Nonlinear Analysis Of Concrete Folded-slab Arch Reticulated Shell

The concrete prismatic reticulated shell and bidirectional folding plate arch reticulated shell are both new spatial grid structures.The prismatic reticulated shell is composed of a series of densely ribbed plates intersecting the ridge line after the cylinder surface is equally divided and it has advantages of large span,good permeability,fire resistance and corrosion resistance.In order to span larger space,the bidirectional folding plate arch reticulated shell can be obtained by raising the arch longitudinally on the basis of prismatic reticulated shell.These two kinds of new reticulated shells have advantages of dense ribbed flat plate and folding plate shell,which makes force more reasonable and convenient for construction,and has a broad application prospect.The paper applys the finite elememt method to calculate and analyse the static performance and elastic stability.Besides,geometric nonlinearity,material nonlinearity and double nonlinearity of these two structures are analysed.The results show that:(1)Increasing ratios of rise to span can improve corresponding bearing capacities of structures.When rise-span ratios of prismatic reticulated shell increase from 1/10 to 1/3,elastic critical loads increase by about 1.5 times,geometric nonlinear critical loads 2.4 times,material nonlinear ultimate loads about 59%,and double nonlinear ultimate loads 1.1 times.In engineering application,in order to avoid the force of shallow reticulated shell,it is suggested that the rise-span ratio should not be less than 1/6.But for the bidirectional folding plate arch reticulated shell,when transverse rise-span ratios increase from 1/10 to 1/4,elastic critical loads increase by about 1.3 times,and material nonlinear ultimate loads only by about 13%.Therefore,it is recommended to take the transverse rise-span ratio 1/6 ? 1/4,while the longitudinal rise-span ratio should be 1/8 ? 1/4.(2)Increasing the thickness of roof board can improve corresponding bearing capacities of structures to some extent.But,it is recommended to take the plate thickness of 80 mm ?100mm.(3)Increasing stiffness of ribbed beames can improve corresponding bearing capacities of structures.When the cross section heights increase from 300 mm to 700 mm,the elastic critical loads of prismatic reticular shell are increased by about 98%,geometric nonlinear critical loads about 33%,material nonlinear ultimate loads about 74%,and double nonlinearultimate loads about 85% and elastic critical loads of the bidirectional folding plate arch reticulated shell increases by about 48%,and material nonlinear ultimate loads about 20%.However,too much ribbed beam stiffness is limited to increase the corresponding bearing capacities of structures.It is suggested to take 1/120 ? 1/80 of the span of structure as the section height of the dense ribbed beam.(4)Increasing stiffness of main arches can improve corresponding bearing capacities of structures.When the cross section heights increase from 500 mm to 900 mm,elastic critical loads of prismatic reticular shell increase by 1.13 times,geometric nonlinear critical loads about 2 times,material nonlinear ultimate loads less than 10%,and double nonlinear ultimate loads about 60%,and elastic critical loads of the bidirectional folding plate arch reticulated shell about 1 times,and material nonlinear ultimate loads about 23%.Too much rigid section is not significant in improving corresponding bearing capacities of structures.Therefore,section heights of main arches should be 1/80 ? 1/50 of the span of structure.(5)The introduction of initial geometric imperfections will reduce corresponding bearing capacities of structures.The geometric nonlinear critical loads and material nonlinear ultimate loads of prismatic reticular shell will be reduced by about 5% ? 15%,and the reduction degree of double nonlinear ultimate loads will be about 10% ? 30%.However,there is no obvious rule on influence of the bidirectional folding plate arch reticulated shell,which needs to be analyzed concretely.(6)The approximate calculation formulas proposed in this paper can reasonably estimate corresponding bearing capacities of structures.