A High-Performance Quadrilateral Flat Shell Element for Seismic Collapse Simulation of Tall Buildings and Its Implementation in OpenSees

Shear walls are important lateral force-resistant components of tall buildings. Hence, a reliable numerical model that can accurately represent the mechanical characteristics and large deformations of shear walls is critical for realistic collapse simulation of tall buildings. Based on the theory of generalized conforming element, a high-performance quadrilateral flat shell element, NLDKGQ, accounting for the large deformation using the updated Lagrangian formulation, is proposed herein and implemented in OpenSees. The reliability of NLDKGQ is validated using classical benchmark problems and reinforced concrete specimens. In addition, its capability in simulating the collapse of a tall building is also demonstrated.     

Politics and social violence in developing democracies: Theory and evidence from Brazil

How do the political institutional features of developing democracies influence how violence occurs? Building on research showing that ‘hybrid democracies’ are more prone to social violence, this article argues that elite competition for power in the context of limited institutional oversight plays an important role in explaining violence. The framework here presents possible mechanisms linking subnational political dynamics and rates of social violence in poorly institutionalised contexts. It highlights how political competition, concentrated political power, and constraints on cooperation can create opportunity structures where violence is incentivised and the rule of law is undermined. This is examined empirically using sub-national homicide data from over 5000 Brazilian municipalities between 1997 and 2010. Findings suggest violence is greater in contexts that are highly competitive – where political actors face credible challenges and have a more tenuous grip on power – and those where power is highly concentrated – where political actors have held power for longer periods or face limited credible challenges. Findings also suggest violence varies depending on whether interactions between state and municipal government are likely to be constrained or cooperative; and are consistent with literatures emphasising the importance of structural explanations of social violence. In light of on-going democratic transitions across the globe, the article highlights the value of understanding links between institutional context, contentious politics and social violence.     

DEM Algorithm for Progressive Collapse Simulation of Single-Layer Reticulated Domes under Multi-Support Excitation

In this paper, the Member Discrete Element Method (MDEM) is modified and perfected for three aspects: the algorithm itself, loading and computational efficiency, and to accurately and quantitatively simulate the progressive collapse for large-span spatial steel structures. In addition, the corresponding computational programs are compiled. First, from the perspective of the method, a meshing principle for discrete element models is determined, a treatment for material nonlinearity and strain rate effect is proposed, and a damping model is established. Next, the Displacement Method is introduced to determine the multi-support excitation for the MDEM, and then motion equations of particles under multi-support excitation are derived. On this basis, the specific process of gravitational field loading is presented. Furthermore, parallel implementation strategies for the MDEM based on OpenMP are constructed. Finally, the collapse simulation of a 1/3.5-scaled single-layer reticulated dome shaking table test model under multi-support excitation is carried out. The comparison demonstrates that the ultimate load and failure mode as well as the complete collapse time of the numerical results are consistent with the experimentally measured responses, and the configuration variations from member buckling and local depression until collapse failure are fully captured. Moreover, the displacement time-history curves obtained using MDEM are almost identical to the experimental measurements, and there is a nuance only in the amplitude. It is verified that MDEM is capable of precisely addressing the collapse failure for large-span spatial steel structures. Additionally, the failure mechanism for structures of this type is naturally revealed.     

Real-Time Dynamic Hybrid Testing Coupling Finite Element and Shaking Table

In this article, a Simulink simulation block with the finite element function is developed on the basis of S-function and implemented as the numerical substructure of real-time dynamic hybrid testing. Thereby, a real-time dynamic hybrid testing system coupling finite element calculation and shaking table testing is achieved. Using the developed system, a shear frame mounted on the soil foundation is tested, in which the shear frame is simulated as the physical model and the foundation is simulated as the finite element model with 132 degrees of freedom. Several cases of the dynamic behavior of soil-structure interaction are studied.     

计算机辅助设计（CAD）在文物修复中的运用

通过计算机辅助设计(CAD)在文物修复这门传统工艺中的运用,进一步提高了在文物修复过程中预想修复效果和制定最佳修复方案的精确性。并借助计算机辅助设计在二维平面、三维立体效果方面的特长,模拟文物破损处复原、去除和保留不同颜色物质、创建和复制器物残缺部分及预览器物安装情况等效果。这样不仅为文物修复提供有利帮助,还使这门传统工艺与当今先进计算机技术得到有机结合。修复实践表明,对那些变形较大,又不想进行破坏性修复的文物来说,三维模拟修复就是唯一的修复方法。     

西安鼓楼油饰彩画主要病害分析

为了对油饰彩画进行科学保护,对具有代表性的西安鼓楼油饰彩画病害进行了调查分析．发现存在的主要病害有失光、褪变色、粉化、龟裂、起甲、脱落、烟熏、降尘等。结合实验室模拟实验对病害成因进行了初步探讨,认为导致病变的内因是木基层含水率及地仗制作工艺;外界环境因素为紫外线、温湿度、大气降尘、油烟熏及降雨等。分析结果可为彩画保护提供科学依据。     

Stochastic Quantification of Soil-Shallow Foundation-Structure Interaction

This article highlights soil-structure interaction (SSI) effects on the seismic structural response accounting for uncertainties in the model parameters and input ground motions. A probabilistic Monte Carlo methodology was used to conduct approximately six million dynamic time-history simulations using an established rheological soil-shallow foundation-structure model. Considering the results yields outcomes that contradict prevailing views of the always beneficial role of SSI. In other words, the likelihood of having amplification in structural response due to SSI is large enough that it cannot be readily ignored. This research provides a significant first step towards reliability-based seismic design procedures incorporating foundation flexibility.     

Full-Scale Experimental Verification of Soft-Story-Only Retrofits of Wood-Frame Buildings using Hybrid Testing

The FEMA P-807 Guidelines were developed for retrofitting soft-story wood-frame buildings based on existing data, and the method had not been verified through full-scale experimental testing. This article presents two different retrofit designs based directly on the FEMA P-807 Guidelines that were examined at several different seismic intensity levels. The effects of the retrofits on damage to the upper stories were investigated. The results from the hybrid testing verify that designs following the FEMA P-807 Guidelines meet specified performance levels and appear to successfully prevent collapse at significantly higher seismic intensity levels well beyond for which they were designed. Based on the test results presented in this article, it is recommended that the soft-story-only retrofit procedure can be followed when financial or other constraints limit the retrofit from bringing the soft-story building up to current code or applying performance-based procedures.     

The Experimental Study of Palaeolithic Heat‐Treatment Technology: A Case from the Shuidonggou Rock Resources,North‐West China

The application of heat‐treatment technology on lithic raw materials is an important feature of early modern human behaviour. The evidence of heat‐treated stone artefacts discovered at Localities 2 and 12 of the Shuidonggou Late Palaeolithic site, North‐West China, provides an important example for studying this technology among ancient humans in Asia during the Late Palaeolithic. The mechanism and effects of heat treatment on raw materials and the role of this technology in producing stone tools were studied by means of a simulation experiment and related analytical methods. These facilitated an in‐depth analysis of the heat‐treatment activities of the Shuidonggou occupants and their implications for cognitive ability and survival strategies of human populations at that time.     

东周时期青铜剑首同心圆的制作技术研究

东周时期盛行佩剑之风,在剑上集中了多项杰出的装饰技术,其中位于青铜剑首端部的同心圆装饰以其精湛的制作技术引起了科技史界的关注。剑首同心圆由多圈高同心度、高凸起、薄壁状凸棱组成。对东周时期的多件剑首同心圆的考察表明剑首同心圆应用了类似轮制法成形工艺,预先单独铸造成形,后与剑茎铸接成一体。通过对车削法、石范铸造、失蜡铸造、陶范铸造等剑首同心圆可能的成形方法的分析,推测古人很可能不预制陶模,而是用轮制法直接车制出具有同心圆的剑首陶范,以陶范铸造法铸造剑首同心圆,此法是东周时期最可行的成形方法．其基础是新石器时代已采用的轮制法制陶技术及商周时期成熟的陶范处理技术。通过模板轮制法的模拟试验．成功地复制了青铜剑首同心圆。其过程为配制极细的泥料、制作带齿的模板、采用轮制法制作同心圆陶范并在相应的凸棱上刻下绳纹、焙烧陶范与浇注青铜液。