Vol.29/No.4 (116) (2014)
| Title | A Study on Damage Detection of Beam Structures Using the Pseudo Local Flexibility Method |
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| Author | Ting-Yu Hsu, Shen-Yuan Shiao, Wen-I Liao |
| Keywords | Pseudo local flexibility method, beam structure, damage detection, health monitoring |
| Abstract | The local flexibility method, which can determine local stiffness variations of beam structures by using measured modal parameters, is one of the more promising vibration-based approaches. The local flexibility method is founded on “local” virtual forces that cause nonzero stresses within a local part of the structure. In this study, this basic rule has been broken. The “pseudo-local” virtual forces that cause concentrated stresses in a local part and nonzero stresses in the other parts of a structure are employed. The theoretical basis of the proposed “pseudo local flexibility method” (PLFM) is derived. The effects of the number of modes on the damage detection results are studied using both numerical and experimental hyper-static beam models. The results show that significantly fewer modes are required for the PLFM to estimate the damage location and extent with acceptable accuracy. Therefore, the feasibility of the PLFM is higher because only a limited number of high quality modes can be identified in real world applications. |
| Title | Study on the shear cracking behavior of the full-size high strength reinforced concrete beams |
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| Author | Chien-Kuo Chiu, Tsung-Ching Chen, Fang-Ching Lin and Kai-Ning Chi |
| Keywords | high strength, reinforced concrete, shear crack, beam specimens, residual crack width, serviceability, reparability |
| Abstract | The main propose of this work is to investigate the shear crack development and suggest the design formulas that can ensure serviceability and reparability for shear-critical high-strength reinforced concrete (HSRC) beam members based on the experimental data of ten full-size simple-supported beam specimens (Span-depth ratio is 3.33). According to the experimental results, the design formulas that can ensure the serviceability and reparability are recommended for shear-critical HSRC beam members. Based on the crack development of each specimen, the average ratio of the residual total shear crack widths to the residual maximum shear crack width for the HSRC beam specimens is approximately 4.5; then, in the crack-based assessment, this work recommends setting the ratio as 4.0 to estimate residual maximum shear cracking. Additionally, the ratio of maximum peak shear crack width to residual maximum crack width, it can be increased by shortening stirrup spacing and increasing stirrup strength, and its overall average value is 2.44. This work suggests the applicable value of a HSRC shear-critical beam to be 2.5. Besides of the post-earthquake damage assessment, these results can also be used to build the performance-based design for HSRC structures. |
| Title | The Effect of the Construction Joint Created between Precast Beam and Cast-in-Place Slab on the Seismic Behavior of Reinforced Concrete T-Beams |
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| Author | Yung-Chih Wang, Jhih-Ren Jheng |
| Keywords | Construction Joint, Interface Shear Stress, T-Beams, Seismic Behavior |
| Abstract | The purpose of the experimental study is to observe the seismic behavior of T-shaped cantilever beams. The study investigates the effect of construction joint and shear span (a/d=2.44 and a/d=5.46 ), and verifies the current design equations obtained from monotonic loading experience for evaluating interface shear stress. The test results indicate that the T-shaped short beam with construction joint slipped more obviously at the interface than the beam without construction joint. According to test results, in the negative moment when the slab bars stress in tension, the effective width of T-beam flange with construction joint is 1.4 time wider than the beam without construction joint. In the comparison between slender beams and short beams it was found that slender beams had less cold-joint slip effect than short beams. This is because the area of shear resistance at interface for slender beams is larger than short beams. |
| Title | Seismic rapid evaluation of low-rise street house |
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| Author | Tsung-Chih Chiou, Shyh-Jiann Hwang, Jia-Cherng Song, Lap-Loi Chung |
| Keywords | street house, low-rise RC building, seismic rapid evaluation, reinforced concrete |
| Abstract | It is extremely difficult to carry out the seismic evaluation by professionals for all the street houses due to huge volume in Taiwan. Therefore, rapid evaluation carried out by owners as a preliminary screening can be a feasible scheme. Those buildings labeled with safety concern by rapid evaluation can be further evaluated by professionals. Since the school buildings and the street houses in Taiwan share the same structural characteristics, the empirical formula of seismic capacity for school buildings obtained through detailed evaluation can be applied to street houses. Based on the seismic evaluation data of 1,187 school buildings of the database collected by the National Center for Research on Earthquake Engineering, an empirical formula of the performance ground acceleration and the column-to-floor area ratio was established. The cross sectional areas of brick infill and RC wall can be transformed into the equivalent area of column according to their seismic capacities. Consequently, the performance ground acceleration of a low-rise street house can be rapidly evaluated by the ratio of column sectional area to floor area of building. The seismic rapid evaluation method has been verified by the data bank of damaged buildings collected through earthquake reconnaissance. The seismic capacities obtained from the rapid evaluation method correlate well with the damaged status of low-rise buildings. In general, the rapid evaluation method is conservative but still possesses a screening capacity. This paper presents a method for building owners to roughly evaluate the seismic capacity of their buildings by themselves. |
| Title | Seismic behavior and evaluation of mechanical fittings for fire protection sprinkler piping systems in hospitals |
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| Author | Fan-Ru Lin, Kuo-Chun Chang, Jhen-Gang Huang, Juin-Fu Chai |
| Keywords | sprinkler piping systems, mechanical fittings, grooved couplings, screwed fittings, quasi-static testing, seismic performance evaluation |
| Abstract | Based on the experiences learned from recent earthquakes, it is recognized that the immediate operation of a hospital after strong earthquakes relies heavily on the functional integrity of critical nonstructural components. However,from the literature review of earthquake damages, the reduction of medical functionality has been caused by serious flooding due to the damage of mechanical fittings (including grooved couplings and screwed fittings) of sprinkler system. Hence, the objective of this paper is aimed to investigate the seismic behavior of mechanical fittings to improve the seismic performance of sprinkler systems effectively. The seismic capacities of mechanical fittings in pair with various pipe dimensions were studied through quasi-static tests under cyclic pure-bending loads. The small-bore fittings were further studied to the combined shear and bending effects. Based on the test results, the seismic performance evaluations for vertical and horizontal piping systems were implemented through static and dynamic analyses respectively. |