Papers by Keyword: Load Ratio

Abstract: There are a lot of concerns on safety structure performance by being buildings to be large and high-rise. In particular, damage due to the fire recently leads to a large disaster and therefore a variety of countries operate the regulation on the fire resistance performance depending on the building structure. There are differences on the fire resistance design in each country but 50% of the design load is suggested to be reasonable for the normal temperature during the fire by applying the concept of the loading ratio to the fire resistance design of structures. Since the loading ratio is the factor having a major impact on the evaluation of the fire resistance performance, it should be preferentially considered. The study on setting up the loading ratio to evaluate the fire resistance performance and safety of structures has yet to be fully furnished in South Korea. Therefore, in this paper, the loading ratio proper for the construction status in South Korea is to be taken into account and then the ratio is to be proposed on the single reinforcement beam.

Abstract: The paper presents the test results on the fatigue crack growth under torsion and proportional bending with torsion in the aluminium alloy EN AW-2017A-T4. The tests were performed at the fatigue test stand MZGS-100 at the constant amplitude of moment M_B = M_T = M_BT = 15.84 N⋅m and stress ratio R = -1. Plane specimens with stress concentrators in form of the external one-sided blunt notch were tested. The results of experiments were described on graphs of the fatigue crack length „a” versus numbers of cycles N. A non-uniform fatigue cracks growth on both lateral surfaces of specimens was observed during experimental tests.

Abstract: The paper presents the results of tests on the fatigue crack growth rate for a constant moment amplitude under combined bending with torsion in the aluminium alloy AlCuMg1. The tests were performed under different values of the stress ratio R. Plane specimens with stress concentrators in form of the external one-sided sharp notch were tested. The results of experiments were described on graphs of the fatigue crack growth rate versus changes of the stress intensity factor range ΔK. A non-uniform fatigue cracks growth on both lateral surfaces of specimens was observed during experimental tests.

Abstract: Fatigue crack propagation is studied in thin wires of about 1 mm in diameter of an ultrahigh strength steel (σ_max> 2400MPa) in ambient air and in air with controlled residual humidity. A specific equipment is developed based on an electro-dynamic testing machine equipped with an environmental chamber for air humidity control. Threshold tests are run using a load shedding procedure specifically adapted to the specimen size. The relation between load ratio and crack closure is evaluated from constant K_max tests. The results are discussed on the basis of fracture surface observations and of existing modelling for environmentally assisted fatigue crack propagation.

Abstract: In order to study the application of the liquefied natural gas (LNG) on diesel engine, a turbocharged diesel engine was converted into a dual-fuel engine ignited by diesel fuel. The effects of load ratio on fuel economy and emissions of dual-fuel engine were compared and analyzed at engine speed of 1200 r/min, 1600 r/min and 2200 r/min. The experimental results show that, the specific fuel consumption is reduced with the increase of load ratio at different speeds. As the load ratio increases, CO emission of dual-fuel reduces, but it increases slightly at high loads and full load. When the load ratio is less than 40%, HC emission of dual-fuel is reduced significantly with the increase of load, but increases when the load ratio continues to increase, and finally HC emission is stable. When the load ratio is less than 40 %, NOx emission is relatively low, as the load ratio increases, increases sharply, but at high loads and full load, reduces slightly.

Abstract: Analyze the stress mechanism of micro-pile and existing mechanism, and come up with the analytic method of pile-soil-(foundation) pile cap interaction grounded upon penetration deformation of pile ends and compression of soil between piles. Hyperbolic model is adopted to simulate the development of tip resistance and side resistance in accordance with deformation to reflect the nonlinearity of pile-soil work, Boussinesq solution is utilized to calculate the stresses generated in soil by foundation (pile cap) plate, Mindlin stress solution is used to calculate the stress produced in the soil between piles by side resistance and end resistance, and the stress of soil is the superposition of the two solutions. Through iterative calculation analytic program RTLOAD for the sharing ratio of a single pile is compiled through VC++.

Abstract: Based upon the characteristics of micro-pile in building heightening and transformation (mainly including the mechanism of the press injection increasing the bearing capacity , the rigid connection between micro-pile and its original foundation), through the analysis of its load characteristics in building heightening and transformation, using the theory of pile foundation constructed in reverse order, then the mechanical mechanism of micro-pile and original foundation is studied and the analysis method of soil-pile-foundation (cap) interaction by considering pile tip penetration displacement and soil compression between pile shafts is demonstrated.

Abstract: Structural steel has been used to make building structures higher and wider than that constructed with conventional structural materials such as concrete, brick, etc since 1960’s in Korea. But the steel structure has fatal demerits. One is the deteriation of structural performance when exposed to severe fire and the other is rusting. The structural behavior has to be sustained during unexpected fire and this can be done by fire design. The fire design consists of two methods. One is prescriptive and the other is performance-base fire engineering design. Recently, the fire engineering design has become a reasonable alternative against the prescriptive method in the world. But the fire engineering method is now preparing for adoption into Korea building regulation. The main purpose of this paper is to build the databases of fire resistant and limiting temperatures of beams made of H-section and the results from fire tests under loadings showed that the corelations between the limiting temperatures and load ratios applied were in reverse proportion.

Abstract: A fire occurring at a building causes severe damages to its structural members and brings unexpected collapse. Therefore, the building regulation of each nation has to define fire resistance to prevent building collapse due to high temperatures. In general, the fire resistance of each structural member can be evaluated by two methods. One is prescriptive method that is guided by a specific building regulation containing fire resistance examples or by the application of new examples tested fire experimental procedures. The other is performance based fire engineering design. Being an engineered and scientific method, it utilizes the results obtained from the calculation of fire severities, temperatures of members and so on. The easiest way to evaluate the fire resistance of a steel member is to compare its limiting temperature and maximum temperature. Therefore, constructing the database of the limiting temperatures of structural elements is very important in performance based fire engineering design. This paper is to derive the fire resistance and limiting temperatures of rectangular hollow sections under loads.

Abstract: Fire resistance is required to sustain the structural stability when building elements are exposed to a severe fire condition. To evaluate the fire resistance of structural members such as columns and beams, fire engineers can apply either prescriptive methods or performance-based fire design. These two kinds of fire resistance evaluation methods have been developed independently and performance fire design consists mainly of an advanced and simple methods. The simple method stipulated in New Zealand and the U.K. use the limiting temperature. The values of the limiting temperatures of structural steel members were shown in the BS, SNZ, etc but the temperatures of individuals were not classified. In general steel columns were made of H-section but recently the hollow section is inclined to increase for its higher resistant of structural stabilities than any other sections. But the hollow section shows different pattern when it carry out the loads in the cold and is expected to show different behavior when it is exposed to fire. Therefore the limiting temperature of the hollow section is required for evaluation of fire resistance. The paper is to make the limiting temperature of the circular hollow section (CHS) with or without filling of concrete and variance of applied loads.