Projects

 

Selected research projects:

Project title Research topics Project description

DatA ESPerT (Database Analysis for Evaluation of Seismic Performance Assessment Tools)

Individual Fellowship - Marie Skłodowska Curie Action – Horizon 2020

Probabilistic performance assessment of industrial buildings

In highly industrialized regions, earthquakes severely affect societies in terms of economic, social and environmental consequences due to the complex integrated and highly sensitive industries – even in areas of medium to low seismicity like Europe. Whereas the seismic behavior of typical building structures is broadly understood and reflected in technical guidelines and damage prognosis tools worldwide, event reports and even assessment tools for industrial facilities are scarce, mainly because affected facilities are usually not generally accessible and are, thus, not covered by reconnaissance teams. After the recent Italian earthquakes, event reports were created and collected by many authors in the field. Within the proposed DatA ESPerT project, the researcher will refer to these reports in order to develop mathematical tools within the PBEE theoretical framework to assess the seismic performance of industrial facilities and to give damage prognoses for future earthquakes. Due to the comparable socio-economic context and similar seismic hazard levels, the research results will be valid for many regions in Southern Europe. Additional aspects of the project consider the development of cost/performance curves for seismic mitigation measures and the investigation of the geographical damage distribution in relation to the seismological circumstances in the recent earthquakes.

An adaptive FE²-model for the analysis of the non-linear, thermo-mechanically coupled behavior of fiber-matrix composites

DFG KL 1345/9-1

Computational structural analysis

The analysis of structures with a heterogeneous microstructure, e.g. fiber reinforced concrete or metal composites, requires knowledge of the averaged, effective material parameters. Effective material parameters for heterogeneous composites can be estimated by homogenization processes. The (Finite Element)²-/FE²-method allows for a simultaneous numerical homogenization during the calculation of the overall structure. Therefore, a representative volume element is attached to each integration point of the overall structure. It captures the nonlinear material behavior and provides information on micromechanical processes. The disadvantage of the FE²-method is the high computational cost. It necessitates a finite element analysis of the microstructure in each integration point. Hence, the definition of the finite element model is required for the numerical homogenization to calculate the effective material parameters for each integration point of the overall structure. The research project aims for reducing the computational effort. For this reason, an adaptive FE²-model shall be developed. The coupled numerical homogenization should only be performed in regions where nonlinear material behavior is expected.

Hybrid Galerkin-collocation methods for surface-oriented modeling of nonlinear problems in solid mechanics

DFG KL 1345/10-1

Computational structural analysis

The geometric model employed for the design process in standard Computer Aided Design (CAD) software differs completely from the geometric description used in the well-established Finite Element Method (FEM) for structural analysis. A common method to define solids in CAD is the boundary representation modeling technique that defines the solid in terms of bounded NURBS surfaces (Non-Uniform Rational B-Splines). The final model data contains thus solely the surface topology of the solid but the analysis process requires a description of the interior domain. Hence, the geometry needs to be remodeled by finite element meshing or by deriving a tri-variate NURBS parametrization for Isogeometric Analysis (IGA). The main objective of this proposal is to develop a computational method that combines the features of isogeometric analysis and of the scaled-boundary approach in order to make direct use of the surface modeling technique that dominates in CAD today. Moreover, we seek for methods that apply to a wide class of nonlinear continuum mechanics problems, including an interface to complex three-dimensional constitutive laws. This topic is interdisciplinary in nature and proposed by two groups from civil engineering and mathematics that share the same vision of an exact geometry in the complete simulation process.

Supergeometric shell formulation – elimination of locking effects by means of adapted approximation spaces and multi-field variational principles in isogeometric analysis

DFG KL 1345/7-1

Computational structural analysis

Isogeometric analysis is a new, optimized method which was developed to bridge the gap between design and analysis models. This is achieved by using the same, in CAD software predominant, NURBS basis functions. These functions represent the geometry exactly for every level of discretization and offer by means of high continuity favourable features for strongly curved structures, which are common in shell modeling.

A decisive inhibiting factor concerning the quality of the Finite Element solution are undesired couplings between the strain parts, which lead to an unrealistic stiff system, the so called locking effect. Reliable prevention methods are available for conventional Finite Element approaches with low order basis functions, but isogeometric analysis is in the need of new solutions.

Therefore, in order to reduce locking and develop more efficient and optimized shell models, the project focuses on the implementation of

  1. Interpolations for the rotation
  2. Mixed approaches for the displacements, stresses and strains,
  3. as well as an interface for three dimensional material laws.
PSA-MultiFrag: Probabilistic seismic analysis using multi-dimensional fragility curves Structural dynamics
Master of Science in Structural Engineering and Risk Management of Industrial Facilities Earthquake engineering
DFG funded transfer project „Seismic Risk Assessment of Existing Industrial Facilities“ (grant no. ME 725/9-1)

Seismic Design of Industrial Facilities

Liquid-filled tanks

Industrial facilities must be thouroughly designed to withstand seismic action as they exhibit an increased loss potential due to the possibly wide-ranging damage consequences and the valuable process engineering.

In the framework of the DFG-transfer project ME 725/9-1 we developed a methodology to evaluate the seismic safety of existing facilities. Together with the medium-sized engineering office collaborating with the LBB in the DFG project we carried out a risk assessment according to that methodology on more than 40 facilities of the chemical industry. Furthermore, we developed a user-friendly design concept for the seismic design of liquid-filled tanks.

DFG website of the project

Intelligent Damping Systems Structural vibration control

The main aim of this research project that is funded by the Daimler and Benz Foundation is the development of intelligent damper systems for the vibration mitigation of civil structures. These damper systems should automatically adapt their dynamic properties to the structure's real conditions and loading situation. By using this semiactive effect a higher damper efficiency would be possible. The following proposed solution methods are being investigated:

  • Shape memory alloy damper - SMAD
  • Piezoelectric friction damper - PFD
In order to realize both damper systems the so far started analytical and numerical calculations are being concluded and the new damper systems are being experimentally analyzed.
Sino-German joint research project „Complex Soil-Structure Interaction Issues“ Soil-Structure-Interaction

The project addressed the topic of complex soil-structure interaction phenomena including structure-soil-structure interaction, a topic of considerable scientific and practical importance. Typical applications addressed concern the seismic safety of infrastructures and the behaviour of industrial facilities subject to blast loads (e.g. from possible conflagration of nearby LNG tanks) where adjacent structures interact via the soil. In the past decades there had been a significant progress in the development of sophisticated numerical methods, but a homogeneous half-space had been tacitly assumed in most of the actually available programs, which may lead to unreliable results for markedly heterogeneous soil.

Therefore, the SGC-funded project addressed two types of realistic soil configurations: The first type was stratified soil, using the precise integration method combined with the extended Wittrick-Williams algorithm for solution in the frequency-wavenumber domain. The second type is complex soil with inclusions or intercalations in the near-field and certain far-field inhomogeneities such as variable elastic moduli as functions of depth. The scaled boundary element method with doubly asymptotic continued fractions will be employed.

DFG website of the project

International Conferences and Symposiums Seismic Design of Industrial Facilities

From September 26.-27., 2013 the Chair of Structural Analysis and Dynamics presented the International Conference on Seismic Design of Industrial Facilities (SeDIF-Conference). At this specialised conference 140 academics, researchers and practitioners met from 17 different countries to discuss the challanges of earthquake-resistant design with special respect to plant engineering. The conference was supported by the German Research Foundation (DFG) as international scientific meeting.

Conference website of SeDIF-Conference

Subsequent to SeDIF-Conference the Chinese-German symposium on "Seismic Safety Assessment and Disaster Mitigation of Industrial Facilities" took place in Aachen, which was, as well, organised by LBB. Here, 40 experts from Germany, China and Australia presented innovative research activities and initiated future international cooperation. The symposium was funded by the Sino-German Center for Research.

Adaptive Structural Control by an Intelligent Semiactive Liquid Damper Structural vibration control

In the upoming years the growing possibilities of the control systems are going to revolutionize the design of civil structures and will exceeding the traditional construction methods lead to trendsetting new research areas. One of these areas is going to be the intelligent active structural control, which can satisfy the increasing demands of the modern structures on comfort, economic efficiency, robustness and architecture.

Within this research project funded by the Excellence Initiative of the German Federal and State Governments the main principles of this topic will be created, which will expand the new research area to further fundamental research topics. For the achievement of this goal an active control system of a new semiactive liquid damper is being developed prototypically by an interdisciplinary cooperation between the Chair of Structural Analysis and Dynamics and the Institute of Control Engineering of RWTH Aachen University. The semiactive liquid damper system possesses several economic and technical advantages compared to the conventional passive systems and features further development potential on high level.

MINEA-R: Software for the seismic design of masonry buildings Masonry

The software MINEA-R enables structural engineers to accomplish the proof of stability of masonry structures due to vertical loads and horizontal seismic and wind loads in a quick and efficient way. Depending on the individual requirements of the analysed object MINEA-R provides two- or three-dimensional modelling of the structure.

Additionally, a nonlinear static procedure according to DIN EN 1998 was implemented into the program MINEA-R. This procedure allows to consider the nonlinear deformation characteristics of masonry structures in their seismic design.

More information on the software MINEA-R can be found on www.minea-design.com

Guideline on the Seismic Design of Industrial Facilities and its Components Seismic Design of Industrial Facilities

Current design standards for the seismic design of buildings in Germany are not applicable for buildings that pose an increased risk to the population and the environment. However, operators of industrial facilities that are assessed as “Störfallbetrieb” have to assure that their facilities resist environmental hazards like storms, floods or earthquakes.

In cooperation with the German Chemical Industry Association (VCI) the LBB set up in 2009 a guideline and a corresponding commentary that provides instructions for the earthquake resistant design and construction of facilities of the chemical or related industries according to the state of the art.

In the course of harmonization of technical standards in Europe the DIN 4149:2005 will be replaced by the DIN EN 1998-1 extended by additional parts of DIN EN 1998 (Eurocode 8). Thus, the VCI-guideline and the commentary were adjusted, extended concerning the contents and newly published in 2012.

Download of VCI guideline and commentary
Multidimensional Fragility Analysis Probabilistic Risk Assessment

Probabilistic Safety Analyses for nuclear power plants and industrial facilities of high risk potential need to consider mutual dependencies of individual system components in order to determine the probability of failure of the entire safety-relevant system. The classical fault tree analysis, however, can hardly take interactions between the probabilities of failure of single components into consideration.

In the framework of a project commissioned by a European power supply company we developed a procedure to determine the probability of failure of a coherent process system considering mutual structural and functional interdependencies and to set up a system-related fragility curve.

Siemens / DAAD Soil-Structure-Interaction

The evaluation of Green’s function is significant in applied mechanics and civil engineering since it yields the best description of the dynamic properties of the medium. It is a subject of fundamental interest because of its relevance to soil dynamics, soil-structure interaction, earthquake engineering, seismology, and geophysical methods. Starting from the well-known work of Kelvin, Boussinesq, Cerruti, Lamb and Mindlin, a large number of studies have been made on the basis of wave propagation theory. In this study, an efficient approach to calculate the Green’s function for a multi-layered half space is proposed. The development of the method is guided by the desire to accomplish the following objectives: (1) wide range of frequency interested in seismology and earthquake engineering should be covered. (2) dynamic response of arbitrarily layered medium can be calculated. (3) models involving solid layers of thicknesses ranging from large value to small one should be tackled. (4) response at several points should be simultaneously evaluated. (5) anisotropic multi-layered medium should be considered.

To meet these objectives, both the thin layer method and precise integration method are employed. The advantages of the proposed algorithm are: (a) it overcomes the exponent overflow generally encountered with employing the transfer matrix method; (b) it avoids the huge matrix calculation in the thin layer method; (c) it imposes no limit to the thickness of the layered medium and ensures convergence at the high-frequency range.

Investigation of the dynamic behaviour of Aachen Cathedral Vulnerability Analyses

In 1978, Aachen Cathedral was the first German building to be included into the UNESCO-list of world heritage sites. It is a historic building of universal significance and one of the most important examples of religious architecture. Construction of the Cathedral started approximately 800 a.C.. After more than 1200 years of permanent use considerable damages of the static system were discovered, especially at the masonry, the medieval anchoring system, the roof construction, the vaults and the pillars. Due to the location of the cathedral in a seismic active region it was necessary to determine the seismic vulnerability of the building. The calculations were validated by on-site measurements of the eigenfrequencies. The numerical simulations on a detailed finite-element-model of the cathedral were carried out using the response spectrum method as well as time history methods.