PEER Testbed Study on a Laboratory Building: Exercising Seismic Performance Assessment

From 2002 to 2004 (years five and six of a ten-year funding cycle), the PEER Center organized the majority of its research around six testbeds. Two buildings and two bridges, a campus, and a transportation network were selected as case studies to “exercise” the PEER performance-based earthquake engineering methodology. All projects involved interdisciplinary teams of researchers, each producing data to be used by other colleagues in their research. The testbeds demonstrated that it is possible to create the data necessary to populate the PEER performancebased framing equation, linking the hazard analysis, the structural analysis, the development of damage measures, loss analysis, and decision variables. This report describes one of the building testbeds—the UC Science Building. The project was chosen to focus attention on the consequences of losses of laboratory contents, particularly downtime. The UC Science testbed evaluated the earthquake hazard and the structural performance of a well-designed recently built reinforced concrete laboratory building using the OpenSees platform. Researchers conducted shake table tests on samples of critical laboratory contents in order to develop fragility curves used to analyze the probability of losses based on equipment failure. The UC Science testbed undertook an extreme case in performance assessment—linking performance of contents to operational failure. The research shows the interdependence of building structure, systems, and contents in performance assessment, and highlights where further research is needed. The Executive Summary provides a short description of the overall testbed research program, while the main body of the report includes summary chapters from individual researchers. More extensive research reports are cited in the reference section of each chapter

As-Built 3D Heritage City Modelling to Support Numerical Structural Analysis: Application to the Assessment of an Archaeological Remain

Terrestrial laser scanning is a widely used technology to digitise archaeological, architectural and cultural heritage. This allows for modelling the assets’ real condition in comparison with traditional data acquisition methods. This paper, based on the case study of the basilica in the Baelo Claudia archaeological ensemble (Tarifa, Spain), justifies the need of accurate heritage modelling against excessively simplified approaches in order to support structural safety analysis. To do this, after validating the 3Dmeshing process frompoint cloud data, the semi-automatic digital reconstitution of the basilica columns is performed. Next, a geometric analysis is conducted to calculate the structural alterations of the columns. In order to determine the structural performance, focusing both on the accuracy and suitability of the geometric models, static and modal analyses are carried out by means of the finite element method (FEM) on three different models for the most unfavourable column in terms of structural damage: (1) as-built (2) simplified and (3) ideal model without deformations. Finally, the outcomes show that the as-built modelling enhances the conservation status analysis of the 3D heritage city (in terms of realistic compliance factor values), although further automation still needs to be implemented in the modelling process

MULTISCALE GEOLOGICAL MODELLING FOR FLUID FLOW EVALUATION ON DEFORMED CARBONATES

In this Ph.D. thesis, the effect of both lithological and structural heterogeneities on fluid flow was investigated, in both porous and tight carbonates, by means of multiscale geological models and fluid flow simulations. The petrophysical properties (i.e., porosity, permeability) of the analyzed multiscale fault zones have been investigated by the implementation of 3D models based on different stochastic and deterministic approaches such as the Discrete Fracture Network modelling (DFN), Structure from Motion photogrammetry (SfM), X-ray computed microtomography (micro-CT) and Lattice-Boltzmann Method (LBM). Furthermore, a 2D elastic-petrophysical model of a seismic scale fault zone in tight carbonates was investigated through the seismic modelling pre-stack depth migration (PSDM) technique, performing a sensitivity analysis of different geophysical and geological conditions to test the seismic signature of a seismic scale fault zone internal architecture.The bulk of this doctoral thesis consists of four scientific papers: Chapter 1. From fracture analysis to flow simulations in fractured carbonates: the case study of the Roman Valley quarry (Majella Mountain, Italy), published in Marine and Petroleum Geology 100 (2019) 95–110. Chapter 2. Analysis of fracture roughness control on permeability using SfM and fluid flow simulations: implications for carbonate reservoir characterization, published in Geofluids, Volume 2019, Article ID 4132386. Chapter 3. Pore-scale dual-porosity and dual-permeability modeling in an exposed multi-facies porous carbonate reservoir, published in Marine and Petroleum Geology 128 (2021) 105004. Chapter 4. Outcrop-scale fracture analysis and seismic modelling of a basin-bounding normal fault in platform carbonates, central Italy, submitted in Journal of Structural Geology. The studies related to the first three papers have been carried out within the same study area, the inactive Roman Valley quarry (Majella Mountain, central Italy), well-known for its historical bitumen extraction. This site facilitates the study of a well-exposed analogue of a porous deformed carbonate reservoir and allows gaining information about matrix, fracture and fault characteristics that influenced hydrocarbon migration. Furthermore, the bitumen shows distribution within the quarry helps to further discuss and validate the obtained results. In the first chapter, the main objective was to assess the impact of both stratigraphic and structural heterogeneities on fluid flow at the outcrop scale. This was possible by creating a large-scale DP/P model of the study area, which includes the petrophysical properties (i.e., porosity and permeability) of the matrix and fracture pore systems associated with the different studied lithofacies and fault zones. The studied rocks consist of ramp carbonates belonging to the lower member of the Bolognano Formation (Oligocene-Miocene in age) composed of grainstones, packstones and wackestones. These rocks are crosscut by two high-angle oblique-slip faults WNW- ESE oriented with up to 40 m of throw. The petrophysical properties of matrix and fractures were derived from laboratory measurements and field-based Discrete Fracture Network (DFN) modelling, respectively. Finally, the DP/P model was used to run fluid flow simulation, testing different scenarios of well locations. The fluid distribution in the matrix, resulting from these flow simulations, is consistent with field observations wherebitumen localizes within the most pervious lithofacies (grainstones). In the fault zones, the fracture network gains a relevant fluid flow anisotropy, enhancing the fluid flow along the faults, whereas the across fault fluid flow is controlled by type and lateral continuity of fault rocks, where fault breccias represent conduits and cataclasites localized barriers. Although the use of DFN models is an acceptable representation of the macroscopy heterogeneities associated with sub-seismic resolution faults in a reservoir characterization, at the pore-scale the fluid flow is controlled by the matrix and fracture pore morphology. Therefore, the scale of investigation was changed in the second and third chapters focusing on the effect of pore scale heterogeneities on permeability. Specifically, the second chapter focuses on the analysis of the so-called fracture hydraulic aperture, which differs from the mechanical aperture due to a friction factor related to the roughness of the fracture walls. Samples of fracture surface have been collected from the different lithofacies outcropping within the Roman Valley quarry and digitalized using SfM photogrammetry in a highly controlled laboratory setting, applying a fracture surface micro-topography. This study incorporates fluid flow simulations, using the Lattice-Boltzmann method, and the use of synthetic computer- generated fractures for estimation of the fracture roughness. The quantitative analysis of fault surface roughness was achieved by implementing the power spectral density (PSD), which provides an objective description of the roughness, based on the frequency distribution of the surface asperities in the Fourier domain. This work evaluates the respective controls on permeability exerted by the fracture displacement (perpendicular and parallel to the fracture walls), surface roughness, and surface pair mismatch. The results may contribute to defining a more accurate equation of hydraulic aperture and permeability of single fractures. The third chapter aims to investigate the interaction between the fracture and matrix pore systems at the microscale. To do so, microscale DP/P models were generated by incorporating two different methods of 3D imaging such as, high resolution synchrotron X-ray microtomography (micro-CT) and SfM photogrammetry. Quantitative analyses of pristine rock and DP/P models were performed to evaluate the contribution of macrofracture segments to the porosity and connectivity of the pore network. These results were integrated with fluid flow simulations by applying a sensitivity analysis to evaluate the control exerted by fracture roughness parameters (i.e., asperity height distribution and fractal dimension) on porosity and permeability in various lithofacies. The results of this study demonstrate the utility of obtainingmicroscale DP/P models as complementary approach to explain the geofluids distribution in fractured multi-facies porous carbonates. Finally, the fourth chapter focuses on an integrated outcrop-based characterization and seismic modelling of the internal architecture of a seismic scale fault zone hosted in tight carbonates. This was possible in a key outcrop represented by an active quarry, located at the southeastern boundary of the Fucino Basin (Abruzzo region, central Italy). Here, the footwall damage zone of a seismic scale fault (throw ≈ 300 m), known as Venere Fault (VF), is well-exposed in a 3D view and crosscut by many subsidiary structures. This study presents a workflow to investigate the across strike distribution of petrophysical properties within the VF damage zone, through quantitative fracture analysis and in-situ permeability measurements. A large-scale 2D petrophysical-elastic base model of the VF zone was constrained incorporating results from field analyses and digital outcrop models (DOM) from SfM photogrammetry technique. This base model was tested in ray-based seismic modelling (PSDM; Lecomte et al., 2008), performing a sensitivity analysis of geological and geophysical parameters to investigate the seismic signature of the VF zone. The present contribution hence highlights the great importance of high- resolution structural analysis of fault damage zones for seismic modelling, and subsurface fault characterization

Uncertainty in Structural Interpretation : Lessons to be learnt

This paper is based on work and discussions with numerous people over many years; special thanks to Alan Gibbs for starting me off on an uncertainty track in the first place and for discussions and work with Zoe Shipton, Euan Macrae, Rebecca Lunn, Andrew Curtis and Rob Butler. Thanks to Rob Butler and friends for the “it's all about geometry” quote. Midland Valley Exploration is thanked for academic use of Move software. Zoe Shipton is thanked for reading an initial draft of the manuscript. The comments of two anonymous reviewers and those of E. Riggs improved the manuscript.Peer reviewedPostprin

Image-Based Modeling of Bridges and Its Applications to Evaluating Resiliency of Transportation Networks

Modern urban areas are heavily dependent on transportation networks to sustain their economic life. Hence, when vital components of a regional network are disrupted, economic losses are inevitable. As evidenced by 1989, Loma Prieta and 1994, Northridge earthquakes, the seismic damages experienced by bridges alone result in extensive traffic delays and rerouting, not only hindering emergency response but also causing indirect economic losses that far surpass the direct cost of damage to infrastructure. Nevertheless, in many areas of the U.S., transportation networks lack the resilience required to sustain the potential demands of natural hazards. Traditional hazard assessment methods, in theory, provide the tools required for predicting the vulnerabilities associated with natural hazards. Nonetheless, due to their abstractions of the complex infrastructure and the coupled regional behavior, they often fall short of that expectation. This study proposes a semi-automated image-based model generation framework for producing structure-specific models and fragility functions of bridges. The framework effectively fuses geometric and semantic information extracted from Google Street View images with centerline curve geometry, surface topology, and various relevant metadata to construct extremely accurate geometric representations of bridges. Then, using class statistics available in the literature for bridge structural properties, the framework generates structural models. Both the performance of the geometry extraction procedure and the structural modeling method proposed here are validated by comparison against the structural model of a real-life bridge developed based on as-built drawings.In principle, these models can be utilized to assess physical damage for any type of hazard, but in this study, the focus is limited to seismic applications. Thus to relate the damage resulting from seismic demands from ground shaking, bridge-specific fragility functions are developed for 100 bridge structures in the immediate surroundings of Ports of Los Angeles and Long Beach. Using these fragility curves, the physical damage resulting from a magnitude 7.3 scenario earthquake on Palos Verdes fault is predicted. Subsequently, the effects of the bridge infrastructure damage to the transportation patterns in the Los Angeles metropolitan area are investigated in terms of various resilience metrics

Acoustic Emission Monitoring of the Turin Cathedral Bell Tower: Foreshock and Aftershock Discrimination

Historical churches, tall ancient masonry buildings, and bell towers are structures subjected to high risks due to their age, elevation, and small base-area-to-height ratio. In this paper, the results of an innovative monitoring technique for structural integrity assessment applied to a historical bell tower are reported. The emblematic case study of the monitoring of the Turin Cathedral bell tower (northwest Italy) is herein presented. First of all, the damage evolution in a portion of the structure localized in the lower levels of the tall masonry building is described by the evaluation of the cumulative number of acoustic emissions (AEs) and by different parameters able to predict the time dependence of the damage development, in addition to the 3D localization of the AE sources. The b-value analysis shows a decreasing trend down to values compatible with the growth of localized micro and macro-cracks in the portion of the structure close to the base of the tower. These results seem to be in good agreement with the static and dynamic analysis performed numerically by an accurate FEM (finite element model). Similar results were also obtained during the application of the AE monitoring to the wooden frame sustaining the bells in the tower cell. Finally, a statistical analysis based on the average values of the b-value are carried out at the scale of the monument and at the seismic regional scale. In particular, according to recent studies, a comparison between the b-value obtained by AE signal analysis and the regional activity is proposed in order to correlate the AE detected on the structure to the seismic activity, discriminating foreshock, and aftershock intervals in the analyzed time series

The Importance of Creating Value in Seismic Design

Major earthquakes have resulted in devastating consequences in terms of human and economic loss. In almost all the earthquakes we observe the failure of structures, sometimes due to poor construction but also due to designers not identifying the specific geo-hazards (iIntensity of ground motion, faults, liquefaction, slopes etc) which affect these structures. In many cases these damages could have been avoided if the original design had correctly identified the geohazards at the site and incorporated the philosophy of performance based design. In this paper several examples will be presented where the different stages of risk assessment will be identified and possible solutions incorporated in the final design. The paper provides examples where existing studies and codes in certain countries may be storing up problems for the future.This paper also highlights some gaps in existing knowledge where more research is needed. Design examples will also cover the advantages of performing detailed design accounting for soil structure interaction effects. In many cases these will offer potential saving to the clients and thus provide value in seismic design. Examples are shown where structures which have accounted for the geohazards will be shown to perform satisfactorily during past earthquakes

Mesoscale modelling of a masonry building subjected to earthquake loading

Masonry structures constitute an important part of the built environment and architectural heritage in seismic areas. A large number of these old structures showed inadequate performance and suffered substantial damage under past earthquakes. Realistic numerical models are required for accurate response predictions and for addressing the implementation of effective strengthening solutions. A comprehensive mesoscale modeling strategy explicitly allowing for masonry bond is presented in this paper. It is based on advanced nonlinear material models for interface elements simulating cracks in mortar joints and brick/block units under cyclic loading. Moreover, domain decomposition and mesh tying techniques are used to enhance computational efficiency in detailed nonlinear simulations. The potential of this approach is shown with reference to a case study of a full-scale unreinforced masonry building previously tested in laboratory under pseudodynamic loading. The results obtained confirm that the proposed modeling strategy for brick/block-masonry structures leads to accurate representations of the seismic response of three-dimensional (3D) building structures, both at the local and global levels. The numerical-experimental comparisons show that this detailed modeling approach enables remarkably accurate predictions of the actual dynamic characteristics, along with the main resisting mechanisms and crack patterns