AR 493/ BUILDING TECHNOLOGY 5 ALTERNATIVE BUILDING CONSTRUCTION CHAPTER 1 CAST IN PLACE CONCRETE AND PRECAST CONCRETE INSTRUCTOR: AR. ROBINSON V. BERGANTIÑOS, uap Cast in SITU Concrete • Column, slab, etc. , elements are cast on site and hence it is difficult to control mix, placement and curing • Quality control and maintenance are difficult • Requires time in gaining strength • Increase in strength at SITU by accelerated curing is difficult Precast Concrete • Elements are manufactured in a controlled casting environment and it is easier to control mix, placement and curing • Quality can be controlled and maintained easily • Less labors are required • Precast concrete construction is quick as it can be installed immediately and there is no waiting for it to gain strength I. FLOOR SYSTEM AND ROOF SLAB SYSTEM Floor System – it is defined as a structural system consisting of both the structural floor slab and any beams supporting it. A. Flat Slab • The flat slab is a two-way reinforced concrete slab that usually does not have beams and girders, and the loads are transferred directly to the supporting concrete columns • The thickness of the flat slab is minimum 8” or 0.20m. CHAPTER I I. FLOOR SYSTEM AND ROOF SLAB SYSTEM Advantages of Flat Slab: 1. It minimizes floor-to-floor heights when there is no requirement for a deep false ceiling. Building height can be reduced 2. Automatic sprinkler is easier 3. Less construction time Disadvantages of Flat Slab: 1. In flat slab system, it is not possible to have large span 2. Not suitable for supporting brittle (masonry) partitions 3. Higher slab thickness CHAPTER I I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I B. Flat Plate – a flat plate is a one-way or two-way system usually supported directly on columns or load bearing walls. It is one of the most common forms of construction of floors in buildings. The principal feature of the flat plate floor is a uniform or near-uniform thickness with a flat soffit which requires only simple formwork and I easy to construct. Application: • Short to medium spans with light loading • For LL=50 psi, 15’-30’ spans Conditions: • Architectural layout should be well planned to fully enhance the main area where high flat ceiling with nearly arranged steel/concrete columns are required in the design • Spacing of columns • Punching shear checks at column areas • Long term deflection of the flat plate I. FLOOR SYSTEM AND ROOF SLAB SYSTEM Advantages of Flat Plate • Simple formwork and suitable for direct fix or sprayed ceiling • No beams – simplifying under-floor services • Minimum structural depth and reduced floor-to-floor height Disadvantages of Flat Plate • Medium spans • Limited lateral load capacity as part of a moment frame • May need shear heads or shear reinforcement at the columns or larger columns for shear • May not be suitable for heavy loads CHAPTER I I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I C. Ribbed Floor - consisting of equally spaced ribs that are usually supported directly by columns. They are either one-way spanning systems known as ribbed slab or a two-way ribbed system known as a waffle slab. Types of Ribbed Slab: One-way Ribbed Slab – a one-way slab consists of a series of small reinforced concrete T-beams that are connected with girders that in turn carried by the building column Two-way Ribbed Slab/Waffle slab – this type of slab was designed to decrease the weight of traditional full-concrete slabs. It is also known as waffle slab because they look like waffles with rows of beams running underneath them. I. FLOOR SYSTEM AND ROOF SLAB SYSTEM Advantages of Ribbed Slab: • Savings on weight and materials • Long spans • Attractive soffit appearance if exposed • Economical when reusable formwork pans will be used • Vertical penetrations between ribs are easy CHAPTER I Disadvantages of Ribbed Slab: • Depth of slab between the ribs may control the fire rating • Requires special or proprietary formwork • Greater floor-to-floor height • Large vertical penetrations are more difficult to handle D. Waffle Slab – is a reinforced concrete roof or flooring containing square grids with deep sides and it is also called as grid slabs Waffle Slab Usage: • Can be used as both ceiling and floor slab • The concrete waffle slab is often used for industrial and commercial buildings while wood and metal waffle slabs are used in many other construction sites I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I Characteristics of Waffle Slab: • Suitable for flat areas • The reinforcement in the waffle slab is provided in the form of mesh or individual bars • The thickness of waffle slab recommended is 85 to 100mm while the overall depth of slab is limited to 300 to 600mm • The width of beams or ribs provided in waffle slab are generally 110 to 200mm • Waffle slab requires only 70% of concrete and 80% of steel from the concrete and steel used for stiffened raft I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I Advantages of Waffle Slab • Used for larger span slabs or floors and used when there is limited requirement for number of columns • Good structural stability along with aesthetic appearance • Can be made of concrete or wood or steel • Good vibration control capacity, useful for public buildings to control vibrations created by movements of crowd • Lightweight and requires less amount of concrete • Several services like lighting, plumbing pipes, electrical wiring, air conditioning, insulation materials etc. can be provided Disadvantages of Waffle Slab • Formwork tools required are very costly because of large quantity requirement of pods and some special tools • The floor height should be more hence number of floors is reduced • The services provided in the waffle arrangement without proper maintenance may cause damages to the slab • Skilled workers are required during its construction • They are not suitable for sloped areas. If there is slope area, the area must be levelled with filling or by excavating. • They are not suitable against high winds or cyclonic areas because of their light weight I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I E. Lift Slab – a method of constructing concrete buildings by casting the floor or roof slab on top of the previous slab and then raising (jacking) the slab with hydraulic jacks. I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I Lift Slab System Limitation: • This method shall not be used for multi-storey building, only used for 15-16 storey building. No large span slab is constructed in this type of construction • Hydraulic jacks has positive safety device on it • Can lift only on slabs loaded up to 100,000 pounds at speeds of up to 14ft. An hour NOTE: (See video presentation) F. Slip Form System – it is a method for building large towers or bridges from concrete. The name refers to the “moving form” the concrete is poured into, which moves along the project as the previously poured concrete hardens behind it. The technique has also been applied to road construction. Types of Slip Form System: 1. Vertical Slip form The concrete form maybe surrounded by a platform on which workers stand, placing steel reinforcing rods into the concrete and ensuring a smooth pour. Together, the concrete form and working platform are raised by means of hydraulic jacks. I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I I. FLOOR SYSTEM AND ROOF SLAB SYSTEM CHAPTER I 2. Horizontal Slip Form - same thing with the vertical, together, the concrete form and working platform are moved horizontally by means of hydraulic jacks. CHAPTER I II. WALL PANEL SYSTEM Wall Panel – is a single piece of material, usually flat and cut into a rectangular shape, that serves as the visible and exposed covering for a wall. Wall panels are functional as well as decorative, providing insulation and sound proofing, combined with uniformity of appearance, along with some measure of durability or ease of replacement. A. Flat Type Wall System Advantages: Disadvantages: • Cost saving • Decorative functions • No more mold • Insulating functions • Extra time • Soundproofing functions • An end to touch cleaning • Uniformity of appearance • Watertight guarantee • Durability • Ease Replace ability CHAPTER I II. WALL PANEL SYSTEM Features and Benefits • Special interlocking joint design allows panels to easily lock into for faster installation • Can be combined with other Butler wall systems, bricks, glass and other conventional materials • 16” panel width, combined with the side “return leg” enables application of almost any conventional finish on the interior of the wall system • Factory-installed rigid insulation board for enhanced energy efficiency • Available colors in several visually appealing Applications: Low and Mid-rise offices, Convention centers, Performing Arts centers, Arenas, Airport terminal Buildings, Schools and Universities, and Hospitals II. WALL PANEL SYSTEM CHAPTER I B. Ribbed Type It is the most economical wall system. In fact, this wall system is more economical that wood, concrete or masonry alternatives. Different types of Ribbed type wall panel: WALL RIB CHAPTER I II. WALL PANEL SYSTEM TECH FOUR WALL PANEL THERMAL CLAD REVEAL PANEL II. WALL PANEL SYSTEM Advantages: • Inexpensive • Much variation in styles • Unlimited variation in color though 10 to 40 options are widely available • It is fire resistant, mold and insect resistant • Eco-friendly – material is recyclable, and does offer cool roof benefit CHAPTER I Disadvantages: • Fasteners are generally exposed, which means maintenance/repair every decade or so • As caulking is likely used to seal any gaps between panels, that is additional maintenance concern • Metal can dent or be scratched, which is another item of concern or reason to inspect the roof no more than every 5 years C. Wall Type – a curtain wall system consisting of performed metal cut stone, precast concrete or panelized brick wall units, which may be pre-glazed or glazed after installation. The framing is attached to the building structure and does not carry the floor or roof loads of the building. The wind and gravity loads of the curtain wall are transferred to the building structure, typically at the floor line. II. WALL PANEL SYSTEM elevation Wall Type Benefits • Lightweight • Economical • Easy installation • Faster • Wide range of product design • Comprehensive wall panel Characteristics • Factory assembled • Typical units are five to six feet wide • Fast and process easy installation plan CHAPTER I II. WALL PANEL SYSTEM Advantages: If installed correctly curtain wall systems provide excellent structural integrity, as there are fewer mullions and joints required when compared to most window wall systems. Also, because it acts as a single unit, a curtain wall is highly resistant to moisture, wind, heat and earthquakes. Curtain walls require little maintenance, however improper installation may lead to costly issues CHAPTER I Disadvantages: The additional cost of a curtain wall system (which is often double or triple, the cost of a window wall) doesn’t eliminate issues such as potential damage during transportation or misalignment during installation. Another reported disadvantage of curtain wall systems is noise transmission. Because there is no true separation of floors, sound travels between levels more freely than with a window wall system. D. Window Type Wall Panel – It is achieved by placing glazing between a building’s concrete slabs, using the slabs as structural support. Window walls have a break between the glass, with slab covers used to conceal the concrete. II. WALL PANEL SYSTEM CHAPTER I There are either one-storey in height and made as wise as possible, or cast narrower to span vertically for 2-3 floors II. WALL PANEL SYSTEM CHAPTER I CHAPTER I II. WALL PANEL SYSTEM Advantages: Disadvantages: Aside from advantages such as customizability, ease of installation and cost savings, window walls require less engineering and safety considerations as the exterior wall is broken up by each floors’ concrete slab, providing built-in fire stopping. Also, because the separation of each window wall unit creates a sealed space there is less noise transfer and energy loss. Further, if a unit becomes damaged and needs repair that specific unit can be removed and replaced without affecting the adjoining units. Even with their many positives, window wall systems do have potential drawbacks. Because of the break between the floors, window wall systems often have a less continuous look than curtain wall systems. However, advancements in design have solved this issue with slab covers. Also, more considerations and planning need to occur before installation in order for thermal, air and water performance to meet or exceed those of curtain wall systems. II. WALL PANEL SYSTEM CHAPTER I E. Tilt Up Wall Sytem – It is a technique of site casting concrete walls or elements, typically done on a horizontal surface and once cured, it is tilted vertically into place using a mobile crane. It is temporarily braced into its final standing position and is tied to the building’s roof and flooring system. The term ‘’tilt-up’’ was coined in the late 1940’s to describe a method for constructing concrete walls rapidly and economically without the form work necessary for poured-in-place walls. II. WALL PANEL SYSTEM CHAPTER I Advantages: 1. Economy. In areas where tilt-up design and construction expertise is available – particularly a trained crane and rigging crew. 2. Speed of construction. From the time the floor slab is placed, the typical elapsed time from starting to form the panels until the building shell is completed is four to five weeks. 3. Durability. Tilt-up buildings constructed in the late 1940s show little sign of age (except architectural styling) and some are being handsomely remodeled. 4. Fire resistance. Concrete is an obvious first choice for fire resistance. A 6½-in.-thick wall, for example, has a four-hour fire rating. Disadvantages: 1. Not ideal for complex buildings. Generally a building being used for commercial or industrial uses isn’t going to be very complex, which is why tilt-up walls work so well. This method is perfect for large, rectangular buildings or structures. 2. Difficult to work with on some worksites. A big difference between tilt-up and precast walls is that tilt-up walls are fabricated right on the worksite. 3. Lacking in versatility. Though tilt-up walls are somewhat versatile when it comes to large buildings, they aren’t the best idea for smaller projects. Typically using tilt-up is only good for a minimum size of about 5,000 square feet. II. WALL PANEL SYSTEM CHAPTER I II. WALL PANEL SYSTEM CHAPTER I