1 INTRODUCTION

The Arctic sea ice area is at 70% of the amount found in 1870, and is shrinking rapidly (EPA,2003). Forest cover is being lost at a rate of 10 million hectares per year (EPA, 2003). Thesekinds of negative influences on earth show that in the transiting to the modern age humanity lostthe sustainable lifestyle, modern technology can highly improve and rehabilitate thesustainability in products and production technology. If the lifestyle is changed accordingly theearthly conditions are expected to improve. According to the book of WCED (1987) and theBrundtland-report (UN, 1987) the construction industry is responsible for about 10% of the totalimpact on this planet. Duijvenstein (2005) argued that striving for sustainability should not berestricted to design sustainable buildings but also be incorporated in the district and building inorder to encourage sustainable living. There are several aspects to sustainable building and pro-ducing that have a relation with sustainability. One of these aspects is the conditions and avail-able materials for building. In the best situation there is minimal transportation, minimal inter-ference with local environment and no damage to nature. For this research the focus for findinga suitable material was on the rebuilding of Bam. Bam is a desert city located in the southeast ofIran. Bam was largely destroyed in December 2003 by an earthquake with a magnitude of 6.5on the scale of Richter. It is estimated that Bam needs 40000 houses rebuild. For the rebuildingof this city a large amount of material and energy is needed and it would be beneficial if this re-building would happen as sustainable as possible. Furthermore because there is a serious riskthat a new earthquake will occur within the next 50 years the buildings should be suitable forthis condition. This paper concentrates on the research for finding a building material for thestructure of houses that has both the best specifications for environmentally friendliness as wellas constructional features for earthquake conditions.

2 APPROACH AND MATERIALS

Before it was possible to judge materials for their applicability in the restricted situation it wasnecessary to first decide on the relevant aspects for sustainability by studying the circumstances

ABSTRACT: Implementation of the new technology to answer an old problem requires an in-novative approach. In this study, the aim was decreasing fatalities, caused by material fragmen-tation and collapsing, in an earthquake disaster. Thus, the main goal was an environmentallyfriendly way of materialization for reconstruction in a seismic desert circumstance. To achievethis goal, two main groups of effects on the construction, including desert environmental/ cli-mate and earthquake resonance, were investigated. Although the study is globally applicable, asthe work started with the main case study of Bam, a desert city that recently experienced a dev-astating earthquake. Therefore, we took the local regulations and technologies seriously into ac-count. However, complexity of several aspects, affecting the system, made the study reasonableto be a subject for longer and broader study. We will discuss these aspects and their effectsending the discussion up to a suitable material in this paper.

Glocal structural system in a seismic desert city

S. ShahnooriUniversity of Technology, Faculty of Architecture, Delft, The Netherlands

A.I.M. VoorbijUniversity of Technology, Faculty of Architecture, Delft, The Netherlands

in Bam. This means not only describing the building conditions but also establishing the locallyavailable materials and industry. This part of the study was done by literature research and visitsto the local area. The second part of the research existed of material testing and further literaturestudy. The test for the quality of desert sand for use in concrete was performed in the laboratoryof the civil engineering at TU Delft for the typology and then chemical characteristics. Samplesof 6 different specimens of fine and coarse aggregate, and clay were tested, based on NEN 5919and 5941 (NEN, 1995). The agents of several samples found by these tests proved that the localmaterials have the quality, therefore, are applicable in the concrete mix (as it was supposed thatdesert sand is salty and is polluted, to be used in such a mix). The results of the mineral andchemical tests have been compared with the relevant literatures and interviewed with experts forthe analysis and application.

3 ANALYSIS AND RESULTS OF THE STUDY OF THE LOCAL SITUATION

Although some of the processes and problems are global, this study focuses on Bam. In the endit will be interesting to test whether the solutions found for Bam and the methodology used isapplicable globally. This is what is mending by the term Glocal that is in the title.

3.1 Desert conditions

The temperature changes over 24 hours are in desert areas known to be much higher than invegetated areas the temperature difference (between the highest and lowest) exceeds 50 °C inBam (IRIMO, 2006). This requires housing that can on the one hand withstand the temperaturedifference and on the other hand helps creating a comfortable climate inside the building. Forsustainability, this leads to insulation specification as well as resistance to fast thermal transfer(cooling and heating).Cities such as Bam, that are located in desert areas, are vulnerable to desertification. The di-minishing or destruction of the biological potential of land which can ultimately lead to desertconditions is termed desertification (Pachauri et al, 1997). It is a kind of land degradation thatoccurs in dry (arid, semi-arid and dry sub-humid) areas. One important factor contributing to theacceleration of desertification and something that is occurring in all over the world is deforesta-tion (kaya et al.1997). About 35% of the earth’s land surface is at risk, and about 850 millionpeople are estimated to be directly affected (MEA, 2005).The rate at which rain forests are dis-appearing all over the world is at 2 acres (0.8 hectare) per second. This amounts to 10 millionacres per year for temperate zone forests (Kibert, 2005). In connection with carbon diffusioninto the atmosphere (can be stored in tree mass) and also resulting the climate change, soil ero-sion and consequently land degradation. On a worldwide scale more than 2 billion tons of top-soil is lost annually and now, more than 12.5 billion acres is considered to be degraded (Kibert,2005). 15% of the world’s population inhabits dry lands, while 78.5 million live in areas thathave recently undergone severe desertification (UNCCD, 2005). Figure.4.1. shows the land deg-radation on the earth due to different factors.

4.1. Causes of soil degradation

For the situation in Bam this means that the selected material should not decrease the quality ofthe land by extracting materials that are essential for that.

3.2 Land and soil conditions

Although Bam is located in the desert and there is little water on the surface, the evaporation onthe soil level is not a problem. This is guaranteed by the existence of a large numbers of Quanat.Quanat is a water management system used to provide a reliable supply of water to human set-tlements or for irrigation in hot, arid and semi-arid climates (Figure 1).

Figure.1. an ancient water system in the central desert of Iran called Quanat.

Because Bam is surrounded by mountains and the water coming from rain and snow is trans-ported via the mountains into the deep layers of the land there is a constant supply of water foragricultural activities. The water in the deep layers is transported to the surface by the ancientsystem of Quanat. Bam is a town where most of the economy depends on agricultural exploita-tion. Bam is surrounded by date plantations and any changes to the quality of the top soil wouldseriously harm the economic condition of Bam. Any solution would need to consider the factthat Bam needs a sufficient area of arable land. Figure 2 shows the agricultural area of Bam thatis now in use. Figure 3 shows the situation of it in economical activities and income of people.

Figure 2 The greenery of the city of Bam (the agricultural area on the map)

Figure 3 Share of the different sectors of the economy in Bam region (Based on the Report No.1, 2004,

pp. 11 Statistical Center of Iran).

3.3 Available materials

As Bam is a typical desert city the area provides a lot of sand. Because some desert areas areknown to be part of the bottom of ancient sees, it is possible that the sand around Bam is too saltto be suitable for building material.A lot of the vernacular architecture is based on clay and bricks, which can be found and pro-duced in the area. The adobe constructions were proven to be vulnerable to earthquake shockingand a lot of them were destroyed. Even the ancient citadel that is at least 2500 years old was se-riously damaged by the last earthquake. Excavating the top soil to come to the clay would havea big impact on the quality of the arable land and is expected to have a negative effect on theavailable arable land and therefore on the economic situation in Bam.

3.4 Earthquake conditions

The earthquake occurred as result of activities of the Bam fault, which is located under theboundary of the city right on the edge of eastern side (Zare, 2004). In the earthquake December2003 the main reason for the high level of fatality have been identified as lacking systemizedconstruction and the quality of materials (Shahnoori, 2005).By the site investigation the only structure that withstood the earthquake safely was found to bethe main water tank which has a reinforced concrete construction. The adobe constructions werealmost ruined and the brick structures were about 80-90% collapsed (Kimiro et al. 2005). In thetable 1 the typology of damages regarding the materials use are demonstrated.

Table 1. The observed damages in the structures in site investigations (source: Kimiro et al, 2004)

No. Principal Material Degrees of Damage* Note

No. 1 RC C 14 spans (simple girders)

No. 2 RC D 3 spans (simple girders)

No. 3 RC D 7 spans (simple girders)

No. 1 RC C Reinforcing steel bar buckled

No. 1 Adobe A Total collapse

No. 1 Brick A Center pillar made of steel

No. 2 Adobe A Center pillar made of steel

No. 3 RC B Reinforcing steel bar buckled

No. 4 RC C Occurrence of crack on the pillar only

*Degree of damage: A= collapse, B= medium, C= Light, D= no damage

Share in income

Agriculture 38%

Industry 22.4%

Mining 3.1%

Construction 6%

Service 30.5%

Service

47%

construction

10%

Mining 3.4%

Agriculture 34%

Industry 5.6%

4 RESULTS OF THE MATERIAL TESTS

The main sources of minerals in the city is from the Poshterud river, in the northern boundaryand Birdbrain River in KhajeAskar (a village very closed to the city). The quantity of thesources have been observed and interviewed and the quality have been taken to the Netherlands.The table number 2. demonstrates the final results of different tests on six samples of local ma-terials. This is a summary, which out comes from the Dutch standards (Nederlandse Norm).

Table 2. The summary and final results of tests on local samples and comparison with the standards ofNEN 5919 and NEN 5941

Gravel + sand (fine) Gravel + sand (bigger)

Fine material of organic origin NEN 5919(Color B) good for the con-crete

(Color A) good/better

Highly expanding clay minerals NEN 5941 Not so good and not so bad

As it is going to be used in the reconstruction of a house the characteristics which are lookedthrough are selective. However, based on the fact that has been proven in the last earthquakeand further investigation, the reinforced concrete is basic for an appropriate material for the re-housing in such constrains. In which study continues for the improved version of a concretecomposite. Therefore in the table 3 all the characteristics are chosen for a seismic desert houseand all of the values are relative.

Table 3 The summary of the relative values of different versions of reinforced concrete

Materials

Characteristics* Conventional concrete Fiber reinforced concrete PVA-ECC

Tensile strength 1 1 2

Compressive strength 2 3 4

Weight 1 1-2 3

Stiffness 2 2 3

Ductility 1 1-2 4

Problematic crack prevention 1 2 4

Environmental friendly 1 2 4

Durability 1 2 4

* 1= poor, 2=Acceptable, 3=Good, 4=Excellent

5 ANALYSIS MATERIAL SELECTION

From the literature and on site study it was concluded that both clay and brick had too muchnegative effects on the land and were poor for seismic conditions and constraints. That is whythe second part of the research focused on concrete as structural building material for housing.The characteristics that are compared in table 3 were derived from the information gathered inthe first research.Because the characteristics mentioned in table 3 are equally important there was no need to adda valuation figures to them. This means that ECC qualifies best for rebuilding structures ofhouses in Bam based on table 3.

6 DISCUSSION

When people think of using environmentally friendly material in building they often come upwith natural materials as clay and brick. This paper points out that because the excavation ofclay causes so many negative side effects to the land and soil that it is hardly sustainable. Espe-cially desert cities are at risk of desertification and deforestation, which is known to be one ofthe world’s most threatening environmental effects (Kibert, 2005). Intensive use of clay wouldmake Bam one of the regions that is damaged by human induces soil degradation and deforesta-tion. As the most economical activity in the city is agriculture, using clay in such a large scale ofconstruction (for more than 40000 houses and many of other buildings) is even more problem-atic. Besides, the use of concrete is technologically well evolved and it adheres to the local pos-sibilities. Concrete is strong, stiff and durable which makes it very suitable for the reconstruc-tion of a seismic desert city. It is flexible thus its quality increases further by combination withother materials.

Furthermore concrete is a well known material that is often used in earthquake risky areas. InJapan a lot of researchers seek for solutions that decrease the number of fatalities. Howeversustainability is not an issue with these researches and they are therefore not very applicable inBam. This study proves that even though steel reinforced concrete might be found suitable formany earthquake areas it is probably not the most suitable material for Bam.ECC is a relatively new material that is rather unknown in the building industry. The materialwas developed by Prof. Li more than 10 years ago. The idea behind the material was based onthe experience with existing sorts of concrete such as the fiber reinforced concrete that was de-veloped around 1970. One of the issues with concrete reinforced with steel bars that needed tobe tackled was the cracking around the steel bars and on critical points in the structure. Mark-ovic (2006) studied this matter and mentions two reasons why fiber reinforced concrete couldwork against this cracking. Firstly, the continuity and diameters of the steel bars with the tensilecapacity and the stronger bond with concrete, and secondly the placement of the steel bars isbeing in the main tensile stresses direction, but fibers are randomly placed yet (Markovic,2006).For seismic conditions the ductility of concrete seems highly important. If a material is able toslightly follow the tremor movement it is likely that the material is far less sensitive to frag-mentation and cracking. There are some researches that focus on workability and ductility inrelation to fiber reinforced concrete (Groth, 2000; Kooiman, 2000; Markovic, 2006; Brite-Euram Project, 2002) but they did not come up with inclusive and reliable answers for suchparticular cases.

ECC (Engineered Cementitious Concrete) as studied in this research is mainly made of the sameingredients as the conventional concrete, minus the coarse aggregates, but doesn’t have the dis-advantages of the conventional concrete such as lack of durability, sustainability, failure undersevere loading and resulting expenses for repair (Li, 2004). Additionally the amount of steelshear reinforcement can be drastically reduced since it remains highly ductile in shear (structure,2007). The Michigan department of transportation used it to retrofit a section of the Groovestreet Bridge Deck over I-94, in the summer 2005 (Kahl, 2005). It has been used in a the Schoolof Natural Resources and Environment Center for Sustainable Systems shows that in a 60 yearsservice on a bridge deck the ECC is 37% cheaper, has 40% less energy consumption and creates39% less CO2 pollution than the regular concrete. Besides, in the infrastructures structures suchas high rise building it protects the FPR reinforced rebar from premature rupturing (Structure,2006). Although practically it was not excessively used before, with its high quality will be apopular material soon. For example, it was adopted in the coupling beams of 27- story GlorioRoppongi High Rise in central Tokyo and the 41- story Nabeaure Tower in Yokohama by Ka-jima Corporation in Japan that is shown in figure 3 (Popular Mchanic, 2007).

Figure 3. Nabeaure Tower, Yokohama, Japan. Source: The Concrete Producer , 2006

To make the final solution for Bam even more sustainable it is essential that the design withECC minimizes the life cycle costs of the building. A major goal of sustainability in cement-based building materials is to minimize the life cycle costs of buildings. The eco-cost can belessened in more than one way, but according to Takao Tsumuro (2002) lengthening the lifecy-cle of a concrete construction building, improve insulation, efficient energy consumption allhave a positive effect on the eco-costs. The differences in outside temperature between nightand day are large and these have to be leveled for indoor climate to maintain an acceptable tem-perature inside the house. The building envelope is highly affected by heat and cold and theshell should not only be thermally insulated, but the thermal capacity should be kept up as well.Aside of influencing qualities such as strength, heat resistance and conductivity, the weight re-duction can result in extensive cost reduction. With a lighter construction, the load bearing ca-pacity can be reduced, thus constructing maybe easier. Additionally when it turns out the designcannot prevent the building from collapsing in a severe earthquake the clearance of debris in thearea is eased. After the last earthquake there were approximately 12,000,000 tones of debris inthe affected area, which took a long time to be salvaged and removed.

The study presented in this paper is part of a bigger research into the rebuilding of Bam. It wasnot a fundamental research by nature, but the intention was to find out whether ECC could be asuitable material for Bam. It is very well possible that there are other materials or types of con-crete that are applicable in Bam, but it is also feasible that ECC is a good and sustainable mate-rial for a lot of other areas in the world. This would require further research but we expect that itwill prove to be a reliable material for seismic desert cities all over the globe.

7 CONCLUSIONS

- Concrete is a sustainable material for rebuilding Bam.- ECC is a good material for a building structure in a seismic area.- Ductility is an essential characteristic for a building material in a seismic area.

8 ACKNOWLEDGEMENT

Thanks to Prof. Mick Eekhout for his supports, Prof. Victor Li and Dr. Alan Fraaij for theirguide lines and Ms. Polonia Wardenier for her helps.

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