The flat or curved PLANE STRESS3 (membrane) element can be used in large strain 3-D analysis, for example using the RUBBER material model.

The SOLVIA Material Library includes models for many different applications.

The appropriate analysis formulation is set automatically for an element based on the material specification and the indication of small or large displacements/strains. If large displacements are requested, the total or updated Lagrangian formulation or a co-rotational formulation will be selected depending on the element type. Similarly, the updated Lagrangian Jaumann or total Lagrangian formulation is selected, when large strain analysis is requested.

**Iteration Methods**

The incremental equilibrium equations are solved using the modified or full Newton-Raphson methods with or without line searches, or using the BFGS method.

In nonlinear static analysis the load step can be automatically adjusted during the course of the solution depending on the degree of encountered nonlinearity.

A special automatic load-stepping scheme is available for collapse and post-collapse response calculations.

**Sparse Solver**

Storage of system matrices in a sparse format has been implemented and in combination with a direct sparse solver very significant solution time savings can be observed for static as well as dynamic cases, in particular for analysis of large models. Frequency, complex harmonic and temperature analyses of large models show also very significant decreases in solution times compared with the skyline solver.

**Dynamic Analysis**

Frequencies, mode shapes and modal stresses can be calculated. The presence of rigid body modes is allowed.

The mode superposition method can be employed to calculate the time history response, or to perform response spectrum and harmonic response analysis in SOLVIA-POST. Modal damping ratios specified for each material can be weighted for each mode with respect to the stiffness matrix or the mass matrix.

Implicit direct time integration methods can also be employed for analysis of structural vibration problems, i.e., when the system is primarily excited in a few vibration modes. An explicit time integration can be used to predict wave propagation phenomena.

**Fluid-Structure Interaction (FSI)**

A new fluid element is available to model interaction with an adjoining structure in static and dynamic analyses. Interfaces between the fluid and 2D/3D continuum elements or shell elements are established automatically. Typical applications include earthquake analysis of dams, dynamic loads on fluid tanks and structures submerged in water.

**Large rotations**

All elements including the rigid link can be subjected to arbitrarily large rotations in static and dynamic analysis. In particular the new co-rotational beam element is very effective in large rotation analysis which can be important when, for example, the dynamics of rotor blades is studied under a large number of revolutions.

**Linear Analysis Based on Pre-stressed Configuration**

Mode superposition, response spectrum analysis and complex harmonic analysis can be carried out based on linearization of a pre-stressed configuration. The static contribution from all neglected high frequency modes can be included in response spectrum analysis as well as in the response for each solution step during mode superposition analysis.

**Simulation of Building Processes**

A new Time-Elastic material may be used together with the element Birth/Death option to simulate, for example, a building process where the elements are successively added and where the material parameters may be different in the various linear stages.

**Post-tensioned Tendons**

The 3D tendon line geometry can be defined by non-uniform B-splines for calculation of frictional and pressure forces due to a sequence of applied end forces and length changes from anchorage set when concrete structures modeled by beam elements are post-tensioned.

**Beam Section Stresses**

An arbitrary section can be modeled by plane elements to obtain stress distributions due to sets of section forces/moments including cases with Saint-Venant torsion and transverse shear forces.

**Loads**

Prescribed concentrated and edge loading, pressure and temperature (gradient) loading can be defined, mass proportional loading (e.g., gravity loading and base acceleration) and centrifugal loading can be applied, and nodal displacements can be imposed. The loadings can be prescribed as a function of time. The pressure and edge loading and applied concentrated forces/moments can be deformation dependent. A slave node displacement can be prescribed to be a combination of master node displacements.

**Linearized Buckling**

A linearized buckling analysis by an eigensolution can be performed at a selected load level. The calculated buckling mode shapes can be used to define geometric imperfections of the structural model to simulate nonperfect conditions in the collapse analysis.

**Fracture Mechanics**

Stress intensity factors (energy release rates) can be calculated directly in SOLVIA. The procedure can be employed in plane stress, plane strain, axisymmetric analyses and in three-dimensional analysis (using SOLID elements).

**Complex Harmonic Response**

The harmonic response of models with concentrated dampers and viscous or hysteretic material damping can be analyzed using complex arithmetic. The real and imaginary responses are calculated including active and reactive power flow in elements.

**Oil Film Applications**

Coupled thermal and pressure analyses of hydrodynamic fluid film bearings can be analyzed. The fluid film pressure is calculated from the finite element discretization of Reynolds equation. The temperature analysis employs an unsymmetric conductivity matrix and considers the transport of heat by film convection and conduction. Pre- and post-processing capabilities are available, for example for display of the pressure, temperature, power loss and thickness of the film. The fluid film may be bounded by 3-D pad and rotor bodies, which can deform elastically and thermally and also transport the generated heat.

**Thermal Stresses**

The SOLVIA-TEMP computer program can be employed for calculation of temperatures which are then used for the stress analysis with SOLVIA.

**Contact Conditions**

A very useful, Lagrange multiplier/segment algorithm is available in SOLVIA for contact problems, in which the contact area is initially unknown and varies during the response. The bodies in contact may be flexible or rigid with Coulomb frictional conditions, and the bodies may undergo large deformations in sliding and repeated contact and separation. The algorithm can be used for static and dynamic contact problems.

**Element Birth and Death Options**

All elements in SOLVIA and (SOLVIA-TEMP) can be employed with the element birth and element death options. Using the element birth option, the element is not present in the finite element assemblage until its time of birth, whereas in the element death mode the element is initially present but then vanishes at the time of death. These options are very useful in modeling, for example, the construction or repair of a structure, or the excavation of a tunnel.