问题 问答题

背景


某三跨预应力混凝土连续刚构桥,跨度为80m+135m+80m,采用悬臂浇筑法对称施工,挂篮采用自锚式桁架结构。在施工过程中发现,悬臂现浇混凝土箱梁拆模后准备张拉预应力索时,箱梁腹板混凝土出现了裂缝,且是呈一种有规律地出现于与底板约呈45°的斜裂缝。
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问题

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试分析箱梁腹板混凝土出现裂缝的原因。

答案

参考答案:出现与底板呈45°斜裂缝的原因极大可能是该区域的主拉应力,超过了该处的预应力索和普通钢筋的抗剪力及混凝土的抗拉强度。也有可能是混凝土拆模时间过早,混凝土尚未达到其设计抗拉强度。
除此之外其他的原因分析有还有:
1)混凝土未达到拆模、张拉的龄期或强度。
2)腹板的非预应力普通钢筋网钢筋间距较大,不能满足抗裂要求。
3)施工临时荷载超载或在作用点产生过大的集中应力。

材料分析题

地震日志 5月12日,下午两点多,在县委开会,突发地震,县委命令参会人员立即全部返回岗位,组织抗震救灾。

青川县石坝乡党委书记 舒云 在都江塔堰,在汶川,在德阳,废墟中的孩子们身处绝境,却朝着正在营救他们的人呼喊:“叔叔阿姨快出去,这里危险!” ——新华社记者

他们在震后的农田里忙着收割、插秧,因为他们从来没有想过依赖别人。 ——评论员 阎晓明

“我是学生,捐不出多少钱,但是我可以捐出自己的血,我的血是热的!” ——廊坊学子 赵津楠

上述材料中人们的表现,体现了我们所学的哪些观点?

                                                                                                                                                              

                                                                                                                                                             

                                                                                                                                                             

                                                                                                                                                              

                                                                                                                                                               

                                                                                                                                                             

单项选择题

In a democratic society citizens are encouraged to form their own opinions on candidates for public office, taxes, constitutional amendments, environmental concerns, foreign policy, and other issues. The opinions held by any population are shaped and manipulated by several factors: individual circumstances, the mass media, special-interest groups, and opinion leaders.

Wealthy people tend to think differently on social issues from poor people. Factory workers probably do not share the same views as white-collar, nonunion workers. Women employed outside their homes sometimes have perspectives different from those of full-time homemakers. In these and other ways individual status shapes one’s view of current events.

The mass media, especially television, are powerful influences on the way people think and act. Government officials note how mail from the public tends to "follow the headlines. " Whatever is featured in newspapers and magazines and on television attracts enough attention that people begin to inform themselves and to express opinions.

The mass media have also created larger audiences for government and a wider range of public issues than existed before. Prior to television and the national editions of newspapers, issues and candidates tended to remain localized. In Great Britain and West Germany, for example, elections to the national legislatures were usually viewed by voters as local contests. Today’s elections are seen as struggles between party leaders and programs. In the United States radio and television have been beneficial to the presidency. Since the days of Franklin D. Roosevelt and his "fireside chats," presidents have appealed directly to a national audience over the heads of Congress to advocate their programs.

Special-interest groups spend vast sums annually trying to influence public opinion. Public utilities, for instance, tried to sway public opinion in favor of nuclear power plants. Opposed to them were citizens’ organizations that lobbied to halt the use of nuclear power. During the 1960s the American Medical Association conducted an unsuccessful advertising campaign designed to prevent the passage of Medicare.

Opinion leaders are usually such prominent public figures as politicians, show-business personalities, and celebrity athletes. The opinions of these individuals, whether informed and intelligent or not, carry weight with some segments of the population. Some individuals, such as Nobel Prize winners, are suddenly thrust into public view by the media. By quickly reaching a large audience, their views gain a hearing and are perhaps influential in shaping views on complex issues.

It is obvious that the opinion of famous people()

A.is often ignored by the public

B. is seldom expressed to the point

C. is often imposed on the public

D. has a p influence on people