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How intelligent scheduling is changing construction management process

Introduction to Programming BIM 4D

In recent decades, we have witnessed an intense progress of technology and computer applications. This progress is very noticeable in all aspects of the construction industry and especially in the development of BIM software. In a recent market survey with the Virtual Construction Software programming BIM 4D are reported as a huge support tool for all involved in major construction projects: construction managers, prime contractors and their customers.

In the small group of specialized software for programming BIM 4D, BEXEL Manager stands out for its unique features and capabilities directed toward management, programming (BIM 4D), cost estimation (BIM 5D) and even, facilities management (BIM 6D) of construction projects. I will try to briefly introduce its main features related to construction scheduling, which are a real game changer for future programming processes BIM construction.

Benefits of BIM 4D programming

Traditional programming process begins when planners and project managers often create construction schedules containing thousands of tasks to the level of each work item. Sort these tasks, connect and create dependencies and relationships allocation and balance a lot of resources can be extremely challenging and slow, even for more experienced managers project.

The main objective of the program is to improve 4D BIM planning processes and communication between all parties involved, allowing all participants to visually provide the entire process of building a very understandable and natural. Visual real-time simulations revolutionize complete planning processes, leveling traditional Gantt planning a 4D virtual presentation of the whole project implementation on the screen long before you start building.

The obvious and most significant benefits of BIM 4D programming process are:

Increased savings in time and cost, which can be variable, but reaching up to 500% in terms of the time required for program implementation.
Improving coordination and communication with stakeholders and the general quality of the work schedule.
Greater speed in creating offerings and optimizing budgets.
Improved site design and planning security.
Additional benefits that are not expressed through saving time and costs, but also greatly influence and augment the planning and construction process are the 4D visualizations.

Programming processes and estimation based on the model help the entire team to identify and optimize every detail designed. The efficiency and accuracy of visualization created BIM 4D allows experts project to identify and mitigate risk in the initial stages of the project, long before its construction. It also allows planning teams run different scenarios built to generate the best possible solutions while verifying their impact on costs. All schedule changes and variations made the Gantt chart are immediately updated and viewed in 3D view programming.

BIM 4D programming is much more than just visualization 4D

Today, many software solutions are advertised or used incorrectly as “4D BIM software,” however, there is a clear and obvious difference between viewing BIM 4D and 4D BIM software programming. The “4D BIM software” in general, can produce virtual construction simulation (visualization of construction process).

However, 4D BIM software programming as BEXEL Manager allows users to view the construction process and also virtually plan (create schedule) construction project. Our programming software BIM 4D allows you to create and change tasks / planned activities, change their duration and predecessor / successor tasks as well as optimize and validate the sequence of these activities, all within the software itself, while almost simultaneously, has updated the display changes in the view of 3D programming software.

The intelligent programming concept BEXEL 4D BIM Manager

On the other hand, the scheduling engine BEXEL Manager implements advanced programming algorithms, specially designed to provide the functionality to create fully automated construction schedules, simplifying manual sequencing unpleasant 4D. That’s where the real power of BEXEL Manager.

Unlike other solutions BIM 4D market, where it is necessary to create the schedule activities manually or semi-automatically depending on the elements of the BIM model available, our complete solution BIM 4D-5D-6D uses a visionary concept that allows planners and managers to easily apply their engineering experience.Its engine unique and intelligent programming allows the creation of construction methods and construction activity groups such as planners think and anticipate the processes running on your mind. Similarly, groups can be created different levels of activities of tasks based on the phases of construction, buildings, activities and anticipated elements. The next step is to create logical relationships and dependencies of these groups of activities and methodologies. In the same way most experts are accustomed to the softwares traditional programming, here you can select types of relationships between elements (for example, from end to beginning from start to start, end to end, etc.) and the duration or delay the created relationship.

A brief introduction to BIM 5D and cost management

Additionally, the next logical step in the process construction management BIM is assigned labor, equipment, material resources and costs to tasks and reach the next dimension BIM, ie 5D. Our solution allows multiple custom implement cost classification systems for different versions of costs within the same model, this is feasible in the BIM 5D Cost module named Editor (Editor Cost).

In addition, the user can manage, view and export graphs and reports cost, labor, materials and equipment. Keep track of planned and actual costs, and once construction begins, track and update progress on schedule, and analyze actual versus planned progress, hypothetical scenarios and mitigation strategies.It is very valuable that a user is enabled to handle and manage practically all dimensions BIM (3D, 4D, 5D and 6D) within an integrated software platform.

Automatic generation of 4D BIM schedules based on predefined construction methodologies

In addition, all created methodologies are saved in the software so that the user can store multiple templates to automatically create schedules using pre-defined methodologies and their variations. Once created the methodology of construction, scheduling engine CPM (Critical Path Method) with all its features, is used to find an optimal solution in terms of cost and minimum construction time and the balance of resources, providing fully detailed construction schedules in seconds, even for the most complex projects containing thousands of tasks and respective elements. All methodologies and previously saved templates can be reused for any other similar project,

Visualization and optimization of schedules BIM 4D

BIM 4D initial schedules generated automatically and can be tuned further by the user by placing a specific order of steps and activities with BIM model elements linked in temporal and spatial sense.

The amounts of resources can also be defined and modified for any task or phase subcontractor company. A user can change and improve visual sequences built using custom color schemes for items, tasks and resources. Changes can be made and additional exceptions by implementing custom calendars for tasks and subcontractors.

Management, optimization and classification of a lot of work by any standard model are extremely easy and intuitive programming using built-in filters.Planning teams can also compare visually and within the Gantt chart, different versions of the schedule and planning methodologies directly in the solution, easily switching between different versions cost for any of the scheduling options.

perfect interoperability

Finally, the duration of the entire activity of a task can be changed manually, before finalizing the schedule BIM 4D and video simulation construction. All programs created can be exported from BEXEL Manager to traditional software programming and most commonly used, such as Oracle Primavera or Microsoft Project ™ ™ or Microsoft Excel ™. All activities, durations, links and dependencies of the schedule originally created in BEXEL Manager will be retained and stored in the exported files, enabling seamless interoperability.

Mentioning interoperability, taking into account that the solution also allows the import of schedules traditionally derived from the aforementioned programming tools. As all tasks, duration, links and dependencies created originally explained also they are kept in BEXEL Manager.

Semiautomatic generation BIM 4D simulation based on imported schedule

Unlike most software BIM 4D market, where the process of linking programming tasks imported with the respective elements of the model is mostly done manually, BEXEL Manager uses an intelligent engine for semiautomatic linking elements activities using predefined rules, name / identification of activities and level of hierarchy. With comfortable views of each set of selection of model elements and cross-checking with categories, families, properties of each element, and improved search capabilities based on their properties and other criteria, bind errors are eliminated almost completely.

Once programming is imported, you can make additional adjustments, modifications and verification tasks within the Schedule Editor (Editor Programming) of BEXEL Manager. When all activities are linked, the software generates a video simulation of 4D construction, suitable for real-time review by project stakeholders. The created virtual simulation of 4D construction can also be exported as a video file.

conclusion

Once all stakeholders, mainly planners and project managers embrace the full potential and benefits of smart processes 4D programming, the entire industry will benefit and evolve, leading to a very accessible and tangible future of building BIM, where the 3D parametric design, construction simulations in real time and exchange of information are part of impeccable business every day.
By: Mileta Pejovic, BEXEL Consulting

By: Mileta Pejovic, BEXEL Consulting

Source : www.bimcommunity.com

TEKLA Structure Tutorial Videos

Tekla Structures is one of the most capable and advanced software in this field, but on the other hand, that makes it also a little more complicated because it has more tools, settings, possibilities, and opportunities for customization. Very much like with any other software, it`s possible to learn Tekla by yourself.

Tekla Structures tutorial Part 1

Tekla Structures tutorial Part 2

Tekla Structures tutorial Part 3

Tekla Structures tutorial Part 4

First imprinted concrete, and now knitted concrete

A knitted structure capable of supporting five tonnes of concrete? This is the insane project of the inventors behind Knitted Concrete technology.

As part of their research into digital fabrication, Mariana Popescu and Lex Reiter, both researchers at the ETH Swiss Federal Institute of Technology in Zurich, have produced a 3D textile structure using a computerised rectilinear knitting machine.

This new technology is being used on an architectural scale for the first time in a prototype being shown at an exhibition in Mexico. A five-tonne concrete structure, which has been poured onto knitted textile formwork, supported by a steel cable net. This prototype, known as KnitCandela, pays homage to Spanish-Mexican architect Félix Candela (1910-1997).

KnitCandela, a prototype of a five-tonne concrete structure, which has been poured onto knitted textile formwork.

The formwork was created from a digitally generated pattern, then knitted on a rectilinear machine. In 36 hours, the machine knits a fully shaped 3D textile consisting of four long strips.

The textile is also double layered. The first internal layer is an aesthetic surface with a colourful pattern, forming the visible ceiling within the structure. The second outer layer contains sleeves for the cables of the formwork system and pockets for balloons which, after the entire structure is coated in concrete, become hollow spaces.

There are multiple advantages to using this technology, such as saving on time, cost and materials, reduced waste, etc. The Knitted Concrete process has great potential for use in creating geometrically complex structures of this kind.

Philippe Block, Professor of Architecture and Structure at ETH Zurich, who also worked on the project, explains that the method could be a new form of 3D printing, “only it doesn’t require a completely new kind of machine. A conventional knitting machine will do just fine!”

Source: blog.bouygues-construction.com

WHAT YOU MUST KNOW BEFORE BUYING A 3D LASER SCANNER

In emergent tech sectors it’s common to find start-up companies which are not in command of the core skills required to do their work.

That’s certainly true in the scanning sector.

Like many new industries the sector infrastructure barely exists and for customers, finding a credible service provider can be challenging.

New sectors are like Wild West towns in the 1870s – there may or may not be a sheriff, a marshal, or a judge, and they may or may not have a grip on local law enforcement; they may or may not be well-versed in the law and they’re operating a long way from established civil society.

For customers, it can be a bit of nightmare, so here are a few of the things to look out for.

1. Tech manufacturers need to sell their tech and software, and their key messages often emphasise ease of use and application. Most tech-competent people can get up and running at an extremely basic level, but not with the performance requirements of a company offering professional services for a fee.

It’s only easy to use if you already have high-level intuitive tech skills (we have in-house tech staff who have developed our own training and operational hubs and can do everything, including adapting software and writing code)!

2. There are no generic, industry-wide, approved training courses. Manufacturers (Leica, Z+F, Faro etc) operate differently, manufacture different types of equipment, generating different outputs. Inexperienced companies get confused by this and overwhelmed by the need to learn different systems.

3. People are learning scanning in all sorts of ways – from YouTube and other online sources, and by trial and error (we train scanning operators and those doing post-production in-house, and we’re developing clear training protocols).

4. There’s a divide in the industry, between tech-led firms that have little understanding of BIM / FM / construction / design and build / project management etc; and firms led by people who have all these skills, but whose tech skills are deficient (we have employees with extensive skills and experience in both areas).

5. The entry level costs are peanuts by the standards of many industries; but for the individual sole-trader start-up entrepreneurs who so often pioneer new markets, they’re horrendous! No qualifications are required and most customers have little experience of the tech and haven’t yet acquired the skills to differentiate between a credible and non-credible offer.

Capital apart, the barriers to entry are, therefore, low, and many of the bottom-feeders are people with low-level business skills. (We have a successful, profitable, 17-year old company with great credit references and access to capital).

6. If you’re an individual sole-trader entrepreneurbuying all the equipment and software you need to run a scanning company, you’ll need a fair number of customers – very quickly – to pay-back your start-up costs, so you need to have the skills to grow a business to scale fast.

Why fast? Because the tech is developing so fast that within months / a year or so you’ll need to invest heavily again, to keep pace – and you can’t do that if you haven’t paid-down your initial investment or you can’t raise the capital (we were doing scanning projects across France, Germany and UK within weeks of starting our own operation; we have access to capital, we have a healthy income stream, and we invested in our second generation of technology before even launching a dedicated scanning company).

7. New entrants sometimes fail to realise that one day of scanning could require multiple days of post-production in order to produce something that is useable by most clients.

If you don’t do that, you’ll give the client an output which is clunky, data-heavy, difficult to use and awkward. They won’t get the most out of it, they won’t use it, they’ll consider the money wasted, and they won’t come back for a second bite (we have skilled in-house staff who can process scanned data quickly and make it very easy for customers to use).

8. The software that ‘comes in the box’ with a scanner isn’t sufficient for a professional operation. You need to apply other software, and probably adapt or write software for your specific requirements.

Writing code is simply beyond many of the people who go in to the business (Xmo Strata has always been an IT-literate company and we have introduced numerous IT-led customer solutions; writing code is second nature to our IT staff).

9. Scanning is essentially a professional services operation. Some of the companies in the field simply don’t have the customer-facing communications skills required; their founders have come out of corporates who are used to being on the ‘client’ side of the table and the cultural shift is beyond them (we have run a professional Business-To-Business service company for 17 years).

10. The initial cost of a basic scanner and everything you need to set-up is below six figures, if you do it on the cheap. But some of those in the sector have no experience of running an SME (Small to Medium Sized Enterprise) and think that they can set-up for the cost of the equipment alone.

Undercapitalised companies don’t last very long. If they haven’t provided customers with useable outputs (which is frequently the case) all the work disappears when they go out of business (we have extensive business experience covering not only our own companies but major brands).

The truth is that providing 3D digital scanning and digital modelling as a professional service is not for amateurs; but a generation of amateurs may have to come, and go, along with their customers’ money and much of the work customers have paid for, before that lesson is properly understood.

By Steve Martin, Managing Director, Xmo Strata and ManagingDirector, SpectisGB

THE 10 KEYS THAT DETERMINE HOW LONG A (3D) LASER SCAN TAKES!

How long does it take to do a scan and provide a client with the output they want?

Like so many services … it depends.

A room that is a simple box can be scanned and processed quickly and easily, but room (of the same size or volume) that is not a simple box, and which contains internal walls and pillars, permanent fixtures and fittings, equipment etc may take longer.

Complexity takes time (but is often the reason why scanning is so important).

Here are some of the things that will affect the timing:

1. The size of the area to be scanned.

2. The shape and dimensions of the architecture / interior design / equipment being scanned.

3. Whether a building has to be scanned both inside and out.

4. Are colour scans required – or is black and white sufficient?

5. The number of floors, rooms, corridors, staircases and internal spaces.

6. Whether the roof has to be scanned; how that will be done; and whether the roof is a simple shape or a complex one.

7. Whether ceiling voids have to be scanned, and whether they can be scanned from a single location (internal ‘shaped’ ceilings, around dormer windows or with recesses, may require additional locations).

8. The number of different scan locations the technician has to use in order to cover the requirement.

9. The precise output required.

10. The distance between locations, if there is more than one.

Remember that the scanning is only one part of the operation.

In order to make the scans useable for a client, post-production work is required – and again, how long that takes will depend on the variables of the project (perhaps as little as a day or so, perhaps as much as five days for every day of scanning).

Your service provider will be able to give more information once they have a full brief.

By Steve Martin, Managing Director, Xmo Strata and ManagingDirector, SpectisGB

Bar Bending Schedule Of Box Culvert

Definition of Bar bending

It is the method of bending reinforcing steel into shapes which are important for reinforced concrete construction.

Definition of Bar bending schedule(BBS)

Bar bending schedule alias schedule of bars refers to a list of reinforcement bars, a specified RCC work item that is shown in a tabular form for a smooth view. This table sums up all the necessary particulars of bars ranging from diameter, shape of bending, length of each bent and straight portions, angles of bending, total length of each bar, and number of each type of bar. This information can be used for making an estimate of quantities.

It includes all the details essential for fabrication of steel like bar mark, bar type and size, number of units, length of a bar, shape code, distance between stirrups (column, plinth, beam) etc.

While generating bar schedules, it is important to take proper care about length. In case of bending, bar length will be raised at the bending positions.

Benefits of the Bar Schedule:

When bar bending schedule is applied along with reinforcement detailed drawing, it makes the quality of construction superior.

Once bar bending schedule is prepared, cutting and bending of reinforcement is performed at factory and shipped to job site. This improves quick implementation at site and minimizes construction time and cost as fewer workers are needed for bar bending. Bar bending also circumvents the wastage of steel reinforcement (5 to 10%) and thus project cost is saved significantly.

It offers the perfect estimation of reinforcement steel requirement for all the structural members which are applied to workout complete reinforcement requirement for whole project.

Bar bending schedule offers the steel quantity requirement in a better way and thus delivers an option to make optimal use of the design in case of cost overflow.

The process becomes simple for site engineers to validate and approve the bar bending and cutting length throughout inspection prior to positioning of concrete with the support of bar bending schedule and thus facilitates in superior quality control.

It becomes easier to handle the reinforcement stock necessary for identified time duration.

It will facilitate to fabrication of R/F with structure.

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What is Kanban?

Most projects can be viewed as a process – a series of steps or tasks that achieve some desired result. There are all kinds of processes – simple and complex, individual and team, quick and time-consuming. Sometimes large or over-arching processes consist of a series of smaller pro-cesses.Kanban is a tool for managing the flow of materials or information (or whatever) in a process. Not having the materials, whether it is a part, a document, or customer information, at the time you need it causes delay and waste. On the other hand, having too many parts on hand or too much work in process (WIP) is also a form of waste. Kanban is a tool to learn and manage an optimal flow of work within the process.

There are three basic rules to implementing Kanban:

01. Visualize Workflow

A visual representation of the process lets you see exactly how tasks change from being “not done” to “done right”. The more complex a process is, the more useful and important creating a visual workflow becomes, but kanban can be used if there are just a few steps (do, doing, done) or a lot of steps (plan, design, draft, approve, schedule, imple-ment, test, integrate, deploy).

However complex the project may be, creating a kanban board allows you to see the status of the work being done at a glance.

02. Limit Work in Process (WIP)

Get more done by do-ing less. It may seem counterintuitive, but it is a powerful idea that has been proven time and time again to be true. There is a limit to the number of things you can be working on and still do them well, and that limit is often lower than you think. Whether a project is simple or complex or whether the team is small or large, there is an optimal amount of work that can be in the process at one time without sacrificing efficiency. It’s not uncommon to find that doing ten things at once takes a week, but doing two things at once takes hours, resulting in twenty things being done by the end of the week. Kanban metrics lets you find that optimal number.

03. Measure and Improve Flow

mprovement should al-ways be based on objective measurements, and kanban is no different. Finding and applying good metrics is usually a difficult step, but a few simple measures automatically generated by an application like Kanbanery can give you the information you need to tweak your process to optimize flow and maximize efficiency.

One of the great things about kanban is that you apply it to your existing process. You are simply identifying ways to improve what you are already doing, so you don’t have to start from scratch and you don’t have to worry about “throwing the baby out with the bath water” – meaning that you won’t lose the things you are already doing well. No sudden changes means there is minimal risk in apply-ing kanban as part of your improvement journey.

BRIDGE REHABILITATION TECHNIQUES

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1. Introduction

Modern bridge infrastructure comprises of primarily concrete (reinforced or pre-stressed) and steel structures. Over the service life of a bridge, its constituent materials are continually subjected to fatigue and wear-tear due to dynamic vehicular loads. Overloading due to increase in wheel loads and regular exposure to aggressive external environment may aggravate the situation further.

Post-tensioned concrete bridges may also exhibit loss in pre-stress overtime, resulting in drop in load carrying capacities of the affected members. Poor quality of construction and lack of regular maintenance could potentially lead to major retrofit in a bridge structure. Furthermore, components facilitating expansion/ contraction of bridge and load transfer to the sub-structure, such as expansion joints & bearings, may also require rehabilitation or replacement over time.

Defects in the constituent materials may be manifested in the form of cracking – spalling of concrete, excessive deflection of structure, corrosion of steel components/ reinforcement etc. It is evident that rehabilitation of bridges involves addressing a myriad of problems and no single technique or retrofit method could offer a complete solution. Therefore, answer lies in being able to address each individual problem with an appropriate technique to result in a durable retrofit. This article aims at providing an overview of a variety of structural retrofit techniques available to rehabilitate bridges.

2. Reinforced / Pre-stressed Concrete Bridges

Most of the structural repair and retrofitting techniques used for ordinary reinforced concrete are applicable to reinforced concrete bridges as well. Structural repair techniques include crack injection with low viscosity epoxy and patch repair using an approved material such as polymer modified mortar or non-shrink grout. Strengthening techniques include concrete jacketing, steel plate or FRP (fibre reinforced polymer) bonding on the external surface of the member to be retrofitted.

For strengthening of pre-stressed concrete structures, external post-tensioning or FRP retrofit may be appropriate.

Concrete jacketing

Involves increasing size of the existing reinforced concrete section by adding more reinforcement and concrete. It could be accomplished by either of the following methods:

1. Conventional Concrete – Pouring concrete around the member to be strengthened with additional steel reinforcement properly anchored to the existing section. Ordinary concrete jacketing requires formwork and is time consuming due to long curing time. Furthermore, it is difficult to achieve a dense mix in constrained conditions. Adhesion is also an issue, especially for overhead applications.

2. Sprayed Concrete (Shotcrete) – Pneumatically projecting concrete on to the reinforced (usually with wire mesh) and prepared surface of the member being strengthened with a spray gun. A variety of additives and admixtures are also introduced to expedite strength gain, reduce rebound, reduce water requirement, curb shrinkage and improve adhesion.

The grading of aggregates is critical in sprayed concrete due to the absence of external vibration and the reduction in the quantity of coarse aggregates as a result of rebound. Shotcrete does not require formwork and is useful to retrofit large areas in a relatively short period of time. But, the operation is very messy with enormous loss of sprayed materials, resulting not only wastage of materials but an unsightly-rough surface finish too. It is not economical for small areas of retrofit due to high setup and machinery costs.

3. Pre-Packed Aggregate Grouting – Pumping of cementitious grout into washed/ graded coarse aggregates placed with properly anchored reinforcement around the member to be strengthened in a tightly sealed formwork. It is one of the better ways of jacketing a concrete member as it results in a dense mix with good surface finish.

Regardless of the method deployed, jacketing results in increase in dimensions as well as dead weight of the retrofitted member.

Steel Plate Bonding

This technique involves enhancing strength (shear, flexure, compression) or improving stiffness of deficient reinforced concrete members by bonding steel plates of calculated thickness with adhesives and anchors to the existing sections.

Steel plate not only acts as externally bonded reinforcement to the concrete section but it also improves the moment of inertia (stiffness) of the composite (concrete-steel) section. This technique is useful for the flexural and shear strengthening of bending elements such as beams and slabs and for compression capacity enhancement of columns.

Steel plate bonding is a cumbersome process requiring extensive hacking & drilling in the existing section. Steel plates are hard to lift and need to be tailor made to suit to the as-built dimensions of the members. Resulting surface finish is unsightly and steel plate retrofit is prone to corrosion over time.

FRP Strengthening

A Fibre Reinforced Polymer (FRP) typically consists of high tensile continuous fibres oriented in a desired direction in a speciality resin matrix. These continuous fibres are bonded to the external surface of the member to be strengthened in the direction of tensile force or as confining reinforcement normal to its axis. FRP can enhance shear, flexural, compression capacity and ductility of the deficient member.

Aramid, carbon, and glass fibres are the most common types of fibres used in the majority of commercially available FRPs. FRP systems, commonly used for structural applications, come in many forms including wet lay-up (fibre sheets or fabrics saturated at site), pre-preg (pre-impregnated fibre sheets of fabrics off site) and pre-cured (composite sheets and shapes manufactured off-site).

The properties of an FRP system shall be characterized as a composite, recognizing not just the material properties of the individual fibres, but also the efficiency of the fibre-resin system and fabric architecture.

FRP strengthening is a quick, neat, effective, and aesthetically pleasing technique to rehabilitate reinforced and pre-stressed concrete structures. Unlike steel plates, FRP systems possess high strength to self-weight ratio and do not corrode. But, it is imperative to be aware of the performance characteristics of various FRP systems under different circumstances to select a durable and suitable system for a particular application.

It should be ensured that the FRP system selected for structural strengthening has undergone durability testing consistent with the application environment and structural testing in accordance with the anticipated service conditions. Suitably designed protective coatings may also be applied on an FRP system to protect it from exposure to adverse environmental conditions (acids, saltwater, UV exposure, impact, temperature, fire etc.).

External Post-Tensioning

Over the service life of a pre-stressed concrete member, loss in pres-stress may occur due to a variety of reasons. Post-tensioned bridges can be effectively rehabilitated by external post-tensioning technique to compensate for loss in pre-stress or increase in wheel loads.

In this technique, pre-stressing tendons or bars are located according to pre-determined profile on the external surface of the member to be strengthened according to design. Anchor heads are positioned at the ends of these tendons/ bars to post-tension the member using hydraulic jacks.

Although, this method is quite effective but it requires sufficient strength in the existing concrete to transfer the stress and exposed tendons & anchorages need to be protected against corrosion and vandalism.

3. Steel/ Composite Bridges

Components of a steel bridge need to be continually protected against environmental corrosion. Proper care needs to be exercised to maintain critical elements such as piles, piers, decks, suspension cables etc.

Piles and piers may be rehabilitated using bonded steel plates or FRP strengthening/ protection. Steel bridges are generally covered with a concrete decking, which gets worn off over time due to cyclic dynamic loads. It is a time consuming and cumbersome process to retrofit reinforced concrete decks with conventional methods. The following techniques are useful to rehabilitate a steel bridge deck:

Bridge Deck Replacement

Exodermic™Bridge Deck (www.dsbrown.com) is a modular deck replacement system consisting of a reinforced concrete slab composite with an unfilled steel grid. This arrangement maximizes the use of the compressive strength of concrete and the tensile strength of steel. Top portions of the main bars of the steel grid are specially designed with perforations that get embedded into the concrete to effectively transfer horizontal shear. The concrete component can be precast before the panels are installed on the bridge, or cast-in-place.

Overall thickness of the system ranges between 150mm and 250mm. The system is designed to speed up the construction process while reducing the dead load. A typical application weighs 35 to 50 percent less than a reinforced concrete deck that would be specified for the same span. It not only helps reduce dead load on the sub-structure but also enables bridge structure to sustain higher live loads.

The panelized nature of the Exodermic™ design is well suited for rapid, even overnight, redecking projects.

Bridge Cable Protection

Cableguard™ Elastomeric Wrap system (www.dsbrown.com) is a corrosion protection system exclusively developed to protect bridge cables, applicable during construction or rehabilitation of cable-stayed and suspension bridges.

The patented wrap material is based on cross-linking a chlorosulfonated polyethylene polymer that is manufactured into a three ply (polymer-fabric reinforcement-polymer) laminated construction. It comes in a wide variety of colours and hence, does not require painting.

Cableguard™ Elastomeric wrap is applied directly over existing cable coating using a Skewmaster™ automatic wrapping device to encapsulate the entire cable. Wrap is heated to fuse its overlapped portion and shrink it snuggly to the cable surface to result in an impermeable barrier against intrusion of moisture into the cable.

Although, the Cableguard™ wrap shrinks securely on the cable, it does not fuse or bond to the cable. Therefore, partial removal for inspection of the internal strands is not impaired. Application does not require sandblasting, high-pressure washing or any type of solvent cleaning, eliminating need for containment and disposal of hazardous materials.

Cableguard™ Elastomeric Wrap system presents a watertight sealing mechanism to protect bridge cables from corrosion and premature failure.

4. Rehabilitation of Expansion Joints and Bearings

Expansion Joints

Bridge expansion joints allow movement (expansion and contraction) resulting from temperature changes, shrinkage and creep etc. in the bridge structure, while maintaining its watertight integrity. Like bridge deck, they are continually subjected to dynamic vehicular wheel loads, wear & tear, and fatigue during their service lives.

Depending upon their movement capacities and make, expansion joints may fall into the categories of bituminous, rubberized or mechanical joints. They may also be categorized as bolted-down or positively anchored on the basis of their mode of anchorage with the bridge deck.

Generally, rubberized and finger bolt-down joints tend to loosen over time with the application of wheel loads. Upon loosening, dynamic forces are accentuated further that hamper proper functioning of the system as well as riding quality.

Sealing elements may also get damaged overtime due to wear and tear. Large movement joints such as modular expansion joint assemblies may also require replacement of their elastomeric components during their service lives.

Rehabilitation of bridge expansion joints poses the challenge of replacing the components or complete joint without disrupting traffic flow.

Generally, replacement is carried out lane by lane during off-peak hours to allow the traffic flow while work is underway. To accomplish, replacement of expansion joint with in a short period of time, it is important that the system proposed meets the following criteria:

1. Joint can be installed in a shallow box-out to limit cutting & hacking

2. Joint can be installed lane by lane

3. Nosing material is elastic and bonds well with the deck concrete and expansion joint mechanical elements

4. Nosing material sets quickly (less than an hour or so) without special curing requirements

5. System provides a water-tight integrity Delcrete™ Strip Seal Expansion joint systems (www.dsbrowm.com) meet all above-mentioned criteria and present an ideal solution to rehabilitate bridge expansion joints. Delcrete™ is a pour- in-place, free flowing, two-part polyurethane-based elastomeric concrete.

It has been compounded to bond to a variety of surfaces including steel and concrete. It is non-brittle over extreme temperature ranges, resistant to nearly all chemicals and has one-hour cure time.

Bridge Bearings

Bridge bearings primarily carry out the following functions:

1. Create a desired support system for the bridge superstructure

2. Transfer loads from the super-structure to the sub-structure

3. Allow movement and rotation of the superstructure Like expansion joints, bridge bearings also come in various types, makes and materials.

They fall into two broad categories of elastomeric and mechanical bearings. Elastomeric bearings are generally composed of neoprene or natural rubber, with or without steel plate reinforcement.

Mechanical bearings may be categorized into mechanical pot, roller, rocker, knuckle, or disc bearings. Defects in elastomeric bearings may be manifested in the form of cracking or tearing of elastomeric material, slip of steel reinforcing layer or the bearing itself, excessive shear movement in the bearing etc.

Mechanical bearings may also exhibit signs of distress during their service lives in the form of excessive movement/ rotation, bearing failure at sub-structure or super-structure, dislodging of components such as sliding surfaces/ materials, failure of anchorage systems etc. In most of these situations, it is advisable to replace the complete bearing assembly with a new one.

Therefore, provisions must be made at the design stage itself to ensure easy replaceability of structural bearings at a future date. To replace existing bridge bearing, it is necessary to make alternative arrangements for load transfer from the superstructure to the sub-structure during the duration of replacement.

Normally, hydraulic jacks are used to lift the bridge superstructure for replacement of the affected bearing. If the bridge sub-structure has sufficient space in the vicinity of the bearing to be replaced, then the hydraulic jacks can be placed on the substructure itself, otherwise supporting frame is erected from ground or friction gripped to the bridge pier to support the jacking arrangement. Bearing replacement exercise involves careful consideration of bearing pressures, effective load transfer mechanisms, ensuring balanced-gradual lifting and stability of superstructure, and speed of replacement.

What is RIBA plan of work?

The RIBA Plan of Work is published by the Royal Institute of British Architects (RIBA). The latest version is also is endorsed by the Chartered Institute of Architectural Technologists, the Construction Industry Council, the Royal Incorporation of Architects in Scotland, the Royal Society of Architects in Wales and the Royal Society of Ulster Architects.

It was originally launched in 1963 as a fold out sheet that illustrated the roles of participants in design and construction in a simple matrix format. The first detailed plan of work was published in 1964 (ref. Introduction, RIBA Plan of Work 2007).

Split into a number of key project stages, the RIBA Plan of Work provides a shared framework for design and construction that offers both a process map and a management tool. Whilst it has never been clear that architects actually follow the detail of the plan in their day to day activities, the work stages have been used as a means of designating stage payments and identifying team members responsibilities when assessing insurance liabilities, and they commonly appear in contracts and appointment documents.

The Plan of Work has evolved through its history to reflect the increasing complexity of projects, to incorporate increasing and changing regulatory requirements and to reflect the demands of industry and government reports criticising the industry. It has moved from a simple matrix representing just the traditional procurement route, to include multiple procurement routes, more diverse roles, multi-disciplinary teams, government gateways and to add stages before and after design and construction. It is supported by other RIBA publications such as the RIBA Job Book.

The Plan of Work has been criticised for being too architect focused, for missing many of the client tasks undertaken at the beginning of a project, and for condensing construction into a single stage.

The latest version, published in 2013, has moved online and has undergone a radical overhaul. It is now more flexible, with stages such as planning permission and procurement being moveable, it reflects increasing requirements for sustainability and Building Information Modelling (BIM) and it allows simple, project-specific plans to be created. In addition, the work stages have been re-structured and re-named.:

0 – Strategic definition.
1 – Preparation and brief.
2 – Concept design.
3 – Developed design.
4 – Technical design.
5 – Construction.
6 – Handover and close out.
7 – In use.

There is also a BIM overlay and a sustainability overlay for the plan, but these do not seem to have been updated to reflect the 2013 work stage definitions.

The 2013 Plan of Work has come under some criticism as it is significantly less detailed than the previous 2007 edition, its flexibility and customisability is very limited and the definition and naming of work stages does not reflect the terminology that is used by the industry.

How can floor vibrations be assessed?

Improvements in vibration performance after construction are likely to be difficult to achieve and very costly. The assessment of vibrations should therefore be carried out as part of the serviceability checks on the floor during the design process.

The vibration performance of the floor can be assessed using manual methods, a new simplified web-based tool or finite element methods. Where a BIM model of the building is being created by the design team, the model should contain all the necessary information required to carry out the analysis.

Manual methods

Simplified assessment can be carried out by hand methods of analysis, although such calculations are generally conservative and in some cases to a great extent. Various methods are available, one of which is set out in SCI publication P354.

To avoid the possibility that walking activities could cause resonance or near-resonant excitation of the fundamental mode of vibration of the floor, neither the floor structure as a whole nor any single element within it should have a fundamental frequency of less than 3 Hz.

The assessment procedure involves the following steps:

• calculate the natural frequency of the floor system;

• determine the modal mass, i.e. the mass participating in the vibration;

• calculate the critical rms acceleration and the response factor;

• compare the response factor with the acceptance criteria for continuous vibration.

If the response factor is not acceptable, try a more comprehensive method of analysis such as the new simplified web-based tool or finite element modelling.

Simplified web-based tool

A new Floor Response Calculator is available on www.steelconstruction.info that allows designers to make an immediate assessment of the dynamic response of a floor solution. The results from this tool provide an improved prediction of the dynamic response compared to the ‘manual method’ in SCI P354. The tool may be used to examine complete floor plans or part floor plans, comparing alternative beam arrangements.

The tool reports the results of approximately 19,000 arrangements of floor grid, loading and bay size, which have been investigated using finite element analysis. The designer must select between a variable action of 2.5 kN/m2 and 5 kN/m2, being typical imposed loads on floors. 0.8 kN/m2 is added to allow for partitions.

The designer must also select the arrangement of secondary and primary beams, with typical spans, which depend on the arrangement of the beams. Secondary beams may be placed at mid-span or third points. The pre-set damping ratio of 3% is recommended for furnished floors in normal use.

When a decking profile is selected, an appropriate range of slab depths are then available to be selected. Generally, thicker slabs will produce a lower response factor. When selecting the slab depth, solutions which result in a response factor higher than 8 (the limit for a typical office) are highlighted.

The primary and secondary beams are selected automatically as the lightest sections which satisfy strength and deflection requirements; these cannot be changed by the user.

The selection of the lightest sections is made to produce the most conservative dynamic response, as stiffer beams will reduce the response. A visual plot of the response is also provided for both the steady state and transient response.

Hovering over the plot shows the response factor. Generally the higher response will be in an end bay, where there is no continuity. The fundamental frequency of the floor is presented on the output screen. If the actual design differs from the pre-set solutions in the tool, users should note the following:

• Using stiffer beams will reduce the response

• Using thicker slabs, and stiffer beams, will reduce the response

• The gauge of the decking has no significant impact on the response factor

• Voids that break the continuity of beam lines will lead to higher response factors

Finite element analysis

The most accurate and detailed assessments of floor vibrations are made using finite element (FE) analysis. Simple methods can be applied with reasonable accuracy for orthogonal grids but where a floor plate is not orthogonal (e.g. curved in plan), simple methods are inadequate.

In FE analysis the floor slab, beams, columns, core walls and perimeter cladding are modelled with finite elements with appropriate restraints applied to the elements in the model.

A model of the whole building is often already available for Building Information Modelling (BIM) and an individual floor can be extracted and modified to provide a model that is suitable for vibration analysis.A modal analysis is carried out first to determine the natural frequencies, mode shapes and modal masses.

Steady state and transient responses are then calculated for each mode of vibration and each harmonic of the forcing function (the walking activity). The modal responses are then added up for all the mode shapes and harmonics considered, and a predicted rms acceleration calculated for each point on the floor.

The final step is to divide the acceleration by the base value to determine the response factor. The results can be plotted in a contour plot.

Mitigation

If the floor response is found to be unacceptable during the design assessment, the designer has some freedom to make adjustments to the structural arrangement such that the vibration response is reduced to acceptable levels.

Possible measures include increasing the mass, stiffness and damping of the floor, and relocating or reducing the length of corridors