故宫灵沼轩残损分析及结构性能研究

故宫灵沼轩是我国最早建造的钢铁-砌体组合结构之一,目前损坏较为严重。为更好地保护和修缮该建筑,残损分析和结构性能研究是其修缮保护的科学基础。首先通过现场调研,对该建筑的残损状况进行分析,找出其显见的病害;然后通过精确测绘、材料检测及有限元模拟分析其结构性能,找出其隐在的病害;最后综合残损分析及结构性能分析结果,提出相应的保护措施建议。     

Physics-based Simulation and High-fidelity Visualization of Fire Following Earthquake Considering Building Seismic Damage

This work proposes a framework for the physics-based simulation and high-fidelity visualization of fire following earthquake (FFE) considering building seismic damage. The seismic damage of regional buildings is simulated using multiple degree-of-freedom building models in conjunction with nonlinear time-history analysis. In parallel, a high-fidelity visualization is presented to simulate fire spread and smoke effects. A case study of downtown Taiyuan with 44,152 buildings is performed. The results show that the influence of different ground motions and building seismic resistances on fire ignition and fire spread can be taken into account and that the FFE scene can be displayed realistically.     

New Indices for the Existing City-Centers Streets Network Reliability and Availability Assessment in Earthquake Emergency

During earthquake emergencies in existing city-centers, streets network permits inhabitants to reach safe areas, and rescuers to access damaged zones and help population. However, the network can suffer from blocks due to debris of collapsed or heavily damaged buildings. Understanding urban fabric modifications and classifying elements vulnerability are fundamental steps while dealing with risk-assessment and risk-reduction strategies. This article offers a first quick approach for assessing seismic vulnerability of paths network by considering interferences with building heritage damages. Quick data about existing urban fabric (e.g., buildings typology; streets and buildings geometries) are combined for developing new vulnerability indices for streets network. The earthquake macroseismic intensity is introduced for evaluating probable street blockages and summarizing the overall rating of risks in critical network locations, thus intensity that is not included in other current quick methods for streets-building interference is here taken into account. Risk-reduction strategies based on the proposed indices could minimize the interventions on architectural heritage, maximizing the safety of evacuees. These new indices could be combined with traditional assessment of buildings vulnerability, and evaluations on pedestrians’ and vehicles evacuation flows, for evaluating management strategies.     

Development of Damage Patterns and Fragility Curves in Brick-nogging Buildings from the Thabeikkyin Earthquake,Myanmar, 2012

The Thabeikkyin earthquake (moment magnitude scale of 6.8) occurred on November 11, 2012; its epicenter was located 25 km from Thabeikkyin Township, Mandalay Region, Myanmar. Many buildings were damaged severely during the earthquake. In this study, damage patterns of brick-nogging buildings were firstly developed, and damage grades were characterized to allow for easy classification of the damaged buildings. The damaged data of all building types in the surveyed areas were collected by classifying the four damage levels as no damage, slight damage, moderate damage, and heavy damage. To develop the damage patterns of brick-nogging buildings, damage categories were arranged into three damage grades (slight, moderate, and heavy damage). Secondly, a questionnaire survey was conducted to calculate the seismic intensities of the affected areas. Medvedev–Sponheuer–Karnik (MSK) seismic intensities for the surveyed areas were estimated by analyzing the questionnaire survey responses. Finally, fragility curves for brick-nogging buildings were constructed using the estimated seismic intensities from the survey responses combined with the damage levels. These fragility curves may be useful to assess damage to brick-nogging buildings and to predict the number of damaged buildings in future earthquakes.     

The Baseline Stiffness Method for Damage Detection in Buildings Without Baseline Modal Parameters

A new method called the Baseline Stiffness Method (BSM), used to locate and quantify damage in buildings without baseline modal parameters (undamaged state), is presented. In order to determine this reference state, the BSM uses modal parameters from the damaged state of the building and the lateral stiffness matrix of the first story without damage. Afterwards, by means of an iterative process using singular value decomposition, location and severity of damage are obtained by comparing information about the damaged and non damaged states. Numerical and experimental examples are presented and discussed showing the advantages of the application of the proposed BSM.     

A Multidisciplinary Study on the Seismic Vulnerability of St. Agostino Church in Amatrice following the 2016 Seismic Sequence

ABSTRACT

The big earthquake of August 24, 2016 and subsequent major shocks severely damaged many historic villages in Central Italy and dramatically showed the intrinsic vulnerability of the diffused architectural heritage. The St. Agostino church is one of the collapsed historical buildings, being inside the epicentre village of Amatrice. During the long seismic earthquake swarm, progressively the church was damaged and monitored. This multidisciplinary study of the damage of the church includes correlations of all the data derived from three steps geomatics surveys (3D aerial and terrestrial models): the archival drawings and images documenting previous events distressing the building, the previous strengthening intervention, and finally the seismic site response analysis (from Amatrice’s accelerometric station). Through a back analysis carried out by a finite elements model, it was possible to understand the seismic vulnerability of this historical building, in relation to the previous interventions and damage events. The proposed methodology, based on the interdisciplinary data analysis, provides useful information for the next strengthening projects of damaged historical monument.     

降雨对陕西省榆林市榆阳区明长城破坏的初步分析

降雨是陕西省榆林市榆阳区明长城的主要破坏因素之一。调查中发现,降雨对遗址破坏严重。为了研究降雨对遗址的破坏,在对遗址详细调查的基础上,结合遗址特征与遗址区降雨特点,并参考土壤侵蚀学等方面理论,分析了降雨对遗址的破坏形式及影响因素。结果表明,降雨对遗址的破坏形式可分为直接破坏和间接破坏两大类。其中,主要破坏形式为冲沟侵蚀、片流面蚀和雨蚀剥离。影响因素包括降雨特点、遗址形态、土的性质、植物生长状况和地幔层等,不同破坏形式的主要影响因素各有不同。本结果不仅丰富了降雨对土遗址破坏方面的研究,还为后续陕西榆阳区明长城保护加固措施的选择提供了依据。     

A Microtremor Survey in the Area Shocked by the ML 5.2 Salò Earthquake (North Italy): An Empirical Approach to Determine the Effects of Ground Motions

In this work, the results of a quick microtremor survey performed in the municipalities situated in the epicentre area of the Ml 5.2 2004 Salò earthquake (North Italy) are presented. The aim of this study is to understand if the large amount of damage caused by the event (about 215 million euros only in the areas near to the epicenter) is correlated more to the local surface geology conditions or to the vulnerability of ancient Italian historical centers.

A preliminary seismic zonation was carried out in 5 villages including about 30 measurements of microtremors analyzed by the Nakamura technique (hereinafter HVNR). The points of measurement were carefully selected considering sites located both near damaged buildings and over different local geology conditions (alluvium deposits, fluvial-glacial deposits, debris fans and rock). In order to strengthen the HVNR results and to evaluate the reliability of the Nakamura analysis, a comparison with spectral ratios calculated on earthquakes (hereinafter HVSR) recorded at the strong motion station of Vobarno was made. In general, the outcomes of the survey highlight a possible correlation between local geology conditions and ground motion amplification for different frequency bands. In order to check if this evidence is linked with the damage, a series of macroseismic intensity values were collected for different zones of the investigated area, and a nonparametric correlation approach was used to establish a possible correlation between damage and ground motion amplification for selected frequency bands. The results show, from a statistical point of view, that in the area surrounding the epicenter of the November 24, 2004 mainshock, the damage pattern is not strongly dependent upon the local surface geology but more correlated to the low quality of the civil structures present in the area, including old buildings of the last century.     

Dynamic Characteristic Analysis of Two Adjacent Multi-grid Composite Wall Structures with a Seismic Joint by a Bayesian Approach

Field ambient vibration tests and modal identification using a Bayesian approach are conducted for a building made of multi-grid composite wall structure and divided into two adjacent parts by a seismic joint, to investigate the dynamic characteristics of the special structural type and the effects of the infilled seismic joint. It is found that dynamic interactions between the two structural parts exist possibly induced by the infill of the building separation. Natural frequencies obtained from other two modal parameter identification methods and modal analysis results of finite element models considering dynamic interactions agree with those identified by the Bayesian approach.     

Full-Scale Shaking Table Tests on a Substandard RC Building Repaired and Strengthened with Post-Tensioned Metal Straps

The effectiveness of a novel Post-Tensioned Metal Strapping (PTMS) technique at enhancing the seismic behavior of a substandard RC building was investigated through full-scale, shake-table tests during the EU-funded project BANDIT. The building had inadequate reinforcement detailing in columns and joints to replicate old construction practices. After the bare building was initially damaged significantly, it was repaired and strengthened with PTMS to perform additional seismic tests. The PTMS technique improved considerably the seismic performance of the tested building. While the bare building experienced critical damage at an earthquake of PGA = 0.15 g, the PTMS-strengthened building sustained a PGA = 0.35 g earthquake without compromising stability.     

Soils and Earthen Building Materials Used for the Buddhist Temple Complex

This article presents a comprehensive study of the local soils and historic earthen building materials used in Nako temple complex in Western Himalayas. On-site and laboratory investigations followed a holistic approach to characterize materials and identify historic manufacturing formulas. The interdisciplinary and novel methodology used for analysis of the earthen building materials combine geological, chemical, mineralogical, geotechnical, and mechanical approach. The results presented in this article enable a better understanding of material culture and advance the study of damage and decay processes found in the temple buildings. In addition, a suitable conservation and preservation strategy is presented.     

Modernist Unreinforced Masonry (URM) Buildings of Barcelona: Seismic Vulnerability and Risk Assessment

The main objective of this work is to assess the vulnerability and seismic risk of typical existing modernist unreinforced masonry (URM) modernist buildings and aggregates situated in the Eixample district of Barcelona, part of the architectural heritage of the city. The context of the analysis is the methodology proposed by the Risk-UE project. The buildings are characterized by their capacity spectrum and the earthquake demand is defined by the 5% damped elastic response spectrum, considering deterministic and probabilistic earthquake scenarios. A discussion addresses the basis of the seismic damage states probabilities and the calculated damage index. An important research effort has been focused on the buildings modeling. All the architectural elements and their mechanical properties have been studied and evaluated accurately. It has been evidenced that a detailed and complete knowledge of all the structural elements existing in this type of buildings influence directly their behavior and hence the calculations and the results. The analysis of the isolated buildings and of the aggregate building has been performed for both mentioned seismic scenarios. Finally, a complete discussion of the results is included.     

基于脱榫状态的古建筑木结构燕尾榫节点试验研究

为对古建筑木构架的安全性评价提供依据,通过对脱榫状态下的燕尾榫进行静力试验研究,分析得到残损状态下的木构架力学性能。按照预加载-加载的试验方案对构架进行试验。通过对试验数据的分析,得出了节点主要破坏形式、脱榫量对构架破坏的影响、极限承载力及极限荷载的取值方法并结合理论分析试验数据。     

Allowing Traffic Over Mainshock-Damaged Bridges

A criterion is proposed for deciding whether, after a damaging mainshock, a bridge can still be open for either emergency or ordinary traffic. The criterion is based on the comparison between the collapse risk of the mainshock-damaged structure and the pre-mainshock risk of the intact structure. The approach requires fragilities for multiple damage states for the intact structure, and transition probabilities from these states to collapse for the damaged structure. The aftershock risk decreases with time, hence a decision for reopening might have to wait until the risk level goes down to an acceptable value. A realistic application demonstrates the approach.     

Numerical Modeling of a Church Nave Wall Subjected to Differential Settlements: Soil-Structure Interaction,Time-Dependence and Sensitivity Analysis

ABSTRACT

Historic masonry structures are particularly sensitive to differential soil settlements. These settlements may be caused by deformable soil, shallow or inadequate foundation, structural additions in the building and changes in the underground water table due to the large-scale land use change in urban areas.

This paper deals with the numerical modeling of a church nave wall subjected to differential settlement caused by a combination of the above factors. The building in question, the church of Saint Jacob in Leuven, has suffered extensive damage caused by centuries-long settlement. A numerical simulation campaign is carried out in order to reproduce and interpret the cracking damage observed in the building.

The numerical analyses are based on material and soil property determination, the monitoring of settlement in the church over an extended period of time and soil-structure interaction. A sensitivity study is carried out, focused on the effect of material parameters on the response in terms of settlement magnitude and crack width and extent. Soil consolidation over time is considered through an analytical approach. The numerical results are compared with the in-situ observed damage and with an analytical damage prediction model.     

金陵大报恩寺御碑遗址结构性能及保护技术研究

为了对金陵大报恩寺南北两块御碑遗址进行科学保护,首先通过有限元模拟对南北御碑遗址的现状结构性能进行分析,找出其在正常使用和地震作用时存在的安全隐患;然后根据计算分析结果及整体设计要求提出增设隔震支座的保护技术方案,采用有限元模拟计算对南北两块御碑遗址在增设隔震支座后的结构性能进行分析。计算结果表明:带有御碑的北碑的第一阶自振频率约为不带御碑的南碑的0.087;地震作用下,带有御碑的北碑最有可能破坏的部位是御碑,而不带御碑的南碑最有可能破坏的部位是龟趺头部。施加隔震支座后,南北两块御碑遗址结构的振动频率、最大主拉应力和最大主压应力均明显减小,在7度罕遇地震的情况下均不会发生破坏。研究结果对石碑的结构保护工程研究有参考价值。     

Accuracy evaluation of the semi-automatic 3D modeling for historical building information models

It is stated that 3D recording and modeling of heritage buildings entail accurate building models (as-built). However, this paper presents an analysis of the 3D modeling accuracy for the creation of historical building information models (HBIM), considering the complexity and the deformations of historical buildings, using point cloud data and BIM tools. The 3D modeling processes analyzed are based on a three-stage semi-automatic approach leading to the generation of HBIM, including manual and automatic processes. The three stages consist of: (a) optical and terrestrial laser scanning; (b) meshing processes; and finally (c) 3D solid modeling to be assembled into HBIM. Next, this approach analyzed the mesh deformations generated automatically in comparison to the initial point cloud data. The deformations and the accuracy evaluation have been undertaken using different commercial software. Finally, our modeling approach shows that it can improve the accuracy of the 3D models achieved using existing BIM technologies.     

中国古代砖砌体力学性能研究综述

古代砖砌体建筑由于材料劣化、环境影响,材料特性及力学性能均受到不同程度的影响和损伤,为了保护历史文化的载体,结合古建筑材料获取原始且必要的数据,系统总结了古砖、传统灰浆的制备工艺和材料性能,简要归纳了古砖、传统灰浆和古砖砌体基本力学性能及其测试方法,对比分析了单砖和砌体抗压强度的差异以及古建筑砌体材料力学性能研究现状。并对今后古砌体如弹性模量等力学性能、古砌体材料及结构的损伤机理等的研究提出了展望或建议,可为砖石古建筑的修缮保护提供参考依据。     

Use of Limit State Loss versus Intensity Models for Simplified Estimation of Expected Annual Loss

The expected annual monetary loss (EAL) is a powerful seismic performance indicator for a building as it quantifies repair and replacement costs considering a wide range of possible earthquake scenarios. Existing methods for the estimation of EAL are admirably rigorous but also represent a significant departure from current code assessment methods. By introducing simple loss vs. intensity relationships that are anchored to engineering limit states (set considering both structural and non-structural elements) it is shown that one can predict EAL values quickly, through a closed form expression that could be implemented easily in practice. The validity of the approach is demonstrated by comparing predictions of EAL with those obtained using refined EAL assessments, for a number of case study buildings. The limitations with the accuracy of the approach are discussed and the possibility of developing empirical loss vs. intensity relationships as part of future research is proposed.     

Performance-based Seismic Risk Assessment of Urban Systems

ABSTRACT

Disaster risk mitigation has become a urgent global need. Similar to other natural hazards, earthquakes may cause significant damage on a large scale. In Europe and in other regions with dense urbanization, seismic events can heavily impact historical city centers due to the several structural fragilities. These centers are often part of the worldwide cultural heritage and their preservation is considered a strategic issue. Furthermore, earthquakes may have severe negative short-term economic effects on the impacted communities and adverse longer-term consequences for economic growth. For this reason, the development of an efficient approach for urban seismic risk assessment becomes essential. An original approach is proposed, based on performance concepts and multidisciplinary perspectives. The procedure is applied for validation to the city center of Concordia Sulla Secchia (Italy), damaged by the 2012 Pianura Padana Earthquake (PPE), comparing predicted damage scenarios with the actual post-seismic survey data.