Seismic Performance of Dutch Colonial Buildings

INTRODUCTION

As we are aware a lot of the existing old buildings constitute relics of the Dutch colonial period that are 100 – 300 years old, were found particularly in the big cities in Indonesia such as Padang. A large number of these buildings represent constructions of 1 to 3 floors (low-rise buildings), constitute unreinforced masonry buildings with a floor slab construction that may consist of wood, clay-bricks piled in the shape of a curve which spans between two steel I-beams, or reinforced concrete. Normally building’s foundation  may constitute of a construction of clay-bricks, stone pad and timber logs. The roof frame may consist of a wood or steel structure and covered with roof tiles. The old URM buildings usually were built with masonry wall in consistent thickness for the height of the building and placed crosswise to make a “box-type” structural system. This system is meant to provide more stiffness in both direction and to give resistance for torsional effect.

Now and then the alteration of function of these buildings and repairing the building cosmetically only from the architectural viewpoint, while no structural review has ever been undertaken in renovation would cause a change of gravitation load.

CHARACTERISTIC OF CLAY-BRICK MATERIAL

The characteristic of unreinforced masonry constructions are found in old buildings consist of clay-brick piles which are attached to each other by simple mortar (lime mortar). There are various types of clay-brick piling which can be determined  from its thickness, i.e. 1 to 2 wythe clay-brick (modern building only half wythe clay-brick)

The average dimension of the old masonry unit is around length 250 mm x width 120 mm x thickness 55 mm. Based on the author’s experience conducting the compressive strength test using existing Dutch masonry units which were taken from old building built in 1907 (Semarang, Central Java) are quite variable and average compressive strength, f_m, was found 6.5 MPa.

DAMAGE FEATURES

According to the data that we have recently taken from Padang earthquake, the performance of URM buildings could be damaged and worse could generate a total collapse. The masonry material has characteristics as heavy specific gravity, low ductility and also low tensile strength.

Typical damage features on URM buildings at Arau Street in Padang:

1. Diagonal cracks on the walls
2. Failure on corners of the walls and the openings like doors and windows.
3. Fallen roof parapet.
4. The top framework was usually sliding off from its base
5. Connection damage between foundation and walls, walls and walls and walls and top framework.

Based on recently earthquake experiences, repairation of old or historical buildings it would be commendable to have a Regional Regulation or standard from the Department of Public Works issued which necessitates a review of the structure’s analysis before undertaking renovation. Without the existence of a tight regulation, we will lost a lot of historical buildings in the future earthquake.