Concrete structural members

Adhesion Strength of Joints of Precast Silicate Polymer Concrete Structural Members [5]... 

Concrete Structure Member, Journal Scientific Israel Technology Advanced 13, no. 4 (2011) 96-102. With permission. 

Development of FRP (Fiber-reinforced polymer) -reinforced polymer concrete structural members [81-82]... 

Pultruded FRP bars instead of steel ones for tensile reinforcement of concrete structural members. 

In all blast-resistant structures (steel, concrete, or masonry) special attention should be given to the integrity of connections between structural elements up to the point of maximum response. For example, it is important to prevent premature brittle failure of welded connections to avoid stress concentrations or notches at joints in steel structures and to provide ductile reinforcement detailing in concrete/masonry structure connections. For all materials, it is recommended that connections be designed to be stronger than the connected structural members such that the more ductile member will govern the design over the more brittle connection. 

Steel, aluminum, concrete, and other materials that form part of a process or building frame are subject to structural failure when exposed to fire. Bare metal elements are particularly susceptible to damage. A structural member undergoes any combination of three basic types of stress compression, tension, and shear. The time to failure of the structural member will depend on the amount and type of heat flux (i.e., radiation, convection, or conduction), and the nature of the exposure (one-sided flame impingement, flame immersion, etc.). Cooling effects from suppression systems and effects of passive fire protection will reduce the impact. 

The bottom of the baseplate between structural members shall be open if the baseplate is designed to be installed and grouted to a concrete foundation. Accessibility shall be provided for grouting under all load-carrying members. The bottom of the baseplate shall be in one plane to permit use of a single level foundation. 

Raw sulfur has a high coefficient of thermal expansion. A value of 55 X 10 6/K at room temperature was found during the present work. If similar values were found in concretes, temperature differences between different parts of a single structural member would lead to high stress concentrations. Fillers reduce the value considerably in sulfur mortars values varied between 21 and 58 X 10"6/K and between 11 and 29 X 10 6/K in sulfur concretes depending on the composition of the fillers and mix design. 

Strength. The strength of plain concrete depends on several factors proportioning of ingredients, particularly water-cement ratio, time, temperature, and method of curing. A rich mixture (1 IMor 1 1 2) develops a compressive strength of approximately 4,000 psi for use in thin and heavily reinforced concrete structural beams and columns. Floor slabs and structural members requiring 2,000 to 3,000 psi concrete are made from a 1 2 3H mixture, while a lean mixture of 1 3 6 is used for massive concrete abutments or fills. 

Typical PlacemeTd Specifucaiions for Reinforcement. The minimum clear distance between parallel bars should be 2 times the side dimensions for square bars and 1 4 times the diameter for round bars. Reinforcement of footings and columns should be sealed with at least 3 in. of plain concrete on the ground cont"ct surface. Surfaces exposed to weathering should have at least a 2-in. protective layer of plain concrete. Structures subject to fire hazards should have a fire-resistant coating of concrete 1 in. thick for slabs and 2 to 4 in. thick for structural members. 

Several promising sacrificial anodes such as thermal-sprayed zinc, thermal-sprayed Al-Zn-In, zinc hydrogel, and zinc mesh pile jacket have been developed for use in CP of substructure members especiaUy in marine environments. Industries in some states in cooperation with FHWA carried out some developments and identification of some anodes suitable for impressed current CP of inland concrete structures. 

Even at densities of the order of 5 Amp/m the possible hydrogen-induced cracking does not favor electrochemical method of chloride removal from prestressed concrete structures. Pilot scale treatments showed it to be feasible and simple to treat full-sized reinforced-concrete bridge members, although difficult to conduct the treatment on concrete piers. One of the main difficulties is to predict the duration of treatment to reach the chloride levels to acceptable levels where corrosion is under control. Preliminary studies suggested a total charge of 600-1,500 A-h/m with a total treatment time of 10-50 days. 

Maalej, M. and Li, V.C. (1995). Introduction of strain-hardening engineered cementitious composites in design of reinforced concrete flexural members for improved durability. ACI Structural Journal, 92(2) 167-176. 

K. Satoh and K. Komada Study on peeling behavior of bond interface of concrete members retrofitted by surface overlaying with polymer cement mortar (in Japanese). JSCE Journal of Materials, Concrete Structures and Pavements Vol.59, No.732 (2003), pp.77-87. 

Structural members made of concrete have to be strengthened with reinforcements, usually made of steel. To prevent the rebar from corrosion, concrete covers of more than 35 mm are required according to current design codes, e.g. CEB-FIB Model Code 1990 [1]. The use of corrosion-resistant technical textiles reduces concrete covers significantly, and thus allows for light-weight and slender concrete structures. 

Virmani, Y.P. (1997). Corrosion Protection Systems for Construction and Rehabilitation of Salt-contaminated Reinforced Concrete Bridge Members. Proceedings of the International Conference on Repair of Concrete Structures - From Theory to Practice in a Marine Environment, Svolvaer, Norway, pp 107-122. 

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