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特别感谢：付玉强、刘健、刘明金、刘鑫宇、宁维回、孙清龙
第四课课文
This force
prevents the cracks from developing by eliminating
or considerably reducing the
tensile
stresses at the critical sections at services
load, thereby raising the bending, shear
and torsional capacities of the
sections.
这种力能消除或大大减少使用荷载在跨中及支座等临界截面处产生
的拉应力，
阻止裂缝出现，
从而提高截面的抗弯、抗剪和抗扭能
力。
Although it might appear
that the blocks will slip and vertically simulate
shear slip failure, in
fact they will
not because of the longitudinal force
P
.
虽然看起来好像块体会滑移并发生垂直剪切滑动破坏，但
事实上由于纵向力
p
的作用，这
种情况
不会出现。
But again, because of
the compressive prestress imposed by the
metalbands as a form of
circular
prestressing, they will remain in place.
但又是由于金属箍施加的压应力产生了环形预应力，因而木桶仍保持原样。
Linear prestressing had progressed a
long way from the early days.
线预应力从出现以来，已经有了很大的发展。
The success in the development and
construction of all these structures has been due
in no
small measure to the advances in
the technology of materials, particularly
prestressing
steel, and the accumulated
knowledge in estimating the short and long-term
losses in the
prestressing forces.
所有这些结构物的建造成功，
在很大程度上应归功于材料技术的进步，<
/p>
也应归功于预应力损
失计算方法的不断完善。
阅读材料
According
to the AASHTO technology implementation group,
HPC, which is concrete
thathas been
designed to be more durable, and, if necessary,
stronger than conventional
concrete,
can help highway agencies to build bridges that
are better able to hold p to traffic
and environmental demands.
根
据美国各州公路与运输工作者协会技术实施部的论述，
高性能混凝土是一种经过设计后耐
久性更好，强度比常规混凝土更高的混凝土（必要时）
，公路部
门可以用其修建承受更大车
辆荷载和更高环境要求的桥梁。
The section of mix proportions is the
process of choosing suitable ingredients of
concrete
and determining their relative
quantities with the object of producing as
economically as
possible concrete of
certain minimum properties, notably strength,
durability and a
required consistency.
混合料配合比设计是在最经济而满足强度、
耐久性与所需稠度最
低性能要求的目标下？选择
适宜的混凝土组分并确定其相对数量的过程。
Generally, these methods are based
on fundamental functions: water-to-cement ratio
the
constancy of water demand and
theory of optimum aggregates proportioning, all of
which
determine mixtures with the
required properties.
这些方法通常都是基于如下基本公式进行
的：水灰比、恒定用水量与集料最佳配合比理论，
他们确保混合料能满足相应的性能要求
。
Silica fume is also often
used in ternary combinations with Portland cement
with fly ash or
slag.
硅粉通常与水泥中的粉煤灰和矿渣形成三组分结构。
The stress-strain behavior is depended
on a number of parameters which include material
variables such as aggregate type and
testing variables such as age at testing, loading
rate,
strain gradient and others.
应力应变性能取决于各种参数的取值，包括集料类型等材料变量以及试验龄期、加载速率、
应变梯度与其他各种试验变量。
Lesson5
结构设计原理
①
The successful
designer is at all times fully conscious of the
various considerations that were
成功的设计者
在任何时候都能全面的考虑到结构初步设计中包含的各种因素，
同时还充
分考虑到以后施工中可能遇到的各种问题。
特别感谢：付玉强、刘健、刘明金、刘鑫宇、宁维回、孙清龙
②
Then comes the
analysis (or computation) of the internal gross
forces (thrust ,shears,
…
..
然后开始分析（或计算）由荷载、温度、收缩、徐变或其他设计因素引起的总内力（推<
/p>
力、剪力、弯矩和扭矩）
、应力强度、应变、变形及反力等。
③
The
criteria used to judge whether particular
proportions will result in the desired
behavior
…
用来评价拟定的
（结构）
尺寸是否会获得预期性能的准则反映了知识的积累
（包含理论、
现场试验、模型试验和实践经验）以及直觉和判断力。
④
For
most common civil engineering structures such as
bridges and buildings, the
usual
…
..
对大多数诸如桥梁
和房屋建筑之类的土木工程结构，
过去的常规做法是根据以下方法来
进行设计，
即把允许应力强度和那些由正常使用荷载和其他设计因素所产生的应力强
度
作对比。
⑤
Depending on
the type of structure and conditions involved, the
stress intensities computed..
根据结构类型和设计
条件，
在实际结构的分析模型中由假定的设计条件所计算的应力强
度与实际结构在实际设计条件中所产生的应力强度可能完全一样，也可能不一致。
⑥
The allowable-
stress approach has an important disadvantage in
that it does not provide
…
允许应力法有一个严重的缺陷，
也就是它不能为各类结构及其构件给
出统一的超载能力。
⑦
When proportioning is done on the
strength basis, the anticipated service loading is
first
…
基于强度的结构比例一
旦确定，
预期的使用荷载首先乘以一个合适的荷载系数
（大于<
/p>
1
）
。
荷载系数
的大小由下列因素确定：荷载的不确定性；结构在其使用寿命期间荷载变化的
可能性；对
于荷载组合而言，也与特殊组合的可能性、频率以及持续性有关。
⑧
In recent
decades, there has been a growing concern among
many prominent engineers that.
最近几十年来，很
多著名的工程师已经逐渐注意到，
“安全系数”的定义不仅不适当，
不符合实际情况，更糟糕的是，基于这种概念上的结构设计原理在很多情况下会导致过
分保守，不经济的设计，而在有些情况下又会出现破坏概率太高的冒险设计。
⑨
They feel,
therefore, that the variations of the load effects
and the variations of the structural
因此
，他们感到，荷载作用和结构抗力的变化应该用统计的方法研究，结构残留概率或
结构正
常使用概率也应估计出来。
阅读材料结构分析
①
Such models are
based on idealizations of the structural behavior
of the material and are,
…
这些模型是基于材料的结构特性理想化建立的，因此，在某种程度上不仅完美，这与建
模时的简化假定有关。
②
Structural
design involves the arrangement and proportioning
of structures and their
…
..
结构设计包含结构布置和结构及其构件的尺寸设计。
所形成的结
构应该能够在整个使用
年限内，承受允许范围内的设计荷载。
③
Variable loads
are also referred to as live (or imposed) loads,
and include those caused
by
…
.
可变荷载亦指活载（或冲击
荷载）
，同时还包含除移动荷载（如车辆、火车等）之外，
由施
工作业、封、地震、学、爆破以及温度变化引起的荷载。
④
A structure
that is initially at rest and remains at rest when
acted upon by applied loads
is
…
当结构处于静止状态，以及在
使用荷载作用下仍处于静止状态时，
（我们）称该结构处
于平衡
状态。
第八课
The basic principle for locating
highways is that roadway elements suh as curvature
and
grade must blend with each other to
produce a system that provides for the easy flow
of
traffic at the ddesign
capacity,while meeting design criteria and safety
standards
定线的基本原则是车行道要素如弯道和坡度必须互相结合，
在满足设计规范和安全标准的要
求的同时，提供满足设计通行能力并且
平稳的交通流体系
For example,if it
is found that a site of historic and archeological
importance is located
within an area
being considered for possible route location,it
maybe immediately decided
that any
route that traverses that sita shouldbe excluded
from further consideration
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