防恐建筑结构抗爆防护分类设防标准研究

针对我国尚未制订建筑结构抗爆防护设防标准,制约建筑结构抗爆设计工程应用的现状,研究了适合我国国情的建筑结构抗爆防护分类设防标准。对已发生典型爆炸袭击事件的规模进行了统计分析,确定了建筑结构的抗爆设防烈度;总结爆炸作用下建筑结构破坏特点,确定了建筑结构抗爆防护目标;基于抗爆设防烈度和抗爆防护目标,提出了建筑结构的抗爆防护等级。将建筑结构进行类别划分,确定了不同类别建筑结构的抗爆重要性等级;考虑主要影响因素,确定了建筑结构的爆炸易损性等级;采用风险分析的方法提出了建筑结构的爆炸风险等级。依据抗爆防护等级和爆炸风险等级,建立了建筑结构的抗爆设防标准。基于建筑结构抗爆重要性等级,提出了建筑结构的抗爆设防类别,进而建立了建筑结构的抗爆分类设防标准。     

重要建筑结构抗恐怖爆炸设计爆炸荷载取值探讨

由于爆炸过程的不稳定和爆炸测试的不确定性，由已有的预测爆炸荷载的经验公式和图表所得到的爆炸荷载存在较大差异，不便于工程应用。在查阅了各国抗爆规范和大量文献，搜集了大量已有的经验公式和图表的基础上，分析和计算了不同比例距离下的反射超压和假想比例持续时间。运用统计学方法求得各比例距离下具有90%保证率的反射超压和假想比例持续时间，拟合得到了爆炸荷载反射超压及假想比例持续时间与比例距离的关系曲线，可用于确定建筑结构抗爆设计的爆炸荷载取值。拟合公式确定的爆炸荷载参数稍大于人防规范和UFC规范中的规定取值，偏于安全，较为合理。     

A method for determining fire accidental loads and its application to thermal response analysis for optimal design of offshore thin-walled structures

More than 70% of accidents that occur on offshore installations stem from hydrocarbon fire and explosion, and as they involve heat and blast effects, they are extremely hazardous with serious consequences in terms of human health, structural safety and the surrounding environment. To prevent further accidents, substantial effort has been directed towards the management of fire and explosion in the safety design of offshore installations. The aim of this paper is to present a risk-based methodology procedure to help determine the fire accidental design load of an offshore installation (AL Living Quarter) in association with the thermal response characteristics for structural optimisation. A probabilistic sampling approach with numerical fire simulations was taken to determine the fire accidental load. To determine the optimisation of the thin-walled structures of the living quarter, an A60 based on the results of thermal response analyses was conducted and the temperature distribution calculated. The analysis results suggest incorporating both the design and safety planning aspects of offshore Living Quarter.     

基于损伤性能的抗震结构最优设防水准的决策方法

首先建立了一个符合损伤指数定义的加权线性组合双参数地震损伤模型,并给出了损伤指数的简化计算方法;结合三水准设防原则,提出了一个符合实际的地震损伤性能目标;给出了地震损伤极限状态的实用表达式;在此基础上,探讨了基于损伤性能的两种抗震设计方法常规方法和最小造价设计方法;然后,给出了单体结构地震破坏的宏观模糊概率分析方法;最后,提出了单体结构最优地震设防水准基于损伤性能的决策方法.     

Hydraulic design of granular and geocomposite drainage layers in pavements based on demand-capacity modeling

In this paper, a new approach based on the demand-capacity model is developed for hydraulic design of granular and granular-cum-geocomposite drainage layers in pavements. The demand is given by the intensity-duration curve obtained from the Intensity-Duration-Frequency curve, which is geographic location specific and corrected for climate change. The capacity curve corresponds to critical infiltration rates and critical durations for a drainage layer which is influenced by the hydraulic and geometric characteristics. The design is acceptable if the capacity curve exceeds the demand curve. The design framework is illustrated for typical geometries of highway pavements with three granular gradations and three geocomposites. Based on the developed framework, hydraulic equivalence is defined and evaluated for the drainage layers. The permissible reduction of granular layer thickness for hydraulic equivalence is evaluated if geocomposite is embedded in the subbase layer of pavements. For an optimum gradation based on hydraulic and structural characteristics, the thickness of granular layer with geocomposite could be reduced by 30% compared to the granular layer without geocomposite, which showed similar hydraulic performance. The significance of drainage layer thickness with geocomposite is shown based on the demand for storage to satisfy the drainage requirement for rainfall events of high intensities and long durations.     

Energy appproach in peformance‐based seismic design of steel moment resisting frames for basic safety objective

This study presents an energy approach to the performance‐based seismic design of steel moment resisting frames for the basic safety objective. The seismic demand is expressed in terms of hysteresis energy and its distribution along the height of the frame, based on an associated study. The resistance of a steel moment‐resisting frame to such demand is presented in the form of energy dissipation capacities of critical members, based on the previous experimental studies on full‐scale moment‐connections. An energy‐based design methodology is proposed for performance‐based earthquake resistant design. The proposed design method is examined using design examples and the results are discussed. Copyright © 2001 John Wiley & Sons, Ltd.     

Reliability of design approaches for axially loaded offshore piles and its consequences with respect to the North Sea

In the near future, several offshore wind farms are planned to be built in the North Sea. Therefore, jacket and tripod constructions with mainly axially loaded piles are suitable as support structures. The current design of axial bearing resistance of these piles leads to deviant results regarding the pile resistance when different design methods are adopted. Hence, a strong deviation regarding the required pile length must be addressed. The reliability of a design method can be evaluated based on a model error which describes the quality of the considered design method by comparing measured and predicted pile bearing resistances. However, only few pile load tests are reported with regard to the boundary conditions in the North Sea. This paper presents 6 large-scale axial pile load tests which were incorporated within a new model error approach for the current design methods used for the axial bearing resistance, namely API Main Text method and cone penetration test (CPT)-based design methods, such as simplified ICP-05, offshore UWA-05, Fugro-05 and NGI-05 methods. Based on these new model errors, a reliability-based study towards the safety was conducted by performing a Monte-Carlo simulation. In addition, consequences regarding the deterministic pile design in terms of quality factors were evaluated. It is shown that the current global safety factor (GSF) prescribed and the partial safety factors are only valid for the API Main Text and the offshore UWA-05 design methods; whereas for the simplified ICP-05, Fugro-05 and NGI-05 design methods, an increase in the required embedded pile length and thus in the GSF up to 2.69, 2.95 and 3.27, respectively, should be considered to satisfy the desired safety level according to DIN EN 1990 of β = 3.8. Further, quality factors for each design method on the basis of all reliability-based design results were derived. Hence, evaluation of each design method regarding the reliability of the pile capacity prediction is possible.     

设置BRB桥梁排架墩基于位移抗震设计方法

基于“保险丝”和“损伤控制”的抗震设计理念,提出在桥梁双柱式排架墩中通过设置屈曲约束支撑(BRB)以提高其横桥向抗震性能的构想。首先从获得“抗震能力”的角度对设置BRB桥梁排架墩的抗震设计参数进行系统性分析,推导出与剪跨比和墩柱间距与直径(边长)比相关的BRB核心段最大和最小长度取值范围|再从求解“地震需求”角度建立了设置保险丝的(SDOF)主结构体系弹塑性反应谱基本方程,分析该体系的非线性地震反应一般规律|然后,基于体系的“抗震能力”和“地震需求”,发展了设置BRB的桥梁排架墩基于位移的抗震设计方法,并结合一个具体桥梁排架墩实例说明建议设计方法的可行性。     

基于单自由度体系的钢筋混凝土抗爆墙设计

基于单自由度体系的钢筋混凝土抗爆墙设计,是将抗爆房屋的结构按爆炸荷载传递路径进行逐个分解,再对分解后的构件进行单自由度体系的设计。同时,以构件支座转角位移为限制,确定构件的截面及配筋是否满足对变形的要求。对单自由度体系抗爆计算可采用数值求解的方法,其基本假定是加速度呈线性,求解的关键是时间增量的确定。本文通过工程实例,介绍正面承受爆炸荷载的钢筋混凝土前墙的计算方法,可为类似工程的设计提供参考。     

爆炸荷载作用下钢筋混凝土板破坏评定方法

压力-冲量(P-I)曲线是结构构件在爆炸荷载作用下的初始设计及在爆炸荷载作用后的破坏评定的有效工具。目前,确定结构构件的P-I曲线采用的方法均是基于单自由度结构体系假定的,并且多以结构构件的中点位移作为破坏指标。然而在爆炸荷载作用下,结构构件大多因高阶响应而发生局部破坏,且可能发生弯剪破坏。因此,通过将结构构件简化为单自由度体系模型并且选择结构构件中点位移为单一破坏指标获得的结构构件的P-I曲线,不能准确评定其破坏程度。利用LS-DYNA有限元动力分析软件,建立了典型钢筋混凝土板在爆炸荷载作用下响应和破坏的分析方法,提出了基于钢筋混凝土板跨中截面受弯剩余承载力的破坏指标以及利用数值方法确定钢筋混凝土板跨中截面受弯剩余承载力的步骤。同时,综合分析数值模拟结果,拟合了钢筋混凝土板P-I曲线的数学表达式,提出了一种简化了的确定钢筋混凝土板P-I曲线的方法,采用该方法确定的P-I曲线可用来对任意爆炸荷载作用后钢筋混凝土板的破坏进行评定。     

Die Auswirkung von duktilen Anschlüssen auf die Explosionsresistenz lasttragender Stützen

Effect of ductile connections on blast resistant load bearing columns. Load bearing columns exist in most constructions and are applied for instance as floor columns or as bridge piers. The study performed here addresses the question how the load‐bearing column behaves under blast load and which constructive measures result in an enhanced resistance against the blast pressure wave. Simple single‐cell steel cross section set‐up is changed stepwise by implementation of multi steel cells or by filling the hollow steel section with concrete. In doing so, the column is not generated as an isolated member, but installed in a flexible neighboring system, which allows taking the connection ductility into account. The response behavior of representative steel and composite column types is investigated, the section is searched for local overstresses and the failure mechanisms of the structural member are defined. The evolution of the cross section set‐up and the corresponding changes in the simulation results enable the formulation of decisive parameters which contribute to the enhancement of member blast resistance. The study pursues the specific local resistance design approach and aims at developing constructive protection technology in order to avoid the detected local damages. The column base appears to be the vulnerable section at the column rigidly or less flexible connected to the ground. The strategic use of ductile bearing condition is applied to reduce stress concentration by allowing deformation and energy dissipation, in order to safely transmit the high lateral forces into the fundaments. Structural solutions which represent an invisible protection measure are evaluated in regards to their effectiveness. The numerical analysis of this study is performed by using the MD Nastran software.     

Determination of the behaviour factor of steel moment-resisting (MR) frames by a damage accumulation approach

In most countries, seismic codes are changing, reflecting a new design philosophy based on multiple performance levels. A procedure that defines behaviour factors to reduce the elastic spectrum for different types of structures, considering all possible types of failure, is needed. The paper presents a method for the definition of the behaviour factor (q-factor) for multi-storey steel frames, accounting for cumulative damage in structural components, by means of linear elastic time history analysis, of the Palmgren-Miner rule and of S-N (constant stress or strain range versus number of cycles to failure) curves extrapolated in the low-cycle fatigue range. This technique has been verified by a non-linear procedure that is different from the previous one, as a non-linear time history analysis with damage control has been performed instead of a linear one. The proposed approach can be useful in performance based design, since the linear procedure allows the definition of the q-factor corresponding to different level of damage or collapse prevention.     

预应力混凝土边梁协调扭转的分析

通过对协调扭转的各种典型设计方法的适用性进行比较,指出对于不同的结构,必须合理选用相应的协调扭转分析方法。对承受较大协调扭矩作用的预应力混凝土边梁,协调扭矩的计算可根据不同阶段的受力特点采用其相应的变刚度。同时对次梁、板与边主梁截面形心相对位置的影响进行探讨,指出预压力对边梁抗扭承载力的影响。结合工程实例的有限元分析,说明此类结构的设计要点。     

竖向不规则钢筋混凝土框架结构基于性能的抗震设计方法

考虑结构在地震作用下不同反应阶段的动力特性,采用振型反应谱法,建立结构在不同地震作用水平下的弹塑性需求曲线族,即结构的层间剪力一位移需求曲线.结合结构的能力曲线,提出以楼层为研究对象的层间能力谱法.由结构的性能目标与位移延性的关系,建立性能目标与层间需求曲线的关系,从而得到考虑结构延性的层间需求曲线.通过计算分析表明,层间能力谱法可以有效的用于对竖向不规则结构进行基于性能的抗震设计,可以方便地对不同地震作用水平、不同性能目标的结构进行地震作用计算和配筋计算,并能控制结构在不同地震作用下的变形性能、塑性铰出现顺序及部位,与时程分析方法相比偏于保守,且比直接基于位移的设计方法具有明显的优势.     

采用逆可靠度方法的隧道支护抗力计算

 从风险水平的角度初步量化分级安全储备,提出在给定可靠性水平下直接计算隧道支护抗力的方法。该方法首先基于室内和现场试验的数据,利用广义3倍标准差准则得到参数的统计特征;遵循利用围岩应变值作为隧道支护设计基础的理论,采用极限状态函数建立功能函数方程;然后基于一次逆可靠度算法,结合Nataf变换和Cholesky分解构建详细计算程序;最后计算局部安全系数。以经典软岩参数为例,通过一次二阶矩法(FORM)验证该方法精度;分析相关性和初始应力场对隧道支护抗力的影响。最后计算确定在可接受风险水平下的隧道支护抗力及相应局部安全系数。     

基于力的抗震设计方法与基于位移的抗震设计方法比较研究

首先用基于力的抗震设计方法对一幢8层钢筋混凝土框架结构房屋进行了抗震设计,然后将建筑结构的性能划分为"使用良好"、"保证人身安全"和"防止倒塌"三个水平,给出了相应的层间位移角限值,分别计算了三个性能水平对应的结构基底剪力和顶点位移,以及"使用良好"和"防止倒塌"两种性能水平时的构件截面配筋。用静力非线性分析方法对计算结果进行了验证性分析。最后对两种设计方法及计算结果进行了比较分析。分析结果表明,按"使用良好"性能水平设计的构件截面配筋量与基于力的方法所得结果比较接近。     

Procedure for determining the seismic vulnerability of an irregular isolated bridge

A seismic vulnerability procedure, based on the capacity/demand ratio approach, is applied to an irregular isolated bridge. Special features are incorporated in both, demand estimation and capacity evaluation. The seismic demand is represented by an average pseudo-acceleration spectrum derived from 159 earthquake accelerograms recorded in the region where the bridge is located. The capacity spectrum method is adopted for estimating the structural expected performance for several limit states. The capacity curve derived from a static non-linear procedure is obtained by means of a lateral load pattern that follows the displacement configuration, previously assessed by the use of time history analyses of the bridge supported on non-linear isolator bearings. Based on a moment–curvature analysis of the pier's sections, the maximum curvature ductility was established for each of the four defined performance limit states. Finally, probability density functions of the bridge capacity and demand were assessed and fragility curves were proposed aimed at determining the expected behaviour of the bridge as function of peak ground acceleration (PGA) of the typical strong motions recorded in the area.     

The establishing of performance level thresholds for steel moment‐resisting frame using an energy approach

In this study, an energy design approach is proposed within the framework of the performance‐based seismic design of steel frames. Accumulated plastic rotation is selected as a parameter to establish the performance level thresholds. The test results of steel connections are investigated to quantify the performance level thresholds. The hysteretic energy input is acquired from a previous statistical study of twelve six‐storey steel moment‐resisting frames. The seismic performance of three‐storey steel moment resisting frames using the energy approach is examined. The research concluded that the structure designed by the energy method performed better than the steel frame designed by the equivalent lateral force (ELF) of UBC‐97 in view of accumulated plastic rotation. Performance levels such as functional, life safety and collapse are discussed based on the ductility level and the performance characteristics. Copyright © 2001 John Wiley & Sons, Ltd.     

钢筋混凝土框架-剪力墙结构基于位移的抗震设计方法

根据钢筋混凝土框架-剪力墙结构的特点,将其性能划分为使用良好、保证人身安全和防止倒塌三个水平,并用层间位移角限值予以量化。以作用倒三角形水平分布荷载的等截面弯剪悬臂杆的侧移曲线作为其初始侧移模式。对于使用良好性能水平,将侧移曲线上反弯点对应的楼层处的层间位移角刚好达到相应限值时的侧移曲线作为目标侧移曲线,据此计算等效单自由度体系的等效参数以及原结构的基底剪力和各质点的水平地震作用。对于保证人身安全和防止倒塌的性能水平,根据Pushover曲线与需求曲线的关系对结构予以调整,使结构满足这两个性能水平的要求。     

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.