Wind Load Effects on Manufactured Home Foundations

Transcription

1 Aerican J. of Engineering and Alied Sciences 4 (4): , 2011 ISSN R.K. Dhungana et al., This oen access article is distributed under a Creative Coons Attribution (CC-BY) 3.0 license Wind Load Effects on Manufactured Hoe Foundations 1 Raesh K. Dhungana, 2 Taher M. Abu-Lebdeh and 2 Ellie H. Fini 1 Deartent of SAI Engineering, PLC, 2240 NW, Edond, OK 73013, USA 2 Deartent of Civil, Architectural and Environental Engineering, North Carolina A and T State University, Greensboro, NC 27411, USA Abstract: Proble stateent: Manufactured hoes are suscetible to hurricane daage. Each year, significant losses, in ters of fatalities and roerty daage, are reorted. There is always a revalent concern about lateral load resistance caacity of tie-down syste of anufactured hoes when subjected to windstors. This study is erfored to deterine the effects of hurricane wind on anufactured hoes foundations. Aroach: A 1:120th scale odel of single wide anufactured hoe of size 14 ft by 80 ft was designed for the wind tunnel test. Proer instruentations and siulations were considered to easure wind forces alied on the odel. Sting balance and Pitot static tube were used to easure forces and air velocity during the wind tunnel test. Dislaceents of anchors were observed during the test. Results: The ultiate forces as well as the dislaceents of the anchors were deterined at different angles of wind direction ranging fro Wind seed inside the tunnel was increased at the rate of 5 iles h 1. Conclusion/Recoendations: Test result showed that auger anchors used to suort lateral load are incaable to resist hurricane wind loads. It was found that anchors dislaced 2 in. vertically and 4 in. horizontally at loads less than 4725lb. Tested anufactured hoes anchors exerienced axiu force of 4087 lb when 45 iles h 1 wind acted in transverse direction to the wall. The anufactured hoe anchors dislaced ore than 2 inches in vertical direction and 4 inches in horizontal direction due to this wind load. This research indicated that anufactured hoes ground anchors can sustain wind velocity of 95 iles h 1 when the wind is acting at longitudinal direction. Key words: Wind tunnel, anufactured hoe, ground anchors, wind load, hurricane, siulation INTRODUCTION Mobile hoes have been recently renaed as anufactured hoes because 95% are never oved fro initial site. However, wheels and axles of anufactured hoes have been used as eans of transorting to the hoe-site. Each year, illions of dollars of roerty daage is reorted due to hurricanes (Isla et al., 2011; Beven and Cobb, 2004). For instance, hurricane Isabel who occurred in Seteber, 2003 in North Carolina, USA roduced a roerty daage of 450 illion dollars. Daages that occur every year due to high wind stors have adversely affected the sale of anufactured hoes in areas suscetible to frequent hurricanes. It is an ierative to find an effective way to rotect anufactured hoes and understand the aerodynaic asect of high wind seed on these structures. A tyical anufactured hoe consists of refabricated walls, floor and roof. Standard anufactured hoe Widths (W) are 12, 14 and 16 ft. Lengths (L) vary fro ft in 10 ft increents. Corresonding basic frae bea Sacing s (S) are 6 ft for 12 ft and 14 ft wide hoes and 8 ft for 16 ft wide hoes. The height of the unit (H 1 ) is aroxiately 8 ft. The height off the ground (H 2 ) varies deending on the local terrain. A tyical height is aroxiately 3 ft. The noral roof sloe is between 2:12 and 4:12. Manufactured hoes are, norally, suorted on iers ade of concrete blocks. The coonents are held in lace by etal frae ties or cobination of frae ties and over-the-to-ties. The ties are galvanized etal stras in. thick by 1.25 in. wide with secified iniu strength. Ground anchors are widely used in anufactured hoe installations. They consist of an exlicit anchoring assebly designed to transfer lateral Corresonding Author: Taher M. Abu-Lebdeh Deartent of Civil, Architectural and Environental Engineering, North Carolina, A and T State University, Greensboro, North Carolina 27411, USA Tel: (336) ext 664 Fax: (336)

2 A. J. Engg. & Alied Sci., 4 (4): , 2011 loads to the ground. The ost coon tyes of anchors available are ground anchors, cast-in-lace concrete footings, drilled concrete anchors and cross drive hoes. Full-scale test results of Yokel et al. (1981) clearly showed that, in ost cases, the load-resisting caacity of ground anchors were significantly below anchors. Auger anchors are anufactured in several that required in the installation standards. sizes and with one or two auger disks er anchor. The ost frequently used anchor is the 4 ft long anchor with Manufactured Housing Institute (MHI) erfored a series of structural test on tyical single wide (14 by 62 single 6 in auger disk. The diaeters of the available ft) anufactured hoe, riarily, to address the need shaft are 5/8 in., 11/16 in. and 3/4 in. Manufactured to irove the ability of anufactured housing to hoes designed after July 1994 are based on Federal withstand high wind loads. They concluded that ost of Manufactured Hoe Construction and Safety the eranent horizontal deforation is due to sliage Standards (FMHCSS). The Manufactured Hoe in the tie-down stras and horizontal dislaceent of Construction and Safety Standards has establish three the foundation. Surry et al. (2005) discussed sile wind seed zones I,II and III with wind seeds of 90, odels that have reroduced certain fors of failure under realistic wind loads siulated in a wind tunnel. 100 and 110 h, resectively (Marshall and Yokel, Fritz et al. (2008) atteted to quantify the variability 1995). Manufactured hoes in wind zones I are not of wind effects estiated based on tests conducted at required to have diagonal ties, while for wind zone II six wind tunnel laboratories. The researcher ade a and III it should have diagonal and vertical ties. rediction that odeling of suburban terrain contributes Although the nuber of ties and tie sacing are not significantly to the variability. Macha et al. (1983) secified, it is required that ties should not be closer erfored research to coare wind ressures on a than 2 ft to either end of the hoe. It ilies that anufactured hoe in odel and full scale structure. A anchor and tie sacing will be based on anchor odel of 1:25 was used to easure the wind ressures caacity. It is required that all anchors ust be caable in the odel and was coared with the full scale of resisting an allowable working load equal to or structure ressures. Vereulen and Visser (1980) exceeding 3,150 lb and be caable of withstanding a conducted research on the deterination of siilarity 50% overload, i.e., 4,725lb without failure of either the criteria for wind tunnel odel testing of wind flow anchoring syste or the attachent oint on the attern close to building facades. Tielean (1992) anufactured hoe. Further, aerodynaic wind discussed a criterion for the siulation of atosheric ressure is develoed when air flows over and around the unit which causes daage to anufactured hoes. External ressures drag walls, roof and floor aart. This drag forces can overturns the unit if it is not adequately anchored (McDonald and Mehnert, 1989). Nuerous studies have been conducted on wind boundary layer in wind tunnels for the urose of redicting wind load on low rise buildings. A odel of 1:100 was tested to rove that sall scale turbulence araeter is ore iortant than the siulation of the velocity rofile or integral length scale. The objective of this exeriental study is to load effects on bridges (Saeed et al., 2010) and on low investigate the wind loads effects on the rise buildings such as anufactured hoes and odular hoes. McDonald and Mehnert (1989) reviewed the standard ractice for wind resistant anufactured housing. They concluded that the enforced wind loads design criteria need to be reevaluated. Pearson et al. anufactured hoes anchors and to deterine the ultiate forces as well as the dislaceents of the anchors at different angles of wind direction varying fro The diensions of the odel were deterined based on Buckingha Pi Theore. The (1996) investigated the lateral load resistance as well as basic araeters considered were velocity of wind, the behavior of anufactured hoes soil anchors dislaceent of anchors and wind force on the subjected to axial and shear loads. They conducted anufactured hoe. corehensive tests on the ullout caacity of ground anchors installed in silt, sand and clay soils. The test erfored showed that anchors tyically used to tie MATERIALS AND METHODS down anufactured hoes do not achieve the desired resistance. Harris (1980) conducted an exeriental Materials: The exeriental rocesses involve the testing for wind forces on obile hoes on four basic design of a odel for the wind tunnel test. The odel odels of 25 ft, 40 ft, 50 ft and 60 ft, ade to a scale of was reared based on the size of the wind tunnel. The 1/16. The four basic odels were tested at wind diension of the odel was 8 in. by 1.4 in. by 0.8 inch. directions ranging fro easured with resect to the longitudinal direction of the odel. The study investigated the relationshi between axiu wind velocity and anchorage requireents for the obile The frae structure of the scaled anufactured hoe was reared fro balsa wood and lywood for roof, floor and walls. Nails and steel wires were used to reresent anchor and stra of the rototye. 549

3 Fig. 1: Iage of the utilized wind tunnel Wind tunnel: The wind tunnel test was erfored at the aerosace laboratory of North Carolina A and T State University. The utilized wind tunnel (Fig. 1) is closed circuit, sile and easy to use. The wind inside the tunnel is generated by a fan ositioned on the downstrea side of the wind tunnel. The on and off button of the wind tunnel fan is on the ustrea side. Wind seed can be controlled using a Velocity Frequency Drive (VFD) in lab view software. Secifications of the utilized wind tunnel are listed as follows: (a) Test section diensions: 16 in. Long by 12 in. wide by 12 in. high (b) Closed circuit, closed test section (c) Maxiu velocity: 100 h (d) Instruents connected to the tunnel: Data Acquisition syste and deskto (e) Test section static ressure: atosheric or slightly below (f) Force easuring instruent: Sting balance (g) Velocity easuring instruent: Pitot static tube A 12 inch long and 1/4 inch thick Pitot static tube is used to easures the dynaic ressure observed during the wind flow. It consists of several holes drilled fro outside and central hole down the axis of the tube. The center hole ointed towards the flow direction observes the total ressure and outside hole observes the static ressure. Pitot static tube is allied to the ressure transducer box by two silicon ies. The dynaic ressure is taken as the difference between total ressure (P t) and static ressure (P s). Theoretically, after obtaining dynaic ressure, Bernoulli s equation ay be used to calculate the air velocity inside the wind tunnel by using the equation: V = [2*(P t - P s )/ρ] The laboratory Pitot static tube rovides the ressure reading in inches of water colun and wind velocity in ters of iles er hour. The velocity ressure ranges fro in. of water. The air velocity inside the wind tunnel is calculated by Eq. 1 and 2 as follows: A. J. Engg. & Alied Sci., 4 (4): , V th = (P v /ρ) (1) ρ = x P B /T (2) Where: V th = The Air velocity P v = Velocity ressure in inch of water ρ = Air density in lb/ft 3 P B = The baroetric ressure in inch of ercury T = The absolute teerature The above air velocity equation was used to deterine the accuracy of readings observed by the Pitot static tube. Accuracy of readings for wind velocity observed should be within 2 ercentage oints of the calculated value. Siilarly, the sting balance is an instruent used to easure forces and oents. It is connected to deskto couter, ressure transducer box and Data Acquisition instruent SCC68 interconnect. The sting balance resonds to the change in forces and oents on the odel ounted on it, then transit this resonse to signal conditioning and dislay unit. A three coonent internal sting balance is used in this research. The noral force is used to calculate lift force and axial force to calculate the drag force; thus roviding relevant forces acting on the odel attached to the sting. Data acquisition syste: Sting balance ounted on the odel and Pitot static tube within the wind tunnel are connected to couter that has labview software installed in it. The forces, oent, wind velocity and velocity ressure exerted on the sting balance and Pitot static tube are recorded in the lab view software. Modeling and siulation: For the urose of this study, the widely used odel of the anufactured hoes was chosen for odeling. The design details of the rototye (Fig. 2) are: Length (L) = 80 ft; Width (B) = 14 ft; Heigh (H) =8 ft; Deth of I bea (d) =10 in as er HUD code 24 CFR for 14 ft width hoe; Height of ier (h) = 3 ft; Height of anchor (h 1 ) = 4 ft; Total Height (H 1 ) = ft; Roof sloe (θ) = 14 ; Size of roof = 7.21 ft; Weight of anufactured hoe (W) = lbs or lbs/ft 2 ; Diaeter of anchor = 0.63 in; footings used are single stacked. Selection of a suitable wind tunnel odel scale is a significant ste in the design of the exerient. The selection usually deends on the area of the test section to avoid blockage of the wind tunnel. In this exerient, the size of test area inside the wind tunnel is 16 in. 12 in 12 in. which gradually reduced to 16

4 A. J. Engg. & Alied Sci., 4 (4): , 2011 in. 8 in 8 in. Uon consideration of the above factors, a scale of 1:120 was selected. The odel size details are: Length (L) = 8 in; Width (B) = 1.4 in; Height (H) = 0.8 in; Deth of I bea (d) = 0.08 in; Height of ier (h) = 0.3 in; Height of anchor (h 1 ) = 0.4 in; Total Height (H 1 ) = 1.58 in; Roof sloe (θ) 14 ; Size of roof = 0.72 in; Weight (W) = 1.04 lbs; Sacing of bea = 0.60 in; Diaeter of anchor (d) = in. After deterining the size of the odel, quarter inch thick lywood was cut into desired sizes to reare frae structure of the odel. The wooden ieces were glued together and once the frae is built, the lywood of wall, roof and floor size were ade and glued to the frae. As this research is focused on deterining the dislaceent of anchors due to wind loads so iers were also ade of lywood. A thin steel wire of ¼ in. diaeter was used as the stras connecting the anchors. Nails of 18 5/8 in. were used to reresent the anchors of the odel. Soil was sieved through nuber 100 sieve using echanical vibrator. The soil obtained reresents silt soil foundation in rototye. After attaining geoetric siilarity, the next ste is to deterine kineatic and dynaic siilarity of the odel to reresent the actual anufactured hoe in the field. This can be achieved by diensional analysis (Chongcharoen, 2011; Zaidi et al., 2010). Buckingha i theore is used herein to erfor diensional analysis, fro which six variables (F, V, H, L, ν, ρ) and three fundaental diensions ([M], [L], [T]) exist. Further, three i ters were analyzed to obtain diensionless nubers. Fro these araeters; wind seed, forces and weight of odel inside the wind tunnel are deterined. Pi ters are deterined as follows Eq. 3 and 4: F = f (V, H, L, ν, ρ) (3) F D,L / H 2 V 2 ρ = ϕ [(L / H), (υ / (H Vρ))] (4) Where: ν and ρ = Viscosity and density of air M and L = Mass and length V = The wind velocity Now, fro the above i ters, Reynolds nuber for the odel and rototye should atch [(Re) = (Re) ]. Thus: (ρvl / υ) = (ρvl / υ) (5) Fro Eq. 5, one can deterine wind velocity of the wind tunnel as Eq. 6: ρvl ρvl = υ υ (VL) 3 = (VL) 1.04 * *80 *12 V = 8*1.4 * *14*8* V = V Therefore,V = V (6) Reynolds nuber odeling is confired and thus velocity inside the wind tunnel is taken as the actual wind velocity of the rototye. The final ste is to deterine the forces acting on the rototye due to wind load. The force in the odel was deterined fro the sting balance used in wind tunnel testing. After obtaining the forces fro wind tunnel test, the actual force in the rototye is calculated by equating the coefficient of force for odel and rototye: C F(odel) F = C F(rototye) = ( ρ V A ) ( 1 ρ V A ) ρ V A F = 2 ρ V A F ( F ) (7) It should be noted that the coefficient of force (C F ) becoes coefficient of drag (C D ) when drag force is used and coefficient of lift (C L ) when lift force is used in the analysis. Fig. 2: Scheatic diagra of rototye Test setu and testing rocedures: The wind tunnel test can be briefly described as follows: (1) The odel was laced inside the wind tunnel as required for the test; (2) All couters were connected and Lab VIEW VI software is oened; (3) Wind seed button is used 551

5 A. J. Engg. & Alied Sci., 4 (4): , 2011 for anual or autoatic control of seed. For anual seed, a desired ercent value is entered in anual set window or slider bar. The ercent entered indicates to fan seed. While, for autoatic seed a desired wind seed is entered in iles er hour; (4) The saling button is used to select streaed or snashot data collection. In this study, streaed data er second saling was collected; (5) The test section is checked again in order to avoid obstruction for wind tunnel oeration; (6) After coletion of the test, the wind tunnel was shut down and the rocedures were reeated for different orientation of the anufactured hoes or wind angles as shown in Fig. 3. Each test was reeated three ties for each angle. Data collected were saved, analyzed and averaged. Data analysis: Air velocities and wind forces data were collected fro the Pitot static tube and sting balance using lab view software. Pitot static tube readings for air velocity were verified using Eq. 1 and 2, where it was found that the recorded values were within the erissible error of 2%. Further, using Eq. 7, the forces in the rototye ay be written as Eq. 8: RESULTS Ultiate force in anchor: Considering wind forces acting on the anufactured hoe (Fig. 4) and assuing no lateral load is carried by the iers, the load transferred to the foundation will be carried by the anchors. Thus, the ull out force in the anchor will be the su of drag and lift forces: (F ) anchor = (F ) Drag + (F ) Lift = T D cos45 + T D sin45 (9) The ground anchors ultiate ull out force is deterined using Eq. 9. Maxiu wind velocity and anchors ultiate force at different angles of attack are deterined and shown in Table 1 and Fig. 5. According to Manufactured Hoe Construction and Safety Standards failure of anchor is considered to occur if it oves 2 inch in the vertical direction or 4 inch in horizontal direction due to wind load of 4725 lb. F =(ρ /ρ )(V 2 /V 2 )(A /A )(F )GK z K zt K d I (8) The nuerical values of the force factors are deterined fro (ASCE 7-05, 2005): The gust factor (G) for the rigid building is Wind directionality factor (K d ) for ain wind force resisting syste coonents and cladding is The velocity ressure exosure coefficient (K z ) is 0.7. Toograhic factor (K zt ) is taken as 1. The iortance factor (I) for hurricane rone region with wind seeds of h in category is Fig. 4: Forces acting on the anufactured hoe Fig. 3: Direction of wind load alied in wind tunnel test Fig. 5: Maxiu force versus velocity and wind angle 552

6 Table 1: Maxiu force exerted in anufactured hoe at different velocity and wind angle Angle of Wind velocity Ultiate force attack (θ) (V) h on anchor (F a) lb A. J. Engg. & Alied Sci., 4 (4): , 2011 Table 2: Wind load acting in anufactured hoes at angle of 90, 120 and 135 Force in anchor (F a) (lb) D vertical (D v) (inch) D horizontal (D h) (inch) At At At (a) (b) Table 1 and Fig. 5 show that none of the anchors were caable to sustain the load of 4725lb before failure. Further, anchors exerienced higher force when the wind flow is in a transverse direction to the anufactured hoe. In this direction, the hoe could only resist wind seed of 45 MPH. At 180 (wind flow is along the longitudinal direction), the axiu velocity resisted was 95 MPH before overturning. It is worth to ention that when the odel is tested without anchors, it overturned at uch lower wind velocity. 553 Fig. 6: Force-dislaceent curves of anchors at wind angles of 90, 120 and 135 (c)

7 Dislaceent of anchors: In order to easure the dislaceent of the anchors at each resective alied force, nubers of anchor s ictures were taken during the test. These ictures were analyzed, using adobe hotosho CS5, software to easure the horizontal and vertical dislaceents of the anchor. The easured dislaceents were first converted to the odel scale with resect to the scale of hotograh and then converted to rototye scale and recorded as shown in Table 2 and Fig. 6. Although tests were conducted at different wind angles ranging fro 0-180, but due to sace liitations, only three wind angles (90, 120 and 135 ) will be resented herein. DISCUSSION A. J. Engg. & Alied Sci., 4 (4): , 2011 was At the transverse direction (90 ), it is observed that the failure of anchors occurs at a seed of 45 iles er h due to vertical dislaceent. The ground anchors exerienced an ultiate force of 4087 lb at 45 iles er h wind seed. The dislaceent in the anchor at this seed was 7.93 inches vertical and 2.24 inches horizontal. In case of transverse loading, anchor dislaced ore in vertical direction than in horizontal direction. The coefficient of drag was axiu when the wind was acting in transverse direction. At 120 orientation, the failure of anufactured hoe anchors occurred at wind seed of 60 iles er h. The value of coefficient of drag was close to the coefficient of drag obtained when wind load was at 60. Siilarly, when wind load is alied at 135, the failure velocity of anchor dislaceent was 50 iles er h. The coefficient of drag was which is close to that at 45. The axiu vertical and horizontal dislaceents at the ultiate load of 1900 were 2.45 and 2.71 inches, resectively. The failure velocity of anufactured hoe anchors at 150 was 50 iles er h. The coefficient of drag obtained is alost close to that obtained at 30. A wind seed of 95 iles er h was resisted by the anchors before failure when the wind was in longitudinal direction (180 ). The coefficient of drag was very low at this orientation. In suary, test results show that the drag coefficient increased as wind direction increased fro It was highest at 90 and again lower fro The coefficient of drag was least when the wind was acting at 180. A axiu wind seed of 95 iles er h was resisted by anufactured hoe anchors when wind load was alied along longitudinal direction. The anufactured hoe anchors exerienced highest forces at velocity of 45 iles er h when wind load was acting along transverse direction. Test data such as tie, velocity of wind (V easured ), Pitot static tube readings and axial forces were obtained fro wind tunnel test. The other values such as force in anchor, horizontal and vertical dislaceent were deterined analytically as described earlier. Dislaceents of anchors at resective forces were calculated for 30, 45, 60, 90, 120, 150 and 180. It was observed that at wind angle of 30, the anufactured hoe could resist wind seed of 60 iles er h before 2 inch dislaceent of anchors. The ultiate force in anchor before failure was 2900 lb with a vertical dislaceent of 2.91 inches and horizontal dislaceent of 3.52 inches. Failure was due to vertical dislaceent of anchors. Further, it was observed that the drag is less when wind is acting at 30 coared to other orientation excet 180. Both the force and its corresonding dislaceent increased with wind seed. When the wind is directed at 45, the anufactured hoe anchors fail at wind seed of 50 iles er h where the ultiate load resisted by the anchor was 2498 lb. The vertical and horizontal dislaceent at 2498 lb load were 7.82 and inches resectively. The CONCLUSION coefficient of drag was as deterined fro the sloe of the curve between axial force and Pitot static The ain urose of this investigation was to tube reading. The data observed during the wind tunnel deterine the caacity of the anufactured hoes test was close to the sloe line, which verifies the ground anchors at hurricane wind seed. The accuracy of the observed data. Also, the force versus exeriental results obtained fro wind tunnel test vertical and horizontal dislaceent at 45 shows that showed that none of the auger anchors used in initially the anchor dislaced ore in vertical direction anufactured hoes was able to withstand hurricane at lower wind velocity and with the increase in seed wind. Thus, it is needed to develo an effective tiedown the dislaceent was higher in horizontal direction. syste to resist wind load and iniize daages Siilar nature of results was obtained at other and casualties. The current 4.0 ft anchors inserted in orientations. Siilarly at 60 orientation, the failure of wet silt soil are not caable of withstanding hurricane anufactured hoe anchors occurs when the wind wind loads. However, the anufactured hoe was seed was at 65 iles er h. The coefficient of drag was caable of resisting axiu wind velocity of 95 ore than that of wind load acting on anufactured iles er h when wind was in longitudinal direction of hoes at an angle of 30 and 45. Coefficient of drag the anufactured hoe. On the other hand, in 554

8 A. J. Engg. & Alied Sci., 4 (4): , 2011 transverse direction, the axiu wind seed sustained by the anufactured hoe was 45 iles er h, the anchors exerienced higher forces and the failure occurred before reaching the wind seed of a hurricane. It was seen that anchors were caable to rovide ultiate resistance of 4087 lbs before failure when the wind was acting at transverse direction. The coefficient of drag increases with wind directions fro and reaches the axiu at 90. After 90 the coefficient of drag decreases and reaches the iniu at 180. REFERENCES Beven, J. and H. Cobb, Troical cyclone reort: Hurricane Isabel. National Hurricane Center. Chongcharoen, S., Inversion of covariance atrix for high diension data. J. Math. Stat., 7: DOI: /jss Fritz, W.P., B. Bienkiewicz, B. Cui, O. Flaand and T.C.E. Ho et al., International coarison of wind tunnel estiates of wind effects on low-rise buildings: Test-related uncertainties. J. Struct. Eng., 134: DOI: /(ASCE) (2008)134:12(1887) Harris, R.B., Testing for wind forces on obile hoes. ASTM Secial Techn. Pub., 702: Isla, M.T., M.Z. Hossain and M. Ishida, Trends analyses for several factors affected by troical cyclones. A. J. Environ. Sci., 7: DOI: /ajess Macha, J.M., J.A. Sevier and J.J. Bertin, Coarison of wind ressures on a obile hoe in odel and full scale. J. Wind Eng. Indus. Aerodynaics, 12: DOI: / (83)90065-X Marshall, R.D. and F.Y. Yokel, Recoended Perforance-Based Criteria for the Design of Manufactured Hoe Foundation Systes to Resist Wind and Seisic Loads. 1st Edn., National Institute of Standards and Technology, Gaithersburg, MD., : 61. McDonald, J.R. and J.F. Mehnert, Review of standard ractice for wind resistant anufactured housing. J. Aeros. Eng., 2: DOI: /(ASCE) (1989)2:2(88) Pearson, J.E., A. Longinow and D.F. Meinheit, Wind rotection tie-downs for anufactured hoes. Pract. Period. Struct. Des. Constr., 1: DOI: /(ASCE) (1996)1:4(126) Saeed, A.T., Z.L. Liang, Y.Z. Yun, F.A. Zoubi and O.A. Salih, Full odel wind tunnel study on the xia-zhang bridge under oeration stage. A. J. Eng. Alied Sci., 3: DOI: /ajeass Surry, D., G.A. Ko and F.M. Bartlett, Wind load testing of low buildings to failure at odel and full scale. Nat. Hazards Rev., 6: DOI: /(ASCE) (2005)6:3(121) Tielean, H.W., Probles associated with flow odelling rocedures for low-rise structures. J. Wind Eng. Indus. Aerodynaics, 42: DOI: / (92)90099-v Vereulen, P.E.J. and G.T. Visser, Deterination of siilarity criteria for wind-tunnel odel testing of wind flow atterns close to building facades. J. Wind Eng. Indus. Aerodynaics, 6: DOI: / (80) Yokel, F.Y., W.C. Yancey and C.L. Mullen, Study of reaction forces on obile hoe foundations caused by wind and flood loads. 1st Edn., NTIS, Sringfield, VA., : 84. Zaidi, A.M.A., Q.B.A.I. Latif, I.A. Rahan and M.Y. Isail, Develoent of eirical rediction forula for enetration of ogive nose hard issile into concrete targets. A. J. Alied Sci., 7: DOI: /ajass