A consecutive modal pushover procedure for estimating the seismic demands of tall buildings

The nonlinear static procedure (NSP), based on pushover analysis, has become a favourite tool for use in practical applications for building evaluation and design verification. The NSP is, however, restricted to single-mode response. It is therefore valid for low-rise buildings where the behaviour is dominated by the fundamental vibration mode. It is well recognized that the seismic demands derived from the conventional NSP are greatly underestimated in the upper storeys of tall buildings, in which higher-mode contributions to the response are important. This paper presents a new pushover procedure which can take into account higher-mode effects. The procedure, which has been named the consecutive modal pushover (CMP) procedure, utilizes multi-stage and single-stage pushover analyses. The final structural responses are determined by enveloping the results of multi-stage and single-stage pushover analyses. The procedure is applied to four special steel moment-resisting frames with different heights. A comparison between estimates from the CMP procedure and the exact values obtained by nonlinear response history analysis (NL-RHA), as well as predictions from modal pushover analysis (MPA), has been carried out. It is demonstrated that the CMP procedure is able to effectively overcome the limitations of traditional pushover analysis, and to accurately predict the seismic demands of tall buildings.     

DETERMINATION OF FUZZY RELATIONSHIP BY FUZZY REGRESSION

This paper presents a new approach and procedure for performing fuzzy regression based on JHE method, a method for processing fuzzy information based on the Monte Carlo simulation technique. The new procedure is tested by applying it to determining fuzzy relationships between fuzzy variables. Methods for interpreting results of fuzzy regression are presented and discussed. Examples are presented to demonstrate this new procedure. Potential applications of this fuzzy regression procedure are discussed.     

Design of steel plate shear walls considering inelastic drift demand

The unstiffened steel plate shear wall (SPSW) system has emerged as a promising lateral load resisting system in recent years. However, seismic code provisions for these systems are still based on elastic force-based design methodologies. Considering the ever-increasing demands of efficient and reliable design procedures, a shift towards performance-based seismic design (PBSD) procedure is proposed in this work. The proposed PBSD procedure for SPSW systems is based on a target inelastic drift and pre-selected yield mechanism. This design procedure is simple, yet it aims at an advanced design criterion. The proposed procedure is tested on a four-story test building with different steel panel aspect ratios for different target drifts under selected strong motion scenarios. The designs are checked under the selected ground motion scenarios through nonlinear response-history analyses. The actual inelastic drift demands are found to be close to the selected target drifts. In addition, the displacement profiles at peak responses are also compared with the selected yield mechanism. Future modifications required for this design procedure for different SPSW configurations are identified based on these test cases.     

A consecutive modal pushover procedure for nonlinear static analysis of one-way unsymmetric-plan tall building structures

Seismic responses of unsymmetric-plan tall buildings are substantially influenced by the effects of higher modes and torsion. Considering these effects, in this article, the consecutive modal pushover (CMP) procedure is extended to estimate the seismic demands of one-way unsymmetric-plan tall buildings. The procedure uses multi-stage and classical single-stage pushover analyses and benefits from the elastic modal properties of the structure. Both lateral forces and torsional moments obtained from modal analysis are used in the multi-stage pushover analysis. The seismic demands are obtained by enveloping the peak inelastic responses resulting from the multi-stage and single-stage pushover analyses. To verify and appraise the procedure, it is applied to the 10, 15, and 20-storey one-way unsymmetric-plan buildings including systems with different degrees of coupling between the lateral displacements and torsional rotations, i.e. torsionally-stiff (TS), torsionally-similarly-stiff (TSS) and torsionally-flexible (TF) systems. The modal pushover analysis (MPA) procedure is implemented for the purpose of comparison as well. The results from the approximate pushover procedures are compared with the results obtained by the nonlinear response history analysis (NL-RHA). It is demonstrated that the CMP procedure is able to take into account the higher mode influences as well as amplification or de-amplification of seismic displacements at the flexible and stiff edges of unsymmetric-plan tall buildings. The extended procedure can predict to a reasonable accuracy the peak inelastic responses, such as displacements and storey drifts. The CMP procedure represents an important improvement in estimating the plastic rotations of hinges at both flexible and stiff sides of unsymmetric-plan tall buildings in comparison with the MPA procedure.     

An improved consecutive modal pushover procedure for estimating seismic demands of multi‐storey framed buildings

An improved consecutive modal pushover (ICMP) procedure is proposed to enhance the accuracy of conventional CMP procedure for estimating seismic demands of tall buildings. It accounts for inelastic structural properties and interaction between vibration modes. The displacement increment at the roof of buildings used in each stage of pushover analyses is modified based on the displacement contribution of each mode. The performance of the proposed ICMP procedure is verified against three high‐rise frames subjected to various ground motions. The results obtained from the ICMP procedure are compared with those from the nonlinear time history analysis, conventional pushover analysis, and CMP analysis. The comparison shows the advantages of the ICMP over the other pushover procedures. It is concluded that the ICMP procedure is more accurate than the CMP procedure.     

Condition Assessment by Visual Inspection for a Bridge Management System

Abstract:   The development of a reliable bridge management system (BMS) constitutes a formidable engineering challenge due to both the multiobjective nature of the task and the large amount of information to be considered in formulating the required automated judgments. This article deals with a procedure for bridge condition assessment by visual inspection developed during the planning and preliminary design of the BMS for the public railway networks in Italy. The main modules adopted in the procedure are: bridge inventory, computer-aided visual inspection, automated defect catalog, and priority-ranking procedure. The probabilistic models used to calibrate the condition evaluation algorithm are discussed. Different levels of deficiency have been individuated for each class of bridge structure belonging to the managed stock. The procedure allows comparison and relative ranking of deficiency conditions across different types of bridge structures. The results of a visual inspection campaign conducted for a set of bridges with different structural characteristics are reported and evaluated within the framework of the developed BMS.     

Long-term deflection of cracked composite beams with nonlinear partial shear interaction: I — Finite element modeling

In this paper, a uniaxial nonlinear finite element procedure for modeling the long-term behavior of composite beams at the serviceability limit state is presented. The finite element procedure follows a displacement-based approach. The nonlinear load-slip relationship of shear connectors as well as the creep, shrinkage, and cracking of concrete slab are accounted for in the proposed finite element procedure. The effects of creep and shrinkage of the concrete slab are considered only for uncracked concrete. The nonlinear iterative procedure adopted for tracking the nonlinear behavior of the composite beam implemented the total nodal deformations, not the incremental deformations, as the independent variables of any iteration. The results of the proposed finite element procedure were compared with the experimental results of four composite beams reported in the literature. The proposed finite element procedure was capable of predicting the deflections and stresses of the four beams with an acceptable degree of accuracy. A parametric study was conducted to study the effect of the nonlinearity of load-slip relationship of shear connectors and the cracking of the concrete deck on the long-term behavior of simply-supported composite beams.     

An intelligent procedure for updating deformation prediction of braced excavation in clay using gated recurrent unit neural networks

This paper aims to establish an intelligent procedure that combines the observational method with the existing deep learning technique for updating deformation of braced excavation in clay. The gated recurrent unit (GRU) neural network is adopted to formulate the forecast model and learn the potential rules in the field observations using the Nesterov-accelerated Adam (Nadam) algorithm. In the proposed procedure, the GRU-based forecast model is first trained based on the field data of previous and current stages. Then, the field data of the current stage are used as input to predict the deformation response of the next stage via the previously trained GRU-based forecast model. This updating process will loop up till the end of the excavation. This procedure has the advantage of directly predicting the deformation response of unexcavated stages based on the monitoring data. The proposed intelligent procedure is verified on two well-documented cases in terms of accuracy and reliability. The results indicate that both wall deflection and ground settlement are accurately predicted as the excavation proceeds. Furthermore, the advantages of the proposed intelligent procedure compared with the Bayesian/optimization updating are illustrated.     

丰满混凝土重力坝渗流特性分析

根据丰满混凝土重力坝现场渗流观测资料数据,采用非线性最小二乘法识别坝体混凝土和坝基岩石的渗透系数。基于大坝渗透系数的识别结果,采用三维有限元法分析了大坝坝体和坝基的渗流场。渗流场自由面位置的确定采用压缩网格法,经迭代求得。大坝渗透系数识别采用迭代方法进行,其中搜索方向由Levenberg-Marquardt法确定。工程实验应用表明,所提出的三维非承压水参流场分析和大坝渗透系数识别方法是非常有效的。     

土坝饱和-非饱和渗流数值分析方法研究

本文提出土体非稳定渗流数学模型和新计算方法,用以计算土坝饱和-非饱和区的渗流。在数学方程求解和数值计算中,采用伽辽金有限元法结合隐式向后差分法,编制出简单合理和切实可行的计算程序SUSED。并以唐山陡河土坝为计算对象,从坝中取样通过试验求得计算参数,用本文方法对该坝饱和-非饱和渗流进行数值计算,计算结果规律正常,令人满意,说明上述数学模型和计算方法是行之有效的,适用于稳定渗流和非稳定渗流。     

基于钢结构焊接新规范的工艺评定策划和实践

针对当前钢结构工程焊接施工工艺评定实施不足的现状,介绍了新颁布的GB50661—2011《钢结构焊接规范》对焊接工艺评定要求的变化。结合实例详细介绍钢结构工程焊接工艺评定策划和实践的流程,以及如何确定钢结构工程所需的焊接工艺规程数量和所需要的焊接工艺评定。     

Nonlinear 3D finite element simulation of reinforced concrete flat plates retrofitted with externally bonded CFRP strips

In this study, a comprehensive 3D non-linear finite element modelling procedure is presented for the simulation of reinforced concrete flat plates, retrofitted with externally bonded carbon fibre-reinforced polymer (CFRP) strips and subjected to punching shear loads. The presented modelling procedure may be used to conduct parametric numerical analyses on the response of reinforced concrete elements similar to considered in this study. The modelling procedure is applied on: (i) a solid, un-retrofitted flat plate and (ii) eight flat plates with openings and retrofitted with externally bonded CFRP strips. In the procedure, debonding of CFRP strips from concrete surfaces is accounted for by defining appropriate bilinear shear stress–slip and normal stress–gap relationships. In the model, the corner lift-offs observed at the corners of the flat plates are also considered by defining appropriate restrains and frictional support conditions. Results obtained from the proposed modelling procedure are verified using experimental data available in the literature. From the verification, accuracy of the proposed modelling procedure is confirmed in terms of structural responses such as load displacement relationships and crack propagations of the test specimens.     

浅谈财政投资评审对工程造价的全过程控制

阐述了财政投资评审对财政投资建设项目工程造价全过程控制的必要性,从财政投资项目建设的各个阶段具体分析了如何加强工程造价的全过程控制,强调了财政投资评审在财政投资建设项目工程造价全过程控制中须注意的问题,以更好地发挥财政投资评审的作用。     

A modified response spectrum analysis procedure to determine nonlinear seismic demands of high‐rise buildings with shear walls

The standard response spectrum analysis (RSA) procedure prescribed in various design codes is commonly used by practicing engineers to determine the seismic demands for structural design purpose. In this procedure, the elastic force demands of all significant vibration modes are first combined and then reduced by a response modification factor (R) to get the inelastic design demands. Recent studies, however, have shown that the response of higher vibration modes may experience much lower level of nonlinearity, and therefore, it may not be appropriate to reduce their demand contributions by the same factor. In this study, a modified RSA procedure based on equivalent linearization concept is presented. The underlying assumptions are that the nonlinear seismic demands can be approximately obtained by summing up the individual modal responses and that the responses of each vibration mode can be approximately represented by those of an equivalent linear SDF system. Using 3 high‐rise buildings with reinforced concrete shear walls (20‐, 33‐, and 44‐story high), the accuracy of this procedure is examined. The inelastic demands computed by the nonlinear response history analysis procedure are used as benchmark. The modified RSA procedure is found to provide reasonably accurate demand estimations for all case study buildings.     

Theoretical behavior of HSC sections under torsion

The main purpose of this study is to propose a simple computational computing procedure in order to predict the global behavior of high-strength concrete beams under pure torsion.A computational procedure was developed and validated for normal-strength concrete beams and presented in a previous study. This procedure is revised and corrected in this article so that high-strength concrete beams can also be covered. Theoretical predictions are compared to some experimental results available in the literature.It is shown that the proposed computing procedure gives good predictions for the global behavior of high-strength concrete beams with hollow rectangle cross sections under pure torsion.     

Behaviour of reinforced and concrete-encased composite columns subjected to biaxial bending and axial load

An experimental investigation of the behaviour of reinforced concrete columns and a theoretical procedure for analysis of both short and slender reinforced and composite columns of arbitrarily shaped cross section subjected to biaxial bending and axial load are presented. In the proposed procedure, nonlinear stress–strain relations are assumed for concrete, reinforcing steel and structural steel materials. The compression zone of the concrete section and the entire section of the structural steel are divided into adequate number of segments in order to use various stress–strain models for the analysis. The slenderness effect of the member is taken into account by using the Moment Magnification Method. The proposed procedure was compared with test results of 12 square and three L-shaped reinforced concrete columns subjected to short-term axial load and biaxial bending, and also some experimental results available in the literature for composite columns compared with the theoretical results obtained by the proposed procedure and a good degree of accuracy was obtained.     

Assessment of the Health and Comfort Effects of Chemical Emissions from Building Materials: the State of the Art in the European Union*

Abstract The promotion of healthier indoor air requires the use of building materials whose chemical emissions are free of toxicity and unfavourable sensory properties. Testing and assessment of chemical emissions are essential in order to identify “safe” materials, and to encourage manufacturers to produce, and the market to adopt, such materials. Various testing and assessment procedures for building materials have been developed in European countries such as Germany, Denmark, Sweden, and Finland. Recently the European Collaborative Action “Indoor Air Quality and its Impact on Man” proposed criteria and a testing procedure for the assessment of VOC emissions from solid flooring materials. The innovative aspects of this proposal are: a procedure for the performance of chemical emissions testing; sensory testing coupled with toxicological evaluation; and a procedure to handle compounds for which toxicological information is scarce or absent. This procedure, after validation and experience from practical use, will probably be extended to other building materials.     

操作型工序质量控制的难点及对策

根据工序自身的特点与操作者素质要求的不同，提出了操作型工序控制的概念，并对操作型工序质量控制的难点进行了充分的分析，进而针对这些难点提出了监理工程师在质量事前、事中、事后控制中应采取的积极且具有可操作性的对应策略与方法，以达到减少质量通病，预防和避免质量事故的目的。     

Nonlinear vibration of thin plates with initial stress by spline finite strip method

The spline finite strip method and the incremental time–space finite element procedure are used to analyse large amplitude vibration of plates with initial stresses. Two improvements for the procedure are presented. The free vibration and the internal resonance of plates with initial stress as well as the forced vibration of plates with damping and initial stress are computed. The results compared favourably with those available in other publications.     

建设工程全过程造价控制

通过对建筑工程全过程造价控制问题的分析,从必要性和建设工程各阶段造价控制的问题展开了论述,特别是对项目发包和实施阶段的造价控制问题进行了重点研究,有针对性地提出了解决问题的方法和思路。