A Stroke-Limitation AMD Control System with Variable Gain and Limited Area for High-Rise Buildings

Collisions between a moving mass and an anti-collision device increase structural responses and threaten structural safety.An active mass damper(AMD)with stroke limitations is often used to avoid collisions.However,a strokelimited AMD control system with a fixed limited area shortens the available AMD stroke and leads to significant control power.To solve this problem,the design approach with variable gain and limited area(VGLA)is proposed in this study.First,the boundary of variable-limited areas is calculated based on the real-time status of the moving mass.The variable gain(VG)expression at the variable limited area is deduced by considering the saturation of AMD stroke.Then,numerical simulations of a stroke-limited AMD control system with VGLA are conducted on a high-rise building structure.These numerical simulations show that the proposed approach has superior strokelimitation performance compared with a stroke-limited AMD control system with a fixed limited area.Finally,the proposed approach is validated through experiments on a four-story steel frame.

Study on Evacuation Strategy of Commercial High-Rise Building under Fire Based on FDS and Pathfinder

With the development of economy and society and the growth of population,the high-rise and multi-function of commercial buildings have become an international trend.But it also poses huge fire hazards.Most of the existing studies’research objects are predominantly high-rise residential buildings,without considering the impact of different functional zones(Standard floor,entertainment zone,office zone,equipment room and so on)and personnel distribution of commercial buildings evacuation.And the influence of using elevators to carry evacuees on the refuge floor on personnel evacuation is rarely studied.In this work,the fire scenario of the Yangtze River InternationalConferenceCenter,a high-rise commercial building,is simulated with the Pyrosim programto get the necessary parameters under various fire scenarios and to calculate the available evacuation time TASET.At the same time,according to the complex functional zone of the commercial high-rise building and the distribution of people in different time periods,a reasonable evacuation strategy is developed and simulated by Pathfinder software.The results indicate that unorganized evacuation will lead individuals to take the erroneous evacuation route,resulting in a vast region of congestion;comprehensive consideration of the time staggering and the reasonable distribution of evacuation routes can significantly improve evacuation efficiency,and the TRSET of night and working hours is 36.6%–55.3%and 49.9%–79.6%of unorganized evacuation,respectively.For the night fire,60%of the people use elevator-refuge floor to evacuate is the optimal strategy;for the fire during working hours,half of the people on standard floors use the elevator to evacuate and people on multifunctional floors evacuate in four batches is the best plan.The results of this study can provide viable solutions and a foundation for analyzing the fire evacuation and safety of big commercial high-rise buildings.

A novel control strategy for reproducing the floor motions of high-rise buildings by earthquake-simulating shake tables

To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Table(NEST)has been developed.The testbed consists of three consecutive floors of steel structure.The bottom two floors provide a space to accommodate a full-scale room.To fully explore the flexibility of NEST,we propose a novel control strategy to generate the required shake table input time histories for the testbed to track the target floor motions of the buildings of interest with high accuracy.The control strategy contains two parts:an inverse dynamic compensation via simulation of feedback control systems(IDCS)algorithm and an offline iteration procedure based on a refined nonlinear numerical model of the testbed.The key aspects of the control strategy were introduced in this paper.Experimental tests were conducted to simulate the seismic responses of a full-scale office room on the 21^(st)floor of a 42-story high-rise building.The test results show that the proposed control strategy can reproduce the target floor motions of the building of interest with less than 20%errors within the specified frequency range.

A Study on Factors Influencing Cost Overrun in High-rise Building Construction across India

Cost overrun is a common problem in construction projects worldwide.Most Indian construction projects,particularly those involving high-rise buildings,have had severe cost overruns.For managers,architects,engineers,and contractors,completing building projects within the specified cost budget has become the most important and hard assignment.Since it is common for high-rise building projects to go over budget,the aim of this study is to find out the causes of cost overruns and provide effective measures.The study found 70 cost overrun factors based on a comprehensive literature review and expert opinions.A Google form questionnaire was distributed to 150 construction professionals across India.After following up,101 of the 150 responses were received.A five-point Likert scale was used and the acquired data was analyzed and ranked using the Relative Importance Index(RII)technique.According to the findings of RII,the top ten critical factors influencing cost overruns were frequent change orders during construction by the owner,delay in construction,escalation of material prices,market inflation or deflation,rework,frequent changes in design,inaccurate evaluation of the project timeline,unforeseen ground condition,inaccurate quantity take-off,and delay in progressive payment by the owner.Spearman’s rank correlation test revealed that there is a very significant relationship between the rankings of factors provided by the owner,the consultant,and the contractor.In addition,a factor analysis tool in the SPSS software was also used to categorize the seventy factors into sixteen core components.The top ten critical factors were presented to subject matter experts,and their suggestions were being compiled.These results are expected to help construction professionals minimize cost overruns,improve cost control measures,and initiate future research.

Seismic loss assessment of RC high-rise buildings designed according to Eurocode 8

A probabilistic seismic loss assessment of RC high-rise(RCHR)buildings designed according to Eurocode 8 and located in the Southern Euro-Mediterranean zone is presented herein.The loss assessment methodology is based on a comprehensive simulation approach which takes into account ground motion(GM)uncertainty,and the random effects in seismic demand,as well as in predicting the damage states(DSs).The methodology is implemented on three RCHR buildings of 20-story,30-story and 40-story with a core wall structural system.The loss functions described by a cumulative lognormal probability distribution are obtained for two intensity levels for a large set of simulations(NLTHAs)based on 60 GM records with a wide range of magnitude(M),distance to source(R)and different site soil conditions(SS).The losses expressed in percent of building replacement cost for RCHR buildings are obtained.In the estimation of losses,both structural(S)and nonstructural(NS)damage for four DSs are considered.The effect of different GM characteristics(M,R and SS)on the obtained losses are investigated.Finally,the estimated performance of the RCHR buildings are checked to ensure that they fulfill limit state requirements according to Eurocode 8.

Analysis of the Performances of a New Type of Alumina Nanocomposite Structural Material Designed for the Thermal Insulation of High-Rise Buildings

The sol-gel method is used to prepare a new nano-alumina aerogel structure and the thermal properties of this nanomaterial are investigated comprehensively using electron microscope scanning,thermal analysis,X-ray and infrared spectrometer analysis methods.It is found that the composite aerogel alumina material has a multi-level porous nano-network structure.When employed for the thermal insulation of high-rise buildings,the alumina nanocomposite aerogel material can lead to effective energy savings in winter.However,it has almost no energy-saving effect on buildings where energy is consumed for cooling in summer.

Quantitative investigation on collapse margin of steel high-rise buildings subjected to extremely severe earthquakes

Reponses of structures subjected to severe earthquakes sometimes significantly surpass what was considered in the design.It is important to investigate the failure mechanism and collapse margin of structures beyond design,especially for high-rise buildings.In this study,steel high-rise buildings using either square concrete-filled-tube（CFT） columns or steel tube columns are designed.A detailed three-dimensional（3 D） structural model is developed to analyze the seismic behavior of a steel high-rise towards a complete collapse.The effectiveness is verified by both component tests and a full-scale shaking table test.The collapse margin,which is defined as the ratio of PGA between the collapse level to the design major earthquake level（Level 2）,is quantified by a series of numerical simulations using incremental dynamic analyses（IDA）.The baseline building using CFT columns collapsed with a weak first story mechanism and presented a collapse margin ranging from 10 to 20.The significant variation in the collapse margin was caused by the different characteristics of the input ground motions.The building using equivalent steel columns collapsed earlier due to the significant shortening of the locally buckled columns,exhibiting only 57% of the collapse margin of the baseline building.The influence of reducing the height of the first story was quite significant.The shortened first story not only enlarged the collapse margin by 20%,but also changed the collapse mode.

Vibration Control of a High-Rise Building Structure:Theory and Experiment

In this study,an innovative solution is developed for vibration suppression of the high-rise building.The infinite dimensional system model has been presented for describing high-rise building structures which have a large inertial load with the help of the Hamilton’s principle.On the basis of this system model and with the use of the Lyapunov’s direct method,a boundary controller is proposed and the closed-loop system is uniformly bounded in the time domain.Finally,by using the Smart Structure laboratory platform which is produced by Quancer,we conduct a set of experiments and find that the designed method is resultful.

Dynamic response characteristics of super high-rise buildings subjected to long-period ground motions

Spectrum characteristics of different types of seismic waves and dynamic response characteristics of super high-rise building structures under long-period ground motions were comparatively analyzed. First, the ground response wave （named LS-R wave） of a soft soil site with deep deposit, taking long-period bedrock seismic record as input, was calculated by wave propagation method. After that, a TOMAKOMAI station long-period seismic record from the Tokachi-Oki earthquake and conventional E1-Centro wave were also chosen. Spectrum characteristics of these waves were analyzed and compared. Then, a series of shaking table tests were performed on a 1：50 scale super high-rise structural model under these seismic waves. Furthermore, numerical simulation of the prototype structure under these excitations was conducted, and structure damages under different intensive ground motions were discussed. The results show that： 1） Spectrum characteristics of ground response wave are significantly influenced by soft soil site with deep deposit, and the predominant period has an increasing trend. 2） The maximum acceleration amplification factor of the structure under the TOM wave is two times that under the E1-Centro wave; while the maximum displacement response of the structure under the TOM wave is 4.4 times that under the E1-Centro wave. Long-period ground motions show greater influences on displacement responses than acceleration responses for super high-rise building structures. 3） Most inelastic damage occurs at the upper 1/3 part of the super high-rise building when subjected to long-period ground motions.

Multi-hazard performance assessment of a transfer-plate high-rise building

Many urban areas are located in regions of moderate seismicity and are subjected to strong wind. Buildings in these regions are often designed without seismic provisions. As a result, in the event of an earthquake, the potential for damage and loss of lives may not be known. In this paper, the performance of a typical high-rise building with a thick transfer plate （TP）, which is one type of building structure commonly found in Hong Kong, is assessed against both earthquake and wind hazards. Seismic- and wind-resistant performance objectives are first reviewed based on relevant codes and design guidelines for high-rise buildings. After a brief introduction of wind-resistant design of the building, various methodologies, including equivalent static load analysis （ESLA）, response spectrum analysis （RSA）, pushover analysis （POA）, linear and nonlinear time-history analysis （LTHA and NTHA）, are employed to assess the seismic performance of the building when subjected to frequent earthquakes, design based earthquakes and maximum credible earthquakes. The effects of design wind and seismic action with a common 50-year return period are also compared. The results indicate that most performance objectives can be satisfied by the building, but there are some objectives, such as inter-story drift ratio, that cannot be achieved when subjected to the frequent earthquakes. It is concluded that in addition to wind, seismic action may need to be explicitly considered in the design of buildings in regions of moderate seismicity.

Safety analysis of optimal outriggers location in high-rise building structures

This paper presents the restraining moments of outriggers acting on the core wall and the equation of the horizontal top deflection based on a simplified outrigger model. The deformation compatibility conditions between outriggers and core wall as well as the finite rigidities of outriggers are also considered. One case study was carried out to analyze the horizontal top deflection and the mutation of the restraining moments caused by the variation of outrigger location. The results showed that the method adopted in the paper is simple and reasonable. Some conclusions are valuable to the safety design of high-rise building structures.

Optimization of Grouping Evacuation Strategy in High-rise Building Fires Based on Graph Theory and Computational Experiments

It is difficult to rescue people from outside, and emergency evacuation is still a main measure to decrease casualties in high-rise building fires. To improve evacuation efficiency, a valid and easily manipulated grouping evacuation strategy is proposed. Occupants escape in groups according to the shortest evacuation route is determined by graph theory. In order to evaluate and find the optimal grouping, computational experiments are performed to design and simulate the evacuation processes. A case study shown the application in detail and quantitative research conclusions is obtained. The thoughts and approaches of this study can be used to guide actual high-rise building evacuation processes in future.

A review on research of fire dynamics in high-rise buildings

Since serious fire occurred frequently in recent years, fire safety of high-rise building has attracted extensive attention. A National Basic Research Program （973 program） of China has been set up by Ministry of Science and Technology （MOST） of China in 2012 to meet the research requirements of fire safety in high-rise buildings. This paper reviews the current state of art of research on fire dynamics of high-rise buildings, including the up-to-date progress of this project. The following three subjects on fire dynamics of high-rise buildings are addressed in this review： the ejected flame and fire plume behavior over facade out of the compartment window, the flame spread behavior over facade thermal insulation materiMs, and the buoyancy-driven smoke transportation characteristics along long vertical channels in high-rise buildings. Prospective future works are discussed and summarized.

Effects of high modes on the wind-induced response of super high-rise buildings

For super high-rise buildings, the vibration period of the basic mode is several seconds, and it is very close to the period of the fluctuating wind. The damping of super high-rise buildings is low, so super high-rise buildings are very sensitive to fluctuating wind. The wind load is one of the key loads in the design of super high-rise buildings. It is known that only the basic mode is needed in the wind-response analysis of tall buildings. However, for super high-rise buildings, especially for the acceleration response, because of the frequency amplification of the high modes, the high modes and the mode coupling may need to be considered. Three typical super high-rise projects with the SMPSS in wind tunnel tests and the random vibration theory method were used to analyze the effect of high modes on the wind-induced response. The conclusions can be drawn as follows. First, for the displacement response, the basic mode is dominant, and the high modes can be neglected. Second, for the acceleration response, the high modes and the mode coupling should be considered. Lastly, the strain energy of modes can only give the vibration energy distribution of the high-rise building, and it cannot describe the local wind-induced vibration of high-rise buildings, especially for the top acceleration response.

Seismic performance of high-rise buildings in selected regions in Saudi Arabia according to different seismic codes

The design code for each country is revised and updated based on an expected zone’s seismic intensities,geotechnical site classifications,structural systems,construction materials and methods of construction in order to provide more realistic considerations of seismic demand,seismic response,and seismic capacity.Based on the aforementioned provisions,structures designed according to different seismic codes may yield different performances for the same level of hazard.This study aims to investigate and compare the induced responses related to the earthquake-resistant design of reinforced concrete(RC)buildings according to the Saudi building code(SBC-301),American code(ASCE-7),uniform building code(UBC-97),and European code(EC-8).In order to account for the provision regarding the hazard specification and its effect on the induced seismic responses,four regions in the Kingdom of Saudi Arabia with different seismic levels are selected.The code provisions related to the specification of site classification and its effect on the induced design base shear are investigated as well.Significant differences are observed in the induced responses with the variation in seismic design codes for the considered seismic hazards and site classifications.

EXPERIMENT OF SMOKE-PREVENTING AIR CURTAINS IN HIGH-RISE BUILDING FIRES

In high-rise building fires, the most immediate threat to passenger life and safety evacuation is the smoke inhalation. Some traditional models for smoke prevention and exhaust are analyzed and compared with the smoke-preventing air curtain. The rationality and the feasibility of the air curtain are theoretically expounded. The air volume, tuyere width and jet velocity in the air curtain experiment are designed according to the theoreti- cal calculation model. Experimental results indicate that the effect of air curtain to prevent smoke diffusion is re- markable as the volume ratio of air-smoke is about 0. 6, the jet angle is between 25^o and 35^o, and the jet thickness is between 25 mm and 45 mm. The efficiency of air curtain can reach 98% on the entraining effect. Meanwhile, experiments verify the theorectical calculation.

High-rise building fire pre-warning model based on the support vector regression

Aiming at reducing the deficiency of the traditional fire pre-warning algorithms and the intelligent fire pre-warning algorithms such as artificial neural network,and then to improve the accuracy of fire prewarning for high-rise buildings,a composite fire pre-warning controller is designed according to the characteristic（ nonlinear,less historical data,many influence factors）,also a high-rise building fire pre-warning model is set up based on the support vector regression（ SV R）. Then the wood fire standard history data is applied to make empirical analysis. The research results can provide a reliable decision support framework for high-rise building fire pre-warning.

Wind tunnel test and numerical simulation of wind pressure on a high-rise building

We carried out a wind tunnel test to measure cladding loads for a high-rise building of 295 m in height, which would be located in the business center of Chongqing Municipality, P. R. China. The rigid model was used to determine fluctuating local pressures on the exterior surfaces of the building. The wind tunnel test results show the cr/tical zone of wind pressures on building surfaces in both standalone and interference conditions. The computational fluid dynamics （CFD） was conducted by using the FLUENT Code to compare with the wind tunnel test results, and the steady three-dimensional turbulent flow with Realizable k-ε as a turbulence model was used. The CFD results are agree with the wind tunnel test results in regards to distributions of wind pressures over a high-rise building＇s surfaces.

Research of CBR, DM and smart algorithms based design methods for high-rise building structure form-selection

First, the high-rise building structure design process is divided into three relevant steps, that is, scheme generation and creation, performance evaluation, and scheme optimization. Then with the application of relational database, the case database of high-rise structures is constructed, the structure form-selection designing methods such as the smart algorithm based on CBR, DM, FINS, NN and GA is presented, and the original forms system of this method and its general structure are given. CBR and DM are used to generate scheme candidates; FINS and NN to evaluate and optimize the scheme performance; GA to create new structure forms. Finally, the application cases are presented, whose results fit in with the real project. It proves by combining and using the expert intelligence, algorithm intelligence and machine intelligence that this method makes good use of not only the engineering project knowledge and expertise but also much deeper knowledge contained in various engineering cases. In other words, it is because the form selection has a strong background support of vast real cases that its results prove more reliable and more acceptable. So the introduction of this method provides an effective approach to improving the quality, efficiency, automatic and smart level of high-rise structures form selection design.

Simulation on spread of fire smoke in the elevator shaft for a high-rise building

Spread of fire smoke in the elevator shaft of a high-rise building is influ- enced by many driving facts. We simulate smoke spreading in the elevator shaft, stair room, and pre-chamber with and without different supplied pressurized air. The simulation shows that smoke moves very fast in the elevator shaft. When a 12 floor high-rise building is in fire, smoke can fill up the elevator shaft in less than 1.5 min after a fire started, temperature in the elevator shaft can be higher than 187℃ in 5 rain, and the concentration of CO can also reach a high level. The elevator shaft has a very low visibility in less than about 100 s.