All The Complexities Of Arvila Delitriana In Designing The Brass LRT Arch Bridge

Minister of Research and Technology / Head of the National Research and Innovation Agency Bambang Brodjonegoro with Engineer Arvila Delitriana (Diah / VOI)

JAKARTA - An engineer from the Bandung Institute of Technology, Arvila Delitriana, received praise from President Joko Widodo for his success in designing an arch-shaped LRT bridge in Kuningan, South Jakarta.

It is fitting for Dini, Arvila Delitriana's nickname, to receive praise. Given, the making of this LRT bridge design is quite complicated from other arch bridges.

Minister of Research and Technology / Head of the National Research and Innovation Agency, Bambang Brodjonegoro, also acknowledged that the complexity of the crossing over the Kuningan intersection was not only crowded with vehicles. Many structures have been built there.

"Apart from the very busy intersection, there are also toll roads, flyovers along Jalan Gatot Subroto, then the underpass from Kuningan to Mampang," said Bambang at the Office of the Agency for the Assessment and Application of Technology, Central Jakarta, Monday, 6 January.

With such complexity, the 148 meter long bridge was successfully constructed without adding a supporting column in the middle of the quarter. Remember, there is not enough space in the middle of the intersection to make a pole.

An engineer Arvila Delitriana who designed the LRT arch bridge (Diah Ayu Wardani / VOI

Dini admitted that the LRT Curved bridge is classified as an irregular bridge because it has 3 threads and irregular geometry due to its small curved radius. Thus, the ratio of the height of each supporting pillar is not the same.

"The legs (support) in Gatot Subroto and the one in Kuningan (Rasuna Said) are about 6 meters in height. There is a stiffness that must be balanced. If the legs are different in length like that, the stiffness becomes unbalanced," said Dini.

"From there, we need to make special rules that are not regulated in detail by government regulations. So we have to calculate with a more specific method," he continued.

Beat three overseas designs

Initially, the contractor Adhi Karya had three choices of LRT bridge designs made by a consultant from Prencis. The three designs are the incremental launching method using a steel box grider, cable stayed, and concentrate box grider balanced cantivaler with the middle column.

However, the central government doubts that the three designs are difficult to implement in the road structure and the density of the Kuningan area. Therefore, a new design was sought in the form of Dina's concentrate box grider balance cantiviler method.

"When viewed from a construction perspective, the three designs are very risky. What the international consultants are proposing cannot be implemented, so we ask that Mrs. Dina be able to find a way out of this problem," said Minister of Research and Technology / Head of the National Research and Innovation Agency. Bambang Brodjonegoro.

Bambang admitted that the design price of the Kuningan LRT bridge from a French consultant was indeed cheaper. However, there are new problems when looking at field conditions which have resulted in cost overruns during the construction stage.

"The special conditions (at the Kuningan intersection) make what is designed cheaply becomes expensive during implementation, because the additional column must be built in the middle of placing 3 levels of the track," said Bambang.

Skip the process of analyzing the 7 earthquake shocks

Dini admitted that the earthquake resistance analysis before designing the curved LRT bridge could not only refer to the earthquakes that occurred around Jakarta. The structure of this LRT train track has special properties, so that it cannot be designed by means of an ordinary earthquake design.

LRT Arch Bridge (Diah Ayu Wardani / VOI)

In this project, Dini used a fairly complex seismic design level. He must take earthquake sources from 7 earthquake sources in the world to be synthesized in the Indonesian earthquake, especially Jakarta.

"So, we made a synthetic earthquake which we took from 7 major world earthquake sources which was matched with the earthquake mechanism in Jakarta called Time History Analysis and was non-linear," said Dini.

The earthquake history used is the one that happened in Bigbear, Chile, Livermore, Michoacan, Miyagi, South Sumatra, and Tohoku. These 7 earthquakes have an earthquake characteristic that is close to earthquake conditions around Jakarta.

For information, this arch bridge is one of the most difficult parts of the construction of the Jabodebek LRT line which has three services: Cawang-Cibubur, Cawang-Dukuh Atas, and Cawang-Bekasi.

Arch bridge construction has been completed. Before being operated, the bridge with a concrete meter weighing 9,688.8 tons will be subjected to a load test first. The plan is for the track testing to be carried out in 2021 after the entire track has been completed.