Report #170: Thathara Houses in Himachal Pradesh

by  Aditya Rahul, Ankita Sood, Yogendra Singh, Dominik H. Lang    

The addressed building type has been identified in Himachal Pradesh, a northern state in India. Nowadays, this type of construction practice can be seen for houses and temples, however, earlier photographs suggest that the same style was adopted to build palaces, bridges as well as various other structures. The construction style is named ‘Thathara’ as this term is locally used for wooden planks that make the vertical load-carrying members (columns) locally known as Thola(s). Tholas (a peculiar combination of timber and stone) and wood are primarily used for the vertical and horizontal frame elements, respectively. The region where this building typology is found is characterized by cold climate and witnesses heavy rainfall during the rainy season (from June to July) as well as snowfalls in winter (from October to March). These effects have been considered well in the construction style, like e.g. small openings, a verandah to take sun but prevent from rain and snow, wooden and mud interiors which are good insulators and keep the interiors warm, sloping roofs with adequate projections as well as other features. Being located in the Himalayan region, the area has experienced numerous strong earthquakes and this construction technique has eventually evolved to resist seismic action.


Report # 150 : Timber-reinforced Stone Masonry (Koti Banal Architecture) of Uttarakhand and Himachal Pradesh, Northern India

by Piyoosh Rautela, Girish Chandra Joshi, Yogendra Singh, Dominik Lang

Despite being located in a high seismic risk area, a region in the Himalayan states of Uttarakhand and Himachal Pradesh (Northern India) exhibits an elaborate tradition of constructing multistoried houses. In the Rajgarhi area of Uttarkashi district (Uttarakhand) a large number of intact buildings of the distinct construction type known as Koti Banal can be found. Koti Banal is the name of a village in the Yamuna Valley which represents the traditional knowledge and understanding of earthquake effects on buildings and their earthquake resistant design. Investigations suggest that the region had evolved this elaborate and magnificent earthquake-safe construction style as early as 1,000 years before present. This architectural style further demonstrates the existence of elaborate construction procedures based on principles somewhat akin to that of blockhouse construction. Many features of these buildings are considered as the basics of modern earthquake-resistant design. Generally, ornate multistoried houses with abundant use of wooden beams are characteristic of Rajgarhi area. For buildings of the Koti Banal architecture, locally available building materials such as long thick wooden logs, stones and slates were judiciously used. The height of these structures varies between 7 and 12 m above the base platform which consists of dry stones. These structures are observed to have four (Chaukhat) to five (Panchapura) stories. It is reported that especially buildings of the Koti Banal architecture withstood and performed well during many past damaging earthquakes in the region. In a report on the effects of the 1905 Kangra earthquake (M 7.8), Middlemiss (1910) already describes the well performance of these ?(..) top-heavy constructions? located along steep slopes of the Kangra-Kulu epicentral area, which differed ?entirely from the sun-dried brick-built structures of the Kangra Valley. The performance of these structures has also been corroborated by eye-witness accounts during the 1991 Uttarkashi earthquake which had a magnitude of mb 6.6 in an epicentral distance of 30 km during which many new buildings collapsed while these structures did not suffer any damage. The reasons that these buildings outlived so many centuries mainly lie in their structural configuration which clearly demonstrate that their builders already had the idea of dynamic earthquake actions, particularly out-of-plane failure of masonry walls. The buildings are further characterized by a number of advantageous design features such as regular plan shapes, the sensible use of locally available building materials, the integration of wooden beams over the total height of the building as well as small openings and the arrangement of shear walls.


Report # 92 : Historic, braced frame timber buildings with masonry infill (‘Pombalino’ buildings)

by Rafaela Cardoso, Mario Lopes, Rita Bento, Dina D’Ayala

Pombalino buildings (see Figures 1, 2, 3 and 4) are historic masonry buildings that can be identified by the presence of a three-dimensional timber structure (named “gaiola pombalina”), which is enclosed in internal masonry walls above the first floor. The roofs are built with timber trusses clad with ceramic tiles and the floors are made of timber boards laid on timber joists. Ground floor walls are roughly dressed stone masonry supporting a system of vaults made of clay tiles, with stone arches. Foundations are made of short and small-diameter timber piles connected by a timber grid. These buildings were built after the 1755 earthquake when fear of new earthquakes led to the enforcement of anti-seismic provisions, such as establishing a maximum number of stories and introducing an interior timber structure called “gaiola.” The buildings originally were mixed-use with commercial enterprises on the ground floor and residences on the upper floors. During the 20th century, most Pombalino buildings underwent substantial refurbishment when they were converted and occupied entirely by banks and companies. For the buildings that have maintained their original uses, the main problems result from poor maintenance.The expected collapse mechanisms due to earthquake actions are the overturning of facades (out-of-plane) or shear failure at the plane of the walls at ground floor level (global shear mechanism), leading to a global collapse mechanism. Typical seismic strengthening of these buildings includes the introduction of a concrete/steel ring beam at the level of the roof eaves. The introduction of steel elements/pre-stressed cables or of anchors connecting parallel masonry walls is also common. Steel elements are also used to connect detached timber elements from the floors and gaiola to the masonry. New techniques applying new materials like Fibre Reinforced Polymers (FRP) are also used to increase the strength of the connections of timber elements that compose the gaiola.