Ngày tạo : 14/07/2015Tạp chí KHCN Xây dựng số 4/2007
TS. Nguyễn Đại Minh, KS.
Nguyễn Hoàng Anh
Xác định tải trọng động đất tác dụng lên công trình theo TCXDVN 375 : 2006 bằng qui trình đơn giản,
Determination of seismic loads acting on building structures according to TCXDVN 375: 2006 with a simplified procedure (pp.3-7)
Dr. nguyen dai Minh, Eng. nguyen hoang Anh
This paper presents a simplified procedure for determining seismic loads acting on building structures according to TCXDVN 375: 2006: Design of seismic resistant building structures. The procedure is applicable to calculation and design of building structures in seismic prone regions. When applying this procedure to design, possible mistakes caused by engineers can be avoided.
Unbonded post-tensioned prestressed concrete beams subjected to uniformly distributed loads (pp.8-11)
A/Prof. Dr. Nguyen tien chuong
Unbonded tendons in prestressed concrete structures can freely move along its axis. Due to this feature, the analysis of unbonded prestressed concrete structures is a very complicated problem. Experimental methods are applied to Design standards to solve this problem.
In this paper, the author presents results of a study on the behaviour of Unbonded post-tensioned prestressed concrete beams subjected to uniformly distributed loads. The main result of the study is a system of equations that can be used to determine the flexural strength of the beam.
Adjustment of natural frequencies of multi-storey building with HDR embedded (pp.12-16)
MEng. tran tuan long
Structural vibtation strongly and affects to the design and performans of the construction. One solution reduce the vibration of the structure under seismic-incluced load, is to use a device called HDR (High damping rubber bearing) to isolate the structure from its base.
This article estimates the influence of the structural and the HDR device parameters to the natural frequencies of HDR – embedded structure of multi-storey building.
Oscillation of inverse pendulum equiped with Tunned Mass Dampers (pp.17-23)
A/Prof. Dr. khong doan dien, MEng. nguyen duy chinh
In reality, there are many structures that can be modeled in the inverse-pendulum form such as buildings, antenna tower, drilling rig e.g. Of the development of science and technology, these structures are getting to become higher and larger in size. Increasing the structural sizes will lead to the complicatedly dynamic responses and vibrations unfortunately that affect the ordinarily working condition of the structures. Therefore, studying and decreasing these oscillations are recently very hot problems. Paper represents the way to establish the mechanical and mathematical models in order to determine the vertical and horizontal oscillations of structures with inverse-pendulum form that are installed the absorber. The results obtaining from the investigating of the inverse-pendulum will be applied to study, analyze, calculate, and design optimally to find the parameters of damper that reduces the detrimental oscillations of inverse-pendulum-formed structures.
Towards Better Evaluation of Design Wind Speed of Vietnam (pp.24-35)
MEng. Le Truong Giang, Prof Yukio Tamura, A/Prof. Masahiro Matsui
The aim of this study is to seek an answer for the appropriate procedure to evaluate design wind speeds of Vietnam. Surface wind data of 108 meteorological stations obtained from the National Hydro-Meteorology Data Center and other sources were used in this study. Finally, an appropriate treatment is proposed to deal with extreme winds based on available wind records. In addition, weaknesses or uncertainties in assessment of design wind speeds also are discussed.
Studying for producing self-compacting concrete of grade 200 (pp.36-42)
Dr. Tran Ba Viet, MEng. Le Minh Son
Self-compacting concrete is the type of concrete that can self-leveling owing to its self-weignt and filling up all area of the form, including the area of dense reinforcement.
This paper presents a study for producing self-compacting concrete of grade 200 using materials available in Vietnam. The studying results have shown the limit boundary condition of compotion used for self-compacting concrete of grade 200, the influence of the hot and humid climate condition on the the development of compressive strength, the shrinkage, workability of the produced self-compacting concrete.
Cleaning steel rust with steel rust conversion agent of B-05 (pp. 43-46)
Dr. Pham Van khoan, Eng. tran Nam
Steel rust is the phenomenon that is widely seen on building structures in the Vietnam hot and humid climate conditions. When bare steel is exposed to the external humid environment, yelow rust can appear on the steel surface. If the exposure time is longer, the steel scale will be formated, significantly affecting the quality of steel. For reinforeced concrete structures, steel rust will reduce the boding forec between reinforcement and concrete, increasing the rist of being corroded during the using process. Therefore, steel rust must be cleaned prior to placing concrete.
At present, there are many ways to clean the steel rust. In this paper, the authors introduce a part of the research results on the conversion of steel rust caused by B-05 – one of the converters used to clean steel rust.
The role of polypropylene fiber on reducing plastic shrinkage of concrete hardening in the conditions of Hot and Humid Climate of Vietnam (pp.47-52)
Dr. Nguyen Tien Binh, Dr. Tran Ba Viet
Plastic shrinkage of concrete hardening in the conditions of Hot and Humid Climate of Vietnam is rather high. It often causes strong cracks in the surface of concrete structures, so reduces their quality. That’s why limiting plastic shrinkage is one of the important tasks of Vietnamese experts in solving problems relating to the increase of concrete quality. In this paper, an experimental investigation on the effectiveness of using polypropylene fiber at the ratios of 0.1% and 0.3% by volume for limiting plastic shrinkage of concrete with different monitoring models is presented.
Some matters on permissible tolerances when constructing concrete and reinforced concede structures (pp.53-55)
Eng. tran manh nhat
In this paper, the author presents, analyzes some stipulations, which are, according to the author, not reasonable in the TCXDVN 4453: 1995: Monolithic concrete and reinforced concrete structures – Standard of construction and acceptance. The author also recommends some changes so that this standard can suit the technical capacity available at present. The recommendations by the author should be carefully considered and analyzed from many aspects when deciding to review and amend the standard accordingly.