Wall Wind Research Articles

Use of three-dimensional acellular collagen matrix in deep or tunnelling diabetic foot ulcers: a retrospective case series.

While most xenograft wound matrices are flat sheets not designed for deep or tunnelling wounds, three-dimensional acellular collagen matrices (3D-ACM) can fill deep wound beds and enable full wound wall apposition. This case series examines the use of 3D-ACM in treating diabetic foot ulcers (DFUs) that are deep, tunnelling, undermining, or irregularly shaped. We report outcomes of cases where 3D-ACM was applied to deep or tunnelling DFUs present for at least four weeks. In this retrospective case series, 3D-ACM was applied, healing was monitored and measurements were collected. Additional 3D-ACM was applied as needed. In total, 11 patients with 13 wounds were treated. Improved wound appearance and reduced size were observed at most follow-ups. Mean initial wound depth was 1.6cm, and several wounds showed significant depth reductions shortly after therapy initiation. In total, 62% of wounds (8/13) reached 50% closure by four weeks. Additionally, 54% (7/13) were fully closed by 12 weeks. The remaining 46% (6/13) took between 12-22.3 weeks to heal. Overall mean therapy time was 13.1 weeks (range: 2.0-22.3 weeks). Deeper wounds generally took longer to close. The findings of this case series showed that 3D-ACM could offer a protective microenvironment for wound management for deep or tunnelling DFUs. While some took >12 weeks to close, this may be attributable to large initial depths and volumes, rather than a failure to respond to the treatment modality. Other wounds that require a conforming 3D matrix, enabling full wound wall apposition, may benefit from 3D-ACM. Further investigations would be beneficial to understand the capabilities of this treatment modality.

Wind loading on commercial roof edge metals: A full-scale experimental study

Roof edge metal systems provide an effective interface between the roof of a building to its walls and are used to secure and protect the edge of the roof membrane. Previous studies show that damage involving roof systems mostly occurs because of their failure at perimeter edges under high winds. This study presents an effort to evaluate wind loads on these edge metal elements by conducting full-scale experiments at the NHERI Wall of Wind (WOW) Experimental Facility (EF) at Florida International University. In addition to full-scale aerodynamic and failure assessment test protocols, the experimental campaign, for the first time to the authors’ knowledge, consisted of investigating the effect of wind-induced vibrations on these dynamically sensitive systems. Pressure measurements were conducted at different layers of the edge metals systems by considering the most common installation practices in the industry. The results showed that these roofing elements experience high suctions due to near-parallel wind flows and are susceptible to significant vibration even at low wind speeds, which is a phenomenon not captured in current static pull testing. Moreover, peak pressure coefficients were also observed to increase with wind speeds due to increased dynamic contributions which may amplify the aerodynamic loads by more than about 25%. Furthermore, utilization of edge metal configurations with a higher degree of flexibility was observed to possibly reduce suction on roofing components and appurtenances.

Codification of wind loads on hip roof overhangs of low-rise buildings

Recent funding opportunities for Wind Engineering research have generated a significant amount of knowledge that has the potential to both develop new or enhance existing wind standards and building codes of practice. Building codes tend to get more rigorous over time to better mitigate damage on buildings and structures. Roof overhangs which are an integral part of the roofing system in low-rise buildings, is particularly vulnerable to damage in wind events due to its exposure to wind-induced loads on both upper and lower surfaces. Large scale wind tunnel testing was carried out at the Wall of Wind (WOW) Research Experimental Facility to investigate the wind-induced loads on roof overhangs of low-rise residential buildings. The physical testing protocol included six 1:10 scaled models with varying geometrical parameters such as roof slope and roof overhang width. Peak wind pressures on both the upper and lower surfaces were measured to calculate the simultaneous net pressure coefficients along the overhangs. Area-averaged pressure analysis was carried out to investigate the pressure gradients on single or groups of taps on the overhangs, soffits, and walls. The experimentally derived area averaged GCp values were compared to previous and current versions of wind standards to evaluate their adequacy. The findings revealed that the provisions’ design guidelines are less conservative for some roofing and wall zones, which justified the need for a codification study that can provide enhanced design guidelines for overhangs and adjacent walls. A detailed discussion of the codified design guidelines, which are formed based on statistical determination rather than the enveloped procedures as commonly used, is presented in this paper.

Large-Scale Wind Testing on Roof Overhangs for a Low-Rise Building

Roof overhangs are prone to wind damage because they are subject to wind load at both the upper and bottom surfaces. Wind standards assume that the pressure at the bottom covering of a roof overhang will be the same as the external pressure coefficient on the adjacent wall surface. A large-scale experimental campaign was carried out at the Wall of Wind (WOW) Research Experimental Facility to investigate the validity and possible limitations of such assumptions. The experimental setup considered two 1:10 scaled models [0.61 m (2 ft) and 1.83 m (6 ft) inclined overhangs with a soffit] of a low-rise hip roof building with roof slope 4:12, eave height of 7.5 m (24 ft), and horizontal dimensions of 12.2 m (40 ft)× 15.24 m (50 ft). The two models were tested for open terrain for 40 wind directions (WDs). The study provided information on pressure variations at the top and bottom surfaces of overhangs, adjacent roof areas, and underneath walls. Pressure and correlation coefficients were generated between soffits and underneath walls to quantify the effect of overhang width. The research showed that the 0.61 m (2 ft) overhang experienced higher suction coefficients at the edges compared to the 1.83 m (6 ft) overhang. In addition, the results confirmed that, for both configurations, soffit positive pressure coefficients may be assumed to be equal to the adjacent wall external pressure, as stated by a common standard, while this might not be applicable for negative pressure coefficients. Correlation and regression analyses between soffit pressure taps and wall upper taps show that the 1.83 m (6 ft) soffit appeared to be less correlated with the wall upper taps, compared to the 0.61 m (2 ft) soffit. Finally, area-averaged pressure coefficients for overhangs and adjacent roof areas were compared to the provisions in one standard for each specified zone, and differences were found.

Examination of different wall jet and impinging jet concepts to produce large-scale downburst outflow

Thunderstorm downburst winds are a major cause of severe damage to buildings and other infrastructure. The initiative of the NSF-NHERI Wall of Wind (WOW) Experimental Facility to design and develop a downburst simulator was established to open new horizons for multi-hazard engineering research by extending the current capabilities of the facility to enable the simulation of non-synoptic winds. Five different downburst simulator designs have been tested in the 1:15 small-scale replica of the WOW to identify the optimal design. The design concepts tested herein considered both the 2-D impinging jet and the 2-D wall jet simulation methods. The basic design methodology consists of transforming the available atmospheric boundary layer (ABL) wind simulator into downburst winds by adding an external modification device to the exit of the flow management box. A flow characterization comparison among the five contending downburst simulators, along with comparisons to real downbursts and previous literature findings, has been conducted. The study on the effect of surface roughness length on the height of the peak wind velocity showed that the implementation of a 2-D plane wall jet enables large-scale outflows (higher peak velocity height) with high Reynold numbers, which is advantageous in terms of reducing scaling effects. In general, the current research work showed that four downburst simulation methods were suitable for adoption; however, only one downburst simulator was recommended based on the feasibility of construction in the facility. The chosen downburst simulator consisted of a two louver slat system near the bottom, with a blockage at the top. This configuration enables producing a large rolling vortex passing through the testing section, which would serve adequately in the further study of turbulent flow characterization and testing of larger scale test models.

A novel intrauterine barrier for preventing the recurrence of IUA after TCRA procedure

Intrauterine adhesion (IUA) is the result of abnormal endometrium repair after trauma and infection that damages the basal layer of the endometrium, which is then replaced by scar tissue. In such instances, the endometrium partially or completely loses the ability to conceive the embryo. Even after surgery-based comprehensive treatment, a high rate of adhesion remains. A thin endometrium, poor blood supply, and poor function may also lead to refractory infertility, resulting in a poor reproductive prognosis even when the uterine cavity has been completely restored to normal. Therefore, two key points of postoperative management are the use of an intrauterine barrier to prevent re-adhesion and medicine to promote endometrial repair. However, there is currently no clinically applicable barrier that can meet the personalized dimensions of uterine cavity shape and size or effectively separate the wound wall. We have designed an intrauterine barrier that consists of a unique uterine-shaped, estrogen-release intrauterine device (IUD), which can be combined with an injectable, temperature-sensitive hydrogel. For this study, we will insert an estrogen-release IUD into the uterine cavity following transcervical resection of adhesion (TCRA) surgery, at the same time injecting 3–5 mL of liquid hydrogel at room temperature into the uterine cavity via the cervical channel. Due to its temperature sensitivity, the hydrogel will gradually solidify into a jellylike consistency, filling the uterine cavity with a solid barrier and completely preventing contact with the wounded wall to avoid the recurrence of adhesion. The estrogen-release IUD will be wrapped in the hydrogel barrier, which has many pores that allow sustainable estrogen release to promote endometrial regeneration and repair. This protocol can meet the needs of postoperative management of TCRA, but experimental and clinical studies are still needed to demonstrate its effectiveness. If patients in the study group have a lower adhesion recurrence and higher pregnancy rate compared to controls, our hypothesis will be confirmed that this barrier will prove a clinical application to help the functional repair of the endometrium and achieve a good reproductive prognosis.

To stop bleeding from soft tissues of wounds during trepanation

In case of bleeding from wounds or incisions of the soft tissues of the head E. Makai (Zentrlbl. F. Chir. 1929, No. 37) applies Michel's brackets to the thickness of the wound wall so that skin is captured on one side, and aponeurosis on the other.

Rapid popliteal artery release sensu A.N. Kazantsev in acute thrombosis in patients with COVID-19

Aim. To analyze the outcomes of popliteal thrombectomy using the standard release technique with vascular instruments and rapid release sensu A. N. Kazantsev in patients with acute popliteal artery thrombosis (PAT) and coronavirus disease 2019 (COVID-19).Material and methods. The present prospective single-center study for the period from April 1, 2020 to March 17, 2021 included 157 patients with acute PAT and COVID-19 at the Alexandrovskaya City Hospital. All patients were divided into 2 groups depending on the popliteal artery access: group 1 (n=88; 56%) — rapid release sensu A. N. Kazantsev; group 2 (n=69; 44%) — standard popliteal artery release using vascular instruments (vascular forceps and scissors) and tourniquets. Rapid popliteal artery release was distinguished by the fact that fasciotomy and hemostasis, the fatty tissue behind it and up to the artery was torn with two index fingers. First, the fingers were joined together at the lateral edges and inserted into the wound middle. Then the wound together with tissues was stretched with fingers to proximal and distal edges until the popliteal artery was visualized. Further, a Beckmann retractor was used to fix the torn fiber to the upper and lower wound walls. The tourniquets were not used.Results. Surgical access duration (group 1, 4,5±1,3 minutes; group 2, 11,41±0,9 minutes; p=0,005), as well as the total procedure duration (group 1, 47,5±2,8 minutes; group 2, 62,15±4,5 min; p=0,001) had the lowest values in the group of rapid popliteal artery release. Moreover, all intraoperative bleedings (n=11; 15,9%) was recorded in group 2 as a result of popliteal vein injuries and/or bleeding from popliteal artery. The retrombosis rate in the rapid release group was lower (group 1, 40,9%; group 2, 55,1%; p=0,03). On the first day after surgery, 18% of thrombosis developed in group 1, and 39% in group 2. The mortality rate was highest in the standard artery release group (group 1, 55,7%; group 2, 86,9%; p<0,0001; OR, 0,18; 95% CI, 0,08-0,42). In all cases, the cause of death was systemic multiple organ failure due to severe pneumonia, pulmonary edema, and cytokine storm.Conclusion. The use of rapid popliteal artery release sensu A. N. Kazantsev significantly reduces the thrombectomy duration in the context of COVID-19. This effect is achieved due to a decrease in the incidence of intraoperative bleeding, no need to use tourniquets and vascular instruments. A decrease in the ischemia duration using novel release technique reduces the retrombosis rate, as well as deaths caused by systemic multiple organ failure against the background of hyperperfusion and compartment syndrome. Reducing the operation duration with the use of rapid popliteal artery release sensu A. N. Kazantsev reduces the time of intraoperative mechanical ventilation, which in COVID-19 patients reduces the risks of pneumothorax, pneumomediastinum, emphysema, and pulmonary embolism. Thus, the rapid popliteal artery release sensu A. N. Kazantsev can be recommended for popliteal thrombectomy in patients with COVID-19.

Characterization of wind-induced pressure on membrane roofs based on full-scale wind tunnel testing

Flexible roofing systems (e.g., membrane roofs) are widely used in low-rise commercial and industrial buildings, accounting for over 60% of low-sloped building roofs in North America. Despite their wide usage, the effects of roof flexibility are neither thoroughly studied, nor accounted for in current building design codes and standards. To investigate such roof flexibility effects on wind-induced pressure, full-scale testing was conducted at the NHERI Wall of Wind (WOW) Experimental Facility (EF). The mechanically attached roof system (MARS) and partially adhered roof system (PARS), two of the most commonly used commercial roofing systems with different flexibility characteristics, were considered in this study. “U-shaped” pressure taps were used to measure the wind-induced pressure on the membrane roof, and the pressure coefficients were compared to those measured on a plywood roof. The effects of wind direction and wind speed on the wind-induced pressure coefficients of membrane roofs were studied. The results showed that the membrane deformation due to the membrane roof flexibility resulted in a reduction in the peak pressure coefficients as compared to those of rigid plywood roof. This reduction in wind loads is more significant for the MARS (27%) which has more flexibility than the PARS (19%). The membrane roof flexibility also modifies the non-Gaussian characteristic which results in a lower peak factor than the plywood roof. It was also observed that peak pressure coefficients on the flexible roof increase at higher wind speeds. This study provides an improved understanding of the effect of roof flexibility on wind-induced pressure coefficients. Further research is needed by testing more types and configurations of flexible roofs to formulate new code provisions for wind effects on flexible membrane roofs.

Holistic testing to determine quantitative wind-driven rain intrusion for shuttered and impact resistant windows

Tropical storms are usually associated with heavy rainfall. The interaction between rain and wind during such tropical storms affect various components of a building façade. The amount of water intrusion from wind-driven rain (WDR) can cause damage to the interior contents of the building and might affect the durability of the building. To study and mitigate the impacts of WDR on structures, a test-based WDR intrusion model was developed by the team at the Wall of Wind (WOW) Experimental Facility. Shutter systems are commonly implemented in hurricane-prone zones to mitigate possible breach of building envelope against extreme winds and wind-borne debris. There is very little information on the quantity of water intrusion that is prevented (if any) by the presence of these shutters. This study focusses on rain intrusion quantification into a window configuration, with and without accordion shutter. An impact-resistant window was also tested. The tests were conducted at three different wind speeds, 28 ​m/s, 35 ​m/s and 61 ​m/s corresponding to tropical storm, non-major, and major hurricane, respectively, considering the effects of wind direction and storm duration. Results showed that the water intrusion was reduced by 77–87% for shuttered windows compared to windows without any protection. These results might help validate or enhance the existing risk assessment models.

Aeroelastic Testing of Span-Wire Traffic Signal Systems

Span-wire traffic signals are vulnerable to extreme wind events such as hurricanes and thunder-storms. In past events in the Southeastern Coast of the United States, many failures of span-wire traffic signals were reported. In order to identify their dynamic behavior during extreme wind events and investigate their buffeting response, a large-scale aeroelastic testing was conducted at the NHERI Wall of Wind (WOW) Experimental Facility (EF) at Florida International University (FIU). The WOW is a large-scale open jet wind testing facility, comprised of 12 fans, and capa-ble of simulating winds at speeds up to 70 m/s, corresponding to a Category 5 hurricane. Follow-ing the Froude number criterion, a 1:10 aeroelastic model of a span-wire traffic signal system consisting of two 3-section and one 5-section signals was designed and constructed, based on the properties of its full-scale counterpart. In the testing protocol, various wind directions ranging between 0 and 180 degrees were considered at full-scale wind speeds ranging between 21 m/s and 42.5 m/s. The results of the aeroelastic tests show a similar behavior compared with previous full-scale tests conducted at the WOW. However, an increase in the RMS of accelerations was observed in comparison with those from the full-scale tests. This is attributed to the fact that the aeroelastic model enabled better simulation of low-frequency eddies in the turbulence spectrum compared to the full-scale testing turbulence spectrum.

Brefeldin A inhibits clathrin-dependent endocytosis and ion transport in Chara internodal cells.

The Characeae are multicellular green algae, which are closely related to higher plants. Their internodal cells are a convenient model to study membrane transport and organelle interactions. In this study, we report on the effect of brefeldin A (BFA), an inhibitor of vesicle trafficking, on internodal cells of Chara australis. BFA induced the commonly observed agglomeration of Golgi bodies and trans Golgi network into 'brefeldin compartments' at concentrations between 6 and 500μM and within 30-120min treatment. In contrast to most other cells, however, BFA inhibited endocytosis and significantly decreased the number of clathrin-coated pits and clathrin-coated vesicles at the plasma membrane. BFA did not inhibit secretion of organelles at wounds induced by puncturing or local light damage but prevented the formation of cellulosic wound walls probably because of insufficient membrane recycling. We also found that BFA inhibited the formation of alkaline and acid regions along the cell surface ('pH banding pattern') which facilitates carbon uptake required for photosynthesis; we hypothesise that this is due to insufficient recycling of ion transporters. During long-term treatments over several days, BFA delayed the formation of complex 3D plasma membranes (charasomes). Interestingly, BFA had no detectable effect on clathrin-dependent charasome degradation. Protein sequence analysis suggests that the peculiar effects of BFA in Chara internodal cells are due to a mutation in the guanine-nucleotide exchange factor GNOM required for recruitment of membrane coats via activation of ADP-ribosylation factor proteins. This work provides an overview on the effects of BFA on different processes in C. australis. It revealed similarities but also distinct differences in vesicle trafficking between higher plant and algal cells. It shows that characean internodal cells are a promising model to study interactions between seemingly distant metabolic pathways.

Effect of assembly construction on the wind induced pressure of membrane roofs

In North America over 60% of low slope buildings are roofed with membranes, and the market survey indicates that there is continuous growth in such roof assemblies. To the best knowledge of the authors, there is no in-situ measured data from such roofs. The National Research Council of Canada (NRCC), in collaboration with the Special Interest Group on Dynamic Evaluation of Roofing Systems (SIGDERS) consortium, has undertaken an in-situ monitoring program with the goal of providing valuable data to benchmark the current code provisions, as well as providing supporting data for existing wind uplift test methods to determine roof cladding resistance. This paper presents in-situ data of two most common commercial roof systems: mechanically attached roof system (MARS) and partially adhered roof system (PARS) and provides side-by-side comparison (partially refers to a system with and adhered membrane over some components that are mechanically attached). In order to provide more detail and controllable measurements, MARS and PARS mock-ups were evaluated at the open flow NHERI Wall of Wind (WOW) Experimental Facility (EF) at Florida International University (FIU). The investigations included visual observations (video) and pressure measurements at different roof locations in various wind directions and wind speeds. The visual observations confirmed that, due to construction characteristic, the membrane of the MARS deforms (balloons) under wind suction. The field and WOW pressure measurements revealed that the MARS generates systematic lower peaks pressure in comparison with the PARS. Data from field showed that the average reduction of the MARS is in the order of 20% in comparison to the PARS at locations close to the leading edge when wind is NW and WNW (close to normal). The WOW results showed that the pressure reduction of the MARS is in average 16% in comparison to the PARS when wind is W (normal), and the reduction would decrease to 12% when considering the worst case among all the wind directions tested in the lab.

Experimental Assessment of Wind Loads on Roof-to-Wall Connections for Residential Buildings

Wind hazards are one of the most disastrous events that frequently occur in the United States. Hurricane Irma, which hit the southeast coast in 2017, left a majority of damage concentrated on low-rise buildings and wooden construction in its wake. As revealed by recent hurricane damage reconnaissance, hardware-type roof-to-wall connections are especially vulnerable to high wind suction. There is only limited research on the assessment of wind loads on these roof-to-wall connections, which are important components of the wind load path. Hence, it is essential to have realistic estimates of wind effects on these connections to ensure a safe design. To fill this fundamental knowledge gap, an extensive large-scale aerodynamic testing study has been recently conducted at the NSF-Natural Hazard Engineering Research Infrastructure (NHERI) Wall of Wind (WOW) Experimental Facility (EF) to investigate wind actions resulting from simulated hurricane force winds. A wooden gable roof building of a large length scale of 1:4 was adopted for this study. Seven trusses were used to construct the roof and were connected to the top plate of the side walls. Load cells were mounted at the roof-to-wall connection (RTWC) level to measure the effective net wind-induced forces. The model was tested under different wind directions varying from 0° to 360° with an increment of 5° under varying wind speeds. In addition, three different configurations, i.e., one enclosed and two partially enclosed, were considered to assess different internal pressure scenarios that affect the net load-ing on the roof-to-wall connections and the overall roof system. The RTWC force coefficients distribution along the entire roof was obtained. The results were compared to force coefficients recommended by ASCE 7-16 version for the cases of Main Wind-Force Resisting System (MWFRS) and Component and Cladding (C&C). The experimental results were in between MWFRS and C&C values based on the ASCE provisions in general. However, for partially enclosed case, some values slightly exceeded those based on the ASCE C&C provisions. Also, the overall uplift on the roof was found to be dependent on the location of the opening (i.e., opening on long side versus short side of the building).

Methods for assessment of the course of wound process

Summary: The article is devoted to the analysis of methods for evaluation of the course of wound process. The problem of the treatment of wounds of various etiology is one of the complex sections of clinical medicine. Currently, there is an increase in the proportion of traumatic injuries that can cause wounds. Also common are vascular diseases and endocrine pathology, associated with the development of complications with the formation of tissue defects. The presence of tissue destruction and an infectious agent in the wound determine the development of purulent-inflammatory process in it. The current direction is determination of the criteria for diagnosis and methods of prevention of general and local complications. The purpose of the study was to determine the clinical and laboratory parameters used to reveal the stage of the wound process and to predict the development of complications. The factors that determine the wound healing process and the appropriate techniques for assessing the wound process were studied. Subjective and objective methods are identified among the control methods. The article describes techniques that reflect the condition of tissues forming the wound walls or wound surface; techniques enabling to characterize bacterial flora by qualitative and quantitative indicators; methods allowing to determine the state of local and general body resistance. A brief description of standard techniques – cytological examination of wound exudate, assessment of cytograms, planimetric and bacteriological tests – is given. The data on determination of pH of wound medium and liquid volumetric vulnerometry, estimation of the state of granulation tissue are given. The value of the use of computerized diagnostics and computerized monitoring of the wound process was studied. The importance of methods for objective assessment of the course of the wound process for control of the treatment efficacy and in experimental studies during preclinical trials of medicinal products and medical devices has been demonstrated.

Finite-element modeling framework for predicting realistic responses of light-frame low-rise buildings under wind loads

Low-rise wood frame buildings are one of the most vulnerable structures that are often damaged in windstorms. On the other hand, numerically modeling the structural behavior of wood frame buildings poses significant challenges. This paper presents a computational modeling methodology that can help determine the realistic load paths and load sharing for light-frame low-rise buildings under wind loadings throughout the linear to the nonlinear range. A three-dimensional finite-element (FE) model is developed to capture the behavior of a building under wind loading, a large-scale model of which was tested at the Wall of Wind (WOW) Experimental Facility (EF) at Florida International University to provide experimental results for the validation of the FE modeling. This comprehensive numerical model can accommodate various materials and structural connections with mechanics-based load-deformation characteristics such as sheathing nails and framing-to-framing connections, so as to be capable of predicting the performance of the components and connections that are difficult to model in general but are the most vulnerable parts of a low-rise structure as witnessed during past hurricanes. The predicted structural responses of the computational framework showed reasonable agreement when compared to the experimental measurements in terms of the deflection at roof sheathings and roof-to-wall connections (RTWCs). This validated framework is then used to analyze different modeling effects. Different ways to represent the RTWCs and foundation fasteners are compared, which determines the boundary conditions of the roof assembly and full building simulations, respectively. The modeling of wall stud connections is discussed to fill in the corresponding gaps in the past research. A controversial issue that whether the effect of the rotational capacities of sheathing nails can be ignored or not is also discussed.

Experimental study and FE analysis of tile roofs under simulated strong wind impact

A large number of low-rise buildings experienced serious roof covering failures under strong wind while few suffered structural damage. Clay and concrete tiles are two main kinds of roof covering. For the tile roof system, few researches were carried out based on Finite Element (FE) analysis due to the difficulty in the simulation of the interface between the tiles and the roof sheathing (the bonding materials, foam or mortar). In this paper, the FE analysis of a single clay or concrete tile with foam-set or mortar-set were built with the interface simulated by the equivalent nonlinear springs based on the mechanical uplift and displacement tests, and they were expanded into the whole roof. A detailed wind tunnel test was carried out at Tongji University to acquire the wind loads on these two kinds of roof tiles, and then the test data were fed into the FE analysis. For the purpose of validation and calibration, the results of FE analysis were compared with the full-scale performance of the tile roofs under simulated strong wind impact through one-of-a-kind Wall of Wind (WoW) apparatus at Florida International University. The results are consistent with the WoW test that the roof of concrete tiles with mortar-set provided the highest resistance, and the material defects or improper construction practices are the key factors to induce the roof tiles\' failure. Meanwhile, the staggered setting of concrete tiles would help develop an interlocking mechanism between the tiles and increase their resistance.

An Experimental Study on the Wind-Induced Response of Variable Message Signs

Variable Message Sign (VMS) systems are widely used in motorways to provide traffic information to motorists. Such systems are subjected to wind-induced structural vibration that can lead to damage due to fatigue. The limited information that is available on the safe wind design of VMS motivated a large scale testing that was conducted at the Wall of Wind (WOW) Experimental Facility at Florida International University (FIU). One of the objectives of the present study was to experimentally assess the wind-induced force coefficients on VMS of different geometries and utilize these results to provide improved design guidelines. A comprehensive range of VMS geometries were tested and mean normal and lateral force coefficients, in addition to the twisting moment coefficient and eccentricity ratio, were determined using the measured data for each model, for wind directions of 0o and 45o. The results confirmed that the mean drag coefficient on a prismatic VMS is smaller than the value of 1.7 suggested by American Association of State Highway and Transportation Officials (AASHTO). An alternative to this value is presented in the form of a design matrix with coefficients ranging from 0.98 to 1.28, depending on the aspect and depth ratio of the VMS. Furthermore, results indicated that the corner modification on a VMS with chamfered edges demonstrated a reduction in the drag coefficient compared to sharper edges. Finally, the dynamic loading effects were considered by evaluating the gust effect factor, using the ASCE 7 formulations, for various VMS weights and geometries. The findings revealed a wide range of possible gust effect factors, both above and below the current AASHTO specification of 1.14. Future research may include different geometries of VMS and a wider range of wind directions.

An experimental study to assess the effect of soffit louvered vents on wind loads and wind driven rain intrusion on low rise buildings

Wind-driven rain (WDR) intrusion in buildings during hurricanes often leads to significant damage to building interior and contents, causing major losses. Many buildings in hurricane-prone U.S. coastal states are fitted with soffit vents with louvers that are designed to close during high winds and reduce rain intrusion. This paper focuses on the topic of WDR intrusion through soffit vents and, in particular, studies the effects of louvered soffit vents on (i) reduction of water intrusion, and (ii) overall aerodynamic loading of buildings’ roofs. A gable and a hip roof building retrofitted with open and closed vents were tested at the Wall of Wind (WOW) experimental facility. WDR intrusion studies were carried out only on the hip roof building, while wind pressure distributions were estimated for the gable and hip roof buildings. Results from the WDR intrusion study indicate a marked reduction in water intrusion for the closed vent roofs. Moreover, the net mean and peak pressure coefficients for the closed vent roofs are reduced in magnitude (less suction) compared to the open vent roofs. Future research is recommended to study the effect of different vent sizes and locations, besides considering other roof types (e.g. mono-slope).

Effect of wind-induced internal pressure on local frame forces of low-rise buildings

Given the significant role of internal pressures in the wind-induced loading of low-rise buildings, their correct estimation is critical for the accurate determination of the net (external plus internal) wind effects. This paper presents results of an investigation conducted to study the effect of wind-induced internal pressures on structural frame forces on low-rise buildings with single or multiple dominant openings. Models from the National Institute of Standards and Technology (NIST) aerodynamic database with internal pressure measurements were used. Large-scale experiments were also conducted in the Wall of Wind (WOW) facility at Florida International University (FIU) using a model with multiple openings. Calculations of frame forces were performed using the Database-Assisted Design (DAD) methodology. It was found that internal pressure significantly increases the forces induced by wind with the most unfavorable direction on the frames located close to the openings. However, its effect on the frames located away from the openings was smaller. Effects of internal pressure also varied between different cross-sectional locations of the same frame, depending upon the correlation between forces induced by external and internal pressures. For the highest net frame forces, the reduction factor applied to the response induced by internal pressures, that accounts for the imperfect correlation between the external and internal pressures, was found to be approximately 0.85. Comparison between frame forces calculated using experimentally measured internal pressures and their counterparts evaluated by using ASCE 7–10 provisions for internal pressures showed that the latter result in unconservative estimates of frame forces in both enclosed and partially enclosed buildings. An additional significant result is that the ASCE 7 classification of buildings with equally sized windward and leeward openings as enclosed buildings can lead to the underestimation of net frame responses. It is therefore proposed that this classification be changed to reflect the appropriate internal pressure effects.