script for english

MADRIDEJOS: What is the agenda of this meeting?

ALEJANDRINO: We have invited here a group of engineers to discuss about a new innovation product called precast concrete.

MADRIDEJOS: You can start your presentation gentlemen.

MALABANAN: Sir, in this presentation we are going to discuss about the use of precast concrete products on the construction of several structures. What is a Precast concrete product? Precast or 'prefabricated' concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In simple terms, precast is like a piece of your favorite building block: factory-built and ready for installation. Let’s give a little background about precast concrete. The concept of precast construction includes those buildings where the majority of structural components are standardized and produced in plants a location away from the building, and then transported to the site for assembly. These components are manufactured by industrial methods based on mass production in order to build a large number of buildings in a short time at a low cost. Precast concrete has been part of the construction business history but is only now recognized as an effective product. These innovation products makes the construction of structures such as houses, fences, warehouses and even buildings of lower than five stories, much easier, faster and cleaner. Precast concrete products resolve the issues of substandard materials being used in the lesser prioritized components of the building.

ALEJANDRINO: So that’s what a precast material is all about. But can you enumerate what types of building components are included in the scope of precast concrete?

SURBANO: Sir, there are three typical precast concrete members. These are the slabs, beams and walls. Slabs can be classified as either flat or hollow with choice thickness of 4, 6 or 8 inches. For beams, there are six shapes for beams including common sections like L shapes, T shapes and inverted T shapes. The spans of these beams, sir, can be from 50 feet to 120 feet. Wall panels have a standard width of 8 inches. They can be flat, or have architectural features such as window and door openings, ribs, reveals, textures and built-in insulation.

MADRIDEJOS: But how do you connect these members? Are there many ways to connect them or is there a standard?

SURBANO: How do we connect precast concrete members? There are two ways. The most common method is by use of steel weld plates. Typically, the precast members have embedded plates that can be used as welding surfaces for loose connecting plates or angles. Another connecting method is by Rebar and Grout. Rebar and Grout are usually used with slabs. Reinforcing bars are spliced into parts and grouted in place. That’s how we connect the precast concrete members.

MADRIDEJOS: Ok, so in your report you say that there are multiple systems in which precast concrete members can be built. What are these systems and do they differ?

DIAZ: For precast concrete systems, there are four categories. Depending on the load bearing structure, precast can be categorized as: a large-panel system, Frame system, Slab-column system or mixed system. Large panel system refers to multistory structures composed of large wall and floor concrete panels connected in the vertical and horizontal directions so that the wall panels enclose appropriate spaces for the rooms within a building. These panels form a box like structure. Both vertical and horizontal panels resist gravity load. Wall panels are usually on e story high. When properly joined together, these horizontal elements act as diaphragms that transfer the lateral loads to the walls. Depending on the layout, there are three basic configurations of large panel buildings. There’s the cross-wall system, Longitudinal-wall system and two-way system.

MADRIDEJOS: What’s the difference between the three?

DIAZ: Sir, Cross walls are placed in the short direction of the building, Longitudinal walls are placed in the longitudinal direction and Two way system walls are placed in both directions.

ALEJANDRINO: Ok thank you, can you talk about the other three systems for constructing the precast concrete members?

BANTATUA: Let me talk about precast frames. Precast frames can be constructed using either linear elements or spatial beam-column sub assemblages. Precast beam-column subassemblages can be placed away from the critical frame regions; however, linear elements are generally preferred because of the difficulties associated with forming, handling, and erecting spatial elements. The use of linear elements generally means placing the connecting faces at the beam-column junctions. The beams can be seated on corbels at the columns, for ease of construction and to aid the shear transfer from the beam to the column.

SOTO: The third category of precast construction is the Slab-column systems. These systems rely on shear walls to sustain lateral load effects, whereas the slab-column structure resists mainly gravity loads. There are two main systems in this category: One is the Lift-slab system with walls and the other is prestressed slab-column system. Lift-slab systems, as you can see gentlemen, were introduced in the last decade of the soviet union from 1980 – 1989. Also known as the “Seria KUB”, the load bearing structure consists of precast reinforced concrete columns and slabs. Precast columns are usually two stories high and all precast structural elements are assembled by means of special joints.

MADRIDEJOS: How about the prestressed slab-column system?

BATOL: Prestressed slab-column system uses horizontal prestressing in two orthogonal directions to achieve continuity. The precast concrete column elements can be ranged from 1 to 3 stories high. The reinforced concrete floor slabs fit the clear span between columns. After erecting the slabs and coluns of a story, the columns and floor slabs are prestressed by means of prestressing tendons that pass through ducts in the columns at the floor level and along the gaps left between adjacent slabs. After prestressing, the gaps between the slaps are filled with in situ concrete and the tendons then become bonded with the spans.

ALEJANDRINO: I assume that the mixed-system is a combination of the first three. Am I right?

BATOL and SOTO: Yes sir. It’s more of a frame panel with walls, slabs and columns.

ALEJANDRINO: You say that pre-cast concrete makes construction of walls and structural frames easier. Can you enumerate all the advantages of Precast concrete that is most appropriate for the marketing of these products?

JOCSON: In general, precast building systems are more economical when compared to conventional multifamily residential construction or apartment buildings in many countries. There are many advantages of precast concrete. Aside from producing a standard in the dimensional design of structures and having a rapid speed of erection for members,
Precast concrete also has high quality because of the controlled conditions in the factory.
Prestressing is easily done which can reduce the size and number of the structural members.
Entire building can be precast - walls, floors, beams, etc.

ALEJANDRINO: Then what do you think are its main disadvantages?

JOCSON: There are also some disadvantages of precast concrete
Precast members are very heavy members and cranes are required to lift panels. Another is that connections may be difficult and joints between panels are often expensive and complicated.
Also precast components need bracing during on-site erection of structure and skilled workmanship is required in the application of the panel on site.

ALEJANDRINO: How about its response to earthquake?

TABON: There is a general concern among the earthquake engineering community regarding the seismic performance of precast construction. Based on experience in past earthquakes in Eastern and Central Asian countries where these systems are used, it can be concluded that their seismic performance has been fairly satisfactory. However, when it comes to earthquake performance, the fact is that “bad news” is more widely recognized than “good news”, therefore making these systems more effective on places that earthquakes rarely occur. However, few engineers are aware of the good seismic performance of several LARGE-panel buildings under construction at the same sites. Large-panel buildings as described in the WHE report 55 from the Russian federation, such as the Seria 111 were similar to the precast concrete frame system of Sera IS which received no damage during the seismic activity of 2003.

ALEJANDRINO: So what is your conclusion about this product?

SOTO: In the expanding constructions business industry, we could say that precast concrete is a good investment for your company to produce since it is of a cheaper cost that on site construction.

BANTATUA: It also allows contractors to do a better job since their work is minimized.

MADRIDEJOS: Then I declare this proposal be approved. (Everybody claps)