The seismic performance of one-third scale double units three-storey tunnel form reinforced concrete building tied up with foundation beam tested under in-plane lateral cyclic loading are performed and analysed in this paper. This building is designed according to BS 8110, constructed in heavy structural laboratory and tested under in-plane lateral cyclic loading using displacement control method. The specimen is tested on a strong floor starting from 0.01% drift until 1.25% drift with an increment of 0.25% drift. From visual observation, the initial crack starts at +0.25% drift with more cracks observed at +1.0% drift. The ultimate lateral strength is reached at +1.25% drift and the experiemental work is stopped at this drift due to the danger of collapsing the tunnel form RC building. Based on the experimental hysteresis loops, the ultimate in-plane lateral strength is 93kN, maximum displacement ductility ( ) is 2.5, average elastic stiffness is 6.11kN/mm, average secant stiffness is 2.94 kN/mm and equivalent viscous damping (EVD) for the first cycle is 15% and second cycle is 6%. It can be concluded that this type of building will survive in a low to moderate earthquake but will collapse in a strong or severe earthquake due to the existence of a plastic hinge zone at wall-foundation interfaces.
Clay soils are considered as a problematic soil in term of water absorption rate. The ideas of soil improvement method had been widely used to modify the physical and mechanical properties of clay soil. This study aims to identify the optimum percentage mixing of natural fibers in influencing the compaction characteristics. X – ray fluorescent test (X-RF) and Standard Proctor test has been performed to determine the chemical composition of natural fibers and compaction characteristics of soil samples. Natural fibers such as banana, kenaf, and coconut coir were used as a natural soil stabilizer with varying percentage mixing to increase the properties and stability of soil samples. Experimental data obtained from compaction test shows that the appropriate maximum dry density and optimum moisture content for each natural fiber are at 0.5% natural fibers mixing. In this study, the maximum dry density and optimum moisture content for untreated samples are 1650kg/m3 and 7.8%, respectively. Meanwhile, for treated soil samples that mixed with banana, coconut and kenaf fibers are 1760kg/m3 , 1780kg/m3 , 1670kg/m3 and 8.2%, 8%, 11%, respectively. Hence, 0.5% mixing with banana fibers indicated the best possible amount of dry density and moisture content among other natural fibers. Therefore, this study proved that natural fibers can act as a good natural soil stabilizer in increasing stability of clay soil.
Repairing and strengthening the structures are gaining more attention from many researchers and structural engineers after the structures suffered damages from natural disasters. Tunnel form RC buildings which are not designed according to seismic code of practice are very vulnerable to ground motion when located to near field earthquake. This paper presents the method of repair and strengthening of 3-storey tunnel form building subjected to in-plane lateral cyclic loading. The building was strengthened using the combination method of steel angle, steel plate and Carbon Fiber Reinforce Polymer (CFRP) sheet. The results show that the lateral strength capacity is increase by 15.66%, ductility increase by 53.57% and equivalent viscous damping increase by 28.88% for the first cycle and 33.65% for the second cycle. However, the stiffness of the structure reduce by 56.6%. It can be concluded that this method can be adopted for the damage of tunnel form building system.
Tunnel form construction is widely known as modern construction method that enables the construction of horizontal and vertical elements simultaneously. It is quickly construct low cost, high quality and earthquake safe to construct cellular buildings. Main objective of this study is to determine the seismic retrofitting performance of a double unit tunnel form building when retrofitted using additional RC wall, steel angle and Carbon Fiber Reinforced Polymer (CFRP) when tested under in-plane lateral cyclic loading. A comparison of tunnel form building was made before and after retrofitting in terms of lateral strength, stiffness, ductility and equivalent viscous damping. Result indicates that retrofitting method using additional RC wall, steel angle and CFRP was able to increase the lateral strength, ductility and equivalent viscous damping under in-plane lateral cyclic loading. The result also shows the effectiveness of additional RC wall, steel angle and CFRP in improving the shear resistances and deformation capacities of concrete structures and delaying their stiffness degradation under earthquake loading.
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