 25 m. The possible reasons of collapse of the roof system are inspected in this paper. During the observation on the site, several pipe elements and connection parts (Mero nodes and bolts) were gathered and then visual inspections and experimental studies were conducted on those parts. The meteorological records and observations of local persons were combined together to estimate the intensity of snow load in the region and it is compared with the code specified values. A mathematical model was prepared to evaluate the vertical load carrying capacity of the roof structure. The experimental and theoretical works conducted in this study indicate that the possible reasons of the collapse are underestimating of snow load intensity and some mistakes made in the elastic design of the truss.
Article
Sandwich panels are attached to cold-formed steel purlins in roofs of industrial buildings to provide insulation. As the strength of the attached purlins is considerably increased due to the lateral and rotational restraints provided by the sandwich panels, estimating these restraints is important in the design of purlins. The rotational restraint is generally determined by experiments, as no design rules exist for sandwich purlin-sheeting systems. In this paper, a non-linear finite element model is presented to estimate the rotational restraint provided by the sandwich panels to the attached purlin. The model is validated with experimental tests and is in good agreement. In order to develop a design method for estimating the rotational restraint in sandwich purlin-sheeting systems, the model could be useful for parametric studies to investigate the influencing factors.
Article
Wind effects on roofing systems are dynamic, because of wind's fluctuation in time and space. Therefore a dynamic means of evaluating roofing systems is beneficial for identifying the component in a roofing system that has the weakest resistance against wind uplift forces. The Special Interest Group for Dynamic Evaluation of Roofing Systems (SIGDERS) commissioned a unique North American roofing facility, which has been used to evaluate a mechanically fastened modified bituminous membrane roof system under three different test methods: the Factory Mutual FM-4470 static test standard, the UEAtc (European Union of Agreement) procedure, and the SIGDERS-developed dynamic load cycle. Comparison of the results of these tests shows that UEAtc and SIGDERS tests produce failure modes similar to those observed in the field. The SIGDERS load cycle was completed in much less time than the UEAtc procedure.
Article
As part of the study on the effects of parapets on wind-induced loads on low buildings, measurements of the pressures on parapet surfaces have been carried out. Pressures were measured on both the exterior and interior for several parapet heights, h=0.46, 0.9, 1.8, 2.7 m, and building heights, H=4.6, 9.1, 18 m, for both a uniform perimetric parapet and an isolated parapet on one wall. These data were used to quantify the local (component and cladding) and structural wind loads on the parapets. It was found that the worst structural load coefficients over all wind angles are approximately constant with h and H because of opposing trends of the pressures on the interior and exterior parapet surfaces. That is, the loads increase on the interior surface with H (as they do for roof loads), while decreasing on the exterior surface. The current structural load coefficients prescribed by the ASCE 7-02 capture this well for the building configurations considered. However, the suction component and cladding loads on the interior surface of isolated parapets are not well captured by the code.
Article
Very high intermittent suctions have been found to occur near corners of low rise building roofs. This paper investigates the effectiveness of parapets mounted at the roof-edge on mitigating these high suctions. The study included full perimeter parapets, both solid and perforated and parapets placed only at the ridge and the corner zones. The parapets used in the study had a 0.2 m full scale height which is more feasible for installation on typical homes than the taller parapets that have been considered in previous studies. The peak pressure coefficients in the corner zone were reduced by over 50% with the solid and perforated parapets placed along the perimeter of the building. Perforated parapets with a perforation ratio of 33% and having a length of 10% of the building dimension at the corners and at the ridge performed best resulting in about a 60% reduction in the peak pressure coefficients at the corners.
Article
In April 2003 the UK Engineering and Physical Sciences Research Council (EPSRC) and a diverse group of interested parties began funding a number of major projects looking at the impacts of climate change on the built environment, transport and utilities. One of these projects, entitled AUDACIOUS, is concerned with the impact of climate change on all aspects of urban drainage systems. The main objective of this project is to investigate key aspects of the effects of climate change on existing drainage in urban areas, and hence provide tools for drainage managers and operators to adapt to uncertain future scenarios. A major element of this work is the development of a set of numerical models to simulate the performance of urban drainage systems under the type of extreme rainfall events associated with climate change. Once developed, it is intended to utilise such models in a diagnostic design capacity, to assist in the formulation of strategies to improve the performance of new and existing urban drainage systems under different climate change scenarios. This paper details the work that has been undertaken at Heriot-Watt University as part of the AUDACIOUS project. To date, this has involved the development of a numerical model to simulate the performance of roof drainage systems (both conventional and siphonic) under extreme rainfall events. The necessary experimental work is described, and the development of the model is detailed. Comparisons between model output and laboratory data are illustrated. Finally, conclusions are drawn regarding the progress to date, and plans for the next stage of the project are outlined.
Article
Roof wind design consist of three parts: determination of wind loads, evaluation of wind uplift resistance and correlating the resistance with the design load such that the resistance is higher than the load requirement. Wind uplift resistance of a system with its respective components is evaluated in laboratory testing. This paper presents a novel approach to estimate wind uplift resistance when components are substituted during field application. Wind dynamics, on a mechanically attached single-ply roofing assembly, lift the membrane and cause fluttering, introducing stresses at the attachment locations. In such assemblies, the fastener-deck interface is a critical design factor. First, by taking steel deck as a component this paper systematically characterizes the various steel decks that are commonly used in low slope application. Second component, namely the fasteners and its engagement strength with deck have been quantified for variations of its design, size and sources. Based on this component characterization, fastener pullout resistance (FPR) is identified as a verification factor for system wind resistance estimation. When variations occur in the fastener-deck interface between the proposed and the existing configurations, the present research through case studies has proved that: "as long as the FPR of the proposed configuration is higher than the existing configuration then wind uplift ratings can be maintained". This is valid as long as both the configurations have all the remaining roofing components similar with comparable layout. Based on this verification, the study recommends that the testing lab should report the FPR along with the wind uplift resistance such that FPR can be used as a verification factor to accept design/field alternatives. Crown Copyright (c) 2008 Published by Elsevier Ltd. All rights reserved.
Article
Over the past three years a UK EPSRC research programme has been underway at Heriot-Watt University investigated siphonic roof rainwater systems. This text aims to report the principle findings of the project to date. A brief description of experimental and numerical aims is given. The priming procedure which occurs in an idealised system is documented. The test procedures employed are described, and experimental results are illustrated. The framework employed to numerically model the ambient hydraulics is described in some detailed. Conclusions are drawn regarding the operational characteristics of siphonic roof rainwater systems as a whole.
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