CN106403798A - Device and system for measuring internal displacement of concrete and installation method of system - Google Patents

Abstract

The invention provides a device, a system and an installation method for measuring the internal displacement of concrete. The device for measuring the internal displacement of concrete includes a shell, a shrapnel, a probe and a casing. The fixed end of the shrapnel is connected to the shell, and there are gaps between the first surface of the shrapnel and the shell and between the second surface of the shrapnel and the shell. gap, the first and second surfaces are provided with strain gauges, the strain gauges are close to the fixed end of the shrapnel, the position corresponding to the free end of the shell is provided with a first through hole with an inner diameter larger than the sleeve, the probe is connected to the free end and probed One end of the needle protrudes from the housing through the first through hole, and the sleeve is movably sleeved on the probe. The device has good sealing performance and long service life. The system for measuring the internal displacement of concrete includes a plurality of the above-mentioned devices, which are connected through conduits, and the system has high precision. The installation method of a system for measuring the internal displacement of concrete makes the formwork bear against the probe, so that the probe has a certain preload, and at the same time makes the sleeve contact the formwork; it can measure the two-way displacement.

Description

A device, system and installation method for measuring internal displacement of concrete

technical field

The invention relates to the field of concrete internal displacement measurement, in particular to a device, system and installation method for measuring concrete internal displacement.

Background technique

On the high-speed rail ballastless track, the relative displacement between the limit boss at the bottom of the track slab and the surrounding structure will occur. Therefore, continuous observation of the service state of the ballastless track is required to provide measurement data for the evaluation of the state of the ballastless track, so as to improve the ballastless track. Ballast track maintenance and repair efficiency.

At present, when using a displacement measuring device to measure the displacement occurring inside a concrete structure, it is difficult to replace other devices for measuring the internal displacement of the concrete after the concrete sets, so the measuring device is required to have a long life and not be easily damaged.

Contents of the invention

The first object of the present invention is to provide a device for measuring the internal displacement of concrete, which has good sealing performance, is not easily damaged, and has a long service life.

The second object of the present invention is to provide a system for measuring the internal displacement of concrete. The system can quickly and continuously measure various displacements after the internal changes of the concrete structure, and has high precision, is not easy to be damaged, and has a long service life.

The third object of the present invention is to provide a method for installing the system for measuring internal displacement of concrete, so that the system for measuring internal displacement of concrete can measure two-way displacement, and at the same time, the system for measuring internal displacement of concrete has good airtightness.

The present invention is achieved like this:

A device for measuring the internal displacement of concrete, comprising a shell, shrapnel, probe and casing, the shrapnel is arranged inside the shell, and the opposite ends of the shrapnel are a fixed end and a free end, the fixed end is connected to the shell, and the shrapnel includes There are gaps between the first surface and the second surface opposite to each other, between the first surface and the shell and between the second surface and the shell, the first surface and the second surface are provided with strain gauges, the strain gauges are close to the fixed end, and the shell The position corresponding to the body and the free end is provided with a first through hole with an inner diameter larger than the sleeve, the probe is connected to the free end and one end of the probe protrudes from the housing through the first through hole, and the sleeve is movably sleeved on the probe.

Further, in a preferred embodiment of the present invention, the length of the sleeve is shorter than the length of the probe.

Further, in a preferred embodiment of the present invention, the sleeve is movably embedded in the first through hole, and the outer wall of the sleeve is in contact with the first through hole.

Further, in a preferred embodiment of the present invention, the strain gauge includes a first strain gauge and a second strain gauge, the first strain gauge is on the first surface, the second strain gauge is arranged on the second surface, and the first The strain gauge is parallel to the second strain gauge.

Further, in a preferred embodiment of the present invention, the strain gauge further includes a third strain gauge and a fourth strain gauge, the third strain gauge is arranged on the first surface, the fourth strain gauge is arranged on the second surface, and the fourth strain gauge is arranged on the second surface. The positions of the first strain gauge and the third strain gauge on the first surface are the same as the positions of the second strain gauge and the fourth strain gauge on the second surface.

Further, in a preferred embodiment of the present invention, a second through hole is opened at the end of the housing close to the fixed end, and the second through hole is connected with a conduit.

Further, in a preferred embodiment of the present invention, the shell is provided with a first screw hole, and the elastic piece is provided with a second screw hole, and the housing and the elastic piece are connected through the first screw hole and the second screw hole by screws and nuts; The second screw hole is close to the strain gauge and spaced apart from the strain gauge.

A system for measuring internal displacement of concrete, comprising a plurality of devices for measuring internal displacement of concrete, and multiple devices for measuring internal displacement of concrete are connected through conduits.

Further, in a preferred embodiment of the present invention, the system for measuring internal displacement of concrete further includes a template, and the template abuts against the probe.

An installation method of a system for measuring the internal displacement of concrete, which includes: placing a device for measuring the internal displacement of concrete in a concrete pit, adjusting the probe and the casing to expose the end of the probe away from the shrapnel and part of the casing; Pour concrete on the outer side of the probe to fix the shell, place a formwork on the end of the probe away from the shrapnel, and make the formwork withstand the probe, move the formwork toward the shell, make the shrapnel elastically deform and make the probe have a preload, adjust the sleeve The tube contacts the form and concrete is poured on the side of the form facing away from the shell.

The beneficial effects of the present invention are: the device for measuring the internal displacement of the concrete obtained by the above-mentioned design of the present invention, since the first surface and the second surface of the shrapnel are provided with strain gauges, and the probe is connected with the free end of the shrapnel, when the probe follows the When measuring the displacement of the structure, the shrapnel is bent, and the two sides of the shrapnel produce a strain δ of equal magnitude and opposite direction. The displacement value has a linear relationship with δ, and the displacement value can be measured through the strain gauge and the data processing detection device. Due to the use of strain gauges as the main tool for measurement, the device has fast testing speed and accurate measurement results. Secondly, the position corresponding to the housing and the free end is provided with a first through hole with an inner diameter larger than the sleeve, the probe is connected to the free end and one end of the probe protrudes from the housing through the first through hole, and the sleeve is movably sleeved on the probe. Needle, so the casing can not only ensure the sealing of the shell, prevent concrete from entering the device for measuring the internal displacement of concrete, but also further protect the probe, making the whole device not easy to damage and prolonging the service life.

The system for measuring internal displacement of concrete provided by the present invention includes the above-mentioned multiple devices for measuring internal displacement of concrete. The conduits of multiple devices for measuring the internal displacement of concrete are connected and communicated. The internal displacement of multiple concrete structures at different distances on the same horizontal line is detected simultaneously by multiple devices for measuring the internal displacement of concrete, and the average value is taken to obtain more accurate results.

The installation method of the system for measuring the internal displacement of concrete provided by the present invention uses the formwork to withstand the probe, so that the probe has a certain amount of preload, the shrapnel is deformed, and at the same time, the casing is contacted with the formwork. When the concrete on both sides is far away, the probe with a certain amount of preload can move outward; when the concrete on both sides is close, the probe can move inward, so the two-way displacement can be measured. At the same time, the system for measuring the internal displacement of concrete installed by using the method has good airtightness and accurate measurement results.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Fig. 1 is the schematic diagram of the device for measuring the internal displacement of concrete provided by the embodiment of the present invention;

Fig. 2 is a schematic diagram of a first perspective view of the device for measuring internal displacement of concrete provided by an embodiment of the present invention after removing the shell;

Fig. 3 is a schematic diagram of a second angle of view of the device for measuring the internal displacement of concrete provided by the embodiment of the present invention after removing the shell;

Fig. 4 is a schematic diagram of the device for measuring the internal displacement of concrete provided by the embodiment of the present invention in use;

Fig. 5 is a schematic diagram of a system for measuring internal displacement of concrete provided by an embodiment of the present invention.

Icons: 100-device for measuring internal displacement of concrete; 110-shell; 111-first end; 112-second end; 120-shrapnel; 120a-fixed end; 120b-free end; 121-first surface; 122-second surface; 130-strain gauge; 131-first strain gauge; 132-second strain gauge; 133-third strain gauge; 134-fourth strain gauge; 150-wire; 160-sleeve; 170- Probe; 181-pipe; 191-screw; 192-nut; 200-system for measuring internal displacement of concrete; 300-formwork.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is some embodiments of the present invention, but not all of them. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "middle", "length", "width", "upper" and "lower" are based on the orientation or positional relationship shown in the drawings , is only for the convenience of describing the present invention and simplifying the description, but does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical A connection can also be an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be an internal communication between two elements or an interaction relationship between two elements. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the present invention, unless otherwise clearly specified and limited, a first feature being "on" or "under" a second feature may include direct contact between the first and second features, and may also include the first and second features Not in direct contact but through another characteristic contact between them. Moreover, "above", "above" and "above" the first feature on the second feature include that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. "Below", "beneath" and "under" the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

This embodiment provides a device 100 for measuring internal displacement of concrete. As shown in FIG. 1 , the device 100 for measuring internal displacement of concrete has a housing 110 . It should be noted that the shape, size and material of the casing 110 are not limited. In this embodiment, in order to adapt to the internal structure of the concrete, the casing 110 is a cuboid made of stainless steel. The housing 110 includes a first end 111 and a second end 112 opposite to each other.

Specifically, for the sake of detailed description, FIGS. 2-5 show the structure of the device 100 for measuring internal displacement of concrete without the housing 110 , that is, the internal structure of the device 100 for measuring internal displacement of concrete. As shown in FIG. 2 , the device 100 for measuring internal displacement of concrete further includes a shrapnel 120 . The opposite ends of the spring are a fixed end 120a and a free end 120b. The elastic piece 120 is disposed inside the housing 110 , and the fixed end 120 a of the elastic piece 120 is connected to the first end 111 ; meanwhile, the free end 120 b of the elastic piece 120 is not in contact with the second end 112 . The elastic piece 120 includes a first surface 121 and a second surface 122 opposite to each other. There are gaps between the first surface 121 and the casing 110 and between the second surface 122 and the casing 110 . It can be understood that the two sides of the elastic piece 120 are not in contact with the housing 110 .

The first surface 121 and the second surface 122 are provided with strain gauges 130 . The strain gauge 130 is located close to the fixed end 120a and spaced apart from the fixed end 120a. In this embodiment, in order to increase measurement accuracy and facilitate processing, the strain gauge 130 is pasted on the elastic piece 120 . Secondly, it should be noted that the thickness of the elastic piece 120 is as small as possible, so that the accuracy of measuring the displacement will be relatively improved. In this embodiment, preferably, the thickness of the elastic piece 120 is 1mm.

Compared with the traditional method of measuring displacement, using the strain gauge 130 as the main tool for measurement has the following advantages: 1. High sensitivity, fast measurement speed and accurate measurement results. 2. It is easy to realize fully automatic data collection, multi-point synchronous measurement, long-distance measurement and remote control detection during the test process, especially suitable for the detection of the internal structure of concrete. 3. The strain gauge 130 has a small gauge length and is easy to paste. 4. Light weight. 5. It has a wide range of applications and can be successfully measured under special conditions such as high temperature, low temperature, high pressure, and high speed. 6. It is easy to operate and the test method is easy to master.

The device 100 for measuring the internal displacement of concrete also includes a probe 170 and a sleeve 160. The housing 110 is provided with a first through hole (not marked) with an inner diameter larger than the sleeve 160 at a position corresponding to the free end 120b. The probe 170 and The free end 120 b is connected and one end of the probe 170 protrudes from the housing 110 through the first through hole, and the sleeve 160 is movably sleeved on the probe 170 . It should be noted that the inner diameter of the first through hole is not limited. Preferably, the sleeve 160 is movably embedded in the first through hole, and the outer wall of the sleeve 160 is in contact with the first through hole. In other words, the diameter of the first through hole The inner diameter is adapted to the sleeve 160, and the sleeve 160 is in contact with the first through hole and can be displaced relative thereto.

Specifically, in this embodiment, one end of the sleeve 160 is close to the second surface 122 . The probe 170 passes through the sleeve 160 and is connected to the second face 122 . In other words, the sleeve 160 can slide relative to the housing without affecting the movement of the probe 170 . A casing 160 is provided on the casing to ensure the sealing of the casing during pouring and concreting. It should be noted that, in this embodiment, preferably, the material of the sleeve 160 is light and hard material, and the sleeve 160 does not affect the normal displacement of the probe 170, so that the measurement result is more accurate. Second, the presence of the sleeve 160 further protects the probe 170 from damage.

The working principle of the device 100 for measuring the internal displacement of concrete is: since the first surface 121 and the second surface 122 are provided with strain gauges 130, when the probe 170 is displaced along with the measurement structure, the elastic piece 120 is bent, and the two sides of the elastic piece 120 are formed. Strain δ of equal magnitude and opposite direction. Secondly, the displacement value has a linear relationship with δ, and the displacement value can be measured through the strain gauge 130 and the data processing and detection device.

Further, in this embodiment, the length of the sleeve 160 is shorter than the length of the probe 170 . It should be noted that, in other embodiments, the relative lengths of the cannula 160 and the probe 170 are not limited.

2 and 3, in this embodiment, the strain gauge 130 includes a first strain gauge 131 and a second strain gauge 132, the first strain gauge 131 is arranged on the first surface 121, and the second strain gauge 132 is arranged on on the second side 122 . Wherein, the first strain gauge 131 is parallel to the second strain gauge 132 , and the third strain gauge 133 is parallel to the fourth strain gauge 134 . Further, in order to increase measurement accuracy, a third strain gauge 133 and a fourth strain gauge 134 are further included, the third strain gauge 133 is disposed on the first surface 121 , and the fourth strain gauge 134 is disposed on the second surface 122 . The first strain gauge 131 , the second strain gauge 132 , the third strain gauge 133 and the fourth strain gauge 134 are connected by wires 150 , using the "full bridge method". Again, preferably but not limited thereto, the positions of the first strain gauge 131 and the third strain gauge 133 on the first surface 121 are the same as the positions of the second strain gauge 132 and the fourth strain gauge 134 on the second surface 122 . It should be noted that the strain gage 130 can also use strain rosettes, and the bonding angle can be 0°, 45° or 90°.

Referring to FIGS. 1 and 2 again, it is convenient to organize the wires 150 without affecting the measurement accuracy. The end of the housing 110 near the fixed end 120a is provided with a second through hole (not marked in the figure), and the second through hole is connected with a conduit 181 . Preferably, the conduit 181 is in this embodiment, the conduit 181 is "L" shaped, and a PVC pipe is used. The plane where the nozzle of the conduit 181 is located is perpendicular to the plane where the first surface 121 is located. Further, to facilitate adjustment of the nozzle orientation of the conduit 181 , the conduit 181 can rotate relative to the casing 110 . That is, the position where the mouth of the conduit 181 faces is not limited. The nozzle orientation of the catheter 181 can be adjusted according to the actual measured direction.

As shown in Figure 1 and Figure 2, the housing is provided with a first screw hole (not shown), and the shrapnel 120 is provided with a second screw hole (not shown), the position of the first screw hole is the same as that of the second screw hole correspond. That is, the housing 110 and the elastic piece 120 can be connected to each other through the first screw hole and the second screw hole by using the screw 191 and the nut 192 . The housing 110 and the elastic piece 120 are connected by screws 191 and nuts 192 to further increase the stability between the two.

In order not to hinder the movement of the free end 120 b of the elastic piece 120 , the first screw hole and the second screw hole are close to the strain gauge 130 , and are spaced apart from the strain gauge 130 , that is, not in contact with the strain gauge 130 . It should be noted that the number of the first screw holes and the second screw holes is not limited. In this embodiment, in order to increase the stability between the housing 110 and the elastic piece 120 , the number of the first screw holes and the second screw holes are both two. Secondly, screws 191 and nuts 192 can also be used to compress the wires 150 connected to the first strain gauge 131, the second strain gauge 132, the third strain gauge 133, and the fourth strain gauge 134, so as to prevent the wires 150 from falling off and affecting the measurement of concrete. Stability of device 100 with internal displacement.

Please refer to FIG. 5 , the embodiment of the present invention also provides a system 200 for measuring internal displacement of concrete. The system 200 for measuring internal displacement of concrete includes the above-mentioned multiple devices 100 for measuring internal displacement of concrete. The conduits 181 of a plurality of devices 100 for measuring internal displacement of concrete are connected and communicated. A plurality of devices 100 for measuring the internal displacement of concrete simultaneously detect the internal displacements of multiple concrete structures at different distances on the same horizontal line, and take the average value to obtain more accurate results.

This embodiment also provides an installation method of the system 200 for measuring internal displacement of concrete, as shown in FIG. 1 , FIG. 2 and FIG. 4 .

In the first step, a groove is opened in the concrete to place the device 100 for measuring the internal displacement of the concrete. After the device 100 for measuring the internal displacement of the concrete is placed, the conduit 181 is extended to the outside of the concrete to lead out the wire 150 inside the casing 110 .

The second step is to protect the probe 170, expose the outer end of the probe 170 away from the shrapnel 120 and part of the casing 160, and pour concrete on the outside of the casing 110 to fix the device 100 for measuring the internal displacement of the concrete.

The third step is to place the template 300 at the end of the probe 170 away from the elastic piece 120, and fix the template 300 with the outer end of the probe 170. The template 300 can be made of foam board, rubber pad, wood board, etc. It should be noted that, in order to measure the two-way displacement, it is first necessary to make the template 300 withstand the probe 170, that is, move the template 300 toward the housing 110, so that the probe 170 has a certain amount of preload, and elastically deform the shrapnel 120, and at the same time The casing 160 is adjusted so that it contacts the template 300 , and there is no gap between the probe 170 and the outside world, which ensures the sealing of the housing 110 .

It should be noted that the principle of measuring the two-way displacement is: since the probe 170 has a certain amount of preload, that is, the shrapnel 120 is deformed (the position shown in Figure 4), when the concrete on both sides is far away, there is a certain amount of preload. The pressure probe 170 can move outward; when the concrete on both sides approaches, the probe 170 can move inward, so the two-way displacement can be measured.

In the fourth step, concrete is poured on the side of the formwork 300 away from the shell 110 to complete the installation.

The fifth step is to debug each equipment, and then the internal displacement of concrete can be continuously collected. It should be noted that in the debugging process, the relationship between the strain gauge 130 and the shrapnel 120 needs to be calibrated at first so that the two can form a definite linear relationship.

To sum up, the device 100 for measuring the internal displacement of concrete provided by the present invention can continuously collect the internal displacement of concrete, and at the same time, the device 100 for measuring the internal displacement of concrete has fast test speed, accurate measurement results, long service life and is not easily damaged. Secondly, since the sleeve 160 is movably embedded in the casing, the probe 170 passes through the sleeve 160 . Therefore, the casing 160 can ensure the airtightness of the casing, preventing concrete from entering the device 100 for measuring the internal displacement of the concrete, and the casing 160 can prevent the probe 170 from being overstressed at the beginning, bending or being damaged in other ways, further making the The probe 170 can work normally, so that the working time of the whole device 100 for measuring the internal displacement of concrete becomes longer.

The system 200 for measuring the internal displacement of concrete can simultaneously detect the internal displacements of multiple concrete structures at different distances on the same horizontal line, and take the average value to obtain more accurate results.

The installation method of the system 200 for measuring the internal displacement of concrete is to make the template 300 withstand the probe 170 so that the probe 170 has a certain amount of preload, the shrapnel 120 is deformed, and the casing 160 contacts the template 300 at the same time. The system 200 for measuring internal displacement of concrete can measure two-way displacement, and the system 200 for measuring internal displacement of concrete has good airtightness.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A device for measuring the internal displacement of concrete, characterized in that it comprises a housing, a shrapnel, a probe and a sleeve, the shrapnel is arranged inside the housing, and the opposite ends of the shrapnel are fixed ends and free end, the fixed end is connected to the housing, the elastic piece includes a first surface and a second surface opposite to each other, between the first surface and the housing and between the second surface and the housing There are gaps between the bodies, the first surface and the second surface are provided with strain gauges, the strain gauges are close to the fixed end, and the position corresponding to the free end of the housing is provided with a The first through hole of the sleeve, the probe is connected to the free end and one end of the probe protrudes from the housing through the first through hole, and the sleeve is movably sleeved on the probe. 2. A device for measuring the internal displacement of concrete according to claim 1, wherein the length of the sleeve is shorter than the length of the probe. 3. The device for measuring the internal displacement of concrete according to claim 1, wherein the casing is movably embedded in the first through hole, and the outer wall of the casing is in contact with the first through hole. through-hole contacts. 4. A device for measuring the internal displacement of concrete according to claim 1, wherein the strain gauge comprises a first strain gauge and a second strain gauge, and the first strain gauge is on the first surface , the second strain gauge is disposed on the second surface, and the first strain gauge is parallel to the second strain gauge. 5. A device for measuring the internal displacement of concrete according to claim 4, wherein the strain gauge further comprises a third strain gauge and a fourth strain gauge, and the third strain gauge is arranged on the first strain gauge. On the surface, the fourth strain gauge is arranged on the second surface, and the positions of the first strain gauge and the third strain gauge on the first surface are the same as those of the second strain gauge and the The positions of the fourth strain gauges on the second surface are the same. 6 . The device for measuring the internal displacement of concrete according to claim 1 , wherein a second through hole is opened at the end of the housing close to the fixed end, and a conduit is connected to the second through hole. 7 . 7. A device for measuring the internal displacement of concrete according to claim 1, wherein the housing is provided with a first screw hole, and the shrapnel is provided with a second screw hole, and the housing and the The elastic piece is connected to the second screw hole through the first screw hole by using a screw and a nut; the second screw hole is close to the strain gauge and is spaced apart from the strain gauge. 8. A system for measuring internal displacement of concrete, characterized in that it comprises a plurality of devices for measuring internal displacement of concrete according to claim 6, and a plurality of devices for measuring internal displacement of concrete are connected through the conduit. 9. The system for measuring internal displacement of concrete according to claim 8, characterized in that, the system for measuring internal displacement of concrete further comprises a template, and the template abuts against the probe. 10. A method for installing the system for measuring internal displacement of concrete as claimed in claim 9, characterized in that it comprises: placing the device for measuring internal displacement of concrete in a concrete pit, adjusting the probe and the The casing exposes one end of the probe away from the shrapnel and part of the casing, pouring concrete on the outside of the casing to fix the casing, and at the end of the probe far away from the shrapnel placing the template, and making the template bear against the probe, moving the template toward the housing, elastically deforming the shrapnel and preloading the probe, and adjusting the casing Contacting the formwork, concrete is poured on the side of the formwork remote from the shell.