Revision of seismic design codes corresponding to building damagesin the “5.12” Wenchuan earthquake

A large number of buildings were seriously damaged or collapsed in the "5.12" Wenchuan earthquake. Based on field surveys and studies of damage to different types of buildings, seismic design codes have been updated. This paper briefly summarizes some of the major revisions that have been incorporated into the "Standard for classification of seismic protection of building constructions GB50223-2008" and "Code for Seismic Design of Buildings GB50011-2001." The definition of seismic fortification class for buildings has been revisited, and as a result, the seismic classifications for schools, hospitals and other buildings that hold large populations such as evacuation shelters and information centers have been upgraded in the GB50223-2008 Code. The main aspects of the revised GB50011-2001 code include: (a) modification of the seismic intensity specified for the Provinces of Sichuan, Shanxi and Gansu; (b) basic conceptual design for retaining walls and building foundations in mountainous areas; (c) regularity of building configuration; (d) integration of masonry structures and precast RC floors; (e) requirements for calculating and detailing stair shafts; and (f) limiting the use of single-bay RC frame structures. Some significant examples of damage in the epicenter areas are provided as a reference in the discussion on the consequences of collapse, the importance of duplicate structural systems, and the integration of RC and masonry structures.

Damage investigation of girder bridges under the Wenchuan earthquake and corresponding seismic design recommendations

An investigation of girder bridges on National Highway 213 and the Doujiangyan-Wenchuan expressway after the Wenchuan earthquake showed that typical types of damage included： span collapses due to unseating at expansion joints; shear key failure; and damage of the expansion joint due to the slide-induced large relative displacement between the bottom of the girder and the top of the laminated-rubber bearing. This slide, however, can actually act as a form of isolation for the substructure, and as a result, the piers and foundation of most of the bridges on state route 213 suffered minor damage. The exception was the Baihua Bridge, which suffered severe damage. Corresponding seismic design recommendations are presented based on this investigation.

Lessons learned from the “5.12” Wenchuan Earthquake:evaluation of earthquake performance objectives and the importance of seismic conceptual design principles

Many different types of buildings were severely damaged or collapsed during the May 12, 2008 Great Wenchuan Earthquake. Based on survey data collected in regions that were subjected to moderate to severe earthquake intensities, a comparison between the observed building damage, and the three earthquake performance objectives and seismic conceptual design principles specified by the national ＂Code for Seismic Design of Buildings GB50011-2001,＂ was carried out. Actual damage and predicted damage for a given earthquake level for different types of structures is compared. Discussions on seismic conceptual design principles, with respect to multiple defense lines, strong column-weak beam, link beam of shear walls, ductility detailing of masonry structures, exits and staircases, and nonstructural elements, etc. are carried out. Suggestions for improving the seismic design of structures are also proposed. It is concluded that the seismic performance objectives for three earthquake levels, i.e., ＂no failure under minor earthquake level, ＂＂repairable damage under moderate earthquake level＂ and ＂no collapse under major earthquake level＂ can be achieved if seismic design principles are carried out by strictly following the code requirements and ensuring construction quality.

Performance-based seismic design of nonstructural building components:The next frontier of earthquake engineering

With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.

Seismic damage of highway bridges during the 2008 Wenchuan earthquake

Many highway bridges were severely damaged or completely collapsed during the 2008 Wenchuan earthquake. A field investigation was carried out in the strongly affected areas and over 320 bridges were examined. Damage to some representative highway bridges is briefly described and a preliminary analysis of the probable causes of the damage is presented in this paper. The most common damage included shear-flexural failure of the pier columns, expansion joint failure, shear key failure, and girder sliding in the transversal or longitudinal directions due to weak connections between girder and bearings. Lessons learned from this earthquake are described and recommendations related to the design of curved and skewed bridges, design of bearings and devices to prevent girder collapse, and ductility of bridge piers are presented. Suggestions for future seismic design and retrofitting techniques for bridges in moderate to severe earthquake areas are also proposed.

Seismic design analysis of the country masonry school buildings in the meizoseismal area

Several reinforcing schemes are illustrated that are based on the loading characteristics of typical country masonry school buildings with sparsely spaced transversal walls and large depth. From the seismic damage observed following the Wenchuan Earthquake, the effects of reinforcing schemes, tie-columns and tie-beams on the seismic resistance of masonry buildings are analyzed. The concept of improving the ductility of these types of buildings is presented. Finally, some suggestions are proposed for the design of masonry buildings with sparsely spaced transversal walls and large depth.

Recent progress of seismic research on tall buildings in China Mainland

As a result of rapid economic growth and urbanization in the past two decades,many tall buildings have been constructed in China Mainland,offering researchers and practitioners an excellent opportunity for research and practice in the field of structural engineering. This paper reviews progress by researchers throughout China Mainland on the seismic research of tall buildings,focusing on three major topics that impact the seismic performance of tall buildings. These are:(1) new types of steel-concrete composite structural members such as steel-concrete composite shear walls and columns,(2) earthquake resilient shear wall structures such as shear walls with replaceable structural components,self-centering shear walls and rocking walls,and(3) performance-based seismic design,including seismic performance index,performance level and design method. The paper concludes by presenting future research needs and directions in this field.

Damage to urban buildings in zones of intensities Ⅷ and Ⅶ during the Wenchuan earthquake and discussion on some typical damages

The outline and typical characteristics of damages to building in Jiangyou city and Anxian county （intensity Ⅷ）, Mianyang city and Deyang city （intensity Ⅶ） are introduced in the paper. The damage ratios, based on the sample statistics of multi-story brick buildings together with multi-story brick buildings with RC frame at first story （BBF）, are presented. Then some typical damages, such as horizontal cricks of brick masonry buildings, X-shaped cricks on the walls under windows, the damages to columns, beams and infill walls of frame buildings and the damage to half circle-shaped masonry walls, are discussed.

Building damage in Dujiangyan during Wenchuan Earthquake

A field damage survey of 1,005 buildings damaged by the Wenchuan Earthquake in Dujiangyan City was carried out and the resulting data was analyzed using the statistical method. It is shown that buildings that were seismically designed achieved the desired seismic fortification target; they sustained less damage than the non-seismically designed buildings. Among the seismically designed buildings investigated, RC frame buildings performed the best in terms of seismic resistance. Masonry buildings with a ground story of RC frame structure were the second best, and masonry buildings performed the worst. Considering building height, multistory buildings sustained more severe damage than high-rise buildings and 2- and 3-story buildings. Compared to residential buildings, public buildings, such as schools and hospitals, suffered more severe damage.

Probability-Based Seismic Performance Evaluation for Buildings

Recent developments in earthquake engineering indicate that probabilistic seismic risk analysis (PSRA) is becoming increasingly useful for the evaluation of structural per-formance in accordance with building codes. In recent years, the field of seismic resis-tance design has been undergoing a critical shift in focus from strength to performance. However, current earthquake resistant design procedures do not relate building performance to probability. A lack of sufficient empirical data has highlighted gaps in this research. This study integrated results from the analysis of structural fragility and seismic hazard in Taiwan to perform PSRA to examine the effectiveness of building code in mitigating the risks associated with earthquakes. Factors taken into account included the effect of construction materials, building height, and building age. The results of this study show that the probability of exceeding damage associated with the CP level in buildings of light steel, pre-cast concrete, and masonry, exceeds 2%. These buildings fail to meet the performance objectives outlined in FEMA-273.

MIDAS/Building双塔大跨度连体建筑抗震设计

双塔大跨度连体建筑结构形式及受力较为复杂,其结构安全性设计特别是抗震设计尤为重要。以某双塔大跨度连体建筑为例,基于MIDAS/Building结构分析设计系统及SATWE对整体结构进行小震反应谱分析,考虑施工模拟及P-delta影响,计算其水平及竖向地震作用,得到整体结构受力与位移参数,并进行设计验算。通过比较两种软件计算结果,可以看出该工程各项指标均符合规范要求,具有良好的抗震性能。基于计算结果,提出一些改进措施,为类似结构的计算与抗震性能分析提供参考。

Towards understanding,estimating and mitigating higher-mode effects for more resilient tall buildings

Rapid urbanization has resulted in increased demand for tall buildings in many large and medium-sized cities around the world.Current code-based standards for seismic design are primarily aimed at minimizing life-safety risks under major earthquakes.While reinforced concrete(RC)high-rise buildings designed following current code requirements are expected to achieve collapse-prevention,the contribution of higher modes of vibrations to the dynamic response of these structures can produce seismic demands significantly larger than those obtained from prescriptive code-based procedures,causing unexpectedly higher structural and non-structural damage to these buildings.These imply considerable costs associated with the loss of residences and business operations as well as the post-earthquake recovery of cities.This paper presents a concise review of the current state-of-the-art and state of research pertaining to the understanding,estimation and mitigation of higher-mode effects on the seismic response of tall and slender RC structures.The paper is organized into four main foci:(1)analytical studies on understanding and quantifying higher-mode effects,(2)available experimental work on this topic,(3)advances in code practices in accounting for higher-mode effects in seismic design of RC tall buildings,and(4)recent developments in innovative systems intended to mitigate higher-mode effects in RC tall buildings.The paper concludes by briefly summarizing future challenges facing the construction of earthquake-resilient RC tall buildings that are essential in building resilient cities of the future.

框架剪力墙高层结构地震荷载力学响应分析

高层建筑的抗震性能直接关系到整个结构的安全性,本文以某医院框架剪力墙高层建筑为例,从小震弹性时程分析、中震等效弹性分析、大震弹塑性时程分析三个方面研究了结构的力学响应特征,结果表明:小震作用下,所有结构构件和整体结构性能满足规范要求;在中震作用下,结构的最大层间位移角为1/400,其中关键构件性能验算通过,普通构件和耗能构件均满足性能要求;结构在大震作用下X向和Y向的最大顶点位移分别为0.185m和0.212m,关键构件的损坏程度均为轻度损坏,整个结构仍能保持稳定。本文对结构地震荷载的力学响应分析可为类似工程提供参考。

高烈度地区的多层教学楼隔震设计

为解决高烈度地区多层教学楼易受地震灾害破坏的问题,阐述隔震设计的意义及隔震系统组成,对高烈度地区多层教学楼隔震设计以及隔震建筑与非隔震建筑的造价、抗震性能对比等展开研究,指出针对于高烈度地区的教学楼建筑,隔震设计必不可少。

地震对建筑结构的影响及抗震设计研究

地震作为一种不可预测的破坏性自然现象,对居民以及社会的影响非常大,尤其是对于建筑结构安全性和耐久性的影响尤为显著。文章主要深入探讨了建筑结构抗震设计中经常出现的问题和挑战,同时也强调了抗震结构设计在建筑结构设计方面的重要性和运用。面对地震灾害,如何保证建筑结构的安全成为亟待解决的问题。文中针对这些问题提出了相应的抗震设计措施和建议,旨在解决地震情况下人们居住环境安全等问题,确保人民群众的生命财产不受侵害。通过这些合理的抗震设计措施,可以在地震灾害发生时对建筑结构起到良好的保护作用,从而提高建筑的安全性和稳定性,减少地震带来的损失和破坏。

框架结构建筑检测及结果分析

为了保证框架结构建筑使用期间的安全性,文章以某城市的三层框架结构建筑为研究对象,利用回弹法、电磁感应法等对建筑结构的混凝土强度、钢筋保护层厚度、墙体砖强度等进行检测,检测结果均满足设计要求。基于基底剪力法开展抗震鉴定,发现建筑结构抗震性能较差,须对墙体和梁进行加固,研究成果可为类似建筑物检测提供借鉴。

建筑抗震设计的工程技术发展趋势分析

随着工程科技的进步,抗震建筑设计正趋向于更高效、经济、安全的方向。本研究对现阶段建筑抗震设计的技术和方法进行了深入系统的分析和探讨。首先,我们通过详细研究了各种地震破坏案例,指出了当前建筑抗震设计面临的问题和挑战。然后,我们对先进的抗震工程技术,如隔震技术、消能技术和弹性设计等进行了深入分析,并探讨了它们在未来建筑抗震设计中的应用前景。研究结果表明,这些新兴的抗震工程技术能在减少地震破坏、降低经济损失和保护人类生命安全方面起到重要作用。这一研究的结果对于推动中国抗震建筑设计技术的发展,以及指导实际工程抗震设计具有重要的理论和实际意义。

现代建筑结构设计中的抗震技术应用与研究

抗震设计的未来充满机遇与挑战。智能化趋势增强了建筑物在地震中的自适应能力,通过实时监测与响应,显著提升安全性。同时,新型材料的创新为抗震设计提供了强有力的支持,使建筑在韧性和环保性方面更为突出。然而,设计仍面临诸多挑战,如地震的不可预测性、标准法规的不足,以及老旧建筑改造的难题。建筑师和工程师需不断探索与创新,提升抗震设计水平,确保在自然灾害中最大限度地保护生命和财产安全。未来的抗震设计将在建设安全、可持续城市环境中发挥重要作用。

汶川大地震公路桥梁震害初步调查

2008年5月12日我国四川省汶川县发生8级大地震,造成大量公路桥梁破坏。本文详细介绍了百花大桥、小鱼洞大桥、庙子坪大桥、龙尾大桥等9座典型公路桥梁的震害情况及原因。这个地区的桥梁主要为桥面连续简支梁桥,支座多为直接搁置的板式橡胶支座,地震中稳定性较差,主梁与桥墩连接较为薄弱,更多地发生横、纵向移位,乃至最终落梁。这种薄弱连接一定程度上降低了桥墩的地震荷载,总体上看桥墩震害较轻,但从破坏的桥墩、拱肋、盖梁来看,直接剪切或形成弯曲塑性铰后的剪切破坏较为多见。提出了公路桥梁抗震设计若干建议,涉及桥台抗震稳定性及强度校核、曲线梁桥和高墩桥梁设计、支座及防落梁措施设计、桥墩及构件延性设计、场地液化等多个方面。强调了抗震构造措施能够维持公路桥梁大震后应急通行功能的"最强设计原则"。

汶川地震重灾区典型钢筋混凝土框架结构震害现象

介绍了5·12四川汶川地震近震源区钢筋混凝土框架结构的震害现象,从房屋整体跨塌、房屋整体严重歪斜、房屋部分集中垮塌、房屋部分楼层垮塌、房屋底层侧移过大等方面总结了震害现象,从剪切、剪压、压屈、压弯、塑性铰等破坏方面分析了梁柱震害现象.从结构平立面布置、结构体系和结构构件等方面初步分析了钢筋混土框架结构破坏的主要原因.