SEANepThesis

Learning from the past

Recent two earthquakes one in Bhuj, west India and other in Bam, southern Iran has caused large scale human and property loss. The main cause behind the catastrophe can be attributed to building destruction.   Despite known seismicity of both the regions and availability of knowledge on aseismic construction, there were obvious reasons that hindered seismic protection in the region. Some of these are socio-cultural reasons, techno-legal regime, lack of knowledge dissemination mechanism, lack of understanding between demand and supply mode to name with. This paper attempts to explore these attributes and its implication to Nepal which is located in one of the most seismically active belts in the world.

Concepts and Realization of Continuous Fiber Flexible Shear Reinforcement

Minimization of workmanship deficiency in infrastructure construction industry has always been desirable. One of the listed major causes of the failure of many reinforced concrete piers during Hyogoken-Nanbu earthquake in 1995 was the construction workmanship [1]. Earthquake Resistant Design Codes in Japan, January 2000 [2] specifies arrangement of shear reinforcement for most concrete bridge piers at a spacing of no longer than 150mm against earlier specifications3 of 300mm. Furthermore, intermediate ties are also specified to be at the same closer spacing as ties for increasing ductility of piers. This means an increased need of precautions must be exercised in order not to lose construction workmanship.

Major cracks in the concrete like diagonal shear cracks, have tendency to separate the cracked portion of the concrete from each other; thus reducing the strength of concrete in the compressive zone under flexure with reduced energy absorption characteristics. Stirrups provide restraint against such a tendency of separation by acting as a vertical tensile member. For the proper development of confining action of stirrup, semicircular or acute-angled hook is necessary at the end of tie surrounding the longitudinal reinforcement. To the speedy and efficient construction technology, the arrangement of crowded lateral ties and provision of standard hook anchorage poses one of the possible factors of reduced workability.

Lately, carbon fiber has been used as new materials for construction especially for strengthening existing weak piers. But, it has seldom been used as internal shear reinforcement. Usual Fiber Reinforced Polymer (FRP) rods, unlike steel, are difficult to be formed into desired shape of shear stirrups in the construction field. Carbon fibers conduct electricity, so its direct contact with steel might give problem of corrosion. As a probable solution to all the stirrup-related difficulties, a research team at Hybrid Structures Laboratory, Hokkaido University, in collaboration with researcher from Nippon Steel Composites had come up with an innovative form of utilizing carbon fibers as continuous flexible shear reinforcement, the CFFR, an acronym for Continuous Fiber Flexible Reinforcement [3], [4], [5]. In this talk program, Construction Technology, Failure modes, Bent-portion Non-linearity of CFFR (and its implementation in FEA) will be discussed along with specialized member level and material level experimental database.

Use of Reinforcing Steel

Rebar is an integral part of civil engineering and plays a very important role in construction works.  Since concrete is low in tensile strength, reinforcing steel fulfills that shortcoming of concrete.  Not only does reinforcing steel help in tensile strength, but it also aids in flexural strength, torsional strength, and ductility of the concrete.  Different stresses due to temperature changes and environmental changes cause the concrete to expand and contract in different manners.  The reinforcing steel holds the concrete together stronger than if the concrete are not reinforced.

Nowadays we see lot of pictures of collapsed buildings and structures which shock us deeply. The structural failures do not bring only material and financial loss but also causes unnecessary loss of innumerable human lives. As professionals and human beings, we have responsibility towards our society and we feel that we have not acted properly. In general, failures of structures are caused mainly due to flowing three reasons:

• Deficiency in design
• Poor quality of building materials, probably cement & rebar
• Deficiency in implementation of construction