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.

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  1. Z

    How do I find the force in each beam of a truss problem?

    http://www.siz.co.il/my.php?i=oogytirin1tt.jpg I have to find force in 1. 2. 3. 4. Beam. How can i do that? Thanks
  2. D

    Intro Level Question -- Truss Analysis

    Homework Statement http://puu.sh/lKP9T/b6aea483b5.png http://puu.sh/lKPdk/a99777477e.png http://puu.sh/lKPkj/a9f199e959.jpg My question is the last picture/slide which says F_DB = F_DA how? why is that? Homework Equations F_DB = F_DA ? The Attempt at a Solution
  3. C

    Truss Free Body Diagram & initial conditions

    Homework Statement Complete a free body diagram for the truss structure with a weight attached to node 2 (this is known as 151N) Homework EquationsThe Attempt at a Solution I have attached my Free Body Diagram The diagram is to display what is know at the start of the problem before working...
  4. N

    Building a truss with matlab -- Need help

    Homework Statement I am suppose to build a truss using a MATLAB code given to me. I have to identify the joint coordinates, member assembly, and load matrix. The code is suppose to calculate the deflections like fea. I have put everything in but when the code runs my deflections are "NaN" which...
  5. V

    How to identify members in a truss as compression or tension?

    Homework Statement Is this correct? The sum of the forces in the Y have to be zero and there is only two y-components so it's pretty simple to determine this. There are also only two x-components so those will also cancel each other out as they have to go in opposite directions to balance as...
  6. V

    Finding the Reaction Force in a Truss

    Homework Statement Homework Equations In static equilibrium the forces are = 0 Method of Joints The Attempt at a Solution i don't know how to find the reaction forces of A and B. i know how to calculate the force of each member by working backwards from where F is applied but once I do...
  7. GiantSheeps

    Stargazing Remote Controlling Truss Dobsonian Telescope?

    Is it possible to rig a Truss Dobsonian telescope like this one so that you can control it remotely from inside of a building while the telescope itself is on the roof of the building? Then is it possible to attach some sort of adapter to the telescope that would allow you to hook up a camera...
  8. W

    Solve Truss Joints Using Method of Joints

    Homework Statement Determine the axial forces in the members of the truss and indicate whether they are in tension or compression. Homework Equations Fx = 0 Fy = 0 Mp = 0 The Attempt at a Solution I attempted to find the reactions at the supports first. So: Fx = 0 = Bx + 800cos(250)N Fy...
  9. H

    Calculating Reaction Forces in Truss Structures

    [PLAIN]http:// I am having trouble with this truss problem. I have attached my work so far. I used the entire structure as a system first and did the sum of the forces equals zero but I don't know how I can finish the moment at a because I don't know the x and y distances for the 500N force...
  10. M

    Find zero force members of a truss

    I was wondering how members CL and JE are zero members? They both have forces applied to them, so why would it be zero? The attached image is the solution.
  11. A

    Finding Reaction Forces on Pin Supports in a Static Equilibrium System

    Homework Statement I am given the forces on picture and I´m asked to find the reactions on both supports. I see they are pin supports so they ask me for 4 unknowns. Homework Equations Sum of forces in both directions equal to zero Sum of torques wrt a convenient point equal to zero THREE...
  12. EdajMay

    Truss Analysis : Method of Joints only (Picture provided)

    Hello, In my statics course, we had to design a bridge, and now, I have to calculate the internal forces in every member of the truss. At first, I have found Ay and Oy with the moment of force, but then, I am stuck since the truss is not perfectly aligned. Sadly, I can't use the method of...
  13. F

    Identifying zero force members in truss

    http://imgur.com/lPIRaie 1. What are the Zero force members in this truss? 2. Is the truss internally statically determinate? Im not too sure what question 2 is but I would guess yes? Many thanks~
  14. thegreengineer

    Vector mechanics for engineers -- Confusion described below

    Homework Statement Look I have an exercise about trusses in vector mechanics. It's the following: https://scontent-lax3-1.xx.fbcdn.net/hphotos-xfp1/v/t1.0-9/12003339_1645511085733429_8210043018491702007_n.jpg?oh=4955534403fb6f3f5f9a40c9c0b8ecbc&oe=569761ED I have to determine the forces in...
  15. S

    Methods of Section: Truss problem

    1. The problem statement, Have to find the forces in AC & BC using the methods of section. all variables and given/known data Distance AB = 79cm BC = 63 AC = 98 d = 3.833 AZ = 62.881 ZC = 75.16 Point B is a roller and point A is a Pin Whats given is 39.94N Forces @ C going down Homework...
  16. J-dizzal

    Truss analysis, section method

    Homework Statement Determine the forces in members BC and CG. The forces are positive if in tension, negative if in compression.[/B] Homework Equations ΣF=0 ΣM=0 The Attempt at a Solution I don't know where I am going wrong, My equations include the applied force, since there is only one.
  17. S

    Internal Forces on a Truss (Again)

    Homework Statement Hello, in the attached file shows a picture of the problem I need to resolve. The question asks to calculate the internal force in the member BC. There is a pin support located at joint A and D, which is not shown in my diagram, and it is also symmetrical, which makes things...
  18. N

    Engineering statics: Truss Analysis Question

    Homework Statement So I was working on this problem, and my only questions are wether BE and CE can be assumed to be no force members? Also if I am not sure a member is a no force member, will it be revealed once I do the calculations, Homework Equations ΣF = 0 The Attempt at a Solution I...
  19. S

    Truss Analysis with Non-Parallel Supports and Point Load: Is My Method Correct?

    Homework Statement Hi there, I've been having problems with this kind of truss in the attached file. I'm used to resolving forces where the supports are located along the same x-axis, but this time I have the supports on the y-axis and a point load in the same direction. I haven't shown it...
  20. H

    How Do You Calculate Reaction Forces in Complex Roof Trusses?

    Hi all, I am having trouble with a work/course related issue. As part of a project assignment I have decided to research the failure of some of the roof structure members at my place of work. To do this I need to calculate the reactions forces in the roof supports, but some trusses have two...
  21. C

    Does Angling a pin support on a truss change anything?

    Homework Statement If you had a simple 2D truss with a pin and a roller support, would making the pin on a 30 degree incline change the supporting reactions? Homework EquationsThe Attempt at a Solution Can't see why since it still supports a horizontal and vertical, don't know hwy the angle...
  22. J

    Reaction forces on simple 2 strut truss

    Homework Statement Calculate reaction forces R1x, R1y, R2x, R2y. Load of 100N. Node 1 and 2 are fixed. Distances listed on image. Homework Equations [/B] I have: ∑Fx = 0 = R1x + R2x ∑Fy = 100 = R1y + R2y ∑M2 = 0 = (-100 x 0.1) + R1 x 0.06 + R1y x 0.02 ∑M1 = 0 = (-100 x 0.04) + (-R2x x...
  23. B

    Truss Homework: Solving for Joint Forces using Method of Joints

    Homework Statement http://oi59.tinypic.com/2h65cm1.jpg[/B]Homework EquationsThe Attempt at a Solution [/B] All triangles: angles A = B = 53.13 degrees, angle C = 73.74 degrees from cosine law and the 180 degree ruleBut it looks like all of the joints in the bridge have more than 2...
  24. C

    Simple Statics Question: Truss Structure

    Homework Statement Homework Equations ∑M = 0, ∑Fx = 0, ∑FY = 0 The Attempt at a Solution If so, If so, I will be using the method of sections to cut along the red line as indicated in the picture. This gives me 3 equations of equilibrium as shown above. However, before solving these...
  25. T

    Finding Force in Element D-C of a Truss

    Homework Statement I've solved all but one force. I can't seen to get the force within element D-C. All relevant variables are shown on the pics attached i.e loads, supports, dimensions etc... Homework Equations Sum of forces in x=0, sum of forces in y=0, sum of moments=0 on Here are links...
  26. J

    Truss problem. How to calculate the force in the member?

    Briefly, I need to design a framework which would support a plug which is used to fill in the hole in water tank, 4.8m above the ground. In other words, 10.69kN load at angle of 30 degrees is therefore applied to the framework. So I came up with my design. The problem is that I get zero value...
  27. P

    Most Effective 7 Members Truss in Scilab

    Hello everyone, I'm attempting to come up with a way to calculate the most efficient 7 members truss layout using Scilab. The assignment is to make a highway sign support. It has to be L shaped and the truss system is only for the top horizontal part. Two supports. The sign is hanging at the...
  28. F

    Truss Analysis using joints method 2D analysis

    Given a warren truss, where the load is 2kN/m so the weight per joint is 10kN, since the ends are supported by ground not truss, can anyone please verify my way of solving for the tension and compression at point B. See attachment Your help is greatly appreciated. So I figured out that AB is...
  29. H

    Drawing Free-Body Diagrams for Pin-Jointed Truss Structures

    I have attached the problem as an image. I am unsure of how to draw the free body diagram of the truss structure. Would there be reaction forces in the Y-direction at the supports A and E? if there are, then the member AB would not be a two-force member. If there isnt, then Fy of the whole...
  30. SteliosVas

    Designing a Truss: Calculating Forces & Loads

    Homework Statement So we have to design a truss for our Civil engineering project, calculate forces in members using method of sections and method of joints. However as both trusses are symmetrical we only need to take one of them The truss is 45 meters long, 2.5 meters high, and 2.5 meters...
  31. gfd43tg

    Why am I only getting 4/24 points on my Truss analysis with Matlab?

    Hello, I have been working on this Truss problem and have not managed to get it right. I have checked my equations over and over and everything seems to check out, but I only get 4/24 on the autograder. Here is my paper worked out. Here is my Code. Because I don't like the opposite sign...
  32. L

    How to Solve a Space Truss Statics Problem with Ball and Socket Supports?

    Homework Statement A telescope mirror housing is supported by 6 bars in form of a space truss with geometry defined by the figure below. The total mass is 3000[kg] with center of mass being point G. The distance between: z axis and points A, B and C is 1 [m] z axis and points D, E and F is...
  33. A

    How can I properly constrain a 3D truss beam in ANSYS using only beam elements?

    Hello! I'm trying to model my truss with FEM using only beam elements in ANSYS, but I am experiencing difficulties with the constraints between the members (or coupling of the DOFs). For instance, I want my truss chords to be continuous and my lattice members to be pinned to them. I couple...
  34. D

    Virtual Work Method on a Truss

    Homework Statement I want to calculate the horizontal deflections at joints A and F (using Virtual Work method taught in Structural Engineering). Cross-Sectional Area (A) and E values are provided in the problem, and the attachment has all relevant dimensions and applied loads.Homework...
  35. V

    Will truss linkages diminish vibrations?

    Is it possible to have a body supported by truss linkages and isolate them from any stresses and impulses? Say, we are supporting a platform on the top of a set of rigid, pin jointed and cross-linked members. If small impulses act on the bottom on the linkages(upwards), is there any...
  36. B

    MHB How to Solve a Statics Truss Problem at Joint C Using the Joint Method?

    can you help me continue this problem. I'm stuck @ joint C. please use joint method. please click the image to fully view it. thanks!
  37. N

    Help understanding how to determine Compress or Tension in Truss

    Homework Statement A small square truss shown is supported by a pin joint at I and a roller at A. Label all members of the truss by Z (for zero force member), C (for compression) or T (for tension). Homework Equations The Attempt at a Solution So this was an exam question...
  38. N

    Help understanding Truss answer

    Homework Statement The truss is suspended by two pin joints. Each segment is 3 m wide and 4 m high. The applied force is F = 1 N. What is the force in member 2? Homework Equations Sum of force = 0 The Attempt at a Solution Using method of sections (to get force at 3), so...
  39. N

    Solving Simple Truss Problem: Find Reaction Force at A

    Homework Statement The truss is suspended by two pin joints at A and B. Each of the four segments is 3 m wide and 4 m high. Find the reaction force at A Homework Equations d The Attempt at a Solution sum of forces y = -ay + by -f=0 Can someone tell me what the moment at B...
  40. N

    What are the components of the reaction force at A for a truss bridge?

    Homework Statement For the bridge shown in the diagram, find the components of the reaction force at A. Homework Equations sum of force = 0 The Attempt at a Solution sum of force y = 0 = Ay+by-F=0 Moment at B = 0 =-Ay*4 +F*3 therefore Ay = 3F/4 and Ax =0 (roller)
  41. N

    Solving a Truss: Methodial of Joints

    Homework Statement The truss is suspended by two pin joints. Each segment is 3 m wide and 4 m high. The applied force is F = 6 N. What is the force in member 10? Include the sign for tension (positive) or compression (negative). Homework Equations T=rf sum of forces = 0 The...
  42. I

    Truss Analysis - Method of Joints

    Ok so first I considered the entire structure (which is in equilbrium) and resolved to find out that HA = -4.8 kN, VA= -0.9 kN and VE=0.9 kN. (these answers were correct according to mark scheme) Then I considered each joint separately (in order to find the forces in each of the members). I...
  43. T

    Solving Truss Force Issue: CD & DE Equal to 0?

    In the attached problem, I don't understand why members CD and DE are equal to 0. I was under the impression that the combined vertical components of BC and CD should equal 6+downward components of BC and EF, as to counteract the force straight down, but this is not the case. My questions...
  44. M

    What is a Short Link in a Truss (Statics)?

    My book has some questions involving "short links" connecting trusses to a support. It doesn't seem to explain what short links do. Can anyone shed some light? I attached a picture of what they look like. I really just can't find any information on what they do. Is it supposed to be very obvious?
  45. E

    How to Find Thrust in Truss Analysis with Hydraulic Rams?

    Homework Statement I am required to find the thrust exerted by the hydraulic rams CG and EB. A load of weight 8 kN is placed at F vertically downwards. The system is in mechanical equilibrium. AB = BC = CD = 2m. Homework Equations At mechanical equilibrium \sum F_x = \sum F_y = \sum M_a = 0 (a...
  46. R

    Statically indeterminate truss

    Homework Statement Calculate the member forces in the statically indeterminate truss. Member AF and BE is not connected at the intersecting point. The cross sectional area is the same for all the members. Illustration of...
  47. L

    How Can You Correctly Calculate Forces in a Truss Analysis Problem?

    Homework Statement As shown by the attachment we are given the distances and the 28kN force Homework Equations Relevent equations are equations of equilibrium; ƩFy & ƩFx = 0; ƩM = 0; The Attempt at a Solution First found By by summing the moments around point A; (clockwise...
  48. B

    Statics Question Moment for a Truss

    Homework Statement I need to find the moment about G. Please ignore the question in the image. http://img13.imageshack.us/img13/6086/4cv0.jpg Uploaded with ImageShack.us Homework Equations r X F The Attempt at a Solution Moment about G = -(30*800) + (-300*50) + 60 A + 17.32*500 +...
  49. M

    Method of Joints Truss Analysis

    Hello, I was curious, for the method of joints truss analysis, when considering a joint, is it assumed that all forces at that joint are radiating away from the joint (meaning tension), even if it was already found from a previous joint that the member is acting in compression? I'm not sure if...
  50. Y

    Statics: Forces in a truss, method of joints

    Homework Statement Using the method of joints, determine the force in each member of the truss shown. State whether each member is in tension or compression. Homework Equations ƩFx=0 ƩFy=0 ƩM=0 The Attempt at a Solution I got the forces at C and D by using the equilibrium...
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