Prosodic strengthening in the articulation of English /æ/

김사향,조태홍 한국음운론학회 2012 음성·음운·형태론 연구 Vol.18 No.2

The current study investigates how prosodic strengthening induced by boundary and accent influences the articulation of English low front vowel /æ/ in add, had, and pad. Using Electromagnetic Articulograph (EMA), lip and jaw opening maxima, and tongue dorsum maxima in the horizontal (x) and vertical (y) dimensions were measured during the vocalic production. Boundary-induced strengthening was found in the tongue height (TD-y) dimension in all three words: /æ/ was lower domain-initially than -medially. In other measures, the boundary effect was conditioned by accent and the location of /æ/ within words. Domain-initial strengthening was found with the jaw opening maxima, with larger opening in a higher prosodic position, but it was only when the target words were unaccented. Also, the vowel in add tended to get fronted in a domain-initial position, but the same tendency was not observed in had and pad, suggesting the possibility that initial strengthening effect is conditioned by ‘phonological’ distance from the boundary edge. (had is phonologically similar to pad in that /h/ and /p/ occupy a phonological onset position.) Accent-induced strengthening was robust in all four articulatory measures. Results show that an accent-independent boundary effect is observed on vowels even in a language with lexical stress, and that the articulatory planning for the boundary-induced strengthening on vowels interacts with accent-induced strengthening.

Prosodic strengthening in the articulation of English /æ/

Sahyang Kim,Taehong Cho 한국음운론학회 2012 음성·음운·형태론 연구 Vol.18 No.2

The current study investigates how prosodic strengthening induced by boundary and accent influences the articulation of English low front vowel /æ/ in add, had, and pad. Using Electromagnetic Articulograph (EMA), lip and jaw opening maxima, and tongue dorsum maxima in the horizontal (x) and vertical (y) dimensions were measured during the vocalic production. Boundary-induced strengthening was found in the tongue height (TD-y) dimension in all three words: /æ/ was lower domain-initially than -medially. In other measures, the boundary effect was conditioned by accent and the location of /æ/ within words. Domaininitial strengthening was found with the jaw opening maxima, with larger opening in a higher prosodic position, but it was only when the target words were unaccented. Also, the vowel in add tended to get fronted in a domain-initial position, but the same tendency was not observed in had and pad, suggesting the possibility that initial strengthening effect is conditioned by ‘phonological’ distance from the boundary edge. (had is phonologically similar to pad in that /h/ and /p/ occupy a phonological onset position.) Accent-induced strengthening was robust in all four articulatory measures. Results show that an accent-independent boundary effect is observed on vowels even in a language with lexical stress, and that the articulatory planning for the boundary-induced strengthening on vowels interacts with accent-induced strengthening.

Strengthening of concrete damaged by mechanical loading and elevated temperature

Ahmad, Hammad,Hameed, Rashid,Riaz, Muhammad Rizwan,Gillani, Asad Ali Techno-Press 2018 Advances in concrete construction Vol.6 No.6

Despite being one of the most abundantly used construction materials because of its exceptional properties, concrete is susceptible to deterioration and damage due to various factors particularly corrosion, improper loading, poor workmanship and design discrepancies, and as a result concrete structures require retrofitting and strengthening. In recent times, Fiber Reinforced Polymer (FRP) composites have substituted the conventional techniques of retrofitting and strengthening of damaged concrete. Most of the research studies related to concrete strengthening using FRP have been performed on undamaged test specimens. This contribution presents the results of an experimental study in which concrete specimens were damaged by mechanical loading and elevated temperature in laboratory prior to application of Carbon Fiber Reinforced Polymer (CFRP) sheets for strengthening. The test specimens prepared using concrete of target compressive strength of 28 MPa at 28 days were subjected to compressive and splitting tensile testing up to failure and the intact pieces of the failed specimens were collected for the purpose of repair. In order to induce damage as a result of elevated temperature, the concrete cylinders were subjected to $400^{\circ}C$ and $800^{\circ}C$ temperature for two hours duration. Concrete cylinders damaged under compressive and split tensile loads were re-cast using concrete and rich cement-sand mortar, respectively and then strengthened using CFRP wrap. Concrete cylinders damaged due to elevated temperature were also strengthened using CFRP wrap. Re-cast and strengthened concrete cylinders were tested in compression and splitting tension. The obtained results revealed that re-casting of specimens damaged by mechanical loadings using concrete & mortar, and then strengthened by single layer CFRP wrap exhibited strength even higher than their original values. In case of specimens damaged by elevated temperature, the results indicated that concrete strength is significantly dropped and strengthening using CFRP wrap made it possible to not only recover the lost strength but also resulted in concrete strength greater than the original value.

Behavior and stress check of concrete box girders strengthened by external prestressing

Yu Zhang,Dong Xu,Chao Liu 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.2

The deterioration of existing bridges has become a major problem around the world. In the paper, a new model and an associated stress checking method are proposed for concrete box girders strengthened by external prestressing. The new model called the spatial grid model can analyze all the spatial behaviors clearly by transforming the box girder into discrete orthogonal grids which are equivalent to plate elements. Then the three-layer stresses are employed as the stress checking indices to evaluate the stress state of the plate elements. The initial stress check before strengthening reveals the cracked and potential cracking areas for existing bridges, making the strengthening design more targeted and scientific; the subsequent stress check after strengthening evaluates the strengthening effect and ensures safety. A deficient bridge is selected as the practical example, verifying the accuracy and applicability of the proposed model and stress checking method. The results show that principal stresses in the middle layer of plate elements reflect the main effects of external prestressing and thus are the key stress checking indices for strengthening. Moreover, principal stresses check should be conducted in all parts of the strengthened structure not only in the webs. As for the local effects of external prestressing especially in the areas near anchorage and deviator, normal stresses check in the outer and inner layers dominates and local strengthening measures should be taken if necessary.

Experimental study on RC frame structures strengthened by externally-anchored PC wall panels

최승호,Jin-Ha Hwang,Deuck Hang Lee,Kang Su Kim,Dichuan Zhang,Jong Ryeol Kim 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.4

Infill wall strengthening method has been widely used for seismic strengthening of deteriorated reinforced concrete (RC) frame structures with non-seismic details. Although such infill wall method can ensure sufficient lateral strengths of RC frame structures deteriorated in seismic performances with a low constructional cost, it generally requires quite cumbersome construction works due to its complex connection details between an infill wall and existing RC frame. In this study, an advanced seismic strengthening method using externally-anchored precast wall panels (EPCW) was developed to overcome the disadvantage inherent in the existing infill wall strengthening method. A total of four RC frame specimens were carefully designed and fabricated. Cyclic loading tests were then conducted to examine seismic performances of RC frame specimens strengthened using the EPCW method. Two specimens were fully strengthened using stocky precast wall panels with different connection details while one specimen was strengthened only in column perimeter with slender precast wall panels. Test results showed that the strength, stiffness, and energy dissipation capacity of RC frame specimens strengthened by EPCWs were improved compared to control frame specimens without strengthening.

An experimental investigation of the flexural strengthening of preloaded self-compacted RC beams using CFRP sheets and laminates composites

Lattif, Youssef,Hamdy, Osman Techno-Press 2022 Advances in concrete construction Vol.13 No.4

This paper performs an experimental study on the flexural behavior of preloaded reinforced self-compacted concrete beams strengthened with carbon fiber reinforced polymers CFRP. A group of six preloaded strengthened beams was investigated along with one unstrengthened beam used as a reference beam RB. All beams have the same dimensions and reinforcement details: three beams are strengthened with CFRP laminates against flexural failure and three beams are strengthened with CFRP sheets. For simulating actual conditions, the beams are loaded before strengthening. Then, after strengthening, the beams are tested for flexural strength using 4-point loads where cracked and ultimate load and failure mode, along with load-deflection relation are recorded. To study the different configurations of strengthening, one layer, two layers, and U-wrap formation of laminates and sheets are considered. The results show that strengthing the RC beams using CFRP is an effective method to increase the beam's capacity by 47% up to 153% where deflection is reduced by 5%-80%. So, the beams strengthened with CFRP laminates have higher load capacity and lower ductility in comparison with the beams strengthened with CFRP sheets.

Flexural performance of wooden beams strengthened by composite plate

Tahar, Hassaine Daouadji,Abderezak, Rabahi,Rabia, Benferhat Techno-Press 2020 Structural monitoring and maintenance Vol.7 No.3

Using bonded fiber-reinforced polymer laminates for strengthening wooden structural members has been shown to be an effective and economical method. In this research, properties of suitable composite materials (sika wrap), adhesives and two ways of strengthening beams exposed to bending moment are presented. Passive or slack reinforcement is one way of strengthening. The most effective way of such a strengthening was to place reinforcement laminates in the stretched part of the wooden beam (lower part in our case), in order to investigate the effectiveness of externally bonding FRP to their soffits. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the wooden beam, the sika wrap composite plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. This research is helpful for the understanding on mechanical behaviour of the interface and design of the composite-wooden hybrid structures. The results showed that the use of the new strengthening system enhances the performance of the wooden beam when compared with the traditional strengthening system.

先加力 후 補修-補强한 鐵筋콘크리트 壓縮部材의 構造特性에 관한 實驗的 硏究

신용석,최진석,김판선,조철희,손순채,김정섭 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)

This study examined the Stress and structural characteristics of reinforced concrete compressive member repair and strengthening by CFS and GFS after pre-loading. The following results were obtained. The results of compressive testing by the kind of fiber suggested that: In CFS, Specimen increased by about 26.9% and strengthening after pre-loading, by about 111.8%, compared with after strengthening, In GFS, Specimen increased by about 69.0% and repaired and models after pre-loading, by about 76.7%, compared with after strengthening. In the compressive testing, strengthen with CFS-Specimen showed a brittle fracture and strengthen with GFS-Specimen represented ductile fracture. More increasing in stress of Specimen, and repair and Strengthening specimen after pre-loading than loading specimen after strengthening suggested the strengthen effect of fiber.

네트형 외부 긴장재에 의한 슬래브교 보강 실험

한만엽,강태헌,최석환 한국구조물진단유지관리공학회 2011 한국구조물진단유지관리공학회 논문집 Vol.15 No.5

국내의 지형 특성으로 인해서 교량의 많은 부분이 슬래브교 형식이다. 차량이 대형화하고 교통량이 증가하면서 노후 슬래브교의 보강이 필요한 경우가 많다. 본 연구에서는 노후화된 슬래브교를 효과적으로 보강할 수 있는 외부 긴장재 보강공법을 제안하였다. 종방향 및 횡방향 외부 프리스트레싱을 이용한 네트형 보강법은 슬래브 중앙부의 처짐을 효과적으로 보강할 수 있는 방법이며, 하부공간을 침해하지 않으므로 실제 적용성이 뛰어나다. 실험을 통해서 제안한 보강법으로 인해서 향상되는 내하력의 크기를 검증하였다. 실험에서는 세 가지 서로 다른 하중조건에 대하여 처짐 및 변형률을 계측하여 보강의 효과를 비교, 분석하였다. 네트형 긴장재 보강 전후의 휨강성의 증가량은 재하 종류별로 30.7~107.3% 증가하였다. 보강 전후 처짐의 감소율은 27.6~52.2%에 달하였다. 종방향 및 횡방향 프리스트레싱으로 인한 네트형 보강법은 슬래브교의 중앙부 보강에 매우 효과적이며, 중앙에 집중되는 하중 뿐만 아니라 편기 재하되는 하중에 대해서도 유사한 보강효과가 있다. 또한 네트형 보강법은 필요에 따라 재긴장이 가능하므로 유지보수 및 사용성 측면에서 장점이라 할 수 있다. Large portion of the domestic bridges are slab bridges reflecting the geographical characteristic of the country, where exists lots of inclines and small winding brooks. Many of the slab bridges are damaged and superannuated as they become obsolete. Deterioration is accelerated when the traffic density becomes large and heavy vehicles pass frequently. A strengthening method for deteriorated slab bridges was studied in this work. The examined net-type strengthening method uses both longitudinal and transverse prestressing for strengthening. In this way, the deflection at the center of the slab can be better controlled, and consequently, the slab is more efficiently strengthened. Three slab specimens were fabricated for the experimental test and subjected to three different loading conditions, and the load bearing capacities and deflections of slabs were examined. Flexural stiffness of slabs increased by 30.7~107.3%, and deflection of slabs decreased by 27.6~52.2% after net-type strengthening. The net-type prestressing is efficient to the strengthening for the center of a slab, and its efficiency is also valid under eccentric loadings. Since extra prestress forces can be added in the future, if necessary, the net-type strengthening system is advantagous for the maintenance and repair of slab bridges.

Field test of an old RC bridge before and after NSM strengthening

Lee, Heeyoung,Jung, Woo Tai,Chung, Wonseok Elsevier 2018 Composite Structures Vol.202 No.-

<P><B>Abstract</B></P> <P>In this paper, a post-tension near-surface mounted (NSM) strengthening system is proposed to strengthen concrete structures with a relatively low amount of labor and without altering the appearance or dimensions of the structures. The main objective of this study was to investigate the structural behavior of an old reinforced concrete T (RCT) type bridge before and after using post-tension NSM strengthening systems. The 12.5 m RCT type bridge was tested using the truck loading test. The displacements of the bridge at mid-span were measured during the test. A finite element analysis model was also developed and verified with the test result. This study showed that the structural capacity and performance of the bridge were enhanced with post-tension NSM strengthening systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An old reinforced concrete T bridge was strengthened with post-tension NSM strengthening systems. </LI> <LI> Truck loading field tests were conducted to evaluate the strengthening effect before and after NSM strengthening. </LI> <LI> Post-tensioned NSM CFRP can effectively improve static and dynamic behavior of concrete bridges. </LI> <LI> FEA model was developed and verified with the experimental results. </LI> </UL> </P>