# What is Statically indeterminate: Definition and 44 Discussions

In statics and structural mechanics, a structure is statically indeterminate when the static equilibrium equations - force and moment equilibrium conditions - are insufficient for determining the internal forces and reactions on that structure.

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1. ### Engineering Struggling with a Structural Analysis Problem?

Diagram of the problem below. I have 45 minutes to finish all parts of this question without reference material. The Mechanics of Materials section of these tests are largely Structural Analysis, which I was not taught to this level in my undergrad degree so I am teaching myself via Youtube...
2. ### Engineering Statically indeterminate shaft

I have drawn the bending moment diagram to try to help me determine the moment, but I am certain my values are wrong. I have included a picture of my gearbox design, where the bottom shaft is what I'm trying to calculate. I've been able to calculate the top shaft moments and reaction forces...
3. ### A Statically indeterminate systems

I am interested in the following question: whether we can use the principle of virtual work to solve approximately (in the limit of small deformations) the statically indeterminate systems or this principle is ultimately equivalent to the the system of the independent equilibrium equations?
4. ### Shear Force on Bolts mounting gearbox to engine

Hello, I have designed a gearbox that bolts on to a fixed engine and fixed pump. It is completely supported by them. The total mass of the gearbox and the components attaching it to the engine and pump is 7.7kg. Its centre of mass is 0.167m along the x-axis and 0.09m along the z-axis from the...
5. ### Statically Indeterminate Truck - Finding reaction forces at supports

If you do the sum of vertical forces and sum of moments, you're always left with an unknown. Vertical Forces: Ray + Rby + Rcy = 59kN + 45kN (1) Sum of Moments about A: (59 x 1.85) - (Rby x 3.7) - (Rcy x 4.8) + (45 x 6.5) = 0...
6. ### Statically indeterminate beam problem

Homework Statement Homework Equations Beam problem Deflection Statically indeterminate The Attempt at a Solution Am I correct? Or should the assumed deflection at B be the difference in deflection between B and C? Thanks
7. ### Mechanics of materials: Statically Indeterminate member

Homework Statement Find reactions at ends and deflection at C Homework Equations RA + RE = 115kN ##\delta##Total = ##\sum## (PiLi)/(AiEi) The Attempt at a Solution RA + RE = 115kN Then apply superposition: (Get rid of RE) divide whole member into 4 elements and add. ##\delta##Total =...
8. ### Mechanics of Materials: Statically Indeterminate Problems

Homework Statement Hi! So my question isn't really about a specific problem, but more of when to use which method. I'm having trouble knowing when to use the method of super position, the force method, or just being able to go straight into just writing the equilibrium equation and the...
9. ### Statically indeterminate or statically determinate

Homework Statement in this question , it's stated in the beginning that there are 6 reactions ... But , the author gave the equation r = n +3 , r = 4 , n = 1 ...It's statically determinate ...Homework EquationsThe Attempt at a Solution IMO , the author's is wrong . his original 's intention is...
10. ### Mechanics, statically indeterminate reactions

Suppose I have a beam and I would like to constrain it (two dimensional structure). At one end I've chosen to use support which constrains motion only in "x" and "y" direction (horizontally and vertically), but it doesn't prevent a body from rotation. Because of that, another beam's end have...
11. ### Civil Engineering - Bar Question

Hey everyone, I'm at my limits here trying to solve a question, I can't seem to figure out how the lecturer gets the solution to the following problem... Can someone please direct me the correct methodology or better yet give me some guidance on what to do? Thank you. The Questions and...
12. ### Statics: Statically Indeterminate Unstable Plane Truss

Homework Statement The signboard truss is designed to support a horizontal wind load of 800 lb. If the resultant of this load passes through point C, calculate the forces in members BG and BF. [/B]Homework Equations For a solution using the method of sections for plane trusses,any three...
13. ### Moment and reaction of shaft - Statically Indeterminate

A shaft of diameter 10 inch is supported by 3 ball bearings. An external force (F, given) from pulley (diameter not given) also acts on the shaft. The supports are subjected to bending load (moment and transverse shear) and torsion load due to pulley. Yield Stress at Tension given. Assume no...
14. ### Statically indeterminate tube in Torsion

Hey guys. It's been a long time since I've done anything beyond a simple shear stress calculation, so have what will hopefully be a basic question. I've found similar examples but not ones I was confident I could apply to mine. As per the dodgey paint sketch I've made below, I have this...
15. ### Statically indeterminate (deflection)

For these types of question, I know deflection equation is needed to find the reaction. However, my question is that when should i use the max. deflection equation and when should i use only simple deflection equation for my calculation ? Thank you very much!
16. ### Statically indeterminate problem

Homework Statement Calculate the stress in every segment of the system. AD and BC are laton and AB is steel. Homework Equations geometry compatibility-δ(A/D) +δ(A/B) - δ(C/B) = 0 F(D) - F(C) - 50 =0 The Attempt at a Solution I supossed that DA and BC are in compression and AB is in...
17. ### Statically indeterminate axially loaded problem

Homework Statement stat indet.jpg Homework Equations FAB = FBC etc... The Attempt at a Solution FAB = FBC + 300kN = FCD = FDE + 600kN Sorry for another post. I'm really not sure where to go with this one...
18. ### Axial Deformation on Statically indeterminate beam

Homework Statement I am trying to find a solution to the below attached image. The area for AB=CD = 0.8m^2 Area of BC = 0.3m^2 Force at B = 140 kN (left) Force at C = 60 kN (right) AB=CD = Concrete with a E of 25,000N/mm^2 CD = Steel with an E = 200,000N/mm^2 Homework Equations PL/AE The...
19. ### Cantilever statically indeterminate beam with point load

hi please if anyone can tell me how i can get the following equation (attachments) of deflection for statically indeterminate cantilever beam with point load (attachments). I'm not an engineering student and having difficulty in coming up with boundary conditions. looking for help. thanks
20. ### Axial deformation of statically indeterminate bodies

Hi can someone please guide me to an explanation of axial deformation of indeterminate bodies and the method of forces in that too Thanks Chirag
21. ### Statically indeterminate built in beams

Hi, I don't know if anyone can help. I would like to be able to calculate the bending moment and deflection of a beam that is: Built in on both ends (no rotation) It has 2 different distributed loads not equ ispaced along the beam and has 2 point loads which are also not eqi spaced. I can...
22. ### Calculating the moment along a statically indeterminate beam

Homework Statement How could I calculate the piecewise formula for M(x)? Homework Equations The Attempt at a Solution From constructing a free body diagram it looks like up until the pin support, M(x) = -Fy*x (Fy being the force pointing upwards at the wall) but I am confused...
23. ### 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...
24. M

Hello, I was wondering why it might be advantageous in some applications to create a structure that is statically indeterminate? Thanks
25. ### Statically indeterminate beam

1. How do I find an expression for the reaction force (Xc) in C? The beam is fixed in A and there is a roller connection in C. The roller connection is placed at the center of the beam. Length of beam is L. The beam is loaded with a triangular load from A to B (Q kN per meter). Illustration...
26. ### 2 span beam with 2 points loads. Statically indeterminate?

Hey guys, I'm just pondering a beam problem fir a structure that I'm analysing. It appears statically indeterminate to me? The beam is bolted to a support at locations A,B & C. There are two point loads between span B-C. There are no symmetrical distances or support locations etc. Initially...
27. ### Statically indeterminate fixed end beam problem

Im having difficulties performing stress analysis on a component i designed for a project. I've ran FEA in solidworks giving me the Von Mises stress and the displacement due to the load. My supervisor has asked me to back up the fea with hand calculations but I am have a hard time. The part...
28. ### Statically Indeterminate Shaft

Homework Statement Determine the load (vertical only) on the three bearings at A, B and C. The shaft is loaded at one end with force F (see attached diagram).Homework Equations Cantilever Beam Deflection Deflection at End = PL^3/(3EI) Deflection at Point X = Px^2/(6EI)*(3l-x)The Attempt at a...
29. ### Statically indeterminate beam (fixed ends) and the moments at the supports

I'm working through my professor's solution for this problem, and I don't understand how he comes up with the reaction force at B without taking into account the moment at B. Any help would be greatly appreciated. http://img832.imageshack.us/img832/6953/sibi.png [Broken]
30. ### Determining a statically indeterminate structure

Is this structure statically indeterminate? I'm thinking it actually statically determinate, since there are three unknowns (Ax, Bx, By) and three equations. The external loading Px, Py are known. I also solved for the forces in the members of the truss and they seem to work out, but my...
31. ### 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...
32. ### Understanding statically indeterminate beams

As a physics student, I never came across the following problem: A uniform beam of mass M and length L rests on three identical supports: one at each end of the beam and one in the middle. What are the forces of reaction on each of the supports? I now realize that that was the case because...
33. ### Statically indeterminate beam question

I have been trying to solve this question using the superposition method, but cannot seem to get the correct answer. Can anyone help? Question & formulae are attached. Cheers, G
34. ### Statically Indeterminate Beam

I have a fixed-end fixed-end beam with two roller supports as well and a load applied in the center of the beam, as shown below. I've chosen my redundant forces to be the force at B (point up), the force at C (pointing up), the force at D (pointing up) and the moment at D...
35. ### Statically Indeterminate Beam to the Sixth Degree

As the title says, I have a statically indeterminate beam to the sixth degree and I'm attempting to use the superposition method (aka force method) to solve for the reactions. My additional equations will be the angle at points A, B, C, and D as well as the deflection at points B and C. Is...
36. ### Cantilever beam (statically indeterminate)

hello everyone, i have a small problem in calculating a particular loading case of a cantilever beam which is shown on the attached image. i have found many loading cases of cantilever beams which i am able to solve, however for this one i couldn't find anything unfortunately. the bending...
37. ### Is this another statically indeterminate structure?

Is this another statically indeterminate structure? (urgent) Homework Statement [PLAIN]http://1.bp.blogspot.com/__d7SU8yZ6pk/S4JApel7HdI/AAAAAAAAAKo/NhmSNIOxNik/s1600-h/IBq4.jpghttp://1.bp.blogspot.com/__d7SU8yZ6pk/S4JApel7HdI/AAAAAAAAAKo/NhmSNIOxNik/s1600-h/IBq4.jpg [Broken] Homework...
38. ### Statically Indeterminate Bar with alternating area and length

http://img197.imageshack.us/img197/5981/probie.png [Broken] So first I did a force balance (dFx=0) P=PB-PC=8.5kN RD= RA - P RA = RD + P I know the total change in length is equal to 0, so dAB + dBC + dCD = 0 ==> (RA*L1)/(E*A1) + (P*L2)/(E*A2) + ((RA-P)*L1)/(E*A1) = 0...
39. ### Need help with a Statically Indeterminate System

Homework Statement Three steel bars are pin-connected to a rigid member K. Determine the force developed in each bar. Determine the load carried be each of the tension members and the elongation of each member http://img3.imageshack.us/img3/6850/problemdiagram.jpg [Broken] Known...
40. ### Statically Indeterminate Systems

Homework Statement A composite shaft consists of a brass bar 50mm in diameter and 200mm long, to each end of which are concetrically friction-welded steel rods of 20mm and 100mm long. During a tensile test to check the welds on the composite bar, at a particular stage the overall extension...
41. ### Statically Indeterminate Torsion Members

Homework Statement A solid circular bar ABCD with fixed supports at ends A and D is acted upon by two equal and oppositely directed torques T_0. The torques are applied at points B and C, each of which is located at a distance x from one end of the bar. (The distance x may vary from zero to...
42. ### An introduction to the analysis of statically indeterminate systems

It is assumed that the reader is familiar with the basic concepts of structural analysis. Further on, I am aware of the possible inconsistencies and errors in this writing, and hereby invite all who have comments and objections to contribute and help to make this small tutorial useful for...
43. ### Statically Indeterminate Stepped Bar Problem

I've been having difficulty with this problem for the past 5 hours. I am understanding some part, but I can't get the final answer. http://img223.imageshack.us/img223/1103/1015zz1.th.jpg [Broken] This is what I got so far: EFx = Ra + Rb - P = 0 Ra + Rb = P Sab = Sac + Scb =...
44. ### Statically Indeterminate Problem

Before you start going through equations and trying to solve this I just need a simple question answered about this problem. 1) Is it correct for me to assume that the pressure on both walls is equal? If so, I think the normal stress of the aluminum and steel bars are equal. Problem...