ANALISIS KUAT LAYAN STRUKTUR ATAS JEMBATAN (BALOK MENERUS) AKIBAT RUNTUHNYA SALAH SATU PILAR JEMBATAN (STUDI KASUS JEMBATAN GANTIWARNO, KLATEN, JAWA TENGAH)

Abstract

The upper structure of the Gantiwarno bridge in Klaten, Central Java, was built using the continuous concrete beam bridge structure, which was supported by abutment at the ends and two pillars between them. In its service, one of the pillars had collapsed causing the inability of the upper bridge structure to provide support for the necessary loads. This study aims to observe; 1) the moment resistant of the main concrete beam section and its difference compared to the positive and negative maximum moment produced from the result of SAP90; 2) deflection and natural frequency value of the bridge in the normal condition of the upper structure and in the damaged condition. Through the observations, the study intends to understand the remaining strength of the upper structure, due to the collapse of one of the pillars, in supporting the services load. The result showed that the percentage of the “D” load allowed to pass the bridge structure in its damaged condition is 2.7859% (motorcyclists were still able to pass the bridge). There was a significant decrease of 68.312% of the structure natural frequency in its damaged condition. The deflection in its normal conditions was far from the maximum deflection permitted. It was also the case in its damaged condition. Therefore, the service strength of this bridge is determined by the moment resistant of the existing main concrete beam section and not by the deflection.