CN110146049B - Method for evaluating surface roughness of prefabricated bottom plate of concrete laminated slab - Google Patents
Method for evaluating surface roughness of prefabricated bottom plate of concrete laminated slab Download PDFInfo
- Publication number
- CN110146049B CN110146049B CN201910538700.9A CN201910538700A CN110146049B CN 110146049 B CN110146049 B CN 110146049B CN 201910538700 A CN201910538700 A CN 201910538700A CN 110146049 B CN110146049 B CN 110146049B
- Authority
- CN
- China
- Prior art keywords
- area
- rough surface
- sand
- roughness
- bottom plate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/30—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring roughness or irregularity of surfaces
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Road Repair (AREA)
- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
Abstract
The invention provides a method for evaluating the surface roughness of a prefabricated bottom plate of a concrete laminated slab, which belongs to the technical field of the performance evaluation of an assembled buildingCalculated value of muiThe calculation of (2): spreading test sand with volume V on the rough surface of the prefabricated bottom plate, completely filling the test sand into the gaps of the rough surface, measuring and calculating the spreading area S, mui= V/S; (2) calculating the rough surface concave-convex depth mu of the member: μ = k × μcWherein k represents an estimated coefficient, μcExpressed as component roughness equivalent, K = shi/viWherein s represents the upper surface area of the rough surface model, and hiRepresenting the height, v, of the rough surface modeliA volume representing a rough surface model; (3) when the depth mu of the rough surface of the member is not less than 4.0mm, the member is judged to be qualified.
Description
Technical Field
The invention relates to the technical field of performance evaluation of fabricated buildings, in particular to a method for evaluating the surface roughness of a prefabricated bottom plate of a concrete laminated slab.
Background
Rough surfaces must be manufactured on the joint surfaces of the prefabricated bottom plates of the composite slabs in the prefabricated concrete structure to enhance the adhesive force of new and old concrete and ensure common stress. The 'JGJ 1-2014 industry standard' stipulates that a prefabricated part joint surface connected by post-cast concrete is adopted, and rough surface treatment is carried out according to design requirements during manufacturing. If no specific design is required, the rough surface can be made by chemical treatment, roughening or chiseling. The area of the rough surface is not less than 80% of the combined surface, and the concave-convex depth of the rough surface of the prefabricated slab is not less than 4 mm. However, since the existing specifications do not limit that a certain method is required for rough surface treatment, when rough surface treatment is carried out on prefabricated parts in actual engineering, a roughening method is often adopted, and the roughening method is divided into a mechanical roughening method and a non-mechanical roughening method, so that rough surfaces formed by different methods are greatly different. In addition, the specification gives the requirement of the depth of the rough surface concave-convex, but does not give a measuring method, and the measuring method is given by some local standards, but is difficult to grasp and operate in the actual engineering. In order to solve the problems of quantitative measurement and operability of the surface roughness of the prefabricated bottom plate of the concrete composite slab, a method for simply and effectively measuring and evaluating the surface roughness of the prefabricated bottom plate of the concrete composite slab is urgently needed to solve the practical problems in engineering.
Disclosure of Invention
In view of the above, the invention provides an evaluation method for surface roughness of a prefabricated bottom plate of a concrete composite slab, and aims to solve the technical problems that in the prior art, the evaluation method for the surface roughness of the prefabricated bottom plate of the concrete composite slab is difficult to operate, low in accuracy and low in uniformity.
The invention provides a method for evaluating the surface roughness of a prefabricated bottom plate of a concrete laminated slab, which comprises the following steps:
(1) conversion value mu of measured area roughnessiThe calculation of (2): spreading test sand with volume V on the rough surface of the prefabricated bottom plate, completely filling the test sand into the gap of the rough surface during spreading, measuring and calculating the spreading area S,
μi= V/S equation (1)
(2) Calculating the rough surface concave-convex depth mu of the member:
μ=k×μcformula (2)
Wherein k represents an estimated coefficient,. mu.cRepresenting a component roughness conversion value;
K=shi/vi formula (3)
Wherein s represents the upper surface area of the rough surface model, and hiRepresenting the height, v, of the rough surface modeliA volume representing a rough surface model;
(3) when the depth mu of the rough surface of the member is not less than 4.0mm, the member is judged to be qualified.
Further, in the step (2), the component roughness is converted into a value mucConversion of roughness to muiOfAnd (4) average value.
Further, in the step (1), the calculation of the paving area S specifically includes the following steps:
(1-1) preparing a plurality of sand measuring cylinders with the volume of V, and filling the sand for the test into the sand measuring cylinders;
(1-2) pouring test sand into the middle of the test area, and slowly pushing the test sand from the middle to four sides by using a push flat brush to form a square;
(1-3) respectively measuring the length and the width for five times at the quartering parts of the length and the width, taking the average value of the length and the width to obtain the average length a and the average width b, if the a/b is more than or equal to 0.8 and less than or equal to 1.2, calculating the paving area S, and if the a/b is more than 1.2 or the a/b is less than 0.8, repeating the step (1-2).
Further, in the step (1), the method further comprises the following steps of selecting a measurement area:
when the area of the bonding surface of the prefabricated bottom plate is 2m2When the measurement areas are below the preset area, at least three measurement areas are arranged, and each measurement area is increased by 2m2A measuring area is added;
the prefabricated bottom plate of truss muscle is set up, and the survey district is arranged between the truss muscle, simultaneously, avoids built-in fitting, reserves the hole.
Further, the inter-measurement-area distance is greater than or equal to 0.5 m.
Furthermore, the push flat brush comprises a brush handle and a rubber skin, wherein the rubber skin is horizontally and fixedly connected to the end part of the brush handle, and the rubber skin at least comprises a horizontal end face for pushing flat the test sand.
Furthermore, the sand for the test is dry sand with the particle size of 0.075-0.60 mm.
Compared with the prior art, the method for evaluating the surface roughness of the precast bottom plate of the concrete laminated slab breaks through the limitation of solving the concave-convex depth of the rough surface by the traditional extreme value method, adopts the sanding method to solve the conversion value of the rough surface, establishes mathematical geometric models through different production processes of the rough surface to obtain different estimation coefficients, further establishes the relation between the conversion value of the roughness of the sanding method and the concave-convex depth of the rough surface, obtains the concave-convex depth of the rough surface by directly selecting the estimation coefficients, and is simple to operate and high in accuracy.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 is a schematic structural diagram of a sand measuring cylinder provided in an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a push-flat brush according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a measurement area measurement provided in an embodiment of the present invention;
FIG. 4 is a table of estimated coefficients for matte surfaces provided by an embodiment of the present invention;
FIG. 5 is a schematic structural view of a paving tool provided in accordance with an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a guide frame according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a paving frame according to an embodiment of the present disclosure;
FIG. 8 is an expanded schematic view of a paving stand in operation according to an embodiment of the present invention;
fig. 9 is a bottom view of the telescopic rod according to the embodiment of the present invention;
FIG. 10 is a simplified schematic illustration of a process for embodying a paving tool, provided in accordance with an embodiment of the present invention;
reference numerals: 1. a brush handle; 2. rubber skin.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Referring to fig. 1 to 4, it can be seen that the method for evaluating the surface roughness of a precast floor slab of a concrete composite slab according to an embodiment of the present invention includes:
(1) conversion value mu of measured area roughnessiThe calculation of (2): spreading test sand with volume V on the rough surface of the prefabricated bottom plate, completely filling the test sand into the gap of the rough surface during spreading, measuring and calculating the spreading area S,
μi= V/S equation (1)
(2) Calculating the rough surface concave-convex depth mu of the member:
μ=k×μcformula (2)
Wherein k represents an estimated coefficient,. mu.cRepresenting a component roughness conversion value;
K=shi/vi formula (3)
Wherein s represents the upper surface area of the rough surface model, and hiRepresenting the height, v, of the rough surface modeliA volume representing a rough surface model;
(3) when the depth mu of the rough surface of the member is not less than 4.0mm, the member is judged to be qualified.
Compared with the prior art, the method for evaluating the surface roughness of the precast bottom plate of the concrete laminated slab breaks through the limitation of solving the concave-convex depth of the rough surface by the traditional extreme value method, adopts the sanding method to solve the converted value of the rough surface, establishes mathematical geometric models through different production processes of the rough surface to obtain different estimation coefficients, further establishes the relation between the converted value of the roughness of the sanding method and the concave-convex depth of the rough surface, obtains the concave-convex depth of the rough surface by directly selecting the estimation coefficients, and has the advantages of simple operation, high accuracy and strong practicability.
In the step (1), the method specifically comprises:
preparation of measurement tool:
a sand measuring cylinder: the volume is 300mL, the material can be made of organic glass, and the specific size can be 100mm in inner diameter and 38.2mm in height;
a steel tape: 5m, the minimum division value is 1 mm;
a steel ruler: the minimum division value is 1 mm;
a flat pushing brush: the brush head is 10mm high, and the front end is a rubber skin with the height of 8 mm;
test sand: dried sand with the particle size of 0.075-0.60 mm.
B, calculating a paving area S:
(1-1) preparing a plurality of sand measuring cylinders with the volume of V (300 ml in the embodiment), and filling the sand for the test into the sand measuring cylinders, wherein the specific process is that sand is slowly filled into the sand measuring cylinders along the sides of the sand measuring cylinders to ensure that the sand planes in the cylinders slowly and uniformly rise, the final filling amount is more than the upper openings of the sand measuring cylinders, and after the sand measuring cylinders are filled, the surfaces are scraped off along the central lines of the cylinder openings to two sides by using a steel ruler to remove redundant sand. The sand is naturally accumulated in the sand measuring cylinder, and the sand cannot be vibrated and inserted;
(1-2) selection of measurement area, the area of the joint surface of the member is 2m2When the measurement areas are below the preset area, at least 3 measurement areas are arranged, and each measurement area is increased by 2m2Adding 1 measurement area, selecting a representative area as a component measurement area, uniformly distributing the measurement areas, setting the components of the truss ribs, arranging the measurement areas among the truss ribs, and avoiding the positions which are not beneficial to sand paving detection, such as embedded parts, reserved holes and the like;
(1-3) pouring test sand into the middle of the test area, and slowly pushing the test sand from the middle to four sides by using a push-flat brush to form a square, wherein the paving shape is made to be square as much as possible in the paving process;
(1-4) respectively measuring the length and the width for five times at the quartering parts of the length and the width, taking the average value of the length and the width to obtain the average length a and the average width b, if the a/b is more than or equal to 0.8 and less than or equal to 1.2, calculating the paving area S, and if the a/b is more than 1.2 or the a/b is less than 0.8, repeating the step (1-3).
(1-5) the paving area S = a × b, wherein a is the average length of the paving quadrangle and b is the average width of the paving quadrangle.
The above steps(2) In the component roughness conversion value mucConversion of roughness to muiThe average value of the coefficient is that when the rough surface of the prefabricated part in the actual engineering is processed, the roughening method is often adopted, the roughening method is divided into a mechanical roughening method and a non-mechanical roughening method, the estimated coefficient can be calculated by adopting a formula 3, the specific corresponding relation is shown in figure 4, in the calculation, the numerical value can be directly searched through the figure 4, for the rough surface of the groove formed by mechanical roughening, the width of the continuous three grooves is measured by a straight steel ruler before sanding, and the net distance between two adjacent grooves is accurate to 1mm, the average value of three measurement results is taken, the ratio of the width to the net distance is calculated and is accurate to 0.1, when the rough surface formed by the two types of processes exists at the same time, if the ratio of the width of the grooves to the clear distance between the grooves in the rough surface formed by the mechanical roughening method is not less than 0.5, preferably, the estimation coefficient of the non-mechanical napping method in the attached figure 4 is selected as the estimation coefficient of the concave-convex depth of the rough surface of the whole measuring area; if the ratio of the width of the grooves to the clear distance between the grooves in the rough surface formed by the mechanical roughening method is less than 0.5, the estimated coefficient of the mechanical roughening method shown in fig. 4 is preferably selected as the estimated coefficient of the roughness depth of the rough surface in the whole measuring region.
For safety reasons, the minimum value of the estimated coefficient in the rough surface estimated coefficient table of the mechanical roughening method or the non-mechanical roughening method in fig. 4 is taken.
C, calculating the rough surface concave-convex depth mu of the component:
and (3) judging that the component is qualified if the concave-convex depth mu of the rough surface of the component is more than or equal to 4.0mm by adopting the formula (2).
Continuing to refer to fig. 2, the push-flat brush comprises a brush handle 1 and a rubber sheet 2, wherein the rubber sheet 2 is horizontally and fixedly connected with the end of the brush handle 1, and the rubber sheet 2 at least comprises a horizontal end surface for pushing flat the test sand. Preferably, the vertical section of the rubber sheet 2 can be made into a triangle, so that the rubber sheet can be pushed flat conveniently.
As a preferred embodiment, in order to smoothly pave the test sand into a square in the step (1-3), the test sand can be paved by the paving tool 3, specifically, the paving tool 3 comprises a guide frame 31 and a paving frame 32, the guide frame comprises a first guide surface 311 arranged vertically, a second guide surface 312 arranged transversely, and a third guide surface 313 arranged between the first guide surface 311 and the second guide surface 312, the included angle between the first guide surface 311 and the second guide surface 312 is 90 degrees, the included angle between the third guide surface 313 and the first guide surface 311 and the second guide surface 312 is 45 degrees, the paving frame 32 comprises a first body 321, a second body 322 and a third body 323, wherein the end of the second body 322 is rotatably connected with the end of the first body 321 through a 90-degree hinge 324, and the second body 322 is of a telescopic structure, specifically, the paving tool comprises a first telescopic body 3221, a second telescopic body 3221, a third telescopic body 323, Second flexible body 3222, spring 3223, first flexible body 3221 is "the concave type structure of falling", second flexible body 3222 card is established on first flexible body 3221, and both bottoms parallel and level, second flexible body 3222 produces the self-adaptation shrink through spring 3223, in the in-service use process, divide test sand in the sand measuring cylinder equally to two in the frame 32 that paves, pave along first guide face 311 or the slip of second guide face 312 through driving first body 321, in the process of paving, second body 322 flattens gradually, and laminate with third guide face 313 always through extending structure, finally form approximately square or square structure. As a preferred embodiment, in order to make the first body 321 fit with the first guide surface 311 or the second guide surface 312, the first body 321 may be connected to the first guide surface through a structure of a clamping groove and a clamping rail, and in order to facilitate pushing, a handle may be disposed outside the third body 323, and the third body 323 may be paved manually, automatically by using an air cylinder, or pulled by using a motor or a motor in cooperation with a rope. When the test sand is spread, the spreading can be suspended when the local unevenness is found, and the test sand in the second body 322 is uniformly spread by the leveling brush and then the spreading is continued (when the test sand is uneven left and right).
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (6)
1. A method for evaluating the surface roughness of a prefabricated bottom plate of a concrete composite slab is characterized by comprising the following steps of:
（1) Conversion value mu of measured area roughnessiThe calculation of (2): spreading test sand with volume V on the rough surface of the prefabricated bottom plate, completely filling the test sand into the gap of the rough surface during spreading, measuring and calculating the spreading area S,
μi= V/S equation (1)
(2) Calculating the rough surface concave-convex depth mu of the member:
μ=k×μcformula (2)
Wherein k represents an estimated coefficient,. mu.cExpressing the component roughness equivalent, the component roughness equivalent mucConversion of roughness to muiAverage value of (d);
k=shi/vi formula (3)
Wherein s represents the upper surface area of the rough surface model, and hiRepresenting the height, v, of the rough surface modeliA volume representing a rough surface model;
(3) when the depth mu of the rough surface of the member is not less than 4.0mm, the member is judged to be qualified.
2. The method for evaluating the surface roughness of the precast floor for concrete composite slab according to claim 1, wherein the calculating of the paved area S in the step (1) specifically comprises the steps of:
(1-1) preparing a plurality of sand measuring cylinders with the volume of V, and filling the sand for the test into the sand measuring cylinders;
(1-2) pouring test sand into the middle of the test area, and slowly pushing the test sand from the middle to four sides by using a push flat brush to form a square;
(1-3) respectively measuring the length and the width for five times at the quartering parts of the length and the width, taking the average value of the length and the width to obtain the average length a and the average width b, if the a/b is more than or equal to 0.8 and less than or equal to 1.2, calculating the paving area S, and if the a/b is more than 1.2 or the a/b is less than 0.8, repeating the step (1-2).
3. The method for evaluating the surface roughness of a precast floor for a concrete composite slab according to claim 1, wherein the step (1) further comprises selecting the measurement area:
when the area of the bonding surface of the prefabricated bottom plate is 2m2When the measurement areas are below the preset area, at least three measurement areas are arranged, and each measurement area is increased by 2m2A measuring area is added;
the prefabricated bottom plate of truss muscle is set up, and the survey district is arranged between the truss muscle, simultaneously, avoids built-in fitting, reserves the hole.
4. The evaluation method for the surface roughness of a precast floor for concrete composite slab according to claim 3, wherein the inter-measurement-area distance is 0.5 m or more.
5. The method for evaluating the surface roughness of the precast floor slab for concrete composite slab according to claim 2, wherein the leveling brush comprises a brush holder (1) and a rubber skin (2), the rubber skin (2) is horizontally and fixedly connected to the end of the brush holder (1), and the rubber skin (2) comprises at least one horizontal end surface for leveling the test sand.
6. The method for evaluating the surface roughness of the precast floor slab of the concrete composite slab as claimed in claim 1, wherein the test sand is dry sand having a particle size of 0.075 to 0.60 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910538700.9A CN110146049B (en) | 2019-06-20 | 2019-06-20 | Method for evaluating surface roughness of prefabricated bottom plate of concrete laminated slab |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910538700.9A CN110146049B (en) | 2019-06-20 | 2019-06-20 | Method for evaluating surface roughness of prefabricated bottom plate of concrete laminated slab |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN110146049A CN110146049A (en) | 2019-08-20 |
| CN110146049B true CN110146049B (en) | 2020-01-07 |
Family
ID=67596088
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910538700.9A Expired - Fee Related CN110146049B (en) | 2019-06-20 | 2019-06-20 | Method for evaluating surface roughness of prefabricated bottom plate of concrete laminated slab |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN110146049B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112325835B (en) * | 2020-10-22 | 2021-07-02 | 昆山市建设工程质量检测中心 | Method for detecting roughness of point-shaped pit joint surface of precast concrete member |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0878492A (en) * | 1994-08-31 | 1996-03-22 | Nippon Steel Corp | Method for evaluating roughness of semiconductor wafer |
| CN204007582U (en) * | 2014-07-09 | 2014-12-10 | 同济大学 | A kind of concrete joint surface roughness measuring device |
| CN104807390B (en) * | 2015-04-24 | 2018-11-30 | 河海大学 | A kind of concrete surface pattern measurement instrument and its test method |
| CN107063058B (en) * | 2016-12-13 | 2019-04-26 | 上海市建筑科学研究院 | A kind of assessment method of precast concrete combination surface roughness |
| CN109855518B (en) * | 2019-02-15 | 2019-09-03 | 南京市建筑安装工程质量检测中心 | Assembly concrete roughness detecting method |
-
2019
- 2019-06-20 CN CN201910538700.9A patent/CN110146049B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CN110146049A (en) | 2019-08-20 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107621250B (en) | Roughness detection method for concrete prefabricated part joint surface | |
| CN110146049B (en) | Method for evaluating surface roughness of prefabricated bottom plate of concrete laminated slab | |
| Belem et al. | Fractal analysis of shear joint roughness | |
| CN109252662B (en) | One-step forming construction method for vertical shaft bridge frame through cast-in-place concrete floor | |
| CN211235179U (en) | Simultaneous forming die | |
| CN113718582B (en) | Airport cement concrete pavement surface texture treatment method | |
| CN218493149U (en) | Mortar laying device for construction | |
| CN204059987U (en) | Bars In Poured Concrete Slab strip thickness control device | |
| JP2020172785A (en) | Concrete floor surface construction tool and concrete floor surface construction method | |
| CN212602513U (en) | Concrete curing means for bridge beam slab | |
| CN109211774B (en) | Indoor shear test method for pile rock interface research based on approximate normal distribution of wavelengths | |
| CN210684360U (en) | Overhead brick | |
| CN204302074U (en) | The die trial of thin layer Mortar shrinkage test specimen | |
| CN106192699A (en) | A kind of homophase out-phase road surface cutting method and device | |
| CN210032685U (en) | Construction thickness adjusting device of regularization screeding | |
| CN114032731A (en) | Imitation reduction method for special road of automobile test yard | |
| CN206987118U (en) | A kind of house internal partition wall | |
| CN110043008B (en) | Method for smoothing wall surface and preventing cracking | |
| CN203603478U (en) | Special hole reserving mold for measuring pay-off line through internal control method | |
| CN210316614U (en) | Brickwork horizontal mortar joint control instrument | |
| CN210621380U (en) | Road construction device | |
| CN218246032U (en) | Civil engineering cost is budget toolbox for management | |
| CN201296893Y (en) | Connection chock block for road oil coat construction | |
| CN210651188U (en) | Sand rubber setting gauge with easily replaced setting piece | |
| CN214621007U (en) | A device for 3D prints concrete wall surface roughness test |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20200107 Termination date: 20200620 |
|
| CF01 | Termination of patent right due to non-payment of annual fee |