CS202808B1

CS202808B1 - Method of protection of tensometer scanners on the reinforcement of the reinforced concrete elements against the humidity and mechanical failure

Info

Publication number: CS202808B1
Application number: CS720178A
Authority: CS
Inventors: Jozef Kucka
Original assignee: Jozef Kucka
Priority date: 1978-11-06
Filing date: 1978-11-06
Publication date: 1981-02-27

Description

Vynález sa týká spósobu ochrany tenzometrických snímačov na výstuži železobetonových prvkov proti vlhkostí a mechanickému poškodeniu.The invention relates to a method of protecting strain gauge sensors on reinforcement of reinforced concrete elements against moisture and mechanical damage.

Pri experimentálnom výskume v stavebníctve sa na meranie deformácií prvkov, modelov a konštrukcií používajú tenzometrické snímače, pričom sa v prevažnej miere umiestňujú na icfi povrchu. Poměrně náročné je meranie j deformácií priamo na ocelověj výstuži železobetónových prvkov, pretože tenzometrický snímač, nalepený na výstuži vrátane jeho prívodov je podrobený íntenzívnemu mechanickému namáhaniu pri procese betónovania a dlhotrvajúcemu pósobeniu vlhkosti ako pri betonovaní, tvrdnutí a dozrievaní betónu, tak i počas jeho normového uloženia, až do prevedenia vlastného experimentu. Typický časový úsek od výroby do prevedenia skúšky je 28 dní, pričom v případe dlhodobého opakovaného zaťaženia skúška a meranie trvá 3 až 7 dní. Je třeba hlavně zabezpečit, aby tenzometrický snímač bol schopný funkcie počas vlastného merania, kedy je podrobený velkým mechanickým deformáciám, a v jeho blízkom okolí móžu v betóne vznikat trhliny řádové až do šířky milimetra.In experimental construction research, strain gauges are used to measure the deformations of elements, models and structures, and are predominantly placed on icfi surfaces. It is quite difficult to measure the deformations directly on the steel reinforcement of reinforced concrete elements, because the strain gauge, which is glued to the reinforcement including its leads, is subjected to intensive mechanical stress during the concreting process and long-term exposure to moisture. , until the experiment is run. A typical period from production to test execution is 28 days, and in the case of long-term repeated loading, the test and measurement takes 3 to 7 days. In particular, it is necessary to ensure that the strain gauge sensor is capable of functioning during the actual measurement, when it is subjected to large mechanical deformations, and in its vicinity, cracks in the order of millimeters may occur in the concrete.

Uvedený problém sa v súčasnosti rieši rozličnými sposobmi, z ktorých každý má svoje výhody a nevýhody. Tak například metoda lepenia tenzometrov do vyfrézovanej drážky, ktorá sa vyplní špeciáinym tmelom zmenšuje efektívny prierez tyče v meranom mieste. Spoločným me· novateíom v zahraničí používaných metód je používanie špeciálnych tenzometrov a tmelov, ktoré u nás nie sú bežne dostupné.This problem is currently being addressed in different ways, each with its own advantages and disadvantages. For example, the method of gluing the strain gauges into a milled groove, which is filled with a special sealant, reduces the effective cross-section of the bar at the measured point. The common determinant of methods used abroad is the use of special strain gauges and sealants that are not commonly available in our country.

Spósob ochrany, ktorý je predmetom vynálezu odtraňuje uvedené nevýhody a umožňuje používat pře meranie deformácií na armatúre i tenzometrické snímače s celulózovou podložkou, mimoriadne citlivé na vlhkost. Umožňuje dosiahnuť izolačný odpor až 510⁹ ohmov, čo zaručuje ich perfektnú funkciu. Metóda zároveň vylučuje případné pósobenie ochranného tmelu na snímač a následnú změnu jeho parametrov. Nevyžaduje oslabenie armatúry v mieste merania a nesposobuje prakticky zásah do meraného prvku z hladiska jeho únosnosti a súdržnosti. Metóda je univerzálna, tj. vhodná i pře snímače s ínou ako celulózovou podložkou.The method of protection of the invention obviates the above-mentioned disadvantages and makes it possible to use strain gauges with cellulose backing which are particularly sensitive to moisture, using the strain gauge on the armature. It allows to achieve an insulation resistance of up to 510 ⁹ ohms, which guarantees their perfect function. At the same time, the method eliminates the possible application of protective sealant to the sensor and subsequent change of its parameters. It does not require weakening of the valve at the measuring point and does not practically affect the measured element in terms of its bearing capacity and cohesion. The method is universal, ie. also suitable for sensors with china as a cellulose pad.

Pře analýzu ohybových zložiek deformácií a zaručenie spoíahlivosti sa nejčastejšie používajú dva snímače umiestnené na armatúre oproti sebe.In order to analyze the bending components of deformations and to ensure reliability, two sensors placed on the armature opposite each other are most often used.

Podstata vynálezu spočívá v tom, že na odmaštěný úsek tyče, na ktorý je nalepený tenzometrický snímač sa v okolí snímača. nanesie vrstvička lepidla na báze chlóroprenového kaučuku a na snímač se po vysušení nanesie vrstvička včelieho vosku. Na vývody tenzometra sa prl202808 spájkujú izolované vodiče, na ktorých koncoch je nanesená vrstvička lepidla, pričom medzi vývody tenzometra a vrstvičku včelieti^ vosku je vložená élektroizolačná fólia^ Vodiče Sú k tyči priviazané konopnou niťou a na snímač a jeho okolie sa nanesie vrstva tmelu, načo sa zhotoví bandáž ovinutím PVC fóliou.It is an object of the invention to provide a grease-free section of a bar on which a strain-gauge sensor is adhered in the vicinity of the sensor. a layer of chloroprene rubber based adhesive is applied and a beeswax layer is applied to the sensor after drying. Insulated conductors are soldered to the strain gauge terminals, with an adhesive layer applied at the ends of the strain gauge, with an electro-insulating foil inserted between the strain gauge terminals and the beeswax layer. the bandage is made by wrapping with PVC foil.

Při poměrně malej pracnosti sa dosahujú dobré výsledky i pri použití tenzometrov s celulózovou podložkou v náročných podmienkach, aké nastávajú počas betonáže, v štádiu tvrdnutia a dozrievania betónu, ako i pri vlastnej skúške a meraní.With relatively low labor intensity, good results are achieved even when using strain gauges with cellulose backing in demanding conditions such as during concreting, in the stage of hardening and maturing of concrete, as well as in the actual test and measurement.

Na pripojenom obrázku je znázorněný mechanicky vyčištěný a odmaštěný úsek tyče 1, na ktorý sa nalepia tenzometrické snímače 2, a na povrch tyče sa vo vzdlalenosti cca 3 mm od obvodu snímačov nanesie v šírke cca 1 cm tenká vrstva lepidla 3 na báze chlóroprénového kaučuku, ktoré sa nechá vyschnúť. Pre zabezpečenle vývodov tenzometrov sa pripravia vodiče s PVC iziláciou tak, že sa nařežu na potřebná dížku a na jeden koniec sa nanesie na dížku cca 10 cm vrstvička lepidla na báze chlóroprénového kaučuku.The attached figure shows a mechanically cleaned and degreased section of the rod 1 on which the strain gauges 2 are glued and a thin layer of chloroprene rubber-based adhesive 3 is applied to the rod surface at a distance of about 3 mm from the circumference of the sensors. is allowed to dry. To secure the strain gauge terminals, PVC wires are prepared by cutting them to the required length and applying a 10 cm layer of chloroprene rubber based adhesive to one end.

Na celú armatúru sa umiestni požadovaný počet dvojíc tenzometrov. Takto připravené armatúry sa umiestnia na sušlacu lavicu, kde sa tenzometre pomocou infražiaričov vysušia do tejThe required number of pairs of strain gauges shall be placed on the entire fitting. The prepared fittings are placed on a drying bench, where the strain gauges are dried to

Claims

Method of protection of strain-gauge sensors on reinforcement of reinforced concrete elements against moisture] and mechanical damage characterized by the fact that a layer of glue is applied to the degreased section of the rod on which the strain-gauge sensor is glued. is soldered isolated vomiery the grid insulation resistance strain gauges opposite the valve is greater than 10 ⁹ ohms. After finishing the drying, e.g. applied with an electric soldering iron on a strain gauge and 3 mm around them, ie. up to the area where there is a thin layer of adhesive 3, an approximately 0.5-1 mm thick layer of beeswax 4 which has previously been dehumidified in a suitable drier. This prevents atmospheric moisture from entering the strain gauge.

Treated PVC conductors 6 are soldered to the strain gauge terminals S, which are bent back through the strain gauge, whereby a suitable electro-insulating foil 7 is inserted under the strain gauge outlet 5 and a part of the conductor 6. The conductors 6 are tied to a fitting e.g. hemp yarn 8. On this treated strain gauge and its surroundings a ca 3 mm thick layer of rubber-based sealant 9 is applied, which adheres perfectly to the adhesive-treated points of the valve and the outlets, thus preventing moisture penetration to the strain gauges. The wax layer serves as the first protection against moisture and at the same time prevents long-term bonding of the mastic components to the strain gauge. In order to prevent coarse injection of the shot during concreting and vibration on the sealant having plastic properties, the strain gauges treated in the above manner are finally bandaged e.g. PVC tape 10, about 0.1 m thick. Strain gauge sensors protected in this way have their parameters within the prescribed limits several months after concreting.

In the present invention, there is provided an adhesive layer at the ends of which an adhesive layer is inserted between the strain gauge terminals and the beeswax layer and the wires are tied to the rod with hemp thread, and a layer of sealant is applied to the sensor and its surroundings. .