Low-rise Commercial Buildings Research Articles

Progressive collapse fragility of substandard and earthquake-resistant precast RC buildings

Several natural and man-made disasters have highlighted that precast reinforced concrete (RC) buildings often have insufficient levels of structural robustness, which is the last line of defence under extreme events. Even though robustness studies were originated by the progressive collapse of the Ronan Point precast RC building in 1968, such a structural feature of disaster resilience has been partially investigated in case of precast RC buildings to date. In this study, a precast RC frame structure representative of low-rise commercial buildings is analysed under different column loss scenarios, which can produce the partial or total collapse of the structural system. Two building classes are considered, namely, buildings designed only to gravity loads and buildings designed for earthquake resistance. Structural robustness is probabilistically assessed through a fragility analysis procedure, using three-dimensional fibre-based finite element models with nonlinear links simulating connections, large-displacement incremental dynamic analysis, and multiple performance limit states for damage assessment. The output of the study is threefold: (i) a detailed assessment of the effects of column loss on precast RC frame buildings, quantifying the major role of structural detailing and beam-column connections; (ii) a fragility-informed evaluation of beneficial effects of seismic detailing on structural robustness, which can drive designers in retrofitting of existing precast RC buildings and decision-makers towards prioritization-related issues; and (iii) the generation of typological fragility curves for progressive collapse risk assessment in both single- and multi-hazard environments. Progressive collapse fragility curves can be convolved with more classical fragility models describing the failure of single components (under, e.g., flow-type landslide impact, vehicle collision or blast) and hazard, to assess systemic structural risk.

Optimized design of low-rise commercial buildings under various climates – Energy performance and passive cooling strategies

The design of low-rise commercial building envelopes is mainly driven by functional large volumes, and low-cost and lightweight materials that often present weak thermal performances. Thermal and visual comfort is a key parameter for these buildings' purpose, but poor envelope designs have significant consequences on the high-energy demand for HVAC and artificial lighting systems. Considering the resources outside the building envelope for both cooling and heating seasons, this study aims to optimize the building design under various climates. Energy for ventilation, heating and lighting, and summer thermal discomfort are mitigated considering natural resources such as solar energy, low sky temperatures, ground inertia, and ambient air. For this specific building typology, main thermal fluxes are transmitted through large surfaces of soil (to the ground) and roof (to the environment). In the study, we found that summer thermal discomfort can be minimized, and near zero for some climates, without active cooling system. This objective is balanced by the energy demand objective; a multiobjective optimization using the NSGA-II algorithm gave optimal solutions according to local climate and global warming effects. This methodology and numerical results presented here can be helpful to design new commercial buildings and improve energy efficiency of existing ones. Most adapted set of design parameters for passive cooling solutions such as cool roofs and night natural ventilation are mapped for various climate, including climate change effects.

Network Performance of Contention Window in VANET

In this paper, we tried to presented the effect of different contention window (CW) size in a realistic road environment with mobility management and different propagation loss model was implemented in ns-3. We focus on the WAVE module of ns-3. Our contribution is to create a realistic two-lane both way highway road environment surrounding by fields, low-rise commercial buildings, street lamps and road signs for vehicular safety messages are Cooperative Awareness Message (CAM) and Decentralized Event Notification Message (DENM). Medium to low traffic density. On the other section, we describe in detail the simulation setup scenario during the implementation. Finally, we present our simulation results that we obtained from the highway scenario.

Network Performance of Contention Window in VANET

In this paper, we tried to presented the effect of different contention window (CW) size in a realistic road environment with mobility management and different propagation loss model was implemented in ns-3. We focus on the WAVE module of ns-3. Our contribution is to create a realistic two-lane both way highway road environment surrounding by fields, low-rise commercial buildings, street lamps and road signs for vehicular safety messages are Cooperative Awareness Message (CAM) and Decentralized Event Notification Message (DENM). Medium to low traffic density. On the other section, we describe in detail the simulation setup scenario during the implementation. Finally, we present our simulation results that we obtained from the highway scenario.

Naturally comfortable and sustainable: Informed design guidance and performance labeling for passive commercial buildings in hot climates

This work develops guidance and tools to understand the performance, improve the design, and simplify the evaluation of naturally ventilated low-rise commercial buildings in warm and hot climates. We conducted ∼50,000 detailed energy and airflow simulations in 427 locations across Brazil, varying 55 parameters representing building morphology, fenestration, construction properties, internal gains, operating times, wind modifiers, flowpaths, window control, and soil traits. Comfort performance was quantified by the average annual fraction of occupied hours that exceeded the upper limit of an adaptive comfort zone, and investigated with sensitivity analysis and machine learning methods. Results indicated that, after climate, building size (both footprint area and number of stories) and internal gains were most influential and were positively associated with discomfort. Adding air movement with ceiling fans and providing for night ventilation both proved highly effective comfort interventions. Except for roof solar absorptance, opaque envelope changes, including increasing insulation or thermal mass, had only marginal impacts. A support vector regression metamodel, requiring 29 easily obtainable inputs plus a weather file, was fit to the simulation results and successfully validated (R2=0.97). The metamodel was developed as a simplified compliance path for naturally ventilated buildings to enhance Brazil’s commercial building performance labeling program, which, because it currently provides such a path only for air conditioned buildings, may discouraging decision-makers from considering even more efficient passive solutions. We use a case study to show how the metamodel, which we will distribute publicly, can also serve as a design tool, and demonstrate that modifying a small set of parameters can drastically improve thermal performance and achieve sustainable comfort in hot and warm climates.

Soy-based polyurethane spray foam insulations for light weight wall panels and their performances under monotonic and static cyclic shear forces

This work was dedicated to the investigation of the strengthening effects of soy-based rigid polyurethane (PU) foam cores, neat and composite foams containing wood fiber, on the performance of small-scale wooden wall panels under monotonic and static cyclic shear loads. Adding wood fiber resulted in a reduction in the density (23%) and compressive strength (63%) of the foam while specific tensile modulus, ratio of tensile modulus to density of foam, increased about 39%. Both monotonic and static cyclic shear tests showed that inclusion of the composite foam core increased the maximum strength of panels significantly. Panels containing composite foam cores had an average shear strength of 12.0kN compared to 10.7kN and 8.0kN for panels with neat foam and empty panels, respectively. The results of this research demonstrated for the first time that, in addition to their thermal insulation capabilities, soy-based rigid PU foams significantly contribute to the shear strength of wooden wall panels. This characteristic is important especially in the construction of residential and low-rise commercial buildings.

Shear resistance of cold-formed steel framed shear walls with 0.686 mm, 0.762 mm, and 0.838 mm steel sheet sheathing

The cold-formed steel (CFS) framed shear walls using steel sheet sheathing is a code approved lateral force resisting system in residential and low-rise commercial buildings in the United States. The current design specifications in the US provide nominal shear strength for a limited range of CFS shear wall configurations in terms of sheathing thickness and wall aspect ratio. This paper presents a research project aimed to add shear strength values for 0.686 mm, 0.762 mm, and 0.838 mm steel sheet sheathed CFS shear walls with aspect ratios of 2:1 or 4:1. The project consisted of two series of tests. The first series was monotonic tests for determining the nominal shear strength for wind loads. The second series was the cyclic tests using CUREE protocol to obtain the shear strength for seismic loads. The studied shear walls used 0.838 mm or 1.092 mm thick CFS framing members. The sheathing was only attached to one side of the frame. No. 8 modified truss head self-drilling screws were used for all the test specimens. This paper details the testing methods, specimen configurations, and the test results.

Innovative testing facility to mitigate hurricane‐induced losses

The growth of hurricane‐induced losses from US$1.3 billion per year before 1990 to US$36 billion per year after 2000 [National Science Board, 2007] is a direct result of over 50 years of accumulated socioeconomic decisions to invest in physical infrastructure and community development along coastlines. Fifty percent of the U.S. population now lives within 80 kilometers of a coast [National Academy of Sciences, 1999]. With hurricane losses surpassing the US$100 billion mark in 2005 (http://www.nws.noaa.gov/om/hazstats.shtml) and over 1400 fatalities in 2004–2005 [Government Accountability Office, 2006], it is hard to identify any other societal need or engineering problem that is as challenging, recurring, and multi disciplinary or with as far‐reaching impacts as hurricanes.The devastation brought by recent hurricanes that have struck U.S. coastal states demonstrates the need for mitigation tools that can significantly reduce losses. A current research initiative by the International Hurricane Research Center (IHRC) at Florida International University (FIU) will allow for the first time full‐scale testing of the impact of hurricane‐force winds, wind‐driven rain, and flying debris on houses and low rise commercial buildings. The Wall of Wind testing facility, an innovative research capability developed by an IHRC research team, is the first major initiative to operate a full scale facility dedicated to hurricane damage mitigation [Leatherman et al., 2007].

Wind Damage Observations and Implications

Literature containing observations of windstorm damage to buildings is condensed into descriptions of failure modes exhibited by several common building types. Failure modes are reviewed and building types that constitute the largest contributor in windstorm damage costs are identified. Buildings that receive some engineering attention but are constructed largely in a traditional and routine fashion (e.g. low-rise commercial buildings) are especially susceptible to wind-induced damage, and contribute to large economic losses through damage to inventory and loss of business. Wind and earthquake caused damages are compared, and observations regarding damage dissimilarities are examined.