What is Truss: Definition and 239 Discussions

A truss is an assembly of beams or other elements that creates a rigid structure.In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object". A "two-force member" is a structural component where force is applied to only two points. Although this rigorous definition allows the members to have any shape connected in any stable configuration, trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes.
In this typical context, external forces and reactions to those forces are considered to act only at the nodes and result in forces in the members that are either tensile or compressive. For straight members, moments (torques) are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes, as is necessary for the links to be two-force members.
A planar truss is one where all members and nodes lie within a two-dimensional plane, while a space truss has members and nodes that extend into three dimensions. The top beams in a truss are called top chords and are typically in compression, the bottom beams are called bottom chords, and are typically in tension. The interior beams are called webs, and the areas inside the webs are called panels, or from graphic statics (see Cremona diagram) polygons.

View More On Wikipedia.org
  1. E

    Question about truss joint analysis in ansys workbench

    Dear Friends, Hi,I am senior mechanical engineering student and I'm working on my final project which is designing an AGV vehicle.I designed a space chassis for it and have a problem with analyzing the joint I designed using Solidworks.I do not know how can I should define support...
  2. M

    KNCalculating Member Forces in Truss Structures

    Attached is a picture of the truss. I am trying to calculate the member forces. I know a moment is = force * perpedicular distance, but in this case, for example, if i am taking moments about A, Would the equation be -(1*2KN)+(1*c) = 0 or using an alternative perpedicular distance...
  3. J

    Statics, forces in each memeber of a truss

    Homework Statement I´ll show the problem using a picture: Homework Equations Sum Forces = 0 Sum Moments = 0 The Attempt at a Solution Well, I´m a bit confused because I need to take care of the weight of the own structure. 1.- First attempt to solve to problem, since the structure is...
  4. J

    Statics, forces in each memeber of a truss

    Homework Statement I´ll show the problem with a picture: Homework Equations Sum forces = 0 ; The Attempt at a Solution Well I tried to solve the forces equations at the joint D, but I see three unkown quantities ED, BD and CD, and I have two equations, one for the X axis, and...
  5. A

    Why Do Truss Problem Distances Seem Incorrect?

    Homework Statement Ok, I have everything done for this problem... I just don't understand how they got some of the distances! Just look at the uploaded images... - Where did 2/3 m come from? (The vertical distance from the support to E) - Where did 1 m come from? (The vertical distance from E...
  6. V

    Calculate Vertical Displacement at Point C with Virtual Loads in Truss

    Hi I am trying to calculate the vertical displacement at point C for the following diagram https://www.physicsforums.com/attachments/57161 So far i have calculated the forces in each member and i now need to calculate the Virtual forces! I applied a virtual load at point c of 1 KN. I also...
  7. medeek

    Designing a Wood Truss with Medeek Calculator App

    I recently started programming a basic web based app. that calculates the forces within a standard wood truss. I thought it might be of some interest to visitors to the Physics forums. I've added most of the common types of trusses used in residential construction, with more to come later...
  8. P

    Find the reactions the pin A and roller D exert on the truss

    Homework Statement The rigid truss supports the loads shown. Find the reactions the pin A and roller D exert on the truss. All concentrated loads act on the pins joining the truss membersHomework Equations ƩMa= -5ft(3kips)-10ft(2kips)-.707(1kip)10ft+Dy(15ft) Dy=2.80 kips*ft The Attempt at a...
  9. P

    Truss analysis, determining internal forces

    Homework Statement I've been given the above truss and have to analyze it's internal forces as part of the problem, the other part of the problem is to analyze for which lengths members will fail, in what order and for which force F, however this is not the part that I find difficult. In...
  10. K

    Truss - ned someone to look through my calculations.

    Homework Statement Original figure is here: http://tinypic.com/r/svrm39/6. The task is to calculate forces in N1, N2 and N5 with the correct sign.(+ or -) The Attempt at a Solution Figures and calculations attached. I fear it might be messy - especially when it comes to use of...
  11. D

    Solving Truss Problems: Finding Unknown Forces | Learn Mechanics

    Homework Statement You are given truss ABC. In joint C there is a horisontal force F(13,2kN). a is the measurement between A and B, and b is the measurement between A and C. Calculate forces Nac and Nbc. Homework Equations ƩMa=0 ƩFy=0 ƩFx=0 The Attempt at a Solution My main...
  12. C

    Basic Statics problem, forces on a Truss

    Homework Statement The truss is supported by a pin at A and roller at B. Determine the support reactions. Homework Equations sum of forces along y-axis, sum of forces along x-axis, sum of all torques The Attempt at a Solution Sum of x= Fax+ Fbx+ 5sin45=0 Sum of...
  13. M

    Solving a Truss: Forces in X & Y Directions?

    Can sombody help me out with this truss, i want to know firstly, i know i am to solve the forces in the x and y direction if possible, however, my question is, would the 2KN, 4KN and 2KN forces be forces in the y direction because they are not along the y-axis but diagonal. Thanks
  14. T

    Converting Uniform Load to Point Forces on Truss Pin Joints

    If there is a uniformly distributed load due to gravity on a truss, how do I convert this into point forces on the three pin joints on the truss? I am having trouble trying to work it out as I'm pretty sure there will be both forces in the x and in the y for each of the joints, but I can't...
  15. A

    Solving Truss Homework: Finding All Forces in Members

    Homework Statement I need to find all the forces acting in the members of this truss. Homework Equations Sum x = 0 Sum y = 0 Sum Mom. at any point = 0 The Attempt at a Solution i have tried using the method of sections and method of joints to solve this truss, but i cannot...
  16. L

    Truss Prob: finding the force in a member

    Homework Statement The diagram is attached. I must solve using method of sections the force in member HG. Homework Equations ƩF(y) = 0, ƩF(x) = 0, ƩM = 0 The Attempt at a Solution My hand-drawn pic shows the section. Solving vertically, ƩF(y) = 0 F(DG)cos45 = 10 F(DG) =...
  17. E

    Weird Statics Truss Problem - Finding reactions

    So I'm looking for the reaction forces at the left end of the truss before I solve for the forces in the members of the truss in terms of F and theta. I summed forces in the x, y direction, took moments about point A,B, to get 4 equations in 4 unknowns (Ax, Ay, Bx, By). However, although Ax,Bx...
  18. A

    Truss Analysis - Sections Method

    I was analyzing a truss and when I checked my answer there was a "new" point where the moment was taken about that was not in the original diagram. After reading the text I could not find anything that stated why, when, or how to do this? I've attached the image of the answer. Can I figure...
  19. C

    Can this truss structure be statically indeterminate?

    I have designed this truss but I'm reading on the internet that this equation, 2j = m + r IS NOT enough to determine whether a structure is statically determinate. It has to do with the arrangement of the members as well? How can I tell beyond the equation I guess is my question? Also...
  20. O

    Truss - Method of Joints in terms of load P

    Hello guys. I would like someone to check that I am doing this problem correctly. The answer given in the book is 0.577(P) for FAB and FAE which differs from the answer I get. Homework Statement Determine the force in each member of the truss in terms of the load P and state if the members...
  21. M

    Geometry in a Truss: Find Internal Forces & X

    I'm to work out the internal forces in this truss. I know to get the reaction forces first, so I take the moment at the pin support to find the reaction at the roller support. I can't get my head around at how to find x through the geometry to add that force to the moment though. Is there not...
  22. N

    Determing the Force in Each Member of the Loaded Truss

    Homework Statement Determine the force in each member of the loaded truss. The force is positive if in tension, negative if in compression. I have attached an image of the problem Homework Equations The Attempt at a Solution I defined the positive y-axis to be from B to...
  23. S

    Statics Truss Problem Involving Method of Sections

    Homework Statement In the traveling bridge crane shown all crossed members are slender tie rods incapable of supporting compression. Determine the forces in members DF and EF and find the horizontal reaction on the truss at A. Show that if CF=0, DE=0 also. -Determine force in members...
  24. P

    Structural Mechanics - Statics / Truss

    Homework Statement The simply supported timber foot bridge shown in figure 5 spans 7 metres and, as shown, is carried by two Engineering grade Douglas Fir beams. The uniformly distributed load due to the self weight of the foot bridge and beams is 96 kg/m. The bridge is required to carry a...
  25. R

    Truss optimization and analysis

    We were given a small project to do before a test in my engineering statics class, i understand the goals of the project and understand the steps i need to take (i believe) however i don't understand how to simplify the distributed load into something i can anylize as we haven't seen anything...
  26. L

    Solid Mechanics- Ultimate Load in truss.

    Homework Statement A 3/4-in.-diameter rod made of the same material as rods AC and AD in the truss shown was tested to failure and an ultimate load of 29 kips was recorded. Using a factor of safety of 3.0, determine the required diameter (a) of rod AC, (b) of rod AD. Homework Equations...
  27. G

    How Do You Calculate Forces in a Truss System?

    Please answer the following problem. You can post the answers here, I just want to confirm if my answers are correct. This is a truss analysis problem. Problem: Determine the forces in members AC, BC, BD, CD and GF for the truss shown in the figure. Indicate if the member is tension or...
  28. U

    Magnitude of moment about axis (Space Truss)

    Homework Statement Determine the magnitude of the moment of the force F about the axis CA of the tripod ABCD, if F = {40i -30j -100k}N. Image attached. 2. The attempt at a solution Based on a similar question I found in the textbook my method to solve this question: Find UCA =...
  29. G

    Designing a Pratt Truss Bridge

    Homework Statement I'm designing a pratt bridge for class that looks like this: http://www.garrettsbridges.com/photos/pratt-truss-bridge/attachment/pratt-truss-bridge-2/ I have a two dimensional drawing of one side of the bridge. 2. Homework Equations / 3. The Attempt at a Solution...
  30. S

    Statics Truss Problem, Stuck at force in one member. Please help

    Homework Statement Figured it would be easier if I showed a picture http://img210.imageshack.us/img210/707/problemcz.jpg Homework Equations Ʃm=0 Ʃfx=0 Ʃfy=0 The Attempt at a Solution Here is my attempted solution, I am missing member BD and not sure which way to solve it, I...
  31. W

    STATICS truss/ math equation - joint by joint

    studying for my test, I have a truss joint equation with 2 variables ƩFx = 0 : 4/15 (15kN) - 10/10.44(Fbd) - 4/5(Fbe) = 0 12 = .957(Fbd) + .8(Fbe) ƩFy= 0 : 3/5 (15kN) - 6kN - 3/10.44(Fbd) + 3/5(Fbe) = 0 6 = 9 -.287(Fbd) + .6(Fbe) -3 = .287(Fbd) + .6(Fbe) this is where I'm...
  32. G

    Question for Truss- method of joint

    Does anyone know how to solve the question below? I have no idea to do it with some missing angle inside the triangle. [PLAIN]http://img267.imageshack.us/img267/374/truss.jpg Shot at 2012-07-01
  33. D

    Stress and Strain (Finding the thickness of truss members)

    Hi guys i have a exam coming up soon and stress is starting to kick in. I am good with stress and strain, but I am just confused on this question and don't understand what i need to be doing. I've tried every formula and i just can't seem to get question 5 out. The answears for this question is...
  34. N

    Solving Trusses w/ Couples: Examples & Calculations

    I have solved a number of example questions referring to Trusses. I have one where the forces do not balance correctly when I check through. A difference with this truss is that there is a couple applied to the truss. I have been using the method of Joints to do the working out. Does the...
  35. E

    How can I optimize my truss design for maximum stability and efficiency?

    Hi I’m doing a project where we have to design a truss. I’ve made a design and I’ve figured out the reaction forces. There is a support in the middle and one on the left side, both of them are only vertical reactions and finally there is a load of 250N on the right being applied. I don’t...
  36. G

    Can a truss with released ends still form a mechanism?

    Dear all! I have encountered a problem with modelling a truss. When modelling on an analysis software, you must release the ends of the joints, but not all or it will form a mechanism, therefore you release all but one of the joint. But what I have here, is a truss that is released on all ends...
  37. A

    Calculating Nodal Forces in a Simple Truss: Homework Solution

    Homework Statement Calculate nodal forces in truss (illustrated below). Homework Equations Force (horizontal) = FCosTheta The Attempt at a Solution Force in node A (horizontal) = FCosTheta = (5000)(Cos60) = 2500 N Force in node A (vertical) = 5000/2 = 2500 N Force in...
  38. Y

    Calculation of the Truss Member

    Homework Statement Calculate the type and magnitude of the forces in the following member. i) AB ii) FG iii) BC Homework Equations ƩFx = 0, ƩFu = 0, ƩM = 0 The Attempt at a Solution I have calculated the AB and BC which are 80kN and 100kN respectively by using Take moment at G : (-80 * 12) +...
  39. J

    Truss analysis using method of joints

    The question is to calculate the forces ina ll members of the trussnby method of joints. First i have calculated the reaction forces for A and B by taking the moment from both these points. These came too: Ay=25N and By=25N I do not know where to go from here, what point should i analyse...
  40. R

    Baltimore Truss Analysis Problem

    Homework Statement Find the force in member JQ for the Baltimore truss where all angles are 30º, 60º, 90º or 120º. Homework Equations Length from A to N can be taken as 6 units. The Attempt at a Solution To use method of sections.
  41. T

    Forces on Equilateral triangle truss

    Hey Guys, My question involves finding all of the forces acting upon each member. It is known that each side of the triangle has a length of l. It is also known that the force is acting at the very top of the triangle in the x direction (to the right) labelled as F. Attempt: I found moments...
  42. J

    What Is the Maximum Mass That Keeps Truss Forces Within Limits?

    Homework Statement Determine the largest mass m of the suspended block so that the force in any member does not exceed 52 kN(T) or 47 kN(C). Homework Equations ƩM = 0 ƩFy = 0 ƩFx=0 The Attempt at a Solution Did I assume the arrows right? Would this be the right track to...
  43. J

    Solving an Asymmetric Truss: Seeking Help

    Homework Statement http://desmond.imageshack.us/Himg839/scaled.php?server=839&filename=truss1.png&res=medium asymmetric truss, with given loads need to find reaction forces Homework Equations sum F = 0 sum M = 0 The Attempt at a Solution summed up the moments about A and D...
  44. J

    Truss Analysis: Method of Joints

    I'm doing this truss analysis by method of joints and I have determined the forces at "A" and "G" and have moved on to determine the loads at each joint. I have determined the angle to be 63.34 for the 10' and 53.13 for the 15'(I took the inverse tangent of 20/10=63.34 and I took the inverse...
  45. K

    How to identify forces of compression or tension in simple truss?

    Homework Statement Hello. I have some troubles with a truss problem. In fact i believe i have correctly identified the direction of the forces involved in the rods, but i cannot identify which rod is in compression or which is in tension. Are there any tips/rules to identify only with a force...
  46. T

    2d statics truss, joint method

    Homework Statement Determine force of each member using joint method Homework Equations T = F x D The Attempt at a Solution Answers are: Fab 2465 T Fbd 1200 T Fbc 1375 C Fdc 750 C Fde 860 T (This one is what I tried) Fce 649 C Fac 1922 C Thanks.
  47. T

    Force in members of truss; section method

    Homework Statement Homework Equations torque = force x distanceThe Attempt at a Solution words: hopefully this one is clearer than the last one and someone can follow what I did and figure out where I went wrong. Thanks. Answer is Ffg=5kn T, Ffh = 20 kn T (only these two members are being...
  48. N

    Finding the forces of a truss

    Homework Statement i am trying to figure out the forces of the different members of this truss in which looks like a a square that is split into two triangles and is affixed to another triangle the same size I have already found the moment of the reactions and already found the reaction forces...
  49. L

    How Do You Solve Truss Reactions and Pulley Accelerations?

    Homework Statement For the truss find the reactions at point A and B. For pulley, find the relation bet acc of A and block B. Homework Equations The Attempt at a Solution For the truss, take moments at B. F212 + NA12=F110 NA=-2kN which is wrong. Where did I go wrong? ans is...
  50. E

    What is the best software for truss buckling analysis?

    Hello everybody! From time to time, I'd like to compute the minimum force that buckles a truss, and hand computations get quickly too complicated. So: could you recommend me a piece of software for that? What I need: - Quickly learned and installed, for Windows, free of nearly (I know...
Back
Top