The Effect of Core Eccentricity on the Structural Behavior of Concrete Tall Buildings

The main purpose of this paper is to investigate the effect of core eccentricity on the structural behavior of concrete tall buildings.Concrete buildings of 55 floors with plan dimensions 48.0×48.0 m2 were investigated.Three cases of main core locations are studied:centric(A),eccentric by one sixth(B)and one third(C)of building width.The three-dimensional finite element method has been used in conducting structural analysis through ETABS software.Gravity and lateral(wind and seismic)loadings are applied to all building cases.It has been concluded that the core location is the prime parameter governing the structural behavior of tall buildings.Although the first two cases(A,B)have acceptable and similar structural behaviors conforming to code limits,in the third case(C),the building behavior came beyond code limits.The author introduced remedial action by adding two secondary cores in the opposite direction of the main core(C-R)to restore the building behavior to the code limits.The results of this action were satisfactory.

MULTIMODAL CONTROL OF SEISMIC RESPONSES OF TALL BUILDINGS

Multimodal control for seismic responses of tall buildings is performed by using MTMDs. Installation and main parameters of MTMDs are described, equations of motion of the coupled system of tall buildings and MTMDs are built under earthquake excitations, and parametrical optimization for multimodal control is carried out under excitations of harmonic ground motion. An 11 story frame building controlled by MTMDs is simulated under the excitation of El Centro earthquake (1940, NS), and its displacement response at the top floor in the case of multimodal control is reduced by 20% more than the case of single modal control. Some conclusions are given as the MTMDs is an effective, reliable and practical passive measurement for controlling seismic responses of tall buildings and the multimodal control has better adaptability and reliability by comparison with the single modal control.

Seismic response of tall building considering soil-pile-structure interaction

The seismic behavior of tall buildings can he greatly affected by non-linear soil-pile interaction during strong earthquakes.In this study a 20-storey building is examined as a typical structure supported on a pile foundation for different conditions:(1) rigid base,i.e.no deformation in the foundation:(2) linear soil-pile system;and (3) nonlinear soil-pile system. The effects of pile foundation displacements on the behavior of tall building are investigated,and compared with the behavior of buildings supported on shallow foundation.With a model of non-reflective boundary between the near field and far field, Novak's method of soil-pile interaction is improved.The computation method for vibration of pile foundations and DYNAN computer program are introduced comprehensively.A series of dynamic experiments have been done on full-scale piles, including single pile and group,linear vibration and nonlinear vibration,to verify the validity of boundary zone model.

Modified consecutive modal pushover procedure for seismic investigation of one-way asymmetric-plan tall buildings

The effects of higher modes and torsion have a significant impact on the seismic responses of asymmetric-plan tall buildings. A consecutive modal pushover (CMP) procedure is one of the pushover methods that have been developed to consider these effects. The aim of this paper is to modify the (CMP) analysis procedure to estimate the seismic demands of one-way asymmetric-plan tall buildings with dual systems. An analysis of 10-, 15- and 20-story asymmetric-plan buildings is carried out, and the results from the modified consecutive modal pushover (MCMP) procedure are compared with those obtained from the modal pushover analysis (MPA) procedure and the nonlinear time history analysis (NLTHA). The MCMP estimates of the seismic demands of one-way asymmetric-plan buildings demonstrate a reasonable accuracy, compared to the results obtained from the NLTHA. Furthermore, the accuracy of the MCMP procedure in the prediction of plastic hinge rotations is better than the MPA procedure. The new pushover procedure is also more accurate than the FEMA load distribution and the MPA procedure.

Tall Buildings with Dynamic Facade Under Winds

Burgeoning growth of tall buildings in urban areas around the world is placing new demands on their performance under winds.This involves selection of the building form that minimizes wind loads and structural topologies that efficiently transfer loads.Current practice is to search for optimal shapes,but this limits buildings with static or fixed form.Aerodynamic shape tailoring that consists of modifying the external form of the building has shown great promise in reducing wind loads and associated structural motions as reflected in the design of Taipei 101 and Burj Khalifa.In these buildings,corner modifications of the cross-section and tapering along the height are introduced.An appealing alternative is to design a building that can adapt its form to the changing complex wind environment in urban areas with clusters of tall buildings,i.e.,by implementing a dynamic facade.To leap beyond the static shape optimization,autonomous dynamic morphing of the building shape is advanced in this study,which is implemented through a cyber–physical system that fuses together sensing,computing,actuating,and engineering informatics.This approach will permit a building to intelligently morph its profile to minimize the source of dynamic wind load excitation,and holds the promise of revolutionizing tall buildings from conventional static to dynamic facades by taking advantage of the burgeoning advances in computational design.

Recent progress of seismic research on tall buildings in China Mainland

As a result of rapid economic growth and urbanization in the past two decades,many tall buildings have been constructed in China Mainland,offering researchers and practitioners an excellent opportunity for research and practice in the field of structural engineering. This paper reviews progress by researchers throughout China Mainland on the seismic research of tall buildings,focusing on three major topics that impact the seismic performance of tall buildings. These are:(1) new types of steel-concrete composite structural members such as steel-concrete composite shear walls and columns,(2) earthquake resilient shear wall structures such as shear walls with replaceable structural components,self-centering shear walls and rocking walls,and(3) performance-based seismic design,including seismic performance index,performance level and design method. The paper concludes by presenting future research needs and directions in this field.

Passive control of along-wind response of tall building

Most of modern tall buildings using lighter construction materials with high strength and less stiffness are more flexible, which occurs excessive wind-induced vibration, resulting in occupant discomfort and structural unsafety. It is necessary to predict wind-induced vibration response and find out a method to mitigate such an excessive wind-induced vibration at the preliminary design stage. Recently, many studies have been conducted in using actuator control force based on the linear quadratic optimum control algorithm. It was accepted as a common knowledge that the performance of passive tuned mass damper(TMD) could increase by incorporating a feedback active control force in the design of TMD, which is called active tuned mass damper(ATMD). However, the fact that ATMD is superior to TMD to reduce wind-induced vibration of a tall building is still a question. The effectiveness of TMD for mitigating the along-wind vibration of a tall building was investigated. Optimum parameters of tuning frequency and damping ratio for TMD under a random load which has a white noise spectra were used. Fluctuating along-wind load acting on a tall building treated as a stationary Gaussian random process was simulated numerically using the along-wind load spectra. And using this simulated along-wind load, along-wind responses of a tall building with and without TMD were calculated and the effectiveness of TMD in mitigating the along-wind response of a tall building was found out.

Extended consecutive modal pushover procedure for estimating seismic responses of one-way asymmetric plan tall buildings considering soil-structure interaction

Performance based design becomes an effective method for estimating seismic demands of buildings. In asymmetric plan tall building the effects of higher modes and torsion are crucial. The consecutive modal pushover （CMP） procedure is one of the procedures that consider these effects. Also in previous studies the influence of soil-structure interaction （SSI） in pushover analysis is ignored. In this paper the CMP procedure is modified for one-way asymmetric plan mid and high-rise buildings considering $SI. The extended CMP （ECMP） procedure is proposed in order to overcome some limitations of the CMP procedure. In this regard, 10, 15 and 20 story buildings with asymmetric plan are studied considering SSI assuming three different soil conditions. Using nonlinear response history analysis under a set of bidirectional ground motion; the exact responses of these buildings are calculated. Then the ECMP procedure is evaluated by comparing the results of this procedure with nonlinear time history results as an exact solution as well as the modal pushover analysis procedure and FEMA 356 load patterns. The results demonstrate the accuracy of the ECMP procedure.

System of Combined Foundation for Tall Buildings

Location of the heavily loaded building on the ground of the small load capacity requires application of the appropriate foundation structure. The required foundation system is most often deep, it is expensive and its cost increases significantly when the building is located in earthquake area or in mining damage sector. The proposed structural system of the combined foundation makes possible to design and to construct a very stable and relative inexpensive foundation structure, which can obtain an extremely large horizontal surface and which can be placed not deeply beneath the terrain level. It can be a very solid support structure for a tall building placed on very weak subsoil and at the same time located in seismic area. This system can be applied not only for new buildings but it can be used for the existing buildings and moreover for straighten of the inclined objects. Due to special arrangement of component parts the combined foundation possesses inherent features of a vibration damper, what is highly desirable if buildings have to be located in earthquake areas. When the aboveground storeys structure has some similar patterns with structural form of the combined foundation then the structural system of the whole building obtains coherent structural characteristics and it is called the combined structural system of the tall building. Suitable application of this system makes possible to design high-rise buildings having interesting and unique architectonic forms, what is presented on a selected example.

Structural Design of a Tall Building with Underpinning Structure in Guangzhou

This paper introduces the structural design optimization of a tall building with reinforced concrete frame-core shear walls in Guangzhou downtown.To decrease the construction cost,wide flat beam with 400 mm ×650 mm rectangular cross-section are adopted for main beam.Special measures are used to decrease noncoincident centers of mass and stiffness.Because subway tunnels cross the building underground,inclined columns,the second and third floor underground together function as the underpinning structures.Different from traditional transform beam,the proposed underpinning structures show good performance without using large dimensional bending members.Special attentions should be paid to the beams connecting with the inclined column in the underpinning structures,and these beams show large tensile or compressive forces.Settlement observations after completion construction indicate that the building as well as the proposed design measures work well.

Slenderness Ratio Influence on the Structural Behavior of Residential Concrete Tall Buildings

The main concern of this paper is to study the influence of the building slenderness ratio on the structural behavior of the residential concrete tall buildings aiming to deepen structure and architect designers understanding for such type of buildings. The study is emphasized only on Kuwait city design conditions for wind and seismic loadings. The paper presents an actual case study for adding two thirty stories residential towers with two different slenderness ratios to an existing residential complex. Wind loading is considered using both code values and wind tunnel results. Three dimensional finite element techniques through ETABS software are used in conducting analysis for structures presented here. A serviceability study is performed to ensure that buildings have sufficient stability to limit lateral drift and peak acceleration within the acceptable range of occupancy comfort. In addition, an ultimate strength study is carried out to verify that all the structural elements are designed to withstand factored gravity and lateral loads in a safe manner according to the international building codes. Analysis results are presented and discussed. A brief idea about foundation design of the new towers and its connection to the existing foundation is presented. Finally conclusions are summarized as guidelines for the structural professions of concrete residential tall buildings.

Across and along-wind responses of tall building

Most modern tall buildings using lighter construction materials are more flexible, which can lead to excessive wind-induced vibrations resulting in occupant discomfort and structural unsafety. It is necessary to predict and mitigate such wind-induced vibration at the preliminary design stage. Fluctuating across and along-wind loads acting on a tall building that could not be formulated theoretically were simulated numerically in the time domain using known across and along-wind load spectra. These simulated wind loads were used to estimate the across and along-wind responses of a tall building, which are less narrow-banded processes, based on the state space variable approach. The simulated across-wind response of root-mean-square value(0.0047) and that of KAREEM's(0.0040) and the simulated along-wind response of root-mean-square value(0.021) and that of SOLARI's(0.027) were compared. It is found that these are good approximations of closed form responses. Therefore, these numerically simulated across and along-wind loads can be used for across and along-wind responses estimation for the wind-resistant design of a tall building at the preliminary design stage.

ODE-Solver-Oriented Computational Method for the Structural Dynamic Analysis of Super Tall Buildings

The paper is to introduce a computational methodology that is based on ordinary differential equations （ODE） solver for the structural systems adopted by a super tall building in its preliminary design stage so as to facilitate the designers to adjust the dynamic properties of the adopted structural system. The construction of the study is composed by following aspects. The first aspect is the modelling of a structural system. As a typical example, a mega frame-core-tube structural system adopted by some famous super tall buildings such as Taipei 101 building, Shanghai World financial center, is employed to demonstrate the modelling of a computational model. The second aspect is the establishment of motion equations constituted by a group of ordinary differential equations for the analyses of free vibration and resonant response. The solutions of the motion equations （that constitutes the third aspect） resorted to ODE-solver technique. Finally, some valuable conclusions are summarized.

Effects of corner modifications on wind loads and local pressures on walls of tall buildings

In this study, the aerodynamic characteristics of tall buildings with corner modifications (e.g., local wind force coefficients, mean pressure distributions, normalized power spectrum density, and extreme local pressure) were examined. Wind tunnel experiments were conducted to measure the wind pressures on building models with different heights and recessed corners of different ratios. At a wind direction of a = 0° (i.e., wind blowing on the front of a building), corner modifications effectively reduced wind forces in all cases. Specifically, small corner modification ratios reduced wind forces more effectively than their larger counterparts. However, corner modifications resulted in extreme local pressure on building surfaces. In addition, for small corner modification ratios, the probability of extreme local pressure occurring at a = 0° was high. This probability was also high for large corner modification ratios at a = 15° (i.e., wind blowing slightly obliquely on the front of a building) because wind blowing obliquely creates substantial vortex shedding on one side surface and extreme negative pressure over one building side surface. Results of computational fluid dynamic modeling were adopted to determine details of the aerodynamic characteristics of tall buildings with corner modifications.

Shear wall layout optimization of tall buildings using Quantum Charged System Search

This paper presents a developed meta-heuristic algorithm to optimize the shear walls of tall reinforced concrete buildings.These types of walls are considered as lateral resistant elements.In this paper,Quantum Charged System Search(QCSS)algorithm is presented as a new optimization method and used to improve the convergence capability of the original Charged System Search.The cost of tall building is taken as the objective function.Since the design of the lateral system plays a major role in the performance of the tall buildings,this paper proposes a unique computational technique that,unlike available works,focuses on structural efficiency or architectural design.This technique considers both structural and architectural requirements such as minimum structural costs,torsional effects,flexural and shear resistance,lateral deflection,openings and accessibility.The robustness of the new algorithm is demonstrated by comparing the outcomes of the QCSS with those of its standard algorithm.

A Computational Model for Pedestrian Level Wind Environment Around Tall Buildings

A computational model has been developed for the simulation of pedestrian level wind environment around tall buildings by coupling the numerical simulation of the full scale site and meteorological station materials. In the first step, the hybrid/mixed finite element method is employed to solve the two dimensional Navier Stokes equation for the flow field around tall buildings, in view of the influence of fluctuating wind, the flow field is revised with the effective wind velocity. The velocity ratio is defined in order to relate numerical wind velocity to oncoming reference wind velocity. In the second step, the frequency occurred discomfort wind velocity as a suitable criterion is calculated by use of the coupling between the numerical wind velocity and the wind velocity at the nearest meteorological station. The prediction accuracy of the wind environment simulation by use of the computation model will be discussed. Using the available wind data at the nearest meteorological station as well as the established criteria of wind discomfort, the frequency of wind discomfort can be predicted. A numerical example is given to illustrate the application of the proposed method.

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.

Investigation Responses of the Diagrid Structural System of High-rise Buildings Equipped with Tuned Mass Damper Using New Dynamic Method

Due to the shortage of land in cities and population growth,the significance of high rise buildings has risen.Controlling lateral displacement of structures under different loading such as an earthquake is an important issue for designers.One of the best systems is the diagrid method which is built with diagonal elements with no columns for manufacturing tall buildings.In this study,the effect of the distribution of the tuned mass damper(TMD)on the structural responses of diagrid tall buildings was investigated using a new dynamic method.So,a diagrid structural systems with variable height with TMDs was solved as an example of structure.The reason for the selection of the diagrid system was the formation of a stiffness matrix for the diagonal and angular elements.Therefore,the effect of TMDs distribution on the story drift,base shear and structural behaviour were studied.The obtained outcomes showed that the TMDs distribution does not significantly affect on improving the behaviour of the diagrid structural system during an earthquake.Furthermore,the new dynamic scheme represented in this study has good performance for analyzing different systems.Abbreviation:TMD-tuned mass damper;SATMD-semiactive-tuned mass dampers;MDOF-multiple degrees of freedom;m_(i)-mass of ith story of the building;c_(i)-damping coefficient of the ith story of the building;k_(i)-stiffness of ith story of the building;x_(i)-displacement of the ith story of the building;md-mass of damper;c_(d)-damping coefficient of the damper;k_(d)-stiffness of damper;x_(d)-displacement of TMD;M_(i)-generalized mass of the ith normal mode;C_(i)-generalized damping of the ith normal mode;K_(i)-generalized stiffness of the ith normal mode;K_(i)(t)-generalized load of the ith normal mode;Y_(i)(t)-generalized displacement of the ith normal mode;[M]-matrices of mass;[C]-matrices of damping;{P(t)}-consequence external forces;N_(i)(τ)-interpolation functions;[Ai]-mechanical properties of the structure.

Leveraging Publicly Available Building Energy Data as a Design Firm in the United States

Publicly available building energy data are exploding--thirteen American cities and 14 states now require them by law. This emergence of data nudges building owners and tenants to reduce energy consumption by comparing their usage to that of similar buildings. However, vast untapped energy reductions and deeper physical understandings can still be extracted from these data. This paper extends the energy saving impact and provides key insight into building performance through publicly-disclosed data by describing three initiatives at a large design finn. An internal high performance design reporting program compares projects from around the world and across offices. A case study of 706 buildings in New York City illustrates the value of tracking large-scale patterns to a design firm. Per capita energy and carbon usage is correlated to life expectancy to better inform neighborhood and city design. As more data freely flow out into the public, engineers must strategically engage it.

Wind response of high-rise building in diversified inlets to construct wind turbine system on roof

Many skyscrapers have installed wind turbine systems to use new renewable energy. In particular, building an integrated wind power generation system by installing a wind power generator inside a building is an attractive method to secure safe energy. However, most studies have dealt with the efficiency of wind turbines and the response effects of wind induced vibration; space preparation for wind turbine installations has not been sufficiently considered. This work reviewed the shapes of openings where wind turbines can be installed in skyscrapers, and the characteristics of wind induced vibration responses occurring in the building with changes in cross sectional area. Nine wind power models were constructed to carry out the experiment. According to the experimental results, wind speed varies with shape of opening in the order of C-type>S-type>R-type. Moreover, wind speed increases as the area is reduced.