Truss Type Research Articles

Construction worker fatalities related to trusses: An analysis of the OSHA fatality and catastrophic incident database

This study was conducted to gain a better understanding of the risks associated with truss installation in building projects. The Occupational Safety and Health Administration (OSHA) fatality and catastrophic incident database was analyzed for the years inclusive of 1990–2009. The database includes over 15,000 incidents, 211 of which pertain to trusses. The incidents were analyzed as to the number of fatalities per incident, the type of truss, the truss material, the activity taking place at the time of the accident, the release of the hoisting equipment, the initiation of the accident, the presence of bracing materials, the type of construction, the length of the trusses, the location of the incident, the type of accident (fall, caught-in/between, struck by, or electrocution), and the year the fatality occurred. Many of the accidents occurred at elevation and were initiated in large part by moving or falling objects. The study recommends that further research should focus on the stabilization of incomplete roof structures and the implementation of best practices for fall protection while performing truss-related work.

Mechanical Behaviors of Wire-woven Metals Composed of Two Different Thickness of Wires

Wire-weaving is virtually only a practical method to fabricate multi-layered truss type cellular metals, except for stacking multiple single layered structures. To date, the wire-woven metals have been fabricated of wires of a uniform thickness. In this work, variations of wire-woven metals fabricated of two different thickness wires in out-of-plane and in-plane directions are introduced. The mechanical properties subjected to compressive or shear loading are investigated.

Numerical and experimental evaluation of a double inverted trussed beam reinforced with steel cable

A special type of queen-post truss was evaluated numerically and experimentally. The system consists of a main beam with a double rectangular cross section, into which are fitted two struts that are connected to steel cables anchored to transverse steel dowels embedded at the ends of the main beam. The system, which can be used as a support for concrete formwork, for structural rehabilitation and for numerous other applications, is lightweight, easy to handle, and stronger and stiffer than a simple beam. From experimental study, on average, beams are 97% stronger than ones without cable reinforcement, and the gain in stiffness was 43%. The numerical model was analyzed via the finite element method.

하모니 서치 알고리즘과 고유진동수 제약조건에 의한 트러스의 단면과 형상 최적설계

We present the optimum design for the cross-sectional(sizing) and shape optimization of truss structures with natural frequency constraints. The optimum design method used in this paper employs continuous design variables and the Harmony Search Algorithm(HSA). HSA is a meta-heuristic search method for global optimization problems. In this paper, HSA uses the method of random number selection in an update process, along with penalty parameters, to construct the initial harmony memory in order to improve the fitness in the initial and update processes. In examples, 10-bar and 72-bar trusses are optimized for sizing, and 37-bar bridge type truss and 52-bar(like dome) for sizing and shape. Four typical truss optimization examples are employed to demonstrate the availability of HSA for finding the minimum weight optimum truss with multiple natural frequency constraints.

Investigation of Bed Joint Reinforcement Influence on Mechanical Properties of Masonry under Compression

The results of investigations of compressed reinforced masonry walls subjected to axial compression are presented. Tests were carried out using specimens made of clay bricks and cement-lime mortar. As reinforcement, smooth and spiral twisted longitudinal rods, two types of structural wire mesh and truss type reinforcement were used. Two percentages of bed joint reinforcement, about 0.1% and 0.05% were applied. For each type of reinforcement, three masonry walls were tested. Additionally, nine unreinforced models were also tested. The main aim of the investigations presented is to determine the effect of different types of reinforcement on the load capacity and failure. Measurement of the strains of reinforcing bars permitted the recording of the strain level at the moment of crack appearance and also at the moment of failure.

부분 무기둥 비계구조 골조 거동에 관한 실험적 연구

There is a critically structural problem of scaffolding system when one of scaffold columns is remove to be used as a gangway for their temporary office in the structure before finishing all such as an apartment or office building. This is not used to checking to structurally checking at a construction site. This study is to find out which system at a site will be more effective and low-cost-high effectiveness of aluminum ladder, timber ladder, <TEX>${\phi}$</TEX>1/2 inch steel pipe truss with a type of concave, convex warren truss ladders. Theses are structurally tested with horizontal set as a truss type with 1.8 meter long. Concentrated load has been loaded at the upper center of the system and checked its strain at the bottom center, using aluminum-use strain gage and steel-use gauge have been attached concave warren truss with diameter 1/2 inch has 14% stronger than convex truss. Convex truss has almost same strength as an aluminum ladder truss, it is found out.

Reinforcement schemes for cold-formed steel joists with a large web opening in shear zone—An experimental investigation

The floor joists of cold-formed steel (CFS) structures often require large web openings. Reinforcement of such openings may mitigate the detrimental effects arising from such web openings. This paper is based on an experimental investigation conducted to establish reinforcement schemes for CFS joists with a large web opening located in high shear zones. The investigation considered a large web opening cut out in the middle of the web of a lipped channel section. Circular and square large web openings of about 65% web depth were considered. The shear tests involved short span specimens, simply supported at the ends, and subjected to a mid-span point load. This paper presents the experimental set-up, and the test results associated with 27 individual tests consisting of nine sets of three identical tests. These test sets consist of cold-formed steel joists sections with (a) no web opening, (b) webs having circular or square openings, (c) webs having reinforced openings. Three different reinforcement schemes were investigated, however, the test results indicated that the proposed “Vierendeel truss type reinforcement scheme” can restore the original shear strength of such sections having circular or square openings. Overall, this study establishes a cost-effective reinforcement scheme for cold-formed steel joists having a large web opening in high shear zone.

An improved algorithm in railway truss bridge optimization under stress, displacement and buckling constraints imposed on moving load

Railway truss bridges are amongst the essential structures in railway transportation. Minimization of the construction and maintenance costs of these trusses can effectively reduce investments in railway industries. In case of railway bridges, due to high ratio of the live load to the dead load, the moving load has considerable influence on the bridge dynamics. In this paper, optimization of the railway truss bridges under moving load is taken into consideration. The appropriate algorithm namely Hyper-sphere algorithm is used for this multifaceted problem. Through optimization the efficiency of the method successfully raised about 5 percent, compared with similar algorithms. The proposed optimization carried out on several typical railway trusses. The influences of buckling, deformation constraints, and the optimum height of each type of truss, assessed using a simple approximation method.

모형실험에 의한 트러스형 리프트 게이트의 진동 특성

본 연구에서는 4대강 사업으로 건설중인 트러스형 리프트의 진동특성을 검토하기 위하여 모형실험이 수행된다. 경간 40 m, 높이 9 m의 트러스형 리프트게이트를 축척 1/25로 모형이론에 따라 아크릴과 납으로 모형을 제작하고, 폭 1.6 m, 길이 25 m, 높이 0.8 m의 수로에서 실험된다. 먼저 모형의 고유진동수가 측정되고 모형을 검증하기 위하여 유한요소 해석결과와 비교된다. 검증된 모형에서 상하류 수위와 문비 개방고에 따른 진동가속도 진폭이 측정된다. 또한 문비의 진동을 줄 일수 있는 하부형상을 검토하기 위하여 문비 최하부의 각도가 <TEX>$20^{\circ}$</TEX>, <TEX>$35^{\circ}$</TEX>, <TEX>$50^{\circ}$</TEX>인 모형을 제작하고 실험결과를 서로 비교한다. 실험 결과는 수문 조작 시 유지관리지침의 기본 자료를 제공하고, 수문의 진동특성과 진동을 줄일 수 있는 수문의 하부형상을 검토한다. A model test is performed to investigate the dynamic behavior of truss type lift gate which is being constructed by the four major rivers project. The gate dimensioned 40 m in width, 9m in height is scaled with the ratio of 1:25 and is made of acryl panel and supplemented weight by lead in the concrete test flume dimensioned 1.2 m in width, 0.5 m in height and 30m in length. Firstly natural frequencies of the model gate are measured and compared with the numerical results for the calibration. The amplitudes of the vibration are measured under the different gate opening, upstream water level conditions. Also models with bottom angle <TEX>$20^{\circ}$</TEX>, <TEX>$35^{\circ}$</TEX> and <TEX>$50^{\circ}$</TEX> are tested and compared to find out a proper shape of bottom structure which minimizes the gate vibration. These test results presents a basic data for the guide manuals of gate management and a design method to reduce the gate vibration of truss type lift gate.

Computational Analysis of a Truss Type Fuselage

The strength of a welded truss type fuselage of a light aircraft – named SAFAT 01 – is considered in this paper. The aircraft is a monoplane with high strut-braced wings configuration with flaps. The fuselage is of welded tubular steel fabric-covered construction. According to its production contract; the aircraft is fully produced and assembled in Sudan whereas the documentation is limited to technical side only with no information available about design procedures and calculations. This makes it difficult to further modify or upgrade the aircraft. The fuselage geometry has been modeled using a CAD program. The main dimensions have been obtained using 2-D drawings and the missing dimensions and data due to lack of documents were extracted experimentally from a built aircraft. Aerodynamic loads were determined using computational fluid dynamic program for the horizontal tail. Static structural analysis was conducted by finite element method (FEM) using fastened connection property between the tubes. The results were observed in three main parts; rear part which supports the vertical and horizontal stabilizers and the rear landing gear; the mid part which provides cantilever reaction for the wing and supports front landing gear, and the front part on which the engine is mounted. The Von Mises stresses, displacements and principal stresses were observed in the three parts and found acceptable except for a small region near the attachment between wing and fuselage. However, further experimental validation is needed. Presently, experimental and dynamic analyses are being conducted and the results will be published later.

강박스-트러스 하이브리드 곡선 교량의 거동 분석

강박스-트러스 하이브리드(HiTAB: Hybrid Truss And Box) 교량은 낮은 형고로 저항이 가능한 정모멘트 구간에는 강박스 구조를 활용하고, 운반에 제약을 받을 뿐만 아니라 높은 형고의 거더를 활용해야 하는 부모멘트 구간에는 트러스 구조를 적용한 신형식 교량이다. 이는 경간장 80~150 m 내외의 장경간 교량으로 활용이 가능하여 경제성이 우수한 구조형식이지만, 곡선구간 적용 시 교량에 발생하는 비틀림으로 인해 트러스 구조의 안전성이 저하될 우려가 있다. 그러므로 강박스-트러스 하이브리드 교량의 상용화를 위해서는 직선 교량 뿐만 아니라 곡선 교량의 거동 분석 및 평가가 반드시 필요하다. 따라서 본 연구에서는 다양한 곡률을 가지는 강박스-트러스 하이브리드 곡선 교량에 대해 구조해석을 수행하였으며, 이를 직선 교량의 부재력과 처짐에 대한 비교를 통해 거동 분석 및 평가를 수행하였다. 또한 강박스-트러스 하이브리드 교량의 직선 형식으로 곡선 교량에 적용 가능한 한계곡률을 제시하였다. Steel Box-Truss Hybrid bridge consisted with steel box type in positive moment that is allowed to resist with low depth and truss type in negative moment not only has restriction of delivery but has to use high depth is new type bridge. This can be used as 80m~150m long span bridge and is economical structural type. But safety of truss type is concerned because of torsion that occurs when Steel Box-Truss Hybrid bridge applies a curved bridge. Therefore, it is necessary to analyse and evaluate straight and curved bridge for commercialization of Steel Box-Truss Hybrid bridge. In this study, structural analysis of Steel Box-Truss hybrid curved bridge with various curvature is performed and compared with member force and displacement of Steel Box-Truss Hybrid straight bridge. Also the applicable limited curvature of Steel Box-Truss Bridge form is proposed.

COMPUTATIONAL ANALYSIS OF A TRUSS TYPE FUSELAGE

The strength of a welded truss type fuselage of a light aircraft – named SAFAT 01 – is considered in this paper. The aircraft is a monoplane with high strut-braced wings configuration with flaps. The fuselage is of welded tubular steel fabric-covered construction. According to its production contract; the aircraft is fully produced and assembled in Sudan whereas the documentation is limited to technical side only with no information available about design procedures and calculations. This makes it difficult to further modify or upgrade the aircraft. The fuselage geometry has been modeled using a CAD program. The main dimensions have been obtained using 2-D drawings and the missing dimensions and data due to lack of documents were extracted experimentally from a built aircraft. Aerodynamic loads were determined using computational fluid dynamic program for the horizontal tail. Static structural analysis was conducted by finite element method (FEM) using fastened connection property between the tubes. The results were observed in three main parts; rear part which supports the vertical and horizontal stabilizers and the rear landing gear; the mid part which provides cantilever reaction for the wing and supports front landing gear, and the front part on which the engine is mounted. The Von Mises stresses, displacements and principal stresses were observed in the three parts and found acceptable except for a small region near the attachment between wing and fuselage. However, further experimental validation is needed. Presently, experimental and dynamic analyses are being conducted and the results will be published later.

Vibration suppression control of smart piezoelectric rotating truss structure by parallel neuro-fuzzy control with genetic algorithm tuning

The main goal of this paper is to develop a novel approach for vibration control on a piezoelectric rotating truss structure. This study will analyze the dynamics and control of a flexible structure system with multiple degrees of freedom, represented in this research as a clamped–free–free–free truss type plate rotated by motors. The controller has two separate feedback loops for tracking and damping, and the vibration suppression controller is independent of position tracking control. In addition to stabilizing the actual system, the proposed proportional–derivative (PD) control, based on genetic algorithm (GA) to seek the primary optimal control gain, must supplement a fuzzy control law to ensure a stable nonlinear system. This is done by using an intelligent fuzzy controller based on adaptive neuro-fuzzy inference system (ANFIS) with GA tuning to increase the efficiency of fuzzy control. The PD controller, in its assisting role, easily stabilized the linear system. The fuzzy controller rule base was then constructed based on PD performance-related knowledge. Experimental validation for such a structure demonstrates the effectiveness of the proposed controller. The broad range of problems discussed in this research will be found useful in civil, mechanical, and aerospace engineering, for flexible structures with multiple degree-of-freedom motion.

Design and experiment of a cradle truss type floating raft system

In this paper, a new design concept of an isolated cradle trusslike structure to support vibrating machinery is proposed. The acoustic and vibratory energy transmission in this isolation system is investigated to improve the vibration isolation performance of conventional floating raft system. The finite element method and experimental measurements are used to understand the dynamic behavior of this cradle truss. In conjunction with experiments, a vectorial four pole parameter numerical model is used to identify power flow of the floating raft isolation system. The proposed floating raft design achieved a vibration reduction of 30–40dB in the frequency range of 20–600Hz. It is also shown that the loss factors of the cradle truss configured floating raft are up to 4dB than conventional floating flat raft.

Unified analytical solution for dynamic elastic buckling of beams for various boundary conditions and loading rates

The problem of dynamic elastic buckling of Euler–Bernoulli beams subjected to axial loads is studied analytically. The dynamic axial loading is accomplished by a constant displacement rate of one end of the beam with respect to the other. The axial loading rates are considered slow enough to obviate the need to account for axial wave propagation effects. The dynamics of the beam is formulated in the modal domain considering the lowest static buckling mode. The dynamic stability of the beam is investigated as a response problem assuming an initial deformed geometry in terms of an eccentricity favouring the mode shape. The governing partial differential equation is condensed into a unified ordinary differential equation for various boundary conditions using a single dimensionless parameter in terms of beam geometry, material properties, loading rate, and appropriate coefficients corresponding to different boundary conditions. The results obtained for the dynamic response of beams for various values of the dimensionless parameter and initial eccentricity suggest that the solutions can be combined into a single unified analytical expression for the dynamic buckling load. It is shown that the corresponding dynamic response curves can also be collapsed into a single curve using the dimensionless peak load and the associated time parameter. The accuracy of the unified analytical expression for dynamic buckling is verified against exact solution of the ordinary differential equation considering three problems in terms of dimensional quantities for different boundary conditions and loading rates. Further the validity of the single mode dynamic buckling formulation is examined by comparing the results obtained for various boundary conditions with the numerical results from the dynamic response of a large number of degree of freedom finite element model of the beam without any restriction on the deformation mode shape. This unified solution has potential application in optimum design for dynamic collapse of truss type structures subjected to dynamic loads.

Influence of stiffness in bolted connections in wooden plane structure of truss type

Trusses are structural systems commonly used in projects, being employed mainly in roof structures, present in most rural buildings. The design of trusses, as well as other structural systems, requires the determination of displacements, strains and stresses. However, the project is developed from an ideal model of calculation, considering free rotation between the elements of a connection. This paper presents a computer program for the analysis of bidimensional wooden trusses with connections formed with two screws per node. The formulation is based on the flexibility method, taking into account the influence of the effect of semi-rigid connections formed by two screws. An example of a structure is presented and analyzed by the program developed here, highlighting the importance of behavior analysis on semi-rigid connections.

Reliability analysis for lateral stability of tongwamen bridge

Tongwamen Bridge is a critical link between Dongmen Island and the land in Shipu town, Zhejiang province, China. It is a 238 m span, half-through, concrete-filled steel tubular (CFST) X-type arch bridge. The width of the deck is only 10 m, yielding a width-to-span ratio of 1/23.8. The plane truss type section rib was adopted, which made of two CFST chords and web member system. The lateral stability is the key issue to this bridge. However, the existing researches on Tongwamen Bridge's lateral stability are all the deterministic structural analysis. In this paper, a new strategy for positioning sampling points of the response surface method (RSM), based on the composite method combining RSM with geometric method for structural reliability analysis, is employed to obtain the reliability index of lateral stability. In addition the correlated parameters were discussed in detail to find the major factors. According to the analysis results, increasing the stiff of lateral braces between the arch ribs and setting the proper inward-incline degree of the arch rib can enhance obviously the reliability of lateral stability. Moreover, the deck action of non-orienting force is less than the two factors above. The calculated results indicate that the arch ribs are safe enough to keep excellent stability, and it provides the foundation that the plane truss rib would be a competitive solution for a long-span, narrow, CFST arch bridge.

Experimental analysis of reinforced concrete block masonry spandrels using pre-fabricated planar trussed bars

Masonry spandrels together with shear walls are structural components of a masonry building subjected to lateral loads. Shear walls are the main components of this structural system, even if masonry spandrels are the elements that ensure the connection of shear wall panels and the distribution of stresses through the masonry piers. The use of prefabricated truss type bars in the transversal and longitudinal directions is usually considered a challenge, even if the simplicity of the applications suggested here alleviate some of the possible difficulties. This paper focus on the experimental behavior of masonry spandrels reinforced with prefabricated trusses, considering different possibilities for the arrangement of reinforcement and blocks. Reinforced spandrels with three and two hollow cell concrete blocks and with different reinforcement ratios have been built and tested using a four and three point loading test configuration. Horizontal bed joint reinforcement increased the capacity of deformation as well as the ultimate load, leading to ductile responses. Vertical reinforcement increased the shear strength of the masonry spandrels and its distribution play a central role on the shear behavior.

트러스형 리프트 게이트의 진동현상에 관한 모형실험

A model test is carried out to investigate the vibration of truss type lift gate in the four major rivers project. The gate model scaled with the ratio of 1 : 25 is made of acryl panel dimensioned 1.6 m in width, 0.28 m in height in the concrete test flume. Firstly natural frequencies of the model gate are measured and the results are compared with the numerical results in order to verify the model. The amplitudes of the vibration are measured under the different gate opening and water level conditions. The results are analyzed to study the characteristics of the gate vibration according to the small gate opening, the large gate opening and the overflow conditions. These test results presents a basic data for the guide manuals of gate management and a design method to reduce the gate vibration of truss type lift gate. Finally, the vibration of truss type lift gate are assessed in comparison with those of formerly tainter gate.

Effectiveness of Truss Supporting During Replacement of Damaged Column in a High-Rise Frame Structure Building

Truss supporting (TS) is a technique to support a building frame for replacing column when its stiffness reduces due to any kind of damage. This paper deals about the effectiveness of TS during replacement of damaged column in a high-rise frame structure building. For the case study of the effectiveness of TS, six columns that are damaged columns at different positions in the ground and first floors were taken into consideration. A suitable type of truss was modelled to transfer the load of damaged column to the lower column just below the damaged column. The numerical analysis of the 2-D frame with undamaged columns, damaged column and damaged column with truss supporting, was carried out using finite element software STAAD Pro 2004. The deflection, axial force, shear force and bending moment of the structural elements (beam & column) for TS case were obtained almost same as their design values