Waterproof design method for reinforced concrete structures and long-term performance maintenance method

Abstract

The present invention proposes a waterproof design method and a long-term performance maintenance method for reinforced concrete structures, wherein the concrete is provided with steel bars and the top surface of the concrete is covered with a waterproof layer. The method comprises the following steps: clarifying the essential mechanism of cracking of the waterproof layer caused by cracking of the concrete at a microscopic scale; based on the essential mechanism, applying the crack width value of the top surface of the concrete as a forced displacement in the opposite direction to the bottom surface of the waterproof layer; iteratively calculating the crack height of the waterproof layer; ensuring that the remaining uncracked solid thickness of the waterproof layer is still greater than the minimum solid thickness that meets the waterproof requirements without considering the cracking of the concrete. It was found that at the moment of initial cracking of the concrete, the thickness of the waterproof layer in the longitudinal tension can have a significant impact on the final crack height of the waterproof layer, but when the thickness approaches the nanometer scale, the calculation result of the crack height tends to be stable. The present invention contributes to the long-life design of the waterproof layer and is applicable to bridges, roads, tunnels, buildings, and hydraulic structures.

Description

Technical Field

[0001] The present invention relates to the field of bridge structure design and is also applicable to the fields of design, construction, assembly construction and waterproofing technology of roads, tunnels, buildings and hydraulic structures, and particularly to a design method for a waterproof layer of a reinforced concrete structure and a method for maintaining its long-term performance. Background Art

[0002] Existing technology

[0003] Extending the lifespan of reinforced concrete structures to 150-200 years has become a current research hotspot and a long-term strategic issue. Water is the most significant factor affecting the durability of reinforced concrete structures, and reducing water erosion on reinforced concrete is crucial for maintaining the long-term performance of various engineering structures. For example, regarding bridge structures, there were no clear regulations regarding the installation of waterproof layers on bridge decks. However, through nearly 30-40 years of engineering experience, particularly the extensive experience gained from repairing and reinforcing existing bridges over the past 10-20 years, we have gradually come to understand that concrete bridge failures are primarily caused by carbonation, chloride ionization, alkali content, and alkali-aggregate reaction (AAR) caused by active aggregates, as well as frost heave damage and steel corrosion—all factors closely related to water. Therefore, the installation of waterproof layers has become a crucial means of reducing concrete bridge failures and extending their service life.

[0004] However, even if a waterproof layer is set up, the performance requirement for the elongation at break of the waterproof layer material in bridge design is usually as high as 800% or more, which is much greater than the ultimate tensile strain of 1% of steel bars and the ultimate tensile strain of 0.01% of concrete. Figure 1 Even with densely reinforced concrete structures, cracking can still lead to water leakage, severely reducing the service life of the structure and requiring frequent repairs. Water damage at the continuous deck has become a common problem, especially for prefabricated concrete beam bridges with simply supported structures and continuous decks.

[0005] Technical issues

[0006] Clearly, existing waterproofing layers have failed to maintain the performance expected. The fundamental reason for this is that existing technology still lacks a clear design method for waterproofing layers when reinforced concrete structures crack. Crack-resistant waterproofing layer design fails to consider the microscopic nature of concrete cracking and its impact on the waterproofing layer. Furthermore, existing testing methods for waterproofing materials involve performing uniaxial tensile and shear tests on individual waterproofing layer specimens to measure tensile strength, shear strength, elongation at break, bond strength, low-temperature flexure, and impermeability. These methods fail to consider the interaction between concrete and the waterproofing layer, particularly the impact of the sudden release of strain energy during the transient process of concrete cracking. Summary of the Invention

[0007] To solve the above problems, the present invention provides a waterproofing design method and a long-term performance maintenance method for reinforced concrete structures. This design method proposes the mechanism by which concrete cracking leads to cracking of the waterproof layer, and provides a calculation method for the crack resistance of the waterproof layer. It can facilitate the waterproofing design of bridges and various reinforced concrete structures and achieve their long-term performance maintenance, thereby significantly extending their service life.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0009] A method for waterproofing a reinforced concrete structure, wherein the reinforced concrete structure comprises concrete, a waterproof layer, and steel bars; the steel bars are arranged in the concrete, and the top surface of the concrete is covered with the waterproof layer;

[0010] The design method based on the reinforced concrete structure waterproofing comprises the following steps:

[0011] S1. For the average thickness H The waterproof layer is longitudinal along the tensile direction of the concrete, the direction perpendicular to the tensile direction of the concrete and parallel to the surface of the waterproof layer is transverse, and the direction perpendicular to the surface of the waterproof layer is vertical. L The waterproof layer segment has a lateral width of B Take any value that satisfies L ≥4 H ;

[0012] S2. Assume that there is a virtual interface layer in the waterproof layer segment, and the thickness of the virtual interface layer along the longitudinal direction is T cr , the vertical height of the virtual interface layer is H , the width of the virtual interface layer in the horizontal direction is B The lengths of the waterproof layer segments on both sides of the virtual interface layer are L / 2- T cr / 2, the waterproof layer segments on both sides are connected via the virtual interface layer;

[0013] S3. A vertical rigid support is provided on the bottom surface of the waterproof layer segment;

[0014] S4. Apply forced displacements in opposite directions and away from the virtual interface layer to the bottom surfaces of the waterproof layer segments on both sides of the virtual interface layer. W cr / 2, W cr The longitudinal width of the crack produced on the top surface of the concrete under the action of external force;

[0015] S5. Calculate the vertical distance between the lowest position of the virtual interface layer and the bottom surface of the waterproof layer segment and define it as z , let 0 <d z <0.1 H According to the stress-strain constitutive relationship of the waterproof layer material and conventional mechanics methods, the forced displacement in S4 is calculated. z The relative displacement of the two sides of the virtual interface layer at T z ,△ T z The value is positive if it is relatively far away;

[0016] S6. If △ T z ≥ ε cr T cr and z +d z < H , ε cr is the elongation at break of the waterproof material, then it is considered z The virtual interface layer at the location is broken and the distance from the bottom surface of the waterproof layer segment is deleted. z Chuzhi z +d z The virtual interface layer at z Chuzhi z +d z The waterproof layer segments on both sides of the virtual interface layer at the position are disconnected, and the waterproof layer segments on both sides are restored to the spatial positions before the forced displacement is applied, and then the process goes to S4; otherwise, the process goes to S7;

[0017] S7. Crack height of the waterproof layer H cr Take the vertical distance between the lowest position of the current virtual interface layer and the bottom surface of the waterproof layer segment z And take safety into account z ,Right now H cr = z +d z ;

[0018] S8. If H - H cr >0, the waterproof layer is not completely broken after the concrete cracks, and the waterproof layer design is terminated; otherwise, the thickness of the waterproof layer is increased. H , go to S1.

[0019] The technical principles and effects of the above invention are as follows: (1) The elastic modulus of concrete material is usually tens of thousands of times that of waterproof material, so the concrete at the bottom of the waterproof layer can be regarded as a vertical rigid support for the waterproof layer; (2) The thickness of the waterproof layer is usually only at the millimeter level, while the size of the concrete structure in the thickness direction is at least at the tens of centimeters level, and the elastic modulus of the waterproof layer is much smaller than that of the concrete and steel bars. Therefore, the stress of the concrete structure shared by the waterproof layer before and after the concrete cracks can be ignored. Therefore, the width of the concrete crack depends entirely on its steel bar configuration and the size of the external load it is subjected to. The crack width of the concrete will hardly be affected by the waterproof layer, that is, the cracking of the concrete is equivalent to applying various stresses to the bottom surface of the waterproof layer on both sides of the crack. W cr / 2 forced displacement (combined with the attached Figure 2 The present invention analyzes the simplified mechanical model of cracking of the fiber-free waterproof layer), which is the essential mechanism of cracking of the waterproof layer caused by concrete cracking; it should be noted that the cracking height of the waterproof layer caused by the forced displacement H cr It is necessary to perform iterative calculations according to steps S4 to S6 to obtain an accurate solution; (3) Combined with the attached Figure 14 It can be seen that when L ≥4 H hour, H cr The calculation results are basically not affected by the longitudinal segment length taken when calculating the stress of the waterproof layer. L The impact of L If the value is too small, it will cause large calculation errors, but it can also avoid L When the value is too large, it will lead to excessive computational complexity; (4) According to the method of the present invention, it can be ensured that when the reinforced concrete structure cracks instantaneously under the most unfavorable load, the waterproof layer on the top surface will not be completely cracked. This is a key measure to maintain the long-term working performance of the waterproof layer, and it is also a key issue that the existing technology has not considered and paid attention to. (5) When the fracture occurs at z, the position above z+dz is not necessarily fractured. In fact, the cycle of steps S4 to S6 is similar to the concept of calculus. Through iterative calculation, the height position of the crack development is gradually explored upward until it stops cracking upward or the crack height of the entire waterproof layer is reached. H cr Run through H . Where dz is the differential of z.

[0020] Preferably, the average thickness of the waterproof layer in S1 is H It is calculated based on the solid thickness of the waterproof layer after solidification and maintenance.

[0021] The technical principle and effect of the above invention are as follows: the design and construction of the waterproof layer in the existing technology are controlled according to the liquid thickness after the application, but the actual waterproof layer has become solid when the concrete structure is subjected to stress and cracks, and most waterproof coatings can reduce their thickness after solidification by more than 30% compared with the liquid thickness as their water or other organic solvent components evaporate. Therefore, when the stress is calculated according to the liquid design thickness value of the existing technology, there will be significant errors in the results, so it should be calculated according to the solid thickness after solidification and maintenance.

[0022] Preferably, in S2 T cr The average of the horizontal distances between adjacent wave crests on the concrete surface within any 100 μm×100 μm range is taken. The wave crests and troughs on the concrete surface are measured using equipment with a maximum resolution in the range of 1 nm to 1 μm.

[0023] The technical principles and effects of the above invention are: (1) combining Figure 3 (Schematic diagram of the mechanism of concrete cracking causing waterproof layer cracking based on interface roughness analysis of the present invention) It can be seen that the surface of the concrete structure is uneven at the micro level, and there are a large number of undulating peaks and troughs at the micro scale, which causes the interface between the waterproof layer and the concrete to be rough and undulating. The peaks of the concrete are embedded in the waterproof layer like shear nails in the steel-concrete composite structure, and the waterproof layer will fill the troughs of the concrete to wrap the peaks of the concrete. Therefore, the interaction between the concrete and the waterproof layer is not only the chemical adsorption force and friction force between the two materials, but more of the mutual extrusion and bite force. Therefore, when the concrete cracks and opens on both sides of the crack, it will also drive the waterproof layer to open to both sides of the crack, that is, The moment the concrete cracks, the waterproof layer will be torn; (2) The trough of the concrete surface is relatively weak, and cracks generally occur from the trough. When the concrete crack at the trough opens to a certain width, the normal tension of the interface between the concrete at the trough and the waterproof layer will exceed the chemical adsorption force between the two, thereby causing interface separation; at the same time, the concrete outside the adjacent crests on both sides of the trough will produce an extrusion effect on the outer waterproof layer, thereby pushing the waterproof layer outside the crest to continue to open to both sides of the crack; therefore, the force of the waterproof layer after the concrete cracks is essentially the following: for a waterproof layer micro-segment (i.e., a virtual interface layer) with a longitudinal thickness equal to the distance between the adjacent crests on both sides of the trough, the bottom surface of the waterproof layer on both sides of the micro-segment is subjected to the force of opening to both sides. W cr / 2 forced displacement, the waterproof layer of the micro segment is pulled into an elastic-plastic state and eventually cracks to H cr The waterproof layer outside the micro-segment is squeezed and basically in elastic state, and there is a tensile-compressive interface between it and the tensile micro-segment. It can be seen that the thickness of the virtual interface layer isT cr The value should be the horizontal distance between adjacent wave crests (i.e., the longitudinal length of the micro-segment); (3) According to the microscopic observation data of the concrete surface, the horizontal distance between the wave crests and troughs on its surface is within the scale range of 1nm to 1μm. Therefore, it is necessary to measure the undulating characteristics of the concrete surface based on the equipment at this scale and then calculate its statistical mean, so as to calculate and design the stress of the waterproof layer based on its statistical probability based on the concept of the probabilistic limit state method.

[0024] Preferably, in S2 T cr The average value of the distances between material molecules or molecular clusters when the waterproof layer is not subjected to external forces other than gravity is taken.

[0025] The technical principle and effect of the above invention are: Figure 4 (Schematic diagram of the mechanism of concrete cracking inducing waterproof layer cracking based on molecular scale analysis of the present invention) It can be seen that when designing from a safety perspective, T cr Take a smaller value to calculate the stress on the waterproof layer. At this time, we can consider it according to the limit principle, that is, assuming that the interaction force between the molecules or clusters of concrete materials and the most adjacent molecules or clusters of waterproof layer is infinite, and there will be no interface separation or slip between the two. At this time, the essence of the cracking of concrete and waterproof layer is that the longitudinal distance between its molecules or clusters suddenly changes from nanometer level to millimeter level, that is, the distance increases by nearly 100,000 times and appears as cracks visible to the naked eye - of course, the increment of the longitudinal distance will decrease rapidly as the vertical distance between the molecules or clusters of waterproof layer and the concrete surface increases, but for the waterproof layer material near the concrete surface, its fracture elongation performance of only 800% is completely insufficient to withstand the longitudinal distance increment of nearly 100,000 times. Therefore, when the concrete cracks, the waterproof layer material near its surface will inevitably crack as well, and crack vertically to a certain height. H cr The cracking stops after that, so the key to solving the cracking of the waterproof layer is to find the solution. H cr value.

[0026] Preferably, in S2 T cr The value can be any value within the range of 10nm to 100nm.

[0027] The technical principles and effects of the above invention are: (1) Figure 13 , after computational research, it was found that T cr The smaller the value, the higher the crack height of the waterproof layer. H cr The bigger, T cr rightH cr The thickness of the waterproof layer in the longitudinal direction at the moment of initial cracking of the concrete has a significant impact on the final cracking height of the waterproof layer; (2) T cr As small as 100nm, H cr The value of tends to be constant, and the scale of 10nm~100nm is also close to the scale of cement stone voids or hydrated calcium silicate gel in concrete; In addition, from the perspective of energy, T cr When the size is small enough, the bottom surface of the waterproof layer segments on both sides of the virtual interface layer is pulled and pushed by the concrete and moves from the longitudinal symmetry center line ± T cr / 2 position moves to ± W cr The work done at the position of / 2 is similar, because the force of concrete pushing and pulling the waterproof layer is F The peak value depends on the tensile strength of the waterproof material. T cr The relationship between the force and the work done by the force is W cr minus T cr ,when T cr At the nanometer level, much smaller than W cr (millimeter level), the stroke of work is also not much different (i.e. W cr - T cr ≈ W cr ),therefore T cr The work done at the nanometer level tends to be constant, that is, ∫( W cr - T cr )d F ≈∫ W cr d F , so H cr (3) Therefore, when it is difficult to measure the peaks and valleys of the concrete surface and the distance between the molecules or molecular clusters of the waterproof layer material, it can also be directly measured according to T cr The value is taken in the range of 10nm to 100nm to calculate the stress on the waterproof layer more safely.

[0028] Preferably, in S4 W cr =W 0(0.74 h 0+ c s + d s / 2) / (0.74 h 0), where W 0 is the crack width value calculated according to the industry standard of the designed reinforced concrete structure. W The load used when 0 is the basic load combination value under the ultimate limit state. h 0 is the distance from the center of the steel bar to the compressive edge of the concrete, c s is the thickness of the steel bar cover, d s is the diameter of the steel bar.

[0029] The technical principles and effects of the above invention are as follows: (1) The crack width calculated by the existing specifications is the concrete crack width at the steel bar position. Figure 5 ( W cr The calculation diagram of reinforced concrete bending members shows that the internal force arm of the steel bar is generally taken as 0.87. h 0, that is, the distance from the steel bar to the line of action of the resultant force in the concrete compression zone is 0.87 h 0, it can be deduced that the crack height of the concrete crack is 0.87 h 0-(1 h 0-0.87 h 0)=0.74 h 0, considering that the elastic modulus of concrete material is large (much larger than that of waterproof material), it can be considered that the gap after concrete cracking is approximately triangular, so according to the geometric relationship of similar triangles, it can be deduced that W cr = W 0(0.74 h 0+ c s + d s / 2) / (0.74 h 0); (2) The cracking of the waterproof layer is mainly due to the height of the cracks. The higher the cracks are, the worse the waterproof performance will be. When the cracks in the reinforced concrete structure recover to a smaller width, the height of the cracks in the waterproof layer will not recover. Therefore, the height of the cracks in the waterproof layer should be calculated according to the most unfavorable basic combination value of the load borne by the reinforced concrete structure below, rather than according to the load frequency combination value when checking the crack width of the reinforced concrete structure itself.

[0030] Preferably, the tensile stress-tensile strain constitutive relationship of the material in S5 is implemented according to the stress-strain curve measured by the uniaxial tensile test, and the compressive stress-compressive strain constitutive relationship of the material in S5 is implemented according to the stress-strain curve measured by the uniaxial compression test, and the loading time of the uniaxial tensile and compression tests does not exceed 10s.

[0031] The technical principles and effects of the above invention are as follows: the stress-strain curve of the waterproof material has nonlinear characteristics, and a creep effect will occur when the loading time is long, which is significantly different from the stress-strain curve when the loading time is short. Therefore, the calculation should be performed according to the stress-strain curve measured by loading in a short time to obtain a more accurate calculation result.

[0032] Preferably, the stress-strain constitutive relationship of the waterproof layer material other than the virtual interface layer in S5 is elastic, and its elastic modulus is E e = σ 1% / ε 1% , σ 1% is the stress at 1% elongation when the waterproof layer is subjected to a uniaxial tensile test, ε 1% is the strain at 1% elongation when the waterproof layer is subjected to a uniaxial tensile test; the material stress-strain constitutive relationship of the virtual interface layer is determined by the following formula:

[0033] In the formula σ x 、 ε x are the longitudinal stress and longitudinal strain of the virtual interface layer, σ cr The elongation of the waterproof layer material after uniaxial stretching to break ε cr The corresponding stress.

[0034] The technical principles and effects of the above invention are as follows: (1) When concrete cracks, the cracking of the waterproof layer is a transient process, in which the nonlinear creep of the waterproof material is very small. The waterproof material of the non-virtual interface layer is mainly subjected to compression and shear, so it basically presents a linear elastic stress characteristic. When constitutive measurement tests cannot be carried out due to limited conditions, its elastic modulus can be simplified to the stress divided by the strain under small deformation; (2) The waterproof material of the virtual interface layer is mainly subjected to tension, and its constitutive relationship cannot be simply regarded as elastic. It can be simplified to a brittle material according to the above formula, and its deformation parameter can be simplified by dividing the stress before large deformation to cracking by the strain to simplify the calculation.

[0035] Preferably, in S5, Δ is calculated Tz Finite element modeling is used for calculation, the virtual interface layer is simulated by discrete crack interface unit or nonlinear spring, the waterproof layer segments on both sides of the virtual interface layer are meshed by plane stress unit, and the mesh size at the virtual interface layer is not greater than d z , the nodes of the plane stress elements on both sides of the virtual interface layer are connected through discrete crack interface elements or nonlinear springs of the virtual interface layer, and material nonlinearity and geometric nonlinearity effects are taken into account during the calculation process;

[0036] Normal stiffness modulus of discrete crack interface elements K n = E s / T cr , tangential stiffness modulus K t = K n / [2×(1+ v )], E s is the deformation modulus of the virtual interface layer and E s = σ cr / ε cr , σ cr Stretch the waterproof material to its breaking elongation ε cr The corresponding stress is v is the Poisson's ratio of the waterproof layer material; the axial force of the nonlinear spring F x and axial displacement△ T x The relationship is determined by the following formula:

[0037] In the formula S z For vertical position z The vertical size of the grid at , and the △ T x =△ T z .

[0038] The technical principles and effects of the above invention are as follows: (1) The cracking of the waterproof layer material is a process with both geometric nonlinearity and material nonlinearity, and it is necessary to use discrete crack interface units or nonlinear springs to simulate the process. In addition, multiple cracks generally do not appear at the same time, that is, the cracking of the waterproof layer is mainly unidirectional, so the use of plane stress units can significantly reduce the calculation amount of the nonlinear finite element model; (2) According to the discrete crack interface unit, the cracking of the waterproof layer is mainly unidirectional, and the plane stress unit can significantly reduce the calculation amount of the nonlinear finite element model. K n =interface normal stress σ n / Normal relative displacement under this stress△ T x From the definition of , we can see that K n = σ n / △ T x =( E s ε x ) / ( ε x T cr )= E s / T cr , ε x is the strain of the discrete crack interface element.

[0039] Preferably, when the waterproof layer contains fiber reinforcement material, the direction perpendicular to the longitudinal direction and the vertical direction is defined as the transverse direction, and the transverse width of the waterproof layer is defined as B The total cross-sectional area of ​​the fiber reinforcement material in the longitudinal direction within the range A r Should meet the following requirements: A r ≥ K r BH cr σ cr / f rd , where K r is the safety factor and K r >1, B is the horizontal width of the waterproof layer, f rd is the design tensile strength value of the fiber reinforced material, c r It is the vertical distance from the fiber reinforced material to the top surface of the concrete.

[0040] The technical principle and effect of the above invention are: Figure 6 It can be seen that when the total cross-sectional area of ​​the fiber reinforced material is large, the fiber reinforced material will bear the crack height of the waterproof layer when there is no fiber reinforced material. H cr The tensile force within the range will not be broken, so when the waterproof layer cracks to the height of the fiber reinforcement material, the cracks will hardly expand upwards. After the fiber reinforcement material is set, the cracking mode and trend of the waterproof layer are changed, and the "vertical tearing trend along the virtual interface layer" of the waterproof layer is changed to the "longitudinal peeling trend along the fiber reinforcement material". Figure 17 The refined nonlinear finite element calculation results also reflect this feature.

[0041] The present invention also provides a method for maintaining the long-term performance of reinforced concrete structure waterproofing, which is based on the above-mentioned reinforced concrete structure waterproofing design method. H - H cr ≥ K f H min , K f is the safety factor and K f >1, H min The waterproof layer design is terminated when the minimum waterproof layer thickness that meets the waterproof performance requirements is not considered without considering the cracking of concrete; otherwise, the waterproof layer thickness is increased to H + , until H + ≥ H cr +K f H min , then the waterproof layer design is completed.

[0042] The technical principle and effect of the above invention are: according to the method of the present invention, the remaining uncracked thickness of the waterproof layer after cracking under the most unfavorable load is still greater than H min It is a key measure to achieve long-term performance maintenance of waterproof layer and reinforced concrete structure, and it is also a key issue that the existing technology has not considered and paid attention to.

[0043] The beneficial effects of the present invention are summarized as follows:

[0044] The present invention proposes a waterproofing design method for reinforced concrete structures and a method for maintaining their long-term performance. The method analyzes the mechanism by which concrete cracking leads to cracking of the waterproof layer and provides a crack resistance calculation method for the waterproof layer design process. This method facilitates the design of waterproof layers in reinforced concrete structures such as bridges and roads, effectively maintains the long-term performance of the waterproof layer, and thus further extends the service life of the waterproof layer. The present invention has the following beneficial effects:

[0045] 1. The present invention proposes the essential mechanism of cracking of waterproof layer caused by cracking of concrete, that is, the cracking of concrete is equivalent to applying various W cr / 2 forced displacement, and when the concrete cracks, the bottom surface of the waterproof layer will inevitably crack. The key lies in the crack height of the waterproof layer. H cr The calculation of the remaining solid thickness of the waterproof layer after cracking is ensured to be still greater than the minimum solid thickness of the waterproof layer that meets the waterproof performance requirements without considering the cracking of concrete. The mechanism proposed by the present invention is the key issue ignored by the prior art.

[0046] Second, the present invention found that at the moment of initial cracking of concrete, the thickness of the waterproof layer in the longitudinal direction is T cr Final cracking height of waterproof layer H cr There is a significant impact and it is demonstrated that T cr The stress analysis is carried out by taking values ​​at the micron to nanometer scale; and further, a calculation method for the crack resistance of the waterproof layer and a long-life design method are given, which can facilitate the waterproof design of various reinforced concrete structures and achieve their long-term performance maintenance, thereby significantly extending their service life.

[0047] 3. The present invention discovered the longitudinal thickness of the virtual interface layer of the waterproof layer T cr The final crack height of the waterproof layer close to the nanoscale H cr The calculated results tend to be constant, proving that H cr Basically not affected by the thickness of the waterproof layer H , the longitudinal segment length used in the waterproof layer stress calculation L ( L ≥4 H Poisson's ratio of the waterproof layer v The calculation results of the present invention clarify the key influencing factors of the crack height of the waterproof layer, which is helpful to improve the design of the waterproof layer and is applicable to bridges, roads, tunnels, buildings and hydraulic structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1It is a schematic diagram of a concrete structure with a waterproof layer and steel bars and cracks thereof commonly used in the background art of the present invention;

[0049] Figure 2 Schematic diagram of a simplified mechanical model for analyzing cracking of a waterproof layer without fiber reinforcement material according to the present invention;

[0050] Figure 3 Schematic diagram of the mechanism of concrete cracking inducing waterproof layer cracking based on interface roughness analysis of the present invention;

[0051] Figure 4 This is a schematic diagram of the mechanism of concrete cracking inducing waterproof layer cracking based on molecular scale analysis of the present invention;

[0052] Figure 5 yes W cr Schematic diagram of the calculation;

[0053] Figure 6 This is a simplified mechanical model for analyzing cracking of waterproof layers with fiber-reinforced materials.

[0054] Figure 7 1 is an overall front view of the refined initial finite element model of the waterproof layer segment established in Example C of the present invention;

[0055] Figure 8 The initial finite element model in Example C of the present invention is W cr Schematic diagram of deformation when = 0.1mm;

[0056] Figure 9 The initial finite element model in Example C of the present invention is W cr Schematic diagram of deformation when = 0.18mm;

[0057] Figure 10 The initial finite element model in Example C of the present invention is W cr Schematic diagram of deformation when θ = 0.18 mm (only the elements near the virtual interface layer are shown);

[0058] Figure 11 The initial finite element model in Example C of the present invention is W cr Schematic diagram of the discrete crack interface unit stress when = 0.18mm;

[0059] Figure 12 The initial finite element model of Example C of the present invention is W cr Schematic diagram of deformation when = 0.2mm;

[0060] Figure 13 The initial finite element model of Example C of the present invention at different interface thicknesses T cr Comparative schematic diagram of the cracking results below;

[0061] Figure 14 The initial finite element model of Example C of the present invention is in different longitudinal lengths. L Schematic diagram of the comparison of cracking results under ;

[0062] Figure 15 The initial finite element model of Example C of the present invention is H Schematic diagram of the comparison of cracking results under ;

[0063] Figure 16 1 is a schematic diagram of the entirety of the initial finite element model of Example C of the present invention after fiber reinforcement material is added;

[0064] Figure 17 The initial finite element model is added with fiber reinforcement W cr Schematic diagram of deformation when = 0.2mm;

[0065] Figure 18 The initial finite element model is added with fiber reinforcement W cr Schematic diagram of fiber stress when = 0.2mm;

[0066] Figure 19 This is a photo of the anti-cracking test of the waterproof layer without fiber reinforcement material in Example C of the present invention.

[0067] Figure 20 This is a photo of cracking and water leakage in the waterproof layer without fiber reinforcement material in Example C of the present invention;

[0068] Figure 21 These are photos showing the crack resistance test and cracking condition of the waterproof layer with fiber reinforcement material in Example C of the present invention.

[0069] Description of reference numerals:

[0070] 1-concrete; 12-rebar; 13-crack; 14-virtual interface layer; 15-fiber reinforcement; 111-concrete material molecules or clusters;

[0071] 2- waterproof layer; 21- left half waterproof layer; 22- right half waterproof layer; 222- waterproof layer molecules or clusters;

[0072] 3-microscopic interface; 31-peak; 32-trough;

[0073] G Z -Vertical rigid support. DETAILED DESCRIPTION

[0074] The present invention is further described in detail below in conjunction with test examples and specific implementation methods, but this should not be understood as the scope of the above-mentioned subject matter of the present invention being limited to the following embodiments. All technologies implemented based on the contents of the present invention belong to the scope of the present invention.

[0075] Example A

[0076] The present invention provides a design method for waterproofing a reinforced concrete structure, wherein the reinforced concrete structure includes concrete 1, a waterproof layer 2, and steel bars 12; the steel bars 12 are provided in the concrete 1, and the top surface of the concrete 1 is covered with the waterproof layer 2; the design method for waterproofing a reinforced concrete structure includes the following steps:

[0077] S1. The average thickness of the waterproof layer 2 is H The tensile direction along the concrete 1 is the longitudinal direction, the direction perpendicular to the tensile direction of the concrete 1 and parallel to the surface of the waterproof layer 2 is the transverse direction, and the direction perpendicular to the surface of the waterproof layer 2 is the vertical direction. The longitudinal length is L The lateral width of the waterproof layer 2 segment is B Take any value that satisfies L ≥4 H ;

[0078] S2. Assume that there is a virtual interface layer 14 in the waterproof layer 2 segment. The mid-axis plane of the virtual interface layer 14 coincides with the longitudinal middle section of the waterproof layer 2 segment. The thickness of the virtual interface layer 14 in the longitudinal direction is T cr , the height of the virtual interface layer 14 along the vertical direction is H , the width of the virtual interface layer 14 along the lateral direction is B The lengths of the waterproof layer 2 segments on both sides of the virtual interface layer 14 are L / 2- T cr / 2, the segments of the waterproof layer 2 on both sides of the virtual interface layer 14 are connected through the virtual interface layer 14;

[0079] S3. Set up vertical rigid support G on the bottom surface of waterproof layer 2 segment Z ;

[0080] S4. The bottom surface of the waterproof layer 2 segments on both sides of the virtual interface layer 14 are respectively applied with forced displacements in opposite directions and away from the virtual interface layer 14. W cr / 2, W cr is the longitudinal width of the crack 13 generated on the top surface of the concrete 1 under the action of external force;

[0081] S5. Calculate the vertical distance between the bottom of the virtual interface layer 14 and the bottom surface of the waterproof layer 2 segment and define it as z , let 0 <d z <0.1 H According to the stress-strain constitutive relationship of the waterproof layer material and conventional mechanics methods, the forced displacement in step S4 is calculated. z The relative displacement of the two sides of the virtual interface layer 14 at △ T z ,△ T z The value is positive if it is relatively far away;

[0082] S6. If △ T z ≥ ε cr T cr and z +d z < H , ε cr is the elongation at break of the waterproof material, then it is considered z The virtual interface layer 14 at the location is broken and the distance from the bottom surface of the waterproof layer segment is deleted. z Chuzhi z +d z The virtual interface layer 14 at z Chuzhi z +d z The waterproof layer 2 segments on both sides of the virtual interface layer 14 at the position are disconnected, and all the waterproof layer 2 segments are restored to the spatial positions before the forced displacement is applied, and then steps S4-S6 are repeated; otherwise, step S7 is entered;

[0083] S7. Crack height of waterproof layer 2 H cr Take the vertical distance between the bottom of the current virtual interface layer 14 and the bottom surface of the waterproof layer 2 segment z And take safety into account z ,Right now H cr = z +d z ;

[0084] S8. If H - H cr >0, the waterproof layer 2 is not completely broken after the concrete 1 cracks, and the design of the waterproof layer 2 is terminated; otherwise, the thickness of the waterproof layer 2 is increased. H , then go to step S1.

[0085] In this embodiment, the virtual interface layer 14 in step S2 coincides with the mid-axis plane of the waterproof layer 2 segment. Under the action of the cracking of the concrete 1, the left half waterproof layer 21 and the right half waterproof layer 22 are forced to move in opposite directions and away from the virtual interface layer 14. W cr / 2, thus causing the waterproof layer 2 segment to crack at the virtual interface layer 14. When designing the waterproof layer 2, since the thickness of the waterproof layer 2 is much smaller than the thickness of the reinforced concrete structure at the bottom of the waterproof layer 2, and the elastic modulus of the waterproof layer 2 is much smaller than that of the concrete 1 and the steel bars 12, the stress on the concrete 1 structure shared by the waterproof layer 2 before and after the cracking of the reinforced concrete structure can be ignored. This makes the width of the crack 13 of the reinforced concrete structure completely dependent on the configuration of its steel bars 12 and the external load it is subjected to. The crack width of the concrete 1 will not be affected by the waterproof layer 2 at all, that is, the cracking of the concrete 1 is equivalent to applying opposite directions to the bottom surface of the waterproof layer 2 on both sides of the crack 13. W cr / 2 forced displacement, resulting in cracking of waterproof layer 2.

[0086] On the premise of clarifying the cracking mechanism of the waterproof layer 2, the design method of the waterproof layer 2 further determines the cracking height of the waterproof layer 2 caused by the cracking displacement of the reinforced concrete structure through iterative calculation of steps S4-S6. H cr , so that when △ T z < ε cr T cr When the waterproof layer 2 is further designed and improved, the process proceeds to step S7 to ensure that when the reinforced concrete structure is instantaneously cracked under the most unfavorable load, the waterproof layer 2 on the top surface is not completely broken, thereby ensuring the waterproofness of the waterproof layer 2 on the top surface of the reinforced concrete structure. Figure 2 As shown, the vertical distance between the lowest position of the virtual interface layer 14 and the bottom surface of the waterproof layer 2 segment is defined as z , so when z The relative displacement of the two sides of the virtual interface layer 14 at △ T z ≥ ε cr T cr Then the waterproof layer 2 segment is z The virtual interface at is completely broken, if the waterproof layer 2 segment is z If the virtual interface at the position is completely broken, return to the initial step and iterate the thickness of the waterproof layer 2 until △ T z < ε cr Tcr , so that the waterproof layer 2 will crack under the most unfavorable load z The virtual interface at the point will not be completely disconnected. Since the elastic modulus of concrete is usually tens of thousands times that of waterproof material, Figure 2 As shown, the reinforced concrete structure at the bottom of the waterproof layer 2 can be regarded as a vertical rigid support G for the waterproof layer 2. Z . Further, combined with the attached Figure 14 It can be seen that when L ≥4 H hour, H cr The calculation result is basically not affected by the longitudinal segment length taken when calculating the force of waterproof layer 2. L The impact of L If the value is too small, it will cause large calculation errors, while avoiding L If the value is too large, it will lead to excessive computational complexity.

[0087] In a preferred embodiment, the average thickness of the waterproof layer 2 in step S1 is H Calculation is based on the solid thickness of the waterproof layer 2 after curing and curing. In this embodiment, the design and construction of the waterproof layer 2 in the prior art are controlled based on the liquid thickness of the waterproof layer 2 after application. However, the actual waterproof layer 2 is already in a solid state when the concrete 1 structure is subjected to stress and cracks. Most waterproof coatings can reduce their thickness by more than 30% after curing compared to the liquid thickness as their water or other organic solvent components evaporate. Therefore, if the stress calculation is based on the liquid design thickness value of the prior art, the result will have a significant error. Therefore, the calculation should be based on the solid thickness after curing and curing.

[0088] like Figure 3 As shown, in step S2 T cr The average of the horizontal distances between adjacent peaks 31 on the surface of the concrete 1 within any 100 μm×100 μm range is taken. The peaks 31 and troughs 32 on the surface of the concrete 1 are measured using equipment with a maximum resolution in the range of 1 nm to 1 μm.

[0089] In this embodiment, based on Figure 3From the schematic diagram of the mechanism of cracking of concrete 1 causing cracking of waterproof layer 2 based on the interface roughness analysis, it can be seen that the surface of the concrete 1 structure is uneven at the microscopic level, and there are a large number of undulating peaks 31 and troughs 32 at the microscopic scale, which causes the microscopic interface 3 between waterproof layer 2 and concrete 1 to be rough and undulating. The peaks 31 of concrete 1 are embedded in waterproof layer 2 like shear nails in a steel-concrete composite structure, and the waterproof layer 2 will fill in the troughs 32 of concrete 1 to wrap the peaks 31 of concrete 1. Therefore, the interaction between concrete 1 and waterproof layer 2 is not only the chemical adsorption force and friction force between the two materials, but more of the mutual extrusion and bite force. Therefore, when concrete 1 cracks and opens to both sides of the crack 13, it will also drive the waterproof layer 2 to open to both sides of the crack 13, that is, the moment concrete 1 cracks, the waterproof layer 2 will be torn. Moreover, the trough 32 on the surface of the concrete 1 is relatively weak, and cracks 13 usually occur at the trough 32. When the crack 13 of the concrete 1 at the trough 32 opens to a certain width, the normal tension of the micro interface 3 between the concrete 1 and the waterproof layer 2 at the trough 32 will exceed the chemical adsorption force between the concrete 1 and the waterproof layer 2, thereby causing the micro interface 3 between the concrete 1 and the waterproof layer 2 to separate; at the same time, the concrete 1 outside the adjacent crests 31 on both sides of the trough 32 will exert an extrusion effect on the outer waterproof layer 2, thereby pushing the waterproof layer 2 outside the crest 31 to continue to open to both sides of the crack 13; therefore, the force nature of the waterproof layer 2 after the concrete 1 cracks is that for a micro segment of the waterproof layer 2 (i.e., the virtual interface layer 14) with a longitudinal thickness equal to the distance between the adjacent crests 31 on both sides of the trough 32, the bottom surfaces of the waterproof layer 2 on both sides of the virtual interface layer 14 are each subjected to a force that opens to both sides. W cr / 2 forced displacement, the waterproof layer 2 of the virtual interface layer 14 is pulled into an elastic-plastic state and eventually cracks to H cr The height of the virtual interface layer 14 is such that the waterproof layer 2 outside the virtual interface layer 14 is squeezed and is basically in elasticity and there is a tension-compression interface between the waterproof layer 2 and the tensioned segment. It can be seen that the thickness of the virtual interface layer 14 is T cr The value should be the horizontal distance between adjacent wave crests 31, that is, the longitudinal length of the micro segment.

[0090] Furthermore, according to the attached Figure 3As can be seen from the microscopic observation data of the surface of concrete 1, the horizontal distance between the peaks 31 and troughs 32 on the surface of concrete 1 is between 1 nm and 1 μm. Therefore, it is necessary to measure the undulating characteristics of the surface of concrete 1 using equipment at this scale and then calculate its statistical mean. This is to facilitate the force calculation and design of the waterproof layer 2 based on its statistical probability based on the concept of the probabilistic limit state method. Therefore, the measuring equipment usually includes optical microscopes, atomic force microscopes, scanning electron microscopes, etc., to accurately measure the undulating characteristics of the surface of concrete 1 on both sides.

[0091] See also Figure 4 , in step S2 T cr Take the average value of the distance between material molecules or molecular clusters when the waterproof layer 2 segment is not subjected to external forces other than gravity. Figure 4 Schematic diagram of the mechanism of cracking of concrete 1 leading to cracking of waterproof layer 2 based on molecular scale analysis. To ensure the safety of waterproof layer 2, T cr A smaller value is taken to calculate the stress on the waterproof layer 2. At this time, the limit principle can be considered, that is, assuming that the force between the concrete material molecules or clusters 111 and the adjacent waterproof layer molecules or clusters 222 is infinite so that there will be no interface separation or slip between the two. At this time, the essence of the cracking of the concrete 1 and the waterproof layer 2 is that the longitudinal distance between their molecules or clusters suddenly changes from the nanometer level to the millimeter level, that is, the distance increases by nearly 100,000 times and appears as a crack 13 visible to the naked eye. Although the longitudinal distance increment will decrease rapidly as the vertical distance between the waterproof layer molecules or clusters 222 and the surface of the concrete 1 increases, for the waterproof layer material near the surface of the concrete 1, its fracture elongation performance of only 800% is completely insufficient to withstand the longitudinal distance increment of nearly 100,000 times. Therefore, when the concrete 1 cracks, the waterproof layer material near its surface will inevitably crack as well, and crack vertically to a certain height. H cr Then the cracking stops, so the key to cracking the waterproof layer 2 is to solve H cr The value of H cr The thickness of the waterproof layer 2 is designed with a value of to ensure that the waterproof layer 2 will not be completely broken after the concrete 1 cracks, further ensuring its strength, avoiding damage to the waterproof layer 2, and maintaining good anti-seepage performance.

[0092] like Figure 13 As shown, in step S2, 10nm≤ T cr ≤100nm. In this embodiment, calculations have shown that T cr The smaller the value, the higher the crack height of the waterproof layer 2. H crThe bigger, T cr right H cr The thickness of the waterproof layer 2 in the longitudinal direction at the moment of initial cracking of the concrete 1 has a significant impact on the final cracking height of the waterproof layer 2. T cr As small as 100nm, H cr The value of tends to be constant, and the scale of 10nm~100nm is also close to the scale of cement stone voids or hydrated calcium silicate gel in concrete 1; In addition, from the perspective of energy, T cr When the virtual interface layer 14 is small to a certain extent, the bottom surface of the waterproof layer 2 segments on both sides is pulled and pushed by the concrete 1, and the distance from the longitudinal symmetry center line ± T cr / 2 position moves to ± W cr The work done at the position of / 2 is almost the same, because the force of concrete 1 pushing and pulling waterproof layer 2 F The peak value depends on the tensile strength of the waterproof material. The peak value of the force of concrete 1 pushing and pulling the waterproof layer 2 is T cr The relationship between the force and the work done is not significant. W cr minus T cr ,when T cr At the nanometer level, much smaller than W cr (millimeter level), the stroke of work is also not much different (i.e. W cr - T cr ≈ W cr ),therefore T cr The work done at the nanometer level tends to be constant, that is, ∫( W cr - T cr )d F ≈∫ W cr d F , so H cr Therefore, when it is difficult to measure the peaks 31 and valleys 32 on the surface of the concrete 1 and the distance between the molecules or molecular clusters of the waterproof layer material, it is also possible to directly press T crThe force on the waterproof layer 2 is calculated by taking values ​​in the range of 10nm to 100nm. In a preferred embodiment, when the waterproof layer 2 needs to reserve a larger safety factor, T cr Take 10nm.

[0093] See also Figure 5 , in step S4 W cr = W 0(0.74 h 0+ c s + d s / 2) / (0.74 h 0); among them, W 0 is the crack width calculated according to the industry standard of the designed reinforced concrete structure. W The load used when 0 is the basic load combination value under the ultimate limit state. h 0 is the distance from the center of the steel bar 12 to the compressive edge of the concrete 1, c s is the protective layer thickness of the steel bar 12, d s is the diameter of the steel bar 12.

[0094] The width of the crack 13 calculated by the existing specifications is the width of the concrete crack 13 at the position of the steel bar 12. The internal force arm of the steel bar 12 of the reinforced concrete 1 bending member is generally taken as 0.87 h 0, that is, the distance from the steel bar 12 to the line of action of the resultant force in the compression zone of concrete 1 is 0.87 h 0, it can be inferred that the crack height of concrete 1 crack 13 is 0.87 h 0-(1 h 0-0.87 h 0)=0.74 h 0, considering that the elastic modulus of concrete material is much greater than that of waterproof material, it can be considered that the gap after the crack of concrete 1 is approximately triangular, so according to the geometric relationship of similar triangles, it can be deduced that W cr = W 0(0.74 h 0+ c s + d s / 2) / (0.74 h 0), thus achieving W crAt the same time, considering that the cracking of the waterproof layer is mainly a problem of crack height, the higher the crack, the worse the anti-seepage performance of the waterproof layer, and the crack height of the waterproof layer will not recover when the crack of the reinforced concrete structure recovers to a smaller width value, the crack height of the waterproof layer should be calculated according to the most unfavorable load basic combination value borne by the reinforced concrete structure below, rather than the load frequent combination value when checking the crack width of the reinforced concrete structure itself.

[0095] In a preferred embodiment, the tensile stress-tensile strain constitutive relationship of the waterproofing material in step S5 is implemented based on the stress-strain curve measured by a uniaxial tensile test. The compressive stress-compressive strain constitutive relationship of the material in step S5 is implemented based on the stress-strain curve measured by a uniaxial compression test. The loading time for both the uniaxial tensile test and the uniaxial compression test does not exceed 10 seconds. The stress-strain curve of the waterproofing material has nonlinear characteristics, and creep effects occur when loading for a long time, which differs significantly from the stress-strain curve measured with a short loading time. Therefore, the calculation should be performed based on the stress-strain curve measured with a short loading time to obtain the most accurate results.

[0096] Furthermore, in step S5, the stress-strain constitutive relationship of the waterproof layer material of the non-virtual interface layer 14 is elastic, and its elastic modulus is E e = σ 1% / ε 1% , σ 1% is the stress at 1% elongation during uniaxial tensile test of waterproof layer 2, ε 1% is the strain at 1% elongation during the uniaxial tensile test of the waterproof layer 2; the material stress-strain constitutive relationship of the virtual interface layer 14 is determined by the following formula:

[0097] in, σ x is the longitudinal stress of the virtual interface layer 14, ε x is the longitudinal strain of the virtual interface layer 14, σ cr The elongation of the waterproof layer material after uniaxial stretching to break ε cr The corresponding stress.

[0098] In this embodiment, the cracking of the waterproof layer 2 when the concrete 1 cracks is a transient process. The nonlinear creep of the waterproof material during this cracking process is very small. The waterproof material of the non-virtual interface layer 14 is mainly subjected to compression and shear, so it basically presents a linear elastic stress characteristic. When the constitutive measurement test cannot be carried out due to limited conditions, its elastic modulus can be simplified to the stress divided by the strain under small deformation. The waterproof material of the virtual interface layer 14 mainly bears tension, and its constitutive relationship cannot be simply regarded as elastic. It can be simplified to a brittle material according to the above formula, and its deformation parameter can be calculated by dividing the stress before cracking by the strain to simplify the calculation.

[0099] In step S5, △ is calculated by finite element modeling T z The virtual interface layer 14 is simulated by discrete crack 13 interface units or nonlinear springs. The waterproof layer 2 segments on both sides of the virtual interface layer 14 are meshed by plane stress units. The mesh size at the virtual interface layer 14 is not larger than d z The nodes of the plane stress elements on both sides of the virtual interface layer 14 are connected through the discrete crack 13 interface elements or nonlinear springs of the virtual interface layer 14. The material nonlinearity and geometric nonlinearity effects are taken into account during the calculation process. The normal stiffness modulus of the discrete crack 13 interface element is K n = E s / T cr , tangential stiffness modulus K t = K n / [2×(1+ v )], E s is the deformation modulus of the virtual interface layer 14 and E s = σ cr / ε cr , σ cr Stretch the waterproof material to the breaking elongation ε cr The corresponding stress is v is the Poisson's ratio of the waterproof layer material; the axial force of the nonlinear spring F x and axial displacement△ T x The relationship is determined by the following formula:

[0100] In the formula S z For vertical position zThe vertical size of the grid at , and the △ T x =△ T z .

[0101] The cracking of waterproof layer material is a process with both geometric nonlinearity and material nonlinearity. It is necessary to use discrete crack 13 interface elements or nonlinear springs to simulate the cracking process of waterproof layer material. In addition, cracks 13 generally do not appear in multiple directions at the same time, that is, the cracking of waterproof layer 2 is mainly caused by unidirectional force. Therefore, the use of plane stress elements can significantly reduce the calculation amount of nonlinear finite element model. K n =interface normal stress σ n / Normal relative displacement under this stress△ T x From the definition of , we can see that K n = σ n / △ T x =( E s ε x ) / ( ε x T cr )= E s / T cr , ε x is the strain of the discrete crack 13 interface unit.

[0102] like Figure 6 As shown, the waterproof layer 2 includes a fiber reinforced material 15, and the direction perpendicular to the longitudinal direction and the vertical direction is defined as the transverse direction. The transverse width of the waterproof layer 2 is B The total cross-sectional area of ​​the fiber reinforcement material 15 in the longitudinal direction within the range A r Should meet the following requirements: A r ≥ K r BH cr σ cr / f rd , where K r is the safety factor and K r >1, B is the lateral width of the waterproof layer 2,f rd is the design tensile strength value of the fiber reinforced material 15, c r It is the vertical distance from the fiber reinforcement material 15 to the top surface of the concrete 1.

[0103] In this embodiment, a fiber reinforcement material 15 is provided in the waterproof layer 2. When the total cross-sectional area of ​​the fiber reinforcement material 15 is large, the fiber reinforcement material 15 will bear the crack height of the waterproof layer 2 when the fiber reinforcement material 15 is not provided. H cr The waterproof layer 2 will not be broken by the tensile force within the range, so when the crack 13 of the waterproof layer 2 is cracked to the height of the fiber reinforcement material 15, the crack 13 will no longer expand upward. After the fiber reinforcement material is provided, the cracking mode and trend of the waterproof layer are changed, and the "vertical tearing trend along the virtual interface layer" of the waterproof layer is changed to the "longitudinal peeling trend along the fiber reinforcement material". Figure 17 The refined nonlinear finite element calculation results further reflect this feature.

[0104] Example B

[0105] Based on the above-mentioned reinforced concrete structure waterproof design method, the present invention also provides a method for maintaining the long-term performance of reinforced concrete structure waterproofing. H - H cr ≥ K f H min , K f is the safety factor and K f >1, H min The design of waterproof layer 2 is completed in order to meet the minimum waterproof performance requirements without considering the cracking of concrete 1. H - H cr < K f H min , increase the thickness of the waterproof layer 2 to H + , until H + ≥ H cr +K f H min , then the design of waterproof layer 2 is completed. H minTake the minimum waterproof layer 2 thickness required by the industry specification of the designed reinforced concrete structure.

[0106] In this embodiment, by ensuring that the remaining uncracked thickness of the waterproof layer 2 after cracking under the most unfavorable load is still greater than K f H min , so that the waterproof layer 2 can effectively resist the tensile force after the concrete 1 cracks, avoid the waterproof layer 2 from breaking as the concrete 1 cracks, effectively improve the service life of the waterproof layer 2, and improve its anti-seepage performance.

[0107] Example C

[0108] In order to verify the technical effect of the present invention, the longitudinal length L =10mm, vertical thickness H =1mm, horizontal width B =1mm waterproof layer 2 segments to establish a refined initial finite element model as follows Figure 7 The main modeling parameters are as follows: (1) The waterproof layer 2 of the non-virtual interface layer 14 adopts the linear elastic material constitutive parameters, and its elongation at break is ε cr =800% and tensile strength σ cr =0.5MPa (equivalent to the performance parameters of the common PB-I type polymer modified asphalt waterproof coating for roads and bridges), elastic modulus E e =1.0MPa, Poisson's ratio v = 0.3, plane stress unit is used for meshing, the mesh size near the virtual interface layer 14 is 0.01mm × 0.01mm, and the mesh size away from the virtual interface layer 14 is thickened to 0.05mm × 0.01mm to reduce the calculation amount of finite element analysis; (2) the longitudinal thickness of the virtual interface layer 14 T cr = 20nm, a two-dimensional discrete crack interface unit is used for simulation. The nodes on both sides of the discrete crack interface unit are rigidly coupled with the nodes of the plane stress unit. The constitutive structure of the discrete crack interface unit is brittle material, and its normal stiffness modulus is K n = E s / T cr = σ cr / ε cr / T cr =0.5 / 800% / 20e-6 =3125N / mm 3 , tangential stiffness modulusK t = K n / [2×(1+ v )]=3125 / [2×(1+0.3)]=1202N / mm 3 , it is defined that when the normal tensile stress of the discrete crack interface unit reaches 0.5MPa (that is, the relative longitudinal displacement of the nodes on both sides of the discrete crack interface unit reaches 800%× T cr When) K n The value suddenly changes to 0, which is equivalent to the occurrence of brittle cracking and the deletion of the virtual interface layer 14 at the corresponding position. At this time, the normal tensile stress of the interface unit of the discrete crack 13 also suddenly changes to 0; (3) Vertical rigid supports are set for all nodes at the bottom of the waterproof layer 2 on both sides of the virtual interface layer 14 to simulate the vertical constraint of concrete 1 on the waterproof layer 2, and a leftward rigid support is applied to all nodes on the bottom surface of the waterproof layer 2 segment on the left side of the virtual interface layer 14. W cr / 2 forced displacement, correspondingly applied to the bottom surface of the right waterproof layer 2 segment W cr A forced displacement of / 2, W cr According to the 100 levels of loading from 0 to 0.2 mm, each load step W cr The increment is 0.002mm.

[0109] The calculation results of the above initial finite element model are as follows Figures 8 to 12 As shown, the analysis shows that: (1) Figure 8 This shows that the above model is loaded into W cr =0.1mm, we can know the crack height of waterproof layer 2 at this time. H cr =0.14mm, at this time there is still a large margin of uncracked height; (2) Figures 9 and 10 This indicates that the above model is loaded into W cr =0.18mm, we can know the crack height of waterproof layer 2 at this time. H cr =0.51mm, at this time the waterproof layer 2 has serious cracks; Figure 11 This indicates that the above model is loaded into W cr=0.18mm, the stress of the discrete crack 13 interface unit is 0, and it can be seen that the stress value of the cracked area is 0 and no longer participates in the stress. The stress of the interface unit at the top tip of the waterproof layer crack is significantly greater than the stress of the uncracked interface unit at other locations, which is consistent with the stress distribution in the conventional crack extension theory; (3) Figure 12 It further shows that the above model is loaded into W cr = 0.2mm, it can be seen that the waterproof layer 2 segments on both sides of the virtual interface layer 14 have been completely separated, that is, the cracks in the waterproof layer 2 have penetrated the full height range of the waterproof layer 2, which means that the width of the crack 13 in the actual concrete 1 structure is W cr When it reaches 0.2mm, it is used H =1mm thick waterproof layer 2 will be completely cracked and fail, so the design of waterproof layer 2 should be improved. Figure 19 The specimen with reinforced concrete beam 12 and waterproof layer 2 was loaded and tested. When the crack 13 of concrete 1 first appeared, the waterproof layer 2 began to leak (see Figure 20 ), it can be seen that the test results are consistent with the calculation conclusion of the present invention.

[0110] Based on the initial finite element model, the longitudinal thickness of the virtual interface layer 14 is T cr The crack height is calculated by taking different values ​​in the range of 10nm~10000nm. H cr The results are plotted on a logarithmic scale. Figure 13 , we can see that: (1) when T cr When the scale is above 100nm, T cr The larger the value, the higher the crack height of waterproof layer 2. H cr The smaller, T cr right H cr have a significant impact; (2) when T cr As small as 100nm, H cr tends to a stable value.

[0111] Based on the initial finite element model, the longitudinal length of the model L When different values ​​are taken in the range of 0.4mm~10mm, the crack height is calculated. H cr The results are plotted on Figure 14 , we can see that: (1) whenL <4 H= 4mm, L The larger the value, the higher the crack height of waterproof layer 2. H cr The bigger, L right H cr have a greater impact; (2) when L ≥4 H= After 4mm, H cr The change of tends to be stable. It can be seen that when calculating the cracking of waterproof layer 2, it should be ensured that L ≥4 H ,at this time H cr The calculation results are basically not affected by L The impact of L If the value is too small, a large calculation error will occur.

[0112] Based on the initial finite element model, the vertical thickness of the model H When different values ​​are taken in the range of 0.3mm~1mm, the crack height is calculated. H cr The results are plotted on Figure 15 , we can see that: except H When the value is too small, the waterproof layer 2 will crack earlier. H cr The calculation results are basically not affected by H That is, when the waterproof layer 2 is not too thin, the crack height has basically nothing to do with its own vertical thickness value.

[0113] Based on the initial finite element model, the Poisson's ratio of the waterproof material v = 0.2, 0.3, 0.4, and found H cr The calculation results are basically not affected by v impact.

[0114] Furthermore, if Figure 16 As shown, based on the initial finite element model, the vertical distance from the bottom surface of the waterproof layer 2 is c r = 0.2mm, a linear elastic truss element with a common node as the plane stress element is established to simulate the influence of the fiber reinforced material 15. The design tensile strength of the fiber reinforced material 15 is 400 MPa. The cracking of the waterproof layer 2 is calculated as follows: Figure 17-18As shown in FIG. 1 , it can be seen that the crack 13 of the waterproof layer 2 does not develop upward after the crack reaches the position of the fiber reinforcement material 15, and the maximum stress of the fiber reinforcement material 15 is 225 MPa, which is much smaller than its designed tensile strength. Figure 21 The actual specimen shown was subjected to a loading test. During the test, when the width of the crack 13 between the steel bar 12 and the concrete 1 beam reached 1.5 mm, the waterproof layer 2 still did not leak. It can be seen that the test results are consistent with the calculation conclusion of the present invention.

[0115] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A waterproof design method for reinforced concrete structure, characterized in that: Steel bars are provided in the concrete, and the top surface of the concrete is covered with a waterproof layer; The design method comprises the following steps: S1. The average thickness of the waterproof layer is H The longitudinal direction along the tensile direction of the concrete is the longitudinal direction, the direction perpendicular to the surface of the waterproof layer is the vertical direction, and the longitudinal length is L waterproof layer segments, and meet the L ≥4 H ; S2. Assume that there is a virtual interface layer in the waterproof layer segment, and the thickness of the virtual interface layer in the longitudinal direction is T cr , the vertical height is H , the waterproof layer segments on both sides of the virtual interface layer are connected through the virtual interface layer; S3. A vertical rigid support is provided on the bottom surface of the waterproof layer segment; S4. Apply forced displacements in opposite directions and away from the virtual interface layer to the bottom surfaces of the waterproof layer segments on both sides of the virtual interface layer. W cr / 2, W cr The longitudinal width of the crack produced on the top surface of the concrete under the action of external force; S5. Calculate the vertical distance between the bottom of the virtual interface layer and the bottom surface of the waterproof layer segment and define it as z , let 0 <d z <0.1 H , according to the constitutive relationship of the waterproof layer material and conventional mechanical methods, calculate the z The relative longitudinal displacement of the two sides of the virtual interface layer at △ T z ,△ T z The relative distance is positive; S6. If △ T z ≥ ε cr T cr and z +d z < H , ε cr is the elongation at break of the waterproof material, then delete the distance from the bottom of the waterproof layer segment z Chuzhi z +d z The virtual interface layer at the position is restored, and all waterproof layer segments are restored to the position before the forced displacement is applied, and then go to S4; otherwise, go to S7; S7. Crack height of the waterproof layer H cr = z +d z ; S8. If H - H cr >0, end the waterproof layer design; otherwise, increase the thickness of the waterproof layer H , go to S1.

2. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: The average thickness of the waterproof layer in step S1 H It is calculated based on the solid thickness of the waterproof layer after curing and maintenance.

3. The waterproof design method for reinforced concrete structure according to claim 1, characterized in that: In the step S2 T cr The average of the horizontal distances between adjacent wave crests on the concrete surface within any 100 μm×100 μm range is taken. The wave crests and troughs on the concrete surface are measured using equipment with a maximum resolution in the range of 1 nm to 1 μm.

4. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: In the step S2 T cr Take the average value of the distance between material molecules or molecular clusters when the waterproof layer segment is not affected by external forces other than gravity.

5. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: In the S2 step, 10 nm ≤ T cr ≤100nm.

6. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: In the step S4 W cr = W 0(0.74 h 0+ c s + d s / 2) / (0.74 h 0); in, W 0 is the crack width value calculated according to the industry standard of the designed reinforced concrete structure. W The load used when 0 is the basic load combination value under the ultimate limit state. h 0 is the distance from the center of the steel bar to the compressive edge of the concrete, c s is the thickness of the protective layer of the steel bar, d s is the diameter of the steel bar.

7. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: The tensile stress-tensile strain constitutive relationship of the waterproof layer material in step S5 is implemented according to the stress-strain curve measured by the uniaxial tensile test, and the compressive stress-compressive strain constitutive relationship of the waterproof layer material in step S5 is implemented according to the stress-strain curve measured by the uniaxial compression test. The loading time of the uniaxial tensile test and the uniaxial compression test does not exceed 10s.

8. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: In the step S5, the stress-strain constitutive relationship of the waterproof layer material other than the virtual interface layer is elastic, and its elastic modulus is E e = σ 1% / ε 1% , σ 1% is the stress at 1% elongation when the waterproof layer is subjected to a uniaxial tensile test, ε 1% is the strain at 1% elongation when the waterproof layer is subjected to a uniaxial tensile test; the material stress-strain constitutive relationship of the virtual interface layer is determined by the following formula: in, σ x is the longitudinal stress of the virtual interface layer, ε x is the longitudinal strain of the virtual interface layer, σ cr The elongation of the waterproof layer material at break after uniaxial stretching ε cr The corresponding stress.

9. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: In the step S5, Δ is calculated by finite element modeling. T z The virtual interface layer is simulated by discrete crack interface units or nonlinear springs, and the waterproof layer segments on both sides of the virtual interface layer are meshed by plane stress units. The mesh size at the virtual interface layer is not larger than d z , the nodes of the plane stress elements on both sides of the virtual interface layer are connected through the discrete crack interface elements or nonlinear springs of the virtual interface layer, and the material nonlinearity and geometric nonlinearity effects are taken into account during the calculation process; The normal stiffness modulus of the discrete crack interface element K n = E s / T cr , tangential stiffness modulus K t = K n / [2×(1+ v )], E s is the deformation modulus of the virtual interface layer and E s = σ cr / ε cr , σ cr Stretch the waterproof material to the breaking elongation ε cr The corresponding stress is v is the Poisson's ratio of the waterproof layer material; the axial force of the nonlinear spring F x and axial displacement△ T x The relationship is determined by the following formula: In the formula S z For vertical position z The vertical size of the grid at , and the △ T x =△ T z , B is the lateral width of the waterproof layer.

10. The reinforced concrete structure waterproofing design method according to claim 1, characterized in that: The waterproof layer includes a fiber reinforced material, the direction perpendicular to the longitudinal direction and the vertical direction is the transverse direction, and the transverse width of the waterproof layer is B The total cross-sectional area of ​​the fiber reinforced material in the longitudinal direction within the range A r Should meet the following requirements: A r ≥ K r BH cr σ cr / f rd , where K r is the safety factor and K r >1, f rd is the design tensile strength value of the fiber reinforced material, c r is the vertical distance from the fiber reinforced material to the top surface of the concrete, σ cr The elongation of the waterproof layer material after uniaxial stretching to break ε cr The corresponding stress.

11. A method for maintaining the long-term waterproof performance of reinforced concrete structures, characterized in that: The method for maintaining the long-term performance of waterproofing of reinforced concrete structures is implemented based on the design method according to any one of claims 1 to 10. H - H cr ≥ K f H min , K f is the safety factor and K f >1, H min The design of the waterproof layer is completed if the minimum waterproof layer thickness that meets the waterproof performance requirements is not considered without considering the cracking of concrete. H - H cr < K f H min , then increase the thickness of the waterproof layer to H + , until H + ≥ H cr +K f H min , then the design of the waterproof layer is completed.

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