Category: Stone Masonry

Stone masonry is a traditional form of construction that has been practiced for centuries in regions where stone is locally available. Stone masonry has been used for the construction of some of the most important monuments and structures around the world. Click HERE for an introduction to stone masonry construction.

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Report # 172 : Dry Stone Construction in Himachal Pradesh

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

The addressed building type has been identified in Himachal Pradesh, a northern state in India. It is a
relatively recent construction typology, which can be seen prevalent in the areas where people have
been forced to leave their traditional construction practices due to scarcity of wood. Thus, this
construction style is nothing but the traditional housing style omitting the wooden elements, be it
Kath-Kunni style of the Kullu, Shimla or Kinnaur districts or Thathara style of Chamba district. Due
to the region’s heavy precipitation both in terms of rainfall (June to July) as well as snowfall (October
to March), rubble stones are preferred over the alternative locally available construction material, i.e.
mud. However, these buildings possess high seismic vulnerability due to low in-plane and out-ofplane
strength of their dry stone walls. This report identifies the main sources of seismic vulnerability
of dry stone buildings and also suggests a retrofitting scheme to reduce the seismic vulnerability of
such buildings.

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Report # 114 : Stonework building with wooden timber roof

by Masoud N. Ahari, Alireza Azarbakht

Stonework buildings are a common type of rural construction in many parts of Iran (Figure 32). It is widely used in the mountainous areas because of the ease of attaining the building material. More than 71,000 stonework buildings were built in 1968-1972 in comparison to 54,000 brick masonry buildings in these years [1]. Unfortunately these buildings are often found in highly seismic parts of Iran (see maps on WHE webpage for Iran). Buildings of this type are up to two stories high, with height/width aspect ratio on the order of 0.3-0.5. The building materials consists of stone, wood, mud mortar and straw. The major elements of these systems are stonewalls which carry both gravity and lateral loads. These walls consist of stone or stone ballast with mud mortar and straw. For reasons of thermal insulation the thickness of these walls is not less than 50 centimeters (usually 70 centimeters). Details of wall are shown in Figures 11 to 20. The roof includes wooden joists and a set of secondary joists which are plastered with a thick layer of mud (Figures 21 and 22). Different views of this kind of building are shown in Figures 1 to 3. Also a typical building view, plan and layout are shown in Figures 4 to 10. Weak points of this construction type are: the presence of a heavy roof; inadequate behavior of the walls under out-of-plain forces (Figures 23 and 24); poor shear capacity of the mortar; inadequate connection between roof and walls; inadequate connection between intersecting walls; and lack of diaphragm action in floors and roof where the roof elements (wooden beams) do not work together in earthquakes and may collapse (Figures 25 and 27). In general, this kind of structure is frequently used as a house and stable in mountainous villages, but its earthquake performance is not acceptable. Any proper rehabilitation techniques may save many people’s lives.

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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.

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Report # 138 : Stone masonry residential buildings

by Qaisar Ali, Taj Muhammad

In the Northern part of Pakistan, which mostly consists of mountainous terrain and where building stones are more abundantly available than any of the alternate building material, people commonly construct single story stone masonry buildings for residential purpose. A variety of building typologies are in use. An approximate distribution of common types of such buildings is:- Stone masonry houses without mortar with earthen roof (Fig 1a). 10% Stone masonry houses in mud mortar with earthen roofs (Fig 1c). 40% Stone masonry houses in cement mortar with earthen roof (Fig 1d). 10% Stone masonry houses in cement mortar with G.I.Sheet roof (Fig 1f). 30% Stone masonry houses with R.C roofing (Fig 1g) 10%. Construction of houses in rubble stone masonry, in dry or in mud mortar, was most common and was generally practiced in the past in these areas. It is still in practice in most construction. Presently, among all, about 50% of the buildings are of this type. In new construction mud mortar is steadily being replaced with cement mortar. Wall thickness in all cases usually varies from 1 to 1 ½ ft. Roofs are usually earthen and generally consist of thatch covered with mud/earth and supported on wooden beams (or logs) and rafters. Some time wooden columns are also provided beneath the beams along the walls or in between the walls to support the roofing. Wooden rafters, planks and G.I. sheets are also used in modern construction for roofing. Any particular or regular layout is not used for construction of these residential buildings. It varies depending on the available space. Size of the building also varies from a single room to more than one room as per requirement of the family (Figs 3a–3c). These structures are considered, from experience, to be strong enough to withstand the applied gravity loads, but their seismic performance has not properly been investigated and is believed to be vulnerable to earthquake of even moderate shaking, particularly when confining elements such as wooden columns are not used. In a typical type of construction, historically known to be well resistant to seismic effects, horizontal and vertical wooden members are provided in the walls. These horizontal and vertical members are inter-connected at corners and other locations through wooden nails. The remaining space of the wall is then built in stone masonry of any type. This type of construction was commonly practiced in remote North parts of this region in the past and is still in practice for improved seismic performance in some of the buildings (figs 5a–5e).

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Report # 121 : Unreinforced stone wall rural housing (lower and middle income)

by Riccardo Vetturini, Fabrizio Mollailoli, Paolo Bazzurro

Typical house occupied by low-income and middle-class families in rural areas of central Italy. The building studied in this report is located in the municipality of Nocera Umbra, province of Perugia, Umbria region, Italy. This type of building, with minor differences in construction practice and material, is frequently found throughout central Italy. The four-story building was constructed more than 200 years ago and is located on a steep hillside, with the elevation facing the valley completely above grade; the uphill elevation is two stories above grade, with the two stories below ground-level surrounded on two sides by earth-retaining stone masonry walls. This building was severely damaged by the 1997 Umbria-Marche earthquake and was further weakened by the elements before repair and reconstruction efforts began in 2003. Figures 1 through 5 show the damaged building before reconstruction. Figure 6 helps to locate this building in the cluster of buildings around the old citadel. The exterior elevation facing the downhill slope is displayed in Figure 7. The overall floor plan of this building is L-shaped; it accommodates two residential units and has a basement with four separate spaces and entrances for housing farm animals and storing tools. Building plans showing the extent of wall and floor reconstruction can be seen in Figures 8 to 10. Figures 12 to 14 display details of the seismic retrofit. Most buildings of this type, however, are smaller in size, rectangular in shape, and often have one unit. It is very common for these buildings to share perimeter walls with adjacent buildings. In these rural regions it is typical for many generations of a single family to live in the same residence and the building has undergone numerous additions and modifications over its life span to accommodate changing living requirements. The construction modifications are typical of Italian rural regions. The architecture is fairly plain with few architectural details of significant historic value; these were repaired and restored during the seismic reconstruction project. Gravity loads in the building are carried by thick unreinforced stone walls constructed using a technique referred to as “a sacco”. The walls consist of two outer stone wythes that are poorly connected by a limited number (if they are present at all) of bond-stones. The space between the two outer wythes is filled with an inner core of smaller rubble masonry, poorly consolidated and poorly graded by a mixture of lime or mud mortar. This construction technique results in walls with limited vertical and lateral capacity because of the presence of voids between the stone masonry and the lack of effective continuity between the inner and outer wythes. The pre-earthquake construction technique and the quality of the mortar in the stone masonry walls were poor. The lack of continuity between the original stone masonry walls and the walls constructed during the various structural additions worsened their condition (see Figure 4). The majority of the floor slabs are constructed of timber beams with intermediate timber joists. Other areas of more recent vintage consist of vaulted floor construction assembled from steel beams and clay-infill bricks arching between them with a lightweight concrete topping layer. Poor seismic performance is expected, mostly because of the ineffective connection between interior and exterior wythes of the walls and existing structural deficiencies (e.g., flues, niches, etc.); lack of effective wall-to-wall, wall-to-slab, and wall-to-roof connections; and lack of continuous foundation-to-roof walls due to the vertically unaligned openings on the facade. Very thick walls present throughout the building, especially at the foundation level, and occasional iron tie-rods add to the structural strength.

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Report # 120 : Unreinforced stone wall rural housing (upper income)

by Riccardo Vetturini, Anacleto Cleri, Fabrizio Mollailoli, Paolo Bazzurro

This is a typical house occupied by affluent families in rural areas of central Italy. The building discussed in this report is called “Palazzo Spinola” and is located in the town of Foligno in the Umbria region (see Figures 1 and 2). The building has four stories above ground and a completely below-grade basement. Floor plans and cross sections are shown in Figures 3 to 9. Significant geometrical complexity has resulted from additional construction since it was originally built in the seventeenth century. The original construction includes only a portion of the interior building as well as the entire exterior facade. The building has an interior courtyard within the perimeter of the building. It contains a well and a cloister (a covered path with ornate columns) that separates it from the grounds. These are also part of the original construction and have significant artistic value. The upper portion of the cloister is accessible and serves as a connection between the two exterior wings of the residence. The thick walls are constructed using a typical technique called “a sacco.” This construction technique consists of two outer wythes that are poorly connected by transversal bond-stones (“diatoni”) and filled with essentially unconsolidated inner cores of rubble masonry, poorly cemented with lime mortar. The floor slabs may be of mixed construction, depending on the era. The ground floor has “a padiglione” vaulted ceilings, which are constructed of solid bricks assembled in fairly regular fashion. The second-floor ceilings are vaulted and partly frescoed. Some of the ceilings in the residence have great artistic value, with painted wooden panels (“cassettoni”). The floor slabs on the upper stories are considerably simpler in construction and are made of timber trusses with hollow-clay tiles in between. The structure supporting the roof is made of timber trusses with both vertical and diagonal struts and bottom chords. Some trusses are more complex, similar to Palladian trusses. Buildings of this type are expected to demonstrate fairly poor seismic performance, mostly due to the ineffective connection between interior and exterior wall wythes and existing structural deficiencies (e.g., flues, niches, etc.); lack of effective wall-to-wall, wall-to-slab, and wall-to-roof connections; and the unbalanced outward thrust of the vaults. The structural strengths are represented by very thick walls present throughout the building, especially at the foundation level, and by the occasional iron tie-rods.

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Report # 119 : Urban residential buildings of the 19th century in the city of Basel

by Kerstin Lang, Hugo Bachmann

This building type was mainly constructed as residential buildings in the second half of the 19th century until the beginning of the 20th century in the vastly expanding city of Basel, but also in other Swiss cities. The buildings are made of unreinforced masonry with timber floors, are four to five stories high and are attached to each other. The unreinforced masonry walls are usually made of simple stone (more or less regularly cut) or brick masonry, the thickness of the stone masonry walls being larger. The mortar used is usually lime mortar. In some cases, a mixed masonry was used, especially at the ground floors, with larger, well cut stones for the outer layer of the façade walls and simple stones or bricks arranged behind. The buildings are rather regular in plan and elevation. However, the timber floors are often not anchored to the masonry walls and the front and back façades usually have rather large openings for the windows whereas the side walls are solid walls used as fire division wall. The seismic performance of these buildings is expected to be rather poor.

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Report # 113 : “Casa Torre” construction: multistory tower masonry with stone pillars and wood or arched beams

by Mauro Sassu, Chiara Cei

This construction originated during the Middle Ages in response to the threat of military invasions. The building plan is a square lattice, 5-7 meters, formed by three or four floors, with one room on each floor, and a total height of 15-20 m. It is a common technique found in Pisa but also found frequently in many municipalities of Tuscany and adjacent districts. The structure of the building is supported by four stone columns connected by arches (circle or oval) or by beams at each floor; the floor is supported by a series of wood beams (especially pine) with wood tables and/or clay blocks. The upper floors of the earlier historic buildings often contained a wood balcony supported by cantilevered wood beams. Some balconies were fully enclosed structures with clay-tile roofing. The entrance on the first floor could be accessed by means of a detachable wood staircase.

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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.

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Report # 80 : Low-strength dressed stone masonry buildings

by Ravi Sinha, Vijaya R. Ambati

80a

Construction of stone masonry buildings using easily available local materials is a common practice in both urban and rural parts of India. Stone masonry houses are used by the middle class and lower middle class people in urban areas, and by all classes in rural areas. In rural areas, these buildings are generally smaller in size and are used as single-story, single-family housing. In urban areas, these buildings are up to 4 stories high and are used for multifamily housing. This is a typical load-bearing construction, in which both gravity and lateral loads are resisted by the walls supported by strip footing. If the locally available stone is soft, dressed (shaped) stones are commonly used and can be chiselled at low- or moderate cost. Mud or lime mortar has been used in traditional constructions; however, more recently, cement mortar is being increasingly used. Because soft sandstone is readily available in the Kutch region of Gujarat in the western part of India, stone block masonry constructions are widely used for both single- and multi-story constructions. These houses are usually built by local artisans without formal training and the resulting constructions are structurally weak and incapable of resisting large seismic forces. In the Kutch region, which was affected by the 2001 Bhuj earthquake, this construction type is commonly used with a gable end timber roof truss or RCC roof slabs. Thousands of these houses collapsed in the 2001 Bhuj earthquake resulting in the deaths of large numbers of people. This construction type is inherently unsuitable for areas of moderate-to-high seismic hazard, such as the Kutch region of Gujarat.

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