Lattice Shell Research Articles

Experimental Study on a New Connection Method of Latticed Shell Joint

In this research, the axial and eccentric pressure tests and finite element analysis (FEA) of a latticed shell joint with different parameters were carried out. The experimental and FEA results showed that the annular plate yielded first, followed by steel tube 1, and then steel tube 2 under the axial pressure and eccentric pressure. The ultimate bearing capacities of connection method II under axial pressure and eccentric pressure were 15% and 11% higher than that of connection method I, respectively. The wall thickness of steel tube 2 was reduced by 2 mm, and the ultimate bearing capacities under axial pressure and eccentric pressure is reduced by 15% and 11%, respectively. The wall thickness of steel tube 1 was reduced by 2 mm, and the ultimate bearing capacities under axial pressure and eccentric pressure is reduced by 6% and 9%, respectively. With the decrease of the concrete thickness, the ultimate bearing capacity under axial pressure and eccentric pressure reduced by 18% and 17%, respectively. The ultimate bearing capacity analysis showed that the height of the concrete and the thickness of steel tube 2 had a greater effect on the ultimate bearing capacity than the thickness of steel tube 1.

Damage-Endurance-Based Seismic Performance Assessment for Long-Span Lattice Shells with Prestressed Elements

Damage-Endurance-Based Seismic Performance Assessment for Long-Span Lattice Shells with Prestressed Elements

Assessment and design considerations for single layer cylindrical lattice shells subjected to seismic loading

This paper examines the main considerations related to the seismic design and assessment of single layer steel cylindrical lattice shells, and offers recommendations for their practical application. Geometric configurations covering a wide range of rise to span ratios are considered within the investigation. An insight into the relative influence of seismic loading on shell design, in comparison to gravity conditions, is firstly provided through the use of digital parametric engineering procedures. This is followed by linear elastic response assessments which are used to propose a simplified procedure for estimating the internal seismic forces for the purpose of member sizing in early design stages. Suitable approaches for pushover analysis are then discussed and used to identify inherent plastic mechanisms. The results of incremental nonlinear dynamic analysis, using a suite of fourteen records, are also employed in order to validate the findings and to further assess the ultimate response under realistic seismic loading conditions. Based on the findings, representative ranges for behaviour factors and displacement modification coefficients are derived alongside discussions on their implementation within codified seismic design procedures. Apart from providing recommendations for simplified design approaches, the assessments presented in this paper can also be used to support detailed performance based guidelines as well as for informing geometry and size optimisation strategies.

An improved adaptive web sampling method for node deviation inspection of single-layer latticed shells

The node positions of single-layer latticed shells in service usually deviate from their design positions, and a few nodes of the shell may exist larger positional deviations than other nodes, which could result in a progressive collapse or overall buckling of the shell. To avoid the significant loss of structure failure, these nodes with large positional deviations should be considered in the structural inspection sampling. However, existing sampling methods in the structural inspection are designed for independent products that ignore the dependence in these nodes and are unsuitable for node positional deviation inspection of single-layer latticed shells. To solve this problem, the node positional deviation aggregation is defined and calculated based on the theory of spatial local autocorrelation, and an improved adaptive web sampling (IAWS) method is proposed in this paper, which consists of three parts: calculation of node connection matrix, adaptive web sampling, and supplementary sampling. Specially, the supplementary sampling is proposed to improve the overall sampling accuracy for adaptive web sampling, and the selection of supplementary samples is based on the relationship between the sample position and the total node deviation reckoning error derived in this paper. Besides, two performance indicators are adopted to evaluate the overall reckoning accuracy of sample methods, and two new performance indicators are proposed to assess the deviation aggregation area sampling accuracy. The numerical analysis results of two Kiewitt shells and a cylinder shell show that IAWS can provide a higher sampling accuracy than random sampling, systematic sampling, and adaptive web sampling.

Aerodynamic optimization design of single-layer spherical domes using kriging surrogate model

This paper aims to provide an aerodynamic optimization procedure to improve the aerodynamic performance of single-layer spherical domes, by coupling the kriging surrogate model with computational fluid dynamics (CFD) and finite element analysis (FEA). Firstly, a series of wind tunnel tests on the mean pressures and wind-induced behavior of a single-layer spherical latticed shell, were carried out to investigate the effect of dome geometric parameters. Then, the Reynolds-averaged Navier-Stokes equations and RSM turbulence model were utilized for simulating the wind loads on spherical domes, and the numerical results are validated with experimental data. On this basis, the single-objective aerodynamic optimization of spherical domes based on ordinary kriging surrogates has been carried out to find out the optimal geometric parameters (rise/span and wall-height/span ratios). The objectives were minimizing the highest mean suction and the maximum vertical displacement, respectively. The optimization results showed that the optimal design of spherical domes exhibits a reasonable aerodynamic performance improvement compared with the near optimal solutions. In addition, the highest mean suction and the maximum vertical displacement can be reduced by decreasing the wall-height of the dome, and a good trade-off between the two objectives can be achieved by selecting suitable dome geometric parameters.

Stability analysis of single-layer special-shaped folded-plane latticed shell

Single-layer special-shaped folded-plane latticed shell had been applied in Shenyang culture and art center. In order to analysis its static stability, explore the form of buckling modes and find out its critical load factor, this paper analysis the optimized structure with MIDAS Gen. Eigenvalue buckling analysis and nonlinear buckling analysis showed that the in-plane stiffness of the structure is very large, and the out-plane stiffness is small, the upside structure is prone to instability. The critical load factor for this structure is 10.32, the structural overall stability is fine according to the code. This structures is sensitive to the initial geometric imperfections which could lower structural stability of the system.

Shape optimization and buckling analysis of novel two-way aluminum alloy latticed shells

The circumferential profile of cylinder, as a classic shape, has been widely adopted in single-layer latticed shells. Previous research into these structures primarily concentrated on their buckling behavior. In this work, a novel two-way aluminum alloy cable-stiffened single-layer latticed shell is proposed to explore a shape optimization procedure of such structure. In addition, the buckling behavior of the optimized structures and classic cylindrical latticed shells are examined and compared. The optimization procedure adopts a linear algorithm, in which the structural strain energy is selected to be the optimization objective. Buckling analyses are also performed to compare the buckling behavior of this novel latticed shell with classic cylindrical and optimized shapes. The comparisons show that the load-carrying capacities are clearly enhanced by optimizing the shell shapes. The results presented in this article are anticipated to aid engineers in the design of two-way aluminum alloy latticed shells with an optimal shape.

Experiment of six-member basic structure with a pre-embedded-bolt joint for single-layer latticed shells

Experiment of six-member basic structure with a pre-embedded-bolt joint for single-layer latticed shells

Highly efficient CFRP anisogrid lattice structures for central tubes of medium-class satellites: Design, manufacturing, and performance

A design and manufacturing method for highly efficient CFRP anisogrid lattice shells aiming at central tubes for medium-class satellites is presented in the paper. Central tubes are designed to withstand high inertial forces that are induced by the supported satellite mass and equipment during the launch phase. This requires buckling and material strength other than adequate stiffness. In addition, the typical structure includes several interfaces that are subjected to significant load transfer and need to be properly integrated in the body of the shell. A specifically adapted version of the filament winding technology showed itself to be particularly suitable for this application. The modified process implements a “parallel winding” deposition strategy in conjunction with high modulus dry carbon fibers and resin infusion. However, design and manufacturing issues need to be investigated as a whole in order to minimise the structural weight and be competitive with conventional CFRP structures. In order to demonstrate the performance achievable with an optimal lattice structure, a comprehensive testing campaign was built around two full-scale prototypes: 1) the Technological Model (TM), aimed at the manufacturing process setup and mechanical properties characterization, and 2) the Demonstrator (DM), aimed at global stiffness and strength evaluations culminated with the collapse of the structure.

Lattice shells composed of two families of curved Kirchhoff rods: an archetypal example, topology optimization of a cycloidal metamaterial

A nonlinear elastic model for nets made up of two families of curved fibers is proposed. The net is planar prior to the deformation, but the equilibrium configuration that minimizes the total potential energy can be a surface in the three-dimensional space. This elastic surface accounts for the stretching, bending, and torsion of the constituent fibers regarded as a continuous distribution of Kirchhoff rods. A specific example of fiber arrangement, namely a cycloidal orthogonal pattern, is examined to illustrate the predictive abilities of the model and assess the limit of applicability of it. A numerical micro–macro-identification is performed with a model adopting a standard continuum deformable body at the level of scale of the fibers. A few finite element simulations are carried out for comparison purposes in statics and dynamics, performing modal analysis. Finally, a topology optimization problem has been carried out to change the macroscopic shear stiffness to enlarge the elastic regime and reduce the risk of damage without excessively losing bearing capacity.

Research on the progressive collapse resistance of single-layer cylindrical latticed shells with AH joints

Progressive collapse accidents of single-layer latticed shells introduce a serious threat to public safety. The progressive collapse-resisting capacity (PCRC) has gradually become an essential requirement in the design of spatial structures. In this study, the progressive collapse test and numerical simulation of a single-layer cylindrical latticed shell were conducted to evaluate the effect of the joint stiffness on the PCRC of fabricated single-layer latticed shells. A combined spring model was established to simulate the semi-rigid performance of fabricated joints in the FEA. The failure mechanism of single-layer cylindrical latticed shells with different joint systems was thoroughly discussed from multiple perspectives. The results show that the combined spring model can accurately simulate the progressive collapse of a single-layer latticed shell with semi-rigid joints. The progressive collapse of the cylindrical latticed shell with type-II AH joints showed brittle features during the test. Most joints experienced connection failure. Although the rigid jointed shell and latticed shell with type-II AH joints have much higher PCRC, the semi-rigid jointed shell with type-I AH joints has better ductility during progressive collapse. This paper offers a reference for the progressive collapse-resisting design of latticed shells with fabricated joints.

Quasi-static compression and hygrothermal stability of BMI/CE co-cured composite lattice cylindrical shell

Composite lattice cylindrical shell is a typical lightweight structure, which has been widely used in aerospace structures in recent years. In this paper, combined with the high temperature resistance of bismaleimide (BMI) resin and the dimensional stability of cyanate ester (CE) resin, it is proposed to cure T800 carbon fiber/CE composite composed grid and T800 carbon fiber/BMI composite composed skin at one time. The stability of shell height, out-of-roundness and axial pressure resistance of T800/BMI shell, T800/CE shell and T800/BMI-CE shell under hygrothermal conditions are compared and analyzed by experiment and simulation, and the mechanism and feasibility of this design method are verified and discussed.

Use of Spectrum-matched versus Scaled Records to Evaluate Seismic Responses of a Latticed Shell

ABSTRACT Analysis of alatticed spherical shell is carried out by using the scaled and spectrum-matched records. The seed records for scaling and spectrum matching are selected, so their ground motion intensity measures are consistent with chosen targets. The analysis results indicate that the use of the spectrum-matched records leads to the coefficient of variation (COV) values of the load effects to be similar or smaller than the lowest COV values obtained by using the records scaled to the target ground motion intensity measure. Use of the spectrum-matched records for this structural type is preferred for some design checking situations.

Methods to Reduce Material Intensity of Tail Sections of Launch Vehicles

A technique has been developed for reducing the material intensity of highly stressed tail sections of launch vehicles, taking into account strength and stability constraints as well as technological requirements. A cylindrical longitudinally and transversely ribbed waffle-grid (lattice) shell with rectangular holes is taken as the design scheme of the tail section, with its lower end being fastened at locations of support brackets, and the upper one being loaded with longitudinal compressive forces, evenly distributed along the contour, due to the action of the weight of higher-located structure elements. The optimization algorithm is based on the principle of ensuring discrete uniform strength of individual elements (substructures). The structural geometric dimensions of cross-sections of a standard tail section and the stiffness parameters of longitudinal and transverse load-bearing frames, the wall thicknesses of shell elements, the dimensions of lattice shells, etc., are selected from the requirements of stress-strength reliability: constraints on the limiting values of equivalent stresses (strength conditions), compressive stresses of the local and general buckling, and a number of design and technological requirements. The direct calculation of the tail section and the search for its variable geometric parameters are proposed to be performed using an interactive numerical-analytical (finite element method – engineering analysis) algorithm. The initial calculation of the static stress-strain state of the lattice-reinforced tail section was carried out by the finite element method, which is implemented in the NASTRAN package. To discretize the shell and its ribbing, flat finite elements were used. In the process of the finite-element numerical modeling of the tail section state, the reliability of the obtained results of calculating the equivalent stresses was analyzed by studying the convergence of the results of calculations on a series of meshes with different refinement. Results of the application of the developed technique to reduce the mass of the standard tail section of the Antares launch vehicle are presented.

Evaluation of Load Factor to Be Applied in Buckling Design of Cylindrical Lattice Shells Under Asymmetric Snow Load

The load factor is one of the keys in anti-buckling design for safety together for construction cost, and studies have been becoming demanded in a recent situation that super large and super light spatial structures have been constructed. This paper investigates the relationship between reliability index β and snow load factor γs for anti-buckling design of a simply supported cylindrical lattice shell roof under simultaneous action of both dead load and asymmetric snow load. The cylindrical lattice shell analyzed is composed of an equilateral triangle grid of which members are of steel circular hollow sections. Members are connected rigidly to nodes at their both ends. The snow distribution as a main target is assumed in a way that the snow depth on the half of the arch-like roof is half of the amount on the other half roof. The snow fall depth is here assumed 50cm evaluated as 100-year return period, and its probability is assumed as Gumbel distribution with 100-year reference period. The probability distribution of buckling strength Pcr including geometrical and material nonlinearities is approximately evaluated based on a first-order perturbation. The reliability is calculated based on AFOSM, and the relationship in a form of β to γs is finally expressed for design use.

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.

Semi-Rigid Connection in Timber Structure: Stiffness Reduction and Instability Interaction

Latticed shells and domes usually consist of hundreds, sometimes thousands, beam elements connected by rigid or semi-rigid joints. These connecting elements result, generally, very sophisticated, made with different materials and constituted by disparate connection systems. Recently, the stiffness connections were studied, numerically and experimentally, as one of the most important factors influencing significantly the structural response of space structures and domes. Very often, in the design process, the joints are assumed to be hinged or clamped. This assumption may result significantly far from the actual condition of in-service structure and components, leading to not understanding or not being able to prevent sudden catastrophic collapses (buckling, snap-through). Thus, the inclusion of joint stiffness reduction in the numerical model is necessary, more and more also due to the types of external loads, such as overloads that occur during the life of the structure or, especially, seismic solicitations. In this paper, the stability of an existent timber dome has been studied increasing the yieldingness of the connecting nodes according to an original approach. In addition, sensitivity of this kind of structure to the amplitude and the geometrical imperfections shape have been also considered. Numerical analyses have been conducted with local displacement controls, to take into account the geometric nonlinearity effects. Results evidenced that the dome is affected by instability interaction for particular slenderness and stiffness reduction of the connections.

Collapse Mechanism of Single-Layer Cylindrical Latticed Shell under Severe Earthquake

In this paper, the results of finite element analyses of a single-layer cylindrical latticed shell under severe earthquake are presented. A 3D Finite Element model using fiber beam elements is used to investigate the collapse mechanism of this type of shell. The failure criteria of structural members are simulated based on the theory of damage accumulation. Severe earthquakes with peak ground acceleration (PGA) values of 0.5 g are applied to the shell. The stress and deformation of the shell are studied in detail. A three-stage collapse mechanism “double-diagonal -members-failure-belt” of this type of structure is discovered. Based on the analysis results, measures to mitigate the collapse of this type of structure are recommended.

Analysis and comparison of the characteristics of two kinds of dampers

Low cycle reciprocating load tests were exerted to two new kinds of arc steel rod dampers which are suitable for latticed shell, and the finite element models of the two dampers were built, On the base of comparing experimental results and finite element calculation results, The influences to the characteristics of the two dampers of related parameters were analyzed. The resilience model of the two types of dampers were made on the basis of a large number of simulation calculations, and the stiffness degradation laws were researched too. Then the two kinds of dampers were arranged in latticed shell separately, and the influences to latticed shell were researched. Test and analysis indicate that the diameter of the arc steel rod has great influence on the characteristics of the two dampers, and The energy dissipation characteristics of double-layer arc steel rod damper are better than that of single layer arc steel rod damper.