Einfluß der Deckenschlankheit auf den Durchstanzwiderstand nach DIN 1045‐1, SIA 262, Ö‐Norm B 4700(01) und Eurocode prEN 1992‐1‐1

Influence of the Slab Slenderness on the Punching Resistance according to DIN 1045‐1, SIA 262, Ö‐Norm B 4700(01) and Eurocode prEN 1992‐1‐1 In the last three years the new design codes [1] — [4] were established. The punching resistance of each code was developed on the state of the art. But the formulas show significant differences. Parametric studies documented, that the punching resistance of less slender flat slabs ( λ = length between the supports / effective depth = l/d = 20) is increased according to SIA 262 and Ö‐Norm B 4700(01) in comparison to DIN 1045‐1. EC prEN 1992‐1‐1 neglects the influence of the flat slenderness, however the maximum punching capacity of stirrups is on the design level of double headed studs or stud‐rails. This is contradictory to the current design experience and punching test results [5]. In this contribution the influence of the slab slenderness on the punching resistance with and without shear reinforcement is discussed. In addition, the extremely high maximum punching shear capacity according prEN 1992‐1‐1 is judged by the codes DIN 1045‐1, SIA 262 and Ö‐Norm B 4700(01).     

Quantifizierung der Schadenspotentiale infolge Erdbeben – Teil 2: Modellstudie Baden‐Württemberg

Assessment of damage and loss potentials due to earthquake (2): Model study Baden Wuerttemberg. For the study area of Baden‐Wuerttemberg an intensity‐oriented and thus empirical approach of seismic risk analysis is taken. Explaining the essential work steps, the proximity to reality and the scatter of the results are discussed. Regional differences in the building substance and consequences for the damage expectation to be derived thereof are illustrated. A regionalisation factor is suggested, which reflects the vulnerability of building types and leads to a modification of damage functions; it is derived from extensive data surveys from the model region. The procedures and the processing levels implemented in the model are structured transparently and presented in the paper. The scenarios refer to historical earthquakes with remarkable detailing of the available regional shake maps. For these events it can be proven that losses corresponding to the intensity are calculated if the most important influence factors from soil and building vulnerability are considered. Losses from maximum events are determined by simply increasing the intensity; for worst‐case‐scenarios the respectively strongest shake effects for all communities are superimposed summarily. By applying the gross domestic capital and other statistical property values a relative loss can be derived. The communities are differentiated regarding inhabitant numbers in order to illustrate differences in how heavily affected they are. The calculated scenarios confirm that in the model region, small and medium‐sized towns deserve more attention regarding earthquake preparation than large city centres.     

钢筋混凝土框架结构实际抗震承载力分析

在对结构进行抗震性能评估及基于性能的抗震设计中,需要求出结构的实际抗震承载力。从我国现行抗震规范入手,对钢筋混凝土框架结构的实际抗震承载力进行研究。首先根据现行规范中构件截面抗震承载力设计表达式,由构件内力组合值的各分项系数并考虑内力调整系数,以及非结构构件和构造配筋的影响,初步计算出构件的超强系数λ;然后对具体结构按现行规范算出结构的实际承载力标准值,得到超强系数λ值;再用ETABS软件对结构进行静力弹塑性分析验证。最后得到混凝土框架结构的超强系数最小值为2。     

Quantifizierung der Schadenspotentiale infolge Erdbeben – Teil 1: Rekonstruktion des Bebens in der Schwäbischen Alb vom 03. September 1978

Assessment of damage and loss potentials due to earthquake (1): reconstruction of the “Albstadt” – quake in the Swabian Albs in September 03, 1978. Due to lack of strong earthquakes, there is almost no data or experience available concerning the behaviour and vulnerability of common buildings in German seismic zones. The consideration of their earthquake resistance or vulnerability is still outside the scope of official investigations. A scale is missing to calibrate results of seismic risk assessment and to prove their reliability. For these purposes, an outstanding importance has to be attested to the September 03, 1978 Earthquake in the Western Swabian Alb, the heaviest one in Germany over the last 50 years. The 1978 Albstadt earthquake provides an impression of the severity of design earthquakes (in lower range) defined by DIN 4149: 2005 for the highest zone 3. Due to the limited time elapsed since the quake, it can be assumed that the building inventory is comparable to the situation today and might be generalized to other communities in that zone today. The present study can be regarded as a continuation of research activities directed towards the assessment of damage and loss potentials in German cities initiated by Deutsches Forschungsnetzwerk Naturkatastrophen (DFNK), while introducing recently elaborated and more refined approaches. The detailed survey and documentation of damage cases provide the basis to test the applicability of the developed GIS‐based seismic risk assessment technologies to other seismic regions. For this purpose, the main damage zones and the distribution of mean damage grades in Albstadt/Tailfingen are reconstructed and the loss will be recalculated for the building inventory at the time of the quake in 1978. The vulnerability of building types is evaluated on the basis of the European Macroseismic Scale EMS‐98. The classification of EMS‐98 is used to transform the existing damage observations into a scheme of damage grades. In addition to the empirical approach, selected damage cases are examined by a recently developed evaluation tool for masonry structures, combining experience and analysis in a hybrid way to detect critical zones, as well as the extent and the level of damage. All results indicate a remarkable agreement with the reported situation.     

基于历史地震记录的楼面加速度放大系数研究

楼面加速度放大系数(FAA)是房屋在地震作用下楼面加速度峰值与地面加速度峰值的比值,反映了建筑主体结构对地面加速度的放大作用,在对建筑非结构构件进行抗震承载力计算时,FAA是必需的重要参数之一。对于FAA的合理取值方法,当前规范大都基于少量的历史楼面地震记录或者简单房屋结构有限元模型,开展统计和计算分析,难以反映各种建筑结构FAA的实际分布特征,使得计算获得等效地震力与其非结构构件实际承受的地震作用相差较大。以美国加利福尼亚强震记录数据库(CSMIP)为基础,以新的建筑高度分类方法为基准,分别计算得到混凝土结构、钢结构和砌体结构房屋的FAA。数据分析结果表明,现行规范难以合理地包络实际观测得到的FAA值。因此,采用抛物线模型,分别拟合FAA沿建筑高度分布曲线,并针对不同的高度类型和结构类型,分别给出对应的曲线参数。所拟合的曲线能够很好地反映出实测FAA分布特点。此外,对于屋面附近的楼层,建议适当提高FAA数值以反映高层建筑中楼面鞭梢效应而造成的突变。最后通过对建筑结构高度进行分类来考虑自振周期对FAA的影响。     

Zur Beurteilung des Ankündigungsverhaltens von Spannbetonbrücken nach dem Riss‐vor‐Bruch‐Kriterium. Vorschläge zur Vorgehensweise bei gefährdeten Brücken

Interpretation of the Preannouncement Behaviour of Prestressed Concrete Bridges by applying the “Crack‐before‐Collapse‐Criterion” Proposals for further Proceeding with Critical Bridges Due to extending lifetimes of prestressed concrete bridges the importance of the durability increases. With numerical calculations and investigations of structures according to DIN 1076 it is intended to recognize and prevent possible failure of the structures in time and to minimize the risk for the owner during the remaining lifetime. Especially older prestressed concrete bridges with tension wires endangered to stress‐corrosion‐cracking need to be numerically investigated and judged concerning their preannouncement behaviour according to the “crack‐before‐collapse‐criterion”. According to the numerical results of the “crack‐before‐collapse‐criterion” and supplemental calculations it is possible to evaluate the existing risk for the owner concerning failure of the structures. The design of the concerned structures will be discussed. Based on results of performed investigations proposals for further proceeding with older critical bridges will be given along with recommendations how to limit the remaining risks. For newer bridges the analysis according to the “crack‐before‐collapse‐criterion” is a measure of a sufficient sturdiness.     

Zur Erdbebenbemessung im Holzbau

Seismic design in timber construction. Images from earthquake areas all over the world with a devastating impact on humans, nature and built‐up areas reach us almost every day. Many people do not know that the risk of an earthquake exists in Germany as well. Even experts disregarded the issue of earthquakes in Germany for a long time. The building regulation approved of earthquake regulations took place in 1998 for the first time. The standard DIN 4149:2005 applies to all German federal states since 2007. Many experts commonly think of timber being less suitable for structures in earthquake areas. The use of wood in engineering terms under seismic load and the economical design of a load‐bearing structure will be exemplified in this paper. The recently introduced timber construction code DIN 1052:2004 is the solely German standard for timber construction in addition to the Eurocode 5. Due to the semi‐propabilistic safety system the timber construction code is compatible with the earthquake code. Designing according to timber requirements and considering ductility and also oscillating duration of wood constructions, these buildings are outstandingly adequate to be used in all earthquake areas.     

Seismic damage analysis of reinforced concrete buildings based on statistics of structural lateral resistance

The largest revision of the building code in Japan was released in 1981, in which the examination of ultimate lateral strength of structure is required. As a result, the capacity of the earthquake resistance of buildings is different between those designed before and after the revision of the code.The objective of this paper is to evaluate the seismic reliability of two groups of reinforced concrete buildings; one is the building group designed by the current code (after the 1981 revision) and the other is the building group designed by the former code (before the revision). The site is assumed to be Sendai city, Japan. Seismic reliability analyses of buildings are carried out and the probability of structural responses exceeding certain response levels during 100 years is evaluated for each type of building group. In addition to the uncertainty of earthquake forces, the uncertainties of structural characteristics, such as lateral resistance and the first natural period of structures, are considered based on the statistics of existing buildings.     

Rechnerische Beurteilung der Schubtragfähigkeit einer Spannbetonbrücke mit geringem Querkraft bewehrungsgrad

Assessment of the shear strength of an existing post‐tensioned concrete bridge with a low amount of shear reinforcement – First application of the ”Flexural Shear Crack“ model in practice In recent years it was reported several times, that within a static assessment according to current standards the shear strength of post‐tensioned bridges, which were built in Austria before 1989, cannot be fulfilled any more. However, test results prove, that especially prestressed structures have additional load bearing capacities, which cannot be reproduced with current calculation models. In the framework of a pilot project a new developed shear model (Flexural Shear Crack Model) was used. In this paper the approach as well as the main results of a statical reevaluation of an existing post‐tensioned road bridge at the Tauern Autobahn A10 will be presented.     

Seismische Ertüchtigung von Bauwerken: Fallstudie Schweiz

Seismic retrofitting of buildings: case study Switzerland. Over the past years, the seismic standards in Switzerland became more and more stringent. Considering the very slow renewal of the building stock, seismic retrofitting of existing buildings started to be an issue. At the beginning, some existing buildings were upgraded to the same seismic safety level as new buildings. The upgrading costs showed a broad scatter in function of many parameters. To avoid disproportionate upgrading costs, risk‐based regulations for seismic assessment of existing buildings were recently introduced.     

Prüfung der Standorteignung für Windenergieanlagen: Ein pragmatischer Ansatz

Site‐specific assessment of wind turbines: A pragmatic approach In Germany formal building regulations often request site‐specific assessments of all Wind Turbine Generators (WTG) including new and existing ones. When using the current technical methods and guidelines, the assessment cannot be completed for all WTG, if the wind farm consists of different WTG types (produced by different manufacturers). Thus, in order to comply with the regulations, operators of WTG are forced to curtail the power of many WTG. In the present document a technical method is described extending the existing methodo logy for site‐specific assessments according to DIBt 2012. The technical method describes a simplified load estimation model, which would enable other expert engineers – not only the manufacturer of the WTG – to carry out capacity checks as well.     

极罕遇地震作用下建筑结构一致风险抗倒塌设计方法研究

结合当前国际上以“抗倒塌”为目标进行地震动参数区划和以“一致倒塌风险”为设防目标进行结构抗震设计的发展趋势,针对我国现行建筑抗震设计规范体系中抗倒塌能力评估的局限性,建议了四种一致风险抗倒塌设计方法,详细介绍了四种方法的评价指标与计算过程。考虑极罕遇地震作用,基于极罕遇地震一致风险谱对地震动记录进行了挑选与调幅。以RC框-剪结构作为典型案例,采用四种抗倒塌设计方法进行验算,结果表明：同时考虑地震危险性与结构不确定性影响的全概率方法验算未通过,其余验算方法均通过,这说明了忽略结构所在场地危险性影响会造成结构倒塌性能评估的不准确性,未考虑结构体系多种不确定性影响会高估结构的抗倒塌性能,因此有必要推行“一致风险”的结构设计理念。     

Methodology for developing earthquake‐resilient structures

This paper proposes a methodology for developing earthquake‐resilient structures (ERSs). This is achieved by following principles of full cycle performance control and embracing a holistic approach to design led analysis (DLA) of ERS. Collapse prevention (CP) and postearthquake realignment and repairs (PERRs) are the basic traits of ERS. Despite the availability of several systems involving combinations of gap opening link beams (GOLBs), rigid rocking cores, buckling‐restrained braces, replaceable energy dissipating moment connections, and so forth, neither CP nor PERR are addressed in any code of practice. Although most of these devices have passed several tests of experiments and time–history analysis they have rarely been examined as integral parts of actual buildings. Real buildings cannot be ideally recentered unless specifically designed and detailed for CP and PERR. Almost all simple beam–column joints, especially standard hinged supports absorb small but sufficient amounts of residual strains that hinder PERR. The proposed methodology is introduced by way of developing an earthquake‐resilient rocking core‐moment frame, as the lateral resisting component of a gravity resisting structure that has been detailed not to develop residual effects while sustaining large lateral deformations.     

Seismic demand of an RC special moment frame building

Seismic design of a building is usually performed by using a linear static procedure. However, the actual behavior of a building subjected to earthquake is inelastic and dynamic in nature, and inelastic dynamic analysis is required to evaluate the safety of the structure designed by the current design codes. In this study, an RC special moment‐resisting frame building was designed by IBC 2003. Maximum plastic rotation, dissipated energy of some selected members, and the drift demand were calculated to examine whether the inelastic behavior of the building followed the intention of the design code. In addition, the effect of internal moment‐resisting frames (gravity load resisting system) on resisting lateral load was investigated. According to the analysis result, the building designed by IBC 2003 showed the inelastic behavior intended in the code and satisfied the design drift limit. Copyright © 2007 John Wiley & Sons, Ltd.     

提高建筑结构抗地震倒塌能力的设计思想与方法

工程结构的抗震能力是社会抗震防灾系统的第一道防线。建筑物的倒塌是造成地震灾害的主要原因。建筑物在地震中的破坏程度,大体决定了震害的严重程度。因此,建筑结构的抗震能力,特别是抗地震倒塌能力,是地震区抗震防灾能力的最重要组成部分。文中运用系统科学的思想,介绍了提高建筑结构整体抗震能力的设计思想,结合汶川地震中建筑震害的教训,重点针对建筑结构抗地震倒塌能力,讨论了建筑结构抗震设计中应注意的问题和改进建议。研究结果表明:建筑结构系统的安全储备分为基本安全储备、整体安全储备与意外安全储备三个层次。结构的整体抗震能力和抗地震倒塌能力取决于整体安全储备和意外安全储备,意外安全储备不足是汶川地震建筑结构震害严重的主要原因。结构系统的意外安全储备主要来自其鲁棒性、整体稳定性和整体牢固性。目前对于结构系统的整体安全储备和意外安全储备的研究很不够,结构设计规范的相关规定和要求也有待进一步完善。     

Die Rolle des Prüfingenieurs im System der vorbeugenden Gefahrenabwehr

The task of the check engineer in the preventative risk management system. The historical development of building regulations is characterised by the principle of preventative risk management. The current building regulation demands, that public safety and order, especially life, health and natural conditions are not endangered by buildings. The building control is the task of the state and shall be administered by the building authorities. Usually the building control of structural stability and fire protection is delegated by the authorities to state approved check engineers. It is of main importance, that check engineers are not dependent on the investor's economic interests. Up to now this independence has been ensured, because the check engineers are appointed directly by the building authorities. Due to deregulations in recent years some federal states changed their building regulations in such a form, that the risk management was not guaranteed completely. The independence of check engineers and thus the quality of risk management was severely weakened by allowing private commissions. In additon several structures were released from the obligation of checking. These changes disagree with the safety concept of DIN 1055‐100, which is adjusted wih the European Codes. The required safety level presupposes the independent checking of the structural design. Further risks of independence and quality of building checks by the check engineers can occur due to an uncritical use of the European Services Directive. In accordance with the experiences of the check engineers current risk analyses show, that it is essential for a modern preventative risk management system to align extent and intensity of authorized controlling to the hazard potential of the particular building project. Corresponding to the proposal of the German Association of Check Engineers on the IABSE‐Symposium 2007 the controlling measures should be graduated on the basis of Eurocode EN 1990 according to three hazard classes.     

On repairable earthquake resisting archetypes with a view to resiliency objectives and assisted self‐centering

Performance‐based seismic design, as an alternative to conventional methods of approach, has served engineers and the public rather well during the last two decades. Neither approach guaranties catastrophic collapse prevention nor post‐earthquake realignment and repairs (PERR) due to major seismic events. As a result, most code‐compliant buildings can be regarded as relatively safe but practically disposable. The paper presents a new philosophy that leads to sustainable design of new structures and the upgrading of existing earthquake resisting moment frames. Repairability‐based design (RBD) relies on softening and control rather than strength and resistance to elevate seismic performance to economically viable, physical collapse prevention, damage control, and post‐earthquake realignment and repairs. The new approach was inspired by design led analysis (DLA), performance control (PC), and recent developments in rocking core‐moment frame design. DLA is a displacement based method of analysis with built‐in results. PC is the ability to design a structure in such a way as to expect predetermined modes of response at certain stages of loading, extents of damage, and drift ratios. This paper advocates higher performance objectives than current codes of practice do. Several demonstrative examples have been provided.