混凝土施工中控制裂缝的措施

本文对混凝土施工中容易产生裂缝的原因进行了分析,并针对不同的裂缝原因,提出应采取的控制措施。     

泵送砼裂缝的防治

本文论述了泵送砼结构裂缝产生的原因及裂缝的具体裂缝的防治措施。     

现浇钢筋混凝土楼板裂缝分析与防治

本文针对多个鉴定工程现浇钢筋混凝土楼板出现的裂缝现象,分析其裂缝产生的原因,并提出了一些避免或减少裂缝产生措施及处理方法,仅供参考。     

浅析沥青砼路面裂缝的原因及其防治措施

本文对沥青砼路面裂缝产生原因进行较为详细的分析,并对其防治方法进行了论述。     

混凝土结构非结构裂缝的成因与控制

对混凝土结构非结构裂缝做了简要的形成机理与成因分析，并提出控温减缩及从混凝土材质方面考虑降低水化热，减少混凝土收缩，提高混凝土的密实度，减少裂缝的措施。     

减少混凝土的收缩裂缝措施简介

主要对混凝土产生收缩裂缝问题进行了原因分析,并提出了减少收缩裂缝的措施。     

关于水泥混凝土路面裂缝原因分析及防治措施

本文明确的指出砼路面出现裂缝的诸多因素和防治的措施,并指出了若干具体的技术上的实施手段。     

商品混凝土裂缝的成因和防治措施

主要阐述了商品混凝土早期收缩裂缝、干缩裂缝、温度裂缝产生的原因和预防措施。     

建筑物框架结构未设置伸缩缝的设计方法

本文论述了某高校食堂全现浇框架结构未设置伸缩缝 ,而采用UEA补偿收缩混凝土的设计方法。通过理论与实践证明 ,此方法是行之有效的。     

简述大体积混凝土裂缝的产生原因及防治

随着国民经济和建筑技术的发展,大型现代化技术设施或构筑物不断增多,于是大体积混凝土逐渐成为构成大型设施或构筑物主体的重要组成部分。但是混凝土是抗压强度高、抗拉强度低的复合材料,因此混凝土极易被拉断,在混凝土表面产生裂缝。裂缝一旦形成,会降低结构的耐久性,削弱构件的承载力,同时会可能危害到建筑物的安全使用。因此如何采取有效措施防止大体积混凝土的开裂,是一个值得重视的问题。     

木材干缩影响因素及减少干燥开裂的方法

在干燥过程中，木材各向干缩不均会产生开裂现象，进而降低产品质量，造成木材资源的浪费。从木材干缩问题入手，探讨了木材的干缩机理及影响因素，介绍了国内外学者在解决木材干缩问题上的一些方法和成果；总结了减少干燥开裂的方法，为干燥预处理提供了一定的方法和理论依据。     

防止和减轻超长混凝土结构温度收缩裂缝的建议

根据工程设计实践和体会，注重结构概念设计，简要分析了温度收缩裂缝的基本特点，重点介绍了对超长混凝土结构如何有效设置后浇带及其它一些控制和抵抗温度收缩应力的具体设计措施。     

浅谈砌体结构裂缝产生的原因与防治

砌体结构的房屋在中小城市建筑物中占的比例较大,分布较广,而砌体结构中的一般细小裂缝由于不危及使用,往往被人忽略.但这些裂缝在较长时间内还不稳定,降低了建筑物的抗震能力,在地震时容易引发墙体破坏,甚至墙体倒塌,必须重视解决.本文根据本人几年的工作经验,提出自己对砌体结构裂缝产生的原因及其防治的浅显建议.     

超长砼结构温度收缩裂缝的成因及防治措施浅析

根据笔者的设计实践，简析了温度收缩裂缝的成因和基本特点，提出了防止和减轻超长砼结构温度收缩裂缝的设计措施。其中重点介绍了超长砼结构温度后浇带的设置。     

温度对人工林落叶松木材干缩及密度的影响

通过在不同的恒定的温度场中的试验,研究分析了人工林长白落叶松(Larix olgensis A.)木材干缩率、干缩比、心边材干缩差异及基本密度在不同温度条件下的变化规律,为合理地制定木材干燥工艺基准提供科学理论依据。     

Relationships of anatomical characteristics versus shrinkage and collapse properties in plantation-grown eucalypt wood from China

To explore the influence of the basic density on collapse-type shrinkage properties and to quantify the relationships of the main anatomical features with shrinkage and collapse properties, all above-mentioned parameters were determined and analyzed for three species of collapse-susceptible eucalypts, Eucalyptus urophylla, Eucalyptus grandis, and E. urophylla × E. grandis, planted in South China. The correlation coefficients were also determined and the corresponding regression equations were established with the anatomical parameters measured by using multiple linear regression. The results indicated that: (1) basic density was strongly positively linearly related to both unit tangential shrinkage (r = 0.970) and unit radial shrinkage (r = 0.959), weakly positively related to total shrinkage (r = 0.656 and 0.640 for tangential and radial, respectively), and weakly negatively related to residual collapse (r = 0.632 and 0.616 for tangential and radial, respectively). (2) The main factors affecting unit shrinkage were cell wall proportion (WP), microfibril angle (MFA), and double fiber cell wall thickness (DWT); factors playing an important role in total shrinkage were WP, ray parenchyma proportion (RP), and MFA, while RP had the highest effect on residual collapse (r = 0.949 and 0.860 for tangential and radial, respectively). (3) All corresponding regression models obtained were very suitable for the evaluation of relationships between the anatomical parameters and unit shrinkage, total shrinkage, and residual collapse, as measured using a moisture content of 28% as the fiber saturation point for all specimens.     

Prediction of transverse shrinkages of young-growth Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) with ultrasonic measurements

Abstract

The objective of this study was to examine the potential of acoustic measurement as a rapid and nondestructive method to predict the dimensional stability of young-growth Sitka spruce and western hemlock. Ultrasonic velocity, peak energy, specific gravity, and radial and tangential shrinkages were measured on twenty-four 25-×102-×y 25-mm specimens obtained from a 58-year-old stand in Southeast Alaska. We found that specific gravity and peak energy of ultrasonic signals were not good predictors of transverse shrinkage, as indicated by poor correlations. Ultrasonic velocity, on the other hand, was found to be a significant predictor of transverse shrinkage and therefore has good potential to be used as a field method to evaluate dimensional stability. The single-parameter prediction model explained 86% of transverse shrinkages in western hemlock and 71% of transverse shrinkages in Sitka spruce. Further study is needed to test the capability and feasibility of using acoustic velocity to predict both longitudinal and transverse shrinkages of wood in standing trees.