Analysis of Strength, Stiffness, and Stability The Formwork Construction in LRT Jabodebek Project

The Upper Longitudinal Beam casting on the Jabodebek LRT Project requires a shoring to be able to withstand the workloads. To avoid the failure of formwork construction, formwork must meet the strength, stiffness, and stability requirements for each formwork component material. The analysis is carried out on the value of bending stress, deflection, and shear that occur in each component of formwork. From the analysis carried out each obtained as follows. Strength requirements with flexural stress values that occur in Plywood, Girder GT 24, and Steel Waller SRZ materials, each of which is smaller than σ permit = 100 kg / cm2, 70000 kg / cm2, and 1200 kg / cm2. Stiffness requirements with deflection values that occur on Plywood and Girder GT 24 material are Δ permit = l / 400. Whereas the SRZ Steel Waller fulfills Δ permit = l / 240. Stability requirements with shear stress values that occur in Plywood, Girder GT 24, and Steel Waller SRZ materials, each of which is smaller than τ permit = 12 kg / cm2, 1400 kg / cm2, and 696 kg / cm2. Peri Up Shoring can support all formwork loads. So it can be said that the construction of the Upper Longitudinal Beam formwork is in a safe condition.


Introduction
In the construction of concrete work, there area three main components that must be completed carefully and will succeed in the structural work. The three components are concrete mixture, concrete reinforcement and formwork.
Formwork is a temporary mold that is used to hold concrete as long as the concrete is poured and shaped in accordance with the desired shape. Because it functions as a temporary mold, formwork will be removed or dismantled if the concrete that has been poured has reached sufficient strength. To avoid formwork failures due to working loads and other factors, a formwork construction must meet the strength, stiffness and stability requirements. Formwork is said to be strong if when receiving loads -the workloads formwork material is not broken. The strength of formwork becomes a major component in producing quality structural dimensions that are in accordance with the plan. Formwork is said to be rigid, when when receiving loads -loads that work formwork material does not change shape. Formwork must also be stable, so that when receiving the formwork load does not collapse. This requirement must be met considering that formwork is work that is carried out repeatedly in high rise buildings and requires a large fee for rental costs and make it.
The construction of Light Rail Tansit Infrastructure Project is implemented by PT. Adhi Karya (Persero) Tbk. Formwork construction that is used for casting Transversal Beam and Lower Longitudinal Beam at Cawang Station is a steel profile structure fabricated by PT. Adhi Karya subcontractor's according to the needs of construction in the field. The construction process of the steel scaffolding construction requires lifting equipment such as a crawler / mobile crane. The steel formwork construction cannot be used for the construction of the Upper Longitudinal Beam because there is no wiggle room for the crane when assembling the steel scaffolding construction if the floor plate on the Concourse Level has been casted. Longitudinal Beam elevation is ± 4,588 to the Concourse Level floor plate. So we need a formwork scaffolding system to withstand the forces that emerge when the Longitudinal Beam casting takes place. So this research aims to analyze the strength of the formwork structure against the flexural stress, deflection and shear stress of the material permits used so that it can be ensured that the formwork construction is safe. VOLUME 2 │ NUMBER 2 │ MARCH 2020 Available online at http://proceedings.worldconference.id.

Literatur Review
According to Amien Sajekti (2009) quoted by Doloksaribu (2018), that formwork is a temporary mold for fresh concrete and as a support is used scaffolding (shore). [3] According to Asiyanto (2010) quoted by Fitriansyah (2018), Formwork is a tool of concrete structures, for molding concrete into the desired shape, size, and controlling its position and alignment. [5] Reference and scaffolding or formwork or formwork is a temporary construction in the form of a mall / mold on both the upper and lower sides of the desired concrete shape. Formwork functions as desired construction, while Scaffolding serves as a helper strengthening the form of construction. According to Wigbout (1997), formwork construction works perform 5 functions, namely: [4] 1. Formwork determines the shape of the concrete construction to be made. The simple form of a concrete construction requires a simple formwork. 2. Formwork must be able to safely absorb the load caused by concrete species and various external loads and vibrations. In this case the change in shape that arises and the friction can be allowed as long as it does not exceed these tolerances. 3. Formwork must be able to be simply installed, removed and moved. 4. Preventing loss of wetness from new concrete. 5. Provides thermal insulation. In planning a formwork, the following data are needed: 1.   (Source: Author, 2020) Planning of a formwork shoring on the beam must of course take into account its strength, stiffness, and stability. In order to guarantee the achievement of strength, rigidity, and stability of formwork construction, it must be designed as a general structural design. Following is the flowchart methodology used in the completion of this Research.

IV.1. Data Dimention Upper Longitudinal Beam
Refer to Shop Drawing (LRT-CV-ST-DW-L2-TRLV-01 sd 47) getting form PT. Adhi Karya as a main contractor on Light Rail Transit JABODEBEK that is known the Upper Longitudinal Beam beam dimension data shown in Figure 3 and Table 1 below.
From the dimensional data in Figure 3 and

IV.2.3 Resume Control Stress, Strain, and Deflection
The static calculation of the formwork shoring structure above, it can be concluded in Table 2 :

IV.3.2 Resume Control Stress, Strain, and Deflection
The static calculation of the formwork shoring structure above, it can be concluded in Table 3 :

IV.4.2 Resume Control Stress, Strain, and Deflection
The static calculation of the formwork shoring structure above, it can be concluded in Table 4. :

Conclusion
Based on the analysis and recapitulation of the value of bending stress, deflection and shear stress in the beam formwork components of the Upper Longitudinal Beam: a) Upper Longitudinal Beam formwork fulfills strength requirements with flexural stress values that occur on Plywood, Girder GT 24, and Steel Waller SRZ materials, each of which is smaller than σ permit = 100 kg / cm 2 , 70000 kg / cm 2 , and 1200 kg / cm 2 . b) Upper Longitudinal Beam formwork meets the requirements of stiffness with deflection value occurring on Plywood and Girder GT 24 material is jin permit = l / 400. Whereas the SRZ Steel Waller fulfills Δ permit = l / 240.