Impact of Vertical Ground Excitation on a Bridge with Footing Uplift

Ground motions recorded in the epicentral region of an earthquake often have a strong vertical component with dominant high frequencies. Damage to bridges in near-source regions due to strong vertical ground motion has been reported. The beneficial effects of footing uplift on structural performance in form of reduction of seismic response of structural members have been confirmed in previous research. The uplift of bridge piers has been utilised in a very limited number of bridge structures, e.g., the South Rangitikei railway bridge in New Zealand. However, the near-fault seismic behaviour of bridges with footing uplift has been even less addressed. In this study shake table investigations were carried out on the response of a single-span bridge model with footing uplift subjected to simultaneous vertical and horizontal excitations. Near-fault ground motions recorded in the Canterbury earthquake sequences of 2010 and 2011 were used. The experimental results show that inclusion of vertical ground motions produce stronger axial force in the pier and larger bending moment in the deck. Concurrent horizontal and vertical excitations may also cause more frequent footing uplift than the solely horizontal excitations.     

Application of an Extended Bouc-Wen Model in Seismic Response Prediction of Unbonded Fiber-Reinforced Isolators

The focus of this article is on seismic-response prediction of Stable Unbonded-Fiber Reinforced Elastomeric Isolators (SU-FREIs). The lateral load-displacement of a SU-FREI can be characterized with a gradual softening that is followed by stiffening. An extended Bouc-Wen Model is developed to simulate the response behavior of SU-FREIs under seismic events. To examine the accuracy of model, the response of a base isolated structure to different input earthquakes were simulated and compared with the results of a previous shake table study. Results of this study indicate that the proposed Bouc-Wen Model is robust and reasonably accurate in seismic analysis of SU-FREIs.     

Probabilistic Seismic Hazard Model of West Bengal,India

We deliver a next-generation Probabilistic Seismic Hazard model of West Bengal based on improved seismogenic source characterization considering both the Layered Polygonal sources & Tectonic sources in the hypocentral depth range of 0–25 km & 25–70 km, seismic local-specific site condition, and adaption of appropriate region specific ground motion prediction equations in a logic tree framework. The surface consistent Probabilistic seismic hazard distribution in terms of Peak Ground Acceleration (PGA) & 5% damped Pseudo Spectral Acceleration (PSA) at different time periods for 10% probability of exceedance in 50 years have been generated and the design response spectra computed.     

Considering Soil-Nonlinearity Effect on Seismic Performance Evaluation of Structures based on Pushover Analysis

According to the most of current seismic codes, nonlinear soil behavior is commonly ignored in seismic evaluation procedure of the structures. To contribute on this matter, a pushover analysis method incorporating the probabilistic seismic hazard analysis (PSHA) is proposed to evaluate the effect of nonlinear soil response on seismic performance of a structure. The PSHA outcomes considering soil nonlinearity effect is involved in the analysis procedures by modifying the site-specific response spectrum. Results showed that incorporation of nonlinear soil behavior leads to an increase in displacement demand of structures which should accurately be considered in seismic design/assessment procedure. Results of implemented procedure are confirmed with the estimated displacement demand including soil-structure interaction (SSI).     

Design Principles for Minimum Torsional Response of Wall-Frame Concrete Structures

A seismic design procedure is described incorporating the well-accepted property that the stiffness of reinforced concrete elements is strength dependent and the requirement that the method of assigning strength to elements should be aiming at minimum torsional phenomena. Such a response allows a direct comparison with the findings of a static nonlinear analysis, which may provide the limits of story drifts and the induced plastic rotations in potential plastic hinges. The requirement of a practically translational response implies that the element strength assignment should be based on planar considerations and the initially elastic response should be of minimum torsion.     

Interpretation of archaeological small-scale features in spectral images

The paper's focus is the use of spectral images for the distinction of small archaeological anomalies on the basis of the authors work. Special attention is given to the ground truthing perspective in the discussion of a number of cases from Norway. Different approaches to pattern-recognition are considered in the light of the increasing availability of hyperspectral images that are difficult to analyse using visual inspection alone.     

'Geographical Expeditions': Assessing the benefits of a student-driven fieldwork method

A student-driven fieldwork method, focused in a local metropolitan area, is described and assessed. Developed for a second-level course in cultural geography, it was inspired by the 'Geographical Expeditions' originally devised by William Bunge in the 1960s. It is one solution to maintaining fieldwork in the syllabus for a large class, at the same time as providing benefits for participants in terms of challenge and autonomy. Student responses are compared with the merits of fieldwork as claimed in the literature. In view of concerns expressed about increasing student 'disengagement' from commitment to university study, active participation in a 'Geographical Expedition' is a strong motivating factor.     

Floor Response Spectra for Bare and Infilled Reinforced Concrete Frames

The objective of this article is to study the effects of structural nonlinear behavior on Floor Response Spectra (FRS) of existing reinforced concrete frames. This study examines how the FRS vary with the level of post-elastic behavior in buildings of different number of stories and masonry infill wall configurations. The effect of damping modeling assumptions is also investigated. Differences and similarities with findings from the literature are discussed. On the basis of the obtained results, a commentary on the adequacy of basic assumptions used in predictive equations proposed by different seismic codes is offered.     

基于融合光谱分析的墓葬壁画颜料色彩虚拟修复方法研究北大核心

墓葬壁画是一种重要的彩绘文物,对其进行揭取搬迁并加固修复是目前主要的保护方式。而在揭取搬迁时,对壁画绘画内容和颜料进行数字化记录及特性分析,是后续壁画表层合理修复的重要依据。光谱成像技术作为一种属性与视觉同步感知的信息探测手段,可以用于壁画表面颜料层的高维信息记录与材质属性分析;同时,利用高光谱伪彩色显示技术可以实现颜料色彩的虚拟复原。基于此,提出一种基于融合光谱分析与带通能量积分的壁画颜料色彩虚拟修复方法,并利用采集的颜料光谱数据、壁画高光谱成像数据与模拟真实场景下的混合颜料光谱数据进行壁画颜料识别与色彩虚拟复原实验。实验结果表明,对于选取的唐墓壁画上的红、黄、蓝、绿四种颜料,其融合光谱识别结果是:武惠妃墓的红色颜料为朱砂/银珠、韩休墓的黄色颜料为石黄/雌黄、武惠妃墓的蓝色颜料为石青/青金石、韩休墓的绿色颜料为石绿的匹配度最大;同时,基于上述识别结果,得到了纯色复原和壁画基底绘制复原的壁画颜料色彩虚拟复原结果,可以为壁画实体修复提供颜料层视觉修复的参考依据。上述研究成果在壁画保护及活化利用领域具有重要的创新示范意义。