Evaluation of force-based and displacement-based out-of-plane seismic assessment methods for unreinforced masonry walls through refined model simulations     

Michele Godio  Katrin Beyer 《地震工程与结构动力学》2019,48(4):454-475

The performance of force-based and displacement-based seismic assessment methods for the life-safety limit state check of out-of-plane loaded unreinforced masonry walls is evaluated on the basis of refined numerical simulations. For this purpose, a discrete element model of a vertically spanning wall is built and validated against experimental results from static and dynamic test conditions. The model is then analysed for a large range of wall configurations. For each configuration, a static pushover analysis and a series of incremental dynamic analyses are run, the latter permitting to determine the capacity of the wall under dynamic loading. The accuracy of the assessment methods in predicting the acceleration at which the walls collapse is evaluated. It is found that the displacement-based method is more accurate, robust, and safe than the force-based method. The comparison also shows that for walls characterised by a relatively high ratio of axial load to Euler's critical load, both assessment methods lead to an overestimation of the wall capacity. As a remedy, a modification to the methods based on a recently developed mechanical model is put forward and tested. For the force-based method, it is additionally suggested to set for walls with relatively high overburden ratios the behaviour factor equal to 1. To ensure reproducibility of this study, all input and output files of the numerical simulations are made publicly available.  相似文献   

A hydropedological approach to simulate streamflow and soil water contents with SWAT+     

Johan van Tol  Katrin Bieger  Jeffrey G. Arnold 《水文研究》2021,35(6):e14242

Reflecting internal catchment hydrological processes in hydrological models is important for accurate predictions of the impact of climate and land-use change on water resources. Characterizing these processes is however difficult and expensive due to their dynamic nature and spatio-temporal variability. Hydropedology is a relatively new discipline focusing on the synergistic integration of hydrology, soil physics and pedology. Hydropedological interpretations of soils and soil distribution can be used to characterize key hydrological processes, especially in areas with no or limited hydrometric measurements. Here we applied a hydropedological approach to reflect flowpaths through detailed routing in SWAT+ for a 157 ha catchment (Weatherley) in South Africa. We compared the hydropedological approach and a standard (no routing) approach against measured streamflow (two weirs) and soil water contents (13 locations). The catchment was treated as ‘ungauged’ and the model was not calibrated against hydrometric measurements in order to determine the direct contribution of hydropedology on modelling efficiency. Streamflow was predicted well without calibration (NSE > 0.8; R² > 0.82) for both approaches at both weirs. The standard approach yielded slightly better streamflow predictions. The hydropedological approach resulted in considerable improvements in the simulation of soil water contents (R² increased from 0.40 to 0.49 and PBIAS decreased from 40% to 20%). The routing capacity of SWAT+ as employed in the hydropedological approach reduced the underestimation of wetland water regimes drastically and resulted in a more accurate representation of the dominant hydrological processes in this catchment. We concluded that hydropedology can be a valuable source of ‘soft data’ to reflect internal catchment structure and processes and, potentially, for realistic calibrations in other studies, especially those conducted in areas with limited hydrometric measurements.  相似文献   

Analytical and empirical models for predicting the drift capacity of modern unreinforced masonry walls     

Bastian Valentin Wilding  Katrin Beyer 《地震工程与结构动力学》2018,47(10):2012-2031

Displacement‐based seismic assessment of buildings containing unreinforced masonry (URM) walls requires as input, among others, estimates of the in‐plane drift capacity at the considered limit states. Current codes assess the drift capacity of URM walls by means of empirical models with most codes relating the drift capacity to the failure mode and wall slenderness. Comparisons with experimental results show that such relationships result in large scatter and usually do not provide satisfactory predictions. The objective of this paper is to determine trends in drift capacities of modern URM walls from 61 experimental tests and to investigate whether analytical models could lead to more reliable estimates of the displacement capacity than the currently used empirical models. A recently developed analytical model for the prediction of the ultimate drift capacity for both shear and flexure controlled URM walls is introduced and simplified into an equation that is suitable for code implementation. The approach follows the idea of plastic hinge models for reinforced concrete or steel structures. It explicitly considers the influence of crushing due to flexural or shear failure in URM walls and takes into account the effect of kinematic and static boundary conditions on the drift capacity. Finally, the performance of the analytical model is benchmarked against the test data and other empirical formulations. It shows that it yields significantly better estimates than empirical models in current codes. The paper concludes with an investigation of the sensitivity of the ultimate drift capacity to the wall geometry, static, and kinematic boundary conditions.  相似文献   

Receiver function study in northern Sumatra and the Malaysian peninsula   总被引：1，自引：0，他引：1  

Katrin Kieling  Dirk Roessler  Frank Krueger 《Journal of Seismology》2011,15(2):235-259

In this receiver function study, we investigate the structure of the crust beneath six seismic broadband stations close to the Sunda Arc formed by subduction of the Indo-Australian under the Sunda plate. We apply three different methods to analyse receiver functions at single stations. A recently developed algorithm determines absolute shear-wave velocities from observed frequency-dependent apparent incidence angles of P waves. Using waveform inversion of receiver functions and a modified Zhu and Kanamori algorithm, properties of discontinuities such as depth, velocity contrast, and sharpness are determined. The combination of the methods leads to robust results. The approach is validated by synthetic tests. Stations located on Malaysia show high-shear-wave velocities (V _S) near the surface in the range of 3.4–3.6 km s^− 1 attributed to crystalline rocks and 3.6–4.0 km s^− 1 in the lower crust. Upper and lower crust are clearly separated, the Moho is found at normal depths of 30–34 km where it forms a sharp discontinuity at station KUM or a gradient at stations IPM and KOM. For stations close to the subduction zone (BSI, GSI and PSI) complexity within the crust is high. Near the surface low V _S of 2.6–2.9 km s^− 1 indicate sediment layers. High V _S of 4.2 km s^− 1 are found at depth greater than 6 and 2 km at BSI and PSI, respectively. There, the Moho is located at 37 and 40 km depth. At station GSI, situated closest to the trench, the subducting slab is imaged as a north-east dipping structure separated from the sediment layer by a 10 km wide gradient in V _S between 10 and 20 km depth. Within the subducting slab V _S ≈ 4.7 km s^− 1. At station BSI, the subducting slab is found at depth between 90 and 110 km dipping 20° ± 8° in approximately N 60° E. A velocity increase in similar depth is indicated at station PSI, however no evidence for a dipping layer is found.  相似文献   

The household production function approach to valuing climate: the case of Japan     

David Maddison  Katrin Rehdanz  Daiju Narita 《Climatic change》2013,116(2):207-229

According to household production function theory households combine marketed goods and nonmarket environmental goods to produce service flows of direct value to the household. This readily explains why, as an input to household production activities, households might have preferences over the climate. Using techniques more frequently employed to account for differences in the demographic composition of households we use household production function theory to estimate climate equivalence scales using household expenditure data drawn from 51 Japanese cities over the period 2000–2009. Our results indicate that warmer temperatures result in a small but statistically highly significant reduction in the cost of living. Combining these estimates with climate change scenarios associated with the IPCC A2, A1B, and B1 emissions scenarios other things being equal points to a slight reduction in Japanese households’ cost of living.  相似文献   

Flood frequencies reveal Holocene rapid climate changes (Lower Moulouya River,northeastern Morocco)     

Christoph Zielhofer  Jens Bussmann  Hanoun Ibouhouten  Katrin Fenech 《第四纪科学杂志》2010,25(5):700-714

Current high‐resolution palaeoenvironmental records reveal short‐term Holocene coolings. One of these major Holocene rapid climate changes occurred between 3.2 and 2.7 cal. ka BP. The sensitivity of river systems vis‐à‐vis slight and short‐term Holocene climatic variations is a subject of controversy in the scientific community. In this paper, we present a 4.0 to 1.4 cal ka BP palaeoflood record from the Lower Moulouya River (northeastern Morocco) to demonstrate the high sensitivity of semiarid rivers in the southwestern Mediterranean towards Holocene environmental changes. The Lower Moulouya flood deposits are characterised by thick, well‐stratified, predominantly clayey to silty overbank fine sediments. These cohesive sediments show evidence of excellent preservation conditions against fluvial erosion and contain a continuous record of mid to late Holocene flood sequences. The Moulouya palaeoflood record can be interpreted in the context of regional and global high‐resolution proxy data, revealing a strong coupling with Holocene rapid climate changes. The centennial‐scale Moulouya palaeohydrological history will be discussed with palaeoenvironmental data from the same record (palaeomagnetics, sedimentary charcoal record, anthracological analyses, snail analyses) to generate new ideas about the mid to late Holocene hydrological cycle in the southwestern Mediterranean. The deduced features of pronounced Lower Moulouya flooding and the decreased fire recurrence during Holocene cooling remain somewhat inconsistent with the interpretation of other palaeohydrological and paleaoecological records from the southwestern Mediterranean. However, enhanced Lower Moulouya flood frequencies between 3.2 and 2.7 cal. ka BP agree with increased floodplain aggradation in other major river systems of Mediterranean North Africa. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Force–displacement response of in‐plane‐loaded URM walls with a dominating flexural mode          下载免费PDF全文

Sarah Petry  Katrin Beyer 《地震工程与结构动力学》2015,44(14):2551-2573

This article presents a new mechanical model for the non‐linear force–displacement response of unreinforced masonry (URM) walls developing a flexural rocking mode including their displacement capacity. The model is based on the plane‐section hypothesis and a constitutive law for the masonry with zero tensile strength and linear elastic behaviour in compression. It is assumed that only the compressed part of the wall contributes to the stiffness of the wall and therefore the model accounts for a softening of the response due the reduction of the effective area. Stress conditions for limit states are proposed that characterise the flexural failure. The new model allows therefore linking local performance levels to global displacement capacities. The limit states criteria describe the behaviour of modern URM walls with cement mortar of normal thickness and clay bricks. The model is validated through comparison of local and global engineering demand parameters with experimental results. It provides good prediction of the effective stiffness, the force capacity and the displacement capacity of URM walls at different limit states. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Seismic shear distribution among interconnected cantilever walls of different lengths          下载免费PDF全文

Katrin Beyer  Sabrina Simonini  Raluca Constantin  Avigdor Rutenberg 《地震工程与结构动力学》2014,43(10):1423-1441

Mid‐rise to high‐rise buildings in seismic areas are often braced by slender reinforced concrete (RC) walls, which are interconnected by RC floor diaphragms. In design, it is typically assumed that the lateral forces are distributed in proportion to the wall's elastic stiffness. Pushover analyses of systems comprising walls of different lengths have, however, shown that large compatibility forces can develop between them, which should be considered in design, but the analyses have also shown that the magnitude of the computed forces is very sensitive to the modelling assumptions. Using the results of a complex shell element model as benchmark, different simple hand‐calculation methods and inelastic beam element models are assessed and improved to yield reliable estimates of the base shear distribution among the individual walls comprising the interconnected wall system. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Revised stratigraphy and eruption rates of Ceboruco stratovolcano and surrounding monogenetic vents (Nayarit,Mexico) from historical documents and new radiocarbon dates     

Katrin Sieron  Claus Siebe 《Journal of Volcanology and Geothermal Research》2008

More than a dozen new radiocarbon dates reconstruct the eruptive history of Ceboruco volcano. Six of these further constrain previous results for the important plinian Jala eruption, which occurred near 1060 ± 55 yr BP. A calibrated radiocarbon age of AD 990–1020 was obtained as best overlap range for all samples. Pottery fragments found directly underneath the pumice deposit indicate that this area was inhabited by human populations that witnessed the eruption. This age therefore represents an important time marker in the prehistory of this region, because an area of > 560 km2 was devastated and covered by a thickness of > 50 cm of pumice and ash fallout.  相似文献   

Larval Brachyuran Crab Timing and Distribution in Relation to Water Properties and Flow in a High-Latitude Estuary     

Megan Murphy  Katrin Iken 《Estuaries and Coasts》2014,37(1):177-190

Crab larval dispersal and, thus, adult population size can be influenced by oceanographic conditions, especially in highly dynamic and variable environments such as high-latitude estuaries. This study's primary goal was to understand larval timing, abundance, and distribution in relation to oceanographic effects between the more estuarine inner and more oceanic outer part of the subarctic estuary of Kachemak Bay (south-central Alaska, USA). Temperature and salinity measurements and plankton tows were taken along the boundary between the two bay parts from 31 March to 28 October 2008 on spring and neap tides. Summer water flow and stratification in Kachemak Bay were chiefly buoyancy driven, and predominant flow patterns were not affected by the large tidal range in the region. Larvae of seven brachyuran species were found over the sampling period, with seasonally different peak abundances. Larval spatial distribution patterns, presence of most larval stages for each species, and their seasonal timing and persistence within the water column suggest that most species are locally transported within or close to Kachemak Bay. The larval assemblage was correlated with seasonal changes in water temperature, and peak abundances of some species coincided with spring tides and/or frontal systems between the in- and outflow regions of the bay. The strong influence of freshwater on the local circulation pattern in the summer indicates that larval transport will likely be strongly affected by future changes in glacial melt and precipitation.  相似文献