Energy-Based Penetration Model for Local Impact- Damaged Concrete Members

Title: Energy-Based Penetration Model for Local Impact- Damaged Concrete Members

Author(s): Hyeon-Jong Hwang, Sanghee Kim, and Thomas H.-K. Kang

Publication: Structural Journal

Volume: 114

Issue: 05

Appears on pages(s): 1189-1200

Keywords: impact load; kinetic energy; penetration; perforation; residual velocity

Date: 9/1/2017

Abstract:
Numerous empirical equations have been developed that predict the local damage of a concrete target subjected to an impact load. This is in part due to the fact that the local failure mechanism of concrete on collision is complicated. In this present study, an energy-based model is analytically proposed to better estimate the penetration depth and residual velocity of a projectile. The resistant energy of the concrete target and kinetic energy of the projectile are considered for spalling, tunneling, and scabbing failure modes. The predicted penetration depth and residual velocity are then compared to those from 414 existing test specimens. Based on the comparison, the proposed model predicts a variety of test results with reasonable precision. Further, to prevent the perforation failure of a concrete target, a safety factor is proposed that can be applied to the developed model.

Shear Performance of Pretensioned Concrete I-Girders Employing 0.7 in. (17.8 mm) Strands

Title: Shear Performance of Pretensioned Concrete I-Girders Employing 0.7 in. (17.8 mm) Strands

Author(s): A. Katz, H. Yousefpour, H. Kim, R. Alirezaei Abyaneh, J. Salazar, T. Hrynyk, and O. Bayrak

Publication: Structural Journal

Volume: 114

Issue: 05

Appears on pages(s): 1273-1284

Keywords: 0.7 in. (17.8 mm) strands; anchorage-induced shear failure; development length; horizontal shear failure; pretensioned; transfer length

Date: 9/1/2017

Abstract:
An experimental program was conducted to study the effects of using 0.7 in. (17.8 mm) diameter prestressing strands on the performance of pretensioned concrete I-girders under shearcritical loading. Four full-scale Texas bulb-T girders (Tx-girders) with different concrete release strengths, member depths, shear span-depth ratios, and strand patterns were tested. The mild-steel reinforcement in the specimens was detailed according to the common practice in Texas for girders fabricated using conventional, smaller-diameter strands. All specimens exhibited considerable strand slip prior to failure. In three of the specimens, shear failure also resulted in prominent horizontal cracking at the interface between the web and the bottom flange. However, distributed yielding of the stirrups was confirmed in all specimens, indicating shear-tension failure. The capacities of all specimens were conservatively estimated using the general procedure in the AASHTO LRFD Bridge Design Specifications and the detailed method in ACI 318-14 provisions.

Tests of Continuous Concrete Slabs Reinforced with Basalt Fiber-Reinforced Plastic Bars

Title: Tests of Continuous Concrete Slabs Reinforced with Basalt Fiber-Reinforced Plastic Bars

Author(s): Ilker Fatih Kara, Mehmet Alpaslan Köroglu, and Ashraf F. Ashour

Publication: Structural Journal

Volume: 114

Issue: 05

Appears on pages(s): 1201-1213

Keywords: basalt fiber-reinforced polymer; continuous slab; cracking; flexural failure; reinforced concrete; shear failure

Date: 9/1/2017

Abstract:
This paper presents experimental results of three continuously supported concrete slabs reinforced with basalt fiber-reinforced polymer (BFRP) bars. Three different BFRP reinforcement combinations of over and under reinforcement ratios were applied at the top and bottom layers of continuous concrete slabs tested. One additional concrete continuous slab reinforced with steel bars and two simply supported slabs reinforced with under and over BFRP reinforcements were also tested for comparison purposes. All slab sections tested had the same width and depth but different amounts of BFRP reinforcement. The experimental results were used to validate the existing design guidance for the predictions of moment and shear capacities, and deflections of continuous concrete elements reinforced with BFRP bars. The continuously supported BFRP reinforced concrete slabs illustrated wider cracks and larger deflections than the control steel-reinforced concrete slab. All continuous BFRP reinforced concrete slabs exhibited a combined shear-flexure failure mode. ACI 440.1R-15 equations give reasonable predictions for the deflections of continuous slabs (after first cracking) but stiffer behavior for the simply supported slabs, whereas CNR DT203 reasonably predicted the deflections of all BFRP slabs tested. On the other hand, ISIS-M03-07 provided the most accurate shear capacity prediction for continuously supported BFRP reinforced concrete slabs among the current shear design equations.

Effect of Steel Fibers on Minimum Shear Reinforcement of High-Strength Concrete Beams

Title: Effect of Steel Fibers on Minimum Shear Reinforcement of High-Strength Concrete Beams

Author(s): Chul-Goo Kim, Hyerin Lee, Hong-Gun Park, Geon-Ho Hong, and Su-Min Kang

Publication: Structural Journal

Volume: 114

Issue: 05

Appears on pages(s): 1109-1119

Keywords: high-strength concrete; minimum shear reinforcement; reinforced concrete; shear strength; steel fiber; stirrup

Date: 9/1/2017

Abstract:
Minimum shear reinforcement is required for reinforced concrete (RC) flexural members to prevent brittle shear failure considering uncertainty of concrete shear strength in current design codes. In ACI 318-14, the use of steel fibers for minimum shear reinforcement is permitted within limited ranges of design parameters such as a concrete compressive strength lower than 40 MPa (5.8 ksi), beam depth smaller than 600 mm (24 in.); and fiber volume ratio over 0.75%. In this study, the effect of steel fibers on the shear strength was studied for high-strength concrete beams (60 MPa [8.7 ksi]). The main test parameters were the concrete strength, use of steel fibers, and use of stirrups. The test results showed that steel fibers with a volume fraction of 0.75% significantly increased the shear strength of high-strength concrete beams. This is mainly because the high-strength concrete increased the contribution of the steel fibers by increasing the tension zone depth. Such effect of steel fibers was confirmed by results from previous studies. The test results also showed that the limitation of concrete strength can be increased from 40 to 60 MPa (5.8 to 8.7 ksi).

Structural Responses of External Post-Tensioned Tendons to Increasing Localized Damage

Title: Structural Responses of External Post-Tensioned Tendons to Increasing Localized Damage

Author(s): Jun Ki Lee

Publication: Structural Journal

Volume: 114

Issue: 05

Appears on pages(s): 1155-1166

Keywords: bridges; corrosion; damage; post-tensioning; stress redistribution; tendon

Date: 9/1/2017

Abstract:
This paper presents an experimental investigation of the structural effect of moderate to severe levels of localized damage in external post-tensioned tendons. Eight large-scale specimens with multiple seven-wire strands were fabricated, and the wires in the strands were consecutively fractured until a severe level of damage was identified using three controlled methods: accelerated galvanic corrosion, fatigue loading, and direct exposure to an acid solution. During this process, the structural effects induced by the applied damage were monitored based on visual inspection, acoustic sensors, transverse displacement, and vibration signals, depending on the experimental conditions. Experimental results showed that the behaviors of the damaged specimens were continuously governed by the residual tensile force, which was appreciably redistributed after wire fracture(s) in the strands, especially when the level of damage was moderate. As a result, the rate of decrement in the structural response became larger as the level of damage increased; however, they were not as sensitively influenced relative to the level of applied damage.

Effect of Temperature on Chloride Diffusion in Saturated Concrete

Title: Effect of Temperature on Chloride Diffusion in Saturated Concrete

Author(s): B. Touil, F. Ghomari, A. Bezzar, A. Khelidj, and S. Bonnet

Publication: Materials Journal

Volume: 114

Issue: 05

Appears on pages(s): 713-721

Keywords: activation energy; coefficient of migration of chlorides; pozzolan; temperature

Date: 9/1/2017

Abstract:
The degradation of reinforced concrete (RC) structures exposed to marine environments is largely due to the transfer of chloride ions through the material. The prediction of the penetration of these ions in the concrete by the diffusion coefficient is a fundamental indicator for the characterization of its durability. Tests simulating chloride diffusion in saturated areas are developed at a constant temperature; however, in reality, the temperature fluctuates with the seasons and diurnal variations. To simulate the coupled temperature diffusion of chloride in RC structures in permanent contact with the Mediterranean Sea, an experimental program was developed in the laboratory to assess the migration coefficients of a pozzolanic concrete (CPZ10) and compared to ordinary concrete (OC). The tests of migration are made under an electric field, at different temperatures, from 5 to 50°C (41 to 122°F). Also, a study of the activation energy was made and compared with the Arrhenius theory. The test results showed that the migration coefficient of concrete increases with increasing temperature. The activation energy values of natural pozzolan incorporated concretes were lower than OC.

Steps In Construction of Residential Building 

Construction of residential building needed following paper work before the beginning of actual construction. These steps are;

Preparation of drawings as per necessities of customers.
Estimation of fabric value, labor value & contingencies.
Approval of drawings & estimates from shopper.
Approval of drawings from town Development Authority. it's most significant as a result of residential building drawings ought to meet the authority outlined rules.
Start of construction work either through contractor or labor employed on routine.
Marking of plot boundaries.
Cleaning of plot.
Preparation of web site layout as per drawing.
After the completion of documentation work, the particular construction on plot begins. Following ar the steps;

EARTH WORK

Generally excavation is distributed for the development of wall foundations. Excavation ought to be distributed as per the drawings outlined lengths & widths. once excavation, layout the inspiration and backfill the remaining excavated space around foundation with soil.

Floor levels of residential buildings ar over the natural ground level. Fill the world with soil up to floor levels and compact the soil. currently earth work of residential building is finished.

CONCRETE add FOUNDATION

It is terribly necessary to see the degree of foundation before concrete work. There ar patches wherever excavated depth slightly exceeds and contrariwise. Level the inspiration base to same level. currently pour the concrete as per drawing specs. usually concrete of quantitative relation 1:4:8 is employed for foundation. generally it's even 1:5:10 or 1:6:20.Here 1:4:8 means;

1 half cement per boxy

4 elements of sand per boxy

8 elements of coarse aggregates

Depth of foundation varies from 9” to 18” and ordinarily for many of the cases it's thought of as 12’’ depth. Keep foundation breadth equals to its depth.

DAMP PROOF COARSE (D.P.C)

To protect walls from wet, a layer of damp proof coarse material is set down at floor level. Thickness of this concrete layer is 0f one in.. Material of damp proof coarse layer consists of concrete quantitative relation 1:1.5:3 with a mix of water proof material 1kg/bag.

MASONRY WORK

Masonry work is carried out with cement mortar. Cement mortar is a mixture of cement & sand. Ratio of cement mortar varies from 1:4 to 1:6. Here (1:6) mean, 1 part cement and 6 parts of sand. Dampen about 25 bricks with a hose pipe and clean away all loose dirt from the top of footing and moisten about a meter of surface at one end of the foundation with the hose pipe. Throw a mortar line just behind the threaded level line and lay bricks on the mortar bed. Make sure bricks exactly follow the threaded horizontal level line.

LINTEL

Masonry work of buildings is carried out in one go till roof. Openings for windows & doors are left during masonry works. Reinforced cement concrete beams are laid down on the top of openings. So, those loads of structure above openings not directly come on to the door frames.

ROOFING

Roof slab of building is poured after completion of masonry works. Now a days, roofing is of reinforced cement concrete slab. Slab thickness & reinforcement details should be according to approved drawings.

PLASTERING & POINTING

Form work is removed after 14 days of slab pouring. Now plaster work begins. Mortar for plaster work is generally of 1:3 or 1:4 is used. Thickness of plaster layer should not be more than 0.75inch. Cure the surface about 7 days. So that, plaster gain proper strength.

Generally, internal walls of buildings are covered with plastered layer and external walls with pointing. It is better plaster the external walls rather than pointing.

DOORS & WINDOWS

Traditionally, doors and windows of woods are used. But, steel & aluminum is also not a bad choice. In case of wooden doors & windows, frames are fixed in walls during masonry work. Panels are then fixed with hinges after plaster work. Steel and aluminum doors are fixed after completion of paint work.

SERVICES

Services are very important for every single house. Different types of services are provided during construction. These are Electricity supply, gas supply, water supply, sanitary etc. Conduits for electric supply are fixed in walls before plastering. Similarly water supply and sanitary lines are also laid before pouring of building floor. Note that gas lines are not fixed in walls or slabs. Gas line remains open in air.

About The Author:-

Sp.Aswinpalaniappan M.E.,*

Member of American Concrete Institute

Sri Raaja Raajan College of Engineering and Technology

Karaikudi, Tamil Nadu 630301

Modeling Techniques for Strain-Range-Dependent Hardening Behavior of Low-Yield-Point Steel Shear Panel Dampers

AUTHORS

Li-Yan Xu, Ph.D.; Mu-Xuan Tao; Xin Nie; Jian-Sheng Fan; and Ertugrul Taciroglu, M.ASCE

Abstract

Shear panel dampers made of the low-yield-point steel exhibit significant overstrength under cyclic loading—a phenomenon that has been observed to depend not only on accumulated plastic deformations but also the loading amplitudes. This type of material behavior cannot be captured by using nominal metal plasticity models, and thus an extension—dubbed in this paper as the stepwise hardening model—is proposed. This model incorporates a set of kinematic and isotropic hardening variables that can be selectively activated or deactivated based on the strain amplitude. It can be incorporated into standard plasticity models using the so-called finite-element birth-death technique, which is available in most commercial finite-element analysis packages. In this paper, the authors implement the proposed extension onto the standard J2$J_2$ plasticity model in general finite-element software using its parameter design language. The utility of the model is demonstrated by calibrating its parameters using force-displacement data from laboratory tests, and by carrying out numerical simulations to examine the evolution of damper shear force and energy consumption under different loading histories. The numerical studies performed in this paper indicate that the modified model can capture the hysteretic characteristics of low-yield-point steel dampers very well, which include their nonlinear transient and load–amplitude-dependent responses, as well as Bauschinger effects.

Supplemental Materials

•  supplemental_data_st.1943-541x.0001896_xu.pdf (150 KB)

5 belongings you have to be compelled to understand once Building a brand new Home

5 belongings you have to be compelled to understand once Building a brand new Home Building your new house is Associate in Nursing exciting and every now and then overwhelming expertise, except for your builder it's terribly routine, that is why you would like to be a vigorous participant all told aspects of the house building method to make sure you finish up with "YOUR" dream home.

Building your new home can not be a passive exercise, as a result of there ar such a large amount of selections that "must be" created by you. If you're unable or unwilling to form these selections, you'll force your builder to form them and run the chance that your new home will not prove the method you visualised it or value what you thought. Here ar five belongings you should understand and take into thought once building your new home:


1. understand your numbers

Before you begin building your new home, run some numbers to see whether or not you'll be able to afford to make the house you would like. Most house plans provide a value to make tool (usually for a nominal fee) to allow you Associate in Nursing correct estimate of construction prices supported wherever you are building. The numbers embody the prices of construction, tax advantages, funds for the payment and slush account, and different connected calculations.

Once you have determined you'll be able to afford to make the house you would like — purchase your house set up and head to the bank to rearrange for finance. confine mind that home construction disposition could be a very little totally different than regular mortgage finance. initial you'll have a home construction line of credit that may be accustomed pay subcontractors and suppliers UN agency perform work and supply provides. Once your home is created, you'll want a residential mortgage to pay off the development line.

2. Check the name of your builder

Many builders ar out there, however not all ar created equal. Do to a small degree analysis to search out out that builders have the simplest name. whether or not you hunt for info on-line or get recommendations from your family and friends, verify whether or not a builder is revered for doing quality work similarly as being timely. Our architects and designers advocate that you simply use solely builders UN agency ar members of the National Association of Home Builders (NAHB).

3. Build with merchandising in mind

No matter what proportion you're keen on the house that you simply ar building, it's unlikely that it'll be the last home you'll ever own. Knowing that, you ought to be conscious of its potential merchandising price. do not add such a large amount of upgrades that you simply price your home for the neighborhood. and do not opt for something too out of the standard. raise yourself if the options {you're|you ar} considering putting in are probably attending to attractiveness to others.

4. assume inexperienced

Make sure you are doing your analysis to maximise energy-efficiency within the style of your new home. Your designer and builder will facilitate make sure that your windows ar South-facing thus you get the maximum amount sunshine as doable heating your home. you'll be wanting to makes positive that loos, laundries and garages ar on the side of your home and have little windows to reduce heat loss. pay time selecting your insulation and HVAC systems, similarly as energy-efficient appliances and WaterSense taps and bogs.

5. do not forget the punch

Part of the ultimate section of building a brand new house is to travel over your "punch list." A punch list could be a list created at the tip of construction that shows what has to still be done or what has to be repaired on the new construction. You and your contractor can produce this list the week before closing after you bear your final rehearse. you ought to be taking notes when you visit your construction website or do a rehearse.

If you have got a true agent, it is a sensible plan to possess them participate within the punch list as a result of they're not showing emotion hooked up to your home and will have an improved eye for characteristic flaws.

When making a punch list for your new home, confine mind that issues usually fall under 2 categories: affordable flaws and unreasonable flaws. affordable flaws ar flaws that fall inside the tolerances of building construction (or insignificant flaws that typically don't have an effect on the standard of the new home). On the opposite hand, unreasonable flaws ar flaws that got to be mounted. These issues do have an effect on the standard of the house. Once any unreasonable flaws ar corrected in your new home, this is often known as substantial completion, which implies the new house is livable  and may be occupied. Before closing on your new home, you'll need one final rehearse to verify that the things on your punch list were mounted. As long because the new home has reached the purpose of considerable completion, you ought to be able to proceed with closing albeit everything wasn't completed.

Be sure you place the money for the completion of your punch list in written agreement. this may enable you to maneuver into your new home whereas still requiring the builder to finish the things on the punch list. The punch list marks Associate in Nursing exciting time within the method of building your new home, as a result of your house is virtually done! keep in mind to not get thus excited that that you simply pass your punch list, as a result of you do not wish regret that you simply did not take the time to mend these issues.

Design Tip
No matter what sort of utility you have got, most are feeling the warmth with rising energy prices. Typically, forty fifth of your utility bill goes for heating and cooling with quite half householders within the U.S. mistreatment gas to heat their homes. the nice news is, notwithstanding what reasonably heating or ventilation you have got in your home, you'll be able to economize and increase your comfort by properly maintaining and buying the correct energy economical instrumentation.

About The Author:-
Sp.Aswinpalaniappan M.E.,*

Member of American Concrete Institute

Sri Raaja Raajan College of Engineering and Technology

Karaikudi, Tamil Nadu 630301

10 THINGS to contemplate BEFORE beginning style AND CONSTRUCTION OF YOUR PROJECT

10 THINGS to contemplate BEFORE beginning style AND CONSTRUCTION OF YOUR PROJECT

Choosing the correct general contractor could ultimately be the foremost vital issue you'll do to realize a top quality outcome for your design-build project. Considering these ten factors can assist you notice the correct contractor for your wants.

1. Range of Services- one among the primary belongings you ought to think about is whether or not or not a contractor will give everything you wish in-house, or if they're going to use subcontractors. A design-build team keeps each field services and construction services beneath one roof to supply additional economical results.
2. Bid Details - Did your potential general contractor supply a hard and fast bid or a “time and materials” bid? One bid sort is also higher than the opposite, betting on the character of your project.
3. Warranties and Guarantees - will your contractor supply warranties for materials and workmanship? Do they need a satisfaction guarantee? check that you perceive the complete stipulations of those vital components.
4. Knowledge and Resourcefulness - will your contractor look like he extremely is aware of what he’s talking about? will he have an idea if sudden setbacks were to arise throughout the design-build process? responsive these queries will assist you avoid hiring somebody WHO might be out of their depth.
5. Oversight/Management - WHO can check that that the development team follows the approved plans and guidelines? Utilizing a contractor that additionally offers field services will keep the work on-target.
6. Cleanliness - will the design-build team keep a clean site? A sloppy work space might spell equally sloppy results for your project.
7. Sticking to the arrange - will the final contractor have a history of delivering work that's on budget and on time? You can’t afford a idler in these crucial areas.
8. Problem Resolution - raise former purchasers however the contractor worked to resolve any sudden problems which may have return up. Did he collaborate to realize Associate in Nursing acceptable resolution, or was he defensive and combative?
9. Budget - will your contractor have strategies in situ to stay the project on budget? Do they avoid practices that end in value overruns?

     10.Quality craftsmanship - At the top of the day, quality craftsmanship is an important outcome              for any design-build project. raise former purchasers if they were proud of the contractor’s                work,or visit former worksites for yourself to examine however they stand the check of your                 time.                                                                                                                                                      About The Author:-

Sp.Aswinpalaniappan M.E.,*
Member of American Concrete Institute

Sri Raaja Raajan College of Engineering and Technology

Karaikudi, Tamil Nadu 630301

Planning and style of web Zero Energy Residential Building

Planning and style of web Zero Energy Residential Building

The planned engineering project on "Net zero residential building" is found at Urapakkam. The NZERB has G+1 floor. the combination space surface coated by net zero energy residential building is ninety nine sq. meters. coCnfiguration ought to be accomplished for the planned NZERB victimization Indian commonplace codes. There ar 3 main phases during a construction project that ar coming up with, planning and estimation. the primary stage during a project is coming up with, within which preparation of layout of plot needs to be done. To conclude the project an in depth estimate of the residential building has conjointly been ready.
 With the increasing development within the country day by day would like of "net zero energy residential building" has conjointly raised. Adopting such building formation will save energy consumption regionally and moreover as on world scale and that we conjointly get vast quantity of saving on our electricity bill. the right style and alignment of the building will build the building cheaper than that of the traditional kind of buildings. Usage of hollow bricks and rejection of columns and beams can lead to lowering of temperature within the building.

Objective of this project

1. style a building with web zero energy conception.

2. To eliminate the need of active energy hundreds on the building.

3. comparison net zero energy building with typical building.


Designing conception of web zero energy building depends upon several factors. Net-zero energy buildings begin with energy-conscious style. A zero-energy residential building could be a building with zero web energy consumption. A net-zero energy (NZE) building is one that depends on renewable sources to supply the maximum amount energy because it uses, sometimes as measured over the course of a year.


To eliminate the need of active energy hundreds on the building star panels ar used. star panels is one among the technologies wont to bring home the bacon net-zero standing. To eliminate the need of active energy hundreds star techniques ar used that embody the employment of electrical phenomenon panels and star thermal collectors to harness the energy.
The ground floor of the building incorporates one hall, 2 bedrooms, one dinning, one room. The allocations of the rooms within the set up has been through with due thought of sun diagram as per the necessity of zero energy building. The set up has been ready victimization car CAD code.

The future scope of such residential building is extended to planning the "Net Zero Energy Residential Building" that produces its own electricity, therefore we will save a large quantity in electricity bill. Use this Civil project report for your reference and study solely.

About The Author:-
Sp.Aswinpalaniappan M.E.,*

Member of American Concrete Institute

Sri Raaja Raajan College of Engineering and Technology

Karaikudi, Tamil Nadu 630301

Evaluating long-term strength of rock under changing environments from air to water

Evaluating long-term strength of rock under changing environments from air to water

Significance Statement

The long-term stability of a rock mass should be accounted for during the design and construction of subsurface structures within a rock mass. Such subsurface structures include: underground power plants, repositories for radioactive waste, caverns for storage of natural gas or liquefied petroleum gas. It therefore becomes a necessity to understand the time-dependent fracturing of a rock and its direct influence on the strength. More so, time-dependent fracturing has been invoked as an important mechanism responsible for the increase in seismicity preceding earthquake ruptures and volcanic eruptions. It is known that evaluating the long-term strength of a rock is important in ensuring the long-term stability of a rock mass, considering the design and construction of various structures within it. The long-term strength of rock is normally evaluated under the same environmental conditions. However, in practice, the environment is persistently changing and must be accounted for in evaluating the long-term strength of the rock.

Researchers led by Professor Yoshitaka Nara at Kyoto University in Japan developed a new technique to evaluate the long-term strength of rock under changing environmental conditions, with a focus on the influence of water on subcritical crack growth in rocks. They aimed at providing clarity on the influence of water on the long-term strength of the rock and the long-term integrity of a rock mass surrounding various structures. They also hoped to provide further insight on the time-dependent deformation and fracturing in rock to evaluate its long-term strength by utilizing subcritical crack growth, which provides insight into the weathering of a rock mass over the long term. Their research work is now published in the Engineering Fracture Mechanics.

The research team conducted their tests by investigating the effects of water on the long-term strength of various rock samples including: gabbro and sandstone in both air and water medium. They first analyzed the mineral composition of the two rocks to be used in order to understand their cleavage and crystal morphology. Porosities, Young’s modulus, uniaxial compressive strength and the fracture toughness of the rocks were also obtained.

The research team observed that the long-term strength of the rocks decreased rapidly when the environmental conditions changed from air to water. They further observed that when the environmental conditions were changed repeatedly from air to water medium, the long-term strength achieved was identical to that obtained in a continuous water environment. In totality, the authors of this paper agreed that the water environment had the most significant effect on the long-term strength reduction in rock.

Knowledge exists that subcritical crack growth in rocks accelerates most in under water environments. The remarkable decline in the long-term strength of a rock in a water environment indicates a significant acceleration of crack propagation in the rock. Therefore, to ensure the long-term stability of a rock mass surrounding various structures, it is essential to understand the effects of water in which crack propagation is accelerated for the long-term strength estimation in aquatic environs. Effects of water should therefore be considered in the long-term use of rock structures.

 Thank you to Author

Yoshitaka Nara is currently Associate Professor in the Graduate School of Engineering, Kyoto University, Japan. He has completed Ph.D. in March 2004 in Hokkaido University, Japan. From April 2004 to March 2011, he has been a Postdoc in Hokkaido University. From October 2008 to October 2009 and from March 2010 to August 2010, he has stayed in University College London, UK, as a Postdoc. From April 2011 to March 2014, he has belonged to Kyoto University, Japan, as Assistant Professor. During this term, he has stayed in University of Minnesota, USA, from August to October in 2011, and University College London from March to May in 2012, as a visiting researcher. From April 2014 to March 2016, he has belonged to Tottori University, Japan, as Associate Professor. From April 2016, he has been in his current position.

His research interests concern the studies of subcritical crack growth, fracture toughness, crack distribution, and permeability of rocks to consider the application to rock engineering projects, such as geological disposal of radioactive wastes, carbon capture and storage, constructions of underground power plants, etc.

Reference

Yoshitaka Nara, Mayu Tanaka, Tomoki Harui. Evaluating long-term strength of rock under changing environments from air to water. Engineering Fracture Mechanics volume 178 (2017) pages 201–211.

http://www.sciencedirect.com/science/article/pii/S001379441630443X