What is a Total Station

Although taping and theodolites are used regularly on site – total stations are
also used extensively in surveying, civil engineering and construction because
they can measure both distances and angles.

A typical total station is shown in the figure below

The appearance of the total station is similar to that of an electronic theodolite,
but the difference is that it is combined with a distance measurement component
which is fitted into the telescope.
Because the instrument combines both angle and distance measurement in the
same unit, it is known as an integrated total station which can measure horizontal
and vertical angles as well as slope distances.
Using the vertical angle, the total station can calculate the horizontal and vertical
distance components of the measured slope distance.
As well as basic functions, total stations are able to perform a number of different
survey tasks and associated calculations and can store large amounts of data.
As with the electronic theodolite, all the functions of a total station are controlled
by its microprocessor, which is accessed thought a keyboard and display.
To use the total station, it is set over one end of the line to be measured and
some reflector is positioned at the other end such that the line of sight between
the instrument and the reflector is unobstructed (as seen in the figure below).
-The reflector is a prism attached to a detail pole
-The telescope is aligned and pointed at the prism
-The measuring sequence is initiated and a signal is sent to the reflector and a
part of this signal is returned to the total station
-This signal is then analysed to calculate the slope distance together with the
horizontal and vertical angles.
-Total stations can also be used without reflectors and the telescope is pointed at
the point that needs to be measured
-Some instruments have motorised drivers and can be use automatic target
recognition to search and lock into a prism – this is a fully automated process and
does not require an operator.
-Some total stations can be controlled from the detail pole, enabling surveys to
be conducted by one person

A total station is levelled and centred in the same way as a theodolite.
Most total stations have a distance measuring range of up to a few kilometres,
when using a prism, and a range of at least 100m in reflector less mode and an
accuracy of 2-3mm at short ranges, which will decrease to about 4-5mm at 1km.

Although angles and distances can be measured and used separately, the most
common applications for total stations occur when these are combined to define
position in control surveys.
As well as the total station, site surveying is increasingly being carried out using
GPS equipment. Some predictions have been made that this trend will continue,
and in the long run GPS methods may replace other methods.
Although the use of GPS is increasing, total stations are one of the predominant
instruments used on site for surveying and will be for some time.
Developments in both technologies will find a point where devices can be made
that complement both methods.

How to Leveling the Total Station

• Leveling the Total Station must be accomplished to sufficient accuracy otherwise the instrument will not report results
• Leveling the instrument takes 30 to 45 minutes  make sure you can see all targets from the instrument station before going through the process

Step 1: Tripod Setup

Tripod legs should be equally spaced

Tripod head should be approximately level

Head should be directly over survey point

Step 2: Mount Instrument on Tripod

• Place Instrument 
  on Tripod

• Secure with 
  centering screw 
  while bracing the 
  instrument with 
  the other hand

• Insert battery in 
  instrument before 
  leveling

Step 3: Focus on Survey Point

Focus the optical plummet on the survey point

Step 4: Leveling the Instrument

•  Adjust the leveling foot screws to center the

survey point in the optical plummet reticle

• Center the bubble in the circular level by

adjusting the tripod legs

• Loosen the horizontal clamp and turn instrument until plate level is parallel to 2 of the leveling foot screws

•  Center the bubble using the leveling screws- the bubble moves toward the screw that is turned clockwise

• Rotate the instrument 90 degrees and level using the3rd leveling screw

• Observe the survey point in the optical plummet and center the point by loosening the centering screw and sliding the entire instrument

•  After re-tightening the centering screw check to make sure the plate level bubble is level in several directions

How to Primary Setup of Total Station

Benefits of steel reinforced concrete slabs

Here are the benefits of steel reinforced concrete slabs:
• Steel reinforcing is simple to place.
• Steel reinforcing reduces random cracking.
• Steel reinforcing reduces and controls crack width and
helps maintain aggregate interlock.
• Displacement and curling can be minimized when steel
reinforced concrete is provided.
• Strength is increased with steel reinforced concrete—
even the smallest cross sectional area of steel reinforcement
will provide reserve strength of l 6 percent and more.
• Most importantly, steel reinforcement saves money over
the life of the slab.
• Finally, admixtures are not an alternative to steel reinforcement;
they both do different things in the concrete.

Therefore, admixtures cannot be substituted for steel reinforcement.
The steel reinforcement industry is dedicated to providing
quality steel reinforcement to the construction industry. It is
also essential that steel reinforcement be sized, spaced, and
placed properly. It is vital to have a well-graded and compacted
granular subbase.
Of course, total quality can only be achieved when well
qualified suppliers and contractors are on the construction
sites.
References
1. Lanning, Anne, “Synthetic Fibers,” Concrete Construction, July 1992.
2. Ringo, Boyd C., and Anderson, Robert B., “Designing Floor Slabs On
Grade Step-by-Step Procedures Sample Solutions and Commentary “Second
Edition, The Aberdeen Group, 1996.
3. Anderson, Robert B., “Innovative Ways to Reinforce Slabs-On-
Ground” WRI Publication TF-705, 1996.
4. “Supports for Welded Wire Reinforcements in Slabs-On-Grade,” WRI
Publication TF-702.

Design Loads for Residential Buildings .

The load combinations in Table 3.1 are recommended for use with design specifications based on allowable stress design (ASD) and load and resistance factor design (LRFD). Load combinations provide the basic set of building load conditions that should be considered by the designer. They establish the proportioning of multiple transient loads that may assume point-in-time values when the load of interest attains its extreme design value. Load combinations are intended as a guide to the designer, who should exercise judgment in any particular application. The load combinations in Table 3.1 are appropriate for use with the design loads determined in accordance with this chapter.
The principle used to proportion loads is a recognition that when one load attains its maximum life-time value, the other loads assume arbitrary point-in-
time values associated with the structure’s normal or sustained loading conditions. The advent of LRFD has drawn greater attention to this principle (Ellingwood et al., 1982; Galambos et al., 1982). The proportioning of loads in this chapter for allowable stress design (ASD) is consistent with and normalized to the proportioning of loads used in newer LRFD load combinations. However, this manner of proportioning ASD loads has seen only limited use in current code-recognized documents (AF&PA, 1996) and has yet to be explicitly recognized in design load specifications such as ASCE 7. ASD load combinations found in building codes have typically included some degree of proportioning (i.e., D + W
+ 1/2S) and have usually made allowance for a special reduction for multiple transient loads. Some earlier codes have also permitted allowable material stress increases for load combinations involving wind and earthquake loads. None of these adjustments for ASD load combinations is recommended for use with Table 3.1 since the load proportioning is considered sufficient

It should also be noted that the wind load factor of 1.5 in Table 3.1 used for load and resistant factor design is consistent with traditional wind design practice (ASD and LRFD) and has proven adequate in hurricane-prone environments when buildings are properly designed and constructed. The 1.5 factor is equivalent to the earlier use of a 1.3 wind load factor in that the newer wind load provisions of ASCE 7-98 include separate consideration of wind directionality by adjusting wind loads by an explicit wind directionality factor, KD, of 0.85. Since the wind load factor of 1.3 included this effect, it must be adjusted to 1.5 in compensation for adjusting the design wind load instead (i.e., 1.5/1.3 = 0.85). The 1.5 factor may be considered conservative relative to traditional design practice in nonhurricane-prone wind regions as indicated in the calibration of the LRFD load factors to historic ASD design practice (Ellingwood et al., 1982; Galambos et al., 1982). In addition, newer design wind speeds for hurricane-prone areas account for variation in the extreme (i.e., long return period) wind probability that occurs in hurricane hazard areas. Thus, the return period of the design wind speeds along the hurricane-prone coast varies from roughly a 70- to 100-year return period on the wind map in the 1998 edition of ASCE 7 (i.e., not a traditional 50-year return period wind speed used for the remainder of the United States). The latest wind design provisions of ASCE 7 include many advances in the state of the art, but the ASCE commentary does not clearly describe the condition mentioned above in support of an increased wind load factor of 1.6 (ASCE, 1999). Given that the new standard will likely be referenced in future building codes, the designer may eventually be required to use a higher wind load factor for LRFD than that shown in Table 3.1. The above discussion is intended to help the designer understand the recent departure from past successful design experience and remain cognizant of its potential future impact to building design.
The load combinations in Table 3.1 are simplified and tailored to specific application in residential construction and the design of typical components and systems in a home. These or similar load combinations are often used in practice as short-cuts to those load combinations that govern the design result. This guide makes effective use of the short-cuts and demonstrates them in the examples provided later in the chapter. The short-cuts are intended only for the design of residential light-frame construction.

Note:
1The load combinations and factors are intended to apply to nominal design loads defined as follows: D = estimated mean dead weight of
the construction; H = design lateral pressure for soil condition/type; L = design floor live load; Lr = maximum roof live load anticipated
from construction/maintenance; W = design wind load; S = design roof snow load; and E = design earthquake load. The design or nominal
loads should be determined in accordance with this chapter.
2Attic loads may be included in the floor live load, but a 10 psf attic load is typically used only to size ceiling joists adequately for access
purposes. However, if the attic is intended for storage, the attic live load (or some portion) should also be considered for the design of
other elements in the load path.
3The transverse wind load for stud design is based on a localized component and cladding wind pressure; D + W provides an adequate and
simple design check representative of worst-case combined axial and transverse loading. Axial forces from snow loads and roof live loads
should usually not be considered simultaneously with an extreme wind load because they are mutually exclusive on residential sloped
roofs. Further, in most areas of the United States, design winds are produced by either hurricanes or thunderstorms; therefore, these wind
events and snow are mutually exclusive because they occur at different times of the year.
4For walls supporting heavy cladding loads (such as brick veneer), an analysis of earthquake lateral loads and combined axial loads should
be considered. However, this load combination rarely governs the design of light-frame construction.
5Wu is wind uplift load from negative (i.e., suction) pressures on the roof. Wind uplift loads must be resisted by continuous load path
connections to the foundation or until offset by 0.6D.
6The 0.6 reduction factor on D is intended to apply to the calculation of net overturning stresses and forces. For wind, the analysis of
overturning should also consider roof uplift forces unless a separate load path is designed to transfer those forces.

What is Structural Systems

Over many years, engineers have observed that some structural systems perform
better in earthquakes than others. Based on these observations, the Provisions
design criteria for building structures are based on the structural system used.
Structural systems are categorized based on the material of construction (e.g.,
concrete, masonry, steel, or wood), by the way in which lateral forces induced by
earthquake shaking are resisted by the structure (e.g., by walls or frames), and by
the relative quality of seismic-resistant design and detailing provided.
The Provisions recognizes six broad categories of structural system:

• Bearing wall systems,
• Building frame systems,
• Moment-resisting frame systems,
• Dual systems,
• Cantilever column systems, and
• Systems not specifically designed for seismic resistance.

In bearing wall systems, structural walls located throughout the structure provide
the primary vertical support for the building’s weight and that of its contents as
well as the building’s lateral resistance. Bearing wall buildings are commonly
used for residential construction, warehouses, and low-rise commercial buildings
of concrete, masonry, and wood construction. Figures 21, 22, and 23 show typical
bearing wall buildings.

Building frames are a common structural system for buildings constructed of
structural steel and concrete. In building frame structures, the building’s weight
is typically carried by vertical elements called columns and horizontal elements
called beams. Lateral resistance is provided either by diagonal steel members
(termed braces) that extend between the beams and columns to provide horizontal
rigidity or by concrete, masonry, or timber shear walls that provide lateral
resistance but do not carry the structure’s weight. In some building frame
structures, the diagonal braces or walls form an inherent and evident part of the
building design as is the case for the high-rise building in San Francisco shown in
Figure 24. In most buildings, the braces or walls may be hidden behind exterior
cladding or interior partitions.
Moment-resisting frame systems are commonly used for both structural steel and
reinforced concrete construction. In this form of construction, the horizontal
beams and vertical columns provide both support for the structure’s weight and
the strength and stiffness needed to resist lateral forces. Stiffness and strength are
achieved through the use of rigid connections between the beams and columns
that prevent these elements from rotating relative to one other. Although somewhat
more expensive to construct than bearing wall and braced frame structural
systems, moment-resisting frame systems are popular because they do not
require braced frames or structural walls, therefore permitting large open spaces
and facades with many unobstructed window openings. Figure 25 shows a steel
moment-resisting frame building under construction.
Dual systems, an economical alternative to moment-resisting frames, are commonly
used for tall buildings. Dual system structures feature a combination of
moment-resisting frames and concrete, masonry, or steel walls or steel braced

frames. The moment-resisting frames provide vertical support for the structure’s
weight and a portion of the structure’s lateral resistance while most of the lateral
resistance is provided either by concrete, masonry, or steel walls or by steel braced
frames. Some dual systems are also called frame-shear wall interactive systems.
Cantilever column systems are sometimes used for single-story structures or in
the top story of multistory structures. In these structures, the columns cantilever
upward from their base where they are restrained from rotation. The columns
provide both vertical support of the building’s weight and lateral resistance to
earthquake forces. Structures using this system have performed poorly in past
earthquakes and severe restrictions are placed on its use in zones of high seismic
activity.

In regions of relatively low seismic risk, the NEHRP Recommended Seismic
Provisions permits the design and construction of structural steel buildings that
do not specifically conform to any of the above system types. These buildings are
referred to as “structures not specifically detailed for seismic resistance.”

In addition to these basic structural systems and the primary materials of construction,
the Provisions also categorizes structural systems based on the quality
and extent of seismic-resistant detailing used in a structure’s design. Systems that
employ extensive measures to provide for superior seismic resistance are termed
“special” systems while systems that do not have such extensive design features
are typically called “ordinary” systems. The Provisions also includes design rules
for structural systems intended to provide seismic resistance that is superior to
that of “ordinary” systems but not as good as that of “special” systems; these systems
are called “intermediate” systems.

What is Buildings

Generally, a building can be defined as an enclosed structure intended for human
occupancy. However, a building includes the structure itself and nonstructural
components (e.g., cladding, roofing, interior walls and ceilings, HVAC systems,
electrical systems) permanently attached to and supported by the structure. The
scope of the Provisions provides recommended seismic design criteria for all
buildings except detached one- and two-family dwellings located in zones of
relatively low seismic activity and agricultural structures (e.g., barns and storage
sheds) that are only intended to have incidental human occupancy. The Provisions
also specifies seismic design criteria for nonstructural components in buildings
that can be subjected to intense levels of ground shaking.

What is Load Combinations

As per IS 1893 (Part 1): 2002 Clause no. 6.3.1.2,
the following load cases have to be considered for
analysis:
1.5 (DL + IL)<>
1.2 (DL + IL ± EL)<>
1.5 (DL ± EL)<>
0.9 DL ± 1.5 EL<>
Earthquake load must be considered for +X, -X,
+Z and –Z directions. Moreover, accidental
eccentricity can be such that it causes clockwise
or anticlockwise moments. Thus, ±EL above
implies 8 cases, and in all, 25 cases as per Table 3
must be considered. It is possible to reduce the
load combinations to 13 instead of 25 by not
using negative torsion considering the symmetry
of the building. Since large amount of data is
difficult to handle manually, all 25-load
combinations are analysed using software.
For design of various building elements (beams or
columns), the design data may be collected from
computer output. Important design forces for
selected beams will be tabulated and shown
diagrammatically where needed. . In load
combinations involving Imposed Loads (IL), IS
1893 (Part 1): 2002 recommends 50% of the
imposed load to be considered for seismic weight
calculations. However, the authors are of the
opinion that the relaxation in the imposed load is
en conservative. This example therefore, considers
100% imposed loads in load combinations.
For above load combinations, analysis is
performed and results of deflections in each
storey and forces in various elements are
obtained.

How to Test Soil Compaction

There are many types of Soil compaction tests which are performed on soil. Some of these are :-

1) The Sand Cone Method
One of the most common test to determine the field density of soil is the sand-cone method. But it has a major limitation that this test is not suitable for saturated and soft soils

The formula used are
Volume of soil, ft³ (m³)=[weight of sand filling hole, lb (kg)] /[ Density of sand, lb/ft³ (kg/m³)]

% Moisture = 100(weight of moist soil – weight of dry soil)/weight of dry soil

Field density, lb/ft³ (kg /m³)=weight of soil, lb (kg)/volume of soil, ft³ (m³)

Dry density=field density/(1 + % moisture/100)

% Compaction=100 (dry density)/max dry density

Maximum density is found by plotting a density–moisture curve.

2) California Bearing Ratio
The California bearing ratio (CBR) is used as a determine the quality of strength of a soil under a pavement. It also measures the thickness of the pavement, its base, and other layers.
CBR = F/F_o
where
F = force per unit area required to penetrate a soil mass with a 3-in² (1935.6-mm² ) circular piston (about 2 in (50.8 mm) in diameter) at the rate of 0.05 in/min (1.27 mm/min)

F₀ = force per unit area required for corresponding penetration of a standard material.

3) Soil Permeability
Darcy’s law is applicable in determining the soil permeability. Darcy law states that
V = kiA

where
V = rate of flow, cm³ /s,
A = cross-sectional area of soil conveying flow, cm²
k = Coefficient of permeability which depends on grain-size distribution, void ratio and soil fabric. The value varies from 10 cm/s for gravel to less than 10^–7 for clays.

Compression test for concrete, should test cubes or test cylinders be adopted?

Basically, the results of compression test carried out by using cubes are higher than that by cylinders. In compression test, the failure mode is in the form of tensile splitting induced by uniaxial compression. However, since the concrete samples tend to expand laterally under compression, the friction developed at the concrete-machine interface generates forces which apparently increase the compressive strength of concrete.

 However, when the ratio of height to width of sample increases, the effect of shear on compressive strength becomes smaller. This explains why the results of compression test by cylinders are lower than that of cubes. Reference is made to Longman Scientific and Technical (1987).

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.