Floating House Platform Stability Test with a Lightweight Concrete Cover Made of Expanded Polystyrene System (EPS)

Coastal area which affected by floods and tides has problems about safety and comfortable environment. The world of floating construction has introduced substructure foundations made from expanded polystyrene system (EPS) with a lightweight concrete cover. The styrofoam platform must meet the buoyancy, stability and center height test requirements. The research aims to analyze the magnitude of the buoyant force (Fa) against downward force due to the load weight on platform. The platform is strong and stable when upward force (Fa) is greater than total structure weight (G). The object will float if buoyant force (Fa) is greater than the gravitational force (g). The balance is stable if center of object gravity (Bo) is below the center of buoyancy (Ao), otherwise it will be in arbitrary balance. The height of centrum can be determined m > 0, means the object is stable. The research results show that 6.12x5.12x0.68m Styrofoam platform with a buoyancy force of 18,246.6 kg is able to withstand an additional load of 3647.62 kg with an SF value of 2.59. It means there is a linear relationship between magnitude of loading value and sinking height of Styrofoam platform. The safety factor value decreases as the sinking height of platform increases. The stability value of Fa/G is 3.01>1.2. The metacentrum’s height is 16.531 > 0, so the platform with a lightweight concrete cover is declared stable and safe to use.


1.
Introduction The problem of housing needs regarding the influence of sea tides for communities in coastal areas has its own challenges.The need for housing that is more adaptive and durable, resistant to ups and downs, is urgently needed [1].Eco-friendly residence is really needed in areas affected by flooding and sea tides [2].Fortunately, improvements in construction sector have introduced floating houses which may solve the problem [3].The problem is the need of several design models and floating house prototypes that are eco-friendly, economical, aesthetically livable and can be applied in coastal areas [4].Floating houses require a solid foundation with high stability and to its buoyancy.A solid foundation with high stability and buoyancy is needed in making a floating house.A lightweight concrete cover on a styrofoam floating house platform will improve its aesthetics, particularly its strength, comfort, and cleanliness [5].The foundation of floating house must meet the requirements for buoyancy, stability and metacentrum height.The research aims to determine the characteristics of a styrofoam platform with a lightweight concrete cover as a cover made from expanded polystyrene system (EPS) material regarding its stability, buoyancy force and metacentrum to obtain safety factor value which may be safe to use.The research was conducted in a hydrology laboratory on a lake, behind Engineering faculty building of UNISSULA, Semarang.

Floating House Styrofoam Platform
A floating house is a building structure that floats on water surface.The floating foundation must have high buoyancy and stability to support the building above which can move up or down according to the water level.In Indonesia and several developed countries, the use of floating foundation in floating houses is quite simple, using wooden sticks or bamboo.A floating house with a styrofoam foundation design using styrofoam as its structural foundation can be a better choice in terms of buoyancy, stability and aesthetics.The styrofoam platform is more effective and efficient compared to PVC platform [3].
Handayani [5] stated that Styrofoam is a material that has a low density so it floats easily in water.The foundation/platform is a substructure that supports entire load of building above it [6].Styrofoam has a high buoyant force so it can float well on water surface [7].

Analysis of Styrofoam Platform Buoyancy Force
A styrofoam platform buoyancy analysis (Fa) performs the buoyancy magnitude analysis which will be compared with downward force due to load weight acting on floating platform.A stable floating foundation is when the EPS buoyancy (Fa) is greater than structure total weight (G).The object will be float if the EPS buoyancy (Fa) is greater than EPS gravity (g).The calculation formula for EPS buoyancy (Fa) is explained below: with: Fa : EPS buoyancy l : length w : wide h : height ρ : liquid density g : gravity

Styrofoam Platform Load Analysis Styrofoam platform load can be classified into two forms [4]: a. Static Load:
Loading is carried out regularly and does not cause large accelerations and vibrations on the structure or structural elements.A small acceleration loads can be applied by increasing static  A floating object is in stable equilibrium if the object's center of gravity (Bo) is below the center of buoyancy (Ao) and otherwise is in arbitrary equilibrium [8].The formula for the height of metacentrum is determined by: with : Io = Inertia moment of an object supported on a surface Liquid V = Volume of liquid displaced by the object AoBo = Distance between buoyancy center and object center The object is stable when the height of metacentrum, m > 0, m then the object is said to be in 0 = 0 neutral stability, and if m < 0 the object is unstable.

Research Methods
The research consists of three stages; 1) Making a styrofoam platform test object with a lightweight concrete cover with 6.12 m length and 5.12 m width, a thickness of 0.68 m. 2) Testing the buoyancy of styrofoam platform, 3) Analyzing the balance and center of styrofoam platform.The equipments used were a peilschaal, a ruler, a concrete block as a load.Loading the platform with concrete blocks is carried out in stages by measuring each height of the platform sinking which occurs as the static load increases.

Results and Discussion
The overall dimensions of styrofoam platform and lightweight concrete cover are 31,334.The whole volume of platform is 21,307 m3 with 4125, 632 kg total weight.The load used in the test is 3,647.62kg, over its plan 2,486 kg.The total load used in the test was 3,647.62 kg, which exceeded the design load of only 2,486 kg.The load consists of 60 concrete blocks, each block weighing around 60kg-80kg.The blocks are added gradually as loads on the floating platform.With each additional load, the height of the sinking platform is recorded using a ruler and reading the drop on the peilschaal.

5.
Conclusions and Suggestions

Conclusion
The styrofoam platform with dimensions 6.12 x5.12 x 0.68 m with total load of 6043.55 kg is able to withstand an additional load of 3647.62 kg with an SF value 2.59.There is a linear relationship between Metacentrum's height is 16.531 > 0 thus the platform is in stable condition and can be applied.

Suggestions
The use of a floating structures with a lightweight concrete styrofoam cover has its own advantages which are potentially very much needed by wider community, especially for use in coastal areas which further research and studies can be conducted in the future regarding tides and sea waves.

Figure 1 .
Figure 1.Floating House Platform Design made from Styrofoam.

Figure 4 .
Figure 4. Linear Graph of Load with Platform Sinking Height.

Figure 5 .
Figure 5. Graph of Styrofoam Platform Sinking Height against Safety Factor.
loading value and the sinking height of styrofoam platform and the value of the safety factor decreases as the load increases.The stryrofoam platform with lightweight concrete cover with a buoyancy 18,246.6 kg, working weight 6,043.55kg, has a stability value Fa/G of 3.01 > 1.2.

Table 1 .
Styrofoam Platform Data with Lightweight Concrete Cover.

Table 2 .
Styrofoam Platform Loading Test Results Data.

Table 1 and
Table 2declare that the ability of a styrofoam platform measuring 6.12 x 5.12 x 0.68 m is able to withstand 3647.62 kg dead load with SF value of 2.59.

Table 3 .
Styrofoam Platform Data with Lightweight Concrete Cover.