| Summary: | 博士 === 國立中興大學 === 土木工程學系所 === 100 === The main purpose of the research is to study the mechanical behavior of the reinforced lightweight aggregate concrete walls after high temperature. The study includes three sections. The first section is to study the basic mechanics of the walls. The second section is to study the energy absorption of the walls after high temperature. The third section is to study the behaviors of connections for the precast walls after high temperature.
The research parameters in the first section include steel spacings, lightweight/normalweight aggregates, wall sizes and with/without high temperatures. The study results indicate that after high temperature the load-carrying capacities, stiffness and ductilities of RLAC (Reinforced Lightweight Aggregate Concrete) walls are all better than those of RNAC (Reinforced Normalweight Aggregate Concrete) walls. When the steel spacings in RLAC walls after high temperature are smaller the yielding loads and ultimate loads are greater but the ductilities are worse. All of these phenomena are the same as the phenomena that have been already known in regular walls under normal temperature.
The main purpose of the second section is to study the mechanical behavior of RLAC walls and RNAC walls under repeated loading after fires. The research parameters include spacings of bars, sizes of coarse aggregates and the sizes of walls. The research results show that after fires when bar spacing is smaller the wall stiffness and the wall ultimate strength are higher but the ductility and energy dissipation are smaller. The bar spacing does not affect the wall cracking strength apparently. As for the wall size effect, when the wall width is bigger, the wall stiffness and the energy dissipation are bigger. After fires, the stiffness, ductility and energy dissipation of RLAC walls are not obviously different, while those of RNAC walls have obvious declines. This means that the RLAC walls have better mechanical behavior under repeated loading after fires than RNAC walls do.
The main purpose of the third section project is to study the mechanical behavior of the connections for precast walls made of RLAC and RNAC after fire-resistance tests. Three types of connections, dry type of (61), wet type of (81) and bearing type of (56E), were selected for the tests. Tension tests were performed for all types of the connections. But, shearing test was performed only for the connections of bearing type of (56E). The test results show that the mechanical behavior of all selected types of connections after fire-resistance tests are almost the same. For example, in the load-displacement diagrams of tension tests, both types of specimens (lightweight and normalweight specimens) have two particular points, cracking load and ultimate load, able to be read. But, there is only one point, ultimate load, able to be read in shearing test. In the shearing tests, all of specimens failed as soon as the cracks occur. Besides, on the ultimate loads and ductilities, test results show that the connections casted in lightweight concrete perform better than those in normalweight concrete.
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