Roof Truss Research Articles

Fatigue damage of the heel joint of welded roof truss

The investigation of the welded roof truss behavior under the complex influence of static and cyclic loads is carried out. The truss is made of the shaped pipes and its size is 24000x2400 mm. The technique of computer simulation experiment by means of SolidWorks Simulation software is used. It is found that the maximum stresses are formed in the area of thermal impact from the weld in the truss heel joints. During the truss operation, these stresses initiate the emergence of fatigue cracks and their growth until the structure ultimate state. The fatigue curve for the investigated structure is constructed. It is determined that the design service life of the truss under operational load modes is going to be 52 years.

On the investigation of providing space truss roofs with ductility until failure under monotonically increasing vertical loads

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 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.

Construction defects and wind fragility assessment for metal roof failure: A Bayesian approach

Post-damage observations reveal that construction error is one of the major contributors to roof damage for houses subjected to extreme winds. In this study, a Bayesian approach was developed to probabilistically quantify the construction defect rates in roof connections, which enables a systematic integration of expert judgement, human reliability analysis (HRA) techniques and limited construction defect data. The reductions of uplift capacities for defective roof connections were also probabilistically modelled based on experimental evidence and engineering judgement. The developed construction defect model was incorporated in a reliability-based fragility method to assess the wind damage to metal roof cladding and timber roof trusses for contemporary houses in non-cyclonic regions of Australia. It was found that, the effects of construction defects are significant for the predicted roof cladding fragility, whereas for roof truss fragility, such effects are lower.

Technical Aspects of Renovation of the 16th-Century Roof Truss

The main causes of damage to wooden structures in historic buildings are the effects of weather conditions and related aging processes. In the case of the roof truss of a 16th-century church in Lubów, the technical condition is additionally affected by leaking roof covering, damaged gutters, downpipes and flashings. Some elements of the wooden structure underwent biological corrosion, which lost its strength values. The roof truss of a 16th-century church in Lubów comes from the period of construction of the building. Due to the historic values of the structure of the truss, the renovation works do not intervene when the works would change its form, shape and type. The truss renovation is based on the assumption of maintaining original construction solutions, location of elements and cross-sections.

A considered response to structural movement and damage to the interior of St Stephen’s Church, Westbourne Park, London W2

St Stephen’s Church, Westbourne Park, London had suffered extensive structural movement and cracking to the interior over a long period. The source of the problem was not sufficiently understood or adequately addressed by previous repairs in 1990. Careful observation, investigation and analysis concluded that the primary source of the problem was lateral spread of the roof trusses. This action, combined with the very thin mortar joints in the internal stonework, had led to spalling of the stone and horizontal cracks in the clerestory walls of the nave. Repairs were specified to address these issues, approval sought through the process of ecclesiastical exemption, and robust remedial and preventative works carried out. This paper seeks to explain the thinking behind the process of analysis, design and specification of these works, and (while acknowledging previous works) examines the problems starting from first principles. It is intended to give the reader guidance on the assessment of unusual or long-standing structural problems and the confidence, when necessary, to propose and execute what might otherwise be considered radical interventions in a historic public building.

Sensitivity Study of Dynamics Variability for Mild-carbon Steel Structures Affected by Corrosion

Background:Corrosion propagation mainly occurs due to environmental conditions and to the absence of adequate maintenance. The corrosion propagation affects the structural performances of slender and thin structures, in particular in the case of structure very sensitive to the wind action and its dynamical phenomena, because commonly they are designed with a precise optimization of the stiffness/mass ratio. The static and dynamic wind action represent an immediate safety hazard in the case of structural stiffness and mass reduction due to the corrosion depth.Objective:This paper discusses the dynamics behavior variability due to the corrosion depth propagation for two significant examples of slender and thin structure (i.e.tower and truss roof).Methods:The structures assumed as case of study are made of mild carbon. The corrosion depth variability was estimated based on literature references. The structural natural frequencies and modal shapes are assumed as significant magnitudes to discuss the effect of the corrosion on the structural elements.Results:Results have shown that the corrosion depth gives a significant reduction of frequencies and modification of modal shapes.Conclusion:Results have shown that the corrosion depth affect the structural behavior long before a structural collapse. It suggests that a monitoring must be done to estimate the structure reliability for the Serviceability limit state under Characteristic design loads.

Stability of steel struts with externally anchored prestressed cables

Externally anchored prestressed cables can be employed to enhance the stability of steel truss compression elements significantly. To demonstrate this concept, a system comprising a tubular strut subjected to an external compressive load and a prestressed cable anchored independently of the strut is studied. Energy methods are utilized to define the elastic stability of the perfect and imperfect systems, after which the first yield and rigid–plastic responses are explored. The influence of the key controlling parameters, including the length of the strut, the axial stiffness of the cable and the initial prestressing force, on the elastic stability, the inelastic response and the ultimate strength of the system is demonstrated using analytical and finite element (FE) models. To illustrate the application of the studied structural concept, FE modelling is employed to simulate the structural response of a prestressed hangar roof truss. A nearly two-fold enhancement in the load-carrying capacity of the truss structure is shown to be achieved owing to the addition of the prestressed cable.

Behaviour of H-section purlin connections in resisting progressive collapse of roofs

When a truss roof is subjected to sudden local damage, purlins are capable of bridging the damaged truss unit, thereby increasing the robustness of the integrated roof system. To investigate the bridging capacity purlins can provide, experiments were carried out on bolted fin plate connections that join thin-walled H-section purlins to the main truss, investigating their behaviour under a main truss-removal scenario. Eight specimens with varied connection details were tested. Results of all experiments are provided in detail, including the full-range vertical resistance versus displacement curves, the collapse-resisting mechanisms, and the failure modes, being either bolt shear failure or combined bolt bearing and net-section tensile failure. Experimental results showed that better bridging capacity can be achieved by adopting relatively larger diameter bolts, reducing the bolt group height, applying higher preloading force when installing bolts, and increasing the end distance for the bolt holes. Meanwhile, a theoretical model is proposed to predict the vertical resistance versus displacement response of the purlin-to-connection assembly. This model is capable of capturing the slip of bolts, and the gradual yielding and failure of the connection components, and thus gives predictions that are in reasonably good agreement with the experimental results.

Flexural Strength Test For Concrete Beam With Mild Steel and Reinforcing Iron

Mild steel in buildings tends to only be used as a roof frame. The phenomenon in the field that lightweight steel roof truss can be combined with mortar mixture. In general this union is found on the walls of the construction of the red stone horses. This phenomenon is captured and applied dynamically, creatively, and innovatively with new idioms. Mild steel can be used as a beam reinforcement. This research is important in order to find alternative reinforcement of beams other than iron and strong beam reinforcement. This study aims to determine the ratio of flexural strength between concrete from mild steel reinforcement and concrete from steel reinforcement. This study uses a concrete flexural strength test and simple test beam method. The test beam is loaded and centered directly. Press testing machine is used as a flexural test device. The machine is equipped with two support beams and one load beam, load construction, and support blocks. Six beams are used as specimens. Test objects are made of different reinforcement. Concrete beams are made from a cross section of 600 mm x 150 mm x 150 mm, used reinforcing iron diameter of 6 mm, and amounting to three (first test object). Concrete beams are made from a cross section of 600 mm x 150 mm x 150 mm, mild steel is used with the profile shape C73.35.10 mm, and there are three pieces (second test object). This study concluded that the test beam was made from a cross section of 600 mm x 150 mm x 150 mm. and mild steel (profile C73.35.10 mm) has twice the maximum flexural strength compared to 600 mm x 150 mm x 150 mm cross section beam and reinforcing iron (6 mm diameter).

Experimental study of an unsymmetrical prefabricated hybrid steel-bamboo roof truss

A 12 m hybrid unsymmetrical steel-glued laminated bamboo (glubam) truss used in a roof construction was designed with building information model (BIM) platform software. The hybrid truss composed of glued laminated bamboo (glubam) as top chords and web members, and steel pipes used as bottom chords. Based on such design outcomes, the manufacture, transportation, prefabrication and installation details, with corresponding advantages, are reported. Experiments of glubam chords and connections were performed. The behaviors of glubam chords along with its load-displacement/strain curves, are given in this research. Experimental results on full-scale truss indicate that it can fulfill the mechanical requirements with respect to deflection limitations and loading bearing capacity. The performance of the truss with end-connection change and under unsymmetrical loading conditions was also experimentally studied and discussed in this research. The prefabricated hybrid truss obtained a relatively right balance between structural requirements and economic benefits, thanks to easy manufacture, transportation, prefabrication, and installation.

Structural perfomance of cold-formed wall frame under combined gravity and lateral loading

Light steel framing is generally based on the use of standard C or Z shaped steel sections produced by cold rolling from strip steel, which is normally refers to cold formed steel sections. Light steel framing is already well established in residential construction in North America, Australia and Japan. Cold formed steel sections are widely used in many sectors of construction, including mezzanine floors, industrial buildings, commercial buildings and hotels and are gaining greater acceptance in the residential sector. In Malaysia, cold formed steel sections are frequently use in roofing systems such as roof trusses and purlins. The light steel framing system has yet to be practiced in Malaysia. There is a need to investigate the economic aspects of the light steel framing system in our local industry, conduct comprehensive testing and parametric studies to create the guidance and procedures of the analysis and design of such building. This paper presents a lightweight system for wall panels made of cold-formed steel sections. Three wall panel samples are tested experimentally under combined gravity and lateral loading to investigate the performance of the panel in terms of strength, stiffness and ductility. The results from the experiments show the wall panel using back-to-back and box arrangement able to increase the lateral stiffness and strength as compared to single section wall panel. The increment of strength can goes up to 39% under combined gravity and lateral loading while for lateral stiffness the increment can goes up to 83%. The performance of the panel can be applied to the light steel structure that can materialize the new residential building mode of low cost, high efficiency and large scale. The significance of this study is to reduce the use of labour by introducing pre­fabricated panel section, which is environmentally friendly and reduce congestion on site, and able to reduce overall construction cost by using precast construction with higher strength and stiffness capacity.

Investigation of buckled truss bars of a space truss roof system

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.

Analisa Produktivitas Tenaga Kerja Pada Pekerjaaan Rangka Atap

Productivity is an important factor in determining the success of a construction work. Increased productivity will reduce work time, and that means it will reduce costs. In general, the value of productivity is determined by the factor of the volume of work, implementation time, and the number of workers. In order to get the job done well, a planning effort is needed by paying attention to these factors. For this reason, this study was conducted to determine the value of productivity in one component of building construction work, namely lightweight steel roof truss work. The object of study was the work of lightweight steel roof truss 4 (four) project sites, namely the 4 x 25 Shop Houses Construction Project in Meulaboh, West Aceh, the Building of the Rector & Administration Bureau Building of STKIP Bina Bangsa Getsempena Banda Aceh, the Construction of the Getsempena Lhoksukon North Aceh STIKES Building and the Construction of North Aceh RIKI STIKes Building, Bina Nusantara Idi, East Aceh. The roof truss material used is type C Truss 75 0.75 Thickness. The volume of roof truss work is planned to be 2022.38 m2. The study was conducted through field observations by directly recording the volume of work, the duration of each stage of work, and the number of workers involved. The results of the analysis show that the productivity value for roof truss works is obtained by an average of 2,062 m2 / hour or 16,499 m2 / day. In the implementation of roof truss work, the amount of labor used is the same in all segments, so the value of productivity tends to be determined by the magnitude of the ratio between the volume of work and the effective time of implementation. Thus, if the amount of work volume can be completed in a shorter time then the value of productivity will increase

RELIABILITY ASSESSMENT OF WOODEN TRUSSES OF A HISTORICAL SCHOOL

Records show that the National Structural Code of the Philippines (NSCP) wind load requirement increases over time. Increase wind velocity from stronger typhoon events translates to additional wind pressure. These changes pose a threat to existing historical structures such as Gabaldon schools which were designed and constructed more than a hundred years ago. The Department of Education (DepEd) continues its efforts in its conservation. Reliability assessment of wooden trusses is necessary to check if there is a need to retrofit to maintain its function and preserve its significance in the country’s history. In the analysis of the roof trusses affected directly by wind load, all loads are considered as constant except for the uniformly distributed wind load. These constant loads serve as the initial stresses acting within the truss members. Uniformly distributed wind load produces additional stress on top of the initial stress. Any changes in the amount of wind load constitute proportionally to changes in the stresses of truss members. A commercially available software makes it easier to identify corresponding stresses for several amounts of wind load. Using a spreadsheet, a simple graphical model and equation are generated expressing the relationship between wind velocities against axial force, shear force and bending moment. Mechanical properties of wood establish the limits of its strength in terms of wind velocity using the graphical model and equation obtained. The result reveals the limitation of each truss member in terms of wind velocity that even ordinary people can now easily perceived and understood.

Experimental Study Of Installation Of Non Centric Light Steel C Profile On Light Steel Beam Frame

Light steel is one of materials that support the growth of construction technology at this time and it is generally used on roof truss contruction. The profile of light steel is a kind of steel profile which has dimension of thickness that is relatively thin with ratio of wide dimension of each profile element towards its huge thickness. In the assembling and installation, roof truss of light steel which is often encountered, cross section of C profile is connected by attaching body parts of two profiles or connecting wing parts with giving the connecting canal. This research uses the experimental method by flexural test with two points loading. The light steel which is used in this reserach is light steel of C profile by Ton Dong brand. The size is 75 x 35 x 0,75 mm andthe dimensions of beam frame specimenis 180 cm lengthand 25 cm hight, as many as 3 specimens with non centric profile overview. The research result shows that the average value of flexural strength is5,25 kNand the average of tensile strenght is 2281,67 N, while the result of experimental test uses UTM ( Universal Testing Machine ) , the maximum strength is 5,92 kN and deflection 38,95 mm. The result of SAP 2000 analysis, the maximum deflection is 2,04 mm and 6 kN load. Â Keywords : Light steel of C profile, Light steel beam frame, Test of flexural stength.

Penalaran Berbasis Kasus Untuk Menentukan Pajak Bumi Dan Bangunan

Calculating land and building taxes requires a measure of land area and estimated costs when building a house. As such, tools are needed that can predict building material requirements appropriately and quickly. The CBR approach can be used to solve these problems, where the method is able to reason to solve problems based on existing cases as a solution to new problems. The system built in this study is a CBR system to determine the building material needs of a house. The consultation process is carried out by entering a new problem compared to the old case then the similarity value is calculated using the nearest neighbor. calculation with data on land area of 100 meter2, building area of 38 meter2, quality of type 2 building, 2 bedrooms, 1 bathroom, lightweight steel roof truss and cast tile, then the accuracy value is 0.985 of type 38 from base case so that there is an earth tax and buildings amounting to Rp. 100,389.4. The test results of 111 data test cases, obtained 9 cases that have similarity values below 0.8

Combination of non-destructive tests for assessing decay in existing timber elements

ABSTRACTExisting timber structures often present elements with different levels of decay and the choice to maintain them comes from the structural assessment, made by a civil engineer on the basis of the results coming from the on-site survey. The choice may also rely on visual inspection combined non-destructive tests. In that case, the choice to maintain an element will greatly depend on the accuracy and reliability of the results obtained through these tests. This work aims to assess the properties of timber elements through non-destructive tests, using resistance drilling, pin penetration, ultrasound, and acoustic emission tests. The tests were carried out on three timber elements from two old timber roof trusses. The results are analysed regarding the specimen size and the use of multiple non-destructive test parameters. Decay was initially identified by means of visual inspection and different levels of decay were identified taking into account their influence on the non-destructive test results and on the predictability of models based on single and multiple regression analysis. Moreover, the obtained classification was found to increase the reliability on the prediction of density.

Distortional buckling of a CFS channel section with and without stiffened flanges

Cold-formed steel (CFS) sections are commonly applied to modern engineering structures, such as roof truss, purlin and industrial goods rack. This study proposes an analytical model to investigate the distortional buckling behavior of CFS-lipped channel sections considering two load scenarios (i.e., axial compression and pure bending). The formulae and analytical solution for calculating the distortional buckling critical stress of CFS channel sections are derived on the basis of the total potential energy principle. The proposed model is extended to the channel section columns and beams with a stiffened flange. CUFSM and generalized beam theory (GBT) are used to conduct numerous channel section columns and beams to validate the proposed method. Results obtained from the proposed model are compared with those calculated using GBT and/or finite-strip code CUFSM. These numerical results are consistent with the model calculations for channel section with and without stiffeners.

Technical Feasibility Study of the Use of Softwoods in Lattice Structure “Howe” Type for Roofing (Gaps between 8-18 Meters)

Introduction: Wood is a material of biological origin widely used in construction, and its mechanical properties allow the material to form the lattice structure of roofs used in warehouses of industrial use, however, the paradigm as to the behaviour of the material makes the design decision less susceptible.
 Aims: This work intends to verify the feasibility and optimize the use of unconventional wood in triangular roof truss structures in regions of flat topography, with a characteristic wind speed of 30 m/s.
 Methods: The design methodology was fully based on the recommendations of ABNT NBR 7190
 For the elements dimensioning, it was necessary to define the geometric and structural parameters that directly influence the actions and loads, as well as the behaviour of the structural elements.
 Results: The choice of wood in this context, it was proposed the elaboration of projects of roofing structures with the following characteristics: "Howe" latticework (inclination of 10º - steel roof tile); Spans of 8, 10, 12, 14, 16 and 18 meters (ratio width: length, in plan, environment of 1: 3); Typology of the lateral openings of the building - (relationships between main opening area: other openings) 1:1, 2:1, 6:1 and insulated coverings (coverage on a medium of reduced dimensions).
 Conclusion: The ratio of the volume of wood per floor area (m³.m-²) for C20 and C30 grade timber was determined, as well as the consumption of metallic pins per floor area, following the requirements of Brazilian standards, proving the technical feasibility.

Behaviour of plasterboard-lined steel-framed ceiling diaphragms

Behaviour of low rise cold-formed steel-framed residential structures when subject to lateral loading (e.g. wind and earthquake loads) is significantly influenced by both structural and non-structural elements. The ceiling is normally considered as a horizontal diaphragm for the distribution of such lateral loads to the bracing walls. In Australia, the ceiling diaphragm, in single and two storey cold-formed steel-framed houses, is made of plasterboard lining fixed to ceiling battens which in turn are screwed to the roof trusses. Determination of the stiffness and strength of the ceiling diaphragm is crucial for accurate distribution of the lateral load to the lateral resisting elements (e.g. bracing walls). This paper presents experimental results from tests of typical ceiling diaphragms. Further, a detailed finite element model is described which was validated against the experimental results. The model is capable of reproducing the initial stiffness, non-linear deformation and ultimate strength. The finding from this work would assist engineers in designing the lateral load resisting system for houses.