Abstract:
A floor slab bridge structure is capable of enhancing the strength with which bridge girders and concrete bridge piers are rigidly joined so as to effectively suppress expansion and contraction, deflection, and distortion of the bridge girders, and to synergistically enhance the strength of connection concrete itself against the expansion and contraction, distortion, etc., to thereby be effective to prevent collapse of a bridge due to a large earthquake. Slab concrete is hammer-set between sides of respective bridge girders, which are spaced apart in a bridge width direction, along a length direction of the bridge girders. Connection concrete, in which bridge girder portions supported on bridge bottom surfaces of concrete bridge piers supporting the bridge girders are embedded, is additionally deposited on the bridge bottom surfaces to form a floor slab bridge structure constituting a rigid joining structure. The slab concrete and the concrete bridge piers are thus joined together through the connection concrete.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a floor slab bridge structure formed by hammer-setting slab concrete between sides of respective bridge girders, which are aligned in a bridge width direction, in a length direction of the bridge girders and comprising a composite structure of the bridge girders and the slab concrete. 
   2. Description of Related Art 
   Conventional floor slab bridges adopt a flexible joining structure, in which bridge girders are supported on bridge bottom surfaces of concrete bridge piers through rubber bearings and expansion and contraction, deflection, or distortion of the bridge girders are absorbed by the rubber bearings. 
   However, such flexible joining structure involves a problem that there is a fear of bridge collapse due to a large earthquake, and rubber bearings suffer degradation in function due to age deterioration and are very expensive. 
   On the other hand, Patent Document 1 (JP-A-2000-319816) proposes, as a method of construction in place of the flexible joining structure with the rubber bearings, a method of construction in which bridge girders are supported on bridge bottom surfaces of concrete bridge piers through non-rubber bearing. Connection concrete is additionally deposited on the bridge bottom surfaces, and bridge girder portions are embedded in the connection concrete, to thereby form a rigid joining structure of the bridge girders and the individual bridge piers. 
   However, the method of construction, in which rigid joining is achieved through independent connection concrete additionally deposited on the individual concrete bridge piers, is not functionally effective to provide strength for expansion and contraction, distortion, etc. of bridge girders extending between bridge piers, and to ensure the strength of independent connection concrete itself for expansion and contraction, distortion, etc. of bridge girders. Therefore, with such independent connection concrete, stress concentration and cracks or the like are generated in the bridge girders and the independent connection concrete such that the structure does not effectively function as an earthquake resistant structure against a large earthquake. 
   SUMMARY OF THE INVENTION 
   The invention provides a floor slab bridge structure wherein slab concrete is hammer-set between sides of respective bridge girders, which are spaced apart in a bridge width direction and extend along a bridge length direction to form a floor slab composed of a composite structure of the bridge girders and the slab concrete. Connection concrete, in which bridge girder portions supported on bridge bottom surfaces of concrete bridge piers supporting the bridge girders are embedded, is additionally deposited on the bridge bottom surfaces to form a rigid joining structure. The slab concrete and the concrete bridge piers are concrete-joined together through the connection concrete. 
   A rigid joining structure is constructed by providing the concrete bridge piers upright on buried foundation pillars, or by striking sheet piles in opposition to a bank while assembling them to construct an earth-retaining wall connected in a bridge width direction, supporting the concrete bridge piers on upper ends of the sheet piles projecting above the surface of the water or the ground, and concrete-joining the bridge piers and the slab concrete through the connection concrete. 
   Also, the bridge girders are supported directly on the bridge bottom surfaces of the concrete bridge piers, or supported indirectly on sleeper materials provided on the bridge bottom surfaces, and the sleeper materials are embedded in the connection concrete. As the sleeper materials, it is possible to use concrete sleeper materials hammer-set and formed on the bridge bottom surfaces of the concrete bridge piers, or steel materials, etc. 
   Also, as means for reinforcement of a concrete joining structure with the connection concrete, the bridge girder portions supported on the bridge bottom surfaces of the concrete bridge piers and the concrete bridge piers are connected to each other by connecting bars, which are inserted and embedded in the bridge piers and the connection concrete. 
   In the invention, the term “bridge piers” generally refers to an abutment and a bridge pier. 
   According to the invention, the connection concrete and the slab concrete cooperate with each other to form a gate type Rahmen structure. It is possible to enhance the strength, with which the bridge girders and the concrete bridge piers are rigidly joined by the connection concrete, to effectively suppress the expansion and contraction, deflection, and distortion of the bridge girders, and to synergistically enhance the strength of the connection concrete itself against the expansion and contraction, distortion, etc. Therefore, the structure is very effective to prevent bridge collapse due to a large earthquake. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a view showing a floor slab bridge, according to the invention, as viewed in cross section on a surface of a bridge girder in a bridge length direction. 
       FIG. 2  is a view showing the floor slab bridge as viewed in cross section on a surface of a slab concrete in the bridge length direction. 
       FIG. 3  is a view showing a further example of a floor slab bridge, according to the invention, as viewed in cross section on a surface of a bridge girder in a bridge length direction. 
       FIG. 4  is a view showing a further example of a floor slab bridge as viewed in cross section on a surface of a slab concrete in the bridge length direction. 
       FIG. 5  is a cross sectional view showing a floor slab bridge in a bridge width direction. 
       FIG. 6  is a cross sectional view showing a gate type Rahmen structure formed by slab concrete, connection concrete, and concrete bridge girders on a floor slab bridge. 
       FIG. 7  is a view showing a floor slab bridge as viewed in cross section on a horizontal surface. 
       FIG. 8  is a view showing, on an enlarged scale, an essential part of a floor slab bridge as viewed in cross section in a portion of a connection concrete, in which connecting bars are provided. 
       FIG. 9  is a view showing, on an enlarged scale, an essential part of a floor slab bridge as viewed in cross section in a portion of a connection concrete, in which suspended reinforcing bars are provided. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   Embodiments of the invention will be described below with reference to  FIGS. 1 to 9 . 
   As shown in  FIGS. 1 ,  3 ,  5 , and the like, a plurality of bridge girders  1  are spaced apart in a bridge width direction and supported on bridge piers  2  spaced apart in a bridge length direction. Slab concrete  3  is hammer-set and formed between sides of the respective bridge girders  1  along a length direction of the bridge girders  1 . A floor slab  4  is composed of a composite structure of the bridge girders  1  and the slab concrete  3 . 
     FIG. 1  shows a single span floor slab bridge comprising bridge piers  2 , which are respectively mounted on opposite banks of a river and on which both ends of bridge girders  1  are supported, and  FIG. 3  shows a plural span floor slab bridge comprising bridge piers  2 , which support end and intermediate portions of the bridge girders  1 . The present invention encompasses the single span floor slab bridge and the plural span floor slab bridge. 
   The bridge girders  1  each comprise a steel girder or a concrete girder, and as a preferred example, a floor slab  4  composed of a composite structure of bridge girders  1  and a slab concrete  3  is formed by using H-steel bridge girders  1 , which each comprise an upper flange  1   b  at an upper end of a web plate  1   a  and a lower flange  1   c  at a lower end thereof, and hammer-setting concrete in spaces defined by the upper and lower flanges  1   b ,  1   c  and the web plates  1   a  between adjacent bridge girders  1  in the bridge width direction to form a slab concrete  3 . 
   Upper openings  5  extending in a bridge length direction are provided between adjacent, upper flanges  1   b , lower openings  5 ′ extending between the adjacent, lower flanges  1   c  in the bridge length direction are closed by closure members, and concrete is hammer-set, that is, filled in the spaces through the upper openings  5  to form the slab concrete  3 . 
   The closure members that close the lower openings  5 ′ are removed or caused to remain as they are, after the slab concrete  3  is formed. In those regions, in which a connection concrete  11  (described later) is hammer-set and which face a bridge bottom surface  10  of a bridge pier  2 , however, concrete is hammer-set in spaces between the bridge girders without closing the lower openings  5 ′ whereby a slab concrete  3  is formed and simultaneously therewith a part of the concrete is caused to flow out toward the bridge bottom surface  10  through the lower openings  5 ′ to be concrete-joined to the bridge bottom surface  10 . 
   Simultaneously, roadbed concrete  6  joined integrally is hammer-set through the upper openings  5  and formed on all the upper flanges  1   b , and road pavement  7  is applied to an upper surface of the roadbed concrete  6 . 
   Longitudinal reinforcing bars  16  extending in the bridge length direction and transverse reinforcing bars  8  extending in the bridge width direction are assembled together in the roadbed concrete  6 . That is, the longitudinal reinforcing bars  16  and the transverse reinforcing bars  8  are assembled together to be placed on the upper flanges  1   b , and suspended reinforcing bars  9  assembled with the transverse reinforcing bars  8  or the longitudinal reinforcing bars  16  are suspended and embedded in the slab concrete  3  through the upper openings  5 . 
   The suspended reinforcing bars  9 , for example, are bent in a U-shape with both arms thereof assembled with the transverse reinforcing bar  8 , and are bent in an inverted U-shape to form a suspended reinforcing bar  9 ′ with a connecting portion of the suspended reinforcing bar  9 ′ assembled with the longitudinal reinforcing bars  16  or the transverse reinforcing bar  8  and with both arms thereof inserted through at least the upper flange  1   b  of the bridge girder  1  to be embedded in the slab concrete  3 . 
   Longitudinal reinforcing bars  16 ′ are assembled with the suspended reinforcing bars  9  or  9 ′ to be embedded in the slab concrete  3 , and web insertion rods  17  inserted through all the web plates  1   a  are embedded in the slab concrete  3 . 
   Stated again, the H-steel bridge girders, or T-steel bridge girders, or I-steel bridge girders, which are made of a steel material, various concrete bridge girders, etc. are used as the bridge girders  1  and spaces are provided between the respective bridge girders  1  to form upper openings  5  between upper ends of adjacent bridge girders  1 . Concrete is hammer-set, that is, filled in the spaces to form the slab concrete  3 , and simultaneously therewith, roadbed concrete  6  joined integrally is hammer-set through the upper openings  5  and formed on upper surfaces of all the bridge girders  1  to construct road pavement  7  on an upper surface of the roadbed concrete  6 . Then the longitudinal reinforcing bars  16  and the transverse reinforcing bars  8  placed on upper end surfaces of all the bridge girders  1  are embedded in the roadbed concrete  6 , the suspended reinforcing bars  9 ,  9 ′ are suspended and embedded in the slab concrete  3 , and web insertion rods  17  inserted through webs of all the bridge girders  1  are embedded in the slab concrete  3 . 
   Of course, a multiplicity of the suspended reinforcing bars  9 ,  9 ′, the transverse reinforcing bars  8 , and the web insertion rods  17  are arranged at intervals in the bridge length direction and a multiplicity of the longitudinal reinforcing bars  16 ,  16 ′ are arranged at intervals in the bridge width direction. 
   Further, a connection concrete  11 , in which bridge girder portions  1 ′ supported on bridge bottom surfaces  10  of concrete bridge piers  2  supporting lower end surfaces of the bridge girders  1  are embedded, is additionally deposited on the bridge bottom surfaces  10  to form a rigid joining structure of a gate type Rahmen, in which the slab concrete  3  and the concrete bridge piers  2  are concrete-joined together through the connection concrete  11 , and the bridge girders  1  are joined to the bridge piers  2  through the slab concrete  3  and the connection concrete  11  as shown in  FIGS. 2 ,  4 ,  6  or the like. 
   That is, after the concrete bridge piers  2  are constructed, the lower end surfaces of the bridge girders  1  are supported on the bridge bottom surfaces  10 , and in the case of H-steel bridge girders  1 , lower flanges  1   c  thereof are supported on the bridge bottom surfaces  10 , and the connection concrete  11  is hammer-set and formed on the bridge bottom surfaces  10 . 
   As shown in  FIGS. 2 and 4 , the connection concrete  11  is concrete-joined to the slab concrete  3  through the upper openings  5  of the bridge girders  1  by making the concrete bridge piers  2  substantially bulky, and covering upper surfaces of the bridge girder portions  1 ′, or upper surfaces of the upper flanges  1   b  in the case of H-steel bridge girders  1 , with a top  11   a  of the connection concrete  11 , that is, embedding upper ends (the upper flanges  1   b ) of the bridge girders  1  in the top  11   a  of the connection concrete  11 . The top  11   a  of the connection concrete  11  constitutes a part of the roadbed concrete  6 . 
   Further, as clearly shown in  FIGS. 2 ,  4 , and  7 , bridge girder end surfaces of bridge length ends are covered by rear sides  11   b  of the connection concrete  11 . That is, the bridge girder end surfaces are embedded in the rear sides  11   b , and the connection concrete is concrete-joined to the slab concrete  3  through end openings at the bridge girder end surfaces. The slab concrete  3  on the bridge girder portions  1 ′ constitutes a part of the connection concrete  11 . 
   Further, outer side surfaces of the bridge girder portions  1 ′ in the bridge width direction are covered with left and right sides  11   d  of the connection concrete  11  in the bridge width direction. That is, the outer side surfaces are embedded in the left and right sides  11   d  of the connection concrete  11 . 
   Therefore, there is provided a structure, in which the floor slab  4  of the composite structure is bridged and connected between respective portions of the connection concrete  11 . 
   As shown in  FIG. 3 , the concrete bridge piers  2  are provided upright on buried foundation pillars  18 , and as described above, a gate type Rahmen structure is constructed, in which the connection concrete  11  concrete-joins (rigidly joins) between the bridge piers  2  and the slab concrete  3 , and the bridge girders  1  are rigidly joined to the bridge piers  2  through the slab concrete  3  and the connection concrete  11 . 
   Also, as shown in  FIG. 1 , a gate type Rahmen structure is constructed in a unique method of construction by striking sheet piles  12  in opposition to a bank while assembling them to construct an earth-retaining wall connected in the bridge width direction, supporting the concrete bridge piers  2  on upper ends of the sheet piles  12  projecting above the surface of the water or the ground, concrete-joining (rigidly joining) the bridge piers  2  and the slab concrete  3  through the connection concrete  11 , and rigidly joining the bridge girders  1  to the bridge piers  2  through the slab concrete  3  and the connection concrete  11 . 
   A structure is provided, in which steel sheet piles made of a steel sheet having joints on both side edges as shown in the figure are used as the sheet piles  12 , a multiplicity of the sheet piles  12  are connected together by the joints and struck to form a sheet pile base and the earth-retaining wall, and the concrete bridge piers  2  are supported on an upper end of the sheet pile base. 
   Alternatively, a structure is provided, in which a multiplicity of sheet piles  12  made of a steel column or a concrete column are struck to form a sheet pile base and the earth-retaining wall, and the concrete bridge piers  2  are supported on an upper end of the sheet pile base. 
   The bridge girders  1  are supported directly on the bridge bottom surfaces  10  of the concrete bridge piers  2 , or sleeper materials  13  are provided on the bridge bottom surfaces  10  and the bridge girders  1  are supported on the sleeper materials  13 , that is, the bridge girders  1  are supported indirectly on the bridge bottom surfaces  10  through the sleeper materials  13 , and the sleeper materials  13  are embedded in the connection concrete  11 . 
   Stated in detail, concrete hammer-set through the upper openings  5  is filled in the spaces between the bridge girders to form the slab concrete  3  and to simultaneously flow onto the bridge bottom surfaces  10  through the lower openings  5 ′ to concrete-join the slab concrete  3  with the concrete bridge piers  2 . 
   Accordingly, the connection concrete  11  hammer-set and formed on the bridge girder portions  1 ′ on the bridge piers  2  constitutes a part of the slab concrete  3 . 
   Spaces are defined between the floor slab  4  and the bridge bottom surfaces  10  by interposing the sleeper materials  13  therebetween, connection concrete  11  is filled in the spaces through the lower openings  5 ′ to be concrete-joined to the bridge bottom surfaces  10 , and a bottom  11   c  of the connection concrete  11  filled in the spaces covers lower surfaces of the bridge girder portions  1 ′, or lower surfaces of lower flanges  1   c  in case of H-steel bridge girders. That is, the lower flanges  1   c  are embedded in the bottom  11   c  of the connection concrete  11  and simultaneously therewith the sleeper materials  13  are embedded in the bottom  11   c  of the connection concrete  11 . 
   Also, in the case where the sleeper materials  13  are not interposed, a part of the slab concrete  3  flows onto the bridge bottom surfaces  10  through the lower openings  5 ′ to be concrete-joined to the bridge bottom surfaces  10 . 
   Sleeper materials made of H-steel, or sleeper materials made of concrete are used as the sleeper materials  13 . As a preferred example, there are provided concrete sleeper materials  13  deposited integrally on the concrete bridge piers  2  from substantially central portions of the bridge bottom surfaces  10 . 
   Further, the sleeper materials  13  are provided independently for each bridge girder  1 , and the sleeper materials  13  successively extending in the bridge width direction are provided such that, for example, the concrete sleeper materials  13  successively extending in the bridge width direction are provided integrally with and transversely to the concrete bridge piers  2 . 
   In case of H-steel bridge girders  1 , the lower flanges  1   c  are supported directly on the bridge bottom surfaces  10  of the concrete bridge piers  2 , or supported on the sleeper materials  13  provided on the bridge bottom surfaces  10 . That is, the H-steel bridge girders  1  are supported indirectly on the bridge bottom surfaces  10  through the sleeper materials  13 , and the sleeper materials  13  are embedded in the bottom  11   c  of the connection concrete  11 . 
   Connection concrete  11  is filled in spaces defined between the floor slab  4  and the bridge bottom surfaces  10  by the sleeper materials  13 . In other words, connection concrete  11  is filled in spaces defined between the lower flanges  1   c  of the H-steel bridge girders and the bridge bottom surfaces  10 , through the lower openings  5 ′ to be concrete-joined to the bridge bottom surfaces  10 , and the bottom  11   c  of the connection concrete  11  filled in the spaces covers lower surfaces of the bridge girder portions  1 ′, or lower surfaces of the lower flanges  1   c  in case of H-steel bridge girders. That is, the lower flanges  1   c  are embedded in the bottom  11   c  of the connection concrete  11 , and simultaneously therewith the sleeper materials  13  are embedded in the bottom  11   c  of the connection concrete  11 . 
   Likewise, in the case where T-steel bridge girders, or I-steel bridge girders, which are made of a steel material, and concrete bridge girders of various configurations are used as the bridge girders  1 , the lower end surfaces of the respective bridge girders  1  are supported directly on the bridge bottom surfaces  10  of the concrete bridge piers  2 , or the lower end surfaces of the bridge girders  1  are supported on the sleeper materials  13  provided on the bridge bottom surfaces  10 . That is, the bridge girders  1  are supported indirectly on the bridge bottom surfaces  10  through the sleeper materials  13 . And, concrete is filled in the spaces through the lower openings  5 ′ to embed the sleeper materials  13  in the bottom  11   c  of the connection concrete  11 . 
   Also, as a concrete joining structure with the connection concrete  11 , that is, means for reinforcement of a rigid joining structure, the bridge girder portions  1 ′, which are supported on the bridge bottom surfaces  10  of the concrete bridge piers  2  and embedded in the connection concrete  11 , and the concrete bridge piers  2  are connected to each other by connecting bars  14 , which are embedded in the bridge piers  2  and the connection concrete  11  and made of a connecting wire or connecting pipe member. The connecting bars  14  cooperate with the connection concrete  11  to form the rigid joining structure. 
   The connecting bars  14  extend longitudinally in the concrete bridge piers  2  substantially over total heights thereof, and upper ends thereof project upward from the bridge bottom surfaces  10 , the projecting portions extending through the bridge girder portions  1 ′ and/or a portion corresponding to the slab concrete  3  to be connected to the bridge piers  2 . 
   For example, in the case where the bridge girders  1  comprise H-steel bridge girders, the projecting portions of the connecting bars  14  are inserted through through-holes provided in the lower flanges  1   c  and the upper flanges  1   b , nuts (stoppers)  15  are threaded onto male threaded portions of the connecting bars  14 , which project from upper surfaces of the upper flanges  1   b , and the nuts  15  are seated on the upper flanges  1   b  to connect the bridge girder portions  1 ′ to the bridge piers  2 . 
   Likewise, in the case where T-steel bridge girders, or I-steel bridge girders, which are made of a steel material, and concrete bridge girders of various configurations are used as the bridge girders  1 , upper end projecting portions of the connecting bars  14  are inserted through the upper flanges  1   b  and girder bodies, and stoppers such as the nuts  15 , etc. are seated on the upper flanges  1   b  and the girder bodies. 
   In an example shown in  FIG. 8 , an elongate seat plate  20  extending in the bridge width direction is mounted on upper surfaces of the bridge girders  1 , or upper surfaces of upper flanges  1   b  in the case of H-steel bridge girders, the upper end projecting portions of the connecting bars  14  are inserted through through-holes provided in the elongate seat plate  20 , and nuts  15  are threaded onto the upper end projecting portions (male threaded portions) on an upper surface of the seat plate  20  to be seated on the elongate seat plate  20 . 
   In addition, the connecting bars  14  partially extend through that portion of the connection concrete  11 , which corresponds to the slab concrete  3 , to project upward through the upper openings  5 , the upper end projecting portions of the connecting bars  14  are inserted through the through-holes provided in the elongate seat plate  20 , and nuts  15  are threaded onto the upper end projecting portions (male threaded portions) on the upper surface of the seat plate  20  to be seated on the elongate seat plate  20 . 
     FIGS. 1 and 3  show specific examples of the connecting bars  14 . As illustrated in  FIG. 1 , for example, a reinforcing bar is bent into a U-shape to form two connecting bars  14  connected to each other, and the respective connecting bars  14  are embedded longitudinally in the concrete bridge piers  2  to be connected to the bridge girder portions  1 ′ with upper ends thereof embedded in the connection concrete  11 . 
   Also, as illustrated in  FIG. 3 , a plurality of discrete connecting bars  14  are used, and the respective connecting bars  14  are embedded longitudinally in the concrete bridge piers  2  to be connected to the bridge girder portions  1 ′ with upper ends thereof embedded in the connection concrete  11 . 
   Also, in the case where the concrete bridge piers  2  are supported on the upper ends of the sheet piles  12  as shown in  FIG. 1 , sheet pile connecting reinforcing bars  19  extending through the upper ends of the sheet piles  12  are assembled between two connecting bars  14 , which are bent into U-shapes and connected to each other, and the connecting bars  14  and the upper ends of the sheet piles  12  are firmly connected to each other through concrete. That is, the concrete bridge piers  2  are firmly connected to the upper ends of the sheet piles  12  by the connecting bars  14  and the sheet pile-connecting reinforcing bars  19 . 
   Of course, the connecting bars  14  and the sheet pile-connecting reinforcing bars  19  are arranged in plural in the bridge width direction. 
   The embodiment described above shows the slab concrete  3  in the case where concrete is filled in a whole volume of spaces between adjacent bridge girders  1  as shown in the figure, that is, a whole volume of spaces between side surfaces of the bridge girders  1  and deposited integrally on the roadbed concrete  6 . 
   As a further example, it does not matter whether the slab concrete  3  extending in the bridge length direction is hammer-set and formed only in upper portions of spaces between the bridge girders  1 , no concrete is hammer-set in lower portions of the spaces and the lower portions of the spaces are caused to remain in the bridge length direction, or a lightweight material such as foam is filled in the lower portions of the spaces. In either case, the slab concrete  3  continues in spans between the bridge piers  2  and is connected at both ends thereof integrally with the connection concrete  11 . 
   In the case of using, for example, H-steel bridge girders as the bridge girders  1 , the slab concrete  3  is filled closely between upper flanges  1   b  and lower flanges  1   c  thereof, or the slab concrete  3  is filled up to upper portions of web plates  1   a  from the upper flanges  1   b  and roadbed concrete  6  is deposited integrally to embed the upper flanges  1   b  in the slab concrete  3  and the roadbed concrete  6  while the lower flanges  1   c  and lower portions of the web plates  1   a  are exposed from the slab concrete  3  to cause lower portions of the spaces, which extend in the bridge length direction, to remain on the lower flanges  1   c , that is, a lower portion of the slab concrete  3 . 
   In the case where the slab concrete  3  is hammer-set and formed in upper portions of the spaces between the bridge girders  1  to cause lower portions of the spaces to remain, connection concrete  11  is filled in whole spaces between the bridge girders  1  in a region, in which the connection concrete  11  is hammer-set and formed, that is, in a region above the bridge bottom surfaces  10 , and a part of the connection concrete  11  is caused to flow onto the bridge bottom surfaces  10  through the lower openings  5 ′ to be concrete-joined. 
   As described above, the term “concrete bridge piers”  2  generally refers to an abutment and a bridge pier in the preferred form of the invention.