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The effect of changes in mating elements on the bearing capacity of Nodes
DOI: http://dx.doi.org/10.20534/ESR-16-9.10-189-191
Mamajanov Rustam Rahimjanovich, Development and Science Director of JSC "Uztyazhpromproekt"
E-mail: r-mamajanov@mail.ru
The effect of changes in mating elements on the bearing capacity of Nodes
Abstract: This paper presents the results of tests of natural fragments of metal trusses nodes. It is established that, at a differential element in the compounds up to 3.0 mm is practically no effect on the coefficient of friction.
Keywords: assembly, clearance, test, fragment, metal farm differences, friction, shear bearing capacity.
A series of metal bridges have been built for the railways of the Republic of Uzbekistan in recent years. All of the superstructure of railway bridges kept in constant operation, meet the modern requirements of normative documents and ensure the safety and uninterrupted movement of trains.However, a survey of wiring nodes through some metal trusses showed that a perfect seal contact surfaces are not provided. Here, local leakages detected with gaps of 1.0 to 2.0 mm (see. Photos) at their allowable values norms — 0.3 mm.
Existing gaps arranged randomly and any dependence of these values and the number of leaks from the connected elements form not found.
As a result of the inspection nodes after 3-5 years of operation superstructures determined that despite the contraction of the dense high-strength bolts, water still gets in the gaps. After the rain it was possible to detect moisture drips from under fosonok on vertical There were also one-sided visible gaps between the nut and
edges and moisture under the luminaire contributes to the develop- washer or the washer and plate. In some cases these gaps width ment of surface corrosion. reached 2.0 mm.
Figure 1. Diagram of the work connection during testing of full-scale fragments a) — without a drop of connected elements b) — with 4.5 mm difference of connected elements
Section 10. Technical sciences
To assess the impact of structural defects noted on the carrying capacity of joints special experimental studies have been conducted.
It was produced 3 series of samples, fragments of field units through farms. Each series consisted of 4 samples with differences connected elements 3 and 4.5 mm. Simultaneously, the same samples had been made without differential.
Testing of fragments of the nodes held in the research laboratory of Subaku of company Nippon steel Engineering Co. Ltd under the leadership of engineer Kiuchi. The author participated in the development of test methods, and materials processing.
Tests were carried out on the hydraulic lift with capacity of 4000 kN. To measure the value of sliding established brand. Strain measuring accuracy — 0.01 mm.
The geometric dimensions of the experimental fragments correspond to the actual used on the Railways of Japan for farms up to a length of130 m.
As a result of test of these pieces obtained compound operation diagrams (Fig. 1).
As can be seen from Fig. 1 compounds include loading chart plots preliminary displacement, the total shear zone and showing the inclusion of the bolts for shear and crushing.
Strike-slip movements in the range of 0.035-0.05 mm correspond to overcome the total friction force, and the lower value of these values correspond to samples without differences of connected elements.Shifts in the compounds increased from the middle to the edges. Pre offset corresponding to the straight line correspond to shear strain of 0.035-0.05 mm. General deformation structures are determined by precisely this value. Further increase in all fragments shift occurs without increasing the shearing force. The above-mentioned section of the site called a general shift [1; 2].
Figure 2 shows the shear force P corresponding to the beginning of the preliminary displacement differential values in experimental samples.
From Figure 2, we can see that the P value of shearing forces greatly depends on the differential bolt and the connected elements of the location of the joint. The low-est value of shear corresponds to the extreme number of bolts from the joint with a difference of 4.5 mm connected elements. This shows that by increasing the reduced differences in the contact plane of the connecting member and the bolts on the transmission of forces is uneven rows.
The nature of the general shift of development depends on many factors-black, inaccurate installation bolts, fluctuations in the connecting member, etc. The process of enabling operation of the bolts in shear and bearing strength occurs at this period.
Figure 2. - Dependence of shearing force P of the
In practice, due to the existing black individual bolts are included in the work of the shear and crushing the initial stage compounds. In experimental studies [2-4] noted that this phenomenon is a pronounced increase in shear strength and deflection line of a general shift from the horizontal. It is found that movement of a total shift difference depends on the diameters of holes and bolts. According to experimental data [2], these movements make up this difference of 0.3-0.4. As a result of the in-clusion of bolts in the connection work there is a gradual transition from the area of general shift to the site cut and creasing.
When the hole diameter difference and bolts 1.0 - 1.6 mm displacement reach-es 2-4 mm and this point characterizes the onset of flow connection. Further in-crease in load leads to intensive development deforming wall holes and bolts. By the time of the destruction of the connection offset values reach up to 30 mm and a breaking load of up to 4 times higher than the load at a total shift [2, 4].
In the table are listed the value of the friction coefficient ^ obtained from test-ing of experimental pieces. The table shows that the
magnitude of the differential connecting elements A
coefficient of friction ^ in the compounds decreases with increasing differences of elements in the joints. At the drop of connections to 3.0 mm experimental values of the coefficient of friction is almost equal to the normative values. A further increase in the differential value leads to a marked decrease in Clearances at differences of up to 3.0 mm is rec-ommended to fill sealants to prevent moisture from entering the compound. Table 1. - The change in the coefficient of friction | in dependence on the dif-ferential of elements in compounds
Changes in the joints, mm № samples The values of the coefficient of friction ^
0,0 1 0,62
2 0,63
3,0 3 0,49
4 0,53
4,5 5 0,50
6 0,43
Evaluation of the influence of meteorological factors on the aeration zone and the groundwater regime using Gis.
The following conclusions can be drawn on the basis of the research:
With the increase in the differential of connected elements of friction coefficient decreases.When a drop of 3.0 mm revealed a marked decrease in coefficient of friction.
Gaps, with a difference of elements in compounds to 3.0 mm practically don't influence the coefficient of friction and these gaps can be sealed to prevent the ingress of moisture. Gaps greater than 3.0 mm is unacceptable. When you see these gaps it is recommended to fill them with additional plates, the thickness of which is equal to the value of the differential.
References:
1. Vaynblat B. M. High-strength bolts in the construction ofbridges. - M., - Transport, - 1971. - 166 p.
2. Bogdanov T. M. The compounds of metal structures on high-strength bolts. - Moscow, - Transjeldorizdat, - 1963. - 42 p.
3. Kozmin Y. G. Designing bridges and pipes.Metal bridges. - M.: Route, - 2005. - 460 p.
4. Lesokhin B. F. Experimental studies of bolt welded superstructure under load. In collection:.Research of steel and steel-concrete bridge spans. - M. - Transport, - 1970 - P. 164-182.
DOI: http://dx.doi.org/10.20534/ESR-16-9.10-191-193
Muradov Navruz, Research Institute of Irrigation and Water Problems E-mail: ilhom_makhmudov@mail.ru
Evaluation of the influence of meteorological factors on the aeration zone and the groundwater regime using Gis and Mike Sheimitating models
Abstract: As is known in the groundwater regime is influenced by precipitation, surface runoff and evaporation of soil moisture. In the arid climate for crop production in the initial phase of the plant the determining factor is the condition of aeration zone, which is determined by the level of groundwater. And in areas prone to soil salinity, groundwater regime is determined by the state of irrigated lands: the rise of level or increasing salinity pose a risk to soil salinity, soil salinity reduces the productivity of irrigated lands and irrigation water. Along with this assessment of groundwater regime, especially its state level under the influence of precipitation and runoff are difficult scientific problem. The solution of this important agricultural production is the subject of this Article.
Keywords: runoff, groundwater, aeration zone, ground water level, groundwater regime, atmospheric condensation, soil salinization.
Introduction. In areas with an arid climate with groundwater runoff determine the main conditions of crop production. In establishing mode of an irrigation plants, especially cotton, the state of groundwater determines the amount of water-supply via irrigation canals. And for soils affected by salt and in the presence of groundwater toxic salts, state groundwater determine the main conditions of plant life: a small distance from the ground surface leads to salinization and soil degradation, and causes a deep state of increased demand for irrigation water. Prediction of ground water regime is a scientific challenge. The challenge is caused by the presence of a variety of factors that affect the groundwater regime, the most influential of them are precipitation and runoff. At the same time on the groundwater regime has a significant impact the area where it is located, if the territory is located on the river valley, the factors which have an impact on the groundwater regime, more than the areas in the steppe zone, etc. In this regard, as the object of research established Chirchik river basin area in the Tashkent region of Uzbekistan [1]. As a subject of research determined primarily influence of precipitation in conjunction with other components of the water balance of a river basin in ground water areas.
Materials and methods. Object of research is the area of Chirchik river basin, where crop productions are carried out exclusively by irrigation. Therefore, prediction of the state of groundwater enhances the effectiveness of water management in the production of crops, especially of cotton [1; 2].
Figure 1. Topography of Chirchik River Basin (DEM by GIS)
Cotton for the mentioned area is the main crop and occupies more than 60% of the irrigated area of Syrdarya river basin. As the research methods defined the water-balance method of river basin, the method of unspecified filtering and interpolation method of climatic factors, developed by the authors ofthis article. Water balance equation of Chirchik river basin:
^^gw ^^ QChar+Ugam + QOhan + P QChinoz Quse ET E ^^char+Ugam
- Water Inflow to Chirchik River Basin from Ugam River and Char-vak reservoir
