In this paper,a research was conducted on the design technology of continuous beam-arch composite bridges.A brief introduction is given on the of continuous beam-arch composite bridges,its basic mechanical characteris...In this paper,a research was conducted on the design technology of continuous beam-arch composite bridges.A brief introduction is given on the of continuous beam-arch composite bridges,its basic mechanical characteristics is analyzed,and three aspects of design technology is studied,which are rise-span ratio,stiffness ratio,and bridge deck cracking.This article acts as a reference for relevant design units in China to improve the design of continuous beam-arch combination bridges.展开更多
There are costs for doing the right thing,but regret is not one of those costs.I learned this lesson the hard way throughout a 42-year engineering career.As a young engineer,raising a family,I was more adaptable to ma...There are costs for doing the right thing,but regret is not one of those costs.I learned this lesson the hard way throughout a 42-year engineering career.As a young engineer,raising a family,I was more adaptable to management mandates,i.e.,I was more willing to be unethical to keep my job to make money and have health insurance for my family.As I grew in age,experience,and stamina,I was less adaptable,i.e.,I was more ethical.This article tells this story through events at various times in my engineering career1.Ethics define how we do the right thing.展开更多
An efficient and promising approach for effectively dispersing multi-walled carbon nanotubes(MWCNTs)in cementitious composites has been investigated.The naturally occurring organic extracts from species of indigenousl...An efficient and promising approach for effectively dispersing multi-walled carbon nanotubes(MWCNTs)in cementitious composites has been investigated.The naturally occurring organic extracts from species of indigenously known‘Keekar’trees scattered along tropical and sub-tropical regions;is found as an exceptional replacement to the non-natural commercial surfactants.In the initial phase of investigation,ideal surfactant’s content required for efficient dispersion of MWCNTs in solution was determined using ultra-violet spectroscopy.The experimental investigations were then extended to five different cement composite formulations containing 0.0,0.025,0.05,0.08 and 0.10%MWCNTs by weight of cement.It was observed that the natural surfactant produced efficient dispersion at much reduced cost(approx.14%)compared with the commercial alternate.The estimated weight efficiency factor f was found 6.5 times higher for the proposed sustainable replacement to the conventional along with remarkable increase of 23%in modulus of rupture on 0.08 wt%addition of MWCNTs.Besides strength enhancement,the dispersed MWCNTs also improved the first crack and ultimate fracture toughness by 51.5%and 35.9%,respectively.The field emission scanning electron microscopy of the cryofractured samples revealed efficient dispersion of MWCNTs in the matrix leading to the phenomenon of effective crack bridging and crack branching in the composite matrix.Furthermore,the proposed scheme significantly reduced the early age volumetric shrinkage by 39%.展开更多
Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of s...Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of ship hull parts to optimize expenditure.This is relevant in view of the difficulty in reaching farthest corners in ballast tanks,fuel storage tanks,cofferdams etc.Prior maintenance of the deck and hull parts save a considerable amount of the owner's budget.A portable technology like patching becomes more handy and economic.Performance of both unpatched and patched samples during dynamic loading conditions being examined in the present investigation.The high strength steel panels with a dimension of 70mm×15mm×3mm were edge cracked for lengths of 4mm and 7mm,with width of 1mm for both.The edge cracked high strength steel panels are repaired with composite patches using GFRP(glass fiber reinforced plastic),CFRP(carbon fiber reinforced plastic)and AFRP(aramid fiber reinforced plastic).The patching was done by 3 and 5 layered and impact tested by Charpy impact tester at ranges of high temperatures.The amount of energy absorbed in the impact is converted to dynamic fracture toughness values and compared for evaluating the performance of FRP(fiber reinforced plastics).Finite element analysis was done for evaluating the stress intensity factors at different types of patching and testing conditions.Comparatively the AFRP patched samples showed better dynamic fracture toughness values at different temperatures.展开更多
文摘In this paper,a research was conducted on the design technology of continuous beam-arch composite bridges.A brief introduction is given on the of continuous beam-arch composite bridges,its basic mechanical characteristics is analyzed,and three aspects of design technology is studied,which are rise-span ratio,stiffness ratio,and bridge deck cracking.This article acts as a reference for relevant design units in China to improve the design of continuous beam-arch combination bridges.
文摘There are costs for doing the right thing,but regret is not one of those costs.I learned this lesson the hard way throughout a 42-year engineering career.As a young engineer,raising a family,I was more adaptable to management mandates,i.e.,I was more willing to be unethical to keep my job to make money and have health insurance for my family.As I grew in age,experience,and stamina,I was less adaptable,i.e.,I was more ethical.This article tells this story through events at various times in my engineering career1.Ethics define how we do the right thing.
文摘An efficient and promising approach for effectively dispersing multi-walled carbon nanotubes(MWCNTs)in cementitious composites has been investigated.The naturally occurring organic extracts from species of indigenously known‘Keekar’trees scattered along tropical and sub-tropical regions;is found as an exceptional replacement to the non-natural commercial surfactants.In the initial phase of investigation,ideal surfactant’s content required for efficient dispersion of MWCNTs in solution was determined using ultra-violet spectroscopy.The experimental investigations were then extended to five different cement composite formulations containing 0.0,0.025,0.05,0.08 and 0.10%MWCNTs by weight of cement.It was observed that the natural surfactant produced efficient dispersion at much reduced cost(approx.14%)compared with the commercial alternate.The estimated weight efficiency factor f was found 6.5 times higher for the proposed sustainable replacement to the conventional along with remarkable increase of 23%in modulus of rupture on 0.08 wt%addition of MWCNTs.Besides strength enhancement,the dispersed MWCNTs also improved the first crack and ultimate fracture toughness by 51.5%and 35.9%,respectively.The field emission scanning electron microscopy of the cryofractured samples revealed efficient dispersion of MWCNTs in the matrix leading to the phenomenon of effective crack bridging and crack branching in the composite matrix.Furthermore,the proposed scheme significantly reduced the early age volumetric shrinkage by 39%.
文摘Preventive maintenance is an accepted practice in engineering to keep the structural reliability of ship hulls at the highest possible level.Designers ensure a longer period in between the consecutive maintenance of ship hull parts to optimize expenditure.This is relevant in view of the difficulty in reaching farthest corners in ballast tanks,fuel storage tanks,cofferdams etc.Prior maintenance of the deck and hull parts save a considerable amount of the owner's budget.A portable technology like patching becomes more handy and economic.Performance of both unpatched and patched samples during dynamic loading conditions being examined in the present investigation.The high strength steel panels with a dimension of 70mm×15mm×3mm were edge cracked for lengths of 4mm and 7mm,with width of 1mm for both.The edge cracked high strength steel panels are repaired with composite patches using GFRP(glass fiber reinforced plastic),CFRP(carbon fiber reinforced plastic)and AFRP(aramid fiber reinforced plastic).The patching was done by 3 and 5 layered and impact tested by Charpy impact tester at ranges of high temperatures.The amount of energy absorbed in the impact is converted to dynamic fracture toughness values and compared for evaluating the performance of FRP(fiber reinforced plastics).Finite element analysis was done for evaluating the stress intensity factors at different types of patching and testing conditions.Comparatively the AFRP patched samples showed better dynamic fracture toughness values at different temperatures.
