Formwork is the temporary moulds in the construction which is fabricated based on the drawing and design of the structure and into which the concrete is poured to form the required structure.Formwork is an essential p...Formwork is the temporary moulds in the construction which is fabricated based on the drawing and design of the structure and into which the concrete is poured to form the required structure.Formwork is an essential part of the construction as it has been used by the Romans.The formworks must be strong enough to withstand all types of loads.The joint must be in proper condition to avoid any kind of leakages.The materials used for the formworks should be economical,easily available and durable.The formworks can be made up of different materials such as plywood,steel,aluminum,composite material,etc.In steel formwork the plates used for the slab support are made up of galvanized steel and these are fabricated as per the requirements.Aluminum plates are used in the aluminum framework along with the other components made up of aluminum.The selection of a suitable framework is important in any project because it bears about 25%to 30%cost of the total cost of construction.In the present study,different types of formworks such as steel,plywood and aluminum were studied in a project and a comparison was made on the reusability and easiness in handling and maintenance.Also,a comparison of the formwork used in the construction of the 5th and 11th-floor tower based on the specific plan and drawing was done.The results showed that the aluminum formwork was found to be efficient and suitable among all formworks,although the cost was higher compared to other formwork materials.展开更多
Improving the knowledge of rheological and tribological characteristics of fresh concrete is important to contribute to the progress of construction sites and the final quality of the work. The objective of this study...Improving the knowledge of rheological and tribological characteristics of fresh concrete is important to contribute to the progress of construction sites and the final quality of the work. The objective of this study is to identify the effect of a superplasticizer based on polycarboxylic ether on the tribological behavior of fresh concrete at the concrete/formwork and concrete/oil/formwork interfaces. Friction tests on fresh concrete were carried out using a plan/plan tribometer. In order to study the behavior of the superplasticizer close to the formwork, three concretes with 30% of paste and different dosage of superplasticizer were formulated. The results show that the increase of the dosage of superplasticizer reduces the friction stress. The properties of the superplasticizer generate a deflocculating action of concrete grains and lead to a stabilisation of the soap-oil micellae present in the vicinity of the formwork. Thus, the efficiency of superplasticizer depends on the quantity of fines, on the quantity of soap formed and so, on the release agent formulation.展开更多
Utilizing pre-cast ECC panels as participating permanent formwork of concrete members, and the validity of using ECC to disperse the single crack in concrete into multiple ones in ECC were studied. In the process, tot...Utilizing pre-cast ECC panels as participating permanent formwork of concrete members, and the validity of using ECC to disperse the single crack in concrete into multiple ones in ECC were studied. In the process, totally two kinds of ECC with different tensile properties, 7 series of flat panels with different top surface figures and 3 U-shape panels with different inner surface forms were investigated. To evaluate the performance of the permanent formworks, small ECC-concrete composite beams were cast and tested mechanically. The 4-point bending test results show that the use of pre-cast ECC panels as permanent formwork can significantly improve the load capacity and toughness of a concrete member, effectively dispersing single widely opened crack in concrete into multiple ones in ECC. Most permanent formworks show perfect bond with the concrete cast on them, while the ones with partially debonded zone achieve the best mechanical performance. The U-shape permanent formworks show better performances than the flat ones, achieving much betler improvements in both the load capacity and toughness, together with better crack width control.展开更多
By spraying concrete on inner surface,air-supported fabric structures can be used as formwork to construct reinforced concrete shell structures.The fabric formwork has the finished form of concrete structure.Large dev...By spraying concrete on inner surface,air-supported fabric structures can be used as formwork to construct reinforced concrete shell structures.The fabric formwork has the finished form of concrete structure.Large deviation from the desired shape of concrete shells still remains as central problem due to dead weight of concrete and less stiffness of fabric formwork.Polyurethane can be used not only as a bonding layer between fabrics and concrete but also as an additional stiffening layer.However,there is little research on mechanical behaviors of the polyurethane shell structure.This paper presents experimental studies on an inflated fabric model with and without polyurethane,including relief pressure tests,vertical loading tests and horizontal loading tests.Experimental results show that the additional polyurethane layer can significantly enhance the stiffness of the fabric formwork.Compared with the experiment,a numerical model using shell layered finite elements has a good prediction.The reinforcement by polyurethane to improve stiffness of air-supported fabric formwork is expected to be considered in the design and construction of the concrete shell,especially dealing with the advance of shape-control.展开更多
Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete(SCC). However, the ...Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete(SCC). However, the high liquidity of SCC will induce a higher lateral pressure. Therefore, it is important to obtain a better understanding of the template lateral pressure. In this work, nine composite shear walls were experimentally investigated, focusing on the effects of two parameters, i.e., the casting rate and the section width of the formwork. The time-varying pressure was monitored during the SCC pouring. It is found that the increase of casting rate from 3.2 m/h to 10.3 m/h resulted in a higher maximum lateral pressure. The higher casting rate led to a longer time required for the lateral pressure to drop to a steady value. There was no correlation between the section width and the rate of decrease in the initial formwork pressure and stable value. Based on the test results, a formula considering the effect of casting speed for the calculation of SCC formwork pressure was established to fill the gap in the current standards and for engineering applications.展开更多
Formwork construction has been the important and difficult of the construction process, so the design plan is very important. This paper relies on the Shun Ping Yu subordinate Fertgbo bridge rebuilding project, detail...Formwork construction has been the important and difficult of the construction process, so the design plan is very important. This paper relies on the Shun Ping Yu subordinate Fertgbo bridge rebuilding project, detailing the cast-in-place box beam formwork support system safety special construction plan, focuses on box girder formwork design scheme of foundation design, box girder bracket design and box girder formwork design, to provide a reasonable reference for similar projects.展开更多
The application of mobile formwork cast-in-situ beam technology is conducive to providing quality assurance for bridge constructions.At the same time,it can improve the overall mechanization level of the construction ...The application of mobile formwork cast-in-situ beam technology is conducive to providing quality assurance for bridge constructions.At the same time,it can improve the overall mechanization level of the construction process and further accelerate the construction progress,so as to shorten the construction period and improve the economic benefits of enterprises.In fact,this construction method has been widely applied.In order to assure a positive outcome from the use of this technology,this paper analyzes the application of mobile formwork cast-in-situ beam technology in bridge construction to provide reference.展开更多
The use of three-dimensional(3D)printed concrete as formwork is becoming more widely applied within the industry.However,the technology is still not optimized and there are many reports of preliminary cracking during ...The use of three-dimensional(3D)printed concrete as formwork is becoming more widely applied within the industry.However,the technology is still not optimized and there are many reports of preliminary cracking during the curing of cast concrete.This is believed to result from differential shrinkage between the printed and cast concrete.These cracks(in the printed concrete or at the interface between the infill and printed concrete)form a preferential path for aggressive substances and can reduce the durability of the combined concrete element.To ensure the desired service life of the structure,it is important that the differential shrinkage between cast and printed concrete is understood.This study investigated the effect of curing conditions on the differential shrinkage behavior of 3D and cast concrete.The influence of prewetting of the dry-cured 3D printed formwork was also determined.In the experimental program,a vibrated and self-compacting concrete were used as cast material.Linear 3D printed formwork was produced and combined with cast concrete to simulate a concrete structure.Printed formwork was cured for 1,7,or 28 d exposed to the air(relative humidity:60%or 95%)or submerged in water.The length change of the combined elements was observed over 56 d after concrete casting and throughout the thickness of the materials.Results show that increasing the curing period in dry conditions of the printed concrete leads to an expansion of the formwork on the first day after casting.The expansion leads to a non-uniform strain evolution throughout the curing period of the combined element.Printed concrete formwork stored in wet conditions does not expand after the casting process but tends to show a decreasing linear deformation within the whole elements.展开更多
Fabric,as a flexible formwork for concrete,gives builders,engineers,and architects the ability to form virtually any shape.This technique produces a superb concrete surface quality that requires no further touch up or...Fabric,as a flexible formwork for concrete,gives builders,engineers,and architects the ability to form virtually any shape.This technique produces a superb concrete surface quality that requires no further touch up or finishing.Woven polyolefin fabrics are recommended for this application.The texture of this fabric allows water from concrete mix to bleed,and therefore reduces the water-cement ratio of the mix.Due to the reduction in the water-cement ratio,a higher compressive strength in fabric-formed concrete is achieved,which is also suggested by earlier studies.The current research study was conducted to investigate and document the changes in concrete strength and overall quality due to these woven polyolefin fabrics.Use of fabric formwork will result in a decrease in construction cost,construction waste,and greenhouse gas emissions.Two sets of tests were conducted in this research study:a comparison of the compressive strength of fabric-formed versus PVC-formed concrete cylinders,and a comparison of the behaviour of the fabric-formed columns versus cardboard-formed reinforced concrete columns.Variables in this research were limited to two types of fabric that included one with coarse and one with a more refined texture,and two types of concrete that included ordinary and flyash concrete.The laboratory results revealed that the effects of fabric formwork on concrete quality in a large member are limited mostly to the surface zone and the core of the concrete remains the same as a conventionally formed concrete.Even though fabric-formed cylinder tests showed an average of a 15%increase in compressive strength of the concrete samples,the compressive strength of the reinforced columns did not dramatically change when compared to the companion cardboard formed control columns.This research confirmed that fabric formwork is a structurally safe alterna-tive for forming reinforced concrete columns.展开更多
文摘Formwork is the temporary moulds in the construction which is fabricated based on the drawing and design of the structure and into which the concrete is poured to form the required structure.Formwork is an essential part of the construction as it has been used by the Romans.The formworks must be strong enough to withstand all types of loads.The joint must be in proper condition to avoid any kind of leakages.The materials used for the formworks should be economical,easily available and durable.The formworks can be made up of different materials such as plywood,steel,aluminum,composite material,etc.In steel formwork the plates used for the slab support are made up of galvanized steel and these are fabricated as per the requirements.Aluminum plates are used in the aluminum framework along with the other components made up of aluminum.The selection of a suitable framework is important in any project because it bears about 25%to 30%cost of the total cost of construction.In the present study,different types of formworks such as steel,plywood and aluminum were studied in a project and a comparison was made on the reusability and easiness in handling and maintenance.Also,a comparison of the formwork used in the construction of the 5th and 11th-floor tower based on the specific plan and drawing was done.The results showed that the aluminum formwork was found to be efficient and suitable among all formworks,although the cost was higher compared to other formwork materials.
文摘Improving the knowledge of rheological and tribological characteristics of fresh concrete is important to contribute to the progress of construction sites and the final quality of the work. The objective of this study is to identify the effect of a superplasticizer based on polycarboxylic ether on the tribological behavior of fresh concrete at the concrete/formwork and concrete/oil/formwork interfaces. Friction tests on fresh concrete were carried out using a plan/plan tribometer. In order to study the behavior of the superplasticizer close to the formwork, three concretes with 30% of paste and different dosage of superplasticizer were formulated. The results show that the increase of the dosage of superplasticizer reduces the friction stress. The properties of the superplasticizer generate a deflocculating action of concrete grains and lead to a stabilisation of the soap-oil micellae present in the vicinity of the formwork. Thus, the efficiency of superplasticizer depends on the quantity of fines, on the quantity of soap formed and so, on the release agent formulation.
基金Funded by the Hong Kong Research Grant Council(No. CERGUST6138/04E)the Key Program of National Natural Science Foundation of China(No. 50438010)the Research & Application of Key Technology for the South-North Water Transfer Project Construction in China(No.JGZXJJ2006-13)
文摘Utilizing pre-cast ECC panels as participating permanent formwork of concrete members, and the validity of using ECC to disperse the single crack in concrete into multiple ones in ECC were studied. In the process, totally two kinds of ECC with different tensile properties, 7 series of flat panels with different top surface figures and 3 U-shape panels with different inner surface forms were investigated. To evaluate the performance of the permanent formworks, small ECC-concrete composite beams were cast and tested mechanically. The 4-point bending test results show that the use of pre-cast ECC panels as permanent formwork can significantly improve the load capacity and toughness of a concrete member, effectively dispersing single widely opened crack in concrete into multiple ones in ECC. Most permanent formworks show perfect bond with the concrete cast on them, while the ones with partially debonded zone achieve the best mechanical performance. The U-shape permanent formworks show better performances than the flat ones, achieving much betler improvements in both the load capacity and toughness, together with better crack width control.
基金Projects(51178263,51378307)supported by the National Natural Science Foundation of China
文摘By spraying concrete on inner surface,air-supported fabric structures can be used as formwork to construct reinforced concrete shell structures.The fabric formwork has the finished form of concrete structure.Large deviation from the desired shape of concrete shells still remains as central problem due to dead weight of concrete and less stiffness of fabric formwork.Polyurethane can be used not only as a bonding layer between fabrics and concrete but also as an additional stiffening layer.However,there is little research on mechanical behaviors of the polyurethane shell structure.This paper presents experimental studies on an inflated fabric model with and without polyurethane,including relief pressure tests,vertical loading tests and horizontal loading tests.Experimental results show that the additional polyurethane layer can significantly enhance the stiffness of the fabric formwork.Compared with the experiment,a numerical model using shell layered finite elements has a good prediction.The reinforcement by polyurethane to improve stiffness of air-supported fabric formwork is expected to be considered in the design and construction of the concrete shell,especially dealing with the advance of shape-control.
基金Funded by the National Natural Science Foundation of China(No.51178218)the Cooperation Project of Yangzhou Science and Technology Bureau(YZ2016267)
文摘Wall cracking and mold expanding due to concrete vibrations can be effectively solved through the application of precast normal-concrete composite shear walls infilled with self-compacting concrete(SCC). However, the high liquidity of SCC will induce a higher lateral pressure. Therefore, it is important to obtain a better understanding of the template lateral pressure. In this work, nine composite shear walls were experimentally investigated, focusing on the effects of two parameters, i.e., the casting rate and the section width of the formwork. The time-varying pressure was monitored during the SCC pouring. It is found that the increase of casting rate from 3.2 m/h to 10.3 m/h resulted in a higher maximum lateral pressure. The higher casting rate led to a longer time required for the lateral pressure to drop to a steady value. There was no correlation between the section width and the rate of decrease in the initial formwork pressure and stable value. Based on the test results, a formula considering the effect of casting speed for the calculation of SCC formwork pressure was established to fill the gap in the current standards and for engineering applications.
文摘Formwork construction has been the important and difficult of the construction process, so the design plan is very important. This paper relies on the Shun Ping Yu subordinate Fertgbo bridge rebuilding project, detailing the cast-in-place box beam formwork support system safety special construction plan, focuses on box girder formwork design scheme of foundation design, box girder bracket design and box girder formwork design, to provide a reasonable reference for similar projects.
文摘The application of mobile formwork cast-in-situ beam technology is conducive to providing quality assurance for bridge constructions.At the same time,it can improve the overall mechanization level of the construction process and further accelerate the construction progress,so as to shorten the construction period and improve the economic benefits of enterprises.In fact,this construction method has been widely applied.In order to assure a positive outcome from the use of this technology,this paper analyzes the application of mobile formwork cast-in-situ beam technology in bridge construction to provide reference.
文摘The use of three-dimensional(3D)printed concrete as formwork is becoming more widely applied within the industry.However,the technology is still not optimized and there are many reports of preliminary cracking during the curing of cast concrete.This is believed to result from differential shrinkage between the printed and cast concrete.These cracks(in the printed concrete or at the interface between the infill and printed concrete)form a preferential path for aggressive substances and can reduce the durability of the combined concrete element.To ensure the desired service life of the structure,it is important that the differential shrinkage between cast and printed concrete is understood.This study investigated the effect of curing conditions on the differential shrinkage behavior of 3D and cast concrete.The influence of prewetting of the dry-cured 3D printed formwork was also determined.In the experimental program,a vibrated and self-compacting concrete were used as cast material.Linear 3D printed formwork was produced and combined with cast concrete to simulate a concrete structure.Printed formwork was cured for 1,7,or 28 d exposed to the air(relative humidity:60%or 95%)or submerged in water.The length change of the combined elements was observed over 56 d after concrete casting and throughout the thickness of the materials.Results show that increasing the curing period in dry conditions of the printed concrete leads to an expansion of the formwork on the first day after casting.The expansion leads to a non-uniform strain evolution throughout the curing period of the combined element.Printed concrete formwork stored in wet conditions does not expand after the casting process but tends to show a decreasing linear deformation within the whole elements.
文摘Fabric,as a flexible formwork for concrete,gives builders,engineers,and architects the ability to form virtually any shape.This technique produces a superb concrete surface quality that requires no further touch up or finishing.Woven polyolefin fabrics are recommended for this application.The texture of this fabric allows water from concrete mix to bleed,and therefore reduces the water-cement ratio of the mix.Due to the reduction in the water-cement ratio,a higher compressive strength in fabric-formed concrete is achieved,which is also suggested by earlier studies.The current research study was conducted to investigate and document the changes in concrete strength and overall quality due to these woven polyolefin fabrics.Use of fabric formwork will result in a decrease in construction cost,construction waste,and greenhouse gas emissions.Two sets of tests were conducted in this research study:a comparison of the compressive strength of fabric-formed versus PVC-formed concrete cylinders,and a comparison of the behaviour of the fabric-formed columns versus cardboard-formed reinforced concrete columns.Variables in this research were limited to two types of fabric that included one with coarse and one with a more refined texture,and two types of concrete that included ordinary and flyash concrete.The laboratory results revealed that the effects of fabric formwork on concrete quality in a large member are limited mostly to the surface zone and the core of the concrete remains the same as a conventionally formed concrete.Even though fabric-formed cylinder tests showed an average of a 15%increase in compressive strength of the concrete samples,the compressive strength of the reinforced columns did not dramatically change when compared to the companion cardboard formed control columns.This research confirmed that fabric formwork is a structurally safe alterna-tive for forming reinforced concrete columns.
文摘为探究爬模施工进程中索塔空间温度场和应力场分布,掌握塔柱线形特性,提出一种索塔爬模施工仿真分析方法.利用Fortran编程语言开发相应子程序,对结构施加复杂温度边界,实现不同节段混凝土水化放热、收缩徐变.利用Abaqus软件对索塔爬模施工过程进行分析.结果表明:施工过程中索塔空间温度分布不均匀,塔柱表里最大温差达25.9℃,向阳面与背阴面温差最大为9℃;考虑温度效应后,塔柱所受拉应力更大,且空间应力分布具有很强的时变性,索塔线形特征与变化规律也发生改变;施工塔顶累积竖向位移先增大后减小,在爬模第16节段达到最大值20.5 mm;施工过程塔顶累计顺桥向和横桥向位移更大,最大值分别为6.5和22.3 mm.
