A new method for fuzzy reliability analysis of structures (pp. 3-7)

Prof. Dr. Nguyen Van Pho, MEng. Nguyen Dinh Xan and Eng. Nguyen Thac Vu

In 1965, Zadeh introduced fuzzy sets theory. Subsequently, the theory and the mathematics of fuzzy sets were fleshed – out and applied in many research.

In 1999, Li Bing presented a practical engineering method for fuzzy reliability analysis of mechanical structures. In 2003, Qimi Jiang presented a numerical algorithm of fuzzy reliability. All these studies considered for element only.

In this paper, the authors propose a new method for determining the reliability of structures (which consists of many elements), in which three types of variables: deterministic, random and fuzzy are included.

The novel method, Monte–Carlo simulation technique, finite element analysis and linear regression are used.

For reliability assessment, in this paper the authors used model of fuzzy stress–random strength, but it can apply for random stress- fuzzy strength or fuzzy strength–fuzzy stress models.

A numerical example is given to illustrate the mentioned method.

Analysis of statistical series in experimental study (pp. 8-10)

Dr. Nguyen Xuan Chinh

As far as we all know, when analyzing experimental data, the experimental distribution curve is different from the theoretical one. Normally, with a set of data, an experimental curve can be set up. The question put forward is that, for which theoretical curve that experimental curve is indicated ? and vice versa, which theoretical curve indicates/reflects the obtained experimental one?

The "Smoothing" problem of statistical series is the problem of finding out the theoretical distribution one so as it reflects well the experimental function.

This paper presents the analysis of statistical series in experimental study by solving the "Smoothing" problem, namely, in the known theoretical curve layers in which each curve depends on one parameter, we choose the most suitable parameters so that the correspondence between theoretical and statistical distribution is the best.

A method for calculating reliability of structures subject to wind load at Khanh Hoa province (pp.11-14)

MEng. Le Duc Vinh

This paper presents a method for calculating the reliability of structures subject to wind load. Wind load is calculated according to Vietnam standard TCVN 2737-1995 and hydro-meteological data monitored at Nha Trang city during the last 10 years.

The safety obtained when calculating according to TCVN 2737-1995 is higher than that obtained when calculating according to hydro-meteological data monitored at Nha Trang. An example illustrated is the calculation of reliability of a wall panel subject to wind load.

Some questions on the stability of thin quasi-cylindrycal shell (pp.15-21)

Prof. D.Sc. A Moxov A. A, Eng. Cao Duy Khoi

Quasi-cylindrycal shells (the thin shell that approximates to cylindrycal one) can be utilized in many various structures such as: material storage tanks, silos, roofs of buildings, cladding walls, aero plane covers or the cover of machine-tool. In this paper, the authors presents a study on the stability of thin quasi-cylindrycal shell.

Some research and applied results on self-leveling mortar with high performance against chloride-induced corrosion (pp.22-26)

MEng. Nguyen Nam Thang, Dr. Pham Van Khoan

Chloride-induced corrosion of reinforcement in RC structures is a common phenomenon and is considered to be the main cause that damages Vietnam marine RC structures. Techniques and materials are the essential solutions for solving this problem. And, pouring self-leveling mortar with high performance against chloride-induced corrosion is regarded as an effective anti-corrosion technique. In this paper, the authors presents some research and applied results of this technique in repair and rehabilitation of some RC structures damaged due to chloride-induced corrosion.

Some modified parameters in Russian "Civil codes and Rules of SNIP II-7-81 - Construction in seismic area". (pp.27-32)

Dr. Tu Duc Hoa

The Vietnam State System of Coordinate and attentions required to be paid when applying it to design and construction (pp.33-36)

Dr. Ngo Van Hoi

The paper presents the most important feature of the State System of Coordinate (SSC), that is the deformation of all details presented on drawings in SSC. This uncomfortable feature might cause a lot of troubles when executing the building constructions if SCC is used for design. In this paper, the author provides readers with conditions to check the compatibility between dimensions of the detail on the ground surface and those shown on drawings and the way to make them being compatible.

On the application of Vietnam standard TCXD 239:2000, Heavy concrete - guide to assessment of concrete strength in existing structures (pp.37-39)

Dr. Nguyen Duc Thang

Viernam standard TCXD 239:2000, Heavy concrete - guide to assessment of concrete strength in existing structures was developed and issued for application since 2000. This is one of the first standards of Vietnam construction standard system that presents in details on the method of organization, selection, testing and assessment of concrete strength in existing structures. However, it is required to be modified for a more accurate application. This paper introduces the way to convert concrete strength of drilled concrete core sample to the cubic one and principles for evaluating of concrete strength at building structure.

An optimal method with safe probability restraints of the beam stiffened by hinged bar structures under dynamic loads (pp.40-43)

A/Prof. Dr. Le Xuan Huynh, MEng. Tran Viet Anh

One of the combinative structural forms is the structure which is formed by the beam stiffened by hinged bar structures. In this paper, the authors propose an optimal method with safe probability restraints of the beam stiffened by hinged bar structures under moving loads that depend on the time by the harmonize function. The loads, material intensity and geometrical dimensions are random values with the standard distribution and statistical independence. Content of the method is determination of the optimal criterion for the problem with two probability restraints by using the Lagrane method. This study used the sensitive analysis to change the cross-section area of the structural members. The analysis of the stress-strain relationship of the structure was carried out by the Finite element method.

Studying for production of scattered fiber reinforced concrete (pp.44-49)

Dr. Tran Ba Viet

When constructing of high way, bridge deck, runway of the airport,.. in addition to high strength requirement, concrete needs to meet the other requirements such as: strain-resistance under loads, wear-resistance, control of cracks and impact resistance. The type of concrete that can meet all the above requirements is the scattered fiber reinforced concrete. This concrete is self-leveling, high-strength concrete that can be self-filled up.