EVALUATION OF THE CARRYING CAPACITY OF REINFORCED CONCRETE WELDED ARMATURE JOINTS
Bolotov Gennadyi , Chernihiv National University of Technology (95 Shevchenka Str., 14027 Chernihiv, Ukraine)
Bolotov Maksym, Chernihiv National University of Technology (95 Shevchenka Str., 14027 Chernihiv, Ukraine)
Hanieiev Tіmur, Chernihiv National University of Technology (95 Shevchenka Str., 14027 Chernihiv, Ukraine)
Korzachenko Mykola, Chernihiv National University of Technology (95 Shevchenka Str., 14027 Chernihiv, Ukraine)
Urgency of the research. The main of the technological process of buildings construction of precast or precast-monolithic reinforced concrete is the production of mesh reinforcement. The main scope of reinforced concrete works is in the welding operations. This is primarily due to the high welded joints quality compared with mechanical rebar splicing using the Lenton couplers.
Problem statement. At buildings construction by monolithic-frame technology for the rebar joint the arc welding processes is widely used. Besides, in addition to the above methods at the stationary conditions for reinforced frame escalating the contact flash-butt welding with continuous flashing or resistance welding is also used. The experience of flash-butt welding applying for a long period of time in the industrial construction conditions allowed to determine the basic advantages caused by the stable welds quality, the ability to automate the welding process, requires no additional consumables.
Actual scientific researches and issues analysis. The studies of the welded rebar joints operability are made by different researchers allowed to determine the basic requirements for the welding conditions, mainly related to the uniformity of heating and cooling, small isothermal holding time at high temperatures and, most importantly, weldability of rebar.
Uninvestigatigated parts of general matters defining. The building structures quality and reliability depends on not only the raw materials quality, but also, the culture of construction works including the welding.
The research objective. In this regard, the aim of this work is to assess the bearing capacity of welded armature joints of reinforced concrete by means of mechanical tests on break.
The statement of basic materials. The results of the studies of the strength characteristics of reinforced concrete welded armature joints made by flash-butt welding and arc welding in shielding gases are shown in the paper. The flash-butt welding performed in the following modes: сurrent density varied in the range of j = 60…160 А/mm2; isothermal holding time t = 0,8…2 sec; heating effort Fh = 10 ... 20 MPa; rainfall effort Fr = 100 ... 150 MPa. Mechanized arc welding performed in the environment of CO2 on DC reverse polarity value of I = 130A.
Conclusions. It is established that the use of “soft” modes of preheated flash-butt welding provides the receipt of equally-strength with the limit of joints endurance at 639 ... 685 MPa, unlike the arc welded joints, the tensile strength of which didn`t exceed 516 ... 578 MPa, due to the considerable heterogeneity of metal structure and HAZ of the joints.
armature, reinforced concrete, flash-butt welding, arc welding, the characteristics of strength
1. Vrublevskaіa, V.V., Vasilev, A.A., Gurskiі, D.M. (2013). Issledovanie prochnosti krestoobraznykh soedinenii iz stalnoi armatury malykh diametrov, vypolnennykh dugovoi svarkoi poluavtomatom v srede aktivnogo gaza [Research strength of cruciform joints of steel reinforcement of small diameter, made semi-automatic arc welding in active gas atmosphere]. Vestnik Polotskogo gosudarstvennogo universiteta. Seriia B. Promyishlennost. Prikladnye nauki – Herald of Polotsk State University. Series B. Industry. Applied science, no. 3, pp. 80–85 (in Russian).
2. Chvertko, P.N. (2010). Kontaktnaia stykovaia svarka sterzhnevoi armatury klassov A400S-A600S pri stroitelstve konstruktsii iz monolitnogo zhelezobetona [Flesh-butt welding rod reinforcement classes A400S, A600S in the construction of reinforced concrete structures]. Avtomaticheskaia svarka – Automatic Welding, no. 8, pp. 30–34 (in Russian).
3. Bolotov, M.G. (2013). Analitychnyi ohliad osnovnykh prychyn ta naslidky avarii budivel ta sporud, shcho stalysia na terytorii Ukrainy za ostanni piat rokiv [Analytical report of main causes and consequences of accidents of buildings and structures on the territory of Ukraine for the past five years]. Visnyk Chernihivskoho derzhavnoho tekhnolohichnoho universetetu. Seriia «Tekhnichni nauky» – Visnyk of Chernihiv State Technological University. Series “Technical sciences”, no. 4(69), pp. 197–204 (in Ukrainian).
4. GOST 12004-81 (1983). Stal armaturnaia. Metodyi ispyitaniya na rastyazhenie [Reinforcing steel. Methods for tensile testing]. Moscow: Izdatelstvo standartov (in Russian).
5. DSTU 3760:2006 (2007). Prokat armaturniy dlya zalizobetonnih konstruktsiy. Zahalni tehnichni umovi [Rent reinforcement for concrete structures. General specifications]. Kyiv: Derzhspozhivstandart Ukrainy (in Ukrainian).
6. Bolotov, G.P., Oleksienko, S.V., Bolotov, M.G. (2015). Ruchne duhove zvariuvannia budivelnykh stalei maloampernoiu duhoiu modulovanim strumom [Hand arc welding builds steels by littleampere arc with modulation of current]. Tekhnichni nauky ta tekhnolohii – Technical Sciences and Technologies, no. 1 (1), pp. 48–53 (in Ukrainian).
7. GOST 14098-2014 (2014). Soedineniia svarnye armatury i zakladnykh izdelii zhelezobetonnykh konstruktsii. Tipy, konstruktsii i razmery [Welded joints of reinforcement and inserts for reinforced concrete structures. The types and sizes of constructions]. Moscow: Izdatelstvo standartov (in Russian).