paraphrase
azizalwasmi
ansys_2_report.docxAbdullah Alhusainan ME3070
Introduction:
The aim of the technical report is to illustrate an appropriate details and analyses of bridge construction for Highway Agency.
Figures 1(a) and 1(b) show the part cross-section and plan of an integral concrete construction bridge which is 24.0 m wide, 150.0 m long in skew-span and 1.0 m thick. The bridge itself is horizontal in the x-y plane and comprises 8 road carriageways which usually carry a range of car and lorry traffic travelling in both directions. This structure may be considered supported by rotational and sliding bearings along each of the respective opposing skewed ends as shown in Figure 1(b).
Fig 1(a) – Part cross-sectional view of bridge deck
The construction style is a contiguous ‘slab-and-beam’ where the slab-deck is supported at periodic intervals by integral precast bridge-beams. The structure incorporates 25 off M2 design bridge-beams supporting a 200 mm thick deck and 500 mm wide by 600 mm deep string-courses that form the ‘edges’ with all these features manufactured from concrete. For modelling purposes both the pavement and carriageway may be represented by a 100 mm thick asphalt layer between the string-courses, and the bridge may be modelled satisfactorily as a series of plate-elements integral with supportive beam-elements.
.1 Deformed Bridge:
This picture shows bridge collapse in Arizona US, and our bridge has deformed
.2 Bridge Specification:
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Location |
Birmingham, UK (B2 4PE) |
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The bridge will be constructed on LAND |
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Concrete |
Asphalt |
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E =
V = 0.1 |
E = 0.5
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M2 Beams |
25 of M2 Beams are used |
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.3 Bridges:
Bridges, there are many types & many ways of building bridges, in water, land, air ETC. each type of them has its own conditions & specification. With no doubt all bridges need to be constructed with a foundations, which are the supporters.
.4 Bridge Loads:
Beam is the most common type of the bridges that carries a vertical loads by deforming. It undergoes horizontal compression on the top. Within the same time the bottom of the beam is in tension.
Bridge Loadings
Live loads:
· Normal loads.
Dead loads:
· Weight structures.
Environmental Loadings
· Temperature effects.
Boundary conditions must be taking carefully.
· Wind exposure.
2.1 Typical bridge design:
Take a consideration of the form of the design of the bridge, land, water or air:
· Land would include the geological features.
· Air would include connecting between high buildings.
· Water would include rivers of the sea.
Steel is the most effective & versatile material for building a bridge. It can carry loads in compression, tension & shear. There are many types of structural forms, which available to the designers and the most essentials ones are:-
· Beam Bridges.
Deck bridge design: is a roadway, that has surface with one structural elements of the superstructure of the bridge.
· Concrete Box.
· Arch Bridges.
2.2 Bridge design options:
Concrete Box: it is a bridge that has the main beams if it comprise grides of the shape box.
Arch bridges: this bidge has a shape like a curve, where the loads are ditributed partially in horizontal thrust.
Beam slab: It is a system that has a concrete floor which supported by reinforced beams.
3.1 Bridge Assumptions:
A number of assumptions have been made to simplify the analysis which are:
· Pressure loads and axial loadings are the only forces has been exerted on the structure.
· All the loads are transferred into the structure through nodes and element.
· The calculation made based on two dimensional structural model.
· The string course was not include on the calculation because it does not have a big influence on the final deflection.
· The asphalt load was considered as uniform distributed load on the analysis.
· The lorry load was taken as a point load acting at the middle of the lorry distance.
· The total deflection was calculated from combining the results from the UDL deflection & point load deflection.
· Environmental loads and live loads were not involved in the main analysis.
3.2 Hand Calculation:
56.5m
93.5m
180 Tonnes
Where:
Length (L) = 150 000 / Young’s Modulus (E) = 15000 / Second moment of Area (I) = 4.85
Point load of the lorry (p) = 1765800 N
Omega () = 4.5204 / Distance of the point load form the bearing constraint (b) = 56.5
· The deflection for the UDL is:
· The Deflection with a point load is:
4.1 2D Crude Analysis
2D crude was undertaking and it shows the vadility with the hand calculation as in the calculation 10.24m, where in the ansys 9.1m which that means the 2D crude more less the same.
Figure 1 deflection for UDL
The figure below shows the 2D crude with the point load inserted, and it proves the hand calculation, where it is 39.37 m and the ansys is 35.13 m so the difference is 4 m.
Figure 2 Deflection of Point load
5.1 Final 3D Analysis:
3D finite elements analysis shows the understanding of the load under different types of situations with a different conditions. The maximum deflection has been obtained as the below figure shows 122.943 m. So the beam was calculated with the thickness of 3.84 mm, and it has been done by the Ansys software.
Finite element method is one at the methods that applied and used to verify the behaviour of any part of the beams.
Figure 3 3D Bridge
Taking the 3D finite elements analysis of the beam under consideration leads to the capabilities of simulation. This would help the industry in present and future in changing their designing. This method confirms the product is done and it shows the disadvantages and advantages of the product to make sure that the costumer knows the requirement with knowing the basic ideas and concepts.
5.2 Comparing 2D analysis & 3D analysis:
As it has been known that the maximum deflection of 2D crude analysis of the asphalt is 9.1 m and the 2D crude analysis with a point load is 35.1 m, and that shows the failure. Where in total of the maximum deflection is 44.2 m (Ansys) and 49.61 m (Calculation), where the maximum deflection in 3D analysis in the Ansys is 122.94 m. and that means there is failure in this bridge. There some differences between the hand calculation and the Ansys that because some minors errors that lead to the differences.
6.1 2D crude analysis with constraints:
The concrete load and the weight were added, firstly the constraints have been added at the middle of the bridge to check the deflection, and then every 25 m in span there was a key point to locate the constraints path. So the same procedure have been followed until the answer of the deflection came reasonable which is 0.064 m, and it is under 0.5 deflection of span which has been notified.
Figure 4 2D Deflection of span with constraints
To verify every 25 m of span there was a constraint to assist the bridge from failure and to give a better representation. Where (4.1) 2D crude without constraints it failed because there was not any forces to hold the bridge and to prevent it from failure. Like it has been mentioned before the limit of the deflection 0.5 m and the answer was 0.064 m, that means the process and the procedures were reasonable.
6.2 3D analysis with constraints:
This part includes asphalt, truck load and the bridge srtucture, which has combined the beam and the deck bridge.
So basically, the same process that has been used In (6.2) 2D crude with constraints should be done the same way here. And that’s how the answer has been obtimized, which is 0.0772 m. taking under consideration that the answer should be under 0.125 m, because of , where and that shows the maxmimum deflection under the safety factor. So every 25 m there was a constraint along all the bridge as it has be shown in the below figure, with pressure (1177.2 Pa) and the force (1765800 N).
Am in the first lane and the distance that’s given is 50 m, and the truck load is 180,000 Kg). the length of the truck is 13 m/ 2 = 6.5 m + 50 m = 56.5 m and that is where the forces are acting in the bridge, as it has been shown in the firgure below. So the forces have been set on 4 nodel elements and each force acting on element with on each element.
Figure 5 3D Bridge with constraints
So the figure 5 shows the structure and the supporters correct and in a correct location, because it is below the safety factor as it has been mentioned before. To make the bridge has more stiffness and stronger this procedure must be followed to get more correct. From the deck design this would make it better reasonable. This means thedeck bridge desgin is with in the safety factor, and stiffer. This deck bridge design and calculation were done successfully.
7.1 Conclusion:
Doing the 3D finite elements analysis of the deck design bridge, gives the ability of easier designing and gives good understanding of using a simulation, also it gives a technique which makes easier understanding of weather the design works or not. So overall, this deck bridge design went successfully after the supporters, which means it will hold enough under a several conditions. As engineers it is must be to understand the FEA (Finite Element Analysis) to help better creating designs and accurate designs. Using this kind of technique gives many benefits for the designers, and it gives many options that will make the results more precise and accurate. This structural process has led to better solution for a complex problem in the Ansys. This software is appropriate for a complex and big engineers problems. The FEA is a method that finds a suitable solution, and gives better results.
The FEA uses its own method to estimate the result and it gives an estimation of the real forces & other stuff. This technique illustrates weather the product or the design will fail or has enough rigidity. The FEA breaks things down to simplifier image, where it makes clearer for the designers.
As the figure above shows how the FEA works in general, and how it gives an accurate results. I highly recommend to use the FEA to work out an engineer complex problems. Overall, errors are common which in every calculation can be found, which the accidental or random mistakes. It has been known that any software has some glitches and that causes some errors will be done with errors. Figure 6 3D bridge with constraints with a different view. Overall, the hand calculations were proven, by comparing to the results and there are a small differences between them.
8.1 References:
http://www.steelconstruction.info/Bridges
http://encyclopedia.thefreedictionary.com/Arch+bridges
https://en.wikipedia.org/wiki/Box_girder_bridge#/media/File:Concrete_box_girder_bridge.JPG
http://www.ukessays.com/essays/design/analysis-on-beam-design.php
http://www.colorado.edu/MCEN/MCEN4173/chap_01.pdf
http://www.autodesk.com/solutions/finite-element-analysis
