AR0133 - Structural Design Group 4 Diederik Jilderda | 4096649 Rhea Ishani | 5315883 Sarah Hoogenboom | 5266459
Preface Dear reader, We present to you our final report as part of the Technoledge: Structural Design course for the design of a northern lights observatory in Iceland. Over the course of ten weeks we gained a broad spectrum of knowledge about glass structure, ranging from properties to manufacturing to structural verification of connections. This report reflects these different aspects of designing with glass. We start off with the design of our building, sharing our vision and restrictions we placed on ourselves. After that we look into manufacturing, both of the various glass components and the assembly of the structure as a whole. We also take a brief look into safety analysis and sustainability. The meat of the report is the structural design, in which we schematize the building to a hand-calculatable frame. The hand calculations give us values to verify our structural elements, adjusting them if needed. These values will also serve as an input to size our connections. Connection design is the last functional chapter of the report. We hope that this report shows how much we learned in this course. Not only from our successes, but mostly from our struggles did we learn of which we had plenty. But that is what is great about being in college: we can make mistakes and we can learn from them. But in order to learn from your mistakes you first need to be aware of them, so the report ends with a small section about the things we would address in a next step, or that we would have done differently the next time. So without further ado, we wish you a good and informative read! Diederik, Rhea and Sarah
Table of Contents Design 4 Components 11 Assembly 15 Safety Analysis 18 Sustainability 21 Structure 24 Connections 38 Improvements 46 Reflection 47 References 48 Appendices 50
3
Design
Design
Design Brief
Iceland is a scarcely populated artic island. Only 300,000 people live in Iceland, with 2/3rd of the population living in Reykjavik.With only 100,000 people populating the rest of the island, there are many wild, unpolluted places to see the northern lights. To see the aurora borealis it is essential to have dark, clear skies, which coincide with winter, well-below 0˚C temperatures and big amounts of snow. One may have to wait (and freeze at below 0˚C temperatures) for hours in the dark to catch come aurora activity.
The concept is to design an all-glass observatory that allows for maximized views of the aurora borealis while at the same time maintains a pleasant interior temperature and blends in with the surroundings. A function should be proposed for the observatory so that it remains open also during the months when the nights are too bright for the northern lights to be visible (May-August). Proposed locations for the observatory are close to the Skógafoss waterfall at southern Iceland or the Sólheimasandur plane wreck.
The goal of this assigment is to design and engineer an all-glass Aurora Borealis observatory with the following requirements: - Minimum 12m x 25 m plot size (column-free space). - The structure should be made entirely from glass. Thus, both the cladding and the load bearing elements should be made of glass. - The structure should protect the visitors against rain, wind. - The structure respects/fits the site context. - In case of damage, parts must be replaceable. - Special attention should be given to the design of the glass roof to prevent the accumulation of snow (which would result in high loads and block the aurora views). - Attention should be given in the implementation of passive measures to maintain a satisfactory temperature inside the pavilion.
Design
Location
The site selected is located in Iceland with the function of an observatory for the aurora lights. This site is considered to be in the arctic climate and daylighting is limited during the winter months and in the summer months there are approximately 30 days where the sun sets for less than five hours. The aurora lights are best seen during the winter months between September and April and are caused by solar particles interacting with the magnetic field within the earth’s atmosphere, emitting photons of light, which creates the different colors of the aurora lights. In summary, the aurora lights are best seen at night during the winter season and in areas of minimal light pollution caused by adjacent buildings and lighting within the observatory must be minimal while also considering the safety of visitors.
Kirkjufell, Iceland [1] Additional site details include the selected terrain. While Iceland has various types of terrain, beaches, mountains, and plains, a cliffside on the Snæfellsnes peninsula was selected for this project. Utilizing the cliff as a support for the glass structure, a contrast to the coarse rocks, the structural system is not only dependent on the vertical loads but also dependent on the distribution of horizontal loads into the cliffside.
Map of Iceland [2]
6
Design
Design Vision
In addition to the overall design criteria of the project: visibility of the aurora lights as well as a structural design using glass, design criteria were established. The design has characteristics constraints such as the utilization of only flat glass and embedded connections.
The construction constraints include ease of assembly/disassembly on site, repetition of embedded connections, prefabricated unique sections and the number of minimizing unique sized panels within the design.
7
Design
Design Evolution
Here the evolution of our design is shown. We started with a few concepts (like the cast-glass igloo, such a missed opportunity), but settled on this (as Sarah put it) geometric shape.
Over the evolution we ironed out geometric issues such as unintended (double) curved panels and homogenization of panel dimensions, which makes the building far more realistic to manufacture.
8
Design
Design Concept
Following the design brief and a series of experiments in form, the design incorporates the idea of a semicircular cone and facades inclined at an angle of 35° to hold flat glass panels. This evolved to a faceted structure. To eliminate the inclined residual and non-functional areas within the cone (where the glass meets the foundation), the cone was then raised to a height of 2.1 meters).
Dramatic Entrance Entrance from the edge from of the Cliffthe Cliff the edge of
Above the foundation, vertical facades were created to behave as viewing portals at the edges of the structure. This way a dramatic entrance was achieved at the edge of the cliff. To eliminate the accumulation of snow on the roof.The crown was designed to have an inclination of 10°. This further accentuated the form and the entrance portal.
Adding slopeonon Addingaa slope the the crowncrown eliminate accumulation of to to eliminate accumulation of snow snow
Designing the core as a Designing the core to take the compression ring to structure carry loads loads from the entire from the entire strcuture
9
Design
The Design
The interior space bound by the multi-faceted form was divided into two sections i.e the core (which also serves as the means to entry and exit the space) and the viewing area, which has the largest area in the building. The viewing area is designed to accommodate furniture and seating large numbers of people in the observatory. The space is also designed to house viewing portals. The inclined facade provides an uninterrupted view of the sky. The idea was to also align the seating also the multi-faceted core. In the future steps of evolution of design, the miscellaneous service areas are accommodated within the viewing space.
10
Components
Components
Sizing
We sized components according to the guidelines for structural glass design[3]. Since we have relatively long spans, we also size the facade panels as 3x10mm rather than 3x8mm. The depth of the portal frames is sized between 1/12th and 1/15th of their respective lengths. As far as glass type goes, our preference for the facade panels is to use low-iron annealed glass. Since the goal of the structure is to observe the aurora borealis, it is important that this view is as undistorted as possible. The structural elements will be heat strengthened. Although tempered glass has superior structural qualities, when they break they shatter in tiny fragments which lose all their structural integrity. Even in a lamination it is safer to use strengthened glass, which breaks into bigger pieces that can still retain their strength because they are glued together. Our main connections will be embedded connections. The process of embedding a steel element is to first place the bottom panel then laminate a panel with the outline of the steel element cut out and the steel element itself, and finally laminate a new panel on top which sandwhiches the steel element in place. Sandwhiching of embedded connections
12
Components
Component Overview
Below is an overview of the glass components that will be used in the construction of our building.
We labeled every component in pink which can be used to identify specific elements in the assembly manual.
13
Components
Restrictions
Utilizing the product catalogue by AGC glass, a full list of glass dimensions and quantities were determined. Sheets of glass from the float line come in a few set dimensions based on the capacity of the manufacturing plant. The glass utilized was selected from the AGC product catalogue and is called Planibel Linea Azzurra[4].
a maximum thickness of 15mm. Cut and laminated glass for the facades can be transported in a standard 5500mm container box while fins must be transported by Sedak, a manufacturer that has the production capabilities of laminating and treating oversized glass components. The fin panels will be transported the standard method of oversized glass, through truck and then transported via Available dimensions of glass sheets are 3210x2250, 3210x5100, shipment. A 23000mm long inloader must be used for glass units up and 3210x6000, which can be cut and processed in one location. to 16000mm long on glass racks[7]. Six complete fins can be sized Glass facades require the use of three laminations of 25mm glass. from the following oversized glass dimensions: As of now Cuneo and Moustier plant are the only plants that manufactures 25mm thick panels[5]. These panels can be transported Fins - 3x10mm Lamination in a standard 12110mm long container box after being processed[6]. P1 and P3: XL4 16000x12000 To reduce the amount of glass manufactured, the facade panels are sized from the following glass sheet dimensions: Crown Panel - 3x10mm Lamination R1: XL1 6000X7000 Facades Glass - 3x25mm Lamination F4 and F5: 3210x5100 Front Facade F3: 3210x5100 D1: XL1 6000X7000 F2: 3210x6000 F1: 3210x6000 Core - 3x10mm Lamination C1 and C2: 3210x5100 Crown - 3x10mm Lamination R2: 3210x5100 Due to the dimension and span of the portal fins, the glass portals are to be manufactured as oversized glass sheets, which have 14
Assembly
Assembly
Assembly Order
The assembly order occurs in three steps. First the core is constructed, which stabilizes the portal frames in the second construction step. With the core and portals in place, the facade panels can be placed in position to finish the assembly. The core is built taking advantage of the rock formation to stabilize the initial elements. First the vertical fins are placed, to which the panels are connected from bottom to top. Each section stabilizes the next section until the mid panels are placed, after which the core is fully stable. The facade is assembled in a similar fashion, building the facade up section by section where every section helps stabilize the next until the facade is complete.
The design did not have to be altered to enable a proper assembly, however it did influence the design of the connections as will be discussed later. On the next page the assembly order is graphically displayed as a step-by-step manual. For every step the relevant components are called by their tag according to the component list. Before the structure can be assembled however, the crown should be assembled on site so it can be connected to the core in one go. The individual components will be connected with an adhesive.
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Assembly
Step-by-step Manual
Step-by-step assembly of the structure. The labels refer to the specific components used in each respective step, see components overview.
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Safety Analysis
Safety Analysis
Risk Table
Through the risk analysis of the building, the risks that the bulding may face is found in table 1. The risk of falling rocks and erosion acted as a major design directive. To incorporate a cliff, the structure can be placed either at the base of cliff, within the cliff, or on top of the cliff. It was determined that the building will be placed at the
top of a cliff in order to maintain better views of the sky as well as minimize the risks of falling rocks. We aimed to decrease the risks with the recommendation of measures to be taken.
Risk Scenario (Explanation)
(WS)
(BS)
(ES)
RD value
Measures to Mitigate
Structural Damage of Fin
0.5
0.5
15
3.75 < 70
No measures taken
Complete Breakage of Façade Panel
3
0.5
10
15 <70
No measures taken
Vandalism
6
1
10
60<70
Strength of the glass, Laminate
Human Weight
3
2
10
60<70
Fencing, Caution signs
Impact of Rocks and Erosion
10
2
8
160 >70
Lack of Maintenance
6
2
6
72>70
Fire
3
1
40
120>70
Secure the landscape with Concrete and rods, metal netting Recommendation of Maintenance schedule No solution implemented
Natural Events (Avalanche,Volcanos, and Earthquakes) Internal and External Explosion
3
1
100
300>70
No preventative Solutions
3
0.5
100
150>70
No preventative Solutions
Table 1: Risk Analysis
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Safety Analysis
Safety Measures
Additional risk analysis was done for glass components. Structure priority was listed for each part of the building in terms of dependency of maintaining the structural integrity of the building. The portal fins and core are a priority in the structure and then facade is secondary. The level of risk of falling rocks on the facade panels also vary and panels that are closest to the cliff have the highest risk of damage. In the case of stresses that allow for annealed glass, this type of glass would only be utilized furthest away from the cliffside based on breakage characteristics of annealed glass.
Component
# of possible Interactions
RD Rating
Structure Priority (1-4)
Glass Facade
Two
40-160
2-4
Fins
Three
+160
1
Core
Two
+160
1
Crown
two
42
3
Lid
two
42
3
Door Frame
two
60
3
Risk Heat Map
Table 2: Component Priority and Risk Rating 20
Sustainability
Sustainability
Sustainability Measures
Flat glass is considered for this project based on the design vision to utilize only flat panels and to ensure repeatable facade shapes. By utilizing flat glass, additional processing time and energy, such as hot and cold bending, are not required. It was previously suggested to utilize low-iron glass to improve visibility through the glass, but due to the sizing of the glass facades to be 25mm, low-iron glass cannot be utilized. This has beneficial outcomes in the sense that the glass utilized does not require additional processing to guarantee the low-iron purity. The shape of the building aids in creating a stack effect within the building. Floor heating is added to the building and then circulated through the space as the heat rises from the ground floor and to the entrance[8]. Any heat remaining can be then recovered and a system found in the cliffside will process and circulate the heat again. Iceland is known for their use of renewable energy, especially photovoltaics and geothermal energy.The site that was selected for this design is not located in a geothermal area, therefore cannot effectively use and store geothermal energy in this site[9].
A thermal coating is recommended if the design of the facade were to include a cavity. Research was conducted regarding the effects of adding a cavity to the façade panels, but in the end the cavities were not implemented in this design due to the resizing of the facades panels and possible conflict of the cavity with embedded connections. Data found for the thermal coatings are based on the original facade design of 19-15-19-15-19. Although the sizing of the façade panels have changed, this does not invalidate the data showing the cavities are effective means of creating thermal comfort in the glass building design. It was found that an additional cavity of 10mm with 90% Aragon with an insulating coating, such as I-plus ClearLite 1.0, will improve the U-value through the facade and will not have any significant effect on the color rendering values. The following combinations were considered and calculated for U-values to show the significant difference and thermal insulation potential cavities are effective means of creating thermal comfort in the glass building design. U -Value (W/m2K)
Color Rendering Value
Without Cavity
3.6
84
With Cavity
2.1
82
With Cavity and I-Plus Thermal Coating
1.1
83
Table 3 : U-value Comparisons 22
It was found that an additional cavity of 10mm with 90% Aragon with an insulating coating, such as I-plus ClearLite 1.0, will improve the U-value through the facade and will not have any significant effect on the color rendering values. The following combinations were considered and calculated for U-values to show the significant difference and thermal insulation potential.
With glass it is also difficult to integrate climate installations, but the rock formation is an excellent place to put for example ventilation inlets and lighting. Speaking of lighting, in a future architectural step it could have been very intruiging to experiment with the integration of LED-strips along the portal ribs, which could provide a very exciting architecture at night.
We can also take advantage of our geometry. The door will be a source of heat loss, but since the main space is separated from the door area through the core space, we can use the core space as a buffer zone so cold drafts do not enter the main area directly, improving user comfort.
Clear Sight Coating Anti-Reflective
Facade Layering 90% Ar 10mm Cavity Coating I-plus Clear Lite1.0
Floor heating and stack effect
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Structure
Structure
Preparation
This chapter dives into the physics of the structure. Since this is an important chapter we outline the structure of this chapter first. First we take a qualitative look at how the lateral stability of the structure is guaranteed. We then proceed to the quantitative process of verification through hand calculations. In order to be able to perform these, several steps have to be taken:
1. The structure has to be simplified to a simplfied 2D frame 2. The size and combination of loads have to be determined 3. An overview of material properties has to be provided
Once these steps are taken care of, the structure can actually be verified, which involves finding the largest loads on the structure and sizing the elements appropriately. We will not calculate every element of the structure, rather we focus on the crucial elements: the largest facade panel and the portal frame.
Verified elements
After we perform hand calculations we will attempt to verify that our calculations are correct using MatrixFrame for the 2D frame. For more precise values we can model our structure in software such as Diana or Karamba, which can provide very useful to size the connections. In appendix A and B we have included spreadsheets and calculations for the panel and portal calculations.
25
Structure
Stability
In our design the core is crucial to make sure that the structure is stable and has structural integrity. It functions as a pressure core made up of interconnected straight sections.Vertical ribs make sure that these interconnections are stiffened and do not act as hinges, which would cause the core to collapse. The core should transfer (mostly) compressive loads.
The load transfer of horizontal forces follows the same principle, where loads go from the facade panels through the portal frames to the core, where the core panels transfer the loads diagonally to the rock surface connections.
If we consider possible failure of an element, two elements can have major consequences if failure occurs.The first are the portal frames We take a brief look at the load paths. Vertical loads on the facade which connect to ground level and are thus at risk to damage. If one panels are first transferred to the portal frames that support the breaks, there are no alternative load paths for the panels to take. In panels. Part of this load is transferred to the short vertical sections, a future step this could or should be addressed (if possible). the other portion goes to the tall vertical sections. Both sections will have a horizontal component due to the slope of the roof, but The second element is the core panel, which maintains stability. Sinsince the core is (relatively) very stiff we expect the core to take up ce the core is comprised of several panels, loads may still continue the majority of this horizontal load which is finally transferred to to the rock surface in case one panel breaks. The stresses can go the rock formation. around the gap, through the panel above and/or below it. The core panels act somewhat like a truss in the sense that stresses will be concentrated in a certain path (rather than evenly spread out over the entire section). This ensures the lateral stability.
26
Structure
Structural Diagrams
In order to be able to do hand calculations on the structure, a few things are required: load quantities, material properties and structural diagrams including cross sectional properties. First we show the schematization of our structure from a 3D structure to a manageable 2D frame.
Two things to note: the portal is composed of two parts that are connected together through a pin connection. The diagonal part is a monolithic element however, so the kink in the profile is moment-resisting. Finally, below are the cross sections of both parts based off initial rules of thumb for structural elements[3].
The first challenge is to schematize the pressure core as a system of beams and supports, rather than plates. As mentioned before, since the stresses through a panel will mostly be concentrated around a path through the material we schematize the core as a truss. This system is still too complex to solve by hand so a final simplification is done where the core is replaced by a clamped support, since there will be a moment present in the right support. In reality the moment in this support is taken up by the entire core and vertical fin, so dimensioning this element based off the (concentrated) support moment is a very conservative approach.
3D structure
2D with core
900mm
Diagonal section (3x10mm) 600mm
Pressure core diagram
2D with truss
Vertical section (3x10mm)
simplified 2D frame 27
Structure
Load Quantification
Now that the geometry is determined it is time to get a handle on the loads on the structure. In the vertical direction there is a dead load, a snow load, and an accidental load in case people stand on the roof (such as for maintenance, or human stupidity). There is also a horizontal wind load present. For the dead load, wind load and maintenance load we use the values provided in the guidelines[3]. For the snow load however we use the Eurocode pertaining to Iceland[10], since those numbers should be more comparable to the actual snow load on the building. Determining the snow load can be easily done in a few steps. First, the appropriate characteristic snow load on the groun can be found from the map of figure x. In our case, the building is in snow zone 1, so: sk = 2.1 kN/m2. The next step is to account for the context with this equation:
s = μ · Ce · Ct · sk
μ = 0.8(60-35°)/30 = 0.67 Ce = 0.8 Ct = 1.0 Resulting in: s = Qs = 1.1 kN/m2
with: (roof shape) (windswept factor) (thermal factor)
The determined loads are characteristic loads, which are unlikely to be simultaneously present at full force. The Eurocode also prescribes combination factors ψ0 for the ultimate limit state (ULS):
Snow: Wind: Maintenance:
ψ0= 0.7 ψ0= 0.6 ψ0= 0.0
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Structure The loads are summarized in the following table: ψ0 G = γ· t kN/m2 2 Qs = 1.1 kN/m 0.7 2 Qw = 1.0 kN/m 0.6 Qm = 0.4 kN/m2 0.0
Material Properties
The last step that remains before the structure can be verified is to make an overview of the material properties. Below is an overview of all the parameters that we need to perform and verify our hand calculations, taken from the guidelines[3].
The maximum strengths for the glass types are design strengths, not characteristic strengths. Because the properties of materials are never exactly the same but have a statistical variation, the characThese loads will be combined according to Eurocode guidelines, teristic strength has to be reduced by a material factor to account which state that a load combination should be calculated for every for this unpredictability. The design strength has taken this material load as the ‘governing’ load. The governing load will be assumed to factor into account. work at ‘full force’ while the other loads are reduced by their combination factor. The equations are as follows: γglass = 25 kN/m3 E = 69000 N/mm2 Q = 1.35· G + Σ 1.5· Qi· ψi,0 σt,annealed = 25 N/mm2 (10 N/mm2 for long-term loads) Q = 1.20· G + 1.5 Qi + Σ 1.5· Qj· ψj,0 σt,strengthened = 45 N/mm2 σt,tempered = 80 N/mm2 The largest value is the load that should be used for calculations, σc = 200 N/mm2 since this is the most unfavorable situation. Instead of immediately calculating the governing load combination it is also possible to calculate the effect of each load separately and superimpose them afterwards with the same factors to find the most unfavorable outcome (for example on deflections). This will come in handy when the deflection and stress of loads are calculated differently based on whether the full thickness of a panel or the effective thickness should be used.
29
Structure
Overview
Here we present a clear overview of the geometry and parameters which will be used to verify the structure. Loads are transferred through the structure from the panels to the portal frame to the core.This means that are verification will follow the same order, meaning that we first verify and size the most critical facade panel, and then use the new dimension as the dead load input for the portal frame (because the portal frame carries both the self weight of the facade panels and its own self weight). The core is too complex to verify manually. On the right is the schematized structure in the form of a 2D frame, with the expected moment line. Below is a summary of relevant parameters and loads on the structure.These are all the ingredients that are necessary to proceed. ψ0 G = γ· t kN/m2 2 Qs = 1.1 kN/m 0.7 2 Qw = 1.0 kN/m 0.6 Qm = 0.4 kN/m2 0.0
γglass E σt,annealed σt,strengthened σt,tempered σc
= 25 kN/m3 = 69000 N/mm2 = 25 N/mm2 (10 N/mm2 for long-term loads) = 45 N/mm2 = 80 N/mm2 = 200 N/mm2 Expected moment-line 30
Structure
Calculation: Facade Panel
The first element that we verify is the bottom diagonal facade panel. The panel spans from portal to portal and thus we schematize the panel as a simply supported beam. The panel is shaped as a trapezoid, so we use the longest side as the span length. On the facade act a dead load, snow load, wind load and maintenance load.These loads all act perpendicular to the lamination, meaning that for long-term loads the effective thickness is actually smaller than the real thickness. This pertains to only the dead load. This means that for the verification, we calculate the deflections due to each load separately before determining the governing load combination, and superimpose them with the appropriate combination factors after the fact. Before we start we need to address a critical issue.We initially sized the panel to be 5.7m long, however in our calculations the deflections were enormous. During the consult this was explained by a likely calculation error but after endlessly double-checking we found no error. In fact, there is no amount of sizing possible where this panel is feasible, since making it thicker means that also the dead load keeps increasing (at a quicker rate due to the effective thickness). The result is that we had to take drastic measures to at least present a valid structure, and our band-aid solution was to add an additional portal frame between existing portal frames (reducing the span to half, and lowering the stresses on the portals and connections themselves). The calculations are done with this new span in mind (L = 2.85m).
Critical facade panel
Schematization of panel
31
We consider the plate as a beam of 1m wide, so the calculated values are per unit width. We multiply the q-load by 1m and for the moment of inertia we use 1m width, which means that both values cancel each other out in the end. For the dead load we always use the full thickness of the section, never the effective thickness. Starting with the deflection, this can be calculated with the following equation:
dw = 5/384 * qL4 /EI with: I = 1/12 1000 t3 or I* = 1/12 1000 t*3 (for long-term loads) t* = 3V t1^3 etc
We calculated the deflection for all four loads separately first. We then proceeded to combine these with the approprate combination factors, which finally gives us the most unfavorable deflection. These are the combinations in our situation:
1.35G + 1.5(ψ0· snow + ψ0· maintenance + ψ0· wind) 1.20G + 1.5(snow + ψ0· maintenance + ψ0· wind) 1.20G + 1.5(ψ0· snow + maintenance + ψ0· wind) 1.20G + 1.5(ψ0· snow + ψ0· maintenance + wind)
The maximum allowable deflection is: xxx The last step is to perform a unity check, which gives insight in the relation between the loading and the capacity. The unity check should be smaller than 1.0 but ideally around 0.8:
U.C. =
We repeated the same process for the maximum bending stress, with the glass type being strengthened glass:
sigma = M / W M = 1/8 q L2 W = 1/6 1000 t2
The bending stresses can also be superimposed with combination factors. We finally also calculated the unity checks.
U.C. =
32
Structure
Calculation: Portal Frame
We programmed all these steps in a spreadsheet so that we could With the critical panel properly dimensioned now, we can take a easily tweak the sizing of the panels until the result is acceptable. look at the portal frame. Aside from the already acting loads, an adThe results of all iterations are shown in this table. ditional dead load will be present due to the facade panel’s weight. Lamination 15-15-15 19-15-19 19-15-19-15-19 19-19-19-19 15-15-15-15-15 25-25-25
δw (mm) 19.8 11.8 11.8 10.7 27.5 6.5
U.C. 1.74 1.04 1.04 0.94 2.41 0.57
σ (N/mm2) 41.5 33.0 28.5 26.9 63.1 19.2
U.C. 0.63 0.73 0.63 0.60 1.40 0.43
Aside from the additional dead load, the process is exactly the same. We calculate the simplified frame and determine the support reactions and extreme moments in the frame separately for each load, and superimpose these values to determine the most unfavorable situation. We verify the size of the frame based off these calculations and the support reactions will be used to size the connections.
Between 4x19mm and 3x25mm our preference goes to 3x25mm because it requires less lamination adhesive, it is overall slightly thinner and the forces through our embedded connections will not cause excentricities in the cross section. The proper sizing for the most critical facade panel is thus 3x25mm thick. This seems pretty large still despite adding additional portal frames but at least it is feasible.We also made sure that 25mm thick heat strengthened panels of 2850x2900mm are actually available. A final noteworthy issue to address is that this panel is dimensioned based off the longest span possible, although the panels strongly decrease in width towards to top. Those top panels will be strongly overdimensioned as a result which should be addressed in a future step. Portal frame 33
The loads on the portal are the loads which the panels transfer onto the portal.To find the correct q-load, we have to multiply each load with the width of the panel. This width increases linear, from 700mm at the top to 2850mm at the bottom of the diagonal. We can table these values: q1 q2
Dead (kN/m2) Snow (kN/m2) Maintenance (kN/m2) 1.31 0.77 0.28 5.34 3.14 1.14
Wind (kN/m2) 0.70 2.85
Additionally there will be a dead load present due to its self-weight:
qportal = 0.9m· 3· 0.010m· 25 kN/m3 = 0.68 kN/m
The system has five unknown support reactions and one hinge, and is as such statically indeterminate (one degree). This means that an additional equation needs to be introduced to solve the system.The most obvious choice is to split the structure in B and introduce the moment MB. Equations for the rotations of members BA and BC can be set up, and since these rotations have to be equal we have the additional equation necesary to solve the system.
34
The system of equations (under strictly vertical loads) is: sss
This system can be solved for each of the vertical loads (dead load, snow load and maintenance load). The system for the wind load is:
Once MB is known the other support reactions can be determined. The calculations for these can be found in appendix B. The support reactions can be superimposed just like the we did in the panel calculation, yielding the following combinations: Ah (kN) Av (kN) MB (kNm) CP (kN) Dh (kN) Dv (kN) MD (kNm)
Dead -45 118 101 86 62 -47 154
Snow -47 126 104 95 63 -58 158
Maintenance -48 148 106 142 64 -105 160
Wind -44 124 103 102 71 -60 179 35
These results show that the governing load combination is that of maintenance, or otherwise people standing on the roof. The exception is under extreme wind conditions, where the support in D (the core) is placed under more stress. We will use the calculated support reactions to size our connections. The final step here is to verify the strength of our elements, regarding bending, buckling and tension. There are three bending moments to be concerned about: in B, the extreme in member BC and in D. The portal fin in D is 3x10mm laminated, 600mm deep. The bending moment occurs in the same plane as the laminations, so we do not have to worry about the effective thickness. The maximum bending stress in the fin is:
sigma = M/W
Resizing the frame to the same depth as the diagonal part yields:
Under normal circumstances this is too close to the material strength to be comfortable, despite all measures that were already taken in the calculations. In our case however we have been very conservative, in reality this is not a single support taking the load but the entire core. With this argument we deem the construction responsibly and reasonably dimensioned.
The bending moment in B is smaller than in D with the same cross section, so this critical part of the element is also structurally safe. Without software it is quite difficult to calculate the extreme moment in BC by hand. If we assume the maximum qv2-load present across the beam, then the moment in the center would be:
Mbc,center = MB/2 - 1/8· q· L2 = 106/2 - 1/8· 14.67· 11.452 = 144 kNm
This is not the extreme moment in the beam, but it is still a conservative approach considering we greatly increased the total load. This moment is also smaller than MD and so the entire portal frame is verified to be structurally safe. 36
Structure Contrary to our expectations, the vertical member CD is not under compression and as such is not at risk to buckle. The load in member BC is mostly a shear force so buckling likely will not be an issue there either, especially since the roof panels help to keep it laterally stiff (in its weak direction). Regardless, we can calculate the buckling capacity of the diagonal beam. We assume both ends to be hinged supported, meaning that the buckling length is the same as the beam length. Since the beam will most likely buckle in lateral direction (perpendicular to the lamination) we should use the effective thickness. The buckling capacity can be calculated with Euler’s formula:
With a length of 11.45m and a 3x10mm cross section, the buckling capacity of the beam is Fk = 1169 kN, which is more than sufficient to not be at risk of buckling.
MatrixFrame Verification
We intended to verify our hand calculations with MatrixFrame and then model the entire structure with FEM software to find more accurate and detailed stresses. However this is where we came to a screeching halt. Our hand calculations did not match the output from MatrixFrame even though our calculations seemed correct. Similar to the issue with the panel deflection calculations, the initial response in our consult was that we likely made an error. We decided to create a dummy frame in MatrixFrame to test once more and again we found, despite our hand calculations being correct, a significant difference in results. Mauro looked at it during the last consult and could not figure out the mistake, and even after looking at it in his own time had to conclude that MatrixFrame was actually wrong. While we at least were glad that our hand calculations were in order, it did cost us a few precious weeks that we wanted to use for more advanced modelling. On a more positive note, it does prove the value and reliability of hand calculations which is part of what this course is about, so this was a great lesson. The dummy frame comparison is shown in appendix C.
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Connections
Connections
Connection overview
Embedded connections are are utilized in our design as a means of having seamless connections between glass facades. Sizing of the bolted connections, which are embedded in the foundation, and the pin connection, which is laminated and slotted between glass sheets, is completed utilizing bolt sizing requirements.
This equation is uitilized with the following assumptions based on the sizing of the fins and the maximum stress in the portals, which was discusssed in the structural stection of this report.
Hole sizing for connection A was determined to be a single diameter hole of 489.2mm for the facade and portal connection to the foundation. Similarly, It was found that the core and protal connection to the foundation requires a diameter 567.4mm. It is our recommendation to size this connection so it is a splice connection that is embeded. Hole sizing for the pin connection in the portal was determined to be 525.18mm in diameter. 39
Connections
Connection A
Interacts between the foundation and portal. Embedded into the foundation and covered. The end of the portal is laminated with an additional steel shoe.
3x10mm Glass Lamination
Stainless Steel Spacer
Bolted Steel Shoe Nylon Fiber Gas ket
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Connections
Connection B
Interacts between the facade panels and portal. Embedded connection that is laminated between the layers of glass. It is connected to the glass portal with a blind screw and then capped at end and sealed with a silicon gasket within the connection. Sealant used between connections to make connection watertight.
Embedded Steel Section Silicon Padding Blind Screw Silicon Sealant Padding
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Connections
Connection C
Interacts between the core panels and portal. Embedded connection that is laminted beween layers of glass. It is connected to the glass portal with a blind screw and then capped at end and sealed with a silicon gasket within the connection. Sealant used between connections for connectivitiy.
Silicon Sealant Padding Blind Screw Silicon Padding Embedded Steel Section
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Connections
Connection D
Interacts between facade panels and cliffside. Embedded connection in the cliffside that clamps the facade into place. Netting will be used hold the rocks from falling directly onto the facade panel.
Cliff Netti ng Clamp to Roc k
Connection B Concrete Slab Resin Screw
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Connections
Step by Step
Step by Step process for connection B 1.Position portal frame 2.Place first panel
3.Place second panel
4. Connect panels
5. Seal connection
3.Place second core panel
4. Connect panels
5. Seal connection
Step by Step process for connection C 1.Position portal frame 2.Place first core panel
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A Final Word
Improvements That concludes our report. We addressed a large number of different issues and designing an integral structural, taking all these different factors into account, is never easy. Here we suggest issues that we feel could or should have been addressed and that we would like to solve in a future step. The first and most obvious issue is the facade panel size and the number of portals required to keep the facade panels from breaking. We are unsure what the root cause is, considering our spans weren’t exceptionally long, but adding more portals means that we have to add a lot of material and maybe worse, the portals obstruct the view on the northern lights which is highly undesirable. ‘Fixing’ this however would mean that we would have to go back to the drawing table and redesign the entire structure from scratch.
There were two opportunities that we did not grasp because we ran out of time (due to being stuck for two weeks). The first is modelling and optimizing the structure using FEM software, which we attempted to do but could not go through with. The second is to take a closer look at climate. We really wanted to design a facade panel with a cavity, but with the extreme loads and deflections that we were facing we simply could not find a way to integrate the extra weight in the short amount of time that we had left.We were also keen on doing some climate simulations with Grasshopper but our priorities were elsewhere. These are likely other aspects to improve on as well, but we feel that these are the main ones that we would like to address in a future step.
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Reflection In reflection of the course, our group has learned some key items during the progression of the project. We did face some challenges in the design and there were a handful of times that we would be discussing over zoom and suddenly suggest, in a half serious and half joking manner, changing the entire form of the structure. We did end up remaining with a similar form to what we initially proposed, but this did not prevent us from sketching out new ideas weeks into the course project. We see that this shows that we were open to imagining the possibilities of utilizing glass in a structure outside of our project. During the calculations stage of our design, we found it quite interesting that within the group there were two different approaches in making the structural calculations. This sometimes lead to misinterpretations and misunderstandings, but in the end it did make us appreciate that there are many methods of approaching a structural design, whether that is through long form or simplifications.
As a group, we were able to redesign the concept that we presented at the final presentation and then created an improved solution to our structural demands. This in itself was a challenge and there were many hours dedicated post-final presentation to improve our design to a level of which we were more comfortable submitting in a final report. We were open about our thoughts and critiques of our design and did our best to still have a feasible building design. Some improvements that we would make in reflection of the course is to have more of a purpose for our form. Although we can say the purpose is to see the Aurora Lights, having a more well thought out purpose or inspiration would have helped direct our design in a more creative manner.
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References [1] Wikipedia (2014). Kirkjufell. [2] Scott Jessop (n.d.). Iceland map. [3] Oikonomopoulou, F. (2021). Technoledge Structural Design AR0133: Guidelines for engineering & calculating a glass structure. [4] AGC (2021). Linea Azzurra: Neutral float glass with a light azure tint. [5] AGC (2021). Oversized glass. [6] Container Container (2021). Shipping Container Dimensions. [7] Sedak (2021). Logistics. [8] Risberg, D., Risberg, M., & Westerlund, L. (2018). Investigation of thermal indoor climate for a passive house in a sub-Arctic region using computational fluid dynamics. https://doi.org/10.1177/1420326X17753707 [9] Steingrímsson, B. (2009). Geothermal exploration and development from a hot spring to utilization. [10] The European Union (2003). Eurocode 1: Actions on structures - Part 1-3: General actions - Snow loads. EN 1991-1-3 (2003).
Appendix A
Panel Calculations
Appendix B
Panel Spreadsheet
Appendix B
Portal Hand Calculations
Appendix B
Portal Spreadsheet
Appendix C
MatrixFrame dummy frame
Dummy frame Solved by introducing unknown MB in point B, using equations for rotations of sections BA and BC. Alternate method ‘confirms’ hand calculation (next page). MxF result seems in equilibrium for forces and moments although the extreme moment (60.22) is a little off (should be 58.8).
10 kN/m
MB
8m
10 kN/m φBA = -1/3 MB · a / EI φBC = 1/3 MB · b / EI - 1/24 · q · b3 / EI
B
4m
8m 4m
A
C
φBA = φBC -1/3 MB · a / EI = 1/3 MB · b / EI - 1/24 · q · b3 / EI 1/3 · (a+b) · MB = 1/24 · q · b3 MB = 3/24 · q · b3 /(a+b) = 53 1/3 kNm
