The “Building Code Requirements for Structural Concrete” (“Code”) covers the materials, design, and construction of structural concrete used in buildings and where applicable in nonbuilding structures. The Code also covers the strength evaluation of existing concrete structures. Among the subjects covered are: contract documents; inspection; materials; durability requirements; concrete quality, mixing, and placing; formwork; embedded pipes; construction joints; reinforcement details; analysis and design; strength and serviceability; flexural and axial loads; shear and torsion; development and splices of reinforcement; slab systems; walls; footings; precast concrete; composite flexural members; prestressed concrete; shells and folded plate members; strength evaluation of existing structures; provisions for seismic design; structural plain concrete; strut-and-tie modeling in Appendix A; alternative design provisions in Appendix B; alternative load and strength reduction factors in Appendix C; and anchoring to concrete in Appendix D. The quality and testing of materials used in construction are covered by reference to the appropriate ASTM standard specifications. Welding of reinforcement is covered by reference to the appropriate American Welding Society (AWS) standard. Uses of the Code include adoption by reference in general building codes, and earlier editions have been widely used in this manner. The Code is written in a format that allows such reference without change to its language. Therefore, background details or suggestions for carrying out the requirements or intent of the Code portion cannot be included. The Commentary is provided for this purpose. Some of the considerations of the committee in developing the Code portion are discussed within the Commentary, with emphasis given to the explanation of new or revised provisions. Much of the research data referenced in preparing the Code is cited for the user desiring to study individual questions in greater detail. Other documents that provide suggestions for carrying out the requirements of the Code are also cited.

"building code requirements for structural concrete (aci 318-11) and commentary"

In recent years, there has been an increasing interest in the adoption of emerging sensing technologies for instrumentation within a variety of structural systems. Wireless sensors and sensor networks are emerging as sensing paradigms that the structural engineering field has begun to consider as substitutes for traditional tethered monitoring systems. A benefit of wireless structural monitoring systems is that they are inexpensive to install because extensive wiring is no longer required between sensors and the data acquisition system. Researchers are discovering that wireless sensors are an exciting technology that should not be viewed as simply a substitute for traditional tethered monitoring systems. Rather, wireless sensors can play greater roles in the processing of structural response data; this feature can be utilized to screen data for signs of structural damage. Also, wireless sensors have limitations that require novel system architectures and modes of operation. This paper is intended to serve as a summary review of the collective experience the structural engineering community has gained from the use of wireless sensors and sensor networks for monitoring structural performance and health.

http://www-personal.umich.edu/~jerlynch/papers/SVDReview.pdf

A summary review of wireless sensors and sensor networks for structural health monitoring

This article surveys the research and development of Engineered Cementitious Composites (ECC) over the last decade since its invention in the early 1990's. The importance of micromechanics in the materials design strategy is emphasized. Observations of unique characteristics of ECC based on a broad range of theoretical and experimental research are examined. The advantageous use of ECC in certain categories of structural, and repair and retrofit applications is reviewed. While reflecting on past advances, future challenges for continued development and deployment of ECC are noted. This article is based on a keynote address given at the International Workshop on Ductile Fiber Reinforced Cementitious Composites (DFRCC) - Applications and Evaluations, sponsored by the Japan Concrete Institute, and held in October 2002 at Takayama, Japan.

/pdf/on-engineered-cementitious-composites-ecc-pxfsvmonw5.pdf

On Engineered Cementitious Composites (ECC)

This paper presents the development of the PVA-ECC in the context of material design under the guidance of micromechanical tools. Specifically, this work illustrates how the fiber/matrix interface may be engineered to accommodate the requirements imposed by the micromechanical models, thus highlighting the importance of interface tailoring on the composite performance. This micromechanics-based material design approach is broadly applicable to achieving high-performance composites with low fiber content for cost-effective structural applications.

Interface tailoring for strain-hardening polyvinyl alcohol-engineered cementitious composite (PVA-ECC)

Seismic Rehabilitation of Existing Buildings

Although intensive research related to ultra high-performance concrete (UHPC) and its composition has been conducted over the past 2 decades, attaining compressive strengths of over 150 MPa (22 ksi) without special treatment, such as heat curing, pressure, and/or extensive vibration, has been nearly out of reach. This paper describes the development of a UHPC with a compressive strength exceeding 200 MPa (30 ksi), obtained using materials commercially available in the U.S. market and without the use of any heat treatment, pressure, or special mixer. The influence of different variables such as type of cement, silica fume, sand, and high-range water reducer on compressive strength is evaluated. The test results show that the spread value, measured through a slump cone test on a flow table, is a good and quick indicator to optimize the mixture packing density and thus its compressive strength.

Ultra-High Performance Concrete with Compressive Strength Exceeding 150 MPa (22 ksi): A Simpler Way

Ultra-high performance concrete (UHPC) and ultra-high performance fiber reinforced concrete (UHP-FRC) were introduced in the mid 1990s Special treatment, such as heat curing, pressure and/or extensive vibration, is often required in order to achieve compressive strengths in excess of 150 MPa (22 ksi) This study focuses on the development of UHP-FRCs without any special treatment and utilizing materials that are commercially available on the US market Enhanced performance was accomplished by optimizing the packing density of the cementitious matrix, using very high strength steel fibers, tailoring the geometry of the fibers and optimizing the matrix-fiber interface properties It is shown that addition of 15% deformed fibers by volume results in a direct tensile strength of 13 MPa, which is 60% higher than comparable UHP-FRC with smooth steel fibers, and a tensile strain at peak stress of 06%, which is about three times that for UHP-FRC with smooth fibers Compressive strength up to 292 MPa (42 ksi), tensile strength up to 37 MPa (54 ksi) and strain at peak stress up to 11% were also attained 28 days after casting by using up to 8% volume fraction of high strength steel fibers and infiltrating them with the UHPC matrix

Ultra-high performance concrete and fiber reinforced concrete: achieving strength and ductility without heat curing

This paper investigates the behavior of steel fiber-reinforced concrete (SFRC) beams in shear, as well as the possibility of using steel fibers as minimum shear reinforcement. In the study, 28 simply supported beams with a shear span-to-effective depth ratio of approximately 3.5 were subjected to a monotonically increased, concentrated load. The target concrete compressive strength for all of the beams was 41 MPa (6000 psi). The studied parameters included beam depth, fiber length, fiber aspect ratio, fiber strength, and fiber volume fraction. Three types of steel fibers were considered, all with hooks at their ends. The behavior of beams failing in shear prior to or after flexural yielding was also investigated by varying the longitudinal reinforcement ratio. Compared to reinforced concrete (RC) beams without stirrup reinforcement, the use of hooked steel fibers in a volume fraction greater than or equal to 0.75% led to an enhanced inclined cracking pattern and a substantial increase in shear strength.

Shear Behavior of Steel Fiber-Reinforced Concrete Beams without Stirrup Reinforcement

Tensile strain-hardening, high-performance fiber-reinforced cement composites (HPFRCCs) are being more commonly used in earthquake-resistant structures. This article discusses the applications for HPFRCCs, including for members with shear-dominated response such as beam-column connections, low-rise walls, and coupling beams, as well as flexural members subjected to large displacement reversals. The author determines that HPFRCC materials are effective in increasing shear strength, displacement capacity, and damage tolerance in members subjected to large inelastic deformations. The use of HPFRCCs in beam-column connections allowed total elimination of joint transverse reinforcement while leading to outstanding damage tolerance. Similarly, HPFRCC low-rise walls exhibited drift capacities larger than 2.0% with only minor damage at drifts ranging between 1.0 to 1.5%. The author concluded that one of the most encouraging results was observed in HPFRCC flexural members unreinforced in shear, which sustained reversed cyclic shear stresses as high as 2.7 MPa with up to 6.0% plastic hinge rotation. The use of HPFRCC materials leads to an increase in displacement capacity and outstanding damage tolerance, which make these composites attractive for reducing the need for costly post-earthquake repairs.

High-Performance Fiber-Reinforced Cement Composites: An Alternative for Seismic Design of Structures

Current design provisions in the ACI Building Code for reinforced concrete (RC) coupling beams in earthquake-resistant structures require substantial reinforcement detailing to ensure a stable seismic behavior, leading toreinforcement congestion and construction difficulties. As a design alternative, the use of high-performance fiber-reinforced cementitious composites (HPFRCCs) in coupling beams with a simplified reinforcement detailing was experimentally investigated. To validate this alternative, four coupling beam specimens were tested, including an RC control specimen detailed as per the 1999 ACI Building Code. A precast construction process was proposed for the HPFRCC coupling beams in this study. This construction alternative would lead to significant savings in time and workmanship at the job site, and provide good material quality control. Results from large-scale tests demonstrated the superior damage tolerance and stiffness retention capacity of HPFRCC coupling beams. It was also observed that diagonal reinforcement is necessary to achieve large displacement capacity. However, the transverse reinforcement around the diagonal bars was successfully eliminated due to the confinement provided by the HPFRCC material.

/pdf/experimental-study-on-seismic-behavior-of-high-performance-3knqfrk8t8.pdf

Gustavo J. Parra-Montesinos

Papers

Ultra-High Performance Concrete with Compressive Strength Exceeding 150 MPa (22 ksi): A Simpler Way

Ultra-high performance concrete and fiber reinforced concrete: achieving strength and ductility without heat curing

Shear Behavior of Steel Fiber-Reinforced Concrete Beams without Stirrup Reinforcement

High-Performance Fiber-Reinforced Cement Composites: An Alternative for Seismic Design of Structures

Experimental Study on Seismic Behavior of High-Performance Fiber-Reinforced Cement Composite Coupling Beams