## Bridge Deck Analysis By Finite Difference Method

A detailed analysis done by Gautam Chattopadhyay

Names and Symbols used:
Ardeck – area of the deck.
wdeck – width of deck.
span – span length of bridge.
izlong – Moment of inertia of each longitudinal girder about z axis (transverse axis)
iztrans – Moment of inertia of entire deck in transverse direction about longitudinal axis.
flexkl – Flexural rigidity in longitudinal direction.
flexkt – Flexural rigidity in transverse direction.
ngird – number of longitudinal girders.
tslong – Tosional rigidity in longitudinal direction.
tstrans – Torsional rigidity in transverse direction.
econc – modulus of elasticity of concrete.
gconc – shear modulus for concrete.
N (ndiv) – Number of divisions in either direction.

Bridge decks are normally comprised of a grillage system of longitudinal and transverse girders. Longitudinal girders are supported at two ends while the extreme edges in transverse direction remain free. Bridge decks need special methods of analysis when subjected to unsymmetrical loadings. Unsymmetrical loading occurs for the following reasons:

## Analysis and Design Of 2-D Tubular Frame Using USFOS Modeling

Analysis and Design Of 2-D Tubular Frame Using USFOS Modeling by
Department of Civil and Environmental Engineering
National University Of Singapore

Abstract:
USFOS is the analytical tool for predicting both the resistance of structures subject to accidental loads and the residual strength of damaged structures after such loads. It is based on finite element modeling. USFOS covers static collapse analysis, non-linear time series dynamic analysis as well as eigenvalue analysis of typically jackets, jack-ups, topsides and floaters. Primarily the purpose of this paper is to analyze two types of 2-D offshore frame and study the progressive collapse mechanism in these two frames due to different load combinations along X-axis and Y-axis. First the boundary conditions were fixed for the vertical members using USFOS modeling and they were tested for collapse under four different load combinations. Differences in behavior of two frames have been studied and different brace-chord sizes have been fixed. This type of analysis is useful to test if an offshore jacket with some specified size can stand the load coming on it from waves, wind or impact of ships. By utilizing the inherent redundancy found in most offshore structures the progressive collapse limit state can be used to design for accidental damage or extreme loads. Whereas in traditional elastic design redistribution of load is not normally considered. Collapse or plastic limit state design allows for local failure in yield or buckling and even partial collapse, provided the overall integrity of the structure is maintained. In short, plastic limit state design allows the designers to take advantage of any reserve capacity in the structure.

## Economics of R.C.C. Water tank Resting over Firm Ground vis-a-vis Pre-stressed Concrete Water Tank Resting over Firm Ground

By
MS. SNEHAL R. METKAR
(P.G. STUDENT)
DEPARTMENT OF CIVIL ENGINEERING
(STRUCTURAL ENGINEERING IIND YEAR)
P.R.M.T OF TECH. & RESEARCH, BADNERA-AMRAVATI
SANT. GADGE BABA (AMARAVATI) UNIVERSITY (MAHARASHTRA)
COUNTRY INDIA – 444701

GUIDED BY
Prof A. R. Mundhada
(PROFESSOR)
DEPARTMENT OF CIVIL ENGINEERING,
P.R M.I.T.R., BADNERA, AMRAVATI.
MAHARASHTRA, INDIA-4444701,

Abstract
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.

Keywords
Rigid based water tank, RCC water tank, Prestressed Concrete, design, details, minimum total cost, tank capacity

## Computer Diligence For Civil Engineers

Paper on Computer Diligence For Civil Engineers By
H. J. Sreenivasa (Lecturer) and Nagaraj Sitaram (Professor)
Department of Civil Engineering
School of Engineering and Technology,
Jain University
Jakkasandra Post, Kanakapura Taluk, Ramanagara District-562112

Abstract
Very rapid progress has been achieved in the last few years in the development of general-purpose engineering software that are very efficient in predicting the behavior of engineering structures. General characters desired in computers are speed, accuracy, reliability, versatility and diligence. It can store huge volumes of data and with the aid of many input and output devices data of different forms can be fed in to and taken out.

There are many software packages available in the market exclusively for Civil Engineers. They can be put to use for many uses like design of huge structures, virtual reality, solving equations for optimization of resources tender bidding, earth-work estimation, cost estimation, project management, structural drawing predictive model making and much more. Computers also aid satellite surveying. Data transfer, its interpretation and analysis are all done by computers. It helps making of maps, deciding of highways alignment etc very easy for civil engineers.

The paper deals with many types of software available in the market as tools for Civil Engineers. Among them, the most popular ones are, Auto CIVIL (Civil engineering with Auto CAD), STAAD/Pro (Structural Analysis And Design), 3D Home Architect Deluxe (Dream Home), ANSYS (Structural Analysis).

Computers these days have advanced very much and with the advent of powerful PC’s and Internet, computer has become a immensely useful tool for any one in any field. With the advent of Internet, which is often called as mankind’s greatest invention till date, it has yielded very much for the civil engineers. There are many portals dedicated for civil engineers alone. There are construction site updates in the net. With the arrival of E-commerce, the computers have avoided the hassle of travelling to shops to buy goods like cement, timber etc.

Civil engineers have one of the world’s most important jobs; they build our quality of life with creativity and technical skill. The civil engineers plan, design, construct and operate the facilities essential to modern life, ranging from factories, bridges and highway systems to water treatment plants and energy efficient buildings. The Civil engineers meet the challenges of pollution, traffic congestion, drinking water and energy needs for present and future generation. The paper discusses recent applications of computer in the field of civil engineering and addresses the role of application in transferring information, organizing discussion sessions, conferencing and providing technical advice on line.

With the technological revolution and world’s increasing population great threat is posed on natural resources and global environment. The role of planners becomes important and they need to improve the design skills and construction management techniques in a cost effective manner to make our world a better place to live. Civil engineering is the profession focuses on analysis, design, construction and maintenance of buildings, bridges, transportation systems, water and wastewater systems, and other infrastructure of direct relevance to society’s well-being. More recently, amidst growing awareness on environmental protection, this profession is also entrusted with safe guarding the natural environment around us to promote sustainable development.

In all modern scientific and technological endeavors, computers and software play an increasingly important role. Computers can be used to generate models of fundamental physical processes, which can be solved using numerical methods. In almost all the different aspects of Civil Engineering, it is virtually impossible to escape the application of computer technology. This application of computers in Civil Engineering goes beyond the normal black-box application and requires an engineer to be intelligent and cogent user in order to derive physically sound design and analysis. For example, repetitive and highly involved calculations based on regulatory (Indian standard) code may be needed in the design of multistoried buildings where the tolerance of error is very low; probability modeling may be required in the design of transportation systems, dams and bridges etc. and analysis of new class of problems in civil engineering with project management techniques (PERT/CPM). Very rapid progress has been achieved in the last few years in the development of general-purpose engineering software that are very efficient in predicting the behavior of engineering structures. At the same time transferring information over the internet has started to play an important role in achieving economy in the design process as well as delivering engineering solutions efficiently and promptly making it easier for project managers to meet critical deadlines and obtaining/providing technical advise on line, as well as conferencing and participating in discussion sessions. This is not just about saving time and money. The Web gets creative too.

One of the most widely used software tools in the civil engineering profession is computer-aided design (CAD) software which enables engineers to create 3D models, 2D drawings, and schematics of their designs, satellite surveying, data transfer, structural and fluid behaviour modeling etc. There are number of portals and websites dedicated for civil engineers.

Computers:
Computers data handling and analysis capacity have increased manifolds and used in all branches of engineering for design, optimization and innovation as a tool. The computational capabilities are listed. Information processing and calculation are done by computers at a very high speed. It can execute millions of instruction in a fraction of a second. For example if we want to design a multistoried building, to do the analysis and design, we need a group of engineers working together for weeks together. But in a computer you need a single person with software knowledge and civil engineering background to enter the primary data and the computer will give the results in relatively less time.

Satellite surveying is conducted for map preparation and other projects like highway alignment. Satellite surveying without computers is quite difficult to imagine. Since most of the work is done by the host of computers on board and in ground station. The camera in the satellite is completely controlled by the computer. The photograph taken by satellite will be converted into digital images and sent to earth. At the ground station the receiving end there is a computer, which interprets the data and gives us the real image as taken. The photograph taken can be used as base map and for other purpose like the military use since every thing will be in the proper scale. With out the aid of satellite to survey, it would take many weeks and huge manpower to do the work and that too ends up with many kinds of errors.

Condition Monitoring of Structures:
The bridges and other structures are decaying at very faster rate than expected these structures needs constant monitoring. With suitable hardware support (measurement devices like Smart materials, strain gauge, thermometers, environmental devices etc) and suitable interfacing these structures can be monitored and required alarm can be triggered for safety. The advantage is that it can take into account multi criterias, for example in case if a bridge deflection of the span, sinking of pier, foundation decay, bulking of pier etc. simultaneously and substitute them in the any complex stability equation given and come out with the results in no time. It can monitor and indicate the time when additional prestressing is required in PSC structures.

Probes like deflection gauges can be implanted at different points of a buildings at the time of natural disaster like earthquake, cyclone etc. (you can artificially make for study purpose) These outputs can be fed into a computer and a data base can be made and learnt. The designers can further modify designs economically, to contain these hazards safely in future. In another case a probe can be set upstream in case of a submersible bridge and traffic can be blocked in time.

Monitoring hydraulic structures is a work, which can be done by computer brilliantly. The whole administration with a number of probes in the catchment area can be very well administered. In a project, the regulatory odds can be beaten using software with simulation models. The probability of disputes can be predicted and there by handled effectively. There are risk management softwares, which can predict the amount of risk involved in a project very realistically, with which the management can take decisions effectively.

Figure 1 Health monitoring of a Bridge using smart material sensors

Softwares:
There are many types of software available in the market as tools for Civil Engineers. Among them, the most popular ones are:
• Auto CIVIL (Civil engineering with Auto CAD)
• STAAD/Pro (Structural Analysis And Design)
• 3D Home Architect Deluxe (Dream Home)
• ANSYS ( Structural Analysis)

Auto Civil uses Auto CAD in civil engineering field. The usual areas of its applications are:
a) Digital terrain modeling
c) Hydraulics

The digital terrain modeling can be done with Auto contour and Auto DTM in which generation of contour map, point interpolation, 3D residual cut and fill map and even the volume calculations can be done. The roadway design can be done with great ease with Auto roads, which is developed only for this purpose. Similarly Autowater, AutoSewer and Autostorm are the packages, which deal with water supply, sewage, transport and drainage works respectively.

The power tool for Computerized Structural engineering
STAAD.Pro is the most popular structural engineering software product for 3D model generation, analysis and multi-material design. It has an intuitive, user-friendly GUI, visualization tools, powerful analysis and design facilities and seamless integration to several other modeling and design software products. The software is fully compatible with all Windows operating systems(Figure 2). For static or dynamic analysis of bridges, containment structures, embedded structures (tunnels and culverts), pipe racks, steel, concrete, aluminum or timber buildings, transmission towers, stadiums or any other simple or complex structure, STAAD.Pro has been the choice of design professionals around the world for their specific analysis needs.

Figure 2. Shear Force and Bending Moment Diagram from STAAD. Pro

3D Home Architect Deluxe creates complete, professional-looking residential floor plans that let you design a remodel, an addition, or even an entire home. 3D Home Architect Deluxe simplifies the task of accurately drawing plans, letting you experiment with possible alternatives and convey your ideas to others. It displays multiple, independent windows, so you can have several views of a single plan open at once (for example, Plan, Cross-Section/Elevation, and Camera views), plus several versions of each view Figure 3 (for example, Camera views from two angles), and even several different plans (to compare designs). The program is designed in such a way that we can create objects or carry out commands, like drawing walls, placing windows, and changing views. Dimension lines locate walls and openings in walls by showing how far one wall is from another, or how far an opening is down a wall. We can create interior and exterior dimension lines. Using landscape we can create our own dream house. Some of the drawing from the 3D Home Architect is given below.

Figure 3 Three dimensional drawing using 3D Home Architect

The ANSYS program has many finite-element analysis capabilities, ranging from a simple, linear, static analysis to a complex, nonlinear, transient dynamic analysis. ANSYS provides specific procedures to perform analyses for different engineering disciplines.

Figure 4. Analysis in ANSYS

The process involves three general tasks Building the Model, Applying Loads and Obtaining the Solution, Reviewing the Results.

Building a finite element model requires more of your time than any other part of the analysis. By specifying a job name, analysis title and by defining the element types, element real constants, material properties we can model the geometry using preprocessor. In the next step, the analysis type and analysis options is defined by applying loads, load step options and initiate the finite element solution. We choose the analysis type based on the loading conditions and the response you wish to calculate. For example, if natural frequencies and mode shapes are to be calculated, you would choose a modal analysis. You can perform the following analysis types in the ANSYS program: static (or steady-state), transient, harmonic, modal, spectrum, buckling, and sub structuring. After the solution has been calculated, the postprocessor is used in ANSYS to review the results. We can obtain contour displays, deformed shapes, and tabular listings to review and interpret the results of the analysis.

Concluding Remarks
The rapid progress that has been achieved in the last few years in the development of general-purpose engineering software as well as the technology of transferring information over the internet has started to play an important role in achieving economy in the design process as well as delivering engineering solutions efficiently and promptly making it easier for project managers to meet critical deadlines and obtaining/providing technical advise on line, as well as conferencing and participating in discussion sessions. This leads to saving of time and money. With recent advances in computer speed, data storage capacity, animation software the Civil engineers are able to optimize the material utilization, construct earthquake resistant energy efficient buildings and develop smart composite materials for future generations.

## What is Efflorescence in Bricks and Concrete?

Paper of Efflorescence in Bricks and Efflorescence and Leaching in Concrete by Sir. Kaushal Kishore
Materials Engineer, Roorkee

Efflorescence is the usual terms for deposit of soluble salts, formed in or near the surface of a porous material, as a result of evaporation of water in which they have been dissolved.

EFFLORESCENCE IN BRICKS:
Usually sulphate of magnesium, calcium, sulphate and carbonate (and sometimes chloride and nitrates) of sodium and potassium are found in efflorescence. These salts may be traced to the brick itself, sand used in construction, the foundation soil, ground water, water used in the construction and loose earth left over in contact with brick work. Bricks with magnesium sulphate content higher than 0.05 percent should not be used in construction. Soluble salt content in sand (chloride and sulphate together) should not exceed 0.1 percent.

Water, if it finds access to brick work, moves along its pores by capillary action and carries with it dissolved salts. As the solution evaporates from the exposed surface of the brick work, the salts are left as deposit on the surface or on layers just below it. Disintegration or flaking of the brick surface is caused by the mechanical force exerted by salts as these crystallize just below the exposed surface. Magnesium sulphate, in particular, disintegrates bricks and pushes out plaster.

REMEDIES:
1. Well fired bricks should be used in construction.
2. Sand should be tested for its salt content.
3. Proper D.P.C. should be provided in the building.
4. Efflorescence on brick work traceable to salts in the materials can be removed by dry brushing and washing repeatedly. Such efflorescence may re-appear in dry season but usually are less in intensity. Finally these disappear as the salt content of the bricks is gradually leached out.

TESTING BRICKS FOR EFFLORESCENCE
Distilled water to be filled in a dish of suitable size. The dish should be made of glass, porcelain or glazed stone ware. Place the end of the bricks in the dish, the depth of immersion in water being 25 mm. Place the whole arrangements in a warm (for example, 20 to 30oC) well ventilated room until all the water in the dish is absorbed by the specimen and the surface water evaporate. Cover the dish with suitable cover, so that excessive evaporation from the dish may not occur. When the water has been absorbed and bricks appear to be dry, place a similar quantity of water in the dish and allow it to evaporate as before. Examine the bricks for efflorescence after the second evaporation and report the results as:

(a) NIL – When there is not perceptible deposit of efflorescence.
(b) SLIGHT- Not more than 10% area of the brick covered with a thin deposit of salt.
(c) MODERATE- Covering upto 50% area of the brick.
(d) HEAVY- Covering 50% or more but unaccompanied by powdering or flacking of the brick surface.
(e) SERIOUS- When, there is a heavy deposit of salts accompanied by powdering and/or flacking of the exposed surfaces.

EFFLORESCENCE AND LEACHING IN CONCRETE:
When water percolates through poorly compacted concrete or through cracks or along badly made joints, the lime compounds with in the concrete leached out which leads to the formation of salt deposits on the surface of concrete, known as efflorescence. This caused primarily by calcium hydroxide Ca(OH)2 one of the hydration products and slightly soluble in water, migrating to concrete surface through the capillary system. After evaporation, the solid Ca (OH)2 reacts with the atmospheric carbon dioxide CO2 to form calcium carbonate CaCO3, a white deposit on the concrete surface.

Early efflorescence can be removed with a brush and water. Heavy deposits may require acid treatment of the surface of the concrete. The acid used is HCl diluted from the concentrated form in a ration of 1:20 or 1:10. The action of the acid stops when it has been used up by the reaction with lime, but the concrete should be washed in order to remove the salts which have been formed.

Efflorescence and leaching in concrete is harmful. In addition to blemish and ugly appearance, the process of carbonation of concrete is accelerated. In reinforced concrete, the chances of corrosion of steel are increased due to carbonation and higher permeability of concrete. It is therefore necessary the concrete making materials should be of good quality, mineral and chemical admixtures preferably be used, properly proportioned (preferable design mixes) as per required durability and grade of concrete. All the materials should be properly mixed, placed, compacted, finished and cured.

REFERENCES:
1. I.S. : 3495 (Part-III)- 1976 – Method of tests of burnt clay building brick) Part-III, determination of efflorescence (Second Revision)
2. A.M. Neville, Properties of Concrete, Fourth Edition.

We are thankful to Sir Kaushal Kishore for publishing his paper on Efflorescence. This paper will help civil engineers understand what is Efflorescence and how can they get rid of it

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