Latticed Shell Structure Research Articles

Adaptable Bed for Curved-Layered Fused Deposition Modeling of Nonplanar Structures: A Proof of Concept.

Curved-layered fused deposition modeling demands a curved mandrel for each of the designs to fabricate. This results in more fabrication time and material used. To overcome this, an adaptable pin-base mandrel is presented. The fabrication of curved structures with such mandrel uses the extruder as a pushing tool, pushing each of the pins to the depths required for each surface. After the base surface is formed, the conventional process of curved fused deposition modeling (FDM) is used. Several lattice shell structures composed of nonplanar layers were fabricated on FDM mandrels and the adaptable pin-bed proposed here. The comparison of the manufacturing results showed that the adaptable base allows the successful fabrication of the samples. The solution exposed here represents a proof of concept to validate the idea. The adaptable base presented in this study is unique and it brings advantages to the fabrication of curved-layered structures.

The study on bending performance of aluminum alloy honeycomb panel-beam composite grid structure

Long-span space structures are particularly sensitive to their self-weight. In this paper, a honeycomb plate with a high strength and light weight is reliably connected to a single-layer aluminium alloy lattice shell to form a new type of combined lattice shell structure, which substantially improves the overall stiffness and stability of the lattice shell without a plate. The bending performance of the aluminium alloy honeycomb panel-beam combined grid structure (AAH combined grid structure) plays a key role in the stability of the combined lattice shell structure. Therefore, the bending performance of the AAH combined grid structure was studied through six groups of tests and refined finite element models. Then, the calculation formula for the equivalent bending stiffness of the AAH combined grid structure was obtained through a theoretical analysis. The results show that the contribution of the honeycomb structure to the stiffness of the structure is very obvious, and the proposed formula provides the theoretical basis and a practical method for the engineering design of new aluminium alloy combined lattice shell structures in the future.

Dynamic failure mechanism of single-layer reticulated (SLR) shells with bolt-column (BC) joint

Bolt-column (BC) joint is an innovative fabricated semi-rigid joint with strong bending stiffness that can meet the need of rapid construction of latticed shell structure. To investigate the dynamic behavior of SLR shells with BC joints subjected to harmonic load and earthquake load, finite element (FE) modeling of SLR shells with BC joint was built taking geometric and material nonlinearity into account, and the simulation method was validated by comparing with the test result on a cylindrical reticulated shell. Based on this model, effect of joint stiffness on the dynamic response was examined and failure modes of SLR shells jointed with BC joint subjected to harmonic load and earthquake load were studied. Two failure modes, dynamic strength failure which results from the extensive plastic deformation and dynamic instability failure which is induced by the geometric nonlinearity of the shell, were defined. Subsequently, the criteria on differentiating the two failure modes were derived based on response characteristics indicators. Furthermore, investigation on damaged factor of SLR shells jointed with BC joint was conducted, and according to numerous numerical examples, the damaged index of SLR shells with BC joint was derived, which can be utilized to conduct fragility analysis.

Mehanske lastnosti novega spoja iz ene plasti aluminijeve zlitine kombinirane mrežno-lupinaste strukture

Mehanske lastnosti novega spoja iz ene plasti aluminijeve zlitine kombinirane mrežno-lupinaste strukture

The bearing performance of the bolt-sphere joints with stochastic pitting corrosion damage

The bolted spherical nodes are widely used as member joints of lattice shell structures. With long-term service in a corrosive environment, the bearing performance degradation of these nodes due to corrosion especially pitting corrosion is threatening the safety of the entire structure. The paper presents a pilot study on the bearing performance of the bolt-sphere joint portion in the bolted spherical node with stochastic pitting corrosion damage. Aided by the finite element software ABAQUS, the bolt-sphere joints are modeled in 3D incorporating the helical thread contact and progressive damage of material. The pitting corrosion is induced by explicitly adding uniform distributed pits on the intact (pit-free/uncorroded) model while the pit depth is depending on the corrosion rate and service time. With the experimental data from the uniaxial tensile bearing capacity tests on uncorroded joints and the subsequent failure mode characterization, the load-displacement responses and simulated fracture surfaces by the corresponding virtual tests on the intact model are validated. Then the virtual tests are extended to the corroded joints with different corrosion time, by which the corresponding load-displacement curves and simulated failure process are obtained. It is found that the elastic axial stiffness is degenerated by 2.6% and 4.1% and the ultimate bearing capacity is degraded by 3.1% and 5.6%, after 50 years and 100 years of corrosion, respectively. The simulated fracture surfaces indicate that the domination of shear damage is gradually weakened by the increase of pits, leading to a more ductile fracture and a flatter cup-cone fracture surface.

Probabilistic seismic vulnerability assessment of aluminium alloy reticulated shells with consideration of uncertainty

Single-layer aluminium alloy cylindrical shells are established using the powerful finite element (FE) software package ABAQUS. Furthermore, the probability distribution models of different random parameters in structural modelling are summarized. Forty seismic ground motion records are selected to consider the uncertainty of earthquakes. Sensitivity analysis of modelling parameters is conducted to determine the parameters with the greatest influence on seismic responses. The incremental dynamic analysis (IDA) method is performed on aluminium alloy cylindrical latticed shell structures with different structural parameters. After applying the damage index and structural performance levels of the latticed shells proposed in this paper, the probabilistic seismic demand model and probabilistic seismic capacity model are established. The seismic performance and the collapse capacity of different aluminium alloy cylindrical latticed shells are discussed based on the FE results. Furthermore, vulnerability curves are obtained according to the IDA results, which can be utilized to predict the failure probability and to evaluate the structural performance of aluminium alloy cylindrical latticed shells under different levels of earthquakes.

Structural-capacity-reserve-based performance assessment of long-span single-layer lattice shell structures

To achieve a well-balanced structural design, a customized performance assessment approach based on the structural capacity reserve (SCR) is proposed for commonly used long-span single-layer lattice shells. The SCR is calculated by integrating the normalized residual seismic capacity (RSC) over the entire range of possible earthquake-induced damage levels. Six typical RSC ratio curves and the corresponding ranges of the SCR index are discussed and verified for several spherical single-layer lattice shells. The impact of the arrangement of the components on the structural deformability, failure mode, plasticity and damage development as well as the RSC and SCR is clarified for two Schwedler shells. Based on observations from vulnerability and sensitivity analyses, several alternative strengthening schemes are generated for an S12 Schwedler single-layer lattice shell, and the optimal one is determined by means of a multiple-objective evaluation system that includes the SCR. The investigation indicates that normalized RSC ratio curves can reflect the design rationality of structural layouts and that they can clearly capture the dynamic instability of lattice shells. The ability of lattice shells to retain their post-earthquake resistance reserves is found to depend primarily on the locations where damage develops. The localization of fully yielded components has the potential to create several weak regions, leading to a high possibility of substantial loss of resistance reserves. The case study of the S12 Schwedler shell demonstrates the necessity of considering the SCR in a comprehensive structural performance evaluation system.

Structural design of irregular curved lattice shells in China

Irregular curved lattice shell structures are proving increasingly popular in China. However, the behaviour of irregular shells can be substantially different from regular shells in terms of strength, stiffness and stability characteristics as well as joint detailing. This paper reviews a number of projects in China in which irregular shells have been used. The structural system, force transfer path, vulnerable locations and strengthening measures are discussed. This is followed by a case study on a 45 m span greenhouse building featuring novel drum joints in the shell.

Development of latticed structures with bolted steel sleeve and plate connection and hollow section GFRP members

An innovative nodal joint system with thin-walled steel sleeve and plate is examined for development of latticed shell structures using hollow section glass fiber reinforced polymer (GFRP) members. In the proposed system, the GFRP members were connected to a steel gusset-plate space node through bolted sleeve joints (BSJs). The mechanical performance of BSJs was first examined through cantilever bending experiments. Then, the performance of the entire nodal joint system incorporating the space node was examined in bending for both in-plane and out-of-plane stiffness. Its performance was then characterized by nonlinear springs and evaluated at a structural level based on a space latticed structure configuration through finite element (FE) analysis and the resulting structural performance satisfied the ultimate limit state (ULS) and serviceability limit state (SLS) requirements as per relevant standards. A parametric study was also conducted to understand the effect of joint rotational stiffness on the overall structural performances.

Simlating the Stability and Pre-stressed Tension of a Single-Layer Spherical Reticulated Shell Supported by Cable

Along with other developments that have occurred in this era, building requirements include not only function and practicality but also encompass architectural elegance such as lighting and light-weight structures. Conventional latticed shell triangulation creates a poor architectural effect as well as mediocre lighting and excessive and cluttered componentry. A latticed shell with quadrilateral meshing is light and has excellent lighting properties, but it also has low rigidity and inferior stability. This study addresses this problem by deploying in-plane stayed cables and horizontal and vertical cables out-of-plane via a strut, and by developing a new single-layer spherical latticed shell system supported by cables. The effects that various parameters have on the mechanical properties of this structures such as the rise-span ratio, asymmetric load distribution, strut length, initial defects and cable pre-stress, are investigated based on mechanical responses such as structural displacement, internal force, critical bearing capacity and the instability modal. The basic rules of structural stress are summarised and examples of 100 m and 150 m large span latticed shell structures are used to verify and analyse the rules for the mechanical properties of this structure, and to investigate how applicable this type of architecture is in a large-span structure. Based on the sequence used to tension the cable(s) during construction, several plans for pre-stressing in-plane and out-of-plane cable(s) are also proposed. The effect that this pre-stressing sequence has on structural properties such as maximum displacement and critical bearing capacity is investigated at each stage of construction via a numerical simulation of the structure. A proper procedure for constructing this structure is also proposed to provide theoretical support for an actual project.

Analysis of Stiffening Methods and Effects on Irregular Single-layer Lattice Shell Structures

Local stiffening is often a good solution to mechanical property problems of irregular single-layer lattice shell structures. The effects of three local stiffening methods, namely section enlargement stiffening, planar truss stiffening, and space truss stiffening, on their structural stiffness, strength, and overall stability were analyzed in this study. A practical engineering example showed that these three stiffening methods could effectively reduce the deformation of the lattice shell under vertical and lateral loads, reduce the comprehensive stress ratio, and increase the buckling eigenvalue and ultimate bearing capacity factor. The local space truss stiffening method had the best comprehensive effect. The same stiffening methods were applied to a regular lattice shell and the analysis showed that the stiffening effect on a regular shell is quite different from that on an irregular lattice shell. The three stiffening methods could not reduce its deformation under vertical loading but could reinforce the strength and overall stability of the structure effectively. Proper suggestions are proposed according to the preceding analysis in case a single-layer lattice shell structure cannot meet the demands of the design code.

Design, analysis and optimization of anisogrid composite lattice conical shells

Abstract A methodology for structural analysis and optimal design of conical anisogrid composite lattice shell structures subject to different external loads concurrently applied and multiple stiffness constraints is presented. The critical buckling load of the anisogrid lattice conical structure is exactly assessed, independently of the buckling failure mode, by means of a discrete approach. The method makes use of a full FE parametric modeling technique able to manage all the geometrical parameters of the anisogrid composite lattice structure. Additionally, the genetic algorithm NSGA-II is employed to set up an optimization procedure which allows to analyze different sets of geometrical variables, both continuous and discrete, to reach the optimal solution in terms of mass amount and fulfilling of structural and stiffness requirements, aiming at the preliminary design of an actual structure. Numerical case-studies are outlined in order to demonstrate the practical usefulness and versatility of the proposed procedure to industrial cases where the anisogrid lattice conical structure undergoes multiple external loads and various stiffness constraints must be satisfied.

Parametric design and static behavior analysis of single-layer hemi-ellipsoida latticed shell

The parametric design macro programs of two basic types of single-layer hemi-ellipsoidal latticed shell are developed by using APDL (Ansys Parametric Design Language) parameterized design language. The parametric design of single-layer hemi-ellipsoidal latticed shell structures can be built under the condition of giving the macroscopic geometric parameters such as specifical parameter t, parameter k, span S1, span S2, rise f, valley number Kn, radial node number Nx etc. Ansys software is applied to study comparison of characteristics of the Kewitte type net shell structure of different vector height f, radial node number Nx and boundary constraints. The results show that modeling design of hemi-ellipsoidal latticed shell can be built conveniently and quickly by the application of parametric design of macro program. The three-way grid type is more reasonable force performance, and it’s mechanical performance is better when the span ratio is 1/2. Thus it is suggested to give priority in the project.

Structural analysis and optimization of anisogrid composite lattice cylindrical shells

Abstract A structural analysis and an optimization method for anisogrid composite lattice shell structures is proposed, considering cylindrical structures simultaneously subjected to different external loads and multiple stiffness constraints. A discrete approach is used to exactly estimate the critical buckling load of the anisogrid lattice structure, independently of the buckling failure mode. The method makes use of a full FE parametric modeling technique able to manage all the geometrical parameters of the anisogrid composite lattice structure. Then an optimization procedure based on the genetic algorithm NSGA-II has been performed; it allows to analyze different alternatives in terms of geometrical variables, both continuous and discrete, driving the search towards the optimal solution in term of mass and conformity with all structural and stiffness constraints, aiming at the preliminary design of an actual structure. The practical usefulness and applicability of the proposed procedure to industrial cases was demonstrated through numerical examples where the anisogrid lattice structure was subjected to multiple external loads and stiffness constraints simultaneously applied.

The Stability of New Single-Layer Combined Lattice Shell Based on Aluminum Alloy Honeycomb Panels

This article proposes a new type of single-layer combined lattice shell (NSCLS); which is based on aluminum alloy honeycomb panels. Six models with initial geometric defect were designed and precision made using numerical control equipment. The stability of these models was tested. The results showed that the stable bearing capacity of NSCLS was approximately 16% higher than that of a lattice shell with the same span without a reinforcing plate. At the same time; the properties of the NSCLS were sensitive to defects. When defects were present; its stable bearing capacity was decreased by 12.3% when compared with the defect-free model. The model with random defects following a truncated Gaussian distribution could be used to simulate the distribution of defects in the NSCLS. The average difference between the results of the nonlinear analysis and the experimental results was 5.7%. By calculating and analyzing nearly 20,000 NSCLS; the suggested values of initial geometric defect were presented. The results of this paper could provide a theoretical basis for making and revising the design codes for this new combined lattice shell structure.

Static stability behavior of aluminum alloy single-layer spherical latticed shell structure with Temcor joints

In recent years, aluminum alloy single-layer latticed shell has been extensively used in civil and industrial infrastructure. The elasticity modulus of aluminum alloy is low, the rigidity of aluminum joints are weak and the roof load transmission path is different. Therefore, the stability performance of this dome is unique. To clarify the stability performance of aluminum alloy single-layer latticed shell, over 500 aluminum alloy single-layer spherical latticed shells were analyzed with nonlinear finite method. The suggested values of rise/span ratio and initial imperfection were presented. The influencing coefficients of initial imperfection, material nonlinearity and stressed skin effect on stability bearing capacity were obtained. And the structural stability safety coefficient and the approximate calculation formula for stability bearing capacity of aluminum alloy single-layer spherical latticed shell were derived. The influences of joint semi-rigidity were investigated. All the aforementioned results provide a scientific basis for future stability design of aluminum alloy single-layer spherical latticed shell structure.

11.15: Seismic behaviour of single layer cylindrical lattice steel shells

ABSTRACTCylindrical lattice shell structures are commonly used in many applications such as in train stations, gymnasia, and sports halls. In comparison with their behaviour and design under gravity loading, their behaviour under seismic loading has received less attention, particularly in terms of the development of practical design procedures. Current European codes of practice lack specific guidance on the seismic design of these shells. In this paper, the salient considerations influencing the seismic response of single layer cylindrical lattice shells are examined. The effect of key geometric parameters such as the rise to span ratio, length to span ratio, inter‐element angles, as well as the structural mass, on the characteristic natural periods and corresponding vibration modes are investigated using the finite element program OpenSees for two typical situations of boundary conditions. The influence of these parameters on the axial forces and bending moments in the members when subjected to the horizontal and vertical components of an earthquake is also assessed. The response is evaluated in the linear and nonlinear ranges, including representative time history analyses, with due consideration of both material and geometric nonlinearities. The results provide an insight into the main factors that govern the seismic behaviour of single layer cylindrical lattice shells, with a view to supporting the development of practical design and assessment procedures for this structural form.

Novel numerical method for the analysis of semi-rigid jointed lattice shell structures considering plasticity

The joint bending and axial stiffness significantly influence the mechanical performance of lattice shell structures. However, most finite element models of the actual project established in the general finite element software are rigid or hinge-connected for simplicity. These characteristics are inconsistent with the actual situation and may lead to a large error. A novel numerical method was proposed in this paper to estimate the influence of joint stiffness, which includes bending and axial stiffness, on the mechanical behavior of lattice shell structures. This method can be used for inelastic analysis. First, the accuracy of the proposed element model was validated. The model was used to analyze lattice shell structures. The proposed element model can simultaneously consider semi-rigid joints and inelasticity with high accuracy, and it can be conveniently constructed in general finite element software.

Thermal behavior of large-span reticulated domes covered by ETFE membrane roofs under solar radiation

A strong non-uniform temperature was induced by solar radiation for the large-span reticulated domes with ETFE membrane roof, which may induce a significant thermal stress and thermal deformation. In order to obtain the temperature distribution and thermal behavior of large-span reticulated domes with ETFE membrane under solar radiation, a long term field monitoring and numerical analysis were conducted in this paper. Based on the results of both field monitoring and the numerical analysis, the following conclusions were obtained: 1) shelter effects of glass and membrane varies widely. 2) Daily temperature variation can be reduced by a large degree due to introduction of membrane. 3) Average temperature of components is increased by membrane due to ‘greenhouse effect’.4) The seasonal temperature variation has little effect on the components which located at upper part of spatial latticed shell structures, the internal force can be released by deformation. 5) Thermal response of bottom ring beam is reduced by installation temperature and double supports.

An optimum method for latticed shells based on concept of the compression line

To improve the load-carrying capacity latticed shells, an innovative optimum method based on the concept of compression line is proposed in this paper. The basic principle of this method is using the character without moment in compression line. The arc line which forms the contour line of sphere and latticed shell structures is substituted by compression line in this method. Then the latticed shell structures are in the state of compression, and the influence of bending stress reduces greatly. As a result, the load-carrying capacity of the latticed shell structure is increased. Through the geometrical nonlinear analysis of a sunflower-patterned single-layer latticed shell structure with a span of 48m, it is found that the load-carrying capacity of the single-layer latticed shell structure can be improved by 5.48%. Furthermore, the results of 84 structural analyses of single-layer or double-layer sphere and cylinder latticed shell structures show that the optimum method is right and effective. And especially, it is applicable to single-layer latticed shell structure with rise-span ratio 1/5 with the max improvement 6.4% of load-carrying capacity.