Time–frequency analysis of structural dynamic characteristics of tall buildings

This study focuses on the correlations between the structural dynamic properties and the instantaneous response characteristics of a 492-m high building during a typhoon. An instantaneous analysis framework is established based on a combined usage of both linear-phase filtering and time–frequency techniques. This analysis framework can separate each modal response contribution without phase distortions. Random decrement technique is used to estimate the modal damping ratios. It is found that beating phenomenon widely exists in the separated modal response contributions, and the damping ratios correlate with the modulation of phase and amplitude within the beating closely. When the beating amplitude comes close to zero, the instantaneous frequency fluctuates evidently. The more intensive this fluctuation is, the larger the damping ratio becomes. An empirical model is presented to formulate the variations of damping ratio and natural frequency of this building with the fluctuation intensity of the instantaneous frequency.     

Dynamic analysis of three-dimensional bridge–high-speed train interactions using a wheel–rail contact model

A formulation of three-dimensional dynamic interactions between a bridge and a high-speed train using wheel–rail interfaces has been developed. In the interface, contact loss is allowed, the vertical contact is represented by finite tensionless stiffness and the lateral contact is idealized by finite contact stiffness and creepage damping. Such stiffness and damping are nonlinearly dependent on normal contact force. The relative rotations of a wheelset to the rails about its vertical and longitudinal axes are included. Bridge eccentricities and deck displacement due to torsion are accounted for in bridge deck modeling. A numerical algorithm using separate integrations for bridges and trains, and iterations for interface compatibilities is established. A case study of a ten-car train passing over a two-span continuous bridge at various speeds and rail irregularity wavelength ranges is analyzed. The responses of the bridge, car-bodies and wheelsets are investigated for their behavior, acceptability and relations with the wavelengths. Analytical and numerical evaluations of resonant speeds are in good agreement, and the exit span vibration is more amplified than the entrance one at those speeds. The computed relative displacements of all wheelsets to the rail facilitate an explicit assessment for derailment risk.     

Acceleration generation due to strain localization of saturated clay specimen based on dynamic soil–water coupled finite deformation analysis

In the conventional bifurcation and strain localization analyses of geomaterials, the inertia forces are generally ignored, based on the quasi-static equilibrium equation. Even though a great deal of literature exists on dynamic strain localization analyses, information on acceleration generation during the formation of shear bands has not been emphasized. Inspired by the acoustic emission phenomenon in laboratory tests and the seismic acceleration related to the slippage of faults, a dynamic soil–water coupled strain localization analysis is performed in the present paper on a saturated rectangular clay specimen subjected to constant cell pressure under plane strain conditions, employing the SYS Cam–clay model as the elasto-plastic constitutive model for the soil skeleton. An initial geometrical imperfection was introduced to the specimen to trigger one single shear band, and the following results were found: (1) Two types of oscillation occurred within the specimen during acceleration when the specimen was subjected to compression deformation at a constant rate, namely, (a) one caused by the sudden external compression and (b) the second induced by the formation of strain localization/a shear band. With the occurrence of the shear band, if, for example, the vertical rate was equivalent to about 10 cm/s, the accelerations that occurred within the specimen were in the order of several thousand gal, which is similar to those measured during earthquakes; (2) The effects of the time increment, the mesh division, the initial confining pressure, the OCR and the stress-control loading on the generated acceleration in (b) were investigated in detail. It was found that under stress control, even though the formation of the shear band was similar to that under displacement control, the induced acceleration behaved quite differently.     

Input–output analysis of the Chinese construction sector

The construction sector has played a key role in the Chinese economy, which has been experiencing a rapid growth for the past two decades. This development and growth are reviewed in a framework of input–output analysis. The national input–output table (IO table) was used to study the current input–output profile of the Chinese construction sector and the relationship between the construction sector and other sectors. The pull and push effect of the Chinese construction industry to the whole national economy has been estimated. It shows that the pull effect is much larger than the push effect. Furthermore, through the analysis of a series of four IO tables spanning over the last 10 years, it reveals that the pull and push effect of the Chinese construction industry are both getting larger and larger. This means the Chinese construction industry is becoming mature and is in great transition.     

An input–output analysis of Thailand's construction sector

Three input–output (IO) tables compiled between 1995 and 2000 were used to examine the significance of the construction sector and its relationships with other sectors of the Thai economy. The pull and push effect of the Thai construction sector to the national economy indicated that the former is much larger than the latter. Additionally, the relatively high output multipliers and backward linkage indicators showed that the construction sector had the potential to trigger off production in many economic sectors linked to it. An aggregated sectoral analysis revealed the high dependence of construction on manufacturing followed by services. The findings also suggest that the trends of the profile of inputs and outputs are correlated to the economic conditions in Thailand at the time the IO tables were compiled. Finally, the results of employment analysis showed that although the share of construction sector in direct employment generation may not be very large, its economic importance lies in its direct and indirect contribution to employment through strong backward linkage effects. Consequently, when its backward linkages and output multiplier are considered together with the employment opportunities latent within it, then the construction sector could be a major contributor to the economic growth of Thailand.     

Analysis of seismically-isolated two-block systems using a multi–rocking-body dynamic model

A novel multibody rocking model is developed to investigate the dynamic response of two stacked rigid blocks placed on a linear base isolation device. The model is used to investigate the dynamic response of a realistic statue-pedestal system subject to pulse-like ground motions. The analysis shows that, in general, base isolation increases the safety level of the rocking system. However, for large period pulses or small size blocks, the isolator can amplify the ground motion, resulting in a lower minimum overturning acceleration than for the nonisolated system. Further, the amplification or shock spectrum of a linear mass-dashpot-spring oscillator, was found to be the reciprocal of the minimum nondimensional overturning acceleration of the investigated rocking system. Novel rocking spectra are obtained by normalizing the frequency of the pulse by the frequency of the isolator. The analysis also demonstrates how the dynamic response of the two stacked blocks is equivalent to that of a single-block configuration coincident with the whole system assumed monolithic or the upper block alone, whichever is more slender.     

Design and simulation of a solar–wind–biogas hybrid system architecture using HOMER in India

The renewable energy sources are accompanied by certain constraints as reliability, availability and continuous generation. In India, biomass is considered as the second best suitable combination with other renewable energy sources. Both solar and wind are undependable renewable energies as they are unpredictable. Now the key to successful renewable energy harvesting lies in the selection of hybrid system architecture for power generation. In rural areas, light is usually unavailable and if it does, it is mostly an incandescent light used for household lighting instead of fluorescent. System reliability, economy and environmental issues are the three major issues for decentralised electrification. So, finding the best suited hybrid system configuration to overcome these constraints is the need of the hour. It is at this stage that HOMER comes into the picture. HOMER, abbreviated name of hybrid optimization model for electric renewable, successfully realises system configuration before its installation and works for on-grid, off-grid and stand-alone systems, which make it useful for rural to urban applications. It simulates and optimises the best suitable solution for a hybrid system and generates reports incorporating all the aspects in designing a system. Here, a typical hybrid system is considered and the implementation of HOMER software has been incorporated.     

Input–output analysis of Irish construction sector greenhouse gas emissions

Ireland is committed to limiting its greenhouse gas (GHG) emissions to 113% of 1990 levels over the period 2008–12 and to 84% of 2005 levels by 2020 under the Kyoto Agreement and the EU's 2020 target by 2020 respectively. National policies have targeted many industry sectors but have failed to directly tackle GHG emissions associated with construction activity. This paper estimates energy and GHG emissions intensities of the Irish construction sector and subsectors and estimates its contribution to Irish national emissions. This information is used to identify and assess the impacts of policy measures which would result in a reduction in emissions from the sector in a cost-effective manner. Energy and emissions intensities are estimated using input–output analysis techniques applied to Irish construction sector.     

Effects of soil–pile interaction on the response of bridge pier to barge collision using energy distribution method

Abstract

In this paper, the effects of soil–structure interaction (SSI) on the response of a girder bridge pier is evaluated by assessing the energy distributions in the barge–pier collision system. The finite-element models of two example piers of St. George Island Causeway Bridge, which have different structural and geometrical characteristics, are developed in LS-DYNA software to simulate the barge–pier collision scenarios. By comparing the energy distribution results among the barge and pier components, it is obtained that barge bow component has greater value of the internal energy contribution than pier components in the barge collision with more stiff pier. While, in the barge collision with more flexible pier, the pier components including the pier structure, piles and SSI have more internal energy contributions than the barge component. In addition, From the comparison of energy absorbed by the pier structure between the cases with and without SSI, it is found that the effect of the substructure and its relevant SSI on the response of the more flexible pier affected by the produced large deformations and relative displacements of the pier substructure, is more than that of stiff pier which displaces with semi-rigid and global deflections.     

Steel–concrete composite bridge deck slab with profiled sheeting

This paper presents an experimental study of a steel–concrete composite bridge deck slab with profiled sheeting and perfobond shear connectors. Two full-scale deck slab specimens cast onto three concrete blocks were fabricated and tested under static loading to examine the ultimate load-carrying capacity of the proposed deck slab system under sagging and hogging bending actions. The ultimate behaviour of the full-scale deck slab specimens is also compared with that of simply supported deck specimens under hogging bending only. In addition, the load–deflection behaviour of the proposed deck system is compared with that of a reinforced concrete (RC) deck slab. The test results indicate that the ultimate load-carrying capacity of the proposed deck system is at least 220% greater than that of the RC deck system and that the deck weighs about 23% less than the RC deck system. The paper summarizes the test results, findings, and recommendations for future study.     

Development of a baseline for structural health monitoring for a curved post-tensioned concrete box–girder bridge

The establishment of a baseline is essential for long-term structural health monitoring and performance evaluation. Usually, field testing data and finite element (FE) model are two critical tools used to develop the baseline. In this paper, the establishment of the baseline field database for a curved post-tensioned concrete bridge with expansion bearings is first introduced to include the effect of varying temperature conditions on the field testing data. This database uses data collected from a full year and is based on an undamaged status. The development of a baseline FE model for the bridge is then discussed. Model updating for the FE model are detailed in this paper which includes calibration of material properties, utilization of spring bearing elements, and replacement of Mindlin plate elements (MP4) on box–girder by recently developed cracked Mindlin plate elements (MP4C) to represent the bridge service conditions. A good agreement in modal results has been observed between the baseline FE model and the baseline field data. The proposed structural health baseline can be used for near real-time damage detection, development of monitoring techniques, and condition assessment. Finally, as an application of the baseline, this FE model is used for an earthquake simulation with a selected ground motion on the bridge. The seismic analysis demonstrates the beneficial effect of the guided expansion bearings on the bridge deck in the longitudinal direction.     

The Conceptual Framework of the Development of Pudong,Shanghai

On April 18th,1990,Premier Li Peng officially proclaimed that the Central Party Com-mittee and the State Council had approved to develop and open the Pudong District.This is agreat decision and is of strategic significance,particularly in terms of the social economic zonepolicy in the district.     

A multidisciplinary approach for fatigue assessment of a steel–concrete high-speed railway bridge on Sesia river

Steel–concrete composite bridge solutions have been more and more exploited in the new high-speed (HS) lines of European railway networks. New design solutions, introduced during a period of quick expansion for railway networks, amplified open problems related to dynamic effects, train–bridge interaction phenomena, fatigue loadings, structural modelling, fatigue life and comfort. In this article, results obtained by long-term dynamic monitoring of Sesia viaduct, a medium span double-box composite bridge of the new Italian HS network, are described and analysed. Structural modal properties were determined in order to evaluate the real-time dynamic behaviour and its correlation with environmental conditions. A suitable numerical procedure was then implemented in order to identify typology, length and velocity of trains crossing the bridge, to evaluate the intensity of deck vertical accelerations as a function of train speed and to obtain a reliable evaluation of real traffic spectra. A final fatigue assessment on welded connections was executed evaluating fatigue spectra by the aforementioned real traffic spectra and assuming S–N curves obtained by suitably executed experimental tests.     

Large displacement stability analysis of elastic–plastic unsymmetrical sandwich cylindrical shells

The paper presents stability analysis of elastic–plastic, free supported sandwich cylindrical shell with unsymmetrical faces, loaded by longitudinal forces, transversal pressure, and shear. The J₂ incremental Prandtl–Reuss plastic flow theory constitutive relations were used in the analysis and it was assumed that geometrical strain-displacement relations are nonlinear ones. It was also assumed that the shell faces have different thicknesses and these are made of different isotropic compressible materials with linear stress-hardening. Active loading processes are accepted in the analysis, the stability equations are derived using strain energy formulation. Ritz method is used to solve the equations and an iterative computational algorithm was elaborated to get numerical results.     

Experimental validation and sensitivity analysis of a coupled BES–HAM model

In this paper the ability of a coupled BES–HAM model to reproduce realistic data is evaluated by comparing numerical results with measured data from a climatic chamber experiment. Calcium silicate plates are introduced into a test room and a small calcium silicate sample is installed in one of the walls. The response of the test room to relative humidity variations of the supply air is evaluated, while the supply air temperature is kept constant. The measurements confirm that due to the presence of hygroscopic materials in the test room, the relative humidity variations in the room are damped. The calculated temperature and relative humidity in the middle of the test room are well within the uncertainty interval of the measurements. On the other hand the coupled model predicts a larger damping and phase shift of the relative humidity variations inside the sample, yet the agreement between the calculated and the measured temperatures in the sample proves to be good. Finally, a sensitivity analysis is performed to evaluate the dependence of the numerical results on the uncertainty of the input parameters. It is demonstrated that by using a lower vapour resistance factor for the calcium silicate material, the agreement between the measured and calculated data is improved.     

Soil–water–air fully coupling finite element analysis of slope failure in unsaturated ground

In this paper, a program of the finite element method (FEM), named as SOFT, using a finite element–finite difference scheme (FE–FD) for soil–water–air three-phase coupling problems, has been developed based on a rational and simple constitutive model for unsaturated soil proposed by Zhang and Ikariya (2011). In the program, similar to the works by Uzuoka et al. (2009) and Oka et al. (2010b), the FE–FD formulation in saturated condition of soil–water coupling problem, proposed by Oka et al. (1994), has been extended to unsaturated condition in soil–water–air fully coupling scheme, taking the saturation as a state variable. In order to verify the availability of the proposed numerical method, triaxial tests on unsaturated silty clay under fully undrained and unvented conditions, conducted by Oka et al. (2010a), are firstly simulated by the proposed method. The development of pore air pressure and pore water pressure measured in the specimen can be reproduced well by the proposed method. Furthermore, model tests on slope failure in unsaturated Shirasu, carried out by Kitamura et al. (2007), are also simulated by the same numerical method. From the simulation it is known that the slope failure behavior of the model ground observed in the tests can be described, on the whole, with satisfactory accuracy     

Desirability rating analysis for debt financing of public–private partnership road projects

Public–private partnership (PPP) road projects are highly leveraged capital‐intensive projects. Lenders, which provide the major portion of financing in the form of debt instruments, undertake loan approval processes to examine the various aspects of the projects that could influence the debt servicing capability while making credit decisions. In view of this, project sponsors could also assess beforehand how desirable is the project from the debt financing perspective in order to facilitate timely arrangement of debt financing and avoid funding problems. The Desirability Rating Analytical Tool (DRAT) has been developed in order to enable the project sponsor to assess how desirable the project is from a debt financing perspective. DRAT uses the aggregation operator Choquet fuzzy integral to aggregate the information relating to the various aspects of PPP road projects that lenders take into account while making credit decisions. The application of DRAT is illustrated with an example of a PPP road project from a National Highways Development Programme undertaken by the National Highway Authority of India, Government of India. DRAT expressed the result of the information aggregation in the form of a desirability rating profile indicating the degrees of membership to different levels of desirability. The desirability rating profiles of the project provide valuable information for decision making and can help in formulating strategies on improving the performance of the project where it is not performing satisfactorily.     

Exploring the dynamics of the Turkish construction industry using input–output analysis

Construction is commonly regarded as an important industry in economic policy making owing to its strong interactions with other sectors in the economy. Using six national input–output (IO) tables compiled to date and economic data for the period between 1969 and 2006, the behaviour of the Turkish construction sector and its relationships to investment, income and to other sectors in the economy are examined. Analysis reveals that the construction industry is losing its propulsive role and that it tends to exaggerate the fluctuations of the economy. The examination of lead and lag times between changes in GNP, construction activity and investments show that public sector spending cuts, in particular, have significant effects on the amplitude and the timing of slumps of the industry. The analysis of linkage indicators indicates that for the whole period under consideration the construction industry has high linkages with only one other industry. Thus the ‘leading’ role it plays in the economy is questioned.