Foundation design of Al-Wasef complex Under the Supervision of: Dr. Sami Al Hijjaw Prepared by: Mohammad Shalabi Ahmed Al- Qasarwah Iman Bani Shamseh May 2012 An-Najah National University Engineering Collage Civil Engineering Department Type of the building: commercial building . Location: Nablus city, In Albsateen region, near to the west lot. Number of stories: 13 story, 3 stories settle below ground(basement) , one story at the level ground , and 9 stories above the ground. Total area of the building: 6400m² . Project Description Select the most suitable types of foundations for the project. Design the selected footings. Estimate costs of the foundations designed. Foundations are the part of building which receive and transmit the loads to the supporting soil or rocks. Scope of Project Many factors should be taken into consideration in choosing foundation types such as soil properties , economic factors, engineering practice, ....etc . There are two types of foundations : shallow & deep foundations. 6 Isolated Footing. Combined Footing. Mat or Raft Foundations. Strap or Cantilever Footings. Types of shallow foundation 7 Are used to support single columns. This is one of the most economical types of footings and is used when columns are spaced at relatively long distances. Its function is to spread the column load to the soil , so that the stress intensity is reduced .   Isolated Footings 1) When there are two columns so close to each other & in turn the two isolated footing areas would overlap. 2) When the combined stresses are more than the allowable bearing capacity of the soil. 3) When columns are placed at the property line. Combined footing Are used to spread the load from a structure over a large area, normally the entire are of the structure . They often needed on soft or loose soils with low bearing capacity as they can spread the loads over a larger area. They have the advantage of reducing differential settlements. Mat or Raft Foundations They are long & slender members that are used to carry & transfer the load of the structure to deeper soil or rocks of high bearing capacity, when the upper soil layer are too weak to support the loads from the structure. Piles costs more than shallow foundations; so the geotechnical engineer should know in depth the properties & conditions of the soil to decide whether piles are needed or not. Deep foundation- pile footing Bearing capacity is the ability of soil to support a load from structural foundation failure or differential settlement. There are three modes of failure that limit bearing capacity: General shear failure. Local shear failure. Punching shear failure. Bearing capacity The investigation report obtained at ARABEX office. Three bore holes were drilled to the depths of ( 15, 15 , and 20) meter . Representative samples were tested: Geotechnical investigation Borehole No. Depth (m) Moisture Content (%) Passing 200 (%)     PI     Cohesion (KN/m²) Angle of Internal frictionᶲ (°)   1   0.0-7.0 18.6 78 15.7 12 15 7.0-20.0 9.2 - NP       2     0.0-0.50 14.7 82 11.3     0.50-2.5 19.1 74 10.6     2.5-15.0 16.8 79 17.4 10 15   3     0.0-0.50 12.5 80 12.2     0.50-2.5 18.3 73 11.8     2.5-15.0 19.4 83 18.7 12 15 Results of soil testing According to the results of soil testing ,by using Terzagi equation ,it`s found that the bearing capacity of soil is equal to 202 mega pascal (2kg/cm²) at a minimum depth of ten meters (10m) from street level Result The bearing capacity on the surface of the foundation level should be 2.5 kg/ cm² ( improved to be in safe side) Recommended foundation type : mat or raft foundation . It recommended to protect the building from the effects of water and prevent water to reach under foundation . Recommendations Structural design Column loads are calculated using (sap program), the structure subjected to the following loads: 1) Dead Load (own weight). 2) Super imposed dead load =300 kg/m2. 3) Live load =800 kg/m2. Using ACI code, the ultimate loads are calculated considering load combination : Pu =1.2Dead + 1.6Live. Material characteristics used in this project are: f’c =280kg/cm2 (B 350) Where: f’c is the compressive strength of concrete fy = 4200 kg/cm2 Where: fy is the yield strength of steel NO . Of Ultimate Column Load (ton) C1A 1223 C1B 1120 C1C 1140 C1D 850 C2A 800 C2B 884 C2C 850 C2D 818 C3A 500 C3B 636 C3C 640 C3D 610 C3E 680 Assume a depth of mat footing by using a rule of thumb : d for interior column . for edge column . for corner column . where pu is the critical column ultimate load . 2. Check critical column for punching shear . To find the depth of foundation: Pu for critical column = 1223 ton 1223 * 9.81= 12000 KN = 1095 mm Assume d = 1100 mm , h = 1200 mm Chick for punching shear : φVcp = 0.75(1/3) (1800*2 +2500*2)*1200/1000 φVcp = 13652 > 12000 (OK) To find the depth of foundation: 3D – Mat Foundation The values of maximum moment in (X),(Y) directions are taken from SAP14.The figures below show the moment in (X),(Y) direction. Maximum moment in (X) and (Y)directions reinforcement in x direction: we take the maximum moment at the face of columns the area of reinforcement will calculate by the Equation: As =p*b*d 1)at the face of column (from Sap program) Mu =870KN.m/m Use ρmin=0.0018 As = 0.0018 *1000*1200=2160mm² use 10Ф18 mm/m Also between the columns use 10Ф18 mm/m Reinforcement reinforcement in y direction: we take the maximum moment at the face of columns the area of reinforcement will calculate by the Equation: As =p*b*d 1)at the face of column (from Sap program) Mu =930KN.m/m Use ρmin=0.0018 As = 0.0018 *1000*1200=2160mm² use 10Ф18 mm/m Also between the columns use 10Ф18 mm/m Reinforcement Design of Piles: A computer program called AllPiles is used to prepare allowable bearing capacity with each pile length and diameter, table below shown the result: PILES FOUNDATIONS Dimensions of piles and capacities (KN) Diameter in m Length in m 14 16 18 20 0.6 308 352 411 448 0.8 435 532 615 684 1 601 704 833 950 one types of piles is selected in the design of pile foundation in this project which has a diameter of 1 meter and a length of 20 meters : The pile capacity of this pile = 950 KN Column No Service Load ( KN ) Allowable capacity of pile (KN) Service load / Allowable capacity No. of piles Dimension of cap(m*m) C1A 8570 950.3 9.018 9 6.3 * 6.3 C1B 7848 950.3 8.258 8 6.3 * 6.3 C1C 7988 950.3 8.406 9 6.3 * 6.3 C1D 5956 950.3 6.267 6 6.3 * 3.8 C2A 5606 950.3 5.899 6 6.3 * 3.8 C2B 6194 950.3 6.518 7 6.3 * 6.3 C2C 5956 950.3 6.267 6 6.3 * 3.8 C2D 5732 950.3 6.031 6 6.3 * 3.8 C3A 3503 950.3 3.683 4 3.8 * 3.8 C3B 4415 950.3 4.645 5 6.3 * 6.3 C3C 4485 950.3 4.719 5 6.3 * 6.3 C3D 4274 950.3 4.497 5 6.3 * 6.3 C3E 4765 950.3 5.014 5 6.3 * 6.3 Table below shows the allowable applied load and the No. of piles with cap’s dimensions that each group of column has. The equations below is used to determine the area of steel : Calculate Mu Mn = Mu/0.9 Mn = R*b*d² : Mn , b and d are known . Find R From ACI tables using the value of R we’ll find ρ As = ρ * b * d Reinforcement Details of Piles For column C1A: P1U= Ultimate load on C1A = 12000 KN . No. of pile around C1A= 9 piles . 12000KN/ 9piles = 1333 KN per each pile . Shear force = 400 KN Ultimate moment= 2.5 *4000 =10000KN.m   Mn= Mu/Ø = 10000/0.9=11100KN.m Mn=Rbd˄2, for C1A : R= 1.46 so p= 0.0036 then As= p*b*d= 0.0036 * 3600 * 1100= 14256 mm˄2 Example Of Design Cap Cap Number Reinforcement in long direction Reinforcement short direction Cap of C1A 31Ø32 31 Ø32 Cap of C1B 32Ø32 32Ø32 Cap of C1C 31Ø32 31 Ø32 Cap of C1D 24Ø32 14Ø16 Cap of C2A 23Ø32 26Ø32 Cap of C2B 26Ø32 26Ø32 Cap of C2C 24Ø32 26Ø32 Cap of C2D 24Ø32 26Ø32 Cap of C3A 22Ø25 22Ø25 Cap of C3B 18Ø25 18Ø25 Cap of C3C 18Ø25 18Ø25 Cap of C3D 18Ø25 18Ø25 Cap of C3E 18Ø25 18Ø25 Cap reinforcement in two directions (main steel only ) is shown in table : For pile footing Quantity of all pile for concrete The quantity of concrete in cubic meter (m˄3) For each column: Pile Volume = No. Of piles * length of pile Area of pile = Π/4 * Diameter˄2 = Π/4 * 100˄2 = 7854 cm˄2 . The table below summarized the quantity of estimation for all piles: Comparison Of Costs Volume of concrete for piles NO . Of NO . Of Length of Cross section Total volume for Column Piles pile (M) area (M²) each column (M³) C1A 9 20 0.7854 141.372 C1B 8 20 0.7854 125.664 C1C 9 20 0.7854 141.372 C1D 6 20 0.7854 94.248 C2A 6 20 0.7854 94.248 C2B 7 20 0.7854 109.956 C2C 6 20 0.7854 94.248 C2D 6 20 0.7854 94.248 C3A 4 20 0.7854 62.832 C3B 5 20 0.7854 78.54 C3C 5 20 0.7854 78.54 C3D 5 20 0.7854 78.54 C3E 5 20 0.7854 78.54         Total volume 1272.348 Quantity of pile caps for concrete Caps volume: Volume of each cap= Area * height This is summarized in table shown below: Table 7.2 Volume of concrete for caps NO . Of First Second Hight Total volume for Column dimension (M) dimension (M) (M) each Cap (M³) C1A 6.3 6.3 1.2 47.628 C1B 6.3 6.3 1.2 47.628 C1C 6.3 6.3 1.2 47.628 C1D 6.3 3.8 1.1 26.334 C2A 6.3 3.8 1.1 26.334 C2B 6.3 6.3 1.1 43.659 C2C 6.3 3.8 1.1 26.334 C2D 6.3 3.8 1.1 26.334 C3A 3.8 3.8 0.9 12.996 C3B 4.8 4.8 0.9 20.736 C3C 4.8 4.8 0.9 20.736 C3D 4.8 4.8 0.9 20.736 C3E 4.8 4.8 1 23.04       Total volume 390.123 Quantity of steel for piles and caps Length of pile used = 12 m, but length of steel required = 12+12 = 24m, because of lap splices . This is summarized in the table shown below: Now total volume for concrete = Volume for all piles + volume for all caps So total volume= 390.123 + 1272.348= 1662.471 m˄3 total volume of steel for piles NO . Of NO . Of Area of Length of Total volume for Column Piles steel (M²) steel bars(M) each column (M³) C1A 9 0.00393 24 0.84888 C1B 8 0.00393 24 0.75456 C1C 9 0.00393 24 0.84888 C1D 6 0.00393 24 0.56592 C2A 6 0.00393 24 0.56592 C2B 7 0.00393 24 0.66024 C2C 6 0.00393 24 0.56592 C2D 6 0.00393 24 0.56592 C3A 4 0.00393 24 0.37728 C3B 5 0.00393 24 0.4716 C3C 5 0.00393 24 0.4716 C3D 5 0.00393 24 0.4716 C3E 5 0.00393 24 0.4716       Total volume 7.63992 NO . Of Direction Area of steel Length of bar Volume Column   needed (M²) needed (M²)   C1A ONE 0.025 8 0.2 TWO 0.025 8 0.2 C1B ONE 0.02564 8 0.20512 TWO 0.02564 8 0.20512 C1C ONE 0.025 8 0.2 TWO 0.025 8 0.2 C1D LONG 0.019 8 0.152 SHORT 0.0208 5.5 0.1144 C2A LONG 0.01786 8 0.14288 SHORT 0.0208 5.5 0.1144 C2B ONE 0.02079 8 0.16632 TWO 0.02079 8 0.16632 C2C LONG 0.019 8 0.152 SHORT 0.02079 5.5 0.114345 C2D LONG 0.019 8 0.152 SHORT 0.02079 5.5 0.114345 C3A ONE 0.01064 5.5 0.05852 TWO 0.01064 5.5 0.05852 C3B ONE 0.01425 6.5 0.092625 TWO 0.01425 6.5 0.092625 C3C ONE 0.01425 6.5 0.092625 TWO 0.01425 6.5 0.092625 C3D ONE 0.01425 6.5 0.092625 TWO 0.01425 6.5 0.092625 C3E ONE 0.01425 6.5 0.092625 TWO 0.01425 6.5 0.092625       Total volume 3.45729 image3.gif image4.jpeg image5.jpeg image6.jpeg image7.png image8.jpeg image9.jpeg image10.png image11.png image12.png image13.png image14.png image15.png image16.png image17.png /docProps/thumbnail.jpeg