J.S. Daniel paper for high rise building construction cycle

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J.S. Daniel paper for high rise building construction cycle

  1. 1. CONTENT OF THE PRESENTATION: (ABOUT 80 SLIDES) 1- DEFINITIONS OF HIGH-RISE BUILDINGS (5 SLIDES) 2- EXAMPLES OF HIGH-RISE BUILDINGS (1 SLIDE) 3- EXAMPLES OF SKYSCRAPERS (2 SLIDES) 4- INTRODUCTION AND PURPOSE OF THE PRESENTATION (1 SLIDE) 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BLDGS 5.1- FORMWORK (21 SLIDES) 5.2- CONCRETE TECHNOLOGY (7 SLIDES) 5.3- STRUCTURAL SYSTEM (3 SLIDES) 5.4- CONSTRUCTABILITY (7 SLIDES) 5.5- RESOURCES (11 SLIDES) 5.6- ADVANCED TECHNIQUE (14 SLIDES) 6- CASE STUDIED (6 SLIDES) 7- SUMMARY & CONCLUSION (1 SLIDE)High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  2. 2. 1- DEFINITIONS OF HIGH-RISE BUILDINGS 1.1- Basic Definition of High Rise Buildings For the purposes of the Emporis Data Committee (Emporis is one of the worlds largest property resources and source of information about buildings around the world), a high-rise building is defined as a building of 35 meters or greater in height, which is divided at regular intervals into occupied levels. To be considered a high-rise building, an edifice must be based on solid ground, and fabricated along its full height through deliberate processes (as opposed to naturally-occurring formations).High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  3. 3. 1- DEFINITIONS OF HIGH-RISE BUILDINGS 1.2- General Definition of High Rise Buildings A high-rise building is distinguished from other tall man-made structures by the following guidelines: • It must be divided into multiple levels of at least 2 meters height; • If it has fewer than 12 such internal levels, then the highest undivided portion must not exceed 50% of the total height; Indistinct divisions of levels such as stairways shall not be considered floors for purposes of eligibility in this definition. Any method of structural support which is consistent with this definition is allowable, whether masonry, concrete, or metal frame. In the few cases where such a building is not structurally self-supporting (e.g. resting on a slope or braced against a cliff), it may still be considered a high-rise building but is not eligible for any height records unless the record stipulates inclusions of this type.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  4. 4. 1- DEFINITIONS OF HIGH-RISE BUILDINGS 1.3- Encyclopedic Definition of High Rise Buildings A high-rise is a tall building or structure. Normally, the function of the building is added, for example high-rise apartment building or high-rise offices. High-rise buildings became possible with the invention of the elevator (lift) and cheaper, more abundant building materials. Buildings between 23 m to 150 m high are considered high-rises. Buildings taller than 150 m are classified as skyscrapers. The average height of a level is around 4 m high, thus a 24 m tall building would comprise 6 floors. The materials used for the structural system of high-rise buildings are reinforced concrete and steel. Most American style skyscrapers have a steel frame, while residential tower blocks are usually constructed out of concrete.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  5. 5. 1- DEFINITIONS OF HIGH-RISE BUILDINGS 1.4- Definition as per various bodies Although the exact definition is immaterial, various bodies have tried to define what high-rise means: The International Conference on Fire Safety in High-Rise Buildings defined a high-rise as "any structure where the height can have a serious impact on evacuation“. The New Shorter Oxford English Dictionary defines a high-rise as "a building having many stories". Massachusetts General Laws define a high-rise as being higher than 70 feet (21 m). Most building engineers, inspectors, architects and similar professions define a high-rise as a building thats at least 75 feet (23 m).High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  6. 6. 1- DEFINITIONS OF HIGH-RISE BUILDINGS 1.5- Minimum Height of High Rise buildings and Tallest High Rise Buildings The cutoff between high-rise and low-rise buildings is 35 meters. This height was chosen based on an original 12-floor cutoff, used for the following reasons: • Twelve floors is normally the minimum height needed to achieve the physical presence which earns the name "high-rise"; • The twelve-floor limit represents a compromise between ambition and manageability for a worldwide database. Since height information on smaller buildings is usually not readily available, the twelve-floor limit is still used in most areas covered by the websites belonging to The Emporis Network. A building of fewer floors may only be included as a high-rise when its exact height is known. In most cases, a city is considered to have a satisfactory listing of high-rise buildings when all twelve-floor buildings are counted.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  7. 7. 2- EXAMPLES OF HIGH-RISE BUILDINGS IN LEBANON Marina Towers Grand Habtoor Hotel – Beirut Phenicia Hotel Towers - Beirut & Four Seasons Hotel - BeirutHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  8. 8. 3- EXAMPLES OF SKYSCRAPERS Location : Dubai Location : Dubai Location : Shanghai China Location : Kuala Lumpur Location : Dubai Height : 321 Meters Height : 705 Meters Height : 1228 Meters Height : 452 Meters Height : 1050 Meters Floors : 70 Floors : 160 Floors : 300 Floors : 88 Floors : 230 Built : 1999 To Be Completed : 2009 To Be Completed : 2020 Built : 1998 To Be Completed : 2010High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  9. 9. 3- EXAMPLES OF SKYSCRAPERS Tallest Towers Projects in Middle East Views from the 134th floor of Burj DubaiHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  10. 10. 4- INTRODUCTION AND PURPOSE OF THE PRESENTATION 4.1- Introduction of the Presentation Rapidly-paced building construction is dictated by financing concerns. Building owners and developers want to minimize the high interest rate construction loan time period and press toward building completion so that the revenue can be realized (time is money). In cast-in-place multi-storey concrete buildings a “typical floor” construction cycle of 5 to 7 days per floor is easily achievable and 2 and 3 days cycling is not uncommon in some areas. 4.2- Purpose of the Presentation The purpose of this presentation is to present state-of-the-art engineering information on rapid cycle concrete methodology depending among the others on formwork, design load, concrete compressive strength, modulus of elasticity, concrete curing time, construction data, structural system, number of shifts, HSE regulations, construction team performance/productivity & learning curve and advanced planning techniques.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  11. 11. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 - FORMWORKHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  12. 12. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.1 - Introduction: • The fast-paced construction cycle is achieved through teamwork among the trades involved with the building superstructure. This team carries out a predetermined sequence of synchronized activities. Before this team can function, however, mutual agreement and understanding must be reached between the Formwork Contractor and the Designer. The Designer must come to an understanding of how the Formwork Contractor would like to use the newly completed segments of the structure to support formwork for the next floors in the cycle. At the same time, the Formwork Contractor must come to an understanding of what limitations the Designer has on the use of these newly completed segments of the structure as supports for the formwork of the floors to be cast.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  13. 13. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.1 - Introduction: • The process of finding the optimum formwork concept for a structure starts in the tender phase. Often it is here that the real decisions on the cost-effectiveness of a construction project are made. Intelligent formwork-planning software was made as a measure tool for automatic formwork planning. These programs also support the design of special formwork by AutoCAD® and extensive structural analyses and the preparation of bills of materials for working out offers. • Some of the High-Rise Buildings’ Projects call for highly specialized formwork solutions and unique know-how. The Expertise for Automatic Climbing and Project Management ensure reliability end to end, particularly in projects that demand the highest level of scheduling, commercial and engineering expertise. • Time-to-completion can be enhanced by choosing suitable formwork system which move up the tower at all times and never have to be brought back to the ground.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  14. 14. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.2 - Formwork Systems: The most efficient construction coordination plan for a tall building is one that allows formwork to be reused multiple times. Formwork systems used for rapid cycle construction can be grouped into four general categories: Conventional and Gang Systems: these systems may be hand set or panelized. Hand-set systems usually consist of wood shores or shoring supporting plywood-decked shores or shoring supporting plywood decked wood or Aluminum framing. Segments of deck forms can also be made into ganged panels supported by pre-attached shoring frames. Flying Truss Systems: these systems use steel or Aluminum trusses to support plywood- decked wood or Aluminum framing. Adjustable vertical members support the trusses off a previously cast deck. The truss-mounted forms are moved between casting positions by crane.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  15. 15. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.2 - Formwork Systems: Column-Mounted Shoring Systems: these systems are large deck panels with framing members that span between in-place columns or bearing walls with no intermediate vertical shoring. Brackets or screw jacks, anchored to the in-place columns or walls, support the panel perimeter framing which is quite often structural steel beams. The panels are moved between casting positions by crane. Tunnel Form Systems: these systems are factory-made U-shaped steel forms which permit casting of a slab and the adjacent supporting walls at the same time. When sufficient concrete strength is developed, the forms are collapsed or telescoped and moved to the next placement location.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  16. 16. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.3 – Technical Formwork Definition: For the purpose of this presentation, the following definitions apply: o Shores: vertical or inclined support members designed to carry the weight of formwork, concrete and construction loads above. o Re-shores: shores placed snugly under a stripped concrete slab or structural member after the original forms and shores have been removed from a large area, thus requiring the new slab or structural member to deflect and support its own weight and existing construction loads applied prior to the installation of the re-shores. It is assumed that the re-shores carry no load at the time of installation. Afterward, additional construction loads will be distributed among all members connected by re-shores. o Backshores: shores placed snugly under a stripped concrete slab or structural member after the original formwork and shores have been removed from a small area without allowing the slab to deflect or support its own weight or existing construction loads from above.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  17. 17. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.4 – Casting Cycle: The formwork systems most often employed in rapid cycle work are conventional and ganged systems or flying truss systems. Both of these two systems transmit the weight of newly placed concrete to the most recently cast floors below. For sake of comparison, consider a common shore/re-shore cycle used in multistory construction. The interconnected assembly consists of several slabs, one or two levels of shores and a number of sets of re-shores. One commonly employed construction sequence involves four phases in each casting cycle (see figure 1).High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  18. 18. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.4 – Casting Cycle: The first phase is casting of new floor. In the second phase, the lowest storey of re-shores are removed. In the third phase, the lowest story of shores are removed. The fourth phase involves installation of re-shores in the storey vacated in phase three. The combination of shores and re- shores provided must be such that the applied construction loads (generated by the casting of a new slab) do not exceed the capacity of the interconnected slabs or induce excessive deflections. :High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  19. 19. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.5 – Two to Three Days Casting Cycle: If a two or three day cycle is desired, a system of pre-shores, primary forms and shores is used. The system allows fast cycling of some of the forms while maintaining adequate support of the newly cast slabs. A critical consideration in a two or three day cycle operation involves stripping of the forms for the most recently cast slab. This slab, being about 28 hours old, is already supporting the next floor’s form load. It is imperative that all the shores under this slab not to be slackened in one operation. Pre-shores are placed so that, during the stripping process, the 28 hour old slab will never have an unsupported span of more than 2.4m. In this method forms above the pre-shores remain temporarily pinned. Two or three day cycle systems that use dimension lumber framing usually require two or sometimes 21/4 sets of forms and about 8 to 10 levels of re-shoring.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  20. 20. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.5 – Two to Three Days Casting Cycle: Two or three day cycles can also be achieved in flying truss systems. In some cases the truss supported panels are limited to a 2.4m (8 feet) width and are set two foot clear side by side. The 0.6m (2 foot) clearance allows room for lines of permanent shores. Panels are alternately lowered ad decks re-shored, thereby not exceeding the 2.4m (8 feet) clear span limit (see figures 2 & 3).High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  21. 21. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.5 – Two to Three Days Casting Cycle: If a two or three day cycle is desired a system of pre-shores, primary forms and shores is use. Principles of engineering mechanics are applied to assess the effects of the forming operations on the strength and serviceability of the in-place construction. The key element of a re-shoring analysis is the apportioning of the construction loads throughout the system of slabs interconnected by shores and re-shores. How these loads will be distributed is for the most part dictated by the particular shore replacement method to be employed. Assessment of the in- place concrete strength development is critical.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  22. 22. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.6 – Formwork Brand Names & Characteristics: ALUMA System is providing the high performance, time saving Aluminize Flying Tables, which will reduce the project’s floor-cycles from 10 to three days. This improved performance directly impacts on costs by reducing crane time, equipment and labor. Aluminize Tables consist of large 60 m2 tables used in a rolling movement application, weighing only 1,920 kg each. MIVAN System is another Aluminum system formwork which provides rapid, high quality and cost effective formwork solutions that most prestigious high-rise projects has been key to its continued success in the market. Designed and manufactured from lightweight Aluminum panels, the system can be used over 250 times, offering excellent cost efficiency and can be erected by unskilled labor. The high strength-to-weight ratio of MIVAN System’s components also avoids the need for usage of crane in the operation of the equipment on site, as each and every component can be erected, dismantled and moved by hand, thus providing the main contractor with further time and cost savings. The modular nature of the system’s components and the simplicity in erection and dismantling of the equipment enhances labor productivity and reduces operator training periods. It is widely recognized as one of the world’s fastest and most versatile formwork systems, with a typical floor-to-floor construction cycle of just four days.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  23. 23. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.6 – Formwork Brand Names & Characteristics: DOKA System is both fast and can achieve the necessary high quality finish for any project and safety of the system for project’s operatives, particularly for the external formwork, which is also a key factor. DOKA supports the selection, planning and application of its formwork systems with a range of services that prevent cost overruns for formwork utilized on site and thus effectively ease the work of site managers and foremen. PERI System is one of the world’s largest manufacturers and suppliers of formwork, shoring and scaffolding systems. PERI also offers its customers engineering, planning, formwork software, rental service and logistics support.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  24. 24. Description ALUFORMWORK DOKA PERI Frame 100% Aluminum YES YES YES Form facing 100% Aluminum YES NO NO Panel weight/m² 20kg 33kg 33kg Number of frame re-uses 1000 300 300 Number of form-facing re-uses 1000 60-70 60-70 Thickness frame 5cm + 10cm + 10cm Wall Key Liberation YES NO NO Floor Key Liberation YES NO NO 3 in 1 modularity Panel YES NO NO Easy face forming replace YES YES YES Easy to understand for Traditional Workmen NO YES YES Flexible system, easy to assemble and requires very little working skill NO YES YES Components are versatile and suitable for all major applications NO YES YES Gives high labor and material productivity YES YES YES Minimum Quantity of items YES (0 waste) NO NO Good quality of finish is achieved YES (better) YES YES Accuracy YES (better) YES YES Safe & Speedy Construction YES (better) YES YES Cost (1 – High , 2- Medium, 3 – Low) 1 3 2High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  25. 25. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.6 – Formwork Brand Names & Characteristics: DOKA System is both fast and can achieve the necessary high quality finish for any project and safety of the system for project’s operatives, particularly for the external formwork, which is also a key factor. DOKA supports the selection, planning and application of its formwork systems with a range of services that prevent cost overruns for formwork utilized on site and thus effectively ease the work of site managers and foremen. PERI System is one of the world’s largest manufacturers and suppliers of formwork, shoring and scaffolding systems. PERI also offers its customers engineering, planning, formwork software, rental service and logistics support.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  26. 26. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.7 – Cases Studied: 1st Case: A High-Rise Building Project in Dubai was on schedule using DOKA formwork systems in a seven day floor construction cycle. The ground and mezzanine levels will be utilized as offices and retail outlets with a gymnasium, swimming pool and multi-purpose hall destined for the third floor. By the fourth floor, the dimensions for the main tower are almost 37 m x 37 m to give a typical floor area of 1,370 m2 up to the 12th floor. Here with the inclusion of a balcony on each face, the area increases to almost 1,500 m2. At the 26th-floor a larger cantilevered balcony is introduced up to the 36th floor for what are described as some of the largest floor area penthouses in a project of this type in Dubai. Regardless of the balconies however, floors on all levels remain ‘typical’ allowing the contractors to meet the critical 7-day cycle using DOKA 150F climbing formwork system for the external walls by the 12th-floor. At the same time as construction of the tower was underway and working two floors above, the Contractor constructed the project’s central 13.5 m x 13.5 m core shaft to house five lifts and two staircases; once again using the DOKA 150F climbing system.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  27. 27. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.7 – Cases Studied: 1st Case: Throughout slab construction of the 36th storey tower, the Contractor was using two sets of DOKAFLEX tables, each covering 1,400 m2 approximately. As ready-assembled units, the DOKAFLEX tables reduce the number of separate items needed for each floor formwork. Pre-assembled table forms are easily shifted in one piece to the next position to be cast without being dismantled. With fewer separate parts, formwork erection and striking are greatly accelerated; ensuring shortest possible forming times for the contractor.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  28. 28. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.7 – Cases Studied: 2nd Case: Marina Towers - Beirut: The Luxury High-Rise Building comprises of a mix of post-tensioned and conventional cover slabs starting from the first floor up to the 25th floor. The area of each floor is approximately 1,050 m2 and comprises of a core shaft to house lifts, staircases and E/M shafts. The concrete construction for each typical floor was as follows: Vertical elements: Shuttering, reinforcement and pouring vertical elements: 3 days Post-Tension cover slab: ● Shuttering, reinforcement, E&M embedment, Post-Tensioning tendons and pouring PT cover slab: 5 days ● Stressing, post-tensioning cables of cover slab (3 days after pouring of PT slab): 1 day Conventional cover slab: Shuttering, reinforcement, E&M embedment of the conventional over slab and pouring: 6 daysHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  29. 29. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK Therefore, using the DOKA formwork, the construction cycle between one typical floor and the other was 9 days. The striking shutter of cover slab and de-shuttering props of the PT slab was done after stressing PT cables of the PT slab of the floor in subject and the upper floor (1 day work). Also, the striking shutter of the conventional cover slab and de-shuttering of props was done after pouring of the conventional slab of the floor in subject and the upper floor (1 day work). At the same time as construction of the tower was underway and working two floors above, the Contractor constructed the project’s central core’s walls using the DOKA 150F climbing system with a 4.8m height of jump. Therefore, the construction of the concrete core from the 1st service floor (above ground floor) up to top of roof started on 02-Feb-04 and finished on 15-Jan-05 (about 1 year) when the slab of the 1st service floor started on 18-Feb-04 and finished with the pouring of the last slab of top of roof on 28-Feb-05 (also 1 year).High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  30. 30. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.7 – Cases Studied: 3rd Case: The Four Seasons Hotel - Beirut: The Hotel building has a total built-up area of 49,000 m2 allocated to below ground basement on 5 levels and a 110 meters High-Rise Tower (25 floors) above ground and it is finished with flat roof containing swimming pool and various amenities for hotel guests. This luxurious high-rise building was not designed with a central core including lifts, staircases and E/M shafts and the concrete slabs are conventional ones. The Contractor decided to divide each typical floor of 600 m2 of area (starting from the 4th floor) into 2 zones. The concrete construction for each zone of each typical floor was as follows: Vertical elements: Shuttering, reinforcement and pouring vertical elements: 3 days Conventional cover slab: Shuttering, reinforcement, E&M embedment of the conventional over slab and pouring: 5 daysHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  31. 31. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.1 FORMWORK 5.1.7 – Cases Studied: 3rd Case: Therefore, using the DOKA formwork, the construction cycle between one typical floor and the other was 8 daysHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  32. 32. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.2 CONCRETE TECHNOLOGYHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  33. 33. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.2 CONCRETE TECHNOLOGY 5.2.1 – INTRODUCTION Along with advances in the ways that concrete is brought to the site, the types of formwork in which it is cured, and how it is placed at high elevations, its mechanical and chemical properties have made great advances. Building industry professionals are interested in increasing productivity by decreasing the amount of time for concrete to reach its strength and the amount of material required to carry the loads of a structure as well as have improved stability and toughness. It is well known that time, money and labor costs together are a matter of great concern in the building industry. This performance speeds the time for project completion and may reduce cost with the reduction of waiting time and more reuse periods for formwork. Higher strengths that can be achieved by High Performance Concrete (HPC) also add a few other beneficial effects to the structure. These features of HPC make it appropriate for applications to high-rise buildings.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  34. 34. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.2 CONCRETE TECHNOLOGY 5.2.1 – CHARACTERISTICS OF HPC HPC is a mixture which properties include increased strength and better performances in the areas of durability, ductility, permeability, density, mixture stability and chemical resistance, to name only a few. These will change depending on the type of admixture combined with cement, aggregates and water for the final product. High-strength concrete is typically recognized as concrete with a 28-day compressive strength greater than 42 MPa. More generally, concrete with a uniaxial compressive strength and flexural strength greater than that of moderate strength concrete. Strengths of up to 140 MPa have been used in different site applications; where the most recognizable building with high strength concrete is the Twins Petronas Towers Kuala Lumpur, Malaysia; which has concrete with strengths around 138 MPa. Concrete strength enhancement can be achieved through use of admixtures to produce a low water/cement ratio giving high performance concrete. These admixtures promote a high slump, extremely flowable concrete that achieves high strengths while providing superior workability & pump ability. They are also used for concrete requiring high-early stripping strengths.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  35. 35. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.2 CONCRETE TECHNOLOGY 5.2.1 – CHARACTERISTICS OF HPC Once the high strength concrete is placed, the hardened concrete properties can be predicted in addition to other special characteristics. Some of the properties slightly differ from concrete with lower strength while some vary more significantly. In order to examine the performance of high strength concrete in practice, several case studies can be investigated. However, during the last decades high strength concrete has become more popular and researchers continue to develop high strength concrete with better durability to harmful agents. "In general the primary characteristics of high performance concrete can be summarized as workability, high early-age strength, toughness, superior long-term mechanical properties, and prolonged life in severe environment."High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  36. 36. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.2 CONCRETE TECHNOLOGY 5.2.2 – ADVANTAGES & DISADVANTAGES OF HPC High strength concrete resists loads that cannot be resisted by normal strength concrete. Not only does high strength concrete allow for more applications, it also increases the strength per unit cost, per unit weight, and per unit volume as well. These concrete mixes typically have an increased modulus of elasticity, which increases stability and reduces deflections producing concretes with higher compressive and flexural strengths.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  37. 37. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.2 CONCRETE TECHNOLOGY 5.2.2 – ADVANTAGES & DISADVANTAGES OF HPC Along with the inherent advantages of high strength concrete, several less clearly defined disadvantages can materialize: First, increased quality control is needed in order to maintain the special properties desired. High strength concrete must meet high-performance standards consistently in order for it to be effective. Inspection in the field should be of high standards because if the contractor should decide to change the mix design to improve workability, adding water for instance, the change will diminish the properties of the concrete. High quality materials must be used. These materials may cost more than materials of lower quality; but "the economic benefits that can accrue from the use of high strength concrete need not be overemphasized. Consolidation is very important, high strength concrete needs to be compacted well. Therefore high frequency vibrators are required. Under-vibration is of major concern because these types of concretes usually are relatively stiff and contain little air.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  38. 38. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.2 CONCRETE TECHNOLOGY 5.2.2 – CONCLUSION The ACI committee concluded that the use of high strength concrete outweighs the additional expense. Higher economy can be obtained with high strength concrete rather than high strength steel. High strength concrete may require special curing and placement requirements. Delays in delivery and placing must be eliminated and sometimes it may be necessary to reduce batch sizes if placing procedures are slower than anticipated.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  39. 39. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.3 - STRUCTURAL SYSTEMHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  40. 40. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.3 STRUCTURAL SYSTEM 5.3.1 – INTRODUCTION The issues involved with structural design and technology are ones of both natural and human implications. A structure must be designed to carry gravity, wind, equipment and snow; resist high or low temperatures and vibrations; protect against explosions; and absorb noises. Adding to this the human factor means considering rentable spaces, owner needs, aesthetics, cost, safety and comfort. Although one set is not mutually exclusive of the other, careful planning and consideration are essential in an attempt to satisfy and integrate both. Considering structure alone, there are two main categories for high-rise buildings-structures that resist gravity and lateral loads and those that carry primarily gravity loads. Since skyscrapers have the largest needs for resisting high magnitudes of wind, the lateral load resisting system becomes the most important.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  41. 41. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.3 STRUCTURAL SYSTEM 5.3.2 – CONCRETE STRUCTURAL SYSTEMS The concrete systems that are suitable for different ranges of number of stories are shown in below figure. Shear walls, may be described as vertical, cantilevered beams, which resist lateral wind and seismic loads acting on a building transmitted to them by the floor diaphragms. Reinforced concretes ability to dampen vibration and provide mass to a building makes it a good choice of materials. These elements are a variety of shapes such as, circular, curvilinear, oval, box-like, triangular or rectilinear. Many times, a shear wall exists as a core-wall holding internal services like elevators, janitors closets, stairwells and storage areas.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  42. 42. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.4 - CONSTRUCTABILITYHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  43. 43. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.4 CONSTRUCTABILITY 5.4.1 – DEFINITION Degree to which the integration of experience and knowledge in a construction process facilitates achievement of an optimum balance between project goals and resource constraints.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  44. 44. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.4 CONSTRUCTABILITY 5.4.2 – INTRODUCTION The timely execution of a construction project is very important to the owner, who makes plans and commitments on the basis of the projects anticipated completion date. Failure of design professionals to consider how a builder will implement the design can result in scheduling problems, delays, and disputes during the construction process. Constructability of design is a subjective scale that depends basically on a number of interdependent project-related factors. Many design firms have a formal (explicit) constructability program that is launched as early as the conceptual planning stage of the project. This research examines design professionals efforts to pursue constructability and provides recommendations for performing constructability reviews in an efficient and effective manner.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  45. 45. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.4 CONSTRUCTABILITY 5.4.2 – INTRODUCTION Construction technologies vary from region to region all over the world and high-rise building designers have to adapt their scheme to local constructability methods. Design criteria governing tall buildings are detailed by the relevant Codes applicable within a specific locality. The design engineers challenge is to create a structural system complying with the mandatory guidelines and other functional and construction requirements of the building. With buildings becoming leaner and taller, design for lateral loads on tall buildings is usually a greater challenge. Lateral loads include wind and earthquake loads.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  46. 46. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.4 CONSTRUCTABILITY 5.4.3 – CONSTRUCTABILITY IN HIGH-RISE BUILDINGS Constructability is described as the extent to which a design of a high-rise building provides for ease of construction yet meets the overall requirements of the Project. It is an “attitude” that must prevail through: Conceptual Planning Design and Procurement Field Operations Constructability leads to some important benefits:High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  47. 47. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.4 CONSTRUCTABILITY 5.4.4 – BENEFITS OF CONSTRUCTABILITY IN HIGH-RISE BUILDINGS If ease of construction is built into the design, the following directly support project management objectives: Construction planning is made easier Both design and construction costs can be reduced Likewise the construction schedule may be shortened Better quality can be required and expected More realistic commitments can be made to subsequent trades, and to Earlier owner occupation Indirect benefits of design-construction are more difficult to quantify, but nevertheless include team collaboration, parties working for mutual benefit, transfer of expertise from other projects, shorter learning curve, etc.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  48. 48. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.4 CONSTRUCTABILITY 5.4.5 – EXAMPLE OF CONSTRUCTABILITY FACTORS IN HIGH-RISE BUILDINGS o High-rise buildings can be constructed very quickly using post-tensioned concrete systems. o Rapid floor construction cycles are achieved through the use of high early-strength concrete. o The use of standard design details of the post-tensioned elements, minimum congestion of pre-stressed and non-pre-stressed reinforcement, and earlier stripping of formwork can significantly reduce the floor construction time.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  49. 49. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5 RESOURCESHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  50. 50. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.1 – INTRODUCTION One of the most important factors that contributed to the overall success a Project is the familiarization and training of a skilled labor force with a unique forming system. This involves other issues such as productivity, learning curve and management of resources. Minimizing crane time or any other equipment is also a key to construction scheduling.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  51. 51. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.2 – OBJECTIVES AND APPROACHES The objectives in scheduling the floor cycle are to ensure smooth flows of resources and to optimize the use of formwork and other materials. The floor area is usually divided into zones to allow the labor force and formwork materials moving between zones. The preparation of the floor construction cycle would therefore be a resources allocation exercise. However, the process is complex and difficult when it is done manually. Floats are created deliberately in the schedule to ensure the balance in resources and to provide buffers. It is noted that variations in working periods have significant impacts on the time schedule. A planning study proves that a saving of approximately 35% in time could be achieved when the working period is extended by 20%.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  52. 52. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.2 – OBJECTIVES AND APPROACHES In scheduling the floor construction cycle, a simple approach is to adopt a constant duration for the construction of the typical floors. However, this always induces a false impression to site personnel that the construction processes are simple and could be achieved easily. For the construction of high-rise buildings, site planning including activity scheduling and site production layout has to be reviewed and re-plan from time to time in practice as site conditions and resources are dynamic and uncertain. Another major challenge in delivering projects on time is :High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  53. 53. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.3 – AVAILABILITY OF RESOURCES Availability of the required resources which must be provided when needed, in the required quality, quantity and combination. The unprecedented number of projects in the UAE and the region makes the availability of such resources a challenge for successful project delivery. Those involved must carefully plan their resource requirements before implementing a project.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  54. 54. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.3 – AVAILABILITY OF RESOURCES The project schedule plan is an essential tool. Each activity must be analyzed to determine the type of resources required for executing the same. This could be in terms of man-hours for labor resources, equipment hours for equipment and machinery, quantities of materials to be ordered and installed, and others. Extreme care should be given in allocating resources in terms of crews. Assigning resources individually might prove to be of no use in many cases (i.e. crane without operator or steel fixer without reinforcing material). It provides the project team with the ability to visualize the resource requirements during the project life and determine if the availability limits are in line with requirements. If the resource plan depicts that the required project resources are within the set availability limits, the project team must analyze what alternative resources can replace these. If this continues to be an issue, additional resources need to be brought in either by direct hire or outsourcing them to a third party. Should the completion date of the project be adhered to, the resource leveling technique will optimize the use of float time but without exceeding the project completion date.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  55. 55. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.4 – TYPICAL REQUIREMENTS OF RESOURCES This is a comparison in required number of resources in term of site team for same structural system, area and quantity of concrete work but different construction casting cycle and number of working shift.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  56. 56. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.4 – TYPICAL REQUIREMENTS OF RESOURCES The required resources to achieve a cycle of 7 to 8 days for a floor area of 600 m2 in a two shifts’ works are as follows: Formwork Team: 1 foreman, 2 charge hands (or assistant foreman), 4 carpenters, 4 assistant carpenters and 9 labors Field Rebar Team: 1 foreman, 2 charge hands (or assistant foreman), 4 rebar placers, 4 assistant rebar placers and 9 labors. Workshop Rebar Team: 1 foreman, 2 rebar cutters/benders and 4 labors. HVAC/Plumbing Team: 2 HVAC/Plumbers, 2 assistants and 2 labors(1 day work before inspection and placement of concrete) Electrical Team: 2 Electricians, 2 assistants and 2 labors (1 day work before inspection and placement of concrete) Concrete placer/finisher: 1 foreman for casting, 1 charge hand, 2 placers, 4 finishers and 4 labors (1 day work for placement and finishing of concrete)High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  57. 57. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.4 – TYPICAL REQUIREMENTS OF RESOURCES The required resources to achieve a cycle of 4 days for a floor area of 600 m2 in a two shifts’ works are as follows: Day 1 - place the floor forms: Formwork Team: 1 foreman, 2 charge hands (or assistant foreman), 6 carpenters, 6 assistant carpenters and 10 labors Day 2 - place the slab reinforcing steel: Field Rebar Team: 1 foreman, 2 charge hands (or assistant foreman), 6 rebar placers, 6 assistant rebar placers and 10 labors. Day 3 – place E/M reservations and pour the slab: HVAC/Plumbing Team: 3 HVAC/Plumbers, 3 assistants and 3 labors (half day work before inspection and placement of concrete). Workshop Rebar Team: 1 foreman, 2 rebar cutters/benders and 6 labors. Electrical Team: 3 Electricians, 3 assistants and 3 labors (half day work before inspection and placement of concrete). Concrete placer/finisher: 1 foreman for casting, 1 charge hand, 3 placers, 6 finishers and 6 labors (1 day and night work for placement and finishing of concrete)High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  58. 58. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.4 – TYPICAL REQUIREMENTS OF RESOURCES Day 4 - erect the column reinforcing steel and pour the columns to the next floor: Formwork Team: 1 foreman, 1 charge hand (or assistant foreman), 3 carpenters, 3 assistant carpenters and 6 labors. Field Rebar Team: 1 foreman, 1 charge hand (or assistant foreman), 3 rebar placers, 3 assistant rebar placers and 6 labors. Workshop Rebar Team: 1 foreman, 2 rebar cutters/benders and 2 labors. Concrete placer/finisher: 1 foreman for casting, 1 charge hand, 2 placers, 2 finishers and 4 labors (1 day and night work for placement and finishing of concrete)High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  59. 59. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.5- RESOURCES 5.5.4 – TYPICAL REQUIREMENTS OF RESOURCES In order to achieve a 3 days cycle for a floor area of 600 m2, we need to have a three shift work with the previous case’s day 1 and day 2 combined into 1 day that means the cycle will be as follows: Day 1: Place the floor forms and place the slab reinforcing steel in 3 shifts Day 2: Place the E/M reservations/embedded items, inspect and pour the slab in 2 shifts. Day 3: Erect the column reinforcing steel and pour the columns to the next floor in 2 shifts (allow 2 shifts that means 24 hours for concrete curing time of the slab before proceeding with columns of the next floor).High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  60. 60. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUESHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  61. 61. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.1 – INTRODUCTION The advanced techniques for Planning of High-Rise buildings which are besides using Planning software like Primavera or Microsoft Project, are the model techniques. However the building up of simulation models requires Planners to have a good knowledge of simulation. A network based simulation has been used in this study. This simplifies the skills and knowledge required for modeling a simulation network as general reproduction program can be difficult for general users. Planners who have the knowledge in constructing critical path network and bar charts could be able to use the model.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  62. 62. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.2 – APPROACH The constructing of simulation network for modeling is similar to the critical path network using the “Activity on Node” format except that loops are allowed to show the re-cycling of the resources. During the simulation process, the activities may either in an active if the constraints are met or otherwise in an idle mode. Although only one floor cycle is shown in the network, it covers the activities in the four zones, which are handled within the simulation procedure. The ten activities are scheduled in a sequential order. Two loops are put out from the main network indicating the dependence relationship between installation of pre-cast façade, the activities for wall construction and crane-related activities. Normally a tower crane can only be installed for a building block owing to both economic reasons and space availability. Therefore, the crane can only serve one activity at one time and it is important to optimize the usage of a tower crane which is one of the critical resources in high-rise building construction.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  63. 63. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.2 – APPROACH A “Start” and “Stop” node is assigned in the network for controlling the numbers of simulation. During the simulation process, activity boxes are attached with a colored spinning icons showing their status. Resources shared by activities can be represented by graphics moving between the activities boxes.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  64. 64. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.3 – METHODOLOGY In order to optimize the duration of a floor cycle or to determine the daily schedule, modelers can modify the duration of the activities to suit the site conditions. It has to point out that the duration of the activities can be shortened or extended by increasing or decreasing the input resources, mainly the human resources in concrete frame construction generally. Table 1 shows the duration for the activities of a typical floor construction cycle.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  65. 65. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.3 – METHODOLOGYHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  66. 66. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.3 – METHODOLOGY In order to generate realistic results, the duration assigned for the simulation has taken into account the effects on hoisting times due to variations in hoisting height. For example, the hoisting and fixing of eight pre-cast facades takes about 50 minutes at the lower floors and 75 minutes at the upper. Planners can adjust the duration if they identify significant differences between the original input and the actual site conditions. Alternatively, Planners can carry out simple work study techniques on site to collect data for predicting the hoisting time. Apart from modifying the duration to suit the dynamic site conditions, Planning Engineers can review the effects of working hours for a working day to a floor cycle.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  67. 67. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.3 – METHODOLOGY Examining any standard floor cycle, it is evident that there are idling times in the schedule. The idling times are created for leveling the resources. However, manual resources leveling is complex and difficult and optimum solution cannot be easily found. The numbers of working hours for a working day can be input as a constraint in the model. In Lebanon, most of the residential areas in Beirut are densely populated and the government has imposed stringent noise control ordinance to restrict the working hours for using noisy construction plant and equipment. The normal working period to which there is no restriction is between 7:00 a.m. to 7:00 p.m. On the other hand, the normal working hours for the building industry in Lebanon lie between 7:00 a.m. and 4:00 p.m. (or between 8:00 a.m. and 5:00 p.m.) and in UAE the normal working hours lie between 8:00 a.m. to 6:00 p.m. Any time beyond the normal working hours, the trade workers need to be paid with an overtime allowance or extra money. It is vital to minimize the labor costs while meeting the program of the Project.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  68. 68. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.4 – PLANNING AND “WHAT IF” ANALYSIS Planning, being an iterative process, will require different scenarios for different purposes, such as "what-ifs?", and this would be characteristic of CPM also. In this study of Jumeirah Lake Tower, the JGC company has studied four working period scenarios which have been reviewed by using the simulation model. The summary of the simulation results is shown in Table 2.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  69. 69. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.4 – PLANNING AND “WHAT IF” ANALYSIS In the four scenarios, the first working period follows the industry normal working hour and constant activity duration was used. The remaining scenarios have been tested with probabilistic or random activity duration. The simulation results confirm that the first scenario is working approximately on a 6-day cycle. However, it is noted that there are significant saving in time when the durations of activities are varied. In the second scenario, there is a saving of 25.8% even the activities are scheduled within the normal working period. However when the working period is extended by one hour in the third scenario, further decrease in time is minimal. In the last scenario, the working period is extended by two hours, a further saving of 11.4% (a total saving of 37.2%) is produced. It means that the increase of the working hours by 20% is not effective since the labor costs will be increased by 40%. This is a typical time-cost trade off problem when time is approaching to the crash time solution.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  70. 70. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.5 – FLOOR CYCLE SCHEDULEHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  71. 71. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.6 – SIMULATION NETWORK The typical construction floor cycle shown above in Figure 1 can be easily developed into a simulation network in Figure 2.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  72. 72. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.6 – CONCLUSION The above study provides alternatives for Planners to make decisions on initial scheduling and subsequent updating and enables Planners to locate the upper limit of the floor cycle i.e. approaching to the crash time solution. However, it is a general rule in planning that the normal time should be used in the planning stage unless the project duration would have already been overrun. An aggressive Project Manager may consider applying the second scenario in order to shorten the frame construction of 62 days (i.e. 40 x [6.0 – 4.45]) without spending overtime payments. If the project has occurred delays, a more drastic decision will be to extend the working period by two hours as if in the fourth scenario. Therefore, when deciding the appropriate floor cycle duration, Planners have to review the factors and the merits prior to determine the strategies.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  73. 73. 5- FACTORS INVOLVED IN CONSTRUCTION CYCLE OF HIGH-RISE BUILDINGS 5.6- ADVANCED TECHNIQUE 5.6.7 – APPLIED EXAMPLE In the construction of a 42 storey building for Jumeirah Lake Towers, each floor (of 1,200 m2 of area each) is divided into four zones. One set of steel wall form covering the quantity of one zone and two sets of slab timber forms with each set covering the whole area of one floor are used. In order to speed up the construction, precast facades and semi-precast slabs are employed. The construction cycle aims at ensuring smooth and balanced resource allocations between trade workers, concreting work and formwork installation. As a result the resources rotate horizontally between zones at the same floor level and move upward to the upper floor in the next cycle. Figure 1 shows the schedule of a typical 6-day floor construction cycle including ten critical activities. The schedule is prepared assuming that the activities are carried out at constant duration. However, the duration of activities varies due to factors such as supply of materials, skill of workers, learning curves, weather and efficiency of plant and equipment. On the other hand, material hoisting plays an important role in high-rise building construction. As the building “grows”, the transportation time increases and thus extends the duration for the crane-related activities.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  74. 74. 6- CASE STUDIED 6.1 – INTRODUCTION The Project consists of two 24-storey towers attached at the base with a central lobby, one six- storey building that is joined to one of the towers, and a three level post-tensioned parking garage. The buildings house 435 one- and two-bedroom apartments, penthouse apartments, and a full-service health club with an Olympic-size lap pool. One of the most important factors that contributed to the overall success of this project was the collaboration between the general contractor, subcontractors, and design team that resulted in cost-effective and timesaving solutions, as outlined below. Another critical element was familiarization and training of a skilled labor force with a unique forming system.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  75. 75. 6- CASE STUDIED 6.2 – STRUCTURAL SYSTEM The overall plan dimensions of a typical tower floor are 30.8 m by 30.8 m, with spans varying between 4.0 and 7.3 m. A conventionally reinforced 200-mm thick concrete slab was chosen for the floor system. 610 mm square columns are used for the full height of the tower, with varying amounts of reinforcing steel. The lateral force resisting system consists of 355 mm thick shear walls in a 12.2 by 12.2 m core area, and 305-mm thick outrigger walls that extend from the core walls to the exterior of the building. The outrigger walls, used to reduce the drift of the building, are located between the 2nd to 4th, 13th to 15th, and 21st to 23rd floors. Normal weight concrete with a specified compressive strength of 25 MPa is utilized for the framing members, except for the columns and shear walls in the lower 8 floors which are 35 MPa. The foundation consists of 355 mm by 355 mm pre-cast concrete piles with a 120 ton capacity.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  76. 76. 6- CASE STUDIED 6.3 – DESIGN LOADS The buildings are designed in accordance with the Local Building Code. It is important to note that seismic forces governed the lateral design, with the seismic base shear equal to 3.5% of the weight of the building. In addition to specifying concrete compressive strength, modulus of elasticity has been specified for the concrete in several high-rise buildings. A higher modulus of elasticity provides a stiffer structure which has less lateral deflection under wind loads.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  77. 77. 6- CASE STUDIED 6.4 – CONSTRUCTION DATA Four to five days was a typical cycle for each floor. The shear walls were constructed first, three floors ahead of the slabs and columns. The walls were formed with the PERI Formworks system. SKYDECK, the high-strength lightweight Aluminum slab formwork which was also supplied by PERI, was used for the slabs. The SKYDECK allowed for removal of the form panels and beams without removal of the shores, thereby eliminating the need to re-shore. Strength accelerators were used in the concrete mix for the floor slabs in order to achieve 10 MPa within 24 hours. This strength was needed in order to allow safe stripping of the forms. To achieve a four to five day cycle, seven levels of shoring would normally be required. The structural engineer for the project, performed a finite element analysis of the floor slabs and shoring and determined that only four levels of shoring would be needed. The engineers assured the accuracy of the finite element analysis. Measurements obtained from load cells located on judiciously chosen shoring members compared very closely to the results of the analysis. The collaboration between the contractors and the structural engineer resulted in significant savings in time and money.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  78. 78. 6- CASE STUDIED 6.5 – CONSTRUCTION CYCLE A typical cycle was as follows: Day 1 - place the floor forms; Day 2 - place the slab reinforcing steel; Day 3 - pour the slab; Day 4 - erect the column reinforcing steel and pour the columns to the next floor. Minimizing crane time was key to construction scheduling. Time-to-completion was enhanced due to the fact that the PERI systems move up the tower at all times and never have to be brought back to the ground.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  79. 79. 6- CASE STUDIED 6.6 – CONCRETE VERSUS STEEL FRAMING An additional significant cost savings was realized by using the flat plat system, since the underside of the slab was used as the finished ceiling for the floor below. By working closely with the pre-cast concrete contractor, simplicity of formwork was further achieved by supporting the pre-cast panels directly on the columns, thereby eliminating the need for perimeter edge beams. The overall time-to-completion of the project was a clear advantage of the concrete system. Excavation and pile driving began in late November of 1996, and both towers were completed in October of 1997. The faster completion time translates into earlier tenant occupancy, and, thus, an earlier return on the developers investment.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  80. 80. 7- SUMMARY AND CONCLUSION OF THE PRESENTATION New delivery systems, changes in formwork, high-strength concrete, optimum skilled resources, advanced planning techniques, planning skills, constructability, reasonable management, etc. allow to achieve a rapidly paced construction of high-rise buildings in the most advantageous way in cost and time. Choosing a structural system is very complex in todays market. The challenge for engineers and architects today is to make all the systems work together to their maximum capacity and create a habitable environment for the people within the built structure.High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  81. 81. QUESTIONS ?High-Rise Building Construction CyclesAuthor: Jihad S. Daniel
  82. 82. THANK YOUHigh-Rise Building Construction CyclesAuthor: Jihad S. Daniel

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