Project 1 : Understanding Skeleton Structure

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Building Construction 2Semester 3 /2014Tan Heng YeeTaylor Lakeside Campus


  • INDEX1

    Exploration-Design 1-Design 212Mock up model -Structural Analysis-Failure Analysis34

    Final Model- Construction Process- Structural Analysis- Model Testing 1 -Timelapse-Model Testing 2- Timelapse-Success & Failure Analysis5678-910Conclusion11


  • Exploration DESIGN 1100mm away from the tip of the popsicle stick, a 2mm x 50mm slit is cut to enable interlocking of popsicles sticks to form a interlocked square as horizontal component of the tower.Using the same method above, the slit is cut in the middle of the popsicle sticks. Cross bracing is created in order to transfer force diagonally. Cross bracing is slot into the vertical and horizontal components and will be tied to the connecting point.Advantages Cross bracing helps to spread the load evenly to the both sides.A total number of eight vertical components help to strengthen the load carry capacity of the structure.

    DisadvantagesHigh shearing force between the components as the cross bracings are not tie together with the vertical and horizontal components.Middle part of the horizontal component breaks easily when a load applies to it as it only supported by the vertical component.1


  • Exploration - DESIGN 2

    A slit is cut on diagonal structure to connect to the vertical and horizontal component. String is then used to tie all three components together to overcome shear stress.Vertical and horizontal component are connected with toothpick and string to create one surface. A slit is cut 5mm away from the hole on the horizontal component.Two surfaces are connected by interlocking the horizontal components.

    AdvantagesToothpick acts as a support to the whole structure.High friction between the components and the toothpick gives a small shearing force to the components.A total number of eight vertical components help to strengthen the load carry capacity of the structure.

    DisadvantagesHorizontal component cracks easily when the slit is cut too near to the hole which as a result weakens the load carry capacity of it.The popsicle stick cracks easily when a force applies to the pin is press directly into it.A big slit is cut in the narrow area of the diagonal component which as a result causing it to crack.2


  • From design 1 and 2, a problem that we found was the joining part of the vertical component as we have no idea how to connect the upper part of the vertical component to the lower part. Before that, we planned to join the upper part of vertical component by overlapping it end to end to the lower part of vertical component. However, we found that force is not transmit vertically from part to the other part. So, we couldnt use the overlapping method in these designs.Force cant transmit vertically to the lower part of the vertical componentForce transmit vertically to the lower part of the vertical componentIn order to make the force transmits vertically downward, we decided to join them by connecting them end to end to each other. In order to make them more stable, we cut out the rounded part of the vertical components and crafted a inverted V. To increase their strength, we doubled them by joining them with toothpick. For the horizontal components, we cut a slit from 1cm away in the end of them and then joined them by interlocking them to each other to create a surface. After that, we connect it to the vertical component with toothpick and string like the method of Design 1.For the bracing, initially, we planned to use cross bracing. However, we found that we had overused the popsicle stick as we only allow to use maximum 100 sticks. So, we decided to diagonal bracing only. The reasons that we added bracing was to avoid the whole structure from shearing and also it helps to transfer force diagonally to the next component. Besides, we also added bracing at the bottom of the structure to reduce force of the vertical component and to make the whole structure stable.MOCK UP MODELs STRUCTURAL ANALYSIS3


  • Inappropriate installation of the bracingsWhen the uneven force exerted on the tower, compression occurred at one side of the bracings, however bracings of opposite side will experience tension. Due to the uneven spreading of load, the tower will tend to fall on the side where compression occurred.Uneven Contact point with the load and floorDue to the uneven length of vertical members, not every members contact to the floor and the load above. This will directly affect the stability of the tower which is also the main cause for the falling of tower when carrying loadIncompatible vertical membersThe connection of the vertical members are not consistent due to the lack of accuracy. The inverted V of the vertical members were not crafted accurately.T he contact points of the vertical members had gaps after the tying stage. Due to the lack of efficiency, the vertical members are crooked.Slot to slot horizontal bracingsThe cut slots weaken the load carrying capacity of the popsicle sticks.This is due to the narrow surface area of the lock and key joints. This had result in an uneven surface of the square.Unattached jointsLoad cannot transfer straight down through the unattached V joints. In contrast, toothpicks withstand the loadFAILURE ANALYSIS OF MOCK UP MODEL4





  • Zig Zag Pattern of Bracing InstallationDue to the uneven load distribution of the single diagonal bracing arrange in parallel way, we change the arrangement of bracing to zigzag pattern. This is because if one side of the tower experience greater force than the other side ,the compressive force will be offsetting by the tensile force exerting on the opposite bracing. This will increase the strength of the tower. Other than that ,compressive force will not only concentrate on one side if uneven force exertedHorizontal Bracing at the BottomInstead of allowing only four contacting point to the floor, we improved our design by adding one more horizontal bracing to the bottom of tower ,to increase the surface area contacting to the floor. This will further enhance the stability of the tower and compensate the minor unequal length of vertical members due to human error.Changing V joints to flat jointsDue to the technical difficulty, we replaced V join by using flat join , The straight cut surface allowed full contact with the adjoining members. When load was applied, load can transfer straight down through the well joined vertical members .

    Using Vertical Core as FormworkThe eight vertical members are temporary attach to a vertical wooden block which function as a guideline which result having a straight structure. BY using this mechanism , less error will be occurred as different parts were able to collaborate well during assembly process .As a result, the structure was firm even before the tying process. This vertical block was also increase the accuracy and efficiency for the construction of towerIncreased layers of thread on the joinsBracings, vertical and horizontal members are tied as one so they are not likely to slide or shear off. It will hold and fix the members to prevent movement of members in pressure.STRUCTURE ANALYSIS OF FINAL MODEL6


  • Four 10kg load was put on the modelSix 5kg load was added on Total : 40 + 30 = 70kgSix 2.5kg load was added on Total :70+ 15 = 85 kgTen 1.25kg load was added onTotal: 85+12.5= 97.5kgFour 5kg and four 2.5kg was added onTotal : 97.5 +30 = 127.5One 10kg load was added was addedTotal = 127.5 + 10 = 137.5Model Testing 1 -Timelapse7


  • Model testing 2 time-lapse20kg was put on the model.20kg was added on to the model. Total: 40kg(15+15+15kg)= 45kg was added on to the model. Total: 85kg(10+10+10kg)= 30kg was added on to the model. Total: 115kg10kg was added on to the model. Total: 125kg8


  • (2.5+2.5+2.5kg)= 7.5kg was added on to the model. Total: 162.5kg(15+10+10+10kg)= 30kg was added on to the model. Total: 155kg(2.5+2.5+2.5+1.25+1.25kg+)= 10kg was added on to the model. Total: 172.5kg(1.25+1.25+1.25kg)= 3.75kg was added on to the model. Total: 176.25kg

    The upper part of the model was bended toward the right.The model collapsed at the load of 176.25kg.9


  • ANALYSIS OF FINAL MODEL (AFTER TESTING)After the testing, we have noticed that the breaking points are at the connections of the vertical component. This is because when the vertical component is under compression, the vertical component tend to bend. When the vertical components are bent, it becomes weaker as only one stick is holding the weight of the load.

    This problem can be overcome by reinforcing the connections with more thread.Efficiency =Load Held (Kg) / Mass of Tower (Grams) x Height of Tower (cm) =176.25kg / 108g x 30cm =48.96Success

    The efficiency of our model is relatively high. This is due to the success of our design and our design process. At the breaking point of our model, it can be seen that the load fell quite vertically compared to our mock up model. This is due to the more even base of the final model and also the stacking of the loads. In our final testing, we have ensured that the weights are put in such a way that load is distributed evenly to the ground.

    The double layer vertical component had made the model successful. We have estimated that the load will be transferred vertically downward, hence, we reinforced the vertical components by putting double layer. The horizontal and diagonal components have successfully held and braced the vertical component to avoid shearing and compression.FailureStrength of popsicle sticks do not weaken when bentStrength decreased as only one popsicle stick is holding the load transmitted through it.10


  • ConclusionFrom project 1, we have a better understanding of skeletal structure, its relevant structural components, understand how a skeletal structure reacts under loading, understanding of how it works and even be able to manipulate it to solve an oblique design problem. Therefore, we can apply the technique into construction system design by considering the issues of strength, stiffness and stability of structures including modes of structuralsystems, forces, stress and strain and laws of static.11




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