Page 448 - Advanced Design Examples of Seismic Retrofit of Structures
P. 448

394   Advanced Design Examples of Seismic Retrofit of Structures


















            FIG. 6.3 Comparison of different construction details and failure modes of two buildings, both of
            which are categorized as adobe buildings. (A) Adobe building with very slender walls and very light
            inclined roof after the 2009 Yunnan, China earthquake. (B) Adobe building with thick short walls
            and very heavy arched roof after the 2003 Bam, Iran earthquake. ((A) Permission from EERI.
            (B) Photo taken by Mohammad Yekrangnia.)



            found in many parts of the world, minimal skill and experience required for
            building adobe structures is required; and it is among the most energy-saving
            building construction [5].
               Compared to brick-masonry buildings, adobe buildings are generally
            regarded as inferior in terms of seismic performance. However, thin-walled
            masonry structures can easily fail due to gravitational effects shortly after
            experiencing low to moderate seismic actions, whereas thick-walled adobe
            buildings can exhibit significant structural ductility even though the building’s
            construction material itself is brittle [6]. The main cause of severe damage and
            collapse of adobe buildings is lack of integrity of different structural parts
            including weak connection between perpendicular walls and also poor seismic
            performance of wall-to-roof connection, both of which endanger the “box-like”
            behavior of such buildings [4].
               In this chapter, examples of various retrofitting methods and successful
            national experiences on risk reduction of adobe buildings are presented.

            6.2 RETROFIT APPROACHES
            Structural stability is fundamental for the adequate performance of adobe build-
            ings during major earthquakes and for designing appropriate retrofit measures.
            The walls of adobe buildings will crack during moderate to large earthquakes
            because massive adobe walls activate significant amounts of inertial forces, and
            both adobe blocks and mud mortar are low-strength materials. After cracks have
            developed, it is essential that the cracked elements of the structure remain sta-
            ble, upright, and able to carry vertical loads.
               Compared to the more traditional force-based approach, which aims at
            increasing structural elements strength, the stability-based, retrofit design
   443   444   445   446   447   448   449   450   451   452   453