Exercise 6:
7. Tính khơng đồng ìêu và chất lượng thay đồi của bê tông phải được xét đến khi xác định hệ số an toàn. a) Dịch ra tiếng Việt các câu sau:
- “The yield point of the reinforcing steel... in strain without notable increase in stress” (đoạn đầu)
UNIT 9
- “Excessive diagonal stresses develop,... the partial separation of the mm reinforcing steel from the concrete” (đoạn 3)
CONVEYING, PLACING, COMPACTING CURING
Conveying of most building concrete from the mixer or truck to the form is done in wheel-barrow or buggies on horizontal runways or by pumping through steel pipelines. The chief danger during conveying is that of segregation. The individual components of concrete tend to segregate because of their dissimilarity (l). In overly wet (2) concrete standing in containers (3) or forms, the - “This occurs because the strainability... excessive strain
which develops when the concrete ruptures” (đoạn 4) - “In this type or be am, the diagonal cracks me caused...
of the principal stresses results in the tension portion of the be am” (đoạn 5)
- “Since the uniformity and quality... when computing the ultimate calving capacity of a structure" (đoạn cuối)
b) Dịch ra tiếng Anh các câu sau: 1. Steels (be embedded) in the tension zone of concrete
(bắt buộc) l. Dạng phá hoại thứ nhất của dầm bê tông cốt thép được
đặc trưng bởi sự hình thành các vết nứt rộng và độ võng đáng kể cùa dầm.
2. Nowadays, with the development of electronic computers, civil engineers (design) most complicated structures (năng lực).
2. Khi bê tông đạt đến cường độ giới hạn và cốt thép chưa đạt đến giới hạn chảy, dầm bị gẫy nhanh chóng trước khi hình thành các vết nứt lớn.
3. Stirrups in reinforced concrete beams (be divided) into groups of varying spacing if they me required over a long distance (lời khuyên).
4. Longitudinal bars in continuous beams (be bent) up to
resist the tensile stresses over the supports (khả năng). 3. Dạng phá hoại thứ ba của dầm bê tông cốt thép dược đặc trưng bởi sự mờ rộng của căc vết nứt nghiêng và sự tách rời cục bộ giữa cốt thép và bê tông.
5. Prefabricated units (be) widely used in buildings to
speed up the construction (lời khuyên). 4. Sự phá hoại của dầm ứng suất trước căng trước thường do cốt thép bị đứt đột ngột gây ra.
6. The designing engineer always (keep) in mind three things-strength, cost, and practicability (bắt buộc)
5. Sự phá hoại của dầm ứng suất trước căng sau thường do bê tông bị nén vỡ hoặc các vết nứt nghiêng mở rộng. 7. Bending moments (be eliminated) by introducing
hinges into structures (khả năng).
6. Sự phá hoại của dàn bê tông ứng suầt trước do độ võng của dàn tăng lên và biên chịu nén bị gãy.
IV Translation Exercise 6: Exercise 6:
7. Tính khơng đồng ìêu và chất lượng thay đồi của bê tông phải được xét đến khi xác định hệ số an toàn. a) Dịch ra tiếng Việt các câu sau:
- “The yield point of the reinforcing steel... in strain without notable increase in stress” (đoạn đầu)
UNIT 9
- “Excessive diagonal stresses develop,... the partial separation of the mm reinforcing steel from the concrete” (đoạn 3)
CONVEYING, PLACING, COMPACTING CURING
Conveying of most building concrete from the mixer or truck to the form is done in wheel-barrow or buggies on horizontal runways or by pumping through steel pipelines. The chief danger during conveying is that of segregation. The individual components of concrete tend to segregate because of their dissimilarity (l). In overly wet (2) concrete standing in containers (3) or forms, the - “This occurs because the strainability... excessive strain
which develops when the concrete ruptures” (đoạn 4) - “In this type or be am, the diagonal cracks me caused...
of the principal stresses results in the tension portion of the be am” (đoạn 5)
- “Since the uniformity and quality... when computing the ultimate calving capacity of a structure" (đoạn cuối)
heavier gravel components tend to settle, and the lighter materials, particularly water, to rise. Lateral movement, such as flow within the forms, tends to separate the coarse gravel from the nner componets of the mix. The danger of segregation has caused the discarding of some previously common means of conveying, such as chutes (4) and conveyor belts, in favour of (5) methods which minimize the tendency (6).
The final concrete strength depends greatly on the conditions of moisture and temperature during the initial period. The maintenance of proper conditions during this time is known as curing. Thirty percent of the strength or more can be lost by premature drying out (14) of the concrete.
To prevent such damage, concrete should be protected from loss of moisture for at least 7 days and, in more sensitive work (15).. up to 14 days. Curing can be achieved by keeping exposed surfaces continually wet through sprinkling, ponding (16). covering with wet burlap, or the like. Recent methods include the use of sealing compounds which, when properly used, form evaporation - retarding membranes (17), and waterproof papers. In addition to improved strength, proper moist curing provides better shrinkage control (18).
Placing is the process of transferring the fresh concrete from the conveying device (7) to its final place in the forms. Prior to placing, loose rust (8) must be removed from reinforcement, forms must be cleaned, and hardened surfaces of previous lifts (9) must be cleaned and treated appropnately. Placing and compacting are critical (10) in their effect on the fnial quality of the concrete. Proper placement must avoid seregation, displacement of forms or of reinforcement in the forms and poor bond (11) between successive layers of concrete. Immediately upon placing, the concrete should be compacted by means of hand tools or vibrators. Such compacting prevents honeycombing, assures close contact with forms and reinforcement, and serves as partial remedy to poesible prior segregation. Compacting is achieved by hand tamping with a variety of speeial tools, but now more commonly and successfully with high- frequency (12), power- driven vibratore (13). These are of the internal type, immersed in the concrete or of the external type, attached to the forms. The former are preferable but must be supplemented by the latter where narrow forms or other obstacles make immersion impossible.
Chú thích:
(1) dissimilarity sự khác nhau (2) overly wet qúa ẩm ướt (3)
container cái chứa, cái đựng (4) chute máng để bê tông trượt
xuống (5) in favour of dành ưu tiên cho (6) tendency xu hướng (phân tầng) (7) conveying device thiết bị vận chuyển (8) loose rust gỉ bong ra (9) lift lớp bê tông (10) critical rất
quan trọng (11) poor bond sự dính kết tời (12) high-frequency có tần số cao (13) power - drivell vibrator máy đầm rung điều khiển bằng động cơ (14) premature drying out sự khô cứng sớm (15) sensitive work cơng trình có tính chất nhạy bén (16)
ponding sự giữ nước (17) evaporation-retarding membrane
màng làm chậm sự bay hơi (18) shrinkage control sự kiểm tra co ngót.