JP6960353B2

JP6960353B2 - tank

Info

Publication number: JP6960353B2
Application number: JP2018027918A
Authority: JP
Inventors: 正道安永
Original assignee: Kajima Corp
Current assignee: Kajima Corp
Priority date: 2018-02-20
Filing date: 2018-02-20
Publication date: 2021-11-05
Anticipated expiration: 2038-02-20
Also published as: JP2019142542A

Description

本発明はタンクに関する。 The present invention relates to a tank.

LNG（液化天然ガス）、LPG（液化石油ガス）などの極低温の液体を貯留する設備として、地上タンクが用いられることがある。 Ground tanks are sometimes used as equipment for storing ultra-low temperature liquids such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas).

図９は、地上タンクとしてLNGを貯留するLNGタンク１００の例を示したものである。LNGタンク１００は、地盤７中の杭４で支持された底版５上に防液堤２を固定してタンク躯体とし、その内側に鋼板等による内槽３ａと外槽３ｂを設けたものである。外槽３ｂの屋根部は鋼製またはコンクリート製であり、側部の鋼板は防液堤２と一体的に形成される。LNGは内槽３ａにて貯留し、内槽３ａと外槽３ｂの間に断熱材を配置して保冷を行う。 FIG. 9 shows an example of an LNG tank 100 that stores LNG as a ground tank. The LNG tank 100 has a liquid barrier 2 fixed on a bottom slab 5 supported by piles 4 in the ground 7 to form a tank skeleton, and an inner tank 3a and an outer tank 3b made of steel plates or the like are provided inside the tank skeleton. .. The roof portion of the outer tank 3b is made of steel or concrete, and the steel plate on the side portion is integrally formed with the liquid barrier 2. LNG is stored in the inner tank 3a, and a heat insulating material is arranged between the inner tank 3a and the outer tank 3b to keep it cool.

防液堤２は、内槽３ａが破損した場合にLNGの外部への液漏れを防ぐために設けられるコンクリート製の筒状の側壁であり、通常円筒状である。防液堤２は漏液時のLNGの液圧に耐え得る構造とする必要があり、そのため底版５に剛結合され、また図示しないタンク周方向（以下、単に周方向ということがある）の緊張材や縦方向の緊張材の緊張によるプレストレスを導入してコンクリートに所定の圧縮応力を生じさせる（例えば特許文献１、２参照）。 The liquid barrier 2 is a concrete tubular side wall provided to prevent liquid leakage from the LNG to the outside when the inner tank 3a is damaged, and is usually cylindrical. The liquid barrier 2 must have a structure that can withstand the hydraulic pressure of LNG at the time of liquid leakage. Therefore, it is rigidly coupled to the bottom slab 5, and tension in the tank circumferential direction (hereinafter, may be simply referred to as the circumferential direction) (hereinafter, may be simply referred to as the circumferential direction) is not shown. Prestress due to tension of the material or the tension material in the vertical direction is introduced to generate a predetermined compressive stress in the concrete (see, for example, Patent Documents 1 and 2).

防液堤２には、漏液時以外の常時であれば周方向の緊張材によるプレストレスと縦方向の緊張材によるプレストレスが加わっており、漏液時にはこれに加えてLNGの液荷重や温度荷重が作用する。防液堤２には常時、漏液時ともに液密性、気密性が求められており、どちらの状態においても部材の周方向および鉛直方向に圧縮応力が生じている領域（圧縮応力領域）を残すことで液密性や気密性を担保している。 Prestress due to the circumferential tension material and prestress due to the vertical tension material are applied to the liquid barrier 2 at all times except when liquid leaks, and in addition to this, when liquid leaks, the liquid load of LNG and Temperature load acts. The liquid barrier 2 is always required to be liquidtight and airtight at the time of liquid leakage, and in either state, a region (compressive stress region) in which compressive stress is generated in the circumferential direction and the vertical direction of the member is defined. By leaving it, liquidtightness and airtightness are guaranteed.

基準（LNG地上式貯槽指針）では圧縮応力領域が防液堤２の厚さ方向に10cm以上あれば良いとされているが、圧縮応力領域が厚ければ厚いほど液密性、気密性に優れている。周方向の応力については、通常、防液堤２に周方向の緊張材を大量に配置することにより常時、漏液時とも防液堤２の全厚で圧縮応力が生じる（全断面圧縮）ようにされており、問題となるのは鉛直方向の応力である。 According to the standard (LNG above-ground storage tank guideline), the compressive stress region should be 10 cm or more in the thickness direction of the liquid barrier 2, but the thicker the compressive stress region, the better the liquidtightness and airtightness. ing. Regarding the stress in the circumferential direction, usually, by arranging a large amount of tension material in the circumferential direction on the liquid barrier 2, compressive stress is always generated at the total thickness of the liquid barrier 2 even when liquid leaks (compression of the entire cross section). The problem is the stress in the vertical direction.

図１０は防液堤２の高さ方向且つ厚さ方向に沿った断面を示す図である。防液堤２内では周方向PC鋼材１１、縦方向PC鋼材１３（１３ａ、１３ｂ）が配置される。周方向PC鋼材１１は防液堤２の周方向の緊張材であり、防液堤２の全周に亘って配置される。縦方向PC鋼材１３は防液堤２の高さ方向の緊張材であり、縦方向PC鋼材１３ａは防液堤２の全高に亘って配置され、縦方向PC鋼材１３ｂは防液堤２の下部の外側に設けられたハンチ部２１に配置される。 FIG. 10 is a view showing a cross section of the liquid barrier 2 along the height direction and the thickness direction. A circumferential PC steel 11 and a vertical PC steel 13 (13a, 13b) are arranged in the liquid barrier 2. The circumferential PC steel material 11 is a tension material in the circumferential direction of the liquid barrier 2, and is arranged over the entire circumference of the liquid barrier 2. The vertical PC steel 13 is a tension material in the height direction of the liquid barrier 2, the vertical PC steel 13a is arranged over the entire height of the liquid barrier 2, and the vertical PC steel 13b is the lower portion of the liquid barrier 2. It is arranged on the haunch portion 21 provided on the outside of the.

前記したように、防液堤２では周方向PC鋼材１１が大量に配置されるため、その影響で防液堤２の下部には大きな外側引張の鉛直面内曲げモーメント（防液堤２を内側へ曲げようとする曲げモーメント）が常時に発生する。そのため、縦方向PC鋼材１３ａ、１３ｂによって防液堤２の下部のPC鋼材量を多くして上記の曲げモーメントによる引張応力を打ち消している。 As described above, since a large amount of PC steel material 11 in the circumferential direction is arranged on the liquid barrier 2, due to the influence of this, a large outward tension vertical inward bending moment (the liquid barrier 2 is inside) is applied to the lower part of the liquid barrier 2. Bending moment to bend to) is constantly generated. Therefore, the amount of PC steel in the lower part of the liquid barrier 2 is increased by the vertical PC steels 13a and 13b to cancel the tensile stress due to the bending moment.

図１１は、縦方向PC鋼材１３（１３ａ、１３ｂ）による鉛直面内曲げモーメントを０とした場合の、防液堤２の常時の鉛直面内曲げモーメントMと漏液時の鉛直面内曲げモーメントM’を、縦軸を曲げモーメントの値、横軸を防液堤２の下端からの高さとして示す図である。曲げモーメントは防液堤２の周方向の単位長さ当たりの曲げモーメントであり、防液堤２に外側引張の曲げモーメントが生じる場合を負、防液堤２に外側圧縮の曲げモーメント（防液堤２を外側へ曲げようとする曲げモーメント）が生じる場合を正とする。 FIG. 11 shows the normal vertical inward bending moment M of the liquid barrier 2 and the vertical inward bending moment at the time of liquid leakage when the vertical inward bending moment of the vertical PC steel 13 (13a, 13b) is set to 0. It is a figure which shows M'as the value of the bending moment on the vertical axis, and the height from the lower end of the liquid barrier 2 on the horizontal axis. The bending moment is the bending moment per unit length in the circumferential direction of the liquid barrier 2, and is negative when the bending moment of outer tension is generated in the liquid barrier 2, and the bending moment of outer compression (liquid barrier) in the liquid barrier 2. The case where a bending moment (a bending moment for bending the bank 2 to the outside) occurs is positive.

前記したように、防液堤２の下部には常時に大きな外側引張の鉛直面内曲げモーメントMが発生する。一方、漏液時には防液堤２の下部に外側圧縮の鉛直面内曲げモーメントM’が発生するが、前者の曲げモーメントMの方が後者の曲げモーメントM’よりかなり大きい値（絶対値）となる。 As described above, a large vertical inward bending moment M of outward tension is constantly generated in the lower part of the liquid barrier 2. On the other hand, at the time of liquid leakage, a vertical compression inward bending moment M'is generated at the lower part of the liquid barrier 2, but the former bending moment M is considerably larger (absolute value) than the latter bending moment M'. Become.

特許第5516962号Patent No. 5516962 特許第4847994号Patent No. 4847994

現在、より効率が良く合理的な方法で防液堤にプレストレスを導入し、縦方向の緊張材をより低減できる方法が求められている。この点、図１１に示すように常時と漏液時に防液堤２に発生する鉛直面内曲げモーメントM、M’がアンバランスであると、防液堤２に圧縮応力を残すためには、大きい方の曲げモーメントMに合わせた量の縦方向PC鋼材１３が必要となり、無駄が大きくなる。 At present, there is a demand for a method that can introduce prestress to the liquid barrier in a more efficient and rational manner and further reduce the tension material in the vertical direction. In this regard, as shown in FIG. 11, if the vertical bending moments M and M'generated in the liquid barrier 2 at all times and during liquid leakage are unbalanced, in order to leave compressive stress in the liquid barrier 2, it is necessary to leave compressive stress. A vertical PC steel material 13 having an amount corresponding to the larger bending moment M is required, which increases waste.

本発明は上記の問題に鑑みてなされたものであり、縦方向の緊張材の量を低減できるタンク等を提供することを目的とする。 The present invention has been made in view of the above problems, and an object of the present invention is to provide a tank or the like capable of reducing the amount of tension material in the vertical direction.

前述した課題を解決するための本発明は、筒状の側壁と、前記側壁の内側で液体を貯留する内槽とを有するタンクであって、前記側壁には、周方向の緊張材と縦方向の緊張材の緊張によるプレストレスが導入され、前記縦方向の緊張材は、前記側壁の高さ方向且つ厚さ方向の断面を見た時に、前記側壁の下端から高さ方向の所定範囲に亘って曲線状に、且つ前記所定範囲において、前記側壁に生じる鉛直面内の曲げモーメントの高さ方向の分布が、前記液体の漏液時と、漏液時以外の常時とで曲げモーメントの向きが反対であり、且つ絶対値が等しくなるように配置されることを特徴とするタンクである。 The present invention for solving the above-mentioned problems is a tank having a tubular side wall and an inner tank for storing liquid inside the side wall, and the side wall has a tension material in the circumferential direction and a longitudinal direction. Prestress due to the tension of the tension material is introduced, and the tension material in the vertical direction extends over a predetermined range in the height direction from the lower end of the side wall when the cross section in the height direction and the thickness direction of the side wall is viewed. In a curved shape and within the predetermined range, the distribution of the bending moment in the vertical plane generated on the side wall in the height direction is such that the direction of the bending moment is different when the liquid leaks and when the liquid leaks at all times. The tanks are opposite and are arranged so that their absolute values are equal.

また、前記側壁の下部の内側にハンチ部が設けられることが望ましい。 Further, it is desirable that a haunch portion is provided inside the lower portion of the side wall.

前記所定範囲は、前記側壁の下端から、前記周方向の緊張材によるプレストレスにより前記側壁に生じる鉛直面内の曲げモーメントの高さ方向の分布の変曲点であって最も下にある第１変曲点の高さまでの範囲を含むことが望ましい。あるいは、前記側壁の下端から、前記第１変曲点の直上の前記変曲点である第２変曲点の高さまでの範囲を含んでいてもよい。さらには、前記側壁の全高に亘る範囲であっていてもよい。 The predetermined range is the inflection point of the distribution of the bending moment in the vertical plane in the vertical plane caused by the prestress of the tension material in the circumferential direction from the lower end of the side wall in the height direction, and is the lowest first. It is desirable to include the range up to the height of the inflection point. Alternatively, the range from the lower end of the side wall to the height of the second inflection point, which is the inflection point immediately above the first inflection point, may be included. Further, it may be a range extending over the entire height of the side wall.

本発明では、LNGタンクの防液堤等の側壁において、縦方向の緊張材を曲線状に偏芯配置することで、容易に、常時と漏液時の鉛直面内曲げモーメントを符号（曲げモーメントの向き）反対且つ絶対値同等とする事が可能となる。これにより、側壁に圧縮応力領域を残すうえで縦方向の緊張材を最も合理的な配置とし、最少の縦方向PC鋼材量で側壁に圧縮応力領域を残すことが可能になる。 In the present invention, the vertical tension material is eccentrically arranged in a curved shape on the side wall of the liquid barrier of the LNG tank, so that the bending moment in the vertical plane at all times and at the time of liquid leakage can be easily coded (bending moment). Orientation) Opposite and absolute value can be equalized. This makes it possible to make the longitudinal tension material the most rational arrangement for leaving the compressive stress region on the side wall, and to leave the compressive stress region on the side wall with the minimum amount of vertical PC steel.

また、本発明では側壁の下部内側にハンチを設けて縦方向の緊張材の外側への偏芯量を増大させることで、周方向の緊張材によるプレストレスにより鉛直面内曲げモーメントの絶対値が大きくなる側壁下部においても、この曲げモーメントを軽減して常時と漏液時の鉛直面内曲げモーメントを符号反対且つ絶対値同等とする事が容易になる。 Further, in the present invention, a haunch is provided inside the lower part of the side wall to increase the amount of eccentricity to the outside of the tension material in the vertical direction, so that the absolute value of the bending moment in the vertical plane is increased by the prestress caused by the tension material in the circumferential direction. Even in the lower part of the side wall, which becomes large, it becomes easy to reduce this bending moment so that the bending moment in the vertical plane at all times and at the time of liquid leakage are opposite in sign and equal to the absolute value.

縦方向の緊張材の曲線状配置の範囲は、周方向の緊張材によるプレストレスにより側壁に生じる鉛直面内曲げモーメントが大きくなる範囲を含んでいればよく、例えば側壁の下端から前記の第１変曲点や第２変曲点までの範囲を含むものとできる。あるいは側壁の全高に亘って曲線状配置としてもよい。 The range of the curved arrangement of the tension material in the vertical direction may include a range in which the vertical inward bending moment generated in the side wall due to the prestress caused by the tension material in the circumferential direction becomes large, for example, from the lower end of the side wall to the first. It can include the range up to the inflection point and the second inflection point. Alternatively, it may be arranged in a curved line over the entire height of the side wall.

本発明により、縦方向の緊張材の量を低減できるタンク等を提供することができる。 INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a tank or the like capable of reducing the amount of tension material in the vertical direction.

LNGタンク１を示す図。The figure which shows the LNG tank 1. 防液堤２ａを示す図。The figure which shows the liquid barrier 2a. 防液堤２ａの鉛直面内曲げモーメントM1を示す図。The figure which shows the vertical bending moment M1 of a liquid barrier 2a. 防液堤２ａの鉛直面内曲げモーメントM、M’を示す図。The figure which shows the vertical bending moment M, M'of a liquid barrier 2a. 防液堤２ａの鉛直面内曲げモーメントM1〜M4を示す図。The figure which shows the vertical bending moment M1 to M4 of a liquid barrier 2a. 縦方向PC鋼材１５の偏芯量ｄを示す図。The figure which shows the eccentricity d of the vertical PC steel material 15. 鉛直面内曲げモーメントM、M’による防液堤２ａの厚さ方向の応力度分布を示す図。The figure which shows the stress degree distribution in the thickness direction of the liquid barrier 2a by the vertical bending moment M, M'. 偏芯無し、曲線状偏芯配置、直線状偏芯配置の比較について示す図。The figure which shows the comparison of no eccentricity, curved eccentric arrangement, and linear eccentric arrangement. LNGタンク１００を示す図。The figure which shows the LNG tank 100. 防液堤２を示す図。The figure which shows the liquid barrier 2. 防液堤２の鉛直面内曲げモーメントM、M’を示す図。The figure which shows the vertical bending moment M, M'of a liquid barrier 2.

以下、図面に基づいて本発明の好適な実施形態について詳細に説明する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

（１．LNGタンク１）
図１は本発明の実施形態に係るLNGタンク１を示す図である。LNGタンク１は基本的には図９等で説明したLNGタンク１００と同様であり、図９等で説明したものと同様の構成については図等で同じ符号を付して説明を省略する。 (1. LNG tank 1)
FIG. 1 is a diagram showing an LNG tank 1 according to an embodiment of the present invention. The LNG tank 1 is basically the same as the LNG tank 100 described with reference to FIG. 9 and the like, and the same components as those described with reference to FIG. 9 and the like are designated by the same reference numerals in the drawings and the like, and the description thereof will be omitted.

本実施形態のLNGタンク１は、図９等で説明したLNGタンク１００に対し、後述する防液堤２ａの詳細構成において異なる。防液堤２ａは前記と同様、底版５と剛結合され一体化されたコンクリート製の筒状の側壁であり、本実施形態では円筒状である。防液堤２ａの内側には内槽３ａと外槽３ｂが配置されており、防液堤２ａは内槽３ａが破損した場合にLNGの外部への液漏れを防ぐ。 The LNG tank 1 of the present embodiment differs from the LNG tank 100 described with reference to FIG. 9 and the like in the detailed configuration of the liquid barrier 2a described later. Similar to the above, the liquid barrier 2a is a concrete tubular side wall that is rigidly coupled and integrated with the bottom slab 5, and is cylindrical in the present embodiment. An inner tank 3a and an outer tank 3b are arranged inside the liquid barrier 2a, and the liquid barrier 2a prevents liquid from leaking to the outside of the LNG when the inner tank 3a is damaged.

（２．防液堤２ａ）
図２は防液堤２ａを模式的に示す図であり、防液堤２ａの高さ方向且つ厚さ方向に沿った断面を見たものである。 (2. Liquid barrier 2a)
FIG. 2 is a diagram schematically showing the liquid barrier 2a, and is a view of a cross section of the liquid barrier 2a along the height direction and the thickness direction.

防液堤２ａには周方向PC鋼材１１、縦方向PC鋼材１５（１５ａ、１５ｂ）が配置され、これらのPC鋼材の緊張によるプレストレス（圧縮力）が導入される。各PC鋼材にはPC鋼線等が用いられ、これらが防液堤２ａ等に埋設された図示しないシース内に配置される。PC鋼材の緊張後、シース内にはモルタル等の固化材による充填材が充填（グラウト）される。ただし、PC鋼材にアンボンドPC鋼材を用い、シースを必要としない場合もある。なお、防液堤２ａには鉄筋（不図示）も埋設されるが、ここでは説明を省略する。 A circumferential PC steel 11 and a vertical PC steel 15 (15a, 15b) are arranged on the liquid barrier 2a, and prestress (compressive force) due to tension of these PC steels is introduced. PC steel wire or the like is used for each PC steel material, and these are arranged in a sheath (not shown) embedded in the liquid barrier 2a or the like. After the PC steel is strained, the sheath is filled (grouted) with a filler made of a solidifying material such as mortar. However, there are cases where unbonded PC steel is used as the PC steel and a sheath is not required. Reinforcing bars (not shown) are also buried in the liquid barrier 2a, but the description thereof will be omitted here.

周方向PC鋼材１１は防液堤２ａの周方向（図２の紙面法線方向に対応する）の緊張材であり、防液堤２ａの全周に亘って配置される。周方向PC鋼材１１の両端は防液堤２ａの周方向の所定位置に設けた外側への突出部（ピラスター）で定着される。 The circumferential PC steel material 11 is a tension material in the circumferential direction of the liquid barrier 2a (corresponding to the paper normal direction in FIG. 2), and is arranged over the entire circumference of the liquid barrier 2a. Both ends of the circumferential PC steel 11 are fixed by outward protrusions (pilasters) provided at predetermined positions in the circumferential direction of the liquid barrier 2a.

縦方向PC鋼材１５（１５ａ、１５ｂ）は防液堤２ａの高さ方向の緊張材である。縦方向PC鋼材１５ａは防液堤２ａの全高に亘って配置され、下端が底版５内で定着され、上端が防液堤２ａの頂部で定着される。縦方向PC鋼材１５ｂは防液堤２ａの下部に配置され、下端が底版５内で定着され、上端が防液堤２ａの高さ方向の途中で定着される。 The vertical PC steel materials 15 (15a, 15b) are tension materials in the height direction of the liquid barrier 2a. The vertical PC steel 15a is arranged over the entire height of the liquid barrier 2a, the lower end is fixed in the bottom slab 5, and the upper end is fixed at the top of the liquid barrier 2a. The vertical PC steel material 15b is arranged at the lower part of the liquid barrier 2a, the lower end is fixed in the bottom slab 5, and the upper end is fixed in the middle of the liquid barrier 2a in the height direction.

縦方向PC鋼材１５ａは蛇行して配置され、ほぼ全高に亘って曲線状となっている。本実施形態では縦方向PC鋼材１５ａが複数の曲率による曲線状に配置される。 The vertical PC steel material 15a is arranged in a meandering manner and has a curved shape over almost the entire height. In the present embodiment, the vertical PC steel material 15a is arranged in a curved shape due to a plurality of curvatures.

縦方向PC鋼材１５ｂは、同一の高さ範囲にある縦方向PC鋼材１５ａの部分と同様の形状で蛇行して配置され、単一の又は複数の曲率による曲線状となっている。なお、縦方向PC鋼材１５ｂは省略することも可能である。 The vertical PC steel material 15b is arranged in a meandering shape similar to the portion of the vertical PC steel material 15a in the same height range, and has a curved shape with a single or a plurality of curvatures. The vertical PC steel material 15b can be omitted.

防液堤２ａの下部では、ハンチ部２１ａが防液堤２ａの内側に張出すように設けられる。本実施形態のハンチ部２１ａは直角三角形状の断面を有するが、矩形状の断面であってもよい。 At the lower part of the liquid barrier 2a, the haunch portion 21a is provided so as to project inside the liquid barrier 2a. The haunch portion 21a of the present embodiment has a right-angled triangular cross section, but may have a rectangular cross section.

図３は、周方向PC鋼材１１の緊張によるプレストレスにより生じる防液堤２ａの鉛直面内曲げモーメントM1の例を、縦軸を曲げモーメントの値、横軸を防液堤２ａの下端からの高さとして示す図である。前記と同様、曲げモーメントは防液堤２ａの周方向の単位長さ当たりの曲げモーメントであり、防液堤２ａに外側引張の曲げモーメントが生じる場合を負、防液堤２ａに外側圧縮の曲げモーメントが生じる場合を正とする。これは後述する図４、５でも同様である。 FIG. 3 shows an example of the vertical bending moment M1 of the liquid barrier 2a caused by prestress due to tension of the circumferential PC steel material 11, with the vertical axis representing the bending moment value and the horizontal axis representing the lower end of the liquid barrier 2a. It is a figure which shows as a height. Similar to the above, the bending moment is the bending moment per unit length in the circumferential direction of the liquid barrier 2a. The case where a moment occurs is positive. This also applies to FIGS. 4 and 5 described later.

本実施形態のハンチ部２１ａの高さ範囲ｂ（図２参照）は、防液堤２ａの下端から、図３に示す第１符号変更点までの範囲とする。この第１符号変更点は、鉛直面内曲げモーメントM1の符号（曲げモーメントの向き）が最初に逆転する高さを示す。ただし、ハンチ部２１ａの高さ範囲ｂはこれに限らない。 The height range b (see FIG. 2) of the haunch portion 21a of the present embodiment is a range from the lower end of the liquid barrier 2a to the first code change point shown in FIG. This first sign change point indicates the height at which the sign (direction of the bending moment) of the vertical bending moment M1 is first reversed. However, the height range b of the haunch portion 21a is not limited to this.

（３．縦方向PC鋼材１５の偏芯配置）
防液堤２ａ内の縦方向PC鋼材１５の配置は、図４に示すように、防液堤２ａの全高に亘って、漏液時以外の常時に発生する鉛直面内曲げモーメントMの高さ方向の分布と漏液時に発生する鉛直面内曲げモーメントM’の高さ方向の分布の符号が反対となり、且つ絶対値が同等となるように定める。すなわち、鉛直面内曲げモーメントMの高さ方向の分布形状と、鉛直面内曲げモーメントM’の高さ方向の分布形状が、曲げモーメント０の線を中心として対称となるようにする。 (3. Eccentric arrangement of vertical PC steel material 15)
As shown in FIG. 4, the arrangement of the vertical PC steel material 15 in the liquid barrier 2a is the height of the vertical inward bending moment M that always occurs except when the liquid leaks over the entire height of the liquid barrier 2a. The signs of the distribution in the direction and the distribution in the height direction of the vertical bending moment M'generated at the time of liquid leakage are opposite, and the absolute values are set to be the same. That is, the distribution shape of the vertical bending moment M in the height direction and the distribution shape of the vertical bending moment M'in the height direction are made symmetrical about the line of the bending moment 0.

この時、縦方向PC鋼材１５の緊張によるプレストレスによって防液堤２ａに生じさせる必要がある鉛直面内曲げモーメントが図５（ａ）のM2であり、これにより前記の鉛直面内曲げモーメントM1を打ち消して図４のような曲げモーメントM、M’の分布を実現する。 At this time, the vertical inward bending moment that needs to be generated in the liquid barrier 2a by the prestress due to the tension of the vertical PC steel material 15 is M2 in FIG. 5 (a), whereby the vertical inward bending moment M1 is shown. Is canceled out to realize the distribution of bending moments M and M'as shown in FIG.

なお、図５（ｂ）は、LNGの漏液時の液荷重（液圧）により防液堤２ａに生じる鉛直面内曲げモーメントM3と、LNGの漏液時の温度荷重により防液堤２ａに生じる鉛直面内曲げモーメントM4を示す図である。温度荷重は、LNGの漏液時に極低温のLNGによって防液堤２ａの内面の温度が低下する際に、防液堤２ａの内面のコンクリートの収縮を底版５や防液堤２ａの他の部位が拘束することにより発生する荷重である。 In addition, FIG. 5B shows the vertical inward bending moment M3 generated in the liquid barrier 2a due to the liquid load (hydraulic pressure) at the time of LNG leakage, and the liquid barrier 2a due to the temperature load at the time of LNG leakage. It is a figure which shows the vertical bending inward bending moment M4 generated. The temperature load causes the shrinkage of the concrete on the inner surface of the liquid barrier 2a when the temperature of the inner surface of the liquid barrier 2a drops due to the cryogenic LNG when the LNG leaks, and the bottom slab 5 and other parts of the liquid barrier 2a. Is the load generated by restraining.

図４に示す常時の鉛直面内曲げモーメントMは鉛直面内曲げモーメントM1、M2の和として表され、漏液時の鉛直面内曲げモーメントM’は鉛直面内曲げモーメントM1〜M4の和となっている。鉛直面内曲げモーメントM、M’には防液堤２ａや外槽３ｂの屋根部の自重による鉛直面内曲げモーメントを加えてもよいが、その値は小さく影響はほぼ無い。また温度荷重も季節による違いはほぼ無い。 The normal vertical inward bending moment M shown in FIG. 4 is expressed as the sum of the vertical inward bending moments M1 and M2, and the vertical inward bending moment M'at the time of liquid leakage is the sum of the vertical inward bending moments M1 to M4. It has become. The vertical inward bending moments M and M'may be added to the vertical inward bending moments due to the weight of the roof of the liquid barrier 2a and the outer tank 3b, but the values are small and have almost no effect. In addition, there is almost no difference in temperature load depending on the season.

本実施形態では、図５（ａ）のような鉛直面内曲げモーメントM2が発生するように、縦方向PC鋼材１５を防液堤２ａの厚さ方向の中心ａ（図２参照）から偏芯して配置する。図６は、この際に必要な縦方向PC鋼材１５の偏芯量ｄ（図２参照）を、縦軸を偏芯量ｄ、横軸を防液堤２ａの下端からの高さとして示す図である。偏芯量ｄは防液堤２ａの中心ａから外側に偏芯している場合を正、内側に偏芯している場合を負とする。 In the present embodiment, the vertical PC steel material 15 is eccentric from the center a (see FIG. 2) in the thickness direction of the liquid barrier 2a so that the vertical inward bending moment M2 as shown in FIG. 5A is generated. And place it. FIG. 6 shows the eccentricity d (see FIG. 2) of the vertical PC steel material 15 required at this time, with the vertical axis representing the eccentricity d and the horizontal axis representing the height from the lower end of the liquid barrier 2a. Is. The eccentricity d is positive when it is eccentric to the outside from the center a of the liquid barrier 2a, and negative when it is eccentric to the inside.

鉛直面内曲げモーメントM2は、縦方向PC鋼材１５の緊張によるプレストレスの大きさと偏芯量ｄの積によって定まる。プレストレスの大きさは縦方向PC鋼材１５の各高さで一定なので、偏芯量ｄは鉛直面内曲げモーメントM2に比例する。そのため、偏芯量ｄの高さ方向の分布形状は、基本的には鉛直面内曲げモーメントM2の高さ方向の分布形状に沿った（比例した）形になる。従って、本実施形態では縦方向PC鋼材１５を鉛直面内曲げモーメントM2の高さ方向の分布形状に合わせて曲線状に蛇行して配置する。 The vertical inward bending moment M2 is determined by the product of the magnitude of prestress due to the tension of the vertical PC steel material 15 and the amount of eccentricity d. Since the magnitude of prestress is constant at each height of the vertical PC steel material 15, the eccentricity d is proportional to the inward bending moment M2 in the vertical plane. Therefore, the distribution shape of the eccentric amount d in the height direction is basically a shape along (proportional) to the distribution shape of the vertical bending moment M2 in the height direction. Therefore, in the present embodiment, the vertical PC steel 15 is arranged in a curved line according to the distribution shape of the vertical inward bending moment M2 in the height direction.

図６のグラフにおいて、防液堤２ａの下端から高さ10mまでの範囲の偏芯量ｄが、それ以上の高さでの偏芯量ｄとずれているのは、この範囲に縦方向PC鋼材１５ｂが追加配置されるためである。すなわち、縦方向PC鋼材１５ｂを追加することにより、縦方向PC鋼材１５ａによるプレストレスに縦方向PC鋼材１５ｂによるプレストレスが加わり、大きな縦方向プレストレスとなることから、偏芯量を小さくすることが可能である。例えば、防液堤２ａの周方向の単位長さ当たり複数本（ｎ本）の縦方向PC鋼材を同様の曲線状配置によって配置する場合、１本あたりの偏芯量ｄの絶対値は1/ｎで済み、図６のグラフではその分防液堤２ａの下端から高さ10mまでの範囲の偏芯量ｄの絶対値が小さくなっている。 In the graph of FIG. 6, the eccentricity d in the range from the lower end of the liquid barrier 2a to the height of 10 m deviates from the eccentricity d at a height higher than that in the vertical PC. This is because the steel material 15b is additionally arranged. That is, by adding the vertical PC steel material 15b, the prestress caused by the vertical PC steel material 15a is added to the prestress caused by the vertical PC steel material 15b, resulting in a large vertical prestress. Therefore, the amount of eccentricity should be reduced. Is possible. For example, when a plurality of (n) vertical PC steel materials are arranged in the same curved arrangement per unit length in the circumferential direction of the liquid barrier 2a, the absolute value of the eccentricity d per one is 1 /. In the graph of FIG. 6, the absolute value of the eccentricity d in the range from the lower end of the liquid barrier 2a to the height of 10 m is smaller.

なお、ここではｎ＝３であり、図６のグラフの防液堤２ａの下端から高さ10mまでの範囲の偏芯量ｄは、縦方向PC鋼材１５ｂを追加しない場合の１/３となっている。 Here, n = 3, and the eccentricity d in the range from the lower end of the liquid barrier 2a in the graph of FIG. 6 to a height of 10 m is 1/3 of the case where the vertical PC steel material 15b is not added. ing.

縦方向PC鋼材１５の偏芯配置は、例えば、図示しない受け架台にシースを固定した状態で防液堤２ａのコンクリートを打設し、その後シース内にPC鋼材を挿入することで実施できる。アンボンドPC鋼材を用いる場合には、受け架台にアンボンドPC鋼材を直接固定した状態で、防液堤２ａのコンクリートを打設すればよい。縦方向PC鋼材１５の緊張は、周方向PC鋼材１１の緊張後に行う。 The eccentric arrangement of the vertical PC steel material 15 can be carried out, for example, by placing concrete of the liquid barrier 2a in a state where the sheath is fixed to a pedestal (not shown), and then inserting the PC steel material into the sheath. When the unbonded PC steel material is used, the concrete of the liquid barrier 2a may be placed with the unbonded PC steel material directly fixed to the pedestal. The tension of the vertical PC steel material 15 is performed after the tension of the circumferential PC steel material 11.

防液堤２ａは施工当初から底版５に剛結合した状態で構築してもよいし、ピン・スライド等の機構により周方向PC鋼材１１の緊張時に防液堤２ａが底版５に対して移動できるようにしておき、防液堤２ａと底版５を剛結合した後で縦方向PC鋼材１５を緊張してもよい。縦方向PC鋼材１５の偏芯量はこれらの施工方法の違いによっても若干変化し、各施工方法において、前記の鉛直面内曲げモーメントM、M’の符号が反対であり、且つ絶対値が同等となるように定められる。 The liquid barrier 2a may be constructed in a state of being rigidly connected to the bottom slab 5 from the beginning of construction, or the liquid barrier 2a can be moved with respect to the bottom slab 5 when the circumferential PC steel material 11 is tense by a mechanism such as a pin / slide. In this way, the vertical PC steel material 15 may be strained after the liquid barrier 2a and the bottom slab 5 are rigidly bonded. The amount of eccentricity of the vertical PC steel material 15 changes slightly depending on the difference in these construction methods, and in each construction method, the signs of the above-mentioned vertical inward bending moments M and M'are opposite and the absolute values are the same. It is determined to be.

このように、本実施形態では、LNGタンク１の防液堤２ａにおいて、縦方向PC鋼材１５を曲線状に偏芯配置することで、容易に、常時と漏液時の鉛直面内曲げモーメントM、M’を符号反対且つ絶対値同等とする事が可能となる。これにより、防液堤２ａに圧縮応力領域を残すうえで縦方向PC鋼材１５を最も合理的な配置とし、図１１等で説明したように縦方向PC鋼材の量を大きい方の曲げモーメントMに合わせて設計する必要が無くなる。結果、最少の縦方向PC鋼材量で防液堤２ａに圧縮応力領域を残すことが可能になり、無駄が軽減される。 As described above, in the present embodiment, the vertical PC steel material 15 is eccentrically arranged in a curved shape on the liquid barrier 2a of the LNG tank 1, so that the vertical bending moment M in the vertical plane at all times and at the time of liquid leakage can be easily achieved. , M'can be opposite in sign and equal to absolute value. As a result, the vertical PC steel material 15 is arranged in the most rational manner in order to leave the compressive stress region on the liquid barrier 2a, and the amount of the vertical PC steel material is set to the larger bending moment M as described in FIG. 11 and the like. There is no need to design together. As a result, it becomes possible to leave a compressive stress region on the liquid barrier 2a with the minimum amount of PC steel in the vertical direction, and waste is reduced.

すなわち、本実施形態では常時と漏液時の鉛直面内曲げモーメントM、M’が符号反対且つ絶対値同等であることから、鉛直面内曲げモーメントM、M’（のみ）により生じる常時と漏液時の防液堤２ａ内の厚さ方向の応力度分布を考えた場合、図７（ａ）に示すように符号反対になり絶対値が等しくなる。そのため、鉛直方向の応力を常時、漏液時とも全断面圧縮とするには、鉛直面内曲げモーメントM、M’により生じる最大の引張応力ｃを打ち消すだけのプレストレスを縦方向PC鋼材１５で加えていればよい。 That is, in the present embodiment, since the vertical inward bending moments M and M'are opposite to each other and have the same absolute value, the vertical inward bending moments M and M'(only) are caused by the vertical inward bending moments M and M'(only). When considering the stress distribution in the thickness direction in the liquid barrier 2a at the time of liquid, the signs are opposite and the absolute values are equal as shown in FIG. 7A. Therefore, in order to constantly compress the entire cross section of the vertical stress even when the liquid leaks, the vertical PC steel material 15 is prestressed to cancel the maximum tensile stress c generated by the vertical inward bending moments M and M'. You just have to add it.

一方、図１１のように鉛直面内曲げモーメントM、M’がアンバランスであると、防液堤内の厚さ方向の応力度分布も図７（ｂ）のように常時と漏液時でアンバランスとなり、鉛直方向の応力を常時、漏液時とも全断面圧縮とするには、大きい方の曲げモーメントMによる最大の引張応力ｃ’を打ち消すだけのプレストレスを縦方向PC鋼材によって加えていることが必要になり、必要なPC鋼材量が増加する。 On the other hand, when the vertical bending moments M and M'are unbalanced as shown in FIG. 11, the stress distribution in the thickness direction in the liquid barrier is also unbalanced at all times and during liquid leakage as shown in FIG. 7 (b). In order to achieve balance and to keep the vertical stress at all times and to compress the entire cross section even when the liquid leaks, prestress is applied by the vertical PC steel material to cancel the maximum tensile stress c'due to the larger bending moment M. Will be required, and the amount of PC steel required will increase.

例えば図８（ａ）のように、容量23万KLのLNGタンクにおいて高さ45mの防液堤Ａの下端から5.4m高さまでの範囲をハンチ部Ｂとし、防液堤Ａの下端の厚さを1.0m、ハンチ部Ｂより上の部分の厚さを0.65m、防液堤Ａの内径を86mとし、縦方向PC鋼材Ｃを
１．偏芯無し
２．曲線状の偏芯配置（常時と漏液時の鉛直面内曲げモーメントM、M’が符号反対、絶対値同等となるようにする）
３．直線状の偏芯配置（ハンチ部Ｂの外面に沿って傾斜）
とするケースを仮定する。なおこの例ではハンチ部Ｂを直角三角形状とし、防液堤Ａの外側に設けている。 For example, as shown in FIG. 8A, in an LNG tank having a capacity of 230,000 KL, the range from the lower end of the liquid barrier A having a height of 45 m to a height of 5.4 m is defined as the haunch portion B, and the thickness of the lower end of the liquid barrier A is defined as the haunch portion B. 1.0 m, the thickness of the part above the haunch part B is 0.65 m, the inner diameter of the liquid barrier A is 86 m, and the vertical PC steel material C is 1. No eccentricity 2. Curved eccentric arrangement (make sure that the bending moments M and M'in the vertical plane at all times and during liquid leakage are opposite to each other and have the same absolute value)
3. 3. Linear eccentric arrangement (inclined along the outer surface of the haunch portion B)
Suppose the case. In this example, the haunch portion B has a right-angled triangular shape and is provided outside the liquid barrier A.

これらのケースにおいて、ハンチ部Ｂの範囲で常時および漏液時の鉛直方向の応力が全断面圧縮となるのに必要なプレストレスの大きさと、当該プレストレスを加えた時の常時および漏液時の防液堤Ａの下端の鉛直面内曲げモーメントM、M’の値を算出したものが図８（ｂ）である。 In these cases, the magnitude of prestress required for the vertical stress in the range of the haunch portion B to be compressed in the entire cross section at all times and during liquid leakage, and at all times and during liquid leakage when the prestress is applied. 8 (b) shows the calculated values of the vertical bending moments M and M'at the lower end of the liquid barrier A.

図８（ｂ）に示すように、常時と漏液時において全断面圧縮とするためのプレストレスの大きさ（縦方向PC鋼材ＣのPC鋼材量に比例する）は、２．のケースで4044kNとなり、１．のケース（5979kN）に比べて約68％、３．のケース（4903kN）に比べて約82％と小さくなる。 As shown in FIG. 8 (b), the magnitude of prestress (proportional to the amount of PC steel material in the vertical PC steel material C) for compressing the entire cross section at all times and at the time of liquid leakage is 2. In the case of, it becomes 4044kN, and 1. Approximately 68% compared to the case (5979kN), 3. It is about 82% smaller than the case (4903kN).

このように、本実施形態の曲線状の偏芯配置は、偏芯の無い場合だけでなく直線状に偏芯配置した場合に比べてもPC鋼材量の低減効果がある。これは、縦方向PC鋼材Ｃを曲線状の配置とすることによって前記の鉛直面内曲げモーメントM2の分布形状に沿った配置とでき、直線状の偏芯配置を行う場合に比べても無駄を軽減できるためである。なお実際には防液堤の厚さ方向に一定量の引張応力領域を残す設計とする場合もあるが、この場合も上記と同様に鋼材量を低減できる。 As described above, the curved eccentric arrangement of the present embodiment has an effect of reducing the amount of PC steel material not only when there is no eccentricity but also when the eccentric arrangement is linear. By arranging the vertical PC steel material C in a curved shape, the arrangement can be made along the distribution shape of the vertical bending moment M2 in the vertical plane, which is less wasteful than the case of linear eccentric arrangement. This is because it can be reduced. Actually, the design may leave a certain amount of tensile stress region in the thickness direction of the liquid barrier, but in this case as well, the amount of steel material can be reduced in the same manner as described above.

さらに、本実施形態では防液堤２ａの下部の内側にハンチ部２１ａを設けて縦方向PC鋼材１５の外側への偏芯量を増大させることで、鉛直面内曲げモーメントM1の絶対値が大きくなる防液堤２ａの下部においても、この曲げモーメントM1を軽減して常時と漏液時の鉛直面内曲げモーメントM、M’を符号反対且つ絶対値同等とする事が容易となる。 Further, in the present embodiment, the haunch portion 21a is provided inside the lower part of the liquid barrier 2a to increase the amount of eccentricity to the outside of the vertical PC steel material 15, so that the absolute value of the vertical bending moment M1 is large. Even in the lower part of the liquid barrier 2a, it becomes easy to reduce the bending moment M1 so that the bending moments M and M'in the vertical plane at all times and at the time of liquid leakage are opposite in sign and equal to the absolute value.

しかしながら、本発明はこれに限らない。例えば本実施形態では防液堤２ａの全高に亘って縦方向PC鋼材１５を曲線状に配置し、その偏芯量ｄを防液堤２ａの全高に亘って常時、漏液時の鉛直面内曲げモーメントM、M’が符号反対且つ絶対値同等となるようにしたが、曲線状に配置する範囲（所定範囲）はこれに限らない。 However, the present invention is not limited to this. For example, in the present embodiment, the vertical PC steel material 15 is arranged in a curved line over the total height of the liquid barrier 2a, and the eccentricity d thereof is always within the vertical plane at the time of liquid leakage over the total height of the liquid barrier 2a. The bending moments M and M'are opposite to each other and have the same absolute value, but the range (predetermined range) for arranging them in a curved shape is not limited to this.

例えば図３に示すように、鉛直面内曲げモーメントM1が大きくなる範囲は、防液堤２ａの下端から、鉛直面内曲げモーメントM1の高さ方向の分布における最下端の変曲点である第１変曲点、あるいはその直上にある第２変曲点までの範囲と考えられるので、曲線状に配置する範囲は、少なくとも防液堤２ａの下端から上記第１変曲点までの範囲を含むか、防液堤２ａの下端から上記第２変曲点までの範囲を含んでいればよい。これらの範囲で縦方向PC鋼材１５を単一の又は複数の曲率による曲線状に配置することで、当該範囲にて常時と漏液時の鉛直面内曲げモーメントM、M’を符号反対且つ絶対値同等とし、縦方向PC鋼材１５の量の低減効果が得られる。 For example, as shown in FIG. 3, the range in which the vertical inward bending moment M1 increases is the inflection point at the lowermost end in the distribution of the vertical inward bending moment M1 in the height direction from the lower end of the liquid barrier 2a. Since it is considered to be the range from one inflection point or the second inflection point immediately above it, the range to be arranged in a curved line includes at least the range from the lower end of the liquid barrier 2a to the first inflection point. Alternatively, the range from the lower end of the liquid barrier 2a to the second inflection point may be included. By arranging the vertical PC steel material 15 in a curved shape with a single or a plurality of curvatures in these ranges, the vertical inward bending moments M and M'at the time of constant and liquid leakage are opposite and absolute in the range. When the values are the same, the effect of reducing the amount of the vertical PC steel material 15 can be obtained.

また、本実施形態ではLNGタンク１の防液堤２ａの例を説明したが、本発明はプレストレスを導入する筒状の側壁を有するタンクであれば適用可能であり、LPGや水などその他の液体を貯留する地上タンクでも適用できる。 Further, in the present embodiment, an example of the liquid barrier 2a of the LNG tank 1 has been described, but the present invention is applicable to any tank having a cylindrical side wall for introducing prestress, and other tanks such as LPG and water. It can also be applied to above-ground tanks that store liquids.

また本発明は現場打ちのコンクリートによって防液堤２ａを構築する場合のみならず、プレキャストブロックを上下左右に積み重ねて防液堤２ａを構築する場合にも適用可能である。 Further, the present invention is applicable not only to the case of constructing the liquid barrier 2a from cast-in-place concrete, but also to the case of constructing the liquid barrier 2a by stacking precast blocks vertically and horizontally.

以上、添付図面を参照して、本発明の好適な実施形態について説明したが、本発明は係る例に限定されない。当業者であれば、本願で開示した技術的思想の範疇内において、各種の変更例または修正例に想到し得ることは明らかであり、それらについても当然に本発明の技術的範囲に属するものと了解される。 Although preferred embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the technical idea disclosed in the present application, and these also naturally belong to the technical scope of the present invention. Understood.

１、１００：LNGタンク
２、２ａ：防液堤
３ａ：内槽
３ｂ：外槽
４：杭
５：底版
７：地盤
１１：周方向PC鋼材
１３、１３ａ、１３ｂ、１５、１５ａ、１５ｂ：縦方向PC鋼材
２１、２１ａ：ハンチ部 1,100: LNG tanks 2, 2a: Liquid barrier 3a: Inner tank 3b: Outer tank 4: Pile 5: Bottom slab 7: Ground 11: Circumferential PC steel materials 13, 13a, 13b, 15, 15a, 15b: Vertical direction PC steel 21, 21a: haunch

Claims

A tank having a cylindrical side wall and an inner tank for storing liquid inside the side wall.
Prestress due to the tension of the circumferential tension material and the vertical tension material is introduced into the side wall.
When the cross section in the height direction and the thickness direction of the side wall is viewed, the tension material in the vertical direction is curved from the lower end of the side wall to a predetermined range in the height direction , and in the predetermined range, the said material. The distribution of the bending moment in the vertical plane on the side wall in the height direction is such that the direction of the bending moment is opposite and the absolute value is the same when the liquid leaks and when the liquid leaks at all times. A tank characterized by being placed.

The tank according to claim 1, wherein a haunch portion is provided inside the lower portion of the side wall.

The predetermined range is
The height of the lowest first inflection point, which is the inflection point of the distribution of the bending moment in the vertical plane in the vertical plane caused by the prestress of the tension material in the circumferential direction from the lower end of the side wall in the height direction. The tank according to claim 1 or 2 , wherein the tank includes the above range.

The predetermined range is
The tank according to claim 3 , wherein the tank includes a range from the lower end of the side wall to the height of the second inflection point, which is the inflection point immediately above the first inflection point.

The tank according to any one of claims 1 to 4 , wherein the predetermined range extends over the entire height of the side wall.