Contemporary Trends in Formwork Standards—A Case Study

One expression of the renewed attention gained recently by formwork for concrete is the current revision of formwork standards. This paper presents the new Israeli formwork standard as a case study for contemporary trends in formwork standardization. The main novelty in the new standard is its similar treatment of the design of temporary structures to that of permanent structures, resulting in the replacement of the traditional allowable-stress approach with the concept of limit-state design and partial safety factors. The paper presents this concept and discusses its applicability to formwork design. In addition, the paper highlights several other issues of a contemporary nature, which appear to be worth debate by standardization committee members from the industry and academia. In the course of the preparation of the new Israeli standard, American, European, and Australian standards and similar documents were closely studied; some comparisons of design and loading data that may affect construction safety and economy are also presented in this paper.     

模壳焙烧生产线技术改造探讨

介绍了BLX-6B模壳焙烧生产线的改造情况,改造后的模壳焙烧生产线设计上有所创新,采取了多项节能措施,投产后性能优良,节能效果显著,对其技术特性进行了分析。     

Multilevel Formwork Load Distribution with Posttensioned Slabs

Formwork and the associated shoring represent a significant proportion of the costs associated with the construction of multilevel concrete structures. To minimize these costs, a limited number of formwork and shoring sets are recycled up the structure as construction progresses, eliminating the need for a new set of formwork and shoring with each new slab. When a slab is posttensioned using draped tendons, slab lift occurs as a portion of the slab self-weight is balanced. The formwork and shores supporting that slab are unloaded by an amount equivalent to the load balanced by the posttensioning. This produces a load distribution through the structure that is inherently different from that of a conventionally reinforced slab. This paper presents two design methods suitable for modeling the multilevel formwork process for posttensioned slabs: A modification to the simplified analysis method and a finite element model—both techniques will be of immediate use by industry practitioners and of interest to researchers examining the load distribution phenomenon. The paper also summarizes the findings of one of only a few research projects in which actual shore loads were monitored during the construction of a multilevel posttensioned building, which is used to validate the proposed design models.     

Design and Construction of High Multitier Shoring Towers: Case Study

Shoring towers are the common formwork solution for high-clearance construction, but there are not many documented cases of extremely high towers. This paper reports on a project in which 60-m-(200-ft-) high shoring towers were used for slab formwork. The paper describes the design and construction of the formwork, with a focus on aspects unique to high multitier towers. The various considerations made are presented, and data and information are provided that may assist practitioners facing similar engineering undertakings. Special attention is given to the organization of the work, in light of the scarcity of data pertaining to shoring towers of such heights. Measured assembly and disassembly work inputs are presented and analyzed, and the validity of a model to predict work inputs in multitier tower erection is examined.     

“T”型预制看台板模板支设的优选方法

体育场的看台板外形较复杂,在工程实践中,往往采用预制板的形式。无论采用那种形式的预制看台板,模板支设涉及现场预制场地狭小的问题,如果采用传统地模支设,加固较困难。本文系统比较了"T"型预制看台板各类模板的优缺点,得出底模采用钢模,侧模采用木模的优选施工方法;详细阐述了优选方法的各项施工准备、工艺流程、支护工具、施工步骤;提出了模板支设过程中的施工注意事项;分析了优选方法的技术经济优势。     

模壳工艺在密肋楼板中的应用

本文对聚丙烯塑料模壳在大空间、大跨度结构模板支设体系中的应用提出见解 ,并结合包头市华银商贸大厦成功的模板支设方案建立了Φ4 8× 3 .5mm钢脚手管、连接角模等通用机具在模壳支撑体系中的应用方法 ,拓展了模壳施工工艺的适用空间     

Design of Tall Formworks by a Finite-Element Model

The design of formworks for holding fresh concrete possesses a difficult engineering challenge. Present standards assume fresh concrete to have a nonviscous fluid behavior when calculating the lateral pressure to which the formwork walls will be the subject. This paper describes a finite-element model to determine these pressures, taking into account the interaction between the fresh concrete and the formwork wall. The use of this numerical model shows that present standards may underestimate the lateral pressures that can be exerted particularly with respect to tall formworks. The paper also discusses the influence of different mechanical variables on the results returned by the proposed model. The proposed model may be of use to practicing engineers and of interest to researchers examining load distributions in formworks.     

Nonshored Formwork System for Top-Down Construction

Recently, the top-down construction method has been applied to building construction to secure excavation safety by providing rigid diaphragm walls. Usually, proper and economical formwork systems need to be selected for successful top-down construction. This paper proposes a nonshored top-down formwork system (referred to as NSTD) as a modified formwork system for top-down construction. The NSTD method provides sufficient workspace for excavating under the suspended forms. Upon completion of concrete placement and curing on the ground level slab, the formwork system is lowered to the next floor, and the process is repeated down to the lowest underground floor. The advantages of the NSTD method include a reduction in the excavation duration and an improvement in the quality of the underground concrete work by the hanging-type formwork. A case study was performed to verify the validity of the NSTD by comparing its schedule and cost effectiveness with those of traditional top-down methods.     

某厂房工程高支模计算方案

介绍某厂房工程典型高支模的复核计算过程，确保整个高支模系统的安全．     

尾矿浓缩池的施工技术

根据安徽金日盛矿业有限责任公司周油坊铁矿选矿厂尾矿浓缩池施工实例,介绍了池壁圆模板设计、安装及固定,利用池体浇筑施工技术,提高混凝土的抗渗性进行了介绍,并希望对类似工程有参考价值。     

超大跨度预应力混凝土梁施工技术

文章以赤峰国际会展中心工程为背景,深入探讨本工程超大跨度预应力混凝土梁施工的关键技术,详细介绍了施工过程中的材料准备、混凝土梁模板及支撑体系的设计、预应力钢筋安装、混凝土浇筑及养护、孔道灌浆等主要环节,对大跨预应力混凝土梁的施工具有较高的参考价值。     

Comparative Analysis of Shoring Towers for High-Clearance Construction

Formwork for cast-in-place concrete in high-clearance construction is commonly based on multitier shoring towers. The market has responded to the demand for shoring towers by offering numerous proprietary models, from which the constructor can choose. Thus, there is a need for comparative data and selection criteria that are comprehensive, objective, uniformly processed, and systematically organized. This paper presents methodology, formatted data, and findings that purport to assist constructors in rationally selecting the appropriate shoring towers for their projects. For the benefit of industry practitioners, the paper offers an overview of tower configuration and classification, a formatted list of selection criteria generated on the basis of input from formwork manufacturers, and interviews with representatives of formwork service companies, examples of comparative data on selected tower models, and quantitative comparisons based on the introduction of normalized parameters and on formwork solutions for typical cases. This information is particularly vital given the high cost of tower-based formwork relative to the overall construction cost of the supported concrete element, while published erection and dismantling work input data are largely still unavailable for most models and heights of shoring towers.     

Engineering for a 21st Century Lunar Observatory

The design process required for a lunar base observatory is considered. An observatory on the moon with significant capability could be operational by the year 2015. Astronomical observations from a lunar base will require one or more of a wide variety of instruments. Optical telescopes, optical interferometers, radio telescopes, and radio interferometers have often been suggested. Possibilities also exist for options such as high‐energy photon detectors, cosmic ray detectors, and neutrino astronomy instruments on the lunar surface. Successful designs for any of these options will require a step‐by‐step process involving close collaboration of many disciplines. Critical issues to be resolved include those relating to communications, data handling, controls, structures, materials, soil mechanics, and foundation engineering, as well as the research and development sequences and logistical problems.     

Macrolevel and Microlevel Frameworks of Experiential Learning Theory in Construction Engineering Education

The experiential learning theory is one of the best-known learning theories in education and has been explored and developed for decades through various studies in higher education. This learning method is expected to provide a significantly better learning environment for engineering subjects, such as construction techniques and design methods and alternatives, which may occur in most of the construction engineering disciplines. Nevertheless, the theory has hardly been used in construction engineering courses. In this study, the authors perform an in-depth review of the learning theory and present a case study, formwork design example, wherein the theory can be explicitly applied in construction engineering education. Research findings reveal students’ responses to the learning theory and lessons learned. Correlation analysis is conducted to explore how students’ performance in learning can be influenced by this learning theory.     

Seismic Behavior of High-Strength Concrete Columns Confined by Fiber-Reinforced Polymer Tubes

The use of high-strength concrete (HSC) in seismically active regions poses a major concern because of the brittle nature of material. The confinement requirements for HSC columns may be prohibitively stringent when ordinary grade transverse steel reinforcement is used. An alternative to conventional confinement reinforcement is the use of fiber-reinforced polymer (FRP) tubes in the form of stay-in-place formwork which can fulfill multiple functions of: (1) formwork; (2) confinement reinforcement; and (3) protective shell against corrosion, weathering and chemical attacks. The use of stay-in-place FRP formwork is investigated as concrete confinement reinforcement for HSC and normal strength concrete (NSC) columns with circular cross sections. Large-scale specimens with 270?mm circular cross-sections and different concrete strengths were tested under constant axial compression and incrementally increasing lateral deformation reversals. FRP tubes were manufactured from carbon fiber sheets and epoxy resin. The results indicate that inelastic deformability of HSC and NSC columns can be improved significantly by using FRP tubes, beyond the performance level usually expected of comparable columns confined with conventional steel reinforcement.     

Shore‐Slab Interaction in Concrete Buildings

Determining the load distribution during construction is one of the critical factors in assessing the structural safety during the construction of reinforced concrete structures. A simplified method was developed in 1963 for determining the construction loads imposed on slabs and formwork. Use of the simplified method assumes that the rigidity of the shores are infinite, and that the relative flexural stiffnesses of floors are all equal. However, it has been found that the results given by the simplified method generally underestimate the actual loads. The first part of this paper discusses a refined method capable of dealing with shore‐slab interaction in framed structures without the assumptions just mentioned. Secondly, a comparative study of the predicted response for framed structures using the two methods is presented. Finally, the refined method is used to explore the influence of the sudden loss of selected shores.     

Microstructual Evolution of a Nb‐Microalloyed Advanced High Strength Steel Treated by Quenching‐Partitioning‐Tempering Process

The recently developed “quenching and partitioning” heat treatment and “quenching‐partitioning‐tempering” heat treatment are novel processing technologies, which are designed for achieving advanced high strength steels (AHSS) with combination of high strength and adequate ductility. Containing adequate amount of austenite phase is an important characteristic of the above steel, and the partitioning treatment is a key step in Q&P or Q‐P‐T process during which the austenite phase is enriched with carbon and achieves thermal stability. However, the microstructural evolution of the steel during the partitioning process is rather complicated. In present study, evolution of complex microstructure in a low carbon steel containing Nb during the Q‐P‐T process has been studied in detail. The microstructural evolution of the steel was investigated in terms of X‐ray diffraction, scanning electron microscope and transmission electron microscope. The experimental results show that the Nb‐microalloyed steel demonstrates a complex multiphase microstructure which consists of lath martensite with high dislocation density, retained austenite, alloy carbide, transition carbide, and a few twin martensite after the Q‐P‐T process. The experimental results can be helpful for the design of Q‐P‐T heat treatment and for the control of mechanical properties of Q‐P‐T steel.     

简介钢大模清水砼在工程应用中的质量控制

根据钢大模清水砼在某高层住宅工程的施工情况，简单介绍钢大模清水砼施工的质量控制措施。