Vol.29/No.3 (115) (2014)

作者:

Vol.29/No.3 (115) (2014)

TitleFeasibility Study of New RC on the Seismic Design of Bridge Column
AuthorKuang-Yen Liu, Yu-Chi Sung, Kuo-Chun Chang
KeywordsHigh strength concrete and reinforcement, bridge column, seismic performance
AbstractThis study presents the experimental study on the seismic performance of bridge column with high strength concrete and reinforcements, called New RC column. Given a specified plastic moment strength resulted from a predetermined RC column with ordinary materials, the design objective of New RC column is to provide same plastic moment strength but reducing the cross section, quantities of longitudinal and lateral reinforcement simultaneously. Total of one RC column (BMR1), two solid-section New RC columns (NEWRC1, NEWRC5) and three hollow-section New RC columns (NEWRCH1, 2, 3) were manufactured by either cast-in-place or precast and carried out by cyclical loading tests. For New RC specimens, the design compressive strength of concrete, yielding strength of longitudinal and lateral reinforcement are 70, 685, and 785 MPa, respectively, while RC column are 28, 420, and 280 MPa. Experimental results demonstrated that New RC column with sufficient lateral confinement and subjected to relative small axial load ratio can effectively reduce cross section and usage of material without losing desired flexural strength, either equipped with solid or hollow section. Besides, applying posttensioned strands within NEWRC column can provide self-centering mechanism to eliminate residual displacement. In addition, the pushover curve can be well predicted by the conventional program. The seismic performance of New RC column has been confirmed and its application can be expected in the future.
TitleApplication of equivalent static wind loads on bridge design
AuthorYuh-Yi Lin, Ping Wang
Keywordsequivalent static wind loads, bridge design, buffeting, section model, wind tunnel test
AbstractIn this paper, an approach to generate the equivalent static wind loads at the design wind speed based on buffeting theory and the information obtained from wind tunnel tests is presented. Using this approach, bridge engineers are able to obtain the equivalent static wind loads and then easily to combine these wind loads with other loads for use of structural analysis and design. The equivalent static wind loads include static and dynamic effects. The dynamic effects are generally divided into the background and the resonant components. Two methods to generate the background components are presented in this paper. One is LRC approach and the other is based on the inertia load distribution. The comparison of the results between these two methods is discussed. The resonant components basically follow the inertia load distribution. Two examples, including a simply supported beam and a cable-stayed bridge, are used to examine the validity and applicability of the approach. Two types of equivalent static wind loads are generated in the cable-stayed bridge example. One is derived from buffeting theory utilizing static force coefficients, flutter derivatives and wind force spectrum. The other is formulated based on the responses measured from the section model tests.
TitleDesign and nonlinear pushover analysis of earthquake-resistant hybrid coupled structural wall systems
AuthorChung-Chan Hung, Wei-Ting Lu
Keywordscoupled structural walls, nonlinear pushover analysis, earthquake-resisting behavior, structural design
AbstractCoupled structural walls are often used in mid- to high-rise structural systems in earthquake regions. This type of structures is able to provide efficient lateral stiffness to resist earthquake loading and reduce the lateral drift response of the entire structural system. The paper investigates the pushover behavior of hybrid coupled structural walls. The influences of the coupling ratio and structural height on the structural behavior are extensively investigated. Nine different hybrid coupled structural walls with three different coupling ratios and three different heights are designed. The coupling ratios are 20%, 40%, and 60%, respectively, and the structural heights are 10 stories, 20 stories, and 30 stories, respectively. The nonlinear finite element models of the nine designs are constructed. Their behavior is studied using nonlinear pushover analysis. The performance of the various systems is compared in terms of the earthquake-resistant mechanism, the displacement response, and the failure pattern. The evaluation criteria specified in FEMA-356 for 10% and 2% probabilities of exceedance in 50 years are employed for the assessment purpose. The study finds that it is not appropriate to design a coupled wall system with too low a coupling ratio. Suitable coupling ratios are suggested for coupled walls with different structural heights.
TitleA Seismic Design Formula For Equipment And Non-Structural Compments In Building Structures
AuthorLyan-Ywan Lu, Jiun-Hung Hung, Chia-Chiea Hsu
KeywordsNonstructural component, seismic design, seismic load, equipment protection, equipment isolation, acceleration response.
AbstractIn a building structure, the seismic capacity of equipment is an important issue, since it may cause serious functionality and financial losses of the building if the equipment is damaged in an earthquake. Due to the dynamic amplification effect of the underlying structure, the seismic demand of the equipment is very different from that of the primary structure and has to be treated with special attention. In current design codes, the seismic force of equipment is usually estimated by using the formula of the minimum seismic demand for nonstructural components. However, in this formula, the dynamic properties of the primary structure and equipment are not considered; therefore, the seismic force of the equipment may be over- or underestimated. To this end, based on modal superposition and response spectrum methods, a design formula is derived in this study. When the fundamental frequency and damping ratio of the primary structure and equipment are specified, the derived formula is able to estimate the seismic force or acceleration of equipment located on a certain floor level. Nevertheless, the formula is not applicable to the case in which the frequency of equipment is close to the resonance frequency of the structure. The accuracy of the formula is verified by using the data obtained from time history analysis of equipment placed on mid- and low-raised buildings. The simulation result demonstrates that the maximum accelerations of either soft or rigid equipment predicted by the proposed formula are far more accurate than the values predicted by the design code and are very close to the ones obtained from the time history analysis, particularly for low-frequency equipment. This indicates that the formula is particularly suitable for low-frequency equipment, such as base-isolated, slender or pipeline-type equipment.
TitleSeismic Performance of Steel Dual-Core SCBs and Braced Frames with BRBs and SCBs
AuthorChung-Che Chou, Ying-Chuan Chen, Dinh-Hai Pham, Vu-Minh Truong, Ping-Ting Chung
KeywordsDual-core self-centering brace (SCB), Buckling-restrained brace (BRB), Cyclic test, Non-linear time history analysis of frames, Residual deformation
AbstractA new steel dual-core self-centering brace(SCB) is developed in Taiwan to have a flag-shaped re-centering hysteretic response under cyclic loads. Axial deformation capacity of the brace is doubled by serial deformations of two sets of tensioning elements arranged in parallel. In this paper, the mechanics of the new brace is first explained, followed by testing one SCB to evaluate its cyclic performance. Finite element analysis is conducted on the specimen to verify the mechanics and hysteretic responses observed in the test. Finite element analyses are also performed on other 16 dual-core SCBs to evaluate how tensioning element types, initial PT force, and friction force affect the cyclic performance of the brace. Additionally, three braced frames of varying heights are designed using two bracing members, SCBs and buckling-restrained braces (BRBs). Nonlinear time history analyses are conducted on these braced frames to obtain seismic demands under both design and maximum considerable levels of earthquake motions and near-field motions. SCB frames generally exhibit a smaller peak interstory drift and residual drift than BRB frames.
TitleRelationship between Damage States and Load-displacement Curves of RC and Confined Masonry Buildings
AuthorYi-Hsuan Tu, Hwa-Wan Wang, and Lai-Ching Ao
Keywordsearthquake damage, load-displacement curve, reinforced concrete, confined masonry
AbstractAn earthquake damage evaluation procedure that is objective and easy to use for low-rise RC and confined masonry buildings is presented in this paper. The procedure is established by reviewing several existing procedures and integrating their merits. The accuracy of the procedure and its capability of distinguishing the medium damage states were verified by questionnaires to professionals in former research. It was found that the procedure can produce more accurate and conservative result than subjective judgment. In this paper, the procedure is applied to in-situ test and shaking table test specimens to validate the rationality of the evaluation factors and compared with the current damage evaluation procedure used in Taiwan. The comparison shows that the procedure is reasonable and consistent to the current procedure. The relationship between the determined damage states and the load-displacement curve is then summarized from the validation.