ابنيه خشتي مقاوم در برابر زلزله

Adobe Buildings; Relience to Earthqueke

امروزه بيش از يك سوم مردم جهان در ابنيه خاكي زندگي مي كنند. آيين نامه هاي موجود در ايران استفاده از خشت را علي رغم قابليت هاي بسيار محدود كرده است. اين در شرايطي است كه امكان ساخت بنا با اسكلت فولادي يا بتني براي بسياري افراد وجود ندارد .در صورتي كه مقاومت كششي ابنيه خشتي تقويت گردد ، استفاده عمومي در ساخت اين گونه ابنيه مقدور خواهد گرديد. در غالب نمونه هاي باقيمانده از معماري گذشته ايران به كمك تبديل نيروهاي كششي به فشاري اين ضعف برطرف شده است .نتايج پژوهش نشان مي دهد همنشيني خشت،سيمان و ميل گرد جهت تثبيت ساختمان هاي خشتي مناسب است و اگرچه ديوار خشت فشرده تثبيت شده به لحاظ مقاومت و ميزان تغيير مكان ركوردها، واجد امتيازكمتري از ديوار بنايي است، ولي انطباق لازم با آيين نامه هاي موجود را دارا است. همچنين اين سامانه واجدكارايي ساختمان هاي آجري با كلاف فولادي نيز مي باشد.

More than one third of the world populations and 20 million people of rural areas located in Iran are living in buildings made of earthen materials. Structural performance of such buildings revealed to be weak and easily broken if exposed to any lateral earthquake load that inhibit on-time reactions and initiatives of its residents during earthquake. Despite the adobe infirmity and instability against lateral tensions, construction of adobe made buildings would bring about further reduction of operating costs and emission of environmental pollutants compared to other brickwork materials. Therefore, strengthening adobe tensional solidity would enable its public use in construction of a variety of buildings. Remained samples of ancient architecture scaled as public structures quite often have become stable through transformation of tensional forces into compressive ones. Lots of arcs and arches corroborate the idea behind such efforts. However, modular and micro scale residential architecture rule out construction of such huge arches and arcs. Reinforcement of adobe made buildings could be achieved through three areas of restructuring, structural material composition and strengthening adobe solidities. Restructuring is enabled through enhancement of material quality, increasing solidity of lateral walls specifically in the corners, lightening the structure and strengthen infrastructures and bases of the building. Considering adobe made buildings, walls are major issues in building seismic performance. Strengthening the structure stability requires minimization of load concentration on walls (e.g. using horseshoe forms of opening portals or application of underpinning plates meant for load distribution). Walls should be constructed as simple as possible with minimum fractures. Reinforcing adobe solidity through mechanical approaches and increasing pressure and density without any stabilizers requires concentration of adobe seeds and formation of an average aggregated block and capillary property. Regarding physical approach, strengthening adobe movements would be achieved through increasing appropriate stabilizer and creation of restraining network. With regards to strengthening techniques of adobe made buildings and existing standards in Iran (such as guideline no. 2800, 8th chapter, concerning instructions for making building materials and existing standards focusing construction of stabilized adobe made blocks and studies of composing optimized adobe used in reformation and renovation of Arg-e- Bam and Chaghazanbil temple), stabilized adobe made block plan for strengthening adobe made buildings in Iran has been investigated in the present study. Considering characteristics and features of existing soil, evaluation of proposed adobe made block solidity requires a variety of walls’ cross-sections. Stabilization of such idea and performance test of sample wall made of compressed adobe made building requires to be compared with computerized modeling and simulation of similar structures made of simple brick block and vertical skein. Although such system has achieved lower scores compared to common brickwork walls, it is in accordance with existing guidelines. Proposed system enables designers and drawers to consider required equivalent solidification for walls and its skeins that would bring about more accurate design, less total cost of the structure and eliminate the need for high certainty factor. In addition the said system is capable of designing multi-floor buildings far better than common traditional types.