5.2.1 Introduction
Using application software such as STAAD and ETABS, the design of the proposed school building will be utilized precisely and effectively. STAAD was used for
the two trusses that will cover the open spaced of the structure. ETABS designed the whole super structure since the roof deck is made of reinforced concrete. Lastly, the application software SAFE concentrated on the design of the foundation of the structure.
SAFE is an application that focuses on the design of the foundation; the data processed in ETABS can be transferred through this program.
5.2.2 Beam Design
Using ETABS, the design and analysis of beams was computed.
***See Appendix
5.2.3 Column Design
Using ETABS, the design and analysis of columns was computed.
***See Appendix
5.2.4 Slab Design
Using ETABS, the design and analysis of slab was computed.
5.2.4.1 One Way Slab
***See Appendix
5.2.4.2 Two Way Slab
***See Appendix
5.2.5 Design of Truss
The design of the truss in the structure to be considered is the open space found in corridors of the school building. In order to preve nt an overflow of water during typhoons the materials used in the truss analysis are made of Howe Truss. The roof in the truss is made of polycarbonate sheets.
5.2.5.1 Design Consideration
Polycarbonate Sheet (w = 4.0 kg/m2)
Polycarbonate Sheet Thickness, 4.5mm Roof Live Load , RLL = 0.6 kPa
Dead Load ,DL = 0.096 kPa Wind Load , WL = 0.6109 kPa
θ =23.50°
f y = 170 MPa
Bay Distance , L = 3 m
C 3 x 4.1
Ref er ence : Association of Structural Engineers of the Philippines (ASEP) Steel Manual
Actual stress along x-axis:
MPa
Actual stress along y-axis:
MPa
Allowable stress along x-axis:
MPa
Allowable stress along y-axis:
MP
Checking for Adequacy:
Since0.964 falls under 0.9 to 1.0, then the section of the purlins isadequate and economical.
Top Chords, Bottom Chords and Web Members
The Section & Its Properties
Orientation L 20 x 20 x 3
Weight, w(kg/m) 0.88
Area, A (mm ) 112
Radius of Gyration about X,
rx(mm) 5.9
Radius of Gyration about Y,
ry(mm) 5.9
5.2.5.2 Design of Howe Truss
STAAD Model
3D Model
STAAD Output
Table 5.3Support Reactions End Forces
JOINT LOAD
3 1 3 -0.65 0.00 0.00 0.00 0.00 0.00
4 0.65 0.00 0.00 0.00 0.00 0.00
2 3 0.00 0.00 0.00 0.00 0.00 0.00
4 0.00 0.00 0.00 0.00 0.00 0.00
4 1 4 3.27 0.00 0.00 0.00 0.00 0.00
5 -3.27 0.00 0.00 0.00 0.00 0.00
2 4 0.00 0.00 0.00 0.00 0.00 0.00
5 0.00 0.00 0.00 0.00 0.00 0.00
5 1 5 3.43 0.00 0.00 0.00 0.00 0.00
6 -3.43 0.00 0.00 0.00 0.00 0.00
2 5 0.00 0.00 0.00 0.00 0.00 0.00
6 0.00 0.00 0.00 0.00 0.00 0.00
6 1 6 -3.92 0.00 0.00 0.00 0.00 0.00
7 3.92 0.00 0.00 0.00 0.00 0.00
2 6 0.00 0.00 0.00 0.00 0.00 0.00
7 0.00 0.00 0.00 0.00 0.00 0.00
7 1 7 0.00 0.00 0.00 0.00 0.00 0.00
8 0.00 0.00 0.00 0.00 0.00 0.00
2 7 0.00 0.00 0.00 0.00 0.00 0.00
8 0.00 0.00 0.00 0.00 0.00 0.00
8 1 8 0.00 0.00 0.00 0.00 0.00 0.00
9 0.00 0.00 0.00 0.00 0.00 0.00
2 8 0.00 0.00 0.00 0.00 0.00 0.00
9 0.00 0.00 0.00 0.00 0.00 0.00
9 1 9 -10.34 0.00 0.00 0.00 0.00 0.00
10 10.34 0.00 0.00 0.00 0.00 0.00
2 9 0.00 0.00 0.00 0.00 0.00 0.00
10 0.00 0.00 0.00 0.00 0.00 0.00
10 1 10 -16.63 0.00 0.00 0.00 0.00 0.00
11 16.63 0.00 0.00 0.00 0.00 0.00
2 10 0.00 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00
11 1 11 -17.98 0.00 0.00 0.00 0.00 0.00
12 17.98 0.00 0.00 0.00 0.00 0.00
2 11 0.00 0.00 0.00 0.00 0.00 0.00
12 0.00 0 00 0.00 0.00 0.00 0.00
12 1 12 7.19 0.00 0.00 0.00 0.00 0.00
1 -7.19 0.00 0.00 0.00 0.00 0.00
2 12 0.00 0.00 0.00 0.00 0.00 0.00
1 0.00 0.00 0.00 0.00 0.00 0.00
13 1 2 1.95 0.00 0.00 0.00 0.00 0.00
12 -1.95 0.00 0.00 0.00 0.00 0.00
2 2 0.00 0.00 0.00 0.00 0.00 0.00
12 0.00 0.00 0.00 0.00 0.00 0.00
14 1 3 -0.59 0.00 0.00 0.00 0.00 0.00
11 0.59 0.00 0.00 0.00 0.00 0.00
2 3 0.00 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00
15 1 4 0.52 0.00 0.00 0.00 0.00 0.00
10 -0.52 0.00 0.00 0.00 0.00 0.00
2 4 0.00 0.00 0.00 0.00 0.00 0.00
10 0.00 0.00 0.00 0.00 0.00 0.00
16 1 5 4 .49 0.00 0.00 0.00 0.00 0.00
9 -4.49 0.00 0.00 0.00 0.00 0.00
2 5 0.00 0.00 0.00 0.00 0.00 0.00
9 0.00 0.00 0.00 0.00 0.00 0.00
17 1 6 8 .99 0.00 0.00 0.00 0.00 0.00
a -8.99 0.00 0.00 0.00 0.00 0.00
2 6 0.00 0.00 0.00 0.00 0.00 0.00
a 0.00 0.00 0.00 0.00 0.00 0.00
18 1 2 1. 47 0.00 0.00 0.00 0.00 0.00
11 -1.47 0.00 0.00 0.00 0.00 0.00
2 2 0.00 0.00 0.00 0.00 0.00 0.00
11 0.00 0.00 0.00 0.00 0.00 0.00
19 1 3 3.77 0.00 0.00 0.00 0.00 0.00
10 -3.77 0.00 0.00 0.00 0.00 0.00
2 3 0.00 0.00 0.00 0.00 0.00 0.00
10 0.00 0.00 0.00 0.00 0.00 0.00
20 1 5 -4.57 0.00 0.00 0.00 0.00 0.00
10 4 .57 0.00 0.00 0.00 0.00 0.00
2 5 0.00 0.00 0.00 0.00 0.00 0.00
10 0.00 0.00 0.00 0.00 0.00 0.00
21 1 6 -11.27 0.00 0.00 0.00 0.00 0.00
9 11.27 0.00 0.00 0.00 0.00 0.00
2 6 0.00 0.00 0.00 0.00 0.00 0.00
9 0.00 0.00 0.00 0.00 0.00 0.00
5.2.6 Design of Foundation
It is essential to carry out investigation before preparing the design of civil engineering works. The investigation may range in scope from simple examination of the surface soils, with or without a few shallow trial pits, to a detailed study of the soil and ground water conditions for a considerable depth below the ground surface by means of boreholes and in-situ and/ or laboratory test on the soils encountered. The extent of the investigation depends on the importance of the structure, the complexity of the soil conditions, and the information already available on the behavior of the existing foundations similar on soils. Thus, it is not the normal practice to sink boreholes and carry out soil tests for single or two story structure since normally, there is adequate knowledge of the safe bearing pressure of the soil in any particular locality. Only in troublesome soils such as peat or loose fill would it be necessary to sink deep boreholes, possibly supplemented by soil test. More extensive ground conditions where there is no
information available on foundation behavior of similar structures. Since the structure to be design is school building, it is very important to consider the type of soil to design the foundation efficiently and precisely. The type of soil to be design is the clayey soil thereore we use “rat” or matt oundation
Information was extracted from site investigation to facilitate foundation design.
This includes
General topography of the site which affects foundation design and construction e.g., surface configuration, adjacent property, presence of water course, and so on.
Location of buried services such as power lines, telephone cables, water mains, sewer pipes and so on.
General geology of the area within particular reference to the principal geological formations underlying the site.
Previous history and use of the site including information of any defects and failures of structure built on the site.
Any special features such as possibility o0f earthquake, flooding, seasonal swelling etc.
Availability and quality of local construction materials.
A detailed record of soil rock strata, ground water conditions within the zone affected by foundation loading and of any deeper strata affecting the site conditions in any way.
In designing the foundation of the structure, SAFE application was used. SAFE application is software that focuses on foundation design. This software designs different footings, from square footings, rectangular footings, combined footings, to matt footings and other kinds of footings. In the design of footings Structural Analysis of Finite Element was used. Matt Foundation is the type of foundation to be used in the design of substructure of the proposed building. SAFE is the ultimate tool for designing concrete floor and foundation systems. From framing layout all the way through to detail drawing production, SAFE integrates every aspect of the engineering design process in one easy and intuitive environment. It provides unmatched benefits to the engineer with its truly unique combination of power, comprehensive capabilities, and ease-of-use. Laying out models is quick and efficient with the sophisticated drawing tools, or use one of the import options to bring in data from CAD, spreadsheet, or database programs. Slabs or foundations can be of any shape, and can include edges shaped with circular and spline curves. Post-tensioning may be included in both slabs and beams to balance a percentage of the self-weight. Suspended slabs can include flat, two-way, waffle, and ribbed framing systems. Models can have columns, braces, walls, and ramps connected from the floors above and below. Walls can be modeled as either straight or curved.
We used raft foundation in designing soil foundation including different parameters used in mat foundation design. Modulus of subgrade reaction, assumptions and considerations to analyze mat as rigid or flexible foundation, loads that should account in mat foundation design, thickness rigidity relationship of mat, and thickness deflection relationship of mat was analyzed in the foundation design. In this post, we learned about analysis model that are used in computer software SAFE.
In this model finite elements are formed from object based model. Rectangular finite element mesh is developed depending on maximum allowable element size.
Computer oriented method for structural analysis is used to solve plates (raft) supported on elastic foundation. These rectangular finite elements are interconnected to adjacent one only at corners (nodes) and a isolated spring that resembles to soil are used in modeling.
Raft foundation is analyzed in SAFE based on classical theory for thick plates supported on the winkler foundations. The isolated spring assumed in modeling soil is called winkler foundation. This theory takes in to account the deformation due to transverse shear of the plate. This model is shown in the figure below.
Mat foundations can include nonlinear uplift from the soil springs, and a nonlinear cracked analysis is available for slabs. Generating pattern surface loads is easily done by SAFE with an automated option. Design strips can be generated by SAFE or drawn in a completely arbitrary manner by the user, with complete control provided
for locating and sizing the calculated reinforcement. Finite element design without strips is also available and useful for slabs with complex geometries.
Comprehensive and customizable reports are available for all an alysis and design results. Detailed plans, sections, elevations, schedules, and tables may be generated, viewed, and printed from within SAFE or exported to CAD packages.
SAFE provides an immensely capable yet easy-to-use program for structural designers, providing the only tool necessary for the modeling, analysis, design, and detailing of concrete slab systems and foundations.
5.2.6.1 Introduction
In designing the foundation of the structure, SAFE application was used. SAFE application is software that focuses on foundation design. This software designs different footings, from square footings, rectangular footings, combined footings, to matt footings and other kinds of footings. In the design of footings Structural Analysis of Finite Element was used. Matt Foundation is the type of foundation to be used in the design of substructure of the proposed building.
From the recommended soil investigation, the presence of the very loose/soft alluvial deposits between 0 to 9m depth would discourage the use of a shallow foundation. This layer is settlement prone and/or highly compressible based on the SPT blow counts. It is also strongly susceptible to liquefaction during a strong earthquake,
causing major damage to the structure under such an event. The soil bearing capacity is estimated to be less than 25 kpa, considerably too low to support the structure without shear failure and the settlement is extremely very excessive.
Higher bearing pressures of as high as 250 kPa can be generated below the bottom level of the alluvium. However, this will require mat footings and a deep foundation involving piles just to reach the hard strata wherein the stability of the foundation can be assured.
Properties of Concrete to be considered in SAFE software:
Concrete Compressive Strength ’c Mpa Modulus of Elasticity, E = 24650 Mpa
Properties of rebars to be considered in SAFE software:
Weight Per unit Volume, 77 KN/m3 Modulus of Elasticity, E =200000 Mpa Fy = 414 Mpa
Fu= 550 Mpa
Fig. 5.1 Shorter Direction Top Bar
Fig. 5.2Longer Direction Top Bar
Fig 5.3 Shorter Direction Bottom Bar
Fig 5.4 Longer Direction Bottom Bar
Soil Subgrade Modulus
Subgrade modulus of the soil from soft up to the hardest part which is bed rock may vary from 100 to 500 lb/ in3.
From the soil investigation report, the subgrade modulus of the soil was found to be clayey which makes the value up to 100 lb/ in3.
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