Prestressed Concrete Structures Multiple Choice Questions on “Types of Composite Members”.
1. The most common type of composite construction consists of _____________
a) I beams
b) T beams
c) L beams
d) U beams
Clarification: The most common type of composite construction consists of a number of precast prestressed inverted T beams placed side by side and connected by a continuous top slab of insitu concrete and this type of construction is widely used in the construction of bridge decks.
2. The dead weight of the deck can be considerably reduced by using ___________
Clarification: The dead weight of the deck can be considerably reduced by using voids or light weight longitudinal cores in the space between the precast prestressed units and this light weight concrete for the cast in situ slab results in reduced dead loads, leading to economy in the overall costs.
3. The spans exceeding 30m for large span composite bridge decks the precast concrete unit consists of ___________
a) J sections
b) K sections
c) T sections
d) Rectangular sections
Clarification: For large span composite bridge decks of spans exceeding 30m, the commonly used precast prestressed concrete units consist of I section unsymmetrical T or box sections and the concrete cast insitu forms the deck slab interconnecting the precast units and typical cross section of bridge deck with different type of precast units are compiled.
4. The precast prestressed I and T beams have been standardized by ___________
a) Cement and concrete association
b) American standard association
c) British standard association
d) Indian standard association
Clarification: The precast prestressed I and T beams have been standardized by the cement and concrete association for use in the construction of bridge decks of span varying from 7 to 36m and standard I and T units are extensively used as highway bridge beams in U.S.A.
5. The use of prestressed concrete tie beams in a reinforced concrete truss reduces ___________
b) Cross section
c) Curing properties
Clarification: The use of prestressed tie beams in a reinforced concrete truss considerably reduces the cross sectional dimensions of the bottom chord member, which is subjected to high degree of tension in the case of large span trusses.
6. Reinforced and prestressed concrete truss generally used for spans ranging from ___________
a) 18 to 36m
b) 14 to 30m
c) 20 to 30m
d) 11 to 19m
Clarification: Reinforced and prestressed concrete trusses are generally used for spans ranging from 18 to 36m and this form of construction is ideally suited for industrial structures transfer prestressing is also used to develop monolithic action in the lateral direction.
7. The dead load stress developed in the precast prestressed units can be minimized by ___________
Clarification: The dead load stress developed in the precast prestressed units can be minimized by Propping them while casting the concrete in situ this method of construction is termed as propped construction and if the precast units are not propped while placing the insitu concrete, stresses are developed in the unit due to self weight of the member and dead weight of the insitu concrete and this method of construction is referred as unpropped construction.
8. What is the main advantage of composite member?
a) Ease of work
b) Decreased workability
c) Increased depth of foundation
d) Decreased depth of foundation
Clarification: The main advantage of composite member is it facilitates the ease of work at the construction site and it is the fast approaching process by utilizing the self supporting precast stems the shuttering can be minimized.
9. The precast double tees are used in ___________
b) Parking structure
c) Balcony & Parking structure
d) None of the mentioned
Clarification: Precast double tees have been used in partially structures, bridge decks are cast in situ slab, it has long term durability and gives aesthetic flexibility, fire resistance and low maintenance and resists gravity seismic and using loads.
10. The depth variation for L shaped composite beams is ___________
a) 2 to 3 feet
b) 6 to 8 feet
c) 14 to 16 feet
d) 2 to 6 feet
Clarification: In this L section the depth varies from 2 to 3 feet deep, web thickness is usually taken as 16”(0.4m) for the steams of deck sections the ledge provides a bearing surface in which the compacted L beam is subjected to different eccentric loading.