Vol.34/No.2 (134) (2019)

作者:

Vol.34/No.2 (134) (2019)

 

TitleThe Strength of A New Type Connection for Rectangular Steel Tube Structures
AuthorCheng-Cheng Chen, Xiao-Fang Lin
Keywordssteel tube structure, steel tube construction
AbstractIn order to improve construction efficiency of low-rise buildings, a new type of connection for steel tube structures was developed.The new type connection for horizontal and vertical members are designated as BJ and CJ connections, respectively. Each of the new type connection is composed of two identical parts and assembled by two high strength bolts. The strength of this new type connection and the strength of the welds connecting the connection and steel tube were experimentally studied. A total of 51 successful tests were carried out and the following conclusions then are made accordinly: (1) The welds connecting the new type connection and the steel tube possess enough strength to transfer member forces from tubes to the connection. Therefore, it is suggested that the type and size of welds used in the test specimen should be used in the real structures. (2) The design shear strengths for BJ connection are proposed. (3) The design tensile strength and design compressive strength for CJ connection are also proposed.

 

TitleRevisions of CNS 560 Steel Bars Standard in 2018
AuthorKer-Chun Lin
Keywordsdeformed bars, threaded bars, relative projected area of rib, total elongation, uniform elongation
AbstractThis paper is intended to introduce and describe the major revisions of CNS 560 standard for steel bars using in reinforced concrete structures that include: (1) Adding two types of steel grade, SD 550W and SD 690. For the SD 550W steel, it is weldable and applicable for seismic members. For the SD 690 normal steel, a minimum ratio of 1.25 for the actual tensile-to-yield strength ratio is requested for seismic members, but welding is not allowed due to no limitations on its chemical compositions. (2) Creating a new type of threaded bars. The threaded bars are suitable for the grouted and threaded couplers. The requirements of deformation dimensions for the threaded bars are identical to those for the deformed bars, except that the rib pitch shall not exceed 0.5 times the diameter of steel bar. That is to get the same level of bond performance with the deformed bars. Therefore, the threaded bars can be regarded as one kind of the deformed bars. (3) Revising the method of bend test. For the bend test, based on the requirements of ASTM A615 or A706 standard, the steel bar shall not be restricted movement in its longitudinal direction to prevent from effects of the additional axial stress during the bend testing. In addition, it is recommended that the requirements of uniform elongation corresponding to actual tensile strength should be incorporated into the future version of CNS 560 standard as an assessment criterion of steel bar ductility. This conforms to the principles of performance-based design and provide the corresponding deformation demands of structural members.

 

TitleSeismic retrofit of existing high-rise RC buildings: full-scale test and nonlinear dynamic frame analysis using ETABS program
AuthorChung-Che Chou, Ping-Ting Chung, Ping Nian, V-Liam Chin, Yu-Fang Liu, Chen-Yang Ko, Chu-Chun Wang, Ching-Cheng Chen
Keywordshigh-rise RC building, shear retrofit, double K-braced steel frame, U-shaped steel plate, one-sided steel plate, seismic test, nonlinear static pushover analysis, nonlinear dynamic frame analysis
AbstractThis study evaluates the seismic retrofit of existing high-rise RC buildings in New Taipei City, Taiwan. The paper presents structural test results for verifying the design of member retrofit, nonlinear static pushover analysis and dynamic analysis of the high-rise RC building. The superstructure is mainly retrofitted by two methods. One way adopts a one-sided shear retrofit scheme for RC coupling beams, which are retrofitted with reinforced cement mortar or a steel side plate, respectively, from only one side of the beam to simulate the actual condition on site. The other way is to add a double K-type braced steel frame to increase the shear capacity of the RC frame. The RC beams in the basement are retrofitted with steel plates to increase the shear capacity. The full-scare members with shear retrofits were tested at the National Center of Research on Earthquake Engineering (NCREE) in 2016 and 2017. The test results meet the requirements of the strength and ductility based on Taiwan Seismic Specification and ACI 374.2R-13 (2013). In this study, a 24-story high-rise RC building was analyzed using the computer program, ETABS (2016). The nonlinear static pushover analysis and nonlinear dynamic analysis were conducted to evaluate the seismic performance of the building frame under a set of 2500 year-return period earthquakes, further verifying the seismic demands and technology of the seismic retrofit.

 

TitleStudy of Influences of Reduced Elastic Modulus of Concrete on Related Structural Design Codes in Taiwan
AuthorWei-Hsiu Hu, Wen-Cheng Liao
Keywordsmodulus of elasticity, design code for structural concrete in Taiwan
AbstractIn Taiwan, the prediction of Ec calculated by current design code is usually overestimated by 20% of that obtained by experimental results. The revision code of Ec = 12000 (f’c)^0.5 is 80% of current Ec = 15000 (f′c)^0.5 . The reduction of Ec would influent the size of beam and column, design value of base shear and other related structural design codes in Taiwan, such as “Design Code for Concrete Structures”, “Seismic Design Specifications and Commentary of Buildings” and “Allowable Stress Design Specifications and Commentary of Steel Structures”. The objectives of this research are to clarify those influences on these related structural design codes with reduced Ec and to comment and give suggestions to the engineering society. The results show that because of the reduction of Ec, the minimum thickness of reinforced concrete slab should increase by 7.7％ times, moment magnification factor would increase by 1.15 times (if slenderness ratio of column is 40), number of shear concrete stud would increase by 1.124 times (if compressive strength of concrete f′c < 360 kgf/cm^2). Structural design codes that directly or indirectly related to Ec should be modified accordingly because of the reduction of Ec.

 

TitlePreliminary discussions on analysis and design of floating houses
AuthorJhih-Rong Wang, Shih-Hsun Yin, Che-Hao Chang
Keywordsflood-proof house, floating house
AbstractThe main purpose of this paper is to introduce the concept and procedure needed to design a floating house which has flood-proof capability. The house was composed of steel box substructure and lightweight cold-form steel truss superstructure. Several columns were built up around the house, which can guide the house move up and down through a ring system connected to it. The house can float up along the columns due to buoyancy when flood waters invade and return back to the original location of the base when flood waters recede. Since the house has such a floating mechanism, it cannot be fixed to ground directly. Rubber Bearings were needed to pass vertical and horizontal loadings. In this paper, a real case study will be conducted for designing a floating house including a steel box structure preventing from invasion of flood waters, a lightweight truss structure forming the main house structure, rubber bearing pads transferring loads to foundation when the house is located on the ground, and guide columns limiting the horizontal movement of the house when it floats. The design and analysis procedure presented here may provide industry, government, and academic institutions in Taiwan with some design guidance and be beneficial to the development of floating houses.