History Of Civil Engineering

History Of Civil Engineering                                    • Initially, all civil engineers including those who do not have the practice of military engineering, said he started in the eighteenth century France.

• First "Civil Engineer" was an Englishman, John Smeaton of the 1761st

• Civil engineers have saved more lives than all the doctors in history - the development of drinking water and sanitation.

• Henry H. White built the first building will be completed in Bacon KY (Georgetown) College in 1840.

• Fall of 1886, established "State College" (UK) degree in civil engineering.

• John Wesley Gunn of Lexington has received a first degree in civil engineering from A & M College (England) in 1890.

Marine engineering

What is incorporated in the method of underwater pipeline crossings?                                                                                                 Tube immersed under water crossing method associated with the following basic steps:

(I) precast units along the tunnel (steel or concrete shell), a dry dock or shipyard

(Ii) the floats and the trailer with movable partitions for the site

(Iii) Immerse the specimens in a pre-excavated trench

(Iv) Combining a unit for a

(V) covers the complete tunnel

An immersed tunnel steel is sometimes adopted because of ease of manufacture and its relative ease. In addition, shorter construction time required compared to concrete immersed tubes
How does the direction of the approaching speed of ships affected by the pier?

One of the main effects of the angle of speeds approaching vessel is its effect on energy to be absorbed by the defense system. Consider more ships berth at the dock themselves at the same speed but with a different approach, although their kinetic energy is the same, the amount of energy absorbed by the wing is different. The amount of energy absorbed by the wing is:

approach speeds of ships

where W = absorbed by the fender

m = mass of the spacecraft

v = velocity of the ship

k = radius of gyration of the ship

r = distance between the center of gravity of the ship at the contact point for the wings

So, when the direction of approaching the speed of the ship is a normal wing (ie, phi = 90), the amount of energy absorbed is less than the vessel at a speed tangent to the beach.

What Is The Design Of Landings In The Pillars?                                                                    Landings has been designed as a resting place for passengers during docking and undocking of vessels. Typically, the data say landing near the top and the average low water to facilitate the embarkation and disembarkation of passengers (BS6349: Part 2: 1988). Therefore, the level of landing steps may be different from place to place because of different high and say the average level of low water in different places.

If Morison Equation And Diffraction Analysis Will Be Adopted In Determining The Strength Of The Waves On Stilts?                                                       The choice between the Morison equation and diffraction analysis in determining wave forces on the piles depends on the ratio between the diameters of the piles of wavelength. If the relationship between the diameter of the wavelength of the batteries is less than 0.2, the Morison equation is usually

recommended. The reason behind this is that the effect of viscosity and separation is considerably lower than that. On the contrary, if the relationship between the diameter of the mass of the wavelength greater than 0.2, the waves are scattered with a negligible impact of separation. Such as diffraction analysis was adopted to calculate the wave forces on piles

Hudson And The Formula For Van Der Meer Formula Is Commonly Used In The Design Of The Armor. Which Is The Best Choice?                         Hudson formula is often adopted in the preliminary design to obtain rough initial estimate of the size of stone. The formula is derived from the regular wave tests. But this formula does not take into account the following, as Van der Meer formula do: wave period, the level of damage, the permeability of the structure and duration of storm. In addition, the Hudson formula relates to the use of regular waves only.

Compared to the formula of Hudson, Van der Meer formula is more complicated and is derived from the results of a series of physical model tests. They include the examination of the period of the wave, the duration of storm, the level of damage defined and the permeability of the structure. The choice of the appropriate formula depends on the design objectives (ie preliminary design or detailed design).

What Are The Factors That Determine The Stability Of A Single Armored Unit?                                      There are three main factors governing the stability of an armored unit, namely the severity, the treatment of inter-and algae clip. Obviously, it is beyond doubt that the ability of the armored unit to stay in place must be closely related to the gravitational force. Moreover, the geometry of the armored unit affecting its stability. For example, the difference in the ability to intertangle reluctance to get out of the wave varies. Moreover, the forces pushing gravity also affects the stability of the armored unit that depends on friction forces in all directions.
If A Small Boat To Take Into Account The Design Of Wings?                                                                The smaller ship should also be taken into account when designing a system fender. Vertically and the fender system, type and size of all vessels must be considered taking into account the influence of tides in the region. In fact, plans to visit a fender system, engineers must take into account the height and depth as well as smaller and larger vessels in a point of contact is a fender. It is not uncommon for the design of a fender system considers only the largest of the ships dock and pier, which should be avoided, because it does not necessarily work for small boats in the dock of the shipyard.
                                                              

                                                                                                                                                                    If The Wings Rigid Or Flexible To Be Designed To Dock At Piers?                                                        The elasticity of the wings is related to the ability to release the energy stored in the docking of ships. But it has no effect on the reaction force and the deflection of the fender system. The amount of energy that can absorb a wing depends on the deflection curve of reaction and is represented by the area under the curve. The higher is the reaction force would be the largest amount of energy absorbed by the fender, provided that the hull strength is sufficient to withstand the force without permanent deformation. While rigid and flexible wings can have the same deflection under the maximum reaction force acting on the boat dock, the amount of energy absorbed by the rigid wings are much higher than in soft wings. Therefore, rigid wings used for docking.

On the other hand, in mooring operations where vessels are constantly subjected to wave action, it is desirable to keep the pull of the rope to a low value. In this regard, it recommends the use of flaps  Water Can Help Dispel Some Of The Energy Coupling?                                                                                                          Depending on the composition of the pier, the water could help to dissipate the energy of the pier. For example, the closed door, which is a solid wall going straight to the bottom of the sea, the quay wall to repel any water that moves the ship and creates a cushion effect, which dissipates the energy of the pier ( 10-20%). In contrast, an open yard, with piles everywhere and the water can flow through the bottom of the platform, not cushion the effect of the water.

Similarly, the most important is the draft of vessels, less water can escape trapped under the ship to the dampening effect of water can be enhanced to dissipate some energy coupling.
                                                                                                                                                                                                                               

Wood Engineering

 What should be the slope of the roof to avoid stagnation?                                                                                                                                     As with standard roof beams should be a continuous upward slope is equal to 1 / 4 inch / foot (20.8 mm / m) between the discharge and the peak of the roof, above the minimum recommended camber avoid stagnation.

In the case of sufficient slope that is less than 20.8 mm / m, we note that the stiffness of the supporting members or act 5lb/ft2 239.4 N/mm2 load does not cause the diversion of more than 1 / 2 inch or 12.7 mm                                                                                                                                                       What is stress and the radial curvature factor?
For a constant area of ​​cross section of the radial force caused by bending moment in a Member State is calculated using this formula

fr = 3M/2Rbd

where

M = bending moment in lb (N m)

R = radius of center members, (mm)

b = width of cross section, in (mm)

d = depth of section, in. (mm)

When we have a curved portion, the curvature factor is introduced and is calculated as

Cc = 1000-2000 (T / R) 2

where

t is the thickness of rolling (mm)

R is the radius of curvature of the lamination (mm).
What Correction Factors Must Be Done In Design Values?
Its always some variation in the design values ​​calculated by the wood. Therefore, we must apply the necessary adjustment for them.

The extreme fiber bending

Fb = FbCDCMCtCLCFCVCfuCrCcCf

where

FB - adjusted design value

Fb = value of extreme fiber bending

CD load duration factor =

CM = wet service factor

CCT = temperature coefficient

CL = beam stability factor

CF = factor measurement applies only to the visually classified sawn and round timber bending members

Cv = volume factor applies only when the rays are glued or laminated

Cfu = constant factor in the use of only one size of timber beams 2-4 (50.8 to 101.6 mm), and laminated wood beams

Cr = repetitive member factor applies only to the size of the beams, 2-4 (to101.6 50.8 mm) thick

Cc = curvature factor applies only to glulam beams curved parts

CF = form

When the bars are glued, laminated, we have to use smaller of the two-CL or CC

The design value of the voltage

Ft = FtCDCMCtCF

where

FT '- design value adjusted

Ft - Design value for the tension.

Adjustment for shear

Fv = FvCDCMCtCH

where

Fv '- Design adjusted value

Fv-value for the CH-cut design and is the shear factor> = 1 Fvparallel allow for the grain to the wood members.

Adjustments for compression perpendicular to the direction of

Fc1'is the value of the project

FC1 '= Fc1CDCtCb

where

Fc1is design value in compression perpendicular to grain

CB lubrication factor.

The value of the survey corrected for compression parallel to grain

FC = FcCDCMCtCFCp

where

Fc is a compression design value parallel to grain

CP Factor column stability.

Design value adjusted to bring the wood grain parallel to the end

FG '= FgCDCt

where

Fg is the design value for the fine grain, keeping parallel to the grain.

The adjusted value of the survey's modulus E '

E '= ECMCTC

where E = design value of the module

CT = buckling stiffness factor

C = correction factors appropriate
                                                            

Surveying

Introduction to contour                                                                                              Thinning is the science of representation of the vertical dimension of the field in a two-dimensional map. We can understand the outline considering a simple example.

Suppose a right circular cone with a base diameter of 5 m in height and 5 meters is upright on its base. Leave the base to rest on a horizontal plane at zero, as shown in Figure 1.
                                                                                                                                            Zero, the outline of a cone is a circle of 5 meters in diameter. This circle is the boundary of the cone height 0m. We draw on the first corner, an appropriate scale on paper.

Now let's see a piece of 1 meter above the bottom of the cone. This produces a more rounded contour of the corresponding diameter of the cone height of 1m. We do this a second circle, outline map of the same scale. The second circle is smaller in diameter than the first one is a concentric circle inside the first circle.

Similarly, we will continue to draw the shape of a cone-2m, 3m, 4m and 5m at the boundary of our map. We conical structure of the map object is ready. Looking on the map are called contour lines. (See Figure-2)

                                                                                                        As the cone, in this example, the draft hills rising from the ground. The contour map of the terrain will be similar to the cone, except that instead of perfect circles, the level curves

irregular shapes. The important point to note here the similarity is that the mountainous terrain would be represented by contours with elevation increasing toward the center.

In contrast, a pond or depression can be represented by contour lines with decreasing height toward the center.

Explain the terms used in the irregularities                                Define the contour line

A contour line is an imaginary boundary of the land is obtained by joining points of equal elevation. In our example of the cone, each circle is a contour line connecting poDefine Contour Line
A Contour line is an imaginary outline of the terrain obtained by joining its points of equal elevation. In our example of the cone, each circle is a contour line joining points of same level.

Define Contour Interval (CI)
Contour interval is the difference between the levels of consecutive contour lines on a map. The contour interval is a constant in a given map. In our example, the contour interval is 1m.

Define Horizontal Equivalent (HE)
Horizontal equivalent is the horizontal distance between two consecutive contour lines measured to the scale of the map.ints on the same level.

Define the contour interval (CI)

Contours is the difference between consecutive contours on a map. The contour interval is a constant for a given map. In our example, the contour interval of 1m.

Define the equivalent horizontal (HE)

Horizontal equivalent is the horizontal distance between two consecutive contours measured in the scale of the map.

                                                                    Gradient

Gradient of the slope up or down the field between two consecutive contours. The slope or gradient is usually in the format specified in S 1, where 1 represents the vertical component of the slope S and the horizontal component is measured in the same unit.

Slope of two consecutive curves can also express Q, Tan (Theta), as follows:

Q tan (theta) = CI / HE ... both measured in the same department.

What is the difference between equidistance and equal horizontal                                                                                                   There are three main differences between the contour interval and the horizontal equivalent of the following:

S. No interval between the horizontal lines

1 It is based on vertical levels representing the horizontal distance

2 No measuring or scaling is not necessary, because the contour lines are marked with contour lines on a map the distance is measured and converted into distance by multiplying the actual scale of the map

3 In a given map the contour interval is a constant horizontal equivalent varies with the slope. Minimum slope indicates a greater distance

What are the characteristics of the contour lines?   Contours clearly shows characteristics of the soil, as follows:

i) All points on a contour line is the same height.

ii) There are two edges meet or intersect, except in rare cases of long vertical cliff or wall

iii) the contour lines close together indicate a steep slope

iv) Widely spaced contours indicate the slope

v) Equally spaced contours indicate a uniform slope

vi) Closed contour lines with a higher elevation to the center indicates Hills

vii) Closed contour lines to reduce the levels of the center indicates the direction of the pond or other depression.

viii) the contour of the ridge show a greater height at the edges of the loop. Contour lines of the cross-ridge at right angles.

ix lines) contour of the valley show the reduction of the contour lines in the circuit. The contour lines at right angles to the valley.

x) All edges must be sealed with either a map of the border or outside of it.

What areas of contours using?
 Contour maps are useful because they provide valuable information on the ground. Some of these uses are as follows:

i) The nature of the soil and slope can be estimated

ii) the work of the Earth can be estimated for construction projects such as road works, railways, canals, dams, etc. iii) It is possible to find an appropriate place for a project of the contour map of the region.

iv) Inter-visibility of points can be viewed using the contour maps. This is very helpful for locating the communication towers.

v) the military uses contour maps of strategic planning.

What methods of  imperfections?                                                 Two ways are Contouring: -

i) direct method

ii) the indirect

Direct method

In the direct method points to the same height of the land is physically located, and then plotted on a map. This is a very laborious process and requires more time and resources than the indirect method.

Indirect method

In the indirect method of contour in the three methods to be followed:

) Transversal Method

B) square or grid method

C) Method Tacheometric

Explanation of the method of weight loss of the    crosssection?                                                           Method Cross section is the most suitable for the preparation of contour maps of the works of roads, railways, canals, etc.

Usually, this type of terrain has a band very long, but narrow.

The steps are:

i) The axis of the strip is marked first

ii) lines perpendicular to the longitudinal axis of the tape is marked dividing the strip into equal sections

iii) the perpendicular lines are divided into equally spaced divisions, forming the rectangular grid.

iv) levels taken at the intersection lattice for the cross section profile of a strip of land.

v) the contour map is drawn in the office by interpolating the points of equal elevation on the basis of the decision levels at the site.

We are grateful to Mr. Iyer engineeringcivil.com Ramasesh to submit this information useful for us.
Explain Squares Slimming grid method?
 Squares or grid method is suitable for the formulation of the plains or gently sloping grounds.

They agreed steps are as follows:

i) Mark the square grids on the ground to detect. Grid size depends on how the study.

Generally, a grid of 1m x 1m is chosen for small jobs and a larger grid for major work

ii) The levels are taken all over the place and the intersection of the diagonal.

iii) levels taken at the intersection of the diagonals used for verification of the interpolation.

vi) Contour map in the office were drawn by interpolation of points based on the levels of the same height in the corners of the square.
Tacheometric explanation of the method for remodeling?                                                           

Tacheometric method is adopted for contouring of very steep hills.

The steps are as follows:
i) Set up the tacheometer at the top of the steep hill. Tacheometer is a theodolite fitted with stadia diaphragm. The stadia diaphragm has three horizontal parallel hairs instead of one as found in a conventional cross hair diaphragm.

ii) With the help of a tacheometer it is possible to determine the horizontal distance of the point from the telescope as well its vertical level.

iii) The steep hill is surveyed at three levels – the base of the hill, the mid-level of the hill and the top level of the hill.

iv) Using the tacheometer reading are taken all around the hill at equal angular intervals on all these three
levels.

v) The radial plot thus obtained is worked in the office to interpolate points of equal elevation for contour mapping.

                                                                            

Steelworks

If high-performance steel or mild steel reinforcement was designed as a road?
On high-performance steel is the preferred material for the strengthening of concrete pavement for the following reasons:

(I) The main aim of reinforcing steel in concrete is to control cracking. If mild steel is adopted for the reinforcement, initiation of cracking of mild steel becomes overloaded and

will be exposed. High Yield Steel provides the resistance to crack growth. The situation described above is a general with an abnormal load of cement on the road over the limits of design.

(II), high-performance steel is less prone to deformation and bending during routine operations management.

(Iii) In today's market, the steel mesh reinforcement is normally high-performance steel and use steel as reinforcement of the route requires the award of special orders from suppliers.

Analysis and design of the tubular structure 2-D modeling with USFOS
USFOS is the analysis tool to predict both the strength of structures subjected to accidental loads and the residual strength of damaged structures after such charges. It is based on a finite element model. USFOS encompasses the static analysis of the fall, the nonlinear analysis of time series and dynamic analysis of the eigenvalues ​​in general, jackets, accessories, jack-up, and floats. With the main purpose of this paper is to analyze two types of offshore structures in 2-D and study the mechanism of progressive collapse of these two fields, due to different combinations of loads in the X and Y axis First the boundary conditions were established for the vertical elements, using modeling and USFOS were tested to collapse under the burden of four possible combinations. Behavioral differences of the two frameworks have been studied and brace-chord sizes have been fixed.

This type of analysis is useful for testing if a jacket sea with some specified size can tolerate the stress that comes to her from the waves, wind or the effects of ships. Using the built-in redundancy in most offshore structures progressive collapse limit state can be used to design accidental injury or extreme loads. In conjunction with the traditional elastic load-shifting is generally not considered. Reduce or plastic design limit states, it is possible to local failure of performance or buckling, and even the partial collapse if the overall integrity of the structure preserved. In short, the designers of plastic limit state design to take advantage of any spare capacity in the structure.

Behavioral studies Hollow double wall steel composite concrete columns                                                                        This document includes the experimental study of eight concrete filled double skin steel tubular (DSCFT) beam columns placed concentric circular section filled with self-compacting concrete. Tests on the samples was done by applying eccentric loads. The main experimental parameters of beam-columns, slenderness and eccentricity of the load. Test samples studied the behavior of the deviation of the load, the effect of confinement, and the strength of the columns. Experimental observations have shown for the stress-strain curves. Characteristics such as strength, stiffness, ductility and failure are discussed. Predicted load vs deformation relationships are in good agreement with the results of beam-column tests. Columns filled with SCC of DSCFT showed good strength and ductility. The changes are proposed equations to find the maximum compressive strength of the columns filled with SCC DSCFT.

What is the purpose of strengthening the skin depth of the bar?
In BS8110 states that secondary reinforcement should be provided for exceeding 750 deep beams at a distance measured depth 2 / 3 of the face in tension. Experimental work has shown that less or about half the depth of deep beams, the maximum width of cracks caused by bending can be two to three times greater than the width of the crack, even on the surface where the origin of the crack forms.

The presence of cracks is not desirable from an aesthetic point of view. It also raises potential problems of corrosion of reinforcing deep beams. To guard against cracking of the building has been designed on the sides of deep beams to limit the formation of wide cracks in bending. Although the main function of enhancing the skin is the crack width control can be used to provide resistance to bending of the section.

What is the difference between performance of concrete bonding between epoxy and galvanized bars?

Based on the findings of the Board 211 ads, the union of galvanized bars in concrete is lower due to early for the release of hydrogen when the zinc reacts with calcium hydroxide in the concrete and the presence of hydrogen tends to reduce the strength of the bond between galvanized bars and concrete. However, the union will increase over time until the full bond strength of galvanized bars is not reached.

Epoxy-coated bars are bond strength of 20% below the bar at the bottom of the concrete components while bars on top of it there is not much difference compared to the uncoated side bars.

What kind of reinforcing bar corrosion resistant, epoxy-coated bars, stainless steel or galvanized rods?
Based on the experience carried out by the Building Research Establishment, it was shown that the corrosion resistance of galvanized steel, were the worst among the three types of reinforcement bar. For galvanized steel rods began to corrosion occurs when a certain chloride content in concrete (equivalent to 0.4% by weight of cement) was exceeded. But for the epoxy bars, extended the time it takes to cracks that occur when comparing with galvanized steel bars.

The best stainless steel reinforcement corrosion resistant all. Specifically, the austenitic stainless steel has remained non-corrosive, even chlorine contamination occurred in the concrete experience. Reference is made to KWJ Treadaway (1988).

Tie reinforcement son next to and above Class F4 and F5 finishes shall be stainless steel. Why?

If the son of plain steel fasteners are used for reinforcement adjacent to the class F4 and F5 are finished, raise the issue with rust stains which can degrade the appearance of exposed surfaces of concrete. The rate of corrosion of mild steel son home correspond to normal steel reinforcement. But to tie the son with very small diameter, after long exposure he has a good chance of completely rust and the rust will stain the formwork and significantly affect the finishing of concrete. Therefore, the stainless steel wire tie to specified locations in the vicinity of high-quality finish to prevent rust stains from corroded son writing.

Note: Tie the wires are wires used for connecting and strengthening of steel reinforcement bars.
If the ordinary steel tie wires are used to confirm the F4 and F5 the next class to run out, will cause problems with rust stains, which can alter the appearance of exposed concrete surfaces. Amount of corrosion of ordinary steel tie wire is similar to that of normal steel reinforcement. However, tying the threads of a very small diameter, while a long exposure, is a great opportunity to completely rust and rust stains, mold and these significantly affect the concrete surface. Therefore, stainless steel wire binding posts are set in the vicinity of a high quality finish to avoid rust staining typing corroded cables.

Note: The son of this type is the child for fixing and connecting the reinforcing steel bars.

What is the effect of corrosion on steel frames?
Corrosion of rebar in a concrete structure is undesirable in the following ways:

(I) the presence of rust weakens the bond strength of d'armature because corrosion occurs in the ribs raised and bridges the gap between the ribs, the smoothing of the original shape distorted. In strains of the essence of the relationship between concrete and deformed bars of the mechanical lock between the ribs raised and concrete. The reduction of the mechanical blocking of corrosion resulting from the decrease in bond strength with concrete.

(Ii) the presence of corrosion reduces the effective cross-sectional area of ​​reinforcement. Therefore, the ability of available traction force of the reinforcement was reduced by a significant reduction in the surface of the section.

(Iii) corrosion products occupy about three times the initial volume of the steel from which it is formed. These drastic increase in the volume generates significant forces defects near the reinforcement. Therefore, cracks are formed along the reinforcement when the tensile strength of concrete is exceeded.

Column reinforcement, why sometimes designed helical reinforcement instead of normal links?
Use of links to the design of columns in Britain is very popular. But American engineers tend to use stronger links rather normal helical spiral reinforcement due to a potential benefit to protect the columns / cells against seismic loads. Moreover, when the graph drops non-state crack-free concrete and hoop first, followed by any failure of all columns. Concrete cylindrical shells without reinforcement gives a warning before the sudden failure of columns as suggested by GP Manning (1924). In addition, it can take up to a higher workload than usual link reinforcement.

For example, helical reinforcement is taken in the design of batteries thrown overboard by the government.

Note: helical reinforcement concerns the reinforcement is cut in a spiral.

Preload Of Engineering

The economy of RCC water tank rests on solid ground vis-à-vis the prestressing of concrete water tanks resting on firm ground
Water tanks are used to store water and are designed as crack free structures, to eliminate any leakage. In this paper design of two types of circular water tank resting on ground is presented. Both reinforced concrete (RC) and prestressed concrete (PSC) alternatives are considered in the design and are compared considering the total cost of the tank. These water tank are subjected to the same type of capacity and dimensions. As an objective function with the properties of tank that are tank capacity, width &length etc.

A computer program has been developed for solving numerical examples using the Indian std. Indian Standard Code 456-2000, IS-3370-I,II,III,IV & IS 1343-1980. The paper gives idea for safe design with minimum cost of the tank and give the designer the relationship curve between design variable thus design of tank can be more economical ,reliable and simple. The paper helps in understanding the design philosophy for the safe and economical design of water tank.                                                                                          What is stress corrosion of prestressing steel                        Stress corrosion cracking is a crystalline metals under tensile stresses in the presence of corrosive materials. Conditions of stress corrosion cracking occurs in the steel tensile stresses due to external loads or stress-induced internally (eg tendons). In addition, the presence of corrosive agents is essential to stress corrosion cracking start. A key feature is that the stress corrosion fracture of material with no damage observed from the outside. Therefore, stress corrosion cracking caused by the obvious warning signs.
The length of the steel work, if more than one wire or tape is the same, because all the cables / wires out at the same time?
 If the child thread / individually highlighted in the same conduit, then these

stressed the wire / wire stand against the dull and the trap. Therefore, trapped in cable friction is high and is desirable.
 

What are the characteristics of the mortar inside the tendon ducts?

 An oath is a pre serve the following purposes:

(I) To protect the tendon against corrosion.

(Ii) improving the limited capacity of the tendon.

(Iii) the link between the structural and the tendon.

(Iv) In case of failure, the anchor is not subject to all the strain energy.
Because spalling confirmation is required for prestressing anchor is prevented?
  Prestressed anchor blocks of work generally consists of balancing pop reinforcement reinforcement, reinforcement and erosion. Reinforcement of rupture is used when the tensile forces are induced during the operation of the preload and the maximum pressure occurs when the trajectories of the breakdown voltage are concave towards the line of action of the load. The reinforcement is needed to resist these lateral tensile forces. For the reinforcement of balance is necessary when there are several anchorages of prestressing loads are applied sequentially.

During the pre-load, the stresses generated in the chipping area behind the loading of the faces of the anchor blocks. In the area between two anchors, a volume surrounded by concrete compressive stress trajectories. The forces are induced in the opposite direction to the applied forces and forces the output of the concrete anchor. On the other hand, limitations of scale are in place thanks to the compatibility restriction on the effect of Poisson's ratio.
In such circumstances it is used by engineers to lift one end, and at both ends in the preload works?
 During the operation of preload at one end, frictional losses occur and the prestressing force along the tendon decreases until it reaches the other end. These frictional losses include the friction due to a change of curvature of the tendon sheath and also wobble effect due to the difference in the alignment of the canal from the midline. Therefore, the prestressing force in the mid-range or at the other end will be significantly reduced in case of loss of friction is high. Therefore, the bias from both ends of a single span that is half preload tendon at one end, and the remaining half at the other end is made to ensure uniform distribution and to provide symmetry the prestressing force along the structure.

In fact, the stress at the other end is only possible to take advantage of low cost compared with the emphasis on both ends. Number of segments (for example, two blocks) and the irregular arc, lifting is usually done at the end of the longest period in order to obtain a position of force majeure claim the largest positive moment. On the contrary, hijacking the end of a shorter period would be, if the negative moment of the interim control preload on the force. If, however, the entire span is long enough to lift both ends should be considered.

What forces blood parasites?                                                                                                                               In isostatic structures, donors would be some concrete structures to fold up. Therefore precambering usually done to counteract this effect and make it more pleasing in appearance. But for the deformation of statically indeterminate structures of concrete members is hampered by restrictions, and the forces of parasites then developed by the leading force in addition to the bending moment generated by the eccentricity of tendons. The forces developed on the support modifies the response of concrete members subjected to external loads and produce secondary moments (or moments parasites) in the structure.
What are the major potential benefits in the form of use of precast girder bridge prestressed concrete slab above site?                                                                                                             The potential benefits of using the bridge is prestressed precast beams supporting in situ concrete slab above are:

(I) For bridges built over rivers and roads, this form of bridge provides the platform for work by the precast beams so that construction of temporary structures is not necessary.

(Ii) that forms a bridge usually requires no cross beams or membranes (except for the location of the bridge supports), which reduces construction time and costs.

(Iii) It creates the potential for the simultaneous construction of taking several

Why kind of tension is better, preload preload internal or external?                                                                                        Different places the time interval (the third or fourth in points), the tendons are deviated from the correct profile of the concrete span preload external switches. Advantages of external prestressing are listed below:

(I) Due to the lack of connection between the tendon and its structure, exterior prestressing allows the removal and replacement of tendons or two at a time that the bridge could be adapted in case of damage and capacity could be increased easily. This is essential for bridges in urban areas where traffic problems is not desirable.

(Ii) it is usually easy access to anchor points and allows easy inspection.

(Iii) allows adjustment and control of the forces of the tendons.

(Iv) allows the designer more freedom in selecting the cross sectional shape of the bridges.

(V) web could be made thinner, so there is a reduction in dead load.

(Vi) is improved by reducing friction losses, as unintentionally as angular oscillation is eliminated. In addition, the use of polyethylene pipes external prestressing a coefficient of friction lower than the internal corrugated steel pipe prestressing.

(Vii) improvement of the concrete placement networks due to air channels.

A significant difference between the tendon internal and external post-tensioning steel is in the variation of eccentricity of the cable. Deflected shape of the external tendons is not exactly like the bars because of

moving the external tendons are controlled by evil. This is a second-order effect on the workload, and it is very important to the ultimate load.

Based on previous research, to include a small shallow (less than 3 m deep) with internal preload requires less steel reinforcement. However, deep cross section of the bridge, employment

Preload external results in a small amount of steel reinforcement.

Soil Engineering

If adopted high preload in the struts braced excavation?
Pre-loading in the struts braced excavation helps eliminate potential movement. The use of preload reduces the shear stress in the soil, previously established by the excavation. Because of the rigidity of the soil, they can use high preload the struts are not desirable, because the movement of strut local departure could cause damage to public services nearby.
For Peck, the pressure boundary of braced excavation, the total weight or actual weight used in the trapezoidal and rectangular envelope?
Asset utilization and rest the theory is not applicable in the braced excavation. Basically spacers higher tendency to be more crowded, while lower spacers appear to be less responsible in comparison with the theory of the pressure force.

Peck measured reinforcement loads are converted to the pressure of the earth. For example, the limit of the pressure of cohesionless soils is 0.65rHKa

where

r = soil density

H = height of the excavation

Ka = coefficient of active pressure

Some engineers consider r the total weight of the soil to apply any pressure. However, Peck said, "the pressures are not substantially affect the coefficient of active earth pressure and redistribution of

rectangle or a trapezoid. "So an effective weight of soil to use for r the pressure of water is added separately.
The excavation was prepared, why Rankine's theory of lateral earth pressure is not applied?
The excavation was prepared, piling was built first, followed by the installation of braces, as a result of the excavations. After installing the first row of tabs, the depth of excavation is small, so that there is a great performance from the earth. However, as the excavation takes place, the performance of the ground before installing the line number of the spacers. The first row of slats prevents the transfer of near surface. Therefore, the deformation of the walls increases with depth with the lowest land. Because of the effect of the construction method of excavation was prepared, unlike the condition of deformation of the Rankine theory. This is attributed to the effects of the ark in which there is a redistribution of loads up. The top of the excavation will be mounted in the state of elastic equilibrium, while the fund is in a state of plastic equilibrium.
What is the difference between the method of the land of free technical support and method fixed earth support?

For free earth support method, the soils at the lower part of piling is incapable of inducing effective restraint so that it would not result in negative bending moments. In essence, the passive pressures in front of the sheet piles are insufficient to prevent lateral deflection and rotations at the lower end of piling. No passive resistance is developed on the backside of the piling below the line of excavation.

For fixed earth support method, the piling is driven deep enough so that the soil under the line of excavation provides the required restraint against deformations and rotations. In short, the lower end of piling is essentially fixed.                                                                                                                                           Is bleeding to test a prerequisite for the grout?
Bleeding is a form of segregation, where a layer of water migrates to the surface of the grout in the initial phase of the process of cement hydration. Later, some liquid water reabsorbed in the grout due to additional hydration reactions. Even without the problem of bleeding, there is an overall reduction in the volume of grout after treatment of hydration compared to the total individual initial reaction of cement and water. Bleeding tests should be performed to grout for the following reasons:

(I) During the riser duct bleeding water from the mixture of slurry to the formation of channel paths inside the grout mixture. These channels act as potential pathways for materials to go aggressive, because these

channels would not be closed when the additional hydration of the grout.

(Ii) the loss of volume by bleeding inside the product shall render the milk mixture affecting the properties and performance of the grout. It also increases the possibility of corrosion of steel elements protected by the grout. (Tendons, etc.)

(Iii) The test of bleeding, there is a usual requirement for a total re-absorption of water after 24 hours the composition of the grout, because for some cold countries, this layer of water, causing serious problems freezing, leading to freezing.
The presence of colluvial slopes good?

Colluvium refer to the deposit same area running down the mountain slopes under the influence of gravity. It differs from the remaining land, degradation of the discontinuity, part of the textures preserved. The rolling action colluvium destroy these features.

Colluvium shows some important features that deserve attention:

(I) seems to be stronger than the residual soil to erosion and tends to provide protection to the ground below.

(Ii) the relatively low permeability compared to the rest of the ground below to form a perched water table at the base of a thunderstorm.

(Iii) the remains of earth, when the slope cut out the presence of relict joints can affect slope stability. But the base layer of colluvium is also a location map of potential error.
Dykes and decomposed dolerite slope stability?
Decomposed dolerite dikes are rich in clay show a high plasticity. In addition, the material is generally low permeability of the decomposed granite, which has many sides.

The presence of dolerite dykes degrades the direction parallel to the surface of the slope after slope failure can cause intense and prolonged rains. Shortages due to the permeability of the decomposed dolerite dykes, to sit in groundwater could be developed for the dams, and this is substantially more positive pore water pressure, which reduces the shear strength of soil.

The presence of dolerite dikes broken in a direction perpendicular to the surface of the slope can also cause a break in the slope after the storm. The low permeability of the materials tend to act as the construction of dams on the level of local groundwater for water coming down from the upper slopes. The increase in water level behind the "prey" leads to increased water pressure of the pores to reduce the resistance of the soil on slopes, leading to later failure.

What are the effects of pile groups, the stability of a slope?
Soil moisture on the slopes of Hong Kong usually consists of colluvium and rock weathering on fresh. Groundwater flow of the sloping terrain, and can participate in the race and the flow of water main. As the permeability of the soil tends to decrease with depth, the flow of groundwater can occur above the water table, which includes a tour of the lower surface of the water.

The presence of a lot of teams below the water table to prevent the flow of groundwater, which increases the level of groundwater. Significant developments in the slopes with a lot of influence has its roots in a sort groundwater is cut off. Growth of the lower surface of the water due to the effects of dam groups reduce the pile of slope stability, reducing the shear strength of the soil and eventually lead to failures slope.

Rising groundwater levels tend to increase with the angle of the slope and

depth of the groundwater flow.

How can you fill in the geogrid reinforcement?
Geogrid can fill the other side of the grid to meet the key to the other side of the grid. This is why it is different than the capacity of interlocking strips of soil reinforcement. Placing on both sides of the fill could be obtained from the condensation and the static load over the filling.

To trigger intersect the plane of the geogrid, the work must be done to expand the ground and defeat the forces of friction.