This paper describes the findings of a tour of heritage buildings in the Indian state of Gujarat which were affected by the Bhuj earthquake of 26th January 2001. After a general introduction to the earthquake and its effects, a description is given of the damage suffered by princely palaces and religious buildings in Bhuj, JamNagar, Wankaner, Morbi, Maliya, Halvad, Dranghedra and Ahmadabad. 40 photos of the damage are included. The paper closes with conclusions and recommendations concerning the repair and maintenance of heritage buildings in Gujarat, and some observations on how the seismic response of massive masonry structures differs from that of engineered structures in reinforced concrete or steel. A modified version of this paper will be published in the EEFIT general report on the Bhuj earthquake.
Gujarat has a rich heritage of buildings built by the princely rulers of the area over the last 500 years. Some of these buildings are of international importance. Many were seriously damaged during the January 2001 earthquake. The Indian National Trust for Arts and Cultural Heritage (INTACH) has estimated that of 250 heritage buildings inspected in Kachchh and Rajkot, about 40% either collapsed or were seriously damaged, while only 10% remained undamaged.
Some of the heritage buildings in Bhuj, Jamnagar, Wankaner, Morbi, Maliya, Halvad, Dranghedra and Ahmadabad were inspected by Rabindra Vasavada, an architect based in Ahmadabad specialising in conservation and Edmund Booth (www.booth-seismic.co.uk) , a civil engineer based in London specialising in seismic engineering. The inspection was carried out on behalf of the Indian National Trust for Arts and Cultural Heritage (INTACH) , during the period 25th March to 2nd April 2001.
Earthquakes are natural phenomena which are yet to be fully understood. Scientific knowledge about them exists, but their time of occurrence, location and magnitude are difficult to forecast. For this reason, earthquakes are dreaded by human beings and their effects are only to be borne as they happen; depending on their magnitude and duration, there is damage to life and property wherever they strike.
The recent earthquake in western India was one such rare occurrence which has taken the people all over unawares and the damage it has caused in varying degrees has been devastating the life of people in this region. After the calamity, there has been an increased awareness about the phenomenon and there is a general demand for safeguards against any such future occurrences so that the damage to human life and property is minimized. Since there was no major occurrence of such an earthquake in the last century in this region, people in general have got a shock of their lifetime and since it has not previously been experienced for several generations, there was a complete lack of preparedness on the part of the people at large, including the authorities and public welfare institutions.
The regional building techniques have two distinct characteristics. Firstly, there is a large heritage of building methods and appropriation of shelters which is patronized by the people themselves out of their instinctive traditional wisdom and know-how. These types of shelter building practices are still confined to the tribal cultures in the agrarian regions of Saurashtra and Katchchh. These shelter forms, which were a product of the ecology of the area, sustained themselves in the event of such earthquakes and are more or less unaffected. This was because of the form of the shelter and also the materials and techniques with which these were put together. There is always some sort of instinctive ability in people who live close to nature to understand the forces of nature and also develop means in congruity to it so that they exist in a harmonious coexistence. The second type were structures built in villages and urban areas by masons and builders for an occupant which were involving quasi-modern techniques with easily available materials and hybrid techniques. These buildings were of various types and using different structural possibilities offered by contemporary materials. In the villages there was also an element of cheaper construction using waste stones and materials which were not particularly good for building purposes. In the case of masonry construction, it was also a practice to use soil as a binding material and in many cases the soil used was of a very inferior quality. All these factors compounded the effects of the tremor and the material used in masonry just could not resist any lateral pressures for which it had no security. This amounted to large scale collapse of houses in the villages and also to some extent in the towns in the Katchchh region.
Quality of construction, choice of the form of buildings and also the magnitude of the tremor all accounted for the misery suffered by the people in general. The building form has in the first place to be seen as a balanced form which if laterally shaken should be able to retain its equilibrium in all the directions as the tremors are multi directional. For this reason, in addition to designing a balanced form, it is important to provide inbuilt flexibility to the corners, planes and the upper parts of the ztructures. Normally the upper parts of the structures are lighter than the lower parts and should be strengthened and made flexible to absorb the shocks. In addition, it should be a practice to secure the overall form of the building for planar movements. This is necessary parallel to the plane and also along the plane. This is done by introducing keying and lapping of horizontal layers of masonry by longer pieces of stones, continuous bands and plates.
As far as possible it is useful to adopt building materials which are local and natural, used in form of units for construction. The roofs and floors also should be such that the entire construction is possible as an assembly of parts. These materials are more friendly and adaptable for repairs, maintenance and most of all non damaging to human life in the event of failures. In the villages where almost all the houses simply turned into heaps of material debris, the loss of human life was almost none. In contrast to this wherever in the towns and cities, modem industrial materials were used, the chunks of poured concrete crushed many people even in one single building, and it was humanly impossible to remove debris as even lifting debris to salvage injured people required mechanical handling of huge chunks of building elements.
Every calamity is a tragedy for society. The scars of misery continue to hound people for a long time. The quake in this region has been a tragedy of a natural character. When examining the fragments and ruins of the Indus Valley Civilization from this region, archaeologists have always wondered about the missing links in the evolutionary record and many times have come across queer specimens of evidences which suggest mutilated skeletons with fractured parts and accidental postures buried under the layers of strata. Could this also suggest that these regions have been relatively younger in the earth’s evolutionary process and are still in the process of formations? The Harappan civilization also might have experienced their share of such human misery that we are experiencing today after centuries. In that sense such phenomena are cyclic and we in the present times are experiencing the fate of our times in this process of natural evolution. But with the present level of scientific achievements and know-how perhaps are in a better shape (although very relative to say that as each time has its own level of excellence) to chart our future course to safeguard ourselves from recurrences of such a situation. In that sense it is a time for us to apply all the available knowledge and make our environment safer by introducing methods and scientific know-how in building our new environment in our towns and cities and villages. But it is important to remember that to exist in nature, we must integrate ourselves in all ways within the nature that surrounds us and develop a balanced insert which as integrated entity would remain one with the nature and not collapse as an imposed strata. Also remember that the analogue of trees is significant for correct integration, as no tree ever was uprooted or even fell due to these upheavals of the earth’s crust! In most cases it was lack of integration which was the cause of the failure and in that is our lesson to learn for any future, safeguarding strategies for rehabilitation of whatever is damaged and destroyed.
Jamnagar is about 100 km south of the causative fault, and the general level of damage in the town appeared to be around VII MSK. The earthquake was strongly felt and earthquake induced damage was relatively easy to find, but there was no severe disruption to the life of the city and few examples of collapses.
The most important historical building is the Dabargadh (Maharajah’s palace) , which occupies a large site in the old town, and consists of a number of buildings, many with very fine architectural features and detailing (figures 1 & 2) .
Figure 1: Dabargadh, Jamnagar - Darbar Hall
Figure 2 - Dabargadh, Jamnagar- carving detail
The buildings are thought to have been built over successive periods but the existing structures belong mainly to the seventeenth century. The site has been uninhabited for about 30 years and is in an advanced state of decay. Some portions had already collapsed before the January 2001 earthquake, which merely accelerated the process. The urgent need for the building is a general programme of restoration for the entire site.
An interesting feature was a reinforced concrete façade probably built around the beginning of the twentieth century to support the masonry building behind it (figure 3). Although the reinforcement was severely corroded, the overall structure was holding well and there was no sign of earthquake induced damage.
|a) Reinforced concrete strengthening façade b) Detail of corroded reinforcement|
|Figure 3: Dabargadh, Jamnagar- reinforced concrete strengthening façade|
Starting at the end of the nineteenth century, the ruling family in Jamnagar built a number of large palaces on the outskirts of the old town. Two were inspected in some detail, namely the Amah Vilas and Pritap Vilas (figure 4) . These are massive two to four storey buildings, in dressed loadbearing sandstone, but incorporating some steel joists supporting suspended floors.
|Figure 4: Pratap Vilas, Jamnagar|
Both buildings were of good workmanship and had generally been adequately maintained. Ornamentation at roof level was extensively damaged (figure 5) . There was some cracking in the load bearing masonry, particularly at upper levels, but generally the load bearing elements were stable and no part of the structure had collapsed. However, there was more severe structural damage at upper levels in at least two places (figure 6) .
|Figure 5: Ornamentation fallen from roof level of Amah Vilas, Jamnagar||Figure 6: Cracking in Pratap Vilas, Jamnagar|
03: Ranjit Vilas Palace, Wankaner
Wankaner is situated about 95km south of the fault. The main part of the town is on a plain extending north to the Gulf of Katchchh. Rocky hills outcrop to a height of several hundred metres on the southern boundary of the town. Damage levels due to the earthquake in the town appeared to be generally minimal, and this was confirmed by reports. A settlement of traditional buildings apparently of the type that was almost totally destroyed in and around Bhuj appeared undamaged (figure 7).
|Figure 7 - Wankaner - undamaged random rubble buildings|
The palace is situated on top of a ridge on the rock to the south of the town (figure 8) . The main building is a rectangular block of 2 to 3 storeys, with a central hall, circular corner turrets becoming octagonal and a square central tower on the north façade about 40m high. It is built from dressed masonry blocks, in basalt for the foundations and in local yellow and red sandstone for the superstructure. Floor construction is of timber and metal joists, carrying cast in situ mortar floors. Storey heights are around 6m. The building was completed in 1913, with some additions made 10 years later. The quality of construction is high, with the horizontal joints in the masonry very thin.
|Figure 8 - Ranjit Vilas, Wankaner|
The main damage is at the roof terrace level. The corner turrets are both very severely damaged (figure 9) and the eastern baradari (single storey penthouse) has collapsed completely. Many of the balustrades of the terrace have collapsed.
|Figure 9: Ranjit Vilas, Wankaner - eastern corner turret|
The central tower (figure 10) is square in plan. The walls are approximately 900mm thick, reducing above the third floor level, which reduces the mass and weight toward the top. The corner stones appear well keyed together, and the basic structure has not distorted or cracked significantly. At least two of the corners at different levels are braced with a short diagonal steel joist member.The dome on top of the central tower has collapsed, along with part of the clock and some stone work items, destroying two upper floors in the tower, and the steel trussed roof to the hall behind the tower on the upper level.
|Figure 10: Ranjit Vilas, Wankaner - central tower|
The damage to the palace appears much greater than would be expected from that experienced in the town on the alluvial plain below. It is interesting to speculate whether the position of the palace at the top of a steep, rocky ridge gave rise to amplified seismic motions, or whether the ground motions were of a particularly long period. It appears that some mosques in the centre of the town were also damaged, but these were not inspected.
04: Manimandir, Morbi
Morbi lies about 65 km SSE of the fault. Damage was quite evident throughout the town, with some sections (reported to be on soft ground) having extensive collapses. The town appears to have preserved many of its original features and character from a century ago (figure 11) .
Figure 11 - Morbi city gate
The Manimandir palace is a highly ornate building which dates from 1927 (figure 12) . It consists of a quadrangular building very approximately 100m by 100m with a large central courtyard in which there is a temple. The main damage, which is extensive, is at roof level, particularly to the turrets which appear dangerously unstable.
|a) South and west external facades. Note temple projecting from within courtyard to left||b) Detail of damage to roof turrets|
|Figure 12 - Manimandir palace, Morbi|
The old palace (dabargadh) was also reported to be extensively damaged (figure 13) , though no inspection was carried out.
|a) External view||b) Internal view|
|Figure 13 - Dabargadh, Morbi|
05: The main street and the Dabargadh, Maliya
Much of this village, which mainly consists of single storey random rubble masonry houses, has been severely damaged or has collapsed. It lies about 35km south of the fault. The dabargadh lies on the north western corner of the village. The older two storey random rubble masonry buildings of the dabargadh have completely collapsed. The newer two storey building, dates from around 1930, and is also mainly in random rubble masonry. It is severely damaged at first floor level particularly at the northern corners, and the single storey penthouse has completely collapsed (see figure) , taking much of the first floor slab with it; what remains of the floor slab is precarious.
|The Dabargadh, Maliya|
A massive eighteenth century masonry decorated entrance gate appears in reasonable condition, although a second similar gate (also apparently lightly damaged) was apparently demolished soon after the earthquake by a tenant of the former darbar, in order to gain access to some bank property.
There are already clear signs that reconstruction of the village has started, through self help efforts by the villagers themselves.
|Maliya - Self help reconstruction|
6.1 Ayna Mahal Museum Complex
Bhuj was within 20km of the fault break, and suffered very severe damage. The palace complex is in the old walled city. It consists of a collection of buildings in a variety of styles, dating from the 18th century. Some of the buildings are of random masonry construction, and have suffered extensive damage and collapse.
|Collapse of Queens’ Quarters, Bhuj City Palace|
Part of the massive perimeter defensive wall to the complex has been damaged; in places, an additional skin of masonry thought to have been added as a repair after the 1819 earthquake has peeled away exposing the earlier wall beneath. The queens’ quarters, to the east of the complex, has been devastated, and appears beyond repair. The areas occupied by the relatives to the north, are similarly devastated, and have been evacuated.
Collapse of City Wall, revealing ancient wall beneath
|a) Overview||b) Detai|
|Collapse of City Wall, revealing ancient wall beneath|
The inspection concentrated on the eighteenth century building to the east of the complex, which it is considered to contain some unique architecture of great importance. The curator of these buildings, which now function as a museum, Mr P J Jethi, acted as a very helpful guide and source of information.
These buildings are three storeys, and the 450mm thick walls are in dressed good quality limestone masonry. The important rooms are as follows.
6.1.1 Fuvara Mahal (Hall of Fountains)
The Fuvara Mahal or music room was used to perform Vraj Haveli Sangeet. The Lakhapatji Maharao (1752 -l761) made this hall in 1752.
The room is at first floor level, and is 15m square on plan. The central area of the room (figure 14a) is approximately 12m square; it originally contained pools and fountains, and constituted the living area. A 2.4m wide open walkway (figure 14b) extends around the periphery of the room; the walkway is bounded externally by 450mm thick masonry walls and internally by a square grid of timber columns supporting the roof trusses, which span in two directions. The perimeter masonry walls rise about 3m above floor level, where they terminate, and are capped by a 2.4m wide roof slab above the walkway.
|a) central living area||b) Internal view|
|Figure 14 - Fuvara Mahal, Bhuj - interior|
The striking architectural feature is that the internal timber columns rise a further 3.2m or so above the top of the masonry walls and perimeter roof strip, to support a timber truss (figure 15) carrying a flat roof over the centre of the room. The vertical timber sides of the trusses have large openings, and form a clerestory. The roof trusses are unusual structurally, in that there are no horizontal ties at their base; some horizontal restraint is however provided at this level by the roof slab over the walkway acting as a ring beam. The trusses have bolted metal strap connections, which mean that they postdate the rest of the construction; their detailing also looks different. It is possible that they represent a repair after the 1819 earthquake, probably carried out in the mid nineteenth century.
|Figure 15 - Fuvara Mahal, Bhuj - roof truss and clerestory|
The combination of the evaporative cooling effect of the pools and fountains, and the natural convection currents set up by the tall roof and clerestory was climatically designed to suit the hot summer months. These attractive and unusual features indicate that a high degree of importance should be placed on preserving the Fuvara Mahal.
b) Present condition
Part of the north east corner of the perimeter walls, about 2m wide, have collapsed. The central three pairs of timber columns on the north side are tilted outwards (ie north) by about 5% to 7.5% (figure 14b) , pushing the flat roof strip on this side about l50mm across the top of the external wall, which is also sloping outwards, but only by about 3%. The opposite wall is leaning by about the same amount in the same direction. The timber columns on all four corners of the grid are vertical; the other columns have a variety of tilts up to 2%, but usually much less. There is no evidence of structural distress in the timber columns; one member of the roof truss is bowed and slightly split at one point, but generally there is no other sign of structural distress or of material deterioration in the timber. The central roof slab has sagged very significantly, probably between trusses.
6.1.2 Ayna Mahal (Hall of Mirrors) and Hira Mahal (Diamond Chamber)
These are situated on the first floor adjacent to the south side of the Fuvara Mahal; the Hira Mahal lies within the Ayna Mahal. They are both representative of exquisite craftsmanship adorning the traditional interior space, which was designed to create a climatically comfortable environment in a hot desert climate. The mirrors (pieces of mica) fixed on intricate patterns integrated with the structure increased the luminosity of the surfaces enhancing the brilliance of the ambient light which was allowed within the interiors to develop a soothing effect. Such halls of mirrors with jade were important features to display the wealth and prosperity of the princely families. This entire complex needs to be preserved as one of the very few such examples existing as a record of its era.
The structure of this part appears not to be seriously damaged, but is threatened by the collapse of unstable surrounding buildings. During the earthquake, however, many priceless paintings on glass fell from the walls and were irretrievably damaged.
6.1.3 Second floor rooms
The upper floor of the southern part of the Fuvara Mahal comprises the Darbar Hall and an office room, situated directly above the Ayna Mahal & Hira Mahal. This part of the complex is extensively damaged and one of its walls is precariously hanging over the Fuvara Mahal, as mentioned previously. The roof is also very badly damaged, and the hipped end on the west side is already in a dangerous condition.
6.2 Pragmalji Mahal
This is a massive dressed masonry building thought to date from the l870’s (figure 16) , and is situated next to the older buildings described above. From an external inspection, extensive damage can be seen at the upper levels.
|Figure 16 - Pragmalji Mahal, Bhuj|
6.3 Chatris (funeral memorials)
A collection of chatris, commemorating members of the ruling family in Bhuj, used to form an important part of the architectural heritage of Bhuj. They were built between ?1650 and ?1850; ?most predate the 1819 earthquake (dates to be confirmed) . They are situated some distance from the palace complex described above, outside the old city walls.
Figure 17 shows that some were totally destroyed in the January 2001 earthquake, though interestingly some survived, despite their apparently rather unstable form, consisting of a heavy roof supported by unreinforced and effectively pinned masonry columns.
|Figure 17: Chatris, Bhuj|
07: Halvad Palace
Halvad lies about 80km SE of the fault, and is situated on about 6m of alluvial material overlaying rock. Damage generally in Halvad is reported to have been moderate, although some surrounding villages were more seriously affected.
The oldest part of the dabargadh dates back to the early 16th century. Figure 18 shows one of the buildings thought to date from around this time, which must therefore have survived a number of earthquakes, despite its apparently rather unstable structure similar to the chatris in Bhuj (section 6.5) .
|Figure 18: Building in old part of dabargadh, Halvad. Column base detail shows evidence of rocking|
An adjacent quadrangular two storeyed main building around a central courtyard was added approximately three centuries ago (figure 19) . This newer part is adjacent to an artificial lake, which is probably contemporary, and is founded on about 12m of fill retained by a massive masonry wall. The structure of this new palace is masonry stone construction as an envelope to an internal highly ornate timber structure. In the centre of the courtyard is a seven storey octagonal tower (called the Victory tower) of stone masonry construction, some 20m high (figure 20) .
|a) External from lake, showing retaining wall||b) Internal at 1st floor level, showing courtyard and timber arcade|
|Figure 19: Dabargadh, Halvad - main building|
|Figure 20: Dabargadh, Halvad - Victory Tower|
The main building had suffered significant deterioration before the earthquake and some parts had been demolished. The timber roof of one section had been replaced by a reinforced concrete roof; this section survived well. Elsewhere, there were some further collapses, and damage to ornamentation and turrets at high level (see for example figure 19b) . Three corner rooms at the first floor terrace level have developed severe vertical cracks in the masonry and in the north eastern corner the wooden stairs have precariously delinked from its bearing on the walls at terrace level. There is clear evidence that the ground beneath the terrace around the north west corner of the terrace has settled significantly. There are ambitious plans to renovate the palace complex and convert it into a centre for cultural studies.
There is a stepped well in the town (figure 21) , thought to date from the early 16th century, which is contemporary with the founding of the town, and predates construction of the artificial lake. In figure 21, the water level is about 6m below ground level. This is of a traditional construction found throughout Gujarat. The well was undamaged by the earthquake, and there were no reports of damage to any other stepped wells in Gujarat.
|Figure 21 - Stepped well, Halvad, showing water level|
Dhranghedra lies 20km east of Halvad and 115km west of Ahmadabad. It is founded on rock. The general level of earthquake damage in the town was moderate and reported to be less than in Halvad. The palace complex inspected (named Makhashraya Rajmahal) consists of three large linked buildings, namely Sundar Vilas, Surajmal and Ajit Niwas. The complex is a fine example of the intermingling of local craft and artistic traditions with European influences.
8.1 Sundar Vilas
There is some severe cracking in this part, particularly at upper levels, but there appears to be no imminent danger of overall collapse. The domes are heavily cracked, and masonry panels over the windows in the dome have shifted outward significantly, and there is damage to ornamentation (figure 22).
|a) External||b) Internal|
|Figure 22: Sundar Vilas, Dhranghedra - dome|
The central block consists of a Darbar hall, which extends for the full height of the building. It is flanked to the two longer sides, and to the north, by a series of smaller annex rooms with cross walls, and a passage running down the length of the external wall; these are on two levels. The walls are of dressed limestone masonry of high quality. The walls externally have bas relief carvings of eclectic styles which are of great architectural interest (figure 23).
|Figure 23: Darbar Hall Dhranghedra - bas relief showing the ‘Britannic Deity’ Queen Victoria|
To the east and north, the original roof over the passageway and annex rooms has been replaced within the last 2 years by a flat reinforced concrete roof bearing on the top of the walls. The external walls here shown little sign of distress; the balustrades on the top of this eastern external wall have not toppled. To the west, the original timber truss roof supporting clay tiles remains. The top of the west wall has shifted outward by a few centimetres (figure 24) . As a result, two of the roof trusses have fallen, and some of the others have shifted on their bearings. The balustrades and cornice on top of the centre portion of this wall have toppled. There are some signs of cracking in the central Darbar hall but no serious signs of distress.
|Figure 24: Surajmal, Dhranghedra - western corridor|
8.3 Ajit Niwas
This is once again a building with a central porch and a central core of sets of rooms used for audience chamber as well as private areas, situated on two floors. There is a large periphery shielding this core and providing access ways to the private rooms. On a general level, the earthquake damage is on the upper floor peripheral areas where the structure of the building is badly shaken. The roof tops and parapets have tumbled and corner domed structures suffering separation and internal collapses of floors. The ground floor is comparatively unaffected by the earthquake, barring minor cracks at the crowns of many of the arches above doorways and windows.
|Ajit Niwas, Dhranghedra - north facade|
This is one of the most important Muslim sites in Ahmadabad, containing a number of buildings dating from the fifteenth century. Typically, the buildings consist of masonry columns supporting heavy domed masonry roofs. The earthquake caused limited damage to structures on a retaining wall around the large artificial lake which forms part of the complex; the damage may have been associated with movement of the retained soil. There was also some damage to the pavilion outside the Roza (figure 25) and limited damage to the main Friday Mosque. Overall, however, the site survived large unscathed.
|Figure 25: Sarkhej, Ahmadabad - Pavilion outside the Roza|
9.2 Tomb of Sayed Usman at Usmanpura
This consists of a central dome with surrounding columns supporting a heavy masonry roof. Two columns supporting the SE portion of dome had collapsed due to the earthquake and it was evident that the earthquake had caused considerable movement of the columns supporting the roof around the dome; a few of these columns had cracked (figure 26).
|a) Overview||b) Detail at cracks|
|Figure 26: Tomb of Sayed Usman at Usmanpura, Ahmadabad|
9.3 Side Bashir’s Minars near railway station
These two tall minars are called the shaking minars, because they have the feature that inducing sway in one minar causes the other to vibrate as well. They are over 30m high and date originally from the 10th century. The earthquake caused some cracking which had been temporarily restrained by steel rope (figure 27) , but no serious damage.
|Figure 27: Side Bashir’s Minars, Ahmadabad|
9.4 Bhadra Citadel
This suffered partial collapse of the SE bastion flanking the main gateway to the former palace complex. The cylindrical towers which were built concentrically collapsed partially due to the earthquake and the inner core also collapsed which was partially due to the heavy load of the internal earth filling which was done at a later date when the upper portions of the internal cylinder were abandoned. The massive brick structure had developed vertical cracks due to ageing which is also the condition in the NE bastion, which was much less severely affected. However, there is a tilt in the cylindrical masonry which might need attention. The SE bastion is currently being reconstructed.
9.5 Ahmadshah Mosque
This is situated near the Ellis Bridge and is one of the oldest mosques built in the early fifteenth century by Sultan Ahmadshh, the founder of Ahmadabad as a private mosque within the palace complex. The front portion of the mosque suffered damage and was dismantled by ASI for reconstruction. However, overall the damage to the mosque compared to other monuments was considerably less.
10: Discussion and summary
10.1 Overview and funding sources
Gujarat has a very rich heritage of buildings dating from the fifteenth to early twentieth centuries, many of which are of international importance. Many were affected by the earthquake, some quite seriously. The heritage buildings in Ahmadabad are generally under the care of the Architectural Survey of India (ASI) , which is funded by government and despite limited resources have been well maintained. Damage to the Ahmadabad buildings was generally not excessive; temporary repairs have been instigated and permanent repair works are already in hand. The policy of ASI’s senior conservationist for Ahmadabad, V S Nair, of developing a permanent group of skilled masons appears to have been effective in limiting damage and aiding the ability to carry out repair works rapidly.
The situation with the palaces of the former princely rulers of Gujarat is different, in that they have not previously benefited from public funding and many were in a poor state of repair before the earthquake. Some of the buildings have been converted to public use as schools, museums or hotels and this process is likely to continue in order to attract the funding needed not only for earthquake repair work but also (equally importantly) the maintenance necessary to ensure that these priceless monuments survive for the benefit of future generations. Unless this maintenance occurs, they will be lost with or without seismic activity.
10.2 Damage patterns
Typically, damage in engineered structures is greater in the lower half of the structure, reflecting the increased shears and bending moments at lower levels. The damage patterns seen in the Gujarat heritage buildings were exactly the opposite; there were numerous examples of buildings which were heavily damaged at roof and upper levels, but suffered very much less severely on the ground floor. Four possible reasons for the higher damage at the top of masonry buildings are as follows.
This applies particularly to brick mortar construction, where the mortar joints tend to be more exposed to wind and rain at the top and so tend to deteriorate more. This weakens their seismic resistance.
2. More open structure
Both for reasons of aesthetics and because of the reduced gravity loads, masonry buildings often become much more open toward the top than is the case for modern buildings. This weakens their lateral resistance and may make them more prone to damage.
3. Consequences of increased accelerations with height
The swaying in an earthquake causes accelerations to increase towards the top. This especially affects decorative elements, such as parapets and external ornamentation, which were observed to be heavily damaged. However, it also affects main load carrying walls, because the ‘out of plane’ seismic forces (ie the earthquake pushing the wall out at right angles to itself, which is its weak direction) depend directly on the acceleration at that level. By contrast, the ‘in plane’ seismic forces (acting along the length of the wall in its strong direction) increase towards the bottom of the building, because they are accumulated from the floors above.
4. Shear strength of dressed stone masonry depends primarily on friction
The horizontal strength of dressed, good quality stone depends mainly on the vertical load from above, tending to clamp the stone blocks together. This vertical clamping force is less at the top of the building because there is less of the building weighing down from above. Therefore, the seismic resistance is also less towards the top of the building. However, the influence of vertical clamping force, and hence friction, on seismic strength is probably much less important in random rubble masonry dependant on weak mortar to bind it together; this is an aspect on which further investigation is needed.
There are some interesting consequences of this clamping effect. Firstly, it means that adding weight to the top of a building - something that earthquake engineers are always warned not to do - may be much less harmful in dressed masonry buildings than in modern reinforced concrete buildings; it may even be beneficial. It remains true that the additional weight increases the seismic loads, but for masonry buildings it also increases the resistance. There is support for this view in the palace described above at Dhranghedra, where the addition of heavy concrete roofs had served to tie together the tops of two tall masonry walls. These walls suffered very much less damage than identical walls poorly restrained by a lightweight timber truss roof. Similar circumstances are described at Halvad Palace.
The second consequence points to the benefits of prestressing as a means of strengthening good quality dressed masonry construction. It increases the clamping force - and hence shear strength - with no penalty in weight. Although it is not a technology currently in use in Gujarat, it may repay serious consideration for the restoration of historic buildings.
Many of the buildings that were studied showed clear signs that lack of maintenance aggravated the damage they suffered. This finding is common to many other earthquakes (see for example Feilden, Ref 1) . Properly maintained buildings have always been found to stand a much better chance of surviving major earthquake shaking than buildings whose structure has been weakened by the effects of ageing. The original construction quality of all the buildings studied was generally high, but in some cases there were deficiencies observed in construction which also contributed to a higher degree of damage. The quality of construction was also related to the level of craftsmanship involved, which is another factor determining the degree of damage.
Restoring the buildings to their original condition is in many cases as important a task as repairing damage directly caused by the earthquake. Setting up maintenance programmes for the future is also a vital task.
10.4 The role of indigenous materials and crafts in restoration
This is of primary importance. Detailed restoration plans are useless without the necessary materials and skills to implement them. There is a great need to develop a body of trained, accredited craftsmen to carry out the large amounts of restoration work required in Gujarat.
10.5 Use of modern materials and technologies
Modern methods have a potentially important role to play. There were examples of the use of reinforced concrete elements added to historic buildings at Jamnagar, Dhranghedra and Halvad, which undoubtedly reduced the local damage suffered in the earthquake, although the longer term consequences of this type of intervention may be more questionable. However, it is essential that use of modern materials and technology is integrated with traditional techniques in a harmonious and compatible manner to inject new life into the buildings, as discussed by Feilden (ref 2) .
The following suggestions regarding the techniques and modern materials may be of particular value in order to develop specific restoration proposals for heritage buildings in the Gujarat region.
- Stainless steel ropes introduced into the courses of cylindrical masonry structures to secure them against lateral failures.
- Metal straps with bolted connections to secure polygonal forms.
- Epoxy injection grouting for strengthening weakened and cracked masonry.
- Use of corrosion resistant reinforcement in concrete slabs; this can take the form of galvanised steel, or reinforcement in non-ferrous materials such as carbon fibre reinforced plastics
- Jacketing of disturbed wall surfaces by means of applying a mesh of non-ferrous or galvanised steel reinforcement to both sides of the wall, bonded to the wall with a mortar matrix.
- Vertical and horizontal drilling for the insertion of grouted steel reinforcing bars.
|ACKNOWLEDGEMENTS The following report was made possible by generous travel grants from the Charles Wallace Trust and INTACH (UK) Trust, which financed the travelling expenses of Professor Vasavada and Edmund Booth. The local assistance of members of the Gujarat chapter of INTACH is also gratefully acknowledged. The authors benefited from helpful discussions with Sir Bernard Feilden.|
REFERENCESRef 1. Feilden B. Between two earthquakes. Cultural property in seismic zones. ICCROM/Getty Conservation Institute, 1987. Ref 2. Feilden B. Conservation of historic buildings. Butterworth London. Paperback edition 1994.