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  September 2014  
 
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Concrete International September 2014 No. 9 Complete Issue
Design & Detailing

A Tool for Simplified Design of Buildings
ACI Committee 314 has adopted and developed “Guide to Simplified Design for Reinforced Concrete Buildings” (ACI 314R-11). The guide presents design information in an order that follows a typical design process, with procedures introduced as they will be needed in the course of the design of a low-rise building. ACI Committee 314 has also sponsored full-day design seminars for structural engineers, architects, and contractors. The seminars include detailed design examples to help attendees to understand the spirit of the design guidelines presented in the Guide. Additional seminars are being planned.

Proposed Revisions to the Strength Reduction Factor for Axially Loaded Members
Interaction diagrams computed for flanged sections according to ACI 318-11 provisions can result in unreasonable design strengths. In particular, the design interaction diagram can show, in some cases, increased axial load capacity with increased eccentricity at high axial loads. This anomaly is an unintended consequence of the changes to the definition of the strength reduction factor (?) adopted in 2002 and that remains in effect today. The article presents a modified ?-factor definition based on both net tensile strain and axial load. The proposed definition corrects the anomalous results in the design interaction diagram for flanged sections and has the same format as that of the 2011 Code.

The Santa Fe II Tower
With a height of 167 m (548 ft), the Santa Fe II tower in Mexico City is the tallest residential building in all of Mexico. The tower comprises eight lower levels for parking, 44 levels for residential housing, and a rooftop helipad. Other characteristics of the building include a unique façade with many discontinuous white columns and a central core design. The central core transfers most of the lateral loads, allowing elimination of all interior columns. There are only nine columns on the perimeter of the building: four located at the corners of the floor plate, three centered on three of the building sides, and two located near the third points of one side.

Predicting Service Life of Steel-Reinforced Concrete Exposed to Chlorides
Although computer models for predicting the service life of reinforced concrete exposed to chlorides have been developed and enhanced during the past 15 years, there are many real-world considerations that complicate accurate and representative modeling of field structures. Recent advances in both concrete-specific models and general-purpose modeling platforms are permitting detailed investigations of the influences of many of these parameters. The article reviews these real-world considerations and provides some examples of how they are being addressed via advanced modeling capabilities.

ACI Adds Masonry Testing Technician Certification
ACI’s Certification Department is introducing two new masonry-related certification programs in 2014: the Masonry Field Testing Technician and the Masonry Laboratory Testing Technician. Developed by ACI Subcommittee C601-C, Masonry Testing Technicians (MTT), the programs will be available starting September 1. They will provide certification to those technicians working in the laboratory or in the field who can demonstrate technical knowledge and skills for sampling and testing of masonry units, mortars, grout, and prisms.

Underwater Natural Marvel Modeled in Concrete
A diver’s eye view of Point Lobos Marine Reserve without getting wet

Vikings Stadium Engineering Firms Reflect Diversity
Facilities Authority ensures local participation

The International Parking Institute 2014 Awards of Excellence
The recipients of the International Parking Institute (IPI) 2014 Awards of Excellence competition demonstrate that today’s parking garages and lots are likely to be visually appealing and sustainable.

Recap of Recent Industry Awards
PTI, NRMCA, and fib honor achievements in concrete

A More Sustainable Unshrinkable Fill
Unshrinkable fill is a type of controlled low strength material (CLSM) used in lieu of traditional backfill. While it is normally produced using aggregates derived from bedrock, gravel, or natural sand sources, the low maximum strength requirement indicates that alternative materials could be used. The research described in this article investigates the use of reclaimed concrete aggregate (RCA) as a sustainable and economical alternative to the newly extracted materials used in U-fill mixtures. The RCA was produced by crushing returned ready mixed concrete that had been allowed to harden.

Concrete Q & A: Tolerances for Vertical Alignment
Q. Where can I find tolerances for vertical alignment of 24 in. (610 mm) long dowels placed in 2008? Figure R2.2.10.3 of ACI 117-061 shows ±1/4 in. (6 mm) vertical deviations over lengths that are less than or equal to 18 in. (457 mm).

 


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