Vol.32/No.3 (127) (2017)
| Title | Study of Prediction Equation for Modulus of Elasticity of High Strength Concrete in Taiwan |
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| Author | Wen-Cheng Liao, Wei-Xiu Hu |
| Keywords | High Strength Concrete, Modulus of Elasticity, Compressive Strength, Silica Fume, New RC |
| Abstract | The modulus of elasticity of concrete is an important factor in design of RC structures. Modulus of elasticity is also essential for engineers to estimate deflections and stiffness of RC members. Nowadays, Taiwan New RC project is developing to reduce the member sections and increase the available space of high rise buildings by using high strength concrete (f’c > 700 kgf/cm2) and high strength rebars. However, the prediction and calculation of modulus of elasticity of high strength concrete in Taiwan is still mainly referred to ACI318 or ACI363. It was confirmed that modulus of elasticity of high strength concrete is usually overestimated due to less coarse aggregate amount and high paste volume. In order to gain precise modulus of elasticity, it is necessary to find out an equation which can reflect materials characteristic in Taiwan.This study collects 471 data sets of high strength concrete in Taiwan. By regression analysis with certain key parameters, such as silica fume, a new and practical prediction equation based on the ACI318 is proposed. This equation is easy to calculate and reflects the low modulus of elasticity characteristics in Taiwan. It can offer more accurate estimation of modulus of elasticity for New RC member design. |
| Title | The seismic performance of reinforced concrete columns using horizontally lap-spliced crosstie |
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| Author | Tai-Kuang Lee, Cheng-Cheng Chen, Ming-Chin Ho |
| Keywords | horizontally lap-spliced crosstie, lap splice length, RC columns, seismic performance |
| Abstract | A lap-spliced crosstie consists of two J-shaped steel bars (rebars) that have a straight end and an end featuring a 180° hook. In this study, a lateral cyclic load test was conducted on three specimens of large-sized reinforced concrete (RC) columns to investigate the seismic resistance capability of RC columns comprising horizontally lap-spliced crossties with less than Class A splice length. The research results are presented as follows: (a) The confinement effect of horizontally lap-spliced crosstie with less than Class A splice length, was comparable to that of the specimens using crossties featuring a 180° hook on the two ends and conventional crossties. (b) According to the reading data of strain, the horizontally lap-spliced crosstie can develop the required strength and provide satisfactory confinement effect. (c) In order to be safe and conservative, Class A splice (1.0 times the development length) for lap-spliced crossties is recommended. (d) Using lap-spliced crossties in construction is easy and produces a low possibility of construction errors. Therefore, the construction quality of RC column reinforcement and the seismic resistance capability of RC structures can be substantially increased. The case discussed in this study shows that the use of lap-spliced crosstie would increase the amount of transverse steel in each plastic hinge by 11.5 kg and in the clearance height of columns by 17%. |
| Title | Feasibility Study on Building Mass Damper Using Optimum Dynamic Response Control Algorithm for Practical Application |
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| Author | Pei-Rong Chen, Yu-Fang Liu, Bo-Han LEE, Tzu-Kang Lin, Kuo-Chun Chang |
| Keywords | Mid-story isolation system, Tuned mass damper, Building mass damper, Objective function, Optimum Dynamic Response Control Algorithm |
| Abstract | In a mid-story isolated building, the isolation system is incorporated into the mid-story rather than the base of the building. The effectiveness of mid-story isolation design in reducing seismic demands on the superstructure above the isolation system has been verified in many researches. However, the response of substructure may be amplified due to the flexibility and the contribution of the higher modes. On the other hand, although tuned mass damper has been recognized as an effective energy absorbing device to reduce the undesirable vibrations of the attached vibrating system subjected to harmonic excitations, the mass ratio of most TMD was not enough for earthquake resistance due to the limitation of the building space. Therefore, the concept of building mass damper (BMD) design has been developed, which incorporates the TMD design concept into the mid-story isolated building to control the seismic response of both substructure and superstructure. In the BMD design, the superstructure serves as a tuned absorber mass while the stiffness and damping can be provided by the isolation system composed of elastomeric bearings and additional dampers, as the advantages of conventional TMD and mid-story isolation systems can be integrated. A simplified three-lumped-mass structure model, in which three lumped masses are respectively assigned at the building mass absorber, the control layer, and the primary structure, is rationally assumed to represent a building structure with a BMD system. The reason for doing this is that the inherent dynamic characteristics (fundamental modal characteristics of vibration) of both the building mass absorber and the primary structure can be considered comprehensively in the simplified structure model. The feasibility of the optimum BMD (OBMD) design method has been verified in previous studies. In this research, the 57 story steel frame is used to be a bare frame. According to 2% inherent damping ratios of the TMD, BMD and OBMD can be designed respectively. Six real earthquake records with distinct seismic characteristics adopted in this research are selected for the ground acceleration inputs along the longitudinal and transversal direction. On the other hand, the acceleration transfer functions of the simplified three-lumped-mass structural model and the FFT of each ground motion are used to describe the seismic behavior of the TMD, BMD and OBMD. Then, the seismic responses of the OBMD system are thoroughly investigated and the practicability and effectiveness of the OBMD system for seismic design are verified. |
| Title | Evaluation of composite floor vibrations induced by moving loads |
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| Author | Jian-Huang Weng, Chi-Hang Li |
| Keywords | floor vibration, composite floor deck, moving load, generic vibration criteria, one-third octave spectrum, SCI P354 |
| Abstract | In the laboratories or research centers, the vibration-sensitive equipments are often placed on the basement floors. The reason is the impact of environmental vibrations outside the building can be reduced. Another reason is the influence on the structural design will be smaller if the slab thickness needs to be increased because the lateral seismic force of the slab is directly borne by the basement exterior wall. However, basements are often used as parking or loading/unloading spaces so that the vibration induced by vehicle pass-bys may affect the equipments. Although the full height RC partition wall can be used to reduce the vibration and it is also effective to keep the equipments far away from the lane, the result should be confirmed with floor vibration analysis. In this paper, the moving load analysis in SAP2000 is applied to evaluate the floor vibration induced by vehicle traveling inside the building. The publication of Steel Construction Institute: Design of Floor Vibration – A New Approach (SCI P354) is referred as a guideline for structural simulation of the composite floor deck which is commonly used in steel structures. This paper contains simulation of moving load, modeling of composite floor deck and calculation of the generic vibration criteria which is commonly used for high-tech facilities. Finally, an example, design of floor vibration in an animal research facility, is provided to illustrate the design details. |
| Title | Design and Construction of Carbon Fiber Reinforced Polymer Composite Jacketing for Seismic Retrofit of National Freeway Bridges |
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| Author | Kang-Yu Peng, Ming-Shing Wu, Chien-Hung Chen, Chi-Shan Wang, Sheng-fa Lin, Jun-Jjie Zheng |
| Keywords | bridge, seismic retrofit, carbon fiber, jacket, construction |
| Abstract | Chi-Chi earthquake measuring 7.3 on the Richter scale struck Taiwan on September 21, 1999, and caused severe property losses and casualties to central Taiwan. After the earthquake, the seismic safety of the bridge structure has become a very important issue in the national disaster prevention plan. The national freeway is the main traffic artery connecting the north and south in Taiwan, which has great influence on the national economic development and the people’s livelihood. Taiwan Area National Freeway Bureau (TANFB) actively took preventive measures for the bridge structures. The bridge columns jacketing can effectively increase the flexural ductility and shear strength of the bridge in large earthquake. The reinforced concrete jacketing and steel jacketing are the most widely used in the domestic bridge columns seismic retrofit project. In view of the ever-changing materials technology, carbon fiber material has the characteristics of bearing the load, limiting the micro-crack extension, improving the material strength and rigidity. The material can also improve the material anti-fatigue, anticreep performance and service life. When the space is limited, the landscape requirements or construction conditions are not applicable reinforced concrete jacketing and Steel Jacketing , the seismic retrofit program of national freeway bridges using carbon fiber reinforced polymer composite jacketing (CFRP jacketing). With carbon fiber materials’ light weight, high strength, easy constructed and other characteristics, increase the seismic capacity of freeway bridges, and accumulate the experience of domestic design, construction, testing and maintenance. Looking forward to provide more choice for future domestic bridge seismic retrofit project. |