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This paper presents a unique study on the dynamic identification of the tallest glue-laminated timber frame building in the world using forced vibration tests (FVTs) and long-term ambient vibration tests (AVTs). Because the amount of sway in service under wind has become the governing design criterion for tall timber buildings, this paper aims to provide useful information and evaluate available tools and methods for modal identification in tall glulam timber frame buildings. First, combined operational modal analysis schemes based on the variational mode decomposition with the stochastic subspace identification and the random decrement technique were adopted to identify the modal properties from nonstationary ambient data. Then, unique full-scale forced vibration tests were conducted using two different methods to excite the building: measured electrodynamic shakers excitation and unmeasured rhythmic human-induced excitation. Finally, a finite-element (FE) model of the tall glulam frame building was developed and frequency response function (FRF)–based model updating was conducted showing that the FE model was able to predict the modal behavior of the test building. The results show that natural frequencies identified from output-only techniques are in good agreement with the FVT results. Damping ratios obtained from both AVTs and FVTs exhibited amplitude-dependent behavior with a larger variation observed in the FVT results due to larger range of response amplitudes. These results have significant consequences for the design of tall timber buildings under serviceability-level loading, where damping plays an important role. The resulting damping ranges presented in this paper can serve as a useful guideline for practicing engineers in developing their prediction models of tall timber buildings under serviceability-level loading. [ABSTRACT FROM AUTHOR]

The tall building design process typically goes through a time-consuming iterative procedure to ensure the cost efficiency of the proposed structural system, especially in the conceptual design stage where the layout is designed. Despite that, this procedure does not guarantee to yield an optimal layout. Consequently, an automated layout optimization procedure will result in a more economical and sustainable design. This paper presents a novel multiobjective lateral load resisting system (LLRS) (i.e., shear walls) layout optimization framework provided for dynamically sensitive tall buildings subjected to a wind load time history. The developed framework relies on an artificial neural network (ANN) surrogate model for constraints and objective function evaluation to reduce the computational time of the optimization process. The adopted surrogate model is built based on an automated finite element models-generated database using MATLAB code via the Open Application Program Interface of the ETABS software. The ANN surrogate model proved its efficiency in capturing complex variations in the structural response with a correlation coefficient that ranges between 90% and 98%. A nongradient optimization algorithm (NSGA-II) is adopted to identify the optimal shear wall layout to resist the applied dynamic wind load. In order to reduce the number of optimal layout solutions on the Pareto front, a pruning algorithm is used to limit the optimal solutions to 24 layouts. This will enable designers to use the direct selection method to choose an appropriate layout that fits the project's objectives. Also, a case study building is presented where the optimized results are analyzed and discussed in the numerical example to verify the effectiveness of the proposed optimization framework. [ABSTRACT FROM AUTHOR]

An extensive series of wind-tunnel experiments were conducted in the Boundary Layer Wind Tunnel (BLWT) Experimental Facility (EF) at the University of Florida (UF) to investigate the effect of heterogenous terrain on wind flow and pressure distributions on building surfaces. Many studies have already been performed on the effect of upwind terrain on wind characteristics and wind loads on buildings. Previous tests in wind tunnels were mainly designed for uniform upwind terrain or simple two-dimensional roughness changes (e.g., smooth-to-rough change or vice versa). Using the wind-tunnel facility at the UF, we were able to perform an extensive series of tests on heterogeneous upwind terrains. The first part of the testing was focused on wind characteristics by measuring the three components of wind velocity when wind flow passed over different complex upwind terrains. The second part of the testing was intended to obtain the aerodynamic loads of wind over complex terrains on low-rise and midrise building models. The data and metadata are publicly available on the DesignSafe-CI repository under the DOI of 10.17603/Ds2-6hg9-R131. Researchers and practicing engineers can use the collected data to understand the effect of heterogeneous upwind terrain better. [ABSTRACT FROM AUTHOR]

Mitigating tornado damage remains a critical challenge for communities throughout much of the United States. Enhanced construction techniques typically used in hurricane-prone regions are often recommended as at least part of the solution, but the effectiveness of these techniques lacks empirical evaluation. This study investigates the performance of modern wood-frame residential structures in Arabi, LA, constructed to hurricane-resistant standards, that were impacted by a strong tornado on March 22, 2022. Field teams deployed beginning March 25, 2022, just three days after the tornado touched down, capturing perishable data on the building performance using vehicle-mounted surface-level panoramic cameras, forensic engineering investigations, and unmanned aerial systems. This paper describes the field deployments and identifies common failure mechanisms observed by the field teams. Analytical fragility functions are developed based on the load path observations and compared to empirical fragility functions generated from linking the building performance observations with wind speed estimates at each building derived from a parametric wind field model conditioned to tree-fall patterns. The study finds that despite the frequent use of hurricane-resistant hardware, such as hurricane straps and anchor bolts, key weak links elsewhere in the load path compromised the resistance and led to premature failures. The agreement between the empirically- and analytically-derived fragility functions was lacking, demonstrating the challenges that remain in understanding near-surface tornado wind loading and structural response. Nonetheless, the study provides a consensus framework for future tornado assessments that can help improve our understanding of tornado loading through the utilization of reconnaissance data. Further, the study findings on deficiencies in the load paths of homes in hurricane-prone regions have practical value to risk assessments and future construction practices. [ABSTRACT FROM AUTHOR]

For building service and strength design under wind load, torsional moment and response (or torsional-wind load) is a main component. Several factors contribute to torsional-wind load, including asymmetric distribution of wind pressure on the building façade (aerodynamic source), dynamic torsional vibration, and the contribution of resonant components of along-wind and across-wind loads in presence of mass-stiffness eccentricity. In addition, adjacent building influence can be considerable. For low (1 or 2 stories) to midrise (less than 10 stories) buildings, the main component in torsional-wind load typically is aerodynamic source. For tall buildings, contribution due to all sources is significant. In this article, theoretical background and procedures to calculate torsional-wind load, with a focus on the concept of equivalent eccentricity and equivalent static wind load, are discussed. Then, procedures and perspectives in several international standards, including ASCE 7-22, Architectural Institute of Japan-recommendations for loads on buildings (AIJ-RLB-2015), Australian and New Zealand Standard (AS/NZS 1170.2-2011), Korean Design Standard (KDS 41-2019), and ISO 4354-2009, are introduced to clarify differing points of view and how components of torsional-wind load are included. Finally, the main parameters of each standard are compared with wind tunnel test results. The results confirm consistency between the wind tunnel test results and those based on the standards with consideration of their covered ranges. [ABSTRACT FROM AUTHOR]

Nonstructural damage to the cladding and façades systems caused by excessive wind pressure and debris impact is the primary damage to urban high/midrise buildings after hurricanes. This paper focuses on the assessment of damage to urban buildings envelopes due to windborne debris while leaving the wind pressure-induced damage outside the scope. The existing building envelope damage assessment models for urban high/mid-rise buildings often neglect the geometry of building clusters or simply assume a homogeneous configuration, which can introduce errors and uncertainties for urban building clusters with varying geometries and layouts. In this context, this paper proposes a new fragility modeling approach for urban buildings envelopes, which explicitly considers geometric configurations of urban buildings, to improve the accuracy of risk assessment for urban buildings. To develop such a fragility model, first, a physical model of debris impact on building envelopes is established, considering the configuration of the surrounding buildings. Then the fragility function is rigorously formulated by propagating the uncertainties from hurricane wind hazard, local urban wind field, the resistance of the envelope component, as well as debris size, location and generation. Reduced-order modeling and Monte Carlo simulation are employed to construct fragility surfaces. An illustrative example is presented to validate the proposed physical model of debris impact and demonstrate the implementation of the proposed fragility modeling approach. [ABSTRACT FROM AUTHOR]

This paper presents a case study of a realistic application and evaluation of a promising structural health monitoring approach that exploits some topological features of building-like structures to develop a reduced-order, reduced-complexity, not-necessarily-linear, substructure model. The approach not only reliably detects the occurrence of anomalous features that can reflect incipient damage and deterioration but also provides the locations of the structure's regions where a single or multiple changes have been detected. The target structure used in this study is a 52-story building in Los Angeles that is instrumented with a relatively dense sensor array and is being continuously monitored through the efforts of the community seismic network (CSN). Two qualitatively different system identification approaches (global and substructuring) are applied to the large data set of ambient acceleration measurements produced by a strong wind event ("Santa Ana winds") to identify the dominant modal characteristics of the building. The results are shown to match the corresponding results from a high-resolution computational model of the building based on a widely used structural analysis software package (ETABS) developed by Computers and Structures, Inc. The main contribution of this study is to demonstrate the practical feasibility of the proposed substructuring approach with a high-order system using both wind and low-amplitude ambient vibration measurements. The approach also assesses the accuracy and reliability of the estimates of the dominant modal features of the structure to subsequently provide a probabilistic measure of confidence in the extent and location of changes if an anomaly is detected. Due to the minimal computational resources needed to implement the proposed substructuring approach, it is efficient for near-real-time applications where important structures need to be continuously monitored for sustainability as well as resiliency requirements. The method is applicable to linear, nonlinear nonhysteretic, and hysteretic systems, with no restriction on the source of the signal for identification purposes. [ABSTRACT FROM AUTHOR]

To study the effects of the turbulence integral scale on the non-Gaussian properties and extreme wind loads of surface pressure, the surface pressures for two Commonwealth Advisory Aeronautical Research Council (CAARC) scaled models were measured in three turbulent flow fields with different turbulence integral scales. The results show that the surface pressure distribution on the windward surface is fundamentally Gaussian, while the surface pressures on the side and leeward surfaces are markedly non-Gaussian. The deviation from normality strongly depends on the ratio of the turbulence integral scale to the windward width (Lux/D). With changing Lux/D , the fluctuating pressure, skewness, kurtosis, probability density distribution, non-Gaussian peak factors, and extreme wind loads vary significantly. In addition, the surface pressure nonnormality becomes more evident for lower Lux/D wind fields, increasing Sk , Ku , and the fluctuating pressure's peak factor. In contrast, the fluctuating pressure decreases with decreasing wind-field Lux/D , resulting in the underestimation of extreme wind loads. Further, the extreme wind load maximal error margin reaches 30.7% when the simulated turbulence integral scale error margin is 70%, even for nonnormal surface pressures. Hence, nonnormality of the surface pressure and the effects of the turbulence integral scale should be carefully considered when estimating extreme wind loads for CAARC standard tall buildings using wind-tunnel tests. [ABSTRACT FROM AUTHOR]

The choice of spectral targets for ground motion selection has a strong impact on structural demands resulting from nonlinear time history analysis. In particular, the conditional mean spectrum (CMS) has been recognized as an appealing alternative to the uniform hazard spectrum (UHS) as a spectral target due to the former's more realistic shape and reduced conservatism. Using a tall building case study in a high-seismicity region, this paper evaluates the building demands generated by UHS- and CMS-based selection procedures. Theoretically rigorous implementation of CMS-based selection using 17 different conditioning periods is shown to reduce maximum considered earthquake (MCE)–level demands on the case study building by 9%–35% relative to UHS-based selection. Furthermore, the simplified CMS-based procedure in the building code with apt choice of only two conditioning periods is found to satisfactorily capture the demands generated by the theoretically rigorous approach. Findings also highlight the degree of sensitivity of CMS-based results to the choice of conditioning periods and to enforcement of lower bounds on spectral targets, such as 75% of the UHS. The presented analysis procedure can be replicated in future studies for explicit evaluation of simplified CMS ground motion selection in other structural systems or analysis cases. Since its introduction to the building code, the alternative, conditional mean spectrum-based method for ground motion selection has gained traction among practitioners due to its reduced conservatism relative to traditional selection methods. To simplify the implementation of conditional mean spectra in practice, the building code alternative method requires a minimum of only two target spectra be used, so long as their envelope satisfies a lower bound within a specified period range. However, there are few quantitative studies of the impacts of these simplifications on the resulting building demands. In this study, we demonstrate how building demands vary when a tall building in a high-seismicity region is analyzed using either a traditional or a conditional mean spectrum-based selection approach. We find that using two reasonable target spectra in accordance with the alternative method produces acceptable building demands as compared to the demands obtained from performing exhaustive nonlinear analysis with a large number of target spectra. Furthermore, we illustrate how different choices of conditional mean spectrum targets maximize different types of building demands (e.g., interstory drift, base shear, floor acceleration) and how some types of demands are more sensitive to this choice than others. This work provides a procedure for evaluating conditional mean spectrum-based ground motion selection that can be replicated in the future for other buildings or structural systems. [ABSTRACT FROM AUTHOR]

Tornadoes result in death and property loss in communities around the world. To quantify the actions of tornadoes on civil structures, researchers have built physical laboratory tornado simulators to simulate tornadoes in the lab environment and tested building models in the simulated tornadic wind field, which is similar to wind tunnel testing when quantifying the wind effects induced by straight-line winds. Unfortunately, physical tornado simulators are much less common than straight-line wind tunnels, leading to the lack of research on bluff-body aerodynamics on civil structures under tornadic winds. Considering that it is expensive to conduct experimental testing in physical tornado simulators, numerical models of physical tornado simulator has been developed using computational fluid dynamics (CFD) simulations. However, they have not been validated at the level of pressure distribution on the structural surface of the testing model. In this study, the numerical model developed for the large-scale tornado simulator of the Missouri University of Science and Technology (Missouri S&T), which is based on the numerical simulation of the entire process of the physical testing in tornado simulator, will be validated by the measured data on the building model tested in the physical tornado simulator. Then, through the validated numerical simulation model, the bluff-body aerodynamics of buildings under tornadic winds will be revealed. To be specific, CFD simulation is first applied to model the entire process of experimental testing of a low-rise building model in the physical tornado simulator. Then, the obtained results are compared with laboratory-measured data to evaluate the effects of the building model on the wind field and the surface pressure on the building model. Then, the bluff-body aerodynamics on low-rise buildings under tornadic winds will be revealed based on the data obtained from numerical simulations using the relationship between streamline pattern change and velocity magnitude change (mass continuity theorem) and using the relationship between the velocity magnitude change and the pressure change (Bernoulli's theorem), as well as the flow separation and vortex shedding. [ABSTRACT FROM AUTHOR]

The development of structural systems is a constantly evolving process to guarantee safety and serviceability against natural hazards. As a result, diagrid structural systems became a current trend in tubular mid- and high-rise building structures for their significant lateral stiffness and aesthetic potential. Their unique geometric configuration allows the efficient distribution of internal forces that lead to optimal structural designs. However, existing design codes and provisions do not provide specific guidelines for their design under earthquake and wind loading. For this reason, this paper studies the properties of steel diagrid structures, including optimal diagrid angle, diagrid density, and fundamental period, as a function of geometric parameters. This study uses a large set of structural models with aspect ratios (H/B) from 1 to 4, diagrid angles (θ) between 45° and 90°, and diagrid densities (ρd) between 3 and 12. The structural design of each model is obtained using a soft-computing optimization algorithm, denominated hybrid counter propagation neural dynamic (CPND) model, that determines member sizes from a database of commercially available W-shapes following ASCE 7-16 standard and AISC-15 steel construction manual. This investigation confirms that the optimal diagrid angle increases with height, highlights the importance of diagrid density in structural design, and demonstrates the effect of the diagrid angle on the fundamental period. A new set of equations are proposed for: (1) the optimal diagrid angle as a function of height, and (2) the fundamental period of diagrid structures as a function of angle and height. The proposed equations allow the estimation of structural properties for the design of steel diagrid structures. [ABSTRACT FROM AUTHOR]

Flexible civil structures are prone to aerodynamic instabilities, such as long-span bridges and high-rise buildings, and wind-induced vibration is harmful to structural life-span and users' comfort. To address this issue, this study proposes a new aerodynamic countermeasure that is designed to improve the structural aerodynamic performance, i.e., adding a strip seam cover device (SSCD) on the surface of a structure, and the influence of the device on the aerostatic performance of the main structure is presented. Taking the box girder of long-span bridges, for example, the effectiveness and influence factors of the proposed device are investigated in detail. First, the proposed device is introduced and three aerostatic force coefficients are selected as the evaluation indices for the SSCD's effectiveness. Second, the typical streamlined box-girder sectional model of bridges with and without the additional device is compared respectively based on the two-dimensional (2D) computational fluid dynamics (CFD) simulation technique. Results show the bridge girder's pitch moment coefficients can be decreased efficiently. In addition, influences of gap distance (i.e., 30 cm, 60 cm, 90 cm, and 120 cm) between the device and the bridge girder, effective width (i.e., 50 cm, 60 cm, 90 cm, and 180 cm), and void ratio (i.e., 1∶5 , 1∶3 , 1∶2 , 1∶1 , 2∶1 , and 5∶1) of seams are investigated based on wind tunnel tests. Results of the same cases based on the experiment and CFD simulation are very close, showing the accuracy of the simulation and experiment. Experimental results show that the gap distance is recommended to be 60 to 90 cm, the effective width is 90 cm, and the void ratio is recommended to be a value larger than 1∶1. In this case, the pitch moment value and the slope of the curve for the pitch moment coefficient versus wind attack angle are efficiently reduced, which is beneficial for improving the critical wind speed of aerostatic torsional divergence and aerostatic stability. The proposed device can be used to improve the aerostatic and aerodynamic performances of buildings, bridges, and some other structures; moreover, its potential application in the control of vortex-induced vibration is found preliminarily, which will be reported in further study. [ABSTRACT FROM AUTHOR]

This study assesses the wind load provisions for low-rise buildings with Chapters 27 and 28 in ASCE 7-16 and analyzes the dependence of the aerodynamics on the building geometric parameters. A systematic analysis of an aerodynamic database was used for this purpose. The mean and gust-factored uplift, base shear, and area-averaged wall pressure coefficients acting on the building surfaces comprise the main focus of this work. The results indicate that Chapter 27 captures the increasing tendency of roof uplift coefficients with larger roof heights reasonably well. The base shear obtained from the database is observed to vary with roof height, but conflicts with the design wind loads of ASCE 7-16. The ratio of roof height, H , to the horizontal plan dimension parallel to wind direction, L , is the critical nondimensional geometric parameter to model the uplift, leeward wall, and side wall pressure trends for low-rise buildings. It is also observed that the uplift can be used as a predictor of the side wall pressure coefficients for low-rise buildings. The Chapter 28 provisions conservatively envelop the data for relatively low buildings, but underestimate the wind loads for H/L>0.5. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the effects of building geometry on tall-building aerodynamics, accompanying the analysis for low-rise buildings found in the companion paper. Aerodynamic data for total of 30 rectangular-plan buildings were obtained in wind tunnel experiments. This work tested building configurations with plan aspect ratios, L/B (where L is the horizontal dimension parallel to the wind and B is the across-wind dimension) ranging from 0.25 to 4 and height ratios, H/W (where H is roof height and W is the least horizontal dimension) ranging from 1 to 12. Additionally, this work made systematical comparisons with wind load provisions in Chapter 27 of ASCE 7-16. Buildings with ratios of H/W>∼4 have aerodynamic coefficients that are approximately constant, which means that this can be a practical aerodynamic definition of high-rise buildings. There is continuous variation of the aerodynamic coefficients for H/W<4 such that differentiation of mid-rise and low-rise buildings may be considered as arbitrary from an aerodynamics perspective. Wind load coefficients for mid-rise buildings are observed to be lower than for high-rise buildings. However, for both mid-rise and high-rise buildings, largest load coefficients are observed for L/B∼0.67. The plan ratio of L/B captures the variation of the load coefficients for high-rise buildings. For lower buildings, both L/B and H/W ratios are needed to define the wind loads. [ABSTRACT FROM AUTHOR]

Pinnacles on top of tall buildings are vulnerable to vortex-induced vibrations (VIVs). These structures may undergo large-amplitude vibrations that can lead to fatigue damage accumulation. To assess the performance of buildings and its appendages, numerous structural health monitoring (SHM) programs have been installed on tall buildings. This continuous monitoring generates more than 1 trillion data points per year per building. Also, on many occasions, the data generated by SHM programs contain missing observations. The evaluation of fatigue life using conventional methods becomes an impossible task in this case. This paper introduces the use of machine-learning techniques as a potential solution to deal with the burgeoning data generated by tall building monitoring systems. In particular, the present study involves the evaluation of the crosswind fatigue life of the pinnacle of Burj Khalifa subject to VIVs using cluster analysis. This unsupervised machine-learning technique is used to develop a generalized framework robust to missing data to effectively identify and extract VIVs from a large pool of other responses recorded by the monitoring system. The data generated from 2010 to 2014 by the SmartSync monitoring system installed on Burj Khalifa are utilized for this study. The proposed framework is validated using a wind tunnel dataset of a bridge sectional model undergoing VIVs. The VIVs extracted from the SmartSync system through cluster analysis are used to evaluate the crosswind fatigue damage of the pinnacle of Burj Khalifa using conventional closed-form approximations. The proposed cluster analysis framework uses a step-by-step data-driven decision-making approach, thus widening the applicability of the method to other SHM programs. [ABSTRACT FROM AUTHOR]

Cold-formed steel lipped channel beams (LCBs) are used extensively in residential, industrial, and commercial buildings as loadbearing structural elements. Their shear capacities are considerably reduced when the web openings are included for the purpose of locating building services. Past research has shown that the shear capacities of LCBs were reduced by up to 70% due to the inclusion of these web openings. Hence there is a need to improve the shear capacities of LCBs with web openings. A cost-effective way of eliminating the detrimental effects of large web openings is to attach suitable stiffeners around the web openings and restore the original shear strength and stiffness of LCBs. Hence detailed experimental studies were undertaken to investigate the behavior and strength of LCBs with stiffened web openings subject to shear, and combined bending and shear actions. Both plate and stud stiffeners, with varying sizes and thicknesses, were attached to the web elements of LCBs using different screw-fastening arrangements. Simply supported test specimens of LCBs with aspect ratios of 1.0 and 1.5 were loaded at midspan until failure. Numerical studies were also undertaken to investigate the strength of LCBs with stiffened web openings. Finite-element models of LCBs with stiffened web openings under shear, and combined bending and shear actions, were developed to simulate the behavior of the tested LCBs. The developed models were then validated by comparing their results with experimental results and were used in further studies. Both experimental and finite-element analysis results showed that the stiffening arrangements recommended by past research and available design guidelines are not adequate to restore the original shear strengths of LCBs. Therefore, new stiffener arrangements were proposed based on screw fastened plate stiffeners. The details of the research reported in this paper are presented. [ABSTRACT FROM AUTHOR]

Despite much experience that low-rise wood buildings are vulnerable to damage by extreme wind events, few such structures have been tested in fullsize to understand how they respond to wind loads as a whole system. This paper presents a study that measured internal force flows throughout the framing of a typical North American single-story structure with platform construction. Applied forces were concentrated horizontal loads normal to walls and patches of gravity loads on the sloped roof. Two series of load cells were embedded into the system, between the roof trusses and supporting walls and between the floor platform and the foundation. It was observed that even localized external forces have effects that propagate through the entire system. For instance, horizontal loads applied near eave level or to the roof were reacted at the top of the foundation around the entire wall perimeter of the building footprint, both parallel and transverse to the applied loading. For vertical loads, measurements showed that systemic effects dominate the response. Observed three-dimensional behavior stems from the relatively stiff interconnection of roof, wall, and floor platform substructures. [ABSTRACT FROM AUTHOR]

Square lighting poles with sharp or round corners have been observed to exhibit large amplitude oscillations with a frequency that is near that of their first mode. This frequency is one order of magnitude lower than that of the vortex shedding frequency for the observed wind speeds. As such, lock-in resonance between the vortex shedding and the poles motions has been ruled out as the cause of these oscillations. In this work, numerical simulations of flows over square cylinders with different aspect ratios and cross-sectional shapes have been carried out to explore and quantify low-frequency variations of the aerodynamic forces and their sources. The results show that low-frequency components are a basic aspect of the flow over finite length cylinders and are associated with the three-dimensional flow characteristics near the free end of the cylinder. This aspect is related to the loss of synchronization of the vortex shedding which, in turn, results in variations of the mean drag coefficient along the cylinder. This ability to numerically simulate the flow over a lighting pole and detailed results, as presented here, could be used to overcome wind tunnel test limitations imposed by the size of the test section and blockage ratio, and of meeting geometric similarity requirements for high aspect ratio configurations. Consequently, results from such simulations could play an important role in improving code specifications which, to date, have been based on wind tunnel simulations. [ABSTRACT FROM AUTHOR]

The article focuses on efforts to formalize performance-based design (PBD) in wooden structures. It states that according to the National Association of Home Builders, the average U.S. home was around 2,300 square feet, which made the cost of performing a PBD more costly than standard prescriptive designs. It comments on PBD for seismic regions, wind hazards, snow hazards, flood hazards, and durability.

The consistency of measurements in various wind tunnels is of concern to designers and code writers. This study attempts to quantify the variability of wind effects estimates based on tests conducted at six wind tunnel laboratories. Pressure tap measurements were made on wind tunnel models of four buildings. Comparisons were made between estimated 50th percenttiles of (1) peak positive moments in a frame section near the knee joint and (2) peak pressure coefficients of a roof tap nearest a building corner. Modeling of suburban terrain contributes significantly to the variability. Other factors are eave height, wind direction, and frame location within the building. Coefficients of variation were about 10–40%. A subsequent phase of this research entails a detailed analysis of the reasons for the variabilities. The results could help future improvement of wind load factors that account for all relevant uncertainties in the estimation of wind effects and efforts to improve and standardize wind tunnel simulations. [ABSTRACT FROM AUTHOR]

Database-assisted design (DAD) is becoming a realistic possibility whereby archived wind pressure time series on building envelopes from wind tunnel experiments are directly used in structural analysis software for building design. In order for DAD to be of practical use, a data handling system is required. The main task of the system is to perform interpolation in order to obtain wind pressure time series beyond the basic configurations available in the database. The functional dependence of the pressure coefficients is reduced to geometric variables only, greatly simplifying the process of interpolation. It is shown that all interpolation schemes require estimation of the first and second order statistical moments. [ABSTRACT FROM AUTHOR]

In current design practice, spatiotemporally varying wind loads on buildings are modeled as equivalent static wind loads. This loading description serves as pivotal information for estimating response under the combined action of wind and other loads. This paper presents a framework for evaluating the equivalent static wind load for any given peak response of buildings with uncoupled responses in the three primary directions. A new description of the background loading based on the gust loading envelope/peak dynamic loading is presented. The resonant loading is expressed in terms of the inertial load following the respective fundamental structural mode. The equivalent static wind loading for the total peak response is then expressed as a linear combination of the background and resonant components. Following this framework, closed-form formulations using an analytical wind loading model are presented. The gust response factors and the equivalent static wind loads for various alongwind response components at different building elevations are discussed in detail highlighting the advantages of the proposed equivalent static loading. The potential high-frequency force balance technique for ascertaining the equivalent static loading on buildings is also revisited. A commentary is presented to highlight the role of mode shape correction, uncertainty in the modeling of wind loads, and contributions of higher modes to background response. [ABSTRACT FROM AUTHOR]

Parts II. Presents information on a study which developed a procedure to simulate the wind pressure time series on prismatic tall buildings. Simulation procedure; Experimental data; Simulation of local pressure; Simulation of cross-correlated wind pressure; Conclusions.

Details a procedure for the design of controllers for tall buildings under wind loads. Analysis and design of controllers to mitigate the effects of natural phenomenon; Solution to constrained optimization problem; Planar frame model with accelerated constraint; Planar frame model with tighter acceleration constraint; Tall building model with acceleration constraint.

Comments on issues related to wind-load models in structural engineering. Framework for evaluating the equivalent static wind load for any peak response component with uncoupled responses; Discussion on the role of mode-shape correction, uncertainty in wind-load modeling and the contributions of higher modes to background response; Demonstration on the advantages of the modified procedure over the original Iterative Group Implicit algorithm.

Mean recurrence intervals (MRIs) of wind effects for the strength design (SD) of flexible buildings by the wind-tunnel method are based on estimates of total uncertainties that do not account for uncertainties in the dynamic parameters. This paper presents a procedure for assessing this practice. The procedure accounts for the probability distributions of total uncertainties in basic wind effects corresponding to MRIs of 50 or 100 years. The total uncertainties are estimated for two cases. For Case 1, only uncertainties in the wind loading are taken into account. For Case 2, uncertainties in both the wind loading and the dynamic parameters are considered. Cumulative distribution functions (CDFs) of the total uncertainties in the basic wind effects are determined by Monte Carlo simulation. To assure risk consistency, the MRIs of wind effects considered for SD correspond in both cases to the same upper confidence bound of the basic wind effects. For a 305-m-tall symmetrical steel building, the requisite MRIs are larger for Case 2 than for Case 1 by at most 80%. These increases corresponded to wind effects considered for SD larger for Case 2 than for Case 1 by at most 6%. [ABSTRACT FROM AUTHOR]