Steel strand center pull-out test loading device and displacement measurement method
A device and method are used to accurately measure the displacement of steel strands in concrete structures, addressing inefficiencies in existing methods by using a servo actuator and displacement sensor, ensuring precise and convenient measurement.
Patent Information
- Application Number
- CN202411145505.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-20
- Publication Date
- 2024-12-31
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
Existing methods for measuring the displacement of steel strands in precast concrete structures are inefficient and inaccurate, failing to address the need for a reliable method to accurately measure the bonding and anchoring performance of small-diameter steel strands in concrete structures.
A device and method are proposed to measure the displacement of steel strands using a device comprising a device comprising a pedestal, a bottom plate, a screw rod, and a displacement measurement apparatus, which are used to measure the displacement of the steel strand using a servo actuator, a servo actuator, and a displacement sensor, which are used to measure the displacement of the steel strand using a displacement sensor.
The device accurately measures the displacement of the steel strand using a displacement sensor, which is simple and convenient to use, and can be easily disassembled and reassembled for repeated use.
Smart Images
Figure CN119223740A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of a steel strand center pull-out test, and in particular to a steel strand center pull-out test loading device and a displacement measurement method. Background Art
[0002] Compared with traditional buildings, prefabricated buildings have the advantages of energy saving and emission reduction, green environmental protection, industrialized production, rapid construction, and shortened construction period. They can improve the shortcomings of low labor productivity, weak technological innovation, and low building quality in my country's current construction industry. However, most existing prefabricated buildings are connected by rebar, which is very inconvenient in the actual construction process and requires a lot of steel bars.
[0003] The use of high-strength flexible ring cables for connection is widely used in some foreign countries, but its promotion in China is still relatively slow. This connection method is to embed high-strength flexible ring cables in precast concrete specimens. During the actual assembly process, the precast concrete specimens are placed in designated overlap positions, and a certain distance between adjacent precast concrete specimens is left. The overlapping cables are connected by inserting reinforcement bars, and post-cast materials are injected at each joint to form a post-cast strip.
[0004] The new structural system based on small-diameter steel strand ring connection consists of precast concrete specimens, ring-shaped steel strands, steel bars, and post-cast materials. The steel strand rings are embedded in the precast wall panels, and the two precast specimens are connected using inserted bars and grouting materials. Compared with other prefabricated connection methods, the steel strand ring connection can achieve no reinforcement and reduce the amount of steel bars in the specimen production stage, which is more energy-saving and environmentally friendly. The steel strand ring can also be directly used as a lifting point for lifting, which is more convenient and quick in the transportation stage. In the assembly stage, efficient assembly can be achieved, further shortening the construction period. Therefore, the bonding and anchoring performance of the small-diameter steel strand ring and concrete is extremely critical.
[0005] The solid performance test methods for bonding and anchoring small diameter steel strands (rings) with concrete specimens include center pull-out test, beam test, local bond-slip test, etc. Among them, the center pull-out test method is more widely used, but there are fewer displacement measurement methods for steel strands (rings), and they are not perfect enough, so it is difficult to solve the technical problem of how to accurately obtain the relative displacement of small diameter steel strands (rings) in concrete. Therefore, the present invention proposes a center pull-out test loading device and displacement measurement method for steel strands (rings). Summary of the invention
[0006] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a central pull-out test loading device and a displacement measurement method for a steel strand (ring) so as to solve the technical problems mentioned in the above background technology.
[0007] The above technical objectives of the present invention are achieved through the following technical solutions:
[0008] The central pull-out test loading device of the steel strand comprises a pedestal, a bottom steel plate is arranged above the pedestal, a plurality of reaction frame high-strength screw rods are slidably penetrated on the top of the bottom steel plate, and a fixing part is arranged below the bottom steel plate;
[0009] An upper steel plate and a lower steel plate are slidably sleeved on the outer circumferences of several high-strength screw rods of the reaction frame in sequence from top to bottom, and the test specimen is placed between the upper steel plate and the lower steel plate, and the upper steel plate and the lower steel plate are fixedly connected to the high-strength screw rod of the reaction frame through high-strength nuts of the reaction frame, and reserved steel strand channels are provided on the top surfaces of the upper steel plate and the lower steel plate, a servo actuator is provided above the upper steel plate, and a loading plate is fixedly connected to the output end of the servo actuator, an anchor placement slot is provided on the top of the loading plate, a center loading circular hole is provided on the bottom wall of the anchor placement slot, an anchor is placed in the anchor placement slot, the anchor fixes the steel strand, and the steel strand passes through the center loading circular hole, and a displacement measurement aid is provided below the loading plate.
[0010] Furthermore, the displacement measurement auxiliary device includes a column and two auxiliary device measurement steel bars fixedly connected to the upper half of the outer peripheral surface of the column, the top of the column is provided with an auxiliary device central channel, the outer peripheral side of the column is provided with an auxiliary device outer channel, the auxiliary device central channel is communicated with the auxiliary device outer channel, the steel strand passes through the auxiliary device central channel, and the steel strand is fixed in the auxiliary device outer channel by a butterfly nut;
[0011] The top of the auxiliary measuring steel bar is provided with round holes on both sides of the auxiliary device, a thin steel wire is passed through the round hole, the bottom end of the thin steel wire and the top of the bottom steel plate are fixedly connected with a wire-drawing displacement meter, and the side wall of the auxiliary measuring steel bar is provided with a plurality of slot holes on both sides of the auxiliary device;
[0012] Two plastic gaskets are fixedly connected to the bottom of the upper steel plate, and a pin-type displacement meter is fixedly connected to the bottom end of the plastic gasket.
[0013] Furthermore, a measuring steel bar reinforcement rib is fixedly connected between the bottom of the auxiliary device measuring steel bar and the lower half of the outer circumference of the column, and two auxiliary device balancing steel bars are fixedly connected to the upper half of the outer circumference of the auxiliary device measuring steel bar.
[0014] Furthermore, two weights are suspended on the steel strand at the bottom of the test specimen, a weight support auxiliary is fixedly connected between the two weights, the steel strand passes through the weight support auxiliary, and the bottom end of the steel strand is connected to the corresponding pull-wire displacement meter.
[0015] Furthermore, the fixing part includes a plurality of steel pads fixedly connected to the bottom of the bottom steel plate, the bottom surface of the steel pads fits with the top surface of the pedestal, the top of the upper steel plate and the top of the lower steel plate are both provided with circular holes around the steel plate, the top of the bottom steel plate is provided with circular holes around the bottom steel plate, the high-strength screw of the reaction frame passes through the circular holes around the bottom steel plate and the circular holes around the steel plate, and the high-strength screw of the reaction frame is fixedly connected to the bottom steel plate through the high-strength nut of the reaction frame;
[0016] The top of the bottom steel plate is provided with a plurality of circular holes on both sides of the center, and the top of the pedestal is fixedly connected with a plurality of ground anchor bolts, the ground anchor bolts pass through the circular holes on both sides of the center, and the ground anchor bolts are fixedly connected to the bottom steel plate through ground anchor nuts;
[0017] A displacement meter positioning circular hole is opened at the center of the top of the bottom steel plate, and the corresponding wire-type displacement meter is fixedly connected to the displacement meter positioning circular hole.
[0018] Furthermore, it also includes two wire-drawing displacement meter fixing platforms, and the corresponding two wire-drawing displacement meters are respectively placed on the top of the corresponding wire-drawing displacement meter fixing platforms.
[0019] Furthermore, the anchor comprises an anchor sleeve and a three-piece clip disposed in the anchor sleeve, and a steel strand channel is formed in the center of the three-piece clip.
[0020] The displacement measurement method of the center pull test of the steel strand includes the above-mentioned center pull test loading device of the steel strand, and comprises the following steps:
[0021] S1. Place the steel pad on the pedestal, pass the anchor bolts through the circular holes on both sides of the center, and fix them with anchor nuts;
[0022] S2. Pass four high-strength screws of the reaction frame through the circular holes around the bottom steel plate and fix them with high-strength nuts of the reaction frame. Then, position and place the lower steel plate on the high-strength screws of the reaction frame as required, and then place the upper steel plate. A certain space is reserved between the upper and lower steel plates according to the size of the required loading test specimen, and they are fixed with high-strength nuts of the reaction frame.
[0023] S3, connecting the corresponding two wire-type displacement meters to the displacement measurement auxiliary device to measure the steel strands at the loading end;
[0024] S4, the steel strand at the loading end passes through the central hole of the auxiliary device and is fixed by a butterfly nut;
[0025] S5, two weights are hung on the lower steel strand, and the bottom end of the steel strand is connected to the corresponding pull-wire displacement meter;
[0026] S6. Use the anchor to fix the steel strand at the loading end in the anchor placement slot through the anchor sleeve and the three-piece clip;
[0027] S7. The hydraulic servo actuator works to load and measure and calculate the displacement value of the steel strand.
[0028] Furthermore, the calculation method of step S7 is:
[0029] The steel strand is divided into AB segment, BC segment and CD segment from top to bottom, where AB segment is the loading end, BC segment is the bonding anchoring segment, and CD segment is the free end;
[0030] The displacement of the strand needs to measure the relative displacement of point B and point C respectively. The displacement of point B can be obtained by subtracting the elongation of segment AB and the displacement of the upper steel plate from the displacement of point A. The free end segment CD is not subject to external force, so the displacement of point C is replaced by the actual measured displacement of point D. The calculation formula is as follows:
[0031] Deformation S of segment AB AB for:
[0032] S AB =FL AB / (EA)
[0033] Where, F is the tensile load, L AB is the length of segment AB, E is the elastic modulus of the steel strand, and A is the nominal cross-sectional area of the steel strand;
[0034] A thimble displacement meter is arranged on the east and west sides and the rear side of the upper steel plate. The displacement value S 上 for:
[0035] S 上 =(S e +S w +S s ) / 3
[0036] Among them, S e is the real-time displacement of the east side thimble displacement meter, S w is the real-time displacement of the west side thimble displacement meter, S s It is the real-time displacement of the north side thimble displacement meter;
[0037] A wire-type displacement meter is arranged on the east and west sides of the displacement measurement auxiliary device. A for:
[0038] S A =(S 东 +S 西 ) / 2
[0039] Among them, S 东 is the real-time displacement of the east side wire displacement meter, S 西 It is the real-time displacement of the west side wire displacement meter;
[0040] The actual slip S at the loading end B for:
[0041] S B =S A -S AB -S 上
[0042] Among them, S A It is the average of the real-time displacement of the east-side wire-type displacement meter and the real-time displacement of the west-side wire-type displacement meter;
[0043] Since the CD segment is less affected by the external force, the elastic deformation generated by it can be ignored, and the measured displacement of point D can be used to replace the displacement of point C. Therefore, the average slip S of the entire bonding segment is:
[0044]
[0045] That is, the central pull-out test displacement value of the steel strand is obtained.
[0046] In summary, the present invention includes at least one of the following beneficial technical effects:
[0047] 1. The central pull-out test loading device and displacement measurement method of the steel strand can accurately measure the displacement of the steel strand and the steel plate by installing a wire-drawing displacement meter and a thimble displacement meter, solving the inaccurate and unadvanced technical problems of the existing displacement measurement of the bonding anchoring performance test of small-diameter steel strands and concrete;
[0048] 2. The central pull-out test loading device and displacement measurement method of the steel strand only requires the upper steel plate to be installed and disassembled each time loading is performed, which has the advantages of saving time and convenience. The device is simple, convenient and has accurate measurement effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0050] Figure 1 is an axonometric view of a basic loading device in the present invention;
[0051] Figure 2 yes Figure 1 A front view of
[0052] Figure 3 yes Figure 1 Side view of
[0053] Figure 4 yes Figure 1 A top view of
[0054] Figure 5 It is an axonometric diagram of the straight anchor steel strand test piece loading device of the present invention;
[0055] Figure 6 yes Figure 5 A front view of
[0056] Figure 7 yes Figure 5 Side view of
[0057] Figure 8 yes Figure 5 A top view of
[0058] Fig. 9 It is an axonometric view of the steel strand ring specimen loading device of the present invention;
[0059] Fig.10 yes Fig. 9 A front view of
[0060] Fig.11 yes Fig. 9 Side view of
[0061] Fig.12 yes Fig. 9 A top view of
[0062] Fig.13 yes Figure 5 Schematic diagram of the structure of the middle anchor;
[0063] Figure 14-1 and Figure 14-2 yes Fig. 9 A partial enlarged view of the loading plate bearing and external steel strand working together in the loading device for the steel strand ring specimen;
[0064] Fig.15 yes Figure 5 Schematic diagram of the structure of the loading plate;
[0065] Fig.16 yes Fig.15 Floor plan of
[0066] Fig.17 yes Fig.15 Elevation drawing of
[0067] Fig.18 yes Fig.15 AA section profile in;
[0068] Fig.19 yes Figure 5 Schematic diagram of the structure of the upper steel plate and the lower steel plate;
[0069] Fig. 20 yes Fig.19 Floor plan of
[0070] Fig.21 yes Fig.19 Elevation drawing of
[0071] Fig. 22 yes Fig. 20 Middle BB section profile;
[0072] Fig.23 yes Figure 5 Schematic diagram of the structure of the middle and bottom steel plate;
[0073] Fig.24 yes Fig.23 Floor plan of
[0074] Fig.25 yes Fig.23 Elevation drawing of
[0075] Fig.26 yes Fig.24 The CC cross-sectional view in ;
[0076] Fig. 27 yes Fig. 9 Schematic diagram of the structure of the steel plate on the middle ring loading device;
[0077] Fig.28 yes Fig. 27 Floor plan of
[0078] Fig.29 yes Fig. 27 Elevation drawing of
[0079] Fig.30 yes Fig.28 DD cross-sectional view in ;
[0080] Fig.31 yes Figure 5 Schematic diagram of the structure of the displacement measurement auxiliary device;
[0081] Fig.32 yes Fig.31 Floor plan of
[0082] Fig.33 yes Fig.31 Elevation drawing of
[0083] Fig.34 yes Fig.33 EE cross-sectional view in ;
[0084] Fig.35 yes Fig. 9 Schematic diagram of the structure of the middle bearing;
[0085] Fig.36 yes Fig.35 Floor plan of
[0086] Fig.37 yes Fig.35 Side view of
[0087] Fig.38 yes Fig. 9 Middle bearing and Fig.10 Schematic diagram of the working state structure of the smooth round steel column;
[0088] Fig.39 yes Fig.38 The front plan view of
[0089] Fig.40 yes Fig.38 Side view of
[0090] Fig.41 yes Fig. 9 Axonometric view of the middle ring loading plate;
[0091] Fig.42 yes Fig.41 Floor plan of
[0092] Fig.43 yes Fig.41 Elevation drawing of
[0093] Fig.44 yes Fig.41 FF cross-sectional view;
[0094] Fig.45 It is a schematic diagram of the loading device for the straight anchor steel strand specimen;
[0095] Fig.46 It is a schematic diagram of the loading device for the steel strand ring specimen.
[0096] In the figure, 1. servo actuator; 2. loading plate; 2-1. Circular holes around the loading plate; 2-2. Circular hole at the center of the loading plate; 2-3. Anchor placement slot; 3. Upper steel plate; 3-1. Circular holes around the steel plate; 3-2. Reserved steel strand channel; 4. Lower steel plate; 5. Bottom steel plate; 5-1. Circular holes around the bottom steel plate; 5-2. Circular holes on both sides of the center; 5-3. Circular hole for positioning the displacement meter; 6. Base; 7. High-strength screw at the loading end; 8. Loading end high-strength nut; 9, reaction frame high-strength screw; 10, reaction frame high-strength nut; 11, anchor bolt; 12, anchor nut; 13, steel pad; 14, plastic pad; 15, thimble displacement meter; 16, anchor; 16-1, three-piece clip; 16-2, anchor sleeve; 16-3, steel strand channel; 17, displacement measurement auxiliary device; 17-1, slots on both sides of the auxiliary device; 17-2, round holes on both sides of the auxiliary device; 17-3, auxiliary device Central channel; 17-4, auxiliary device outer channel; 17-5, auxiliary device measuring steel bar; 17-6, measuring steel bar reinforcement rib; 17-7, auxiliary device balancing steel bar; 18, wire displacement meter; 19, weight block; 20, weight block support auxiliary device; 21, wire displacement meter fixing platform; 22, test specimen; 23, bearing; 23-1 bearing round hole; 23-2 bearing limit outer rib; 23-3 bearing round ball; 24, lock; 25 , steel strand external connection section; 26, target point; 27, ring device upper steel plate; 27-1, circular holes around the ring device steel plate; 27-2, central circular hole of the ring device steel plate; 27-3, reserved channel of the ring device steel plate; 28, smooth round steel column; 29, smooth round steel column support auxiliary device; 29-1, smooth round steel column positioning channel; 30, ring loading plate; 30-1, circular holes around the ring loading plate; 30-2, reserved channel for steel strand passing through the ring loading plate. DETAILED DESCRIPTION
[0097] The present invention is further described in detail below in conjunction with the accompanying drawings.
[0098] Embodiment 1:
[0099] In Example 1, the steel strand that the central pull-out test loading device acts on is a straight steel strand, also known as a straight anchor steel strand specimen.
[0100] Reference Figures 1 to 8 , Fig.13 , Figures 15 to 26 , Figure 31 to Figure 34 This embodiment is a loading device for testing the bonding and anchoring performance of small-diameter steel strands and concrete, comprising a pedestal 6, a bottom steel plate 5 is arranged above the pedestal 6, a plurality of reaction frame high-strength screws 9 are slidably penetrated on the top of the bottom steel plate 5, and a fixing portion is arranged below the bottom steel plate 5;
[0101] The outer circumferences of several high-strength screw rods 9 of the reaction frame are slidably sleeved with an upper steel plate 3 and a lower steel plate 4 in sequence from top to bottom, and the test specimen 22 is placed between the upper steel plate 3 and the lower steel plate 4, and the upper steel plate 3 and the lower steel plate 4 are fixedly connected to the high-strength screw rod 9 of the reaction frame through the high-strength nut 10 of the reaction frame, and the top surfaces of the upper steel plate 3 and the lower steel plate 4 are provided with reserved steel strand channels 3-2, and a servo actuator 1 is arranged above the upper steel plate 3, and a loading plate 2 is fixedly connected to the output end of the servo actuator 1.
[0102] A plurality of circular holes are provided around the loading plate 2 on the top, and a top plate is provided above the loading plate 2. A plurality of loading-end high-strength screws 7 are slidably penetrated through the top of the top plate. The loading-end high-strength screws 7 pass through the circular holes around the loading plate 2, and the top plate and the loading plate 2 are fixedly connected to the loading-end high-strength screws 7 through the loading-end high-strength nuts 8.
[0103] An anchor placement slot 2-3 is provided on the top of the loading plate 2, and a center loading circular hole 2-2 is provided on the bottom wall of the anchor placement slot 2-3. An anchor 16 is placed in the anchor placement slot 2-3, and the anchor 16 fixes the steel strand, and the steel strand passes through the center loading circular hole 2-2. A displacement measurement aid 17 is arranged under the loading plate 2.
[0104] The displacement measurement auxiliary device 17 includes a column and two auxiliary device measurement steel bars 17-5 fixedly connected to the upper half of the outer peripheral surface of the column. An auxiliary device central channel 17-3 is opened on the top of the column, and an auxiliary device outer channel 17-4 is opened on the outer peripheral side of the column. The auxiliary device central channel 17-3 is communicated with the auxiliary device outer channel 17-4. The steel strand passes through the auxiliary device central channel 17-3, and the steel strand is fixed in the auxiliary device outer channel 17-4 by a butterfly nut;
[0105] The top of the auxiliary measuring steel bar 17-5 is provided with circular holes 17-2 on both sides of the auxiliary device, and a thin steel wire is passed through the circular hole. The bottom end of the thin steel wire and the top of the bottom steel plate 5 are fixedly connected with a wire displacement meter 18. The side wall of the auxiliary measuring steel bar 17-5 is provided with a plurality of slot holes 17-1 on both sides of the auxiliary device;
[0106] Two plastic gaskets 14 are fixedly connected to the bottom of the upper steel plate 3 , and a pin-type displacement meter 15 is fixedly connected to the bottom end of the plastic gasket 14 .
[0107] A measuring steel bar reinforcement rib 17-6 is fixedly connected between the bottom of the auxiliary device measuring steel bar 17-5 and the lower half of the outer circumference of the column, and two auxiliary device balancing steel bars 17-7 are fixedly connected to the upper half of the outer circumference of the auxiliary device measuring steel bar 17-5.
[0108] Two weights 19 are suspended from the steel strand at the bottom of the test specimen 22 , a weight support auxiliary device 20 is fixedly connected between the two weights 19 , and the steel strand passes through the weight support auxiliary device 20 , and the bottom end of the steel strand is connected to the corresponding wire-type displacement meter 18 .
[0109] The fixing part includes a plurality of steel pads 13 fixedly connected to the bottom of the bottom steel plate 5, the bottom surface of the steel pad 13 is in contact with the top surface of the pedestal 6, the top of the upper steel plate 3 and the lower steel plate 4 are both provided with circular holes 3-1 around the steel plate, the top of the bottom steel plate 5 is provided with circular holes 5-1 around the bottom steel plate, the high-strength screw rod 9 of the reaction frame passes through the circular holes 5-1 around the bottom steel plate and the circular holes 3-1 around the steel plate, and the high-strength screw rod 9 of the reaction frame is fixedly connected to the bottom steel plate 5 through the high-strength nut 10 of the reaction frame;
[0110] The top of the bottom steel plate 5 is provided with a plurality of central and two-sided circular holes 5-2, and the top of the pedestal 6 is fixedly connected with a plurality of ground anchor bolts 11, the ground anchor bolts 11 pass through the central and two-sided circular holes 5-2, and the ground anchor bolts 11 are fixedly connected to the bottom steel plate 5 via ground anchor nuts 12;
[0111] A displacement meter positioning circular hole 5 - 3 is opened at the center of the top of the bottom steel plate 5 , and the corresponding wire-type displacement meter 18 is fixedly connected to the displacement meter positioning circular hole 5 - 3 .
[0112] It also includes two wire-drawing displacement meter fixing platforms 21 , and the corresponding two wire-drawing displacement meters 18 are respectively placed on the top of the corresponding wire-drawing displacement meter fixing platforms 21 .
[0113] The anchor 16 includes an anchor sleeve 16 - 2 and a three-piece clip 16 - 1 disposed in the anchor sleeve 16 - 2 , and a steel strand channel 16 - 3 is formed in the center of the three-piece clip 16 - 1 .
[0114] Embodiment 2:
[0115] Reference Fig.45 This embodiment is used to apply the loading device for the central pull-out test of a steel strand described in Embodiment 1, and proposes a displacement measurement method for the central pull-out test of a steel strand, comprising the following steps:
[0116] S1. Place the steel pad 13 on the pedestal 6, pass the ground anchor screw through the circular holes 5-2 on both sides of the center, and fix it with the ground anchor nut 12;
[0117] S2. Pass four high-strength screws 9 of the reaction frame through the circular holes 5-1 around the bottom steel plate and fix them with high-strength nuts 10 of the reaction frame. Then, position and place the lower steel plate 4 on the high-strength screws 9 of the reaction frame as required, and then place the upper steel plate 3. A certain space is reserved between the upper steel plate 3 and the lower steel plate 4 according to the size of the required loading test specimen 22, and they are fixed with high-strength nuts 10 of the reaction frame.
[0118] S3, connecting the corresponding two wire-type displacement meters 18 to the displacement measurement auxiliary device 17 to measure the steel strands at the loading end;
[0119] S4, the steel strand at the loading end passes through the central hole 17-3 of the auxiliary device, and is fixed by a butterfly nut;
[0120] S5, two weights 19 are suspended from the lower steel strands, and the bottom ends of the steel strands are connected to the corresponding pull-wire displacement meters 18;
[0121] S6, using the anchor 16 to fix the loading end steel strand in the anchor placement slot 2-3 through the anchor sleeve 16-2 and the three-piece clip 16-1;
[0122] S7, the hydraulic servo actuator 1 works to load, and the displacement value of the steel strand is measured and calculated.
[0123] Reference Fig.45 , the calculation method of step S7 is:
[0124] The steel strand is divided into AB segment, BC segment and CD segment from top to bottom, where AB segment is the loading end, BC segment is the bonding anchoring segment, and CD segment is the free end;
[0125] The displacement of the strand needs to measure the relative displacement of point B and point C respectively. The displacement of point B can be obtained by subtracting the elongation of segment AB and the displacement of the upper steel plate 3 from the displacement of point A. The free end segment CD is not subject to external force, so the displacement of point C is replaced by the actually measured displacement of point D. The calculation formula is as follows:
[0126] Deformation S of segment AB AB for:
[0127] S AB =FL AB / (EA)
[0128] Where, F is the tensile load, L AB is the length of segment AB, E is the elastic modulus of the steel strand, and A is the nominal cross-sectional area of the steel strand;
[0129] A pin displacement meter 15 is arranged on the east and west sides and the rear side of the upper steel plate. The displacement value S 上 for:
[0130] S 上=(S e +S w +S s ) / 3
[0131] Among them, S e is the real-time displacement of the east side thimble displacement meter 15, S w is the real-time displacement of the west side thimble displacement meter 15, S s It is the real-time displacement of the north side thimble displacement meter 15;
[0132] A wire-type displacement meter 18 is arranged on the east and west sides of the displacement measurement auxiliary device 17. The displacement value S A for:
[0133] S A =(S 东 +S 西 ) / 2
[0134] Among them, S 东 is the real-time displacement of the east side wire displacement meter 18, S 西 is the real-time displacement of the west side wire displacement meter 18;
[0135] The actual slip S at the loading end B for:
[0136] S B =S A -S AB -S 上
[0137] Among them, S A is the average of the real-time displacement of the east-side wire-type displacement meter 18 and the real-time displacement of the west-side wire-type displacement meter 18;
[0138] Since the CD segment is less affected by the external force, the elastic deformation generated by it can be ignored, and the measured displacement of point D can be used to replace the displacement of point C. Therefore, the average slip S of the entire bonding segment is:
[0139]
[0140] That is, the central pull-out test displacement value of the steel strand is obtained.
[0141] This embodiment can accurately measure the displacement of the steel strand and the steel plate by installing the wire displacement meter 18 and the thimble displacement meter 15, solving the problem of inaccurate displacement measurement and backward technology in the existing test of the bonding anchoring performance of small-diameter steel strand and concrete. Each time loading is performed, only the upper steel plate 3 is installed and disassembled, which has the advantages of saving time and convenience. The device is simple, convenient and has accurate measurement effect.
[0142] Embodiment 3:
[0143] In Example 3, the steel strand that the central pull test loading device acts on is a ring-shaped steel strand, also known as a steel strand ring specimen.
[0144] Reference Figures 1 to 4 , Figures 9 to 12 Figure 14 Figures 23 to 30 , Figures 35 to 44 This embodiment is a loading device used for testing the bonding and anchoring performance of small-diameter steel strand rings and concrete, including a pedestal 6, a bottom steel plate 5 is arranged above the pedestal 6, a plurality of reaction frame high-strength screws 9 are slidably penetrated on the top of the bottom steel plate 5, and a fixing portion is arranged below the bottom steel plate 5.
[0145] The outer circumferences of the plurality of high-strength screws 9 of the reaction frame are slidably sleeved with the upper steel plate 27 and the lower steel plate 4 of the ring device in sequence from top to bottom, and the test specimen 22 is placed between the upper steel plate 27 and the lower steel plate 4 of the ring device, and the upper steel plate 27 and the lower steel plate 4 of the ring device are fixedly connected to the high-strength screws 9 of the reaction frame through the high-strength nuts 10 of the reaction frame. Four circular holes 27-1 are opened around the ring device steel plate at the top of the upper steel plate 27 and the lower steel plate 4, and the high-strength screws 9 of the reaction frame pass through the corresponding circular holes 27-1 around the ring device steel plate. The center of the top of the upper steel plate 27 and the lower steel plate 4 of the ring device is opened with a central circular hole 27-2 of the ring device steel plate and a reserved channel 27-3 of the ring device steel plate.
[0146] A servo actuator 1 is arranged above the upper steel plate 3, and a ring loading plate 30 is fixedly connected to the output end of the servo actuator 1. A plurality of circular holes 30-1 are opened on the top of the ring loading plate 30. A top plate is arranged above the ring loading plate 30, and a plurality of loading end high-strength screws 7 are slidably penetrated on the top of the top plate. The loading end high-strength screws 7 pass through the circular holes 30-1 around the ring loading plate, and the top plate and the ring loading plate 30 are fixedly connected to the loading end high-strength screws 7 through the loading end high-strength nuts 8.
[0147] Two smooth round steel column supporting auxiliary devices 29 are fixedly connected to the top of the ring loading plate 30 . A smooth round steel column positioning channel 29 - 1 is opened on one side of the smooth round steel column supporting auxiliary device 29 . A smooth round steel column 28 is commonly arranged in the two smooth round steel column positioning channels 29 - 1 .
[0148] The outer circumferential surface of the smooth round steel column 28 is fixedly sleeved with a bearing 23, and the bearing 23 includes a bearing 23 limiting outer rib and a bearing circular hole 23-1 formed in the center, and a plurality of bearing balls 23-3 are rollingly connected in the bearing 23 limiting outer rib. The top of the ring loading plate 30 is located between the two smooth round steel column supporting auxiliary devices 29 and is provided with a ring loading plate reserved steel strand passing channel 30-2.
[0149] The surface of the test specimen 22 is provided with a circular target point 26, and a non-contact displacement meter is used for measurement. The steel strand at the loading end of the test specimen 22 is overlapped and fixed with the steel strand external connection section 25 through a lock buckle 24, and the overlapped and anchored new steel strand loop passes through the reserved steel strand exit channel 30-2 on the ring loading plate 30, and the new steel strand loop is overlapped on the bearing 23.
[0150] The bottom of the upper steel plate 27 of the ring device is fixedly connected with two plastic gaskets 14, and the bottom end of the plastic gasket 14 is fixedly connected with a pin displacement meter 15. The fixing part includes a plurality of steel pads 13 fixedly connected to the bottom of the bottom steel plate 5, the bottom surface of the steel pads 13 is in contact with the top surface of the pedestal 6, and the reaction frame high-strength screw 9 is fixedly connected to the bottom steel plate 5 through the reaction frame high-strength nut 10.
[0151] The top of the bottom steel plate 5 is provided with a plurality of central and two-sided circular holes 5-2, and the top of the pedestal 6 is fixedly connected with a plurality of ground anchor bolts 11, the ground anchor bolts 11 pass through the central and two-sided circular holes 5-2, and the ground anchor bolts 11 are fixedly connected to the bottom steel plate 5 via ground anchor nuts 12;
[0152] A displacement meter positioning circular hole 5 - 3 is opened at the center of the top of the bottom steel plate 5 , and the corresponding wire-type displacement meter 18 is fixedly connected to the displacement meter positioning circular hole 5 - 3 .
[0153] It also includes two wire-drawing displacement meter fixing platforms 21 , and the corresponding two wire-drawing displacement meters 18 are respectively placed on the top of the corresponding wire-drawing displacement meter fixing platforms 21 .
[0154] Embodiment 4:
[0155] Reference Fig.46 This embodiment is used to apply the loading device for the central pull-out test of the steel strand described in Example 3, and proposes a displacement measurement method for the central pull-out test of the steel strand ring, including the following steps:
[0156] S1. Place the steel pad 13 on the pedestal 6, pass the ground anchor screw through the circular holes 5-2 on both sides of the center, and fix it with the ground anchor nut 12;
[0157] S2. Pass four high-strength screws 9 of the reaction frame through the circular holes 5-1 around the bottom steel plate and fix them with high-strength nuts 10 of the reaction frame. Then, position and place the lower steel plate 4 on the high-strength screws 9 of the reaction frame as required, and then place the upper steel plate 27 of the ring device. A certain space is reserved between the upper steel plate 27 of the ring device and the lower steel plate 4 according to the size of the required loading test specimen 22, and fix them with high-strength nuts 10 of the reaction frame.
[0158] S3, the steel strand external connection section 25 is overlapped with the steel strand of the test specimen 22 through the lock buckle 24, and the overlapped and anchored new steel strand loop is passed through the ring loading plate reserved steel strand passing channel 30-2 on the ring loading plate 30;
[0159] S4, overlap the new steel strand ring on the bearing 23, and then connect it to the smooth round steel column support auxiliary device 29 through the smooth round steel column 28, so as to limit the front and rear displacement of the steel strand and ensure that there is no eccentric loading during loading;
[0160] S5. The test specimen 22 is provided with a circular target 26 and measured using a non-contact displacement measurement system.
[0161] In the measurement method, the upper steel plate 27 of the ring device is used to apply fixed constraints to the upper surface of the steel strand ring test specimen 22, and a central circular hole is left on the upper steel plate 27 of the ring device to ensure that no unnecessary constraints are applied to the upper surface of the steel strand ring specimen during the specimen test, thereby ensuring the accuracy of the test process; the thin steel wire at the free end is directly connected to the pull-wire displacement meter 18 on the bottom steel plate 5, and no weight block 19 is required for assistance.
[0162] Reference Fig.46 The steel strand is divided into AOB segment, ADB segment and DE segment from top to bottom, where the AOB segment is the loading end, the ADB segment is the bonding and anchoring segment, and the DE segment is the free end.
[0163] Under the central tensile load, the load-slip curve of the specimen is mainly determined, where the tensile load of the specimen is directly obtained by the hydraulic servo actuator, and the displacement is obtained by the movement of the non-contact displacement meter to the target point 26. The slip of the strand is the average of the relative displacements of points D and E, where the displacement of point D is obtained by subtracting the displacement of the specimen at point C from the average of the displacements of points A and B. The calculation formula is as follows:
[0164] The displacement SD of point D is:
[0165]
[0166] The average slip S of the entire bonding section is:
[0167]
[0168] That is, the center pull-out test displacement value of the steel strand ring is obtained.
[0169] The end mark of the center pull test is one of the following:
[0170] 1) Concrete vertebral damage occurs;
[0171] 2) The steel strand is broken.
[0172] During loading, the servo actuator 1 applies displacement upwards to the loading plate 2 through the ring device to perform the center pull test of the specimen. The whole test adopts the displacement-controlled loading method with a rate of 0.8 mm / min.
[0173] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.
Claims
1. A central pull-out test loading device for a steel strand, comprising a pedestal (6), characterized in that: A bottom steel plate (5) is arranged above the pedestal (6), a plurality of reaction frame high-strength screw rods (9) are slidably penetrated through the top of the bottom steel plate (5), and a fixing portion is arranged below the bottom steel plate (5); The outer circumferences of the plurality of high-strength screw rods (9) of the reaction frame are slidably sleeved with an upper steel plate (3) and a lower steel plate (4) in sequence from top to bottom, the test specimen (22) is placed between the upper steel plate (3) and the lower steel plate (4), and the upper steel plate (3) and the lower steel plate (4) are fixedly connected to the high-strength screw rods (9) of the reaction frame through high-strength nuts (10) of the reaction frame, and reserved steel strand channels (3-2) are provided on the top surfaces of the upper steel plate (3) and the lower steel plate (4), and a servo motor is provided above the upper steel plate (3). An actuator (1), the output end of the servo actuator (1) is fixedly connected to a loading plate (2), the top of the loading plate (2) is provided with an anchor placement slot (2-3), the bottom wall of the anchor placement slot (2-3) is provided with a central loading circular hole (2-2), an anchor (16) is placed in the anchor placement slot (2-3), the anchor (16) fixes a steel strand, and the steel strand passes through the central loading circular hole (2-2), and a displacement measurement auxiliary device (17) is arranged below the loading plate (2).
2. The central pull test loading device for steel strand according to claim 1, characterized in that: The displacement measurement auxiliary device (17) comprises a column and two auxiliary device measurement steel bars (17-5) fixedly connected to the upper half of the outer peripheral surface of the column, an auxiliary device central hole (17-3) is opened on the top of the column, and an auxiliary device outer hole (17-4) is opened on the outer peripheral side of the column, the auxiliary device central hole (17-3) is communicated with the auxiliary device outer hole (17-4), the steel strand passes through the auxiliary device central hole (17-3), and the steel strand is fixed in the auxiliary device outer hole (17-4) by a butterfly nut; The top of the auxiliary device measuring steel bar (17-5) is provided with circular holes (17-2) on both sides of the auxiliary device, a thin steel wire is passed through the circular hole, the bottom end of the thin steel wire and the top of the bottom steel plate (5) are fixedly connected with a wire-drawing displacement meter (18), and the side wall of the auxiliary device measuring steel bar (17-5) is provided with a plurality of slot holes (17-1) on both sides of the auxiliary device; Two plastic gaskets (14) are fixedly connected to the bottom of the upper steel plate (3), and a pin-type displacement meter (15) is fixedly connected to the bottom end of the plastic gasket (14).
3. The central pull test loading device for steel strand according to claim 2, characterized in that: A measuring steel bar reinforcement rib (17-6) is fixedly connected between the bottom of the auxiliary device measuring steel bar (17-5) and the lower half of the outer peripheral surface of the column, and two auxiliary device balancing steel bars (17-7) are fixedly connected to the upper half of the outer peripheral surface of the auxiliary device measuring steel bar (17-5).
4. The central pull test loading device for steel strand according to claim 3 is characterized in that: Two weights (19) are suspended from the steel strand at the bottom of the test specimen (22), a weight support auxiliary device (20) is fixedly connected between the two weights (19), the steel strand passes through the weight support auxiliary device (20), and the bottom end of the steel strand is connected to the corresponding wire-drawing displacement meter (18).
5. The central pull test loading device for steel strand according to claim 4, characterized in that: The fixing part comprises a plurality of steel pads (13) fixedly connected to the bottom of the bottom steel plate (5), the bottom surface of the steel pad (13) is in contact with the top surface of the pedestal (6), the top of the upper steel plate (3) and the top of the lower steel plate (4) are both provided with circular holes (3-1) around the steel plate, the top of the bottom steel plate (5) is provided with circular holes (5-1) around the bottom steel plate, the high-strength screw rod (9) of the reaction frame passes through the circular holes (5-1) around the bottom steel plate and the circular holes (3-1) around the steel plate, and the high-strength screw rod (9) of the reaction frame is fixedly connected to the bottom steel plate (5) through the high-strength nut (10) of the reaction frame; The top of the bottom steel plate (5) is provided with a plurality of central and two side circular holes (5-2); the top of the pedestal (6) is fixedly connected with a plurality of ground anchor bolts (11); the ground anchor bolts (11) pass through the central and two side circular holes (5-2); and the ground anchor bolts (11) are fixedly connected to the bottom steel plate (5) via ground anchor nuts (12); A displacement meter positioning circular hole (5-3) is provided at the center of the top of the bottom steel plate (5), and the corresponding wire-drawing displacement meter (18) is fixedly connected in the displacement meter positioning circular hole (5-3).
6. The central pull test loading device for steel strand according to claim 5, characterized in that: It also includes two fixed platforms for the draw-wire displacement meter (18), and the corresponding two draw-wire displacement meters (18) are respectively placed on the top of the corresponding fixed platforms for the draw-wire displacement meter (18).
7. The central pull test loading device for steel strand according to claim 6, characterized in that: The anchor (16) comprises an anchor sleeve (16-2) and a three-piece clip (16-1) arranged in the anchor sleeve (16-2), and a steel strand channel (16-3) is formed in the center of the three-piece clip (16-1).
8. A method for measuring displacement of a central pull-out test of a steel strand, comprising a loading device for a central pull-out test of a steel strand according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Place the steel pad on the pedestal, pass the anchor bolts through the circular holes on both sides of the center, and fix them with anchor nuts; S2. Pass four high-strength screws of the reaction frame through the circular holes around the bottom steel plate and fix them with high-strength nuts of the reaction frame. Then, position and place the lower steel plate on the high-strength screws of the reaction frame as required, and then place the upper steel plate. A certain space is reserved between the upper and lower steel plates according to the size of the required loading test specimen, and they are fixed with high-strength nuts of the reaction frame. S3, connecting the corresponding two wire-type displacement meters to the displacement measurement auxiliary device to measure the steel strands at the loading end; S4, the steel strand at the loading end passes through the central hole of the auxiliary device and is fixed by a butterfly nut; S5, two weights are hung on the lower steel strand, and the bottom end of the steel strand is connected to the corresponding pull-wire displacement meter; S6. Use the anchor to fix the steel strand at the loading end in the anchor placement slot through the anchor sleeve and the three-piece clip; S7. The hydraulic servo actuator works to load and measure and calculate the displacement value of the steel strand.
9. The displacement measurement method of the central pull test of the steel strand according to claim 8, characterized in that: The calculation method of step S7 is: The steel strand is divided into AB segment, BC segment and CD segment from top to bottom, where AB segment is the loading end, BC segment is the bonding anchoring segment, and CD segment is the free end; The displacement of the strand needs to measure the relative displacement of point B and point C respectively. The displacement of point B can be obtained by subtracting the elongation of segment AB and the displacement of the upper steel plate from the displacement of point A. The free end segment CD is not subject to external force, so the displacement of point C is replaced by the actual measured displacement of point D. The calculation formula is as follows: Deformation S of segment AB AB for: S AB =FL AB / (IT) Where, F is the tensile load, L AB is the length of segment AB, E is the elastic modulus of the steel strand, and A is the nominal cross-sectional area of the steel strand; A thimble displacement meter is arranged on the east and west sides and the rear side of the upper steel plate. The displacement value S 上 for: S 上 =(S e +S w +S s ) / 3 Among them, S e is the real-time displacement of the east side thimble displacement meter, S w is the real-time displacement of the west side thimble displacement meter, S s It is the real-time displacement of the north side thimble displacement meter; A wire-type displacement meter is arranged on the east and west sides of the displacement measurement auxiliary device. A for: S A =(S 东 +S 西 ) / 2 Among them, S 东 is the real-time displacement of the east side wire displacement meter, S 西 It is the real-time displacement of the west side wire displacement meter; The actual slip S at the loading end B for: S B =S A -S AB -S 上 Among them, S A It is the average of the real-time displacement of the east-side wire-type displacement meter and the real-time displacement of the west-side wire-type displacement meter; Since the CD segment is less affected by external forces, the elastic deformation generated by it can be ignored. The measured displacement of point D can be used to replace the displacement of point C. Therefore, the average slip S of the entire bonding segment is: That is, the central pull-out test displacement value of the steel strand is obtained.