KR102037911B1 - Initial crack preventing pre-stressed concrete pavement method - Google Patents

Abstract

The present invention relates to a pre-stressed concrete pavement method, by first giving a tension force corresponding to the stress causing a crack immediately before the occurrence of the crack of the concrete pavement 10, to achieve a mechanical balance, the tension force In order to prevent breakage of the package body 10 during curing due to the early introduction of the initial tension and the strength of the appropriately set, and when the curing of the package 10 is completed to perform a full-scale tension.
Through the present invention, it is possible to significantly suppress the crack of the prestressed concrete pavement 10, thereby improving the structural stability and durability of the prestressed concrete pavement.

Description

Initial crack suppression prestressed concrete paving method {INITIAL CRACK PREVENTING PRE-STRESSED CONCRETE PAVEMENT METHOD}

The present invention relates to a pre-stressed concrete pavement method, to achieve a mechanical balance by first giving a tension force corresponding to the stress causing the crack immediately before the occurrence of the crack of the concrete pavement 10, the tension force In order to prevent breakage of the package body 10 during curing due to the early introduction of the initial tension and the strength of the appropriately set, and when the curing of the package 10 is completed to perform a full-scale tension.

Prestressed concrete pavement has the advantage of expressing excellent strength and durability even with a pavement 10 of a reduced cross-section compared to other concrete pavement, and the related prior art, such as Patent No. 916973.

The pavement 10 in the prestressed concrete pavement is a concrete slab in which a tension material 11 is embedded. The pavement 10 is set in the longitudinal direction parallel to the longitudinal line of the road in the longitudinal direction, When the direction parallel to the transverse direction is set in the transverse direction, the package body 10 behaves as a plate body having a longer longitudinal direction than the transverse direction, and the main tension member 11 is the longitudinal direction of the package body 10. Is buried.

As in other structures, the concrete slab as pavement 10 is also very important for the maintenance of strength and durability after completion of the curing process. In particular, the bottom is in direct contact with the ground and the top is completely exposed. However, due to the characteristic that the load due to the traffic of the vehicle always acts, the suppression of the initial crack can be said to be a factor that determines the performance of the road pavement 10.

Therefore, regardless of the bare concrete pavement, reinforced concrete pavement and prestressed concrete pavement, by artificially forming a joint for dividing the package 10 at regular intervals on the longitudinal end so that the joint accommodates the deformation of the package (10) Although the cracks in the unit pavement 10 between the shrinkage joints are suppressed, the deterioration of ride comfort and noise increase due to the joints are inevitable in the finished road, so the number of joints in the concrete paving technique is reduced. Efforts have been made to extend the extension of the unit pavement 10, and there may be prestressed concrete pavement at its peak.

In other words, the development of cement concrete pavement technology from bare concrete pavement to reinforced concrete pavement, and then reinforced concrete pavement to prestressed concrete pavement is a process to increase ride distance and reduce noise by extending the distance between joints. Therefore, in the prestressed concrete pavement, the longitudinal extension of the unit pavement 10 is generally set longer than that of the other concrete pavement 10.

Compared to other concrete pavement, the distance between the joints of the prestressed concrete pavement is set to a long distance, it can be obtained a considerable advantage in terms of ride comfort and noise, but this is due to the addition of the reinforcing tension material 11 rather than improving the physical properties of the material itself As the unit package 10 is enlarged, the risk of cracking is inevitably increased.

The present invention was conceived in view of the above-described problems, in the pre-stressed concrete paving method, to form a package (10) formwork at the point to be paved and to install the tension member 11 in the longitudinal direction After the concrete is poured, the sum of shrinkage stress Fs (t) due to dry shrinkage of the package 10 and temperature stress Fh (t) due to temperature difference When the time point setting step (S10) of setting the threshold time point tc coinciding with the tensile strength Ft (t) of the package 10 during curing, and the time point before the allowable time tf based on the threshold time point tc arrives An initial tension step (S20) of tensioning the tension member 11 to form a compressive stress that cancels the shrinkage stress Fs (t) and the temperature stress Fh (t) in the package 10 during curing at that time, and the package (10) When the curing of the concrete is completed, the additional tension to create a design tension in the tension member (11) Early crack suppression type prestressed concrete pavement method characterized in that the tension step (S30) made.

의 관계식으로부터 산출되되,

이고, fck는 설계기준압축강도(㎫)이며, df는 fck가 40㎫ 이하이면 4㎫이고 60㎫ 이상이면 6㎫이며 40㎫ 내지 60㎫ 구간에 대하여는 직선 보간치가 적용될 때

이며,

는 1종 시멘트 습윤양생, 1종 시멘트 증기양생, 2종 시멘트, 3종 시멘트 습윤양생 및 3종 시멘트 증기양생에 대하여 각각 0.35, 0.15, 0.40, 0.25 및 0.12일때

이며, 재령 t일에서의 양생중 포장체(10) 수축응력(㎫)인 Fs(t)는

의 관계식으로부터 산출되되,

는 1종 시멘트, 2종 시멘트 및 3종 시멘트에 대하여 각각 5, 4 및 8이고, H는 상대습도(%)

가 99% 미만일 경우 및 99% 이상일 경우에 대하여 각각

및 0.25일 때,

이고, ts는 포장체(10) 타설후 외기(外氣) 차단 일(日)이고, A는 포장체(10) 단면적(㎟)이며, u는 단면상 외기 접촉 길이(㎜)일 때

이며,

일 때,

이고, 재령 t일에서의 양생중 포장체(10) 온도응력(㎫)인 Fh(t)는

의 관계식으로부터 산출되되,

는 콘크리트의 열팽창계수이고, Tm, Tt 및 Tb는 각각 포장체(10)의 중심부 온도(℃), 상면 온도(℃) 및 저면 온도(℃)임을 특징으로 하는 초기 균열 억제형 프리스트레스트 콘크리트 포장 방법이다.In addition, Ft (t), which is the tensile strength (MPa) of the package 10 during curing at the age of day t, may be referred to as Fc (t) as the compressive strength (MPa) of the package 10 during curing at the age of the day. time

Is derived from the relation of

Fck is the design reference compressive strength (MPa), df is 4 MPa if fck is 40 MPa or less, 6 MPa is greater than 60 MPa, and linear interpolation is applied for the 40 MPa to 60 MPa range.

Is,

Is 0.35, 0.15, 0.40, 0.25 and 0.12 for one type of cement wet curing, type 1 cement steam curing, type 2 cement, type 3 cement wet curing and type 3 cement steam curing, respectively.

Fs (t), which is the shrinkage stress (MPa) of the package 10 during curing at age t,

Is derived from the relation of

Is 5, 4 and 8 for Type 1 cement, Type 2 cement and Type 3 cement, respectively, and H is relative humidity (%)

For less than 99% and for more than 99%

And 0.25,

Where ts is the outside air blocking day after pouring the package 10, A is the cross-sectional area of the package 10 (mm 2), and u is the external air contact length (mm) in the cross-section.

Is,

when,

Fh (t), which is the package 10 temperature stress (MPa) during curing at day t,

Is derived from the relation of

Is the thermal expansion coefficient of the concrete, Tm, Tt and Tb is the initial crack suppression type prestressed concrete pavement method, characterized in that the central temperature (℃), top temperature (℃) and bottom temperature (℃) of the package 10, respectively. to be.

Through the present invention, it is possible to significantly suppress the crack of the prestressed concrete pavement 10, thereby improving the structural stability and durability of the prestressed concrete pavement.

In particular, the improvement of the performance of the package 10 can be achieved only by the action of dividing the tension of the tension member 11 without setting the cross section or adding the tension member 11 and setting the initial tension point. Packaging quality can be improved without increasing

1 is an illustration of prestressed concrete pavement
2 is an explanatory diagram of a threshold time setting method of the present invention;
3 is an explanatory view of the actual strength change of the package to which the present invention is applied
4 is a flow chart of the present invention

The detailed configuration and implementation process of the present invention will be described with reference to the accompanying drawings.

1 illustrates a prestressed concrete pavement 10 to which the present invention is applied. As shown, the pavement 10 is a plate having a rectangular structure having a longitudinally superior longitudinal direction compared to a transverse direction. , A plurality of tension members 11 are embedded in the longitudinal direction.

In the concrete pavement 10, the main cause of the initial random cracking of the curing is the shrinkage stress due to the dry shrinkage, the temperature stress due to the internal and external temperature difference and the temperature difference between the upper and lower surfaces due to the heat of hydration, and these stresses It may be said that a crack occurs at the moment when the tensile strength of the package 10 exceeds.

Accordingly, the above-described tensile strength, shrinkage stress, and temperature stress in the package 10 during curing are determined by Ft (t) and Fs () as a function of the age of the package 10, that is, the time t. Expressed as t) and Fh (t), respectively, as shown in FIG. 2, the point at which the sum of the shrinkage stress Fs (t) and the temperature stress Fh (t) coincides with the tensile strength Ft (t). The occurrence of a random initial crack may be initiated at.

In the present invention, as described above, when the sum of the shrinkage stress and the temperature stress coincides with the tensile strength in the curing process of the concrete pavement 10 was set to the threshold time (tc), as shown in Figure 2, At the critical time point tc, the following equation 1 holds.

Therefore, as shown in FIG. 3, if the package 10 is compressed so that the shrinkage stress and the temperature stress can be offset at a time before the allowable time tf based on the threshold time tc which is the start point of crack generation, cracking occurs. This can be suppressed, and this can be achieved by first tensioning the tension member 11, which is already embedded in the package 10, during curing prior to full-scale tension.

In FIG. 2 and FIG. 3, the thick solid line shows the change in strength of the package, and the spare time tf is a kind of working time required for the tension work of the tension member 11, and the tension material embedded in the package 10 during curing ( The marginal point is reached when the spare time passes after the beginning of the initial tension.

That is, the present invention, as shown in Figure 4, to build the package 10 formwork at the point to be paved, install the tension member 11 in the longitudinal direction, and then cast concrete, the age t (day) The sum of the shrinkage stress Fs (t) due to the shrinkage of the package 10 and the temperature stress Fh (t) due to the temperature difference is equal to the tensile strength Ft (t) of the package 10 during curing. Beginning with a time point setting step (S10) of setting the coincident threshold time point tc, and the shrinkage stress in the package 10 during curing at that time point when a time point before the allowable time tf arrives based on the threshold time point tc. The ultra-tension step (S20) of tensioning the tension member 11 is performed to form a compressive stress that cancels Fs (t) and the temperature stress Fh (t).

In addition, after performing the initial tension step (S20), when the curing of the pavement 10 concrete is completed, the tension tension step (S30) to further tension so that the design tension is formed in the tension member 11 is performed, thereby applying the present invention The rest concrete pavement 10 is finally completed.

That is, in the present invention, the basic principle of crack control of the concrete pavement 10 is to provide a mechanical force by providing a tension force corresponding to the stress causing the crack just before the occurrence of the crack, thereby achieving a mechanical balance, while curing due to the early introduction of the tension force. In order to prevent breakage of the package 10, it can be said to accurately set the timing and strength of the initial tension, the specific detailed process is as follows.

First, in Equation 1, Ft (t), which is the tensile strength (MPa) of the package 10 during curing at day t, is the following equation proposed by the European Concrete Commission (CEB-FIP). Calculated by the relation

In Equation 2, Fc (t) is the compressive strength (MPa) of the package 10 during curing on the day t, and is calculated through the following equation (3).

In the above Equation 3, fm, which is the average converted compressive strength (MPa) of the package 10 during curing, is calculated through the following Equation 4.

In the above Equation 4, fck is the design reference compressive strength (MPa) of the concrete pavement 10, the normal compressive strength is applied 28 days, df is 4MPa if fck is 40 MPa or less, If fck is 60 MPa or more, 6 MPa is applied. If fck corresponds to a 40 MPa to 60 MPa section, a linear interpolation value of two values is applied.

That is, based on the case where the ordered pairs (fck, df) are (40 MPa, 4 MPa) and (60 MPa, 6 MPa), the intermediate values are calculated by linearly interpolating these two values.

는 다음의 수학식 5를 통하여 산출된다.In addition, in Equation 3, the correction coefficient according to the age for intensity expression

Is calculated through the following equation (5).

는 0.35이고, 1종 시멘트를 사용하여 증기양생으로 제작되는 경우

는 0.15이며, 2종 시멘트를 사용하여 제작되는 경우

는 0.40이고, 3종 시멘트를 사용하여 습윤양생으로 제작되는 경우

는 0.25이며, 3종 시멘트를 사용하여 증기양생으로 제작되는 경우

는 0.12가 적용된다.In the above Equation 5, when the package 10 is produced as a wet curing using a kind of cement

Is 0.35, and is produced by steam curing using one kind of cement

Is 0.15 and is manufactured using two kinds of cement

Is 0.40, and it is produced by wet curing using 3 kinds of cement

Is 0.25, and is produced by steam curing using 3 kinds of cement

0.12 applies.

In addition, in Equation 1 described above, Fs (t), which is the shrinkage stress (MPa) of the package 10 during curing at age t, is calculated through the following equation (6).

는 다음의 수학식 7을 통하여 산출된다.In Equation 6, it is a dry shrinkage influence function according to the compressive strength of the concrete pavement (10)

Is calculated through the following equation (7).

는 5이고, 2종 시멘트를 사용하여 제작되는 경우

는 4이며, 3종 시멘트를 사용하여 제작되는 경우

는 8이 적용된다.In Equation 7, Fc (t) is the compressive strength (MPa) of the package 10 described above, and the package 10 is manufactured using one kind of cement.

Is 5, and manufactured using two kinds of cement

Is 4, and is manufactured using three kinds of cement

8 applies.

가 99% 미만일 경우

가 적용되고,

가 99% 이상일 경우 H=0.25가 적용된다.Here, H, which is an influence coefficient according to the external air relative humidity, is an external air relative humidity (%)

Is less than 99%

Is applied,

Is greater than 99%, H = 0.25 applies.

는 다음의 수학식 8을 통하여 산출된다.In addition, in Equation 6, the drying shrinkage influence function according to the drying period of the concrete pavement 10

Is calculated through the following equation (8).

In Equation (8), ts is a period during which the outside air is blocked by developing a packing film or the like on the upper surface of the package 10 during curing after placing the package 10, that is, the outside air blocking day. A is the road cross-sectional area (mm <2>) of the package 10, and u is the outside air contact length (mm) equal to the upper surface length of the cross-sectional package 10 as shown in FIG.

는 다음의 수학식 9를 통하여 산출된다.In Equation 6, the effective modulus of elasticity for each age of the concrete pavement 10 is

Is calculated through the following equation (9).

는 전술한 수학식 5를 통하여 산출되는 강도 발현에 대한 재령에 따른 보정계수이고, 초기접선탄성계수인

는

의 관계식으로 산출되며, 여기서 fm은 전술한 수학식 4를 통하여 산출되는 양생중 포장체(10)의 평균 환산 압축강도(㎫)이다.In Equation 9,

Is a correction factor according to the age for the intensity expression calculated through the above equation (5), the initial tangent elastic modulus

Is

Fm is an average converted compressive strength (MPa) of the package 10 during curing, which is calculated through Equation 4 described above.

On the other hand, in Equation 1 described above, Fh (t), which is the temperature stress (MPa) of the package 10 during curing at age t, is calculated through the following equation (10).

는 콘크리트의 열팽창계수이고, Tm, Tt 및 Tb는 각각 포장체(10)의 중심부 온도(℃), 상면 온도(℃) 및 저면 온도(℃)이다.In Equation 10,

Is the thermal expansion coefficient of concrete, and Tm, Tt, and Tb are the central temperature (° C), the top surface temperature (° C), and the bottom surface temperature (° C) of the package 10, respectively.

Tt, the upper surface temperature of the package 10 during curing, can be easily measured by using a non-contact thermometer or the like, and Tm, which is the central temperature of the package 10, and Tb, which is the bottom temperature, are inside and bottom of the package 10. Measurement is possible by embedding a temperature sensor in the part.

In addition, when the temperature sensor is difficult to embed in the field conditions or when the temperature sensor needs to be recovered, a small package for measurement 10 is installed in the vicinity of the packing point where the weather and ground conditions are the same. The temperature of (10) is measured and utilized, and after the package 10 is completed, the method of disassembling the package 10 for measurement is also applicable.

Meanwhile, in calculating Fc (t), which is the compressive strength (MPa) of the package 10 during curing at age t, by applying the above Equations 3 to 5, various coefficients utilized in these equations are Partial sampling from the measurement package 10 or at the same time as the concrete placement of the package 10 can be corrected through a compressive strength test on a separate specimen placed in the same concrete.

As such, the threshold time tc that satisfies Equation 1 may be calculated through Equations 2 to 10 as described above, and thus, the above-described viewpoint setting step S10 may be performed.

When the threshold time tc is set in the viewpoint setting step S10, a time point before the margin time tf from the threshold time, that is, a time point obtained by subtracting the margin time tf from the threshold time point tc, is calculated and calculated. At this time, an initial tensioning step (S20) of partially tensioning the tension member 11 to form a compressive stress that cancels the shrinkage stress Fs (t) and the temperature stress Fh (t) in the package 10 during curing at that time. Is performed.

That is, prior to the full-scale introduction of the tension force to the tension member 11, preliminary tension to suppress the random initial cracking is carried out, the tension force introduced at this time is the shrinkage stress Fs (t) and temperature stress in the package 10 It is formulated to form a compressive stress equal to the sum of Fh (t), which is the tensile stress Ft (t) of the package 10, as in the relation of Equation 1 above. ) Also, the total tension Pt introduced to the entire tension member 11 in the initial tension stage (S20) can be calculated through the following equation (11).

Here, A is a cross-sectional area of the package 10 as described above, and although not shown in Equation 11, Pt may be slightly increased to reflect an immediate loss rate accompanying tension on the tension member 11.

As such, by performing the initial tension step (S20) to continue curing in a state of suppressing the formation of cracks in the package 10, as shown in Figure 4, so that the design tension is formed in the tension material 11 when curing is completed By further tension tension step (S30) is carried out, the present invention prestressed concrete pavement 10 is completed.

10: package
11: tension material
S10: viewpoint setting step
S20: Ultra-tension stage
S30: tension phase

Claims (2)

Pre-stressed concrete pavement method, the form 10 pavement (10) form the pavement to the point of pavement, the tension member 11 is installed in the longitudinal direction, then the concrete is poured,日), the sum of the shrinkage stress Fs (t) due to shrinkage of the package 10 and the temperature stress Fh (t) due to the temperature difference is the tensile strength Ft (t) of the package 10 during curing. When the time point setting step (S10) of setting the time limit point tc coinciding with) and the time point before the allowable time tf on the basis of the time limit point tc arrives, the shrinkage stress in the package 10 during curing at that time point An initial tensioning step (S20) of tensioning the tension member (11) to form a compressive stress to offset the Fs (t) and the temperature stress Fh (t), and when the curing of the pavement (10) concrete is completed to the tension member (11) Initial crack suppression type frist consisting of the main tension step (S30) to further tension to create a design tension In the cast concrete method,
Ft (t), the tensile strength (MPa) of package 10 during curing at age t, is given by the compressive strength (MPa) of package 10 during curing at age t, Fc (t).

Is derived from the relation of

ego;
fck is the design reference compressive strength (MPa), df is 4 MPa when fck is 40 MPa or less, 6 MPa when 60 MPa or more, and a linear interpolation value is applied for 40 MPa to 60 MPa.

Is;

Is 0.35, 0.15, 0.40, 0.25 and 0.12 for one type of cement wet curing, type 1 cement steam curing, type 2 cement, type 3 cement wet curing and type 3 cement steam curing, respectively.

Is;
Fs (t), the shrinkage stress (MPa) of the package 10 during curing at age t,

Calculated from the relation of;

Is 5, 4 and 8 for Type 1 cement, Type 2 cement and Type 3 cement, respectively, and H is relative humidity (%)

For less than 99% and for more than 99%

And 0.25,

ego;
ts is the outside air blocking day after casting the package 10, A is the cross-sectional area (mm2) of the package 10, and u is the external air contact length (mm) in the cross section.

Is;

when,

ego;
Fh (t), the package 10 temperature stress (MPa) during curing at age t,

Is derived from the relation of

Is the thermal expansion coefficient of the concrete, Tm, Tt and Tb is the initial crack suppression type prestressed concrete pavement method, characterized in that the central temperature (℃), top temperature (℃) and bottom temperature (℃) of the package 10, respectively. . delete

Images