Contreras Railway Viaduct is one of the main structures on the Madrid – Valencia high-speed railway link. Upon completion, the structure became Spain’s largest concrete arch for a rail bridge. Villargordo del Cabriel stretch represents an example of the use of the state-of-the-art construction systems, instigated by the limitations resulting from a layout that allows the running speed of up to 350 km/h, with large radii bends and gradients of less than 30‰ in area with rugged terrain conditions. It is against this background that the arch bridge over the reservoir stands. This is a reinforced concrete arch bridge with a 261 m span and an upper pre-stressed concrete deck that on the construction completion date was world record holder for a concrete railway arch bridge.

The bridge amounts to a total length of 587.25 m. The arch span measures 261 m and the midspan sag is 36.944 m, which determines a span-to-rise ratio of 1/6.77. The arch is embedded in two large plinths that allow the diffusion of the load over the affected ground by means of direct foundations. Tallest pier is 67m high.

The cross section is a box girder with a variable depth ranging from 2.80 m at mid-span to 3.40 m at the ends. The box girder width is also variable ranging from 6.00 m in the centre of the arch to 12.00 m at the foundations, which is the width required to resist the great bending moments of the vertical axis produced by the plan curvature of the arch and the crosswind. The box girder walls range from 0.60 to 1.35 m. The upper deck span distribution is 32.625+12×43.50+32.625 m.

The piers P-6 to P-11 are supported on the lower arch structure. The deck is made of a 3.00 m deep box girder (which determines a 1/14.50 span-to-rise ratio), a 5.00 m wide lower slab, a 6.50 m wide upper one, and series of segments that complete the total section width of 14.20 m. The web thickness is 0.50 m. The webs are thickened over the piers until reaching a total thickness of 1.27 m, to allow the anchoring of the service prestressing cables. The lower slab is 0.30 m thick.

Plan and Elevation of the Arch Bridge

The arch was built by the incremental cantilever method and temporarily supported by stay cables that were anchored onto an auxiliary pylon structure built on the temporary and permanent piers.

 A total of 54 large trucks were involved in load tests performed on the viaduct by the AVE between Madrid and Valencia will save Contreras Reservoir, between the provinces of Cuenca and Valencia. Railway Infrastructure Administrator (ADIF), tested and confirmed that this infrastructure has resisted a total of over 2,000 tons. The tests developed consisted of a first phase in which the board has been subjected to the weight of 54 trucks of 40 tons, which have been placed under different hypotheses to corroborate the response of the structure against the loads. In a second phase, has performed a first test dynamic load, in which the validity of the response of the structure against moving charges is checked. DESIGNER Carlos Fernández Casado (Eng. Javier Manterola), MAIN CONTRACTOR UTE Embalse de Contreras (AZVI + Ctra. San José), VIADUCT SUBCONTRACTOR Estructuras y Montajes (Grupo Puentes)

Interesting, Bridges, Arch Bridges, Railway Engineering, Railway Bridges, Bridges in Spain

CDA has invited proposals from the consulting firms of Pakistan for the design of project  “Signal Free and Controlled Access Corridor for Islamabad highway”.

In an advertisement CDA, has mentioned that it needs the consultancy services of experienced consulting firms / engineering organizations having Project code 1215 (II) registration with PEC and must to have a solid know-how for the design of rigid and flexible pavements along with grade-separation flyovers and underpasses.

The scope of work includes 12.4 km (both flexible and rigid pavement) including grade separating structures, flyovers, bridges, culverts and landscaping, electrical and allied works are also included.
The technical proposals after evaluation will be opened on 15 March 2016 @ 1200 Hrs for the award of the tender.

We all know that concrete is vulnerable to temperature changes it usually shrinks and expands due to some temperature variations, in such a condition most of the times a crack is intentionally introduced so that any expansion or shrinkage in a panel would not produce uncontrolled cracks as a result of stress production within the core of the concrete.

A typical expansion joint is defined as :-

a joint that makes allowance for thermal expansion of the parts joined without distortion.

Parts of Expansion Joint

In a typical expansion joint, it normally contains the following components:

joint sealant,

joint filler,

dowel bar,

PVC dowel sleeve,

bond breaker tape and

cradle bent.

Joint sealant: 

it seals the joint width and prevents water and dirt from entering the joint and causing dowel bar corrosion and unexpected joint stress resulting from restrained movement.
Joint filler: it is compressible so that the joint can expand freely without constraint. Someone may doubt that even without its presence, the joint can still expand freely. In fact, its presence is necessary because it serves the purpose of space occupation such that even if dirt and rubbish are intruded in the joint, there is no space left for their accommodation.

Expansion Joint Preparation

Dowel bar: 

This is a major component of the joint. It serves to guide the direction of movement of concrete expansion. Therefore, incorrect direction of placement of dowel bar will induce stresses in the joint during thermal expansion. On the other hand, it links the two adjacent structures by transferring loads across the joints.

PVC dowel sleeve: 

It serves to facilitate the movement of dowel bar. On one side of the joint, the dowel bar is encased in concrete. On the other side, however, the PVC dowel sleeve is bonded directly to concrete so that movement of dowel bar can take place. One may notice that the detailing of normal expansion joints in Highways Standard Drawing is in such a way that part of PVC dowel sleeve is also extended to the other part of the joint where the dowel bar is directly adhered to concrete. In this case, it appears that this arrangement prevents the movement of joint. If this is the case, why should designers purposely put up such arrangement? In fact, the rationale behind this is to avoid water from getting into contact with dowel bar in case the joint sealant fails. As PVC is a flexible material, it only minutely hinders the movement of joint only under this design.

Bond breaker tape:

 As the majority of joint sealant is applied in liquid form during construction, the bond breaker tape helps to prevent flowing of sealant liquid inside the joint .

Cradle bar: 

It helps to uphold the dowel bar in position during construction.

Keywords for this Post

Others are also looking for 

expansion joint in buildings
concrete expansion joint
expansion joint concrete slab
expansion joint pdf
expansion joint filler
expansion joint types
expansion joint in piping system
expansion joint manufacturers

Sediment transport in streams and rivers is inevitable as the stream or river transport capacity rises and falls with the streamflow. If the transport capacity in a location exceeds the sediment supply, erosion will occur. Streambank erosion must be controlled in critical areas (e.g. near bridge crossings) for safety as well as economic reasons. 

The same is true of bridge piers where general and local scour during a flood event may temporarily or permanently lower the streambed level by several feet, potentially endangering the structure. Articulated concrete block systems (ACBs) are an effective countermeasure if properly designed and installed
Articulating concrete block (ACB) systems are used to provide protection to underlying soil materials. The term “articulating” implies the ability of the system to conform to changes in subgrade while remaining interlocked. 

The interlocking property provided by the special shapes of ACBs also allows for expansion and contraction. They are either hand-placed or installed as pre-assembled mats on top of a filter layer on prepared subgrade, and act as a soil support or “revetment”. ACBs can be used to solve a wide variety of erosion problems:

Keywords for the Post

articulated concrete block cost
articulated concrete block mat
articulated concrete block mattress
articulated concrete block design
articulated concrete block mat cost
revetment mattress
concrete erosion mats
fabric formed concrete revetment mat

For working stress approach, service loads are used in the whole design and the strength of material is not utilized in the full extent. In this method of design, stresses acting on structural members are calculated based on elastic method and they are designed not to exceed certain allowable values.

In fact, the whole structure during the lifespan may only experience loading stresses far below the ultimate state and that is the reason why this method is called working stress approach. Under such scenario, the most economical design can hardly be obtained by using working stress approach which is now commonly used in the design of temporary works.

For limit state approach, for each material and load, a partial safety factor is assigned individually depending on the material properties and load properties. Therefore, each element of load and material properties is accurately assessed resulting in a more refined and accurate analysis of the structure.

In this connection, the material strength can be utilized to its maximum value during its lifespan and loads can be assessed with reasonable probability of occurrence. Limit state approach is commonly used for the majority of reinforced concrete design because it ensures the utilization of material strength with the lowest construction cost input.

Keywords for this post 

difference between working stress and limit state method
difference between working stress method and limit state method of design
difference between working stress method and limit state method pdf
difference between limit state method and working stress method ppt
working stress method wiki
advantages of limit state method
working stress method of rcc design
working stress method definition

In the recent times, Punjab and specially Lahore have been the center point of development including flyovers, highway projects, underpasses, metro bus systems and much more but now the PM have certainly expanding these projects throughout the country. 

Greeline Bus Rapid Transit System in Karachi

Besides criticism and censure the projects have proved to provide luxury with comfort to some portion of the society that have been deprived of such services in the past. 

PM Sharif has announced a project of Greeline Bus Transit System in Karachi after being success or whatever of Orangeline Train in Lahore and Rawalpindi and Lahore Metro Bus System. 

With this Greeline Rapid Transit System more than 300,000 people will be able to travel from KESC power house, Sarjani Town towards Muncipal Park and M.A. Jinnah Road. 

The features of the project are; the cost of the project is estimated to be 16,085 million Rupees with a station to station distance of 800 meters, having special provisions for special persons, 

The accumulative length of the project is estimated to be 18.4 kilometer including 11.7 km elevated and 7.7 km at grade, the special automated ticketing system will be introduced including luxurious busses and waiting portions in stations. 

The 84 MW New Bong Escape Hydropower Project, Azad Jammu and Kashmir (AJK), Pakistan (the “Project”) is a run-of-the river hydropower scheme without any dam, new storage, displacement/resettlement of human habitation, change in the hydrological regime or any other adverse environmental impact.

The Project is a low head hydropower scheme and is strictly run-of-the-river without any storage or new reservoir. The Mangla reservoir, dam and 1000 MW power house, constructed in the early sixties feeds the Project downstream of the Mangla powerhouse, through its tailrace channel. The main purpose of the project activity is to generate electricity for supply to the national grid using clean, renewable and sustainable natural resources and tapping the significant hydropower potential in the country.

The project activity represents development of the first hydropower independent power producer in Pakistan and is expected to act as a catalyst for hydropower development in the country and open the way for private investment in this vital sector. The power generated will be sold, through a 25 year power purchase agreement, to the Government owned National Transmission and Despatch Company Limited (NTDC).

Location of Project
Despite the large hydropower potential, Pakistan’s grid is predominantly hydrocarbon intensive. Due to looming power shortages and increasing demand/supply gap expected from 2007 and onwards at a rate of some 1,000 MW per annum planners are forced turn once again to “quick fix” thermal generation to mitigate the significant power shortages expected.

The Project will contribute clean and renewable hydroelectricity to the deficient national power resources and contribute to GHG emission reduction by displacing the electricity production requirement of fossil fuel-fired power plants to the extent of its generation. The interconnection is close to the load centre and it is expected that new plant will result in reduction of some 4.572 million tons of CO2e emissions over the crediting period of 21 years.

The Project is located 7.5 km downstream of Mangla Dam some 120 km southeast of Islamabad, capital city of Pakistan. The Mangla dam and reservoir were constructed some 40 years ago, with support of the World Bank under the Indus Basin Treaty to impound and store the water of the River Jhelum for irrigation use and incidental power generation. The Project site is easily accessible from the main highway by good metalled roads requirement for new infrastructure is minimal.
The key components of the Project include intake, headrace channel, powerhouse complex, tailrace channel, switchyard, interconnection facility, road-bridge and subsidiary outfall structure.

The switchyard will provide connectivity with the double circuit in-out arrangement with the two existing 132 kV Mangla-Kharian transmission lines pass over the Project Site and connected to the grid system.

All the power generated by the Project will be sold to the National Transmission and Despatch Company (NTDC) under a long term power purchase agreement with a 25 year term.
The project achieved financial closing on December 20, 2009. US dollar financing has been provided by Asian Development Bank (ADB),

 Islamic Development Bank, International Finance Corporation, and the French origin Société de Promotion et de Participation pour la Coopération Economique (“PROPARCO”) whereas Pak rupee financing has been provided by Habib Bank Limited (HBL) and National Bank of Pakistan (NBP).

Laraib Energy Limited (Laraib) is the owner and developer of the ‘New Bong Escape’ Hydroelectric Power Project. This was told to a group of journalists, who are in ADB Press Tour on different developmental projects relating to water and power in different parts of the country.

Laraib is a subsidiary of Hub Power Company Limited (HUBCO) which owns 75 percent of shares of the company. HUBCO is the owner of 1,292 MW Hub Power Station, which is the first and largest power station to have been financed by the private sector in Southern Asia during the 1990s and one of the largest private power projects in the newly industrialized world at that time. The balance 25 percent shares are held by the minority shareholders.

Federal Minister for Science and Technology Rana Tanveer Hussain said the Pak-China Science, Technology, Commerce and Logistic Park would be established in Islamabad at the cost of $1.5 billion.

Hussain, addressing a press conference, said it would be set up as part of the China-Pakistan Economic Corridor and serve as a platform for technological and commercial linkages between the two countries besides promoting investment and financing, e-commerce and research and development.

The Minister said Pakistan would provide 500 hectares of land for the establishment of the Park and all other investment would be made by China. He said three sites had been tentatively identified and a delegation of Xinjiang Production and Construction Corporation would be arriving this month to finalise the site.

He said that the foundation stone of the project is expected to be laid in March next year and it would be completed in ten years in three phases. The minister said that this project would create job opportunities for 1,500 Pakistanis.

The minister stressed the need to move towards latest technology from obsolete one in order to compete with the rest of the world. In this regard, the government would allocate bigger share of the budget next year for the promotion of science and technology, he added.


Khyber Pakhtunkhwa government has decided handing over of six hydel power projects having the capacity of 719 MW electricity to FWO for efficient implementation to overcome power shortage in the province. This was decided in a high level meeting convened to discuss hydel and communication projects in the province at Khyber Pakhtunkhwa House Islamabad on 10 Feb 2016.

Bridges are considered as an important construction with respect to infrastructure and development of a region. This structure is not only important during peace time but also important during war times as is the only access towards some area.

In the world there are many iconic civil engineering structures but bridges are ahead of all due to its difficult construction sites and importance in the heart of the people.
Here are few bridges of the world that are one of their own kind.

Russky Bridge, Russia

The Russky Bridge (Russian: Русский мост – Russian Bridge) is a bridge built across the Eastern Bosphorus strait, to serve the Asia-Pacific Economic Cooperation conference that took place in Vladivostok in 2012. The bridge connects the mainland part of the city (Nazimov peninsula) with Russky Island, where the main activities of the summit took place. The bridge was completed in July 2012 and opened by Russian Prime Minister Dmitry Medvedev. On September 3, 2012, the bridge was officially given its name.

The Helix Bridge

The Helix Bridge, previously known as the Double Helix Bridge, is a pedestrian bridge linking Marina Centre with Marina South in the Marina Bay area in Singapore. It was officially opened on 24 April 2010 at 9 pm, however only half was opened due to ongoing construction at the Marina Bay Sands. It is located beside the Benjamin Sheares Bridge and is accompanied by a vehicular bridge, known as the Bayfront Bridge. The entire bridge was opened on 18 July 2010 to complete the entire walkway around Marina Bay.

Brooklyn Bridge

The Brooklyn Bridge is a hybrid cable-stayed/suspension bridge in New York City and is one of the oldest bridges of either type in the United States. Completed in 1883, it connects the boroughs of Manhattan and Brooklyn by spanning the East River. It has a main span of 1,595.5 feet (486.3 m), and was the first steel-wire suspension bridge constructed. It was originally referred to as the New York and Brooklyn Bridge and as the East River Bridge, but it was later dubbed the Brooklyn Bridge, a name coming from an earlier January 25, 1867, letter to the editor of the Brooklyn Daily Eagle, and formally so named by the city government in 1915. Since its opening, it has become an icon of New York City, and was designated a National Historic Landmark in 1964 and a National Historic Civil Engineering Landmark in 1972.

Sydney Harbour Bridge

The Sydney Harbour Bridge is a steel through arch bridge across Sydney Harbour that carries rail, vehicular, bicycle, and pedestrian traffic between the Sydney central business district (CBD) and the North Shore. The dramatic view of the bridge, the harbour, and the nearby Sydney Opera House is an iconic image of Sydney, and Australia. The bridge is nicknamed "The Coathanger" because of its arch-based design or is simply called "the Bridge" by Sydney residents.

Magdeburg Water Bridge

The Magdeburg Water Bridge (German: Kanalbrücke Magdeburg) is a large navigable aqueduct in central Germany, located near Magdeburg. The largest canal underbridge in Europe, it spans the river Elbe and directly connects the Mittellandkanal to the west and Elbe-Havel Canal to the east of the river, allowing large commercial ships to pass between the Rhineland and Berlin without having to descend into and then climb out of the Elbe itself.

Millau Viaduct Bridge

The Millau Viaduct (French: le Viaduc de Millau, IPA: [vjadyk də mijo]) is a cable-stayed bridge that spans the valley of the River Tarn near Millau in southern France.
Designed by the French structural engineer Michel Virlogeux and British architect Norman Foster, it is the tallest bridge in the world with one mast's summit at 343.0 metres (1,125 ft) above the base of the structure. It is the 15th highest bridge deck in the world, being 270 metres (890 ft) between the road deck and the ground below. The Millau Viaduct is part of the A75-A71 autoroute axis from Paris to Béziers and Montpellier. The cost of construction was approximately €400 million. It was formally inaugurated on 14 December 2004, and opened to traffic on 16 December. The bridge has been consistently ranked as one of the great engineering achievements of all time. The bridge received the 2006 International Association for Bridge and Structural Engineering Outstanding Structure Award.

Akashi Kaikyo Bridge

The Akashi Kaikyō Bridge (明石海峡大橋 Akashi Kaikyō Ō-hashi?) is a suspension bridge, which links the city of Kobe on the Japanese mainland of Honshu to Iwaya on Awaji Island. It crosses the busy Akashi Strait (Akashi Kaikyō in Japanese) as part of the Honshu-Shikoku Highway.
Since its completion in 1998, the bridge has had the longest central span of any suspension bridge in the world, at 1,991 metres (6,532 ft; 1.237 mi).
It is one of the key links of the Honshū-Shikoku Bridge Project, which created three routes across the Inland Sea.

Fremont Bridge

The Fremont Bridge is a double-leaf bascule bridge that spans the Fremont Cut in Seattle, Washington. The bridge, which connects Fremont Avenue North and 4th Avenue North, connects the neighborhoods of Fremont and Queen Anne.
The Fremont Bridge was opened on Friday June 15, 1917, at a cost of $410,000. The first traffic over the bridge was to "owl cars", the last run of the trolleys, and then after 5am the same day to all other traffic. The Lake Washington Ship Canal was dedicated on July 4, 1917, which has caused confusion about the opening date, for this bridge crosses the canal. The Fremont Bridge is the first of four city bascules to cross the canal, the others being Ballard Bridge (1917), University Bridge (1919), and Montlake Bridge (1925). The bridge was added to the National Register of Historic Places in 1982, and is also a designated city landmark, ID #110347.

As we move across highways we see a mess in traffic, cars making noise of horns, you sometimes can’t even see the carpet of highway. The increased population and expansion of residential areas and highways in all directions cause conflicts in directions. We sometimes see an interchange with over 5 highways merging at one line; imagine what a mess it would create.

With this increased population there is a simultaneous advancement in our technology and science, we have learned how to effectively utilize the cross-sections of a structure with plastic designs instead of elastic designs. In this way the trends in the type of bridges and flyovers have been changed over the recent past.

Increased spans was a challenging factor in a highway bridge but the factor we should look for is the increased dead weight and then there comes an idea of utilizing the effective area most and removing the un-necessary portion in the section of a bridge and thus there comes the box girder.
A cellular structure having hollow rectangular section reducing the dead load significantly and thus ensuring greater span and economy.

Structural Section forming a hollow rectangle


Bridge span having top and bottom slabs monolithic with intermediate webs / walls forming one or more rectangular voids

A typical box girder bridge is comprised of top and bottom concrete slabs connected by a series of vertical bridge stems usually called webs that might be inclined or vertical as desired.
A box girder is formed when two web plates are joined by a common flange at both the top and bottom. The closed cell which is formed has a much greater torsional stiffness and strength than an open section and it is this feature which is the usual reason for choosing a box girder configuration.
The box girder consists of concrete, steel or a combination of both. Most of modern elevated structures are built on the basis of the box grider bridge.

The spanning of bridges started with simple slabs. As the spans increased, the design depth of slab is also increased. It is known that material near centre of gravity contributes very little for flexure and hence can be removed. This leads to beam and slab systems. The reinforcement in bottom bulb of beam provided capacity for tensile forces and top slab concrete, the capacity to resist the compression. They formed a couple to resist flexure.

As the width of slab is increased more number of longitudinal girders are required resulting in reduction of stiffness of beams in transverse direction and relatively high transverse curvature. The webs of beams get opened out spreading radially from top slab. Under high transverse bending these will no longer be in their original position. To keep it in their original position the bulbs at bottom should be tied together which in-turn leads to evolution of box girder. Long spans with wider decks and eccentric loading on cross-section will suffer in curvature in longitudinal and transverse direction causing heavy distortion of cross-section. Hence the bridges should have high torsional rigidity in order to resist the distortion of cross-section deck to a minimum.

Accordingly box girders are more suitable for larger spans and wider decks, box girders are to be suitable cross-section. They are elegant and slender. Economy and aesthetics further lead to evolution of cantilevers in top flanges and inclined webs in external cells of box girder. The dimension of cell could be controlled by prestressing.

As the span and width increases the beams and bottom slabs are to be tied to keep the geometry which in turn leads to evolution box girder.

Any eccentric load will cause high torsional stresses which will be counter acted by the box section. The analysis of such sections are more complicated due combination of flexure, shear, torsion, distortion. But it is more efficient cross-section. It is used for larger spans with wide cross-section. It can be used for spans up to 150m depending upon the construction methods. Cantilever method of construction is preferred most.

Soil mechanics and foundation engineering (geotechnical engineering) is a fast developing discipline of civil engineering. Considerable work has been done in the field in the last 6 decades. A student finds it difficult to have access to the latest literature in the field. The author has tried to collect the material from various sources and to present in the form of a text.

The text has been divided into two parts. The first part deals with the fundamentals of soil mechanics. The second part deals with earth retaining structures and foundation engineering. The subject matter has been presented in a logical and organized manner such that it may be taken up serially without any loss of continuity. The book covers the syllabi of undergraduate courses in soil mechanics and foundation engineering prescribed by most of Indian Universities and Institutes. 

An attempt has been made to explain the fundamentals in a simple, lucid language. Basic concepts have been emphasized throughout. The author who has about 25 years of teaching experience, has paid special attention to the difficulties experienced by students. A large number of illustrative examples have been given to show the application of the theory to field problems. Numerical problems, with answers, have been given for practice. Some objective type question have been given at the end of the each chapter. 

The text is profusely illustrated with diagrams and charts. Latest IS codes have been followed, as far as possible. References are given at the end of each chapter. As complete switch over to SI units has not been taken place in India both MKS and SI units have been used. 

The book will be useful for the undergraduate students. The students appearing for various competitive examinations and AMIE will also find the text useful. A large number of charts and tables have been included to make the text useful for practicing engineers. 

Name of the Book

Soil Mechanics and Foundation Engineering 

Author of the Book

Dr. K. R. Arora

Contents of Book

1. Introduction
2. Basic Definition and Simple Tests
3. Particle Size Analysis
4. Plasticity Characteristics of Soils
5. Soil Classification
6. Clay Mineralogy and Soil structure
7. Capillary Water
8. Permeability of Soil
9. Seepage Analysis
10. Effective Stress Principles
11. Stresses due to applied load
12. Consolidation of soils
13. Shear strength
14. Compaction of Soil
15. Stabilization of Soil
16. Drainage, De-watering of Wells
17. Site Investigation
18. Stability of Slopes
19. Earth Pressure theories
20. Design of Retaining Walls and Bulkheads
21. Braced cuts and coffer dams
22. Shafts, Tunnels and underground conduits
23. Bearing Capacity of shallow foundations
24. Design of Shallow Foundations
25. Pile foundations
26. Drilled piers and Caissons
27. Well foundations
28. Machine Foundations
29. Pavement Design
30. Laboratory Experiments

Download the Book

The Content is for Members Only !!!

This Book is available to download for our bronze, Silver & Gold Level members, you can simply click the button below to signup / login for your membership and download the book now.

Prestressing is now a must-to-have phenomenon in every mega project whether it includes flyovers or dam or whatever. During the design procedures a very important question that arises in the mind of the engineer is; whether to use jacking at one end only or from both ends. 

Jacking at one end or both ends

The answer to this question lies and depend on some of the features of the project. 

During prestressing operation at one end, frictional losses will occur and the prestressing force decreases along the length of tendon until reaching the other end. These frictional losses include the friction induced due to a change of curvature of tendon duct and also the wobble effect due to deviation of duct alignment from the centerline. 

Therefore, the prestress force in the mid-span or at the other end will be greatly reduced in case the frictional loss is high. Consequently, prestressing, from both ends for a single span i.e. prestressing one-half of total tendons at one end and the remaining half at the other end is carried out to enable a even distribution and to provide symmetry of prestress force along the structure. 

In fact, stressing at one end only has the potential advantage of lower cost when compared with stressing from both ends. For multiple spans (e.g. two spans) with unequal span length, jacking is usually carried out at the end of the longer span so as to provide a higher prestress force at the location of maximum positive moment. 

On the contrary, jacking from the end of the shorter span would be conducted if the negative moment at the intermediate support controls the prestress force. However, if the total span length is sufficiently long, jacking from both ends should be considered.

Others are also Visiting

  • What is Prestressing force? 
  • What is post-tensioning?
  • Jacking force
  • Jacking at one end only
  • Jacking at both ends

Pakistan’s parliament is set to become the first legislature in the world to function on solar energy after Prime Minister Nawaz Sharif inaugurates the 1MW project . A special ceremony has been planned with all federal ministers invited to the event. The Chinese ambassador is also expected at the ceremony to open the plant funded by China.

Chinese President Xi Jinping and PM Nawaz had launched the project on April 22, 2015. The system is currently generating 80MWh electricity, of which 62MW is used by the Parliament House and the surplus 18MW supplied to the national grid. The project was completed in seven months at a cost of Rs280.61 million. The solar-power plant will help the Parliament House save around Rs12 million in electricity bills every year, officials claim.

The power demand at the legislative house rises to 2.3MW in summers due to the additional load of air conditioners and other cooling equipment. The solar electrification of the parliament building will save approximately 2,500 tons of carbon dioxide per annum with a carbon credit of Rs3.4 million per annum, if the project gets registered under the Clean Development Mechanism. According to the secretariat official, the Pakistan Council of Renewable Energy Technologies (PCRET) had worked out the electricity requirements at the parliament at 2MWh.

1 | Pantheon, Rome
possibly by Apollodorus of Damascus, c126 AD

The ancient Romans didn’t have reinforced concrete (that is, strengthened with steel) but they had concrete, and used it to such heart-stopping effect on the Pantheon that no one has really been able to match it since. The true moment of genius is the way in which, after a certain amount of harrumphing with Corinthian columns and marble decoration at its lower levels, the design resolves itself into the pure circular oculus at its top, unglazed, which causes a beam of light to rake around the interior like an internalised sun.

2 | Unité d’Habitation, Marseille
Le Corbusier, 1952

Concrete has the ability to be primitive and technological, massive and levitating, to combine the properties of steel with those of mud. Le Corbusier knew how to run the gamut of its expressive range better than anyone. He used it as the medium for translating his fascinations both with aeroplanes and other modern machines and with ancient landscapes and temples. His Unité d’Habitation, a massive apartment building in Marseille, is both a liner floated to its site from the nearby Mediterranean and a chunk of the surrounding mountains, rectangularised, ark and Ararat at once.

3 | Los Manantiales restaurant, Mexico City
Félix Candela, 1958

Many architects and engineers have exploited the ability of reinforced concrete to produce structures of exceptional apparent lightness which, despite being made of a form of masonry, hardly seem to touch the ground. Quite a few have used arches and vaults in the form of parabolas, which direct the structural forces inside the material with particular efficiency, which makes the structure lighter still. Félix Candela was one of the earliest and best to pursue these ideas. The anti-gravity effects of the Los Manantiales restaurant were particularly magical.

4 | Bank of London and South America, Buenos Aires
Clorindo Testa, 1966

The Italian-Argentinian architect Clorindo Testa wasn’t particularly interested in getting concrete to look light, at least from the outside, instead heaving it out of the ground into an extraordinary structure that has something of a dinosaur’s skeleton. Yet it still manages to achieve a civilised rapport with the neo-classical facades around it. It also forms a perforated carapace that filters sunlight to the interior and creates both enclosure and openness. It unexpectedly ends up having some of the qualities of a Japanese screen, if with considerable added tonnage.

5 | Saint-Jean-de-Montmartre, Paris
Anatole de Baudot, 1904 (interior)

A slightly gauche attempt to realise the principles of gothic architecture in reinforced concrete but at the same time endearing and heroic. The church was sufficiently ahead of its time that building codes hadn’t caught up, which meant construction had to be delayed while a demolition order was removed. De Baudot didn’t quite work out that you can achieve gothic lightness of construction without gothic details such as pointed arches and vaults. Auguste Perret would later do this with the radiant Notre Dame du Raincy, but Saint-Jean-de-Montmartre makes the list by virtue of being a pioneer.

6 | SESC Pompéia, São Paulo
Lina Bo Bardi, 1986 (sports towers)

A swimming pool, indoor football pitches and other sports courts are stacked up in the fattest of this group of three towers; changing rooms are in another, linked by dynamic bridges, which transforms the normally humdrum movement from cubicle to playing zone into urban theatre. The third, cylindrical, tower stores water. Knowing that a change of political wind could blow away socially minded projects like this, Bo Bardi made it fortress-like: a citadel of liberty, it was called. The window openings, which seem punched out by a caveman, are amazing.

7 | Portuguese National Pavilion, Expo 98, Lisbon
Álvaro Siza 1998

Álvaro Siza is one of the less declamatory and more subtle contemporary architects, which makes this moment of theatre all the more striking. He takes a sheet of concrete and drops it like a pocket handkerchief between two rectangular blocks. The special properties of reinforced concrete, in particular its abilities to hang as well as vault, and achieve high strengths with minimal thickness, are used to the full. A classic of making design look effortless, when the engineering and construction that goes into it is anything but.

8 | Eberswalde technical school library, Germany
Herzog and de Meuron, 1999

By the 1990s it might have been thought that the list of Things to Do With Concrete had been exhausted. Herzog and de Meuron, however, came up with something new, which was to print an eclectic set of images, selected by the artist Thomas Ruff, on to the material. The same images were also printed on horizontal bands of glass, set flush with the concrete, which by day gives the library’s simple oblong shape an apparently homogeneous surface. By night the transparent parts light up and the solid parts don’t, which creates an opposite impression.

9 | St John’s Abbey Church, Collegeville, Minnesota
Marcel Breuer, 1961

A rare error in the smooth-running 10 best machine allows a late entry, a church by the Bauhaus alumnus Marcel Breuer deep in the midwest that makes many tonnes of concrete into mineral origami. I am indebted to a reader, Rolf Erikson, for pointing this project out. Fans of Louis Kahn clamouring for his inclusion won’t be pleased, though. Kahn was indeed magnificent and it was a tough call to leave him out. But the Breuer is more concrete-y.

10 | Poli House (interior), Coliumo, Chile
Pezo von Ellrichshausen, 2005

Apologies to Tadao Ando, Denys Lasdun, Robert Maillart, Oscar Niemeyer, Zaha Hadid, Rachel Whiteread, Pier Luigi Nervi, Frank Lloyd Wright, and Sverre Fehn, all of them magicians with concrete who deserve a place in a top 10. But the last slot goes to a house on a promontory where difficulties of access limited niceties in construction. The result is a structure whose cubic purity is offset by roughness in its substance, and where the traces of the timber moulds of its concrete give it the feeling of an unusually exalted wooden shack.

Harsh weathers for sure effects the working schedules in a civil engineering project. Whether it is too hot or too cold outside the considerations in the mind of a construction manager is "How to fight with this new hurdle". Concrete shrinks and expands due to temperature variations which is very critical as far as fresh pouring is considered because if that is not controlled it may proved fatal for the pour.

Concrete pouring in Cold Weather

This next time whenever you are pouring a concrete you should consider the temperature and measure it at site to avoid such troubles.

  • Keep water – Cement ratio on lower side as much as workable. 
  • Transport concrete mix by covered transit mixers. 
  • Use hot water for mixing concrete at the batching plant. 
  • Keep formwork insulated by wood liner. 
  • Prior to pouring concrete was concrete surface and re-bars hot water. 
  • Maximize resources to quickly complete concrete pouring exercise by using more transport equipment. 
  • Cover the concrete immediately after pouring with proper insulating sheet. 
  • Keep formwork for longer time. Assure that concrete develops sufficient strength for safe removal of forms. 
  • Strip the formwork during rising temperature. 
  • Observe temperature of concrete at all steps. 
  • Vertical day joint in concrete in cold weather. 
  • The large quantity involving more than 200 m3 of concrete in each pilecap led the engineers to plan workability of the site situation. 
  • It should be kept in mind that. 
  • The cold weather does not permit to work upto late hours in the evening. Hence, it was agreed upon to provide day joint at suitable position and to complete the work thereafter. 
  • Accordingly, It is proposed to provide slightly inclined stopper in form of wooden strips to be accommodated between the rebars. This arrangement will allow planned quantity of work during day time in full depth as it would mainly retain the heat of the concrete evolved during the chemical reaction. 
  • The workable position of day joint could be between 1/3 and ¼ span where there are no extra re-bars. 
  • Apply bonding agent in the joint 
  • Before the next pour all loose material at joint shall be cleaned and green cut shall be made. 

Steps to pour concrete in Pile Cap

Following are some of the steps that will guide you to a stable and harmless concrete. 

1. Prepare stable working platform upto bottom level of pile cap. 
2. Excavate and clean the area for pile cap. 
3. Check ground level and place approved lean concrete for the pile cap.
4. Next day mark the layout of the pile cap and the re-bars
5. Place specified reinforcement bars in position as shown in the construction drawing and tie them firmly. Provide spacers below the reinforcement bars to provide desired cover to the reinforcement. 
6. Place shuttering plates all around in position. Provide firm supports to remain in position during concreting. 
7. Wash all transit mixers with hot water immediately before loading. 
8. Transport approved fresh concrete from batching plant to site. 
9. Collect concrete samples for testing as specified. 
10. Start pouring concrete by dropping through chute, till the concrete is place in full depth as shown in the construction drawing and to the length as planned for the day. 
11. While placing concrete, operate vibrators to compact concrete and trowel the top. 
12. Make sure surfaces in contact with concrete are free of ice and snow. 
13. Good quality thermometers shall be kept at site for checking air temperature. 

The finishing in concrete works is vital as for sure the final touches depend on it. The poor finish of concrete is not only wrong from aesthetic point of view but also it shows the strength and integrity of the concrete structure. Besides many defects in concrete one important is honeycombing. 

Hollow spaces and cavities left in concrete mass on surface or inside the concrete mass where concrete could not reach are honeycombs, looking like honey bees nest.

These honeycombs are visible to naked eyes and can be seen after the shuttering formwork is removed. Honey combs which are inside mass of concrete can only be detected by advanced techniques like ultrasonic testing etc.

Causes of Honeycombing Concrete

Honeycomb is due to non-reaching of concrete to all places due to which cavities and hallow pockets are created. 

Honeycombing is used to describe areas of the surface that are coarse and stony. It may be caused due to following :- 

1. insufficient fine material in the mix,
2. incorrect aggregate grading 
3. poor mixing or improper vibration
4. leakage of grout or mortar fraction from the concrete at construction or formwork joints

Remedial Measure for Honeycombing

 This can be corrected by increasing the sand and cement content of the mix and by proper mixing, placing and compaction. The obvious solution here is to ensure that joints are well sealed and leak-free.

Small, shallow areas of honeycombing are probably mainly cosmetic. However, deeper areas will lead to a local reduction in the protection to the reinforcement from the concrete cover and hence possibly durability problems in the future.

The honey combing developed in the concrete/ bottom of the diaphragms may be corrected as under :- 
1. Remove the laitance and clean. 
2. Wash the surface with clean water. 
3. Remove free water. 
4. Prepare approved bonding agent (Sika dur 32) as recommended by the manufacture / approved by the Engineers. 
5. Prepare the concrete mix confirming the approved design. 
6. Fill the honey combing area
7. Trowel with force
8. Finish smoothly with float. 
9. Next Morning cure with water and clean. 
10. Continue curing as desired.
11. The site Engineer, Foreman and workers have been strictly instructed to follow the specification and fully understand the scope of work. 
12. Foreman must remain at site while the work goes on. 

Saad Iqbal

{picture#} Hi there, I am Saad Iqbal from Pakistan - Founder of Iamcivilengineer. I am Currently Working in a Consultancy Firm as Junior Engineer and am a Passionate blogger and a Civil Engineer from UET Taxila, Pakistan. {facebook#} {twitter#} {google#} {pinterest#} {youtube#}


{picture#} Hi there, I am Saad Iqbal from Pakistan - Founder of Iamcivilengineer. I am Currently Working in a Consultancy Firm as Junior Engineer and am a Passionate blogger and a Civil Engineer from UET Taxila, Pakistan. {facebook#} {twitter#} {google#} {pinterest#} {youtube#}
Powered by Blogger.
- Going for an Interview? Get Prepared today by 300+ Civil Engineering Interview Questions Read Here