Different kinds of response analyses can be performed to analyze the dynamic performance of a structure. A dynamic response analysis should always be initiated by an eigenvalue analysis on the natural oscillation modes of the structure to get the specific dynamic behavior. This applies on Earthquake analyses as well as on dynamic oscillations of machines or building structures. A Dynamic Response analysis typically gives input to a Fatigue Analysis where all stresses are kept elastic, a so called High Cycle Fatigue (HCF) analysis or a Stress fatigue analysis.
Fatigue analysis of different kinds is what most of our Structural Engineers have a profound experience of. Our knowledge is applied in Finite Element models, in core cause investigations or in designs recommendations.
When applicable, standards like the ASME is used for fatigue evaluation, otherwise standard theory is used.
Fatigue Crack life Estimations
Remaining crack lives or estimations on existing cracks are made with both linear and non-linear crack growth models. Macroscopic investigations on cracks for evaluation of core cause to crack initiation and growth can be made.
Multi-axial Stress Conditions
To avoid brittle behavior of a ductile material, multi-axial stress conditions must be avoided. This can be done by the usage of our design experience and empirical methodology built on multi-axial factors.
Plasticity and Resistance Towards Collapse
Non-linear material models are often used in Finite Element models where plastic behavior might occur or if a design must be evaluated against collapse. We have the experience in how to use and how to evaluate these models, including how to apply statistical methodology to achieve a conservative design on a structure – this is very important since “hinges” often causes plastic zones to move around.
Buckling and Collapse
To evaluate a slender structure, for instance a cistern, an eigenvalue analysis on buckling could be performed to get the different buckling modes of the structure. This can be completed with a plastic collapse analysis, initiated with a small offset corresponding to the eigenvalue buckling mode. Alternatively a simplified analytical analysis in accordance with Euler theory could be performed.
Thermal loads are often tricky to evaluate. First, the difference between local and global loads must be understood. Second, realistic thermal conditions on the model boundary and starting conditions must be applied. Third, plastic conditions on the structure must be applied and later an evaluation on the appearing results for an optimized design. This includes Low Cycle Fatigue (LCF), often also referred as Thermal Fatigue.
Creep usually appears on very hot structures or where plastic (non-metallic) materials are used. It is important to be aware of that if available material data is spreading, the results will be very different. For understanding of the problem a simplified analysis might be enough.
Explicite Finite Element codes are used for impact analysis such as rock drops into a concrete structure or sheet metal forming in a die structure.
BERDIZ Consulting AB is well aquatinted to evaluate for instance Pumps, Valves, Heat Exchangers, Mixers, T-joints, Flanges, Welds, Turbine parts, Nozzles, Pipe supports and more.
Requirement management on structures and process systems
Requirement management on structures can be applied on different levels during the design process.
During basic design a more schematic analysis is applied on over all systems and structures. During this process it is favorable to develop a Methodology on how Mechanical/Structural Requirements should be revealed on different process systems and structures. It is also important to decide which standards to apply due to security aspects and classification.
During detailed design all possible loads are investigated, assumed to be negligible or covered by envelops. During this process the loads are also combined into possible Load combinations, assumed to be conservative and also enveloped to cover other load combinations. This is usually done in two documents, one explaining and justifying all assumptions, all envelops and why some loads and load combinations could be left out. The second document is just describing which loads to use, how the loads are combined, on which part of the system loads/combinations apply, where the loads can be found and which standards apply for evaluation.
BERDIZ Consulting AB is well aquatinted with all these processes.
BERDIZ can offer evaluation of Steel and Concrete structures, Piping and Supports, Anchors, Studs, Methodology Reports, etc.