CN100346145C - Marine platform ice force measuring method based on local dense strain response - Google Patents

Abstract

The present invention discloses an ice force measuring method for an ocean platform, which is based on local dense strain response. The ice force measuring method comprises the following steps: firstly, a cylinder with certain flexibility is sheathed on a conduit of the ocean platform and can slide vertically along the conduit; secondly, a strain sensing device is stuck to the inner wall of the cylinder; thirdly, silica gel with certain flexibility is filled between the cylinder and the conduit; fourthly, floatable materials which can make the cylinder float on the ocean are arranged on both ends of the cylinder; fifthly, concentrated force of known units is applied to the position of each strain sheet, and the strain data of all positions is measured simultaneously to obtain a strain flexibility matrix; sixthly, the cylinder is impacted by sea ice, strain is generated in the cylinder, and the inversion of dynamic strain data which is obtain by measurement is carried out. Because the ice force measuring method adopts a cylinder structure, the geometric shape of the original conduits can be kept farthest, and the variation of ice load caused by the variation of the geometric shape of an ice facing surface of the structure can be reduced. The ice force measuring method has the advantages of direct measurement and indirect inversion.

Description

Marine platform ice force measuring method based on local dense strain response

Technical field

The present invention relates to a kind of measuring method of offshore platform structure ice load.

Background technology

Ice load is the major control load of marine site, China Bohai Sea oil/gas drilling platform design.The factor that influences ice load is a lot, mainly contains the physico-mechanical properties of sea ice and the coupling of sea ice and platform structure etc.These factors some itself are very complicated, if some single analyzes theoretically then difficulty is bigger, therefore the main means of analysis platform structure ice load are to carry out by experiment at present, comprise model experiment and prototype experiment.General situation is by analyzing the ice load data information that repeatedly experiment is directly obtained, obtain describing exactly to a certain extent the result of ice load again according to some prioris and necessary theoretical analysis, this way is a more feasible way at present.Wherein the resulting ice load data of prototype experiment are obviously true more and reliable.

Since the sixties, once repeatedly the ice load of various ice resistant structures had been carried out direct measurement or utilized the structural response data to carry out indirect inverting both at home and abroad, as shown in the table:

Personnel	The position	Version	The ice type	Ice force measuring method	Date
						Yang Guojin, Wessels	Liaodong Wan	Drilling platform	Mobile ice sheet, pressure ridge, ice pan	The acceleration information inverting is directly measured and used to pressure cell	1988～1992
Blenkarn	The Cook Inlet, Alaska	Drilling platform	Motion sea ice and pressure ridge	Strainometer on the member is tested pile with load cassette	1963～1969
						Lipsett and Gerard	Athabasca river, Pembina river	The river bridge pier	The motion river ice	By load box supporting bridge pier forward position and pile, with reference to performance estimation in the past	1967、1969
Mttnen	The Finland gulf	Beacon	Mobile ice sheet	Pressure cell is directly measured	1975

Frederking	The Rideau river	The river bridge pier	The motion river ice	Bridge pier contour with supercharging pressure pillow (fluid-filled flatjack) parcel 28%	1992
						Haynes	St Regis river	The river bridge pier	The motion river ice	Measure river ice pressure along bridge pier contour parcel CRREL pressure cell	1991
Timco	The Beafurt sea	Movable steel caisson man-made island	Motion sea ice and pressure ridge	MODEF Panel directly measures, strainometer	1980s
						Xu	Bohai Sea Gulf	The JZ-20 drilling platform	Mobile ice sheet	The layout pressure cell is directly measured on the surface of contact	1980s～1990s

By finding out in the table, at present the direct measurement of icing power is mainly realized by pressure cell or load box.The method principle that sensors such as working pressure box are directly measured is simple, workable, but also there are some shortcomings in this method.At first, pressure cell is all selective to the direction and the distribution situation of measured load, and is best for the well-distributed pressure measurement effect perpendicular to the pressure cell surface, and insensitive substantially for circumferential load, thereby is suitable for the pressure survey in the fluid.For the solid contact material, the load that the working pressure box records can depart from actual value (on the low side) gradually along with the increase of material stiffness; Secondly, for fluid pressure type and vibrating wire cell, because mechanical hysteresis effect is apparent in view, its high fdrequency component of the load that measures is with distortion [[Xie Yongli, Wang Xiaomou. about the demarcation and the analysis [J] of Miniature Resistance-Strain-Transforming Pressure Cell. Xian Institute of Highway journal, 1993,13 (3): 23～27.], [Chen Zhijian, the trip celebrating is assorted, Lin Min, Li Tiyan. the applied research [J] of vibrating wire cell in the rigid contact surfaces stress monitoring, Chinese engineering science, 2002,4 (12): 80～85.]]; In addition, pressure cell to the requirement of demarcating than higher, in the laboratory, adopt the mode of oil pressure to demarcate the generally relatively good [Xie Yongli of its effect, Wang Xiaomou. about the demarcation and the analysis [J] of Miniature Resistance-Strain-Transforming Pressure Cell. the Xian Institute of Highway journal, 1993,13 (3): 23～27.], but there is some difference for this situation force way original with it, adopt the result that sand, soil demarcates then often can not satisfactory [Xie Yongli, Wang Xiaomou. about the demarcation and the analysis [J] of Miniature Resistance-Strain-Transforming Pressure Cell. the Xian Institute of Highway journal, 1993,13 (3): 23～27.].

In view of the restriction of various measuring conditions, pressure cell often can only be distributed on limited several platform leg, and also restricted along the distribution angle in one week of leg post, therefore can't realize, omnibearing ice force measurement total to platform.Therefore people attempt dynamically total ice power that the method for the Whole Response (as acceleration responsive) by utilizing structure is come the inverse platform again, but this dynamic load inversion method need compare the accurate structural parameters of complete sum such as natural frequency, damping and mode etc., otherwise inversion result has than mistake.In addition, under measuring point number condition of limited, the layout of measuring point and the precision of measurement data all have bigger influence to inversion result.

Summary of the invention

At the problem of above-mentioned existence, the object of the present invention is to provide a kind of marine platform ice force measuring method based on local dense strain response, go for various load situation.

For achieving the above object, a kind of marine platform ice force measuring method based on local dense strain response of the present invention comprises the steps:

1) cylinder of suit on the ocean platform conduit with certain flexibility, this cylinder can slide up and down along described conduit, and does not have constraining force in vertical direction;

2) described cylinder inner wall along cylinder radially with the equidistant intensive strain sensing device that posts of hoop;

3) between described cylinder and conduit, fill silica gel with certain soft shape;

4) but install at the two ends of described cylinder and to make described cylinder be suspended in deepwater suspension material;

5) apply the known unit concentrated force in each foil gauge position, measure the strain data of all positions simultaneously, obtain the strain flexibility matrix thus, thereby described foil gauge is carried out data scaling;

6) clash into described cylinder by sea ice again,, carry out inverting by the data based following formula of the dynamic strain that measures in the inboard generation of cylinder strain:

${\left\{F\left(t\right)\right\}}_{n\×1}=\left\{\begin{array}{cc}{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×n}^{-1}{\left\{\mathrm{\ϵ}\left(t\right)\right\}}_{n\×1}& (m=n)\\ {\left({\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×m}^T{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{m\×n}\right)}^{-1}{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×m}^T{\left\{\mathrm{\ϵ}\left(t\right)\right\}}_{m\×1}& (m>n)\end{array}\right.$

Calculate actual ice power load, [δ in the formula _ε], { ε (t) } and { F (t) } be respectively strain flexibility matrix, t and ice the strain-responsive data that the effect of carrying measures down and the t ice power load constantly of inverting constantly.

Further, on the described cylinder inner wall pulley is installed, pulley is pressed against on the described conduit, and described cylinder can slide up and down along described conduit by this pulley.

Further, described strain sensing device is foil gauge or strain rosette.

Further, described cylinder is made by aluminium alloy.

Further, but described suspension material is a polyfoam.

The present invention adopts core structure can keep the geometric configuration of former conduit to greatest extent, reduce ice load and meet the variation that the change of ice face geometric configuration causes because of structure, advantage with direct measurement and indirect inverting, as long as sample frequency is enough high, to not have lag-effect, and because strain data directly comes from and the regional area of icing interactional structure, these packets contain the full detail of raw payload, therefore compare with pressure cell, it goes for various load situation.

Description of drawings

Fig. 1 is the structural profile synoptic diagram of device of the present invention.

Fig. 2 is that Figure 1A-A is to diagrammatic cross-section.

Fig. 3 is the dynamic loading of inverting and the comparison of actual measured value.

Embodiment:

At first, want the regional area of structure is demarcated to determine the strain flexibility matrix, then must carry out at the scene, and very difficult; Secondly because the fluctuation on sea level makes the frequent change of regional area; In addition for expose the foil gauge of structural outer surface protect in case with the collision of ice sheet in to damage also be the problem that must consider.Therefore, simple and easy to do for the problem and the feasible measurement that solve above-mentioned existence, we have designed a kind of telescoping structure model, as shown in Figure 1.Adopt core structure can keep the geometric configuration of former spud leg to greatest extent, reduce ice load and meet the variation that the change of ice face geometric configuration causes because of structure.One of suit has the cylinder 1 of certain flexibility on ocean platform conduit 6, cylinder 1 is made by aluminium alloy, the rigidity of cylinder 1 is crossed the low natural frequency of vibration of cylindrical structure that can cause and can not be satisfied in the accurate static(al) inverting much larger than the requirement of icing the carrier frequency rate, thereby for load inverting has in the future increased difficulty, cylinder 1 inwall is equipped with 8 pulleys 3 on 4 equidistant positions, two ends up and down, pulley 3 is pressed against on the conduit 6, cylinder 1 can slide up and down along conduit 6 by this pulley 3, and does not have constraining force in vertical direction; Cylinder 1 inwall radially equidistantly posts foil gauge 2 (also can be strain rosette) with hoop along cylinder 1, the dense distribution on acquiring a certain degree, and foil gauge 2 is pasted on cylinder 1 inside surface simultaneously, can effectively avoid the damage of ice sheet to foil gauge 2 like this; Between cylinder 1 and conduit 6, fill silica gel 5 with certain soft shape; Make cylinder 1 be suspended in deepwater polyfoam in the installation of the two ends of cylinder 1.After installing, apply the known unit concentrated force, measure the strain data of all positions simultaneously, obtain the strain flexibility matrix thus, thereby foil gauge 2 is carried out data scaling in each foil gauge 2 position; And then,, carry out inverting by the dynamic strain data that measure and calculate in cylinder 1 inboard generation strain by sea ice bump cylinder 1.Inverting is calculated and is carried out according to following formula:

${\left\{F\left(t\right)\right\}}_{n\×1}=\left\{\begin{array}{cc}{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×n}^{-1}{\left\{\mathrm{\ϵ}\left(t\right)\right\}}_{n\×1}& (m=n)\\ {\left({\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×m}^T{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{m\×n}\right)}^{-1}{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×m}^T{\left\{\mathrm{\ϵ}\left(t\right)\right\}}_{m\×1}& (m>n)\end{array}\right.$

Calculate actual ice power load, [δ in the formula _ε], { ε (t) } and { F (t) } be respectively strain flexibility matrix, t and ice the strain-responsive data that the effect of carrying measures down and the t ice power constantly of inverting constantly.

For the proof load inversion result, we make sleeve 1 thick about 1.5mm, and diameter 350mm promptly has tangible strain-responsive like this under less load, are convenient to manual loading control.Sleeve 1 inside surface has been arranged 26 foil gauges 2 altogether, spacing 3cm between each sheet.Be dynamically calibrated first, promptly apply dynamic focus pressure time-history curves (by force sensor measuring) in each foil gauge 2 positions respectively, synchronized sampling is measured the response of each foil gauge 2, and sample frequency is 512Hz.To the strain-responsive value of each sampling instant point divided by this force signal constantly, and in time domain, get weighted mean value and promptly obtain the strain-responsive flexibility matrix, we apply equally distributed dynamic pressure time-history curves in the diagram hatched example areas then, and measure this dynamic pressure time-history curves.When inverting evenly distributes dynamic pressure load, according to the strain-responsive of each measurement point of methods analyst mentioned above, and the distributed areas of definite dynamic force.Last load according to above-mentioned each sampling instant point of formula inverting.Fig. 3 is the dynamic loading of inverting and the comparison of actual measured value.Result calculated has clearly reflected the frequecy characteristic and the action rule of actual dynamic loading among the figure, and some is higher in the calculated value summary, and about 5～8N, relative error is about 5%～20% to absolute error basically.In the starting stage, the dynamic loading peak value is lower, and error is bigger, but along with the progressively increase of dynamic loading peak value and stable, error also decreases.

Claims (5)

1, a kind of marine platform ice force measuring method based on local dense strain response is characterized in that, comprises the steps:

1) cylinder of suit on the ocean platform conduit with certain flexibility, this cylinder can slide up and down along described conduit, and does not have constraining force in vertical direction;

2) described cylinder inner wall along cylinder radially with the equidistant intensive strain sensing device that posts of hoop;

3) between described cylinder and conduit, fill silica gel with certain soft shape;

4) but install at the two ends of described cylinder and to make described cylinder be suspended in deepwater suspension material;

5) apply the known unit concentrated force in each foil gauge position, measure the strain data of all positions simultaneously, obtain the strain flexibility matrix thus, thereby described foil gauge is carried out data scaling;

6) clash into described cylinder by sea ice again,, carry out inverting by the data based following formula of the dynamic strain that measures in the inboard generation of cylinder strain:

${\left\{F\left(t\right)\right\}}_{n\×1}=\left\{\begin{array}{cc}{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×n}^{-1}{\left\{\mathrm{\ϵ}\left(t\right)\right\}}_{n\×1}& (m=n)\\ {\left({\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×m}^T{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{m\×n}\right)}^{-1}{\left[{\mathrm{\δ}}_{\mathrm{\ϵ}}\right]}_{n\×m}^T{\left\{\mathrm{\ϵ}\left(t\right)\right\}}_{m\×1}& (m>n)\end{array}\right.$

Calculate actual ice power load, [δ in the formula _ε], { ε (t) } and { F (t) } be respectively strain flexibility matrix, t and ice the strain-responsive data that the effect of carrying measures down and the t ice power load constantly of inverting constantly.

2, a kind of marine platform ice force measuring method according to claim 1 based on local dense strain response, it is characterized in that, on the described cylinder inner wall pulley is installed, pulley is pressed against on the described conduit, and described cylinder can slide up and down along described conduit by this pulley.

3, a kind of marine platform ice force measuring method based on local dense strain response according to claim 1 and 2 is characterized in that, described strain sensing device is foil gauge or strain rosette.

4, a kind of marine platform ice force measuring method based on local dense strain response according to claim 3 is characterized in that described cylinder is made by aluminium alloy.

5, a kind of marine platform ice force measuring method based on local dense strain response according to claim 4 is characterized in that, but described suspension material is a polyfoam.

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