Pratt Truss Research Articles

Enhanced structural health monitoring of ageing Pratt truss bridges: a combined approach of static and dynamic measurements

Enhanced structural health monitoring of ageing Pratt truss bridges: a combined approach of static and dynamic measurements

Research on Topology Optimization Design of Truss Structure

Due to continuous advances in engineering technology and architecture, the use of truss structures is expanding. The design method of ideal truss structure is the main research topic of this paper. The topology optimization method is applied to a bridge design case study. The load and total material utilization ratio of each rod of triangular truss, arch truss and Pratt truss were determined by using structural mechanics solver. By comparing the stress and material consumption of the truss structure, it shows that the truss structure has advantages in stress and can be used in the truss construction of short-distance arch bridge. Truss is the basic unit of the topology optimization method of truss structure proposed in this study. By optimizing the topological shape of the truss, the ideal design of the whole structure is realized. While maintaining structural stiffness and stability, the technology can significantly reduce the weight and cost of the structure.

Research on Economic Optimization Scheme of Pratt Truss Bridge

Economy is an important factor in bridge construction. The economic optimization of truss bridge is of great significance to improving the economic benefit of bridge construction. However, the safety and stability in bridge construction are often valued in traditional truss Bridges, and its economy is often ignored. The purpose of this paper is to study the economic optimization of Pratt truss bridge with 120 m span, 8m and node length of 6m, 10m and 12m respectively. The study of establishing two-dimensional model using structural mechanics solver shows that when the total length of the Pratt truss node is 12m, the total volume of the truss is the smallest, that is, the least materials are used, and the linear relationship between the bridge span and the node length is established to a certain extent. The results of this study provide an effective reference for the economic optimization of similar truss bridge structures.

Design of Automated Bascule Bridge and Collision Avoidance with Water Traffic

Abstract The development of movable bridges is a modern technological advancement that requires the integration of multi-disciplinary concepts such as control, automation, and design. In order to demonstrate how a collision avoidance system works, this research offers the design of an automated double-leaf bascule bridge with a pulley-rope moving mechanism and Pratt truss. The bridge is created where a settled railway or roadway intersection of a navigable stream cannot attain a steep profile. The design took into account the length, height, and width of the bridge as well as automatic ship identification and scaffold leaf movement activity for ship crossing. For the safe passage of cars on the bridge and for stopping vehicles during bridge movement, the system includes a collision avoidance control system and an automated road barrier system. After sensor adjustment, the model bridge’s performance under test produced results that were adequate, with a success rate of 100%.

A Case Study on the Static Behavior of a Pedestrian Bridge Built with a Steel Pratt Truss Deck Bridge Supported by an Inclined Roller Support

Construction of bridges commonly uses trusses due to their lightweight design, which can endure heavy loads and span large distances. However, there are instances when the supports of these trusses do not lie normally on a horizontal surface. For some, the supports lie on inclined foundations, which is the focus of this study. The main objective of this study is to present the basic theory of plane truss analysis with an inclined roller support using the Direct Stiffness Method (DSM) in comparison to the use of the Graphic Rapid Analysis Software Program (GRASP) to analyze the static behavior of the structure. Furthermore, a case study is conducted to check the effects of inclined supports on a plane truss structure. Based on the results, it was discovered that the introduction of inclined roller supports does have a negative effect on the stability of the structure.

Finite element optimization of Pratt trusses using trial and error

Steel production is considered one of the most material and energy-consuming industries, and using less energy is considered vital to promote environmental sustainability. Steel is used as the main building material in the construction of factories, hangars, and workshops in the form of trusses. A truss system is a set of structural elements connected at pin joints, with different types, shapes, and weights. Optimizing truss systems for max strength and minimum weight is a sustainable approach to reducing steel production and promoting environmental sustainability. In this paper 27 Pratt trusses were optimized by trial and error using finite element analysis (FEM) to predict the optimum topology for various cross-sections. Correlations between the span length, cross-sectional area, and height of the trusses were developed to conclude the ideal topology of the Pratt truss that gives minimum compression and tension stresses. The effect of topology on the reaction forces was also addressed. Results showed that the optimum horizontal span length between joints ranged between 3.4 and 3.6 m for minimal compressive stresses and minimum horizontal and vertical reaction forces at supports, and from 3.0 to 3.6 m for minimal tensile stresses.

Design and Comparative Analysis of Pratt Roof Trusses Using Angular and Tubular Steel Sections through Limit State Method

A Pratt truss is a type of truss structure which is used in civil engineering to support heavy loads. It is comprised by the diagonal members and vertical members, which transmits the loads efficiently through a combination of tension and compression which is easy to construction and suitable for both short and medium span. But this project work is made to decide to structural performance employing angular and tubular steel sections by using Limit State Method by considering the economy and strength having 30 m span and rise height 5 m, with the help of software we analyse the truss by using angular and tubular sections. The analysis is carried out through STAAD Pro software and two steel sections were made to find their weight of steel, deflection which decides which structure is more economical to use. The outcomes of this project is that consists of comparative study on Pratt roof truss using angular and tubular steel sections by Limit State Method with help of STAAD Pro software to determine the optimistic, adequate and economic structure, then the loads are applied according to the Is 875 code, assigning steel sections such as channel, I-sections, etc. By the study of project we got the tubular section is economical to use as compared to angular section. Keywords: Structural Analysis, Roof Truss, STAAD PRO, Pratt truss, Limit State Method (IS 800:2007, IS 875-1975 (Part I, II & III)

On Structural Design of Steel Roof Truss Geometry Used in Factory Shed

Use of steel is steadily increasing all over the world in civil engineering related fields due to its superior material properties like high strength and durability, high ductility, light weight etc. Various types of steel structures become more popular because of their high aesthetic appearance. Among these steel structures, roof trusses are widely used to cover large column free open areas like shopping malls, auditoriums, car parking lots, stadiums as well as factory sheds etc. Design of steel truss members is an important aspect to the practicing civil engineers. Hence this paper aims to study the design and analysis of different types of truss geometries used in a factory shed using commercial well-established software package STAAD Pro V8i. Various types of truss geometries like Pratt truss, Howe truss, Fink truss are considered in the present investigations with different aspect ratios. Besides these truss geometries, portal frame geometry is also taken up here to examine the best suitable geometries which are to be used as roofing units in industrial purposes. The results obtained from the present numerical experimentations are studied meticulously to extract a set of meaningful conclusions regarding the design and optimum choice of steel truss geometry which is used as roofing units in industrial sheds. The practical design guidelines along with the best choice of roof trusses are highlighted in the results and discussions section of this paper.

Perencanaan Struktur Cantilever Bentang Panjang Menggunakan Rangka Pratt Truss

In designing a truss cantilever structure with a predetermined long span, it will certainly look for a model of long-span structure with a profile that is able to withstand the given load. This can be done by planning a model of the pratt truss long-span structure. The main purpose of this final task is to produce a design of a long-span cantilever structure that is part of a unique building using a pratt truss model. The long-span pratt truss cantilever structure is analyzed using the MDSolids v.4.1.0 program to compute the inner forces working on each component of the designed frame structure, while the STAAD Pro Connect v.22 program analyzes the deformation of the design cantilever structure profile. The planning of this long-span cantilever structure is designed with reference to SNI 1727:2020 on minimum design load and related criteria for buildings and other structures, and SNI 1729:2020 on specifications for structural steel buildings. The result of the planning obtained is the dimensions of the beam bar profile needed. Pratt truss long-span structure is able for used as a cantilever long-span structure. This is seen from the results of calculations using computer programs where the pratt truss model has a deformation/deflection structure that occurs not exceeding the specified limit, and the results of the profile design used safely in receiving loads, although the results of calculation analysis there are the most critical rod elements in withstanding the load of the axial force of the press, namely the t1 and b2 rods. While the most critical rods in withstanding the load of axial force pull are the rods d1 and a1.English translation.

Analytical and Numerical Reliability Analysis of Certain Pratt Steel Truss

The main aim of this paper was to propose a new reliability index for steel structure assessment and to check it using the example of a popular Pratt truss girder. Structural analysis was completed in the finite element method system Autodesk ROBOT, and probabilistic analysis was implemented in the computer algebra software MAPLE. The stochastic finite element method (SFEM) was contrasted here with the Monte Carlo simulation and the girder span was selected as the input structural uncertainty source. Both methods were based on the same structural polynomial response functions determined for extreme deformation, for extreme stresses and also for the structural joint exhibiting the largest effort. These polynomials were statistically optimized during the additional least squares method experiments. The first four basic probabilistic characteristics of the structural responses, the first-order reliability method (FORM) index, and as the new proposition for this index were computed and presented. This new index formula follows the relative probabilistic entropy model proposed by Bhattacharyya. The computer analysis results presented here show a very strong coincidence of both probabilistic numerical techniques and confirms the applicability of the new reliability index for the input coefficient of variation not larger than 0.15. These studies should be continued for other engineering systems’ reliability and, particularly, for large-scale and multiscale computer simulations. The results presented in this paper may serve in different applied sciences, from biology through to econometrics, experimental physics and, of course, various branches of engineering.

Decision Framework to Balance Environmental, Technical, Logistical, and Economic Criteria When Designing Structures With Reused Components

The reuse of structural components in new buildings has great potential to reduce the environmental impacts of the construction sector but remains uncommon practice. An obstacle to its wider implementation is the lack of robust assessment methods and decision-making tools that consider the full spectrum of benefits and drawbacks. This paper proposes a multi-criteria decision framework that builds on a simulated set of design alternatives with varying ratios of reused and new structural components. A set of performance criteria is presented, addressing procurement risks, construction technique complexity, environmental impacts, and project costs. As the independent criterion evaluations often deliver conflicting results, a multi-criteria decision analysis helps identify the most appropriate solution. The design of a steel Pratt truss is used as a case study to demonstrate the applicability of the framework. Different alternatives with reuse rates above 65% are recommended for each preference scenario, reducing between 35 and 45% of adverse environmental impacts in comparison to an equivalent design made of new elements only. The study underpins the principle that there is no trivial and unique best option when designing with reused components. Multi-criteria decision analyses applied to structures with varying reuse rates constitute a promising tool to support decision-makers.

Fatigue assessment of steel riveted railway bridges: Full-scale tests and analytical approach

This paper describes a double experimental and analytical study of the fatigue behaviour of the Quisi and Ferrandet Bridges, twin 170 m long steel railway bridges constructed between 1913 and 1915 with typical Pratt truss structures and riveted connections. These bridges are part of the Spanish national railway network connecting the towns of Alicante and Denia, one of the key networks in the Valencia Region (Spain). The experimental laboratory investigation involved fatigue testing in one of the ICITECH laboratories at the Universitat Politècnica de València of: (i) a full-scale bridge span and (ii) an upper cross beam from the Ferrandet Bridge. During the tests, Linear Variable Displacement Transducers (LVDTs) and Strain Gauge (SG) sensors were used to capture the possible nucleation and propagation of fatigue cracks. Fatigue test carried out on the cross beam identified: (i) fatigue life of the critical detail, (ii) fatigue hot-spots along the cross beam and (iii) strain redistribution along the riveted element during crack growth. The experimental results from the full-scale bridge were adopted to calibrate an elastic numerical model of the whole structure, which was in turn used to estimate the Quisi Bridge's remaining fatigue life. The definition of the class of detail and remaining fatigue life were calculated by the S–N curves method, according to Eurocode 3, considering the available information on the bridges' loading histories.

Comparative Study of Pratt Truss, Vierendeel Structure, and Plate Girder for Overhead Crane Girder

This paper presents a study to get optimum type of crane girder. Three types of structures were studied: Pratt truss, Vierendeel frame and plate girder. Length of crane girder is 30 m and designed to carry 60 kN. Only (I) and angle steel sections were used to build crane girder. A nonlinear model was adopted to simulate the girder using finite element method. Weight of girder and maximum deflection were the main parameters used to compare. The results of the study identified that Vierendeel frame is the suitable type compared to the others to be designed and installed for this crane.

Quantification of aerodynamic forces for truss bridge-girders based on wind tunnel test and kriging surrogate model

This study presents an investigation to quantify the aerodynamics of truss bridge-girders via wind tunnel test and kriging surrogate model. Currently, the conventional methods documented in design specifications only take into consideration the mean drag force at null attack angle. To gain an in-depth understanding on the aerodynamics of truss bridge-girders, experiments on simplified bridge-girder models with various geometric parameters were carried out in uniform flow. A total of 15 truss bridge-girder models with aspect ratio (the ratio of width to height) B/D = 1.0, 1.3, 1.6, 1.9, and 2.2, solidity ratio (the ratio of projected to envelope areas) Φ = 0.20, 0.25, 0.30, 0.35, and 0.40, and two typical truss topologies (Warren and Pratt trusses) were examined in the most concerned range of wind angle of attack α = [–6°, 6°]. These truss bridge-girder models cover most of the high-speed railway bridges widely used in China. Experimental results show that the truss topology has limited effects on the aerodynamics of truss bridge-girders, whereas the effects of α, B/D, and Φ are significant. Based on these wind tunnel results, the ordinary kriging surrogate model was utilized to approximate the aerodynamics of truss bridge-girders. In using this model, aerodynamic force values for test cases can be interpolated with zero variance and uncertainties in unsampled design zones where geometric parameters can be quantified with Gaussian variance.

Shear Behavior of Concrete Encased Steel Truss Composite Girders

In this study, experimental tests were performed to evaluate the shear performance of encased steel truss (EST) composite girders that can resist loads at construction and composite stages. Four full-scale EST composite girders were fabricated, where the truss type (Pratt truss and Warren truss) and presence of stirrups were set as main test variables. The test results showed that in specimens applied with the Pratt truss, horizontal shear cracking occurring along the interface between concrete and steel was the dominant failure mode. Based on the crack pattern and failure plane observed from the test, the horizontal shear strengths of the Pratt truss specimens were calculated, which provided conservative results. On the other hand, in the specimens with the Warren truss inside, the strengths of the specimens were governed by the shear failure occurring in the screw rod connecting the truss elements prior to the yielding of the diagonal member. The shear strengths of the Warren truss specimens calculated based on the shear failure of the screw rod were similar to that obtained from the test.

Determination of structural and damage detection system influencing parameters on the value of information

A method to determine the influencing parameters of a structural and damage detection system is proposed based on the value of information analysis. The value of information analysis utilizes the Bayesian pre-posterior decision theory to quantify the value of damage detection system for the structural integrity management during service life. First, the influencing parameters of the structural system, such as deterioration type and rate are introduced for the performance of the prior probabilistic system model. Then the influencing parameters on the damage detection system performance, including number of sensors, sensor locations, measurement noise, and the Type-I error are investigated. The pre-posterior probabilistic model is computed utilizing the Bayes’ theorem to update the prior system model with the damage indication information. Finally, the value of damage detection system is quantified as the difference between the maximum utility obtained in pre-posterior and prior analysis based on the decision tree analysis, comprising structural probabilistic models, consequences, as well as benefit and costs analysis associated with and without monitoring. With the developed approach, a case study on a statically determinate Pratt truss bridge girder is carried out to validate the method. The analysis shows that the deterioration rate is the most sensitive parameter on the effect of relative value of information over the whole service life. Furthermore, it shows that more sensors do not necessarily lead to a higher relative value of information; only specific sensor locations near the highest utilized components lead to a high relative value of information; measurement noise and the Type-I error should be controlled and be as small as possible. An optimal sensor employment with highest relative value of information is found. Moreover, it is found that the proposed method can be a powerful tool to develop optimal service life maintenance strategies—before implementation—for similar bridges and to optimize the damage detection system settings and sensor configuration for minimum expected costs and risks.

A swift technique for damage detection of determinate truss structures

This paper introduces a novel and robust probable statistical approach for the applied damage detection of determinate truss structures. This technique involves two steps; the first is called most probable damaged element identification step and the second is called probable damage severity prediction step. In the first step, a new index based on modal residual forces plays a major role to independently identify damage-suspected elements for each considered mode. Then among them, the elements, the most probable to damage, are extracted. In the second step, the probable damage severity for each most probable damaged element is individually predicted using a novel statistical approach. Finally, to justify the validity and robustness of the technique, three commonly used bridge trusses including a 29-bar Pratt truss, a 29-bar Warren truss, and finally, a 37-bar K truss under different damage scenarios are thoroughly studied while their modal parameters are corrupted by noise. The obtained results indicate that the method is innovatively capable of swiftly predicting, for determinate truss structures, not only damaged elements but also their damage severities by carrying out solely few structural analyses.

Identifiability-based model decomposition for hierarchical calibration

The computational model has become an essential tool in many engineering applications. To take full advantage of a computational model, its accuracy must be guaranteed. Validation and verification (VV this method decomposes the system model into smaller models and calibrates the parameters for the decomposed models. However, the method uses only qualitative criteria for model decomposition in the hierarchical calibration. This study identifies the problems of using only these qualitative criteria for hierarchical calibration, and instead proposes to use identifiability, obtained from the Fisher information matrix, as a quantitative criterion. A detailed process for the proposed identifiability-based model decomposition is described. During decomposition, the experiments are designed to meet identifiability requirements. The proposed decomposition method is verified by examining the Pratt truss bridge model as a case study; the method shows accurate calibration results and requires fewer experiments, as compared with two arbitrary decompositions.

Refurbishment of existing timber floors with screwed CLT panels

ABSTRACTA well-known, light, and almost reversiblere furbishment solution for existing timber floors is the use of a top timber flange connected to the joists to build up a “new” composite. This article proposes an improvement of that technique by using a cross-laminated timber (CLT) flange connected to the joists with inclined self-tapping screws. The use of an additional gap between the CLT and the existing joists contributes to increase the bending stiffness too. The inner gap is fixed by timber blocks resistant in compression but non-efficient in bending. These blocks act with the inclined screws to behave as a Pratt truss. An analytical model of the refurbishment is presented and a design example is discussed. Different configurations are finally introduced and compared to highlight pros and cons of the technique.

Forces in Bracing Elements of Timber Trusses

This research analyzes the forces in bracing members of timber trusses through numerical modeling using the computational system Strap, considering the three-dimensional structure behavior. The values obtained are compared to values set by the Brazilian standard ABNT NBR 7190 (1997), which considers the side instability of the bracing elements. The results were also compared with the values proposed by the methods of the European standard EUROCODE 5, the South African Standard SABS 0163 (1994) and with the work developed by Underwood (2000). The computer models represent industrial sheds with 12 to 24 meters spam, 24 to 96 meters long with heights of pillars 3, 4 and 6 meters. The structural models analyzed were the Pratt and Howe truss types, considering wood provide from C30 and C40 strength classes. The results show that the forces acting on the bracing of the three-dimensional models are higher than the values obtained by the method of ABNT NBR 7190 (1997), and the values obtained by the methods proposed by EUROCODE 5 and Underwood (2000) are more reliable in the overall behavior of the structure.