-
Lesson 1
Compression Members
New Words
1. achieve
achievement
2.
eccentricity
center,
中心
;
ec
centric
偏心的；
ec
centricity
偏心，偏心距
3.
inevitable
evitable
可避免的
avoidable;
in
evitable
不可避免的
unavoidable
4. truss
桁架
triangular truss, roof truss, truss
bridge
5. bracing
brace
支柱，支撑；
bracing,
支撑，撑杆
6. slender
细长，苗条；
stout; slenderness
7. buckle
压曲，屈曲；
buckling load
8. stocky
stout
9.
convincingly
convince,
convincing, convincingly
10. stub
树桩，
短而粗的东西；
stub column
短柱
11. curvature
曲率；
curve,
curvature
12. detractor
detract
draw or
take away; divert; belittle
，
贬低，诽谤；
13.
convince
14. argument
dispute, debate, quarrel, reason,
论据（理由）
15.
crookedness
crook
钩状物，
v
弯曲，
crooked
弯曲的
16. provision
规定，条款
Phrases and
Expressions
1. compression
member
2. bending moment
shear force,
axial force
3. call upon (on)
要求，请求，需要
4.
critical buckling load
临界屈曲荷载
critical
关键的，临界的
5. cross-sectional area
6.
radius of gyration
回转半径
gyration
7. slenderness ratio
长细比
8. tangent modulus
切线模量
9. stub
column
短柱
10. trial-and-
error approach
试算法
11. empirical formula
经验公式
empirical
经验的
12. residual stress
残余应力
residual
13. hot-rolled
shape
热轧型钢
hot-rolled bar
14. lower bound
下限
upper bound
上限
16. effective length
计算长度
Definition
（定义）
Compression
members
are
those
structural
elements
that
are
subjected
only
to
axial
compressive forces:
that is, the loads are applied along a
longitudinal axis through the centroid of
the
member
cross
section,
and
the
stress
can
be
taken
as
f
a
=P/A,
where
f
a
is
considered
to
be
uniform over the entire cross section.
受压构件是仅受轴向压力作用的构件，即：荷载是沿纵
轴加在其
截面形心上的，
其应力可表示为
…
，<
/p>
式中，
假定
f
a
在整个截面上均匀分布。
This
ideal
state is never achieved in
reality, however, and some
eccentricity
of the load is
inevitable.
然而，
现实中从来都不可能达到这种
理想状态，
因为荷载的一些偏心是不可避免的。
This
will result
in
bending,
but
it
can
usually
be
regarded
as
secondary
and
can
be
neglected
if
the
theoretical
loading condition is closely
approximated.
这将导致弯曲，但通常认为它是次要的，如果理论
工况是足够近似的，就可将其忽略。
This cannot
always be done if there is a computed bending
moment, and situation of this type will
be considered in
Beam-Columns.
< br>但这并非总是可行的，
如有计算出的弯矩存在时，这种情形将在梁柱
理论
中加以考虑。
The
most
common
type
of
compression
member
occurring
in
buildings
and
bridges
is
the
column
, a vertical member
whose primary function is to support vertical
loads.
在建筑物和桥梁
中最常见的受压构件就是柱，<
/p>
其主要功能就是支承竖向荷载。
In many
instances these members
are
also
called
upon
to
resist
bending,
and
in
these
cases
the
member
is
a
beam-column
.
Compression members can also be found
in trusses and as components of bracing systems. <
/p>
在许
多情况下，
它们也需要抵抗弯曲，在
此情况下，将它们称为梁柱。
受压构件也存在于桁架和
支撑系统
中。
Column Theory
（柱理论）
Consider the long, slender compression
member shown in Fig.1.1a.
考虑如图
1.1.a
所示的
长柱
If
the axial load P is slowly applied, it will
ultimately reach a value large enough to cause the
member to become unstable
and
assume
the shape
indicated by the dashed line.
如果慢慢增加轴
向荷载
P
，它最终将达到一个足够大的值使
该柱变得不稳定
(
失稳
)
，如图中虚线所示。
The
member is said to have buckled, and the
corresponding load is called th
e
critical buckling load
.
这时认为构件已经屈曲，相应的荷载称为临界屈曲荷载。
If
the member is more
stocky
,
as the
one in Fig.1.1b, a larger load
will be required to bring the member to the point
of instability.
如果
该构件更粗短些，如图
1.1b
所示，则需要更大的荷载才能使其屈曲。
For
extremely
stocky
members, failure may be by compressive
yielding rather than buckling.
对特别粗短的构件
，
破坏
可能是由受压屈服引起而非由屈曲引起。
For
these
stocky
members
and
for
more
slender
columns before they buckle, the
compressive stress P/A is uniform over the cross
section at any
point along the length.
对这些短柱以及更细长的柱，在其屈曲前，在其长度方向上任意点处
横截面上的压应力
P/A
都是均匀的。
As
we
shall
see,
the
load
at
which
buckling
occurs
is
a
function of
slenderness
, and for very
slender members this load could be quite small.
我们将会看
到，屈曲发生时的荷载是
长细程
度
的函数，非常细长的构件的屈曲荷载将会很低。
If the member is so slender
(a precise definition of slenderness will be given
shortly) that the
stress just before
buckling is below the proportional
limit
—
that is, the member is
still elastic
—
the
critical buckling load is given by
如果构件如此细长（随后将会给出细长程度的精确定义）以
致即将屈曲时
的应力低于比例极限—即，构件仍是弹性的，临界屈曲荷载如下式给出：
2
P
cr
?
?
2
EI<
/p>
L
2
(1.1)
where
E
is
the
modulus
of
elasticity
of
the
material,
I
is
the
moment
of
inertia
of
the
cross-sectional area with respect to
the minor principal axis, and L is the length of
the member
between points of support. <
/p>
式中
E
为材料弹性模量，
I
为关于截面副主轴的惯性矩，
L
为支座
间的距离。
For Eq1.1
to be valid, the member must be elastic, and its
ends must be free to rotate
but not
translate laterally. This end condition is
satisfied by hinges or pins.
要使方程
1.1
成立，
构
件必须是弹
性的，且其两端必须能自由转动，但不能侧向移动。
This
remarkable
relationship
was
first
formulated
by
Swiss
mathematician
Leonhard
Euler
and
published
in
1975.
此著名公式是瑞士数学家欧拉于
< br>1975
年提出的。
The
critical
load
is
sometimes referred to as the Euler load
or the Euler buckling load. The validity of Eq.1.1
has been
demonstrated
convincingly
by
numerous tests.
因此有时将临界荷载称为欧拉荷载或欧拉临界
荷载。欧拉公式的有效性（正确性）已由许多试验
充分
证实。
It will
be convenient to rewrite Eq.1.1 as follows:
方程
1.1
可方便地写为
P
cr
?<
/p>
?
2
EI
L
2
?
?
2
EAr
2
L
2
?
?
2
EA
(
L
/
r
)
2
(1.1a)
where
A
is
the
cross-sectional
area
and
r
is
the
radius
of
gyration
with
respect
to
the
axis
of
buckling.
The
ratio
L/r
is
the
slenderness
ratio
and
is
the
measure
of
a
compression
member
?
s
slenderness, with large values
corresponding to slender members.
式中
A
为截面面积，
r
为关于
屈曲轴的回转半径，
L/r
为长细比，它是对受压构件细长程度的一种度量，该值越大，构件
越细长。
If
the
critical
load
is
divided
by
the
cross-sectional
area,
the
critical
buckling
stress
is
obtained:
如果将屈曲荷载除以截面面积，便可得到以下屈曲应力：
P
cr
?<
/p>
2
E
F
cr
?
?
A
(
L
/
r
)
2
(1.2)
This is the compressive stress at which
buckling occur about the axis corresponding to r.
这便是
绕相应于
r
的轴发生屈曲时的压应力。
Since buckling will take
place as soon as the load reaches
the
value by Eq.1.1, the column will become unstable
about the principle axis corresponding to the
largest slenderness ratio. This usually
means the axis with the smaller moment of inertia.
由于一
旦荷载达到式
1.1
之值，柱将在与最大长细比对应的主轴方向变得不稳定
（失稳）
，通常该
轴是惯性矩较小的轴。
Thus,
the minimum moment of inertia and radius of
gyration of the cross
section should be
used in Eq.1.1 and 1.2.
因此，应在方程
< br>1.1
和
1.2
中采用截面的最
小惯性矩
和最小回转半径。
Early researchers soon found that
Euler
?
s equation did not
give reliable results for stocky, or
less slender, compression members.
早期的研究者很快发现对短柱或不太细长的受压构件，
欧
拉公式并不能给出可靠的结果，
This is because of
the small slenderness ratio for members of
this type, which results in a large
buckling stress (from Eq.1.2).
这是因为这种构件
的长细比较
小，从而产生较高的屈曲应力。
If
the
stress
at
which
buckling
occurs
is
greater
than
the
proportional
limit
of
the
material,
the
relation
between
stress
and
strain
is
not
linear,
and
the
modulus of elasticity E
can no longer be used.
如果屈曲发生时的应力大于材料的比
例极限，
应
力应变关系就不再是线性的，也不能再用弹性模量<
/p>
E
。
3
This difficulty was
initially
resolved by
Friedrich Engesser, who proposed in
1889 the use of a
variable tangent
modulus E
t
in Eq.1.1.
这一困难最初由
Friedrich Engesser
所克服，他在
1889
年将可变的切线模量
用于方程
1.1.
For
a
material
with
a
stress-strain
curve
like
the
one
in
Fig.1.2, E is not a
constant for stress greater than the proportional
limit F
pl
. The tangent
modulus
E
t
is
defined as the slope of the tangent to the stress-
strain curve for values of
f
between F
pl
and
F
y
.
对于如图
1.2
所示的应力应变曲线
(
的材
料
)
，当应力超过比例极限时，
E
并非常数，当应力
处于
F
< br>pl
和
F
y
之间时，
将切线模量定义为应力应变曲线的切线的斜率，
I
f the compressive stress
at buckling,
P
cr
/A, is in this region, it
can be shown that
如果屈曲时的压应力在此范围时，
可以
证明
P
cr
?
?
2
E
t
I
L
2
(1.3)
This is identical to the Euler
equation, except that E
t
is
substituted for E.
除公式中将
E
代之以
E
t
外，上式
与欧拉公式完全相同。
Effective
Length
（计算长度）
Both
the Euler and tangent modulus equations are based
on the following assumptions:
欧拉和切
线模量方程都是基于如下假定：
1. The
column is perfectly straight, with no initial
crooked
ness.
柱完全竖直，无初始弯曲。
2.
The load is axial, with no eccentricity.
荷载是轴向加载，无偏心。
3.
The column is pinned at both ends.
柱在两端铰结。
The
first
two
conditions
mean
that
there
is
no
bending
moment
in
the
member
before
buckling.
前两
(
假定
)
条件意味着在屈曲前无弯矩存在。
As
mentioned
previously,
some
accidental moment will be present, but
in most cases it can be neglected.
如前所述
，可能偶然会
存在一些弯矩，
但在大多数情况下都可被忽略。<
/p>
The requirement for pinned ends,
however, is a
serious limitation, and
provisions must be made for other support
conditions.
然而，铰结要求是
一个严重的局限，
必须对其它支撑条件作出规定。
The pinned-end
condition is one that
requires
that the member
be
restrained
from lateral translation,
but not rotation, at the ends.
铰结条件要求
约束构件两端不发生侧移，但并不约束转动。
Since
it
is
virtually
impossible
to
construct
a
frictionless pin connection, even this
support condition can only be closely approximated
at best.
由于实际上不可能构造无摩擦铰连接，
即使
这种支撑条件最多也只能是非常近似。
Obviously,
all
columns
must
be
free
to
deform
axially.
显然，所有柱必须在轴向自由变形。
In
order
to
account for other end conditions, the
equations for critical buckling load will be
written as
为了
考虑其它边界条件，将临界荷载写
为如下形式
P
cr
< br>?
?
2
EA
(
KL
/
r
)
2
or
P
c
r
?
?
2
E<
/p>
t
A
(
KL
/
r
)
2
(1.4)
where
KL
is
the
effective
length,
and
K
is
called
the
effective
length
factor.
Values
of
K
for
different
cases can be determined with the aid of the
Commentary to the AISC Specification.
式
中
KL
为计算长度，
< br>K
称为计算长度系数，各种情况下的
K
< br>值可借助于
AISC
（美国钢结构
学会
American Institute of Steel
Construction
）规范的条文说明加以确定。
4
Lesson 2
Introduction to structural
design
New words
1.
framework
2. constraint
3.
collaborate
4. evaluation
5. fixture
6. partition
7. overlook
8. crane
9. fatigue
10. drift
11. enumerate
12. plumbing
13. ventilation
14. accessibility
15. code
16. administer
17. metropolitan
18. consolidate
19.
prescription
20. municipality
21. specification
22. mandate
frame+work=frame
构架，框架
; frame
structure,
框架结构
vt. constrain
约束，强迫；
n. constraint
约束
vt.
合作，通敌；
collaboration,
collaborative
vt. evaluate,
value; assess, assessment
vt. fix,
fixture
固定设备，固定物，夹具
vt. n
分割，划分，
make apart; partition wall
n.
超重机，鹤
.n
疲劳
fatigue strength, fatigue failure
v.n
漂流，漂移，
雪堆
v. list
列举
n. (
卫生，自来水
)
管道，
plumber
管道工
n.
通风，
ventilate,
ventilate a room, a well-ventilated room, vent
通风口
n.
可达性，
access, n.
vt.
通道，接近；
accessible
易接近的，可达到的
n. vt
代码，编码，规范
v.
管理，执行；
administrate,
管理
a.
大城市，
of metropolis
v.
巩固，
strengthen
，
reinforce;
consolidation
n.
规定，命令，药方；
prescribe
n.
市政当局，直辖市，
municipal government
n.
详述，规格
,
规范；
specify
n.
书面命令，委托，
Phrases and expressions
1. functional design
2. bending moment
3. dead load
4.
live load
5. nonstructural components
6. force due to gravity
7.
gravity load
8. building code
9. design specifications
功能设计
弯矩
非结构构件
设计规程
5
10. nonprofit organization
非赢利组织，弄
non-government
organization
11. the
National Building Code
12. the Uniform
Building Code
13. the Standard Building
Code
14. Building Officials and Code
Administrators International (BOCA)
国际建筑公务员与法规管
理人员联合会
15. AISC
美国钢结构学会
American Institute of Steel
Construction
16. AASHTO
美国公路和运输工作者协会
American Association of
State Highway and Transportation
Officials
17. AREA
美国铁道工程协会
the American Railway
Engineering Association
18.
AISI
美国钢铁学会
American Iron and Steel Institute
Introduction to Structural Design
Structural design
The structural design of building,
whether of structural steel or reinforced
concrete, requires the
determination
of
the
overall
proportions
and
dimensions
of
the
supporting
framework
and
the
selection
of the cross sections of individual members.
建筑结构设计，
不论是钢结构还是钢筋混
凝土结构
，都需要确定其支承结构的整体比例和尺寸以及各构件的截面尺寸。
In most
cases
the functional design, including
the establishment of the number of stories and the
floor plan, will
have
been
done
by
an
architect,
and
the
structural
engineer
must
work
within
the
constraints
imposed by this
design.
在大多数情况下，
功能设计，
包括楼层层数和楼层平面的确定，
将要
由建筑师来完成
，
因而结构工程师必须在此约束条件下工作。
Ideally,
the engineer and architect
will
collaborate
throughout
the
design
process
so
that
the
project
is
completed
in
an
efficient
manner.
在理想状态下，
工程师和建筑师将在整个设计过程中协同工作从而高效地完成设计
工作。
In effect, however, the
design can be summed up as follows:
然而，
事实上，设计过程可
概括如下：
The architect
decides how the building should look; the engineer
must make sure that it
doesn
?
t fall
down.
建筑师确定建筑物的外观，
工程师必须确保其不会
倒塌。
Although this is an
oversimplification, it affirms the
first priority of
the structural
engineer: safety. Other important
considerations include serviceability
(how well the structure performs in terms of
appearance and
deflection) and economy.
尽管这样说过分简单，但它明确了工程师的第一个主要任务，即，
确保安全。其它要考虑的因素包括适用性（就外观和挠曲而言其工作性能如何）
。
An
economical structure
requires an efficient use of materials and
construction labor. Although this
can
usually be accomplished by a design that requires
a minimum amount of material, savings can
often be realized by using slightly
more material if it results in a simpler, more
easily constructed
projects.
经济的结构要求对材料和人工的有效使用，
尽管这通常都能通过要求最少材料来取
得，但通过采用稍多的材料，但能使建筑物更简单和更容易建造常常会实现节约的目的。
Loads
The forces
the act on a structure are called
loads
. They belong to one of
two broad categories,
dead load and
live load
.
作用在结构物上的各种力称为荷载，它
们属于一两种广义类型，恒
6
载和活载。
Dead loads are those
that are permanent, including the weight of the
structure itself,
which is sometimes
called the
self-weight
.
恒载是那些永久荷载，包括结构自身的重量，有时
也称为自重。
Other dead loads in a building include the
weight of nonstructural components such
as floor coverings, suspended ceilings
with light fixtures, and partitions.
其它
建筑物恒载包括非
结构构件的重量，
如楼面面层、
带有灯具的吊顶以及隔墙。
All of the loads
mentioned thus far
are forces due to
gravity and are referred to as gravity loads.
至此所提的各种荷载都是由重力
所引起，
因而称
为重力荷载。
Live loads, which can also be
gravity loads, are those that are not as
permanent as dead loads.
活载也
可以是重力荷载，
它们是那些不如恒载那样永久的荷载。
Thi
s
type may or may not be acting on the
structure as any given time, and the location may
not be
fixed.
这类荷载可能也可能不总是作用
在结构物上，且作用位置也可能不是固定的。
Examples of live
load include furniture, equipment, and occupants
of buildings.
活荷载包括家
具、
设置和建筑物的居住者。
In general, the
magnitude of a live load is not as well defined as
that
of a dead load, and it usually
must be estimated. In many cases, a given
structural member must be
investigated
for
various
positions
of
the
live
load
so
that
a
potential
failure
situation
is
not
overlooked.
通常，活荷载的大小不如恒载那样确
定，常常必须估计。在许多情况下，必须
研究活荷载作用在一给定的结构构件的各个位置
以便不会漏掉每个可能的破坏情形。
Building
codes
Building must be designed and
constructed according to the provisions of a
building codes, which
is a legal
document containing requirements related to such
things as structural safety, fire safety,
plumbing, ventilation, and
accessibility to the physically disabled.
< br>建筑物必须根据各种建筑规
范的条款设计和建造，规范是一种法律文件，包含各种
要求，如建筑安全、防火安全、上下
水、通风和体残人的可达性等。
A building code has the force of law and is administered by a
governmental entity
such as a city, a county, or, for some large
metropolitan areas, a consolidated
government.
建筑规范具有法律效力，由政府部位
发布，如城市、县、对于大的城区，如联
合政府。
Buildi
ng codes do not give design provisions, but they
do specify the design requirements
and
constraints that must be satisfied.
建筑规
范并不给出设计规定，但却规定设计必须满足的
各种要求和约束条款。
< br>Of particular importance to the structural engineer is the prescription of
minimum
live
loads
for
buildings.
对结构工程师特别重要的是建筑物的最
小活荷载规定。
Although the engineer is
encouraged to investigate the actual loading
conditions and attempt to
determine
realistic values, the structure must be able to
support these specified minimum loads.
尽管鼓励工程师研究实际荷载工况以确定真实的荷载值，
结构必须能支承这些规定的最小
荷
载。
Design
specifications
In contrast to building
codes, design specifications give more specific
guidance for the design of
structural
members and their connections.
与建筑规范不同，
设计规程给出结构构件及其连接
的更具体的指南。
They
present
the
guidelines
and
criteria
that
enable
a
structural
engineer
to
achieve the objectives
mandated by a building code.
它们给出各种方针和标
准，使结构工程师
能建筑规范所规定的目标。
Design
specifications
represent
what
is
considered
to
be
good
engineering practice
based on their latest research.
根据其最新研究
，
设计规程结出认为是好的
工程作法。
They
are
periodically
revised
and
updated
by
supplements
or
by
completely
new
7
editions.
它们通过补充或通过发布新版本得到定期修订和更新。
As
with model building codes,
design
specifications
are
written
in
a
legal
format
by
nonprofit
organizations.
如同一般建筑规
范，设计规程由非赢利组织编写。
They have no legal standing on their own, but by presenting
design
criteria
and
limits
in
the
form
of
legal
mandates
and
prohibitions,
they
can
easily
be
adopted, by reference, as
part of a building code.
尽管它们本身并无法律地位，<
/p>
但却以法令和禁
令的形式给出设计准则和限制，
< br>以参考文献的形式，
它们可容易地被录入，
并作为建筑规
范
的一部分。
8
Lesson 3
New
words
1. col`loidal
胶状的，胶体的，
`colloid
胶体
2. sieve
n,v.
筛，过筛，过滤
3. sample
.
样品，取样
specimen
4. mesh
n.v
网孔，网格，分网格
5. `cumulative
a.
积累的；
cumulate,
cumulation
6. grading
n.
级配，等级；
grade
7.
sedimentation
n.
沉淀
; sediment
8. suspension
n.
悬浮；
suspend ~bridge cable-
stayed bridge
9. agitate
v.
搅动，混合；
disturb
10.
hydro
meter
n.
（液体）比重计
11.
viscosity
n.
黏性；
viscoidal
12. flaky
n.
薄片状的，
of flake
13. pipette
n.
吸液管
14.
ir
recoverable
a.
不可恢复的
ir
retrievable
15.
con
cave
a.
凹的；
con
vex
凸的
16.
permeability
n.
渗透性
; permeate, permeable
seep
seepage
Phrases and
expressions
1. frost susceptibility
2. sieving method
3. semi-
logarithmic curve
4. grading curve
5. wet sieving
6.
dispersing agent
7. Stoke
?
s law
8.
unit weight
9. coefficient of grading
10. sedimentation method
11.
particle-size distribution
霜冻敏感性
筛分法
半对数曲线
级配曲线
湿法筛分
分散剂
斯托克定律
重度
级配系数
沉降法
粒径分布
Text
Particle Size
Analysis
粒径分析
The range of particle sizes
encountered in soils is very wide: from around
200mm down to
9
the colloidal size of some clays of
less than 0.001mm.
在各种土中所遇到的粒径范围很大，大
到
200mm
小到小于
0.001mm
的一些粘土胶粒。
Although
natural
soils
are
mixtures
of
various-sized particles, it is common
to find a predominance occurring within a
relatively narrow
band of sizes.
尽管天然土都是由各种粒径的颗粒组成，
但通常可发现其主要组成颗粒出现在
一个比较小的粒径范围内。
When
the
width
of
this
size
band
is
very
narrow
the
soil
will
be
termed poorly-graded, if
it is wide the soil is said to be well-graded.
当这一粒径范围非常小时，
称这种土级配较差，
而当其较大时，
称这种土级配良好。
A number of
engineering properties, e.g.
permeability, frost susceptibility,
compressibility, are related directly or
indirectly to particle-size
characteristics.
土的许多工程特性，如渗
透性、霜冻敏感性、可压缩性等都直接或间接的与
土的级配特性有关。
< br>
Fig.3.1 shows the
British Standard range of percentage of particle
sizes.
图
3.1
为粒径百分<
/p>
数的英国标准范围。
The particle-size
analysis of a soil is carried out by determining
the weight
percentage falling within
bands of size represented by these divisions and
sub-divisions.
通过确
定落入由这些粒径分组
和子组所代表的粒径范围的重量百分比，对土进行粒径分析。
In
the
case
of
a
coarse
soil,
from which
fine-grained
particles
have
been
removed
or
were
absent,
the
usual process is a sieve analysis.
对于粗粒土，它里面的细粒土被除去或本身就无细颗粒，常
用的方法就是
筛分法。
A
representative
sample
of
the
soil
is
split
systematically
down
to
a
convenient
sub-sample size and then oven-dried.
此法
是将要分析土的一代表样本系统地分为
方便的子样本，然后烘干。
This
sample
is
then
passed
through
a
nest
of
standard
test
sieves
arranged
in
descending
order
of
mesh
size.
再使烘干的土样通过一组筛孔尺寸由大至小放置<
/p>
的标准试验筛。
The
weight
of
soil
retained
on
each
sieve
is
determined
and
the
cumulative
percentage of the sub-sample weight
passing each sieve calculated.
称量每个筛中剩下
的土样的
重量，并计算出通过每个筛的累计百分数。
From
these figures the particle-size distribution for
the soil is plotted as a semi-
logarithmic curve (Fig.3.2) known as grading
curve.
根据这些数据，
以半对数曲线的形式描出该土的
粒径分布图，即所谓的级配曲线。
细粒
粘
土
胶粒
粉土
细
中
粗
粗粒
砂
细
中
粗
砾石
细
中
粗
非常粗大颗粒
石块
卵石
块石
Where the soil
sample contains fine-grained particles, a wet
sieving procedure is first carried
out
to remove these and to determine the combined
clay/silt fraction percentage.
在土样中含有
细土粒的场合，
首先用湿筛分法将其除去，
并确定粘粒
/
粉粒总共所占的分数。
A
suitable-sized
sub-sample is first
oven-dried and then sieved to separate the
coarsest particles (>20mm).
将一适
< br>量的分土样烘干，并过筛分开最粗的颗粒（
>20mm
的
颗粒）
The sub-sample is then immersed
in
water
containing
a
dispersing
agent
and
allowed
to
stand
before
being
washed
through
a
63
?
m(micron) mesh
sieve.
然后将土样浸入含有分散剂的水中，
并在将其用
63
微米筛过筛前
搁置起来（并将其搁
置一会，再用
63micron
的筛子过筛）
< br>。
The
retained
fraction
is
again
oven-dried and passed through a nest of
sieves.
将筛中保留的部分烘干，并用一组筛子过筛。
After
weighing
the
fractions
retained
on
each
sieve
and
calculating
the
cumulative
percentage
passing each
sieve, the grading curve is drawn.
称量落在
每个筛中土重，并计算出通过每个的
累计百分数后，就可描出级配曲线。
The
combined
clay/silt
fraction
is
determined
from
the
weight
difference
and
expressed
as
a
percentage
of
the
total
sub-sample
weight.
The
coarsest
fraction (>20mm)
can also be sieved and the results used to
complete the grading curve.
由重量
10
差确定粘粒
/
粉粒的总重，并将其表示为子土样总重的百分数
。最粗的部分（即粒径
>20mm
的部分）也可被过筛，并用其
结果完成级配曲线的绘制。
A
further sub-division of particle-size distribution
in the fine-grained fraction is not possible
by
the
sieving
method.
不能用筛分法对细粒部分的粒径分布作进一步分组。
A
process
of
sedimentation
is
normally
carried
out
for
this
purpose.
通常必须用沉降法实现此目的。
A
small sub-sample of soil is
first treated with a dispersing agent and then
washed through a 63
?
m
sieve.
首先将一小子土样用分散剂进行处理，然后洗过
63
的筛子。
The
soil/water suspension
is then made up
to 500 ml, agitated vigorously for a short while
and then allowed to settle.
再从
中取出
500ml
的土
/
水悬浮液，
充分搅拌一会后让其沉降。
The
procedure is based on
Stoke
?
s law,
which states that the velocity at which
a spherical particle will sink due to gravity in a
suspension
is
given
by:
此方法是基于斯托克思定律，即在重力作用下球形颗粒
在某一悬浮液中下降的
速度为
Where d=diameter of particle
颗粒直径
?
s
=unit weight
of the grain of particle
颗粒重度
?
w
=unit weight
of the suspension fluid (usually water)
悬浮液的重度（通过为水的重度）
?
=
vescosity
of the
suspension fluid
（悬浮液的黏度）
The diameter of those particles that
will have settled a given distance in a given time
(t) may
be obtained by rearranging
Eq.3.1:
将式
3.1
变形得在
给定时间
t
内，
沉降一给定距离的那些
颗
粒的直径为
Usually h=100mm,
通常
h=100mm, giving
由此给出
Samples
taken
at
a
depth
of
100mm,
at
an
elapsed
time
of
t,
will
not,
therefore,
include
particles of greater size than the
diameter d given by Eq.3.2;
因此在，
在深度
100mm
处，
t <
/p>
时间
后所取的悬浮液中将不会有粒径大于式
3.2
所给出的土粒
;
but
the
proportions
of
particles
smaller than d in the suspension will
remain unchanged.
但悬浮液中小于
d
的颗粒所占的比例
仍保持不变。
The
procedure using a hydrometer consists of measuring
the suspension density at a
depth of
100mm at a series of elapsed-time intervals.
用液体比重计的方法包括以一系列时间
间隔在深度
100mm
处测定悬浮液的比重。
The
percentage-finer
values
corresponding
to
particular diameter (i.e. particle
sizes) are obtained from the density readings, and
thus a grading
curve for the fine-
grained fraction may be drawn.
通过比重读数得到
小于某一特定粒径的颗粒
的百分数，从而可画出细粒部分的级配曲线。
< br>
Grading Characteristics
The
grading
curve
is
a
graphical
representation
of
the
particle-size
distribution
and
is
therefore
useful in itself as a means of
describing the soil.
级配曲线是粒径分布的一种图形表达，<
/p>
因而可
用来作为描述土的手段。
For
this
reason
it
is
always
a
good
idea
to
include
copies
of
grading
curves in laboratory
and other similar reports.
因此，
人们总是认为在实验室报告或其它报告里
附上几份级配曲线是一种好做法。
It should also be remembered
that the primary object is to
provide a
descriptive term for the type of soil.
还应牢记的是我们的主要目的是提供对土的类
型的描述性术语。
This
is
easily
done
using
the
type
of
chart
by
estimating
the
range
of
sizes
11
included
in
the
most
representative
fraction
of
the
soil.
这可容易地通过采用这种级配曲线做
到，因为用它能估计出土中最有代表
性的成分的粒径范围。
For example, the steep curve
may
be taken to represent a poorly-
graded medium sand, indicating a narrow range of
sizes.
例如，陡
峭的曲线可用来表示级配差的中砂，并
表示其粒径范围比较小。
A
further quantitative analysis of grading curves
may be carried out using certain geometric
values known as grading
characteristics.
通过采用某些称为级配特征的几何值，可进一步对
级
配曲线进行定量的分析。
First
of
all,
three
points
are
located
on
the
grading
curve
to
give
the
following characteristic sizes:
首先，定出级配曲线上的三个点以给出以下特征粒径：
D10=maximum size of the smallest 10
percent of the sample;
只有
10%
土样通过的最大粒径；
D30=
maximum size of the smallest 30 percent of the
sample;
只有
30%
土样通过
的最大粒径；
D60= maximum size of
the smallest 60 percent of the sample
；只
有
60%
土样通过的最大粒径；
From these characteristic sizes, the
following grading characteristics are defined:
根据这些特征
粒径，定义出如下级配特征：
Effective size
有效粒径
Uniformity
coefficient
均匀系数
Coefficient of gradation
级配系数
Lesson 4
New Words
1.
undergo
[
< br>??
nd
????
u]
vt.
经历
,
遭
受
,
忍受
; experience
2.
evaporation
[i
?
v
?
p
??
rei
??<
/p>
n]
n.
蒸发
(
作用
)
evaporate
vapor
3.
attribute
[
??
tribju(:)t]
vt.
把
?归因
于
,
把?归咎于，加于
,
归结于
;
ascribe
，
impute
，
credit
，
assign
，
refer
4.
shrinkage
shrink
[
??
rinkid
?
]
n.
收缩
shrink
5.
capillary
[k
??
pil
?
ri]
adj.
毛细作用的
tension
capillarity
6.
evaporate
[i
?
v
?
p
?
reit]v.(
使
)
蒸发
,
消失
7.
paste
[peist]
n.
糊
,
粘土团
cement paste
8.
ambient
[
< br>??
mbi
?
nt]
adj.
周围的
,
< br>包围着
的
surrounding
ambient air
9.
specimen
[
?
spesimin]
n.
标本
,
样品
,
样
本
,
待试验物
; sample
10.
distribution
[
?
distri
?
b
ju:
??
n]n.
分
配
,
分发
distribute
distributor
11.
upwind
[
??
p
?
wind]adj.
逆风的
adv.
逆风
地
windward;
leeward
12.
diminish
[di
?
mini
?
]v.(<
/p>
使
)
减少
, <
/p>
(
使
)
变小
diminishment; decrease
13.
creep
[kri:p] n.
徐变
;
14.
slippage
slip [
?<
/p>
slipid
?
]
n.
滑动
,
滑移
,
滑
程
slip
15.
humidity
[hju:
?
miditi]n.
湿气
,
潮湿
,
湿
度
;
humid
relative
humidity
16.
aug`ment
[
?
:
??
ment]
v.
增加
,
增大
n.
增加
; increase,
enlarge
augmentation
17.
sustained
[s
?
s
?
teind]ad
j.
持续不变的
,
相
同的
; sustainable
development
18.
fatigue
[f
??
ti:
?
]n.
疲乏
,
疲劳
,
vt.
使疲
12
劳
,
vi.
疲劳
strength
Phrases and Expressions
1.
moisture
content
含水量，含湿度
;
water
content
2.
cement paste
水泥浆
mortar
3.
capillary tension
毛细管张力，微张力
4.
gradation
of
aggregate
骨料级配
coarse
fine (crushed stone, gravel)
5.
The British Code
PC
100
英国混凝土规范
PC100; nowaday BS8110
6.
coefficient
of
thermal
expansion
of
concrete
混凝土热膨胀系数
7.
The B.S Code
英国标准规范
Text
Volume Changes of Concrete
8.
sustained load
永久荷载，长期荷载
9.
permanent
plastic
strain
永久的塑性应变
stress
10.
crystal
lattice
晶格
,
晶格
11.
cement gel
水泥凝胶体
12.
water-cement
ratio
水灰比
13.
expansion
joint
伸缩缝
14.
stability
of
the
structure
结构的稳定性
structural
stability
15. fatigue
strength of concrete
混凝土的疲劳
强度
Concrete undergoes volume changes
during hardening.
混凝土在硬结过程中会经历体积变
化。
If it loses moisture by
evaporation, it shrinks, but if the concrete
hardens in water, it expands.
如果蒸发失去水分，
混凝土会收缩；
但如果在水中硬结，
它
便膨胀。
The causes of the volume
changes
in
concrete
can
be
attributed
to
changes
in
moisture
content,
chemical
reaction
of
the
cement
with water, variation in temperature, and applied
loads.
混凝土体积变化的原因可归结
为含水量的变化、
水泥与水的水化反应、温度变化和所施加的荷载。
Shrinkage
The change in the
volume of drying concrete is not equal to the
volume of water removed.
The
evaporation of free water causes little or no
shrinkage.
混凝土干燥时的体积变化量不等于
它所
失去的水的体积。自由水的蒸发基本不产生收缩。
As
concrete
continues
to
dry,
water
evaporates
and
the
volume
of
the
restrained
cement
paste
changes,
causing
concrete
to
shrink,
probably due to the
capillary tension that develops in the water
remaining in concrete.
随着混凝
土
的不断变干，
水分蒸发，受约束水泥浆的体积也变化，
导致了混
凝土的收缩，这多半是由
于残留在混凝土中的水的毛细张力所致。
Emptying
of
the
capillaries
causes
a
loss
of
water
without shrinkage. But
once the absorbed water is removed, shrinkage
occurs.
毛细管变空导致
无收缩的水分丢失，但一旦失
去吸收的水分，收缩便发生。
Many
factors
influence
the
shrinkage
of
concrete
caused
by
the
variations
in
moisture
conditions.
许多因素都会影响因水分环境发生变化而产生的混凝土收缩。
and
water
content.
The
more
cement
or
water
content
in
the
concrete
mix,
the
greater the shrinkage.
水灰比：水灰比越大，收缩越大；
ition and fineness of cement. High-
early-strength and low-heat cements show more
shrinkage than normal portland cement.
The finer the cement, the greater is the expansion
under
13
moist
conditions.
水泥的成分和细度：早强和低热水泥
的收缩大于普通水泥，水泥越细，其
在潮湿环境中的膨胀越大。
, amount, and gradation of aggregate.
The smaller the size of
aggregate particles, the
greater is the
shrinkage. The greater the aggregate content, the
smaller is the shrinkage.
骨料的类
型、含量及其级配：骨料的粒径越小，收缩越大；骨料含量越大，收缩则越小。
t
conditions,
moisture,
and
temperature.
Concrete
specimens
subjected
to
moist
conditions undergo an expansion of
200
to
300×10
-6
,
but if
they are left to dry in air, they shrink.
High temperature speeds the evaporation
of water and, consequently, increases shrinkage. <
/p>
外部条
件，水分与温度：潮湿环境下的混凝土试件的膨胀量为
200
to
300×10
-6
，但如果让其在空气
中干燥，它们将收缩。高温
加速了水分的蒸发，因此也加快了收缩。
ures.
Admixtures
that
increase
the
water
requirement
of
concrete
increase
the
shrinkage value.
添加剂：
使用水量增加的外加剂也增加了收缩值。
and
shape
of
specimen.
As
shrinkage
takes
place
in
a
reinforced
concrete
member,
tension stresses
develop in the concrete, and equal compressive
develop in the steel. These stresses
are
added
to
those
developed
by
the
loading
action. Therefore,
cracks
may
develop
in
concrete
when a high
percentage of steel is used. Proper distribution
of reinforcement, by producing better
distribution of tensile stresses in
concrete, can reduce differential internal
stresses.
试件的尺寸和
形状：
当收缩在钢筋混凝土构件中发生时，
混凝土中产生拉应力，
同样大小的压力产生于钢
筋中，这些力与荷载引起的力相迭加。因此，当钢筋的配筋率高
时，可能会使混凝土开裂。
钢筋的合理分布、会使混凝土中的拉应力分布更有利，可减小
内部应力差。
The values of final
shrinkage for ordinary concrete vary between
200
and
700×10
-6
.
普通混
凝土的收缩应变终值在
200
< br>
and
700×10
-
6
之间。
For
normal-weight
concrete,
a
value
of
300×10
-6
may be
used.
对常重混凝土，
收缩应变终值可取为
300×10
-6
The
British Code CP100
gives a
value of
500×10
-6
, which
represents an unrestrained shrinkage of
1.5 mm
in
3 m
length in
thin,
plain
concrete
sections.
英国
CP100
规范不出的收缩应变终值为
500×10
-6
，
这表示
3m
长素混凝土薄截面构件的非约束收
缩为
1.5mm. If the member is restrained, a
tensile stress of
about
10N/mm
2
(
1400 psi
)
arises.
如果此构件受到约束，便产生了大约
10N/
mm
2
(
1400
psi
)
的
拉应力。
If concrete
is kept moist for a certain period after setting,
shrinkage is reduced;
如果凝结
后将
混凝土保持在潮湿环境中，
可减小其收缩。
therefore
, it is important to cure the concrete for
a period of no fewer than
7
days
.
因此，将混凝土至少在潮
湿环境中养护
7
天非常重要。
Exposure of concrete to wind increases
the shrinkage rate on the upwind side.
将混凝土置
于风中将增加其在迎风一侧的收缩速率。
Shrin
kage
causes
an
increase
in
the
deflection
of
structural members, which in turn
increases with time.
收缩引起结构构件的挠度增大，而挠度<
/p>
也随时间而增长。
Symmetrical
reinforcement in the concrete section may prevent
curvature and
deflection due to
shrinkage.
混凝土截面的对称配筋可防止因收缩而产生的曲率和挠度。
Generally, concrete shrinks at a high
rate during the initial period of hardening, but
at later
stages the rate diminishes
gradually.
通常，在硬结初期，混凝土收缩较快，但在后期，收缩速
度会慢慢变小。
It can be
said that
15%
to
30%
of the shrinkage value
occurs in
2 weeks
,
40%
to
80%
occurs in
1
month
, and
70%
to
85%
occurs in
1
year
.
可以说
15%
to
30%
收缩量的发生在
前两周，
40%
to
80%
发生在前一个月，
70%
to
85%
发生在第一年。
Expansion Due to Rise in Temperature
升温膨胀
Concrete
expands
with
increasing
temperature
and
contracts
with
decreasing
temperature.
14
The
coefficient
of
thermal
expansion
of
concrete
varies
between
4
and
7×10
-6
per
degree
Fahrenheit
.
混凝土受温膨胀，变冷时收缩。
An
average
value
of
5.5×10
-6
per
degree
Fahrenheit
(
12×10
-6
per
degree Celsius
) can be used for
ordinary concrete.
一般混凝土的平均收
缩值为每华氏度
5.5×10
-6
（或
每摄氏度
12×10
-6
）
。
The
suggests
a
value
of
10
-5
per
degree
Celsius
.
英国标准规范的建议值为每摄氏
10
-5
This value
represents a change of length
of
10
mm
in
a
30-m
member
subjected
to
a
change
in
temperature
of
33
℃
.
If
the
member
is
restrained and
unreinforced, a stress of about
7N/mm
2
(
1000 psi
) may
develop.
这一值表示如果
30m
长的构件温度变化
33
度，其长度变化为
< br>10mm.
如果该构件受到约束但并未配筋，由
此产生
的应力可能约为
7N/mm
2
(
1000
psi
)
。
In long reinforced concrete structures,
expansion joints must be provided at lengths of
100
to
200
ft
(
30
to
60m
).
在较长的钢筋混凝土结构
中，
每隔
100
英尺到
200
英尺
（
30m
至
30m
）
必
须留伸缩缝。
The width of the expansion
joint is about
1 in.
(
25 mm
).
伸缩缝宽度约为<
/p>
1
英寸
（
25m
m
）
Concrete is not a good
conductor of heat, whereas steel is a good one.
The ability of
concrete to carry load
is not much affected by temperature.
混凝
土并非好的热导体，但钢材却
是。因此混凝土的承载能力并不太受温度的影响。
Greep
徐变
Concrete
is
an
elastoplastic
material,
and
beginning
with
small
stresses,
plastic
strains
develop in addition
to elastic ones.
混凝土是一种弹塑性材料，即使受低应力作用，它
就产生
伴有弹性应变的塑性应变。
Under
sustained load, plastic deformation continues to
develop over a
period that may last for
years.
在持续荷载作用下，在很长时间内其塑性变形连续增长，甚至
可达数年。
Such deformation increases
at a high rate during the first
4
months
after application of
the load. This slow plastic deformation
under constant stress is called creep.
此变形在加载后的
前
4
个月最快。这种
在持续应力作用下的缓慢变形称为徐变。
Figure
2.5
shows a concrete cylinder that is
loaded.
图
2.5
表示受荷载
作用的一混凝土圆
柱体。
The instantaneous
deformation is
ε
1
,
which is equal to the stress divided by the
modulus of
elasticity.
其瞬时变形
为
ε
1
，
它等
于应力除以弹性模量。
If the same stress is kept
for a period of
time, an additional
strain
ε
2
, due to
creep effect, can be recorded.
如果将此应力保持
一段时间，
便可测出另一由徐变所产生的应变增量
ε
2
，
If load is then
released, the elastic
strain,
ε
1
, will
be
recovered, in addition to some creep
strain.
如果卸去荷载，弹性应变便得到恢复，同时还产生
一些徐变应变。
The final permanent plastic
strain,
ε
3
, will
be left, as shown in
Figure
2.5
.
最终
会剩下永久塑性应变<
/p>
ε
3
，
如图
2.5
所示。
In this case
ε
3
=(1
－
α
)
ε
2
,
where
α
is the ratio of the
recovered creep strain to the total
creep strain.
在此情况下，
ε
3
=(1
－
α
)
ε
2
,
< br>α
是恢复徐变应
变与总徐变的比值。
The
ratio
α
ranges
between
0.1
and
0.2
.
< br>其值在
0.1
至
0.2
之间。
The
magnitude
of
creep
recovery
varies
with
the
previous
creep
and
depends
appreciably
upon
the
period of the sustained
load.
徐变后效的大小随先前徐变的大小而变化，
且在很
大程度上取决
于荷载的持续时间。
Creep
recovery rate will be less if the loading period
is increased, probably
due to the
hardening of concrete while in a deformed
condition.
如果持荷时间增加，
徐变恢复率
将变小，这大概是由于混凝土在变形硬化所致。
15
Figure 2.5
Deformation in a
loaded concrete cylinder: (a) specimen unloaded,
(b) elastic
deformation,
(c)
elastic plus creep deformation, (d) permanent
deformation after release of load.
The
ultimate magnitude of creep varies between
0.2×10
-6
and
2×10
-6
per unit
stress
(
1b/in.
2
)
per unit length
. A value of
1×10
-6
can be used in practice. The ratio of
creep strain to elastic strain
may be
as high as
4
.
Creep
takes place
in
the
hardened
cement
matrix
around
the
strong
aggregate.
It
may
be
attributed to slippage
along planes within the crystal lattice, internal
stresses caused by changes in
the
crystal lattice, and gradual loss of water from
the cement gel in the concrete.
徐变在强度更高
的骨料周围的硬结的水泥基中产生，
这可能是由于沿晶格中一些
平面发生滑移、
晶格变化所
产生的内部应力、及混凝土凝胶体中
水分不断丢失的结果。
The different
factors that affect the creep of concrete can be
summarized as follows.
影响
徐变的各种不同因素可概括如下：
1. The level of stress. Creep increases
with an increase of stress in specimens made from
concrete of the same strength and with
the same duration of load.
应力大小：
2. Duration
of loading. Creep increases with the loading
period. About
80%
of the
creep
occurs within the first
4 months
;
90%
occurs after about
2 years
.
持荷时间：
3. Strength
and age of concrete. Creep tends to be smaller if
concrete is loaded at a late age.
2
Also, creep
of
2000
psi-
(
14N/mm
-
)
strength
concrete is
about
1.41×10
-6
whereas that
of
4000
2
psi-
(
28N/ mm
-
)
strength concrete is about
0.8×10
-6
per unit stress and
length of time
.
混凝土强
度和龄期：
t conditions. Creep is reduced with an
increase in the humidity of the ambient air.
周围环境条件：
of
loading. Creep increases with an increase in the
rate of loading when followed by
prolonged loading.
加载速率：
tage and
distribution of steel reinforcement in a
reinforced concrete member. Creep
tends
to be smaller for higher proportion or better
distribution of steel.
钢筋混凝土结构中钢筋
的配筋率及其分布：
of
the
concrete
mass.
Creep
decreases
with
an
increase
in
the
size
of
the
tested
specimen.
混凝土尺寸：
,
fineness,
and
content
of
cement.
The
amount
of
cement
greatly
affects
the
final
creep
of concrete, as cement creeps about
15
times as much as concrete.
水泥的类型、细度和含
量：
-cement ratio. Creep increases with an
increase in the water-cement ratio.
水灰比：
and grading
of aggregate. Well-graded aggregate will produce
dense concrete and
consequently a
reduction in creep.
骨料的类型和级配：
of
curing. High-temperature steam curing of concrete
as well as the proper use of a
plasticizer will reduce the amount of
creep.
养护方式：
Creep develops not only in compression,
but also in tension, bending, and torsion.
徐变不
仅产生于受压，它也产生于受拉，受弯和受扭。
The ratio of the rate of creep in
tension to that in compression will be greater
than 1 in the
first
2
weeks, but this ratio
decreases over longer periods.
受拉徐变的速率与
受压徐变的速率之
比在前两周将大于
1
，但会在长时间内减小。
Creep in
concrete under compression has been tested by many
investigators. Troxell, Davis,
16
and Raphael measured
creep strains periodically for up to
20
years
and estimated that of
the total
creep after
20
years
,
18%
to
35%
occurred
in
2
weeks
,
30%
to
70%
occurred in
3
months
, and
64%
to
83%
occurred in
1
year
.
许多研究者都对混凝土的受压徐变进行了试验研究。
For
normal
concrete
loaded
after
28
days
,
C
r
?
0
.
1
3
3
t
,
where
C
r
=
creep
strain
per
unit stress per unit length.
对
28
天龄期加载的普通混凝土，
C
r
?
0
.
13
3
t
，
C
r
=
单位应力下<
/p>
单位时间内的徐变。
Creep augments the
deflection of reinforced concrete beams
appreciably with
time. In the design of
reinforced concrete members, long-term deflection
may be critical and has
to
be
considered
in
proper
design.
随时
间的增加，徐变会大大增加钢筋混凝土梁的挠度。
Extensive
deformation may influence the stability of the
structure.
过大的变形会影响结构的稳
定性。
Sustained loads affect the strength as
well as the deformation of concrete.
持续
加载会影
响混凝土的强度和变形。
A reduction
of up to
30%
of the strength
of unreinforced concrete may
be
expected when concrete is subjected to a
concentric sustained load for
1
year
.
当混凝土在持
续集中荷载作用下长达一年时，其钢筋混凝土的强度可能要降低
30%.
The fatigue strength of concrete is
much smaller than its static strength.
混凝土的疲劳强
度大大低于其静力强度。
Repeated
loading and unloading cycles in compression lead
to a gradual
accumulation
of
plastic
deformations.
受压的重复加载和卸载会导致混凝土塑性变形的逐渐
积累。
< br>If concrete in compression is subjected to about
2
million
cycles, its fatigue
limit is about
50%
to
60%
of the static
compression strength. In beams, the fatigue limit
of concrete is about
55%
of
its static strength.
如果混凝土不断受压加载
2
百万次，
其疲劳强度容许值会降为其静
态抗压强度的
50%
至
60
%.
在梁中，混凝土的疲劳强度约为其静态强度的
55%.
Lesson 5
Loads
New words
1. prescribe
2.
criterion
3. dictate
4. survey
5. variation
6. deterministic
7. rational
8. stochastic
9. pertain
10. cumbersome
11. landscape
12. endeavor
13. deviation
14. constancy
v.
指示，规定
; specify
n.
标准，规范，准则；
standard
v.
规定，指示，命令；
dominate
n.v.
调查，测量；
investigation
n.
变更，变化，差异；
vary,
variable, various
a.
确定性的，
nondeterministic, probabilistic
a.
合理的，理性的；
reasonable, logical
a.
随机的；
stochastic
process, but random variable
v.
适合，属于
; pertaining
a.
讨厌的，麻烦的；
troublesome
n.
地形，风景，景观
v.n.
尽力，努力；
strive
，
put effort to
n.
背离；
deviate,
n.
恒定性，不变性，
constant
17
15. occupant
16. fluctuation
17. `tenant
18. transient
19. sustain
20.
premise
n.
居住者
n.
波动，起伏；
fluctuate
n.
房客，承租人；
a.
瞬时的；
instantaneous
vt.
维持，支撑，持续；
sustainable
n.
前提；
vt.
假定；
Phrases and
Expressions
1. nominal value
2. in practice
3.
at best
4. building code
5. seismic
action
6.
reference (return) period
7.
semiempirical equation
8. wind tunnel
testing
9. mean value
10.
code-prescribed data
11. transient
live load
12. sustained
live load
Text
Loads(1)
标准值，名义值
实际上，在实践上
充其量，最好也只不过
地震作用，
earthquake
load
重现期
半经验公式
empirical
风洞试验
均值；平均
规范规定数值
瞬时活荷载
持续活荷载
Introduction
Normally, a
design specification does not prescribe the
magnitudes of the loads that are to be
used as the basic input to the
structural analysis, with the exception of special
cases such as crane
design
specifications.
除特殊情况设计规程外（如起重机设计规程）
，一般设计规程并不规定
荷载的大小，尽管它是作为结构分析所输入的
基本变量。
It is the role of the
specification to
detail the methods and
criteria to be used in arriving at satisfactory
member and connection sizes
for the
structural material in question, given the
magnitudes of the loads and their effects.
设计规
程的作用就是对于给定的荷载值及其效应，
详细
说明用设计材料能得到满意构件及其连接尺
寸的方法和准则。
T
he specification therefore reflects the
requirements that must be satisfied by
the structure in order that it will
have a response that allows it to achieve the
performance that is
needed.
因此，规程反映了结构必须满足的各种要求，从而使其具有这样一种结构反应，它
能使其
达到所要求的性能。
Loads, on the
other hand, are governed by the type of occupancy
of
the building, which in turn is
dictated by the applicable local, regional, and
national laws that are
more commonly
known at building codes.
另一方面，荷载取决于建筑物的
使用类型，这反过
来取决于相应的地区，地方和国家法规，即常说的建筑规范。
The building code
loads have traditionally been given as nominal
values, determined on the
basis of
material properties (e.g., dead load) or load
surveys (e.g., live load and snow load).
建筑
规范的荷载传统上都是作为标准值给出，
它们是根据材
料特性确定
（如恒载）
或荷载调查所
18
确定（如活荷载及雪荷载）
To
be reasonably certain that the loads are not
exceeded in a given
structure,
the
code
values
have
tended
to
be
higher
than
the
loads
on
a
random
structure
at
an
arbitrary point in time.
为了适
当地确保作用在任一结构上的荷载不超过规范值，后者往往都
要比任一时刻作用任一结构
上的荷载值大些。
This
may,
if
fact,
be
one
of
the
reasons
why
excessive gravity loads are rarely the
obvious cause of structural failures.
事
实上，
这可能就是过
大的重力荷载大都不会导致结构破坏的原因
所在。
Be that at it may, the fact of the
matter is that
all of the various types
of structural loads exhibit random variations that
are functions of time, and
the manner
of variation also depends on the type of load.
尽管可能如此，实际上结构上的各种
荷载都具有随时间而变化的随机变
化特性，且这种变化也取决于荷载类型。
Rather
than
dealing with nominal
loads that appear to be deterministic a nature, a
realistic design procedure
should
take
load
variability
into
account
along
with
that
of
the
strength,
in
order
that
adequate
structural safety
can be achieved through rational means.
不是去处理看上去具有定值特征的标
准荷载，
现实的设计方法
应同时考虑荷载和强度的变异性，
以便以合理的手段得到足够的结
构安全度。
Since the
random variation of the loads is a function of
time as well as a number of other
factors, the modeling, strictly
speaking, should take this into account by using
stochastic analyses
to
reflect
the
time
and
space
interdependence.
由于荷载的随机变化是时
间以及许多因素的函
数，
严格地讲，
通
过采用随机分析方法以反映时间与空间的相互影响，
应使建模对此加以考
虑。
Many studies have dealt with this
highly complex phenomenon, especially as it
pertains to live
load in buildings.
许多研究工作都涉及了这一高度复杂的现象，特别是当其属于活荷载时。
In
practice,
however,
the
use
of
time-dependent
loads
is
cumbersome
at
best,
although
the
relationship must be
accounted for in certain cases (i.e., seismic
action).
然而，实践中采用时间
相关荷载至少半是麻
烦的，尽管在一些情况下必须考虑其相关性（即在有地震作用时）
。
For
most design situations the code
will specify the magnitude of the loads as if they
were static.
对于
大多数设计，
规范将规定荷载的大小，
就象它们是静载似的。
The
ir time and space variation are
covered
through the use of the maximum load occurring over
a certain reference (return) period,
and
its
statistics.
通过采用出现在某一参照期（重现周
期）内的最大荷载及其统计特性，将
它们的时间和空间的变异加以考虑。
For
example,
American
live
load
criteria
are
based
on
a
reference period of 50 years, while
Canadian criteria use a 30-year interval.
< br>例如，
美国活荷载准
则基于
50
年重现周期，而加拿大准则是
30
年。
The
geographical location of the structure plays an
important role for certain loads.
结构的
地理位置对某些荷载起很重要的作用。
It
is
particularly
applicable
to
snow,
wind
and
seismic
action, the first
being of special importance in north-central and
north-eastern areas of the United
States, the second in high wind coastal
and mountain areas, and the last in areas having
earthquake
fault lines.
特别是对
于雪、风和地震作用更是如此。第一种荷载对美国中北部和东北部地区
非常重要，
第二种对具有大风的沿海地区和山岭地区特别重要，
第三种对具有地震
断裂带的
地区则特别重要。
Deign for wind effects is complicated
by a number of phenomena.
由于数个现象使风作用
效果的设计复杂化。
Like snow loads and
earthquake action, wind loads are given more
attention
in certain parts of the
country.
类似于雪荷载和地震作用，在本国的一些地区，对风荷载更加
重视。
At
the
same
time
wind
loads
are
neither
static
nor
uniformly
varying,
and
are
heavily
influenced by the geometry of the
structure as well s the surrounding structures and
landscape.
同
时，
风载不
但非静态，
而且也非均匀变化，
同时还受结构几何形式和周围结
构物及地形的影
响。
To a certain degree
this also applies to the magnitude of the snow
load.
在一定程度上，
这也
19
适用于雪荷载。
Building
codes
treat
these
effects
as
static
phenomena
and
relate
them
to
the
actual
conditions
through
semiempirical
equations.
建筑规范将这些作用作为静力荷载并用半
经验公式将其与实际情况相联
系。
This gives the designer a better
handle on a difficult problem,
but can
lead to difficulties when the real structure
departs significantly from the bases of the code.
这使设计者能更好地处理复杂问题，
但当实际结构与设计规范出
入太大时，
便导致了一些困
难。
For
that reason wind loads, and sometimes earthquake
and snow loads, are determined on the
basis
of
model
test.
为此，风荷载、有时地震荷载和雪荷载都要用模型
试验来确定。
In
particular, wind
tunnel testing has become a useful and practical
tool in these endeavors.
特别是
风洞试验，它已经成为这些努力中一个有用且实用工具。
The loads on the structure are normally
assumed to be independent of the type of structure
and structural material, with the
exception of dead loads.
除恒载外，通常都假定结构上的
荷载
与结构类型及其材料无关。
The response
of a building, however, will be different for
different
materials, depending on the
type of load.
然而，
一建筑物的反应将随其建
材的不同而不同，
这
取决于荷载的类型。
For example, the behavior of a moment-resistant
steel frame will be quite
unlike
that
of
a
braced
frame,
when
subjected
to
lateral
loads,
especially
those
due
to
an
earthquake.
例如，在侧向荷载作用下，特别是当
其由地震所引起时，抗弯钢框架的工作性
能将全然不同于有支撑框架的性能。
On
the
other
hand,
the
response
of
these
two
frames
to
gravity loads will not be all that
different.
另一方面，这两种框架对重力荷载反应的差别却并
没有那么大。
The
size of a structure (height, floor area) has a
significant impact on the magnitudes of most
loads.
一个结构物的大小
（如
其高度，
楼层面积）
对大多数荷载的量值影响很大。
All loads are
influenced by the
increasing height of a multistory building, for
example.
例如，
所有的荷载都受
多层建筑高度增加的影响。
Similarly, the greater
the floor area that is to be supported by a single
member,
the
smaller
will
be
the
probability
that
the
code
live
load
will
appear
with
its
full
intensity over the
entire area.
与这类似，单个构件所支承的楼层面积越大，整个楼层上满
载
规范规定的活荷载的可能性将越小。
In such
cases a live load reduction method is used to
arrive
at more realistic design data.
在此情况下，将采用活荷载折减法以得到更真实的设计值。
20
Lesson 6
New Words
1.
prompt
2.
serviceable
3.
aesthetically
4.
truss
5.
suspension
6.
sag
7.
viscoelastic
8.
rebound
9.
homogenous
10.
isotropic
11.
orthotropic
12.
anisotropic
13.
flammability
14.
machinability
15.
quasi-static
16.
texture
17.
distortion
18.
geotechnics
19.
hydraulics
vt.
促使，鼓动，
spur; incite:
a.
适用的；
service,
serviceable, serviceability
ad.
审美的，美学上的；
aesthetics,
aesthetical
v.
下垂，松驰；
sagging moment,
hogging moment
a.
粘弹性的；
visco-elastic
v.
回弹，跳回；
rebound
test
a.
均质的，同质的；
homo-genous
a.
各向同性的
a.
正交各向异性的；
orthogonal
a.
各向异性的；
an-isotropic
n.
可燃性；
flame,
flammable
n.
可加工性；
machine, machinable
a.
拟静力的；
< br>quasi-
表示类似，拟，准
n.
结构组织，质地；
textile
n.
变形，扭曲；畸变
n.
岩土工程学，土工学
n.
水力学
Phrases and Expressions
1. suspension structure
2.
elastic material
3. plastic material
4. quasi-static loadings
5.
thermal loading
7.
analytical
model
8.
planar
structure
9.
planar load
such as suspension bridge
热负荷
as against linear structure
面荷载
21
Text
Concepts of Structural Analysis
Structures
can
be
classified
in
a
variety
of
ways.
能用各种方法对结构进行分类。
The
casual observer might first consider
classifying structures according to their
respective functions:
buildings,
bridges, ships, aircraft, towers, and so on.
不认真的观察者首先考虑的是根据其相应
功能进行分类，如建筑物、桥梁、
飞机、塔楼等等。
This basis for structural
classification is in
fact
fundamental;
事实上这种结构分类的根据是基本的。
all
structures
have
some
functional
reasons for existence.
所有结构物都因其某些功能而存在。
It is the
need to fulfill some function
that
prompts the designer to give life to a structure.
正是由于要使它们完成某些功能要求才促
使设计者终生致力于结
构设计。
Furthermore, it is the need for a
safe, serviceable, feasible, and
aesthetically
pleasing
fulfillment
of
a
function
that
dictates
the
form,
material,
and
manner
of
loading of a structure.
此外，也
正是对某一功能的安全的、适用的、可行的、和美学上满意
的实现决定了一个结构的形式
、所用材料和加载方式。
Once
the
form
and
material
have
been
determined,
a
structure
may
be
further
classified
according
to
either
its
form
(e.g.,
an
arch,
truss,
or
suspension
structure)
or
the
material
out
of
which it
is constructed (e.g., steel concrete, or timber).
一旦结构的形状和建筑材料确定之后，
可将结构再按其形式分类
（如拱、桁架或悬挂结构）或按其所用材料分类（如钢结构、混凝
土结构或木结构）
。
The form and material of a
structure in turn dictate its behavior, which in
turn
dictates the character of the
analytical model.
结构的形式和建材反过来决定了结构的性能，其
性能进而又分析模型的特点。
Fig.
6.1
illustrates
schematically
the
relationships
among
the
function a structure is
to fulfill, the form and material and loading on
the structure, the behavior of
the
structure, and the analytical model of the
structure.
图
6.1
形象
地说明了结构的功能、形式、
建筑材料、
荷载、
结构性能、
分析模型储因素之间的关系。
At
this point, we need to discuss some
of
the
aspects
of
structural
behavior
indicated
in
Fig.6.1
and
to
explain
their
respective
relationships to
the form and material of the structure.
至此，
我们有必要来讨论一下图
6.1
所示
结构性能的一些方面，
并我解释一下它们各自与结构的形
式和建筑材料的关系。
A structure is
linear
if
its
response
to
loading,
say
displacement
at
a
point,
is
directly
proportional
to
the
magnitude
of the applied load.
如果一结构对其加载的响应，
譬如某点的位移与所施加的荷载
大小成正比，则此结构就是线性的。
If this proportionality does not exist,
the structure is said to
be nonlinear.
如果此比例不存在，则该结构就是非线性的。
Structur
al nonlinearities are of two
types:
结构非线笥分为两类
(1) material
nonlinearities that arise when stress is not
proportional
to strain,
材料非线性，此时材料的应力与应变不呈比例；
and (2)
geometric nonlinearitis that
arise when
the configuration of the structure under load is
markedly changed from the unloaded
configuration.
2
）
几何非线性，此时在荷载作用下其形状与未加载前发生了很大变化。
(the
presence of cables in a structure often
leads to geometric nonlinearity because
displacements can
occur owing to a
change in cable sag, which can be shown to be
nonlinearly related to the force in
the
cable.)(
例如结构中索的存在往往会引起几何非线性，因为索的下垂会产生位移
，可以证
明，
这种位移与索中的内力并不成线性关系
) materials, and therefore structures built from them,
may be classified as
elastic, plastic, or viscoelastic.
因此，<
/p>
结构所采用的建筑材料可能被分类为
弹性、塑性或粘弹性。
Elastic
materials
rebound
to
their
initial
configuration
when
the
load
is
removed, whereas plastic
materials retain a permanent
set(
位置，状态
).
当卸除荷载
后，弹性材
料能回弹以其初始外形，但塑性材料会有一永久变形
The
deformations
of
viscoelastic
materials
depend
on
time
and
therefore
load
history,
whereas
the
deformations
of
elastic
and
plastic
materials
do
not.
粘弹性材料的变形与
时间有关，因而与加载历史有关，但弹性和塑
22
性材料的变形却与时间无关。
A structural
system is unconservative or conservative depending
on
whether or not energy is lost from
the system during a cycle of loading and
unloading.
一个结构
体系是非保守的或保守的，取
决于经过一次加载和卸载该体系中有无能量损失。
Energy
is
generally lost if a
system does not recover its initial shape after
unloading owing either to plastic
behavior of the material or to friction
forces within or between parts of the structure.
如果卸载后
体系并未回到其初始形状，
通常
都有能量损失，
这是要么是由材料非线性引起，
要么是由结
构内部或其构件之间存在摩擦力。
All these behavioral aspects of the
structure will have a significant influence on the
nature of
the analysis used in studying
the structure.
结构的所有这些性能都将对研究结构时的分析方法
起到很大的影响。
In addition, in
developing the analytical model it will be
necessary to consider
whether the
structural material is homogeneous or
nonhomogeneous and
whether it is
irotropic,
orthortropic, or
anisotropic.
而且，在建立分析模型时，必须考虑结构材料是否均质、是
否各
向同性，还是正交各向异性。
(the physical
properties of homogeneous materials are the same
at
each point; those of nonhomogeneous
material are not.
均质材料的物理性能在各点都相同的，
但非均质材料并非如此。
The
physical
properties
of
isotropic
materials
are
the
same
in
all
directions
at
a
point;
各向同性材料的物理性能在各个方向都是相同的
those
of
anisotropic
materials are not.
但各向异性材料却并非如此。
An orthotropic
material is a special anisotropic
material
whose
properties
are
different
in
three
principal
directions
but
whose
properties
in
all
other
direction are dependent on those in the principal
directions.
正交各向异性材料是一种特殊
的各向异
性材料，
它在其三个主轴方向的特性不同，
但在所有其它方向上
的特性则取决于其
三个主轴方向的特性。
) Other
aspects of the structure, although important
design considerations,
will not usually
have a significant impact on the analysis
technique.
结构的其它方面，尽管也是
设计中要考
虑的主要因素，通常将对分析方法影响不大。
These
include
brittleness,
ductility,
flammability,
texture, color, hardness, and machinability.
这些因素包括脆性、延性、可燃性、
质地、颜色、硬度和可加工性。
Finally, the
nature of the loading, which is dependent on the
function of the structure, will
also
influence the analysis.
最后讨论一下加载特点，它取决于
结构的功能，也会影响结构的
分析。
The only
truly static loading on a structure is the dead,
or gravity, loading.
结构上真正的
静
力荷载是恒载，
即重力荷载。
However, if
other loadings are applied gradually enough, they
are
called quasi-static loadings and
may be considered static for analysis purposes.
然而，如果其它
荷载施加的足够缓慢，
就将
其称为伪静力加载，
从而分析时可认为是静力的。
Whethe
r or not
the rate of loading is gradual
enough depends on whether or not the time it takes
to apply the load
is longer than the
fundamental period of vibration of the structure
being analyzed.
加载是否足够
缓慢取决于加
载持续时间是否大于所分析结构的基本周期。
Loads usually need
to be treated as
dynamic only if they
are periodic in nature or if they are applied very
suddenly.
通常只有当荷载
是周期性的或当共是突然
施加的，
才将其作为动力荷载处理。
Even then,
sometimes an
“
impact
factor
”
is
applied to an analysis with a static-loading
result to account for the effect of a suddenly
applied load.
即使在此情况下，有时在分析中
采用一个所谓的“动力系数”来考虑突然施加
荷载的效应，
分析
结果仍以静态加载形式结出。
Loads can also be
categorized as either external
applied
forces
or
internal
initial
distortions.
荷载还可分为外力或内部初始变形。
Thermal
loading is an example of an internal
initial distortion (or initial strain) loading.
热负荷就是内部
初始变形（如初始应变）加载的典型例子。
Unfortunately, the
picture of structural behavior is generally not so
clear as that just painted.
不幸的是，通常对结构性
能的描述并不象上述如此清楚。
That
is,
materials
are
not
either
23
“
linear
”
or
“
nonlinear
”
and
“
elastic
”
or
“
plastic
”
; instead, their behavior
depends on circumstances
such as
environment and rate of loading.
也就是说，材
料并不是“线性”或“非线性”
；也不
是
“弹性”
或
“塑性”
，
其性能取决于环境因素，
如外界情况和加载速率。
T
he picture is further
clouded in that
the type of behavior that must be considered in an
analysis may depend on the type
of
response
being
investigated.
由于分析中所必须考虑的结构性
能类型可能取决于要研究的
结构响应的类型，
这就使这种描述变
得更加含糊不清。
For example, a simpler
analytical model
may suffice to obtain
static displacement and stress results than that
which would be required for
vibration
or
buckling
results.
例如，比较简单的分析模型可能足以得到静
态的位移和应力结
果，但需要更复杂的模型以得到振动或曲屈分析结果。
To clarify this
picture for purposes of a rational presentation of
matrix analysis of structures,
we will
make simplifying assumptions as to the nature of
the behavior structures.
为了阐明这一
< br>问题以讲解清楚结构矩阵分析方法，我们将对结构特性作一些简化假定。
Thus
we
will
consider
only
the
displacement
and
stress
response
due
to
static
loading
of
linear,
elastic,
conservative structures.
因此，
我们将讨论线弹性保守结构因静力加载所引起的位移和应力。
We
will
further
restrict
our
attention
to
discrete-membered
structures
(rigid-and
pin-jointed
frameworks) as opposed to continuous
structures.
我们将进一步将注意力集中到离散杆系结构
< br>（刚结和铰结框架结构）而非连续结构。
However, it is
important to recognize at the outset that
the
concepts
that
will
be
presented
can
be
extended
to
the
solution
of
many
other
classes
of
structural
problems,
including
those
involving
dynamic
response,
material
and
geometric
nonlinearitys, inelasticity,
instability, and continuous systems.
然而
，重要的是要在开始就认识
到我们将要介绍的概念可推广到许多其它结构问题，
其中包括动力响应、
材料及几何非纯属、
非弹性
、
失稳和连续结构体系。
Furthermore, the
same concepts can be applied to problems from
other
areas
of
engineering,
such
as
geotechnics,
hydraulics,
and
heat
transfer,
as
well
as
to
problems
outside
of
engineering
altogether.
而且，同样的概念也可应用于其它工
程领域的问
题，
如土工学、
水力学、<
/p>
热传导以及甚至是工程领域之外的问题。
Finally, to
conserve space and
time, most of our
studies will deal with planar structures subjected
to planar loadings in the plane
of the
structure. This approach will retain enough
generality
that
the
resulting analysis
methods
can be readily extended to three-
dimensional applications.
最后，
为了节省时间和篇幅，
我们研
究的大多数问题将涉及平面内受
平面力作用的平面结构。
这一方法将保持足够的普遍性，
从
而使所得到的分析方法能容易地推广到三维空间问题。
24
Lesson 7
New words
1. tamping
2. fill
3. peat
4.
flexing
5. vegetation
6. poplar
7. shrub
8. seeding
9. pruning
10. pollard
11.
desiccation
12. loess
13. sewer
14. coffer
15. piping
16. matrix
17.
swallet
18. `subsidence
19. excavation
20. seepage
21. rolling
22. untimbered
n.
夯实，捣紧；
tamp,
compact
n, vt.
填方；填土
n.
泥煤，泥炭块；
Partially carbonized
vegetable matter
n.
挠曲；
flex, deflect, flexure,
flexural
n.
植被
n.
白杨
n.
灌木，
arbor
乔木
n.
树苗，秧苗
n. prune
，修剪
vt.
修剪树枝
n.
干燥；
desiccate,
dry
n.
黄土；
loess
plateau
n.
下水道，污水管；
sewage; drainage
n.
围堰；
coffer dam
n.
管涌
n.
胶结材料，矩阵
n.
地下川；溪流入地下的进口
n. settlement; subside,
settle
n.
开挖，
excavate, cut
n.
渗流，渗透；
seep,
permeate
n.
碾压，轧制
n.
无支撑的；
timbering
Phrases and Expressions
1. brick and masonry construction
2. site investigation
场地勘察
3. self-weight loading
4.
surface surcharge
表面超载
5. immediate or undrained settlement
瞬时沉降或不排水迫降
6. water content
7. liquid
limit
8. plasticity index
9.
water table
10. hydrostatic pore
pressure
25
Text
Soil Compressibility and
Settlement
Types of Ground Movement and
Causes of Settlement
The relationship
between ground movement and the stability of
related structures is a complex one.
地面运动和相关结构稳定性之间的关系比较复杂。
First
of
all,
there
are
several
mechanisms
which may produce
ground movement, and furthermore there are many
types of structure, each
with a varying
potential to withstand or to be distressed by
movement.
首先，导致地面运动的机
理有多种，
而且，
结构形式也多种多样，
每一种抵抗地
面运动的能力也不同。
Some buildings,
such as those of brick and masonry
construction, are exceedingly brittle and may
sustain cracks
and even structural
damage following very small foundation
displacements.
一些建筑物，
如砖石
结构，脆性很大，即使在很小的基础位移发生时就可能导致其开裂，甚至结构破坏。
Others
may
be
constructed
to
sustain
movements
of
considerable
magnitude
without
suffering
real
da
mage.
其它结构形式可经受很大的地面运动而不发生真正破坏。
Compaction
Compaction is
a process whereby the soil particles are forced
into a closer state of packing with a
corresponding reduction in volume and
the expulsion of air.
夯实是强迫土粒以更密集的形式堆
积，从而导致其体积减小和空气被排出的过程，
An input
of mechanical energy is required and
this is usually the result of self-
weight loading or a surface surcharge.
夯实需要输入机械能，这
通常是自重加载或地面附加荷载的结果。
Vibrations due to traffic movement, heavy
machinery
and
certain
construction
operations,
such
as
pile-
driving,
have
also
been
known
to
cause
compaction settlement.
而且我们知道，由交通车辆引、重型机械和某些施工工作，如打桩等
产生的振动也是夯实沉降的原因。
In earthquake zones,
seismic shock waves may have a similar
effect.
在地震区，
地震波也
可能具有类似的功效。
The most susceptible soils
are loosely-packed
sands or gravel-
sands and fill material, particularly that which
has been placed without adequate
rolling or tamping.
最易受振动作用的
土包括松砂土、
松砾砂土和填土，
特别是未经充分碾实
和夯实时。
Consolidation
In saturated cohesive soils the effect
of increasing the load is to squeeze out some of
the porewater,
this process is called
consolidation.
在饱和粘性土中，增加荷载的效果就是将一些空隙水从
土
中挤出去，这一过程称为固结。
A
gradual
reduction
in
volume
takes
place
until
internal
pore
pressure equilibrium is reached; a
reduction in loading may cause swelling providing
that the soil
can remain saturated.
其体积逐渐减小直到空隙水压力达到平衡为止；
如果土仍能处于饱和状
态，减载可引起土的膨胀。
A large part of
the remainder of this chapter is devoted to
detailed
study of the consolidation
process and to methods of assessing resulting
settlements.
本章剩余的
大量篇幅将详细研究土
的固结过程及其由此引的起沉降的计算方法。
It
is
essential
to
understand that a change in loading is
required to start the process and that it may
take several
years for the
final settlement to be achieved.
极为重要的就是要明白必须有荷载的变化来产生
26
此过程，且最终沉降可能需要数年才能完成。
Elastic Volumetric
Settlement
弹性体积沉降
In overconsolidated clays increases in
effective stress which do not exceed the yield
point cause
elastic
(approximately)
compression.
在超固结土中，有效土压力的增加将导致土的弹性（大
约为弹性
）
的压缩，
如果土压力未超过其屈服点。
As the stress increases beyond the yield point,
non-linear (consolidation) settlement
occurs.
而当其压力增至超过其屈服点后，非线性（即固
结）沉降便发生。
In heavily overconsolidated
clays, therefore, since the yield point will be
very
high, settlement calculations can
be based on elastic theory, using parameters
referred to effective
stresses.
因此，对严重超固结粘土，由于其屈服点很高，其沉降计算可根据弹性理论进行，
并用其有效应力所对应的诸参数。
Alternatively,
estimates
may
be
based
on
the
slope
of
the
swelling-recompression
curve.
也可根据其膨胀—再压缩曲线的斜率估计其沉降。
The
elastic
behavior of clays is
probably attributable to the flexing of thin and
flaky clay particles.
粘土的弹
性可
能是来自其薄的片状颗粒的弯曲。
Immediate or
Undrained
Settlement
瞬时（或不排水）沉降
Immediate
or
undrained
settlement
is
that
amount
that
takes
place
during
the
application
of
loading, but before any significant
volume change has occurred.
瞬时（或不排水）沉降是
加载
过程中的沉降，此时土还未发生大的体积变化。
Altho
ugh it theoretically occurs in all loading
situations,
with
slowly
applied
loading,
it
is
masked
by
consolidation
settlement
as
volume
changes
occur.
尽管理论上讲，在各种加载过程中都发生此类沉
降，但它被伴有体积变化的
固结沉降所掩盖。
The
calculation
of
amounts
of
immediate
settlement
are
therefore
normally
related to quickly
applied loading e.g., beneath building structure.
因此，
瞬时沉降量的计算通常
与快速加
载有关，
例如，
建筑物下面的沉降。
T
he undrained stiffness (E
u
)
can be assumed as an
elastic constant
for a given depth and so estimates can be obtained
using elastic theory.
可将某一
给定
深度处土的不排水刚度假定为弹性常数，从而用弹性理论估计其沉降量。
Moisture
Movement
水分移动
Some
types
of
clay
show
a
marked
increase
or
decrease
in
volume
as
the
water
content
is
respectively increased or decreased.
当一些粘土的含水量增加或减小时，
会伴随着明显的体积
增大或减小。
Clays
exhibiting
these
characteristics
are
alternatively
called
shrinkable
clays
or
expansive clays and are found in
certain areas of the southern and eastern
countries.
具有此特性
的粘土也称之为可收缩土或
膨胀土，它们常出现在南部和东部的一些地区。
Effects of
Vegetation
植被的影响
Another factor associated with highly
plastic clays that may bring about settlement is
the effect of
the
roots
of
trees.
使高塑性土沉降的另一因素就是树木根的作用。
The
radial
extent
of
some
tree
root
systems
is
greater
than
the
height
of
the
tree;
they
may
also
reach
depths
of
several
meters.
一些树根系的径向沿伸要大于其高度，
它们也可能有几米深。
A movement of 100mm
27
was recorded
in house foundations 25m away from a row of
poplars.
在相距一排白杨树
25m
< br>的
房屋的基础上曾观测到
100mm
的位移。
The removal of such trees means
that more moisture is
held in the soil
and so swelling occurs.
将这些树移走意味着土中的含水量
将增加，
从而土将发
生膨胀。
Wher
e well-established trees and shrubs have to be
removed from a site, a period of one
or
two winters should be allowed so that equilibrium
may be achieved.
在要移走大量树木的场
地
上建造房屋时，要等一两个冬季过后，土中水分达到平衡后再动工。
Effects of Groundwater
Lowering
地下水位下降的效应
As
water
is
pumped
from
an
excavation,
the
water
table
in
the
surrounding
ground
may
be
lowered.
当从开挖的基坑中将水抽出时，
其周围地下水位将会下降。
Settlement can result
from
this reduction in hydrostatic
conditions due to two processes.
由于以下两种
过程，
这种含水量的
减小会导致沉降。
Firstly, in some clays, as discussed above, a
decrease in moisture content will
result in a decrease in volume.
其一，如上所述，在一些粘土中，含水量的减小将导致体积减
小，
The soil above the reduced groundwater level
may therefore shrink.
从而使下降后的地下水
位以上的土收缩；
Secondly, a reduction in
hydrostatic pore pressure results in an increase
of the
effective overburden stress on
the layers below.
其二，空隙静水压力的减小导致下层土的有效<
/p>
覆盖土压应力的增加，
Accordingly, the
soil (especially in soft clays or peat) beneath
the reduced
groundwater level may be
consolidated by the increase in effective stress.
从而可能使下降后的
水位以上的土（特别是粘土或泥炭土）发生
固结。
Effects of Temperature
Changes
温度变化的效应
Quite severe shrinkage can occur in
clay soils as they
dry out beneath
foundations of furnaces,
kilns, ovens
and boilers.
当炼钢炉、砖窑、烤炉和锅炉房基础下的粘土变干时，土可
出现严
重的收缩。
In one case, a
boiler building on
the London Clay
settled 150mm at
the center and
75mm at the sides in less than two
years.
例如，
在不到两年内，
一个建造在伦敦粘土的锅炉房
中心沉降了
150mm
，周边沉降了
75mm. It is usual to
provide an open or rubble-filled air gap
between such heat sources and the
foundation soils.
因此，通过在此类热源和基土之间设置一
敞开的或碎石填充的通气层。
Effects of Seepage and Scouring
渗透和冲刷效应
In
certain sandy soils, such as fine dry sands and
loess, the movement of water can move some of
the
fine
particles.
在某些砂土中，如细干砂土或黄土中，
水的流动能移走一些细小颗粒。
Scouring is the removal
of material by surface water and streams, but this
can also occur where
sewers or water
mains have been fractured.
冲刷是土被地表水或水流带
走的过程，
但这在下水
管或供水主管道破裂的地方也可能发生。
Where excavations are taken well below
groundwater
level within coffer dams
and the like, the upward flow of water may cause a
form of instability
called piping.
在大大低于地下水位的围堰和类似结构中进行开挖作业时，
水的向上运动
可能
会导致一种称为管涌的不稳定。
In arid
areas the same soils are liable to surface erosion
due to
wind action.
在干燥地区，此类土可能会因风作用而产生表面侵蚀。
28
Loss of
Lateral Support
失去横向支撑
A
common
form
of
foundation
movement,
often
leading
to
serious,
even
catastrophic,
building
failure is associated with the
excavation of deep holes alongside the foundation.
一种常见的、通
常会导致严重的、
甚至
是灾难性的建筑物破坏的基础运动，
都是由基础周围开挖深孔所致。
Many cases
have been recorded in which adjacent excavation
has resulted in a failure.
有在建筑
< br>物周围进行开挖造成建筑物破坏的许多实例。
The bearing
capacity of the soil directly beneath a
footing is dependent on the lateral
support afforded it by the soil alongside;
基底土的承载力与
其周围土所提供的侧向支撑有关，
i
n calculating the ultimate bearing capacity of the
soil this is
taken into account.
从而在计算土的极限承载力时是计入这一影响的。
If
this lateral support is
removed, as may
occur in an untimbered excavation, the likely
outcome is a shear slip in the soil
beneath the footing, taking the footing
into excavation.
如果移去这一支撑，如在无支撑开挖时
所出现在那样，可能出现的问题就是基础下土发生剪切滑移，从而将基础带入开挖的坑中。
Similarly, settlement might occur as a
result of movement of natural earth slopes or
cuttings, due
to sliding or flowing.
与之类似，
由于土的滑动或流动所引起的自然坡或切坡的运动也可能
导
致基础沉降。
29
Lesson 8
Structural Steel Behavior
New Words
1.
behavior
2. property
3. fracture
4. manganese
5. quote
6. scatter
7. accentuate
8. damage
9.
raiser
10. initiate
11.
arrest
12. flaw
13. defect
14. transitional
n.
行为，性能，特点，特性；
behave
n.
性能，特点，特性
n. v.
断裂，破裂
n.
锰
vt.
引用，引证，提供，
cite
n.
分散
disperse,
distribute, part, separate, split up, spread
n.
强调
; emphasize
n.
损伤，破坏
n.
抬起者，兴起者，提出者
vt.
起始，开始
begin
vt.
阻止，抑制
apprehend, capture, catch, check, stop
n.
缺陷，裂纹
blemish, crack, damage, defect, fault,
weakness
a.
过渡的，不稳定的，
transit
转变，过渡
transition
Phrases and Expression
1.
mechanical
property
力学性能，机械性能
2.
Young
?
s modulus
of elasticity
3.
account for
是（造成
…
…
的）原因，说明（原因）
4.
heat treatment
5.
cold working
6.
standard tension test
标准拉伸试验
7.
normal
distribution curve
8.
fluctuating load
交变荷载，脉动荷载
9.
high-cycle
fatigue
高周疲劳
low cycle fatigue
10.
stress range
应力幅（范围）
11.
fatigue life
疲劳寿命
30
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