Design of shallow foundations for optical and nursing faculty An Najah National University Collage of Engineering Civil Engineering department Design of shallow foundations for optical and nursing faculty

Submitted To: Dr.Isam Jardaneh Prepared by: Qasem Basem Batyeh Ahmad Kazem Ramahi

The Project The site is located in Nablus city,al Jneed Street, in Najah University. The building is consists of seven stories, and the area of each stories is about 1200m2 ,this building contains 37 columns the aim of this research is to design foundations with more practical and economic.

3D-MODEL

This project contains : Chapter one: Introduction to foundation. Chapter two: Types of foundations. Chapter three: Structural system. Chapter four: Site Investigation. Chapter five: Geotechnical and structural design of foundation. Appendix.

Types of Foundations: Shallow foundations: Shallow foundations are those founded near to the finished ground surface, generally where the founding depth (Df) is less than 3 m. Types of shallow foundations: 1.    Isolated footing.

Shallow foundations types 2.Combined footings.

Shallow foundations types 3.Continuous footings. 4.Strap footing.

Shallow foundations types 5.Mat foundation.

Structural system As we know any structure consist from elements ,these elements can be classified into:   Slab. Columns. Beams. Walls. Foundation.

Description of the building : This project is about the optical and nursing collage, which located at Al Najah University at al- Jneed street . The optical and nursing collage consists of six stories and the roof . three of these stories are basement stories and the other three stories and the roof are over ground . the area of each story is about 1200 m2 .

loads Load calculations: The load calculations in this project was calculated by Sap program. Live load = 400 Kg/ m2 super imposed dead load = 500Kg/m²

structural analysis using sap 2000 In this project we use sap 2000 to analyze the load and find the reaction at all columns . The reaction of footings from column were tabulated on table 3.1 and the reaction on footing from shear wall on table 3.2 .

Site Investigation The Site Investigation of the site were studied through comprehensive site investigation, carried out on November 2009 by Al-Meezan Engineering laboratories. Six boreholes were dug out in site to carry the subsurface investigation.

Site Description The geological section (Figure 4.1) shows that the site has one distinct soil stratum, which is grayish silty clay of low plasticity with pebbles and boulders of varying sizes. The collected sample was tested for physical and mechanical properties .the following are the main soil properties required for foundation design purposes:

Calculating of baring capacity of soil Cohesion ( c ) = 0.7kg/cm2 Angle of internal friction (φ) = 0 Unit weight (γ) = 17.5 kN/m3 According to bearing capacity equations, the allowable bearing capacity is 1.5 kg/cm2.

Geotechnical and structural design of foundation After analysis of the structure and loads of columns and shear walls were found , geotechnical and structural design the proposed project building is presented in this chapter . The first trial is to try to design single footing by using ( found program ) and table 5.1 shows the width of single footing . It was found that the sizes and area of single footing are too large and cause overlap stress between adjacent footings . The second trial is to design mat foundation by using SAP program and this chapter presents detailed design of mat foundation .

Design Mat Foundation Due to the above mentioned reasons and the total excavation for all single footings are more than 50% , then a second foundation choice for the suggested building project is mat foundation . Our proposed structure is symmetry and we use the SAP program for taking the moment .

The picture below takes from SAP shows the mat foundation .

steps for designing the mat foundation 1. check punching shear for finding the depth of mat : Applying the equation of punching shear on the critical column (F6 , K6 ) with load equal 498 ton .

steps for designing the mat foundation Vd = Ф Vcp Acr Acr = d (0.5 + d ) (4) Pu = 498 ton Vd = 0.75 * 1.06 *10 * ( 0.5 +d ) (4)(d) ( ) D = 0.79 m H = 0.85 m

steps for designing the mat foundation 2. The parameter used were : Mat depth = 0.85 m . Fc = 240 kg / cm2 fy = 4200 kg / cm2 loads from table 3.1 and 3.2 . SAP deals with bearing capacity as area spring force= qall * k=1.5*120=180 .

steps for designing the mat foundation 3. calculate steel ratio (𝜌 ) : From SAP we find the ultimate moment on three zones in x- direction and three zones on y-direction . we find the maximum positive moment and the maximum negative moment on each zone. After finding Mu we apply the equation of steel ratio (𝜌 ) then finding area of steel then number of bars .

steps for designing the mat foundation AST = 𝜌 . b . d where b,d in cm . 𝜌min = 0.0018 . ASTmin = 0.0018 * b * h . Take the maximum positive moment and the maximum negative moment in each zone and then find the area of steel ( take the larger area of steel between the AST from moment and the ASTmin ).

Result of analysis of the mat foundation The out put data and there calculations in details are put in zones according to there column strips and middle strips in both direction x and y axis . M11 due to x-axis and M22 due to y-axis . The distributing of steel bars in mat must be in correct way so as to help labors in the site of the work . The reinforcement depends upon the sign of moment . The negative moment take the top steel and the positive moment take the bottom steel bars .

Moment in x direction ( M11 ) : Zone 1 Zone 2 Zone 1

AST min = 15.3 cm2 Zone 1 : X1 = 0 Y1 = 0 X2 = 12.9 m X2= 37.5 m X1 = 12.9 m Y1 = 0 X2 = 25.62 m Y2= 37.5 m M 11 (ton.m) AST ( cm2 ) The bars -122 ( top steel) 45.3 1Y32 / 20cm + 70 (bottom steel ) 26 1Y25 / 20 cm M11 ( ton .m ) AST ( cm2 ) The bars -45 ( top steel ) 16.7 1Y20 / 20 cm + 70 ( bootom steel ) 26 1Y25 / 20 cm

Moment in Y direction ( M22 ) : Zone1 Zone2

ASTmin = 15.3 cm2 Zone 1 : Y1 = 0 X1 = 0 Y2 = 9.4 m X2= 38.56 m M22 ( ton.m ) AST ( cm2 ) The bars -90 ( top steel ) 33.5 1Y28/ 20 cm +20 (bottom steel ) 7.5 < 15.3 1Y20 / 20 cm M22 ( ton.m ) AST (cm2 ) The bars -50 ( top steel ) 18.6 1Y20/20cm +30 (bottom steel ) 11.2 <15.3

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