Roof Truss Research Articles

Vertical load capacities of roof truss cross members

Trusses used for roof support in coal mines are constructed of two grouted bolts installed at opposing forty-five degree angles into the roof and a cross member that ties the angled bolts together. The load on the cross member is vertical, which is transverse to the longitudinal axis, and therefore the cross member is loaded in the weakest direction. Laboratory tests were conducted to determine the vertical load capacity and deflection of three different types of cross members. Single-point load tests, with the load applied in the center of the specimen and double-point load tests, with a span of 2.4m, were conducted. For the single-point load configuration, the yield of the 25mm solid bar cross member was nominally 98kN of vertical load, achieved at 42cm of deflection. For cable cross members, yield was not achieved even after 45cm of deflection. Peak vertical loads were about 89kN for 17mm cables and 67kN for the 15mm cables. For the double-point load configurations, the 25mm solid bar cross members yielded at 150kN of vertical load and 25cm of deflection. At 25cm of deflection individual cable strands started breaking at 133 and 111kN of vertical load for the 17 and 15mm cable cross members respectively.

RETROSPECTIVA CONSTRUCTIVA E HISTÓRICA DEL PANÓPTICO DE IBAGUÉ, COLOMBIA

La ciudad de Ibagué, antiguamente llamada “Villa de San Bonifacio de Ibagué del Valle de las Lanzas”, fue fundada en 1550 por el adelantado conquistador español Don Andrés López de Galarza, quien erige una población en medio de una boscosa región infestada de nativos Pijaos que la atacaron varias veces, razón por la cual pierde el oncepto colonial y solo hasta 1800 retoma el carácter de población. Fue declarada ciudad republicana por excelencia hacia 1850. A finales de esta década aparece el impresionante edificio Panóptico de Ibagué, reconocida construcción de planta en cruz griega, concebida en estilo neorrománico, de estructura muraria en cal y canto y complejas piezas de cerchas rey en su cubierta. Esta edificación creada por William Blackwel bajo la administración de Manuel Casabianca, estuvo destinada a albergar reclusos e internos desde 1892, uso que se extendió hasta 2003. Su intervención y restauración se inició en 2006 y hoy aún está sin finalizar. Por su carácter monumental y lenguaje propio es una de las edificaciones patrimoniales más importantes no solo de los ámbitos municipal y regional sino también en los niveles nacional y continental.

Numerical Modelling of Retrofitted Reinforced Concrete Building Frames

This study presents an overview and investigates the adequacy of the retrofit concept used in the reinforced concrete building frame of a distressed office building complex. The retrofit assessed consists of steel members welded together to form a steel frame with a reinforced concrete beam as base, acting as support for two floor slabs and roof truss of the building. Reinforced concrete building frame with and without retrofit steel frames were analysed using STAAD Pro structural analysis software and the results were compared with recommended standards from relevant codes of practice. Criteria considered include moments, shear forces and displacements/deflections. Results obtained revealed that the retrofit concept meets up with all the recommended standards. The efficiency of the retrofit used was determined in order to evaluate the extent by which the retrofit affects deflection of the beams. For all critical sections, the efficiency of the adopted retrofit concept varied significantly between 49.1-63.2%, 48.3-85.34% and 45.3-90.9%, respectively when deflection serviceability limit state, bending moment and shear force was considered respectively.

The potential of young, green finger-jointed Eucalyptus grandis lumber for roof truss manufacturing

South Africa is a timber-scarce country that will most probably experience a shortage of structural softwood lumber in the near future. In this study the concept of using young, green finger-jointed Eucalyptus grandis lumber was evaluated for possible application in roof truss structures while the timber is still in the green, unseasoned state. Drying will occur naturally while the lumber is fixed within the roof truss structure. The objectives of this study were (1) to investigate the strength and stiffness variation of the finger-jointed E. grandis product in both the green and dry state for different age and dimension lumber, (2) to investigate the variation in density, warp and checking in the lumber when dried in a simulated roof-space environment and (3) to evaluate the potential of this finger-jointed product as a component in roof truss structures. Green finger-jointed E. grandis lumber of ages 5, 11 and 18 years and dimensions 48×73 mm and 36×111 mm from Limpopo province were evaluated. The study showed that the young finger-jointed E. grandis timber had very good flexural, tensile parallel to grain, and shear properties in both the green and dry state. The mean and characteristic modulus of elasticity and modulus of rupture values of the finger-jointed E. grandis product were higher and the variation lower in comparison to currently used South African pine sources. The tensile perpendicular to grain and compression perpendicular to grain strength did not conform to SANS requirements for the lowest structural grade (S5). Both tree age and product dimension were sources for variation in the physical and strength properties. Based on the results from this study the concept of producing roof trusses from green, finger-jointed young E. grandis timber has potential.

関東大震災前後の横浜港における港湾施設の空間構成に関する研究

Port of Yokohama grew up to be a port city representing Japan from the end of Edo era to the middle of the Taisho era. There were many sheds and warehouses in the iron pier and Shinko-wharf. The sheds was used as sorting of cargo and getting on and off for passenger. The two warehouses was used as a long storage of cargo. They were an important element of the port landscape. Today, the preserved warehouses charms many tourists as a symbol of the port of Yokohama. The purpose of this paper is to clarify the space composition of the public shed and warehouse at iron pier and Shinko-wharf before and after the Great Kanto Earthquake. I considered the following three viewpoints 1. This study examines how to use the shed and warehouse. And general size of the shed and warehouse examined and compared to the building of the Port of Yokohama. 2. Analysis of space composition of the shed and warehouse was carried out in two parts. The first one is cargo space. Placement of the pillars and plane composition of partition was revealed in the shed. Relationship of transporting machine(crane, incline, elevator) was revealed in the warehouse. The second is passenger space. There are two types in this space. One is space of only passenger, and the other one is space of the passenger and the pick-up person. 3. This study has revealed what has changed how structure and plan composition of the shed and warehouse. The conclusion is as follows. 1. Oficial port facilities had only sheds before Great Kanto Earthquake in general. But oficial port facilities had not only sheds but also warehouses after Great Kanto Earthquake. And both of sheds and warehouses were placed as port facilities. The longest dimension (90ken) of ridge direction in the sheds and the length of a 10,000 ton ship is the almost same length. The span of the shed were smaller than a standard at the time. But the dimension(14ken) was affected the shed of the port of Kobe. The span of the warehouses were smaller than a standard at the time. I pointed out possibility that the longitudinal dimensions (81.5ken) of the warehouse was designed with reference to the longest dimensions of the shed. 2. Cargo space of the shed was a wide room to sort cargo. On the other hand, cargo space of warehouse was small rooms for disaster prevention. And the shed was an one-storied building. And warehouse was a three-storied building. I pointed out that cargo space in a warehouse increased in the verticalness direction. Passenger space and cargo space of the shed were different in form of the ceiling etc. After the Great Kanto Earthquake, passenger were able to move to the passenger space without walking the cargo space. And waiting room changed from indoor space to outdoor space. Passenger space was not only a space to wait but also a space to enjoy eating. 3. The structure of the shed was wooden and steel before Great Kanto Earthquake. Roof of all the sheds was roof truss. Pillars are arranged along the center of the wooden shed for earthquake. But there was not a pillar in the steel shed. And the structure of the shed was steel structure and RC structure , SRC structure after Great Kanto Earthquake. Roof of the shed was two types( roof truss, flat roof of RC structure). Pillars are arranged along the center of the sheds of flat roof. And there were not a pillar in the sheds of roof truss. These sheds were built with the same structure every quay.

Influence of Orientation of Building on Indoor Conditions in a Roof Truss

Protection of historical roof trusses is an important part of efforts to protect our cultural heritage. These timber structures carry a lot of information about used tools, technologies or construction processes. Roof trusses are generally threatened by many dangers, which could cause irreparable damage and loss of the carried information. Wood destroying insects and fungi are the gravest threat to historical roof trusses in our climatic conditions. Their spreading depends on several specific (interior) conditions. These include critical moisture content in the wood, relative humidity, amount of natural light and ventilation. In addition to these commonly monitored parameters (and their critical levels) we also must not forget the influence of local geography, biotope or orientation to the cardinal. This paper describes temporal fluctuations of some of the mentioned physical parameters in a historical roof truss with regard to external climatic conditions and orientation to the cardinal.

豪雪地域にたつ伝統木造民家の構造材にみる樹種選択

We investigated the species composition of structural timbers used in four traditional houses that were at least 100 years old in a rural village in the central Japanese snowbelt. Three or four species were used per house (five species in total). Beech, oak, and cedar, likely obtained from nearby forests, were used in all four houses. Beech, with a strong tolerance for bending forces, was used for beams and roof trusses, suggesting that there is a specific use of timbers according to woody species in heavy snowfall areas.

Research of Total Mechanical Energy of Steel Roof Truss during Structurally Nonlinear Oscillations

A mathematical model for the calculation of the discrete dissipative system total mechanical energy during free oscillations based on the method of time analysis was given. The features of this parameter behavior (jumps, asymptotes) for elastic structurally nonlinear systems were shown. A possible usage of the mathematical model is illustrated by the calculation of flat steel roof truss during oscillations caused by a sudden failure of one of the bearing elements due to corrosion effects.

Mold Growth Risk Analysis on the Surfaces of an Organic Building Structure Based on <i>In Situ</i> Monitoring

This article deals with the assessment of methodologies for water vapor condensation determination and mold growth risk analysis on the surfaces of an organic building structure based on in-situ monitoring, carried out on the structural elements of renovated roof truss above the greenhouse “Květná zahrada” in Kroměříž. The garden including the building is signed on the UNESCO Word Heritage List for its historical and architectonical value. The monitoring was focused on hygrothermal behavior of a particular attic area during winter term 2014 - 2015. The risks of water vapor condensation and mold growth were then analyzed on the basis of data obtained by the monitoring process. These also include measurement and output data accuracy is included as well. The Results were used as recommendation for a control system of forced ventilation in the monitored attic area.

ДИНАМИЧЕСКИЙ РАСЧЁТ ФЕРМЫ ПОКРЫТИЯ ПРИ СВОБОДНЫХ КОНСТРУКТИВНО НЕЛИНЕЙНЫХ КОЛЕБАНИЯХ

A mathematical model of construction of the total mechanical energy of a discrete statically loaded dissipative system in the process of free oscillations in the form the time analysis method, which is based on the study of the characteristic quadratic matrix equation, was given. The features of the behavior of the parameters of the dynamic response when the elastic structurally nonlinear system to a new state was shown. It is also given the expressions to determine the kinematic (displacements, velocities, accelerations) and force (restoring, dissipative and inertial forces) parameters of the dynamic response. The criteria for assessing the load bearing capacity of the structure at the non-linear operation was suggested. Using a mathematical model is illustrated by the example of the calculation of flat steel statically indeterminate roof truss during the process of free oscillations, which was caused by a sudden failure of one of the bearing elements. Turning off the rod caused by the loss of strength as a result of chemical cracking due to corrosion effect.

Strengthening Timber Roof Trusses During Building Construction and Reconstruction

The relevance of this article is explained by the increasingly extensive efforts associated with construction and reconstruction of buildings and structures having mainly architectural and cultural significance, as well as preserving their pristine ambience and integrity for use by future generations. Furthermore, reconstruction helps to serve a range of social demands, such as the provision of comfortable and safe living conditions for people. The review of research publications shows that wooden structures are the first to lose their load-bearing capacity during the long-term use of buildings and structures. Still, the scientific literature mostly features the traditional labor-intensive methods of timberwork strengthening that further increase its weight, or the methods of external reinforcing with composite tapes. This article, for the first time, discusses the technology of the strengthening timber framing with butterfly-shaped wooden inserts. Joints between existing rafters and wooden inserts are reinforced with two layers of the furniture duct tape and fine composite mesh pressed in between, with the plywood top finishing of the duct tape. The experimental studies that were in progress for two years showed that the technology suggested meeting all the reliability requirements applicable for timber trusses. As compared to traditional technologies, the suggested solution is less labor-intensive and more sparing in terms of the truss weight, as it only adds the weight of furniture duct tape, composite mesh and plywood at the joints. This is the applied research, and its outcome can be used not only for strengthening of roof timber, but also for reinforcing of wooden inter-floor joists.

Refined calculation of lateral bracing systems due to global geometrical imperfections

In Eurocode 3 the analysis of equivalent stabilizing forces due to global geometrical imperfections and in consequence the calculation of the lateral bracing systems of the roof girders is given. The forces are assumed to be uniform N(x)=const within the span of restrained member that has an initial bow imperfection e0. This simplifying assumption is not adequate for the actual non-uniform distribution of forces N(x)≠const and is considered in [6] as slightly conservative. Apart of it the model from Eurocode 3 ignores the geometrical imperfections of the main plane of the restrained truss roof girder, which affect the stress state of purlins and lateral bracing as well. The object of the work is presentation of refined models of calculation of forces due to global, geometrical imperfections of restrained roof rafters, purlins and lateral bracings. Those models incorporate the parabolic distribution of compressive forces in the restrained member N(x)≠const, and its parabolic bow imperfection e0 in the roof plane. Additionally, both the effect of the lack of verticality described by angle ϕ0 and the entire distortion of the main plane of the truss rafter (lack of flatness as an effect of the bow e0 of the compressed upper chord of the truss) are studied. The formulas for equivalent stabilizing forces assuming the parabolic distribution due to above mentioned global, geometrical imperfections, have been proposed. Obtained results have been discussed and illustrated by an example.

CALCULATION OF ROD FORCE OF THE TRUSS CONSTRUCTION

The calculation of the forces of truss construction can be determined by graphical method, known as Cremona method and analytical method, known as Ritter method. Calculations in both ways can take much time and is dependent on the number of connecting points and considerable loading simulations. This paper describes an alternative analytical calculation method, which combines the two methods, namely the connection balance method and the optimization calculation method. And the last method is available in Microsoft Excel Solver (MES). The connection balance method is the fulfillment of the balance equation of SFx = 0 and SFy = 0 at each joint of the truss. The way of the balance fulfillment in this paper is different from the way of Ritter. In the way of Ritter, the balance fulfillment is applied to each connection point, one by one point. The connection point can be calculated if at the point there are maximum two unknown rod force and minimum one known rod force. While by using the MES program, the balance of connecting point is simultaneously computed for the entire construction. MES program works by simulating/finding the value of variables, and at the same time fulfilling the defined objective function and constraint functions. In this case, the variables are all the rod forces, while the constraint functions are the balance equation at all connecting point. An objective function can be taken from one of the SFx = 0 or SFy = 0 from one connecting point only. This paper has recorded 10 different types of geometric shapes of certain truss construction (statically determined) which can be considered to represent the ones in the field (including the form of Howe, Pratt, and Warren for the roof truss and bridge truss). Then the mathematical models that were adjusted to the MES program were created for each of the ten truss constructions. Based on the created mathematical models, the forces of the rods were then calculated using the MES program. For validation purposes, the calculation results are compared with the calculations result using the analytical Ritter method. It can be concluded that the presented calculation method is highly satisfactory, especially for the analysis of statically determined truss construction.

DEFECTS AND FAILURES OF JOINTS OF HISTORIC ROOF TRUSSES AND POSSIBILITIES OF USING FRP MATERIALS IN THEIR REHABILITATION AND STABILIZATION

The survey of selected historic roof trusses performed within the NAKIDF12P01OVV037project revealed numerous failures and defects of joints of roof truss elements ofhistoric and listed buildings. Based on the results of the survey, the article outlines potentialrehabilitation and reinforcement techniques of joints of roof truss elements in which the mostfrequent defects and failures were found using composite fabrics based on high-strength carbonfibres and epoxy resin (CFRP).

Annex and rigid diaphragm effects on the failure analysis and earthquake damages of historic churches

Historical churches, in the most of cases, are characterised by the presence of annexes and rigid diaphragm that influence their seismic response. Therefore, this research aims to investigate the disadvantages and the benefits which emerge during the horizontal dynamic actions between these structures. This study presents some analyses carried out on the Gesù Church in Mirandola, which was damaged by the 2012 Northern Italy earthquake.The first fundamental steps have been the geometrical, material and in particular the seismic damage survey. An undamaged finite element model of the actual configuration of the Gesù church with a perfectly connected annex was created and was also considered the same model as an isolated structure. Through these FE models preliminary modal dynamic analyses were conducted in the linear elastic field. Subsequently non-linear static analyses were carried out to investigate the ultimate capacity of the building.The churches are characterised by large halls without internal thorn walls, slender walls, pushing elements and lack of intermediate horizontal connection. All these factors lead each macroelement to have an independent dynamics, showing the absence of box-like behaviour. Since the roof trusses are one of the few structural elements that can determine a better global behaviour, it has been decided to perform the same numerical analyses even in the FE models without the roof, then considering the extreme case of a not effective simply supported roof.

Strength and stiffness capacity utilisation of timber members in roof truss structures

The main objective of this study was to determine which property, of the six strength and stiffness properties used in structural timber design, was the most influential in the design of nail-plated roof trusses. Thirty recently completed nail-plated roof truss designs were randomly selected from three roof truss manufacturing plants and a total of 8 758 individual truss members were analysed for bending stress, shear stress parallel to grain, tensile stress parallel to grain, compression stress parallel to grain and deflection. The mean strength and stiffness capacity utilised of all the different design properties was well below 50% for all of the different dimension classes. Of all the individual strength properties, the mean bending strength capacity utilised per member was found to be the highest. The results of this study can be used for decision support related to wood property evaluation through‑ out the structural lumber value chain where roof truss members are the end products.

Tornado Risk Analysis for Residential Wood-Frame Roof Damage across the United States

AbstractApproximately 1,200 tornadoes impact the United States every year with a percentage of these resulting in significant damage, injuries, and fatalities. Initially, a probabilistic tornado hazard analysis was performed in order to develop tornado hazard curves at select locations across the United States. This analysis resulted in the annual probability of experiencing a tornado of any strength at the specific locations, which varied as a function of location-specific occurrence rates. Five different residential wood-frame building archetypes were designed at each of the locations based on current residential building code and/or practice. Fragilities for the roof sheathing and truss to wall top-plate connections were developed for each archetype. Because fragilities are independent of location, they were then convolved with the tornado hazard curves to compute annual failure probabilities for select roof components. This represents the first time absolute risk of roof failure due to tornadoes has b...

Raising the roof on design in Russia: Pulkovo airport

Pulkovo International airport near St Petersburg is nearing completion of a €1 billion redevelopment as a vital new gateway into Russia. Its new main terminal opened in December 2013 and by the end of 2015 the airport will have a capacity of 17 million passengers per year. It is also one of the first public–private partnership projects of its kind in Russia. Use of conventional construction techniques in innovative ways was a key factor in successful on-time completion of the new terminal building. Developing a flexible concrete frame allowed the contractor to work productively and continuously through the harsh Russian winters. In addition, early geometric studies developed a diagonal spanning roof truss system to realise the competition-winning architectural design. The Russian market has its own unique set of challenges and this paper outlines the techniques utilised to strike the right balance between local compliance and innovation to deliver a major international transport facility.

Dendrochronologická analýza krovu kostela Nanebevzetí Panny Marie a sv. Ondřeje ve Starém Hobzí

The work deals with dendrochronological analysis of the roof truss of parish church in the locality of Stare Hobzi. The dendrochronological analysis gave an integrated view on a complicated development of this building and it helped us to restore the succession of building adjustments performed on this building. The work is also to introduce the dendrochronology branch to people who participate on or direct perform building-historical research and to show them that it could be an essential helper in their work.

Stability and Load Bearing Capacity of a Bars with Built up Cross Section and Elastic Supports / Badania Stateczności I Nosności Prętów Złożonych Z Podporami Sprężystymi

Abstract The present paper is devoted to the numerical analysis and experimental tests of compressed bars with built-up cross section which are commonly used as a top chord of the roof trusses. The significant impact on carrying capacity for that kind of elements in case of out-of-plane buckling is appropriate choice of battens which are used to provide interaction between separate members. Linear buckling analysis results and nonlinear static analysis results, with material and geometrical nonlinearity, are presented for the bar with built-up cross section which was used as the top chord of the truss made in reality. Diagonals and verticals which are supports for the top chord between marginal joints were replaced by the elastic supports. The threshold stiffness (minimum stiffness) for the intermediate elastic supports which ensures maximum buckling load was appointed for the beam and shell model of the structure. The magnitude of limit load depended on length of the battens was calculated for models with initial geometric imperfections. The experimental tests results for the axially compressed bars with builtup cross section and elastic support are presented.