Abstract

     Autonomous ships would require higher cyber-physical interaction in comparison with traditional shipping operations, thus increasing the vulnerabilities associated with cyber security. The increasing complexity surrounding the innate characteristics of the shipping industry makes it challenging to build a resilient framework for ensuring cyber security. This study proposes a multi-criteria decision-making (MCDM) framework for assessing cyber security risk in the autonomous shipping context. The research was validated through surveying subject matter experts, system designers and seafarers. Different types of equipment and systems are ranked based on their perceived vulnerability to cyber threats. Survey data from 28 subject matter experts are collected and analysed through the Bayesian best–worst method (BWM). At system level, the results indicate that navigational systems are the most vulnerable to potential cyber threats, while propulsion systems are the least vulnerable element in the context of future autonomous shipping operations. On a sub-system level, the three most vulnerable parts are Global Navigation Satellite System (GNSS), Electronic Chart Display and Information System (ECDIS) and the communication devices on shore control centres (SCC), while the least vulnerable parts are engine controls, SCC integration platforms and cargo handling at ports.

Introduction

     Merchant ships have been an integral part of international trade, carrying about 90% of the goods transported globally (OECD 2021). Since its inception, eforts have been made by the stakeholders to make this mode of transport safer, more efcient and more cost efective. The introduction of advanced technologies along with the skills development of the workforce over the years has reportedly increased workplace safety in the maritime domain (Chauvin et al. 2013; Allianz 2020).

     Consequently, modern technologies such as Automatic Identifcation Systems (AIS), Global Navigation Satellite Systems (GNSS) and Electronic Chart Display and Information Systems (ECDIS) have contributed to safer navigation. The increased reliability and efciency of these technologies has resulted in their broader adoption in the shipping industry such that large ships are now being efciently operated by fewer crews (Lee and Sanquist 1996). The notion that it is possible to maintain navigational safety in the future even without any crew onboard has led to the discussion towards the adoption of autonomous shipping technology. Wróbel et al. (2017) stated that the introduction of Maritime Autonomous Surface Ships (MASS) could further reduce the likelihood of navigational accidents, such as collisions and groundings, as human error played a role in the majority of navigational accidents. However, the probability and consequences of non-navigational accidents such as fre and structural failure are likely to increase if no crew members are onboard (Wróbel et al. 2017).

Conclusions

     This study has presented an integrated approach to elicit cyber-security vulnerabilities in the context of future autonomous shipping utilizing a MCDM method. Our results suggest that navigational systems are the most vulnerable to cyber-threats, whereas propulsion control systems are the least. This necessitates communication devices and protocols used for the navigation of autonomous ships be redundant and cyber-safe. Other emerging new systems in the context of autonomous ships, such as the shore control centre and associated equipment, although opaque for the time being, are potentially vulnerable to multidimensional cyber-threats as described in this study. The unpredictable nature of cyber-security threats, along with inherent repercussions, calls for a multifaceted approach to safeguard the future of shipping. A pre-emptive approach should include not only technical guidelines but also policy and industrial ones and best practices in risk management, and in the behavioural and cultural aspects of shipping. In addition, experts concur that only compliancebased actions would not be sufcient to safeguard against cyber threats. Rather, an all-out comprehensive approach, considering the above aspects, would ensure a safe and secure adoption of autonomous shipping.

Highlights

Abstract

Keywords

1. Introduction

2. A range of perspectives on coastal management and COVID-19

2.1. Technology and beach management in the face of COVID-19

2.2. Environmental and social problems at the coast in face of the COVID-19 pandemic

3. Concluding remarks

Ethical statement

Declaration of competing interest

Acknowledgements

References

Abstract

With the increasing need for and emergence of research on ocean and coastal issues in the context of the COVID-19 pandemic, the Ocean & Coastal Management journal presents this Special Issue with relevant articles within the scope of Coastal Management in times of COVID-19. This Special Issue received 43 tentative abstracts, 29 manuscripts were submitted, and finally, 12 articles were accepted. We provide a wide panorama of those twelve articles that integrate the special issue, covering a diverse range of topics regarding coastal management in the COVID-19 pandemic. Seven papers are studies that discuss environmental and social problems during this time in coastal zones, while the other five explore the use of technology to face COVID-19 on beaches. These twelve articles give some insights to improve coastal management, focused on tourist beaches, natural disasters, and fisheries. In sum, this special issue offers an organized compendium of high-level articles, as a contribution to evolve towards the better ocean and coastal management within the rapid emerging of publications about COVID-19.

1. Introduction

COVID-19 has become what may be the most troubling and complex pandemic that humanity has endured. The pandemic has dramatically impacted prevailing social and economic systems and practices, and triggered profound human health, development and socio-psychological impacts on individuals, families, social groups, enterprises and nations around the world (Alcántara-Ayala et al., 2021; Acuto, 2020; Nathan et al., 2020; Schipper et al., 2020; Wells et al., 2020). We have already grown accustomed to hearing that we live in a “new normality”, though in fact there is no such thing as normality in the present situation, but rather a transition towards reconfigured social and human-environment interactions. These changes and associated uncertainties have global ramifications, with significant impacts and implications for coastal cities and settlements, including how to manage coastal and marine activities. This Special Issue explores the impacts and coastal management implications of COVID-19, including beach management, tourism, fisheries, shipping, and other coastal activities impacted by the pandemic.

The COVID pandemic brings to the fore the complex interconnections between human and social-ecological system health and coastal governance in an age of climate and global change. Responding to the pandemic and planning for sustainable coastal development needs to account for this complexity and the associated uncertainties that shape policy provisions and processes (e.g., Walker et al., 2003). These uncertainties take different forms: 1) Technical and methodological uncertainty: For example, the statistical and methodological uncertainties inherent in modelling Sars-Cov-2 aerial transmission on beaches and the determination of a safe distance between beach users; 2) Epistemological uncertainty: For example, limited data and knowledge for prioritizing one set of management actions above others, such as whether or not to (re)open, partially or not, beaches or should take advantage of this moment to promote environmental recovery of these systems?; and 3) Ontological uncertainty (indeterminacy): For example, our lack of understanding about coastal dynamics and the multitude of ways in which people interact with and within coastal social-ecological systems and consequent implications for decision-making in the face of indeterminacy, especially in the long term (e.g.,Funtowicz and Ravetz, 1993; Kovacic, 2015; Bombana et al., 2021). In the face of such uncertainties and complexity, this Special Issue shines a light on a critical question for coastal managers and governors: What are the key coastal governance challenges in this age of COVID-19?

1. Introduction

2. Numerical model description

3. Aerodynamic and sea wave loadings

4. Fragility analysis of wind turbine

5. Conclusions

Acknowledgements

References

Abstract

To more effectively extract the vast wind energy in marine areas, offshore wind turbines have been constructed with slender tower and large rotor. External vibration sources such as aerodynamic, sea wave and seismic loadings can threaten the safety of these energy infrastructures. It is important to evaluate the reliability of offshore wind turbines subjected to external vibration sources. Previous research works on the wind turbine fragility analyses only considered the fragility of the tower by assuming the wind turbine was in the parked condition with the blade mass lumped at the top of the tower. The study of the fragility of the blade which is one of the most important components of a wind turbine has not been reported. In the present study, a detailed three-dimensional (3D) finite element (FE) model of the NREL 5 MW wind turbine is developed in ABAQUS, and the tower and blades are explicitly modelled to realistically estimate the aerodynamic loads and structural behaviours of the wind turbine. The uncertainties of the structural mass, stiffness and damping are taken into account to develop the probabilistic wind-induced demand models for the tower and blades. The dynamic behaviours of the wind turbine subjected to the simultaneous aerodynamic and sea wave loadings are investigated in a probabilistic frame and the fragility curves for both the tower and blades under the parked and operating conditions are derived and discussed.

Introduction

Wind energy as one of the renewable energies is becoming a main contributor to the new electricity generation. The growth and expansion of wind farms increased rapidly in the past decade. As reported by the Global Wind Energy Council (GWEC), the worldwide installed capacity of wind power at the end of 2018 reached 591 GW, with an increase of 9.6% compared to that at the end of 2017 [1]. Due to the fact that the power generated by the wind turbine is proportional to the rotor area and cube of wind speed, multi-megawatt wind turbines with slender tower and large rotor are widely constructed in the state-of-the-art designs. These wind turbines are very flexible and lightly damped 38 since they are normally manufactured by the light-weight high-strength materials. They are thus susceptible to external vibration sources such as aerodynamic and sea wave loadings, which are experienced constantly during the whole lifetimes by offshore wind turbines. Moreover, many wind farms are located in the regions of high seismic activities such as western of United States, Japan and China [2], seismic loading is another possible vibration source during their lifetimes in these regions. The excessive vibrations may slow down the conversion of wind energy to electricity, reduce the 44 fatigue life of the structural components or even lead to the structural collapse in extreme conditions.

Liquefaction potential analysis is a required task in the foundation design process of offshore wind turbine in Taiwan. The standard penetration test (SPT) is mostly used in the preliminary soil investigation of the pilot offshore wind farm in Chang-Bin, Taiwan. Due to the different experimental conditions and operating conditions, the N value (SPT-N) of SPT varies greatly. This study applies statistical methods in conjunction with the New Japan Road Association simplified-empirical method (NJRA method) to incorporate the uncertainty of SPT-N values into the offshore liquefaction potential assessment to quantify the risk of seabed liquefaction. The study statistics the field experimental geotechnical parameters SPT-N and determines the probability density function of the SPT-N distribution of each layer of soil in the offshore wind farm. In order to quantify the risk of seabed soil liquefaction potential, the Monte Carlo random sampling method is used, and by the NJRA method to carry out the seabed liquefaction potential in Changhua, Taiwan. After comparing, the results obtained by the current SPT-based soil liquefaction potential assessment by deterministic approach are conservative. In the ground investigation of offshore wind farm development, the method proposed in this paper can access the thickness of liquefiable soil layers under any given probability for optimizing offshore wind turbine foundation design.

Introduction

The Chang-Bin offshore wind farm of Taiwan Power Company is located in the offshore area of Changhua. The preliminary geotechnical investigation results show that the seabed of Chang-Bin offshore wind farm in Taiwan is mainly composed of silty sand (SM) and low plasticity clay (CL), it contains a small number of low plasticity silt (ML) and silty poorly graded sand (SP-SM) [CSC (2017), Hai-Shia Offshore Wind Energy Co., LtD. (2017a, 2017b), Chien at al. (2014), TORI (2012), TPC (2012, 2018)].. The soil within 80 meters below the seabed can be roughly divided into three layers. The uppermost layer is mainly loose to medium dense sand (SPT-N<30) and the depth is about 25 meters. The soil conditions of Taiwan’s offshore wind farm are very different from the offshore wind farm in the North Sea [Le at al. (2014)]. For a sandy soil within 20 meters of the surface depth, it is highly likely that soil liquefaction will occur when an earthquake occurs [Seed and Idriss (1971)]. The soil liquefaction potential can assess by deterministic approach in Taiwan, which the SPT-N based soil liquefaction potential semi-empirical analysis method is the common adopted in the engineering design in Taiwan [JRA (1996), CPA (2011)], However, soil liquefaction can be affected by soil layer distribution, soil properties, seismic wave transmission, stress conditions, etc. Therefore, quantifying the risk of soil liquefaction in highly seismic region is essential for the development of offshore wind farms.

1- Introduction

2- Theories and methodology

3- Results and discussion

4- Conclusions

References

Abstract

In order to account for rigid-flexible coupling effects of floating offshore wind turbines, a nonlinear rigid-flexible coupled dynamic model is proposed in this paper. The proposed nonlinear coupled model takes the higher-order axial displacements into account, which are usually neglected in the conventional linear dynamic model. Subsequently, investigations on the dynamic differences between the proposed nonlinear dynamic model and the linear one are conducted. The results demonstrate that the stiffness of the turbine blades in the proposed nonlinear dynamic model increases with larger overall motions but that in the linear dynamic model declines with larger overall motions. Deformation of the blades in the nonlinear dynamic model is more reasonable than that in the linear model as well. Additionally, more distinct coupling effects are observed in the proposed nonlinear model than those in the linear model. Finally, it shows that the aerodynamic loads, the structural loads and global dynamic responses of floating offshore wind turbines using the nonlinear dynamic model are slightly smaller than those using the linear dynamic model. In summary, compared with the conventional linear dynamic model, the proposed nonlinear coupling dynamic model is a higher-order dynamic model in consideration of the rigid-flexible coupling effects of floating offshore wind turbines, and accord more perfectly with the engineering facts.

Introduction

In recent years, floating offshore wind turbines (FOWTs) have been receiving increasing attention due to their prominent advantages, such as steadier and stronger wind available resources, lower operational noise, reduced visual pollution and fewer space limitations (Karimirad et al., 2011; Bachynski and Moan, 2012; Pérez-Collazo et al., 2015; Ma et al., 2015). FOWTs are complex rigid-flexible coupled multi-body systems (Namik and Stol, 2010; Wang and Sweetman, 2013; Nejad et al., 2015). Moreover, because the slender blades of an FOWT system typically work at a high rotational speed and are influenced by the motions of the floating platform, rigid-flexible coupled dynamic responses of FOWT systems are more complicated than those of the fixed bottom wind turbines. Rigid-flexible coupled multi-body dynamics have received considerable attentions during the development of modern high-speed airplanes (Shabana, 1997; Bauchau, 2011). In the 1970s, Winfrey (1971) proposed the “kinetoelastodynamics” (KED) method to model the dynamic behaviour of rigid-flexible coupled multi-body systems. In this method, the system is first modelled as a rigid multi-body system to calculate the motion and inertia forces on the system.

1- Introduction

2- Methodology

3- Results

4- Discussion

5- Conclusions

References

Abstract

Uncertainty in capturing the effects of riparian tree shade for assessment of algal growth rates and water temperature hinders the predictive capability of models applied for river basin management. Using photogrammetry-derived tree canopy data, we quantified hourly shade along the River Thames (UK) and used it to estimate the reduction in the amount of direct radiation reaching the water surface. In addition we tested the suitability of freely-available LIDAR data to map ground elevation. Following removal of buildings and objects other than trees from the LIDAR dataset, results revealed considerable differences between photogrammetry- and LIDAR-derived methods in variables including mean canopy height (10.5 m and 4.0 m respectively), percentage occupancy of riparian zones by trees (45% and 16% respectively) and mid-summer fractional penetration of direct radiation (65% and 76% respectively). The generated data on daily direct radiation for 2010 were used as input to a river network water quality model (QUESTOR). Impacts of tree shading were assessed in terms of upper quartile levels, revealing substantial differences in indicators such as biochemical oxygen demand (BOD) (1.58–2.19 mg L−1 respectively) and water temperature (20.1 and 21.2 °C respectively) between ‘shaded’ and ‘non-shaded’ radiation inputs. Whilst the differences in canopy height and extent derived by the two methods are appreciable they only make small differences to water quality in the Thames. However such differences may prove more critical in smaller rivers. We highlight the importance of accurate estimation of shading in water quality modelling and recommend use of high resolution remotely sensed spatial data to characterise riparian canopies. Our paper illustrates how it is now possible to make better reach scale estimates of shade and make aggregations of these for use at river basin scale. This will allow provision of more effective guidance for riparian management programmes than currently possible. This is important to support adaptation to future warming and maintenance of water quality standards.

Introduction

The influence that riparian vegetation exerts on river water temperatures and light availability by intercepting incoming solar radiation has long been studied (Davies-Colley and Rutherford, 2005; Greenberg et al., 2012; Moore et al., 2005; Webb et al., 2008). Shading is a key parameter due to the control it exerts over the amount of direct radiation reaching the river surface making it an important consideration in water quality modelling and management. Solar radiation has direct effects on rates of primary production of both macrophytes and algae (Bowes et al., 2016, 2012b; Wood et al., 2012) which is important for river metabolic regime and is known to be influenced by riparian shade (Bernhardt et al., 2017). Water temperature also directly influences river fauna and dissolved oxygen concentrations. Therefore considerations of shading are of growing importance given the increasing stress on the water environment likely to arise under future climate. Effective and realistic riparian planting schemes to mitigate against these unwanted effects will become increasingly valuable and enhance water ecosystem services (Martin-Ortega et al., 2015). They will provide alternatives to traditional end-of-pipe solutions arising primarily from the EU Urban Wastewater Treatment Directive, which have been assessed through modelling (e.g. at large basin scale across Europe: Grizzetti et al., 2011).

1- Introduction

2- Road transportation

3- Maritime transportation

4- ‘Greening’ other modes of transport

5- Conclusions

References

Abstract

Recent years have witnessed an increased awareness of the negative external impacts of freight transportation. The field of Operational Research (OR) has, particularly in the recent years, continued to contribute to alleviating the negative impacts through the use of various optimization models and solution techniques. This paper presents the basic principles behind and an overview of the existing body of recent research on ‘greening’ freight transportation using OR-based planning techniques. The particular focus is on studies that have been described for two heavily used modes for transporting freight across the globe, namely road (including urban and electric vehicles) and maritime transportation, although other modes are also briefly discussed.

Conclusions

This work set out to answer a question that concerns the role of OR in green freight transportation. Whilst we do not claim to have provided a complete answer, nor believe that such an endeavor is a simple task, we suggest here, on the basis of the work surveyed in this paper, that there are at least three fundamental roles that OR can continue to play in this area of research: 1. To devise methods, tools and algorithms that help design effective transportation plans that capture the trade-off between environmental and economic performance, with the ultimate goal of arriving at win-win solutions. To achieve this goal, however, one must carefully consider, for a particular freight transportation problem (a) who the players are, and the criteria by which they ‘win’. The review of the current body of work in this area, at least on two major modes of transport, has revealed that problems are often solved for a single player (e.g., an individual freight operator), where the win criterion is the ability to jointly reduce internal and external costs, but with an emphasis on the former.

To investigate the seismic performance of railway bridge piers with round-ended hollow section, five 1/6-scale specimens were tested under low-cyclic loading. The two variable parameters were the volumetric stirrup ratio and axial load level. The damage evolution, strain response, and plastic hinge behavior were meticulously explored. The load-drift relationship, displacement ductility, strength/stiffness degradation, dissipated energy, and viscous damping were analyzed in depth. The quantification of seismic performance objectives was implemented by displacement ductility based on damage assessment. The relationships among the ductility and strength/ stiffness degradation and equivalent damping ratio were regressed using the test data. The experiment and analysis results showed that all specimens suffered flexural failure, with flexural cracks covering nearly twothirds of the pier height. The plastic hinge region lengthened and moved upwards along the column due to the existence of solid segment, internal chamfer and variable section. The displacement ductility capacity enhanced noticeably with increasing stirrup ratio. The increasing axial compression ratio led to higher initial stiffness and seismic capacity to some extent, but excessive axial load would decrease ductility with premature concrete crushing. Furthermore, the seismic safety of the piers were ensured under a ductility factor limitation of 4.8 required by the current seismic code for railway engineering of China.

Introduction

With the robust expansion of high-speed rail (HSR) network in recent years, a large number of standard short-span bridges (including simply supported beam bridges and a few continuous beam bridges) have been constructed or are being built in the southwest region of China [1,2]. To accommodate the rugged topography of mountainous areas, the height of these piers is usually over 30 m [3]. For slender railway bridge columns, the round-ended hollow piers are usually selected as the substructure [4], which not only saves material, lowers self-weight and reduces seismic inertial forces compared with traditional solid piers, but also meets with the stiffness requirement for HSR bridges. However, the Southwest China is known for frequent intensive earthquakes (such as the Wenchuan Earthquake in 2008 and the Lushan Earthquake in 2013). The railway bridges with thin-walled slender columns are vulnerable to seismic damage, so their seismic performance need to be studied in depth. To date, numerous experiments have been finished on rectangular (e.g., [5–10]) and circular (e.g., [11,12]) hollow columns. Mander et al. [5] concentrated on the seismic performance of rectangular hollow columns via semi-static tests of four reduce-scaled models. A series of experiments on full or reduce-scaled rectangular hollow columns were conducted by Yeh and Mo [6–8] since 2000. Furthermore, biaxial quasistatic tests were also performed on rectangular hollow pier specimens [9,10]. For circular hollow piers, Zahn [11] and Yeh [12] studied the flexural strength and ductility behavior respectively.

Life line structures such as elevated flyovers and rail over bridges should remain functional after an earthquake event to avoid possible traffic delays and risk to general public. Generally, restraining the structure by reducing the degrees of freedom often cause serious damages that occurs during a seismic event through yielding of the structural components. By allowing the structure to rock through uplift using suitable arrangements can be a plausible seismic resilient technique. In this context, this article proposes a novel seismic resilient pile supported bridge pier foundation, which uses elastomeric pads installed at top of pile cap. The effect of pile soil interaction along with ground response analysis is also incorporated in the full bridge model adopted for the study. One dimensional equivalent linear site response analyses were performed to arrive at the amplified/attenuated ground motions along the depth of soil.The seismic performance of the proposed bridge with new rocking isolation concept is compared with existing bridge located in medium seismic zone of India. With the help of non-linear dynamic time history analysis and nonlinear static pushover analysis, the bridge modelled using the proposed novel rocking isolation technique shows good re-centering capability during earthquakes with negligible residual drifts and uniform distribution of ductility demand along the piers of the bridge considered in this study.

Introduction

Bridges and flyovers are major assets of any country and failure of such structures during seismic event leads to economic loss to the country and traffic disruptions to the general public. Despite their importance, these key infrastructure assets have been designed for many years, neglecting the fact that loads and geo-hazards may change drastically and thus significant upgrades may be required during their service life. Societies expect accelerated constructions, minimal damage and rapid upgrading for bridges which are sources of transportation and thus must be designed to face very strong earthquake in order to avoid permanent drift which are beyond repairs. Collapse of whole bridge caused by extended damage of the piers and/or unseating of the superstructure caused by insufficient deformation capacity of the bearing and other destruction of bridge structure often occurs in an earthquake [1].The concept of ductility is used in the conventional design of bridge pier wherein the pier reinforcement is detailed to develop flexural plastic hinges at the base and top of pier [2]. Although bridges designed in this manner may undergo damages due to severe earthquake excitations as observed in Fig. 1(a)–(d). Rocking isolation in the form of structural rocking or geotechnical rocking of the bridge pier experience far less damage when subjected to high intensity earthquake ground motion with added bonus of pier that recenter due to the increased period of vibration owing to the flexibility of the resilient pier [3,4]. The design of South Rangitikei Railway Bridge in New Zealand in 1981 used structural rocking by adopting the concept of dissipative rocking at the pier-to-foundation interface by means of prestressing tendons which had more rocking sections contributing to dissipation of energy and thus less prone to heavy damages when subjected to severe earthquakes [5,6].

1- Introduction

2- Methods

3- Results

4- Discussion

5- Conclusion

References

Abstract

The Western Gulf Coast provides important habitat for migratory and resident waterfowl. The mottled duck (Anas fulvigula) relies on this region for all of its life-cycle events. Its relatively small population, limited worldwide range, and generally declining population trajectory has earned it a “Red” status on the Audubon WatchList and is a species of concern among state and federal agencies. The Western Gulf Coast (WGC) mottled duck population decline is believed to be primarily caused by the historical conversion and degradation of coastal wetlands and native prairie, and recent declines in cultivated rice. There is general agreement among experts that negative impacts to nesting and brood-rearing habitat are the most important threats to the WGC mottled duck population and increasing recruitment is essential to the growth and sustainability of the population. Our goal was to use available knowledge of mottled duck nesting and brood-rearing requirements to develop a model to aid managers in targeting areas for conservation and management. We developed four spatially explicit models that: 1) identify and prioritize existing mottled duck nesting habitat for conservation (e.g., protection or maintenance); 2) identify and prioritize existing mottled duck brood-rearing habitat for conservation; 3) identify and prioritize areas for grassland establishment; and 4) identify and prioritize wetland basins for freshwater enhancement. Spatial models revealed that only 6 km2 and 9 km2 of nesting and broodrearing habitat, respectively, were identified as highest priority (top 10%) for conservation in the WGC. Brood habitat was identified as potentially limiting recruitment in the Texas Mid Coast and the Laguna Madre subregions of our study area, whereas grassland habitat was potentially limiting recruitment in Chenier Plain and Mississippi River Coastal Wetlands subregions. Spatial models also revealed that there is a high density of areas of high priority for grassland establishment inland in Texas and Louisiana. Likewise, there is a high density of wetland basins of high priority for freshwater enhancement throughout coastal Louisiana and the upper Texas coast. We used two separate measures to assess the performance of our Mottled Duck Decision Support Tool (hereafter MODU-DST) and found that it adequately identified patch suitability, as defined by our model, with ≥79% accuracy. Using data from the Cooperative Breeding Mottled Duck Survey, we also found that breeding mottled ducks were using landscapes with optimal spatial arrangement of nesting and brood-rearing habitat, which is reflected by higher mean priority rankings of nesting and brood-rearing habitat in the landscape.

Introduction

The Western Gulf Coast (WGC) provides valuable habitat for migratory and resident waterfowl. The mottled duck (Anas fulvigula) is a resident species in this region and is closely associated with coastal marsh and inland agricultural habitats, relying on these areas for all its life-cycle needs. Habitat conversion and degradation due to large-scale hydrologic alterations, urban expansion, declines in rice agriculture, and other human activities have raised concerns for the declining WGC mottled duck population. Collective evidence from available population data across the WGC range suggests a long-term steep decline in Texas and a stable to slightly declining trend in Louisiana (Wilson, 2007). Although other threats such as sport harvest (Raftovich et al., 2011), lead poisoning (Anderson et al., 2000; Sanderson and Bellrose, 1986), hybridization (Ford, 2015; McCracken et al., 2001), and predation (Bielefeld et al., 2010; Durham and Afton, 2003; Elsey et al., 2004; Stutzenbaker, 1988) may contribute to mottled duck population declines, loss of nesting and brood-rearing habitats is believed to be the primary cause (Wilson, 2007). Therefore, a priority for increasing the WGC mottled duck population is to increase recruitment by conserving landscapes with nesting and brood-rearing habitats in appropriate spatial configurations.

Introduction

Strong ground shaking during the 2011 off the Pacific coast of Tohoku earthquake (the 2011 Great East Japan Earthquake) damaged pile foundations over wide areas in Miyagi and Chiba prefectures in addition to causing various other forms of foundation damage through liquefaction-induced ground deformation, slope failure and complete destruction by tsunami. Such damage to pile foundations, which has been commonly observed in past major earthquakes, resulted in building structure tilting even though superstructures remained practically intact. Pile foundation repair and careful jacking-up to level were required to restore the buildings for use. Most of the damaged buildings were constructed before the Japanese code requirements for the seismic design of foundations went into effect in 1985, while several of them were constructed after 1985. According to the damage investigation,1 74% of the damaged buildings were constructed before 1985. Since approximately 26% of the damage occurred in buildings constructed since 1985, the year of construction does not appear to be a crucial factor in the damage to piles. In addition, pile damage notably occurred in precast concrete piles known to have non-ductile deformation characteristics, and the soil in which damage was observed consisted of very soft clay, a liquefiable layer and/or non-homogeneous strata in most cases. These conditions indicate that significant effects of nonlinear behavior of piles and soil materials must be considered when simulating the pile failure process. The authors focused on a case in which pile damage resulted in building tilting although the pile foundation design was based on a simple linear elastic analysis in accordance with the existing design code in 1987. An analytical study was performed using a foundation structure model to simulate the distinctive pile failure modes observed during the 2011 off the Pacific coast of Tohoku earthquake. In the analysis model, a remarkably damaged frame was removed and used as a calculation model consisting of piles with soil springs. Based on a previous study2 on the seismic performance of pile foundations during severe earthquakes, nonlinear flexural rigidity of the pile element and rotational stiffness at the pile head were adopted. The nonlinear characteristics of the soil springs were also adjusted in accordance with soil type and depth (overburden pressure). In addition, the pile group effect was considered depending on the position and spacing of each pile in a group. The seismic response of the building and the ground deformation were evaluated based on a free field ground response analysis using ground motions recorded at an observation point near the site. The inertia force and axial force at the pile heads were estimated based on the results of elastic analysis.