Analysis of different elevation buildings with heights of 4, 8, 12, 16, 20, and 24 floors on friction piles

. Foundation is one of the most important parts of the structure. The design and selection of foundations must be carried out properly to strengthen the structure. Different elevation buildings require more careful foundation design than other structures. The bearing capacity and settlement of the soil acting on the pile foundation will be very important to be taken into consideration in the construction of different elevation buildings, because the different elevation buildings have different heights, so the placement of the foundation depths is also different. There is load data to be used, load data will vary according to the elevation of the building. The difference on structure elevation is four-storey buildings until it reaches 24 storey building. Each floor has a height of three meters. The foundation analyzed by using bored pile. The soil data is from Central Jakarta. The foundation will be analyzed under the following condition. The foundation will be placed at the same pile diameters which is one meter and uses different dephts. In this study, the bearing capacity and soil settlement analysis was carried out using bored piles on the conditions described before. The result of this research will provide information about bearing capacity and settlement that occurs on different elevation building if the foundation uses a friction piles. This research concludes that the use of friction piles in ineffective.


Introduction
The development of the era which includes economics and technology has made a lot of progress until now.The development of this era is accompanied by development progress in the field of construction.Infrastructure construction in Indonesia is currently developing.The development of increasingly advanced infrastructure makes people's needs increase.Creating an infrastructure is inseparable from building a foundation.Construction of different elevation buildings needs to pay attention to many things because there are elevation differences between structures.The different elevation buildings are a structure that has different elevations In a 5-8 storey building construction project, deep foundations are usually used for the design of the lower structure.In different elevation buildings, it is necessary to pay close attention to the planning of the foundation because there are many factors that can affect the bearing capacity of the foundation and settlement, such as differences in structural elevation, load weight, soil conditions, etc.Based on the many conditions that affect the bearing capacity and settlement of the foundation, this research will seek the best conditions to be applied to terraced buildings based on the value of the foundation carrying capacity and the amount of soil settlement produced.
Based on what has been said on the background of the problem, it will produce the following problem formulation: *Corresponding author: alfred@ft.untar.ac.idCalculating the amount of required bearing capacity in a different elevation building on single pile and group pile if using a friction piles.Calculating the amount of settlement that occurs in a different elevation building on single pile and group pile if using a friction piles.Analyze the bearing capacity and settlement of the foundation that occurs in a different elevation building if using a friction piles.
Based on the formulation of the problem, the objectives of this study are as follows: 1. Determine of the effect of the difference in the depth of single pile and group pile on the bearing capacity of the foundation in a different elevation building if using a friction piles.Determine of the effect of the difference in the depth of single pile and group pile on the amount of the settlement in a different elevation building if using a friction piles.Conclude the results of the analysis of the bearing capacity and settlement of the foundation if using friction piles.

Literature
The foundation is a part of building construction which is the lower structure of a building [1].The foundation functions as a low structural component of the building whose role is to transmit the load from the upper structure to the ground evenly [2].Foundation type, depth, shape, and material will influence many factors in foundation design.External factors that affect the design of the foundation, namely soil conditions, structural loads, and time required can also affect the selection of the foundation to be used.Deep foundations are used for buildings with four floors or more than four.In different elevation buildings, the foundations that can be used are pile and bored pile foundations.The use of these two piles is determined from factors derived from soil data or conditions on site.

Different elevation buildings
Different elevation buildings are a structure that has different elevations.Differences in the elevation of the structure make the required carrying capacity and settlement that occurs will be different.Different elevation buildings require a special foundation design because there are elevation differences between the structures.Different elevation buildings can be seen in the illustration of Fig. 1.

Deep foundation
Deep foundations are structures that have the function of channeling building loads to the ground at a predetermined depth [3].According to Hardiyatmo [4] deep foundations can be reviewed based on how they support the load, namely:

Friction pile
Friction pile is a type of pile whose bearing capacity is determined by the shear force.The shear force acts between the wall of the pile and the ground surrounding the pile.

End bearing pile
End bearing pile is a type of pile whose bearing capacity is determined by the consistency of the soil at the end of the pile.Generally this pile will be placed on a layer of hard soil.

Point bearing capacity (Qp)
In this research, the bearing capacity of the drilled pile foundation will be sought.The bearing capacity of the pile ends is determined using two methods, namely the Meyerhoff method and the CPT method.Meyerhoff's method can be seen as Equation 1.
The CPT method can be seen as Equation 2.

Frictional resistance (Qs)
In this study the carrying capacity of the pile blankets was sought using two methods, namely the Alpha method and the Reese & Wright method.Alpha method can be seen as Equation 3. The Reese & Wright method can be seen as Equation 4.

Settlement
In this study, land subsidence will be sought.Settlement consists of elastic settlement and primary consolidation settlement.Elastic reduction using the Vesic method.Based on Das's book [3] the Vesic method is divided into 3 components, namely: 1. Shortening of the elastic of the pile (Se( 1)) The settlement of the pile tip due to the working load (Se(2)) Settlement due to friction of the pile cover along the pile due to the working load (Se( 3)) The settlement formula can be calculated using the following Equations 5-14.

S e = S e(1) + S e(2) + S e(3)
(5) The following Equations 15-19 is the formula for primary consolidation: Compressibility index and expansion index

Permission of the settlement
Based on SNI 8460:2017 [5] the amount of the settlement that occurs and the difference in the settlement that is permitted based on the function and stability of the structure has the conditions total settlement ˂ 15 cm + b/600.

Research method
The data collection method used is data collection using documentation techniques, the documentation technique is collecting data from a project as a reference for the soil profile which will be used to calculate the bearing capacity and settlement in this journal.In addition, the literature method is used to find information that supports this topic from books and journals.
The data analysis method begins by looking for theoretical basis and data sources from journals and books to obtain formulas for calculating the carrying capacity and land subsidence.The data analysis method will look for the best depth to use based on the results of bearing capacity and settlement.The foundation will use friction pile.

Project data
To calculate the bearing capacity of foundation and soil settlement, the project data is used in the form of boring logs, sondir, laboratory data in the Central Jakarta area.The project data consists of 2 drill points with a depth of 30 meters, 6 sondir points, and laboratory data.From this project data, final parameters will be made which will conclude the soil conditions at the case study location.The final parameters of the soil can be seen in Table 1-2

Building size and load weight
The different elevation building has a configuration of 24 m × 12 m.All floors of the different elevation buildings use the same building configuration.Configuration illustration can be seen in Fig. 2.

Fig. 2. Building configuration.
The load weight to be used for each floor can be seen in Table 2.

Calculation of point bearing capacity (Qp)
The bearing capacity of the foundation needs to consider of wind forces, earthquake forces, and others.The selection of an effective foundation is chosen by considering the depth of the foundation piles to hard soil [6].The bearing capacity of the foundation takes into account the point bearing capacity and the frictional resistance.Calculation of the point bearing capacity will be calculated with friction pile foundations with different depths.The calculation of the point bearing capacity will use two methods, namely the Meyerhoff method and the CPT method.The results to be used from these two methods are taken to be the minimum in order to determine the smallest pile tip bearing capacity to avoid design failure.Calculation of the bearing capacity will be applied to all floors to be analyzed.Following are the results of the final calculation of the point bearing capacity can be seen in Table 3.

Calculation of frictional resistance (Qs)
The calculation of the frictional resistance will be calculated with friction pile foundations with different depths.The calculation of the frictional resistance will use two methods, namely the alpha method and the Reese & Wright method.The results to be used from these two methods are taken to be the minimum in order to find out the smallest pile cover bearing capacity to avoid design failure.Calculation of the bearing capacity will be applied to all floors to be analyzed.The following results of the final calculation of the pile cover carrying capacity can be seen in Table 4.

Calculation of bearing capacity on bored pile foudantion (Qall)
Based on the calculation of the point bearing capacity and frictional resistance, the value of the foundation bearing capacity can be generated.The following results of the Qall calculation can be seen in Table 5.The correlation between the weight of the load and Qall can be seen in Table 6.

Calculation of group pile
Based on the results of the calculation of the bearing capacity of the pile foundation, on several floors it is necessary to use group piles because the carrying capacity of a single pile is not strong enough to support the weight of the load on several floors.The group pile will use two piles.The method to be used to calculate group piles is block failure.Following are the results of group pile calculations and the final results of carrying capacity calculations can be seen in Table 7.

Calculation of settlement
The calculation of the settlement value for the deep foundation will use the Vesic method.Calculation of settlement will be carried out at a predetermined depth in the bearing capacity calculation.The calculation of settlement consists of elastic settlement and primary consolidation settlement.The following results of the calculation of land subsidence can be seen in Table 8.

Analysis of the calculation on bearing capacity and settlement
Based on the calculation results (Fig. 3), it is known that the result of the resulting foundation bearing capacity will be greater with each increase in elevation but there are irregularities in the 4-storey building, where the bearing capacity of the 4-storey building foundation is the same as the carrying capacity of the 8-storey building foundation.This is due to adjustments to the depth of the foundation in a 4-storey building.Actually, the weight of a 4-storey building can be carried if the foundation is placed at a depth of 14 meters, but the settlement that occurs at a depth of 14 meters exceeds the permit limit based on SNI 8460:2017 so the foundation needs to be deepened so that land subsidence does not exceed the permit reduction limit.It was found that at a depth of 18 meters the settlement that occurred did not exceed the permit limit, but the resulting foundation bearing capacity was twice the weight of the load to be carried.Land subsidence that occurs is relatively moderate at a certain height but does not exceed the permit limit.

Conclusions
Based on the calculations performed, it can be concluded that: 1.Based on the results of the calculation on the bearing capacity of foundation, it is known that the deeper the pile depth, the greater the resulting bearing capacity of foundation.2. Based on the results of the calculation on the settlement on the friction pile, the result of settlement is not too big and does not exceed the permit limit 3. Based on soil data and calculations, it can be concluded that the use of friction pile is ineffective.The reason is the bearing capacity on four-storey building is twice the weight of the load to be carried.

Recommendations
Based on the results of the research conducted, the authors can provide suggestions: 1. Calculations can be checked using a calculation application to find out accurate results.2.An analysis of foundation construction in terms of cost can be carried out to provide information in terms of the cost.

Fig. 1 .
Fig. 1.Illustration of the configuration of different elevation buildings with various heights.

Table 3 .
Results of the final calculation of the point bearing capacity.

Table 4 .
Results of the final calculation of the frictional resistance.

Table 5 .
Summary of bearing capacity.

Table 6 .
Correlation of load weight with Qall.

Table 7 .
The result of the foundation bearing capacity.

Table 8 .
Result of settlement.