Stability Analysis Of Kiewitt-type Latticed Shell Roofs Under Differential Settlements Of Storage Tanks

Differential settlement may lead to deformation of the storage tanks constructed on the soft ground base. And the deformation may lead to the forced displacement of the roofs' support. The stability and bearing capacity of the Kiewitt-type latticed shells as storage tanks' roofs are studied in this thesis, with the emphasis on the effect of differential settlement on the stability of the latticed shell when the cooperative action between latticed shell and tank wall is considered.Extensive nonlinear finite element analyses about the stability of K8 and K6 latticed shell roofs under harmonic settlement were carried out. Compared to the fixed hinged supported latticed shell, the roofs' stable bearing capacity falls off obviously. The number of harmonic waves has little effect on the stability bearing capacity of the latticed shell. The bearing capacity decreases with the increase of the amplitude of the harmonic settlement. Initial geometric imperfections due to installation also lead to reduction in the bearing capacity, and the imperfection sensitivity is reduced obviously when the differential settlement beneath the tank wall is considered. Variations under harmonic settlement as spans, ratios of rise to spans, bars' sectional dimensions are similar with those without consideration. Using the bearing capacity formula in possession and considering the cooperative action between tank wall and latticed shell, two new bearing capacity formulas of K8 and K6-Type latticed shell roofs are put forward.Differential settlement of storage tanks in practice includes whole body settlement and local settlement. The stability of latticed shell roofs under these two types settlements were studied in this thesis. Variations as the change of spans, ratios of rise to spans, bars' sectional dimensions are similar with harmonic settlements. The two new bearing capacity formulas of K8 and K6-Type latticed shell roofs are also applicable to the latticed shell roofs under whole body differential measured settlements. The latticed shell roofs are influenced obviously by local differential settlements. A practical model analysis must be done in order to get the accurate bearing capability if the local differential settlements happened.