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.

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.

Numerical Simulation of Wind Field Characteristics around Two Adjacent High-Rise Buildings

This paper based on Reynolds-averaged Navier-Stokes equations standard ?model [1];the surface pressure on the wind field around two adjacent high-rise buildings was numerically simulated with software Fluent. The results show that with the influence of adjacent high-rise building, numerical simulation is a good way to study the wind field around high-rise building and the distribution of wind pressure on building’ surface. The pressures on the windward surface are positive with the maximum at 2/3 H height and have lower values on the top and bottom. The pressures on the leeward surface and two sides were negative. Due to the serious flow separation at the corner of building’s windward, the wind field has a high turbulent kinetic energy.

Model Reduction Methods for High-Rise Buildings with Active Mass Damper Control Systems

To improve the performance of an active mass damper control system,the controller should be designed based on a reduced-order model. An improved method based on balanced truncation method was proposed to reduce the dimension of high-rise buildings,and was compared with other widely used reduction methods by using a framework with ten floors. This optimized method has improvement of reduction process and choice of the order. Based on the reduced-order model obtained by the improved method and pole-assignment algorithm,a controller was designed. Finally,a comparative analysis of structural responses,transfer functions,and poles was conducted on an actual high-rise building. The results show the effectiveness of the improved method.

Field measurements for calibration of simplified models of the stiffening effect of infill masonry walls in high-rise RC framed and shear-wall buildings

As a type of nonstructural component, infill walls play a significant role in the seismic behavior of high-rise buildings. However, the stiffness of the infill wall is generally either ignored or considered by simplified empirical criteria that lead to a period shortening. The difference can be greatly decreased by using a structural identification methodology. In this study, an ambient vibration test was performed on four on-site reinforced concrete high-rise buildings, and the design results were compared with the PKPM models using corresponding finite element(FE) models. A diagonal strut model was used to simulate the behavior of the infill wall, and the identified modal parameters measured from the on-site test were employed to calibrate the parameters of the diagonal strut in the FE models. The SAP2000 models with calibrated elastic modulus were used to evaluate the seismic response in the elastic state. Based on the load-displacement relationship of the infill wall, nonlinear dynamic analysis models were built in PERFORM-3 D and calibrated using the measured modal periods. The analysis results revealed that the structural performance under small/large earthquake records were both strengthened by infill walls, and the contribution of infill walls should be considered for better accuracy in the design process.

Development of the Separate Air-Supply Type of Pressurization Smoke Control System for the Stairwells of High-Rise Buildings in Korea

The pressurization smoke control system has been commonly used as a smoke control system at the emergency stairs of high-rise buildings. However, a higher possibility of overpressure between the lobby and the accommodation or pressure drop in the lobby could lead to failure in achievement of the purpose of pressurization system, particularly when supplying the leakage and supplementary air flow through one air-supply path at a time. To improve this particular issue, the devise configurations, as well as the different ways to supply the leakage and supplementary air flow through the different flow passages have been proposed. The performance of the trial product was evaluated on the test bed, ultimately providing a safe evacuation environment if high-rise buildings fired.

Method for Evaluating the Influence of Obstruction of Sea Breeze by Clusters of High-Rise Buildings on the Urban Heat Island Effect

This study aims to propose a method for quantitatively evaluating the influence which the obstruction of sea breezes by clusters of high-rise buildings has on the urban heat island effect using a weather simulation model and Geographic Information Systems (GIS). Specifically, a method of evaluating the influence of the obstruction of sea breeze by high-rise buildings on the urban heat island effect was proposed. In the method, two scenarios that imagine urban forms which differ with regard to whether or not they contain high-rise buildings are created and weather simulation is conducted, and the results of the simulations are comparatively analyzed focusing on temperature and wind speed. Evaluation was conducted in two stages, and Shiodome of Minato City in the Tokyo Metropolis was selected as the region for evaluation. In two stages of evaluation, a rise in temperature of approximately 0.3 K and a reduction in wind speed of approximately 1 m/s were observed in a region approximately five to ten kilometers square downwind of high-rise buildings in the period 6 PM to 9 PM, and a higher temperature caused by the obstruction of sea breeze by high-rise buildings was identified. The fact that such a higher temperature was confirmed in the time period from 6 PM onwards, in which the temperature decreases, reveals that obstruction of sea breeze by high-rise buildings dulls the decrease in temperature which occurs from evening onwards, and influences nighttime urban heat island formation.

Survey-Based Analysis of Water Consumption Law in High-Rise Public Buildings and Water-Saving Performance of Pressure-Reducing Measures

Facing the contradiction of water scarcity and water wastage in most cities of China, this study aims at probing into the factors influencing water-use efficiency and assessing water-saving potential by adopting pressure control measures based on field survey conducted in 23 high-rise buildings in Suqian, China and laboratory tests. Results showed that per capita water consumption (PCWC) exceeding water consumption norms is common in these buildings. The hourly water consumption variation law is quite different among different types of buildings. These differences should be considered in designing building water supply systems to lower water and energy consumption. On the basis of correlation analysis, the order of factors influencing the PCWC follows average tap water pressure, percapita building area, and building age, suggesting pressure management in high-rise buildings is a key water-saving measure. Field tests of outflow characteristics under different water pressures indicated that over-pressure outflow (OPO) is a common cause of water wastage in buildings, however, no branch pipe pressure control measures were found in all the surveyed buildings. Laboratory tests showed that branch pipe pressure-reducing measures can lower water consumption and improve the comfortability of use as well. Therefore, in addition to applying high efficiency water-saving devices, we strongly recommend that branch pipe pressure-reducing measures should be strictly implemented in designing new building water supply systems and reconstruction of existing old building water supply systems, thereby, promoting water, energy saving and development of green building.

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.

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.

Evaluation of Disaster Risks, Vulnerabilities and Response Strategies of High Rise Buildings in Lagos Municipality

Although disasters can occur anywhere, certain types of disasters are more likely to have more effects on some buildings than others, especially on those in urban areas. Buildings in Lagos have had nasty experiences from both natural and artificial disasters, claiming lives and properties in the past. This study aims at evaluating the disaster risks, vulnerabilities and response strategies in the high rise buildings in Lagos municipality. Structured questionnaire was administered to building owners, estate managers and disaster managers who manage the high rise buildings. The information obtained was supplemented by personal interviews conducted with tenants and rescue organizations. The study identified collapse of building, fire out break, and communication and power failure as the most likely potential disasters, power failure and collapse had the highest severity of impact, and the degree of preparedness achieved to confront the disasters was below satisfaction. However, the specific status of the response strategies was as expected, but there was room for improvements. The potential disasters were natural, human and environmental and the most vulnerable sectors were other properties rather than the high rise buildings themselves. The magnitude of risk levels could be contained with the level of response strategies already achieved if coordinated.

Influence of Horizontal Flow on Atrium in High-Rise Residential Building

In this study a 10-storied residential building model was employed to clarify the ventilation characteristics of the atrium and the rooms,which were effected by the different forms of lateral openings.The experiment was conducted under the combined effect of wind force and thermal buoyancy,and the similarity requirements were satisfied.The results have shown that the different forms of lateral openings cause the different ventilation effect of the building,and also have some certain regularity.The conclusions provide a theoretical foundation for how to use the ventilation of atrium better in high-rise residential building.

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.

Investigation on Fire Protection System of Highrise Buildings in the Context of Bir Uttam Aminul Haque Avenue in Dhaka, Bangladesh

Rapid high-rise building construction of different occupancies is becoming popular in Dhaka due to its economic gain and functional flexibility. Fire prevention poses a significant difficulty to this type of construction due to its complexity and economic worth as well. Therefore, construction of high-rise building without following the proper fire safety measures, is a common practice at present in the city and it poses a greater threat to urban life considering its associated loss. Even though, most of the owners or authorities do not respect the construction code and the majority of them lack sufficient awareness and basic fire control knowledge and practice. More often, they are unable to comprehend the magnitude and severity of severe fire hazards, and recognize the causes and implementing effective mitigation measures are rare. As a result, the number of fire hazard in high-rise construction is increasing day by day. Hence, investigating the present condition of high-rise buildings (already built) in terms of Fire Protection System is imperative to prevent the upcoming fire hazard. An urban chunk of 33 plots along with Bir Uttam Aminul Haque Avenue, located in Banani, has been chosen for the study area considering its vulnerability to fire hazard. Among these buildings, STAR Tower and HBR Tower, these two high-rise buildings are assessed thoroughly using FRI (Fire Risk Index) Method. The method is semi-quantitative in nature with seventeen parameters associated with fire protection. This assessment represents a scenario in what extent fire codes are being followed in the selected area. It concludes that most of the buildings lack in providing protection against fire hazards for not following the code strictly. This research provides some recommendations which can be followed to improve the fire safety measures in this existing context. It is expected that this research could be a unique addition to firefighting knowledge by contributing to mitigating the consequences of fire related hazards in any densely populated city like Dhaka.

High-Rise Residential Reinforced Concrete Building Optimisation

In the last few decades structure optimisation has become a main task in a civil engineering project. As a matter of fact, due to the complexity and particularity of every structure, the great amount of variables and design criteria to considerate and many other factors, a general optimisation’s method is not simple to formulate. As a result, this paper focuses on how to provide a successful optimisation method for a particular building type, high-rise reinforced concrete buildings. The optimization method is based on decomposition of the main structure into substructures: floor system, vertical load resisting system, lateral load resisting system and foundation system;then each of the subsystems using the design criteria established at the building codes is improved. Due to the effect of the superstructure optimisation on the foundation system, vertical and lateral load resisting system is the last to be considered after the improvement of floor. Finally, as a case example, using the method explained in the paper, a 30-story-high high-rise residential building complex is analysed and optimised, achieving good results in terms of structural behaviour and diminishing the overall cost of the structure.

YKJ-01型附着式升降脚手架在330m超高层建筑的应用

针对某330 m超高层项目,详细介绍了附着式升降脚手架在超高层的应用,主要包括:附着式升降脚手架施工平面布置,附着式升降脚手架参数设计,附着式升降脚手架直爬与斜爬部位处理,建筑结构凹槽位置防护设计,附着式升降脚手架斜爬角度变化,避难层位置附着式升降脚手架处理,高区大堂处格构柱设计,塔式起重机附墙处附着式升降脚手架处理措施,施工电梯处附着式升降脚手架处理措施,卸料平台处附着式升降脚手架处理措施,附着式升降脚手架分片提升断口位置处理,附着式升降脚手架安装、提升、拆除等。

AHP-改进物元法在整体钢平台顶升模架体系安全风险评估中的应用

针对整体钢平台顶升模架体系施工安全性的灰色特征,经实地调研及专家评审,建立了整体钢平台顶升模架体系的安全风险评估模型。首先,考虑人员、设备、环境、管理及技术5个方面,选取19个指标构建安全风险评估指标体系;其次,采用层次分析法计算各指标权重,基于改进物元法确定各指标的风险等级,然后将两者向量相乘,以最大隶属度原则确定整体钢平台顶升模架体系的安全风险等级;最后,将所建立的基于层次分析法(Analytic Hierarchy Process, AHP)-改进物元法的安全风险评估模型应用到某超高层工程实例中,并将评估结果与实际施工情况对比分析。研究表明,该评估模型的计算结果合理且准确可靠,可为超高层整体钢平台顶升模架体系的安全管理提供参考。

基于BIM和NSGA-Ⅲ的超高层建筑施工进度多目标优化研究

基于BIM与NSGA-Ⅲ算法优化框架,结合目标控制优化机制,构建了BIM和遗传算法的高层标准层施工考虑工前和施工阶段延误场景下的两阶段优化模型,解决了超高层建筑工程信息采集、进度-成本-资源需求均衡目标评估分析和施工优化决策等关键技术问题。基于NSGA-Ⅲ算法对模型求解获帕累托前沿解集,后采用优劣解距离法(TOPSIS)获得目标值和工序时间参数部署的最优解。并在实际案例中验证了其可行性和有效性,为科学动态的管理提供决策支撑和算法依据。该模型的应用可以提高超高层施工进度动态优化决策能力,促进施工过程面向智能化、数据化和科学决策化。

基于k-均值聚类算法的高层建筑表面风压分区研究

为分析高层建筑表面的风压特征和关键区域,以高宽比为4∶1的高层建筑风洞试验模型为对象,采用k-均值聚类算法,对0°风向角下模型各个面的风压测压管时程数据进行分析,研究结果表明:建筑左、右侧面以强烈的负压为主导,且角点附近存在负压极值;k-均值聚类算法可以有效地识别不同表面风压场的特征,风压的聚类结果与平均风压系数的分布较为吻合,且能得到代表性的风压测压管。