What is Bridge: Definition and 481 Discussions

A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually something that is otherwise difficult or impossible to cross. There are many different designs of bridges, each serving a particular purpose and applicable to different situations. Designs of bridges vary depending on factors such as: the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, and the material used to make it and the funds available to build it.
The earliest bridges were likely made with fallen trees and stepping stones. The Neolithic people built boardwalk bridges across marshland. The Arkadiko Bridge (dating from the 13th century BC, in the Peloponnese) is one of the oldest arch bridges still in existence and use.

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  1. N

    Properties of Plank wood & bridge question

    Hello everybody, For a group project, we are supposed to propose several designes for a plank bridge over a river. I've tried to find this material's (plank wood) strength properties, or a stress-strain diagram to no avail. Do you know where I can find it? Also, is it reasonable for a...
  2. jtbell

    News Psst Want a new bridge? For free? :-)

    From The Economist, the saga of a proposed new bridge linking Detroit, Michigan with Windsor, Ontario: They aren’t building that: Michigan is getting a swanky new international bridge. Canada is paying
  3. M

    Is the Current in the Middle of a Balanced Wheatstone Bridge Always Zero?

    Homework Statement Show that the current in the middle is zero if all the resistors are equal The Attempt at a Solution KVL for left and right: V - R*i1 - R*i2 = 0 V - R*i3 - R*i4 = 0 i1 + i2 = i3 + i4 KCL: i1 + i3 = i2 + i4 i1 + iG = i2 i3 = iG + i4 I must prove that...
  4. A

    Bridge to abstract math: what is wrong with following proof

    See attached picture. The question asks to prove that the statement which I have written on the first line is true. But I somehow proceeded to proving it is false. Basically what I did was simplify the given expression into the form (P or Q) => R and said this is equivalent to (P=>R) ^...
  5. ElijahRockers

    Solving Wheatstone Bridge: Find Detector Current i_d

    Homework Statement Find the detector current i_d in the unbalanced bridge in the figure if the voltage drop across the detector is negligible. The source voltage v_g is 180V. Homework Equations The Attempt at a Solution I am not sure what to do, or even how to find the...
  6. E

    Single phase half bridge converter working help

    why are we using two diodes instead of two scrs in a single phase half bridge converter? What difference does it make? (say in my attachment s2 and s3 are diodes instead of scrs?) Wont we get the same operation with two scrs itself (only thing you have to fire them together with s1 and s4). I...
  7. T

    Repairing the Chesapeake Bay Bridge

    I recall several years ago a ship damaged the Chesapeake Bay Bridge by plowing through it and taking out several sections. I have always wondered how they fixed the piling that supports the structure. Since both ends of the damaged portion of the bridge remained, the pilings in the damaged...
  8. 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...
  9. G

    Bridge design conceptual questions

    Homework Statement I'm designing a Pratt Bridge (http://www.garrettsbridges.com/photos/pratt-truss-bridge/attachment/pratt-truss-bridge-2/). It must be able to hold 10,000 lbs at pins every 5 feet and be 40 feet long. 2. Homework Equations / 3. The Attempt at a Solution I know how to...
  10. Femme_physics

    Engineering Why is a bridge rectifier necessary in this circuit?

    I am told that in this circuit (above pic) we shortcircuit D1 and D2, and disconnect D3 and D4... then we are to calculate Vrl(average) But the way I see it, if we shortcircuit D1 and D2 the entire circuit is shortcircuit and current only flows like this (below pic)...
  11. P

    Bridge rectifier based mains (line) frequency doubler for an induction motor

    I want to get a larger flow rate out of a common 3 speed induction motor desk fan. Without forking out for an off the shelf VFD, I thought perhaps I could build a frequency doubler using a bridge rectifier. Following the circuit from left to right, I'm thinking that I'll feed the 240V...
  12. J

    Difficult Schedule to Bridge Gap

    Hello everyone, I am one of those non-majors trying to get into graduate school (eventually). Long story short, I have a year left as a business major, during which time I will be taking Calculus 2 and the introductory physics w/lab sequence. I have recently met with both the graduate...
  13. K

    Alternating Current Wheatstone-like Bridge

    Homework Statement The goal of this problem is to find a frequency at which the voltage drop across several components of a circuit will be zero. The circuit is identical to a wheatstone bridge (where two pairs of two resistors in series are wired in parallel) except that opposite...
  14. J

    Oscillation - car losing contact with bridge

    Homework Statement See attachment Homework Equations The Attempt at a Solution Ok so as the bridge is at a point ABOVE eqm acceleration is DOWN and at some point ACC down is greater than gravity acceleration. This is all true but makes no sense to logically. How could the car...
  15. F

    What Makes the Wheatstone Bridge Ideal for Measuring Small Resistances?

    I'm struggling to understand what makes the wheatstone bridge such a good circuit for measuring small resistances. Essentially the bridge is just two voltage dividers and the output voltage is the difference between the two dividers. Ok so the only advantage I can see over a conventional...
  16. O

    Bridge Circuit, Solving 5 Equations

    Homework Statement So I'm trying to solve for all of the currents in a bridge circuit (in terms of the input current and all of the resistances), and by using Kirchhoff's Laws I've got 5 equations that I can use to solve for my 5 unknowns. Unfortunately, I've never really solved this many...
  17. S

    Measuring inductance with Anderson's bridge

    Homework Statement This is more to do with an experiment I'm failing terribly at rather than a direct homework question. I could not find the right section to ask this in. Investigate the inductance of inductors with cores of Perspex and Copper using an Anderson's bridge. For Perspex, compare...
  18. T

    Load on Bridge Trusses for Intro to Engineering

    Homework Statement Calculate the load on each member Homework Equations \sum \tau=0 -because it isn't rotating. \sum F =0 - because it isn't moving. \tau = Fd\sin \theta - to take the torque at any point The Attempt at a Solution I can calculate the torques at each point. I...
  19. S

    Need help with factors affecting suspension bridge failures

    ive read articles and it says that the tacoma suspension bridge failed because of its length and it being too thin so when the wind blew on it it fell. an question i have to answer from school is investigate bridge failures and explain why they failed using physics principles so exactly how...
  20. C

    Router, bridge, or repeater for long distance wireless?

    Greetings, What will give the best connection over very long distances, miles? A router, ethernet bridge, or repeater? And why? I am going to use a dish antennas and transmit at 1 watt. Thanks
  21. EVriderDK

    Circular motion. Uniform and accelerating. (Bridge)

    Homework Statement A bridge takes 2 minutes to open up fully from 0 to 80 degrees. The first 20 degrees it is accelerating, and the last 60 degrees it is traveling with even velocity. I will have to find acceleration for the first 20 degrees and angular velocity for the last 60 degrees...
  22. D

    Thevenin equivalent for strain gauge bridge

    A strain-gauge bridge is made up of four resistive elements, each element having an unstrained resistance equal to R, as shown in the diagram below. When a strain is applied to the bridge elements R2 and R4 increase in resistance by an amount ΔR, whereas R1 and R3 decrease by ΔR, where...
  23. C

    How Do You Calculate UAB in a Wheatstone Bridge with Changing Resistance Values?

    looking for some help for the second part of this question. i got 60 ohms for part one the answer to part 2 shows (delta v = 4.44mv) not sure how to calculate this or what is voltage resolution. regards
  24. 3

    Salt Bridge & Voltaic Cells Experiment

    I did an experiment testing the thickness of a salt bridge (made of filter paper soaked in potassium nitrate) on the voltage produced from Zn and Cu half cells. This is similar to a thread someone made back in 2007. But I have no idea how to explain my findings or whether the thickness...
  25. K

    Statics problem - bridge made of 2 segments

    ƩHomework Statement Bridge consist of two identical segments M and N connected by rods as shown in the picture. Each rod makes angle of 45° with the horizontal line. Determine the axial forces in each rod due to the load P at point G. http://img266.imageshack.us/img266/2156/62688168.th.jpg...
  26. F

    Varying Resistors in Bridge Circuits?

    What happens to the system response if all four resistors are equal. One of the resistors is an RTD.
  27. P

    Build a Balsa Bridge to Hold 20 lbs | Advice & Tips

    Im building a balsa bridge for class but I'm struggling to find a design. The bridge must hold 20 pounds and have a trapezoid clearance. the minimum length is 14cm and the max is 20cm, min to max height is 5-8cm. Width must be 3cm. Here is my design so far, I would build two of these faces and...
  28. C

    Wheatstone bridge with inductances

    Homework Statement Homework Equations Assume we have Vab. Junction Rule: I1 = I3 + I4 => I'1 = I'3 + I'4 I5 = I2 + I3 => I'5 = I'2 + I'3 Loop Rule: V - L1I'1 - L4I'4 = 0 -L1I'1 - L3I'3 + L2I'2 = 0 V - L1I'1 - L3I'3 - L5I'5 = 0 V - L2I'2 - L5I'5 = 0 The Attempt at a...
  29. R

    Why Does Fullwave Bridge Rectification Raise Voltage by 1.41?

    ..fullwave bridge rectification raise the voltage *1.41? I scanned the net but I can't find an explanation as to why, only that it does..
  30. P

    Choas and the bridge from Classical to Quantum physics

    Has there been work done exploring the possible connection between chaotic systems and quantum mechanics? Chaos basically tells us that an infinitesimal change in initial conditions, given enough time, will lead to complete different solutions - another way of stating that is over enough...
  31. S

    Communicating Through an Einstein-Rosen Bridge Without Causality Violation

    Is it possible to communicate through an Einstein-Rosen bridge without violating causality? I suspect that it is possible as long as time dilation occurs during the process of moving one end of the bridge at relativistic speeds as in the following scenario: Imagine an Einstein-Rosen bridge that...
  32. M

    How Does Switching the Battery and Galvanometer Affect a Wheatstone Bridge?

    When we talk of a Wheat Stone Bridge, we say that if the two pairs of resistances in the top row, and the two in the bottom row have the same ratio of the value of their resistances, then no current flows through the connecting wire in the middle. But, that applies if the current is entering...
  33. S

    What is the maximum load current for a bridge rectifier?

    Homework Statement I am in the midst of preparing for my midterm which is tomorrow, and I was going over a past midterm that has the solutions. However, there is one conceptual problem that I am not understanding, in fact, I think it is wrong... The diodes in a bridge rectifier have a...
  34. B

    Arch Bridge Shear and Bending Moment?

    This is my first course in Engineering and the professor told us today that we have to do shear and bending moment diagrams for an arch bridge. Anyone have any clue on how to do this? He gave us no information on how to do it and nothing in a book. Please help??
  35. S

    Half-wave Bridge Rectifier: How to Determine Average Output Voltage?

    Homework Statement Hello all, Looking for some help regarding half wave bridge rectifiers. I'm having trouble grasping how to determine the average output voltage for the sin function. Let Vd=voltage drop across the diode. Let θ=angle conduction begins. Let Vs=denote the ac supplied...
  36. M

    3-regular (cubic) graphs with a bridge

    How can you prove that a cubic graph with a bridge cannot be 3-edge colored? I guess one could try a proof by contradiction, so we assume a 3 edge coloring is possible for such a graph. But then I am not sure in which direction to continue. I have tried to draw such graphs, and clearly...
  37. L

    Wheatstone Bridge Calculation

    Homework Statement A strip of high-strength steel has a length of 30 cm and a cross section of 1 mm by 20 mm. The modulus of elasticity is 200 GPa, and Poission's ratio is 0.25. It is subjected to an axial load of 15,000N. It is instrumented with two axial strain gauges with R=159Ω and a gauge...
  38. M

    Unbalanced Wheatstone Bridge voltage across resisitors

    Homework Statement It is a qualitative problem. No values are given. In an unbalanced Wheatstone Bridge, does the voltage across the resistors R4 and R2 change? In other words is Vr2of balanced bridge=Vr2 of unbalanced bridge? likewse for R4. Homework Equations The Bridge Balance eqn...
  39. M

    Understanding the Voltage Changes in an Unbalanced Wheatstone Bridge

    In an unbalanced Wheatstone Bridge, does the voltage across the resistors R1 and R2 change? In other words is VR2of balanced bridge=VR2 of unbalanced bridge? I was trying to solve a problem that required qualitative analysis. It says VR2 does not change even though the bridge is unbalanced...
  40. J

    Concrete bridge pier formwork design

    Homework Statement I have to design the formwork system for an octagonal bridge pier similar to the type shown below, plus a headstock. http://img577.imageshack.us/img577/5743/prexconcretebridgecolum.jpg Homework Equations The Attempt at a Solution I can use any system I...
  41. S

    Norton Transform on a Wheatstone Bridge

    I have been trying to find the norton equivalent of a wheatstone bridge with the "bridge" resistor as a the load. The Bridge is unbalanced. How do i find the current through the load when it is shorted to find the norton current? It seems easy , but i haven't found any ways of doing it. I...
  42. A

    Rechargable galvanic cell?[remove the salt bridge}

    Rechargable galvanic cell??[remove the salt bridge} In a galvanic cell,a salt bridge is used to maintain potential difference between the two half-cells.Now,once the charge accumulation is maximum,then even the salt bridge cannot maintain potential difference.At this point,what if one removes...
  43. G

    How does a salt bridge prevent charge buildup in a galvanic cell?

    As electrons leave one half of a galvanic cell and flow to the other, a difference in charge is established. If no salt bridge were used, this charge difference would prevent further flow of electrons. Why would the charge difference prevent further flow of electrons ??
  44. W

    DESIGN THE BEAMS for a cheap bridge

    Need to build a bridge 20 foot wide gully. The bridge is 4 ft wide and will be constructed of four by eight ft plywood sheet which is placed on top of 2 composite beams that are 4 ft apart (see link for picture).The 2 composite beams need to take all the load which is 500 lb/ft distributed over...
  45. B

    Measuring Resistance: Bridge Deck Steel Bars & Wire

    Hello, I had to measure the resistance between different sets of bridge deck reinforcement steel bars using a Wavetek HD110T multimeter and a wire. The values varied between 1.9 to 2.8 ohms. When I measured the resistance of the wire itself, it came out to be 2.1 ohm. I could not...
  46. G

    Finding the time for a splash to reach a bystander on a bridge

    Homework Statement My problem is the last one, but it is a continuation of these first two problems, so I thought I'd include them. In Mostar, Bosnia, the ultimate test of a young man’s courage once was to jump off a 400-year-old bridge (now destroyed) into the River Neretva 27 m below...
  47. F

    Ivy Bridge processor and socket 2011/X68 chipset

    The Sandy Bridge processors are not significantly faster than the Nehalems, and they only had dual-channel memory. There is a noticeable difference in performance, but it really isn't worth upgrading. Hopefully, the HUGE performance boost will be with the 8-core/22nm "Ivy Bridge" processors. I...
  48. C

    Structural Supports on a bridge

    Homework Statement A 200 kg walkway is supported by the structure shown in attachment. The walkway is 5m long and the vertical support is 1.5m long. a. What angle are the diagonal supports from horizontal? b. What is the compression in the vertical member? c. What is the tension in the...
  49. F

    Ivy Bridge triple channel memory?

    The Sandy Bridge only has dual channel RAM, which is why the Nehalem pulls ahead in memory-intensive applications and benchmarks. Will the Ivy Bridge include triple-channel memory? The Ivy Bridge is a 22nm die shrink of the Sandy Bridge. And when will the 8-core chips from AMD and Intel be...
  50. L

    Suspension Bridge Parabola Problem

    Please help me. I can't figure out how to solve this problem. The cable of a suspension bridge hangs in the form of a parabola when the load is evenly distributed horizontally. The distance between the two towers is 150m, the points of support of the cable on the towers are 22m above the...
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