趙秋　翟戰(zhàn)勝

摘要：為更好掌握開口肋加勁板的設(shè)計(jì)計(jì)算方法，采用彈性穩(wěn)定分析方法，對無縱向和橫向加勁肋的四邊簡支板、縱向加勁肋等間距布置的四邊簡支加勁板、縱向和橫向加勁肋等間距布置的加勁板進(jìn)行屈曲模態(tài)和臨界屈曲應(yīng)力分析。結(jié)果表明：對于四邊簡支板或四邊簡支加勁板，臨界屈曲應(yīng)力與板寬、板長和板厚均有關(guān)，減小板寬和板長以及增大板厚可提高臨界屈曲應(yīng)力；隨著加勁肋剛度比的變化，四邊簡支加勁板一般表現(xiàn)出3種屈曲模態(tài)，模態(tài)1為加勁肋與被加勁板共同發(fā)生整體屈曲，模態(tài)2為在加勁肋處形成波節(jié)，加勁肋與被加勁板發(fā)生屈曲，模態(tài)3為加勁肋為剛性加勁肋，不會(huì)發(fā)生失穩(wěn)，只有被加勁板發(fā)生局部失穩(wěn)；臨界屈曲應(yīng)力隨加勁肋剛度比的增大而增大，模態(tài)1增大幅度最大，模態(tài)2次之，模態(tài)3逐步趨于定值。

關(guān)鍵詞：開口肋加勁板；彈性穩(wěn)定；屈曲模態(tài)；臨界屈曲應(yīng)力；加勁肋；臨界剛度比

中圖分類號(hào)：TU311文獻(xiàn)標(biāo)志碼：A

Abstract： In order to master the design and calculation method of openrib stiffened plate better， the buckling modes and critical buckling stress of fourside simplysupported plate without longitudinal and transversestiffening ribs，fourside simplysupportedstiffened plate withlongitudinal stiffening ribs arranged by equal distance， stiffened plate with longitudinal and transverse stiffening ribs arranged by equal distance， were analyzed by elastic stabilitytheory. The results show that critical buckling stress is related to plate width， plate length and plate thickness for foursidesimplysupported plate or fourside simplysupportedstiffened plate. Critical buckling stress can be improved with the decrease of plate width and plate length， and with the increase of thickness of plate. There are 3 kinds of buckling modes of fourside simplysupported stiffened plate with changes of stiffness ratios of stiffening ribs. Stiffening ribs and stiffened plate are overall buckling in mode 1. Wave nodes are formed on stiffening ribs， stiffening ribs and stiffened plate are buckling in mode 2. Stiffening ribs will not appear instable， only stiffened plate is buckling in mode 3.Critical buckling stress increases with the increase of stiffness ratio of the stiffening rib， the increase range is maximal in mode 1， and comes second in mode 2. Critical buckling stress tends to be constant value in mode 3.

Key words： openrib stiffened plate； elastic stability； buckling mode； critical buckling stress； stiffening rib； critical stiffness ratio

0引言

對于受壓加勁板來說，穩(wěn)定問題和強(qiáng)度問題同樣重要[12]。受壓加勁板的彈性穩(wěn)定分析在穩(wěn)定問題中屬于第1類穩(wěn)定問題，即平衡分岔失穩(wěn)問題，這是一種理想化的情況，當(dāng)達(dá)到某荷載時(shí)，結(jié)構(gòu)除了可能存在原來的平衡狀態(tài)外，會(huì)出現(xiàn)第2個(gè)平衡狀態(tài)，而在數(shù)學(xué)處理上是求解特征值問題，故又稱為特征值屈曲分析，其目的是求解臨界荷載值[35]。雖然受壓加勁板彈性穩(wěn)定計(jì)算比較簡單，但它是穩(wěn)定承載力分析的基礎(chǔ)。當(dāng)受壓加勁板發(fā)生屈曲時(shí)，其變形形狀經(jīng)常被稱為屈曲模態(tài)[610]。由于受壓結(jié)構(gòu)不同的屈曲模態(tài)將導(dǎo)致不同的穩(wěn)定承載力，對于受壓加勁板來說，由于組成結(jié)構(gòu)各部分剛度的改變，失穩(wěn)將有較多的屈曲模態(tài)[1114]。因此，本文采用理論分析和有限元分析相結(jié)合的方法對受壓彈性穩(wěn)定和屈曲模態(tài)進(jìn)行分析，加深對即將頒布的新規(guī)范的理解，并為受壓加勁板穩(wěn)定承載力計(jì)算提供參考。

1理論與有限元分析方法

1.1受壓板和受壓加勁板穩(wěn)定計(jì)算

1.2有限元模型

有限元模型采用考慮大變形的Shell181殼單元，彈性模量為2.06×105 MPa，泊松比為0.3，模型的邊界條件為四邊均約束Z方向的位移，其中平行于X軸的a/2處兩節(jié)點(diǎn)約束Y方向位移（a為加勁板長度），平行于Y軸的b/2處兩邊中點(diǎn)約束X方向位移。有限元模型如圖1所示。