CN1069411C - Modulus of elasticity method for investigating quality of concrete members - Google Patents

Abstract

The present invention discloses an elastic modulus measurement method for evaluating the integral quality of a concrete component, which adopts a simple dial indicator to measure the deformation value of a post-stretching prestressed concrete component. According to the compaction deformation values delta h of the concrete to determine a static elastic modulus E<h>, and the strength grade R<h> of the component can be found out through the surface appearance and a corresponding strength grade R<h> relation curve; according to the comparison of the R<h> and a component design requirement value, the quality of the component is judged. The method has the advantages of simplicity and low construction cost; the present invention is a nondestructive measurement method for reliably reflecting the integral quality of the measured component and is especially suitable for the strength evaluation of post-stretching prestressed concrete slender components, such as roof trusses and bridges.

Description

The elastic modulus method of evaluation quality of concrete members

The present invention relates to a kind of elastic modulus method of evaluating quality of concrete members, the globality quality that this method is particularly suitable for the concrete slender member of post-stretching pre-stress construction such as roof truss, bridge detects, and belongs to the concrete component Dynamic Non-Destruction Measurement.

Intensity is the topmost technical indicator of concrete component.Can reflect the nondestructive determination of quality of concrete members intuitively, accurately, comprehensively,, avoid accident, save cement, reduce construction costs and be significant for Construction Quality Control.

At present, the concrete component lossless detection method mainly contains rebound method, ultrasonic method, ultrasonic-the resilience overall approach.Rebound method utilizes reisilometer at the selected measuring point of surveying district's concrete surface bullet some, can only obtain the intensity on component partial, surface and easily omission erroneous judgement according to each dbullioscope result's arithmetic mean.Ultrasonic method be used for detection sectional plane long-pending little, reinforcing bar is intensive and many, in when the elongated prestressed component of stretch-draw hole is arranged, disturb big, also easily erroneous judgement.Ultrasonic-resilience overall approach method complexity and expense height applied difficulty.

The purpose of this invention is to provide a kind of simple to operate, expense is low, and can detect the nondestructive determination of prestressed concrete member globality quality intuitively, reliably.

The technical solution used in the present invention is: measure member after the compress variation that produces under the stretching force effect is answered in setting in advance with clock gauge, according to Hooke's law, calculate the static modulus of elasticity of member, look into again: strength grade of concrete corresponding elastic modulus curve during with its pressurized, just can find the strength grade value of detected member, compare with the member designs required value with this value, can judge that just its globality quality is qualified not and in time do not handle.Its concrete composition step is as follows:

Determine the stretch-draw prestressing force that the reinforcing bar of member to be measured or tendon need, and establish it and be Ny (n bundle tendon is nNy);

Determine the useful area S and the effective length L of member stretch-draw pressurized to be measured ₀

A prefabricated respectively table platform for placement clock gauge bearing is pasted one simultaneously respectively and is beneficial to the antifriction piece that the clock gauge head moves at member to be measured two ends.The antifriction piece is generally made with glass, 2 * 2cm ²Size gets final product.

The clock gauge of beating pin → will be contained on the clock gauge bearing with the tendon of to be measured of 0.1Ny power stretch-draw or reinforcing bar → pretension places on the clock gauge table platform, and its pointer heads on vertically that the antifriction piece → when stretching force was returned to 0.05Ny, this went out clock gauge value t this moment ₁₀And t ₂₀→ stretching force is increased to 1.03Ny, this goes out clock gauge displayed value t after 2 minutes to hold lotus ₁₁And t ₂₁→ remove stretch-draw machine, clock gauge platform, clock gauge bearing and clock gauge.

By (t ₁₁+ t ₂₁)-(t ₁₀+ t ₂₀) calculate member compress variation Δ h to be measured; According to Hooke's law, calculate the component elasticity modulus $E_t,E_t=\frac{\mathrm{Ny}{L}_0}{\mathrm{S\&Delta;h}}$

According to modulus of elasticity of concrete E _hWith its corresponding strength grade R _hCurve is found the R of member to be checked _hValue;

According to R _hValue is judged the quality of member to be checked: R _h95% of 〉=design strength, member are certified products; R _h95% of＜design strength, member is correctly handled as dangerous member.

This law detects error in ± 10% to elongate members such as roof truss, bridge, and rebound method error ± 15% more higher than present precision is little.

The elastic modulus nondestructive determination that the present invention adopts, the arbitrary place of member defectiveness, can reflect in its compression deformation Δ h immediately, can directly perceived, errorless, not detect the damage defect of member to be measured with leaking, be a kind of globality quality nondestructive determination intuitively and reliably.Only need clock gauge in the construction, operate simple and easyly, except man-hour, add other expense more in addition hardly, construction cost is very low, is beneficial to the on-the-spot employing of promoting.

Below in conjunction with drawings and Examples the present invention is described in further detail:

Fig. 1 pressurized modulus of elasticity of concrete E _hWith its strength grade R _hE _h-R _hCurve;

When Fig. 2 detects roof truss, the construction floor map;

When Fig. 3 detects roof truss, the construction side schematic view;

Fig. 4 calculates roof truss effective length L ₀When reaching net sectional area S, the related parameter synoptic diagram is arranged;

Fig. 5 roof truss lower edge I-I is analysed and observe relevant calculation parameter synoptic diagram;

1 is the antifriction piece among the figure, how to make size with glass and is about 2 * 2cm ²2 is clock gauge; 3 are the stretch-draw machine; 4 is the clock gauge bearing; 5 is the clock gauge platform; L is a span of roof truss.

Embodiment 1

Evaluation design R ₂₈=44Mp; L=27m prestressed concrete roof truss quality (steel tendon is 2 bundles)

Roof truss is the main prestressed component that is related to the people life property safety, does not allow any mistake in the detection and hides some dangers for, and trial edition invention elastic modulus method carries out the globality quality and detects, and the concrete operations step is as follows:

At first calculate concrete net sectional area S of roof truss lower edge pressurized and effective length L ₀: establish roof truss lower edge length and width and be respectively A, B, lower edge stretch-draw reserving hole diameter is r, and the hole number is n ₁, S=AB-π * n then ₁(r/2) ²The mm of unit ²

S=240×20-2×3.14×(50/2) ²=48873(mm ²)

Because the lower edge concrete cross-section area broad of roof truss two ends compound lever junction, and reinforcing bar, iron plate are intensive, and compression chord is minimum, so this section concrete decrement can be ignored.Length L is calculated in the effective compression that is roof truss lower edge net sectional area ₀=L ₁-2C-2E-2D-F (mm)

27m strides roof truss and has seven nodes, i.e. c=1000mm, D=E=F=800mm, lower edge length overall L ₁=26960mm is with data substitution L ₀Formula gets L ₀=20960 (mm)

Stretching force Ny: setting every bundle is 540000N, during 2 bundles,

Ny=2×540000N=1080000N

Survey the compress variation Δ h of member stretch-draw front and back:

Paste a little glass 1 with sand-cement slurry respectively at roof truss lower edge two ends in advance, its size is 2 * 2 square centimeters and gets final product, and necessarily requires perpendicular to the roof truss lower edge; Prefabricated 2 traveling tables 5 at the roof truss two ends are for placing dial indicators rack platform 4 usefulness, when steel wire is got one's things ready pin when moving Ny * 10% to, pretension is beaten pin, and the clock gauge 2 of two ends installation immediately after finishing is after indicator vertically heads on glass 1, stretching force falls back on Ny * 5% o'clock, the value of two ends meter reading immediately, t ₁₀, t ₂₀After, continue to execute the 103%Ny stretching force, hold lotus and read clock gauge value: t in 2 minutes ₁₁And t ₂₁Recession removes the clock gauge device,

Record t ₁₀=0.732mm, t ₂₀=0.600mm

t ₁₁=7.545mm,t ₂₁=7.370mm

Calculate Δ h=(t ₁₁+ t ₂₁)-(t ₁₀+ t ₂₀)=13.583mm $E_h=\frac{\mathrm{Ny}{L}_0}{\mathrm{S\&Delta;h}}=\frac{1080000\&times;20960}{48873\&times;13.583}=341\&times;{10}^4\left(\mathrm{MPa}\right)$

From E _h-R _hCurve checks in R _h=45.2MPa is with actual measurement roof truss concrete standard lab scale piece compressive strength R ₂₈=44.1Mp is very approaching, and error amount only has 2.5%.R _tWith design strength R ₂₈=44MPa compares, and 〉=95%, be certified products.

Embodiment 2

In this section organizational security section industrial premises construction, for some reason, the roof truss that 25 Pin L=18m of making stride, its strength grade of concrete is not clear.If by all scrapping processing, direct economic loss just reaches 25 Pin * 1800 yuan/Pin=45000 yuan, if please other unit detect with resilience-ultrasonic method, needs the flower check fee: 25 Pin * 400 yuan/Pin (district's uniform price)=10000 yuan.Expense is all very high.For this reason, elastic modulus detection method of the present invention on probation is judged its globality quality.

Because quantity is big, at first surface quality is done to scrap processing with regard to undesirable 8 Pin roof trusses with easy elastic method.Remaining 17 Pin detect with ultrasonic method again, are certified products.This 17 Pin roof truss is continued to pursue Pin with elastic modulus method of the present invention detect, it is qualified to detect 16 Pin, a Pin elastic modulus E _hUnusually, be 2.7 * 10 ⁴M Pa, it contrasts R _h-E _hCurve, concrete grade R _hOnly be 23MPa, the R that this Pin measures with rebound method _h=39.1MPa, ultrasonic method records R _h=40.5MPa is with designing requirement R _hFor 40MPa contrasts mutually, rebound method, ultrasonic method detect and are certified products, and only the inventive method detects and is unacceptable product.

The inventor determines at once: this Pin does to scrap processing, stops grouting immediately, and operating personnel withdraw on-the-spot the continuation immediately and observe.When the workmen withdrew on-the-spot about 40 minutes, a loud noise, this Pin roof truss is disconnected to collapse.If more solito, it is qualified to be judged to, grouting immediately after stretch-draw finishes, 109 tons prestress crushing and consequence that the roof truss energy that fractures causes is hardly imaginable so.

Through post-survey, roof truss fracture place bubble is many, has to leak the phenomenon of shaking: it is few to have formed stone, and place's honeycomb that mortar is many is so this place's intensity is low.Reinvestigate workman on duty and builder, confirm that this place just in time is concrete ramming ending place, concrete is not enough just, fills full with regard to having come off duty, so caused this Pin quality structure hidden danger with the mortar of losing on the ground.

By this embodiment, confirmed that the present invention compares rebound method, ultrasonic method can more reliably be found the inside hidden danger of concrete component effectively: density, homogeneity, defectives such as cavity, and every Pin check fee will spend 10000 yuan to compare with resilience-ultrasonic overall approach only about 30 yuan, 25 Pin only use 650 yuan, can save the construction check fee more than 15 times.

The present invention is a kind of simple to operate, and expense is low, and can intuitively, reliably reflect the nondestructive determination of prestressed concrete member globality quality, can control, improve construction quality effectively, eliminates accident potential.

Claims (1)

1, a kind of elastic modulus method of evaluating quality of concrete members is characterized in that: be made up of following step:

Design or determine the stretch-draw prestressing force Ny that the reinforcing bar of member to be detected or tendon need by typical drawing;

Determine the useful area S and the effective length L of member stretch-draw pressurized to be measured ₀

Prefabricated respectively 1 traveling table and one of stickup for the placement dial indicators rack is beneficial to the antifriction piece that the clock gauge syringe needle moves at member to be measured two ends;

Behind 10% Ny power tension reinforcing steel bar or tendon, it is complete that pretension is beaten pin, clock gauge propped up in not having in advance on the traveling table immediately, and indicator vertically heads on the antifriction piece, reads clock gauge displayed value t when again stretching force being returned to 5%Ny ₁₀And t ₂₀After, will open tensile force and increase, and hold lotus 2 minutes to 103%Ny, read clock gauge displayed value t again ₁₁And t ₂₁, finish recession and remove dial indicators rack platform, seat; According under show that formula calculates member compress variation Δ h to be checked:

Δ h=(t ₁₁+ t ₂₁)-(t ₁₀-t ₂₀) after, calculate elastic modulus E t value according to Hooke's law: $E_t=\frac{\mathrm{Ey}{L}_0}{\mathrm{S\&Delta;h}}$

With reference to modulus of elasticity of concrete E _hWith its respective intensities grade R _hCurve is found the R of member to be measured _hValue;

According to finding R _hBe worth, judge the quality of member to be measured: R _h〉=design strength 95% qualified;

R _h95% of＜design strength is made dangerous member and is disposed.

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