Archive for november 2008

Parametric model of structural system
november 26, 2008

structural-modelIn order to analyze the relation between form and forces, we have modeled a bridge segment. Each bridge segment is a closed structural system supported vertically at the ends. The continuity of the cables from segment to segment serves only visual purpose. This model has shown us, that this visual continuity can only be maintained in a “front view” like when looking at the bridge from afar.

At this state, the model does not contain structural analysis. Only the geometry is defined. Hopefully the structural analysis will be added during the next few days.

All geometry is parametric, meaning that all parts are interdependent and can be altered and adjusted to meet structural demands from the analysis. The width of the bridge deck, the radius of the bridge segment curve, and the horizontal and vertical translation of all bridge parts are controlled by the smallest possible number of inputs. Also, the weight of the bridge deck in Newton/m2 and the cable tension are defined parametrically in the model.

The ribs are approximations of the ribs found in Staad pro. The spacing between the ribs, the thickness and the density can be changed freely. The volume and volume centroid of each rib (center of gravity) are calculated by the program from the geometry and inputs and are put into the static calculations.

Tool for evaluation of static system and geometry
november 20, 2008

We wanted a smart dynamic evaluation of form. We knaw that the forces of each knot i a system can be represented by a number of vectors. To achieve static equilibrium the sum of all vectors should be zero. it is relatively easy to describe all forces working at a given point, but it is a harder job to solve the linear algebra to make overall equilibrium of a larger structure. Especially when you want to change things and get the readings dynamically.

the greencoloured knots in the grasshopper file corresponds to the points in rhino. Only the left three points are programmed, the right are slaves, since the figure is symmetrical. The top line represents the bridge deck, the buttom points represents the end of the ribs, where one cable is attached.

the greencoloured knots in the grasshopper file corresponds to the points in rhino. Only the left three points are programmed, the right are slaves, since the figure is symmetrical. The top line represents the bridge deck, the buttom points represents the end of the ribs, where one cable is attached.

The sum of the forces in a knot representet by the distance between the knot and a point drawn at the end of the summation vector is a visual indication of the resulting force in the point. by this method the resulting force changes instantly when the point is manipulated. In a more complex structure this manual aroach wil probably be to complex, but in our case we believe it will become useful, since grasshopper is a plugin to rhino, where we do almost all drawings of the bridge, and since we can make sliders for all input values.

the number slider represent the tension of the wire at the left initial section. Here there is static equilibrium - the red dods appear on top of each other.

the number slider represent the tension of the wire at the left initial section. Here there is static equilibrium - the red dods appear on top of each other.

 

The slider is set at a lower value, and the point representing the resulting forces drop below the knot to show, that the support from the cable gets insufficient. The distance between the knot and the resulting force is 10kN for one grid unit (one meter)

The slider is set at a lower value, and the point representing the resulting forces drop below the knot to show, that the support from the cable gets insufficient. The distance between the knot and the resulting force is 10kN for one grid unit (one meter)

The funktion of he bridge weight has the constant weight of the bridge deck and central support and the weight of the rib that corresponds to a reference derived from the distance between the knot and the bridge deck.

The funktion of he bridge weight has the constant weight of the bridge deck and central support and the weight of the rib that corresponds to a reference derived from the distance between the knot and the bridge deck.

Vertebralis + Updated = Boomerang
november 20, 2008

We have been taking the vertebralis structure into more consideration linking it to the now almost final design of the cable structure. The design is still being optimized through FEM but after finding a close to optimal structural solution of vertebralis structure we go back to the drawing board to find a design solution with this structural knowledge in mind.

The design fell upon a boomerang design, as inspiration. This gives us overall structural strength, because all parts are connected to all other parts in pressure from the cables in a triangle. All the pressure points from the cables are pointed towards the center point of the section, which is placed as high as possible to get the most advantage of the cables underneath the bridge.
boomerang_1
The expression of the design is smooth and simple, it resembles a bone structure when we cut smooth holes to minimize the overall weight.

boomerang_21

In the total bridge design, we will encounter 8 symmetrical bridgesections, through these sections we will seek to have every boomerang design optimized in FEM severaltimes over to achieve minimum weight and maximum stregnth and expression. This is shown in the following pictures.

boomerang_3boomerang_4

boomerang_51

The final images shows the final design of one section, is still has some tension and pressure problems around the bottom of the upper arms. This is to us acceptable and could be dealt with in various ways without altering the design further. The thickness could be increased on the entire structure. The thickness could be increased only in the areas with extreme problems, this could be done by using the image from FEM and apply weight directly into the model, by having grasshopper read the image and offset the surface at the extreme areas. The flange of could also be increased at the extreme areas to provide an acceptable solution.

Scheme of the bridge
november 19, 2008

The architectural demand for the bridge is that the bridge should be experienced as a complex system of flows. The pedestrian or bicyclist crossing the bridge will get experiences from crossing over or under another path of the bridge, from the choises of paths at the crossroads and from the structural meetings of bridge parts, that is where two paths meet and their cables form new spaces. All of these things should therefor be possible in the final solution.

The scheme of the bridge should also privide the possibility to have open ond closed spaces at intersections and there should be the possibility to choose what rooms to go to from every starting point.

From a structural/architectural point of view the scheme should be as simple as possible to make the structure elegant and clear. The vertical supports of paths near each other should be placed closed to each other, so they can share a pillar.

To make sure that there is allways symmetry when two paths meet, all paths shoud be made from circular arches. This will also facilitate easyer construction of the spacing system between the ribs.

Red circles are where rooms can be made, black circles indicate points of virtical support.

The solution to the left is an interesting form from a purely architectural point of view. The form in the middle is more clear from a structural point of view. The chosen solution is at the right incorporating qualities from both the previous. Red circles are where rooms can be made, black circles indicate points of virtical support. In the last picture two of the red circles indicates that one path crosses another.

curvature rules and sketching
november 16, 2008

fc3b8rste-sideanden-side

Von Miese analysis
november 13, 2008

vertebralis3

Looking at natural structures
november 12, 2008

vertebralisvertebralis2


november 12, 2008

A 3D example of one of the doubble cable bridges from the sketches below.nyt-brokoncept-2

Sketching structure
november 12, 2008

broskitser11broskitser21broskitser31These sketches are investigations of the different structural possibilities and their consequenses. All of the structures have the road in pressure supported by longitudinal tension cables and connection rods in either tension or compression. The purpose is to develope/find a structural system, were the main members form continuous lines in acordans with the models made earlier.


november 5, 2008

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