Academic literature on the topic 'Wind drift serviceability'

The design of lateral load resisting elements of tall buildings in regions of low to moderate seismicity is normally governed by the requirements to meet inter-storey drift limit under wind load. The key objective of the design of tall buildings is to provide adequate lateral stiffness to the buildings to limit their lateral deflections and inter-storey drifts under the lateral load. The current design practice assumes that only the structural skeleton provides lateral resistance against wind load. Although the effects of nonstructural elements on the lateral stiffness are widely acknowledged, the effects are often ignored in the analysis of the buildings. This paper presents a state-of-the-art of review on the effects of nonstructural elements on the lateral deflections and inter-storey drifts of buildings at serviceability limit states. It was found that ignoring the nonstructural elements could significantly underestimate the lateral deflection for certain types of buildings. However, the shape and form of the lateral deflection in the overall building is not significantly affected by the nonstructural elements.

In the past few decades, high-rise buildings have received a renewed interest in many city business locations, where land is scarce, as per their economics, sustainability, and other benefits. Taller and taller towers are being built everywhere in the world. However, the increased frequency of multihazard disasters makes it challenging to balance between a resilient and sustainable construction. Accordingly, it is essential to understand the behavior of such structures under multihazard loadings, in order to apply such knowledge to design. The results obtained from the dynamic analysis of two different high-rise buildings (54-story and 76-story buildings) investigated in the current study indicate that earthquake loads excite higher modes that produce lower interstory drift, compared to wind loads, but higher accelerations that occur for a shorter time. Wind-induced accelerations may have comfort and serviceability concerns, while excessive interstory drifts can cause security issues. The results also show that high-rise and slender buildings designed for wind may be safe under moderate earthquake loads, regarding the main force resisting system. Nevertheless, nonstructural components may present a significant percentage of loss exposure of buildings to earthquakes due to higher floor acceleration. Consequently, appropriate damping/control techniques for tall buildings are recommended for mitigation under multihazard.

In regions of low to moderate seismicity, serviceability limits states such as inter-story drift under wind load govern the design of the lateral load resisting structural systems of high rise buildings. The key objective in this regard is to provide adequate lateral stiffness to control lateral deflections and inter-story drifts. Current design practice assumes that the structural system alone provides lateral resistance against wind, the dominant load considered for countries like Australia. The contribution of nonstructural components (NSCs) such as interior partition walls on lateral stiffness is generally disregarded in the analysis of the buildings, even though it is commonly acknowledged that the NSCs play a significant role on the lateral stiffness of buildings. This technical note presents the results of a parametric study on the effects of NSCs, in particular, the effects of masonry interior partition walls on the fundamental period of buildings. The parameters considered in this study include: the number and length of walls, their material properties, the number of parallel moment resisting frames and the height of buildings. The results of this study indicate that interior walls can have significant effects on the lateral stiffness of buildings.

While designing metal buildings for wind drift, for simplicity of analysis and design, connection at base of column is considered as pinned which provides no rotational restraint. The actual behavior of the connection however, is partially rigid, that provides some rotational stiffness even in case of single row of bolts. Moreover, using a two-dimensional (planar) structural model for analysis ignores any load distribution provided by roof and wall sheeting. Simulation of true behavior of base connection and diaphragm stiffness can substantially reduce drift caused due to lateral forces thereby lessening the conservatism in traditional design practices. This thesis provides results obtained from full-scale experimental testing and analytical study for a metal building.

A full scale load test was conducted to quantify the lateral stiffness of an existing metal building. A static lateral load, consistent in magnitude with the buildingâ s design wind pressure, was applied to the knee of a primary frame, and the resulting lateral displacements and column-base rotations for all primary frames were measured. The test procedure was repeated at several locations. The experimentally obtained results were then validated using two-dimensional and three-dimensional analytical models. The three-dimensional models explicitly simulated the primary and secondary framing, roof and wall diaphragms, and column-base stiffness. A couple of approaches have been proposed to model column-base plate connection varying in complexity and accuracy. Once validated, the FE model is utilized to quantify the relative stiffness contributions of the metal building system components to lateral drift.

While performing analysis some other parameters were also studied. These consisted of effect of base plate thickness and length of anchor bolts on column-base rigidity. Also, effect of including shear deformations and considering the haunch (column-rafter junction) as rigid were studied. Another small but important part of the paper is comparison of wind pressures obtained using different procedure of ASCE 7-05 with database assisted design pressures. Once these parameters are quantified practical engineering guidelines are developed to incorporate the influence of secondary framing, roof diaphragms, wall cladding, and column-base stiffness and wind loads in metal building design.
Master of Science

The design of steel framed buildings must take into consideration the lateral drift of the structure due to wind loading and any serviceability issues that may arise from this lateral movement. This thesis focuses on one of these issues, damage to nonstructural components.

Although there are no specific requirements in the United States governing the effects of wind drift, it is an important issue which may significantly impact the buildings structural performance and economy. Furthermore, because these serviceability issues are not codified, there is a wide variation among design firms in how they are dealt with, leading to a greater economic disparity.

This thesis begins with a comprehensive review of the literature that covers all pertinent aspects of wind drift in steel framed buildings. Next an analytical study of the variations in modeling parameters is performed to demonstrate how simple assumptions can affect the overall buildings stiffness and lateral displacements. A study is then carried out to illustrate the different sources of elastic deformation in a variety of laterally loaded steel frames. The different modeling variables demonstrate how deformation sources vary with bay width, the number of bays and the number of stories, providing a useful set of comparisons.

To ascertain how serviceability issues are dealt with from firm to firm, a survey of the practice is developed to update the one conducted in 1988 (ASCE). In effect, the thesis is presented with the intention of suggesting and establishing a comprehensive, performance based approach to the wind drift design of steel framed buildings.

Master of Science

This thesis is divided into two topics: the development of a procedure for wind serviceability design of steel buildings and the development of a simple linear response history analysis for building codes. In the United States the building codes are generally silent on the issue of serviceability. This has led to a wide variation in design practices related to service level wind loads. Chapter 2 of this thesis contains a literature review which discusses pertinent aspects of wind drift serviceability, including selecting the mean recurrence interval (MRI), mathematical modeling of the structure, and establishment of rational deformation limits. Chapter 3 contains a journal article submitted to Engineering Journal which describes the recommended procedure for damage based wind serviceability design of steel structures. The procedure uses a broad range of MRIs, bases damage measurement on shear strains, includes all sources of deformation in the model, and bases deformation limits on fragility curves. Chapter 4 of this thesis contains a literature review which examines issues related to performing linear response history analysis. Chapter 5 contains a conference paper submitted to the Tenth U.S. National Conference on Earthquake Engineering which serves as a position paper promoting the inclusion of a linear response history analysis procedure in future editions of the NEHRP Recommended Seismic Provisions and ASCE 7. The procedure address the following issues: selection and scaling of ground motions, the use of spectral matched ground motions, design for dependent actions, and the scaling of responses with the response modification coefficient (R) and the deflection amplification factor (Cd).
Master of Science

Structural control systems, including passive, semi-active and active damping systems, are used to increase structural resilience to multi-hazard excitations. While semi-active and active damping systems have been investigated for the mitigation of multi-hazard excitations, their requirement for real-time controllers and power availability limit their usefulness. This work proposes the use of a newly developed passive variable friction device for the mitigation of multi-hazard events. This passive variable friction device, when installed in a structure, is capable of mitigating different hazards from wind and ground motions. In wind events, the device ensures serviceability, while during earthquake events, the device reduces the building’s inter-story drift to maintain strength-based motion requirements. Results show that the passive variable friction device performs better than a traditional friction damper during a seismic event while not compromising any performance during wind events.