Design Guidelines of FRP Reinforced Concrete Building Structures

The “Design Guidelines of FRP Reinforced Concrete Building Structures” was established in 1993 as one of the final outputs of the research committee on fiber-reinforced plastic (FRP) reinforced concrete building structures organized under the Japanese Ministry of Construction's research and development project titled: “Effective Use of Advanced Construction Materials (1988–92).” These Guidelines are a translation of the Japanese guidelines. They describe the design concept for nonprestressed concrete structures reinforced with FRP rebars, and the calculation equations are all relegated to the commentaries due to lack of design data on FRP reinforced concrete structures. A limit-state design method has been adopted under the guidelines. Among the subjects covered are overview, design method, materials, loads and combination, stress and deformation, ultimate state design, serviceability state design, structural requirement, and testing methods for the tensile strength and bond strength of materials. “The Design Guidelines for FRP Prestressed Concrete Members” is separate from these guidelines.     

Design Guidelines to Accommodate Potential Upgrading of Elevator Systems

Upgrading of elevators is carried out in the interests of maintaining building quality and attaining market rental income. Difficulties experienced in the upgrading of elevator systems indicate a need for development of guidelines to be considered in the initial design of buildings to facilitate upgrading of elevator systems in the future. The focus of this paper is on the development of design guidelines for the potential upgrading of elevator systems in high-rise buildings. A case study as to the difficulties encountered in upgrading an elevator system is included. Some types of upgrading and replacement now possible are reviewed. Responses from 92 design professionals (architects and engineers) in nine countries—namely, the United States, Japan, Canada, Australia, United Kingdom, Singapore, Spain, Saudi Arabia, and Kuwait—to a survey on the upgradeability of elevators have been summarized in the form of guidelines for use by building designers.     

Numerical Analysis of FRP-Composite-Strengthened RC Panels with Anchorages against Blast Loads

Extensive research has been conducted to investigate the blast effects on building structures and the protective design methods using the fiber-reinforced polymer (FRP) strengthening concepts in resisting structural damage and preventing injuries against dynamic explosive impacts. Both numerical and experimental studies have proved the effectiveness of FRP in strengthening structures to resist blast loads. However, problems related to end anchorage, bond length, and premature peeling have been concerns when strengthening structures in flexure or shear using FRP. In this paper, numerical analyses of FRP-composite-strengthened RC walls with or without additional anchors are carried out to examine the structural response under blast loads. The results illustrated that an anchor system is often necessary when using external FRP laminates for strengthening RC walls to prevent premature peeling. This study presents three simulations of RC walls, namely, an unstrengthened RC wall, an FRP-composite-strengthened RC wall with end anchorage, and an FRP-composite-strengthened RC wall with both end anchorage and anchors applied at a minimum spacing across the width and height of the RC wall. Commercial software LS-DYNA is used to carry out the structural response analysis. Numerical results show that anchorage of the FRP sheet may prevent peeling damage and therefore enhances the capacity of the FRP-strengthened RC walls against blast loads. However, anchors result in stress concentration and may cause FRP rupture.     

Dynamic Testing of a Masonry Structure on a Passive Isolation System

Lightly reinforced and unreinforced masonry buildings have not performed well in earthquakes. Evaluation of past performance of masonry structures has led to more stringent design and construction requirements in the current building codes, and has raised concerns about the performance of existing lightly reinforced and unreinforced masonry buildings in future earthquakes. Base isolation has been shown to be effective in reducing damage to large building structures, and appears to be particularly effective in protecting stiff masonry structures. Using the base isolation principle, Kansas State University’s stiffness decoupler for the base isolation of structures (SDBIS) was designed to effectively reduce the acceleration and force transferred into a building superstructure during a seismic event. The sliding system uses a passive method to provide damping and to dissipate some of the kinetic energy to reduce relative displacements. In addition, the SDBIS system includes a self-centering element that will recover the majority of the induced displacement and provide resistance to overturning. In order to apply the SDBIS system to the masonry building industry, dynamic testes were performed to evaluate the structural response of a full-size one-story masonry model that was supported by the SDBIS system. Acceleration time-history results are presented for dynamic tests using the July 21, 1952 Kern County earthquake, Station 1095 Taft Lincoln School record, the May 19, 1940 Imperial Valley earthquake, Station 117 El Centro Array #9 record, the February 9, 1971 San Fernando earthquake, Station 279 Pacoima Dam record, and the January 17, 1994 Northridge earthquake, Station 24436 Tarzana Cedar Hill record ground motions. Test results show the system is effective when used with a masonry structure.     

Wind Damage to Masonry Buildings

An examination has been made of the methods of construction of masonry‐walled buildings, and their performance in severe windstorms. Particular emphasis was placed on low‐rise buildings using unreinforced concrete block walls and light roofs, which suffer the majority of wind damage. It is shown that traditionally built, nonengineered buildings have become more wind sensitive in recent years as the result of a reduction in the number of internal walls and a lowering of roof weights. Empirical design procedures regarding wall height‐to‐thickness ratios and roof anchorage have not changed to reflect this increased sensitivity, leaving many modern, nonengineered buildings with insufficient wind resistance. Professionally designed structures often have a similar structural form to traditionally built structures, since the same empirical design rules are often used to size walls and roof anchors. The longer roof spans in these buildings render them even more sensitive to wind uplift loads, and subject to progressive collapse. The inadequacies of present building code requirements are discussed and recommendations for improvements are made.     

Design Philosophy Issues of Fiber Reinfored Polymer Reinforced Concrete Structures

The conventional design philosophy for reinforced concrete (RC) relies heavily on the ductile properties of steel. These ductile properties are used as a “fuse” and conceal the large uncertainty in the determination of modes of failure caused directly by concrete. Current design guidelines for fiber reinforced polymer (FRP) RC structures have inappropriately adopted the same design philosophy used for steel RC, leading either to the adoption of conservative safety factors or reduced structural reliability. A reliability-based analysis of FRP RC beams shows that the current, very conservative partial safety factors for FRP reinforcement on their own do not influence the structural safety of overreinforced concrete elements. Proposals are made for the modification of the material partial safety factors to achieve target safety levels.     

Unique Requirements of Building Information Modeling for Cast-in-Place Reinforced Concrete

The building information modeling (BIM) tools that have matured for structural steel and precast concrete construction are not suitable for production modeling of cast-in-place (CIP) reinforced concrete structures. The main reason is that CIP structures are monolithic in nature, as opposed to the discrete objects that are typical of steel and precast. A consortium of 12 major contractors and design firms collaborated over a one-year period to formulate the functional requirements for development of a BIM tool for cast-in-place reinforced concrete. The functional requirements were derived from a process model used to scope and understand the processes surrounding reinforced concrete design and production. The functional requirements were finally expressed as a set of object schemas, defining relations, methods, and attributes needed. These are essential for software companies to incorporate in their BIM tools to provide for the unique needs of modeling CIP structures.     

Agricultural Product Loads and Warehouse Failures

Two manufactured metal building warehouses loaded with agricultural products failed in service. Inspection revealed considerable damage to the structure and the foundation. The building owner filed suit against the building supplier, the building erector, and the soils testing laboratory whose engineer had designed the foundation. The agricultural product imposed substantial outward lateral pressures on the walls of the structures. Review of the available design documents indicated that these loads had not been accounted for in design. A structural analysis revealed that elements of the structure were underdesigned for the agricultural product loads. In addition, the foundation did not have any slab reinforcement to resist the loads. To prevent similar failures, these loads must be accounted for in design. The steel structure design and foundation design were both deficient. A contributing factor was the lack of communication between the designer of the structure and the designer of the foundation, due to the lack of a single engineer of record to take responsibility for the buildings.     

Geosynthetic Reinforced Multitiered Walls

Current design of mechanically stabilized earth (MSE) walls shows that the tensile stress in the reinforcement increases rapidly with height. To take advantage of both the aesthetics and the economics of MSE walls while considering high heights, multitiered walls are often used. In such walls, an offset between adjacent tiers is used. If the offset is large enough, the tensile stress in the reinforcement in lower tiers is reduced. However, a rational design methodology for multitiered MSE walls that accurately predicts wall performance is lacking. AASHTO 98 design guidelines are limited to two-tiered walls with zero batter. In fact, this design is purely empirical using “calibrated” lateral earth pressures adopted from limited guidelines developed for metallic strip walls. Empirical data available for multitiered walls is limited and it seems to be nonexistent for geosynthetic walls. In fact, generation of an extensive database for tiered walls is a major challenge since there are practically limitless configurations for such systems. As an alternative, this study presents the results of parametric studies conducted in parallel using two independent types of analyses: One is based on limiting equilibrium (LE) and one on continuum mechanics. The premise of this work is that if the two uncoupled analyses produce similar results, an acceptable level of confidence in the results can be afforded. This confidence stems from the fact that LE is currently being used for design of reinforced and unreinforced slopes (i.e., having a slope angle less than 70°); the agreement with continuum mechanics facilitates its extrapolation to use in MSE walls. Parametric studies were carried out to assess the required tensile strength as a function of reinforcement length and stiffness, offset distance, the fill and foundation strength, water, surcharge, and number of tiers. It is concluded that LE analyses may be extended to the analysis of multitiered walls.     

Voluntary guidance for the development of tissue-engineered products

Tissue Engineering is an emerging field of medical research in which there is tremendous activity. Many of these products rely on the use of a cellular component co-formulated with a natural or synthetic biomaterial. At this time, though, there are no consensus safety or efficacy standards for tissue-engineered products. We describe general approaches for assessment of the safety and efficacy of cell-based tissue-engineered products which will lead to reliable medical products for human use. This article provides a general summary of the factors that should be considered in the design and development of cell- and tissue-based products. Seven areas are considered: cell and tissue sourcing; cell and tissue characterization; biomaterials testing; quality assurance; quality control; and nonclinical testing and clinical evaluation. Factors relevant to these areas have been discussed to provide a set of recommendations on which development of products can be standardized. Where relevant, the discussion has been separated in each area to issues that are independent or dependent on cell source. Also, examples are provided of how these guidelines would be applied to two product types that represent somewhat extreme ends of the spectrum for tissue engineering applications. The first example is a product whose mechanism of action is to provide locally-acting structural repair or enhancement in vivo. The second example is a product whose mechanism of action involves systemically distributed physiologically or pharmacologically active products. In general, we have limited the discussion of product types to those that are implanted into the patient for relatively long periods of time. We believe that adoption of these voluntary guidelines would lead to products that are more consistent in quality and performance as well as more rapidly developed.     

底部两层框架——抗震墙砖房抗震设计探讨

根据《建筑抗震设计规范》（GBJ11－89）中有关底层框架－抗震墙砖房的规定,从工程实用的角度出发,探讨了度部两层框架－抗震墙砖房的设计要点,并从过渡层楼板,构造柱的设置、抗震墙的设置、结构形式、抗震墙的构造、钢筋混凝土圈梁、过渡层外纵墙、上部承重砖墙等的构造设计方面提出了抗震构造措施。     

高大空间砌体房屋设计实例

对于在功能和使用上要求层高较高及空间较大的砌体房屋 ,在设计时提出在窗间薄墙处设置构造受力柱及增设圈梁的方法。可提高建筑物抵抗变形的能力和抗剪强度 ,满足安全性、适用性、耐久性等的要求     

典型铁合金渣的资源化综合利用研究现状与发展趋势

典型铁合金渣（硅锰渣,镍铁渣,铬铁渣）面临产量大、利用率低等紧迫问题。目前,我国对铁合金渣的利用主要集中于水泥、混凝土等传统建筑材料,但是其能耗大和产品价值相对局限。随着市场需求以及环保能源意识的提高,对铁合金渣的综合利用不断从传统建筑材料向具有低能耗、高附价值的新型材料方向转型。本文简要介绍了这三种典型铁合金渣的来源及其分类情况,系统分析了它们的化学成分及其矿物组成的差异性,重点概述了它们在水泥、混凝土等传统建筑材料,以及在地质聚合物、无机矿物纤维、微晶玻璃、人造轻骨料、耐火材料、新型墙体材料、特色功能陶瓷等新型材料领域应用的国内外最新研究进展,分类总结不同种类铁合金渣应用于不同材料的优缺点,并对其今后的利用方向与途径提出了展望,指出了要进一步研究并突破主要利用方式的限制瓶颈、制定并完善相关应用及污染控制标准、以及深入开发并推广高附加值产品的重点发展方向。      

Utilization of Precast Concrete Elements in Building

Precast concrete components can be used in building construction within a comprehensive “closed” system, or as separate elements in conjunction with any building method. The feasibility of this second possibility was examined within the framework of a conventional building system and the following alternatives of elements utilization: prestressed modular floor slabs, exterior walls, and a combination of slabs and exterior walls. Each of these alternatives was compared to the conventional system without precast elements. The following criteria were used as a basis for the comparison: the labor requirement, the direct building cost (labor and materials), the construction time, and other considerations of more subjective nature. The findings of the study indicated that the utilization of precast elements might considerably reduce the labor requirement on site, and the project construction time. The direct building costs were almost unaffected by the alternative solutions.     

Preventing Disproportionate Collapse

“Disproportionate collapse” is structural collapse disproportionate to the cause; it is often, though not always, progressive, where “progressive collapse” is the collapse of all or a large part of a structure precipitated by damage or failure of a relatively small part of it. There have been many attempts to develop design guidelines and criteria that would reduce or eliminate the susceptibility of buildings to this form of failure. In recent years, the particular focus has been on the prevention of progressive collapse due to deliberate attack. The present study suggests, however, that these guidelines and criteria may be of limited value. Arguably the most important deficiency in the state of the art of design to prevent disproportionate or progressive collapse is uncertainty about the design event: We have the technology now to design for almost anything, but most recent building failures due to explosions and terrorist attacks have involved insults to the building not anticipated in design guidelines and criteria.     

High Strength Low Alloy (HSLA) Steels in Building Construction

Majority of the buildings,including industrial buildings,are constructed using either structural steel (plates and structural shapes) or deformed bar steel reinforced concrete.Such buildings,however,must be designed to be safe and serviceable during construction and during use and occupancy.These objectives can be easily achieved by the use of steels having superior mechanical properties,ductility,weldability,fire resistance,etc.Over the years,the steel industry has made improvements in steel making technologies resulting in high strength low alloy (HSLA) steels with superior steel properties well suited for building construction.First part of this paper presents the structural design considerations,and the constructional considerations associated with the building structures in general,and steel structures in particular.This second part of the paper looks at the acceptance criteria for HSLA steels for North American building codes and construction.The third part of the paper presents the structural properties of currently available HSLA steels for building construction.The discussion focuses on hot-rolled structural steel shapes as well as deformed steel bars for concrete reinforcement.The paper argues that Niobium microalloying is the key to achieving superior properties in such steels.     

Application of a Virtual Environment System in Building Sciences Education

This paper includes a brief review of the application of virtual environments in building sciences and presents details of the application of virtual structural analysis program (VSAP), a virtual reality based structural analysis system developed at Virginia Polytechnic Institute and State Univ. (Virginia Tech), in education and practice. Different elements and modeling options in addition to the implementation of two major earthquakes within VSAP for the demonstration of the behavior of building structures during seismic activities are presented. Modifications to the VSAP in order to simulate progressive collapse of building structures are discussed. Different versions of this system were used in architectural structures courses at Virginia Tech. Results of feedbacks from students in these classes are presented. From these results it is concluded that the VSAP can be used effectively as an experiential teaching∕learning tool in classroom settings. Possible applications of VSAP as a design and research tool in construction industry are discussed.     

Work Structuring to Achieve Integrated Product–Process Design

This paper presents “work structuring,” a term used to describe the effort of integrating product and process design throughout the project development process. To illustrate current work structuring practice, we describe a case study involving the installation of door frames into walls in a prison. We analyze why various problems existed. To improve the work structuring effort, we apply the “five whys” to develop local and global fixes for the system of precast walls and door frames. The five whys is a technique to elicit alternative ways of structuring work without being constrained by contractual agreements, traditions, or trade boundaries. We discuss the importance of dimensional tolerances in construction and how these affect the handoff of work from one group of workers to the next. We argue that these constraints and tolerance management practices are so embedded that project participants can miss opportunities to better integrate product and process design. We propose shifting the focus of work structuring from maximizing local trade efficiency to improving overall performance in the delivery system of a capital project.     

Construction of a Semi‐Prefabricated Masonry Facade

One of the crucial problems that faces designers, construction managers, general contractors, and subcontractors is creating the most appealing facade of a building at the most cost‐effective price, while satisfying an owner's goal of exploiting the enclosed space to maximum advantage. A brick facade has long been considered a durable and aesthetic solution for the exterior walls. A stud wall with gypsum board sheathing is today's most economical and widely used interior perimeter material. The development of innovative construction techniques that combine this exterior facade with interior perimeter materials in the most cost‐effective and time‐effective manner is the object of continuing trial and error. The industrialization of construction components has long been considered but, as yet, is not widely used, although its future appears bright. This paper analyzes the advantages of a semi‐prefabricated facade based on specific experience.     

Ductile Anchorage for Connecting FRP Strengthening of Under-Reinforced Masonry Buildings

Fiber-reinforced polymer (FRP) composites have been examined as a convenient and cost-effective means of strengthening unreinforced masonry structures. Seismic design in the United States is almost entirely based on the assumption that the structural system provides a ductile failure mode. FRP strengthened masonry walls inherently have brittle failure modes due to the nature of the strengthening system. The concept explored in this article is the introduction of ductility using a hybrid strengthening system. This involves the placement of structural steel or reinforcing steel at critical locations in the lateral force resisting system. This article presents the testing and analysis of a ductile structural steel connection that can be used to strengthen the connection of FRP strengthened shear walls to the foundation. The connection also increases energy dissipation. Results indicate that a ductile failure mode can be attained when the connection is designed to yield prior to the failure of the FRP strengthening.